Light load control method for energy feedback of 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 period, the microcontroller configures a timer to enter an energy feedback control mode, generates a group of primary and secondary side switching signals withphase difference, and further respectively drives a primary side switching tube and a secondary side rectifying tube, so that the terminal voltage of the secondary side is turned over, and the energyof the load is transmitted back to the source through a resonance circuit. Therefore, the output voltage is reduced. After entering the energy feedback control mode, the energy in each period is partially fed back to the primary side. By adding phase adjustment, the problem of excessive output energy in a light load state is solved, the stability of output voltage is ensured, and the voltage regulation capability of the two-stage converter in the light load state is improved.

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.

Images