ROHM Semiconductor – Quasi-resonant power controller enables soft switching at high frequency


ROHM Semiconductor’s BD768xFJ is a series of DC-DC controllers which operate in quasi-resonant mode to provide for soft switching and low EMI.

When incorporated into power-converter designs with an external MOSFET power switch and current-sense resistor, a BD768xFJ device offers the user a great deal of flexibility to match the performance of the circuit to the requirements of the application. The BD768xFJ controllers can switch an external MOSFET at frequencies up to 120kHz, and go into burst-mode operation at light loads in order to enhance efficiency and conserve power. In addition, the controller itself draws just 19μA in stand-by mode.

The BD768xFJ series has been specifically designed to drive Silicon Carbide (SiC) MOSFETs, which are becoming an increasingly popular choice for the power- switch function in power converters with a high AC or DC input voltage. The ROHM controller includes a gate-clamp circuit for
optimal driving of SiC MOSFETs, and a valley-detection function to keep switching losses and electro-magnetic emissions to a minimum.

A built-in brown-out function monitors the input voltage level.


  • Under-voltage drop-out protection
  • Over-voltage protection
  • Over-current protection
  • Soft start


  • Industrial equipment
  • AC power adapters
  • Household appliances
Part NumberFeedback Overload Protection MechanismOver-voltage Protection Mechanism