Need a Logic Level MOSFET for 80V LED Strip

Thread Starter

BarbarianKing17

Joined Jan 19, 2024
1
I am planning to dim my LED tube lights operated at 80V DC. I am using ESP 8266 MCU for PWM output. I need a Logic Level MOSFET for 3.3V threshold and around 100V output. Please give suggestions.
 

ronsimpson

Joined Oct 7, 2019
3,045
What is the LED current?
I need a Logic Level MOSFET for 3.3V threshold
The threshold voltage is where the part just starts to turn on. You need a part that is full on at 3.3V.
You will need a part that is rated for more than the LED current. Don't use MOSFETs at their max current.
MOSFET, 100-150V, low drive voltage Here is a link to 110 parts in stock at Digikey.com in order of current.
 

Irving

Joined Jan 30, 2016
3,897
Learn to use the parametric search at Mouser or Digikey with
Silicon
through-hole
N-channel
1 Channel
Vds(max) > 100 and
Vgs(th) <=1

will give many suggestions
1705673735291.png

Then pick one whose continuous drain current is at least 2 x I(led) = (your LED power rating)/80 eg if you have 16 x 1/2 metre 5v strips @ 15W/metre your power is 16 * 15 * 0.5 = 120W so I(led) = 120/80 = 1.5A so choose a MOSFET > 3A continuous
 
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Irving

Joined Jan 30, 2016
3,897
You will struggle to find a logic level MOSFET with Vds(max) > 100v that will be fully on at 3.3v, you will need a gate driver, either a DIP package or a simple 2-MOSFET design such as this on the left, switching the high side (preferable to switching the low side IMHO). Or, on the right, slightly simpler with the advantage of isolating the 80v side from the MCU...

1705681310346.png1705684465980.png
 

ronsimpson

Joined Oct 7, 2019
3,045
switching the high side
Circuit 1 from post #4. This circuit is very dependent on the 80V being exactly 80V. If the supply is too high, or rings, you may get too much Gate voltage and kill the MOSFET. If the supply is a little low the MOSFET will not turn on.
Circuit 2 is much more forgiving for changes in the 80V supply.

We need to know what the LED current is and how fast you want to turn it on/off. (10khz, once a day?)

Here is another option. This is a solid-state relay. This one can do AC and some can only do DC. The "LED" needs 1.3V and 2mA with a resistor. Isolation!
1705763987449.png
There are many different options. I really low Gate voltage MOSFET is good.
Finding or making a 5 to 10V supply is good. There are some ICs that are voltage doublers that I have used. Often I find the 3.3V supply comes from a 5V or 9V supply that allows us to build a simple circuit that drives any MOSFET.
 

Irving

Joined Jan 30, 2016
3,897
Circuit 1 from post #4. This circuit is very dependent on the 80V being exactly 80V. If the supply is too high, or rings, you may get too much Gate voltage and kill the MOSFET. If the supply is a little low the MOSFET will not turn on.
Circuit 2 is much more forgiving for changes in the 80V supply.
True... though the IRFP9240 can stand +/-30v on the gate. Here's a version good for at least +/-10v on the supply, but I'd go wth the opto-coupled one.

1705860057387.png
 
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