JP2005080349A - Driving device of brushless dc motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a driving device of a brushless DC motor which can effectively use a movable range of the brushless DC motor to an operating temperature of a temperature protecting circuit. <P>SOLUTION: The driving device of the brushless DC motor includes the temperature protecting circuit 16a which has a PTC for detecting temperature rises of FETS 1-6 of an inverter circuit 14, and a transistor Tr which turns ON/OFF in response to the change of a resistance value of the PTC, and outputs a temperature detection signal when the resistance value of the PTC changes in association with the temperature rises of the FETS 1-6 so that the transistor Tr becomes an ON state. A main controller 26 stops rotating or decelerates a rotating speed when a temperature detection signal is inputted. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a brushless DC motor driving apparatus.

  As a brushless DC motor driving device, an inverter circuit composed of a plurality of switching elements, and one that performs PWM control by outputting a PWM signal to each switching element of the inverter circuit (Patent Document 1) are known. .

  In such a brushless DC motor driving apparatus, an overcurrent protection circuit and a temperature protection circuit are provided to protect the switching elements of the inverter circuit.

  FIG. 5 is a circuit diagram showing an inverter circuit 102 for driving a conventional three-phase brushless DC motor (hereinafter referred to as a motor) 100 and a protection circuit 104 having both overcurrent protection and temperature protection.

  As shown in FIG. 5, the inverter circuit 102 includes six FET1 to FET6, and allows a drive current to flow through the three-phase stator windings 106u, 106v, and 106w of the motor 100.

  In the protection circuit 104, one end of a thermistor having a positive temperature coefficient (hereinafter referred to as PTC) connected to the source terminals 108 of the FETs 2, 4, and 6 of the inverter circuit 102 and one end of the resistor R2 are connected. The other end of the resistor R2 is connected to the ground terminal. One end of the resistor R1, one end of the capacitor C, and the output terminal 110 are connected to the other end of the PTC. The other end of the capacitor C is connected to a ground terminal. A DC power supply + Vd is connected to the other end of the resistor R1.

  The protection circuit 104 outputs a current detection signal to the output terminal 110 through the PTC when the load current flowing through the source terminals 108 of the FETs 2, 4, 6 becomes an overcurrent. The output current detection signal is input to the control unit (motor driver IC). When the current detection signal exceeds the reference value, the control unit determines that the current is an overcurrent, and adjusts the PWM signal output to the inverter circuit 102 to stop the rotation of the motor 100 or decrease the rotation speed. This prevents overcurrent from flowing.

Further, when the temperature of each of the FETs 1 to 6 of the inverter circuit 102 rises, the PTC detects it, the resistance value of the PTC rises, and the current from the DC power source + Vd flows to the output terminal 110 through the resistor R1, and this flowing current Becomes a temperature detection signal and is output to the control unit. When this temperature detection signal is input, the control unit stops the rotation of the motor 100 or outputs a PWM signal to the inverter circuit 102 so as to reduce the rotation speed.
JP2003-15888

  In the conventional protection circuit 104, since the voltage value of the current detection signal depends on the resistance value of the PTC, when the motor 100 is at a high temperature and the load current is high, the actual use area is limited.

  That is, as shown by the dotted line in the graph of FIG. 3, the temperature of the FET1 to FET6 does not rise to the extent that the temperature protection is performed, but the resistance value of the PTC rises due to this temperature rise, and the voltage value of the current detection signal And the control unit performs control so as to reduce the torque. Therefore, there is a problem that the maximum torque of the motor 100 starts to decrease despite the temperature being lower than the operating temperature at which the protection circuit 104 performs temperature protection.

  Therefore, in view of the above problems, the present invention provides a brushless DC motor driving device that can be used without the movable range of the brushless DC motor being lowered to the operating temperature of the temperature protection circuit.

  The invention according to claim 1 is an inverter circuit composed of a plurality of switching elements, a control means for outputting a PWM signal to each switching element of the inverter circuit, and each switching element of the inverter circuit from a temperature rise. A temperature-less protection means for protecting the brushless DC motor driving device in which the inverter circuit rotates by passing a drive current through a stator winding of the brushless DC motor, and the temperature protection means detects the temperature of the switching element; The thermistor whose resistance value changes depending on the detected temperature, and when the detected temperature rises to the operating temperature and the resistance value of the thermistor changes to the operating resistance value, the sensor enters the on state or the off state. The temperature switching element and the temperature-sensitive switching element are on or off. Output means for outputting a temperature detection signal to the control means when the state is reached, and the control means stops the rotation of the brushless DC motor when the temperature detection signal is inputted, or sets the rotation speed. A brushless DC motor driving apparatus that outputs a PWM signal to the inverter circuit so as to reduce the voltage.

  According to a second aspect of the present invention, the temperature protection means includes overcurrent protection means for detecting a current flowing through the switching element of the inverter circuit and outputting the current detection signal to the control means via the output means. When the current detection signal exceeds a reference value, the control means outputs a PWM signal to the inverter circuit so as to stop the rotation of the brushless DC motor or reduce the rotation speed. The brushless DC motor driving apparatus according to claim 1.

  The invention according to claim 3 is the brushless DC motor drive device according to claim 2, wherein the voltage value of the temperature detection signal is set to be equal to or higher than the reference value of the control means.

  According to a fourth aspect of the present invention, the temperature-sensitive switching element of the temperature protection means is a pnp type transistor, and the thermistor has a positive temperature coefficient that increases in resistance as the detected temperature increases. The transistor has an emitter terminal connected to one end of the thermistor and a DC voltage source for supplying a positive voltage, and the transistor base terminal connected to the other end of the thermistor and a ground terminal. An output terminal is connected to a collector terminal, the output terminal is connected to the control means, and the output means is configured to turn on the temperature detection signal from the DC voltage source through the transistor and the output terminal when the transistor is turned on. And the overcurrent protection means outputs a current flowing through the switching element of the inverter circuit. Which is a brushless DC motor driving device according to claim 1, wherein the converted voltage and outputs from the output terminal as the current detection signal.

  In the invention according to claim 5, the temperature-sensitive switching element of the temperature protection means is a pnp type transistor, and the thermistor has a negative temperature coefficient in which the resistance value decreases as the detected temperature increases. The emitter terminal of the transistor is connected to one end of the resistance element and a DC voltage source for supplying a positive voltage, the base terminal of the transistor is connected to the other end of the resistance element and the one end of the thermistor, A ground terminal is connected to the other end of the thermistor, an output terminal is connected to the collector terminal of the transistor, the output terminal is connected to the control means, and the output means is configured to turn on the direct current when the transistor is turned on. The temperature detection signal is output from a voltage source via the transistor and the output terminal, and the overcurrent protection means includes: A brushless DC motor driving device according to claim 1, wherein the serial in which to convert the current flowing through the switching elements of the inverter circuit to the voltage output from the output terminal as the current detection signal.

  The invention according to claim 6 is the brushless DC motor driving apparatus according to claim 1, wherein each switching element of the inverter circuit is an FET or an IGBT.

  The invention according to claim 7 is characterized in that at least the inverter circuit and the thermistor are disposed on the same wiring board, and are integrally molded with a molding resin together with the wiring board and a stator of the brushless DC motor. The brushless DC motor drive device according to claim 1.

  In the brushless DC motor drive device according to the first aspect of the invention, the resistance value of the thermistor of the temperature protection means changes with the temperature rise of the switching element of the inverter circuit and becomes the operating temperature of the temperature protection circuit. When the operating resistance value is reached, the temperature-sensitive switching element is turned on or off, and a temperature detection signal is output from the output means to the control means. When the temperature detection signal is input, the control means determines that each switching element of the inverter circuit has risen in temperature above the reference temperature, and stops the rotation of the brushless DC motor with respect to the inverter circuit, or the rotation speed PWM signal is output so that

  In this brushless DC motor driving device, since the temperature detection signal is output only when the operating temperature of the thermistor is reached and the temperature-sensitive switching element is operated, the movable range of the brushless DC motor is expanded.

  In the brushless DC motor driving apparatus according to the second aspect, the overcurrent protection means outputs the current flowing in the switching element of the inverter circuit from the output means as a current detection signal. The control means inputs this current detection signal, and if this signal is equal to or greater than the reference value, it stops the rotation of the brushless DC motor or outputs a PWM signal to the inverter circuit so as to reduce the rotation speed. .

  As a result, when the load current flowing through the switching element of the inverter circuit becomes excessive, the brushless DC motor can be reliably stopped or the rotational speed can be reduced.

  In the brushless DC motor driving device according to the third aspect of the present invention, the voltage value of the temperature detection signal is set to be equal to or higher than the reference value of the control means. Even if detection signals are input, the abnormal state of the brushless DC motor can be easily determined based on whether or not the voltage value of these signals exceeds the reference value.

  In the brushless DC motor drive device according to the invention of claim 4, when the temperature of the switching element of the inverter circuit rises, the temperature protection means increases the temperature of the thermistor having a positive temperature coefficient and reaches the operating temperature. A temperature-sensitive switching element that is a pnp transistor is turned on. Then, the output means outputs a temperature detection signal from the DC voltage source through the transistor and the output terminal. Further, the overcurrent protection means outputs a current detection signal without being affected by the resistance value due to the change in the temperature characteristic of the thermistor because the transistor is in the off state in the temperature range below the operating temperature. Can do.

  In the brushless DC motor driving apparatus according to the fifth aspect of the present invention, when the temperature of the switching element of the inverter circuit rises, the temperature protection means increases the temperature of the thermistor having a negative temperature coefficient and reaches the operating temperature. A temperature-sensitive switching element that is a pnp transistor is turned on. Then, the output means outputs a temperature detection signal from the DC voltage source through the transistor and the output terminal. Further, the overcurrent protection means outputs a current detection signal without being affected by the resistance value due to the change in the temperature characteristic of the thermistor because the transistor is in the off state in the temperature range below the operating temperature. Can do.

  In the drive device for the brushless DC motor according to the sixth aspect of the present invention, each switching element of the inverter circuit is configured by an FET (electrolytic effect transistor) or an IGBT (Insulated Gate Bipolar Transistor), whereby the drive current is brushless. It is possible to reliably flow through the stator winding of the DC motor.

  In the brushless DC motor driving apparatus according to the seventh aspect of the present invention, at least the inverter circuit and the thermistor are arranged on the same wiring board, and the wiring board and the stator of the brushless DC motor are integrally formed by a mold resin. Since it is molded, the thermistor can reliably detect the temperature of each switching element of the inverter circuit.

(First embodiment)
Hereinafter, a drive device 12 for a brushless DC motor (hereinafter simply referred to as a motor) 10 according to a first embodiment of the present invention will be described.

(1) Configuration of Motor 10 The motor 10 is a three-phase brushless DC motor and is a molded motor. That is, the stator and the wiring board are integrally molded with a mold resin to form the frame of the motor 10.

(2) Overall Configuration of Drive Device 12 The overall configuration of the drive device 12 will be described based on the block diagram of FIG.

  The drive device 12 includes an inverter circuit 14, a protection circuit 16, a PWM circuit 20, a logic circuit 22, a speed detection circuit 24, and a main control unit 26.

  Three Hall ICs 28, 28, 28 for detecting the position of the rotor of the motor 10 are provided, and position detection signals of these three Hall ICs 28, 28, 28 are input to the speed detection circuit 24. Is done.

(3) Configuration of Inverter Circuit 14 The configuration of the inverter circuit 14 will be described with reference to FIG.

  The inverter circuit 14 is composed of six FETs 1 to 6, and FETs 1, 3, and 5 are arranged in the upper stage, and FETs 2, 4, and 6 are arranged in the lower stage.

  Specifically, the drain terminal of FET 2 is connected to the source terminal of FET 1, the drain terminal of FET 4 is connected to the source terminal of FET 3, and the drain terminal of FET 6 is connected to the source terminal of FET 5.

  The drain terminals of the FETs 1, 3 and 5 are connected together and connected to the motor power supply + Vm.

  The source terminals of the FETs 2, 4, 6 are connected together and connected to the input terminal 30 of the protection circuit 16.

  The gate terminals of the FETs 1 to 6 are connected to the PWM circuit 20, and the PWM circuit 20 outputs a PWM signal as a gate signal.

  A u-phase stator winding 32u of the motor 10 is connected between the FET1 and FET2, a v-phase stator winding 32v is connected between the FET3 and FET4, and between the FET5 and FET6. Is connected to a w-phase stator winding 32w. The three-phase stator windings 32u, 32v, 32w are Y-connected.

(4) Configuration of Protection Circuit 16 Next, the configuration of the protection circuit 16 will be described with reference to FIG.

  The protection circuit 16 is roughly divided into a temperature protection circuit 16a and an overcurrent protection circuit 16b.

  The temperature protection circuit 16a includes a thermistor having a positive temperature coefficient (hereinafter referred to as “PTC”), a resistor R0, and a pnp type switching transistor Tr.

  A DC power source + Vd is connected to one end of the PTC, and a collector terminal of the transistor Tr is connected. On the other hand, the base terminal of the transistor Tr and one end of the resistor R0 are connected to the other end of the PTC. The other end of the resistor R0 is connected to the ground terminal. One end of a resistor R1 is connected to the emitter terminal of the transistor Tr. The other end of the resistor R1 is connected to the output terminal 38.

  The overcurrent protection circuit 16b includes a resistor R2 and a resistor R3.

  One end of the resistor R2 and one end of the resistor R3 are connected to the input terminal 30 connected to the inverter circuit 14, and the other end of the resistor R3 is connected to the ground terminal. The other end of the resistor R2 is connected to the output terminal 38.

  In addition, PTC is attached to the back side of the wiring board which wired six FET1-6, and can detect the temperature rise of each FET1-6.

  Further, the wiring board on which the PTC and the inverter circuit 14 are wired is integrally molded with the stator of the motor 10 together with the molding resin as described above.

(5) Overall Operation State of Drive Device 12 First, the overall operation state of the drive device 12 will be described.

  When a speed command signal S is input to the main control unit 26 of the control unit 18 from the outside, the main control unit 26 outputs a PWM signal having a rotation speed corresponding to the speed command signal S by the PWM circuit 20 via the logic circuit 22. Output to the gate terminals of the FETs 1 to 6 of the inverter circuit 14. In the inverter circuit 14, the motor 10 is rotated by outputting a three-phase driving current to the three-phase stator windings 32 u, 32 v, and 32 w of the motor 10.

  The three Hall ICs 28, 28, 28 detect the position of the rotor of the rotating motor 10 and output a position detection signal K to the speed detection circuit 24.

  In the speed detection circuit 24, the rotational speed of the motor 10 and the position of the rotor are calculated based on the position detection signals from the three Hall ICs 28 and output to the main control unit 26.

  The main control unit 26 compares the current rotation speed from the speed detection circuit 24 with a speed command signal S input from the outside, and the logic circuit 22 so that the rotation speed becomes a rotation speed corresponding to the speed command signal S. Feedback control. As a result, the motor 10 rotates in response to the speed command signal S input from the outside.

  Further, the main control unit 26 stops the rotation of the motor 10 when the voltage values of the signals input from the protection circuit 16 (that is, the temperature detection signal and the current detection signal) are equal to or higher than a predetermined reference value, or The rotational speed is reduced to protect the inverter circuit 14 from further temperature rise.

(6) Operation State of Protection Circuit 16 Next, the operation state of the protection circuit 16 will be described.

(6-1) A case where the temperature protection circuit 16a of the protection circuit 16 operates will be described.

  Since the PTC has a positive temperature coefficient, when the temperature of the FETs 1 to 6 rises, the resistance value rises, and the value of the voltage V1 across the PTC in FIG. 1 rises.

  However, when the temperature of the FETs 1 to 6 is low, the resistance value of the PTC is low, and the DC power source + Vd flows to the ground terminal via the PTC and R0. Therefore, the transistor Tr is turned off and no signal is output from the output terminal 38.

  When the temperature of the FETs 1 to 6 rises to reach the operating temperature of the PTC, the resistance value of the PTC reaches the operating resistance value, and the transistor Tr is turned on. Then, the current from the DC power source + Vd flows through the transistor Tr, the current flows through the resistor R1, and is output from the output terminal 38 to the main control unit 26 as a temperature detection signal. The temperature of the PTC at which the transistor Tr is turned on is the “operating temperature” in the temperature protection circuit 16a. The voltage value of the temperature detection signal is set to be equal to or higher than the reference value in the main control unit 26.

  In the main control unit 26, since the input temperature detection signal is equal to or higher than the reference value as described above, the rotation of the motor 10 is stopped or the rotation speed is decreased so that the inverter circuit 14 does not further increase in temperature. To protect.

(6-2) A case where the overcurrent protection circuit 16b of the protection circuit 16 operates will be described.

  The load current flowing in the source terminals of the FETs 2, 4, 6 of the inverter circuit 14 is always input to the input terminal 30. The load current input to the input terminal 30 is converted into a voltage by the resistor R3 and output as a current detection signal from the output terminal 38.

  The current detection signal is input to the main control unit 26, and when the current detection signal exceeds the reference value, the main control unit 26 determines that the load current is an overcurrent and stops the rotation of the motor 10, or Protects the load current from overcurrent by reducing the rotation speed.

(7) Effect of Protection Circuit 16 As described above, since the transistors Tr are in the OFF state unless the FETs 1 to 6 of the inverter circuit are raised to the operating temperature of the temperature protection circuit 16a, the resistance of the PTC The overcurrent protection circuit can accurately output the load current of the inverter circuit 14 as a detection signal without being affected by the change in value.

  That is, the temperature protection circuit 16a operates only when the transistor Tr is turned on, and the overcurrent protection circuit 16b is not affected by the resistance value of the PTC in the off state. Therefore, as shown by the solid line in the graph showing the temperature of the PTC and the maximum torque of the motor 10 in FIG. 3, the maximum torque does not decrease to the operating temperature of the temperature protection circuit 16a, and the movable range of the motor 10 is not limited.

  As a result, the maximum current of the motor 10 can be reduced as compared with the prior art, so that it is possible to reduce costs such as lowering the rank of the switching elements.

(Second Embodiment)
The difference between the second embodiment and the first embodiment is that a thermistor is provided in the protection circuit 16.

  In the first embodiment, the PTC is provided between the collector terminal and the base terminal of the transistor Tr. In the second embodiment, as shown in FIG. 4, a resistor R0 is provided between the collector terminal and the base terminal. The thermistor is connected between the base terminal and the ground terminal. However, the thermistor in this case is connected to a thermistor having a negative temperature coefficient (Negative Temperature Coefficient. Hereinafter referred to as “NTC”).

  When this NTC is connected, when the temperature rise of each FET 1 to 6 of the inverter circuit 14 is detected, the resistance value of the NTC decreases, and the transistor Tr is turned on as in the first embodiment.

  Even in the second embodiment, the temperature rise of the FETs 1 to 6 can be accurately detected as in the first embodiment.

(Example of change)
The present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist thereof. Hereinafter, the example of a change is demonstrated.

(1) Modification 1
In each of the above embodiments, an FET (electrolytic effect transistor) is used as a switching element of the inverter circuit 14, but an IGBT (Insulated Gate Bipolar Transistor) may be used instead.

(2) Modification example 2
In each of the above embodiments. Although the wiring board incorporating the inverter circuit 14 and the PTC is molded integrally with the stator with a mold resin, the wiring board and the stator may not be molded.

  The drive device for a brushless DC motor of the present invention is preferably used as a drive source for an air conditioner, a washing machine, or the like.

It is a circuit diagram of the inverter circuit and protection circuit of a 1st embodiment. It is a block diagram of the drive device of a 1st embodiment. It is a graph which shows the relationship between the maximum torque and the temperature of PTC. It is a circuit diagram of the inverter circuit and protection circuit of 2nd Embodiment. It is a circuit diagram of the inverter circuit and protection circuit in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Motor 12 Drive apparatus 14 Inverter circuit 16 Protection circuit 16a Temperature protection circuit 16b Overcurrent protection circuit 18 Control part 20 PWM circuit 22 Logic circuit 24 Speed detection circuit 26 Main control part 28 Hall IC
30 input terminals 38 output terminals

Claims (7)

An inverter circuit composed of a plurality of switching elements; a control means for outputting a PWM signal to each switching element of the inverter circuit; and a temperature protection means for protecting each switching element of the inverter circuit from a temperature rise. ,
In the driving apparatus of the brushless DC motor, the inverter circuit rotates by passing a driving current through the stator winding of the brushless DC motor.
The temperature protection means includes
A thermistor that detects a temperature of the switching element and changes a resistance value according to the detected temperature;
When the detected temperature rises to the operating temperature and the resistance value of the thermistor changes to the operating resistance value, the temperature-sensitive switching element that is turned on or off
An output means for outputting a temperature detection signal to the control means when the temperature-sensitive switching element is turned on or turned off;
Have
When the temperature detection signal is input, the control means stops the rotation of the brushless DC motor or outputs a PWM signal to the inverter circuit so as to reduce the rotation speed. Drive device. The temperature protection means includes an overcurrent protection means for detecting a current flowing through the switching element of the inverter circuit and outputting the current detection signal to the control means via the output means,
When the current detection signal exceeds a reference value, the control means outputs a PWM signal to the inverter circuit so as to stop the rotation of the brushless DC motor or reduce the rotation speed. The brushless DC motor drive device according to claim 1. The brushless DC motor driving device according to claim 2, wherein a voltage value of the temperature detection signal is set to be equal to or higher than the reference value of the control means. The temperature-sensitive switching element of the temperature protection means is a pnp-type transistor;
The thermistor has a positive temperature coefficient with which the resistance value increases as the detection temperature increases,
One end of the thermistor and a DC voltage source for supplying a positive voltage are connected to the emitter terminal of the transistor,
The other end of the thermistor and the ground terminal are connected to the base terminal of the transistor,
An output terminal is connected to the collector terminal of the transistor,
The output terminal is connected to the control means;
When the transistor is turned on, the output means outputs the temperature detection signal from the DC voltage source through the transistor and the output terminal,
The overcurrent protection means includes
The brushless DC motor drive device according to claim 1, wherein the current flowing through the switching element of the inverter circuit is converted into a voltage and output as the current detection signal from the output terminal. The temperature-sensitive switching element of the temperature protection means is a pnp-type transistor;
The thermistor has a negative temperature coefficient in which the resistance value decreases as the detection temperature increases,
One end of the resistance element and a DC voltage source for supplying a positive voltage are connected to the emitter terminal of the transistor,
The other end of the resistance element and one end of the thermistor are connected to the base terminal of the transistor,
A ground terminal is connected to the other end of the thermistor,
An output terminal is connected to the collector terminal of the transistor,
The output terminal is connected to the control means;
When the transistor is turned on, the output means outputs the temperature detection signal from the DC voltage source through the transistor and the output terminal,
The overcurrent protection means includes
The brushless DC motor drive device according to claim 1, wherein the current flowing through the switching element of the inverter circuit is converted into a voltage and output as the current detection signal from the output terminal. The driving device for a brushless DC motor according to claim 1, wherein each switching element of the inverter circuit is an FET or an IGBT. At least the inverter circuit and the thermistor are arranged on the same wiring board,
The drive device for a brushless DC motor according to claim 1, wherein the wiring board and the stator of the brushless DC motor are integrally molded with a mold resin.

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