The CHASSIS IFI F3-01 is a full modular chassis with all functions of the receiver on it exception for the tuning frontend which is located in the cabinet.
TDA2530 RGB MATRIX PREAMPLIFIERThe 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 frequencybehaviour.
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
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
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
TDA2541 IF AMPLIFIER WITH DEMODULATOR AND AFC
DESCRIPTION
The TDA2540 and 2541 are IF amplifier and A.M.
demodulator circuits for colour and black and white
television receivers using PNP or NPN tuners. They
are intended for reception of negative or positive
modulation CCIR standard.
They incorporate the following functions : .Gain controlled amplifier .Synchronous demodulator .White spot inverter .Video preamplifier with noise protection .Switchable AFC .AGC with noise gating .Tuner AGC output (NPN tuner for 2540)-(PNP
tuner for 2541) .VCR switch for video output inhibition (VCR
play back).
.SUPPLYVOLTAGE : 12V TYP
.SUPPLYCURRENT : 50mATYP
.I.F. INPUT VOLTAGE SENSITIVITY AT
F = 38.9MHz : 85mVRMS TYP
.VIDEO OUTPUT VOLTAGE (white at 10% of
top synchro) : 2.7VPP TYP
.I.F. VOLTAGE GAIN CONTROL RANGE :
64dB TYP .SIGNAL TO NOISE RATIO AT VI = 10mV :
58dB TYP
.A.F.C. OUTPUT VOLTAGE SWING FOR
Df = 100kHz : 10V TYP
TDA2590 horizontal oscillator combination
— The TDA2590 is a monolithic integrated circuit designed
as a horizontal oscillator combination for TV receivers and monitors.
It is constructed using the Fairchild Planar* process.
LINE OSCILLATOR USING THE THRESHOLD SWITCHING PRINCIPLE
PHASE COMPARISON BETWEEN SYNC PULSE AND OSCILLATOR VOLTAGE (d>1)
PHASE COMPARISON BETWEEN LINE FLYBACK PULSE AND OSCILLATOR VOLTAGE
(<62) Y
SWITCH FOR CHANGING THE FILTER CHARACTERISTIC AND THE GATE CIRCUIT
{WHEN USED FOR VCR)
COINCIDENCE DETECTOR (¢3)
SYNC SEPARATOR
NOISE SEPARATOR
VERTICAL SYNC SEPARATOR AND OUTPUT STAGE
COLOR BURST KEYING AND LINE FLYBACK BLANKING PULSE GENERATOR
PHASE SHIFTER FOR THE OUTPUT PULSE
OUTPUT PULSE DURATION SWITCHING
OUTPUT STAGE FOR DIRECT DRIVE OF THYRISTOR DEFLECTION CIRCUITS
SYNC GATING PULSE GENERATOR
LOW SUPPLY VOLTAGE PROTECTION.
DA1170 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.
1. A transformerless output vertical deflection circuit, comprising a vertical oscillator circuit for generating a vertical pulse train in response to vertical synchronizing pulses applied thereto, a sawtooth signal generator for generating a series of sawtooth signals, each cycle of said sawtooth signal including a pulse component, a vertical output circuit coupled to said sawtooth generator for amplifying said sawtooth signal including said pulse component and loading a vertical deflection coil, and stabilizing means connected between said vertical oscillator and said sawtooth signal generator for varying the width of the pulse component which is to be fed to said vertical output circuit in response to the average level of DC output voltage fed from the vertical output circuit. 2. A transformerless output vertical deflection circuit claimed in claim 1, wherein said stabilizing means comprises a control circuit means for receiving a series of pulses from the vertical oscillator and a feedback signal from the vertical output circuit and for varying the width of the pulse which is to be fed to the vertical output circuit in response to a DC control signal proportional to the width of the pulse component included in the vertical output signal and smoothing circuit means connected between said vertical output circuit and said stabalizing means for smoothing said feedback signal. 3. A transformerless output vertical deflection circuit claimed in claim 2, wherein said control circuit comprises a charging capacitor which is parallel to a transistor, said transistor being switched on in response to pulses fed from the vertical oscillator wherein said capacitor is charged by the voltage fed from said smoothing circuit, and discharged in response to conduction of the transistor, a differential amplifier circuit which receives the voltage on said capacitor and a fixed voltage, and a gating circuit for producing a pulse which has a width equal to the difference between the width of the pulse fed from the vertical oscillator circuit and the width of pulse fed from the differential amplifier circuit. 4. A transformerless output vertical deflection circuit claimed in claim 2, wherein said control circuit comprises a capacitor which is charged by a fixed power source and is discharged by means of a switching transistor operated by the pulses fed from the vertical oscillator circuit and a differential amplifier circuit receiving the voltage on the capacitor and the output of said smoothing circuit. 5. A transformable output vertical deflection circuit comprising a vertical oscillator for generating a vertical pulse train in response to vertical synchronizing pulses applied thereto, a sawtooth signal generator for generating a series of sawtooth signals each cycle of said sawtooth signal including a pulse component, a vertical output circuit for amplifying said sawtooth signal including said pulse component and loading a vertical deflection coil, and pulse stabilizing means coupled between the vertical oscillator circuit a
Description:
BACKGROUND OF THE INVENTION
The present invention relates to a vertical deflection circuit for use in a television receiver and, more particularly, to a vertical deflection circuit of a type wherein no vertical output transformer is employed. This type of vertical deflection circuit with no output transformer is generally referred to as an OTL (Output Transformerless) type vertical deflection circuit.
It is known that variation of the pulse width of the flyback pulse produced in a vertical output stage of the vertical deflection circuit is the cause in the raster on the television picture tube, of a white bar, flicker, jitter, line crowding and/or other raster disorders. In addition thereto, in the vertical deflection output circuit where the output stage is composed of a single-ended push-pull amplifier having a vertical output transistor, an excessive load is often imposed on the output transistor and, in an extreme case, the output transistor is destroyed.
GBC ELECTRONICS (FORMENTI) UT13045M_TC CHASSIS IFI F3-01 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.
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;
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:
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.
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.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.
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 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.
A Cockcroft-Walton cascade circuit comprises an input voltage source and a pumping and storage circuit with a series array of capacitors with pumping and storage portions of the circuit being interconnected by silicon rectifiers, constructed and arranged so that at least the capacitor nearest the voltage source, and preferably one or more of the next adjacent capacitors in the series array, have lower tendency to internally discharge than the capacitors in the array more remote from the voltage source.
1. An improved voltage multiplying circuit comprising,
2. An improved voltage multiplying circuit in accordance with claim 1 wherein said first pumping capacitor is a self-healing impregnated capacitor which is impregnated with a high voltage impregnant.
3. An improved voltage multiplying circuit in accordance with claim 1 wherein said first pumping capacitor comprises a foil capacitor.
Description:
BACKGROUND OF THE INVENTION
The invention relates in general to Cockcroft-Walton cascade circuits for voltage multiplication and more particularly to such circuits with a pumping circuit and a storage circuit composed of capacitors connected in series, said pumping circuits and storage circuit being linked with one another by a rectifier circuit whose rectifiers are preferably silicon rectifiers, especially for a switching arrangement sensitive to internal discharges of capacitors, and more especially a switching arrangement containing transistors, and especially an image tube switching arrangement.
Voltage multiplication cascades composed of capacitors and rectifiers are used to produce high D.C. voltages from sinusoidal or pulsed alternating voltages. All known voltage multiplication cascades and voltage multipliers are designed to be capacitance-symmetrical, i.e., all capacitors used have the same capacitance. If U for example is the maximum value of an applied alternating voltage, the input capacitor connected directly to the alternating voltage source is charged to a D.C. voltage with a value U, while all other capacitors are charged to the value of 2U. Therefore, a total voltage can be obtained from the series-connected capacitors of a capacitor array.
In voltage multipliers, internal resistance is highly significant. In order to obtain high load currents on the D.C. side, the emphasis in the prior art has been on constructing voltage multipliers with internal resistances that are as low as possible.
Internal resistance of voltage multipliers can be reduced by increasing the capacitances of the individual capacitors by equal amounts. However, the critical significance of size of the assembly in the practical application of a voltage multiplier, limits the extent to which capacitance of the individual capacitors can be increased as a practical matter.
In television sets, especially color television sets, voltage multiplication cascades are required whose internal resistance is generally 400 to 500 kOhms. Thus far, it has been possible to achieve this low internal resistance with small dimensions only by using silicon diodes as rectifiers and metallized film capacitors as the capacitors.
When silicon rectifiers are used to achieve low internal resistance, their low forward resistance produces high peak currents and therefore leads to problems involving the pulse resistance of the capacitors. Metallized film capacitors are used because of space requirements, i.e., in order to ensure that the assembly will have the smallest possible dimensions, and also for cost reasons. These film capacitors have a self-healing effect, in which the damage caused to the capacitor by partial evaporation of the metal coating around the point of puncture (pinhole), which develops as a result of internal spark-overs, is cured again. This selfhealing effect is highly desirable as far as the capacitors themselves are concerned, but is not without its disadvantages as far as the other cirucit components are concerned, especially the silicon rectifiers, the image tubes, and the components which conduct the image tube voltage.
It is therefore an important object of the invention to improve voltage multiplication cascades of the type described above.
It is a further object of the invention to keep the size of the entire assembly small and the internal resistance low.
It is a further object of the invention to increase pulse resistance of the entire circuit.
It is a further object of the invention to avoid the above-described disadvantageous effects on adjacent elements.
It is a further object of the invention to achieve multiples of the foregoing objects and preferably all of them consistent with each other.
SUMMARY OF THE INVENTION
In accordance with the invention, the foregoing objects are met by making at least one of the capacitors in the pumping circuit, preferably including the one which is adjacent to the input voltage source, one which is less prone to internal discharges than any of the individual capacitors in the storage circuit.
The Cockcroft-Walton cascade circuit is not provided with identical capacitors. Instead, the individual capacitors are arranged according to their loads and designed in such a way that a higher pulse resistance is attained only in certain capacitors. It can be shown that the load produced by the voltage in all the capacitors in the multiplication circuit is approximately the same. But the pulse currents of the capacitors as well as their forward flow angles are different. In particular, the capacitors of the pumping circuit are subjected to very high loads in a pulsed mode. In the voltage multiplication cascade according to the invention, these capacitors are arranged so that they exhibit fewer internal discharges than the capacitors in the storage circuit.
The external dimensions of the entire assembly would be unacceptably large if one constructed the entire switching arrangement using such capacitors.
The voltage multiplication cascade according to the invention also makes it possible to construct a reliably operating
arrangement which has no tendency toward spark-overs, consistent with satisfactory internal resistance of the voltage multiplication cascade and small dimensions of the entire assembly. This avoids the above cited disadvantages with respect to the particularly sensitive components in the rest of the circuit and makes it possible to design voltage multiplication cascades with silicon rectifiers, which are characterized by long lifetimes. Hence, a voltage multiplication cascade has been developed particularly for image tube circuits in television sets, especially color television sets, and this cascade satisfies the highest requirements in addition to having an average lifetime which in every case is greater than that of the television set.
A further aspect of the invention is that at least one of the capacitors that are less prone to internal discharges is a capacitor which is impregnated with a high-voltage impregnating substance, especially a high-voltage oil such as polybutene or silicone oil, or mixtures thereof. In contrast to capacitors made of metallized film which have not been impregnated, this allows the discharge frequency due to internal discharges or spark-overs to be reduced by a factor of 10 to 100.
According to a further important aspect of the invention, at least one of the capacitors that are less prone to internal discharges is either a foil capacitor or a self-healing capacitor. In addition, the capacitor in the pumping circuit which is adjacent to the voltage source input can be a foil capacitor which has been impregnated in the manner described above, while the next capacitor in the pumping circuit is a self-healing capacitor impregnated in the same fashion.
Other objects, features and advantages of the invention will be apparent from the following detailed description of preferred embodiments, taken in connection with the accompanying drawing, the single FIGURE of which:
BRIEF DESCRIPTION OF THE DRAWING
is a schematic diagram of a circuit made according to a preferred embodiment of the invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
The voltage multiplier comprises capacitors C1 to C5 and rectifiers D1 to D5 connected in a cascade. An alternating voltage source UE is connected to terminals 1 and 2, said voltage source supplying for example a pulsed alternating voltage. Capacitors C1 and C2 form the pumping circuit while capacitors C3, C4 and C5 form the storage circuit.
In the steady state, capacitor C1 is charged to the maximum value of the alternating voltage UE as are the other capacitors C2 to C5. The desired high D.C. voltage UA is picked off at terminals 3 and 4, said D.C. voltage being composed of the D.C. voltages from capacitors C3 to C5. Terminal 3 and terminal 2 are connected to one pole of the alternating voltage source UE feeding the circuit, which can be at ground potential. In the circuit described here, a D.C. voltage UA can be picked off whose voltage value is approximately 3 times the maximum value of the pulsed alternating voltage UE. By using more than five capacitors, a correspondingly higher D.C. voltage can be obtained.
The individual capacitors are discharged by disconnecting D.C. voltage UA. However, they are constantly being recharged by the electrical energy supplied by the alternating voltage source UE, so that the voltage multiplier can be continuously charged on the output side.
According to the invention, in this preferred embodiment, capacitor C1 and/or C2 in the pumping circuit are designed so that they have a lower tendency toward internal discharges than any of the individual capacitors C3, C4 and C5 in the storage circuit.
It is evident that those skilled in the art, once given the benefit of the foregoing disclosure, may now make numerous other uses and modifications of, and departures from the specific embodiments described herein without departing from the inventive concepts. Consequently, the invention is to be construed as embracing each and every novel feature and novel combination of features present in, or possessed by, the apparatus and techniques herein disclosed and limited solely by the scope and spirit of the appended claims.
Inventors:Petrick, Paul (Landshut, DT)
Schwedler, Hans-peter (Landshut, DT)
Holzer, Alfred (Schonbrunn, DT)
ERNST ROEDERSTEIN SPEZIALFABRIK
US Patent References:
3714528 ELECTRICAL CAPACITOR WITH FILM-PAPER DIELECTRIC 1973-01-30 Vail
3699410 SELF-HEALING ELECTRICAL CONDENSER 1972-10-17 Maylandt
3463992 ELECTRICAL CAPACITOR SYSTEMS HAVING LONG-TERM STORAGE CHARACTERISTICS 1969-08-26 Solberg
3457478 WOUND FILM CAPACITORS 1969-07-22 Lehrer
3363156 Capacitor with a polyolefin dielectric 1968-01-09 Cox
2213199 Voltage multiplier 1940-09-03 Bouwers et al.
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