Reducing pulse error distortion
A class D amplifier that includes circuitry to apply a non-linear correction to pulse error distortion. The amplifier includes an output voltage controlling circuit, comprising at least two switches, controlled by a modulator; an output inductor, coupling the switching circuit to an output terminal; and correction circuitry to provide to the modulator a correction signal characterized by a non-linearity. The correction circuitry includes a current sensor that senses the current from the output inductor to the output terminal.
1. An amplifier comprising:
an output voltage controlling circuit, comprising:
a switching circuit characterized by a duty cycle and comprising at least two switches; and
a modulator configured to control the switches;
an output inductor, coupling the switching circuit to an output terminal; and
correction circuitry comprising:
a current sensor that senses the current from the output inductor to the output terminal; and
a pulse error distortion corrector configured to receive a sensed current measurement from the current sensor, and, based on the sensed current measurement, provide to the modulator a non-linear correction signal which modifies the duty cycle to compensate for pulse width distortion caused by dead time during which the at least two switches are open.
2. An amplifier according to claim 1 , the correction circuitry further comprising a voltage sensor at the output terminal, coupled to the correction circuitry.
3. An amplifier according to claim 2 , wherein the sensed voltage modifies the correction signal by modifying the shape of the non-linearity.
4. An amplifier according to claim 1 , wherein the correction circuitry comprises a soft clipper to provide the correction signal.
5. A method for operating an amplifier, comprising:
opening and closing a plurality of switches according to a duty cycle to control the voltage provide to an output terminal;
measuring current through an inductor to the output terminal; sensing the current through the inductor to the output terminal to provide a sensed current measurement; and
based on the sensed current measurement, applying a non-linear correction signal which modifies the duty cycle to compensate for pulse width distortion caused by dead time during which the plurality of switches are open.
6. The method of claim 5 , wherein the non-linear correction signal is responsive to the voltage at the output terminal.