Synchronous Rectification Control of Multi mode LLC Converter
Power supplies used in energy storage,electrolysis,hydrogen production,and other fields have the characteris-tics of wide output voltage range and large output current.The conventional synchronous rectification technology that de-tects the voltage or current on the rectifier not only significantly increases the system cost,but also increases parasitic os-cillations in the circuit,affecting the safe and stable operation of the circuit.In order to achieve a wide range of output voltage,LLC topologies with efficiency advantages need to operate in various working modes such as below resonance fre-quency,above resonance frequency,and phase-shift.Under different working modes,the phase relationship between the voltage and current waveforms on the secondary side rectifier of the transformer and the voltage and current waveforms on the primary side varies,which brings difficulties to the generation of synchronous rectification control signals.This article proposes a synchronous rectification control scheme based on the control signal of the primary power switch and the sam-pling of the resonant current to improve the efficiency of high-power low-voltage LLC power supplies operating in multiple modes.The paper theoretically analyzes the relationship between the signal of the secondary rectifier and the control signal of the primary switch under different modes,and proposes a synchronous rectification control strategy.Based on the con-trol signal of the primary bridge power switch,the control signal of the secondary synchronous rectifier is generated ac-cording to different working modes.In order to avoid the occurrence of false pulses in the platform area time below the resonant frequency mode,which leads to output parallel circulation,the resonant current is detected to eliminate the gen-eration of false pulses.Verified by building an experimental prototype.
LLC resonant converterresonant current detectingsynchronous rectification
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维普
