Patent ID: 7440294
Filing Date: 2008-10-21
Classification: H02M

Abstract:
1. A power adapter for simultaneously converting an input AC voltage into a low-level output DC voltage and a high-level output DC voltage, comprising: a switch; a transformer having a primary winding, a first secondary winding and a second secondary winding, wherein the primary winding is connected in series with the switch and the first secondary winding and the second secondary winding are connected in series with each other, the transformer is configured to store energy therein when the switch is turned on and transfer the stored energy to the first secondary winding and the second secondary winding when the switch is turned off; a first rectifier/filter circuit connected across the first secondary winding for performing rectification and filtering operation to the energy received by the first secondary winding so as to generate a low-level output DC voltage; a second rectifier/filter circuit connected across the first secondary winding and the second secondary winding for performing rectification and filtering operation to the energy received by the first secondary winding and the second secondary winding so as to generate a high-level output DC voltage, a pulse-width modulator for controlling switching operations of the switch; and a feedback control circuit connected with the first rectifier/filter circuit, the second rectifier/filter circuit and the pulse-width modulator for detecting variations on the low-level output DC voltage and the high-level output DC voltage and in response thereto issuing a feedback signal to the pulse-width modulator to enable the pulse-width modulator to stabilize the low-level output DC voltage at a predetermined level and stabilize the high-level output DC voltage at a predetermined level.