triple switcher
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From: Jan Panteltje on 16 Nov 2009 06:15 On a sunny day (Sun, 15 Nov 2009 18:43:06 -0800 (PST)) it happened MooseFET <kensmith(a)rahul.net> wrote in <cb721d88-65d3-4d08-95a2-3e96c826ce56(a)m7g2000prd.googlegroups.com>: >The ADC on the PIC isn't fast enough to do cycle by cycle voltage >checking so you would have to close the servo loop at way less than >Nyquist. Unfortunately this would also make the filter capacitors >big. You can use the PIC comparator and hysteretic control. You can also use cycle by cycle current mode, and by adding 1 or 2 extra transistors control the current, so make a true current mode switcher. http://panteltje.com/panteltje/pic/pwr_pic/index.html Have not tried the 2 transistor thingy yet, but published a circuit for it here a while back.
From: MooseFET on 16 Nov 2009 09:43 On Nov 15, 1:01 pm, dagmargoodb...(a)yahoo.com wrote: > On Nov 15, 12:20 pm, MooseFET <kensm...(a)rahul.net> wrote: [....] > > I have made a booster regulator with the LM555 that worked just fine. > > I have figured out the design for a bucker that looks like it would > > work but so far without adding a lot of external parts I haven't come > > up with a way to regulate more than one voltage. > > The classic way is a flyback with multiple secondaries, close the loop > on the main voltage, LDOs on the others. > > But of course we all knew that. How about: D1 -------!<------------- ! ! SW3 -+--/o----+------)))))--+-----+---/o------- To C1 SW1 ! L1 ! SW4 \ +---/o------- To C2 SW2 o ! SW5 ! ---/o------- To C3 GND SW1 and SW2 work to maintain the average current in L1 equal to the sum of the load currents. C1 .. C3 share the current among the load sections. It doesn't reduce the number of switching elements but putting the inductors together could save PCB area.
From: MooseFET on 16 Nov 2009 09:45 On Nov 16, 3:15 am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote: > On a sunny day (Sun, 15 Nov 2009 18:43:06 -0800 (PST)) it happened MooseFET > <kensm...(a)rahul.net> wrote in > <cb721d88-65d3-4d08-95a2-3e96c826c...(a)m7g2000prd.googlegroups.com>: > > >The ADC on the PIC isn't fast enough to do cycle by cycle voltage > >checking so you would have to close the servo loop at way less than > >Nyquist. Unfortunately this would also make the filter capacitors > >big. > > You can use the PIC comparator and hysteretic control. > You can also use cycle by cycle current mode, and by > adding 1 or 2 extra transistors control the current, so > make a true current mode switcher. > http://panteltje.com/panteltje/pic/pwr_pic/index.html > Have not tried the 2 transistor thingy yet, but published > a circuit for it here a while back. The added stuff to make it work is as big as just making the whole switcher. The PIC can't directly drive the pass elements.
From: Jan Panteltje on 16 Nov 2009 09:55 On a sunny day (Mon, 16 Nov 2009 06:45:06 -0800 (PST)) it happened MooseFET <kensmith(a)rahul.net> wrote in <828b5506-8b03-490c-a0ab-291210be87eb(a)b25g2000prb.googlegroups.com>: >On Nov 16, 3:15�am, Jan Panteltje <pNaonStpealm...(a)yahoo.com> wrote: >> On a sunny day (Sun, 15 Nov 2009 18:43:06 -0800 (PST)) it happened MooseF= >ET >> <kensm...(a)rahul.net> wrote in >> <cb721d88-65d3-4d08-95a2-3e96c826c...(a)m7g2000prd.googlegroups.com>: >> >> >The ADC on the PIC isn't fast enough to do cycle by cycle voltage >> >checking so you would have to close the servo loop at way less than >> >Nyquist. �Unfortunately this would also make the filter capacitors >> >big. >> >> You can use the PIC comparator and hysteretic control. >> You can also use cycle by cycle current mode, and by >> adding 1 or 2 extra transistors control the current, so >> make a true current mode switcher. >> �http://panteltje.com/panteltje/pic/pwr_pic/index.html >> Have not tried the 2 transistor thingy yet, but published >> a circuit for it here a while back. > >The added stuff to make it work is as big as just making the whole >switcher. The PIC can't directly drive the pass elements. If you mean power MOSFET by pass-elements, then yes it can, as the above links shows. You are a bit limited in frequency then of course, say 76 kHz.
From: dagmargoodboat on 16 Nov 2009 11:46
On Nov 15, 4:09 pm, John Larkin <jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > On Sun, 15 Nov 2009 12:37:31 -0800 (PST), "langw...(a)fonz.dk" > > > > <langw...(a)fonz.dk> wrote: > >On 15 Nov., 19:41, John Larkin > ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> On Sat, 14 Nov 2009 13:40:27 -0800 (PST), MooseFET > > >> <kensm...(a)rahul.net> wrote: > >> >On Nov 14, 10:40 am, John Larkin > >> ><jjlar...(a)highNOTlandTHIStechnologyPART.com> wrote: > >> >> We keep running into the requirement to turn +12 or +5 volts into 3..3, > >> >> 1.2 (fpga core), and usually a third voltage, 1.8 (for drams) or 2.5 > >> >> (fpga Vccint). We'd like to consolidate this to save board area and > >> >> general complexity. Any suggestions? > > >> >> LTM4615 looks interesting, a bit expensive but very small. > > >> >>http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1424,P8... > > >> >> And other ideas? > > >> >> John > > >> >How about LT3507? > > >> Lots of external parts, schottkies and inductors. > > >> >LT3564 seems to get a lot of switcher into a small package. > > >> We already stock the LTC3407, 3411, and 3412, all similar. But it > >> would be great if somebody did a minimal-parts, minimal-size triple > >> synchronous switcher, ideally with internal inductors. I *told* LTC to > >> do this, and, incredibly, they haven't got around to it. It's not as > >> if FPGAs are losing popularity. > > >> The Spartan 6 parts will run from two supplies (Vccint can run from > >> 3.3) but we want to use a DDR dram, at 1.8 volts, so we're back up to > >> three. > > >something like a ISL65426 and an ldo? > > >-Lasse > > The LTM4615 has all that inside, including the inductors and LDO. That > may be the most compact solution, for $24. > > Still no magic bullet. BTW re: LTM4625 -- 22uF cap required per output. -- Cheers, James Arthur |