EUROPHON CTV 16000 TLC YEAR 1979.

The EUROPHON CTV 16000 TLC  is a 16 inches (37cm) portable color tv set with 16 programs with VST search system.

The EUROPHON CTV 16000 TLC  is featured with Infra red remote control system and a  circuit device for a television receiver having a tuner device with a tuner memory operable to control the tuning of the receiver to stations selected by a user, in which there are further provided means for automatically adjusting the controls of the receiver whenever the station to which the receiver is tuned is changed, this means comprising one or a plurality of random access memories addressed by signals from the tuner memory which are characteristic of each individual station, the output signal from the RAM, (or the enabled RAM if there are a plurality of them) representing the contents thereof at the location addressed, is fed to a digital-to-analogue converter which produces an output voltage signal for adjusting the associated receiver control; changes to the content of the RAM can be made by means of an associated counter controlled to count up or down by a push button panel. 

The  invention relates to a circuit device for effecting and memorising adjustments to the setting of the controls of a television signal receiver, especially of a colour television receiver; such controls as the volume, brightness, contrast, colour saturation etc. must often be adjusted when changing stations in order to obtain optimum setting of the controls for each station to which the receiver can be tuned in order to account for differences in the signals from each station. Conventionally, television controls are mechanical control systems using potentiometers inserted into the path of the electric signal to be controlled (direct control) or else supplying a D.C. voltage by means of which electronic voltage control is effected (indirect control).
Such mechanical systems have considerable disadvantages, not only from the point of view of durability, since the potentiometers, being mechanical, are subject to wear, but also from that of performance due to non-linearity and discontinuity in the response. Moreover, such mechanical systems are not easily adaptable to the use of remote controls.

For this reason wholly electronic control systems, which operate indirectly, have been recently introduced. These usually comprise a series of counters which are able to count both up and down, each followed by a suitable digital-to-analogue converter. By energising a counter, selected by operation of one of a number of pairs of push buttons, it is possible to increase or reduce the content of this counter and thereby to cause the corresponding control voltage to vary: such variation is discontinuous, but has sufficient resolution for most purposes.
This latter system eliminates many of the disadvantages of the conventional mechanical controls but it is still not wholly satisfactory because, since each station to which a receiver can be tuned usually has modulation characteristics which are different from those of the others, with every change of station it is necessary to readjust, systematically, the controls of the receiver, that is the volume, brightness, contrast (and colour controls in the case of colour transmission).
In fact at present it is possible in many places to receive a large number of transmitter stations (in some cases more than twenty), and hence television receivers have to allow changeover from one station to another with the greatest simplicity. The technical problem which this invention seeks to solve is the provision of a circuit device which is able to effect adjustment of the controls of a receiver upon changes in the tuning thereof to receive signals from different transmitters, which does not suffer from the disadvantages of known systems.
VST Tuning and remote.Varactor-type tuning circuits are well-known in the art and particularly have been adopted for tuning tuners including both UHF and VHF sections. Such tuning circuits incorporate a varactor diode whose capacitance is dependent upon a tuning voltage applied thereto. There are known methods of developing such tuning voltages, including the so-called automatic tuning in which a sweep is stopped when a predetermined intermediate-frequency signal is produced by applying voltages to the varactor diode from a voltage sweep circuit. A tuning voltage generating apparatus of a voltage synthesizer type comprises a voltage converter which converts into a reference voltage a voltage level of an input pulse signal having a pulse width corresponding to a frequency to be received and a low-pass filter which converts the pulse signal voltage converted by the voltage converter into a direct current voltage which is withdrawn as a tuning voltage.More specifically, the present invention relates to a tuning voltage generating apparatus of a voltage synthesizer type for supplying a tuning voltage to a tuner employing a variable reactance element as a tuning element.

The set is a first in featuring  a new set of PAL decoder chips which has been introduced by Siemens, the TDA2560/TDA2522/TDA2530. The first two of these second -source the latest Philips/Mullard decoder i.c.s, with the TDA2560 as luminance and chrominance signal amplifier and the TDA2522 as the reference oscillator/chrominance demodulator. Interesting features of this set up are the fact that the burst signal passes through the chrominance delay line and the fact that the reference oscillator operates at 8.86MHz, a digital divider providing exactly 90° phase displaced 4.43MHz outputs without the need for a phase shift coil. The first UK produced chassis to use these i.c.s is the Tandberg CTV3, the larger UK setmakers staying for the time being with the TBA560C/TBA540/TCA800 combination. The third i.c. from Siemens is the TDA2530 which supersedes the well known TBA530 luminance/colour-difference signal matrix- ing i.c. The TDA2530 contains a negative feedback driver amplifier and internal clamping in addition to the matrixing network.

The set has a switching power supply. Switching regulators serve as efficient and compact power supplies for instruments such as television receivers. A switching regulator may typically comprise a power transformer having a primary winding coupled to an input voltage source and to a power switch and a secondary winding coupled to a rectifier arrangement for developing a DC supply voltage for the instrument. A regulator control circuit generates pulse width modulated control signals that control the duty cycle of the power switch. A power switch is coupled to an inductance and a source of input voltage. A control circuit is coupled to the power switch for producing the switching thereof to transfer energy from the input voltage source to a load circuit coupled to the inductance. The control circuit is responsive to control voltages for varying the duty cycle of the power switch to control the transfer of energy to the load. A first control voltage representative of a variation in an energy level of the load circuit is developed to control the duty cycle in a manner that regulates the energy level.

It features a TOSHIBA BlackStripe CRT TUBE, and has a completely modular chassis design well dimensioned even for a bigger screen format tv set.

The set is build with a Modular chassis design because as modern television receivers become more complex the problem of repairing the receiver becomes more difficult. As the number of components used in the television receiver increases the susceptibility to breakdown increases and it becomes more difficult to replace defective components as they are more closely spaced. The problem has become even more complicated with the increasing number of color television receivers in use. A color television receiver has a larger number of circuits of a higher degree of complexity than the black and white receiver and further a more highly trained serviceman is required to properly service the color television receiver.
Fortunately for the service problem to date, most failures occur in the vacuum tubes used in the television receivers. A faulty or inoperative vacuum tube is relatively easy to find and replace. However, where the television receiver malfunction is caused by the failure of other components, such as resistors, capacitors or inductors, it is harder to isolate the defective component and a higher degree of skill on the part of the serviceman is required.
Even with the great majority of the color television receiver malfunctions being of the "easy to find and repair" type proper servicing of color sets has been difficult to obtain due to the shortage of trained serviceman.
At the present time advances in the state of the semiconductor art have led to the increasing use of transistors in color television receivers. The receiver described in this application has only two tubes, the picture tube and the high voltage rectifier tube, all the other active components in the receiver being semiconductors.
One important characteristic of a semiconductor device is its extreme reliability in comparison with the vacuum tube. The number of transistor and integrated circuit failures in the television receiver will be very low in comparison with the failures of other components, the reverse of what is true in present day color television receivers. Thus most failures in future television receivers will be of the hard to service type and will require more highly qualified servicemen.
The primary symptoms of a television receiver malfunction are shown on the picture tube of the television receiver while the components causing the malfunction are located within the cabinet. Also many adjustments to the receiver require the serviceman to observe the screen. Thus the serviceman must use unsatisfactory mirror arrangements to remove the electronic chassis from the cabinet, usually a very difficult task. Further many components are "buried" in a maze of circuitry and other components so that they are difficult to remove and replace without damage to other components in the receiver.
Repairing a modern color television receiver often requires that the receiver be removed from the home and carried to a repair shop where it may remain for many weeks. This is an expensive undertaking since most receivers are bulky and heavy enough to require at least two persons to carry them. Further, two trips must be made to the home, one to pick up the receiver and one to deliver it. For these reasons, the cost of maintaining the color television receiver in operating condition often exceeds the initial cost of the receiver and is an important factor in determining whether a receiver will be purchased.
Therefore, the object of this invention is to provide a transistorized color television receiver in which the main electronic chassis is easily accessible for maintenance and adjustment. 

The contrast knob is located rear side above the lid.

Europhon SpA has been established in 1949 in Milan. During the 60's it was one of the main European manufacturer of pocket transistor radios. Record players, stereo systems and television sets were added to the product line later. Between 1949 and 1961, few years after its founder Andrea Zenesini passed away, the Europhon SpA was phased out.

Main manufacturing plants in mid '60s: Milan, Quistello (Mantua), Bozzolo (Mantua) and Trino Vercellese.

Brands: Euronic, Eurostar, Kosmophon, Phonomatic and (after 1965) Superla.

EUROPHON HISTORY:
 It was founded in Milan in 1949 by Andrea Zenesini, and began its activity with the production of radio. In the following years the company gained momentum in the market for radio and extended its production to other types of devices such as televisions.

During the first sixty years, the company expanded and created other establishments in Quistello, Cocoon (MN), Castelleone (CR) and Trino (VC), arriving to count to 1,100 employees and a monthly output of 125,000 pieces. In addition, the company marketed its products Lombard with other smaller brands like Euronic, Eurostar, Kosmophon, Phonomatic and Superla. Also present on foreign markets in 1970 also opened a sales office in Germany, as Europhon Service GmbH in Ottobrunn.

Of particular relevance and success were both above the tabletop radio (such as 800) the pocket transistor radio (of which Europhon was one of the largest European manufacturers in the sixties), the turntable, the mangiadischi (such as fonojet 700) stereos. However, the Europhon also produced a good variety of color tv noteworthy that ranged from 14 to 29 inches.

 In the seventies, the leadership understood as - yet they do not belong to the world of HIFI ', and being in the competition with Eastern Europe in the field of low-cost products - a winning strategy would be to enter the emerging field of "design "on the one hand, and developing technology to produce hi-fi on the other. The first director was the most 'immediate, thanks to the collaboration of designers level, while maintaining a component within the standards, Europhon able' to market industrial design objects destined to leave a mark in history. Objects often with hybrid functions; remember, for example, the "radiorologio" (RadioClock) , the radiotelevisore (RadioTellye !!) and radiolampada (RadioLamp) drawn by Adriano Rampoldi.

 The decline:

At the end of the decade, according to a fate common to many other, Europhon experienced a period of decline more and more, which inevitably led to the crisis in the early eighties. If in the seventies firms in poor conditions came under the unified management of financial GEPI, in the eighties - having regard to the poor results of this - the political forces had set out to create a different rescue, under the forms of public financial REL (Renovation Electronics Spa), born in 1982. This repeats' as performed by GEPI, assuming that the companies - survived the previous decade - now came to an end even: Brionvega Autovox, Seleco, Voxson, SECI. Of Europhon, I note REL 'the 44,36% of the shares, with a cash injection of 15 billion lire..................

.................. between the two decades Europhon began a joint venture with its German subsidiary, which ported a series of technological contributions - a last attempt to excursus into the market for high-fidelity ', launching separate components (which could be combined with rack) objectively superior compared to the past: remember the series Rck 3005, Rck305, Rck2000. Often with minimal changes between them (the metallic exterior colors went from opaque to blacks, following the fashion), a letter after the code that identified the function of the object (if flat plate, tuner, amplifier). It was only in the eighties forwarded - with a delay of over a decade - that Europhon I raise 'standards of its machines to DIN 45500, the quality level that, according to the agreements of 1973 would have to allow manufacturers to mark their equipment as hi-fi.  These devices are labeled "Europhon International" to signify the union between Germany and Italy, and mainly produced in Germany. Nevertheless, 'Europhon not shake' never off his reputation as a producer of cheap items.

The Europhon project 'and also produced one of the few cd player made in Italy at the consumer level, realizing the potential' of the product. This was included in the devices to separate components of the brand, even the stereo "all inclusive" living room - that the company produced, in line glue fashion of the decade (such as the Rck185) - were equipped with CD player. Unique Italian brand made in Italy with such features. Europhon produced - always in line with the era - even stereo "beach" (compact with radio, cassette and speakers) such as Jumbo.

 the closure and Europhon Topvision

If Europhon had innovative ideas, showing some liveliness' in research and development (the line of modular "micro component T" anticipated the minimalist trends of the decade), government interventions in the capital dell'Europhon had no effects needed to make the new possibility 'products known and distributed. Disappeared for years now the founder and dispersed management, without a full business strategy, with economic lines expensive (compared to oriental products) and products "niche" not credible, Europhon you find 'financial conditions and without any dramatic perspective. Unfortunately, the recovery did not take place and the activities were closed down permanently in 1991, resulting in the dismissal of 350 workers who were still in the workforce in the three plants Quistello, Cocoon and Castelleone.
Almost all of the employees suffered, in the nineties, an odyssey of layoffs, relocations fictitious (copy one at the Antares Florence), and mobility. Just the establishment of Quistello was the only one to offer a continuity ': he became - and still is - home of Topvision (initially Europhon Topvision) which produced color televisions until the advent of technology lcd brand Topvision.

The first TV marked Topvision of 1991 were nothing more than the latest models Europhon (www.topvision.it). Today, renamed only Topvision, continues the production, focusing especially on cards for other assemblers, and no more 'for the consumer.
The German Europhon

The German branch, despite the closure of the Italian parent, continued his activities as a distributor of consumer electronics from other companies, such as the Italian Ultravox. Which subsequently became Europhon Deutschland GmbH, a company that is currently marketed under the same name brand products from the satellite receivers Microelectronic NH, from which it is controlled.

 R.I.P. EUROPHON........................

Further Notes:

^ Logo (JPG), su roetta.it. ^ Breve articolo dedicato all'Europhon su Guanciarossa.it ^ VOV Radio Europhon; Milano, build 1969, 2 pictures, Italy, s ^ Belle` Lucio, Europhon Professional II - la radio multibanda italiana, in Radiorama - Panorama Radiofonico Internazionale, nº 47. ^ associazione di radio d'epoca ^ L'Hi-Fi Italiana pronta per la sfida - Si può acquistare un apparecchio hi-fi italiano? - SUONO STEREO HI-FI  novembre 1972 ^ Radioorologio H10 Radio Europhon; Milano, build 1968 ??, 12 ^ Radioorologio H20 Radio Europhon; Milano, build 1970 ?, 4 pi ^ Radio-Uhr H30 Radio Europhon; Milano, build 1973 ??, 29 pict ^ MARCHI Cesare, Il pioniere stereofonico, in "I fabbricanti di miliardi" 1970 ^ REL, IL COLORE DEI SOLDI - la Repubblica.it, in Archivio - la Repubblica.it. URL consultato il 18 marzo 2018. ^ High fidelity, su princeton.edu. ^ Comunicato, su gazzettaufficiale.it. ^ INTERROGAZIONE A RISPOSTA SCRITTA 4/32773 presentata da ROSSI EDO (MISTO) in data 20001129 | OCD - Ontologia della Camera dei deputati ^ Gazzetta Ufficiale, su gazzettaufficiale.it. ^ Gazzetta Ufficiale, su gazzettaufficiale.it. ^ Gazzetta Ufficiale, su gazzettaufficiale.it. ^ Azienda | TopVision, su www.topvision.it. URL consultato il 22 ottobre 2015.

EUROPHON CTV 16000 TLC CHASSIS PSSD 978 INTERNAL VIEW.

The EUROPHON CTV 16000 TLC  CHASSIS PSSD 978 is a heavy steel sheet chassis structure holding a modular unit composition which is well dimensioned like a 26 inches color tv set.

The set is well made and the chassis is clearly oriented on reliability, durability, service easyness...............

EUROPHON CTV 16000 TLC  CHASSIS PSSD 978 Switching power supply, especially for a T.V. receiving apparatus:

 1. Switch mode power supply means, especially for a television receiver, having a working winding (5), a switching transistor (6), a back-coupling winding (7) and a control switch (11) on the primary side of a divided transformer (1), and also having rectifiers (15, 16, 20) for the production of the drive voltages (U1, U2, U3) on the secondary side of the transformer (1), characterized by the following features : (a) Connected to a winding (19) there is a thyristor (24) which is poled in the permitted direction for the voltage at the winding (19) arising during the current conducting phase of the switching transistor (6). (b) One of the drive voltages (U2) is applied to the control electrode of the thyristor (24) with such magnitude that the thyristor (24) remains blocked in the normal working state and fires on the occurrence of an inadmissible rise of the drive voltage (U3).

  Schaltnetzteil, IN GERMAN:

 1. Schaltnetzteil, insbesondere f·ur einen Fernsehempf·anger, mit einer Arbeitswicklung (5), einem Schalttransistor (6), einer R·uckkopplungswicklung (7) und einer Regelschaltung (ii) auf der Prim·arseite sowie mit Gleichrichtern (15,16, 20) zur Erzeugung von Betriebsspannungen (U11U2#U3) auf der Sekund·arseite eines Trenntransformators (1) gekenn zeichnet durch folgende Merkmale: a) An eine Wicklung (19) ist ein Thyristor (24) angeschlos sen, der f·ur die w·ahrend der siromf·uhrenden Phase der Schalttransistoren (6) an der Wicklung (19) auftreten de Spannung in Durchlassrichtung gepolt ist. b) An die Steuerelektrode des Thyristors (24) ist eine der Betriebsspannungen (U2) in solcher H·ohe angelegt, dass der Thyristor (24) im Normalbetrieb gesperrt bleibt und bei einem unzul·assigen Anstieg der Betriebs spannung (U3) z·undet.

2. Netzteil nach Anspruch 1, dadurch gekennzeichnet, dass die Betriebsspannung (U3) ·uber einen Spannungsteiler (25,26) an die Steuerelektrode des Thyristors (24) angelegt ist.

3. Netzteil nach Anspruch 1, dadurch gekennzeichnet, dass die Wicklung (19) eine Sekund·arwicklung des Trenntransforma tors (1) ist.

Description:

Schaltnetzteil, insbesondere f·ur einen Fernsehempf·anger
Bei Ger·aten der Nachrichtentechnik wie z.B. einem Fernsehempf·anger ist es bekannt, die f·ur die einzelnen Stufen notwendigen Betriebsspannungen mit einem Schaltnetzteil aus der Netzspannung zu erzeugen (Funkschau 1975, Heft 5, Seite 40-43). Ein Schaltnetzteil erm·oglicht die f·ur den Anschluss ·ausserer Ger·ate und f·ur die Massnahmen zur Schutzisolierung vorteilhafte galvanische Trennung der Empf·angerschaltung vom Netz. Da ein Schaltnetzteil mit einer gegen·uber der Netzfrequenz hohen Frequenz von ca. 30 kHz arbeitet, kann der zur galvanischen Trennung dienende Trenntransformator gegen·uber einem Netztrafo f·ur 50 Hz wesentlich kleiner und leichter ausgebildet sein. Durch mehrere Wicklungen oder Wicklungsabgriffe und angeschlossene Gleichrichter k·onnen auf der Sekund·arseite des Trenntransformators Betriebs~ spannungen unterschiedlicher Gr·osse und Polarit·at erzeugt werden.
Ein solches Schaltnetzteil enth·alt eine Regelschaltung zur Stabilisierung der Amplitude der auf der Sekund·arseite erzeugten Betriebsspannungen. In dieser Regelschaltung wird eine durch Gleichrichtung der Impulsspannung am Trafo gewonnene Stellgr·osse erzeugt und mit einer Bezugsspannung verglichen. In Abh·angigkeit von der Abweichung wird der Schaltzeitpunkt des auf der Prim·arseite vorgesehenen elektronischen Schalters so gesteuert, dass die Amplitude der erzeugten Betriebsspannungen konstant bleibt.
Bei einem solchen Schaltnetzteil kann die genannte Regelschaltung z.B. durch ein fehlerhaftes Bauteil ausfallen. Die Regelung der Amplitude der erzeugten Betriebsspannungen ist dann unkontrolliert. Die Betriebsspannungen k·onnen dann auf den doppelten oder dreifachen Wert ansteigen. Dadurch besteht die Gefahr, dass das Schaltnetzteil oder die an die Betriebsspannungen angeschlossenen Verbraucher wie z.B. der Heizfaden der Bildr·ohre oder der Zeilenendstufentransistor zerst·ort werden. Der Anstieg der Betriebsspannungen kann dar·uberhinaus einen Anstieg der im Fernsehempf·anger erzeugten Hochspannung und dadurch eine R·ontgenstrahlung ausl·osen.
Es ist auch ein Schaltnetzteil bekannt (DE-OS 27 27 332), bei dem zum Schutz gegen einen zu starken Anstieg der erzeugten Betriebsspannungen aus der Impulsspannung an der Prim·arseite des Trafos eine Stellgr·osse gewonnen wird, die beim ·Uberschreiten eines Schwellwertes den R·uckkopplungsweg unwirksam steuert. Durch die Unterbrechung des R·uckkopplungsweges kann das Schaltnetzteil nicht mehr schwingen, so dass in erw·unschter Weise auch keine Betriebsspannungen mehr erzeugt werden. Diese Schaltung erfordert jedoch eine Vielzahl von Bauteilen und ist daher relativ teuer.
Der Erfindung liegt die Aufgabe zugrunde, eine sicher wirkende Schutzschaltung mit verringertem Schaltungsaufwand gegen die oben beschriebenen Gefahren zu schaffen.
Diese Aufgabe wird durch die im Anspruch 1 beschriebene Erfindung gel·ost. Vorteilhafte Weiterbildungen der Erfindung sind in den Unteranspr·uchen beschrieben.
Die Erfindung beruht auf folgender ·Uberlegung: Der Schalttransistor auf der Prim·arseite wird von der prim·arseitigen R·uckkopplungswicklung w·ahrend seiner stromleitenden Phase mit einem Basisstrom angesteuert. Wenn jetzt eine Sekund·arwicklung w·ahrend dieser stromleitenden Phase stark belastet, z.B. ·uber den Thyristor kurzgeschlossen wird, bricht auch die Spannung an der prim·arseitigen R·uckkopplungswicklung zusammen. Diese Wicklung kann dann f·ur den Schalttransistor nicht mehr einen f·ur den leitenden Betrieb ausreichenden Basis strom liefern. Das Schaltnetzteil schwingt dann nicht mehr, so dass die sekund·arseitigen Betriebsspannungen in erw·unschter Weise zusammenbrechen. Der schaltungstechni- sche Aufwand ist gering. Er besteht vorzugsweise aus einem Thyristor und zwei Widerst·anden.
Ein Ausf·uhrungsbeispiel der Erfindung wird anhand der Zeichnung erl·autert. Darin zeigen Figur 1 ein erfindungsgem·ass ausgebildetes Schaltnetzteil und Figur 2 Kurven zur Erl·auterung der Wirkungsweise. Dabei zeigen die kleinen Buchstaben, an welchen Punkten in Figur 1 die Spannungen gem·ass Figur 2 stehen.
Das Schaltnetzteil gem·ass Figur 1 enth·alt auf der Prim·arseite des Trenntransformators 1 den Netzgleichrichter 2, den Ladekondensator 3, den Strom-Messwiderstand 4, die Prim·arwicklung 5 den Schalttransistor 6, die zur Schwingungserzeugung dienende R·uckkopplungswicklung 7, den zur Steuerung des Schalttransistors 6 dienenden Thyristor 8, die Regelwicklung 9, den zur Erzeugung der Regelspannung dienenden Gleichrichter 10 sowie die zur Stabilisierung der Betriebsspannungen dienende Regelschaltung 11 mit dem Transistor 12 und der eine Referenzspannung lieferndenZenerdiode 13. Die Sekund·arwicklung 14 liefert ·uber den Gleichrichter 15 eine erste Betriebsspannung U1 von 150 V. Ein Abgriff der Wicklung 14 liefert ·uber den Gleichrichter 16 eine zweite Betriebsspannung U2 von 12 V f·ur einen Fernbedienungsempf·anger.
Eine weitere Sekund·arwicklung 19 liefert ·uber den Gleichrichter 20 eine dritte Betriebsspannung U3 von 12 V. Die Polung der Wicklungen 14,19 und der Gleichrichter 15,16,20 ist derart, dass die Gleichrichter 15,16,20 w·ahrend der Sperrphase des Schalttransistors 6 durch die sekund·arseitig auftretenden Impulsspannungen leitend gesteuert sind und die angeschlossenen Ladekondensatoren aufladen.
An das untere Ende der Wicklung 19 ist zus·atzlich der Thyristor 24 angeschlossen. An die Steuerelektrode b des Thyristors 24 ist die Betriebs spannung U2 ·uber den Spannungsteiler 25,26 angelegt.
Die Wirkungsweise der Schaltung wird anhand der Figur 2 erl·autert. Es sei angenommen, dass das Schaltnetzteil im Zeitpunkt tl in Betrieb genommen wird. Mit der Diode 21 wird aus der Netzspannung am Punkt d ein positiver Impuls erzeugt. Dieser gelangt ·uber den Kondensator 23 auf die Basis des Schalttransistors 6 und steuert diesen leitend. Dadurch beginnt das Schaltnetzteil zu schwingen, wobei die Schwingung durch die R·uckkopplungswicklung 7 aufrechterhalten wird. Am Punkt a entsteht dann eine m·aanderf·ormige Wechselspannung mit einer Frequenz von etwa 25-30 kHz.
Die daraufhin in den Sekund·arwicklungen 14,19 erzeugten Impulse erzeugen in der beschriebenen Weise die Betriebsspannungen U1,U2,U3. Der Spannungsteiler 25,26 ist so bemessen, dass der Thyristor 24 gesperrt bleibt, d.h. die Spannung am Punkt 6 jst kleiner als 0,7 V. Der Thyristor 24 hat dann keine Wirkung. Dir Amplitude der Spannungen Ui,U2,U3 wird ·uber die Regelschaltung 11 stabilisiert.
Es sei jetzt angenommen, dass durch einen Fehler in der Regelschaltung 11, z.B. durch Ausfall eines Bauteiles, die Regelung zur Stabilisierung der Betriebsspannungen U1,U2,U3 nicht mehr wirkt und diese Betriebsspannungen stark ansteigen. Dadurch steigt auch die Spannung am Punkt b an.
Im Zeitpunkt t2 erreicht diese Spannung den Wert von 0,7 V, so dass der Thyristor 24 z·undet. Der untere Teil der Wicklung 19 ist jetzt praktisch kurzgeschlossen. Das Netzteil ist dadurch sekund·arseitig so stark belastet, dass die R·uck kopplungswicklung 7 keinen ausreichenden Basisstrom zur Steuerung des Schalttransistors 6 in seine stromleitende Phase mehr liefert. Im Zeitpunkt t2 bricht die Schwingung des Schaltnetzteiles ab, so dass auch die Wechselspannung am Punkt a auf null abf·allt. Den Ladekondensatoren der Gleichrichter 15,16,20 wird kein Strom mehr zugef·uhrt, so dass die Betriebspannungen U1,U2,U3 nicht weiter ansteigen k·onnen, sondern entsprechend den wirksamen Entladezeitkonstanten abfallen. Das Schaltnetzteil w·urde auf diese Weise an sich beliebig lange ausgeschaltet bleiben.
Im Zeitpunkt t3 erscheint am Punkt b der n·achste aus der Netzspannung gewonnene Startimpuls, der den Schalttransistor 6 wieder leitend steuert, so dass die Wechselspannung am Punkt a wieder auftritt. Das Schaltnetzteil geht also in einen getakteten Betrieb ·uber, bei dem die ·ubertragene Leistung entsprechend dem Zeitverh·altnis zwischen Einschaltphase und Ausschaltphase der Spannung am Punkt a betr·achtlich verringert ist. Die Betriebsspannungen U11U2,U3 k·onnen nicht mehr unzul·assig hohe Werte annehmen.

 EUROPHON CTV 16000 TLC  CHASSIS PSSD 978 Switching Power supply voltage stabilizer:

A power supply voltage stabilizer comprising a transformer, of which the primary winding is connected to a switching means for controlling power supply to the primary winding. An oscillator circuit is associated with the switching means in order to control on/off operation of the switching means. An abnormal overvoltage and/or overcurrent detection circuit is provided for terminating the oscillation operation of the oscillator circuit when impending overvoltage and/or overcurrent is detected.

1. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said oscillator circuit including an astable multivibrator, and variable impedance means for varying an oscillation frequency of said astable multivibrator.

2. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said transformer further including an auxiliary winding for developing a voltage proportional to that developed through said secondary winding, said voltage developed through said auxiliary winding being applied to said oscillator circuit for driving said oscillator circuit;
said abnormal condition detection means including an overvoltage detection circuit connected to said auxiliary winding for developing said control signal when an overvoltage is developed through said auxilliary winding;
said oscillator circuit comprising an astable multivibrator, and variable impedance means for varying an oscillation frequency of said astable multivibrator.
3. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said transformer further including an auxiliary winding for developing a voltage proportional to that developed through said secondary winding, said voltage developed through said auxiliary winding being applied to said oscillator circuit for driving said oscillator circuit;
said abnormal condition detection means including an overvoltage detection circuit connected to said auxiliary winding for developing said control signal when an overvoltage is developed through said auxiliary winding;

said overvoltage detection circuit including a latching means for continuously developing said control signal.
4. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means;
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said transformer further including an auxiliary winding for developing a voltage proportional to that developed through said secondary winding, said voltage developed through said auxiliary winding being applied to said oscillator circuit for driving said oscillator circuit;
said abnormal condition detection means including an overvoltage detection circuit connected to said auxiliary winding for developing said control signal when an overvoltage is developed through said auxiliary winding;
said overvoltage detection circuit further includes,
a reference voltage generation means for developing a reference voltage proportional to a voltage applied from said power source; and
comparing means for comparing said voltage developed through said auxiliary winding with said reference voltage in order to develop said control signal when said voltage developed through said auxiliary winding exceeds said reference voltage.
5. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said abnormal condition detection means including an overcurrent detection circuit connected to said primary winding for developing said control signal when an overcurrent flows through said primary winding;
wherein said oscillator circuit includes an astable multivibrator, and variable impedance means for varying an oscillation frequency of said astable multivibrator.
6. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said abnormal condition detection means including an overcurrent detection circuit connected to said primary winding for developing said control signal when an overcurrent flows through said primary winding;
said overcurrent detection circuit including a latching means for continuously developing said control signal;
said oscillator circuit including an astable multivibrator, and variable impedance means for varying an oscillation frequency of said astable multivibrator.

7. The power supply voltage stabilizer of claim 1, 2, 5, or 6, wherein said variable impedance means comprise a photo transistor, and wherein a light emitting diode is connected to said secondary winding for emitting a light of which amount is proportional to a voltage developed through said secondary winding, said light emitted from said light emitting diode being applied to said photo transistor. 8. The power supply voltage stabilizer of claim 7, wherein said light emitting diode and said photo transistor are incorporated in a single photo coupler. 9. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means; and
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said transformer further including an auxiliary winding for developing a voltage proportional to that developed through said secondary winding, said voltage developed through said auxiliary winding being applied to said oscillator circuit for driving said oscillator circuit;
said abnormal condition detection means including an overvoltage detection circuit connected to said auxiliary winding for developing said control signal when an overvoltage is developed through said auxilliary winding;
said overvoltage detection circuit including a latching means for continuously developing said control signal;
said oscillator circuit including an astable multivibrator, and variable impedance means for varying an oscillation frequency of said astable multivibrator.
10. A power supply voltage stabilizer comprising:
a transformer including a primary winding connected to a power source and a secondary winding for output purposes;
switching means connected to said primary winding for controlling power supply to said primary winding;
an oscillator circuit for controlling on/off operation of said switching means;
abnormal condition detection means for developing a control signal for terminating oscillation operation of said oscillator circuit when an abnormal condition is detected;
said transformer further including an auxiliary winding for developing a voltage proportional to that developed through said secondary winding, said voltage developed through said auxiliary winding being applied to said oscillator circuit for driving said oscillator circuit;
said abnormal condition detection means including an overvoltage detection circuit connected to said auxiliary winding for developing said control signal when an overvoltage is developed through said auxiliary winding;
said overvoltage detection circuit including,
a reference voltage generation means for developing a reference voltage proportional to a voltage applied from said power source; and
comparing means for comparing said voltage developed through said auxiliary winding with said reference voltage in order to develop said control signal when said voltage developed through said auxiliary winding exceeds said reference voltage;
said oscillator circuit including an astable multivibrator, and a variable impedance means for varying an oscillation frequency of said astable multivibrator.
11. A power supply voltage stabilizer comprising:
transformer means including a primary winding connected to a power source, a secondary winding for producing an output voltage, and an auxiliary winding for developing a voltage proportional to said output voltage produced by said secondary winding;
switching means connected to said primary winding for controlling the power supply from said power source to said primary winding;
oscillator circuit means for controlling the on/off operation of said switching means;
overvoltage detection circuit means connected to said auxiliary winding for developing a control signal to terminate the oscillation operation of said oscillator circuit means when an overvoltage condition is detected, said overvoltage detection circuit means including,
means for developing a reference potential, and
comparing means responsive to said voltage developed at said auxiliary winding and to said reference potential for comparing said reference potential with said voltage developed at said auxiliary winding and for generating said control signal to terminate the oscillation operation of said oscillator circuit means when said voltage developed at said auxiliary winding exceeds said reference potential.
12. A power supply voltage stabilizer comprising:
transformer means including a primary winding connected to a power source and having a voltage supplied thereto, a secondary winding for producing an output voltage, and an auxiliary winding for developing a voltage proportional to said output voltage produced by said secondary winding;
switching means connected to said primary winding for controlling the power supply from said power source to said primary winding;
oscillator circuit means for controlling the on/off operation of said switching means;
overcurrent detection circuit means connected to said primary winding for developing a control signal to terminate the oscillation operation of said oscillator circuit means when an overcurrent condition is detected, said overcurrent detection circuit means including,
means for monitoring said voltage supplied to said primary winding of said transformer means,
means for measuring the amount of current passing through said primary winding of said transformer means by translating said amount of current into a corresponding amount of voltage potential,
switching means responsive to said corresponding amount of voltage potential for switching to a first switched condition when the corresponding voltage potential exceeds a predetermined voltage potential and for switching to a second switched condition when said voltage potential does not exceed said predetermined voltage potential, and
comparing means responsive to said voltage supplied to said primary winding and connected to an output of said switching means for generating said control signal to terminate oscillation operation of said oscillator circuit means when said switching means switches to said first switched condition in response to the exceeding of said predetermined voltage potential by said corresponding voltage potential.
13. A power supply voltage stabilizer in accordance with claim 11 or 12 wherein said comparing means comprises a double base diode.

Description:

BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a power supply voltage stabilizer and, more particularly, to a power supply voltage stabilizer employing a switching system for controlling power supply to a transformer included in the power supply voltage stabilizer.
In the conventional power supply voltage stabilizer employing a switching system for controlling power supply to a transformer included in the power supply voltage stabilizer, there is a possibility that an abnormal overvoltage will be developed from an output terminal thereof and/or an abnormal overcurrent may flow through the primary winding of the transformer.
Accordingly, an object of the present invention is to provide a protection means for protecting the power supply voltage stabilizer from an abnormal overvoltage and/or overcurrent.
Another object of the present invention is to provide a detection means for detecting an impending overvoltage and/or overcurrent occurring within the power supply voltage stabilizer.
Other objects and further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
The

power supply voltage stabilizer of the present invention mainly comprises a transformer including a primary winding connected to a commercial power source through a rectifying circuit, a secondary winding for output purposes, and an auxiliary winding. A driver circuit including a switching means is connected to the primary winding for controlling the power supply to the primary winding. An oscillator circuit is associated with the switching means to control ON/OFF operation of the switching means, thereby controlling the power supply to the primary winding.
To achieve the above objects, pursuant to an embodiment of the present invention, an overvoltage detection circuit is connected to the auxiliary winding. The overvoltage detection circuit functions to compare a voltage created in the auxiliary winding with the rectified power supply voltage, and develop a control signal, when an impending overvoltage is detected, for terminating operation of the oscillator circuit, thereby precluding power supply to the primary winding.
In another embodiment of the present invention, an overcurrent detection circuit is provided for detecting an impending overcurrent flowing through the primary winding to develop a control signal for terminating operation of the oscillator circuit.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the present invention and wherein:
FIG. 1 is a circuit diagram of a basic construction of a power supply voltage stabilizer of the present invention;
FIG. 2 is a block diagram of an embodiment of a power supply voltage stabilizer of the present invention, which includes an oscillator circuit and an over voltage detection circuit;
FIG. 3 is a circuit diagram of an embodiment of the overvoltage detection circuit included in the power supply voltage stabilizer of FIG. 2;
FIG. 4 is a circuit diagram of an embodiment of the oscillator circuit included in the power supply voltage stabilizer of FIG. 2;
FIG. 5 is a waveform chart for explaining operation of the oscillator circuit of FIG. 4;
FIG. 6 is a block diagram of another embodiment of a power supply voltage stabilizer of the present invention, which includes an oscillator circuit and an overcurrent detection circuit; and
FIG. 7 is a circuit diagram of an embodiment of the overcurrent detection circuit included in the power supply voltage stabilizer of FIG. 6.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now in detail to the drawings, and to facilitate a more complete understanding of the present invention, a basic construction of a power supply voltage stabilizer of the present invention will be first described with reference to FIG. 1.
The power supply voltage stabillizer mainly comprises a transformer T including a primary winding N ₁ connected to a commercial power source V, a secondary winding N ₂ connected to an output terminal V ₀ , and an auxiliary winding N ₃ . An oscillator circuit OSC is associated with the primary winding N ₁ and the auxiliary winding N ₃ to control the power supply from the commercial power source V to the primary winding N ₁ .
A rectifying circuit E is connected to the commercial power source V for applying a rectified voltage to a capacitor C ₁ . A negative terminal of the capacitor C ₁ is grounded, and a positive terminal of the capacitor C ₁ is connected to the collector electrode of a switching transistor Q ₅ through the primary winding N ₁ of the transformer T. The oscillator circuit OSC performs the oscillating operation when receiving a predetermined voltage, and develops a control signal toward the base electrode of the switching transistor Q ₅ to control the switching operation of the switching transistor Q ₅ . The switching transistor Q ₅ functions to control the power supply to the primary winding N ₁ , thereby controlling the power transfer to the secondary winding N ₂ and the auxiliary winding N ₃ .
The auxiliary winding N ₃ is connected to a capacitor C ₃ in a parallel fashion via a diode D ₁ . A positive terminal of the capacitor C ₃ is connected to the oscillator circuit OSC to supply a drive voltage Vc ₃ . A negative terminal of the capacitor C ₃ is connected to the emitter electrode of the switching transistor Q ₅ and grounded. The positive terminal of the capacitor C ₃ is connected to the primary winding N ₁ via a diode D ₂ and a capacitor C ₂ in order to stabilize the initial condition of the oscillator circuit OSC.
The secondary winding N ₂ functions to develop a predetermined voltage through the output terminal V ₀ . A smoothing capacitor C ₀ is connected to the secondary winding N ₂ via a diode D ₀ , and a series circuit of a resistor R ₀ and a light emitting diode D _i is connected to the smoothing capacitor C ₀ in a parallel fashion. The light emitted from the light emitting diode D _i is applied to a photo transistor Q ₈ employed in the oscillator circuit OSC. The light emitting diode D _i and the photo transistor Q ₈ are preferably incorporated in a single package as a photo coupler.
The light amount emitted from the light emitting diode D _i is proportional to the output voltage developed from the output terminal V ₀ . The photo transistor Q ₈ exhibits the impedance corresponding to the applied light amount. The oscillator circuit OSC is so constructed that the oscillation frequency is varied in response to variation of the impedance of the photo transistor Q ₈ . Accordingly, the ON/OFF operation of the switching transistor Q ₅ is controlled in response to the output voltage level, thereby stabilizing the output voltage level.
In the above constructed power supply voltage stabilizer, there is a possibility that an abnormal overvoltage is developed through the secondary winding N ₂ and the auxiliary winding N ₃ when the oscillator circuit OSC or the light emitting diode D _i is placed in the fault condition.
FIG. 2 shows an embodiment of the power supply voltage stabilizer of the present invention, which includes means for precluding occurrence of the above-mentioned overvoltage. Like elements corresponding to those of FIG. 1 are indicated by like numerals.
The power supply voltage stabilizer of FIG. 2 mainly comprises the transformer T, the oscillator circuit OSC, a driver circuit 1 including the switching transistor Q ₅ , and an overvoltage detection circuit 3.
The positive terminal of the capacitor C ₃ is connected to the driver circuit 1 and the oscillator circuit OSC to apply the driving voltage thereto. The positive terminal of the capacitor C ₃ is also connected to the primary winding N ₁ through the diode D ₂ and a parallel circuit of the capacitor C ₂ and a resistor R ₂ in order to stabilize the initial start operation of the oscillator circuit OSC. The secondary winding N ₂ is connected to an output level detector 2, which comprises the light emitting diode D _i as shown in FIG. 1. The ON/OFF control of the switching transistor Q ₅ is similar to that is achieved in the power supply voltage stabilizer of FIG. 1.
The secondary winding N ₂ and the auxiliary winding N ₃ are wound in the same polarity fashion and, therefore, the voltage generated through the auxiliary winding N ₃ is proportional to that voltage generated through the secondary winding N ₂ . The overvoltage detection circuit 3 is connected to receive the voltage at a point a as a power source voltage, and the voltage at a point b which is connected to the positive terminal of the capacitor C ₃ . When the voltage level at the point b exceeds a reference level, the overvoltage detection circuit 3 develops a control signal for terminating the operation of the oscillator circuit OSC.
FIG. 3 shows a typical construction of the overvoltage detection circuit 3.
The voltage at the point a is applied to a series circuit of resistors R ₃ and R ₄ , and grounded. The voltage at the point b is applied to the connection point of the resistors R ₃ and R ₄ via a diode D ₃ . The connection point of the resistors R ₃ and R ₄ is grounded through resistors R ₅ and R ₆ and a Zener diode Z ₁ . A double-base diode (Trade Name Programmable Unijunction Transistor) P ₁ is provided for developing the control signal to be applied to the oscillator circuit OSC. The anode electrode of the programmable unijunction transistor P ₁ is connected to the connection point of the resistors R ₃ and R ₄ , the gate electrode of the programmable unijunction transistor P ₁ is connected to the connection point of the resistors R ₅ and R ₆ , and the cathode electrode is connected to the oscillator circuit OSC.
When the voltage level of the point b exceeds a reference level VZ ₁ , the programmable unijunction transistor P ₁ is turned on to develop the control signal for terminating the oscillation operation of the oscillator OSC. In this way, the impending abnormal overvoltage is detected to protect the circuit elements. The ON condition of the programmable unijunction transistor P ₁ is maintained as long as the main power switch is closed, because the overvoltage detection circuit 3 is connected to receive the voltage from the point a.
The voltage detection circuit 3 does not necessarily employ the programmable unijunction transistor. Another element showing the latching characteristics such as a negative resistance element can be employed instead of the programmable unijunction transistor.
FIG. 4 shows a typical construction of the oscillator circuit OSC.
The oscillation circuit OSC mainly comprises an astable multivibrator including transistors Q ₁ , Q ₂ and Q ₃ , and an output stage including a transistor Q ₄ . The astable multivibrator is connected to receive the voltage appearing across the capacitor C ₃ , and develops an output signal of which frequency is determined by the circuit condition as long as the multivibrator receives a voltage greater than a predetermined level.
The output signal of the output stage is applied to the base electrode of the switching transistor Q ₅ included in the driver circuit 1 in order to switch the switching transistor Q ₅ with a predetermined frequency. A transistor Q ₉ is interposed between the base electrode of the transistor Q ₃ and the grounded terminal. The transistor Q ₉ is controlled by the control signal derived from the overvoltage detection circuit 3. Accordingly, the transistor Q ₃ is turned off to terminate the oscillation operation when the abnormal overvoltage is detected by the overvoltage detection circuit 3.
Now assume that a voltage Vc ₃ is developed across the capacitor C ₃ . When main power supply switch is closed, the voltage Vc ₃ varies in a manner shown by a curve X in FIG. 5. When the voltage Vc ₃ reaches a predetermined level, the astable multivibrator begins the oscillation operation. More specifically, the transistor Q ₁ is first turned on because the base electrode of the transistor Q ₁ is connected to a capacitor C ₄ of which the capacitance value is relatively small. At this moment, the transistor Q ₂ is held off.
Because of turning on of the transistor Q ₁ , the capacitor C ₄ is gradually charged through a resistor R ₄ and the transistor Q ₁ . Accordingly, the base electrode voltage of the transistor Q ₁ is gradually increased and, hence, the emitter electrode voltage of the transistor Q ₁ is also increased to turn on the transistor Q ₂ . When the transistor Q ₂ is turned on, the transistor Q ₃ is also turned on. The base electrode voltage of the transistor Q ₂ which is bypassed by a resistor R ₁ is reduced and, therefore, the transistor Q ₂ is stably on. At this moment, the transistor Q ₁ is turned off.
When the transistor Q ₃ is turned on, the transistor Q ₄ is turned on to develop a signal to turn on the switching transistor Q ₅ . Upon turning on of the transistor Q ₃ , the charge stored in the capacitor C ₄ is gradually discharged through paths shown by arrows in FIG. 4. Therefore, the base electrode voltage of the transistor Q ₁ is gradually reduced. When the base electrode voltage of the transistor Q ₁ becomes less than a predetermined level, the transistor Q ₁ is turned on, and the transistor Q ₂ , Q ₃ and Q ₄ are turned off. Accordingly, the transistor Q ₅ is turned off. After passing the initial start condition, the driving voltage Vc ₃ is held at a predetermined level as shown by a curve Y in FIG. 5 to maintain the above-mentioned oscillation operation.
The photo transistor Q ₈ is disposed in the discharge path of the capacitor C ₄ in order to control the discharge period in response to the impedance of the photo transistor Q ₈ . That is, the oscillation frequency is controlled in response to the light amount emitted from the light emitting diode included in the output level detector 2.
FIG. 6 shows another embodiment of the power supply voltage stabilizer of the present invention, which includes means for precluding occurrence of an abnormal overcurrent. Like elements corresponding to those of FIG. 2 are indicated by like numerals.
In the power supply voltage stabilizer of FIG. 1, there is a possibility that an abnormally large current flows through the primary winding N ₁ when the magnetic flux is saturated due to requirement of large current at the secondary winding side. The power supply voltage stabilizer of FIG. 6 includes an overcurrent detection circuit 4 for detecting an impending abnormally large current.
A resistor R ₉ is interposed between the emitter electrode of the switching transistor Q ₅ included in the driver circuit 1 and the grounded terminal. The overcurrent detection circuit 4 is connected to receive a signal from the connection point of the resistor R ₉ and the emitter electrode of the switching transistor Q ₅ , thereby developing a control signal for terminating the oscillation operation of the oscillation circuit OSC.
FIG. 7 shows a typical construction of the overcurrent detection circuit 4.
The voltage at the point a is applied to a series circuit of resistors R ₁₀ and R ₁₁ , and grounded. The collector electrode of a transistor Q ₁₀ is connected to the connection point of the resistors R ₁₀ and R ₁₁ through resistors R ₁₂ and R ₁₃ . The emitter electrode of the transistor Q ₁₀ is grounded. The base electrode of the transistor Q ₁₀ is connected to the connection point of the resistor R ₉ and the emitter electrode of the switching transistor Q ₅ via a resistor R ₁₄ .
When the switching transistor Q ₅ is turned on, a current flows through the resistor R ₉ . When the voltage drop across the resistor R ₉ exceeds a predetermined value due to a large current, the transistor Q ₁₀ is turned on to turn on the programmable unijunction transistor P ₁ . That is, when a large current flows through the primary winding N ₁ , the programmable unijunction transistor P ₁ develops the control signal to terminate the oscillation operation of the oscillator circuit OSC.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications are intended to be included within the scope of the following claims.




TDA1170 vertical deflection FRAME DEFLECTION INTEGRATED CIRCUITGENERAL DESCRIPTION f The TDA1170 and TDA1270 are monolithic integrated
circuits designed for use in TV vertical deflection systems. They are manufactured using
the Fairchild Planar* process.
Both devices are supplied in the 12-pin plastic power package with the heat sink fins bent
for insertion into the printed circuit board.
The TDA1170 is designed primarily for large and small screen black and white TV
receivers and industrial TV monitors. The TDA1270 is designed primarily for driving
complementary vertical deflection output stages in color TV receivers and industrial
monitors.
APPLICATION INFORMATION (TDA1170)
The vertical oscillator is directly synchronized by the sync pulses (positive or negative); therefore its free
running frequency must be lower than the sync frequency. The use of current feedback causes the yoke
current to be independent of yoke resistance variations due to thermal effects, Therefore no thermistor is
required in series with the yoke. The flyback generator applies a voltage, about twice the supply voltage, to
the yoke. This produces a short flyback time together with a high useful power to dissipated power
ratio.




TDA1190 ; TDA1190Z:
ONE CHIP tv SOUND SYSTEM
FAIRCHILD LINEAR INTEGRATED CIRCUITS
GENERAL DESCRIPTION - The TDA1190 and TDA1190Z are silicon monolithic
integrated circuits in 12-pin plastic power packages.
They perform all the functions needed for TV sound systems, including IF limiter-amplifier, FM detector, AF preamplifier and power output stage.

The TDA1190 is specified for 5.5 MHz (PAL) sound systems and the TDA1190Z is specified for 4.5 MHZ (NTSC) sound systems. They are constructed using the Fairchild Planar‘ epitaxial process.
They provide an output power of 4.2 W into a 16 S2 load at V+ = 24 V, or 1.5 W into an
8.0 Q load at V+ = I2 V. This performance, together with the FM-IF section characteristics of high sensitivity, high AM rejection and low distortion, enables them to be used in almost every type of television receiver. No external shielding is needed.

The basic differences between the TDA1190 and TDA1190Z are:

The TDA1190Z is designed for a larger volume control potentiometer
The TDA1190 includes one of the gain adjust resistors on the chip, while in the TDA119OZ
both are required in the external circuitry.

IF VIDEO WITH TBA1440 (SIEMENS)



TDA2530 RGB MATRIX PREAMPLIFIER
The TDA2530 is an integrated RGB -matrix preamplifier for colour television receivers,
incorporating a matrix preamplifier for RGB cathode drive of the picture tube with
clamping circuits. The three channels have the same layout to ensure identical frequency
behaviour.
This integrated circuit has been designed to be driven from the TDA2522 Synchronous
demodulator and oscillator IC.
















TDA2522 PAL TV CHROMA DEMODULATOR COMBINATION
FAIRCHILD LINEAR INTEGRATED CIRCUIT
GENERAL DESCRIPTION- The TDA2522 is a monolithic integrated circuit designed as
a synchronous demodulator for PAL color television receivers. It includes an 8,8 MHz
oscillator and divider to generate two 4.4 MHz reference signals and provides color difference outputs.
PACKAGE OUTLINE 9B

The TDA2522 is Intended to Interface directly with the TDA2560 with a minimum oF external components. The TDA2530 may be added if RGB drive is required. The TDA2522
is constructed using the Fairchild Planar* process.







TDA2560 LUMINANCE AND CHROMINANCE CONTROL COMBINATION
The TDA2560 is a monolithic integrated circuit for use in decoding systems of COLOR
television receivers. The circuit consists of a luminance and chrominance amplifier.
The luminance amplifier has a low input impedance so that matching of the luminance
delay line is very easy.
It also incorporates the following functions:
- d.c. contrast control;
- d.c. brightness control;
- black level clamp;
- blanking;
- additional video output with positive-going sync.
The chrominance amplifier comprises:
- gain controlled amplifier;
- chrominance gain control tracked with contrast control;
- separate d.c. saturation control:
- combined chroma and burst output, burst signal amplitude not affected by contrast and
saturation control;
- the delay line can be driven directly ‘by the IC.

APPLICATION INFORMATION (continued)
The function is quoted against the corresponding pin number
Balanced chrominance input signal (in conjunction with pin 2)
This is derived from the chrominance signal bandpass filter, designed to provide a
push-pull input. A signal amplitude of at least 4 mV peak-to-peak is required
between pins l and 2. The chrominance amplifier is stabilized by an external feedback
loop from the output (pin 6) to the input (pins I and 2). The required level at pins l
and 2 will be 3 V.
All figures for the chrominance signals are based on a colour bar signal with 75%
saturation: i.e. burst-to-chrominance ratio of input signal is 1 1 2.
Chrominance signal input (see pin 1)
A. C.C. input
A negative-going potential, starting at +l,2 V, gives a 40 dB range of a. c. c.
Maximum gain reduction is achieved at an input voltage of 500 mV.
Chrominance saturation control
A control range of +6 dB to >-14 dB is provided over a range of d. c. potential on
pin 4 from +2 to +4 V. The saturation control is a linear function of the control
voltage.
Negative supply (earth)
Chro minance signal output
For nominal settings of saturation and contrast controls (max. -6 dB for saturation,
and max. -3 dB for contrast) both the chroma' and burst are available at this pin, and
in the same ratio as at the input pins 1 and 2. The burst signal is not affected by the
saturation and contrast controls. The a.c. c. circuit of the TDA2522 will hold
constant the colour burst amplitude at the input of the TDA2522. As the PAL delay
line is situated here between the TDA256O and TDA2522 there may be some variation
of the nominal 1 V peak-to-peak burst output of the TDA2560, according to the
tolerances of the delay line. An external network is required from pin 6 of the
TDA256O to provide d. c. negative feedback in the chroma channel via pins I and 2.
Burst gating and clamping pulse input
A two-level pulse is required at this pin to be used for burst gate and black level
clamping. The black level clamp is activated when the pulse level is greater than
7 V. The timing of this interval should be such that no appreciable encroachment
occurs into the sync pulse on picture line periods during normal operation of the
receiver. The burst gate, which switches the gain of the chroma amplifier to
maximum, requires that the input pulse at pin 7 should be sufficiently wide, at least
8 ps, at the actuating level of 2,3 V.

+12 V power supply
Correct operation occurs within the range 10 to 14 V. All signal and control levels
have a linear dependency on supply voltage but, in any given receiver design, this
range may be restricted due to considerations of tracking between the power supply
variations and picture contrast and chroma levels.
Flyback blanking input waveform
This pin is used for blanking the luminance amplifier. When the input pulse exceeds
the +2, 5 Vlevel, the output signal is blanked to a level of about 0 V. When the input
exceeds a +6 V level, a fixed level of about 1, 5 V is inserted in the output. This
level can be used for clamping purposes.
Luminance sigal output
An emitter follower provides a low impedance output signal of 3 V black-to-white
amplitude at nominal contrast setting having a black level in the range 1 to 3 V. An
external emitter load resistor is not required.
The luminance amplitude available for nominal contrast may be modified according
to the resistor value from pin 13 to the +12 V supply. At an input bias current
114 of 0,25 mA during black level the amplifier is compensated so that no black
level shift more than 10 mV occurs at contrast control. When the input current
deviates from the quoted value the black level shift amounts to 100 mV/rnA.

Brightness control
The black level at the luminance output (pin 10) is identical to the control voltage
required at this pin, A range of black level from l to 3 V may be obtained.
Black level clamp capacitor
Luminance gain setting resistor
The gain of the luminance amplifier may be adjusted by selection of the resistor
value from pin 13 to +12 V. Nominal luminance output amplitude is then 3 V
black-to-white at pin 10 when this resistor is 2, 7 l



GENERAL BASIC TRANSISTOR LINE OUTPUT STAGE OPERATION:

The basic essentials of a transistor line output stage are shown in Fig. 1(a). They comprise: a line output transformer which provides the d.c. feed to the line output transistor and serves mainly to generate the high -voltage pulse from which the e.h.t. is derived, and also in practice other supplies for various sections of the receiver; the line output transistor and its parallel efficiency diode which form a bidirectional switch; a tuning capacitor which resonates with the line output transformer primary winding and the scan coils to determine the flyback time; and the scan coils, with a series capacitor which provides a d.c. block and also serves to provide slight integration of the deflection current to compensate for the scan distortion that would otherwise be present due to the use of flat screen, wide deflection angle c.r.t.s. This basic circuit is widely used in small -screen portable receivers with little elaboration - some use a pnp output transistor however, with its collector connected to chassis.

Circuit Variations:
Variations to the basic circuit commonly found include: transposition of the scan coils and the correction capacitor; connection of the line output transformer primary winding and its e.h.t. overwinding in series; connection of the deflection components to a tap on the transformer to obtain correct matching of the components and conditions in the stage; use of a boost diode which operates in identical manner to the arrangement used in valve line output stages, thereby increasing the effective supply to the stage; omission of the efficiency diode where the stage is operated from an h.t. line, the collector -base junction of the line output transistor then providing the efficiency diode action without, in doing so, producing scan distortion; addition of inductors to provide linearity and width adjustment; use of a pair of series -connected line output transistors in some large -screen colour chassis; and in colour sets the addition of line convergence circuitry which is normally connected in series between the line scan coils and chassis. These variations on the basic circuit do not alter the basic mode of operation however.

Resonance
The most important fact to appreciate about the circuit is that when the transistor and diode are cut off during the flyback period - when the beam is being rapidly returned from the right-hand side of the screen to the left-hand side the tuning capacitor together with the scan coils and the primary winding of the line output transformer form a parallel resonant circuit: the equivalent circuit is shown in Fig. 1(b). The line output transformer primary winding and the tuning capacitor as drawn in Fig. 1(a) may look like a series tuned circuit, but from the signal point of view the end of the transformer primary winding connected to the power supply is earthy, giving the equivalent arrangement shown in Fig. 1(b).

The Flyback Period:
Since the operation of the circuit depends mainly upon what happens during the line flyback period, the simplest point at which to break into the scanning cycle is at the end of the forward scan, i.e. with the beam deflected to the right-hand side of the screen, see Fig. 2. At this point the line output transistor is suddenly switched off by the squarewave drive applied to its base. Prior to this action a linearly increasing current has been flowing in the line output transformer primary winding and the scan coils, and as a result magnetic fields have been built up around these components. When the transistor is switched off these fields collapse, maintaining a flow of current which rapidly decays to zero and returns the beam to the centre of the screen. This flow of current charges the tuning capacitor, and the voltage at A rises to a high positive value - of the order of 1- 2k V in large -screen sets, 200V in the case of mains/battery portable sets. The energy in the circuit is now stored in the tuning capacitor which next discharges, reversing the flow of current in the circuit with the result that the beam is rapidly deflected to the left-hand side of the screen - see Fig. 3. When the tuning capacitor has discharged, the voltage at A has fallen to zero and the circuit energy is once more stored in the form of magnetic fields around the inductive components. One half -cycle of oscillation has occurred, and the flyback is complete.

Energy Recovery:
First Part of Forward Scan The circuit then tries to continue the cycle of oscillation, i.e. the magnetic fields again collapse, maintaining a current flow which this time would charge the tuning capacitor negatively (upper plate). When the voltage at A reaches about -0.6V however the efficiency diode becomes forward biased and switches on. This damps the circuit, preventing further oscillation, but the magnetic fields continue to collapse and in doing so produce a linearly decaying current flow which provides the first part of the forward scan, the beam returning towards the centre of the screen - see Fig. 4. The diode shorts out the tuning capacitor but the scan correction capacitor charges during this period, its right-hand plate becoming positive with respect to its left-hand plate, i.e. point A. Completion of Forward Scan When the current falls to zero, the diode will switch off. Shortly before this state of affairs is reached however the transistor is switched on. In practice this is usually about a third of the way through the scan. The squarewave applied to its base drives it rapidly to saturation, clamping the voltage at point A at a small positive value - the collector emitter saturation voltage of the transistor. Current now flows via the transistor and the primary winding of the line output transformer, the scan correction capacitor discharges, and the resultant flow of current in the line scan coils drives the beam to the right-hand side of the screen see Fig. 5.

Efficiency:
The transistor is then cut off again, to give the flyback, and the cycle of events recurs. The efficiency of the circuit is high since there is negligible resistance present. Energy is fed into the circuit in the form of the magnetic fields that build up when the output transistor is switched on. This action connects the line output transformer primary winding across the supply, and as a result a linearly increasing current flows through it. Since the width is
dependent on the supply voltage, this must be stabilised.

Harmonic Tuning:
There is another oscillatory action in the circuit during the flyback period. The considerable leakage inductance between the primary and the e.h.t. windings of the line output transformer, and the appreciable self -capacitance present, form a tuned circuit which is shocked into oscillation by the flyback pulse. Unless this oscillation is controlled, it will continue into and modulate the scan. The technique used to overcome this effect is to tune the leakage inductance and the associated capacitance to an odd harmonic of the line flyback oscillation frequency. By doing this the oscillatory actions present at the beginning of the scan cancel. Either third or fifth harmonic tuning is used. Third harmonic tuning also has the effect of increasing the amplitude of the e.h.t. pulse, and is generally used where a half -wave e.h.t. rectifier is employed. Fifth harmonic tuning results in a flat-topped e.h.t. pulse, giving improved e.h.t. regulation, and is generally used where an e.h.t. tripler is employed to produce the e.h.t. The tuning is mainly built into the line output transformer, though an external variable inductance is commonly found in colour chassis so that the tuning can be adjusted. With a following post I will go into the subject of modern TV line timebases in greater detail with other models and technology shown here at  Obsolete Technology Tellye !