Patent ID: 7768807

Claim:
A circuit comprising control circuitry and a converter, wherein: the converter is an isolated bi-directional dc/dc converter that includes a transformer having a primary and a secondary, boost mode main switching circuitry coupled to the primary of the transformer, buck mode main switching circuitry coupled to the secondary of the transformer and boost mode overshoot protection circuitry; the buck mode main switching circuitry includes a first switch coupled between a first lead of the secondary and a first terminal of a load, a second switch coupled between a second lead of the secondary and the first terminal of the load, a third switch coupled between the first lead of the secondary and a second terminal of the load, and a fourth switch coupled between the second lead of the secondary and the second terminal of the load; the control circuitry is coupled to the first, second, third and fourth switches and is operable to control the buck mode main switching circuitry to change from a base state to a first half cycle state during a first half cycle, the base state being where the first, second, third and fourth switches are all turned off, the first half cycle state being where the first switch is turned on and the second, third and fourth switches are all turned off; the control circuitry is further operable to control the buck mode main switching circuitry to change from the first half cycle state to the base state at an end of the first half cycle; and the control circuitry is further operable to control the buck mode main switching circuitry to change from the base state to a second half cycle state during a second half cycle, the second half cycle state being where the third switch is turned on and the first, second and fourth switches are all turned off.