Patent ID: 7852649

Claim:
A power supply comprising: a power supplying circuit; a power controlling circuit having an output terminal coupled to an input terminal of the power supplying circuit; a first switch; a pulse width modulation signal source coupled to a first terminal of the first switch; and a feedback circuit comprising: a first operational amplifier having a first input terminal coupled to a first reference voltage source, and a second input terminal coupled to a second terminal of the first switch; a first resistor having a first terminal coupled to an output terminal of the first operational amplifier; a first diode having a first terminal coupled to a second terminal of the first resistor; a first capacitor having a first terminal coupled to a second terminal of the first diode, and a second terminal coupled to ground; a second resistor having a first terminal coupled to the second terminal of the first diode; a second diode having a first terminal coupled to a second terminal of the second resistor; a third resistor having a first terminal coupled to a second terminal of the second diode, and a second terminal coupled to the second terminal of the first capacitor; a second operational amplifier having a first input terminal coupled to a second reference voltage source, a second input terminal coupled to the second terminal of the second diode, and an output terminal coupled to an input terminal of the power controlling circuit; and a fourth resistor having a first terminal coupled to the output terminal of the second operational amplifier, and a second terminal coupled to the first terminal of the third resistor.