Second-Stage Primary-Side Regulation Dimmable LED Driver Controller

The RT7331S is a second-stage dimmable constant current LED driver. It drives the converter in the Quasi-Resonant (QR) mode to achieve the higher efficiency. By using Primary Side Regulation (PSR), the RT7331S controls the output current accurately without a shunt regulator and an opto-coupler at the secondary side, reducing the external component count, the cost, and the volume of the driver board.

The RT7331S is compatible with the analog dimming. The output current can be modulated by the PWM duty ratio or the average level of DIM pin.

The RT7331S embeds comprehensive protection functions for robust designs, including LED open-circuit protection, LED short-circuit protection, output diode short-circuit protection, VDD Under-Voltage Lockout (UVLO), VDD Over-Voltage Protection (VDD OVP), over load protection, input Under-Voltage protection, internal Over-Temperature Protection (OTP), and cycle-by-cycle current limitation.