OB2279

GENERAL DESCRIPTION

OB2279 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 externally programmable and 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.

VDD low startup current and low operating current contribute to a reliable power on startup design with OB2279. A large value resistor could thus be used in the startup circuit for reduced power loss.

The internal slope compensation improves system large signal stability and reduces the possible sub-harmonic oscillation at high PWM duty cycle output. Leading-edge blanking on current sense input removes the signal glitch due to snubber circuit diode reverse recovery and greatly reduces the external component count and system cost in the design.

OB2279 offers comprehensive protection coverage including Cycle-by-Cycle current limiting(OCP), VDD Under Voltage Lockout(UVLO), VDD Over Voltage Protection(OVP), VDD Clamp, Gate Clamp, Over Load protection(OLP) and Over Temperature protection (OTP), etc.  

Different latch shutdown options are offered on OB2279 in different device version.  V version has OVP Latch shutdown. T version supports both OVP and OTP latch shutdown. L version provides all OVP, OTP and OLP latch shutdown control.

Excellent EMI performance is achieved with On-Bright proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output.

Tone energy at below 20KHZ is minimized in operation. Consequently, audio noise is eliminated during operation.

 

FEATURES

• On-Bright Proprietary Frequency Shuffling Technology for Improved EMI Performance

• Power On Soft Start

• Extended Burst Mode Control For Improved Efficiency and Minimum Standby Power Design

• Audio Noise Free Operation

• External Programmable PWM Switching Frequency

• Internal Synchronized Slope Compensation

• Low VIN/VDD Startup Current(3uA) and Low Operating Current (2.3mA)

• Leading Edge Blanking on Current Sense Input

• Complete Protection Coverage with selective protections for Latch Shutdown

• VDD Over Voltage Protection(OVP) – Latch Shutdown

• Over Temperature Protection(OTP) – Auto recovery or Latch Shutdown

• Over Load Protection. (OLP) – Auto recovery or Latch Shutdown

• VDD Under Voltage Lockout with Hysteresis (UVLO)

• Gate Output Voltage Clamp (16.5V)

• Built-in OCP CompensationcFto Achieve Minimum OPP Variation over Universal AC Input Range.

   

  APPLICATIONS

  Offline AC/DC flyback converter for

• Adaptor

• Monitor/TV/Set-Top Box Power Supplies

• Open-frame SMPS

• Printer Power

   

  TYPICAL APPLICATION