OB2550P is a high performance offline PSR controller for low power AC/DC charger and adapter applications. It operates in primary-side sensing and regulation. Consequently, opto-coupler and TL431 could be eliminated. Proprietary Constant Voltage (CV) and Constant Current (CC) control is integrated as shown in the figure below.

In CC control, the current and output power setting can be adjusted externally by the sense resistor Rs at CS pin. In CV control, multi-mode operations are utilized to achieve high performance and high efficiency. In addition, good load regulation is achieved by the built-in cable drop compensation. Device operates in PFM in CC mode at large load condition and it operates in PWM with frequency reduction at light/medium load. The chip consumes very low operation current. It achieves less than 30mW standby power to meet strict standby power standard.

OB2550P offers comprehensive protection coverage with auto-recovery feature including Cycle-by-Cycle current limiting, VDD over voltage protection, feedback loop open protection, short circuit protection, built-in leading edge blanking, VDD under voltage lockout (UVLO), OTP etc.

OB2550P is offered in SOT23-6 package.

Figure.1. Typical CC/CV Curve


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

n  High precision constant voltage and current regulation at universal AC input

n  Multi-mode PWM/PFM operation for efficiency improving

n  Less than 30mW standby power consumption at 230V with typical application circuit

n  Programmable CV and CC regulation

n  Built-in dynamic signal detection from 2nd-side synchronous rectification

n  Built-in line voltage and primary winding inductance compensation

n  Programmable cable drop compensation

n  No need for control loop compensation

n  Precise internal over temperature protection

n  Audio noise free operation

n  Built-in leading edge blanking (LEB)

n  Ultra low start-up current and low operating current

n  Comprehensive protection coverage with auto-recovery

l  VDD over voltage protection

l  VDD under voltage lockout with hysteresis (UVLO)

l  Cycle-by-cycle current limiting

l  Feedback loop open protection

l  Output short circuit protection

l  Over temperature protection (OTP)


Low Power AC/DC offline SMPS for

n  Cell Phone Charger

n  Digital Cameras Charger

n  Small Power Adapter

n  Auxiliary Power for PC, TV etc.

n  Linear Regulator/RCC Replacement