Ess Technology, Inc.

Peter John Frith

A Martin Mallinson

Robert Lynn Blair

Yongsheng Xu

Dustin Forman

An apparatus and method are disclosed for providing output signal swings that are greater than the supply voltage in a class-D amplifier. The amplifier circuit boosts the voltage across the amplifier load, such as a loudspeaker, by using capacitors to 'charge pump' the voltage across the load and thus increase the voltage temporarily. This is done by using two or more output bridges rather than one, and connecting the bridges through the capacitors. For signals of less than the supply voltage, only an inner bridge, similar to a full bridge of the prior art, operates. For signals above the supply voltage, an outer bridge charges capacitors, which are then used to 'boost' the voltage on the bridge output for the short period of the Class-D switching period. Thus, only relatively small value boosting capacitors are needed, as they do not need to supply charge for very long.

Method and apparatus for achieving high-output signal swing from class-D amplifier

Method and apparatus for achieving very high-output signal swing from class-D amplifier

Method and apparatus for achieving very high-output signal swing from class-D amplifier using fewer components

An apparatus is disclosed for inputting digital data on the output channel(s) of an audio subsystem in an audio device, without interfering with normal operation of the audio subsystem. The described circuit includes a resistive element in parallel with the expected load device, such as a headphone or speaker. The resistive element receives a modulated digital signal from a data source or a switch, and the instantaneous current through the resistive element due to the modulated digital signal is reflected in a current feedback mechanism of the audio subsystem. Demodulation logic retrieves the digital signal from the current measured by the current feedback mechanism. A capacitor is provided to prevent the current in the resistive element from the digital signal from impacting the average DC current that the feedback mechanism uses to evaluate the load device.

Data input on audio device analog output port

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Kelowna, Canada

Peter John Frith