Patent ID: 8174243

Claim:
A battery charger comprising: a switching controller configured to form a switching control signal suitable to control a power switch to control current through a primary inductor of a transformer; a pseudo generator circuit configured to receive an auxilary voltage from an auxiliary winding of the transformer and generate a current sense signal that is representative of current flow through a secondary winding of the transformer; a sampling circuit configured to sample the auxiliary voltage at a substantially zero crossing of the current sense signal and form a sampled signal responsively to the current sense signal; an error amplifier coupled to receive the sampled signal and form an error signal wherein the switching controller uses the error signal to form the switching control signal and wherein the pseudo generator circuit is copied to receive the error signal and store a first signal that is representative of the error signal, and configured to decay the first signal at a first rate that is representative of a decay rate of the current flow through the secondary winding; and a current limit circuit configured to receive the current sense signal and terminate an on-cycle of the switch responsively to a first value of the current sense signal.