A pulse width modulated (PWM) controller has an input terminal for receiving a pulsed input signal having a first duty cycle, a power supply terminal for receiving a power supply voltage. a minimum duty cycle reference voltage signal, and a control circuit for providing a pulse-width-modulated (PWM) output signal having a second duty cycle related to the first duty cycle of the pulsed input signal. The PWM output control signal having a minimum duty cycle that is adjustable in response to a change in the power supply voltage. In an embodiment, the second duty cycle and the first duty cycle are correlated in a substantially linear relationship. In an embodiment, the PWM control circuit also has a triangle wave generation circuit for generating a triangle wave signal configured to oscillate between an upper limit voltage and a lower limit voltage, which are adjustable in response to a change in the power supply voltage.