OB3334A

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

n High PF (>0.9)

n Low THD (<10%)

n High precision constant current regulation at universal AC input

n Primary-side sensing and regulation without TL431 and opto-coupler

n Low system cost and high efficiency

n Quasi-resonant operation

n Programmable CC regulation

n Built-in primary winding inductance compensation

n Built-in line compensation

n Built-in load compensation

n Programmable OCP compensation

n LED short circuit protection

n LED open loop protection

n Cycle-by-cycle current limiting

n Built-in leading edge blanking (LEB)

n VDD under voltage lockout with hysteresis

n VDD over voltage protection

n Over temperature protection (OTP)

APPLICATIONS

n LCD Monitor

n LCD TV

n Flat panel display

 

TYPICAL APPLICATION