Three-level full-bridge soft switch current conversion circuit and control method therefor

Abstract

The invention discloses a three-level full-bridge soft switch current conversion circuit and a control method therefor, and the circuit comprises an input capacitor C1, an input capacitor C2, a three-level full-bridge inversion circuit, a transformer, and an output circuit. A connection line between the three-level full-bridge inversion circuit and the primary side of the transformer is in seriesconnection with a saturation inductor and a blocking capacitor. The invention proposes a control method for the circuit, and the method is simple and effective. The method can cooperate with a currentconversion circuit to achieve a soft switch effect, also can simplify the design complexity of the drive circuit, just needs two pulse transformers and a matched drive circuit, and can achieve the drive isolation and drive power transmission of eight switching tubes without an additional isolation power supply.

Description

technical field [0001] The invention relates to the field of DC-AC-DC converter circuits, in particular to a three-level full-bridge soft-switch converter circuit and a control method thereof. Background technique [0002] The traditional two-level converter circuit has the advantages of simple topology and easy control, and is widely used in various DC-AC-DC converter circuits. However, the two-level converter circuit also has problems such as high requirements for the withstand voltage of the switching tube, large switching stress, and difficulty in increasing the frequency, which are greatly restricted in high-voltage input applications. The three-level inverter circuit has half the withstand voltage of the switch tube as the two-level inverter circuit, the switch stress is small, and it is easier to achieve high frequency. In the case of high voltage input, the application advantage is obvious. [0003] Chinese patent 01127182 "Zero-voltage and zero-current switching hy...

AI Technical Summary

Problems solved by technology

[0003] Chinese patent 01127182 "Zero-voltage and zero-current switching hybrid full-bridge three-level DC converter", although it belongs to a three-level inverter circuit, half of it is a two-level bridge arm, so it also has a two-level converter circuit shortcoming

[0005] When only parasitic capacitance is used, the soft switching effect is poor due to the small capacitance

When a large capacitor is connected in parallel at both ends of the switch tube, under no-load or light-load conditions, the parallel capacitor will be discharged directly through the switch tube, which will affect the reliability of the device, and the parallel capacitor of the switch tube will reduce the controllability of the circuit. characteristics, especially at low power output

In addition, due to the need to achieve midpoint potential balance, the control logic of the inverter circuit is relatively complex, which significantly increases the number and cost of the control circuit components, and the increase in the number of components will reduce the reliability of the circuit

The dynamic voltage clamping of the switching tube is a problem that must be solved in every three-level DC-AC-DC converter circuit. Adding flying capacitors at both ends of the clamping diode can achieve the effect of dynamic voltage clamping of the switching tube, but it will increase circuit complexity

Using a specific control method, the dynamic voltage clamping of the switching tube can also be realized, but it is usually accompanied by complex control, the switching tube needs to be individually controllable, and the design of the driving circuit is complicated.

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