US 12,136,883 B2
Method for operating in burst mode active clamp flyback converters and corresponding active clamp flyback converter apparatus
Claudio Adragna, Monza (IT); Massimiliano Gobbi, Castel San Giovanni (IT); and Giuseppe Bosisio, Sesto San Giovanni (IT)
Assigned to STMICROELECTRONICS S.r.l., Agrate Brianza (IT)
Filed by STMICROELECTRONICS S.r.l., Agrate Brianza (IT)
Filed on Sep. 23, 2022, as Appl. No. 17/951,703.
Claims priority of application No. 102021000025133 (IT), filed on Sep. 30, 2021.
Prior Publication US 2023/0096383 A1, Mar. 30, 2023
Int. Cl. H02M 3/335 (2006.01); H02M 1/00 (2006.01); H02M 1/34 (2007.01)
CPC H02M 3/33569 (2013.01) [H02M 1/0035 (2021.05); H02M 1/342 (2021.05); H02M 3/33507 (2013.01); Y02B 70/10 (2013.01)] 24 Claims
OG exemplary drawing
 
1. A method, comprising:
comparing a control signal of an active clamp flyback converter to a plurality of three or more thresholds;
counting a number of consecutive switching cycles during which a clamp switch of the active flyback converter remains off; and
selectively transitioning the active clamp flyback converter between a plurality of operational states by controlling a power switch and the clamp switch of the active clamp flyback converter, the plurality of operational states including:
a run state of operation of one or more consecutive switching cycles of the active flyback converter, each switching cycle during the run state of operation comprising sequentially turning the power switch on, turning the power switch off, turning the clamp switch on and turning the clamp switch off;
an idle state of operation of one or more consecutive switching cycles of the active flyback converter during which the power switch and the clamp switch are off;
a first burst state of operation of one or more sets of consecutive switching cycles, each set of consecutive switching cycles of the first burst state including:
a determined number of switching cycles during which the power switch is turned on and off and the clamp switch is off; and
a switching cycle in a determined position in the set of switching cycles comprising sequentially turning the power switch on, turning the power switch off, turning the clamp switch on and turning the clamp switch off; and
a second burst state of operation of one or more sets of consecutive switching cycles during which the power switch is turned on and off and the clamp switch is off,
wherein the selectively transitioning is based on the comparing of the control signal to the plurality of three or more thresholds and the count of the number of consecutive switching cycles during which the clamp switch remains off.