JP2008193865A - Motor driving device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor driving device that surely prevents a switching element such as an FET used in an inverter circuit of a motor from being broken due to a temperature rise. <P>SOLUTION: The motor driving device includes each thermal fuse 22 that detects a temperature of each FET 24 in an inverter circuit 14 for supplying a drive current to a motor 10 so as to turn OFF the inverter circuit 14 when the detected temperature exceeds a first reference temperature T1. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor drive device such as a brushless DC motor, and more particularly to a motor drive device that prevents a switching element from being destroyed by heat generation.

Brushless DC motors are used in air conditioners, washing machines, and electric tools. This brushless DC motor is PWM controlled by an inverter circuit. Since power components with high heat generation such as FETs are used for the electronic components that make up the inverter circuit, thermistor detects the temperature when the FET exceeds a predetermined temperature, and decelerates or stops the motor. A technique has been proposed (see, for example, Patent Document 1).
JP 2005-80349 A

  In the case of the protection circuit using the thermistor in Patent Document 1 as described above, when an abnormality occurs in the thermistor and the temperature detection operation stops functioning, the temperature of the FET rises above the allowable temperature and is destroyed. There is a problem of being.

  Therefore, in view of the above problems, the present invention provides a motor drive device that can reliably prevent switching elements such as FETs used in an inverter circuit of a motor from being destroyed due to a temperature rise.

  The invention according to claim 1 is a motor drive device comprising a motor, an inverter circuit that supplies a drive current to the motor, and a control circuit that controls the inverter circuit, wherein the inverter circuit includes a plurality of switching elements. And a temperature fuse for detecting the temperature of the switching element and turning off the inverter circuit when the detected temperature is equal to or higher than a first reference temperature T1.

  The invention according to claim 2 is the motor drive device according to claim 1, wherein the thermal fuse is provided on the back surface of the printed wiring board to which the switching element is fixed.

  The invention according to claim 3 is the motor drive device according to claim 1, wherein the thermal fuse is provided in the middle of the power supply wiring of the control circuit.

  The invention according to claim 4 is the motor drive device according to claim 1, wherein the thermal fuse is provided in the middle of the wiring of the speed command signal of the motor supplied to the control circuit.

  The invention according to claim 5 is the motor drive device according to claim 1, wherein the thermal fuse is provided in the middle of a reset signal supply wiring of the control circuit.

  The invention according to claim 6 is the motor drive device according to claim 1, wherein the thermal fuse is provided in the middle of a current limit signal supply wiring from the inverter circuit to the control circuit.

  In the invention according to claim 7, a temperature detection element is further provided on the back surface of the printed wiring board to which the switching element is fixed, and the temperature detected by the temperature detection element is equal to or higher than a second reference temperature T2 (where T2 <T1). The motor driving apparatus according to claim 1, wherein the control circuit turns off the inverter circuit.

  The invention according to claim 8 is the motor drive device according to claim 1, wherein the motor is a brushless DC motor.

  According to the present invention, when the switching element is heated to a temperature equal to or higher than the first temperature, the thermal fuse operates, the inverter circuit is stopped, and the switching element can be protected from heating.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1 and 2.

  The present embodiment relates to a drive device 12 for a brushless DC motor 10 and is used in, for example, an electric tool, an air conditioner, a washing machine, and the like. The brushless DC motor (hereinafter simply referred to as a motor) 10 is a molded motor in which a motor frame is formed of a mold resin.

(1) Configuration of Drive Device 12 of Motor 10 The configuration of the drive device 12 will be described based on FIG.

  The motor 10 is a three-phase brushless DC motor, and a driving device 12 that supplies a driving current to a stator winding of the motor 10 includes an inverter circuit 14 and a control unit 16 as shown in FIG. Yes. The inverter circuit 14 and the IC constituting the control unit 16 are attached to a printed wiring board (hereinafter simply referred to as a PC board) 26 and are integrally formed with a stator of the motor 10 by a mold resin.

  The inverter circuit 14 is configured by a full bridge circuit by six FETs 24-1 to 24-6, and supplies a drive current to each of the three-phase stator windings. The inverter circuit 14 is supplied with a direct current from the drive power supply VCC.

  The control unit 16 performs PWM control of the inverter circuit 14 and turns the motor 10 ON / OFF and accelerates / decelerates by a speed command signal VST input from the outside. The control unit 16 is supplied with power from a control power source VIN. A reset signal is input to the control unit 16, and this reset signal is supplied with the voltage VR in a normal state, and when it is desired to reset, the supply of the voltage VR is stopped. In addition, a temperature detection signal is input from the thermistor 18 and a current detection signal for detecting an overcurrent is input from a current detection line 20 connected to the ground side wiring of the inverter circuit 14.

  The control unit 16 includes a main control unit, a speed detection circuit, a logic circuit, and a PWM circuit. When a speed command signal VST is input from the outside to the main control unit, a PWM signal having a rotational speed corresponding to the speed command signal VST is output to the gate terminal of each FET 24 of the inverter circuit 14 through a logic circuit. In the inverter circuit 14, the motor 10 is rotated by outputting a three-phase driving current to the three-phase stator winding of the motor 10.

  Three Hall ICs (not shown) are provided in the vicinity of the rotor of the motor 10, and position detection signals are output from the three Hall ICs to the speed detection circuit. The speed detection circuit calculates the rotational speed of the motor and the position of the rotor based on the position detection signals from the three Hall ICs and outputs them to the main controller. The main control unit compares the current rotation speed from the speed detection circuit with a speed command signal VST input from the outside, and feedback-controls the logic circuit so that this rotation speed becomes a rotation speed corresponding to the speed command signal VST. . As a result, the motor 10 rotates in response to the speed command signal VST input from the outside.

  The main control unit stops the rotation of the motor 10 or the rotation speed when the signal input from the protection circuit, that is, the voltage value of the temperature detection signal input from the thermistor 18 is equal to or higher than a predetermined reference value. To protect the inverter circuit 14 from further temperature rise.

(2) Configuration of Temperature Protection In this embodiment, four temperature fuses 22 are provided to further protect each FET of the inverter circuit 14 from the heating temperature. The operating temperature of the thermal fuse 22 is a first reference temperature T2 that is higher than the second reference temperature T2 that is the operating temperature of the thermistor 18. The thermal fuse 22 may be of a type that is cut by temperature and permanently cuts off the circuit, or may be of a type that conducts again when the temperature drops.

  The thermal fuse 22 is attached to the back surface of the PC board 26 and the back surface of the FET 24 of the inverter circuit 14. As a result, the temperature of the FET 24 can be reliably detected. The thermistor 18 described above is also attached to the back surface of the FET 24.

  The thermal fuse 22 is provided in the middle of the supply wiring 28 for supplying the control power to the control unit 16, in the middle of the supply wiring 30 for supplying the speed command signal VST, on the supply wiring 32 for supplying the reset signal, and in the current for supplying the current detection signal. Each is provided in the middle of the detection line 20.

(3) Operation Contents of Thermal Fuse 22 In the motor 10 having the above configuration, when the motor 10 is heated by a large load or the like, normally, the thermistor 18 detects the heating of the FET 24, and the detected temperature exceeds the second reference temperature T2. Then, a temperature detection signal is output from the thermistor 18 to the control unit 16, and the inverter circuit 14 decelerates or stops the motor 10.

  However, when the thermistor 18 is broken for some reason and does not operate normally, the temperature of the inverter circuit 14 becomes equal to or higher than the second reference temperature T2. When the temperature further rises and becomes equal to or higher than the first reference temperature T1, the thermal fuse 22 is cut and the inverter circuit 14 is stopped. When the thermal fuse 22 is cut, the supply of the control power supply VIN of the control unit 16 is stopped, the supply of the reset signal voltage VR is also stopped, the current detection signal from the current detection line 20 is also stopped, and the speed command signal VST is also stopped. Therefore, the inverter circuit 14 can be surely stopped and its temperature rise can be prevented.

  As described above, when the thermistor 18 is destroyed and the temperature further rises and reaches the first reference temperature, the temperature fuse 22 operates and the inverter circuit 14 is reliably turned off, so that the motor 10 is heated, or the FET 24 Will not be destroyed. In particular, since the thermal fuses 22 are respectively provided at four locations, the inverter circuit 14 can be reliably turned off.

(5) Modified Example In the above embodiment, the FET 24 is provided as a switching element of the inverter circuit 14, that is, a power element, but an IGBT (Insulated Gate Bipolar Transistor) may be used instead.

  In the above-described embodiment, the temperature fuses 22 are provided at four locations. However, the present invention is not limited to this, and the inverter circuit 14 can be turned off if one or more locations are provided.

It is a block diagram of the drive device which shows one Embodiment of this invention. It is a side view of the state which attached the thermistor and the thermal fuse to the PC board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 Control part 18 Thermistor 20 Current detection line 22 Thermal fuse 24 FET
26 PC board 28 Supply wiring line 30 Supply wiring line 32 Supply wiring line

Claims (8)

In a motor drive device having a motor, an inverter circuit that supplies a drive current to the motor, and a control circuit that controls the inverter circuit,
The inverter circuit has a plurality of switching elements,
A motor drive device comprising: a temperature fuse that detects the temperature of the switching element and turns off the inverter circuit when the detected temperature is equal to or higher than a first reference temperature T1. The motor drive device according to claim 1, wherein the thermal fuse is provided on a back surface of a printed wiring board to which the switching element is fixed. The motor driving apparatus according to claim 1, wherein the thermal fuse is provided in the middle of a power supply wiring of the control circuit. The motor driving apparatus according to claim 1, wherein the temperature fuse is provided in the middle of a wiring of a speed command signal of the motor supplied to the control circuit. The motor driving apparatus according to claim 1, wherein the thermal fuse is provided in the middle of a reset signal supply wiring of the control circuit. The motor driving device according to claim 1, wherein the thermal fuse is provided in the middle of a current limit signal supply wiring from the inverter circuit to the control circuit. When a temperature detection element is further provided on the back surface of the printed wiring board to which the switching element is fixed, and the detected temperature of the temperature detection element is equal to or higher than a second reference temperature T2 (where T2 <T1), the control circuit The motor drive device according to claim 1, wherein the inverter circuit is turned off. The motor driving apparatus according to claim 1, wherein the motor is a brushless DC motor.

Images