Zero-voltage zero-current switching three-level DC converter

In order to eliminate the circulating current existing on the primary side of the converter in the zero state of the zero-voltage switching three-level DC converter, several zero-voltage zero-current switching three-level DC converter circuits are proposed. As shown in the following figures 1. This circuit and zero The main difference of the voltage switch three-level DC converter is: the addition of the coupling capacitor CSS and the addition of the auxiliary switch SAUX and the clamping capacitor CAUX in the secondary winding of the transformer; the coupling capacitor CSS separates the outer tubes VT1, VT4 and the inner tube VT2 respectively. , connected to the switching process of VT3. 2. This circuit uses a blocking capacitor as the blocking voltage source to reduce the primary side current of the transformer to zero in the zero state, thereby achieving zero current switching of the inner switching tube. 3. This Figure: In order to prevent the primary side current of the transformer from continuing to flow in the reverse direction after it decreases to zero in the zero state, diodes VT2 and VT3 are connected in series to the VT2 and VT3 branches respectively, eliminating the negative effects caused by adding saturated inductance.