How to boost a PWM signal from 0 - 3.3 V to 4.5 - 12 V?

[aallan]

Hi,

I have a PWM signal (zero to 3.3 volts) generated from a microcontroller. I want to use this to drive 10 high-power LEDs. Depending on the LEDs, their supply voltage could be 4.5V to 12V, and they could draw up to 1A each.

Does anyone have any thoughts on how to boost the signal? I have looked at transistors and MOSFETs and op-amps, but I am struggling to find a good solution.

Any advice?

Thanks

 

[samnang39]

Re: PWM Booster

Dear friend

you can use Trasister Mosfet ...... it is the easyest thing this the good solution

 

[aallan]

Re: PWM Booster

Hi, thanks for yout reply.

Would something like this be sufficient?

https://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=6886958

Would I require any additional circuitry such as diodes or resistors to protect the MOSFET?

Thanks.

 

[aallan]

Re: PWM Booster

Hi,

Ok, so a mosfet seems like the best solution.

The attached pictures show two options for connecting. Is there an advantage of one over the other? The picture with the LED at the top seems the most common, but would the lower LED layout also work?

Also, in both cases, what is the function of R1, the 1MΩ resistor? Is this required?

Thanks

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[tyassin]

Re: PWM Booster

Hi

Depending on the FET, you have to consider the Vgs(on). In the top picture you have the full PWM voltage(3.3V) as Vgs.

In the bottom picture you have the 3.3V-V_led-V_R. Voltage over LED and resistor.

Typical LEDs require around 2V so this means that you only have around Vgs=1V.

So go for the top configuration.

Regards

 

[aallan]

Re: PWM Booster

Thanks!

Yes, the LEDs are high-power LEDs and take quite a few volts, so the top configuration seems like the way to go!

Any thoughts on the 1 MΩ resistor? Is this really required?

Andrew

 

[keith1200rs]

Re: PWM Booster

Any thoughts on the 1 MΩ resistor? Is this really required?

Andrew

No. The micro will pull the gate to 0V anyway.

Keith