JPH0635552A - Pulse power unit - Google Patents

Abstract

PURPOSE:To apply the stable gate voltage having a high rising speed to an insulated input type switching element. CONSTITUTION:A load 14 and a switching element 12 are provided in series to a power source 10. A driving circuit 18 generates periodically the control voltage higher than the voltage that actuates the element 12 in a linear area. When a differentiating circuit 46 detects the start of generation of the control voltage, a transistor TR 44 is turned on and a capacitor 42 is discharged. Therefore the TR 50 conducts to clamp the voltage to a low level at a connection point 34. Then the capacitor 42 is charged by the voltage generated by a high voltage generating part 36. The conduction state of the TR 50 is changed and the voltage is raised at the point 34. Then the element 12 is turned on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pulse power supply device, and more particularly to a device using an insulated input type switching element such as MOSFET or IGBT.

[0002]

2. Description of the Related Art A pulse power supply device controls ON / OFF of a switching element provided between a DC power supply and a load to supply electric power from the DC power supply to the load. It is common to use a bipolar transistor as a switching element in a normal pulse power supply device.
In a pulse power supply device used for noble metal plating or the like, an insulation input type switching element such as MOSFET or IGBT is used in place of the bipolar transistor in consideration of forward bias ASO and controllability.

[0003]

However, the MOSFE
When T or IGBT is used as a switching element, its equivalent input capacitance is larger than that of a bipolar transistor, and its gate threshold voltage is as large as about 3V.
Even if a pulse signal is input to the gates of these switching elements as a control signal, the time from the input to the turning on of the switching element is delayed due to the charging of the equivalent input capacitance. That is, the rising is delayed. It is possible to supply a high voltage gate control signal when a fast rise is required, but since the linear region for the gate control signals of these switching elements is as narrow as 3 to 5 V,
When a high voltage gate control signal is input, overshoot occurs, and it takes a long time to stabilize the input of the gate control signal.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and therefore, a DC power supply and an isolated input type which is connected in series to this DC power supply and supplies power to a load. Switching element, a control voltage generating means for generating a control voltage higher than a voltage required to operate the switching element in a linear region at regular intervals, and a first detecting means for detecting the current or voltage of the load. And first control means for controlling the value of the control voltage supplied from the control voltage generation means to the switching element according to the detection signal of the first detection means and the set value, and the generation of the control voltage. The second detection means for detecting the start, and the control voltage is clamped to a low voltage according to the detection signal from the second detection means at the start of the generation of the control voltage, and then the control voltage is increased to increase the control voltage. A second control means for supplying to the switching element, is intended to comprise.

[0005]

According to the present invention, in the state where the control voltage has already been generated, the switching element is turned on and a current flows from the DC power supply to the load. The first detection means detects the current or voltage of the load, and the first control means controls the control voltage supplied to the switching element according to the detection signal and the set value, that is, the conduction of the switching element. Control the state and control the load current or voltage to a constant value. When the control voltage disappears, the switching element is turned off and the load current becomes zero.

When the control voltage starts to be generated again, it is detected by the second detecting means, and the second detecting means detects the second voltage in response to the detection signal.
Control means clamp the control voltage to a low voltage and then increase it. When a certain time has elapsed after the control voltage was generated, the control is performed by the first detection means and the first control means in the same manner as described above.

[0007]

EXAMPLE In this example, the present invention is applied to a pulse power supply device used for precious metal plating or the like, and has a DC power supply 10 as shown in FIG. The DC power supply 10 is for rectifying and smoothing a commercial AC power supply, for example. Between the both ends of this DC power supply 10, for example, MOSFET or IG
An insulated input type switching element 12 which is a BT and a load 14 are connected in series.

A control voltage from a drive circuit 18 is supplied to the gate of the switching element 12 via resistors 15 and 16. The drive circuit 18 inputs a pulse command signal, which is a pulse signal having a predetermined frequency as shown in FIG. 2A, from an input terminal 19, and outputs the pulse command signal.
As shown in (3), the control voltage which is inverted and boosted is generated. The maximum value of this control voltage is set to a voltage higher than the voltage required to operate the switching element 12 in the linear region, for example, 3V to 5V, and has a fast rise.

A current detector 20 is provided between the switching element 12 and the load 14, and the load current detected by the current detector 20 is amplified by an amplifier 22 having a built-in low frequency pass filter. It is supplied to the error amplifier 24. The error amplifier 24 includes a control level setter 26
The control level setting signal is also supplied from.

The error amplifier 24 is an error amplification output obtained by amplifying the difference between the output signal of the amplifier 22 and the control level setting signal,
For example, 2 to 4 V is applied to the base of the PNP transistor 30 via the resistor 28. The collector of this transistor 30 is grounded, and the emitter is a diode 32.
It is connected to the connection point 34 of the resistors 15 and 16 via. The diode 32 has its anode at the connection point 3
At 4, the cathode is connected to the emitter of transistor 30.

An NP is provided between the connection point 34 and the ground potential point.
The collector-emitter circuit of the N-transistor 35 is connected. A pulse command signal is supplied to the base of the transistor 35.

The output of the error amplifier 24 is the high voltage generator 3
6 is supplied. The high voltage generating unit 36 is composed of, for example, an operational amplifier, and increases the output of the error amplifier 24 by 1.2 times to 1.5 and outputs it.

Voltage dividing resistors 38 and 40 are connected in series between the output side of the high voltage generating section 36 and the ground potential point, and both ends of the ground side voltage dividing resistor 40 are charged. Capacitor 42 is connected in parallel.

Further, an NP is connected in parallel with the capacitor 42.
The collector-emitter conductive path of N-transistor 44 is connected. In addition, this switching transistor 44
The output of the differentiating circuit 46 is supplied to the base of the.
The differentiating circuit 46 detects the fall of the pulse command signal and generates a positive pulse signal as shown in FIG. 2 (c).

The voltage across the voltage dividing resistor 40 is supplied to the base of the PNP transistor 50 via the buffer 48. The collector of the transistor 50 is grounded, and the emitter is connected to the connection point 34 via the diode 52. The diode 52
Has its anode connected to the connection point 34 side and its cathode connected to the emitter side of the transistor 50.

In such a pulse power supply device, as shown in FIG.
After the time t0 in (a) has passed and until the time t1, the pulse command signal at the input terminal 19 is L.
It is at the level, and the transistor 35 is off.
The control voltage from the drive circuit 18 is at a high level, and the switching element 1 is connected via the resistors 16 and 15.
Since it is supplied to the gate of No. 2, the switching element 12 is turned on and current is supplied to the load 14.

This current is detected by the current detector 20, amplified by the amplifier 22, and supplied to the error amplifier 24. The error amplifier 24 amplifies the error between the output of the amplifier 22 and the control level setting signal from the control level setting device 26 as shown by the solid line in FIG. 2 (d), and this error amplification signal is passed through the resistor 28. It is supplied to the base of the transistor 30.

At this time, the base and emitter of the transistor 30 are forward-biased, the transistor 30 conducts with a conductivity corresponding to the error amplification output, and the voltage at the connection point 34 corresponds to the error amplification output, for example, a switching element. 12
Voltage of 3 to 5V required to operate the device in the linear region
Controlled by. That is, as shown by the dotted line in FIG.
The control voltage is higher than the voltage for operating the switching element 12 in the linear region, but the voltage actually applied to the gate of the switching element 12 is controlled to 3 to 5 V as shown by the solid line. This control is performed so that a constant current flows through the load 14 while the pulse command signal is at the L level.

The error amplified output is also output to the high voltage generation unit 36.
To 1.2 to 1.5 times. The voltage of the high voltage generator 36 charges the capacitor 42 and is supplied to the base of the transistor 50 via the buffer 48. This base voltage has an error amplification output of 1.2.
Since the voltage is generated based on the output of the high voltage generating unit 36 which is 1.5 to 1.5 times, the voltage is higher than the voltage at the connection point 34, and the transistor 50 is turned off.

Next, at time t1, when the pulse command signal becomes H level, the output of the drive circuit 18 becomes 0,
At the same time, the transistor 35 is turned on and the switching element 12 is turned off. As a result, the current flowing through the load 14 becomes zero, and no new signal is supplied to the amplifier 22, but since the amplifier 22 has a built-in low-pass filter, an output is generated and this is supplied to the error amplifier 24. The error amplifier 24 also produces an error output. At this time, since the output of the drive circuit 18 is 0, the transistor 30 is off, but the high-voltage creating unit 36 creates a high voltage, which causes the capacitor 42 to be charged.

Next, at time t2, the pulse command signal falls to L level and the control voltage rises. At this time, the transistor 30 is turned on to clamp the voltage at the connection point 34 as described above.
At the same time, according to the fall of the pulse command signal,
As shown in (c), the differentiating circuit 46 produces an output and the transistor 44 is turned on. This makes the capacitor 4
2 is discharged and the base voltage of the transistor 50 is shown in FIG.
It decreases as indicated by the alternate long and short dash line in (d).

At this time, since the control voltage is applied from the drive circuit 18 to the connection point 34, the emitter-base voltage of the transistor 50 becomes a forward direction, the transistor 50 becomes conductive, and the voltage of the connection point 34 becomes It is clamped to a value obtained by adding the forward voltage of the diode 52 and the emitter-collector voltage of the transistor 50.

When the output of the differentiating circuit 46 disappears, the capacitor 42 is charged again by the high voltage of the high voltage generating section 36, and the base voltage of the transistor 50 also increases with this charging. Accordingly, the voltage at the connection point 34 also increases. Therefore, the voltage applied to the gate of the switching element 12 gradually increases from the value obtained by adding the forward voltage of the diode 52 and the emitter-collector voltage of the transistor 50. The charging time constant (determined by the values of the capacitor 42 and the resistor 38)
Is selected to be substantially equal to the rising time of the control voltage. For example, if the rising of the control voltage is 10 μS, the charging time constant is also selected to be 10 μS.

When the voltage is applied to the gate of the switching element 12 in this manner, as is apparent from the comparison between FIGS. 3A and 3B, from time t2 when the voltage is applied to the switching element 12, At time t21 when the gate input capacitance of the switching element 12 is charged and the time required for the gate voltage to exceed the threshold voltage elapses, the switching element 12 turns on and current flows from the switching element 12 to the load 14.

Eventually, the base voltage of the transistor 50 becomes equal to or higher than the voltage at the connection point 34, and the transistor 50 is turned off. After that, the voltage at the connection point 34 is controlled by the transistor 30, the diode 32, the error amplifier 24, and the like, as described above.

If the transistor 30 and the diode 3
2. When the control voltage higher than the voltage required to operate the switching element 12 in the linear region is controlled by the drive circuit 18 only by the error amplifier 24 and the like, when the control voltage rises, the switching element 1
Although it takes time for the voltage supplied to 2 to overshoot and reach a stable state, in this embodiment, the high voltage generating unit 36, the resistors 38 and 40, the transistors 44 and 50,
By providing the capacitor 42, the diode 52, the differentiating circuit 46, etc., the gate voltage of the switching element 12 does not overshoot.

Although the buffer 48 is provided in the above embodiment, it is unnecessary in some cases. Also, the transistor 3
Although PNP transistors are used for 0 and 50, NPN transistors can also be used. Further, in the above embodiment, the current of the load 14 is detected and the switching element 12 is controlled accordingly, but the voltage of the load 14 may be detected and the switching element 12 may be controlled accordingly. .

[0028]

As described above, according to the present invention, the rise of the control voltage is detected, the gate voltage is clamped to the low voltage at the time of the rise of the control voltage, and then the gate voltage is gradually increased. Since it is configured, even if a control voltage with a fast rise is used, the gate voltage does not overshoot, and a fast and stable gate voltage can be applied to the gate of the switching element.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a pulse power supply device according to the present invention.

FIG. 2 is a waveform chart of each part of the embodiment.

FIG. 3 is a diagram showing a relationship between a gate voltage and an output current of the switching element of the same example.

[Explanation of symbols]

 10 DC Power Supply 12 Switching Element 14 Load 18 Drive Circuit (Control Voltage Generating Means) 20 Current Detector (First Detection Means) 24 Error Amplifier (First Control Means) 30 Transistor (First Control Means) 32 Diode ( 1st control means) 36 high voltage creation part (2nd control means) 40 resistor (2nd control means) 42 capacitor (2nd control means) 44 transistor (2nd control means) 50 transistor (1st control means) 2 control means) 52 diode (second control means)

Claims (1)

[Claims] 1. A DC power supply, an insulating input type switching element connected in series to the DC power supply to supply power to a load, and a control voltage higher than a voltage required to operate the switching element in a linear region. Of the control voltage generating means for generating a constant voltage, a first detecting means for detecting a current or a voltage of the load, and a switching signal for the switching element according to a detection signal and a set value of the first detecting means. First control means for controlling the value of the control voltage supplied from the control voltage generation means, second detection means for detecting the start of generation of the control voltage, and second detection at the start of generation of the control voltage. A second control means for clamping the control voltage to a low voltage in accordance with a detection signal from the means, increasing the control voltage thereafter, and supplying the voltage to the switching element.