ESP8266 dimmable LED lamp

Thread Starter

Gaurav Gupta_1568212829

Joined Sep 11, 2019
12
I have to build a dimmable 9 Watts LED lamp circuit using ESP8266 PWM. I will use 9 no of 1 watt 6 volts led in series. The max voltage will be 54 volts and max current will be 166 mA . Now, which MOSFET should I use to control the voltage? I am trying to find a MOSFET in smaller package like SOT-23 with Vds of atleast 65-70V and drain current of nearly 500 mA so that MOSFET can operate without heating issues.

This is the solution I have decided to use. But I am having hard time to find the MOSFET with above required specification. So, I want to know if this is the right method to dim the lamp or is there any other approach for this.

If this method is right than let me know how should I find a right MOSFET?
 

Thread Starter

Gaurav Gupta_1568212829

Joined Sep 11, 2019
12
Thank you @danadak for giving me your time. I have another query regarding the MOSFETS that is the maximum PWM voltage of ESP8266 will be 3.3V. So which specification of MOSFET should I check to find compatible MOSFET.

Thank you once again.
 

danadak

Joined Mar 10, 2018
3,611
The spec for Rdson will stipulate the Vgs needed. So in this case
you need your switch to operate with low Rdson when Vgs is <=
3.3V.

Regards, Dana.
 

danadak

Joined Mar 10, 2018
3,611
Look at datasheet for part. You will see a curve of Vgs vs Rdson, or at minimum
usually two Vgs and their respective Rdson spec.



Basically yes, you want a low Rdson at Vgs 3.3. If a part was speced at 2.5, to produce
a given Rdson, then if you drive it with 3.3 even lower Rdson will occur.

Your Rdson key component in switch dissipation, and effectiveness as a switch that
drops little or no V across it.

So yes to 3.3V or lower is better in this design.


Regards, Dana.
 
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