GENERAL DESCRIPTION
OB3334A is an offline LED backlight controller with high power factor, low THD and high constant current (CC) precision. It can achieve low system cost for an isolated lighting application by primary side control in a single stage converter. It significantly simplifies the Led backlight system design by eliminating the secondary side feedback components and the opto-coupler.
The proprietary CC control scheme is used and the system can achieve high power factor with constant on-time control scheme. Quasi-resonant (QR) operation and clamping frequency greatly improves the system efficiency. The constant output current is compensated for tolerance of transformer inductance variation. And the line compensation and load compensation are built in OB3334A for high precisely constant output current control.
The OB3334A supports PWM to analog dimming which allows flexible control of the backlight luminance. The LED current is directly modulated by PWM duty cycle on PWM pin.
OB3334A offers comprehensive protection coverage including LED open loop protection, LED short circuit protection, cycle-by-cycle current limiting, built-in leading edge blanking, VDD under voltage lockout (UVLO), etc.
OB3334A is offered in SOP-8 package.
FEATURES
High PF (>0.9)
Low THD (<10%)
High precision constant current regulation at universal AC input
Primary-side sensing and regulation without TL431 and opto-coupler
Low system cost and high efficiency
Quasi-resonant operation
Programmable CC regulation
Built-in primary winding inductance compensation
Built-in line compensation
Built-in load compensation
Programmable OCP compensation
LED short circuit protection
LED open loop protection
Cycle-by-cycle current limiting
Built-in leading edge blanking (LEB)
VDD under voltage lockout with hysteresis
VDD over voltage protection
Over temperature protection (OTP)
APPLICATIONS
LCD Monitor
LCD TV
Flat panel display