Patent ID: 7098630

Claim:
Means for controlling a power supply circuit for providing electric power to a load ( 7 ), comprising: a power supply stage having an LC circuit with an inductor ( 4 ) and filter capacitors ( 5 ) and ( 6 ), and a control stage for creating a special switch sequence, wherein the power supply stage comprises a bridge circuit ( 1 ) including two semiconductor members ( 2 , 3 ) connected in series between positive (+V 0 ) and negative (−V 0 ) power supply rails, each semiconductor member comprising a switchable member for conducting current to or from the load ( 7 ) in the forward direction of the semiconductor member under control of a control drive circuit, with a free-wheel diode connected in parallel with the switchable member for conduction of current in the opposite direction; wherein the control stage comprises a monitor circuit for monitoring the bridge voltage (E) of the connection between the two semiconductors members ( 2 ), ( 3 ) and the current (I) through the inductor ( 4 ), said monitor circuit comprising a first comparator ( 12 ) for comparing when the current (I) through the inductor exceeds a reference value (Iref) and a second comparator ( 13 , 14 ) for comparing when the bridge voltage (E) changes polarity towards the corresponding rail polarity; a drive circuit adapted to provide a firing pulse to one of said switchable members of said semiconductor members for initiating the conduction thereof; said drive circuit being adapted to terminate the conduction of said switchable member when said first comparator ( 12 ) determines that the current (I) through the inductor exceeds said reference value (Iref) and to provide another firing pulse when said second comparator ( 13 , 14 ) determines that the bridge voltage (E) changes polarity towards the corresponding rail polarity, said drive circuit comprising a means for measuring the current (I) through the inductor comprising a measuring winding ( 17 ) and an integrator consisting essentially of an analog RC network (R 6 , C 3 ).