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Capacitor Protection for LED

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hareesh_mohan

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Hi guys ,

in one of the electronic circuits , i found a capacitor parallel to LED. What is the actual function of capacitor across led

-> ESD protection ?
-> To increase the turn off time of LED ?

Help me to understand this ciruit
 

hareesh_mohan said:
Hi guys ,

in one of the electronic circuits , i found a capacitor parallel to LED. What is the actual function of capacitor across led

-> ESD protection ?
-> To increase the turn off time of LED ?

Help me to understand this ciruit
Click to expand...

For the protection of the diode use the series resistor to allow the required current to flow in the LED for the required brightness. The capacitor will allow to help the LED to become OFF slowly depending on the capacitance used when the DC power is suddenly removed.

thanks and regards
 

It depends on how the LED is connected. In some crude power supplies, an LED is used as the voltage reference and the capacitor across it may be to reduce the noise it produces. If the LED is fed from rectified AC, the capacitor may be there to prevent annoying flickering. In one instance here, the LED is on long wires and the capacitor is simply to prevent them acting like antennas which could feed signals back into my circuitry.

Brian.
 

????? Yes, if you have unstabe LEDs I suppose. But in 40+ years of using LEDs I've never come across one. :-?

Brian.
 

If possible post the schematic here...
 

It reduces spikes in supply voltage which cause high current through LED and may cause damage to LED. It filters rectified ac reducing flicker.
 

Capacitor's impedance is inversely proportional to frequency, that means high frequency swings see capacitor as a short circuit , so the high frequency currents follow the path from the capacitor rather than the LED, saving the LED from damaging, and so this is how the capacitor saves the LED from High Frequency currents, basically it bypasses the LED.
 

BhavaniT said:
Capacitor's impedance is inversely proportional to frequency, that means high frequency swings see capacitor as a short circuit , so the high frequency currents follow the path from the capacitor rather than the LED, saving the LED from damaging, and so this is how the capacitor saves the LED from High Frequency currents, basically it bypasses the LED.
Click to expand...

All the answers are based on assumptions of what type of power source is used. So, until we have the exact circuit diagram difficult to say the correct reason.
 

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