JPH03265460A - Power supply circuit for controlling transistor - Google Patents

Abstract

PURPOSE:To eliminate a transformer and to reduce the weight and the size by charging first and second charging circuits with positive and second DC voltages from a DC power supply for driving a load through utilization of ON/OFF operation of a switching transistor for driving the load. CONSTITUTION:When a transistor Tr 5 is turned OFF, a DC voltage +DV is applied from a power supply 7 through the path AA of a power supply circuit 1 for driving the transistor to a load 9 and a capacitor Cl is charged to the Zener voltage +VDC of a Zener diode ZD1. Consequently, a capacitor C3 is charged upto +DV along a path BB. When the Tr 5 is turned ON, a path CC is formed and the dC voltage +DV of the capacitor C3 is fed through the collector-emitter of the Tr 5 to a capacitor C2 thus charging the capacitor C2 upto the Zener voltage (-VDC) of a Zener diode ZD 2. Positive or negative DC voltage + or -VDC is fed to a driving circuit 3, with the emitter of the Tr 5 as a reference, depending upon ON or OFF of the Tr 5.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a bridge circuit such as an inverter bridge circuit using switching transistors that drive a load such as a servo motor, and in particular, to By utilizing the on/off operation of the switching transistor itself, without using a transformer,
The present invention relates to a transistor control power supply circuit that supplies positive and negative control DC voltages to the input terminals of switching transistors in order to operate the switching transistors at high speed.

[Conventional technology]

FIG. 3 shows a conventional inverter bridge circuit for driving and controlling a three-phase servo motor.

In FIG. 3, a three-phase servo motor is connected to an inductive load 70,
72.74 and turn these loads on.
Load driving switching transistors 50, 52, 54, 5658, and 60 are provided for off-driving. These transistors 50, 52, 54, 56.58
．． 60 is.

It is driven on and off according to the switching control signal SWI-3W6 applied to the drive circuits 20, 22, 24, 26, 28, and 30. Switching control signal SWI~S
W6 is, for example, a control signal based on the PWM method.

In order to operate the transistors 50, 52, 54, 56, 58 and 60 at high speed.

It is necessary to supply positive and negative voltages with respect to the emitters to the bases of the transistors 50, 52, 54, 56, and 58, 60. For this reason, transistor control power supply circuits 12, 14, 16, and 18 are provided.

Among these control power supply circuits, power supply circuit 14゜16.1
8 respectively transfer the voltage from the AC power supply 10 to the transformer 1
1 secondary coil 121 and insulated secondary coil 122 ~
2 which reduced the primary voltage of transformer 110 through 124
The neutral point of the secondary coils 122-124 is connected to the emitter of the transistor 50.52.54. The secondary AC voltage from the secondary coil is rectified by a diode D, further smoothed by a capacitor C, and applied to the emitters of the transistors 50, 52, and 54 as positive and negative control DC voltages.

Note that the transistors 56, 58.6 shown at the bottom of the second drawing
Since 0 is commonly controlled, there is no need to provide the above control power supply circuit.

[Problem to be solved by the invention]

In the case of the three-phase inverter bridge circuit for driving a three-phase servo motor shown in FIG. 3, four transformer tertiary coils are required. In particular, the AC power supply 10 uses a low frequency commercial frequency power supply.

The transformer 12 having four secondary coils becomes large.

On the other hand, there is a demand for smaller inverter bridge circuits, and as long as such large transformers are used, there is a problem that this objective cannot be achieved.

This problem is not limited to inverter bridge circuits, but also occurs in other circuits in which positive and negative DC voltages are applied as control voltages to the input terminals of load-driving switching transistors in order to switch them at high speed. ing.

Therefore, (1) the present invention aims to reduce the size and weight of the above-mentioned transistor control power supply circuit. Instead of generating DC voltage using
The on/off operation of the load driving switching transistor itself is used to charge the voltage of the control DC power supply.
This is based on the concept of supplying the voltage for controlling the transistor.

For this reason, (1) the transistor control power supply circuit of the present invention is a transistor control power supply circuit that applies positive and negative DC voltages to the input terminals of a load drive switching transistor that is turned on and off at a predetermined cycle via a drive circuit. As such, a first charging circuit and a second charging circuit are provided.

[Operation] The first charging circuit charges the voltage of the control power supply when the transistor is off, and supplies a positive control voltage to the input terminal of the transistor using this charging voltage when the transistor is on. At the same time, the boot capacitor for supplying power to the second charging circuit is charged.

Further, the second charging circuit charges the voltage of the control power supply from the boot capacitor via the output terminal of the transistor when the transistor is on, and uses this charging voltage to charge the voltage of the transistor when the transistor is off. Supply a negative control voltage to the output terminal.

〔Example〕

A first embodiment of the present invention will be described with reference to FIG. 1st
The figure shows an example of driving one phase of a three-phase servo motor.

One phase of the servo motor is shown as a load 9, and an NPN transistor 5 is used as a load driving switching transistor for driving this load 9. A DC voltage +DV from the load driving power source 7 is applied to the load 9 via the transistor 5 . Further, a transistor drive circuit 3 is provided that turns on and off the transistor 5 based on the switching signal SW. This on
As the off control, in this embodiment, on/off control based on PWM control is performed.

The output terminal of the transistor 5, that is, the positive and negative DC voltages VDC and -VDC with respect to the emitter, are connected to the transistor 5.
The transistor control power supply circuit 1, to which the transistor control power supply circuit 1 is connected as shown in the figure, includes a dropping resistor R1, a third backflow prevention diode D3, a first capacitor CI, and a first capacitor CI. Zener diode ZD 1. First and second backflow prevention diodes DI and D2. Second capacitor C2, second Zener diode ZD2. and boot capacitor C
3 are connected as shown in the figure.

The first capacitor C1 is a capacitor that is charged from the DC voltage +DV of the load driving power supply 7 and provides a positive DC voltage +VDC to the emitter of the transistor 5, and is connected in parallel to the first capacitor C1. The first Zener diode ZD1 defines the magnitude of the positive DC voltage +VDC.

Similarly, the second capacitor C2 charges the DC voltage element DV of the load driving power supply 7 via the third capacitor C3, so that the emitter of the transistor 5 becomes a negative DC voltage -
This is a capacitor that provides VDC, and a second Zener diode ZD2 connected in parallel to this second capacitor C2 defines the magnitude of the negative DC voltage -VDC.

The dropping resistor R1 is a resistor for dropping the DC voltage +DV from the load driving power supply 7 to a voltage that charges the first capacitor CI, since it is too high to directly apply it to the first capacitor C1. be.

The operation of the circuit shown in FIG. 1 will be described below.

In the initial state, transistor 5 is in an off state. In this off state, the DC voltage +DV of the load driving power supply 7 is not applied to the load 9 via the transistor 5, but is applied to the transistor control power supply circuit l. Accordingly, the DC voltage +DV from the load driving power supply 7 is applied to the dropping resistor R1, the diode D3, . It is applied to the first capacitor C1, the emitter of the transistor 5, and the load 9.

The first capacitor CI has a positive voltage voltage V defined by the Zener voltage of the first Zener diode ZDI.
Charges up to DC.

The first capacitor C1 is the first Zener diode ZD
At the same time that the voltage is charged to the positive voltage VDC specified by the Zener voltage of I, the path BB shown by the dashed line in FIG.
Along the line, the boot capacitor C3 is charged. At this time, the diode D2 functions to prevent backflow to the second capacitor C2.

As described above, in response to the OFF operation of the transistor 5, the positive DC power supply voltage +VD is increased with respect to the emitter of the transistor 5.
C is supplied.

Next, when the transistor 5 is turned on via the drive circuit 3, the DC voltage +DV of the load drive power source 7 is applied to the load 9.

By turning on the transistor 5, a path CC shown by a broken line in FIG. 1 is formed. As a result, the DC voltage +DV charged in the boot capacitor C3 is applied to the second capacitor C2 via the collector and emitter of the transistor 5.

The second capacitor C2 is connected to the second Zener diode ZD
Charge to Zener voltage of 2. At this time, diode D
1 functions to secure the route CC.

As described above, in response to the ON operation of the transistor 5, the negative DC power supply voltage -VD is set with respect to the emitter of the transistor 5.
C is supplied.

Furthermore, when the transistor 5 is turned off by the drive circuit 3, the path A shown in solid line in FIG.
A is formed, the first capacitor C1 is charged,
At the same time, boot capacitor C3 is charged. When transistor 5 is turned on again, the second capacitor C2 is charged by discharging the boot capacitor C3, as described above.

In this way, the transistor control power supply circuit 1 shown in FIG. 1 responds to the on/off operation of the transistor 5 by
A positive DC voltage of 9 +VDC, - is applied to the terminal of transistor 5.
VDC can be supplied.

Since this circuit does not require a transformer and is composed only of electronic circuit elements, it can be made smaller and lighter.

FIG. 2 shows a transistor control power supply circuit according to a second embodiment of the present invention. This example is a switching system for driving loads.
N-channel FETs 5A and 5B were used as transistors. The drive circuit 3 is also shown in dark blue in detail. however,
The load driving power source 7 is omitted.

Regarding the circuit elements in the transistor control power supply circuit 1 shown in FIG. 2, the same reference numerals as the circuit elements in the transistor control power supply circuit 1 shown in FIG. 1 indicate the same circuit elements as in FIG. ing. The basic operation of the transistor control power supply circuit 1'' is the same as that of the transistor control power supply circuit 1 shown in FIG.

However, this transistor control power supply circuit 1' is further provided with a third Zener diode ZD3 that limits the discharge of the capacitor C1.

Furthermore, a series regulator consisting of a dropping resistor R2 and a transistor Q1 is used in place of the dropping resistor R1 in FIG. By using this series regulator, only the current required to charge the capacitor C1 flows through the dropping resistor R2, and the load on the dropping resistor is reduced. This improves the current supply capability of the control power source, which is determined by the capacitance of the dropping resistor.

The drive circuit 3 includes a light emitting diode LED driven by a switching control signal SW and a photodiode PD disposed opposite the light emitting diode LED.
A photocoupler 31 consisting of a transistor Q2 operated by this photodiode PD and a buffer circuit 33
and 34. It has nine resistors 35 and 36. Diode circuit 37 is connected to buffer circuits 33 and 34
It is arranged for the protection of

Depending on whether the switching signal SW is turned on or off.

The transistor Q2 of the photocoupler 31 is also turned on and off, and the FET5A,
Turn 5B on and off.

The transistor control power supply circuit 1'' is based on this FET5.
In response to the on/off operation of A and 5B.

As mentioned above, since the positive and negative DC voltages 1 VDC and -VDC are supplied to the gates of these FETs 5A and 5B, NPN) run raster 5. Although the N-channel FETs 5A and 5B have been described as examples, the same applies to cases where PNP transistors, P-channel FETs, and other transistors such as IGBTs are used.

In addition, the transistor control power supply circuit of the present invention is not only applied to inverter bridge circuits, but also to various other circuits that apply positive and negative voltages to the output terminals of transistors in order to perform high-speed switching operations of transistors. Applicable to

〔Effect of the invention〕

As described above, one aspect of the present invention utilizes the on/off operation of a switching transistor for driving a load to charge positive and negative DC voltages from a DC power source for driving a load, and to charge the input terminal of the transistor without using a transformer. Since the circuit configuration is such that positive and negative direct current can be applied to the circuit, a transistor control power supply circuit that is smaller and lighter can be realized.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a transistor control power supply circuit according to a first embodiment of the present invention. FIG. 2 shows a transistor control power supply circuit according to a second embodiment of the present invention. FIG. 3 shows an inverter bridge circuit using a conventional transistor control power supply circuit (explanation of symbols) 1. 1゛...Transistor control power supply circuit 23 - Drive circuit. 5°5A. 5A・・Load driving switching transistor.・Load driving power supply. ·load.

Claims (1)

[Scope of Claims] 1. A transistor control power supply circuit that applies positive and negative voltages to the input terminals of a load driving switching transistor that is driven on and off at a predetermined cycle via a driving circuit, comprising: a charging circuit and a second charging circuit, the first charging circuit charges the voltage of a control power supply for supplying a positive control voltage to the input terminal of the transistor when the transistor is off; 2. A transistor control power supply circuit, wherein the charging circuit is configured to charge the voltage of a control power supply for supplying a negative control voltage to the input terminal of the transistor when the transistor is on.