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Q&A LED driver with feedback through light. Which feedback topology is better?

I’d like to create a stable IR LED light source. I’ve read that LED efficiency changes with temperature. I’ve seen two designs which used feedback through light to correct the LED temperature dri...

1 answer · posted 9mo ago by misk94555‭ · edited 9mo ago by misk94555‭

Question feedback LED-driver

#2: Post edited by

misk94555‭ · 2024-04-02T03:53:12Z (9 months ago)

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I’d like to create a stable IR LED light source. I’ve read that LED efficiency changes with temperature. I’ve seen two designs which used feedback through light to correct the LED temperature drift and aging. They used slightly different topologies.
The first topology has one feedback loop (through light).
~~![LED driver schematic](https://electrical.codidact.com/uploads/kll19wle118cnrcvdq9nc2695v72)~~
The second topology has two nested feedback loops. The inner look controls constant current through the LED. The outer loop brings in the feedback through light.
~~![LED driver schematic](https://electrical.codidact.com/uploads/ocp1kyw2epclr8gst04rom2htsak)~~
Which topology is preferable?
I need to flash the LED with 100us pulses. The present choice of LED is [Vishay TSHG6410](https://www.vishay.com/docs/81870/tshg6410.pdf).
(By the way, I'm interested in other ways of compensating an LED for temperature too.)

I’d like to create a stable IR LED light source. I’ve read that LED efficiency changes with temperature. I’ve seen two designs which used feedback through light to correct the LED temperature drift and aging. They used slightly different topologies.
The first topology has one feedback loop (through light).
![LED driver schematic](https://electrical.codidact.com/uploads/s091wdnzaht5wvnffhh9yr1prq2f)
The second topology has two nested feedback loops. The inner look controls constant current through the LED. The outer loop brings in the feedback through light.
![LED driver schematic](https://electrical.codidact.com/uploads/oisd5t0lnljj2pzi72m5ge9g5f7c)
Which topology is preferable?
I need to flash the LED with 100us pulses. The present choice of LED is [Vishay TSHG6410](https://www.vishay.com/docs/81870/tshg6410.pdf).
(By the way, I'm interested in other ways of compensating an LED for temperature too.)

#1: Initial revision by

misk94555‭ · 2024-03-16T01:35:36Z (9 months ago)

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LED driver with feedback through light.  Which feedback topology is better?

I’d like to create a stable IR LED light source.  I’ve read that LED efficiency changes with temperature.  I’ve seen two designs which used feedback through light to correct the LED temperature drift and aging.  They used slightly different topologies.

The first topology has one feedback loop (through light).

![LED driver schematic](https://electrical.codidact.com/uploads/kll19wle118cnrcvdq9nc2695v72)

The second topology has two nested feedback loops.  The inner look controls constant current through the LED.  The outer loop brings in the feedback through light.

![LED driver schematic](https://electrical.codidact.com/uploads/ocp1kyw2epclr8gst04rom2htsak)

Which topology is preferable?  
I need to flash the LED with 100us pulses.  The present choice of LED is [Vishay TSHG6410](https://www.vishay.com/docs/81870/tshg6410.pdf).

(By the way, I'm interested in other ways of compensating an LED for temperature too.)

feedback LED-driver

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