Patent ID: 7596004

Claim:
A switched-mode power supply system comprising: two input terminals including a negative input terminal and a positive input terminal that receive a DC input supply voltage; a capacitive buffer assembly connected between the input terminals and comprising two buffer capacitors connected in series; a first switch and a second switch of the MOSFET or IGBT power transistor type, which are driven by a first and a second control circuit respectively; a primary inductive assembly; at least one secondary winding magnetically coupled to the primary inductive assembly to deliver a DC output voltage; the primary inductive assembly is connected in series between the positive input terminal and the first switch and the second switch, a source of the first switch is connected to the negative input terminal, a drain of the first switch is connected to a source of the second switch, and a drain of the second switch is connected to the primary inductive assembly; a current injection module configured to inject current at a mid-point of the two buffer capacitors to generate a current imbalance at the mid-point; and a balancing circuit configured to balance leakage currents of the two buffer capacitors, a first end of the balancing circuit is connected to the mid-point of the two buffer capacitors to balance voltages across terminals of the two buffer capacitors.