OB2278 pdf datasheet

OB2278 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
OB2278. 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 subharmonic
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.
OB2278 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).
OB2278 offers 3 different version with selective
protections set as latch shutdown mode. V version
OB2278 has OVP Latch shutdown only. T version
OB2278 supports both OVP and OTP latch shutdown.
L version OB2278 provides all OVP, OTP and OLP
latch shutdown control.
Excellent EMI performance is achieved with soft
switching control at the totem pole gate drive output.