Flyback Design Guide

The LinkSwitch-LP family is designed to replace inefficient
line frequency linear transformer based power supplies with
output powers < 2.5 W in applications such as cell/cordless
phones, PDAs, digital cameras, and portable audio players.
LinkSwitch-LP may also be used as auxiliary supplies employed
in applications such as white goods.
LinkSwitch-LP combines a high voltage power MOSFET switch
with an ON/OFF controller in one device. It is completely
self-powered from the DRAIN pin, has a jittered switching
frequency for low EMI and is fully fault protected. Auto-restart
limits device and circuit dissipation during overload and output
short circuit conditions while hysteretic over-temperature
protection disables the internal MOSFET during thermal
faults. EcoSmart® technology enables designs to easily attain
< 150 mW no-load consumption, meeting worldwide energy
efficiency requirements.
LinkSwitch-LP is designed to operate without the need for a
primary-side clamp circuit for output powers below 2.5 W and
thus, dramatically reduces component count and total system
cost. Figure 1 shows a LinkSwitch-LP based 2 W power supply
without a primary-side clamp. The LinkSwitch-LP family
has been optimized to give an approximate CV/CC output
characteristic when feedback is provided from an auxillary or
bias winding on the transformer. This is ideal for applications
replacing a line frequency transformer, providing a compatible
output characteristic but with reduced overload, short circuit
current and variation with input line voltage.