Patent ID: 11888406
Assignee: APPLE INC.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 8:
9. A method performed by a controller of an AC-AC converter having a stack of four switching devices, wherein an input of the AC-AC converter is coupled across the stack of four switching devices and an output of the AC-AC converter is taken from first terminal coupled to a connection point of first and second switching devices of the stack and a second terminal coupled to a connection point of third and fourth switching devices of the stack, the method comprising:
during a positive half cycle of an AC input voltage:
operating first and second switching devices of the stack with an alternating 50% duty cycle; and
turning on and leaving on third and fourth switching devices of the stack; and

during a negative half cycle of the AC input voltage:
operating the third and fourth switching devices of the stack with an alternating 50% duty cycle; and
turning on and leaving on the first and second switching devices of the stack;

wherein:
during the positive half cycle, the duration of the on-times of the first and second switching devices determine the magnitude of the AC voltage between the first and second terminals; and
during the negative half cycle, the duration of the on times of the third and fourth switching devices determine the magnitude of the AC voltage between the first and second terminals.