Buck + CLCL resonant converter cascaded DC/DC power converter topological structure

Abstract

The invention provides a Buck + CLCL resonant converter cascaded DC / DC power converter topological structure. A CLCL form topological structure is utilized to replace a half-bridge LLC structure in an existing Buck + LLC converter, and the technical problems that a low-efficiency Buck circuit is adopted for voltage regulation, LLC is limited to be a fixed frequency, the efficiency is relatively low under heavy load and light load, and when the fixed-frequency LLC design is carried out, the selection of the K value is too large, so that the ZVS is easy to lose, and the parameter design is difficult are solved. Especially, when the mode that the duty ratio of the BUCK converter is fixed and the frequency of the CLCL converter is adjusted is adopted, the efficiency curve of the system can be greatly improved under the condition of wide input.

Description

technical field [0001] The invention belongs to the technical field of power conversion devices in switching power supplies, and in particular relates to a DC / DC power converter topological structure composed of a Buck circuit and a CLCL topological structure cascaded. Background technique [0002] In the existing switching power supply, the power conversion topology in the form of BUCK+LLC cascading is widely used. The primary switching tube can realize soft switching in the full load range. The device has a high degree of integration and has a working time It has the advantages of small conduction loss and high power density. However, this topology still has the following defects and deficiencies: [0003] (1) In normal use, the efficiency of the cascaded topology is mainly limited by the Buck topology, but due to the weak voltage regulation characteristics of the LLC topology, when the Buck voltage regulation is used, it will have a great impact on the system efficiency;...

AI Technical Summary

Problems solved by technology

[0003] (1) In normal use, the efficiency of the cascaded topology is mainly limited by the Buck topology, but due to the weak voltage regulation characteristics of the LLC topology, when the Buck voltage regulation is used, it will have a great impact on the system efficiency;

[0004] (2) When LLC is designed, since it is necessary to reduce the resonance current to achieve low current stress when the MOS tube is turned off, and to improve the efficiency under light load conditions, the excitation inductance Lm of the LLC is usually selected very large, and the excitation inductance Lm and the resonance inductance The ratio K of Lr is usually selected above 10 to obtain higher light-load efficiency, but the improvement of light-load efficiency brings about a small resonance energy caused by excessive Lm, and it is impossible to achieve full-range soft switching. Therefore, for low-power applications not applicable

[0005] (3) LLC topology adopts frequency conversion method for voltage regulation, but because of PFM control, it is difficult to model the control loop, and when the circuit is operating in a wide range, the frequency range is large, so it is not suitable for extremely light loads and requires a wide range In the case of input and output, it is mainly limited to the occasion of step-down isolation

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