Electronics > Beginners
How to Build a Temperature Cutoff Circuit for High Power LED
kandrey89:
Hi,
I'm trying to design a temperature cutoff circuit for a high powered LED that will be water cooled, if the user forgot to turn on the water cooling and the board overheats, the temperature sensor on the board will trigger the cutoff circuit to cut power to the LED.
I've briefly looked on digikey for a temperature cutoff IC but couldn't find what I wanted.
Do you know of an IC that does the following:
Senses thermistor? temperature
Uses resistor to setup cutoff temperature
Has a built in gate driver to drive an external power mosfet (that will cutoff the power to an LED)
Maybe has a resistor to setup restart delay before re-engaging the gate drive so the LED doesn't toggle on and off due to temperature hysteresis
SeanB:
How about a thermal switch on the heatsink, 70C will be more than hot enough for the LED. Will open when too hot, so can be used to either diable the driver, or disconnect power.
https://www.digikey.com/product-detail/en/sensata-technologies/1NT01L-7937/1862-1060-ND/8558208
https://www.digikey.com/product-detail/en/cantherm/F20B070051ZA0060/317-1057-ND/306819
https://www.digikey.com/product-detail/en/sensata-airpax/67F070/723-1190-ND/1631957
All 3 at Digikey for US suppliers, so try from there.
kandrey89:
It's a 4 channel LED head, 60W per channel. I need to place thermistors on the MCPCB for reaction time and more precise temperature sensing.
Those thermostats are huge, will not fit on MCPCB nor anywhere on the outside of the LED head, besides the outside of the LED head will be much much cooler than MCPCB near the LEDs because of flowing water. I also need to guard against low flow, which might cool the heatsink a bit but the LEDs would overheat.
Thus why I wrote those requirements, the IC would be in a separate box with mosfets and misc items from the LED head, and the thermistors would be connected by wire.
Zero999:
The LED forward voltage has a negative temperature coefficient, so as long as the current remains the same, a drop in voltage means the temperature is rising. The down side is it varies from device to device, so some calibration will be required, but it has the advantage of being a proxy for the actual junction temperature.
GerryR:
If you are going to design it yourself, why not feed the thermistors into window comparitors. If you are going to put the controls into a separate box, then consider running the thermistor wires to some 1/32 DIN PID temperature controllers, which are fairly inexpensive and programmable. Just a thought.
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