Switch mode power circuit

A method of generating a measure of hard switching amplitude in a switch mode power supply circuit, the circuit including at least one inductive component coupled to an associated switch for cyclically connecting the inductive component to a source of power, the circuit including a signal output representative of a voltage at a junction of the at least one inductive component to the associated switch, the method including the steps of:

• (a) providing the circuit with a hard switching amplitude detector for deriving the measure of hard switching amplitude occurring in operation in the associated switch, the detector including a signal processing path for receiving the signal output and generating the measure of hard switching amplitude therefrom;
• (b) imperfectly differentiating the signal output using a signal differentiator circuit included in the signal path for generating a corresponding imperfectly differentiated signal;
• and
• (c) integrating the imperfectly differentiated signal in a temporally-gated manner in a signal integration circuit included in the signal path for generating the measure of hard switching.

A switch mode power supply circuit comprising:

• a transformer that includes a primary winding electrically isolated from a secondary winding;
• a primary switch for cyclically connecting the primary winding to a power source;
• a signal output representative of a primary voltage at a junction of the primary winding to the primary switch;
• and
• a hard switching amplitude detector connected at a junction of the secondary winding to a secondary switch, the hard switching amplitude detector including a signal processing path for receiving the signal output and for generating a measure of hard switching amplitude occurring in operation of the primary switch, the signal path including a signal differentiator circuit for imperfectly differentiating the signal output to generate a corresponding imperfectly differentiated signal, a signal integrator circuit for integrating the imperfectly differentiated signal in a temporally-gated manner for generating the measure of hard switching, and a control unit to provide gating signals to the signal differentiator circuit and the signal integrator circuit.