JPH0523017Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a horizontal circuit for a television receiver.

<Summary of the invention> The present invention is a television receiver, in particular, a television receiver with a large screen and a built-in left/right pincushion distortion correction circuit. The anode voltage generated in the high voltage winding of the flyback transformer is corrected by controlling the peak value of the flyback pulse generated in the primary winding of the transformer. As a result, even if the anode current changes, the anode voltage is held constant, and as a result, changes in the horizontal and vertical amplitudes of the image due to changes in the anode current are suppressed. At the same time, by changing the correction rate of left and right pincushion distortion correction according to the anode current of the CRT and performing appropriate left and right pincushion distortion correction according to the ripple content of the anode voltage, even if the anode current changes, it is always correct. The left and right pincushion distortion is corrected.

<Prior art> Fig. 11 shows an example of a conventional horizontal circuit having left and right pincushion distortion correction circuits and a circuit for correcting an anode voltage according to changes in anode current, and 1 is a horizontal output transistor. An excitation pulse P is supplied to the horizontal output transistor 1 from a previous stage (not shown), whereby the horizontal output transistor 1 performs a switching operation together with the damper diode 2. 4 is a resonance capacitor, 6 is a horizontal deflection coil, 7 is an S-shaped correction capacitor, and 8 is a left and right pincushion distortion correction circuit, and this correction circuit 8 is composed of an inductor 9, a capacitor 10, and a left and right pincushion distortion correction signal generation circuit 11. has been done.

Left and right pincushion distortion correction signal generation circuit 1 described above
1 to the inductor 9 constituting the left and right pincushion distortion correction circuit ₈ .
is applied to the connection point A of the capacitor 10, the horizontal deflection current i _y flowing through the horizontal deflection coil 6 is amplitude-modulated by the left and right pincushion distortion correction signal voltage v _a as shown in FIG. Distortion correction can be performed.

12 is a flyback transformer, 12a is a primary winding of the flyback transformer 12, and 12b is a high voltage winding of the flyback transformer 12. The primary winding 12 of the flyback transformer 12 described above
DC power supply +B for operating the horizontal deflection circuit is connected to a, and the high voltage winding 12b of the flyback transformer 12 receives the flyback pulse _vce generated between C and E on the primary winding 12a side. The voltage is boosted and supplied to the high voltage rectifier circuit 13 to generate an anode voltage _VHV , which is applied to the anode 16a of the CRT 16.

33 is an anode current detection circuit, and the voltage Vb at the output terminal B decreases linearly as the anode current _IHV increases, as shown in FIG. The output terminal B of _the anode current detection circuit 33 described above has the following functions:
It is connected to a so-called beam limiter circuit that limits the amplitude or black level of the video signal of a video amplification circuit (not shown), and the output terminal B is connected to the voltage Vb necessary for driving the variable capacitance circuit 37. Current amplification circuit 26 that amplifies current
It is connected to the.

The variable capacitance circuit 37 described above is the resonant capacitor 4
are connected in parallel to each other, and the capacitance changes as the anode current _IHV increases or decreases. Note that FIG. 12 shows an actual circuit example of the variable capacitance circuit 37. here 3
8, 41 are capacitors, 39 is a transistor, 4
0 is a damper diode, 42 is a resistor, and as the DC voltage applied to the base 37b of the transistor 39 changes, the resistance between the collector and emitter of the transistor 39 changes, and the capacitance/resistance in the variable capacitance circuit 37 changes. The capacitance is changed by changing the synthetic components of the .

Therefore, the operation for stabilizing the anode voltage V _HV including the variable capacitance circuit 37 described above is as follows.
For example, when the anode current _IHV increases, the anode voltage _VHV tends to decrease due to the resistance of the circuit, but on the other hand, the output terminal B of the anode current detection circuit 33
The voltage Vb decreases, and the voltage at the control terminal of the variable capacitance circuit 37, that is, the base 37b of the transistor 39, also decreases via the current amplification circuit 26. Then, the resistance value between the collector and the emitter of the transistor 39 increases, thereby the capacitance within the variable capacitance circuit 37 decreases, and the combined capacitance with the resonant capacitor 4 also decreases. The relationship between the peak value of the flyback pulse v _ce and the capacitance of the resonant capacitor is approximately expressed by the following equation, where Cr is the capacitance of the resonant capacitor, and K is the other related proportionality constant.

v _ce = K1/√Cr …(1) Therefore, as mentioned above, the capacitance of the resonant capacitor
When Cr becomes smaller, the peak value of the flyback pulse v _ce increases, and the pulse induced in the high voltage winding 12b of the flyback transformer 12 also increases, and the anode voltage V _HV , which was about to decrease, returns to an appropriate value. It will be corrected.

Conversely, when the anode voltage V _HV is corrected by decreasing the anode current I _HV , the above-described correction operation is performed in reverse.

<Problems to be solved by the invention> A horizontal circuit having the conventional left and _{right pincushion} distortion correction circuit 8 shown in FIG. In this case, the variable capacitance circuit 37 for anode voltage V _HV correction is controlled by DC voltage, and further,
Since it is connected to the horizontal output circuit to which a very high voltage flyback pulse _vce is applied (usually around _1000Vpp at its peak value), the transistor 39 constituting the variable capacitance circuit 37 has a very high breakdown voltage. In addition, a device with a large loss is required, and therefore a heat sink is also required, making the anode voltage V _HV stabilizing circuit using this method extremely expensive.

In addition, as the anode current I _HV increases, the anode voltage increases as shown by the solid line in Figure 17 due to the fluctuation of the load factor.
A ripple in the vertical scanning period occurs in V _HV (the anode voltage V HV when the anode current I _HV is minimum is shown by the broken line), and as a result, the anode current I _HV in the CRT 16 is speed-modulated, and _as a result, for example, 1st
If the correction amount of the left and right pincushion distortion correction circuit 8 is adjusted so that the left and right pincushion distortion correction is best when the anode current _IHV is at its minimum, as shown by the broken line in Figure 6a, then as the anode current _IHV increases, the 16
As shown by the solid line in Figure A, left and right pincushion distortion occurs in the image. Conversely, if the left and right pincushion distortion correction is optimally adjusted when the anode current _IHV is maximum, as shown by the solid line in Figure 16a, the anode current
When I _HV decreases, the image produces trapezoidal distortion as shown by the broken line in FIG. 16b.

<Means for Solving the Problems> In the present invention, a DC power supply is connected to both ends of the horizontal output transistor 1, which is controlled to be turned on and off in a horizontal period, via the primary winding 12a of the flyback transformer 12. A series circuit of a pair of resonant capacitors 4 and 5 is connected to both ends of the horizontal output transistor 1,
A series circuit of a pair of damper diodes 2 and 3, and a series circuit of a horizontal deflection coil 6 and an inductor 9 to which a vertically periodic parabolic left-right pincushion distortion correction signal v _a is applied are connected in parallel to each other, and the pair of resonance A connection midpoint between the capacitors 4 and 5, a connection midpoint between the pair of damper diodes 2 and 3, and a connection midpoint between the horizontal deflection coil 6 and the inductor 9 are connected to each other, and the connection midpoint is
This provides a horizontal circuit whose capacitance changes according to the anode current _IHV of the CRT 16 and which is connected to a variable capacitance circuit 17 which performs switching operation in response to the flyback pulse _vce from the flyback transformer 12. .

<Function> As a result, even if the anode current I _HV of the CRT 16 changes, the capacitance of the variable capacitance circuit 17 changes accordingly, so that the peak value of the flyback pulse v _ce and the left and right pincushion distortion correction signal v _a are Corrected to an appropriate value.

<Embodiments> Hereinafter, embodiments of the horizontal circuit of the present invention will be described in detail based on the drawings. FIG. 1 is a block diagram of one embodiment of the horizontal circuit of the present invention, and FIG.
This is a circuit diagram showing a specific circuit configuration of the embodiment shown in the figure, and in each of these figures, the constituent parts corresponding to the constituent parts in the horizontal circuit explained with respect to Fig. 11 are as shown in Fig. 11. The same codes are used as those used in .

In FIGS. 1 and 2, 1 is a horizontal output transistor, and an excitation pulse P is supplied to this horizontal output transistor 1 from a previous stage (not shown), so that the horizontal output transistor 1 is connected in series. A pair of damper diodes 2 and 3
At the same time, a switching operation is performed. 4 and 5 are a pair of resonant capacitors connected in series, 6 is a horizontal deflection coil, 7 is an S-shaped correction capacitor, 8 is a left and right pincushion distortion correction circuit, an inductor 9, a capacitor 10, and a left and right pincushion distortion correction signal generation circuit. It consists of 11.

Then, the connection midpoint between the pair of damper diodes 2 and 3, the connection midpoint between the pair of resonance capacitors 4 and 5, and the connection point between the S-shaped correction capacitor 7 and the left and right pincushion distortion correction circuit 8 are connected to each other. , the connection point is connected to a variable capacitance circuit 17, which will be described later.

Flyback transformer 12, high voltage rectifier circuit 1
3. The configurations and operations of the anode current detection circuit 33 and current amplification circuit 26 are the same as those of the conventional example, so their explanations will be omitted. Note that FIG. 2 shows a specific circuit excitation of the high voltage rectifier circuit 13, anode current detection circuit 33, and current amplification circuit 26.

In the figure, 14 is a rectifier diode,
15 is a stray capacitance that the CRT 16 itself has. Also, 34 is a bypass capacitor;
5 and 36 are anode current detection resistors. Furthermore, 27 and 30 are transistors for current amplification by Darlington connection, 28 is a bias resistor, 29 is a protection diode for preventing destruction due to the reverse breakdown voltage between the base and emitter of the transistor 30, and 31, 3
2 is a voltage dividing resistor.

23 is a flyback pulse _vce for switching drive of the variable capacitance circuit 17 described later.
The drive pulse v _dp is generated by shaping the waveform as shown in Fig. 3.
A switching drive pulse shaping circuit for generating a driving current is provided. 24 is a resistor constituting the circuit 23.
A capacitor 5 constitutes the circuit 23 .

17 is a variable capacitance circuit, hereinafter referred to as the circuit 1
As elements constituting 7, 18 is a capacitor, 1
9 is a transistor, 20 is a damper diode, 2
1 is a protection diode for preventing destruction due to reverse breakdown voltage between the base and emitter of the transistor 19, and 22
is resistance.

Here, the actual operation of the horizontal circuit of the present invention having the above configuration will be explained with reference to the drawings.

1 and 2, a flyback pulse v _cd shown in FIG. 5a is generated between the cathode side C of the damper diode 2 and the anode side D of the damper diode 2, and the flyback pulse v cd shown in FIG. The cathode side of the diode 3 (the damper diode 2
A flyback pulse v _de shown in FIG. The peak value of v _ce is approximately the sum of the peak values of flyback pulses v _cd and v _de , as shown in FIG. 5c. Then, by applying the flyback pulse v _ce to the primary winding 12a of the flyback transformer 12,
A boosted flyback pulse (not shown) is generated in the high voltage winding 12b, rectified by the high voltage rectifier circuit 13 (anode voltage V _HV ), and applied to the anode 16a of the CRT 16. Note that if the anode current I _HV is at its minimum here, the 15th
As shown in the figure, the voltage Vb at the output terminal B of the anode current detection circuit 33 is at its maximum, and at this point the DC voltage at the output terminal F of the current amplification circuit 26 increases.
Vf also reaches its maximum in proportion to voltage Vb, but the drive pulse v _dp of the switching drive pulse shaping circuit 23 is superimposed at point F,
Actually, as shown in FIG. 3, the drive pulse
The peak value of v _dp becomes voltage Vf, and at this time voltage Vf is at its maximum. Therefore, the resistance value between the collector and emitter of the transistor 19 decreases during the flyback pulse period, and as a result, the capacitance value of the variable capacitance circuit 17 increases. Flyback pulses v _cd , v _de , and
The state of v _ce is shown by the solid lines in Figure 5 a, b, and c.
Furthermore, if we look at the flyback pulse v _de occurring between points D and E in terms of the vertical scanning period, the seventh
As shown in the figure, the parabolic left and right pincushion distortion correction signal voltage va of the vertical scanning period from the left and right pincushion distortion correction signal generation circuit 11 shown in FIG.
is superimposed via the inductor 9, which converts the horizontal deflection current iy flowing through the horizontal deflection coil 6 into the eighth
As shown in the figure, the left and right pincushion distortion of the image is corrected by amplitude modulation.

Next, if the anode current I _HV increases and reaches its maximum, the anode voltage V _HV will decrease due to the resistance of the circuit, and the flyback transformer 12 will decrease accordingly.
Since the load factor on the primary winding 12b _side of _{the main} winding 12b of do. However, as shown in FIG. 15, the voltage at the output terminal B of the anode current detection circuit 33
Vb becomes minimum, therefore, variable capacitance circuit 1
The peak value Vf of the drive pulse v _dp at point F of the input terminal No. 7 becomes small as shown in FIG. Therefore,
The resistance value between the collector and the emitter of the transistor 19 increases during the flyback pulse period, so that the capacitance value of the variable capacitance circuit 17 decreases, and the combined capacitance value with the resonant capacitor 5 also decreases. As a result, as can be seen from the relationship in equation (1) above, the peak value of the flyback pulse v _de occurring between D and E is as shown by the solid line in Figure 6b. The wave height value of _{the flyback} pulse v de increases by the amount that the wave height value of the flyback pulse v _de was about to become smaller.
Therefore, as shown by the solid line in FIG. 6c, the peak value of the flyback pulse v _ce is corrected to the same state as when the anode current I _HV is at its minimum. The peak value of the pulse and the anode voltage _VHV applied to the anode terminal 16a of the CRT 16 are also corrected to the state when the anode current _IHV is at its minimum.

On the other hand, in the above state, the level of the parabolic left and right pincushion distortion correction signal in the vertical scanning period superimposed on the flyback pulse v _de occurring between D and E is determined by the resonance capacitor 5 and the variable capacitance circuit 17. As the combined capacitance becomes smaller and the integral time constant with the inductor 9 becomes smaller, it becomes larger as shown in FIG. The amplitude modulation level of the correction becomes larger.

<Effects of the invention> As is clear from the above detailed explanation, the horizontal circuit of the invention suppresses fluctuations in the anode voltage due to changes in the anode current, and reduces the vertical scanning period of the anode voltage due to changes in the anode current. Since left and right pincushion distortion correction is performed at the same time at a level proportional to the ripple content, even if the anode current is changed by adjusting the contrast or brightness control of the equipment, or
Even if the anode current fluctuates greatly due to the image information displayed on the CRT, the amplitude in the horizontal and vertical directions is always stable, and a stable image is reproduced with almost no left-right pincushion distortion or trapezoidal distortion. That will happen.

Further, in the present invention, since the resonant circuit of the horizontal output circuit is divided into two and the variable capacitance circuit is controlled at the midpoint thereof, the withstand voltage of the transistor of the variable capacitance circuit may be small; By operating the transistor by switching, the loss becomes very small, so the power consumption of the transistor can be small, and a heat sink is not required, so that an inexpensive circuit can be provided.

In the embodiment of the present invention, the left and right pincushion distortion correction signals for correcting the left and right pincushion distortion are applied directly to the horizontal deflection circuit via the inductor, but the left and right pincushion distortion correction signals are applied directly to the horizontal deflection circuit through the inductor. Of course, the circuit of the present invention can also be applied to horizontal circuits that apply .

[Brief explanation of the drawing]

Fig. 1 is a block diagram of one embodiment of the horizontal circuit of the present invention, Fig. 2 is a specific circuit diagram of the horizontal circuit of Fig. 1, and Figs. 3 to 10 are waveform diagrams for explaining the present invention. , FIG. 11, and FIG. 12 are conventional horizontal circuits, and FIGS. 13 to 17 are waveform diagrams and characteristic diagrams for explaining the conventional example and the horizontal circuit of the present invention. DESCRIPTION OF SYMBOLS 1... Horizontal output transistor, 2... Damper diode, 3... Damper diode, 4... Resonance capacitor, 5... Resonance capacitor, 6... Horizontal deflection coil, 7... S-shaped correction capacitor, 8...
Left and right pincushion distortion correction circuit, 9...Inductor,
10... Capacitor, 11... Left and right pincushion distortion correction signal generation circuit, 12... Flyback transformer, 12a... Primary winding, 12b... High voltage winding,
13... High voltage rectifier circuit, 14... Rectifier diode, 15... CRT stray capacitance, 16... CRT, 1
6a... Anode, 17... Variable capacitance circuit, 18
...Capacitor, 19...Transistor, 20...
...damper diode, 21...protection diode,
22... Resistor, 23... Switching drive pulse shaping circuit, 24... Resistor, 25... Capacitor, 26... Current amplification circuit, 27... Transistor, 28... Bias resistor, 29... Protection diode, 30 ...transistor, 31, 32...voltage division resistor, 33...anode current detection circuit,
34... Bypass capacitor, 35, 36... Resistor for anode current detection, 37... Variable capacitance circuit,
38...Capacitor, 39...Transistor, 4
0... Damper diode, 41... Capacitor,
42...Resistance.

Claims (1)

[Claims for Utility Model Registration] 1. A DC power supply is connected to both ends of a horizontal output transistor 1 which is controlled to be turned on and off in a horizontal period via a primary winding 12a of a flyback transformer 12. At both ends,
A series circuit of a pair of resonant capacitors 4 and 5, a series circuit of a pair of damper diodes 2 and 3, a horizontal deflection coil 6, and an inductor 9 to which a vertically periodic parabolic left-right pincushion distortion correction signal v _a is applied. The series circuits are connected in parallel to each other, and a connection midpoint between the pair of resonant capacitors 4 and 5;
A midpoint of the connection between the pair of damper diodes 2 and 3 and a midpoint of the connection between the horizontal deflection coil 6 and the inductor 9 are connected to each other, and the midpoint of the connection is set in accordance with the anode current _IHV of the cathode ray tube 16 A horizontal circuit in a television receiver, characterized in that it is connected to a variable capacitance circuit 17 whose capacitance changes. 2 The variable capacitance circuit 17 receives the flyback pulse from the flyback pulse transformer 12.
A horizontal circuit in a television receiver according to claim 1, characterized in that the switching operation is performed at v _ce .