Three-level Soft-switching Forward and Flyback Direct-to-Direct Conversion Circuit Topology

Abstract

The invention discloses a three-level soft switch forward-flyback DC / DC converter circuit topology structure, comprising a single-phase three-level half-bridge inversion circuit, a soft switch auxiliary circuit, a coupling transformer, an uncontrolled full wave rectifying circuit, a filtering circuit and a load resistor. The three-level technology is utilized to reduce voltage stress of a switch tube; the soft switch auxiliary circuit is utilized to make an advanced tube and a lagging tube decoupled in a working process of the circuit, and enables the lagging tube to have enough energy to realize zero voltage switching when the lagging tube is under a light load; magnetic integration technology is utilized to integrate two transformers on a magnetic core, wherein the two transformers alternatively work in a forward state and a flaback state; a DC filtering circuit can be constituted by filtering capacitors without filtering resistors by utilizing the fact that a flyback transformer is capable of filtering inductance;. As a result, the topology structure has advantages of being applicable to a high voltage input occasion, realizing the soft switch in a relatively wide load range, and high power density.

Description

technical field [0001] The invention relates to the technical field of power electronic DC-DC conversion, in particular to a three-level soft switch with high power density, high input and high transformer utilization, and capable of realizing zero-voltage soft switching within a wide load range Forward-flyback direct-to-direct conversion circuit topology. Background technique [0002] DC-DC converters have a wide range of applications, and with the continuous development of technology, people's requirements for the voltage and power level of power electronic devices have also been continuously improved. Therefore, in order to reduce the voltage level of the switching tube, improve efficiency, and reduce costs, Brazilian scholars J.Pinherio and I.Barbi proposed the concept of a three-level DC converter. In addition, high frequency is also the goal that people are pursuing, so the power The switching loss of devices has attracted much attention, and soft switching technology...

AI Technical Summary

Problems solved by technology

But there are certain problems, for example, because only the energy of the leakage inductance participates in the resonance of the junction capacitance in the switch, it is difficult for the lagging arm to achieve soft switching under light load conditions; the efficiency of the converter is low, and the zero state time is long; the resonant inductance There is a phenomenon of duty cycle loss on the secondary side of the transformer. The larger the transformer leakage inductance, the greater the duty cycle loss, and the smaller the secondary duty cycle; the secondary rectifier diode voltage peak is large

In order to achieve soft switching in a wide load range for the lagging bridge arm, the leakage inductance of the transformer can be increased, but this reduces the utilization rate of the transformer, and two saturated inductors can also be added as switches, respectively connected to the anode of the rectifier diode In series, but the power density of the circuit decreases and the cost becomes larger

[0004] In the direct-to-direct converter, the forward conversion circuit has high power and high reliability, but its transformer needs to reset the magnetic core, and there is an extra freewheeling diode, which makes the circuit more components and increases the cost; the flyback conversion circuit The structure is simple and the cost is low, but its peak current is large and the output voltage ripple is large

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