the relationship between the direct current voltage signal vcf the duty cycle d of the pwm input signal and the environmental temperature of fig3 fig9 can be drawn according to eqn 5 fig1 shows a graphic chart of the relationship between the direct current voltage signal vcf the triangular input signal the duty cycle d of the pwm input signal and the environmental temperature of fig5 fig9 can be drawn according to eqn 5 vmin can be calculated by eqn 7 fig1 is a graphic chart showing relationships between the environmental temperature rotation speed of the brushless direct current motor and t the duty cycle d of the pwm input signal in accordance with the present invention more specifically for example as shown in fig1 the control pulse signal generated by the control pulse output circuit 140 in fig1 is used to control the rotation speed of the motor the logic control circuit 30 in fig1 can output the control pulse signal to various bridge circuits of the driver circuit 40 based on the directional control signal generated by the hall signal generation circuit 10 for controlling the direction of the coil current and can control the direction of the current in the coils of the motor and the average load of the current based on the duty cycle of the control pulse signal so as to control the rotation speed of the motor it is important to note that the higher the duty cycle d of the control pulse signal the faster the rotation speed of the motor the lower the duty cycle of the control pulse signal the slower the rotation speed of the motor when the environmental temperature is lower than t 1 and the duty cycle d of the pwm input signal is.