Build a UPS for USB devices: 04/11/2002 EDN -
Design Ideas / Portable systems often include
circuitry that derives power from an external
source, such as USB. When the system disconnects
from the USB supply, a battery takes over and
supplies current via a dc/dc converter. A diode-OR
connection (Figure 1.
Isolated Driver Forms Solid State Circuit Breaker:
03/03/98 EDN-Design Ideas / This circuit allows
standard TTL logic levels to safely drive a
high-power dc load, circuit provides also
overcurrent circuit breaker functionality
Microcontroller Watches, Controls AC Power:
06/22/95 EDN-Design Ideas / circuit allows an
isolated microcontroller to both sense and control
ac power to an externally plugged-in device
Power source is insensitive to load changes:
04/04/2002 EDN - Design Ideas / For the heating and
cooling elements common in industrial systems,
resistance is not a fixed quantity. These elements
include such devices as
positive-temperature-coefficient heaters and
thermoelectric coolers. Their resistance can change
more than 100% during operation, and the result is a
change in power dissipation for elements receiving
drive from a fixed voltage or current source. .
Short dc power line pulses afford remote control:
10/25/2001 EDN - Design Ideas / If you face
the challenge of adding a second, independently
controlled light source to an existing ceiling lamp
controlled by a wall switch, you may find that
stringing a second power line is impossible. First,
you can replace the wall switch by the circuit in
Figure 1. Pushing the on switch S1 or S2 for
approximately 1 sec inserts the 12V zener diodes D1
or D2 in series with the ... .
Soft start controller is gentle on loads:
11/22/2001 EDN - Design Ideas / The control circuit
in Figure 1 senses a given load and automatically
soft-starts the load by synchronously adjusting the
power to that load. You can also manually adjust the
power delivered to the load by controlling the phase
angle of the line voltage across the load. The
phase-angle adjustment for every ac half cycle
covers 0 to 180 . .