the present invention discloses a half - bridge llc resonant converter with self - driven synchronous rectifiers , which utilizes a primary ic controller and a gate driver to drive the secondary synchronous rectifiers . in correspondence with the gate drive output voltages of the primary ic controller to the primary switch transistors , the gate driver for the secondary synchronous rectifiers comprises a differential transformer if the primary ic controller outputs two ground - referenced gate drive voltages , which cannot directly drive the primary switch transistors but can be imposed on the differential transformer ; or comprises a dc shifter , a dc restorer and a differential transformer if the primary ic controller outputs two gate - source voltages , which can directly drive the primary switch transistors but cannot be imposed on the differential transformer . the drive voltages of the primary switch transistors are unipolar ; however the drive voltage of the secondary synchronous rectifiers can be bipolar or unipolar . under the valid operation mode , this converter can decrease the rectifier conduction losses to increase the power converter efficiency .