OB2252 is a highly integrated current mode PWM
control IC optimized for high performance, low
standby power and cost effective off-line flyback
converter applications in sub 10W range.
PWM frequency is internal constant and it is 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
OB2252. A large value resistor could thus be used in
the startup circuit to minimize the standby power.
The internal slope compensation improves system
large signal stability and reduces the possible subharmonic
oscillation at higher than 50% PWM duty
cycle output. Leading-edge blanking on current
sense(CS) input removes the signal glitch due to
snubber circuit diode reverse recovery and thus
greatly reduces the external component count and
system cost in the design.
OB2252 offers complete protection coverage with
automatic self-recovery feature including Cycle-by-
Cycle current limiting (OCP), over load protection
(OLP), VDD over voltage clamp and under voltage
lockout (UVLO). Excellent EMI performance is
achieved with On-Bright proprietary frequency
shuffling technique together with soft switching
control at the totem pole Base drive output.
The tone energy at below 20KHZ is minimized in the
design and audio noise is eliminated during operation.