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

nPrimary-side Sensing and Regulation Without TL431 and Opto-coupler

nHigh Precision Constant Voltage and Current Regulation at Universal AC Input

nMulti-mode PWM/PFM operation for efficiency improving

nMeet 30mW no load standby power standard

nGood dynamic response

nProgrammable CV and CC Regulation

nBuilt-in Line Voltage and Primary Winding Inductance Compensation

nProgrammable Cable Drop Compensation

nNo Need For Control LoopCompensation

nPrecise Internal Over Temperature Protection

nAudio Noise Free Operation

nDrive BJT Switch

nBuilt-in Leading Edge Blanking (LEB)

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

nComprehensive Protection Coverage with auto-recovery

lVDD Over Voltage Protection

lVDD Under Voltage Lockout with Hysteresis (UVLO)

lCycle-by-Cycle Current Limiting

lFeedback LoopOpen Protection

lOutput Short Circuit Protection

lOver Temperature Protection (OTP)

APPLICATIONS

Low Power AC/DC offline SMPS for

nCell Phone Charger

nDigital Cameras Charger

nSmall Power Adapter

nAuxiliary Power for PC, TV etc.

nLinear Regulator/RCC Replacement

TYPICAL APPLICATION

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