Capacitor In Switch Mode Power Supplies
Switch mode power supply contain some large
filter capacitors that can hold dangerous charges even if the unit has not been used for several days. Typical
values of this type of filter capacitor are 220uf 250volt, 150uf 400volt and 330uf 450volt! If you are going to
work on the power supply circuits, it's a good idea to discharge that capacitor first. There are three ways to
discharge the big filter capacitor in a power supply.
with a screw driver (not recommended).
The reason for not using the
screw driver to discharge a capacitor is
-the printed circuit board or circuitry can be damage due to the
discharging the high voltage capacitor.
I once blow the power
section using this method. However, if you know
that the capacitor stored
voltage is not too large, you can easily discharge
it with a small screw
-if the capacitor holds a
heavier charge of electricity. Discharging the
capacitor may melt the tip of the screw driver and
the copper on the
-Sometimes a heavier spark may
cause small disintegrated solder
or copper to fly out from the circuit board and
may injured your eyes.
leads of a socketed 100 watt electric bulb on the leads of
This method had been used by
many technicians around the world for the
light bulb will act as an
indicator to see if the capacitor still holds
charge. If there is a charge the light bulb
will light and after discharged
the light bulb will goes
leads of a high wattage resistor on the leads of the
I use a 2.2k ohm 10 watt
resistor to discharge the high voltage capacitor
a switch mode power supplies. It is simple
to use and very effective.
takes only couple of seconds to fully discharge the capacitor.
Conclusion- I strongly suggest for those who
use screw driver to discharge a capacitor to swift to the second and third method as these
is the safest method to protect the circuit and most
importantly is yourself.
Click here to learn testing electronic components like a Pro!!
Author By : Jestine Yong