JP4724165B2 - Inverter circuit device with temperature detection circuit - Google Patents

Description

  The present invention relates to an inverter circuit device including a temperature detection circuit that can perform overheat protection and overcurrent protection.

  First, with reference to FIG. 6, the operation of the inverter circuit device including the temperature detection circuit and the control circuit thereof will be briefly described.

  A reference signal having a frequency corresponding to the rotation speed setting signal is output to the driver circuit 2 from the control circuit 1 constituted by a microcomputer or DSP. This reference signal is composed of three pulse-width-modulated rectangular waves each having a phase difference of 120 degrees and three rectangular waves that are generally 180 degrees behind the pulse-width-modulated rectangular waves. Yes.

  Three pulse-width-modulated rectangular waves each having a phase difference of 120 degrees are input to the control electrodes of the switching elements Q1, Q2 and Q3 of the upper arm constituting the inverter circuit via the driver circuit 2, and this switching element ON / OFF control.

  Further, the pulse-width-modulated rectangular wave whose phase is delayed by 180 degrees with respect to the pulse-width-modulated rectangular wave similarly turns on / off the switching elements Q4, Q5 and Q6 of the lower arm via the driver circuit 2. Control.

  The diodes D1, D2, D3, D4, D5, and D6 connected to the switching elements Q1, Q2, Q3, Q4, Q5, and Q6 are regenerative diodes.

  Therefore, three pulse width modulated rectangular waves each having a phase difference of 120 degrees and three pulse width modulated rectangular waves each having a phase difference of 180 degrees with respect to the pulse width modulated rectangular waves The output terminals of the inverter circuit to be controlled off, that is, switching elements Q1 and Q4, switching elements Q2 and Q5, and connection points U, V, and W of switching elements Q3 and Q6 are obtained three-phase pulse width modulated voltages. The load current flowing through the motor M approximates a sine wave.

  In the above-described inverter circuit, it is necessary to change the rotation speed of the motor M according to the temperature or to stop the inverter circuit from being damaged when the temperature rises more than necessary. Therefore, the temperature detection circuit 3 is provided to detect an abnormal temperature rise in the inverter circuit, and the detected heating abnormality signal is added to the control circuit to stop the motor M.

  As the temperature of the inverter circuit changes, a dedicated terminal is required for the control circuit in order to apply the temperature detection signal detected by the temperature detection circuit to the control circuit, so that the number of terminals of the control circuit increases.

  In addition, when the temperature of the inverter circuit is overheated above a predetermined temperature, the circuit element is prevented from being damaged. In addition to controlling the current flowing in the switching circuit, the operation of the inverter circuit is stopped. It is necessary to let

  Further, as shown in FIG. 7, the thermistor 3 a is used to detect the temperature in the temperature detection circuit 3. Conventionally, an inverter circuit is attached to the printed circuit board 4, and the thermistor 3a is provided on the heat sink 5 to which the inverter circuit is attached. Therefore, an accurate temperature rise of the inverter circuit cannot be detected, and a space is required.

The present invention relates to a switching circuit that controls the rotation of the motor, a drive circuit that drives the switching circuit using a pulse-width-modulated rectangular wave, and detects a current of the switching circuit, and the current is above a certain level. When there is an overcurrent detection circuit that outputs an abnormal signal that changes from one level to the other, and a thermistor, the resistance value of the thermistor that changes gently according to the temperature is used to change the resistance value. And a control circuit for controlling the output from the drive circuit in response to the abnormal signal and the temperature detection signal, and the control circuit is configured to output the temperature detection signal as a temperature detection signal. A dual-purpose terminal that serves both as a temperature detection terminal to be applied and an abnormal terminal to which the abnormal signal is applied, and in accordance with a signal from the dual-purpose terminal, Control the circuit, the control circuit immediately stops the output of the drive circuit when the abnormal signal changes, the output of the drive circuit according to the gradual change when the temperature detection signal changes The temperature detection circuit connects the thermistor and the protection resistor in series between the first voltage level and the second voltage level, and sets the potential at the connection point between the thermistor and the protection resistor. An inverter provided with a temperature detection circuit , wherein the temperature detection signal is forcibly set to a certain voltage level and output to the control circuit when the abnormal signal changes. Circuit device.

  In the present invention, the temperature detection element and the overcurrent detection element of the temperature detection circuit are connected, and the detected signal is applied to the same terminal of the control circuit. Control and overcurrent detection can be performed.

  Further, since the overheat protection signal detection circuit is connected to the temperature detection circuit, the operation is stopped when the circuit rises to a predetermined temperature or more, and it is possible to protect the circuit from being overheated and destroyed.

  Furthermore, since the circuit is equipped with a switching circuit and a drive circuit on a heat dissipation / wiring board, the temperature of the switching circuit is accurately adjusted by a thermistor using the characteristic that the substrate temperature is almost uniform due to its good heat transferability. It can be detected and the current supplied to the load can be controlled according to the temperature change.

  FIG. 1 shows a block diagram of an inverter circuit device provided with a temperature detection circuit of the present invention.

  The inverter circuit in the present invention is input to the switching circuit 9 composed of the switching elements Q1, Q2, Q3 of the upper arm and the switching elements Q4, Q5, Q6 of the lower arm, and the control electrode of each switching element, A driver circuit 2 that controls on / off of the switching element and a control circuit 1 that is input to the driver circuit 2 and generates a control signal are provided.

  A load such as a motor M is connected to connection points U, V, and W of the switching elements Q1 and Q4, switching elements Q2 and Q5, and switching elements Q3 and Q6 of the switching circuit 9. As described above, the control circuit 1 outputs a rectangular wave that has been subjected to pulse width modulation to the drive circuit 2 to control the switching circuit 9.

  A feature of the present invention is that a temperature detection circuit 10 is connected to the control circuit 1. The temperature detection circuit 10 detects a temperature change of the inverter circuit including the control circuit 1, the driver circuit 2, and the switching circuit 9, and has a resistor 11 connected to the power supply VDD and one end connected to the resistor 11. The thermistor 12 is connected to the FAULT terminal of the control circuit 1.

  A drain / source electrode of an overcurrent protection FET 13 is connected in parallel to the thermistor 12. The drain electrode of the overcurrent protection FET 13 is connected to the power supply VDD via the diode 14 and is connected to the control circuit 1 as a FAULT terminal together with one end of the thermistor 12.

  The gate electrode of the overcurrent protection FET 13 is connected to an overcurrent detection circuit 16 that detects an overcurrent flowing through the resistor 15. The overcurrent protection FET 13 is incorporated in the driver circuit 2, but may be provided in the temperature detection circuit 10.

  FIG. 2 is an attachment diagram in which the temperature detection circuit 10 used in the inverter circuit device provided with the temperature detection circuit of the present invention is attached to the heat dissipation / wiring board 17. The heat-radiation wiring board 17 uses an aluminum substrate whose surface is oxidized and insulated.

  Printed wiring is applied to the surface of the insulated heat-radiation wiring board 17, and the switching elements Q1, Q2, Q3 of the upper arm of the switching circuit 9, and the switching elements Q4, Q5, Q6 of the lower arm. The driver circuit 2 and the like are attached.

  It is desirable that the thermistor 12 be mounted as close as possible to the switching circuit 9 and the driver circuit 2 that increase the temperature during operation on the heat radiation / wiring board 17. However, in the case of the present invention, since aluminum is used for the substrate material, the substrate temperature becomes almost uniform because of its good heat transfer characteristics. Therefore, if it is mounted in the substrate, the temperature of the inverter circuit can be set regardless of its position. It can be detected accurately.

  Three pulse-width-modulated rectangular waves each having a phase difference of 120 degrees outputted from the control circuit 1 are connected to the switching elements Q1, Q2, Q3 of the upper arm constituting the switching circuit 9 via the driver circuit 2. The switching element is input to the control electrode to control on / off of the switching element.

  Further, the pulse width modulated rectangular wave whose phase is delayed by 180 degrees with respect to the pulse width modulated rectangular wave from the control circuit 1 is similarly switched via the driver circuit 2 through the switching elements Q4, Q5, Q6 of the lower arm. ON / OFF control.

  Therefore, three pulse width modulated rectangular waves each having a phase difference of 120 degrees and three pulse width modulated rectangular waves each having a phase difference of 180 degrees with respect to the pulse width modulated rectangular waves The output terminals of the switching circuit 9 to be controlled off, that is, the switching elements Q1 and Q4, the switching elements Q2 and Q5, and the connection points U, V, and W of the switching elements Q3 and Q6 are applied with three-phase pulse width modulated voltage. Then, a load current is supplied to the motor M to rotate the motor M.

  When the motor M rotates and the temperature of the switching elements Q1, Q2, Q3, Q4, Q5, Q6 and D1, D2, D3, D4, D5, D6 etc. rises, the temperature of the heat radiation / wiring board 17 also transfers heat. It rises immediately. As shown in FIG. 3, when the temperature of the heat radiation / wiring board 17 rises, the resistance value of the thermistor 12 decreases from 100 KΩ at 25 ° C. to about 2.8 KΩ at 125 ° C.

  Therefore, in the circuit shown in FIG. 5, when the resistance value of the resistor 11 is 10 KΩ, the resistance value of the resistor 19 is 5.1 KΩ, and the power supply voltage VDD is 15 V, the temperature detection of the thermistor 12 is performed as shown in FIGS. The signal V (ITRIP) was about 0.7 V at 25 ° C., but changed to about 4.3 V at 125 ° C.

  This changed temperature detection signal is applied to the control circuit 1 from the FAULT terminal, controls the rectangular wave pulse-modulated by the control circuit 1, passes a motor current according to the temperature change to the motor M, and sets the rotation speed. Can be changed.

  As shown in FIGS. 3 and 4, when the temperature (Tc) of the heat radiation / wiring board 17 rises and the V (ITRIP) voltage rises, if the voltage exceeds the set Vref voltage, the comparator 20 Inverted, the FAULT terminal becomes Lo level. When the FAULT terminal becomes Lo level, the control circuit 1 determines that an abnormality has occurred and stops driving the drive circuit 2 and cuts off the pulse width modulated rectangular wave generated from the control circuit 1 to operate the motor. To prevent the switching element from being damaged by heating.

  By the way, when the motor M is locked or the like and an overcurrent flows through the driver circuit 2 and the switching circuit 9, the current flowing through the resistor 15 increases. When the current flowing through the resistor 15 exceeds a set value, the overcurrent detection signal is detected by the overcurrent detection circuit 16. In FIG. 1, the overcurrent detection signal detected by the overcurrent detection circuit 16 is applied to the gate electrode of the overcurrent protection FET 13. As a result, the overcurrent protection FET 13 is turned on and the FAULT terminal becomes Lo level.

  The overcurrent protection FET 13 is turned on and an overcurrent abnormality signal that is at the Lo level is output. At this time, an abnormality signal is transmitted to the control circuit 1 through the same FAULT terminal that outputs the temperature detection signal. Then, the pulse-width-modulated rectangular wave generated from the control circuit 1 is cut off to stop the operation of the motor M, thereby preventing overcurrent destruction of the switching element and motor failure.

  With reference to FIG. 5, it will be described in detail that when the temperature of the heat radiation / wiring board of the inverter circuit device having the temperature detection circuit becomes equal to or higher than a set temperature, the current flowing through the motor M is cut off and overheat protection can be performed. The temperature detection circuit 10 is provided with a comparator 20 for detecting overheating. The thermistor 12 is connected to one input terminal of the comparator 20 and the reference voltage Vref is applied to the other terminal.

  Similarly to the above, when the temperature of the inverter circuit device rises, the resistance value of the thermistor 12 decreases and a temperature detection signal is detected. The temperature detection signal is applied to the control circuit from the ITRIP terminal, controls the pulse-width-modulated rectangular wave output from the control circuit 1, passes the motor current according to the temperature change to the motor M, and responds to the temperature. The functions that can change the rotation speed are the same.

  However, as shown in FIG. 4 described above, in this circuit, when the temperature exceeds a certain temperature and the temperature detection signal V (ITRIP) detected by the thermistor 12 and applied to one input terminal of the comparator 20 becomes equal to or higher than the reference voltage Vref, the comparator An overheat abnormality signal TT is generated from the 20 output terminals.

  When the overheat abnormality signal TT is applied to the control circuit 1, the pulse width modulated rectangular wave generated from the control circuit 1 is cut off, and the operation of the motor M is stopped to cause overcurrent breakdown or motor failure of the switching element. To prevent.

  Further, the overcurrent detection circuit 16 is connected to the resistor 15 through which the overcurrent flows, and an overcurrent detection signal detected from the overcurrent detection circuit 16 is added to one end of the resistor 19 so that the overcurrent is detected at the same terminal as in FIG. And overheat protection.

It is a block diagram explaining the inverter circuit apparatus provided with the temperature detection circuit of this invention. It is the model which attached the temperature detection circuit of this invention to the wiring board for heat dissipation. It is a table | surface which shows the temperature of the thermistor used for the inverter circuit apparatus provided with the temperature detection circuit of this invention, resistance value, and voltage. It is a characteristic view which shows the relationship between the temperature of a thermistor used for the inverter circuit apparatus provided with the temperature detection circuit of this invention, and a voltage. It is a block diagram which shows the other Example of the inverter circuit apparatus provided with the temperature detection circuit of this invention. It is a block diagram explaining the conventional inverter circuit. It is a model figure which attached the temperature detection circuit of the conventional inverter circuit.

Explanation of symbols

Q1, Q2, Q3, Q4, Q5, Q6 Switching element 1 Control circuit 2 Driver circuit 9 Switching circuit 10 Temperature detection circuit 12 Thermistor 13 Overcurrent protection FET
17 Heat Dissipation Wiring Board 20 Overheat Detection and Overcurrent Protection Comparator

Claims (4)

A switching circuit that controls the rotation of the motor;
A drive circuit that drives the switching circuit using a pulse-width modulated rectangular wave;
An overcurrent detection circuit that detects the current of the switching circuit and outputs an abnormal signal that changes from one level to the other when the current exceeds a certain level;
A temperature detection circuit that has a thermistor and outputs the change in the resistance value as a temperature detection signal using the resistance value of the thermistor that changes gradually according to the temperature;
A control circuit for controlling an output from the drive circuit in response to the abnormal signal and the temperature detection signal;
The control circuit has a dual-purpose terminal that serves both as a temperature detection terminal to which the temperature detection signal is applied and an abnormal terminal to which the abnormal signal is applied, and controls the drive circuit according to a signal from the dual-purpose terminal, and the control The circuit immediately stops the output of the drive circuit when the abnormal signal changes, and gradually changes the output of the drive circuit according to the gradual change when the temperature detection signal changes,
The temperature detection circuit connects the thermistor and a protection resistor in series between a first voltage level and a second voltage level, and uses a potential at a connection point between the thermistor and the protection resistor as the temperature detection signal, When the abnormal signal has changed, the temperature detection signal is forcibly set to a certain voltage level and output to the control circuit;
An inverter circuit device comprising a temperature detection circuit characterized by   2. The temperature according to claim 1, wherein the temperature detection circuit and the switching circuit are on the same substrate, the substrate uses a metal, and the temperature of the switching circuit is detected by the thermal conductivity of the metal. An inverter circuit device provided with a detection circuit. The inverter circuit device having a temperature detection circuit according to claim 2 , further comprising the drive circuit on the substrate. The inverter circuit device having a temperature detection circuit according to claim 3 , wherein the substrate is made of aluminum.

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