PWM from pic to analog voltage - Electronic Circuits Projects Diagrams Free

carmusic · 22nd May 2009, 09:23 PM

Hi i need to design a variable output voltage with high efficiency. i need maximum 100ma at 12V. I was planning to use the pwm signal from A pic to control the voltage, can i do that with just a mosfet, inductor and capacitor? and maybe a flybak diode?

blueroomelectronics · 22nd May 2009, 09:28 PM

Yes, it's how the Junebug kit I sell generates VPP

http://en.wikipedia.org/wiki/Boost_converter

carmusic · 22nd May 2009, 09:44 PM

Thanx i will probably use buck topology,

blueroomelectronics · 22nd May 2009, 09:59 PM

What's your source voltage?

carmusic · 22nd May 2009, 10:00 PM

about 12V, my pwm signal is 5 V, i must be able to vary from about 3 to 12volt output at 100ma max

Hero999 · 22nd May 2009, 10:03 PM

Does it matter if the polarity is inverted?

carmusic · 25th May 2009, 04:35 PM

yes i cannot invert polarity since i use a common ground for other measurement. I will use a P channel mosfet switch, can you help me choosing right inductor and capacitor?. I was thinking using about 10uH and 0.47uf. i dont care if there is 500mv ripple. with higher caps, i have trouble getting low voltage output with low charge (my pwm cannnot go under 1% duty).

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22nd May 2009, 09:23 PM	#1
carmusic	PWM from pic to analog voltage Hi i need to design a variable output voltage with high efficiency. i need maximum 100ma at 12V. I was planning to use the pwm signal from A pic to control the voltage, can i do that with just a mosfet, inductor and capacitor? and maybe a flybak diode?

22nd May 2009, 09:28 PM	#2
blueroomelectronics	Yes, it's how the Junebug kit I sell generates VPP http://en.wikipedia.org/wiki/Boost_converter __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/ Last edited by blueroomelectronics; 22nd May 2009 at 09:29 PM.

22nd May 2009, 09:44 PM	#3
carmusic	Thanx i will probably use buck topology,

22nd May 2009, 09:59 PM	#4
blueroomelectronics	What's your source voltage? __________________ Bill Smart Kits build Smart People http://www.blueroomelectronics.com/

22nd May 2009, 10:00 PM	#5
carmusic	about 12V, my pwm signal is 5 V, i must be able to vary from about 3 to 12volt output at 100ma max

22nd May 2009, 10:03 PM	#6
Hero999	Does it matter if the polarity is inverted? __________________ I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong. Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

25th May 2009, 04:35 PM	#7
carmusic	yes i cannot invert polarity since i use a common ground for other measurement. I will use a P channel mosfet switch, can you help me choosing right inductor and capacitor?. I was thinking using about 10uH and 0.47uf. i dont care if there is 500mv ripple. with higher caps, i have trouble getting low voltage output with low charge (my pwm cannnot go under 1% duty).