A portable electronic device with an IrDA transmitter LED is used to
transmit both IrDA signals and remote control infrared signals. The
device transmits remote control infrared signals with reduced power
consumption. During a relatively longer remote control signal pulse, an
inductor saturates and stores energy when a drive current flows from a
power supply, through the inductor and then through the LED. An
energy-transferring circuit transfers a portion of the energy stored in
the inductor to the power supply. Energy is transferred when the drive
current is cut and the voltage across the inductor surges, which causes
an overflow current to flow through a diode in the energy-transferring
circuit and to the power supply. The inductor is a planar coil of traces
on a printed circuit board and therefore costs less to manufacture than
does a toroidal coil of wires.