Richtige Fernseher haben Röhren!

Richtige Fernseher haben Röhren!

In Brief: On this site you will find pictures and information about some of the electronic, electrical and electrotechnical technology relics that the Frank Sharp Private museum has accumulated over the years .

Premise: There are lots of vintage electrical and electronic items that have not survived well or even completely disappeared and forgotten.

Or are not being collected nowadays in proportion to their significance or prevalence in their heyday, this is bad and the main part of the death land. The heavy, ugly sarcophagus; models with few endearing qualities, devices that have some over-riding disadvantage to ownership such as heavy weight,toxicity or inflated value when dismantled, tend to be under-represented by all but the most comprehensive collections and museums. They get relegated to the bottom of the wants list, derided as 'more trouble than they are worth', or just forgotten entirely. As a result, I started to notice gaps in the current representation of the history of electronic and electrical technology to the interested member of the public.


Following this idea around a bit, convinced me that a collection of the peculiar alone could not hope to survive on its own merits, but a museum that gave equal display space to the popular and the unpopular, would bring things to the attention of the average person that he has previously passed by or been shielded from. It's a matter of culture. From this, the Obsolete Technology Tellye Web Museum concept developed and all my other things too. It's an open platform for all electrical Electronic TV technology to have its few, but NOT last, moments of fame in a working, hand-on environment. We'll never own Colossus or Faraday's first transformer, but I can show things that you can't see at the Science Museum, and let you play with things that the Smithsonian can't allow people to touch, because my remit is different.

There was a society once that was the polar opposite of our disposable, junk society. A whole nation was built on the idea of placing quality before quantity in all things. The goal was not “more and newer,” but “better and higher" .This attitude was reflected not only in the manufacturing of material goods, but also in the realms of art and architecture, as well as in the social fabric of everyday life. The goal was for each new cohort of children to stand on a higher level than the preceding cohort: they were to be healthier, stronger, more intelligent, and more vibrant in every way.

The society that prioritized human, social and material quality is a Winner. Truly, it is the high point of all Western civilization. Consequently, its defeat meant the defeat of civilization itself.

Today, the West is headed for the abyss. For the ultimate fate of our disposable society is for that society itself to be disposed of. And this will happen sooner, rather than later.

OLD, but ORIGINAL, Well made, Funny, Not remotely controlled............. and not Made in CHINA.

How to use the site:

- If you landed here via any Search Engine, you will get what you searched for and you can search more using the search this blog feature provided by Google. You can visit more posts scrolling the left blog archive of all posts of the month/year,
or you can click on the main photo-page to start from the main page. Doing so it starts from the most recent post to the older post simple clicking on the Older Post button on the bottom of each page after reading , post after post.

You can even visit all posts, time to time, when reaching the bottom end of each page and click on the Older Post button.

- If you arrived here at the main page via bookmark you can visit all the site scrolling the left blog archive of all posts of the month/year pointing were you want , or more simple You can even visit all blog posts, from newer to older, clicking at the end of each bottom page on the Older Post button.
So you can see all the blog/site content surfing all pages in it.

- The search this blog feature provided by Google is a real search engine. If you're pointing particular things it will search IT for you; or you can place a brand name in the search query at your choice and visit all results page by page. It's useful since the content of the site is very large.

Note that if you don't find what you searched for, try it after a period of time; the site is a never ending job !

Every CRT Television saved let revive knowledge, thoughts, moments of the past life which will never return again.........

Many contemporary "televisions" (more correctly named as displays) would not have this level of staying power, many would ware out or require major services within just five years or less and of course, there is that perennial bug bear of planned obsolescence where components are deliberately designed to fail and, or manufactured with limited edition specificities..... and without considering........picture......sound........quality........

..............The bitterness of poor quality is remembered long after the sweetness of todays funny gadgets low price has faded from memory........ . . . . . .....
Don't forget the past, the end of the world is upon us! Pretty soon it will all turn to dust!

Have big FUN ! !
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©2010, 2011, 2012, 2013, 2014 Frank Sharp - You do not have permission to copy photos and words from this blog, and any content may be never used it for auctions or commercial purposes, however feel free to post anything you see here with a courtesy link back, btw a link to the original post here , is mandatory.
All sets and apparates appearing here are property of
Engineer Frank Sharp. NOTHING HERE IS FOR SALE !

Thursday, March 15, 2012

IRRADIO MOD. 2022/A CORALL 22" CHASSIS NORDING S4 PAL INTERNAL VIEW.






















The CHASSIS is a modular type and was the first IRRADIO /NORDING with a PLL Frequency synthesizer driven with a Ucontroller SIEMENS SDA series based.

TBA120S

TDA2611A 5 W audio power amplifier

The TDA2611A is a monolithic integrated circuit in a 9-lead single in-line (SIL) plastic package with a high supply voltage
audio amplifier. Special features are:
· possibility for increasing the input impedance
· single in-line (SIL) construction for easy mounting
· very suitable for application in mains-fed apparatus
· extremely low number of external components
· thermal protection
· well defined open loop gain circuitry with simple quiescent current setting and fixed integrated closed loop gain.

RATINGS
Limiting values in accordance with the Absolute Maximum System (IEC 134)
Supply voltage VP max. 35 V
Non-repetitive peak output current IOSM max. 3 A
Repetitive peak output current IORM max. 1,5 A
Total power dissipation see derating curves Fig. 2
Storage temperature Tstg -55 to + 150 °C
Operating ambient temperature Tamb -25 to + 150 °C


TBA396 TDA3950 MC1327

TDA1170 vertical deflection FRAME DEFLECTION INTEGRATED CIRCUIT

GENERAL 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.



TDA9503, Line Circuits for TV Receivers (18-Pin Plastic Package)
These integrated circuits are advanced versions of the well-known types TDA1940, TDA1940F, TDA1950 and TDA1950F are identical
TBA940/950, TDA9400/9500 etc. integrated line oscillator circuits. except the following: at pin 2 the types having the suffix "F" supply ,
They comprise all stages for sync separation and line synchronisation horizontal output pulses of longer duration compared with the basic I
in TV receivers in one single silicon chip. Due to their high degree of types Integration, the number of external components is very small.
This integrated circuit contains the horizontal sweep generator (HO), the amplitude filter (AS), the sync-signal separating circuit (SA) and the frequency/phase comparator (FP). For the purpose of suppressing noise pulses which are caused via the operating voltage during the upper and the lower inversion point of the horizontal sweep generator (HO) which contains a single capacitor (C) and a first threshold stage circuit (SS1) with two fixed thresholds, there are provided a second and a third threshold stage circuit (SS2, SS3), to the inputs of which the sawtooth signal is applied, and with the thresholds thereof, approximately 2 μs prior to reaching the upper or the lower peak value of the sawtooth signal, are being passed through thereby. The output signal of the second threshold circuit (SS2) and the output signal of the third threshold stage circuit (SS3) which is applied via the pulse shaper circuit (IF), are superimposed linearly and, via the stopper circuit (blocking stage) (SP) serve to control the application of the composite video signal (BAS) to the amplitude filter (AS), or else they are applied to a clamping circuit which serves to apply the operating points of the amplitude filter (AS) and/or of the sync-signal separating circuit (SA) to such a potential that these two stages, for the time duration of these output pulses, are prevented from operating.
1. An integrated circuit for color television receivers, comprising a voltage- or current-controlled horizontal sweep generator (HO), an amplitude filter (AS), a synchronizing-signal separating circuit (SA) and a frequency/phase comparator (FP) which serves to synchronize the horizontal sweep generator (HO), with said generator being a sawtooth generator containing a single capacitor
(C) and a first threshold stage circuit (SS1) having two fixed thresholds, said integrated circuit further comprising:

a second and a third threshold stage circuit (SS2, SS3) each being supplied with the sawtooth signal on the input side, comprising each time one threshold which, approximately 2μs prior to the reaching of the upper or the lower peak value of the sawtooth signal, is being passed thereby;

a pulse shaper circuit (IF) coupled to the output of said third threshold stage circuit (SS3) which pulse shaper circuit reduces the duration of the output pulse thereof to about the duration of the output pulse of said second threshold stage circuit (SS2), and

a stopper circuit (blocking stage) (SP) coupled to the outputs of both said pulse shaper circuit (IF) and said second threshold stage circuit (SS2), said stopper circuit having a signal input to which there is applied a composite video signal (BAS) and a signal output which is coupled to the input of said amplitude filter (AS).



2. The invention of claim 1 wherein the outputs of both said pulse shaper circuit (IF) and said second threshold stage circuit (SS2) are coupled to a clamping circuit which applies the operating points of said amplitude filter (AS) and said sync-separating signal (SA) to such a potential that they are prevented from operating.

3. An integrated horizontal sweep circuit comprising:

a generator for generating a sawtooth signal;

an amplitude filter having an input for receiving a composite video signal and having an output;

a sync-signal separating circuit having an input coupled to said amplitude filter output and having an output;

a frequency/phase comparator having a first input coupled to said separating circuit output,

a second input receiving said sawtooth signal and an output for controlling said generator; and

a control circuit responsive to said sawtooth signal for inhibiting said composite video signal when said sawtooth signal is within predetermined signal level ranges about the upper and lower inversion points of said sawtooth signal.



4. An integrated circuit in accordance with claim 3 wherein:

said generator comprises a capacitor, circuit means for charging and discharging said capacitor, and a first threshold circuit controlling said circuit means in response to said sawtooth signal reaching a first level corresponding to said first inversion point and a second level corresponding to said second inversion point.



5. An integrated horizontal sweep circuit comprising:

a sawtooth signal generator;

an amplitude filter having an input receiving a composite video signal and having an output;

a sync-signal separating circuit having an input coupled to said amplitude filter output and having an output;

a frequency/phase comparator having a first input coupled to said separating circuit output, a second input receiving said sawtooth signal and an output for controlling said generator; and

a control circuit responsive to said sawtooth signal for inhibiting operation of said amplitude filter and/or said sync-signal separating circuit when said sawtooth signal is within predetermined signal level ranges about the upper and lower inversion point of said sawtooth signal.



6. An integrated circuit in accordance with claim 5 wherein:

said generator comprises a capacitor, circuit means for charging and discharging said capacitor and a first threshold circuit controlling said circuit means in response to said sawtooth signal reaching a first level corresponding to said first inversion point and a second level corresponding to said second inversion point.



Description:

BACKGROUND OF THE INVENTION

The invention relates to an integrated circuit for (color) television receivers, comprising a voltage- or current-controlled horizontal-sweep generator, an amplitude filter, a synchronizing signal separating circuit (sync-separator) and a frequency/phase comparator which serves to synchronize the horizontal sweep generator which is a sawtooth generator consisting of a single capacitor and of a first threshold stage having two fixed switching thresholds, cf. preamble of the patent claim. Such types of integrated circuits, for example, are known from the technical journal "Elektronik aktuell", 1976, No. 2, pp. 7 to 14 where they are referred to as TDA 9400 and TDA 9500.

Especially on account of the fact that the amplitude filter as well as the horizontal sweep generator in the form of the aforementioned sawtooth generator, are integrated on a single semiconductor body, it is likely that noise interference pulses coming from the individual stages, and via the supply voltage line, may have a disturbing influence upon the horizontal sweep generator, i.e. upon the threshold stage thereof, in such a way that either the lower or the upper or successively both switching thresholds are exceeded before the time by the voltage at the capacitor, owing to the noise superposition, so that the generator will show to have a "wrong" frequency or phase position. This frequency/phase variation, of course, is compensated for by the circuit, with the aid of the synchronzing pulses, but only in such a way that the noise effect remains visible in the television picture.

SUMMARY OF THE INVENTION

The invention is characterized in the claim is aimed at overcoming this drawback by solving the problem of designing an integrated circuit of the type described in greater detail hereinbefore, in such a way that noise pulses acting upon the capacitor voltage or the internal reference voltages for the switching thresholds (see below) in the proximity of the two switching thresholds, are prevented from having the described disadvantageous effect. Accordingly, an advantage of the invention results directly from solving the given problem.

Other objects, features and advantages of the present invention will become more fully apparent from the following detailed description of the preferred embodiment, the appended claims and the accompanying drawing in which:

BRIEF DESCRIPTION OF THE INVENTION

The invention will now be described in greater detail with reference to the accompanying drawing. This drawing, in the form of a schematical circuit diagram, shows the construction of an integrated circuit according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

T

he horizontal sweep generator HO comprises the capacitor C as connected to the zero point of the circuit, and which is charged and discharged via the two shown constant current sources CS1 and CS2, thus causing the intended sawtooth voltage to appear thereat. Moreover, the horizontal sweep generator HO comprises the first threshold stage circuit SS1, having an upper and a lower threshold. As soon as the capacitor voltage exceeds one of the thresholds, the first threshold stage circuit SS1 switches over to the other threshold. The two thresholds are defined by the voltage divider P as connected to the operating voltage U, and in which the corresponding threshold inputs are connected to corresponding tapping points. The output of the threshold stage circuit SS1 controls the electronic switch S, so that the constant current source CS2 as connected thereto, is either disconnected from or connected to the zero point of the circuit. Accordingly, in the disconnected state, the capacitor C is charged via the constant current source CS1 arranged in series therewith while in the connected state the capacitor C is discharged across the aforementioned constant current source CS2 arranged in parallel therewith, if, as a matter of fact, the current of the constant current source CS1 arranged in series with the capacitor C, is smaller than that of the parallel-arranged constant current source CS2.

Now, for the purpose of avoiding the aforementioned drawbacks, there is provided a second and a third threshold stage circuit SS2 and SS3, respectively, as well as the pulse shaper circuit IF. To the respective input of the two threshold stage circuits SS2, SS3, there is applied the capacitor voltage, in the form of the sawtooth signal, and these stages have a threshold voltage which, approximately 2 μs prior to the reaching of the upper or the lower peak value of the sawtooth voltage, is being passed thereby. This means to imply that the threshold voltage of the second threshold stage circuit SS2 is somewhat lower than the voltage of the upper threshold of the first threshold stage circuit SS1, and that the threshold voltage of the third threshold stage circuit SS3 is somewhat higher than the voltage of the lower threshold of the first threshold stage circuit SS1. The two thresholds of the threshold stage circuits SS2, SS3 can thus be realized in a simple way by providing further tapping points at the voltage divider P, as is shown in the accompanying drawing. Thus, the second threshold stage circuit SS2 is provided for at a voltage divider tapping point below the tapping point chosen for the upper threshold, and the tapping point for the third threshold stage circuit SS3 is provided for above the tapping point which has been chosen for the lower threshold of the first threshold stage circuit SS1.

Since, within the area of the lower inversion point of the sawtooth signal there results an excessively wide output pulse of the third threshold stage circuit SS3, the pulse shaper circuit IF is arranged subsequently thereto, for reducing the duration of the output pulse as applied to its input, to about the duration of the output pulse of the second threshold stage circuit SS2. This pulse shaper circuit IF, for example, may be realized by a monoflop, in particular by a digital monoflop (=monostable circuit).

The output pulses of the second threshold stage circuit SS2 and of the pulse shaper circuit IF are then super-positioned linearly, with this being denoted in the drawing by a simple interconnection of the two respective lines. The combined signal is applied to the input of the stopper circuit (blocking stage) SP, to the signal input of which there is fed the composite video signal BAS, and the output thereof controls both the amplitude filter AS and the synchronizing signal separating circuit SA.

The combined signal may also be used to control a clamping circuit applying the operating points of the amplitude filter AS and/or of the sync-signal-separating circuit SA to such a potential which prevents it from operating.

If now the sawtooth signal reaches the range of its upper or its lower inversion point, the composite video signal BAS is not applied to either the amplitude filter AS or the sync-signal separating circuit SA, so that shortly before and shortly after the inversion points, signals are prevented from being processed in the two stages AS, SA. This, in turn, has the consequence that during these times noise pulses are prevented from superimposing upon the operating voltage U, so that there is also prevented an unintended triggering of the first threshold stage circuit SS1.

Moreover, it is still shown in the drawing that the amplitude filter AS, the sync-signal separating circuit SA and the frequency/phase comparator FP are arranged in series in terms of signal flow, with the latter, in addition, receiving the sawtooth signal, and with the output signal thereof acting upon the two current sources in a regulating sense. In the drawing, this is indicated by the setting arrows at the two current sources.

While the present invention has been disclosed in connection with the preferred embodiment thereof, it should be understood that there may be other embodiments which fall within the spirit and scope of the invention as defined by the following claims.

IRRADIO MOD. 2022/A CORALL 22" CHASSIS NORDING S4 PAL Controlled power supply for a television receiver equipped with remote control:BLAUPUNKT SWITCH MODE POWER SUPPLY.Blaupunkt-Werke GmbH (Hildesheim, DT)

A single isolation transformer supplies both the remote control receiver and the television receiver. A pulse generator such as a blocking oscillator which energizes the primary winding of the isolation transformer has its pulse width controlled in response to the loading of the circuit of the secondary winding of the isolation transformer, as measured by the voltage across a resistor in the circuit of a primary winding. This measuring resistor is interposed between the emitter of the switching transistor of the blocking oscillator and the receiver chassis. A transistor switching circuit for cutting off the low voltage supply to the scanning circuit oscillators of the television receiver is responsive to the output of the remote control receiver, to a signal from an operating control of the television receiver, and to an indication of overcurrent in the picture tube, independently.

1. A power supply circuit for a television receiver equipped for remote control comprising, in combination:

an on-off switch for connecting and disconnecting the television receiver and its power supply circuit respectively to and from the electricity supply mains;

pulse generating means arranged for energization through said on-off switch;

an isolation transformer having its primary winding supplied with the output of said pulse generating means;

a power conversion circuit connected to the secondary winding of said isolation transformer for energization thereby, for supplying an operating voltage for the scanning circuits of the television receiver and for supplying a plurality of other voltages to said receiver, at least one of which other voltages is also supplied to said scanning circuits;

a remote control signal receiver for remote control of said television receiver and controlled switching means responsive to said remote control receiver for switching said television receiver between a stand-by condition and an operating condition, both said remote control receiver and said controlled switching means being connected to a secondary winding of said isolation transformer for energization thereby, said controlled switching means having a switching path for connecting and disconnecting said scanning circuits of said television receiver respectively to and from a source of said operating voltage in said power conversion circuit and

means for reducing energy transfer through said pulse generating means to said isolation transformer when said television receiver is in the stand-by condition.

2. A power supply circuit as defined in claim 1, in which said pulse generating means includes rectifying means energized through said on-off switch for supplying direct current for energization of said pulse generating means. 3. A power supply circuit as defined in claim 2, in which said energy transfer reducing means includes means for varying the width (duration) of pulses generated by said pulse generating means in response to the extent of loading of the secondary circuit of said isolating transformer as measured in the primary circuit of said transformer. 4. A power supply circuit as defined in claim 2, in which said pulse generating means includes a blocking oscillator and said energy transfer reducing means includes means for reducing the width (duration) of the pulses generated by said blocking oscillator. 5. A power supply circuit as defined in claim 4, in which said blocking oscillator includes a switching transistor (5) and a load measuring resistor (7) interposed in a connection between the emitter of said switching transistor and the receiver chassis, and in which said pulse width reducing means is responsive to the voltage drop across said load measuring resistor. 6. A power supply circuit as defined in claim 5, in which said pulse width reducing means includes a controllable resistance (10) in the circuit of said blocking oscillator controlled in response to the voltage drop across said load measuring resistor. 7. A power supply circuit as defined in claim 1, in which said operating voltage connected and disconnected to said scanning circuits by said controlled switching means is the low voltage supply voltage (U 3') of the line scan and picture scan oscillators of the television receiver and in which said controlled switching means is controlled so as to switch off said low voltage supply voltage to put the television receiver in the stand-by condition. 8. A power supply circuit as defined in claim 7, in which said controlled switching means includes a first switching transistor (15) at the collector of which there is applied a direct current supply voltage (U 3) energized through said isolating transformer and a second switching transistor (24) for controllably short-circuiting the base bias of said first switching transistor, whereby a stabilized low voltage (U 3') exists at the emitter of said first switching transistor (15) when a positive signal is supplied from an operating control of the television receiver or from said remote control receiver to the base of said second switching transistor (24). 9. A power supply circuit as defined in claim 7, in which said controlled switching means is responsive independently to an overcurrent condition in the picture tube for switching off said low voltage supply voltage (U 3') in response to said overcurrent condition.
Description:

The present invention relates to a power supply unit including a blocking oscillator for utilization with a television receiver provided with ultrasonic remote control, and more particularly to a television receiver the operating conditions of which are normal operation, a stand-by operation, and the turned-off condition, and a power supply unit therefor that includes an isolating transformer.

In recent times television receivers have frequently been provided with ultrasonic remote control devices for the purpose of offering easier control. As more and more television receivers are utilized in combination with additional equipment, it becomes increasingly necessary to connect the receivers only indirectly to the electric power mains (house wiring). In a known advantageous solution of this problem, a power supply unit includes an isolating transformer which is wired up with a blocking oscillator in the primary circuit. The blocking oscillator is supplied with a d-c voltage which is obtained by rectification of the supply voltage. Compared to the isolating transformers which are directly mains-operated, these so-called switch-mode power supply units have the advantage that they can be made in considerably smaller size, as they are operated at a significantly higher frequency, and the further advantage that they require less expensive means for rectification.

It is necessary to supply television receivers equipped with ultrasonic remote control with the possibility for a stand-by operation in which only the ultransonic receiver is supplied with power and, in some cases, also the heating current for the picture tube. Usually a separate power supply unit is provided for the ultrasonic receiver and the heating of the picture tube, a unit that includes an isolating transformer of its own, the primary winding of which is directly mains-fed. Upon transition from normal operation to stand-by operation, the power supply unit of the blocking osciallator is switched off, so that the television receiver receives only the relatively small quantity of energy required for the ultrasonic receiver and, in some cases, also for the heating of the picture tube.

Because of the required second isolating transformer, this known circuit has the disadvantages that it requires both greater space and greater expenditure.

It is the object of the present invention to develop a simplified power supply unit which does not have the above-mentioned disadvantages.

SUMMARY OF THE INVENTION

Briefly, the television receiver and the ultrasonic receiver are connected to the same isolating transformer; means for the switching from normal operation to stand-by operation and vice versa are placed in the secondary circuit of the isolating transformer, and means are arranged in the primary circuits of the isolating transformer for reducing the amount of energy made available for stand-by operation purposes.

The main advantages of the present invention are that no separate isolating transformer is required for supplying the current during the stand-by operation, and that, during the stand-by operation, it is nevertheless only the power required for this operation which is consumed.

An advantageous embodiment of the present invention obtains reduction of the energy quantum transmitted through the power supply during stand-by by reduction of the pulse width of the pulses generated by the blocking oscillator.

Another advantageous embodiment of the present invention utilizes measurement in the primary circuit of the isolating transformer of variation in load occurring in the secondary circuit as a control variable for determining the pulse width.

A further advantageous embodiment of the present invention obtains the control variable for the pulse width across a measuring resistor interposed in the connection of the emitter of the switching transistor of the blocking oscillator to the chassis.

Still another advantageous embodiment of the present invention provides that the voltage drop across the measuring resistor controls a controllable resistor.

The advantageous embodiments described above offer highly simple and advantageous possibilities for measuring the variation in load upon switching between normal and stand-by operation, as well as for the consequent control of the energy transmitted via the isolating transformer.

The possibility of a simple and inexpensive switching between normal and stand-by operation is achieved by effecting the switching between normal and stand-by operation by means of switching on or switching off, respectively, the low voltage supply of the line scan oscillator, and, especially, by a first switching transistor which short-circuits the base bias of a second switching transistor at the collector of which a direct current supply voltage is present and at the emitter of which a stabilized low voltage exists, when a positive signal is supplied from the operating control of the television receiver or from the remote control receiver to the base of the first switching transistor.

The circuit arrangements just mentioned offer the advantage that they may simultaneously be utilized as a protective circuit. This is achieved by a switching-off device for the low voltage which can also be triggered at any time by a signal built up by overcurrent in the picture tube.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is further described by way of illustrative example by reference to the annexed drawings in which:

FIG. 1 is a circuit diagram, partly in block form, of an embodiment of the invention;

FIG. 2 is a circuit diagram of one form of means for interrupting the power to the picture circuits in the stand-by condition in connection with the circuit of FIG. 1, and

FIG. 3 is a circuit diagram of one way of controlling the pulse width of the blocking oscillator 4 in response to the switching circuit 8 in the circuit of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

An on-off power switch 2 of the television receiver is connected to the supply terminals 1, providing a primary operating control for the receiver. Consquently, the supply voltage is also present at the output of the operating control 2 when the television receiver is turned on thereby, and arrives at a rectifying stage 3 comprising means for rectifying and smoothing the supply current as well as for suppressing interference. A d-c voltage, feeding a blocking oscillator stage 4, is present at the output of the recifying stage 3. The main part of the blocking oscillator 4, symbolically represented in FIG. 1 by a fragmentary circuit diagram, is a switching transistor 5, in the load circuit of which the primary winding of an isolating tranformer 6 is placed. A measuring resistor 7 is connected between the emitter of the switching transistor 5 and the chassis, across which measuring resistor a voltage is taken and applied to a load-dependent control circuit 8. The voltage taken at the measuring resistor 7 is fed via a resistor 9 to the base of a transistor 10 which serves as a controllable load for the blocking oscillator 4. A resistor 11 and a capacitor 12, each of which is connected to chassis with its other terminal, are also connected to the base of the transistor 10. The emitter of transistor 10 is connected to chassis, while the collector of the transistor 10 is connected back to the blocking oscillator stage 4.

In the secondary circuit of the isolating transformer 6, a d-c voltage supply stage or power conversion circuit 13 is placed, substantially consisting of a rectifying circuit 14, which, in the example shown, is provided with six outputs at which the voltages U 1 to U 5 can be taken off with respect to the sixth output connected to the chassis. At the terminal U 3, there is, in addition, a branch feeding both the collector-to-emitter path of the transistor 15 and also, through a resistor 16, the collector-to-emitter path of the transistor 15a. The emitter of the transistor 15a is directly connected to the base of transistor 15. The emitter of the transistor 15 is connected to chassis via a series connection of a resistor 17, a potentiometer 18, and a further resistor 19. The tap of the potentiometer 18 is connected to the base of a further transistor 20. The transistor 20 is connected to chassis by means of its emitter via a Zener diode 21, the collector of the transistor 20 controlling the base of the transistor 15a. The emitter of the transistor 20 is connected to the emitter of the transistor 15 via a resistor 22. A terminal for tapping off the voltage U 3' is connected to the emitter of the transistor 15.

The base of the transistor 15a is connected to a switching stage 23 responsive to a remote control ultrasonic receiver by a conductor leading to the collector of a switching transistor 24 which is connected to chassis via its emitter. The base of the switching transistor 24 is connected to an input terminal 28 leading into the television receiver via two resistors 25, 26 and a capacitor 27 connected in series, that input terminal 28 passing on switching signals from the receiver to the switching transistor 24, as will be explained in more detail below.

The cathode of a diode 29, which is connected to chassis via its anode, is connected to the junction point of the resistor 26 and the capacitor 27. The junction point of the two resistors 25, 26 is connected to chassis via a capacitor 30. The base of the switching transistor 24 is connected to chassis via a resistor 31. Furthermore, that base electrode is also connected to a terminal 32 to which an electrical switching signal is applied which is either built up in response to an ultrasonic signal received by the remote control receiver 32' or is supplied from an operating control of the television receiver. At the terminal 32, the switching transistor 24 receives the signal containing the information whether the television receiver is to work in the normal operating condition, i.e. to receive and process the sound and video signals, or in the stand-by condition in which it is substantially only the ultrasonic receiver that is supplied with current.

When a positive signal arrives at the base of the switching transistor 24, the latter becomes conductive, and causes chassis potential to be present at the base of transistor 15a. The transistor 15 is thereby blocked, and there is no longer any voltage at the terminal U 3'. Since the voltage U 3' serves as an operating voltage for the line and picture scan oscillator, the deflecting stages of the receiver cannot work and no high voltage and other related supply voltages are generated at the line circuit transformer. In consequence, by means illustrated diagrammatically in FIG. 2, the electric circuits connected to the terminals U 1 to U 3 are interrupted. The voltages U 4 and U 5 serve for supplying the ultrasonic receiver, i.e. they are required for the stand-by operation.

In case no counteracting means should be provided for, the variation in load would cause a voltage rise in the secondary circuit of the isolating transformer 6, which effect is, of course, not desired. Therefore, a measuring resistor is connected in the primary circuit in the emitter line of the switching transistor 5 of the blocking oscillator 6, the variation in load in the secondary circuit appearing at the measuring resistor 7 as a current variation. The current change thus produced, causes a variation in the base bias of the transistor 10, the capacitor 12 having an integrating effect to avoid undesired effects due to interference pulses and abrupt load fluctuations.

The change of the working point of the transistor 10 causes a change in the pulse width in the blocking oscillator stage 4, as more fully shown in FIG. 3, so that the energy quantum transmitted via the isolating transformer 6 is such that the required voltages are present in the secondary circuit. It should also be mentioned that the load-dependent switch 8 and the circuit of FIG. 3 are represented only by way of illustration and that many circuit arrangements may be devised by straight-forward application of known principles for controlling the pulse width.

The circuit connected between the terminal 28 and the base of the switching transistor 24 serves as a part of a protective circuit for the picture tube. Any overcurrent is measured at the low-end resistor 31 of the high-voltage cascade in conventional techinque. The voltage thus produced is fed to the base of the switching transistor 24, and causes the television receiver to be switched over to stand-by operation, so that no damage can be done to the picture tube. Thus, the device performing the switching between normal operation and stand-by operation is advantageously and simultaneously utilized as a protective circuit. The circuit 23, as shown, provides for stabilizing the potential at the base of transistor 24 and for integrating such possibly occurring overload peaks as are not intended to triggering the protective circuit.

Using the circuit diagram according to FIG. 3 it is possible in a simple manner to control the pulse width of the blocking oscillator 4 in response to the switching circuit 8.

According to the circuit diagram of FIG. 2 the terminal U1 is connected to a line scan oscillator circuit 40, the terminal U2 to a picture scan oscillator circuit 41 and the terminal U3 to a circuit 42 for a sound output stage. The circuits 40, 41, 42 get their operating voltage from the terminal U3'. If the operating voltage U3' is zero, the circuits 40, 41, 42 are interrupted. In this case the voltages at the terminals U1, U2, U3 remain.

The described circuit of this invention for controlling the voltage in the secondary circuit of the isolating transformer 6 offers the advantage that it is exclusively arranged in the primary circuit, and, therefore, permits an uncomplicated design which is easy to realize. To control the pulse width by measuring the load fluctuations at the low-end resistor of the switching transistor 5, represents a very useful means for control since, thereby the transmitted energy can effectively and easily be controlled.

The blocking oscillator stage 4 shown in detail in FIG. 3 incorporates an externally triggered blocking oscillator arranged to be triggered through an oscillator operating preferably at the line scanning frequency, which is to say its wave form is not particularly critical and it should be provided with means to keep it in step with the line scanning frequency, as is known to be desirable. The transistors 51 and 52 of the triggered output stage of the blocking oscillator circuit could be regarded as constituting a differential amplifier the inputs of which are defined by the base connections of the respective transistors 51 and 52. The input voltage applied to the base connection of transistor 52 is the Zener voltage of the Zener diode 53, thus a constant reference voltage. The operating voltage for the transistors 51 and 52 and for the Zener diode 53 is obtained from the supply voltage UB, which is to say from the rectifier 3. The diode 67 protects the transistor 52, for example at the time of the apparatus being switched on, against damage from an excessively high emitter-base blocking voltage. The capacitor 65 prevents undesired oscillation of the circuit of transistors 51 and 52, which could give rise to undesired disturbances.

At the base of the transistor 51, there is present as input voltage for the circuit a composite voltage that is the sum of three voltages. These are, first, the line scan frequency trigger voltage coupled through the capacitor 63; second, a bias voltage dependent upon the loading of the blocking oscillator stage resulting from the load on the secondary of the transformer 6, but detected by the voltage across the resistor 7 and actually controlled by the load-sensitive control circuit 8, and, third, a regulating voltage applied at the terminal 71 of the resistor 70, which regulating voltage is proportional to the voltage of the secondary winding of the transformer 6 and can accordingly be provided by one or another of the output circuits of the rectifier 14 of FIG. 1 or by a separate winding of the transformer 6 and a separate rectifier element connected in circuit therewith. This regulating voltage and the control voltage provided by the control circuit 8 are applied to the resistor 61 which completes the circuit for both of these bias voltages and their combined effect constitutes the bias voltage for the transistor 51 which determines its working point.

The circuit of the transistors 51 and 52 operates as an overdriven differential amplifier. When the trigger voltage exceeds the threshold determined by the base voltage of the transistor 51, the circuit produces an approximately rectangular output voltage pulse of constant amplitude. Since the trigger voltage is recurrent, the result is a periodic succession of rectangular output voltage pulses, but the duration or pulse width of these pulses depends upon the loading and the output voltage of the stage. The output voltage of the circuit constituted by the transistors 51 and 52 comes from the emitter connection of the transistor 52 and is furnished to the switching transistor 5, preferably through a driver stage 54, such as a transformer or another transistor stage for better matching of the circuit impedances. Of course, the collector circuit of the transistor 5 includes the primary winding of the transformer 6 of FIG. 1.

The described power supply unit thus represents a well functioning component subject to but a small number of potential sources of error, due to the simple design, and permits considerable reduction of costs in comparison with circuits and equipment heretofore known.

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