REDUCED CROSSTALK AND MATCHED OUTPUT POWER CLASS D AUDIO AMPLIFIER WITH OPPOSITELY POLARIZED TRIANGLE WAVES

摘要

A multi-channel Class D audio amplifier is provided to substantially reduce channel-to-channel crosstalk by employing in each channel a local triangle ramp generator controlled by a single global digital timing signal. The noise critical timing/integrating capacitor for the triangle ramp generator resides locally in each channel and adjacent to the PWM comparator of that channel and referenced to the local ground of that channel. The amplifier can also include a duty cycle limitation circuit to limit output power availability depending on the impedance of any attached loads (speakers).

主权项

1. A class D amplifier, comprising:
two or more pulse width modulator comparators adapted to receive a respective channel of audio signals, and compare each of the received respective channel of audio signals with respective triangle wave signals and generate respective pulse width modulated signals for each of the received channels of audio signals; two or more switching stage amplifiers adapted to receive the two or more pulse width modulated signals and amplifying each respectively according to a predetermined gain based on a channel identity of the received audio channel; two or more filter stages adapted to filter each of the two or more amplified pulse width modulated signals; two or more speakers adapted to receive a respective one of the two or more filtered amplified pulse width modulated signals; and a triangle wave generator adapted to generate the triangle wave signals, the triangle wave generator including a DC servo circuit, the DC servo circuit comprising
a first resistor connected at a first end to the triangle wave output signal of the triangle wave generator,a first amplifier connected to a second end of the first resistor at an inverting input of the first amplifier,a second capacitor connected to the second end of the first resistor and an output of the amplifier, and wherein the output of the amplifier is connected to a current adjusting input of a first current source, such that the DC servo circuit is adapted to monitor a first DC voltage on the triangle wave, and provide a second, oppositely polarized DC voltage to counteract the first DC voltage on the triangle wave, such that at least two local triangle waves are generated such that a positive going portion of the triangle wave and a negative going portion of the triangle wave are kept substantially equal in duration, amplitude, and slope, by the DC servo circuit.