JPH07283959A - Horizontal amplitude correction circuit - Google Patents

Abstract

(57) [Summary] [Purpose] The purpose is to correct changes in screen size due to high-voltage fluctuations. [Structure] A detection circuit 25 is provided at a high voltage terminal of a secondary coil of an FBT that generates high voltage, and an amplified voltage is amplified by an amplification circuit 26 and input to a parabolic amplification circuit 28 to vary a DC voltage of a parabolic signal. Correct the horizontal amplitude of the monitor with.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a horizontal amplitude correction circuit and, more particularly, to keeping a screen size constant against variations in high voltage.

[0002]

2. Description of the Related Art As shown in FIG. 2, a conventional horizontal deflection circuit generates a parabolic signal with a vertical period so that the raster amplitude becomes larger toward the center of the screen in the parabolic signal generation circuit 1 in order to correct the left and right pincushion distortion. Then, the parabolic signal is input to the parabolic amplifier circuit 2. On the other hand, to adjust the horizontal amplitude of the screen, the input terminal 3 of the parabola amplifier circuit 2 is used.
A horizontal amplitude adjusting voltage was applied to the variable voltage and the DC voltage of the parabolic signal was varied to adjust the voltage. The parabolic signal thus formed is amplified and driven by the horizontal output circuit 4 to pass a deflection current to the horizontal deflection coil 5 to horizontally deflect the CRT.

The connection of the high voltage generating circuit and the deflection circuit is as follows. The collector of the horizontal output transistor 6 is connected to the power supply + B via the primary coil 7a of the flyback transformer and the resistor 16 and is also connected to one end of the horizontal deflection coil 5. High voltage (HV) is generated in the secondary coil 7b of the flyback transformer, and CR (not shown)
It is connected to the anode of T. On the other hand, the other end of the horizontal deflection coil 5 is connected via a series circuit composed of a capacitor 8, a coil 9 and a capacitor 10, and together with these series circuits forms a load circuit of the horizontal output transistor 6. The collector of the transistor 11 of the horizontal output circuit 4 is
It is connected to the intersection of the coil 9 and the capacitor 10 of the load circuit.

Between the collector and emitter of the horizontal output transistor 6, a series circuit of damper diodes 12 and 13 and a series circuit of resonance capacitors 14 and 15 are provided.
Each is connected in parallel. However, diode 1
The intersection of 2 and 13 and the intersection of the capacitors 14 and 15 are connected to each other, and the connection point is further connected to the intersection of the coil 9 and the capacitor 8. Then, the parabolic signal amplified from the collector of the transistor 11 is applied to the coil 9, the deflection current is modulated into a parabolic wave, and the left and right pincushion distortion is corrected.

A monitor provided with the circuit having the above-mentioned configuration, for example,
When the image signal from a personal computer or the like is displayed, the horizontal size of the screen changes when the screen becomes bright or dark, so the change was corrected by inserting the resistor 16 into the circuit. When the change is large, there is a problem that the correction cannot be completed. In addition, the horizontal frequency is 15.7KHZ, 31.3K in the monitor that adopts the multi-scan method to support the video signals with different resolutions.
It is necessary to switch to HZ, 48.3KHZ or the like, and the + B voltage of the power source changes each time the horizontal frequency is switched. Therefore, as shown in FIG. 3, a switching terminal is provided in the primary coil 7 of the flyback transformer, and switching is performed every time the frequency is changed by the relay 16, and the secondary coil of the flyback transformer is provided.
The high pressure value generated in 7b was kept constant. In this circuit, since the capacitor 18 is connected between the terminal of the relay 17 and the ground in order to stabilize the voltage, the correction function of the resistor 16 for correcting the horizontal size of the screen is lost, and a correction circuit in place of the resistor 16 is required. Has become.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to correct a change in screen size due to a high voltage fluctuation.

[0007]

In order to solve the above problems, according to the present invention, a parabolic amplifier circuit varies a direct current voltage of a parabolic signal from a parabolic signal generating circuit, amplifies the varied parabolic signal, and outputs a horizontal output. Driven by a circuit,
In a horizontal deflection circuit of a monitor that supplies a deflection current to a horizontal deflection coil, ground one end of a secondary coil of an FBT through a diode and a series circuit of a first resistor and a second resistor, and ground the other end of the secondary coil. A detection circuit that outputs a detection signal from a connection point of the first resistance and the second resistance; and an amplification circuit that amplifies the detection signal from the detection circuit, and the output of the amplification circuit is input to the parabolic amplification circuit, A horizontal amplitude correction circuit characterized in that the horizontal amplitude of the monitor is corrected by varying the DC voltage of the parabolic signal.

[0008]

According to the above construction, the detection circuit is provided at the high voltage terminal of the secondary coil of the FBT that generates high voltage, the detected voltage is amplified by the amplifier circuit and input to the parabola amplifier circuit, and the DC voltage of the parabolic signal is converted. The horizontal amplitude of the monitor is corrected by making it variable.

[0009]

Embodiments of the present invention will be described in detail with reference to the accompanying drawings. As shown in FIG. 1, the flyback transformer 2
One end of the secondary coil 21 of 0 is connected to the high voltage terminal 45 via the rectifying diode 22, and is grounded via the series circuit of the resistor 23 and the resistor 24, and the other end of the secondary coil 21 is grounded. The detection circuit 25 includes resistors 23 and 24.
It is composed of a series circuit. The output of the detection circuit 25 is connected to the operational amplifier 27 of the amplifier circuit 26, and the output of the amplifier circuit 26 is connected to the output terminal 46 of the parabolic amplifier circuit 28. The parabola generation circuit 30 is connected to the input terminal 29 of the parabolic amplifier circuit 28, and the DC voltage of the parabolic signal is changed by inputting the horizontal amplitude adjustment voltage for adjusting the horizontal amplitude of the screen to the input terminal 31. The horizontal amplitude is adjusted. On the other hand, the output terminal 32 is connected to the horizontal output circuit 33.

The collector of the horizontal output transistor 34 is connected to the power source + B via the primary coil 35 and the relay 47 of the flyback transformer 20, and is also connected to one end of the horizontal deflection coil 36. The other end of the horizontal deflection coil 36 is connected through a series circuit including a capacitor 37, a coil 38 and a capacitor 39, and forms a load circuit of the horizontal output transistor 34 together with these series circuits. Horizontal output circuit
The collector of the transistor 40 of 33 is connected to the intersection of the coil 38 and the capacitor 39 of the load circuit. A series circuit of damper diodes 41 and 42 and a series circuit of resonance capacitors 43 and 44 are connected in parallel between the collector and the emitter of the horizontal output transistor 34. However, the intersections of the diodes 41 and 42 and the intersections of the capacitors 43 and 44 are connected to each other, and the connection point is further connected to the intersection of the coil 38 and the capacitor 37.

In the above structure, a high voltage is generated in the secondary coil 21 of the flyback transformer 20, and the diode 2
The high-voltage DC voltage rectified in 2 is connected to the anode of the CRT (not shown) via the terminal 45. The + B voltage fluctuates when the monitor screen becomes bright or dark due to video signals from a personal computer, etc.
As a result, the high voltage (HV) of the terminal 45 changes, and the horizontal size of the screen changes. If the high voltage (HV) becomes high, the midpoint of the series circuit of the series circuit resistor 23 and the resistor 24 becomes high as the voltage of the terminal 45 rises, and the input voltage value of the operational amplifier 27 rises. As a result, the voltage of the output of the operational amplifier 27 is reduced by an amount commensurate with it, the DC voltage value of the parabolic wave is lowered in the parabolic amplifier circuit 28, and the screen size is corrected to the original size. And high voltage (HV)
Becomes low, the midpoint of the series circuit of the series circuit resistor 23 and the resistor 24 becomes low as the voltage at the terminal 45 drops, and the input voltage value of the operational amplifier 27 rises. As a result, the output of the operational amplifier 27 raises the voltage by an amount commensurate with it, the DC voltage value of the parabolic wave in the parabolic amplifier circuit 28 increases, and the screen size is corrected to the original size.

[0012]

As described above, according to the present invention, the change in the high voltage on the secondary side of the flyback transformer is detected by the detecting section, and the detected direct current voltage of the parabolic wave is controlled. Even if the horizontal screen size changes due to the change, the screen size can be corrected correspondingly, the correction limit of the conventional correction circuit is eliminated, and even a large change can be corrected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a horizontal amplitude correction circuit of the present invention.

FIG. 2 is a circuit diagram of a conventional horizontal amplitude correction circuit.

FIG. 3 is another circuit diagram of a conventional horizontal amplitude correction circuit.

[Explanation of symbols]

 25 Detection circuit 26 Amplification circuit 28 Parabola amplification circuit 30 Parabola generation circuit 33 Horizontal output circuit

Claims (1)

[Claims] 1. A parabolic amplifier circuit varies a direct current voltage of a parabolic signal from a parabolic signal generation circuit, amplifies the varied parabolic signal, and drives the horizontal output circuit.
In a horizontal deflection circuit of a monitor that supplies a deflection current to a horizontal deflection coil, ground one end of a secondary coil of an FBT through a diode and a series circuit of a first resistor and a second resistor, and ground the other end of the secondary coil. A detection circuit that outputs a detection signal from a connection point of the first resistance and the second resistance; and an amplification circuit that amplifies the detection signal from the detection circuit, and the output of the amplification circuit is input to the parabolic amplification circuit, A horizontal amplitude correction circuit characterized in that the horizontal amplitude of the monitor is corrected by varying the DC voltage of the parabolic signal.