Provided are circuits and methods for use with a power supply that provides a main output including a main DC voltage having a first AC voltage ripple, or a main DC current having a first AC current ripple. A ripple cancellation converter provides a second AC voltage ripple connected in series with the main output, such that the first AC voltage ripple is substantially cancelled; or a second AC current ripple connected in parallel with the main output, such that the first AC current ripple is substantially cancelled. As a result, substantially ripple-free DC output power is provided.