Measuring circuit of the DC component of the current flowing through the primary winding of the output transformer of an inverter

Claim 1

A measuring circuit of the D.C. component of the current flowing through the primary winding of the output transformer of an inverter, comprising a detection device producing a signal representative of the current flowing through said winding, an integrator designed to integrate said signal detected on a period of the A.C. component of the current, the integrator output signal being reset at the beginning of each of said periods and being applied to a sample and hold stage designed to sample it just before it is reset, in such a way as to supply on output a signal representative of the mean amplitude of the D.C. component present during the previous period and wherein the integrator output signal is applied to the sample and hold stage via an intermediate stage comprising a first operational amplifier whose positive input is grounded and whose negative input is connected to the integrator output by a first resistor and to the sample and hold stage input by a second resistor, a third resistor being arranged between the output of the first operational amplifier and the sample and hold stage input, in such a way as to limit the maximum possible variation of the measuring circuit output signal during the sampling period.