KR19980030860U - Monitor's High Voltage Regulation Circuit - Google Patents

Abstract

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 changing according to the brightness of the CRT screen in the monitor.

The circuit of the present invention is provided with a horizontal oscillation means for generating a horizontal drive signal by receiving a synchronization signal during normal operation and blocking the output of the horizontal drive signal when a signal is input through the X-ray terminal. A monitor in which a horizontal output transistor switches the B + voltage applied to the primary winding of the FBT to generate a high voltage in the secondary winding of the FBT, wherein the high voltage is monitored by rectifying and smoothing the voltage induced in the tertiary winding of the FBT. Voltage detecting means; And B + voltage adjusting means for adjusting the B + voltage according to the detected voltage of the voltage detecting means.

Accordingly, the high voltage regulation circuit according to the present invention can stabilize the anode voltage fluctuating according to the change of the anode current by directly controlling the B + voltage applied to the primary winding of the FBT to prevent the screen size from being changed. .

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 changing 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 FBT point of view, 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]

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. 'Va' is also the anode voltage of the water tube.

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 current is generated and flows through this deflection coil, thereby deflecting 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 outputting the power supply 110 converts the DC voltage into a predetermined B + voltage to the primary winding of the FBT 130, and the voltage of the primary winding is horizontal. The output unit 160 switches according to the horizontal drive signal H. drive to generate a high voltage on the secondary winding side. In addition, the high voltage generated in the secondary winding of the FBT is applied to the anode of the CRT, and the voltage divided in the resistors is applied to the focus grid and the screen grid of the CRT, respectively.

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 divided through the division resistors R1 and R2 of the zener diode ZD1. It is applied to the cathode side. The anode side of the zener diode ZD1 is connected to the X-RAY protection terminal of the oscillator 140. At this time, when the high voltage HV of the FBT 130 is normal, a low voltage (that is, below the rated voltage of the zener diode) is applied to the zener diode ZD1 to maintain the zener diode ZD1 in the off state. .

As described above in such a general monitor, when the screen is brightened and the anode current increases, the anode voltage is lowered, thereby increasing the screen size.

Therefore, in order to prevent the screen size from changing according to the size of the anode current, it is necessary to control the magnitude of the anode voltage by directly controlling the B + voltage when the anode current is changed.

Accordingly, an object of the present invention is to provide a high voltage regulation circuit for directly controlling B + voltage to stabilize the high pressure in order to meet the necessity as described above and to prevent the size of the screen from being changed due to the change in high voltage.

In order to achieve the above object, the circuit of the present invention has a horizontal oscillation means configured to generate a horizontal drive signal by receiving a synchronization signal during normal operation and to block the output of the horizontal drive signal when a signal is input through the X-ray terminal. And a horizontal output transistor switching the B + voltage applied to the primary winding of the FBT according to the horizontal driving signal to generate a high voltage in the secondary winding of the FBT. Voltage detection means for rectifying and smoothing to monitor the high pressure; And B + voltage adjusting means for adjusting the B + voltage according to the detected voltage of the voltage detecting means.

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

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

* Explanation of symbols for main parts of the drawings

110: power supply 120: DC-DC converter

130: FBT140: oscillation part

150: horizontal drive unit 160: horizontal output unit

200: high voltage regulation circuit

Hereinafter, exemplary embodiments 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 a power supply 110, a DC-DC converter 120, an FBT 130, a horizontal oscillation unit 140, a horizontal driving unit 150, and a horizontal output unit. A diode D21 for rectifying the voltage induced in the tertiary winding of the FBT 130 in the monitor provided with 160, and a smoothing capacitor C21 for removing ripple of the voltage rectified in the diode D21. And the split resistors R24 and R25 for bringing down the output voltage of the diode D21, and the collector connected to the B + line through the resistor R22 and the base to the transistor Q21 connected to the split resistor R24. It is composed.

Next, look at the operation of the circuit of the present invention configured as described above are as follows.

The power supply 110 receives the AC power AC and outputs predetermined DC voltages to each part of the monitor. The DC-DC converter 120 is a boost up or buck type converter and receives a DC voltage and applies a predetermined B + voltage to the primary winding of the FBT 130.

FBT (130) is a primary winding (T ₁₎ and a secondary winding that is a high voltage is induced (T _2), 3 winding for Organic the induced voltage of the low voltage (T _3), a secondary winding applied to the B + voltage It is composed of a rectifying unit for rectifying the induced voltage to generate a high pressure in accordance with the operation of the horizontal output unit 160. The FBT used in the embodiment of the present invention is a laminated type, and the laminated type FBT has an advantage of reducing reliability of the short layer of the secondary winding.

The high voltage (H.V) induced in the secondary winding of the FBT 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.

The oscillator 140 receives the synchronization signals H.sync and V.sync and generates a H.drive signal locked thereto, and the horizontal driver 150 outputs the horizontal drive output from the oscillator 140. H.drive) signal is sufficiently amplified and output to the horizontal output unit 160. In the horizontal output unit 160, a sawtooth wave current flows in the horizontal deflection coil H.DY by turning on / off an internal horizontal output transistor according to a horizontal drive signal input through the horizontal driver 150.

At this time, when the horizontal output transistor is turned off, the energy accumulated in the primary winding of the FBT 130 is guided to the secondary winding and the tertiary winding of the FBT. That is, the horizontal output transistor also serves as a switching element of the power supply circuit so that a high voltage is generated in the secondary winding of the FBT.

On the other hand, when the anode current flowing in the secondary winding of the FBT 130 in such a monitor increases, the anode voltage is lowered as in Equation 2 above. When the anode voltage is lowered, as shown in Equation 1, the amount of deflection increases, thereby increasing the size of the screen.

When the anode voltage is lowered, the voltage of the flyback pulse FBP induced in the FBT is also lowered, so that the voltage of the node A smoothed in the rectifying diode D21 and smoothed in the smoothing capacitor C21 is also lowered.

When the voltage of the node A is lowered, the base current of the transistor Q21 is reduced, and thus the collector current flowing through the resistor R22 is also reduced. When the current of the collector decreases, the current flowing through the resistor R22 also decreases, and the voltage drop in the resistor R21 becomes smaller than in the normal state, thereby increasing the B + voltage.

As the B + voltage increases, the pulse voltage of the primary winding of the FBT 130 also increases as shown in Equation 3, and eventually, the voltage of the anode induced in the secondary winding increases.

[Equation 3]

Therefore, when the anode current increases and the anode voltage decreases, the B + voltage is increased to stabilize the high voltage by increasing the anode voltage again, thereby preventing the size of the screen from being changed.

On the contrary, when the anode current flowing in the secondary winding of the FBT 130 decreases, the anode voltage is increased as in Equation 2 above. As the anode voltage increases, the size of the screen becomes smaller because the amount of deflection becomes smaller according to Equation (1).

As the anode voltage increases, the voltage of the flyback pulse FBP induced by the FBT also increases, so that the voltage at the node A rectified by the rectifying diode D21 and smoothed by the smoothing capacitor C21 also increases.

As the voltage of the node A increases, the base current of the transistor Q21 increases, thereby increasing the collector current flowing through the resistor R22. As the current of the transistor collector increases, the current flowing through the resistor R21 also increases, so that the voltage drop across the resistor R21 becomes larger than in the normal state, thereby lowering the B + voltage.

When the voltage B + is lowered, the pulse voltage of the primary winding of the FBT 130 is also lowered as shown in Equation 3, and eventually, the voltage of the anode induced in the secondary winding is lowered.

Therefore, when the anode current decreases and the anode voltage increases, the B + voltage is lowered to stabilize the high voltage by lowering the anode voltage again, thereby preventing the screen size from being changed.

As described above, the high voltage regulation circuit according to the present invention stabilizes the variation of the anode voltage according to the change of the anode current by directly controlling the B + voltage applied to the primary winding of the FBT, thereby changing the screen size. You can prevent it.

Claims (3)

In the normal operation, a horizontal oscillation means is generated to receive a synchronous signal and generate a horizontal drive signal, and when the signal is input through the X-ray terminal, a horizontal oscillation means is arranged to block the output of the horizontal drive signal. In the monitor configured to generate a high voltage in the secondary winding of the FBT by switching the B + voltage applied to the primary winding of Voltage detecting means for monitoring the high voltage by rectifying and smoothing the voltage induced in the tertiary winding of the FBT; And And a B + voltage adjusting means for adjusting the B + voltage according to the detected voltage of the voltage detecting means. 2. The diode of claim 1, wherein the voltage detecting means includes a diode D21 for rectifying the voltage induced in the tertiary winding, a smoothing capacitor C21 for removing the ripple of the voltage rectified in the diode D21, and a diode. A high voltage regulation circuit for a monitor, comprising: split resistors (R24, R25) for lowering the output voltage of (D21). The high voltage of the monitor according to claim 1, wherein the B + voltage adjusting means comprises a transistor (Q21) having a collector connected to the B + line through a resistor (R22) and a base connected to the split resistor (R24). Regulation circuit.