Patent ID: 7342812

Claim:
A module for estimating the output current of a switch mode power supply (SMPS), said SMPS including a transformer with at least a primary winding coupled to an input of the SMPS and a secondary winding coupled to an output of the SMPS and having a power switching device to switch power to said primary winding of said transformer responsive to a drive signal, the module comprising: a current sense input to receive a current sense signal sensing a current in said primary winding of said transformer; a voltage sense input to receive a voltage sense signal from at least one of said primary and an auxiliary winding of said transformer; a drive signal input to receive said drive signal; a signal averager coupled to said drive signal input and to said current sense input to average said current sense signal over a period when said drive signal is controlling said power switching device to apply power to said primary winding and to provide an averaged current sense signal; a timing signal generator coupled to said voltage sense input to generate a timing signal indicating a duration of a period during which said secondary winding is providing power to said SMPS output; a multiplier coupled to an output of said signal averager and to an output of said timing signal generator to multiply said averaged current sense signal by a fraction of a total cycle period of said SMPS, indicated by said timing signal, during which said secondary winding is providing power to said SMPS output; and an output coupled to an output of said multiplier to provide a signal estimating said output current of said SMPS.