The increase in the amount of energy transmitted from the source H to L occurs with decreasing of the control frequency. To ensure soft switching of the H inverter switches, there is a possibility to include additional parallel capacitor C. Additional capacitor C is switched by tran- sistor TS (Fig. 1). When the TS transistor is turned off, resultant capacitance consist of the relatively small output capacitance of the TS transistor connected in series with the capacitor C.