eem2am
Banned
current limiter circuit
Hello
I am doing a LED lamp powered by SEPIC SMPS.
It is 10W and the LEDs will be end up being switched in one by one by FETs, so that the lamp comes on “chaser” style.
Here is the schematic
https://i25.tinypic.com/qoziat.jpg
Anyway, since any hold-up on the output caps may cause a LED overcurrent after switch-on, we have a hi-side PNP current limiter in the circuit.
Hi side PNP current limiter close up
https://i31.tinypic.com/2jd25uw.jpg
Anyway, am I right in saying that this PNP current limiter would not be able to allow us to set an accurate current limit, and that the particular current limit would depend on the particular characteristics of the particular diodes and transistor that are used in it ?
So we would not be able to guarantee say a 330mA current limit since the diode Vf’s and the PNP transfer characteristics would vary from part to part.
Can you say whether or not the above shown current limiter would allow us to accurately set the current limit?
Hello
I am doing a LED lamp powered by SEPIC SMPS.
It is 10W and the LEDs will be end up being switched in one by one by FETs, so that the lamp comes on “chaser” style.
Here is the schematic
https://i25.tinypic.com/qoziat.jpg
Anyway, since any hold-up on the output caps may cause a LED overcurrent after switch-on, we have a hi-side PNP current limiter in the circuit.
Hi side PNP current limiter close up
https://i31.tinypic.com/2jd25uw.jpg
Anyway, am I right in saying that this PNP current limiter would not be able to allow us to set an accurate current limit, and that the particular current limit would depend on the particular characteristics of the particular diodes and transistor that are used in it ?
So we would not be able to guarantee say a 330mA current limit since the diode Vf’s and the PNP transfer characteristics would vary from part to part.
Can you say whether or not the above shown current limiter would allow us to accurately set the current limit?