JPH0434612Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] This invention relates to a vertical deflection linearity correction circuit for correcting linearity distortion due to screen brightness in a vertical deflection circuit of a television receiver. [Technical Background of the Invention] A conventional device of this type is shown in FIG. 6. In this FIG. 6, 1 is a vertical sawtooth wave voltage input terminal synchronized with a vertical synchronizing signal, and the vertical sawtooth wave voltage signal of this vertical sawtooth wave voltage input terminal 1 is amplified by a vertical deflection amplifier 2 to drive a vertical deflection yoke 5. I'm starting to do that. The output end of this vertical deflection amplifier 2 is grounded via a vertical deflection yoke 5, a DC blocking capacitor 6, and a current feedback resistor 7. The connection point between the vertical deflection yoke 5 and the DC blocking capacitor 6 is connected to the input terminal of the vertical deflection amplifier 2 via the DC feedback circuit 3, and the connection point between the DC blocking capacitor 6 and the current feedback resistor 7 is connected to the input terminal of the vertical deflection amplifier 2 via the DC feedback circuit 3. It is connected to the input end of the vertical deflection amplifier 2 via an AC feedback circuit 4. The vertical deflection yoke 5 is a vertical deflection yoke for vertically deflecting the electron beam of a cathode ray tube of a television receiver, and is attached to the neck of the cathode ray tube. Next, the operation will be explained. The vertical sawtooth voltage signal synchronized with the vertical synchronization signal is amplified by the vertical deflection amplifier 2, and a sawtooth wave current synchronized with the vertical synchronization signal is caused to flow through the vertical deflection yoke 5. At this time, the vertical sawtooth wave current becomes a sawtooth wave current 8 with a constant amplitude necessary for vertically deflecting the cathode ray tube to which the vertical deflection yoke 5 is attached.
At this time, the direct current blocking capacitor 6 prevents direct current from flowing through the vertical deflection yoke 5, and the direct current feedback circuit 3 holds the output direct current voltage of the vertical deflection amplifier 2. Further, AC feedback is applied to the vertical deflection amplifier 2 by an AC feedback circuit 4 and a current feedback resistor 7 to determine the gain. If a variable resistor is provided in this AC feedback circuit 4, the amplitude value of the sawtooth wave current can be changed. [Problems in the Background Art] Since the conventional vertical deflection circuit is configured as described above, a sawtooth wave current with a constant amplitude flows through the vertical deflection yoke 5, and the electron beam deflected in the vertical direction of the cathode ray tube is The raster of is also constant. Here, as shown in Fig. 7, if a part of the screen has low brightness areas a1, a2 and high brightness area b1, the anode voltage (high voltage) of the cathode ray tube is high in the low brightness areas a1, a2, and the high brightness areas At b1, the anode voltage (high voltage) becomes low. The deflection sensitivity of a cathode ray tube is given by θ for deflection sensitivity and Ea for high pressure.

[Purpose of invention]

This invention was made in order to eliminate the above-mentioned conventional drawbacks, and aims to provide a brightness-following type vertical deflection linearity correction circuit that can dynamically change the linearity of the vertical deflection current. [Summary of the invention] The vertical deflection linearity correction circuit of this invention is
A control transistor is activated in response to the brightness of the cathode ray tube, a power supply capacitor is charged in accordance with the brightness during operation, and a horizontal switching circuit is operated with a horizontal drive pulse to generate a horizontal current from the discharge current of the power supply capacitor. This horizontal current excites a saturable transformer and superimposes the horizontal current on the vertical deflection current of the vertical deflection circuit to correct vertical deflection linearity. [Embodiment of the invention] Hereinafter, an embodiment of the vertical deflection linearity correction circuit of the invention will be described based on the drawings. FIG. 1 is a circuit diagram showing the configuration of one embodiment. In this Fig. 1, the parts indicated by numerals 1 to 7 are the same as in Fig. 6, and in order to avoid duplication, the parts are given the same numerals, and the parts different from Fig. 6 are emphasized. I will explain this in detail. In FIG. 1, the parts indicated by reference numerals 9 and after are newly added parts according to this invention, and are the parts that are characteristic of this invention. That is, 9 is a drive pulse for a horizontal switching transistor 10 that performs horizontal period switching, 11 is a damper diode, and 12 is a resonant capacitor. The emitter of the horizontal switching transistor 10 is grounded, and the collector is connected to the voltage control transistor 1 via the primary coil L ₁ of the saturable transformer 19.
It is connected to emitter 6. A damper diode 11 and a resonant capacitor 12 are connected between the collector and emitter of the horizontal switching transistor 10.
parallel circuits are connected. Both ends of the secondary coil L ₂ of the saturable transformer 19 are connected to both ends of the dump resistor 20 . This dump resistor 20 is connected between the vertical deflection yoke 5 and the DC blocking capacitor 6. On the other hand, high voltage detection resistors 14 and 15 are inserted in series between the cathode ray tube high voltage and the ground, and a connection point between these high voltage detection resistors 14 and 15 is connected to the base of a voltage control transistor 16. The collector of this voltage control transistor 16 is connected to a power supply 17, and the emitter is connected to a power supply capacitor 18.
It is grounded through. Next, the operation of this invention will be explained. The circuit consisting of the horizontal switching transistor 10, the damper diode 11, the resonant capacitor 12, and the primary coil L1 side of the saturable transformer ₁₉ operates similar to a type of horizontal deflection circuit, and horizontal switching is performed by the horizontal drive pulse 9. The transistor 10 is driven to cause a vertical sawtooth wave current to flow through the primary coil _L1 side of the saturable transformer 19. This current is induced in the secondary coil _L2 side of the saturable transformer 19. On the other hand, the conventional vertical deflection circuits 1 to 7 function to superimpose a horizontal deflection current 20 on the vertical deflection current 8 flowing through the vertical deflection yoke 5 as shown in FIG. In this Figure 2,
21 is the current that follows the brightness, 22 is the envelope waveform integrated by the vertical deflection yoke, the current on the left side of Fig. 2 is the vertical current waveform to which the correction signal is added, and the right side is the corresponding corrected cathode ray tube. It's a screen. 23a, 23 in the right part of this figure 2
b is a portion with low brightness, 24 is a portion with high brightness, the broken line shows the pattern 25 before correction, and the solid line shows the pattern 26 after correction. As described above, by superimposing the horizontal sawtooth wave current obtained by the power supply capacitor 18 and the horizontal switching circuit that switches with the horizontal drive pulse from the secondary coil L ₂ of the saturable transformer 19 on the vertical deflection current 8, the correction signal is Although an added vertical current waveform is obtained, the principle of operation of the saturable transformer 19 will now be explained. FIG. 3 is a diagram for explaining the principle of this saturable transformer 19. As shown in the figure, a current at the vertical deflection frequency is passed through the coil H on the input side. This current is normally supplied from a flyback transformer (not shown) in the television receiver circuit. If this current is I _M , a current I _V corresponding to this current I _M flows through the output coil V, but when no current flows through the output coil, the output coil has a voltage. It has the characteristic that when an uninduced current flows through the output coil, the voltage _EV is induced and increases accordingly. In general, the principle of what is called an open magnetic path reactor is that, as shown in Figure 3, there are two transformers with magnetic bias applied, and the output coils V are wired so that they are in opposite phase to each other. Normally, no output voltage would come out, but by passing current through the output coil V, the balance between the left and right magnetic biases is disrupted, and the two transformers T ₁ ,
It is designed so that a voltage difference of T ₂ is generated.
The operation according to the B-H curve is as shown in Fig. 4a, Fig. 4b, Fig. 5a, and Fig. 5b. Figures 4a and 4b are transformers T ₁ and 4b, respectively.
This is the characteristic of T ₂ , and it is balanced by the current Iv = o of the coil V on the output side in Fig. 3, and the output voltage
The case where Ev=o is shown, and Figures 5a and 5b respectively show that the bias point of transformers T ₁ and T ₂ moves when the current Iv = Io, and the output voltage becomes Ev = Eo. There is. Here, the explanation is shown in Figures 1 and 2.
Returning to the illustrated example. When the brightness on the cathode ray tube screen partially changes as shown in FIG. 7, the high voltage is high in the low brightness areas of the screen, and low in the high brightness areas. In FIG. 1, high voltage detection resistors 14 and 15 detect a cathode ray tube high voltage, and a voltage control transistor 16 is controlled to be turned on or off in accordance with the potential at the connection point thereof. When the voltage control transistor 16 is on, the power supply capacitor 18 is charged with the current from the power supply 17 through the voltage control transistor 16, and the voltage control transistor capacitor 18 is charged, and when the voltage control transistor 16 is turned off, the power supply Charging of capacitor 18 is stopped. On the other hand, a horizontal switching circuit including a horizontal switching transistor 10, a damper diode 11, and a resonant capacitor 12 generates a horizontal drive pulse 9.
The on/off switching operation is performed by the . When the horizontal switching transistor 10 is turned on, the charging voltage of the power supply capacitor 18 is applied as a power supply to the horizontal switching circuit, and the electric charge of the power supply capacitor 18 is transferred to one of the saturable transformers 19.
It flows through the next coil _L1 to the horizontal switching circuit. As a result, the horizontal current i of this horizontal switching circuit is determined by i=Vcc/L ₁ t, and becomes a horizontal sawtooth wave current. Here, Vcc is the voltage stored in the power supply capacitor 18, _L1 is the inductance of the saturable transformer 19, and t is the horizontal frequency period period. In a circuit that operates in this way, when the cathode ray tube high voltage 13 becomes low, the high voltage detection resistors 14, 1
5 and controls the voltage control transistor 16 to lower the power supply voltage of the horizontal switching circuit (the voltage stored in the power supply capacitor 18). For this reason, the amplitude of the horizontal current i decreases, and therefore the amplitude of the horizontal current superimposed on the vertical deflection current as described above also decreases, and the vertical deflection sensitivity is lowered in high brightness areas to correct linearity. It is something. Conversely, in a portion of the screen where the brightness is low, the amplitude of the horizontal deflection current i increases, the vertical deflection sensitivity increases, and the linearity is corrected to the solid line portion on the right side of FIG. 2, resulting in a correction pattern 26. Incidentally, since the horizontal deflection current 20 in FIG. 2 has a large reactance of the vertical deflection yoke 5, it is integrated as shown by the dotted line in the figure. In the above embodiment, the high voltage 13 of a cathode ray tube is used as the high voltage, but a luminance signal or an ABL current may be detected and an inverting circuit may be added. Alternatively, a resonant circuit may be provided between the saturable transformer 19 and the vertical deflection circuit, and the circuit may be shared to perform vertical DPC correction. [Effects of the invention] As described above, according to the vertical deflection linearity correction circuit of this invention, by superimposing the horizontal current that follows the brightness on the vertical deflection current through the saturable transformer, fluctuations in vertical linearity due to changes in brightness are suppressed. Since the vertical deflection current is corrected, the linearity of the vertical deflection current can be dynamically changed, and the original screen pattern can be reproduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the vertical deflection linearity correction circuit of this invention, and FIG. 2 is a diagram showing the vertical deflection current corrected by the vertical deflection linearity correction circuit and the corrected cathode ray tube screen.
Figure 3 is a diagram for explaining the principle of the saturable transformer in the vertical deflection linearity correction circuit as above.
4a and 4b are diagrams showing the relationship between the current on the input side and the magnetic field when the output currents of the first and second transformers of the saturable transformer of FIG. 3 are balanced,
Figures 5a and 5b are diagrams showing the relationship between the current on the input side and the magnetic field when the input currents of the first and second transformers of the third saturable transformer are unbalanced. FIG. 7 is a diagram showing a cathode ray tube screen in which vertical linearity changes due to changes in brightness in the vertical deflection circuit of FIG. 3...DC feedback circuit, 4...AC feedback circuit, 5
... Vertical deflection yoke, 6 ... DC blocking capacitor, 7 ... Current feedback resistor, 10 ... Horizontal switching transistor, 11 ... Damper diode,
12... Resonance capacitor, 14, 15... High voltage detection resistor, 16... Voltage control transistor, 18...
...power supply capacitor, 19...saturable transformer.

Claims (1)

[Scope of utility model registration request] A vertical deflection circuit, a voltage control transistor that operates according to the brightness of the cathode ray tube, a power supply capacitor that is charged according to the brightness when the voltage control transistor operates, and a power supply capacitor that is driven by a horizontal drive pulse to charge the power supply capacitor. It consists of a horizontal switching circuit that generates a horizontal current using a discharge current, and a saturable transformer that is excited by the horizontal current generated by the horizontal switching circuit and superimposes this horizontal current on the vertical deflection current flowing through the vertical deflection circuit. Vertical deflection linearity correction circuit.