JPH0834697B2 - DC brushless motor inverter circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inverter circuit for a DC brushless motor, and more particularly to an inverter circuit for a DC brushless motor that directly drives the motor with a high-voltage DC power supply. is there.

[Prior Art] Conventionally, an inverter circuit is used to drive a DC brushless motor. FIG. 2 is a circuit diagram showing an inverter circuit of a conventional DC brushless motor. This inverter circuit has a well-known circuit configuration, and is disclosed, for example, in Japanese Patent Laid-Open No. 63-206187.

In the figure, 1 is a DC power supply, 2 is a motor winding,
A semiconductor switch group 3 outputs the winding current of the motor winding 2. Specifically, the semiconductor switch group 3 has PNP transistors Qu1, Qu2, Qu3 in the upper stage and diodes Du1, Du2, Du3 connected between the emitters and collectors of the transistors Qu1, Qu2, Qu3. And the lower part is composed of NPN transistors Qd1, Qd2, Qd3 and diodes Dd1, Dd2, Dd3 connected between the emitters and collectors of these transistors Qd1, Qd2, Qd3.

In the inverter circuit of the DC brushless motor configured as described above, the DC voltage is supplied from the DC power supply 1 to the semiconductor switch group 3. Then, the respective transistors Qu1, Qu2, Qu3, Qd1, Qd of the upper and lower stages of the semiconductor switch group 3
By appropriately controlling the operation of 2, Qd3 by a drive signal from a control means (not shown), a predetermined winding current is supplied to the motor winding 2, and a rotor (not shown) provided with a permanent magnet is supplied. It is rotating.

[Problems to be Solved by the Invention] In the inverter circuit of the conventional DC brushless motor as described above, it is driven by a DC power supply of a relatively low voltage. That is, in the conventional DC brushless motor, the DC high voltage is once dropped to the DC low voltage and driven by the DC power supply of this relatively low voltage (for example, about 30V DC). Then, the speed of the motor is controlled by changing the power supply voltage.

However, if this is performed using a DC high-voltage power supply (DC 130V to 300V or so) that is a rectified commercial power supply, the semiconductor switch group 3 of the inverter circuit may be destroyed. That is, in this case, naturally, high withstand voltage type elements are used for the respective transistors of the semiconductor switch group 3, but the operation of the transistors Qd1, Qd2, Qd3 in the lower stage portion affects the transistor Qu1 in the upper stage portion. , Qu2, Qu3 are activated, the upper-stage transistors Qu1, Qu2, Qu3 and the lower-stage transistors Qd1, Qd2, Qd3 are in a so-called short-circuit state, and the upper-stage transistors Qu1, Qu2, Qu3 are damaged. .
This will be specifically described with reference to FIG.

For example, when an ON signal, which is a driver signal, is input to the base of the transistor Qd1 in the lower part, the transistor Qd1 operates with the collector potential saturated, and at that time, the rate of change of this collector potential with time (dV / dt)
Is large, the potential of the emitter of the upper-stage transistor Qu1 drops sharply with respect to the base, and under this influence, a displacement current (arrow in the figure) flows from the emitter->base-> collector of the upper-stage transistor Qu1. As a result, the transistor Qu1 operates even though it should originally be in the off state, and the transistors Qu1 and Qd1 in the upper stage portion and the lower stage portion enter the through state, causing a large current to flow and damage.

In addition, to prevent this
There was also an inverter circuit that applied a reverse bias so that Qu1 would not operate. However, the inverter circuit according to this method requires a special power source, the circuit configuration is complicated, and the cost is high.

Therefore, an object of the present invention is to provide an inverter circuit for a DC brushless motor, which has a simple circuit configuration and in which each element of the semiconductor switch group is not damaged even with a DC high-voltage power supply.

[Means for Solving the Problems] An inverter circuit of a DC brushless motor according to the present invention is a high withstand voltage type PNP transistor Qu1, Qu2 which constitutes an upper stage of a semiconductor switch group 3 which outputs a winding current of a brushless motor. , Qu3 and diodes Du1, Du2, Du3, and high withstand voltage type NPN transistors Qd1, Qd2, Qd3 and diodes Dd1, Dd2, Dd3 which form the lower part of the semiconductor switch group 3.
, The collector is connected to the base of the PNP transistor Qu1, Qu2, Qu3, the emitter is connected to the power supply side transistors Q4, Q5, Q6, and the base of the transistor Q4, Q5, Q6 and the PNP transistor Qu1, Capacitors C1, C2, C3 inserted between the collectors of Qu2, Qu3 and the transistors Q4, Q5, Q6
And a protection circuit including diodes D4, D5, and D6 inserted between the base and the power source with the cathode on the positive side of the power source.

[Operation] In the inverter circuit of the DC brushless motor of the present invention, the high withstand voltage type of the upper stage portion of the semiconductor switch group 3 is used.
Insert transistors Q4, Q5, Q6 between the base and emitter of PNP type transistors Qu1, Qu2, Qu3.
Base of Q4, Q5, Q6 and the transistors Qu1, Qu2,
Insert capacitors C1, C2, C3 between the collector of Qu3,
Since diodes D4, D5, D6 are inserted between the bases and emitters of the transistors Q4, Q5, Q6 to form a protection circuit, the lower stage transistors Qd1, Qd2, Qd3 and the upper stage transistor Qu1, It is possible to prevent Qu2 and Qu3 from operating at the same time, and the upper and lower transistors Qu1, Qu2, Qu3, Qd1,
Since Qd2 and Qd3 do not pass through and a large current does not flow, damage to the transistors Qu1, Qu2 and Qu3 can be prevented.

[Embodiment] FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor according to an embodiment of the present invention. In the figure, 1 to 3 are the same or corresponding constituent parts as in the conventional example.

In the figure, Q4, Q5 and Q6 are PNP type transistors C1, C1 inserted between the base and emitter of the high withstand voltage type PNP type transistors Qu1, Qu2 and Qu3 in the upper part of the semiconductor switch group 3.
C2 and C3 are capacitors inserted between the bases of the transistors Q4, Q5 and Q6 and the collectors of the upper transistors Qu1, Qu2 and Qu3, and D4, D5 and D6 are the bases and emitters of the transistors Q4, Q5 and Q6. It is a diode inserted between and. The concrete connection of the transistors Q4, Q5, Q6 and the diodes D4, D5, D6 is made by connecting the collectors of the transistors Q4, Q5, Q6 to the PN
It is connected to the bases of P-type transistors Qu1, Qu2, Qu3, the emitter is connected to the power supply side, and the base is connected between the capacitors C1, C2, C3 and the diodes D4, D5, D6. Further, the diodes D4, D5, D6 are connected with their cathodes on the positive side of the power supply.

The inverter circuit of the DC brushless motor of this embodiment is configured as described above, and the transistors Q4, Q5, Q
6, a capacitor C1, C2, C3 and diodes D4, D5, D6 form a protection circuit, and this protection circuit protects the transistors Qu1, Qu2, Qu3 in the upper stage. Since the basic operation of rotating the motor by the inverter circuit of this DC brushless motor is the same as that of the above-mentioned conventional example, its explanation is omitted here. Therefore, here, the specific operation of the protection circuit will be mainly described.

For example, an ON signal, which is a driver signal, is input to the base of the transistor Qd1 in the lower stage, and this transistor Qd1
When 1 is activated, a displacement current (arrow in the figure) flows from the emitter to the base of transistor Q4. As a result, the capacitor C1 is charged. When the transistor Q4 operates, the voltage between the base and the emitter of the transistor Qu1 becomes the collector saturation voltage of the transistor Q4, and the transistor Qu1 is surely turned off.

Therefore, as in the past, due to the rate of change (dV / dt) in the collector potential of the transistor Qd1 with time, the upper-stage transistor Qu1 may malfunction and the upper-stage and lower-stage transistors Qu1 and Qd1 may be in the through state. Since it does not exist, damage to the upper transistor Qu1 can be prevented.
In particular, when the lower transistor Qd1 is switched at high speed by PWM control, for example, the rate of change of the collector potential of the transistor Qd1 with respect to time (dV / dt)
Therefore, it can be said that the effect of protecting the upper transistor Qu1 is great.

The diode D4 is inserted to discharge the electric charge charged in the capacitor C1, and when the transistor Qd1 in the lower stage is turned off and the collector potential rises, a current flows from the capacitor C1 through the diode D4. .

As described above, in the inverter circuit of the DC brushless motor of this embodiment, the upper stage portion of the semiconductor switch group 3 that outputs the winding current of the brushless motor is a high withstand voltage type PNP.
Type first transistors Qu1, Qu2, Qu3 and diode Du
1, Du2, Du3, the lower stage is composed of the second high-voltage type NPN type transistors Qd1, Qd2, Qd3 and the diodes Dd1, Dd2, Dd3, and the collector is the upper stage transistor.
Third transistors Q4, Q5, Q6, which are connected to the bases of Qu1, Qu2, Qu3 and whose emitters are connected to the power supply side, and the bases of the transistors Q4, Q5, Q6 and the transistors Qu1, Qu of the upper stage
Capacitors C1, C2, C3 inserted between the collectors of 2, Qu3
And a diode D4, D5, D6 inserted between the bases of the transistors Q4, Q5, Q6 and the power source with the cathode on the power source side to form a protection circuit.

Therefore, it is possible to prevent the transistors Qd1, Qd2, Qd3 in the lower stage and the transistors Qu1, Qu2, Qu3 in the upper stage from operating at the same time, and the transistors Qu1, Qu2, Qu in the upper and lower stages
Since 3, Qd1, Qd2, Qd3 do not pass through and a large current does not flow, damage to the transistors Qu1, Qu2, Qu3 can be prevented. Therefore, the DC high voltage power supply (DC130V ~ 30V
Even if the voltage (about 0 V) is directly supplied, the semiconductor switch group 3 of the inverter circuit is not destroyed and the safety and reliability are improved.

Besides, this is transistor Q4, Q5, Q6, capacitor C
This can be realized simply by adding a protection circuit consisting of 1, C2, C3 and diodes D4, D5, D6.
It does not require a special power supply like the inverter circuit that applies reverse bias to 2, Qu3, and the circuit configuration is relatively simple,
Manufacturing costs can also be reduced.

By the way, in the above-mentioned embodiment, the main purpose is to protect the PNP transistors Qu1, Qu2, Qu3 in the upper part of the semiconductor switch group 3, but the present invention can also be applied to the protection of NPN transistors. However, high withstand voltage transistors are usually
Since the PNP-type transistor has a smaller allowable capacity than the NPN-type transistor, the configuration of this embodiment is more effective.

[Effects of the Invention] As described above, the inverter circuit of the DC brushless motor of the present invention is of a high withstand voltage type that constitutes the upper stage of the semiconductor switch group that outputs the winding current of the brushless motor.
A protection circuit in which the PNP type first transistor and the high withstand voltage type NPN type second transistor forming the lower stage operate simultaneously prevents the lower stage transistor and the upper stage transistor from operating at the same time. Therefore, the transistors in the upper part and the lower part are not in the through state. Therefore, since a large current does not flow and damage to the transistor can be prevented, even if a high DC voltage is directly supplied to this inverter circuit, the semiconductor switch group is not destroyed, so it is highly safe and reliable. Since no power supply is required and the circuit configuration can be realized with a relatively simple structure, the manufacturing cost is low.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an inverter circuit of a conventional DC brushless motor. In the figure, 1 ... DC power supply, 2 ... Motor winding, 3 ... Semiconductor switch group, Qu1, Qu2, Qu3 ... Transistor, Du1, Du2, Du3 ...
… Diodes, Qd1, Qd2, Qd3 …… Transistors, Dd1, Dd
2, Dd3 …… Diode, Q4, Q5, Q6 …… Transistor, D4,
D5, D6 ... Diodes, C1, C2, C3 ... Capacitors. In the drawings, the same reference numerals and symbols indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A high-withstand-voltage PNP-type first transistor and diode that form an upper stage of a semiconductor switch group that outputs a winding current of a brushless motor, and a high withstand voltage that forms a lower stage of the semiconductor switch group. Mold NPN
Second transistor and diode, a collector connected to the base of the upper PNP first transistor, and an emitter connected to the power supply side, and a third transistor base. A protection circuit including a capacitor inserted between the collectors of the upper PNP transistors and a diode inserted between the base of the third transistor and the power supply with the cathode on the positive side of the power supply; Inverter circuit of DC brushless motor characterized by.