L6599AFD Resonant Controller STMicroelectronics L6599AFD Resonant Controller is a double-ended controller specific for resonant half bridge topology. It has a high accuracy oscillator which operates with a frequency of up to 500kHz. The output voltage is regulated by modulating the operating frequency. L6599AFD has a two-level overcurrent protection (OCP): frequency-shift and latched shutdown. An interface with the PFC controller enables the pre-regulator to be switched off during fault conditions.