Patent ID: 8169795

Claim:
An audio power conversion system, comprising: a power supply having a positive supply rail and a negative supply rail for supplying power to a single ended class D amplifier; and a supply pump reduction circuit, connected to the supply rails and adapted to redistribute a pumping charge from said power supply by forcing a current-flow from a rail with a relatively higher voltage to a rail with a relatively lower voltage, wherein said supply pump reduction circuit comprises a high frequency transformer having a first and a second winding alternatingly connectable during a first and second cycle to said positive and negative supply rails, so as to cause a current to migrate from the rail with the highest voltage to the rail with the lowest voltage, while balancing said transformer, and wherein said supply pump reduction circuit further comprises: a first capacitor connected between a first common point and a second common point, a first switch connected between said second common point and a first terminal of the first transformer winding, a second switch connected between said second common point and a second terminal of the second transformer winding, a second capacitor connected between said first common point and a third common point, a third switch connected between said third common point and said first terminal on said first transformer winding, a fourth switch connected between said third common point and said second terminal on said second transformer winding and wherein a second terminal of said first transformer winding and a first terminal of said second transformer winding are connected to said first common point, so that a resonant tank is formed by a leakage inductance of said transformer and said capacitors, said resonant tank obeying the relationship: t ON ≅ 2 · π · L Leakage · ( C 15 + C 16 ) , where t ON is the time during which said switches are switched ON, C 15 is the capacitance of said first capacitor, and C 16 is the capacitance of said second capacitor thereby enabling zero current switching of said switches.