JPS6141336Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention is a television receiver that corrects changes in the horizontal and vertical amplitude of the image receiving screen in response to fluctuations in power supply voltage, and controls the screen to always maintain a constant screen amplitude. The present invention relates to a receiving screen amplitude control circuit for a digital receiver.

Conventionally, in television receivers, the electron beam emitted from the electron gun of the picture tube is deflected by passing a sawtooth wave deflection current through a deflection coil, and the electron beam is projected onto the phosphor screen of the picture tube. It is well known that the image is formed by It is well known that the amplitude of this screen is proportional to the magnitude of the deflection current flowing through the deflection coil, and is also approximately inversely proportional to the square root of the anode voltage of the picture tube.

Further, the deflection current flowing through the deflection coil is proportional to the DC power supply voltage supplied to the deflection circuit. This DC power supply voltage is generally obtained by rectifying the commercial AC voltage and stabilizing it with a stabilizing power supply circuit, etc., but in order to maximize the utilization rate of the power supply, it is common to obtain it by rectifying the commercial AC voltage and stabilizing it with a stabilizing power supply circuit. Normally, it is not possible to obtain a stabilized DC voltage with respect to the voltage. For example, when the commercial AC voltage fluctuates from 90V to 110V, the DC power supply voltage cannot be stabilized below 95V and will drop.

Therefore, when the DC power supply voltage decreases in this way, the deflection current decreases and the amplitude of the screen becomes small. Next, the picture tube anode voltage is generally obtained by boosting the flyback pulse and rectifying it, but its load fluctuation characteristics usually change by about 10% with respect to changes in the picture tube anode current. For this reason, the anode current of the picture tube is reduced, and as the image becomes darker, the picture tube anode voltage increases. As a result, the screen amplitude becomes smaller.

As mentioned above, in television receivers, the screen amplitude changes depending on the power supply voltage and the brightness of the image, so in order to prevent the screen from being chipped due to this, the amplitude should be adjusted in advance by about 10% to 13%. Do an over scan. As a result, the screen amplitude becomes larger than necessary, resulting in disadvantages such as a reduction in the amount of information displayed on the screen and a darkened image.

This invention was made in view of the above points,
Fluctuations in the DC power supply voltage are detected by a first voltage dividing circuit and added to the amplifier circuit, fluctuations in the picture tube anode voltage (hereinafter referred to as anode voltage) are detected by a second voltage dividing circuit and added to the amplifier circuit, By amplifying these fluctuations in the amplifier circuit and supplying the detection signal of the power supply voltage fluctuation to the vertical deflection circuit and horizontal deflection circuit, fluctuations in the DC power supply voltage due to fluctuations in the commercial power supply and dark screens can be avoided. This prevents the deflection current from decreasing due to changes in the anode current of the picture tube and the amplitudes of the screen becoming smaller when the image tube becomes warmer, so that a constant screen amplitude can be obtained and overscan can be reduced. An object of the present invention is to provide an image amplitude control circuit that improves screen quality.

Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. Reference numerals 1A and 2A in the figure are first voltage dividing elements, which are disposed between the DC power supply voltage E _B and the ground, and detect fluctuations in the DC power supply voltage E _B to connect the input terminals of the buffer amplifier circuit 4. It is connected so that it can be supplied to 3. This buffer amplifier circuit 4 is connected to a constant voltage circuit 6 via a terminal 5,
The current change due to the potential difference between the voltage B ₂ obtained from the circuit 6 and the terminal 3 can be supplied through the connection terminal 8 to be transmitted to the control amplifier circuit 7. On the other hand, the picture tube anode voltage E _H is supplied from a horizontal transformer (described later) of the horizontal deflection circuit 9 to the input terminal 8 of the control amplifier circuit 7 via second voltage dividing elements 1B and 2B for detecting fluctuation current. There is. That is, the voltage dividing elements 1B and 2B are arranged between the output terminal _EH of the horizontal deflection circuit 9 and the ground. One of the output terminals of the control amplifier circuit 7 is connected to the input terminal 11 of the vertical deflection circuit 10, so that the output of the vertical deflection circuit 10 can be controlled. The other output terminal is the primary terminal 1 of the saturable reactance 12, both of which are grounded.
3, and its secondary end is connected to be input to the horizontal deflection coil (inside the horizontal deflection circuit 9).
This saturable reactance 12 is controlled by the control amplifier circuit 7.
This utilizes changes in output inductance due to changes in the output signal.

The power supply voltages B ₁ and B ₃ are derived from the power supply voltage E _B of the horizontal oscillation circuit (inside the horizontal deflection circuit 9) which is supplied to the horizontal deflection circuit 9 by the horizontal deflection transformer (inside the horizontal deflection circuit 9). It is then converted and output. And voltage _B1 is control amplifier circuit 7
The voltage B 3 is supplied to the power supply voltage terminal 14 of the vertical deflection circuit 10 so that the voltage B ₃ can be supplied as the power supply voltage of the vertical deflection circuit 10 . On the other hand, the constant voltage B ₂ from the constant voltage circuit 6 described above can be supplied as a power source to a part of the control amplifier circuit 7. Further, the picture tube anode voltage (hereinafter referred to as anode voltage) E _H similarly changes due to fluctuations in the voltage E _B .

The operation of the screen amplitude control circuit configured as described above will be explained.

(1) If the DC power supply voltage E _B decreases, the DC voltage B ₃ of the vertical deflection circuit 10 will also decrease in proportion to it. Then, both the vertical deflection current and the horizontal deflection current decrease. Now, when the DC power supply voltage E _B decreases, the current flowing through the voltage dividing elements 1A and 2A decreases, so the potential of the terminal 3 also decreases. On the other hand, since the voltage _B2 is stabilized by the constant voltage circuit 6, the potential difference between the terminals 5 and 3 increases, and the current flowing through the terminals 5 and 8 increases. Then, the potential of the terminal 8 increases, and the input current of the control amplifier circuit 7 increases.
Then, this input current is amplified and the control amplifier circuit 7
Current flowing through both outputs (between terminals 11 and 8,
(between terminals 13 and 8) and between terminals 14 and 8). These changes in current then reduce the voltage at terminal 11.

As mentioned above, the terminal 11 is connected to the vertical deflection circuit 1.
Since the output control circuit 10 is connected to control the operation of the output control circuit 0, the output amplitude voltage of the vertical deflection circuit 10 can be increased (the operation of the vertical deflection circuit 10 will be described later).

On the other hand, when the current flowing through the primary winding of the saturable reactance, that is, the current flowing between terminals 13 and 8 increases, the inductance of the secondary winding decreases, so that the horizontal deflection coil (described later) in the horizontal deflection circuit 9 decreases. Since the inductance of the oscillator is decreased, the horizontal deflection current increases, and the decrease in the horizontal oscillation output due to the decrease in the DC power supply voltage can be compensated for.

(2) Next, consider the case where the anode voltage E _H increases by making the screen darker. When the anode voltage E _H increases, the current flowing through the element 1B that detects the change in E _H increases, and the input current of the control amplifier circuit 7 increases. Since the output current also increases, the current flowing through the primary winding of the saturable reactance 12 increases. By this,
Since the inductance on the output side of the saturable reactance 12 decreases, the effective portion of the horizontal deflection coil (actually connected in series with the secondary coil) decreases, and the horizontal deflection current flowing through the horizontal deflection coil increases. , it is possible to compensate for a decrease in horizontal amplitude due to an increase in anode voltage E _H .

Further, when the anode voltage E _H decreases, the opposite operation is performed, and the control amplifier 7 operates so that the anode voltage E _H increases via the variable reactance.

Furthermore, stabilization of the voltage B ₂ obtained by the constant voltage circuit 6 is an essential condition for detecting changes in the DC power supply voltage E _B . This is because the DC voltage B ₁ is a part of the power supply voltage of the control amplifier 7, and is a voltage that changes as the DC power supply voltage E _B changes. Also, DC voltage
_B1 may also be stabilized like the constant voltage power source _B2 , but this is not preferable because the capacitance of the elements (constant voltage elements) constituting the constant voltage circuit 6 becomes large.

FIG. 2 shows a circuit diagram of a specific circuit configuration related to the above-mentioned screen amplitude control circuit.

In Fig. 2, reference numerals 10 and 9 enclosed by dotted lines indicate specific circuits of the vertical deflection circuit and horizontal deflection circuit of Fig. 1. Here, the configuration of the vertical deflection circuit 10 of Fig. 2 will be explained. The output terminal of the vertical oscillator 15 is connected to the base of a transistor _Q4 . The collector is connected to a power source _B3 , and the emitter is connected to one end of a charge/discharge capacitor _C2 via a resistor _R17 . The other end of this capacitor is grounded. The collector of a transistor _Q5 is connected to one end of a charge/discharge capacitor _C2 , and similarly, its collector is connected to the input terminal of a vertical amplifier circuit 16. The base of the transistor _Q5 is grounded via a resistor R19, and is also connected to a resistor _R20 .
A power supply _B3 is connected via _R18 . The output terminal of the vertical amplifier circuit 16 is connected to a deflection coil 17. In addition, the output terminal 11 of the control amplifier 7 is connected to
is connected to the emitter of transistor _Q5 , which is grounded through an adjustable resistor _R20 .

Now, in the vertical deflection circuit 10, the transistor _Q4 is turned on by the pulse voltage obtained from the output terminal of the vertical oscillation circuit 15, and the capacitor _C2 is charged. The collector of the transistor _Q5 is connected to the capacitor _C2 , and by passing current through this collector, the charge stored in the capacitor _C2 is discharged, so that a sawtooth wave voltage is generated at the collector of _Q5 . occurs. By amplifying this voltage in the vertical amplification output circuit 16 and applying it to the vertical deflection coil 17, a sawtooth wave deflection current flows through the vertical deflection coil 17, and vertical deflection is performed. Also, since the emitter of transistor Q ₅ is connected to a variable resistor R ₂₀ , by varying this resistance value, the peak value of the sawtooth wave voltage can be adjusted by varying the collector current at the emitter of transistor Q ₅ . Since the vertical amplitude can be changed, the vertical amplitude can be adjusted.

In the horizontal deflection circuit 9, the transistor _Q6 to which the pulse signal of the horizontal oscillation pulse generation circuit (not shown) is input is a horizontal output transistor, and
Its emitter is grounded and its collector is grounded via a damper diode D ₂ and also via a resonant capacitor C ₃ . Also, S-shaped correction capacitor C ₄ and flyback transformer T ₁
It is connected to the primary winding side of the

S-shaped correction capacitor C ₄ is horizontal deflection coil 1
8 is connected to the secondary output terminal of the saturable reactance 12.

One terminal on the primary side of the flyback transformer _T1 is supplied with a DC power supply voltage _E.sub.B. code D ₃
is a high voltage rectifier diode, and the picture tube anode voltage E
It is configured to output _H. rectifier diode
The pulse voltage obtained at the winding of the flyback transformer _T1 is rectified by _D4 and the smoothing capacitor _C5 , and DC voltages _B1 and _B3 are output. Next, the configuration of the parts related to the present invention will be explained. In FIG. 2, symbols Q ₁ to Q ₃ are transistors, and C ₁
is a capacitor, and R ₁ to R ₁₆ are resistors. Resistors R ₂ , R ₃ , R ₄ , R ₅ and R ₆ in FIG. 2 correspond to the first voltage dividing circuit, and R ₃ and R ₄ are connected in parallel. Further, _R3 is a thermistor for temperature compensation.
DC power supply voltage E _B is supplied to resistor R ₂ ,
The base of the transistor _Q1 , which detects the variation in E _B , is connected to the connection point between the resistor _R5 and the parallel circuit of the resistor _R4 and thermistor _R3 . And resistance R ₅
is a variable resistor whose adjustment terminal is also connected to the base of transistor _Q1 . Transistor Q ₁
The collector of Q 1 is connected to ground through a resistor R ₈ and to the base of a transistor Q ₂ , and similarly the collector of Q ₁ is connected to a diode D ₃ through a resistor R ₁ .
is connected to the cathode of and said resistance
R ₁ corresponds to voltage dividing element 1B, and resistor R ₈ corresponds to voltage dividing element 2B. Capacitor C ₁ is resistor R ₁
Since it has a relatively high resistance, the ripple voltage of the anode voltage E _H is caused by the stray capacitance of the circuit.
This is a smoothing capacitor that prevents a phase lag from being applied to the base of transistor _Q1 , and is placed between the base of transistor _Q2 and ground. The emitter of the transistor _Q1 is configured to be supplied with a constant voltage output _B2 via a resistor _R7 , and the emitter of the transistor _Q2 is also configured to be able to be supplied with a constant voltage output _B2 via a resistor _R9 . The emitter of transistor _Q2 is. It is grounded through a resistor _R10 , and its collector is connected to the base of a transistor _Q3 . A resistor _R14 is connected between the base and emitter of the transistor _Q3 , and is connected so that the DC voltage _B1 is supplied to the emitter of the transistor _Q3 via the resistor _R13 . Also, the emitter output is connected via resistor _R16 .
It is connected to the emitter of the transistor _Q5 of the vertical deflection circuit 10. On the other hand, the collector of the transistor Q ₃ is connected to the emitter of the transistor Q ₂ via a resistor R ₁₁ , and the collector of the transistor Q ₃ is connected to one of the primary windings W _P of the saturable reactance 12 via a resistor R ₁₅ . It is connected to terminal 13 of. Primary winding W _P of saturable reactance 12
The other terminal of the secondary winding W _S is grounded, and the other terminal of the secondary winding W _S is connected to the horizontal deflection coil 18 . Further, the DC voltage B ₁ is supplied to a resistor R ₁₂ and a constant voltage diode D ₁ that constitute the constant voltage circuit 6 to obtain a stabilized voltage. That is, the power supply voltage _B1 is configured to be supplied to the cathode of the constant voltage diode _D1 whose anode is grounded via the resistor _R12 .

Incidentally, although the operation of this circuit has been described above, it will be explained again. If the DC power supply voltage E _B decreases, the voltage B ₃ also decreases proportionally, so both the vertical and horizontal deflection currents decrease. However, when the DC power supply voltage E _B decreases, the voltage dividing resistor R ₂
Since the current flowing through _R6 decreases, the voltage at the base of transistor _Q1 decreases. On the other hand, DC voltage
Since B ₂ is stabilized by the constant voltage diode D ₁ , the current flowing through the resistor R ₇ (the terminals 5 and 3
Since the current flowing through resistor 8 increases, the base voltage of transistor Q ₂ increases, causing the base current of Q ₂ to increase. Along with this, the base current and collector current of transistor _Q3 increase, so naturally the emitter current increases. This increases the current flowing through resistor _R13 and lowers the emitter voltage of transistor _Q3 . If the potential difference between the emitters of transistor Q ₅ and transistor Q ₃ increases, the resistance
Since the current flowing through _R16 increases, the transistor
The collector current of Q ₅ increases and the transistor Q ₅
Since the peak value of the sawtooth wave voltage obtained at the collector becomes larger, the vertical deflection current increases, and it is possible to compensate for the decrease in vertical amplitude caused by the decrease in E _B .

Next, if the voltage E _H fluctuates, the current flowing through the resistor R ₁ will fluctuate, the base voltage of the transistor Q ₂ will rise, and the base current and collector current of the transistor Q ₃ will fluctuate accordingly. Primary side inductance W of saturation reactance 12
The current flowing through _P changes, and the inductance W _S on the secondary side decreases. As described above, it is possible to compensate for the decrease in horizontal amplitude due to fluctuations in E _H of the anode voltage. Also, as the collector current of transistor _Q3 increases, the emitter current also increases, so the resistance
The current flowing through R ₁₃ increases, and as described above, it is possible to compensate for fluctuations in vertical amplitude due to fluctuations in anode voltage E _H .

Next, the voltage gain of this control amplifier circuit 7 can be set as R ₉ +R ₁₀ /R ₉ ×R ₁₀ ×R ₁₁ +1 (times) by using the collector of transistor Q ₃ as an output terminal. Connecting resistor R ₉ is transistor Q ₂
This is an effective means when you want to operate in a region where the collector voltage of transistor Q ₃ is lower than the emitter voltage of transistor Q _3. If you want to operate in a region where the collector voltage of transistor Q 3 is higher, resistor R ₉ becomes unnecessary. In that case, the voltage gain is R ₁₀ +R ₁₁ /R ₁₀
becomes.

By connecting the low resistor R ₉ in this manner and by appropriately setting the low resistor value of each of the resistors R ₉ to R ₁₁ , an arbitrary circuit bias state and voltage gain can be obtained. As is well known, the voltage gain of the output signal appearing at the emitter of the transistor _Q3 is determined by the primary inductance W of the saturable reactance 12.
If the resistance of _P is ignored, it can be set arbitrarily within the range allowed by the dynamic range by changing the resistance ratio of resistors _R13 and _R15 . The sensitivity for detecting changes in the anode voltage E _H is determined by the ratio of the voltage dividing resistor R ₁ to the resistor R ₈ . In order to increase the sensitivity, the voltage dividing resistor R ₁ can be made smaller or the resistor R ₃ can be made larger.

However, since direct current flows through the resistors R ₁ and R ₈ in steady state as well as the change in anode voltage E _H , increasing the sensitivity will cause the base voltage of transistor Q ₂ in steady state to increase. Become. Therefore, taking into consideration the dynamic range, the base voltage of the transistor _Q2 can be set as high as possible, and the gain and bias of the control amplifier circuit 7 can be set by the above-mentioned _R9 to _R11 . Resistance from this point as well
It is preferable to connect R ₉ .

The sensitivity for detecting fluctuations in the DC power supply voltage E _B is determined by the resistance, because if the constant voltage DC voltage B ₂ is determined by the voltage of the constant voltage diode D ₁ , the voltage dividing ratios of the voltage dividing resistors R ₂ to R ₆ are naturally limited. It can be set by the resistance value of _R7 . If we reduce the resistance R ₇ ,
Transistor Q ₁ when DC power supply voltage E _B fluctuates
Since the amount of change in the collector current increases, the sensitivity increases.

Once the gain of the detection sensitivity control amplifier circuit (7 in FIG. 1) is determined as described above, the horizontal amplitude control sensitivity is determined by setting the resistance value of the resistor _R15 .
Further, the control sensitivity of the vertical amplitude is determined by the settings of the resistor R ₁₆ and the resistor R ₁₃ .

Next, the saturable reactance 12 and the control amplifier circuit 7
The relationship between the output currents will be explained. The width of the dynamic range of the saturable reactance 12 is proportional to the size of its shape, so if the dynamic range is widened, the shape becomes large and expensive. Therefore, in order to effectively use the minimum necessary dynamic range, the operating point should be adjusted. The operating point of the control amplifier circuit 7 can also be changed by resistors R ₈ to R ₁₁ , etc., but when R ₈ is changed, the DC power supply voltage E _B ,
The sensitivity of detecting the anode voltage E _H by the voltage dividing resistors (R ₁ and R ₂ to R ₆ ) changes, and changing the resistors R ₉ to R ₁₁ changes the gain. Therefore, in the embodiment of the present invention, the collector current of the transistor _Q1 is varied by varying the resistor _R5 , which is an element of the voltage dividing resistor, so that the base voltage of the transistor _Q2 can be adjusted to an optimal value.

In this case, the control amplifier circuit 7 (transistor Q ₂
and Q ₃ ) need not be changed, and since the collector output impedance of transistor Q ₁ is very high, there is no need to change the input impedance of control amplifier circuit 7 (Q ₂ and Q ₃ ), so that the anode voltage E _H There is no need to change the detection sensitivity for fluctuations in .

Next, temperature compensation in an embodiment according to the present invention will be explained.

When the ambient temperature increases, first the transistor Q ₁
The base-to-emitter voltage V _BE becomes smaller (V
_BE has a temperature coefficient of approximately -2mV/°C). Then, the current flowing through the resistor _R7 increases, and the current flowing through the resistor _R8 also increases, so that the collector current of the transistor _Q3 increases and the screen amplitude increases. Furthermore, considering the dynamic range of the circuit of the present invention, the Zener voltage of the constant voltage diode D ₁ is required to be 5 V or more, so the temperature coefficient of the constant voltage diode D ₁ becomes positive and the constant voltage DC voltage B ₂ increases. .
In this case as well, the current in resistor _R7 increases, and the screen amplitude increases in a similar manner. Also transistor Q ₂
The base-emitter voltage of transistor _Q2 also decreases, and if the base voltage of transistor Q2 is determined by the voltage drop across resistor _R8 , then transistor _Q2
The emitter voltage of transistor Q3 will rise, and the collector voltage of transistor _Q3 will be increased by the control amplifier circuit 7 ( _Q2
and Q ₃ ) will increase by the voltage gain times.
As a result, the screen amplitude becomes larger.

As described above, since the temperature drifts of each element are all in the same direction, compensation is necessary. Therefore, for overall compensation, a thermistor _R3 was connected between the DC power supply E _B and the base of the transistor _Q1 . As is well known, thermistor _R3 has a negative temperature coefficient, so as the ambient temperature rises, its resistance value decreases. As a result, the base voltage of transistor _Q1 rises, resulting in the same operation as if the DC power supply voltage rose, and it is possible to compensate for the increase in screen amplitude. The degree of compensation (compensation temperature coefficient) depends on the selection and resistance of thermistor _R3 .
It can be determined by appropriately setting the resistance values of R ₂ and R ₄ .

By the way, the resistor R ₁ is connected so as to directly detect the change in the anode voltage E _H. Conventionally, this resistor R ₁ is connected to the anode voltage E in a region where the anode current is small.
A dummy resistor (not shown) connected to reduce the change in _H may be used. In addition, even if the anode voltage E _H is not directly detected, as shown in Figure 3, it can be detected using a resistor voltage divider circuit for creating the picture tube focus voltage E _F , but the anode voltage and focus voltage may be in a proportional relationship. It is valid if That is, FIG. 3 shows a circuit diagram of another embodiment of the present invention.

FIG. 3 is a circuit diagram of the flyback transformer of the horizontal deflection circuit, and the same elements as in FIG. 2 are given the same reference numerals and will be explained. In the diagram, a diode
_D5 and capacitor 6 form a rectifier circuit that generates a focus voltage, and the focus voltage is connected to a series resistor.
This is obtained by adjusting the resistance R ₂₂ of R ₂₁ , R ₂₂ and R ₂₃ using the sliding terminal. The base of the transistor _Q2 is configured to receive an input from a resistor _R23 .

Next, regarding the detection of the DC power supply voltage E _B , in FIGS. 1 and 2, the DC power supply voltage E _B is directly detected. This is voltage E _B and voltage B ₁
If B 3 and B ₃ are in a proportional relationship, it is possible to detect the voltage B ₁ or B ₃ without directly detecting the anode voltage E _B . In this embodiment, other configurations are omitted.

Next, resistor R ₁₆ is connected between the emitter of transistor Q ₃ and transistor Q ₅ , but the same purpose can be achieved by connecting resistor R ₁₆ between the collector of transistor Q ₃ and the base of transistor Q ₅ . can do. In that case, the resistance R ₁₃ becomes unnecessary, so the dynamic range of the amplifier 7 (Q ₂ and Q ₃ ) becomes wider. . However, transistor Q ₅ and resistor
If R ₁₈ , resistor R ₁₉ , etc. are built into an integrated circuit (IC), only resistor R ₂₀ is connected outside the IC, so the connection as shown in Figure 2 is used. This is advantageous because it eliminates the need to change the IC.

As described above, according to the present invention, when the amplitude of the picture tube image fluctuates due to fluctuations in the commercial power supply or changes in brightness during broadcast reception, the first The fluctuation signal detected by the voltage divider circuit and the second voltage divider circuit that divides the anode voltage is amplified by the control amplifier circuit, and the detected output current compensates for the oscillation output of each vertical and horizontal deflection circuit. , the fluctuation of the screen amplitude of the television receiver due to the above conditions is corrected, and a constant screen amplitude is always obtained, which reduces the overscanning rate and allows more information to be displayed on the screen. It has the advantage of being able to be photographed. Also, with the same high voltage, it will be brighter and
This has the effect that a clear image can be obtained and the deflection power can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing one embodiment of the invention, Fig. 2 is a circuit diagram showing a specific circuit configuration of the invention, and Fig. 3 is a circuit showing another embodiment of the invention. It is a diagram. 1A, 1B, 2A, 2B...Voltage dividing element, 4...
Buffer amplifier circuit, 7... Control amplifier circuit, 6...
Constant voltage circuit, 12...Saturable reactance, R ₃
...Thermistor, etc., R ₁ and R ₂ , R ₄ to R ₁₁ ,
R ₁₃ , R ₁₅ and R ₁₆ ...resistor, Q ₁ to Q ₃ ... transistor, D ₁ ... constant voltage diode, C ₁ ... capacitor.

Claims (1)

[Claims for Utility Model Registration] A circuit that controls the screen amplitude by being coupled to a vertical deflection circuit and a horizontal deflection circuit that sweep the screen of a picture tube, which comprises a plurality of resistive elements connected in series, A first voltage divider circuit, which includes a variable resistance and a resistance element with negative temperature characteristics, divides and extracts the DC power supply voltage for the horizontal deflection circuit, and a second voltage divider circuit which extracts a voltage proportional to the picture tube anode voltage. 2 voltage dividing circuit, a constant voltage circuit into which the first power supply voltage is input and takes out a stabilized output voltage, and a divided voltage output from the first voltage dividing circuit is supplied to the base, and the emitter is connected to the constant voltage circuit. a buffer amplifier circuit having a first transistor to which an output voltage from a voltage circuit is supplied and whose collector outputs an inverted output in response to a change in a base input; an output of the buffer amplifier circuit and the second voltage dividing circuit; a second transistor whose base is supplied with a divided voltage output from the circuit, whose emitter is supplied with a divided output voltage from the constant voltage circuit; and whose base is supplied with a collector output of the second transistor. , a third transistor whose emitter is supplied with the first power supply voltage and whose collector is connected to the emitter of the second transistor via a resistor, and detects a change in the base input of the second transistor. and a control amplifier circuit for amplifying, and controlling a vertical deflection circuit and a horizontal deflection circuit using changes in the current flowing through the emitter-collector current path of the third transistor of the control amplifier circuit to adjust the magnitude of each deflection current. A screen amplitude control circuit comprising means for changing the amplitude of the screen.