Converter circuits

Claim 1

An improved chopper circuit for converting the voltage from an input DC source into an alternating output voltage including an output transformer with at least one primary winding whose ends are coupled to one pole of said DC source via first and second switching devices respectively, the other pole of said DC source being coupled to a mid-tapping of said primary winding, control signal generating means providing first and second phase pulse sequences and coupling means to respectively apply said first and said second phase pulse sequences to said first and said second switching devices to alternately switch them ON and OFF one at a time, wherein the improvement comprises: a second transformer whose primary winding is in series with one of said first and second switching devices; first and second peak rectifying means coupled to a corresponding secondary winding of said second transformer to produce first and second signals respectively; a square wave multivibrator normally providing a balanced square wave output; a differential amplifier to compare the amplitude of said first signals with the amplitude of said second signals and provide in response thereto an output signal proportional to the differences of the two signals; means to apply said output signal to said multivibrator to modify the pulse widths of said first and second pulse sequences so that the current pulse widths through said first and second switching devices are maintained substantially equal to one another.