Patent ID: 9534611
Date: 2017-01-03
CPC Classifications: F04D,H02P,Y02B

Claim:
1. A fan driving circuit to drive a first fan and a second fan, the first fan and the second fan connected in parallel and both electrically connected to an anode of a direct current (DC) power, the fan driving circuit comprising: a pulse width modulation signal generation module that generates pulses to drive the first fan and the second fan; a first terminal of the pulse width modulation signal generation module electrically connected to an external power, a second terminal of the pulse width modulation signal generation module electrically connected to the first fan and the second fan; a phase lock and delay module electrically connected to the pulse width modulation signal generation module, the phase lock and delay module sending pulse width modulation signals to the pulse width modulation signal generation module to make the pulse width modulation signal generation module generate different phase waves; a first pulse output comparator comprising a first pulse output comparator first input, a first pulse output comparator second input and an first pulse output comparator output, wherein the first pulse output comparator first input is electrically connected to the phase lock and delay module to receive the pulse width modulation signals generated by the pulse width modulation signal generation module, the first pulse output comparator second input receives a reference voltage, and the first pulse output comparator output is electrically connected between the second fan and ground, wherein the first pulse output comparator sends pulses to the second fan according to the pulse width modulation signals; and a first capacitor electrically connected between the anode of the DC power and the ground; wherein the fan driving circuit uses an inductor of the first fan to generate a Lenz current when the pulse width modulation signal generation module is in a non-working cycle, wherein the Lenz current is stored in the first capacitor and is used to drive the second fan; wherein the pulse width modulation signal generation module comprises a second capacitor with a first end and a second end, and a voltage comparator with a voltage comparator first input, a voltage comparator second input and an voltage comparator output wherein the voltage comparator first input is electrically connected to the external power, the voltage comparator second input receives a reference voltage, the voltage comparator output is electrically connected to the first fan and the first end of the second capacitor, and the second end of the second capacitor is electrically connected to the external power.