Overheating protection circuit and overheating protection method based on speed command voltage

Abstract

The invention discloses an overheating protection circuit based on speed command voltage. The circuit is positioned between peripheral speed command voltage Vsp and chip speed signal input voltage Vsp; the circuit comprises a current clamping diode D1, an RC filter circuit, an NPN triode Q1, a buffer resistor R3, a thermistor NTC and a divider resistor R2, wherein the RC filter circuit comprises a filter resistor R1 and a filter capacitor C1; a main circuit forms between the peripheral speed command voltage Vsp and the chip speed signal input voltage Vsp; one end of the current clamping diode D1 is connected to the main circuit, and the other end of the current clamping diode D1 is communicated with a power supply Vcc; the filter resistor R1 is connected to the main circuit in series, one end of the filter capacitor C1 is connected to the main circuit, and the other end of the filter capacitor C1 is grounded; the C electrode of the NPN triode Q1 is connected to the main circuit, the E electrode of the NPN triode Q1 is connected to the buffer resistor R3, and the B electrode of the NPN triode Q1 is respectively connected to the thermistor NTC and the divider resistor R2; the thermistor NTC is simultaneously connected with VDD, and the voltage divider resistor R2 is simultaneously grounded. The overheating protection circuit has the advantages of high controllability, stability and reliability, and an integrated power chip is protected from being damaged by thermal shock.

Description

technical field [0001] The invention relates to an overheat protection circuit and an overheat protection method of a brushless DC motor for an air conditioner. Background technique [0002] At present, there are two types of overheating protection schemes for brushless DC motors used in air conditioners. A protection method by applying overheat protection to the reset circuit. Generally, a voltage hysteresis is set in the reset circuit to prevent malfunction. Because the internal temperature of the motor cannot change suddenly, this voltage hysteresis causes the motor to appear fast and slow in speed under certain conditions, and even stop and turn sometimes. Another way is to apply overheating protection to the current limiting protection circuit. This method uses a PTC thermistor, and due to the temperature resistance characteristics of the element, the action range of the overheating protection is relatively large. And this method will limit the current capability o...

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Problems solved by technology

[0005] The above-mentioned patents all use a comparator as a key device to adjust the speed command voltage Vsp, which is expensive, complicated circuit, and impractical; moreover, when the overheating protection starts, the Vsp voltage is directly pulled below 1V to stop the motor. When the overheating protection lowers Vsp forcibly, because the motor stops, the air conditioner cannot receive FG feedback, and will continue to increase the Vsp voltage. When the overheating protection is released, because the air conditioner inputs Vsp to the motor too high, the intelligent power module of the motor will Burned during startup; In addition, the above-mentioned patent places an NTC-type temperature sensor on the surface of the smart power chip, which is difficult to operate in practical applications, and the measured data is not very accurate

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