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.
FEATURES
Primary-side Sensing and Regulation Without
TL431 and Opto-coupler
High Precision Constant Voltage and Current
Regulation at Universal AC Input
Multi-mode PWM/PFM operation for efficiency
improving
Meet 30mW no load standby power standard
Good dynamic response
Programmable CV and CC Regulation
Built-in Line Voltage and Primary Winding
Inductance Compensation
Programmable Cable Drop Compensation
No Need For Control Loop Compensation
Precise Internal Over Temperature Protection
Audio Noise Free Operation
Drive BJT Switch
Built-in Leading Edge Blanking (LEB)
Ultra Low Start-up Current (Typ. 1uA) and Low
Operating Current (Typ. 360uA)
Comprehensive Protection Coverage with
auto-recovery
VDD Over Voltage Protection
VDD Under Voltage Lockout with
Hysteresis (UVLO)
Cycle-by-Cycle Current Limiting
Feedback Loop Open Protection
Output Short Circuit Protection
Over Temperature Protection (OTP)
on
TYPICAL APPLICATION
O
n-
©On-Bright Electronics
Br
ig
Figure.1. Typical CC/CV Curve
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APPLICATIONS
Low Power AC/DC offline SMPS for
Cell Phone Charger
Digital Cameras Charger
Small Power Adapter
Auxiliary Power for PC, TV etc.
Linear Regulator/RCC Replacement
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