The LM5021 off-line pulse width modulation (PWM) controller
contains all of the features needed to implement highly
efficient off-line single-ended flyback and forward power converters
using current-mode control. The LM5021 features
include an ultra-low (25 μA) start-up current, which minimizes
power losses in the high voltage start-up network. A
skip cycle mode reduces power consumption with light loads
for energy conserving applications (ENERGY STAR?,
CECP, etc.). Additional features include under-voltage lockout,
cycle-by-cycle current limit, hiccup mode overload protection,
slope compensation, soft-start and oscillator synchronization
capability. This high performance 8-pin IC has
total propagation delays less than 100nS and a 1MHz capable
oscillator that is programmed with a single resistor.