[SOLVED] LED as resistance in PS filter?

[oneoldude]

Is there anything fundamentally wrong in using an LED as part of the resistance in a low current power supply filter?

Assuming the currents and voltages work out properly, it seems that the LED's resistance can be put to use in improving filtration.

This is what I mean:



Thanks

 

[crutschow]

You need to make sure your load current doesn't exceed the maximum current rating of the LED.

You do realize that the voltage output of your filter varies with the load(?).

 

[oneoldude]

You need to make sure your load current doesn't exceed the maximum current rating of the LED.

Yes. What I have in mind will not draw more than 20 mA.

You do realize that the voltage output of your filter varies with the load(?).

Yes, its unregulated.

Thanks

 

[crutschow]

OK. The incremental (AC) ON resistance of an LED is fairly low so it won't contribute much to your filter rolloff. The main advantage of your circuit is that the LED current is supplied by the load so doesn't draw any additional current from the power source.

 

[oneoldude]

Good point. I figured the LED may as well do some work other than consuming energy all by itself.

The main reason I considered this is that when the load is plugged into the PS it turns on the LED showing that the load is powered and all is nominally fine. It also saves a switch.

Thanks