Patent ID: 8400095
Filing Date: 2013-03-19
Classification: H02P

Abstract:
1. A speed-control circuit for a BLDC (Brushless Direct Current) motor comprising: a pulse generator, coupled to detect a speed signal of said BLDC motor for generating a pulse signal in response to a rising-edge or a falling-edge of said speed signal; a current source circuit, controlled by said pulse signal; a first filter circuit, coupled to said current source circuit, for generating an average signal; an error amplification circuit, coupled to receive said average signal and a speed-reference signal for generating a speed-control signal; and a PWM (Pulse Width Modulation) circuit, generating a switching signal to drive said BLDC motor in response to said speed-control signal; wherein a pulse width of said switching signal is determined by said speed-control signal; and wherein said PWM circuit comprises: an oscillator, generating a clock signal and a ramp signal; a flip-flop, generating said switching signal; and a comparator, receiving said ramp signal and said speed-control signal and generating a reset signal; wherein said clock signal is utilized to enable said switching signal, and said reset signal is utilized to disable said switching signal.