Pulsed width modulated control method and apparatus

A motor control circuit, comprising:

• a signal conversion circuit for converting a pulsed input signal having a first duty cycle to an analog signal having a magnitude inversely correlated to the first duty cycle of the pulsed input signal;
• a triangle wave generation circuit for generating a triangle wave signal configured to oscillate between an upper limit voltage and a lower limit voltage, the upper limit voltage and the lower limit voltage being adjustable in response to a change in the power supply voltage;
• a pulse generation circuit coupled to the signal conversion circuit, the triangle wave generation circuit, and a minimum duty cycle reference voltage signal, the pulse generation circuit being configured to provide a PWM pulse signal having a second duty cycle correlated to the first duty cycle of the pulsed input signal, the PWM pulse signal having a minimum duty cycle related to the triangle wave signal and a minimum duty cycle reference voltage signal;
• a Hall signal processing circuit;
• a logic circuit coupled to the pulse generation circuit and the Hall signal processing unit, the logic circuit being configured to provide motor control signals;
• and
• a bridge driver circuit coupled to the logic circuit for receiving the motor control signals and configured to control a speed of the motor.

A motor system, comprising:

• a motor;
• and
• a motor control circuit, including:
• a signal conversion circuit for converting a pulsed input signal having a first duty cycle to an analog signal having a magnitude inversely correlated to the first duty cycle of the pulsed input signal;
• a triangle wave generation circuit for generating a triangle wave signal configured to oscillate between an upper limit voltage and a lower limit voltage, the upper limit voltage and the lower limit voltage being adjustable in response to a change in the power supply voltage;
• a pulse generation circuit coupled to the signal conversion circuit, the triangle wave generation circuit, and the minimum duty cycle reference voltage signal, the pulse generation circuit being configured to provide a PWM control signal having a second duty cycle linearly correlated to the first duty cycle of the pulsed input signal, the PWM control signal having a minimum duty cycle related to the triangle wave signal and a minimum duty cycle reference voltage signal;
• a Hall signal processing circuit for detecting a direction in a current flow in a coil of the motor;
• a logic circuit coupled to the pulse generation circuit and the Hall signal processing unit, the logic circuit being configured to provide motor control signals;
• and
• a bridge driver circuit coupled to the logic circuit for receiving the motor control signals and configured to control a speed of the motor in response to the PWM control signal.