+V <------* *-----*-----@@@@@-----
SW | L |
| | |
Power --- Shottkey \|/ IR
supply /|\ diode --- emitting
| | | diode
SW is actually a transistor which switches on and off
at a fixed frequency with 25% time on, 75% time off.
During the 25% on-time of each cycle, the Shottkey
diode is off, the IR emitting diode is on. Current is
drawn from the power supply. Due to the L in series,
current builds up slowly and a magnetic field is also
building up inside L.
When SW turns off, the current from the power supply
is cut off. The magnetic field inside L will generate
an electrical potential to keep the current flowing.
Thus the Shottkey diode will turn on and the IR
emitting diode will still stay on. This will last about
another 25% of a cycle.
Thus the IR generated will still have about 50% duty