JPH0132444Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horizontal screen amplitude adjustment circuit that greatly reduces circuit loss.

Conventionally, in display devices using cathode ray tubes, there have been two types: a flyback transformer system in which the deflection circuit and high voltage generation circuit are not separated in terms of circuits as shown in Figure 1-A, and a deflection circuit and high voltage generation circuit as shown in Figure 1-B. There is a deflection/high pressure separation method that separates the
The method shown in Figure 1-A produces ringing on the screen.
If you change the horizontal screen width, the high voltage will also change.
It has problems such as the screen width changing due to temperature changes. Therefore, the method shown in FIG. 1-B is mainly used in display devices and the like where performance is important.

As shown in Fig. 1-B, the horizontal screen width adjustment method uses a horizontal deflection output circuit 1 consisting of a horizontal deflection output transistor Q0, a resonant capacitor C0, and a damper diode D0, and a power supply. The horizontal screen width is adjusted by changing the value of the resistor R inserted between the terminal 10 and the level of the deflection output pulse supplied to the deflection yoke DY.
As shown in Figure 3, the horizontal deflection output transistor Q
The voltage control transistor Q1 is controlled by the detection voltage generated at the zero emitter resistor R1 and the control circuit 3 to change the voltage supplied to the horizontal deflection output circuit 1, thereby adjusting the horizontal screen width. As shown in FIG. 4, a control voltage is generated from the reference voltage input to the control circuit 4 and a voltage corresponding to the horizontal screen width, and a current flows through the control transistor Q2 using the control voltage.
That is, the horizontal screen width is adjusted by controlling the current flowing through the horizontal deflection output circuit 1 and the deflection yoke DY. There are methods such as, but the heat dissipation device becomes large because the heat loss of resistors and control transistors reaches tens of watts, it is impossible to widen the variable range of horizontal screen width, it is impossible to increase the horizontal frequency, etc. It has various problems such as reduced reliability due to heat generation.

The present invention aims to provide a horizontal screen width adjustment circuit with low heat loss that eliminates the above-mentioned problems.

The contents of the present invention will be explained below with reference to the drawings.

FIG. 5 is a block diagram of the horizontal screen width adjustment circuit according to the present invention, which includes the horizontal deflection output circuit 1, deflection yoke DY, pulse transformer T, integration circuit 5, voltage comparator circuit 6, impedance conversion circuit 7, and pulse width adjustment circuit. - current conversion circuit 8. FIG. 6 shows an embodiment of FIG. 5, in which the horizontal deflection pulse inputted from the input terminal 9 is amplified by the horizontal deflection output transistor Q0, and then sent to the deflection yoke DY and the oscillation circuit 2 for high voltage generation. It is supplied to the primary side of the pulse transformer T. A pulse similar to the horizontal deflection pulse supplied to the primary side and at a lower level is induced on the secondary side of the pulse transformer T,
The signal is sent to an integrating circuit 5 composed of a resistor R11 and a capacitor C11, converted into a sawtooth wave, and input to the base of a transistor Q11. The voltage comparator circuit 6 is composed of a resistor, a transistor Q11, and a transistor Q12, and the horizontal screen width is determined by the sawtooth wave input to the base of the transistor Q11 and the variable resistor VR11 input to the base of the transistor Q12. A pulse having a pulse width corresponding to the horizontal screen width is output to the collector of the transistor Q12. The pulse is amplified by transistor Q13,
The impedance is reduced by the impedance conversion circuit 7, which is a symmetric emitter follower circuit composed of transistors Q14 and Q15, and is input to the gate of the field effect transistor Q16. A pulse width-current conversion circuit 8 is constituted by a field effect transistor Q16 and a chiyoke coil L inserted between the drain of the field effect transistor Q16, the horizontal deflection output circuit 1, and the deflection yoke circuit 11. An average current proportional to the width of the pulse input to the gate of the current flows through the chiyoke coil L. That is, since the average current also flows through the field effect transistor Q16, the heat loss in FIG. 6 is reduced to about 10% to 20% of the conventional example.

As explained above, the horizontal screen width adjustment circuit according to the present invention has very low heat loss, so the heat dissipation device can be made smaller, screen width fluctuations due to thermal changes are small, and performance deterioration of components due to heat is minimal. This improves reliability, reduces heat loss so it can handle high horizontal frequencies, and the circuit itself forms a feedback circuit, which stabilizes the screen width. There is something of great value.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the horizontal deflection and high voltage generation system in a display device using a cathode ray tube, Figures 2 to 4 are conventional examples of horizontal screen width adjustment circuits, and Figures 5 and 6 are 1 shows a block diagram and an embodiment of a horizontal screen width adjustment circuit according to the present invention. 1, 1'... horizontal deflection output circuit, 2... oscillation circuit,
3, 4...Control circuit, 5...Integrator circuit, 6...Voltage comparator circuit, 7...Impedance conversion circuit, 8
...Pulse width-current conversion circuit, 9...Input terminal, 10
...Power supply terminal, 11...Deflection yoke circuit, DY...
Deflection yoke, T...pulse transformer, L...chiyoke coil, Q0 to Q2, Q11 to Q15...transistor, Q16...field effect transistor, C0, C
1, C11... Capacitor, D0... Diode,
R, R11 to R14...Resistor, VR11...Variable resistor.

Claims (1)

[Scope of utility model registration request] In a display device using a cathode ray tube in which the horizontal deflection output circuit and the high voltage generation circuit are separated in terms of circuits, an integrating circuit that generates a sawtooth wave from the horizontal deflection output pulse, and correspondence between the sawtooth wave and the horizontal screen width. a voltage comparator circuit consisting of two transistors and a plurality of resistors to create a pulse having a pulse width corresponding to the horizontal screen width from the reference voltage, and a symmetrical emitter circuit to reduce the impedance of the pulse. An impedance conversion circuit using a coupling circuit, and a pulse width-to-current conversion circuit consisting of a yoke coil and a field effect transistor that control current flowing through the horizontal deflection output circuit and the deflection yoke circuit by the low impedance pulse. A horizontal screen width adjustment circuit.