JP2017073932A - High-voltage power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a high-voltage power supply circuit capable of turning an output voltage into a rectangular wave even in a case where a switching circuit is on/off-controlled at a low frequency.SOLUTION: A high-voltage power supply circuit comprises a piezoelectric transformer 2 that outputs a voltage value higher than a load voltage value, from a secondary side. At the secondary side of the piezoelectric transformer 2, a waveform shaping circuit 7 that cuts an output voltage value of the piezoelectric transformer into the load voltage value is connected. At the secondary side of the piezoelectric transformer 2, a load 3 is connected via the waveform shaping circuit 7. Between the secondary side of the piezoelectric transformer 2 and the load 3, a trailing processing relay 9 is provided. A relay control circuit 10 outputs an off signal to both the switching circuit 4 and the trailing processing relay 9 to turn off both of them in synchronization with each other. In stead of the piezoelectric transformer, a coil transformer can be used.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a high voltage power supply circuit in which the response speed of the output voltage of the high voltage power supply is improved.

  For example, as a high-voltage power supply circuit used for a static eliminator, a circuit that converts an input voltage into a rectangular wave voltage using a piezoelectric transformer and outputs the voltage to a load is known. In this type of high voltage, a voltage corresponding to the value of the flat portion is applied to the load during the time of the flat portion of the rectangular wave. Therefore, by controlling the duty of the rectangular wave, The power supply can be controlled.

  In this type of high-voltage power supply circuit, as shown in Patent Document 1 and Patent Document 2, the input voltage is turned on / off by a switching circuit having a constant frequency to control the duty of the rectangular wave. In this case, it is difficult to increase the response speed of the rectangular wave, that is, the rising / falling speed of the rectangular wave in a load with a large load current or load capacity. In particular, since the output charge / discharge time depends on the load, it is difficult to increase the response speed (rise / fall time).

JP 2009-163951 A JP 2012-155857 A JP 2010-049829 A

  In order to solve such a problem, for example, as shown in FIG. 8 of Patent Document 3, it is conceivable to increase the rising speed by using a Zener diode as an output.

  However, for example, when the switching circuit is continuously turned on and off at a low frequency such as 100 Hz to make the output voltage a rectangular wave, the time is spent only on the rise time, and the peak value of the rectangular wave requires the load. In some cases, the voltage does not reach the voltage value, or the rectangular wave falls immediately after the peak value reaches the voltage value, the flat portion of the rectangular wave disappears, and the voltage value required by the load cannot be secured for a predetermined time.

  FIG. 2 shows an output voltage waveform of a high-voltage power supply circuit to which, for example, a 10 MΩ resistive load is connected in the prior art. As can be seen from this waveform, a rectangular wave is output in which the rise time and fall time are short, a flat portion is secured at the maximum peak value, and the output is reduced to the ground potential at the minimum peak value.

  FIG. 3 shows an output voltage waveform of a high-voltage power supply circuit to which, for example, a capacitance of 500 pF is added in the prior art. As can be seen from this waveform, when a capacitive load is connected, the rise and fall times are delayed due to the effect of the charge / discharge time, the switching circuit cannot follow the on / off speed, and the output voltage The maximum peak value becomes a mountain shape without a flat portion, and the minimum peak value cannot fall to the ground potential.

  The object of the present invention is to set the output voltage value to, for example, twice the load voltage value so that the rise time is halved and the output voltage is rectangular even when the switching circuit is turned on / off at a low frequency. An object of the present invention is to provide a high-voltage power supply circuit that can be a wave.

The high-voltage power supply circuit of the present invention is characterized by having the following configuration.
(1) An input power supply that outputs a constant voltage.
(2) A transformer that converts a voltage from the input power source into a predetermined pulse wave and outputs a voltage value higher than a load voltage value.
(3) A driving circuit for the transformer.
(4) A waveform shaping circuit that is connected to the secondary side of the transformer and cuts the output voltage value of the transformer into a load voltage value.
(5) A load connected to the secondary side of the transformer via the waveform shaping circuit.
(6) A fall processing relay provided between the secondary side of the transformer and the load.
(7) A relay control circuit that outputs an off signal to the fall processing relay when the rectangular wave falls.

The high-voltage power supply circuit of the present invention preferably has the following configuration.
(1) The transformer is a piezoelectric transformer.
(2) The relay control circuit outputs an off signal to both the drive circuit and the falling processing relay, and turns them off in synchronization.
(3) The output voltage value of the piezoelectric transformer is at least twice the load voltage value.
(4) The waveform shaping circuit has a Zener diode.

  In the present invention, the output voltage value of the piezoelectric transformer is set higher than the load voltage value, and the portion higher than the load voltage value of the output waveform from the piezoelectric transformer is cut by the waveform shaping circuit. Therefore, a flat portion equal to the load voltage value is always formed in the output voltage value output from the waveform shaping circuit, and a rectangular wave in which the load voltage value continues for a predetermined time can be output to the load. In addition, the present invention improves the falling speed of the rectangular wave by the falling relay by the control signal from the relay control circuit, so that even when a capacitive load is connected, the falling response is excellent. A square wave can be output to the load.

The circuit which shows 1st Embodiment of the high voltage power supply circuit of this invention. In the prior art, the output voltage waveform diagram when a resistive load is connected. In the prior art, the output voltage waveform diagram when a capacitive load is connected. FIG. 6 is a waveform diagram of an output voltage when a capacitive load is connected to a high-voltage power supply circuit that uses a relay or the like to increase the falling speed. The wave form diagram of the output voltage at the time of connecting a capacitive load to 1st Embodiment. The circuit which shows 2nd Embodiment of the high voltage power supply circuit of this invention.

  Hereinafter, an embodiment of the present invention will be specifically described with reference to FIG.

[1. First Embodiment]
(1) Configuration The high-voltage power supply circuit according to this embodiment includes an input power supply 1 that outputs a constant voltage, a piezoelectric transformer 2 that converts a voltage from the input power supply 1 into a load voltage value, and a secondary side of the piezoelectric transformer 2. It has a load 3 connected. The load 3 is a capacitive load 3 having a predetermined resistance value and a capacitance value and a large capacitance value. The piezoelectric transformer 2 is controlled by a drive circuit, which will be described later, and outputs a pulse wave having a predetermined peak value and period from a constant voltage value from the input power supply 1, and the peak of the pulse wave is greater than the load voltage value. Output a voltage that is twice as high as the load voltage value in this embodiment.

  In the present embodiment, since the output voltage to the load 3 is determined by the Zener diode of the waveform shaping circuit 7 that clamps the output voltage from the piezoelectric transformer 2, for example, when the voltage is doubled, the voltage between the rectifier circuit 6 and the Zener diode By setting the value to the same voltage value between the output part of the waveform shaping circuit 6 and the GND, a double output voltage is obtained. As a method for controlling the output voltage from the piezoelectric transformer 2, phase angle control, frequency control, power supply line dropper control, or the like is used. If the boost ratio is insufficient, the LC resonance L can be compensated for by an autotransformer or the like.

  A switching circuit 4 to which a constant voltage from the input power supply 1 is supplied is connected to the primary side of the piezoelectric transformer 2. The switching circuit 4 is connected to an oscillation circuit 5 that controls the on / off interval. The switching circuit 4 and the oscillation circuit 5 constitute a drive circuit for the piezoelectric transformer 2.

  A rectifier circuit 6 is connected to the secondary side of the piezoelectric transformer 2, and a waveform shaping circuit 7 that cuts the upper part of the output voltage value of the piezoelectric transformer 2 to a voltage value required by the load 3 is connected to the output side of the rectifier circuit 6. Is done. In this embodiment, the waveform shaping circuit 7 includes a plurality of Zener diodes and a Zener current limiting resistor connected in series, and the output voltage of the piezoelectric transformer 2 that has passed through the rectifier circuit 6 at the end on the cathode side thereof. Applied. An output voltage for the load 3 is taken out from the middle stage of the plurality of connected Zener diodes.

  In the present embodiment, the output voltage value of the piezoelectric transformer 2 is set to be twice the load voltage value, and the waveform shaping circuit 7 is a portion higher than the load voltage value in the output waveform of the piezoelectric transformer 2. Is cut. Therefore, the waveform of the voltage value output from the waveform shaping circuit 7 to the load 3 is a rectangular wave having a flat portion whose maximum voltage value is equal to the load voltage value. The anode side of the waveform shaping circuit 7 is grounded together with the end of the load 3 on the ground side.

  An output value detection circuit 8 that detects the output voltage value of the piezoelectric transformer 2 and outputs it to the oscillation circuit 5 is connected to the output side of the rectifier circuit 6. The output side of the output value detection circuit 8 is connected to the oscillation circuit 5. A constant voltage from the input power supply 1 is input to the oscillation circuit 5 and a waveform of the output voltage of the piezoelectric transformer 2 from the output value detection circuit 8 is input. The drive signal transmitted at the frequency of the output voltage of 2 is output. In response to the input of the drive signal, the piezoelectric transformer 2 boosts the voltage (drive voltage) of the drive signal at a boost ratio determined by the drive frequency, and outputs an output voltage from the secondary side.

  A falling relay 9 is connected in parallel with the load 3 on the secondary side of the piezoelectric transformer 2, that is, in the present embodiment, between the waveform shaping circuit 7 and the load 3. A relay control circuit 10 is connected to the relay 9, and the relay 9 is actuated by an OFF signal from the relay control circuit 10 to cut off an output current from the piezoelectric transformer 2 to the load 3. That is, since the breaking speed of the relay 9 is much faster than that of the capacitive load 3, the output voltage value of the piezoelectric transformer 2 applied to the load 3 is rapidly cut off, and a rectangular wave having a fast falling speed is loaded. 3 will be output.

  The relay control circuit 10 is also connected to the switching circuit 4, and an off signal from the relay control circuit 10 is supplied to the switching circuit 4. As a result, the relay control circuit 10 outputs an off signal to both the switching circuit 4 and the relay 9 to turn them off in synchronization.

  As the relay 9, a semiconductor relay, a semiconductor switch, or other switches can be used. In the present invention, the configuration is not particularly limited as long as the relay control circuit 10 repeatedly turns on and off at a predetermined frequency with an off signal. As the relay control circuit 10, a circuit that outputs an on / off signal, a waveform signal of a predetermined frequency, etc. can be used. Even if a control signal is supplied from the outside of the high voltage power circuit, the control signal is generated in the high voltage power circuit. You can do it.

(2) Operation In this embodiment, since the output voltage value of the piezoelectric transformer 2 is higher than the load voltage value, a pulse wave having a high peak value as shown by the dotted line in FIG. The Since the output voltage of the piezoelectric transformer 2 is higher than the load voltage value, this waveform value is compared with the case where the output voltage value from the piezoelectric transformer 2 is equal to the load voltage value as shown in FIGS. The rise of the waveform is short.

  Such a pulse wave having a high peak value output from the piezoelectric transformer 2 is input to the waveform shaping circuit 7. The waveform shaping circuit 7 cuts a voltage value higher than a predetermined load voltage value in the output voltage waveform of the piezoelectric transformer 2 according to the constant voltage output characteristic of the Zener diode. For this reason, a flat portion equal to the load voltage value is necessarily formed in the output voltage waveform output from the waveform shaping circuit 7, and a rectangular wave whose load voltage value continues for a predetermined time may be output to the load 3. it can.

  When the rectangular wave output from the waveform shaping circuit 7 to the load 3 reaches its falling point, the relay 9 is turned off by the off signal from the relay control circuit 10 and the waveform shaping circuit 7 is short-circuited. 3 is cut off from the output voltage from the piezoelectric transformer 2. Therefore, the falling of the rectangular wave is performed quickly without being affected by the capacity of the load 3. In this case, since the OFF signal from the relay control circuit 10 is output to the switching circuit 4 simultaneously with the relay 9, the ON / OFF operation of the switching circuit 4, that is, the falling of the rectangular wave of the output voltage from the piezoelectric transformer 2 Then, the timing of the interruption of the voltage supplied to the load 3 by turning off the relay 9 is synchronized.

  In the present embodiment, an output value detection circuit 8 is provided at the subsequent stage of the rectifier circuit 6 and voltage detection after rectification is performed, so that the output voltage from the piezoelectric transformer 2 does not become an overvoltage, and the waveform shaping circuit 7 These members and the load 3 are protected.

(3) Effects According to the present embodiment, the rise time and fall time of the output voltage value of the piezoelectric transformer 2 can be shortened. For example, when only the relay 9 is provided, as shown in FIG. 4, although the fall time is shortened, it takes time to rise, and the voltage above the waveform of the output voltage value cannot be maintained. On the other hand, in this embodiment, since the output voltage value of the piezoelectric transformer 2 is twice the load voltage value, the output voltage draws a waveform as shown by the dotted line in FIG. 5 and rapidly rises to its peak. . As a result, the rise time required from the ground potential to the load voltage value is halved compared to FIG.

  In this state, when the portion of the output voltage exceeding the load voltage value is cut by the waveform shaping circuit 7, a rectangular wave with a flat load voltage value can be obtained as shown by the solid line in FIG. As a result, the load 3 is applied with a rectangular wave voltage having a fast rising and falling speed and a load voltage value that continues for a predetermined time.

  Even when a capacitive load 3 or the like is connected, a relay 9 is provided after the waveform shaping circuit 7 and the relay 9 is turned off by the relay control circuit 10 to improve the falling speed of the rectangular wave. A rectangular wave excellent in falling response can be output to the load 3. Further, since the relay 9 is provided at the subsequent stage of the waveform shaping circuit 7, the withstand voltage of the relay 9 can be lowered by the voltage stepped down by the waveform shaping circuit 7.

  When the rectangular wave falls, an off signal is output to both the switching circuit 4 and the fall processing relay 9 constituting the drive circuit, and both are turned off in synchronization. The falling timing of the rectangular wave and the falling timing of the rectangular wave supplied to the load 3 can be synchronized. As a result, the inconvenience that the relay 9 is turned on at the flat portion of the rectangular wave of the output voltage and the falling starts is solved.

  In this embodiment, since a Zener diode is used as the waveform shaping circuit 7, there are effects of improving the rising speed and reducing the loss of load power as compared with other waveform shaping circuits using resistors or the like.

[2. Second Embodiment]
FIG. 6 is a second embodiment of the present invention. In the present embodiment, the output voltage from the piezoelectric transformer 2 and the output voltage from the waveform shaping circuit 7 are not fed back to the oscillation circuit 4, and the output voltage value setting circuit 8 a of the piezoelectric transformer 2 is connected to the drive circuit of the piezoelectric transformer 2. Is provided. In the present embodiment, since the output value of the setting circuit 8a is the output voltage value desired to be obtained by the piezoelectric transformer 2, the set value is set to, for example, twice the load voltage value.

  According to the present embodiment, since the output voltage is determined by the Zener diode between the waveform shaping circuit 7 and GND, the clamp value of the output voltage for the load 3 is determined without detecting the feedback voltage for the drive circuit. That is, as much output voltage from the rectifier circuit 6 as the voltage of the Zener diode between the output terminal of the waveform shaping circuit 7 and the rectifier circuit 6 is required.

  According to this embodiment, in addition to the effects of the first embodiment, the output voltage from the waveform shaping circuit 7 can be fed back to the drive circuit of the piezoelectric transformer 2, and the detection accuracy of the output voltage can be increased. .

[3. Other Embodiments]
The present invention is not limited to the above-described embodiments, and includes other embodiments as follows.
(1) Instead of providing the relay 9 between the waveform shaping circuit 7 and the load 3, the relay 9 may be provided at another location on the secondary side of the piezoelectric transformer 2. For example, these circuits may be provided in parallel or in series between the rectifier circuit 6 and the waveform shaping circuit 7 or between the piezoelectric transformer 2 and the rectifier circuit 6. A relay 9 can be connected in series with the load 3.

(2) The output voltage value from the piezoelectric transformer 2 is not limited to twice the load voltage value. The falling speed of the voltage waveform supplied to the load 3 changes according to the time constant determined by the capacity and resistance of the load 3 or the frequency applied to the load 3. Therefore, the output voltage value from the piezoelectric transformer 2 is adjusted according to the degree of delay of the falling speed by the load 3 so that the flat portion of the rectangular wave continues for the time required by the load 3.

(3) As the drive circuit for the piezoelectric transformer 2, a known circuit can be used as appropriate in addition to the output value detection circuit 8, the oscillation circuit 5 and the switching circuit 4 as shown in the figure.

(4) As the waveform shaping circuit 7, a circuit having the same action as a Zener diode, for example, a clamper may be used. Even when a Zener diode is used, the current limiting resistor shown in FIG. 1 may not be provided depending on circuit characteristics.

(5) Although the piezoelectric transformer 2 has been described as an example of the transformer, a winding transformer can also be used. However, since the piezoelectric transformer 2 is more responsive to the control frequency from the drive circuit, generation of a pulse wave, control of the output voltage, etc. can be performed easily and accurately.

DESCRIPTION OF SYMBOLS 1 ... Input power supply 2 ... Piezoelectric transformer 3 ... Load 4 ... Switching circuit 5 ... Oscillation circuit 6 ... Rectification circuit 7 ... Waveform shaping circuit 8 ... Output value detection circuit 8a ... Output voltage value setting circuit 9 ... Falling processing relay 10 ... Relay control circuit

Claims (5)

An input power supply that outputs a constant voltage;
A transformer that converts a voltage from the input power source into a predetermined pulse wave and outputs a voltage value higher than a load voltage value;
A drive circuit for the transformer;
A waveform shaping circuit connected to the secondary side of the transformer and cutting the output voltage value of the transformer into a load voltage value;
A load connected to the secondary side of the transformer via the waveform shaping circuit;
A falling processing relay provided between the secondary side of the transformer and the load;
A relay control circuit that outputs an off signal to the fall processing relay at the fall of the rectangular wave;
High voltage power supply circuit equipped with.   The high-voltage power supply circuit according to claim 1, wherein the transformer is a piezoelectric transformer.   3. The high-voltage power supply circuit according to claim 1, wherein the relay control circuit outputs an off signal to both the drive circuit and the falling processing relay to turn them off in synchronization.   The high-voltage power supply circuit according to any one of claims 1 to 3, wherein an output voltage value of the transformer is twice or more a load voltage value.   The high-voltage power supply circuit according to any one of claims 1 to 4, wherein the waveform shaping circuit includes a Zener diode.

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