KR100248288B1 - High voltage regulation circuit of monitor - Google Patents

Abstract

According to the present invention, a high voltage regulation circuit for stabilizing a high voltage by directly controlling a B + voltage in order to prevent the size of a screen from being fluctuated according to the brightness of a CRT screen in a monitor detects the magnitude of the anode current flowing in the high voltage line. A node current detector 10; When the anode current is changed and the B + voltage is changed, the voltage control unit 20 receives a control signal output from the anode current sensing unit 10 and adjusts the voltage at both ends of the correction capacitor Cs to be constant. When the anode current is normal, the voltage at both ends of the correction capacitor is varied in proportion to the variable B + voltage, and when the anode current is changed, the voltage at both ends of the compensation capacitor is variable but the voltage at both ends of the correction capacitor is constant. It is possible to maintain the size of the screen, thereby preventing the size of the screen from changing.

Description

Monitor's High Voltage Regulation Circuit

The present invention relates to a high voltage regulation circuit for stabilizing high voltage by directly controlling the B + voltage in order to prevent the size of the screen from varying according to the brightness of the CRT screen in the monitor.

In general, CRT beam current (i.e. anode current) varies depending on the brightness of the screen. This is a load change from the point of view of the FBT. The high voltage of the FBT is changed according to the change of the beam current, and the screen size is changed accordingly. In general, when the screen is dark and the beam current is small, the high pressure becomes high and accordingly, the horizontal size becomes small. On the contrary, when the screen is bright, the horizontal current increases because the beam current increases and the high pressure is lowered.

That is, in the CRT, the size of the screen depends on the amount of deflection (the larger the deflection amount, the larger the screen, and the smaller the deflection amount, the smaller the screen). The deflection amount is approximately expressed by the following equation (1).

[Equation 1]

'는 편향코일의 길이이며, 'L'은 편향점에서 형광면까지의 거리이다. 또한, 'Va'는 수상관의 아노드 전압(anode voltage)이다.Here, 'B' is the magnitude of the magnetic field, which is proportional to the product of the number of turns of the deflection coil and the current (i _dy ) flowing in the coil,

'Is the length of the deflection coil, and' L 'is the distance from the deflection point to the fluorescent surface. In addition, 'Va' is the anode voltage of the water pipe.

및 L은 고정상수이므로 편향량은 'B'에 따라 가변되는데, 편향코일의 턴수도 고정 상수값을 가지므로 통상 편향코일에 흐르는 전류(i_dy)에 따라 편향량이 정해진다. 따라서, 수평 및 수직 편향회로에서는 톱니파 전류를 발생하여 이 편향코일에 흐르게 함으로써 빔을 편향시켜 화면을 형성하게 된다.When the voltage of the anode is constant in Equation 1,

Since L and L are fixed constants, the amount of deflection varies according to 'B', and since the number of turns of the deflection coil also has a fixed constant value, the amount of deflection is usually determined according to the current i _dy flowing in the deflection coil. Therefore, in the horizontal and vertical deflection circuits, a sawtooth wave current is generated and flows through the deflection coil to deflect the beam to form a screen.

However, since the voltage of the anode is changed in practice, the amount of deflection changes according to the anode voltage. As shown in Equation 1, as the anode voltage increases, the amount of deflection decreases and the screen size decreases accordingly. It can be seen that as the node voltage decreases, the amount of deflection increases and the screen increases.

On the other hand, the voltage (high voltage) of the anode of the CRT is expressed by the following equation (2).

[Equation 2]

Here, 'Va ₀ ' is the anode voltage when the anode current is '0', 'Rs' is the internal resistance of the CRT, and 'Ia' is the anode current.

Therefore, as the current Ia of the anode increases, the voltage Va of the anode decreases, and when the voltage Va of the anode decreases, the amount of deflection increases according to Equation 1, thereby increasing the size of the screen. On the contrary, as the current Ia of the anode decreases, the voltage Va of the anode increases, and as the voltage of the anode increases, the amount of deflection decreases according to Equation 1, thereby reducing the size of the screen.

However, since the current Ia of the anode increases when the brightness of the screen becomes bright, and decreases when the screen becomes dark, the size of the screen eventually changes according to the brightness of the screen. As the current increases, the size of the screen becomes larger, and when the screen becomes dark, the anode current decreases and the screen becomes smaller.

Meanwhile, referring to the configuration of a general monitor, as shown in FIG. 1, the power supply 110, the DC-DC converter 120, the high voltage generator (FBT) 130, the oscillator 140, the horizontal driver 150, and the horizontal The output unit 160 and the like.

Referring to FIG. 1, the DC-DC converter 120 converts the DC voltage output from the power supply 110 into a predetermined B + voltage and applies it to the primary winding of the FBT 130, and applies the B + voltage of the primary winding. The horizontal output unit 160 switches according to the horizontal drive signal H. drive to generate a high voltage HV at the secondary winding side of the FBT 130.

At this time, the high voltage (HV) generated in the secondary winding of the FBT 130 is applied to the anode of the CRT, divided by the resistors, and then applied to the focus grid FOCUS and the screen grid SCREEN of the CRT, respectively. have.

In addition, the voltage induced in the cubic coil of the FBT 130 is rectified in the diode D1 and smoothed in the electrolytic capacitor C1 and then applied to the DC-DC converter 120 as the control voltage Vc. When the anode current increases and the high voltage decreases, the control voltage Vc decreases, and when the control voltage Vc decreases, the B + voltage increases to restore the high voltage.

However, as described above, when the voltage B + increases, the voltage across the correction capacitor Cs increases, and the magnitude of the current i _dy flowing in the deflection coil increases as a whole. As a result, the magnetic field B increases, according to Equation (1). The deflection amount of the electron beam is increased as a whole. That is, even if the high pressure is restored to the original state as described above, the size of the screen increases as the amount of deflection of the electron beam increases.

In order to improve the phenomenon that the size of the screen changes according to the brightness of the screen as described above, a method of separating the high voltage circuit and the deflection circuit is used, but the price is very high because expensive semiconductor switching elements and transformers must be added. There is this.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, and provides a high-voltage regulation circuit of a monitor having a constant screen size according to the brightness of the screen even when the high-voltage circuit and the deflection circuit are integrally configured. Its purpose is to.

In order to achieve the above object, the circuit of the present invention, by switching the B + voltage applied to the primary winding of the FBT in accordance with the horizontal drive signal output from the horizontal oscillator to generate a high voltage in the secondary winding of the FBT, the FBT A method of detecting a high voltage through a voltage induced in a tertiary winding of the monitor by applying a control voltage to a DC-DC converter, wherein the B + voltage is varied, and when the B + voltage is varied, the voltage across the correction capacitor is varied;

An anode current detector for sensing a magnitude of the anode current flowing in the high voltage line;

The voltage control unit is configured to adjust the voltage across the correction capacitor by receiving a control signal output from the anode current sensing unit when the anode current is varied and the B + voltage is variable.

1 is a block diagram showing the configuration of a general monitor;

2 is a circuit diagram showing the configuration of a monitor to which the high voltage regulation circuit according to the present invention is applied.

* Explanation of symbols for main parts of the drawings

10: anode current sensing unit 11: driving voltage divider

15: first buffering means 20: voltage regulator

21: comparator 22: second buffering means

120: DC-DC converter 130: FBT

Cs: compensation capacitor

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 2, the high voltage regulation circuit according to the present invention includes an anode current sensing unit 10 for sensing the magnitude of the anode current flowing in the high voltage line, and when the anode current is varied so that the B + voltage is varied. The voltage adjusting unit 20 receives the control signal output from the anode current sensing unit 10 and adjusts the voltage at both ends of the correction capacitor Cs to be constant.

Here, the anode current detection unit 10 is a driving voltage divider for varying the control voltage applied to the first buffering means 15 by varying the divided voltage ratio of the driving voltage (Vi) in accordance with the magnitude of the anode current. (11) and the first buffering means (15) for supplying a control signal whose voltage value is varied according to the control voltage applied from the driving voltage dividing unit (11) to the voltage adjusting unit (20).

The driving voltage dividing unit 11 is connected in series with an eleventh resistor R11 for dividing the driving voltage Vi and the eleventh resistor R11 to divide the driving voltage Vi, and at the same time, And a twelfth resistor R12 connected between the FBT 130 and serving as a passage for the anode current, wherein the first buffering means 15 divides the control voltage (node B) into a thirteenth resistor R13. And the fourteenth resistor R14, {the common contact point of the thirteenth resistor R13 and the fourteenth resistor R14}, and the base terminal, are proportional to the magnitude of the voltage applied to the fourteenth resistor R14. An eleventh transistor Q11 for outputting an emitter current and a fifteenth resistor R15 to which a control signal having a voltage value proportional to the emitter current of the eleventh transistor Q11 is applied.

When the anode current is varied, the control voltage (potential of node B) applied to the twelfth resistor R12 is varied and the control voltage is applied to the first buffering means 15, and the fifteenth resistor R15 is applied. Is applied to the voltage adjusting unit 20.

Here, the voltage adjusting unit 20 may include a B + voltage divider for dividing the B + voltage, a capacitor divider for dividing the voltages across the correction capacitor Cs, and a first divided voltage output from the capacitor divider. A comparator 21 for comparing the potential of C) and the second divided voltage (potential of the node D) or the control signal output from the anode current sensing unit 10 outputted from the B + voltage divider and the comparator ( The second buffering means 25 adjusts the magnitude of the voltage B + applied to the voltage across the correction capacitor Cs according to the comparison signal output from 21).

The B + voltage divider includes a twenty-first resistor (R21) and a twenty-second resistor (R22) so that a voltage (potential of node C) applied to the twenty-second resistor (R22) is applied to the non-inverting terminal of the comparator 21. The capacitor divider includes a twenty-third resistor (R23) and a twenty-fourth resistor (R24), and a voltage (potential of the node D) applied to the twenty-fourth resistor (R24) is applied to the inverting terminal of the comparator 21. And {the ratio of the twenty-first resistor R21 to the twenty-second resistor R22} is smaller than the {ratio of the twenty-third resistor R23 to the twenty-fourth resistor R24}.

The second buffering means 25 is a 21st transistor Q21 biased so that the emitter current increases when the comparison signal output from the comparator 21 increases, and the base end of the 21st transistor Q21 A twenty-second transistor (Q22) connected to the terminal terminal, the collector terminal connected to the B + voltage line, and the emitter terminal connected to {the common contact point of the correction capacitor (Cs) and the capacitor divided part} (node A); When the emitter current of the transistor Q21 increases, the emitter current of the twenty-second transistor Q22 decreases and is biased to limit the B + voltage applied to the voltage across the correction capacitor Cs.

Next, the operation and effects of the present invention configured as described above will be described in detail by dividing the case where the anode current is varied from the normal case.

Before describing the operation of the FBT 130, the FBT 130 includes a primary winding T _{1 to} which a B + voltage is applied, a secondary winding T _{2 to} which a high voltage is induced, and a low voltage. It consists of a tertiary winding (T ₃ ) for inducing induced voltage, a rectifying unit for rectifying the voltage induced in the secondary winding, etc. generates a high voltage (HV) in accordance with the operation of the horizontal output unit (160).

The high voltage HV induced in the secondary winding of the FBT 130 is applied to the anode of the CRT, and the focus voltage and the screen voltage divided by the resistor are applied to the focus grid and the screen grid of the CRT, respectively. do.

In this case, the high voltage (HV) is varied according to the magnitude of the anode current flowing through the high voltage line, which is the secondary winding of the FBT 130. When the anode current is increased, the high voltage (HV) is reduced as shown in Equation 2. Will be lowered. In addition, as described above, when the high voltage H.V decreases, the size of the screen increases because the deflection amount of the electron beam increases as shown in Equation 1.

1, if the anode current is normal,

In general, in the multi-mode monitor, the B + voltage is varied for each mode, and the B + voltage of the high voltage is applied to the FBT 130 as the high resolution mode is increased. As described above, when the B + voltage increases, the on time of the horizontal driving signal is shortened, and the high voltage induced in the secondary winding of the FBT 130 is maintained at a constant state.

Of course, when the B + voltage is increased and the on time of the horizontal driving signal is shortened as described above, the voltage between both ends of the correction capacitor Cs must also be increased in proportion to the B + voltage, so that the deflection amount of the electron beam is constant so that the screen size is constant. Can be.

That is, as described above, if the B + voltage increases when the anode current is normal, the voltage between both ends of the correction capacitor Cs should also increase accordingly. This is possible by the following operation.

As described above, when the voltage B + increases, a base current flows into the twenty-second transistor 22 through the twenty-fifth resistor R25 of the second buffering means 25, and the twenty-second transistor Q22 is turned on, and the twenty-second transistor is turned on. While the transistor Q22 is turned on, the B + current of the B + voltage line flows to {the common contact of the compensation capacitor Cs and the capacitor divider} (that is, the node A), so that the potential of the node A increases. In other words, the voltage across the correction capacitor Cs increases.

At this time, the voltage between both ends of the correction capacitor Cs should not be higher than the voltage B +. When the potential of the node A reaches a predetermined level, the 21st transistor Q21 is turned on to reduce the base current of the 22nd transistor Q22. By blocking the flow of B + current, the potential of node A is no longer raised.

[Equation 3]

[Equation 4]

That is, the first divided voltage (potential of node C) represented by Equation 3 and the second divided voltage (potential of node D) represented by Equation 4 are respectively represented as non-inverting input terminals and inverting input terminals of comparator 21. When the first divided voltage is greater than the second divided voltage, the comparator 21 outputs a comparison signal of (+) to turn on the twenty-first transistor Q21.

When the twenty-first transistor Q21 is turned on, a portion of the base current of the twenty-second transistor Q22 flows into the emitter current of the twenty-first transistor Q21, and the base current of the twenty-second transistor Q22 decreases. In addition, since the emitter current of the 22nd transistor Q22 is reduced, the potential of the node A does not increase any more while the B + current applied to the node A decreases.

와

의 비} 만큼 작은 전압을 유지하게 된다.At this time, since {the ratio of the twenty-first resistor R21 to the twenty-second resistor R22} is designed to be smaller than the {ratio of the twenty-third resistor R23 to the twenty-fourth resistor R24}, the potential of the node A is Than B + voltage {

Wow

Maintain the voltage as small as.

In summary, when the anode current is normal, the mode is changed, and when the B + voltage changes, the potential of the node A changes so that the screen size can be kept constant.

2, if the anode current changes,

On the other hand, if the anode current increases as the screen becomes brighter, the high voltage output from the secondary winding of the FBT 130 decreases and the size of the screen increases, and if the B + voltage is increased to increase the high pressure normally, the correction capacitor Cs The size of the screen increases as the voltage at both ends thereof increases, as described above.

The present invention does not increase the voltage across the correction capacitor (Cs) even if the anode current is increased to compensate for this, so that the size of the screen can be kept constant. Can be implemented.

As the screen becomes brighter and the anode current rises, the divided voltage ratio of the eleventh resistor R11 and the twelfth resistor R12 is changed to decrease the control voltage (the potential of the node B). At this time, the potential of the node B is applied to the non-inverting input terminal of the comparator 21 through the first buffering means 15, so that the input voltage of the non-inverting input terminal is lower than the second divided voltage.

Meanwhile, when the high voltage (HV) is lowered as described above, the control voltage Vc monitored through the tertiary winding of the FBT 130 is applied to the DC-DC converter 120, and the DC-DC converter 120 is B +. The voltage is increased to make the high voltage (HV) normal.

At this time, when the voltage B + rises as described above, the first divided voltage obtained by Equation 3 may be smaller than the second divided voltage obtained by Equation 4, but rather than the control signal output from the first buffering means 15. Because of the magnitude, the comparator 21 outputs a positive comparison signal. That is, the voltage of the inverting input terminal of the comparator 21 is equal to the control signal output from the first buffering means 15 by the second divided voltage. The sum voltage is lower than the control signal. Accordingly, the first divided voltage of the non-inverting input terminal is greater than the sum voltage of the inverting input terminals, so that the comparator 21 outputs a positive comparison signal.

The comparison signal turns on the 21st transistor Q21. When the 21st transistor Q21 is turned on, the base current of the 22nd transistor Q22 decreases and the emitter current decreases so that the B + current becomes the node A. Restrict to proceed.

That is, since the potential of the node A hardly increases, the voltage at both ends of the correction capacitor Cs can be kept constant.

In summary, when the anode current increases, when the high voltage decreases, the B + voltage increases, but the voltage across the correction capacitor maintains a constant size, thereby maintaining a constant size of the screen.

As described above, in the high voltage regulation circuit according to the present invention, the voltage across the correction capacitor is varied by a proportional amount of B + voltage when the anode current is normal, and when the anode current is changed, the B + voltage is The voltage of both ends of the correction capacitor may be kept constant so that the size of the screen may be prevented from varying.

Claims (3)

The high voltage is generated in the secondary winding of the FBT by switching the B + voltage applied to the primary winding of the FBT 130 according to the horizontal driving signal output from the horizontal oscillator, and the high voltage through the voltage induced in the tertiary winding of the FBT. Detecting and detecting the voltage of the correction capacitor Cs by applying a control voltage to the DC-DC converter 120, wherein the voltage across the correction capacitor Cs is varied when the voltage B + is changed; An anode current sensing unit 10 sensing the magnitude of the anode current flowing in the high voltage line; When the anode current is changed and the B + voltage is changed, the voltage adjusting unit 20 receives a control signal output from the anode current sensing unit 10 and adjusts the voltage at both ends of the correction capacitor Cs to be constant. High-voltage regulation circuit of the monitor, characterized in that consisting of. The method of claim 1, wherein the anode current detection unit 10 is a driving voltage divider 11 for outputting a control voltage variable according to the magnitude of the anode current; And The high voltage regulation of the monitor, characterized in that the first buffering means 15 for supplying a control signal whose voltage value is varied according to the control voltage applied from the driving voltage divider 11 to the voltage adjusting unit 20. Circuit. According to claim 1, wherein the voltage adjusting unit 20 is a B + voltage divider for dividing the B + voltage, A capacitor divider for dividing a voltage across both ends of the correction capacitor Cs; A comparator 21 for comparing the divided voltage output from the capacitor divider and the control signal output from the divided voltage output from the B + voltage divider or the anode current sensing unit; And a second buffering means (25) for adjusting the magnitude of the B + voltage applied to the voltage across the correction capacitor in accordance with the comparison signal output from the comparator.

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