OB2550

GENERAL DESCRIPTION

OB2550 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 as well at large load condition and it operates in PWM with frequency reduction at light/medium load. The chip consumes very low operation current, it can achieve less than 30mW standby power to meet strict standby power standard.

OB2550 offers comprehensive protection coverage with auto-recovery features 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.

OB2550 is offered in SOT23-6 package.

Figure.1. Typical CC/CV Curve

FEATURES

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  Meet 30mW no load standby power standard

n  Good dynamic response

n  Programmable CV and CC Regulation

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  Drive BJT Switch

n  Built-in Leading Edge Blanking (LEB)

n  Ultra Low Start-up Current (Typ. 1uA) and Low Operating Current (Typ. 360uA)

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)

APPLICATIONS

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

 

TYPICAL APPLICATION