Patent ID: 6104248
Filing Date: 2000-08-15
Classification: H03F

Abstract:
An audio amplifier operable to provide an amplified audio output signal, said audio amplifier being powered from a power source that exhibits a predetermined DC voltage, said audio amplifier comprising:a power amplifier having an input terminal connected for receiving the audio input signal being amplified, an output terminal for supplying the amplified audio output signal to a loudspeaker, a positive power input terminal for supplying positive operating potential to said power amplifier, and a negative power input terminal for supplying a negative operating potential to said power amplifier;a positive-going tracking-up converter for supplying positive operating potential to said positive power input terminal of said power amplifier with the magnitude of said positive operating potential exceeding positive portions of said amplified audio output signal by a predetermined first offset voltage, said positive-going tracking-up converter including a first pulse-width modulation means for supplying a pulse-width modulated signal representative of positive portions of the audio signal being amplified and a first switching means responsive to said pulse-width modulated signal for switching said positive-going tracking-up converter between first and second operational states, said positive-going tracking-up converter further including a first inductor and a first capacitor that are operatively connected to said first switching means so that current flow increases through said first inductor when said positive-going tracking-up converter is in said first operational state and the current flow through said first inductor is supplied to said first capacitor when said positive-going tracking-up converter is in said second operational state, the voltage developed across said first capacitor being supplied to said positive power input terminal of said power amplifier as said positive operating potential; anda negative-going tracking-up converter for supplying negative operating potential to said negative power input terminal of said power amplifier with the magnitude of said negative operating potential exceeding negative portions of said amplified audio output signal by a predetermined second offset voltage, said negative-going tracking-up converter including a second pulse-width modulation means for supplying a pulse-width modulated signal representative of negative portions of the audio signal being amplified and a second switching means responsive to said pulse-width modulated signal for switching said negative-going tracking-up converter between first and second operational states, said negative-going tracking-up converter further including a second inductor and a second capacitor that are operatively connected to said second switching means so that current flow increases through said second inductor when said negative-going tracking-up converter is in said first operational state and the current flow through said second inductor is supplied to said second capacitor when said negative-going tracking-up converter is in said second operational state, the voltage developed across said second capacitor being supplied to said negative power input terminal of said power amplifier as said negative operating potential.