Push-pull - flexible switching converter with serial-connected resonance unit

The invention discloses a push-pull flexible switching converter with a serial-connected resonance unit, wherein the converter comprises a primary push-pull circuit, an isolation transformer, a secondary rectification circuit and an output circuit. The LC resonance unit is connected in series between the isolation transformer and the secondary rectification circuit; and proper charging/discharging capacitance values of a power switch tube of the primary push-pull circuit and proper inductance and capacitance values of the LC resonance unit are set, so that the converter works in a flexible switching state, the power switch tube is switched on with zero voltage and switched off with zero current, and the disconnection peak of a secondary-side rectification unit can be eliminated. Thus, the conversion efficiency is improved, switching noises are reduced, and the converter can be lightened. The converter of the invention is simple in structure, the size of the resonance unit in the converter is small, and the converter can be lightened; the conversion efficiency is higher than that of a traditional converter; and the switching noises due to switching operation can be eliminated, and the electromagnetic compatibility of the converter can be improved.