Feedforward active filter for output ripple cancellation in switching power converters
AssigneeThe Board of Trustees of the University of Illinois
InventorsPhilip T. Krein, Pallab Midya
Life of this patent
Estimating the term…
Abstract
An active filter provides ripple cancellation in a DC-DC converter. The feedforward filter applies to any converter with an output filter inductor. The filter is inherently stable, performs in both continuous and discontinuous conduction modes, and applies to resonant converters. A suitable linear amplifier, combined with a current transformer, results in a low loss implementation. An adaptive tuning scheme compensates for inductance variation and drift. The filter is usable with buck, push-pull, and boost converter topologies. The result is output ripple below 10 mV.sub.RMS. The filter is effective on converters with outputs as low as 2 V and currents beyond 30 A.
Claims10
A switching power converter usable to deliver an ideally constant electrical energy to a load comprising:
- an input stage for receiving an input signal;
- means for converting said input signal into an output signal for delivering electrical energy to the load;
- a filter having an energy storage element to filter said output signal prior to delivery to the load;
- a sensor circuit for detecting an AC ripple signal at said energy storage element;
- compensation signal generation means for determining a compensation signal based upon said AC ripple signal and a characteristic value of said energy storage element;
- and
- an energy coupling element coupled to said compensation signal generation means for providing said compensation signal to the load to minimize AC ripple in said output signal.
A method of minimizing ripple in electrical energy delivered to a load from an input source through a switch power converter having a passive energy device for filtering an output signal delivered to the load to produce the electrical energy, the method comprising the steps of:
- sensing an AC ripple signal at the passive energy device which is indicative of an output ripple to be minimized;
- generating a compensation signal based upon said AC ripple signal and a characteristic value of the passive energy device;
- and
- feeding the compensation signal to the load through an AC coupling to minimize ripple in the output signal delivered to the load.
Dependencies are inferred from the claim text.