In order to achieve electrical isolation and output control

the traditional half-bridge LLC resonant converter mostly adopts the secondary-side regulation (SSR)control method based on opto-couplers. However

opto-couplers introduce nonlinearity

aging effect

temperature drift and difficulty of integration

which reduces the output accuracy and reliability of the converter. Primary-side regulation (PSR) control method can remove the opto-coupler and simplify the circuit topology

but the nonlinear current of the resonant converter increases the difficulty of output current prediction and circuit complexity. This paper proposed a high precision constant-current output control scheme for PSR half-bridge LLC resonant converter. The magnetization current is restored through the RC branch of the primary-side auxiliary winding circuit

and voltage operation is used to remove the transformer magnetization current and acquire the output diode current wave. With proper selection of the dc bias voltage

adaptive high precision control of the output current can realized. An experimental prototype is built with an input of 380~420 V and an output of 48~78 V/1.30 A. After experiments

the output current accuracy reaches ±2.3%

and the peak efficiency of the system reaches 95.8%

which achieves a good output current accuracy.