Variable voltage source from 0 to 10v and 2A using microcontroller pwm (0 to 5 v)

[palakpatel6188]

Hello
I am generating 0 to 5 v using microcontroller pwm and I got it .and this pwm output i am giving it to the mosfet gate. here i want to generate 0 to 10 v variable voltage with 2a source.
pwm frequenct is 20Khz.
pwm duty cycle changing from 0 to 100 %.



and i am getting variable voltage from 0 to 10 v and 2A source by using this circuit at output terminal.


what should be the value of R1,R2,C1,C2.
here i am using r1 and c1 to make pulsating dc to pure dc of the pwm of microcontroller.
here i am using r2 and c2 to make pure dc output from 0 to 20v 2a source.
but question is that if i will rc circuit.will it affect the voltage?
what should be the equation of the rc filter?
will it affect the current?
is the curcuit right for 0to 20v generation 2a source.
please suggest me..
thanks.

 

[barry]

I'm afraid you've got a problem there. As the load varies, R2 is going to drop more or less voltage, so you have no regulation. If you've got DC at the gate of the mosfet, then why do you need an RC on the MOSFET output?

BTW, your scope picture is very pretty, but doesn't have any information!

 

[Venkadesh_M]

you are not going to benefit by doing pwm, bcs you are dropping lot of power in resistor. The Mosfet shd be top side or the load in the top side not the resistor. you can do this with some top side mos driver ICs or with a transistor resistor pair.

 

[palakpatel6188]

i just have current of 2A source it does not matter that how much load want.i just want that voltage goes from 0 to 20 v as my pwm duty cycle varies.now what should be the value of r2 and c2?
i am connecting load at output.

 

[Venkadesh_M]

no need for R1, C1 that will increase power loss. you can replace R2 by diode. C2 is according to load and pwm frequency.

your MOSFET shd be at least 4A. i don think its good circuit, you cant even touch the components. the 80 w 5 ohm resistor will burn like a fire...

 

[barry]

I think you need to read up on PWM. There is no need for any of those resistors in the output; just put your load between the power and the drain, or,suggested, use a high-side drive if you've got a ground-referenced load.

Venkadesh, there's very little power loss in R1-it's just functioning as a low-pass filter. And, depending on what your load is, you can even eliminate R1/C1.

 

[Venkadesh_M]

Hi barry,

I mean that R1 C1 will cause distort square wave and will drift the MOSFET from switching to linear mode. that will even worse the case.

for a good pwm circuit the switching should be idle.

A diode in place of R2 will avoid the stored energy from C2 waste through MOSFET.

Actually this is a booster chopper it should have a inductor inplace of 5 ohm. the L will have the rise time and will avoid this all problems.

 

[barry]

Hi barry,

I mean that R1 C1 will cause distort square wave and will drift the MOSFET from switching to linear mode. that will even worse the case.

for a good pwm circuit the switching should be idle.

A diode in place of R2 will avoid the stored energy from C2 waste through MOSFET.

Actually this is a booster chopper it should have a inductor inplace of 5 ohm. the L will have the rise time and will avoid this all problems.

Right. I was just thinking OP wanted to use PWM and filter as a cheap A/D converter. But to really utilize the efficiency of PWM OP needs to, well, understand PWM better.