JPH0628010B2 - High voltage control circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a high voltage control circuit, and particularly to a high voltage control circuit capable of continuously controlling to an arbitrary value, including ON / OFF control of a high voltage output. The present invention relates to a voltage control circuit.

[Prior Art] FIG. 2 is a circuit diagram of a conventional high voltage control circuit.

In the figure, 1 is a high voltage DC power supply, 17 is a high voltage output terminal, 18 is a variable resistor for fine adjustment, 19 to 22 are resistors for voltage division, 23 is a rotary switch for coarse adjustment, and 24 is on / off control. High voltage relay for.

In the conventional high voltage control circuit having the above configuration, the high voltage relay 24 is used as a high voltage switch element for output on / off control, and the voltage output to the high voltage output terminal 17 is turned on / off. The output is on / off. Further, the voltage value of the high voltage output at this time is a value obtained by dividing the high voltage output of the DC high voltage power supply 1 by the resistors 18 to 22.

On the other hand, for the adjustment of the high-voltage output voltage value, a variable resistor 18 for fine adjustment and a rotary switch 23 for coarse adjustment are used as continuous variable control elements of the output voltage. Then, the voltage division ratio of the resistor is changed by these, and the high voltage output terminal 1
The high voltage output output to 7 was continuously variable.

[Problems to be Solved] The conventional high voltage control circuit described above has the following problems.

Since the high voltage output on / off control is performed by turning on / off the mechanical contact of the high voltage relay, arc discharge and chattering occur at the contact part. As a result, the high voltage waveform is disturbed at the time of turning on / off, it takes time to stabilize, and much noise is generated.

In order to make the high-voltage output voltage continuously variable, a high resistance value was switched with a rotary switch for coarse adjustment of the high voltage, and a variable resistor was used for fine adjustment. The value changes in steps,
As a result of the output voltage also changing stepwise, the generation of noise was unavoidable.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a high voltage control circuit capable of performing high voltage on / off with low noise and high speed, and continuous control of high voltage. .

[Means for Solving Problems] In order to achieve the above object, the high voltage control circuit of the present invention is
It can be activated in the active region or the saturation region by changing the bias voltage to the gate, and when it operates in the active region it functions as a variable resistor for voltage division, and when it operates in the saturation region it functions as a switching element. The first field-effect transistor and the first field-effect transistor are connected in series with the resistor interposed therebetween, and the gate bias of the first field-effect transistor is turned off so that the drain of the first field-effect transistor. , A second field effect transistor that is turned on when a high impedance state is generated between the sources, and the resistor and the second field effect transistor.
A high-voltage output circuit that extracts a high-voltage output from the connection point with the field-effect transistor, a high-voltage DC power supply that applies a high DC voltage to the high-voltage output circuit, a low-voltage switch and a variable power supply for gate bias, The bias voltage is applied to the gate of the first field effect transistor and the bias voltage value is controlled to operate the first field effect transistor from the active region to the saturation region, and the impedance of the first field effect transistor is adjusted. The output control circuit controls the high voltage output by changing the output voltage.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram of a high voltage control circuit according to an embodiment of the present invention. The parts common to or corresponding to the conventional example are denoted by the same reference numerals.

In the figure, 1 is a DC high voltage power supply, 2 is a P-gate field effect transistor, and n P-gate field effect transistors 2 ₁ to 2 _n are connected in series to obtain a withstand voltage characteristic. Of these, the P-gate field effect transistors 2 ₂ to 2 _n have their gates connected to the voltage balancing resistors 7 ₁ to.
And it has a connection to the self-bias by 7 _n, 5 ₂ ~5 _n.

This field effect transistor 2 can be operated in the active region or the saturation region by applying a bias voltage to the gate and changing the bias voltage value, and when operated in the active region, it functions as a kind of voltage dividing variable resistor. When it operates in the saturation region, it functions as a switching element.

Next, 3 is a resistance, which prevents the output voltage from being short-circuited when the P-gate field effect transistors 2 ₁ to 2 _n and the N-gate field effect transistors 4 ₁ to 4 _n are simultaneously turned on. Here, 4 (4 ₁ -4 _n ) is an N-gate field effect transistor, and like the P-gate field transistor 2, m pieces are connected in series to obtain withstand voltage characteristics. Of these, N gate field effect transistors 4 ₁ to 4
_n-1 has its gate connected to the voltage balancing resistors 8 ₁ to 8 _m , 6 ₁
The connection is self-biased by ~ 6 _m .

Further, 9 and 10 are gate bias resistors for driving the field effect transistor 11, and 12 and 13 are gate bias resistors for driving the field effect transistor 4 _n . Then, 14 _1, 14 ₂ gate overvoltage protection Zener diode, 15 a switch for turning on / off the bias voltage of the field effect transistor 2 _1, 16 also field-effect transistor 2 ₁ of the bias power supply, 17 a high voltage output It is a terminal. The low voltage switch 15 and the gate bias variable power source 16 configure an output control circuit as described later.

In the above configuration, when the switch 15 is off, the voltage of the DC high-voltage power supply 1 is applied to the Zener diode 14 ₁ to prevent the gate of the field effect transistor 4 _{n from} becoming an overvoltage. Then, at this time, the Zener voltage obtained through the resistor 12 drives the field effect transistor 4 _n ,
Turn this on.

That is, when the switch 15 is off and the gate bias is not applied to the P-gate field effect transistor 2, the drain and source of the field effect transistor 2 are in a high impedance state.

As a result, the field effect transistors 4 ₁ to 4 _n-1 are similarly turned on, and the output voltage of the high voltage output terminal 17 becomes about the sum of the gate voltages of the field effect transistors 4 ₁ to 4 _n-1 . This is a value that can be ignored compared to the high voltage of the input,
It can be said that the output is off.

Next, when the switch 15 is turned on, the field effect transistor 2 ₁ is biased by the bias power supply 16, and the field effect transistor 2 ₁ and other field effect transistors 2 ₂ to 2 _n are also turned on, and the resistors 9 and 10 are turned on. The input voltage is applied to both ends. Therefore, the field effect transistor 1
1 turns on, pulls in the gate bias voltage of the field effect transistor 4 _n , and turns it off.

As a result, all the field effect transistor 4 ₁ to 4 _n is off. Therefore, a high voltage obtained by dividing the voltage of the DC high voltage power supply 1 is generated at both ends of the high voltage output terminal 17. The voltage division at this time involves the impedance between the resistors 8 ₁ to 8 _m , 9 and 10 and the field effect transistors 2 ₁ to 2 _n .

Further, at this time, the field effect transistors 2 ₁ to 2 _n can be operated in the active region by changing the voltage value of the bias power supply 16. When the active region is operated in this manner, the impedance of the field effect transistor changes and the voltage division ratio changes, so that the high voltage output terminal 17
It is possible to arbitrarily change the output voltage of. In this case, since the field effect transistor is used as the switch element, high-speed high-voltage switching is possible, and since it is an electronic switch circuit, low noise and high speed at the time of on / off can be achieved.

As described above, in this embodiment, the P-gate and N-gate field effect transistors are respectively connected in series as the high voltage voltage control element, the lowermost element is provided with the gate voltage adjusting circuit, and the elements other than the lowermost element are self-contained. By using it as a bias operation, it is possible to eliminate the disturbance of the output voltage waveform and the generation of noise when the high voltage is turned on and off, and further improve the operating speed. Also, adjust it during continuous control of the output voltage. The output voltage can be arbitrarily controlled by continuously changing the low voltage control voltage value of the circuit.

[Effects of the Invention] As described above, according to the present invention, by controlling the high voltage output by the field effect transistor, the ON / OFF of the high voltage output and the continuous control are reduced in noise and speeded up. The effect is that a circuit can be provided.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a high voltage control circuit according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of a conventional high voltage control circuit. 1: DC high-voltage power supply 2 ₁ to 2 _n: P-gate field-effect transistor 3: resistor 4 ₁ to 4 _n: N gate voltage effect transistor _{5 1 ~5 n, 6 1 ~6} m: resistor 7 ₁ to _7-n, 8 ₁ to 8 _m : Resistor 11: N-gate field effect transistor 12, 13: Resistor 15: Low voltage switch 16: Variable power supply for gate bias 17: High voltage output terminal

Claims (2)

[Claims] 1. When the bias voltage to the gate is changed, it can be activated in an active region or a saturation region, and when it is operated in the active region, it functions as a variable resistor for voltage division, and when it is operated in the saturation region. A first field effect transistor (2) which functions as a switching element, and the first field effect transistor (2)
Of the first field effect transistor (2) are connected in series with the field effect transistor (2) and the resistor (3) in between, and the gate bias of the first field effect transistor (2) is turned off. A connection point between the resistor (3) and the second field effect transistor (4), including a second field effect transistor (4) which is turned on when the drain and the source are in a high impedance state. It consists of a high voltage output circuit that takes out a high voltage output from the high voltage output circuit, a DC high voltage power supply (1) that applies a DC high voltage to this high voltage output circuit, a low voltage switch (15) and a gate bias variable power supply (16). And applying a bias voltage to the gate of the first field effect transistor (2) and controlling the bias voltage value to operate the first field effect transistor (2) from the active region to the saturation region. First field effect transistor A high-voltage control circuit, comprising: an output control circuit for controlling a high-voltage output by changing the impedance of the input circuit (2). 2. The first and second field-effect transistors each include one field-effect transistor connected to the lowest voltage level and capable of controlling the gate voltage, and a plurality of self-bias-connected field-effect transistors. The high voltage control circuit according to claim 1, wherein the high voltage control circuits are connected in series in multiple stages.