Feedforward active filter for output ripple cancellation in switching power converters
First Claim
1. 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.
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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 mVRMS. The filter is effective on converters with outputs as low as 2 V and currents beyond 30 A.
107 Citations
10 Claims
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1. A switching power converter usable to deliver an ideally constant electrical energy to a load comprising:
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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. - View Dependent Claims (2, 3, 4, 5, 6)
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7. 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:
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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. - View Dependent Claims (8, 9, 10)
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Specification