Bridgeless AC-DC converter with power factor correction and method for doing so

Abstract

Bridgeless AC-DC converter (700), including: a totem pole network (720) with a first input configured to be coupled to a second terminal of an AC voltage source, a second input configured to be coupled to a first terminal of the AC voltage source via a coil, an output terminal to provide an output voltage, and a feedback terminal; an output capacitor (760) with a first terminal coupled to the output terminal and a second terminal coupled to a bulk ground terminal; a detection element coupled between the return port and the bulk ground port; and a control circuit (780) coupled to the feedback terminal of the totem pole network, wherein the control circuit comprises: a pulse width modulation circuit (820) that modulates the turn-on time of an active switch in the totem pole network on a cycle-by-cycle basis in response to a current-limiting trigger signal, CLTRIP, and a current limiting circuit (830) with an input for receiving a current sensing signal, CS, which is derived from a current through the sensing element, and with an output for providing the current limiting trigger signal, wherein the current limiting circuit activates the current limiting trigger signal to shorten the turn-on time according to a duration during which the current sensing signal exceeds a current limit threshold.

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