Patent ID: 8248047

Claim:
A power supply circuit to supply a determined voltage to an element, the power supply circuit comprising: a single-phase pulse width modulation (PWM) signal controller; a first transistor and a second transistor, wherein an enable pin of the PWM signal controller is connected to a collector of the second transistor, an emitter of the second transistor is grounded, a base of the second transistor is connected to a collector of the first transistor and connected to a power supply via a first resistor; an emitter of the first transistor is grounded, a base of the first transistor is connected to an enable control signal receiving terminal via a second resistor to receive an enable control signal; a first field-effect transistor (FET) and a second FET; and a first inductor and a second inductor, wherein a phase pin of the PWM signal controller is connected to a voltage output terminal via the first inductor to output the determined voltage, the phase pin of the PWM signal controller is also connected to a first terminal of a third resistor, a second terminal of the third resistor is grounded via a first capacitor, a high-pass driving pin of the PWM signal controller is connected to a gate of the first FET via a fourth resistor, a drain of the first FET is connected to the power supply via the second inductor, a source of the first FET is connected to a drain of the second FET and the phase pin of the PWM signal controller, the gate of the first FET is also connected to the drain of the second FET via a fifth resistor, a low-pass driving pin of the PWM signal controller is connected to a gate of the second FET, a source of the second FET is grounded; wherein the first transistor is turned on and the second transistor is turned off in response to the enable control signal receiving terminal receiving the enable control signal, the high-pass driving pin of the PWM signal controller outputs a high level voltage signal and a low level voltage signal in an alternating order to control the first FET to turn on and turn off repeatedly, the low-pass driving pin of the PWM signal controller outputs a low level voltage signal and a high level voltage signal in an alternating order to control the second FET to turn off and turn on repeatedly, the phase pin of the PWM signal controller outputs a PWM signal to a first terminal of the first inductor, and the power supply outputs a first voltage to the first terminal of the first inductor via a second capacitor and a sixth resistor in turn, and then a second terminal of the second inductor outputs the determined voltage to the voltage output terminal.