Primary-Side Regulation Dimmable LED Driver Controller with Active-PFC


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The RT7331 is a dimmable constant current LED driver with active power factor correction. It supports high power factor across a wide range of line voltages, and it drives the converter in the Quasi-Resonant (QR) mode to achieve the higher efficiency. By using Primary Side Regulation (PSR), the RT7331 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 RT7331 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 RT7331 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 / over voltage protection, internal Over-Temperature Protection (OTP), and cycle-by-cycle current limitation.


Key Spec.
Status Active
Supply Voltage (min) (V) 11
Supply Voltage (max) (V) 34
Topology Buck-Boost;Flyback
Output C.C.
MOSFET Integrated No
Dimming Control Analog;PWM
Features Cycle-by-Cycle Current Limit;LED Open Protection;LED Short Protection;OCP;OVP;SCP;Thermal Protection;UVP
Package Type SOP-8
  • Tight LED Current Regulation
  • Smart CC/CV Mode Control
  • Wide Dimming Range (1% to 100%)
  • Power Factor Correction
  • THD Optimization (THD < 10%)
  • Quasi-Resonant (QR) Operation
  • Fast Startup
  • Adjustable CV level
  • Soft Drive for the Better EMI Performance (Source 400mA/Sink 500mA)
  • Multiple Protection Features
    ► LED Open-Circuit Protection
    ► LED Short-Circuit Protection
    ► Over Load Protection
    ► Input Under / Over Voltage Protection
    ► Output Diode Short-Circuit Protection
    ► VDD Under Voltage Lockout
    ► VDD Over Voltage Protection
    ► Internal OTP
    ► Cycle-by-Cycle High / Low Line Current Limitation (1V/1.2V typ.)
Technical Documents
TitleLast UpdateShareDownload
Power Solutions for LED Lighting Applications2018/11/22