Discharge Capacitor In Switch Mode Power Supplies

Switch mode power supply contain some giant filter capacitors that can hold unsafe charges even if the unit has not been used for several days. Typical values of this type of filter capacitor are 220uf 250volt & 330uf 400volt! In case you are going to work on the power supply circuits, it is a pleasant suggestion to discharge that capacitor first.

There is ways to discharge the sizable filter capacitor in a power supply.

)Discharge it with a screw driver (not recommended).

The reason for not using the screw driver to discharge a capacitor is because

-the printed circuit board or circuitry can be destroy due to the spark generated while discharging the high voltage capacitor.
I once blowed the power section using this method. However, in case you know that the capacitor stored voltage is not giant, you can fundamentally discharge it with a small screw driver.

-if the capacitor holds a heavier charge of electricity. Discharging the capacitor may melt the tip of the screw driver & the copper on the printed circuit board.

-Sometimes a heavier spark may cause small disintegrated solder lead or copper to fly out from the circuit board & may injured your eyes.

)Place the leads of a socketed 100 watt electric bulb on the leads of the capacitor.

This method had been used by lots of technicians around the globe for the light bulb will act as an indicator to see if the capacitor still holds the charge. If there is a charge the light bulb will light & after discharged the light bulb will goes off.

)Place the leads of a high wattage resistor on the leads of the capacitor.
I use a.2k ohm0 watt resistor to discharge the high voltage capacitor in a switch mode power supplies. It is simple to make use of & effective .It takes only couple of
seconds to fully discharge the capacitor.

Conclusion

I strongly recommend for those who use screw driver to discharge a capacitor to swift to the second & third method as these is the safest method to protect the circuit & most importantly is yourself.