Variable voltage with high power, from a µC

[PinheadBE]

Hi,

I'm in the need of being able to generate a variable voltage between 3.0 V and 5.0 V, with an output current that can go up to 6 A.
This will be commanded by a micro-controller.

What I already have thought of:
- Using PWM, commanding a MOSFET.   But I have to place a cap somewhere (a low-pass filter).  Since the current is not stable and can vary largely up to 6 A, where do I have to place it, and what value to use ?
- Using DAC.   After that, I have to amplify the current.   A BJT transistor mounted in an emitter-following configuration seems adequate.   But can I do that with a MOSFET ?

Any help welcome

Thanks

[DavidAlfa]

TPS55289 ? Has i2c control with 10mv steps.

You can use the DAC, but feed it to an op-amp and let it control a BJT.
Mosfets are harder to control, better use a BJT for this.

[PinheadBE]

VQFN.....  Not a chance I'm able to solder this 

In fact, the micro-controller already exists and generates 6 PWM signals driving each a mosfet for a part of the circuit (a lot of LED's) that can work with that.

In another part of the circuit, I have to be able to slightly dim special LED's (like blinking ones, flame effects,....) .   Those LED's do integrate an IC, and I suspect it will not be happy with PWM....

I made some tests, and to dim them, I can make the voltage vary between 3 V and 5 V.

So, my preference would go to a simple circuit able to convert the existing PWM signal in a voltage.   That way, I will be able to use the same control board as for the simple LED's, with a simple add-on.   This circuit having to be repeated more than 20 times, it should be very basic (I cannot afford a buck/boost converter for each channel    )

[DavidAlfa]

Do you really need 6amps for each channel?
A linear regulator will cause a ton of heat.
There're very inexpensive buck converters for 2-3A, if you could use one for each channel then you could control then by filtering the PWM to control the feedback signal.

Googling "dac controlled buck converter" shows plenty of topics.