JPH0638632B2 - High stable high voltage circuit - Google Patents

Description

TECHNICAL FIELD The present invention relates to a highly stable high voltage circuit.

[Conventional technology]

In recent years, a stereoscopic television has been developed which displays a signal for the left eye and a signal for the right eye for each field, and is viewed in spectacles with a liquid crystal shutter in synchronization with the signal. However, since the actual field frequency is reduced to 1/2, flicker occurs, and it cannot withstand long-term viewing.

Therefore, the stereoscopic television system shown in FIG. 2 can be considered. FIG. 2 will be described below.

In FIG. 2, 26 is an electron beam, 27 is a phosphor, and 2
Reference numeral 8 is a fiber plate, 29 is a polarizing plate for the right eye, and 30 is a polarizing plate for the left eye.

The electron beam 26 scans the phosphor 27, and the emission brightness of the phosphor is controlled by the current value thereof to form an image. Modulation of the electron beam is performed alternately for the right eye and the left eye signals for each horizontal line. A fiber plate 28, a right-eye polarizing plate 29, and a left-eye polarizing plate 3 corresponding to the horizontal line.
0 is provided, so if you look at the screen with glasses that have a polarizing plate with the same characteristics as the polarizing plate for the right eye for the right eye and a polarizing plate with the same characteristics as the polarizing plate for the left eye for the left eye. Looks like. Further, since the substantial field frequency does not decrease, flicker does not occur.

However, in this method, it is necessary to precisely control the electron beam 26 on the phosphor screen corresponding to the horizontal stripe polarization plate. For that purpose, the high pressure value applied to this CRT must be extremely stable. For example, in order to keep the error in the vertical direction of the scanning lines within 0.5 lines within 525 scanning lines, it is necessary to suppress the high voltage fluctuation to 0.2%. As a highly stable high-voltage circuit for this purpose, there is JP-A-59-103472 which uses a plurality of flyback transformers.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, the control for balancing the output currents of the plurality of flyback transformers is performed on the primary side,
The problem is that the control response speed is slow and the power supply voltage control has both constant voltage control and current balance control to stabilize high voltage, so the power supply voltage control capacity margin is reduced and it is difficult to obtain sufficient stability. was there.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a high-voltage circuit that is capable of balancing the output currents of a plurality of flyback transformers at high speed and has high stability.

[Means for solving problems]

The above-mentioned object is to connect the primary side of a plurality of flyback transformers to one high-voltage output circuit, and further provide an addition voltage source at the secondary side low-voltage side terminal of the flyback transformer to perform pulse width modulation on the primary side. This is achieved by performing constant voltage control by control and performing output current balance control of the flyback transformer by controlling the addition voltage source on the secondary side.

[Action]

The multiple flyback transformers have their primary side connected to a common high-voltage output circuit and their secondary side connected to a common high-voltage output terminal, so the output resistance of the flyback transformer is improved by half. is doing. The constant high voltage output voltage is detected, compared with the reference voltage, and the constant voltage control is performed by controlling the conduction period of the switching transistor of the high voltage circuit (pulse width modulation control) by the error. Also,
The secondary voltage side low voltage side terminal of the flyback transformer is provided with a summing voltage source, and a circuit for detecting the output currents of the plurality of flyback transformers is provided so that the outputs of the detection circuits are equal to each other. Control at high speed.

As described above, it is possible to realize a high-voltage circuit in which output currents of a plurality of flyback transformers are balanced at high speed and stability is high.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. First
In the figure, 1 is a switching transistor, 2 is a damper diode, 3 is a resonance capacitor, 4a and 4b are flyback transformers, 5a and 5b are high-voltage rectifying diodes, 6 is a high-voltage output terminal, 7a and 7b are capacitors, and 8
a and 8b are current detection resistors, 9 is an addition voltage source, 10 is an addition voltage source control circuit, 11 is an addition voltage source, 12 is a power input terminal, 13, 14, 16, 17, 18, 19 are resistors, 1
Reference numeral 5 is a reference voltage input terminal, 20 is an operational amplifier, 21 is a comparator, 22 is a horizontal 1st sawtooth wave input terminal, 23 is a drive transistor, 24 is a power supply input terminal, and 25 is a drive transformer.

Next, the operation will be described with reference to the drawings.

When a drive pulse is generated in the base of the switching transistor 1, the switching transistor 1 performs a switching operation, a pulse current flows in the primary side of the flyback transformers 4a and 4b, and a high voltage is induced in each secondary side. This high voltage is rectified by the rectifier diodes 5a and 5b, and a high DC voltage is output to the high voltage output terminal 6. The high DC voltage output to the high-voltage output terminal 6 is the resistor 13, 1
4 is divided by 4 and the operational amplifier 20 is connected via the resistor 17.
Is added as one input of. The reference voltage input to the reference power supply input terminal 15 as the other input of the operational amplifier 20 is applied via the resistor 16. Operational amplifier 2
0 amplifies the error between these two inputs, and the comparator 21
Is added as one input of. In addition, the comparator 21
One sawtooth wave with a horizontal cycle is input to the other input of. As a result, the output of the comparator 21 generates a pulse whose pulse width is modulated by the error between the reference voltage and the high voltage detection voltage. This pulse is amplified by the drive transistor 23, and the switching transistor 1 is driven via the drive transformer 25. This operation is controlled such that if the high voltage decreases, the conduction period of the switching transistor 1 increases and the high voltage increases, so that the high voltage becomes constant.

Further, the flyback transformer 4 is connected to the current detection resistor 8a.
Since a voltage proportional to the high voltage output current of a is generated in 8b in proportion to the high voltage output current of the flyback transformer 4b, these two voltages are input to the addition voltage source control circuit 10 to generate the addition voltage source. 9 is controlled so that these two voltages become equal.

Therefore, the high-voltage output circuit, which is a time constant circuit, is not within the harp of the output current balance control of the flyback transformer, so that the control response speed is high. Further, since the constant voltage control and the current balance control are separated into the primary side and the secondary side, a sufficient capacity for the constant voltage control can be obtained, so that a highly stable high voltage circuit can be realized.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.
In FIG. 3, 9a and 9b are addition voltage sources, 10a and 1b.
0b is an addition voltage source control circuit, 31 is a total current detection resistor,
32 is a buffer amplifier, and 33a and 33b are subtractors. 3 is different from that of FIG. 1 in the configuration of the current balance circuit of the flyback transformer.

The operation of this current balance circuit will be described with reference to the drawings.
A voltage proportional to the total high voltage output current is generated in the total current detection resistor 31. The buffer amplifier 32 converts this voltage into a voltage value of 1/2 and applies it as one input of the added voltage source control circuits 10a and 10b. Also, the current detection resistors 8a and 8b
Since a voltage proportional to the output current of the flyback transformers 4a and 4b is generated at both ends of the subtractor 33a, 3b.
3b to detect the added voltage source control circuit 10a, 10b
Add as the other input of. As a result, the output current of each flyback transformer is always controlled to be equal.

Up to now, the case where two flyback transformers are used has been described, but it is clear that the same configuration can be made even when three or more flyback transformers are used.

〔The invention's effect〕

As described above, according to the present invention, the primary side of a plurality of flyback transformers is connected to one high-voltage output circuit, and an additional voltage source is connected to the secondary side low-voltage side terminal of the flyback transformer. Since the output current balance control of the flyback transformer is performed by providing the constant voltage control by the pulse width modulation control on the primary side and the addition voltage source on the secondary side, This has the effect of realizing a high-voltage circuit that is balanced at high speed and has high stability.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a high-stable high-voltage circuit of the present invention, FIG. 2 is a principle diagram of a stereoscopic television to which the present invention is applied, and FIG. 3 is a high-stable high-voltage circuit of the present invention. It is a block diagram showing an example of. 1 ... Switching transistor, 2 ... Damper diode, 3 ... Resonance capacitor, 4a, 4b ... Flyback transformer, 5a, 5b ... High voltage rectification diode,
6 ... High voltage output terminal, 7a, 7b ... Capacitor, 8
a, 8b ... Current detection resistance, 9, 9a, 9b ... Addition voltage source, 11 ... Addition voltage source, 12 ... Power supply input terminal, 1
3, 14, 16, 17, 18, 19 ... Resistor, 15 ...
... reference voltage input terminal, 20 ... operational amplifier, 21 ... comparator, 23 ... drive transistor, 24 ...
Power input terminal, 25 ... Drive transformer, 26 ... Electron beam, 27 ... Phosphor, 28 ... Fiber plate, 2
9 …… Right eye polarizing plate, 30 …… Left eye polarizing plate, 32 ……
Buffer amplifier, 33a, 33b ... Subtractor.

Claims (1)

[Claims] 1. A high voltage circuit comprising a high voltage output transistor, a damper diode, a resonance capacitor and a flyback transformer, wherein a plurality of flyback transformers are provided and the primary side of the plurality of flyback transformers is connected to one high voltage output transistor. , A plurality of addition voltage sources are provided at the secondary side low voltage side terminals of the plurality of flyback transformers, and a plurality of circuits for detecting output currents of the plurality of flyback transformers are provided so that the outputs become equal. In addition to providing a plurality of control circuits for controlling the plurality of added voltage source, provided with a circuit for detecting a high output voltage, comparing the output voltage of the detection circuit and a preset reference voltage,
A high-stable high-voltage circuit characterized in that the conduction period of the high-voltage output transistor is controlled so that the error between the two becomes small.