OB2271Q is a highly integrated current mode PWM control IC optimized for high performance, low standby power and cost effective offline flyback converter applications.

At normal load condition, it operates in QR mode in high line input voltage. To minimize switching loss, the maximum switching frequency in QR mode is internally limited to 120 KHz. When the loading goes low, it operates in PFM mode with valley switching for high power conversion efficiency. When the load is very small, the IC operates in ‘Extended Burst Mode’ to minimize the standby power loss. Additionally, in the low line input voltage, the IC operates in fixed frequency (100KHz) CCM mode at the heavy loading. As a result, high conversion efficiency can be achieved in the whole loading range.

VCC low startup current and low operating current contribute to a reliable power on startup and low standby design with OB2271Q.

OB2271Q offers comprehensive protection coverage with auto-recovery including Cycle-by-Cycle current limiting (OCP), over load protection (OLP), internal over temperature protection (OTP), brownout protection, VCC under voltage lockout (UVLO), and over voltage protection (OVP).  Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique.

The tone energy at below 22KHz is minimized in the design and audio noise is eliminated during operation.

OB2271Q is offered in SOT23-6 package.


   Power on soft start reducing MOSFET Vds stress

   Multi-Mode Operation

      o   120KHz maximum clamping frequency in QR mode @ Full Load in high line voltage

      o   100KHz minimum clamping frequency in CCM mode @ Heavy Load in low line voltage

      o   Valley switching operation @ Green mode

        o    Burst Mode @ Light Load & No Load

   Frequency shuffling for EMI @ all load

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

   Audio noise free operation

   Forced pulse generation

   Comprehensive protection coverage

o    VCC Under Voltage Lockout with hysteresis (UVLO)   

o    VCC Over Voltage Protection (VCC OVP)  

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

o    Internal Over Temperature Protection (OTP) with auto-recovery

o    Over Load Protection (OLP) with auto-recovery

o    Brownout protection with auto-recovery

o    Output diode short protection with auto-recovery

o    Output Over Voltage Protection(Output OVP) with auto-recovery


Offline AC/DC flyback converter for

   General power supply

   Power Adapter