Resonant converter based on ON/OFF control

Abstract

The invention provides a resonant converter based on ON / OFF control. The resonant converter comprises a primary side square wave inversion circuit I, a primary side LLC resonance circuit II, a transformer T, a secondary side full-bridge rectification circuit III and an output resistance load Ro. The resonant converter is characterized in that two auxiliary two-way switches are added to the primaryside square wave inverter circuit I; ON / OFF control is adopted for the auxiliary two-way switches, so that the resonant converter can work in a full-bridge LLC resonant converter mode and can also work in a half-bridge LLC resonant converter mode. Due to the topological structure of the resonant converter and the switching type control mode of the resonant converter, the switching frequency change range of the resonant converter is narrow, ultra-wide-range voltage gain adjustment is achieved, zero-voltage switching of a primary side switching tube is achieved, zero-current switching of a secondary side rectifying diode is achieved, and switching loss is reduced.

Description

technical field [0001] The invention relates to the technical field of isolated DC-DC converters, in particular to a resonant converter with a new topology based on ON / OFF control. Background technique [0002] Isolated DC-DC converters are currently widely used, including data centers, server power supplies, electric vehicle on-board battery chargers, photovoltaic DC microgrids, fuel cells, LED drive circuits, etc. In many of the above applications, the converter needs Meet the wide voltage working requirements. [0003] Converters mainly include two types, the first is a full-bridge converter with pulse width modulation (PWM), and the other is a resonant converter with pulse frequency modulation (PFM). Due to the large circulating current, the narrow soft switching range of the lagging arm, the high voltage stress of the rectifier diode, and the reverse recovery of the diode, the phase-shifted full-bridge converter cannot achieve high efficiency. The difference is that t...

AI Technical Summary

Problems solved by technology

[0004] The LLC resonant converter controlled by pulse frequency is difficult to achieve a wide gain range due to the limitation of the switching frequency range, and it cannot better meet the application occasions with wide voltage requirements.

Also, pulse frequency modulation control increases the complexity of resonance parameter design

In particular, when the switching frequency of the resonant converter is much lower than the resonant frequency, there will be a large circulating current in the resonant circuit, which will generate additional conduction loss and switch turn-off loss, which will reduce the efficiency of the converter. The fundamental wave analysis method (FHA ) accuracy is also reduced, and it is difficult for the converter to precisely regulate the output voltage

In particular, when the switching frequency of the resonant converter is higher than the resonant frequency, the rectifier diode on the secondary side loses the zero-current switching (ZCS) capability, which increases the electromagnetic interference and rectification loss of the system, and reduces the stability of the converter.

In addition, the resonant converter works in a wide frequency range, which is not conducive to the magnetic integration design of magnetic components, and reduces the excellent characteristics of the converter such as efficiency and power density.

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