OB2281 is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications.

PWM switching frequency at normal operation is internally fixed and is trimmed to tight range. At no load or light load condition, the IC operates in extended ‘burst mode’ to minimize switching loss. Lower standby power and higher conversion efficiency is thus achieved.

VCC low startup current and low operating current contribute to a reliable power on startup and low standby design with OB2281.

OB2281 offers comprehensive protection coverage with auto-recovery including Cycle-by-Cycle current limiting (OCP), over load protection (OLP), and VCC under voltage lockout (UVLO). It also provides the protections with latched shut down including over temperature protection (OTP), and over voltage protection (OVP).  Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique.

The tone energy at below 25KHz is minimized in the design and audio noise is eliminated during operation.

OB2281 is offered in SOT23-6 package.



  • Power on soft start reducing MOSFET Vds stress

  • Frequency shuffling for EMI

  • Extended burst mode control for improved efficiency and low standby power design

  • Audio noise free operation

  • Over power operation with increased frequency

  • Comprehensive protection coverage

    • VCC Under Voltage Lockout with hysteresis (UVLO)   

    • VCC Over Voltage Protection (VCC OVP)  

    • Cycle-by-cycle over current threshold setting for constant output power limiting over universal input voltage range

    • Over Load Protection (OLP) with auto-recovery

    • External (if NTC resistor is connected at PRT pin)or internal Over Temperature Protection (OTP) with latched shut down

    • Output Over Voltage Protection(Output OVP) with latched shut down, and  the OVP triggered voltage can be adjusted by the resistor connected between auxiliary winding and PRT pin

    • Output diode short protection with auto-recovery



      Offline AC/DC flyback converter for

  • Printer, Storage power supply

  • Power Adapter