Bidirectional isolation type DC/DC converter

Abstract

The invention provides a bidirectional isolation type DC / DC converter and a control method thereof. The bidirectional isolation type DC / DC converter comprises at least two LLC resonant converter units; each LLC resonant converter unit comprises two switching networks and a resonant unit; each resonant unit comprises a resonant capacitor, a resonant inductor and a transformer, a first interface of the first switching network is connected in series with the resonant capacitor, the resonant inductor and one winding of the transformer and then is connected to a second interface of the first switching network, and two ends of the other winding of the transformer are respectively connected with two interfaces of the second switching network; and all the LLC resonant converter units are divided into two types, the first switching networks of all the first-class LLC resonant converter units are connected in series with the second networks of all the second-class LLC resonant converter units, and the second switching networks of all the first-class LLC resonant converter units are connected in parallel with the first networks of all the second-class LLC resonant converter units. Bidirectional gain and efficiency consistency and smooth power commutation can be realized.

Description

technical field [0001] The invention relates to the technical field of DC / DC converters, in particular to a bidirectional isolation DC / DC converter. Background technique [0002] The size of passive components in an isolated DC / DC converter can be greatly reduced as the switching frequency continues to increase, but its switching loss will increase significantly. As a typical topology of the isolated DC / DC converter, the LLC resonant converter with unidirectional power flow can realize the zero-voltage switching of the primary switching tube of the transformer and the zero-current switching of the secondary switching tube in the full load range, thus Reduce switching loss, improve conversion efficiency, and reduce electromagnetic interference. Due to the above advantages, the LLC resonant converter is widely used in the occasion of unidirectional power flow to achieve higher power density. At the same time, the LLC resonant converter has different resonance characteristics...

AI Technical Summary

Problems solved by technology

However, in order to ensure the same gain in both directions, the parameters of the resonant network need to be calculated and verified complexly, and when the power direction changes, the control strategy of the switching devices on both sides also needs to be changed, making the control difficult

For the cascade solution of non-isolated DC / DC converters and LLC resonant converters, the LLC resonant converter operating at the resonant frequency can achieve efficient power transmission when the power flows in both directions, but its gain and power cannot be controlled , so a non-isolated DC / DC converter is required to control the gain and power

However, cascaded non-isolated DC / DC converters also pass all the power at the same time, and most of them cannot achieve soft switching, resulting in large losses

[0004] Therefore, there is an urgent need for a bidirectional isolated DC / DC converter to overcome the difficulties of single-stage LLC resonant converters in applications where power flows bidirectionally and the problems of complex control and large losses in existing bidirectional power topologies.

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