AC Line Powered LED Strings -This shows 4 different ways to string
white LEDs that are powered by a 120vac or 240vac power line. The
circuit was designed by Ken Schultz
COUPLED BI-DIRECTIONAL POWER MOSFET RELAY
The circuit uses an inexpensive C-MOS inverter package and a few small
capacitors to drive two power MOS transistors from a 12v to 15v supply.
Since the coupling capacitor values used to drive the FETs are small,
the leakage current from the power line into the control circuit is a
tiny 4uA. Only about 1.5mA of DC is needed to turn on and off 400 watts
of AC or DC power to a load.
in Electronic Design, Nov. 8, 1990.
SOLID STATE RELAY REQUIRES ONLY 50uA DRIVE CURRENT
Circuit level shifts ac signals: AC signals can emanate from many sources, and
many of these sources are incompatible with the most popular
interface voltages, such as TTL. A temptation always exists to
coactively couple the ac signals because capacitive coupling
strips off the dc level. Capacitive coupling sometimes doesn't
work, because the coupled signal's voltage swings around ground,
so you have to add dc offset to make....
This circuit demands a control current that is 100 times smaller than
that needed by a typical optically isolated solid state relays. It is
ideal for battery-powered systems. Using a combination of a high current
TRIAC and a very sensitive low current SCR, the circuit can control
about 600 watts of power to load while providing full isolation and
Published in Electronic Design, Dec 2, 1996.
Why limit your power supply's input range?: EDN-Design
Ideas / Taking only a cursory look at the input-voltage
ratings of your power-supply IC can limit the usable
input-voltage range. With careful examination of an IC's
operating specifications and circuit topology, you may be able
to work around that input-voltage limitation.