Patent ID: 7411406
Filing Date: 2008-08-12
Classification: G03G

Abstract:
1. A current measurement circuit for measuring the output current of a power supply, the current measurement circuit comprising: a simulation capacitor having a capacitance proportional to a parasitic capacitance of a transformer in a power supply, the simulation capacitor having a first electrode and a second electrode, the first electrode being coupled to a hot terminal of an output winding of the power supply transformer and the second electrode being coupled to a first node; a second sense resistor coupled to the first node and to ground so that current flowing through the simulation capacitor flows through the second sense resistor; a first sense resistor coupled to a second node and to ground through which a current flows, the current flowing through the first sense resistor having a component representative of the output current of the power supply and a component representative of the parasitic current; and a differential amplifier coupled at an inverting input to the first node and at a non-inverting input to the second node, the differential amplifier generating an output signal that is proportional to the output current of the power supply.