Dear Jim, Thank You for the insights. Next I will experiment/play with buck, etc.. I prefer the PIC as I can vary the algorithm and understand experimentally things that would be otherwise less straightforward and funny to learn. Cheers, Mario At 16.59 2014.01.06, jim@jpes.com wrote: > > Some general guidance comments... > > The slower the clock, the higher the indutance needed to get to where >you want to get,=20 > as you have already observed. However, if you increase the operating >frequency, you can=20 > use lower inductances to get the output you want because you are >switching on and off more > often. >=20 > Higher operating frequency has another benefit in that you can use >smaller capacitors for=20 > filtering. For learning about SMPS's, this probably isn't an issue.=20 >But for real world=20 > stuff, it is definitely something to consider. > > Another specification to look at regarding inductors is the "Series >Resistance". If this=20 > value gets too high, you'll incur I2R losses in the coil, which will >lead to heating. > While on the subject of series resistance, make sure the capacitors you >use has a relatively=20 > low "ESR" (Equivalent Series Resistance). This is mostly for >efficiency benefit. > > There are many many apnotes and tutorials regarding SMPS's online.=20 >Including some from Microchip. > Seek these out and look them over. There is much to learn, and these >resources will definitelty help. > There are complete college courses on SMPS's. Many of them online too. > (Check MIT Opencourseware). > > I have some experience with SMPS's, so if you have sepcific questions, >I can try to answer them. > However, note that my experience involves switching controllers from >various mfg's, and not PIC's=20 > specifically. But the principles are the same. > > Regards, > > Jim > >=20 >=20 > >=20 > > > > > > > > > > >Regards, > >Jim > >> -------- Original Message -------- >> Subject: [EE] Boost SMPS turn-OFF best current value >> From: Electron >> Date: Mon, January 06, 2014 9:04 am >> To: "Microcontroller discussion list - Public." >>=20 >>=20 >> Hello, >> I'm playing with a self-made boost converter, all the logic >> is made via a PIC and its ADC's. >>=20 >> I'd like to ask some general questions: >>=20 >> in my first experiments, I was turning ON the transistor switch, >> then monitoring the current in the inductor, then turn OFF the >> transistor till the current reached 0, and again in a loop. >>=20 >> My aim is to get the most possible power out of the power supply. >>=20 >> Now I think that if I turn OFF the transistor earlier, say 100mA >> below the "OFF" threshold (maximum current), instead of reaching >> 0, then the average current will be higher, and I will get more >> power from the circuit. >>=20 >> Is my reasoning correct? >>=20 >> What is the criteria to choose the inductor? As my PIC-based >> circuit is relatively slow, I noticed that only inductors around >> 10mH work, whatever has a smaller inductance probably charges >> and discharges too quickly to work. >>=20 >> So the best inductor I should choose is the one that has (of >> course) the least possible resistance, but an high enough >> inductance to let my slow PIC work correctly? >>=20 >> No other recommendations? >>=20 >> For example, don't inductors have a maximum voltage rating? >>=20 >> Thanks. >>=20 >> PS: it's really funny to play with SMPS via PIC software!! >>=20 >> Cheers, >> Mario >>=20 >> --=20 >> http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist > >--=20 >http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive >View/change your membership options at >http://mailman.mit.edu/mailman/listinfo/piclist --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .