Forums

A PIC based boost converter

Started by Jan Panteltje November 22, 2011
On a sunny day (Wed, 23 Nov 2011 15:40:20 -0600) it happened John S
<sophi.2@invalid.org> wrote in <jajp88$qg2$4@dont-email.me>:

>On 11/23/2011 3:28 PM, Jan Panteltje wrote: >> On a sunny day (Wed, 23 Nov 2011 15:07:48 -0600) it happened John S >> <sophi.2@invalid.org> wrote in<jajnb8$qg2$1@dont-email.me>: >> >>> On 11/23/2011 3:05 PM, Jan Panteltje wrote: >>>> On a sunny day (Wed, 23 Nov 2011 12:18:44 -0800 (PST)) it happened >>>> "langwadt@fonz.dk"<langwadt@fonz.dk> wrote in >>>> <761a9bb1-4083-4555-afa8-eef6d073f27f@h3g2000yqa.googlegroups.com>: >>>> >>>>> On 23 Nov., 12:08, Jan Panteltje<pNaonStpealm...@yahoo.com> wrote: >>>>>> >>>>> snip >>>>>> It would be short circuit proof IF it was not for the >>>>>> boost configuration where the diode would conduct from input to output. >>>>>> So for that in this sort of regulator you need a normal fuse. >>>>>> For the rest of loads it nicely current limits. >>>>> >>>>> I remember seeing some put a cap in series with the diode to make it >>>>> short >>>>> circuit proof >>>> >>>> mm but caps do not conduct DC? >>>> >>>>> >>>>> -Lasse >>>>> >>>>> >>> >>> True. That would make it short-circuit proof. Right? >> >> OK :-) >> But what about output? >> >> Maybe like this? >> in >> | >> L >> | C a k >> ---||---------|>|--------- out >> | | | >> |MOSFET --- | >> /switch / \ === >> | --- --- >> | | | >> /// /// /// >> >> 2 diode losses.. >> > >Yes. If no added diode, no output. That's why I said "What Output?" > >However, you must admit that it will work to limit current.
Yes, sure, in some situations this could be a really good solution.
On 11/23/2011 3:46 PM, Jan Panteltje wrote:
> On a sunny day (Wed, 23 Nov 2011 15:40:20 -0600) it happened John S > <sophi.2@invalid.org> wrote in<jajp88$qg2$4@dont-email.me>: > >> On 11/23/2011 3:28 PM, Jan Panteltje wrote: >>> On a sunny day (Wed, 23 Nov 2011 15:07:48 -0600) it happened John S >>> <sophi.2@invalid.org> wrote in<jajnb8$qg2$1@dont-email.me>: >>> >>>> On 11/23/2011 3:05 PM, Jan Panteltje wrote: >>>>> On a sunny day (Wed, 23 Nov 2011 12:18:44 -0800 (PST)) it happened >>>>> "langwadt@fonz.dk"<langwadt@fonz.dk> wrote in >>>>> <761a9bb1-4083-4555-afa8-eef6d073f27f@h3g2000yqa.googlegroups.com>: >>>>> >>>>>> On 23 Nov., 12:08, Jan Panteltje<pNaonStpealm...@yahoo.com> wrote: >>>>>>> >>>>>> snip >>>>>>> It would be short circuit proof IF it was not for the >>>>>>> boost configuration where the diode would conduct from input to output. >>>>>>> So for that in this sort of regulator you need a normal fuse. >>>>>>> For the rest of loads it nicely current limits. >>>>>> >>>>>> I remember seeing some put a cap in series with the diode to make it >>>>>> short >>>>>> circuit proof >>>>> >>>>> mm but caps do not conduct DC? >>>>> >>>>>> >>>>>> -Lasse >>>>>> >>>>>> >>>> >>>> True. That would make it short-circuit proof. Right? >>> >>> OK :-) >>> But what about output? >>> >>> Maybe like this? >>> in >>> | >>> L >>> | C a k >>> ---||---------|>|--------- out >>> | | | >>> |MOSFET --- | >>> /switch / \ === >>> | --- --- >>> | | | >>> /// /// /// >>> >>> 2 diode losses.. >>> >> >> Yes. If no added diode, no output. That's why I said "What Output?" >> >> However, you must admit that it will work to limit current. > > Yes, sure, in some situations this could be a really good solution.
However, I don't like the current spikes it will produce. I would probably look for a cleaner solution.
"John S"  wrote in message news:jajot1$qg2$3@dont-email.me...

> I would be interested to know how you arrived at your efficiency =
numbers.=20
> I have run your circuit and I cannot get the same results.
> I used the LTSpice ability to get the power in R2, averaged it, then > got the (negative) power in V1, averaged it, then divided output > by the input. I got about 69.8% with V1 at 3V.
I have changed the circuit a bit now, but I run the simulation long = enough=20 for the output to stabilize (5-10 mSec), and then I select the last 5 = mSec=20 or so for the calculation. I use I(V1)*V(IN) for input power, and=20 I(R3)*V(Vout) for output power. I just ran the new circuit at 2 VDC with 5.25 Vout (292 mW), and = efficiency=20 is 81.8% between 10 mSec and 15 mSec. At 3 VDC I got 88.3% efficiency with 5.49 Vout (341 mW). At this voltage = the=20 circuit operates in burst mode. At 1.5 VDC I got 73% efficiency with 4.75 Vout (226 mW) It even works down to 0.7 VDC with 1.78 Vout (31.4 mW), at 62% = efficiency. I'm sure it can be optimized to do a bit better, and an actual circuit = may=20 not do as well, but I have built a similar circuit and it worked OK. I = even=20 built a more powerful version using a MOSFET and a gate driver, and I = think=20 it worked OK down to about 6 volts and as high as 16 volts, which were=20 beyond what I needed for the 12 VDC battery application. Adding a good=20 voltage reference and an op-amp with some hysteresis in the feedback,=20 controlling the MOSFET driver, should give tight regulation and high=20 efficiency, at the cost of some output ripple. But mostly I think this circuit is handy to boost nominal 1.5 VDC to = about 5=20 VDC for logic and maybe 8 VDC for MOSFET gate drive. Paul Here's the newer circuit: -------------------------------------------------------------------------= ----------------- Version 4 SHEET 1 1476 680 WIRE 768 -32 144 -32 WIRE -272 0 -320 0 WIRE -208 0 -272 0 WIRE -96 0 -208 0 WIRE 208 0 -96 0 WIRE 208 16 208 0 WIRE -96 32 -96 0 WIRE 672 64 592 64 WIRE 672 96 672 64 WIRE 208 112 208 96 WIRE 240 112 208 112 WIRE 464 112 304 112 WIRE 496 112 464 112 WIRE 592 112 592 64 WIRE 592 112 496 112 WIRE -208 128 -208 0 WIRE -320 160 -320 0 WIRE -96 160 -96 112 WIRE -16 160 -96 160 WIRE 208 160 208 112 WIRE 288 160 208 160 WIRE 496 160 496 112 WIRE 768 160 768 -32 WIRE -96 176 -96 160 WIRE -16 176 -16 160 WIRE 288 192 288 160 WIRE 592 192 592 112 WIRE 672 208 672 176 WIRE 704 208 672 208 WIRE 208 224 208 160 WIRE 672 240 672 208 WIRE -96 272 -96 256 WIRE -16 272 -16 240 WIRE -16 272 -96 272 WIRE 48 272 -16 272 WIRE 144 272 144 -32 WIRE 144 272 128 272 WIRE -96 304 -96 272 WIRE 288 336 288 256 WIRE 496 336 496 224 WIRE 496 336 288 336 WIRE 672 336 672 320 WIRE 672 336 496 336 WIRE -320 384 -320 224 WIRE -208 384 -208 208 WIRE -208 384 -320 384 WIRE -96 384 -96 368 WIRE -96 384 -208 384 WIRE 176 384 -96 384 WIRE 208 384 208 320 WIRE 208 384 176 384 WIRE 288 384 288 336 WIRE 288 384 208 384 WIRE 384 384 288 384 WIRE 592 384 592 272 WIRE 592 384 464 384 WIRE 768 384 768 256 WIRE 768 384 592 384 WIRE 176 432 176 384 FLAG 176 432 0 FLAG 464 112 Vout FLAG -272 0 IN SYMBOL npn 144 224 R0 WINDOW 0 43 29 Left 0 WINDOW 3 26 59 Left 0 SYMATTR InstName Q1 SYMATTR Value 2N2222 SYMBOL ind2 -80 128 R180 WINDOW 0 36 80 Left 0 WINDOW 3 36 40 Left 0 SYMATTR InstName L1 SYMATTR Value 100=B5 SYMATTR Type ind SYMBOL ind2 192 0 R0 WINDOW 3 37 69 Left 0 SYMATTR Value 100=B5 SYMATTR InstName L2 SYMATTR Type ind SYMBOL res -112 160 R0 SYMATTR InstName R1 SYMATTR Value 220 SYMBOL voltage -208 112 R0 WINDOW 123 0 0 Left 0 WINDOW 39 7 138 Left 0 WINDOW 3 13 109 Left 0 SYMATTR SpiceLine Rser=3D.1 SYMATTR InstName V1 SYMATTR Value 1.5 SYMBOL schottky -80 368 R180 WINDOW 0 24 72 Left 0 WINDOW 3 24 0 Left 0 SYMATTR InstName D3 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL schottky 240 128 R270 WINDOW 0 20 73 VTop 0 WINDOW 3 0 32 VBottom 0 SYMATTR InstName D5 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap 480 160 R0 SYMATTR InstName C1 SYMATTR Value 100=B5 SYMBOL schottky 304 256 R180 WINDOW 0 24 72 Left 0 WINDOW 3 -20 -2 Left 0 SYMATTR InstName D7 SYMATTR Value 1N5818 SYMATTR Description Diode SYMATTR Type diode SYMBOL cap -336 160 R0 SYMATTR InstName C2 SYMATTR Value 100=B5 SYMBOL cap -32 176 R0 SYMATTR InstName C3 SYMATTR Value .002=B5 SYMBOL res 576 176 R0 SYMATTR InstName R2 SYMATTR Value 100 SYMBOL res 480 368 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R3 SYMATTR Value 1 SYMBOL npn 704 160 R0 WINDOW 0 43 29 Left 0 WINDOW 3 26 59 Left 0 SYMATTR InstName Q2 SYMATTR Value 2N2222 SYMBOL res 656 80 R0 SYMATTR InstName R4 SYMATTR Value 4.3k SYMBOL res 656 224 R0 SYMATTR InstName R5 SYMATTR Value 750 SYMBOL res 144 256 R90 WINDOW 0 0 56 VBottom 0 WINDOW 3 32 56 VTop 0 SYMATTR InstName R6 SYMATTR Value 47 TEXT 24 24 Left 0 !K1 L1 L2 1 TEXT -24 416 Left 0 !.tran 15m startup TEXT 792 48 Left 0 ;81.9% eff at 2 VDC, 32 kHz, 5.49V, 292mW output TEXT 792 72 Left 0 ;88.3% eff at 3 VDC, 27 kHz (burst), 5.3V, 340mW = output TEXT 792 0 Left 0 ;62% eff at 0.7 VDC, 28 kHz, 1.78V, 31 mW output TEXT 792 24 Left 0 ;73% eff at 1.5 VDC, 23 kHz, 4.75V, 226mW output
"langwadt@fonz.dk" <langwadt@fonz.dk> wrote:

>On 23 Nov., 22:05, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote: >> On a sunny day (Wed, 23 Nov 2011 12:18:44 -0800 (PST)) it happened >> "langw...@fonz.dk" <langw...@fonz.dk> wrote in >> <761a9bb1-4083-4555-afa8-eef6d073f...@h3g2000yqa.googlegroups.com>: >> >> >On 23 Nov., 12:08, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote: >> >> >snip >> >> It would be short circuit proof IF it was not for the >> >> boost configuration where the diode would conduct from input to output. >> >> So for that in this sort of regulator you need a normal fuse. >> >> For the rest of loads it nicely current limits. >> >> >I remember seeing some put a cap in series with the diode to make it >> >short >> >circuit proof >> >> mm but caps do not conduct DC? >> > >in normal operation the switch node is not DC > >but when there's no dc path from input to output, current flow stops >when you >stop switching
Even though its pulsed, it still is DC. Hint: current flows in one direction. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico@nctdevpuntnl (punt=.) --------------------------------------------------------------
Here is a variation of the circuit, which puts out a (roughly) constant=20
current of about 2 amps at up to 35 watts. It uses only 15 parts, =
including=20
the load, which I represent as a 15 volt zener instead of a string of =
high=20
power LEDs. I read efficiencies of about 87% from 10 to 15 volts, but =
the=20
output actually drops at higher voltage. This circuit needs optimizing, =
but=20
shows the possibilities for a very simple design.

Paul

-------------------------------------------------------------------------=
---------------------

Version 4
SHEET 1 1048 680
WIRE -32 0 -208 0
WIRE 208 0 -32 0
WIRE -32 16 -32 0
WIRE 208 16 208 0
WIRE -32 112 -32 96
WIRE 208 112 208 96
WIRE 240 112 208 112
WIRE 320 112 240 112
WIRE 432 112 384 112
WIRE 560 112 432 112
WIRE -208 144 -208 0
WIRE 240 144 240 112
WIRE 432 192 432 112
WIRE -32 208 -32 192
WIRE -32 208 -112 208
WIRE -32 224 -32 208
WIRE 192 224 -32 224
WIRE -32 256 -32 224
WIRE -112 272 -112 208
WIRE 304 272 176 272
WIRE 336 272 304 272
WIRE 432 272 432 256
WIRE 432 272 400 272
WIRE 560 272 560 112
WIRE 240 288 240 240
WIRE 432 288 432 272
WIRE 48 304 32 304
WIRE 96 304 48 304
WIRE 176 304 176 272
WIRE 304 320 304 272
WIRE 48 352 48 304
WIRE 160 352 128 352
WIRE -208 384 -208 224
WIRE -112 384 -112 352
WIRE -112 384 -208 384
WIRE -32 384 -32 352
WIRE -32 384 -112 384
WIRE 160 384 160 352
WIRE 160 384 -32 384
WIRE 240 384 240 368
WIRE 240 384 160 384
WIRE 304 384 240 384
WIRE 432 384 432 368
WIRE 432 384 304 384
WIRE 560 384 560 336
WIRE 560 384 432 384
WIRE 560 416 560 384
FLAG 560 416 0
SYMBOL ind2 -16 112 R180
WINDOW 0 36 80 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName L1
SYMATTR Value 10=B5
SYMATTR Type ind
SYMBOL ind2 192 0 R0
SYMATTR InstName L2
SYMATTR Value 10=B5
SYMATTR Type ind
SYMBOL res -48 96 R0
SYMATTR InstName R1
SYMATTR Value 300
SYMBOL voltage -208 128 R0
WINDOW 123 0 0 Left 0
WINDOW 39 0 0 Left 0
SYMATTR InstName V1
SYMATTR Value 15
SYMBOL res 416 272 R0
SYMATTR InstName R2
SYMATTR Value 0.5
SYMBOL npn 32 256 M0
WINDOW 0 33 47 Left 0
SYMATTR InstName Q2
SYMATTR Value 2N3904
SYMBOL res 192 288 R90
WINDOW 0 2 38 VBottom 0
WINDOW 3 30 37 VTop 0
SYMATTR InstName R3
SYMATTR Value 499
SYMBOL schottky 320 128 R270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D3
SYMATTR Value MBR735
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 544 272 R0
SYMATTR InstName C1
SYMATTR Value 330=B5
SYMBOL schottky 400 288 M270
WINDOW 0 32 32 VTop 0
WINDOW 3 0 32 VBottom 0
SYMATTR InstName D4
SYMATTR Value 1N5818
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL zener 448 256 R180
WINDOW 0 24 72 Left 0
WINDOW 3 -109 3 Left 0
SYMATTR InstName D1
SYMATTR Value BZX84C15L
SYMATTR Description Diode
SYMATTR Type diode
SYMBOL cap 288 320 R0
WINDOW 3 31 47 Left 0
SYMATTR Value 5=B5
SYMATTR InstName C3
SYMBOL res 144 336 R90
WINDOW 0 0 56 VBottom 0
WINDOW 3 23 51 VTop 0
SYMATTR InstName R4
SYMATTR Value 2k
SYMBOL nmos 192 144 R0
SYMATTR InstName M1
SYMATTR Value STD30NF06L
SYMBOL res -96 368 R180
WINDOW 0 36 76 Left 0
WINDOW 3 36 40 Left 0
SYMATTR InstName R5
SYMATTR Value 100
SYMBOL res 224 272 R0
SYMATTR InstName R6
SYMATTR Value 0.2
TEXT 272 40 Left 0 !K1 L1 L2 1
TEXT -96 408 Left 0 !.tran 20m startup
TEXT 480 32 Left 0 ;88% eff, 12 VDC in, 1.88 A, 33.75 W
TEXT 480 0 Left 0 ;86.7% eff, 10 VDC in, 1.95 A, 35.3 W
TEXT 480 64 Left 0 ;87.5% eff, 15 VDC in, 1.58 A, 26.62 W, 23 kHz=20

Jan Panteltje wrote:

> On a sunny day (Tue, 22 Nov 2011 19:15:07 -0500) it happened Jamie > <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in > <cUWyq.117643$Cr1.1733@newsfe03.iad>: > > >>The problem looks obvious from here. > > > It works fine. > > > >>You are using a Xformer by the >>looks of it for your current sense? That would be fine when there is >>actual moving current how ever, in the case where output load is >>nulling this factor, I guess you're not going to see much effects. > > > Sorry I cannot decrypt that. > Study switch mode design.
Ha, you're so funny. Have fun with your endeavors.. Jamie
On 11/23/2011 6:27 PM, Jamie wrote:
> Jan Panteltje wrote: > >> On a sunny day (Tue, 22 Nov 2011 19:15:07 -0500) it happened Jamie >> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in >> <cUWyq.117643$Cr1.1733@newsfe03.iad>: >> >> >>> The problem looks obvious from here. >> >> >> It works fine. >> >> >> >>> You are using a Xformer by the looks of it for your current sense? >>> That would be fine when there is >>> actual moving current how ever, in the case where output load is >>> nulling this factor, I guess you're not going to see much effects. >> >> >> Sorry I cannot decrypt that. >> Study switch mode design. > > Ha, you're so funny. > > Have fun with your endeavors.. > > Jamie
He has been. He has supplied something of substance especially compared to your posts of almost indecipherable verbiage. What have you posted of any value other than your ill-informed criticism? Please point to something.
On Nov 23, 5:09=A0am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
> Any drift in the current transformer is regulated out by the output volta=
ge
> sense loop. > The current form is the current form in the inductor, and that is a TRIAN=
GLE
> waveform, not a peak. > As drawn in the diagram.
So, you aren't doing peak current mode switching, as every switching circuit with a current sense and comparator does? So, you don't mind that you have no DC current reference? So in short, you've created a voltage-mode boost converter with current feedback that...just kind of sits there? Yuuuuck.
> There is no difference with the drain current, > as the comparator looks at the top of the upgoing side of the triange.
Yes there is. The drain current stops for about half a cycle on average. Current transformers don't happen to work at DC. Tim
"Tim Williams"  wrote in message=20
news:72c931c1-6e16-4224-aa12-1756c9f14cd4@m7g2000vbc.googlegroups.com...

> On Nov 23, 5:09 am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
>> Any drift in the current transformer is regulated out by the output >> voltage sense loop. >> The current form is the current form in the inductor, and that is a >> TRIANGLE waveform, not a peak. >> As drawn in the diagram.
> So, you aren't doing peak current mode switching, as every > switching circuit with a current sense and comparator does?
> So, you don't mind that you have no DC current reference?
> So in short, you've created a voltage-mode boost converter > with current feedback that...just kind of sits there?
> Yuuuuck.
>> There is no difference with the drain current, as the >> comparator looks at the top of the upgoing side of the triange.
> Yes there is. The drain current stops for about half a cycle on > average. Current transformers don't happen to work at DC.
I thought there were some problems with the design, but I was not = motivated=20 enough to analyze it. I think it's cool to have some of the features = that=20 the PIC offers, but the basic circuit seemed overly complex for whatever = the=20 specs may be. I looked at a previous thread on "Favorite boost = converter"=20 but there were no details. But if you really just need a power supply = with=20 normal specs, there are many available for cheap. I just bought an = LM2596=20 step-down converter on eBay for $3.25 including shipping: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3D250936549019&ssPageN= ame=3DADME:L:OC:US:1123 The same company has many other small boards available cheap, such as = this=20 LM3577 boost converter for $0.99 + $4.90 shipping: http://www.ebay.com/itm/LM2577S-DC-DC-4-35V-Adjustable-Step-up-Power-Supp= ly-Non-isolated-Boost-Module-3A-/250937571266?pt=3DLH_DefaultDomain_0&has= h=3Ditem3a6d0b77c2 This one is rated for an input of 0.9 to 6V, and an output of 3.3-9V, = for=20 $3.25 and free shipping. http://www.ebay.com/itm/DC-DC-3V-5V-9V-Voltage-adjustable-step-up-Power-T= ransformer-Module-40-85-/260899918844?pt=3DBI_Circuit_Breakers_Transforme= rs&hash=3Ditem3cbed8d3fc I love to design my own circuits and add special features, but when you = just=20 need a particular solution for a need, there's usually something = available=20 better and cheaper than you can do it yourself. Faster? Not so much.=20 Shipping from China is about 3 weeks. Paul=20
On a sunny day (Wed, 23 Nov 2011 19:27:04 -0500) it happened Jamie
<jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in
<69gzq.48122$jK1.12044@newsfe17.iad>:

>Jan Panteltje wrote: > >> On a sunny day (Tue, 22 Nov 2011 19:15:07 -0500) it happened Jamie >> <jamie_ka1lpa_not_valid_after_ka1lpa_@charter.net> wrote in >> <cUWyq.117643$Cr1.1733@newsfe03.iad>: >> >> >>>The problem looks obvious from here. >> >> >> It works fine. >> >> >> >>>You are using a Xformer by the >>>looks of it for your current sense? That would be fine when there is >>>actual moving current how ever, in the case where output load is >>>nulling this factor, I guess you're not going to see much effects. >> >> >> Sorry I cannot decrypt that. >> Study switch mode design. > >Ha, you're so funny. > >Have fun with your endeavors.. > >Jamie
I still cannot decrypt that, you are saying that at zero load there is no current, and then what? In that case one input of the the current limiter comparator will be zero, and the other input will be set by Vout. Any Vout will flip that comparator to off, and the PWM stops.