JPH06165575A - Inverter circuit of DC brushless motor - Google Patents

Abstract

(57) [Abstract] [Purpose] Prevents instantaneous ON operation of the upper and lower transistors with a simple circuit configuration and prevents damage to the elements. [Structure] High withstand voltage transistor Q at the upper stage of semiconductor switch group 1 for outputting winding current of a brushless motor
1 is a PNP type single or Darlington configuration, the lower stage transistor Q2 is an NPN type, and a diode 1 for preventing penetration is provided between the collector of the upper stage transistor Q1 and the collector of the lower stage transistor Q2.
Insert 1. [Effect] The junction capacitance between the base and collector of the transistors in the upper and lower stages is reduced, and the transistor in the lower stage is prevented from being turned on by the operation of the transistor in the lower stage.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Inverter circuits have been widely used for driving DC brushless motors. The configuration of this type of inverter circuit is disclosed in, for example, Japanese Patent Laid-Open No. 63-206.
No. 187 and Japanese Patent Application Laid-Open No. 3-112369.

That is, the inverter circuit is composed of a group of semiconductor switches for outputting the winding current of the brushless motor,
It has an arm corresponding to the number of phases, which is composed of an upper transistor and a lower transistor. The upper part of each arm is composed of high withstand voltage type transistors and diodes, and the lower part is composed of high withstand voltage type transistors and diodes.

The transistors in the upper and lower stages of each arm are turned on / off to rotate the motor in a predetermined direction. Especially, the transistors in the lower stage are PWM controlled to adjust the speed and the generated torque,
Switching on / off at high speed. Therefore, during PWM driving by turning on / off the transistor in the lower stage, when the transistor is turned on, the transistor in the upper stage also turns on until a current that passes through the emitter / base of the transistor in the upper stage flows, and momentarily. A large current may flow through the transistors in the upper and lower parts, which may damage each element of the semiconductor switch group.The damage to the elements due to the penetration of the transistors in the upper and lower parts is still prevented by the protection circuit. There is.

For example, a protection circuit composed of a transistor, a capacitor, and a diode is formed for the upper-stage transistor, or an inductor inserted between the emitter of the upper-stage transistor and the DC power source, and the base of the upper-stage transistor. By forming a protection circuit with a resistor inserted between the DC power source and the DC power source, damage to the element is prevented.

[0006]

In the conventional inverter circuit as described above, the protection circuit does not work when the transistor in the upper stage portion has a Darlington structure in order to increase the output of the inverter, and the upper and lower stage portions do not work. The problem that the element is damaged due to the instant-on operation of the transistor is included.

The present invention has been made in order to solve such a conventional problem. Even if the upper-stage transistor has a Darlington configuration, the instantaneous on operation of the upper-stage transistor and the lower-stage transistor is prevented by a simple circuit configuration. It is an object of the present invention to provide an inverter circuit for a DC brushless motor that can achieve the above.

[0008]

In a DC brushless motor inverter circuit according to a first aspect of the present invention, an upper stage transistor of a semiconductor switch group has a PNP type single or Darlington configuration, and the lower stage transistor is an NPN transistor.
In addition to being a mold, a diode for preventing penetration is inserted between the collector of the upper transistor and the collector of the lower transistor.

In the inverter circuit of the DC brushless motor according to the second invention, the upper stage portion of the semiconductor switch group is P
A Darlington structure is formed by combining NP-type and NPN-type transistors, and a bias resistance is not provided between the base and the emitter of the NPN-type transistor to prevent the penetration due to the diode characteristic between the base and the emitter.

[0010]

In the first aspect of the invention, since the junction capacitance between the collector of the lower transistor and the base of the upper transistor is reduced by inserting the diode, the current passing between the emitter and the base of the upper transistor is reduced. Even if the upper part has a Darlington structure, the transistor in the lower part is prevented from turning on due to the operation of the transistor in the lower part.

In the second aspect of the invention, the diode characteristic between the base and the emitter of the NPN type transistor in the rear stage of the upper stage Darlington transistors has a function equivalent to that of the diode in the first aspect. The operation of the lower-stage transistors prevents the upper-stage transistors from turning on.

[0012]

EXAMPLES Example 1. FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor as an embodiment of the present invention. In the figure, the detailed circuit configuration is shown for the one-phase arm (U-phase arm) 2 of the semiconductor switch group 1, but the other-phase arms (V-phase arm and W-phase arm) 3,
Since 4 has the same circuit configuration, it is omitted.

In the figure, 5 is an AC power source, 6 is a rectifying circuit for converting AC to DC, and 7 is a smoothing capacitor. In the figure, a semiconductor switch group 1 that constitutes an inverter main circuit is composed of three-phase arms 2, 3, and 4 of U, V, and W, and a motor winding 8 of a DC brushless motor is connected to the phase output of each phase. There is. The arms 2, 3 and 4 of each phase have PNP type transistors Q1, Q3 and Q5 each having a high withstand voltage in the upper stage and emitters of the transistors Q1, Q3 and Q5.
Due to the flywheel diode 9 connected between the collectors, the lower stage part is a high withstand voltage type NPN type transistor Q2, Q4, Q6 and each of these transistors Q2.
It is composed of a flywheel diode 10 connected between the emitter and collector of Q4 and Q6, and is respectively connected between the collectors of the upper stage transistors Q1, Q3 and Q5 and the collectors of the lower stage transistors Q2, Q4 and Q6. A diode 11 for preventing penetration is inserted.

In this inverter circuit, the upper stage transistors Q1, Q3, Q5 and the lower stage transistors Q2, Q4, Q6 of each phase of the arms 2, 3, 4 and the lower stage transistors Q2, Q4, Q6 are driven on / off by a driver signal to generate a direct current. The brushless motor is driven to rotate in a predetermined direction. PWM control is applied to the transistors Q2, Q4, Q6 in the lower part in order to adjust the speed and generated torque, and high-speed on / off switching is performed.

For example, when the transistor Q3 is on and the transistor Q2 is on / off, the current i1 shown in the figure flows during PWM driving. When the current of i2 passing through the emitter / base of the transistor Q1 flows with respect to the turning on of the transistor Q2, the transistor Q1 also turns on, and a large current of i3 instantaneously flows through the transistors Q1 and Q2.

However, in this inverter circuit, since the diodes 11 are respectively inserted between the collectors of the transistors Q1, Q3, Q5 in the upper stage and the collectors of the transistors Q2, Q4, Q6 in the lower stage, the transistors in the lower stage are inserted. The junction capacitance between the collectors of Q2, Q4, Q6 and the bases of the upper stage transistors Q1, Q3, Q5 decreases, and the current of i2 decreases. Therefore, the transistors Q1, Q3, Q5 in the upper stage are prevented from being turned on by the operation of the transistors Q2, Q4, Q6 in the lower stage, and the damage of the element is prevented with a simple structure.

Example 2. FIG. 2 is a circuit diagram showing a configuration of an arm 2 for one phase of an inverter circuit showing another embodiment of the present invention. The inverter circuit of this embodiment is the same as that of the above-mentioned first embodiment, but the transistors Q1 and Q in the upper stage portion.
3 and Q5 are two PNP type transistors Q1
This is an example in which a Darlington configuration is adopted for the purpose of increasing the output of the inverter, by replacing with a and Q1b.
Also in the case of this embodiment, the diode 11 can prevent the through current as in the case of the first embodiment, and the damage due to the heat generation of the element can be prevented.

Example 3. FIG. 3 is a circuit diagram showing a configuration of an arm 2 for one phase of an inverter circuit showing still another embodiment of the present invention. That is, the switching element portion of the upper stage has a Darlington configuration by combining the PNP transistor Q1d of the front stage and the NPN transistor Q1c of the rear stage. No bias resistor is inserted between the emitter and base of the NPN transistor Q1c in the subsequent stage, and the diode characteristic between the base and emitter of the NPN transistor Q1c works equivalently to the diode 11 shown in the first and second embodiments. It is configured as follows. In the inverter circuit of this embodiment, as in the first embodiment, a through current can be blocked, damage to the device due to heat generation can be prevented, and the efficiency of the circuit can be improved.

Example 4. FIG. 4 is a circuit diagram showing a configuration of an arm 2 for one phase of an inverter circuit showing still another embodiment of the present invention. That is, as in the case shown in FIG. 3, the upper switching element portion has a Darlington structure in which a front PNP transistor Q1d and a rear NPN transistor Q1c are combined. A bias resistor 12 is provided between the emitter and the base of the NPN transistor Q1c in the subsequent stage, and the diode 11 is inserted between the emitter of the NPN transistor Q1c and the transistor Q2 in the lower stage as in the first embodiment. is there. Even if the inverter circuit of this embodiment has the Darlington configuration, the through current can be blocked as in the first embodiment, and the damage due to the heat generation of the element can be prevented.

[0020]

As is apparent from the description of the embodiment, according to the first invention, the junction capacitance between the collector of the lower transistor and the base of the upper transistor is reduced by inserting the diode. , The current passing between the emitter and base of the upper transistor decreases,
Even if the upper part has a Darlington structure, the transistor in the lower part is prevented from turning on due to the operation of the transistor in the lower part, and damage to the switching element due to a through current can be prevented with a simple structure.

According to the second invention, the diode characteristic between the base and the emitter of the NPN type transistor of the latter stage among the transistors of the Darlington structure of the upper stage functions equivalent to the diode in the first invention. It is possible to prevent the upper transistor from being turned on by the operation of the lower transistor, improve the efficiency of the circuit, and prevent the switching element from being damaged by the through current.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an inverter circuit of a DC brushless motor as an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of an arm for one phase of an inverter circuit showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing a configuration of an arm for one phase of an inverter circuit showing still another embodiment of the present invention.

FIG. 4 is a circuit diagram showing a configuration of an arm for one phase of an inverter circuit showing still another embodiment of the present invention.

[Description of symbols] 1 semiconductor switch group 2 arm 8 motor winding 11 diode Q1 transistor Q2 transistor Q3 transistor Q4 transistor Q5 transistor Q6 transistor Q1a transistor Q1b transistor Q1c transistor Q1d transistor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshiro Tatsuya 1-3 Komabacho, Nakatsugawa-shi, Gifu Mitsubishi Electric Corporation Nakatsugawa Works

Claims (2)

[Claims] 1. An inverter circuit in which a semiconductor switch group for outputting a winding current of a brushless motor includes a high withstand voltage type transistor and a diode in an upper stage and a lower with a high withstand voltage type transistor and a diode. The upper-stage transistor has a PNP-type single or Darlington configuration, the lower-stage transistor is NPN-type, and a through-hole is prevented between the collector of the upper-stage transistor and the collector of the lower-stage transistor. An inverter circuit for a DC brushless motor, which is characterized by inserting a diode. 2. An inverter circuit in which a semiconductor switch group for outputting a winding current of a brushless motor includes a high withstand voltage type transistor and a diode at an upper stage and a lower withstand voltage type transistor and a diode. , The upper part has a Darlington structure by combining a PNP type transistor and an NPN type transistor, and a penetration resistance is prevented by a diode characteristic between the base and the emitter without providing a bias resistor between the base and the emitter of the NPN type transistor. Inverter circuit for DC brushless motor.