Current Mode PWM ControllerFreq Shuffling with Latch Shutdown
OB2279 is a highly integrated current mode PWM
control IC optimized for high performance, low
standby power and cost effective offline flyback
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.
OB2279 is offered in SOP-8 and DIP-8 packages.
■ 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
■ 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
o VDD Over Voltage Protection(OVP) – Latch
o Over Temperature Protection(OTP) – Auto
recovery or Latch Shutdown
o Over Load Protection. (OLP) – Auto recovery
or Latch Shutdown
o VDD Under Voltage Lockout with Hysteresis
o Gate Output Voltage Clamp (16.5V)
o Built-in OCP Compensation to Achieve
Minimum OPP Variation over Universal AC
Offline AC/DC flyback converter for
■ Notebook Adaptor
■ LCD Monitor/TV/PC/Set-Top Box Power
■ Open-frame SMPS
■ Printer Power