Over heat protection circuit for a brushless dc
AssigneeSunonwealth Electric Machine Industry Co., Ltd.
InventorsAlex Horng, Ta-Lun Ko
Life of this patent
Estimating the term…
Abstract
A over heat protection circuit for a brushless dc motor includes a thermal sensitive resistor, a resistor and a transistor. The thermal sensitive resistor and the resistor are commonly connected to a base of the transistor while an emitter of the transistor connecting to a motor coil. The thermal sensitive resistor has a resistance value which can be changed in response to an operational temperature. The thermal sensitive resistor is preset to operate at a safety temperature within a predetermined thermal preference. When the operational temperature of the motor coil exceeds the safety temperature, the over heat protection circuit may to cut off a motor current so that the motor coil is protected.
Claims5
An over heat protection circuit for a brushless de motor, comprising:
- a thermal sensitive resistor having a resistance value adapted to change within a predetermined thermal preference in response to changing of an operational temperature of the motor;
- a resistor serially connected to the thermal sensitive resistor at a connection point at which to commonly provide with an adjustable voltage value which is supplied from a voltage source;
- and
- a transistor including a base, a collector and a emitter;
- the base is connected to the connection point located between the thermal sensitive resistor and the resistor so that the adjustable voltage value is input to the base;
- the collector is connected to the voltage source;
- the emitter is connected to the motor for controlling;
- wherein when the operational temperature of the motor is greater than a safety temperature or overheated, the resistance value of the thermal sensitive resistor is correspondingly adjusted, and greater or less than a predetermined reference;
- and the adjustable voltage value of the thermal sensitive resistor and the resistor is inadequate to turn on the base of the transistor so as to cut off a motor current and to thereby stop the motor.
Dependencies are inferred from the claim text.