A PWM controller for a voltage regulator comprises an error amplifier to generate an error signal from a difference between the output voltage of the voltage regulator and a reference voltage, and a comparator to compare the error signal with a ramp signal to generate a PWM signal to switch the pair of high side and low side switches of the voltage regulator to produce the output voltage and an output current. When the output current is greater than a threshold, the PWM controller adjusts the reference voltage or the frequency of the ramp signal to reduce the frequency of the PWM signal, thereby reducing the switching loss caused by the switches.