Abstract: A fan driving circuit drives a first fan and a second fan which are connected in parallel and connected to an anode of a direct current power. The fan driving circuit includes a pulse width modulation signal generation module, a phase lock and delay module, a first pulse output comparator and a first capacitor. The width modulation signal generation module is connected between an external power and the first fan. The phase lock and delayed module is electrically connected to the pulse width modulation signal generation module. The first capacitor is connected between the DC and the ground. The first fan is supplied as normal by a PWM power supply, the second fan is powered by “shadow” and out-of-phase pulses taken from an inductor in the first fan and stored in the capacitor, to achieve a “two-for-one” power supply aspect, which saves power and reduces operational noise.

Abstract: A fan driving circuit drives a first fan and a second fan which are connected in parallel and connected to an anode of a direct current power. The fan driving circuit includes a pulse width modulation signal generation module, a phase lock and delay module, a first pulse output comparator and a first capacitor. The width modulation signal generation module is connected between an external power and the first fan. The phase lock and delayed module is electrically connected to the pulse width modulation signal generation module. The first capacitor is connected between the DC and the ground. The first fan is supplied as normal by a PWM power supply, the second fan is powered by “shadow” and out-of-phase pulses taken from an inductor in the first fan and stored in the capacitor, to achieve a “two-for-one” power supply aspect, which saves power and reduces operational noise.