Control circuit of brushless direct-current motor, brushless direct-current motor and air conditioner

The utility model provides a control circuit of a brushless direct-current motor, a brushless direct-current motor and an air conditioner. The control circuit of the brushless direct-current motor includes a control chip, a power inverting circuit and a protection circuit including a voltage-dividing resistor and a thermistor; the protection circuit can output a voltage signal which changes correspondingly to the control chip according to the changes of a current signal and a temperature signal which are outputted by the power inverting circuit; the control chip compares the received voltage signal with a preset voltage signal, when the numerical value of the voltage signal is larger than the numerical value of the preset voltage signal, the control chip stops driving the power inverting circuit, and therefore, the rotation speed of a motor body can be decreased, and the operation of fan blades of the air conditioning can be slowed down; the protection circuit of the control circuit of the brushless direct-cu