Circuit with improved dynamic response for measuring current in pulse width modulated amplifiers

A method of measuring current flowing through a load driven by a pulse width modulation (PWM) circuit in response to PWM control signals, the method comprising:

• generating a cancellation current using flux cancellation circuitry and applying the cancellation current to a secondary winding of a transformer, a primary winding of the transformer being coupled to the load;
• generating a flux cancellation circuitry output which is indicative of a level of current through the load;
• inverting the flux cancellation circuitry output using an inverter to provide an inverted flux cancellation circuitry output;
• and
• selectively and alternately coupling the flux cancellation circuitry output and the inverted flux cancellation circuitry output to a load current output to provide a load current output signal indicative of the level of current through the load.

A circuit for measuring current flowing through a load driven by a pulse width modulation (PWM) circuit in response to PWM control signals, the circuit for measuring comprising:

• transformer means, having primary and secondary windings, for providing galvanic isolation from the load, the primary winding being connected to the load;
• current cancellation means for applying a cancellation current to the secondary winding, the current cancellation means providing an output which is indicative of a level of current through the load;
• load current output means for providing an output signal indicative of the level of current through the load;
• inverter means for providing an inverted current cancellation means output;
• and
• switch means for selectively and alternately coupling the current cancellation means output and the inverted current cancellation means output to the load current output means in response to first and second signals generated as a function of the PWM control signals.