JP2621682B2 - DC brushless motor inverter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter circuit of a DC brushless motor, and more particularly to an inverter circuit of a DC brushless motor that directly drives a motor by a high-voltage DC power supply.

[0002]

2. Description of the Related Art Conventionally, an inverter circuit has been used to drive a DC brushless motor. FIG. 3 is a circuit diagram showing an inverter circuit of a conventional DC brushless motor. This inverter circuit has a well-known circuit configuration,
For example, it is disclosed in JP-A-63-206187.

In the figure, 1 is a DC power supply, 2 is a motor winding, and 3 is a semiconductor switch group for outputting a winding current of the motor winding 2. This semiconductor switch group 3
More specifically, the upper part is composed of PNP transistors Qu1, Qu
2, Qu3 and diodes Du1, Du1 connected between the emitter and collector of each of the transistors Qu1, Qu2, Qu3.
Du2 and Du3, and the lower stage is composed of NPN transistors Qd1, Qd2 and Qd3, and these transistors Qd1, Qd2 and Qd3.
It comprises diodes Dd1, Dd2 and Dd3 connected between the emitter and the collector of Qd3.

In the DC brushless motor inverter circuit having this configuration, a DC voltage is supplied from the DC power supply 1 to the semiconductor switch group 3. And the semiconductor switch group 3
Upper and lower transistors Qu1, Qu2, Qu
3, the operation of Qd1, Qd2, Qd3 is appropriately controlled by a drive signal from a control means (not shown), so that the motor winding 2
Is supplied with a predetermined winding current to rotate a rotor (not shown) having a permanent magnet.

[0005] This type of DC brushless motor inverter circuit is driven by a relatively low voltage DC power supply. That is, the conventional DC brushless motor is driven by a DC power supply of a comparatively low voltage (for example, about 30 V DC) which temporarily drops a high DC voltage to a low DC voltage. 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 (about 130 V to 300 V DC) which is merely a rectified commercial power supply, the semiconductor switch group 3 of the inverter circuit may be destroyed. That is, in this case, of course,
Although a high withstand voltage type element is used for each transistor of the semiconductor switch group 3, the lower transistors Qd1, Qd
Under the influence of the operation of d2 and Qd3, the upper-stage transistors Qu1, Qu2 and Qu3 operate, and the upper-stage transistors Qu1, Qu2 and Qu3 and the lower-stage transistors Qd1 and Q3
This is because d2 and Qd3 are in a so-called short-circuit state, and the upper-stage transistors Qu1, Qu2 and Qu3 are damaged. this,
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 at the lower stage, the transistor Qd1 operates in a state where the collector potential is saturated. At that time, the rate of change (dV / If dt) is large, the potential of the emitter of the upper-stage transistor Qu1 drops sharply with respect to the base.
Emitter → base → collector and displacement current (arrow in the figure)
Flows. As a result, the transistor Qu1 operates even though the transistor should be in the off state, and the upper and lower transistors Qu1 and Qd1 enter a through state, causing a large current to flow and causing damage.

In order to prevent this, there is a method of applying a reverse bias so that the transistor Qu1 does not operate. However, the inverter circuit according to this method requires a special power supply, complicates the circuit configuration and costs. It will be expensive.

Therefore, an inverter circuit of a DC brushless motor as shown in FIG. 4 has been conventionally considered.
FIG. 4 is a circuit diagram showing another conventional DC brushless motor inverter circuit disclosed in Japanese Patent Application No. 1-245497. In the drawing, reference numerals 1 to 3 are the same or corresponding components as those in FIG.

In the figure, Q4, Q5 and Q6 are PNP transistors C1 and C1 inserted between the base and the emitter of the high withstand voltage type PNP transistors Qu1, Qu2 and Qu3 in the upper stage 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 transistors Q4 and Q6.
Diodes inserted between the bases and emitters of Q5 and Q6. The concrete connection of the transistors Q4, Q5, Q6 and the diodes D4, D5, D6 is such that the collectors of the transistors Q4, Q5, Q6 are connected to the bases of the PNP transistors Qu1, Qu2, Qu3, and the emitters are connected to the power supply. And connect the base to capacitors C1, C2, C3
And diodes D4, D5 and D6.
The diodes D4, D5 and D6 are connected with their cathodes on the positive side of the power supply.

In this DC brushless motor inverter circuit, transistors Q4, Q5, Q6, a capacitor C
1, C2, C3 and diodes D4, D5, D6 constitute a protection circuit, and the protection circuit protects the upper-stage transistors Qu1, Qu2, Qu3.

This protection circuit operates as follows. For example, when an ON signal, which is a driver signal, is input to the base of the lower transistor Qd1 and the transistor Qd1 operates, a displacement current (arrow in the figure) flows from the emitter to the base of the transistor Q4. Thereby, the capacitor C
1 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 reliably turned off.

Therefore, as in the inverter circuit of the DC brushless motor shown in FIG. 3, the transistor Qu1 in the upper stage operates erroneously due to the rate of change (dV / dt) of the collector potential of the transistor Qd1 with respect to time. Since the transistors Qu1 and Qd1 in the upper part do not enter the through state, damage to the transistor Qu1 in the upper part can be prevented.

The diode D4 is inserted to discharge the charge stored in the capacitor C1.
When the lower transistor Qd1 is turned off and the collector potential rises, current flows from the capacitor C1 through the diode D4.

[0014]

In the inverter circuit of a conventional DC brushless motor as described above, in order to prevent damage to each element of the semiconductor switch group, a protection circuit as described in FIG. It was provided for each phase of the switch group 3.

However, in this protection circuit, the collector is connected to the bases of the upper-stage transistors Qu1, Qu2, Qu3,
Transistors Q4, Q5,
Q6, capacitors C1, C2, C3 inserted between the bases of the transistors Q4, Q5, Q6 and the collectors of the transistors Qu1, Qu2, Qu3 in the upper stage, and the base and power supply of the transistors Q4, Q5, Q6. Between the diodes D4, D5,
D6, and these protection circuits need to be provided for each phase of the semiconductor switch group 3, resulting in an extremely complicated circuit configuration. For this reason, the number of components is large, the wiring is complicated, and the circuit board is also large. Therefore, it has been difficult to make the inverter compact and modular.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a DC brushless motor inverter circuit having a simple circuit configuration and in which each element of a semiconductor switch group is not damaged even with a DC high voltage power supply.

[0017]

According to a first aspect of the present invention, a high withstand voltage type transistor and diode which form an upper part of a semiconductor switch group for outputting a winding current of a brushless motor and a lower part of the semiconductor switch group are formed. A high withstand voltage transistor and a diode, an inductor inserted between the emitter of the high withstand voltage transistor in the upper stage and the DC power supply, a base of the high withstand voltage transistor in the upper stage and a DC And a protection circuit comprising a resistor inserted between the power supply and the power supply.

Further, in the second invention, a high withstand voltage type transistor and diode forming the upper part of the semiconductor switch group for outputting the winding current of the brushless motor, and a high withstand voltage forming the lower part of the semiconductor switch group Type transistor and diode, a diode inserted between the emitter of the high withstand voltage transistor in the upper stage and the DC power supply with the positive side of the power supply as the anode, and a base of the high withstand voltage transistor in the upper stage. And a protection circuit comprising a resistor inserted between the DC power supply.

[0019]

In the DC brushless motor inverter circuit according to the first aspect of the present invention, an inductor is inserted between the emitter of the high withstand voltage type transistor which forms the upper part of the semiconductor switch group and the DC power source, and the upper part of the upper part has a high voltage. Since a protection circuit is configured by inserting a resistor between the base of the withstand voltage type transistor and the DC power supply, the collector potential of the high withstand voltage type transistor in the upper part is affected by the operation of the lower part transistor. The inductor 7 delays the sudden change and the instantaneous current flows. When the lower stage transistor is activated, the upper stage transistor is also instantaneously activated, and the upper and lower stage transistors penetrate. Current can be prevented from flowing.

Further, in the DC brushless motor inverter circuit according to the second invention, a diode is inserted between the emitter of the high withstand voltage type transistor constituting the upper part of the semiconductor switch group and the DC power supply, with the positive side of the power supply as the anode. Then, since a protection circuit is configured by inserting a resistor between the base of the high withstand voltage type transistor of the upper part and the DC power supply, the base-emitter of the upper part transistor is set in a reverse bias state. , Prevents the instantaneous current from flowing due to the sudden change in the collector potential of the upper transistor due to the operation of the lower transistor, preventing the lower transistor and the upper transistor from operating simultaneously, The upper and lower transistors do not pass through, and a large current does not flow through the transistors.

[0021]

Embodiments of the present invention will be described below.

<Embodiment of First Invention> FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor according to one embodiment of the first invention. In the figure, the same reference numerals and symbols as those of the above-mentioned conventional example indicate the same or corresponding components as those of the above-mentioned conventional example. Although the circuit is described in detail for only one phase of the semiconductor switch group 3 in the figure, the same circuit configuration is used for the other two phases. That is, also in the other two phases, the upper part has a withstand voltage type PNP transistor Qu2, Q2.
u3 and diodes Du2 and Du3, and the lower part is composed of high voltage NPN transistors Qd2 and Qd3 and diodes Dd2 and Dd3, and the respective resistors and the like are similarly arranged (not shown). ).

In the figure, 4 is an AC power supply, 5 is a rectifier circuit for converting AC to DC, 6 is a smoothing capacitor, 7 is an inductor functioning as a choke coil, and R1 to R7 are resistors. The inductor 7 is inserted between the emitters of the high voltage PNP transistors Qu1, Qu2, Qu3 in the upper stage and the rectified DC power supply, and the resistor R
1 is a high withstand voltage type PNP transistor Qu1,
It is inserted between the bases of Qu2 and Qu3 and the DC power supply. 3U, 3V, and 3W indicate each phase of the semiconductor switch group 3. The reflux diodes Du1, Du2, and Du3 paired with the high withstand voltage type PNP transistors Qu1, Qu2, and Qu3 in the upper stage have the cathode on the positive side of the power supply and are connected between the DC power supply and the inductor 7. ing.

In the inverter circuit of this DC brushless motor, a protection circuit is formed by the inductor 7 and the resistor R1, and the protection circuit uses the upper transistors Q1, Q2.
u2 and Qu3 are protected.

This protection circuit operates as follows. For example, when an ON signal, which is a driver signal, is input to the base of the transistor Qd1 at the lower stage and the transistor Qd1 operates, the rate of change (dV / dt) of the collector potential with respect to time increases. Although the upper-stage transistor Qu1 attempts to turn on due to the displacement current, the inductor 7 functions as a choke coil, and the instantaneous current flows is delayed. For this reason, even if the transistor Qu1 in the upper stage operates instantaneously in response to an instantaneous change, even if the transistors Qu1 and Qd1 in the upper and lower stages are simultaneously operated, a large current does not flow. Therefore, even when the lower transistor Qd1 is switched at high speed by PWM control or the like, the upper transistor Qu1 can be protected without being damaged.

As described above, in the inverter circuit of the DC brushless motor of this embodiment, the upper stage of the semiconductor switch group 3 for outputting the winding current of the brushless motor is provided with the high withstand voltage type PNP transistors Qu1, Qu2, Qu3. And high-voltage NPN transistors Qd1, Qd2, Qd3 and diodes Dd1, Dd2, Dd3 in the lower stage, and high-voltage PNP in the upper stage. An inductor 7 inserted between the emitters of the transistors Qu1, Qu2, Qu3 and the DC power supply;
The upper withstand voltage type PNP transistor Qu1,
A protection circuit is constituted by the resistor R1 inserted between the bases of Qu2 and Qu3 and the DC power supply.

Therefore, the transistors Qd1,
Due to the influence of the operation of Qd2 and Qd3, the collector potential of the high withstand voltage type transistors Qu1, Qu2 and Qu3 in the upper stage changes abruptly and the instantaneous current flows through the inductor 7, and is delayed.
Since a large current does not flow in the instantaneous simultaneous operation state of the lower-stage transistors Qd1, Qd2, Qd3 and the upper-stage transistors Qu1, Qu2, Qu3, the transistors Qu1, Qu2, Qu3
Can be prevented from being damaged. As a result, the semiconductor switch group 3 of the inverter circuit is not destroyed even if the DC high-voltage power supply (about 130 V to 300 V DC) just rectifying the commercial power is directly supplied to the inverter circuit of the DC brushless motor. Safety and reliability are improved.

Moreover, this can be realized only by adding a protection circuit including the inductor 7 and the resistor R1, and there is no need to provide a protection circuit for each of the U, V and W phases of the semiconductor switch group 3 as in the conventional case. It can be realized with a very simple circuit configuration. Therefore, the number of components is reduced, the wiring is simplified, and the circuit board is also reduced, so that the inverter can be easily downsized and modularized. Further, a special power supply is not required unlike an inverter circuit for applying a reverse bias to the transistors Qu1, Qu2, Qu3 in the upper stage, and the manufacturing cost can be reduced.

<Embodiment of Second Invention> FIG. 2 is a circuit diagram showing an inverter circuit of a DC brushless motor according to one embodiment of the second invention. In the drawing, the same reference numerals and symbols as those of the above-described conventional example and embodiment denote the same or corresponding components as those of the above-described conventional example and embodiment. Although the circuit is described in detail for only one phase of the semiconductor switch group 3 in the figure, the same circuit configuration is used for the other two phases. That is, also in the other two phases, the upper part is composed of withstand voltage type PNP transistors Qu2 and Qu3 and the diodes Du2 and Du3, and the lower part is high withstand voltage type NPN transistor Q2.
d2, Qd3 and diodes Dd2, Dd3.
Each of the resistors and the like are similarly arranged (not shown).

In the figure, reference numeral 8 denotes a high withstand voltage type P in the upper part.
A diode inserted between the emitters of the NP-type transistors Qu1, Qu2, Qu3 and the rectified DC power supply.
1 to R7 are each a resistor. The diode 8 has a cathode with a high withstand voltage type PNP transistor Qu1, Q
At least one or more anodes are connected in series as the emitter side of u2 and Qu3, and the anode is inserted as the positive side of the rectified DC power supply. The resistor R1 is a high withstand voltage type PNP transistor Qu1 or Qu2 in the upper stage. , Qu3 and the DC power supply. In addition, the high withstand voltage type PN
The reflux diodes Du1, Du2, Du3 paired with the P-type transistors Qu1, Qu2, Qu3 have their cathodes on the positive side of the power supply and are connected to the anode side of the diode 8.

In the inverter circuit of this DC brushless motor, a protection circuit is formed by the diode 8 and the resistor R1, and the transistors Qu1 and Q1 in the upper stage are formed by the protection circuit.
u2 and Qu3 are protected.

This protection circuit operates as follows. For example, when the upper transistor of the other phase other than the U phase is turned on and the lower transistor Qd1 of the U phase is turned on, the current is supplied to the upper transistor of the other phase through the diode 8. Then, after flowing through the motor winding 2, the current flows through the lower transistor Qd1 of the U phase. At this time, a predetermined voltage drop occurs in the diode 8, and the resistance R1 on the base side of the upper-stage transistor Qu1 of the U-phase connected to the power supply side
Is higher than the potential of the emitter, the base-emitter of the transistor Qu1 is in a so-called reverse bias state, and the transistor Qu1 does not turn on. Therefore, it is possible to prevent the upper-stage transistor Qu1 from operating in response to an instantaneous change, and the upper-stage and lower-stage transistors Qu1 and Qd1 do not enter a through state, so that a large current does not flow. Therefore, even when the lower transistor Qd1 is switched at high speed by PWM control or the like, the upper transistor Qu1 can be protected without being damaged.

As described above, in the inverter circuit of the DC brushless motor of this embodiment, the upper stage of the semiconductor switch group 3 for outputting the winding current of the brushless motor is provided with the high withstand voltage type PNP transistors Qu1, Qu2, Qu3. And high-voltage NPN transistors Qd1, Qd2, Qd3 and diodes Dd1, Dd2, Dd3 in the lower stage, and high-voltage PNP in the upper stage. At least one or more diodes 8 inserted between the emitters of the transistors Qu1, Qu2, Qu3 and the DC power supply with the positive side of the power supply as the anode, and the high withstand voltage type PNP transistors Qu1, Qu2,
A protection circuit is constituted by the resistor R1 inserted between the base of Qu3 and the DC power supply.

Therefore, the high withstand voltage type PNP in the upper stage
By setting the base-emitters of the transistors Qu1, Qu2, and Qu3 in a reverse bias state, the NPN transistors Qd1, Qd2, and Qd3 of the high withstand voltage in the lower part are affected by the operation of the high withstand voltage in the upper part. Transistors Qu1, Qu2, Q
It is possible to prevent the instantaneous current from flowing due to a sudden change in the collector potential of u3. For this reason, the transistors Qd1,
Qd2, Qd3 and the upper-stage transistors Qu1, Qu2, Qu3 can be prevented from operating at the same time, and the upper-stage and lower-stage transistors Qu1, Qu2, Qu3, Qd1, Qd2, Qd3 do not pass through and a large current flows. Since there is no transistor Qu1,
Qu2 and Qu3 can be prevented from being damaged. As a result, a DC high-voltage power supply (about 130 V to 300 V DC) which merely rectifies a commercial power supply to the inverter circuit of the DC brushless motor.
Directly, the semiconductor switch group 3 of the inverter circuit is not destroyed, so that safety and reliability are improved.

Moreover, this can be realized only by adding a protection circuit consisting of the diode 8 and the resistor R1, and there is no need to provide a protection circuit for each of the U, V and W phases of the semiconductor switch group 3 unlike the conventional case. It can be realized with a very simple circuit configuration. Therefore, the number of components is reduced, the wiring is simplified, and the circuit board is also reduced, so that the inverter can be easily downsized and modularized. Further, a special power supply is not required unlike an inverter circuit for applying a reverse bias to the transistors Qu1, Qu2, Qu3 in the upper stage, and the manufacturing cost can be reduced.

In the first embodiment of the present invention, the purpose is mainly to protect the PNP transistors Qu1, Qu2, and Qu3 in the upper stage of the semiconductor switch group 3. However, the present invention can also be applied to the protection of NPN transistors. It is. However,
In general, a high breakdown voltage type transistor has a smaller allowable capacity than a PNP type transistor than an NPN type transistor. Therefore, the configuration as in this embodiment is more effective.

[0037]

As described above, the inverter circuit of the DC brushless motor according to the first invention constitutes a protection circuit for protecting the high withstand voltage type transistor in the upper part of the semiconductor switch group by the inductor and the resistor. Due to the effect of the operation of the lower transistor, the collector potential of the high withstand voltage type transistor of the upper stage changes abruptly and the instantaneous current flows is delayed by the inductor , and the upper transistor is activated when the lower transistor is activated. Also operate instantaneously, and a through state of the upper and lower transistors occurs, but a large current does not flow through the transistors. Therefore, since a large current does not flow and the transistor can be prevented from being damaged, even if a high DC voltage is directly supplied to the inverter circuit, the semiconductor switch group is not destroyed, so that the safety and reliability are high, and furthermore, this is specially designed. Since a simple power supply is not required and the circuit configuration can be easily realized, the manufacturing cost is reduced.

Further, in the inverter circuit of the DC brushless motor according to the second invention, the protection circuit for protecting the high withstand voltage type transistor in the upper part of the semiconductor switch group by the diode and the resistor is constituted. In the reverse bias state between the base and the emitter, it is possible to prevent the lower transistor and the upper transistor from operating at the same time due to the influence of the operation of the lower transistor, and the upper and lower transistors are in a through state. No.
Therefore, since a large current does not flow and the transistor can be prevented from being damaged, even if a high DC voltage is directly supplied to the inverter circuit, the semiconductor switch group is not destroyed, so that the safety and reliability are high, and furthermore, this is specially designed. Since it can be realized with a simple circuit configuration without requiring a simple power supply, the manufacturing cost is also reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor according to one embodiment of the first invention.

FIG. 2 is a circuit diagram showing an inverter circuit of a DC brushless motor according to one embodiment of the second invention.

FIG. 3 is a circuit diagram showing an inverter circuit of a conventional DC brushless motor.

FIG. 4 is a circuit diagram showing an inverter circuit of another conventional DC brushless motor.

[Explanation of symbols]

 Reference Signs List 1 DC power supply 2 Motor winding 3 Semiconductor switch group 3U U-phase semiconductor switch group 3V V-phase semiconductor switch group 3W W-phase semiconductor switch group 4 AC power supply 5 Rectifying circuit 7 Inductor 8 Diode Qu1, Qu2, Qu3 Transistor Du1, Du2, Du3 diodes Qd1, Qd2, Qd3 Transistors Dd1, Dd2, Dd3 Diodes R1, R2, R3, R4, R5, R6, R7 Resistance

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiko Hotta 1-3-3 Komabacho, Nakatsugawa-shi, Gifu Pref. JP-A-59-94906 (JP, A) JP-A-53-110030 (JP, A) JP-A-2-280672 (JP, A) JP-A-57-91678 (JP, A)

Claims (2)

(57) [Claims] 1. A high withstand voltage type transistor and diode forming an upper part of a semiconductor switch group for outputting a winding current of a brushless motor, and a high withstand voltage type transistor and diode forming a lower part of the semiconductor switch group. An inductor inserted between the emitter of the high voltage transistor of the upper stage and the DC power supply, and a resistor inserted between the base of the high voltage transistor of the upper stage and the DC power supply. And a protection circuit comprising: a DC brushless motor inverter circuit. 2. A high withstand voltage type transistor and diode forming an upper part of a semiconductor switch group for outputting a winding current of a brushless motor, and a high withstand voltage type transistor and diode forming a lower part of the semiconductor switch group. A diode inserted between the emitter of the high withstand voltage transistor of the upper part and the DC power supply with the positive side of the power supply as the anode, and a diode between the base of the high withstand voltage transistor of the upper part and the DC power supply. And a protection circuit comprising a resistor inserted into the inverter circuit of the DC brushless motor.