Switching Power Supplies By Darryl Smith, VK2TDS
By Darryl Smith, VK2TDS
These are notes of an impromptu lecture
given to the Fisher?s Ghost Amateur Radio Club on 18 March 1997. They are not
meant to be an introduction into switching power supplies only. One note of
warning. Switching or switch-mode power supplies often operate with high
voltage DC, with large capacitors. These capacitors may take weeks to discharge
if their discharge resistor has blown, and will kill you easily.
Conventional power supplies have the
Switching Power Supplies have some things
backward. They have
The Diode and the capacitor rectify the
incoming mains voltage generating high voltage direct current. This is done
without using a transformer, so a device is added to reduce the turn on current
to the capacitor.
Once DC has been generated the transformer
is powered by rapidly turning on and off the DC supply to the transformer. The
effect of this is to create a very high frequency AC signal from the DC signal
in a similar way to an audio amplifier.