Apparatus and method for zero voltage switching in bridgeless totem pole power factor correction converter

摘要

Power factor correction (PFC) apparatus, controllers, and methods for operating bridgeless totem pole power factor correction converters in which AC input voltage polarity is detected for designation of active and freewheeling switches of the totem pole circuit, a nominal freewheeling switch on-time is determined according to a Volt×Second balance relationship, and the voltage across the designated active switch is sensed and used to selectively modify or offset the nominal freewheeling switch on-time to provide a computed freewheeling switch on-time for the next switching cycle to facilitate zero voltage switching of the active switch.

主权项

1. A controller for controlling a bridgeless totem pole power factor correction (PFC) converter, the controller comprising:
a driver circuit operative to provide switching control signals to selectively operate first and second switches of the PFC converter in each of a plurality of switching cycles; a detection circuit coupled with first and second AC input nodes of the PFC converter and operative to detect positive and negative AC input half cycles based at least partially on a voltage polarity at the first and second AC input nodes; a selection circuit operative to designate the first switch as an active switch and designate the second switch as a freewheeling switch for negative AC input half cycles, and designate the second switch as the active switch and designate the first switch as the freewheeling switch for positive AC input half cycles; a sensing circuit operative to sense a voltage across the designated active switch following turn off of the designated freewheeling switch for a given switching cycle; a control circuit operative to:
compute a nominal freewheeling switch on-time for the given switching cycle at least partially according to a Volt×Second balancing relationship using an active switch on-time for the given switching cycle, andselectively offset the nominal freewheeling switch on-time for the given switching cycle based at least partially on the voltage across the designated active switch for the given switching cycle to provide a computed freewheeling switch on-time for a next switching cycle; and a pulse circuit operative to provide an active switching pulse signal to the driver circuit to actuate the designated active switch for the active switch on-time in the given switching cycle, and to provide a freewheeling switching pulse signal to the driver circuit to actuate the designated freewheeling switch for the computed freewheeling switch on-time for the next switching cycle to facilitate zero voltage switching of the designated active switch.