Current Mode PWM ControllerFreq Shuffling with Latch Shutdown
OB2279 is a highl y integ rated current mode PWM
control IC optimized fo r high performance, low
standby pow er and cost effe ctive offline fly back
PWM switching frequenc y at norm al operation is
externally programmable and trimmed to tigh t range.
At no load or light load condition, t he IC operates in
extended ‘bu rst mode’ to minimize switching loss.
Lower stan dby p ower and high er conversion
efficiency is thus achieved.
VDD low startup current and low operating curre nt
contribute to a reliable po wer on startu p design with
OB2279. A large value resistor could t hus be used i n
the startup circuit for reduced power loss.
The internal slope com pensation im proves sy stem
large signal stability and reduces the possible sub-
harmonic oscillation at high PWM dut y cycle output.
Leading-edge blankin g on current sense input
removes the signal glitch du e to snubber circuit diode
reverse r ecovery and greatly reduces the external
component count and system cost in the design.
OB2279 offers co mprehensive protection coverage
including Cy cle-by-Cycle current li miting(OCP),
VDD Under Voltage Lockout(UVLO), VDD Over
Voltage Protection(OVP), VDD Cl amp, Gate Cla mp,
Over Load protection(OLP) and Over Tem perature
protection (OTP), etc.
Different latch shutdown optio ns are offered on
OB2279 in d ifferent device version. V version has
OVP Latch shutdown . T v ersion supp orts both OVP
and OTP latch shutdown. L version provides all OVP,
OTP and OLP latch shutdown control.
Excellent EMI perform ance is achieved with On-
Bright pr oprietary freq uency shuffli ng techni que
together with soft switching control at the totem pole
gate drive output.
Tone energ y at below 20KHZ is minim ized in
operation. C onsequently, audio no ise is elim inated
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 Im proved
Efficiency and Minimum Standby Power Design
■ Audio Noise Free Operation
■ External P rogrammable PWM
■ Internal Synchronized Slope Compensation
■ Low VIN/V DD Startup Current(3uA) and Low
Operating Current (2.3mA)
■ Leading Edge Blanking on Current Sense Input
■ Complete Protection Coverage with selectiv e
protections for Latch Shutdown
o VDD Ov er Voltage Protection(OVP) – Latch
o Over Tem perature Protection(OTP) – Auto
recovery or Latch Shutdown
o Over Load P rotection. (O LP) – Aut o r ecovery
or Latch Shutdown
o VDD Under Voltage Lockout with Hysteresis
o Gate Output Voltage Clamp (16.5V)
o Built-in OCP Com pensation 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