A light-load control method for energy feedback of a buck-boost LLC two-stage converter

Abstract

The invention discloses a light-load control method for energy feedback of a Buck-Boost LLC two-stage converter, and belongs to the technical field of power generation, power transformation or power distribution. In each light-load working cycle, the microcontroller configures the timer to enter the energy feedback control mode, and generates a set of switching signals of the primary and secondary sides with a phase difference, and then drives the switching tubes of the primary side and the switching tubes of the secondary side respectively. The rectifier tube reverses the terminal voltage on the secondary side, and realizes that the energy of the load passes through the resonant circuit and then transfers back to the source, thereby reducing the output voltage. After entering the energy feedback control mode, part of the energy will be fed back to the primary side every cycle. By adding phase adjustment, the invention solves the problem of excess output energy under the light load state, ensures the stability of the output voltage, and improves the voltage regulation capability of the two-stage converter under the light load state.

Description

technical field [0001] The invention relates to a Buck-Boost LLC converter, in particular to a light-load control method for energy feedback of a Buck-Boost LLC two-stage converter, and belongs to the technical field of power generation, power transformation or power distribution. Background technique [0002] The LLC resonant converter can realize the zero-voltage turn-on of the switch tube and the zero-current turn-off of the rectifier tube on the secondary side in the full load range, and has the characteristics of high efficiency, but the LLC resonant converter has weak voltage regulation ability and often uses pulse frequency modulation Stable output voltage, which is not conducive to the design of magnetic components and electromagnetic interference. The Buck-Boost LLC two-stage converter can be improved by pre-stage voltage regulation, and the superposition of the current of the pre-stage and post-stage during the dead time can enhance the soft switching capability of...

AI Technical Summary

Problems solved by technology

However, putting the circuit into burst mode will cause a large output voltage ripple, and adding a preload will reduce the efficiency of the converter by dissipating energy

However, the research on energy feedback control is currently limited to LLC circuits. Directly applying the energy feedback control method to the Buck-Boost LLC cascaded topology has problems such as excess energy in the bus capacitor, excessive stress on the power tube, and large output ripple.

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