Energy-efficient consumer device audio power output stage

A method of improving efficiency of an amplifier for providing a power output to an audio transducer, said method comprising:

• receiving an indication of a magnitude of a signal to be amplified by said amplifier;
• selecting an operating mode of a charge pump power supply that provides a bi-polar power supply output symmetric about a reference potential;
• and
• supplying a bi-polar power supply voltage to said amplifier from said charge pump in conformity with said selected operating mode, wherein in a first operating mode of said charge pump power supply, said power supply voltage is equal to a first voltage and in a second operating mode of said charge pump power supply, said power supply voltage is substantially equal to a rational fraction of said first voltage, wherein in both of the first operating mode and the second operating mode, the bipolar power supply voltage is substantially symmetric about the reference potential, and wherein in the second operating mode a first flyback capacitor and a second flyback capacitor are coupled in series during a first charging phase of the charge pump power supply, and separately provide charge to corresponding ones of a pair of power supply rail connections providing the bipolar power supply output, during a second discharging phase of the charge pump power supply.

A charge-pump power supply circuit, comprising:

• a pair of power supply input terminals;
• a pair of power supply output terminals forming a bi-polar output of said charge-pump power supply circuit that is substantially symmetric about a reference potential;
• a first flyback capacitor;
• a second flyback capacitor;
• and
• a switching circuit for alternatively coupling said second flyback capacitor in a first operating mode between a positive one of said power supply input terminals and a negative one of said power supply input terminals connections in first charging phase and between said negative only of the power supply input terminals and a negative one of said power supply output terminals in a second discharging phase, and wherein when said charge pump power supply is in said first operating mode, said switching circuit couples said positive one of said power supply input terminals to said positive one of said pair of power supply output terminals, and wherein in a second operating mode the switching circuit couples the first flyback capacitor and the second flyback capacitor in series during the first charging phase of the charge pump power supply, and separately provide charge to corresponding ones of the pair of power supply output terminals during the second discharging phase of the charge pump power supply.