Post by thread:[EE]: New! One Cell Switching Regulator Schematics

>>This Independence Day I designed a couple of small cheap switching >>regulators that use very few parts and make 5 volts from 1 battery cell. I've seen a number of these designs on the PICLIST from time to time. Why build this out of discrete components like this when you can buy an IC based item? Is it a cost thing, or does this give better results, or is it just a "because I can" type of thing? Not to undermine your work, mind you, I think it's just spiffy, but why? Mike H. _________________________________________________________________ MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. http://join.msn.com/?page=features/virus -- http://www.piclist.com hint: The PICList is archived three different ways. See http://www.piclist.com/#archives for details.

At 11:27 PM 7/8/2003 -0700, you wrote: >Hi- >Do any of you have a circuit for a switching supply that uses a 7805 or >similar for the control circuit? >David Here: http://us.st.com/stonline/books/pdf/docs/2143.pdf Figure 23 on page 20. But I wouldn't use it- look at how huge the inductor has to be compared to modern switching regulators. Best regards, Spehro Pefhany --"it's the network..." "The Journey is the reward" .....speffKILLspam.....interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspam_OUTTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Because some of us have bags of transistors gathering dust? What I need is some equally cheap inductors.. 75 turns on a half inch form? ( don't know if I trust these online calculators) What frequency does it humm? At 08:51 PM 7/8/03 -0500, you wrote: {Quote hidden}>>>This Independence Day I designed a couple of small cheap switching >>>regulators that use very few parts and make 5 volts from 1 battery cell. > >I've seen a number of these designs on the PICLIST from time to time. >Why build this out of discrete components like this when you can buy >an IC based item? Is it a cost thing, or does this give better results, or >is it just a "because I can" type of thing? > >Not to undermine your work, mind you, I think it's just spiffy, but why? > >Mike H. > >_________________________________________________________________ >MSN 8 helps eliminate e-mail viruses. Get 2 months FREE*. >http://join.msn.com/?page=features/virus > >-- >http://www.piclist.com hint: The PICList is archived three different >ways. See http://www.piclist.com/#archives for details. > > > > >--- >Incoming mail is certified Virus Free. >Checked by AVG anti-virus system (http://www.grisoft.com). >Version: 6.0.491 / Virus Database: 290 - Release Date: 6/18/03 -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

On Tue, 8 Jul 2003 21:45:54 -0700, Bob Blick <KILLspambobblickKILLspamCOVAD.NET> wrote: >> Not to undermine your work, mind you, I think it's just spiffy, but why? > > Easy question. Olin's design has 29 parts, mine only needs 13 ;-) However, donB4t yours drain -waste-more mA from the cell, at least OlinB4s resistors are 5 times greater ? (just a question, I do not know really). BTW, is there a design to pulse drive at least two white LEDs from a single 1.5v cell ? Please, change subject tag in case of a reply to the last question. Cheers, Diego. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

On Tuesday 08 July 2003 23:45, Bob Blick scribbled: > > Not to undermine your work, mind you, I think it's just spiffy, but why? > > Easy question. Olin's design has 29 parts, mine only needs 13 ;-) > > Cheerful regards, > > Bob Sounds like you have a lot of spare time. So should I put in my "order" for a 11-15V input, 5V out, 300mA max out, buck converter that is size- & cost-effective when compared to a 7805. :-) Since the challenge/competition seems to motivate you, I'll go ahead and say that I can do it within $1, inductor and other passives all included. I really can't though. Cheers, -Neil. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

Diego Sierra said: > However, donB4t yours drain -waste-more mA from the cell, at least > OlinB4s resistors are 5 times greater ? (just a question, I do not know > really). Hi Diego, I haven't built Olin's, but he states the efficiency at approx 66% and no-load current of 1.25 milliamps. My PFM circuit has about the same efficiency and no-load current (700 microamps at 1.1 volt input, 1.5 milliamps at 1.6 volts input). The PWM circuit has about the same efficiency. It is capable of much greater loads and has higher no-load current while still using a tiny inductor (it runs at 300 KHz!). I was trying for something simple in a step-up, something you might actually want to build. Roman Black designed a step-down converter with 12 parts, and it works great. This is the step-up equivalent. Cheers, Bob -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservEraseMEspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> BTW, is there a design to pulse drive at least two white LEDs from a > single 1.5v cell ? I was playing with that last weekend. I was actually trying to drive a string of 4 white LEDs, which requires about 13V. I did get it to work from a little over 1V, but the efficiency wasn't very good. I also didn't like the relatively high cutout voltage compared to what a NiMH battery can do. In the end I decided to go with 2 cells. This will be able to function even with rechargeable batteries until they are well drained. I intend the batteries, switch, and most of the circuit to go on the back of a hat, with the LEDs clipped to the visor. Two rechargeable AA cells isn't that bad for over 9 hours of continuous light. All the electronics are packed onto a 2.5 x 2.1 inch circuit board, using all thru hole components. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Picdude said: > Sounds like you have a lot of spare time. heh. I don't think anyone has spare time these days. But I finally have space to do some work at home again, and snatched a few hours. > for a 11-15V input, 5V out, 300mA max out, buck converter that is size- > & cost-effective when compared to a 7805. :-) Since the > challenge/competition seems to motivate you, I'll go ahead and say that > I can do it within $1, inductor and other passives all included. I > really can't though. That sounds like Roman Black's circuit: http://www.romanblack.com/a02.htm and you have 30 cents left over! I bet if you used that 30 cents you could improve it, make it run at a higher frequency, and get the size down. Or spend the 30 cents on an output crowbar, I never trust buck converters. Cheers, Bob -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservEraseME.....mitvma.mit.edu with SET PICList DIGEST in the body

How about a link to that circuit for us Spelunkers :) -----Original Message----- From: Olin Lathrop [EraseMEolin_piclistEMBEDINC.COM] Sent: Wednesday, July 09, 2003 2:59 PM To: RemoveMEPICLISTEraseMEEraseMEMITVMA.MIT.EDU Subject: Re: [EE]: New! One Cell Switching Regulator Schematics > BTW, is there a design to pulse drive at least two white LEDs from a > single 1.5v cell ? I was playing with that last weekend. I was actually trying to drive a string of 4 white LEDs, which requires about 13V. I did get it to work from a little over 1V, but the efficiency wasn't very good. I also didn't like the relatively high cutout voltage compared to what a NiMH battery can do. In the end I decided to go with 2 cells. This will be able to function even with rechargeable batteries until they are well drained. I intend the batteries, switch, and most of the circuit to go on the back of a hat, with the LEDs clipped to the visor. Two rechargeable AA cells isn't that bad for over 9 hours of continuous light. All the electronics are packed onto a 2.5 x 2.1 inch circuit board, using all thru hole components. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservspam_OUTKILLspammitvma.mit.edu with SET PICList DIGEST in the body -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservTakeThisOuTspammitvma.mit.edu with SET PICList DIGEST in the body

David VanHorn wrote: > Micros in general, should not directly interface to the "real world". > Their outputs are only designed to drive small loads, and to > read conditioned signals. Well, Microchip says that "High current sink/source" of the I/O pins are one of the benefits with the PICmicro line compared with "other" micros. And the S/T inputs are there to help read un-conditioned signals, not ? Now, maybe that both "small loads" and "high current" as well as "conditioned" needs to be specified more closly :-) Jan-Erik. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email EraseMElistservspamspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

On Wednesday 09 July 2003 14:59, Bob Blick scribbled: > That sounds like Roman Black's circuit: > http://www.romanblack.com/a02.htm > > and you have 30 cents left over! I bet if you used that 30 cents you could > improve it, make it run at a higher frequency, and get the size down. Or > spend the 30 cents on an output crowbar, I never trust buck converters. This would be superb to use, even with the greater board-space required, if I could find the components for the prices he mentions. For example, I can't find the 470uh 0.7ohm inductor anywhere for under a $1. Cheers, -Neil. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email RemoveMElistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

Bob, Diego, and Olin (in alphbetical order)- Now we need a combined circuit: 0.8-20V in and 5V out. Is that actually doable? David Bob Blick wrote: {Quote hidden}>Diego Sierra said: > > > >>However, donB4t yours drain -waste-more mA from the cell, at least >>OlinB4s resistors are 5 times greater ? (just a question, I do not know >>really). >> >> > >Hi Diego, > >I haven't built Olin's, but he states the efficiency at approx 66% and >no-load current of 1.25 milliamps. My PFM circuit has about the same >efficiency and no-load current (700 microamps at 1.1 volt input, 1.5 >milliamps at 1.6 volts input). The PWM circuit has about the same >efficiency. It is capable of much greater loads and has higher no-load >current while still using a tiny inductor (it runs at 300 KHz!). > >I was trying for something simple in a step-up, something you might >actually want to build. Roman Black designed a step-down converter with 12 >parts, and it works great. This is the step-up equivalent. > >Cheers, > >Bob > >-- >http://www.piclist.com#nomail Going offline? Don't AutoReply us! >email listservSTOPspamspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body > > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservSTOPspamEraseMEmitvma.mit.edu with SET PICList DIGEST in the body

> Now we need a combined circuit: 0.8-20V in and 5V out. Is that actually > doable? Anything is doable, but this is not easy since it has to be able to step up AND down. This either requires: 1 - A floating input voltage or allow one side of the input voltage to be the opposite rail of the output voltage (for example, + side of input voltage is output voltage ground). 2 - A layered boost-buck approach. This is bad because you get hit with the inefficiency twice. 3 - A transformer instead of inductor as the switching element. Each one of these is either messy, inefficient, inconvenient, or expensive in various cases. If the input power comes from captive batteries, then #1 is reasonable, otherwise back to messy, inefficient, ... ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listserv@spam@spam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

part 1 675 bytes content-type:text/plain; (decoded 7bit) > How about a link to that circuit for us Spelunkers :) Um, OK, it's attached. The circuit works as shown, but I think efficiency can be tweaked by adjusting some part values. For now I know the topology will work, and more optimum part values will have to wait for then next time I get some spare time. Since the output voltage and current, and therefore power requirements are well known, it should be possible to make the driver circuit supply just enough power without much excess capacity. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservKILLspammitvma.mit.edu with SET PICList DIGEST in the body part 2 3131 bytes content-type:image/gif; (decode) part 3 11011 bytes content-type:image/gif; (decode) part 4 2 bytes -

Olin Lathrop wrote: > > BTW, is there a design to pulse drive at least two white > > LEDs from a single 1.5v cell ? > > I was playing with that last weekend. I was actually trying > to drive a string of 4 white LEDs, which requires about 13V. > I did get it to work from a little over 1V, but the efficiency > wasn't very good. ... > I intend the batteries, switch, and most of the circuit to > go on the back of a hat, with the LEDs clipped to the visor. There was a post(sorry for resending): "Re: [EE]: Low voltage boost regulator" >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> Olin Lathrop wrote: > I had a need to produce 10-15V at 20mA or so from a > single AA battery, or maybe two at most. This is > significant power for an AA cell, so efficiency is > important. This means it would be desirable to have > a FET switching the inductor, but that is impossible > to do efficiently on just 1V... LEDs on your cap for hiking again? Perhaps LM2623 would be better? Mike. AN-1250: Inductive Based Switching Regulator Circuits Provide High Efficiency White LED Drives AN-1258: LM2623 Boost Converter - A Simple Technology Twist Produces the Industry's Most Versatile Supply From http://www1.national.com/ds.cgi/LM/LM2623.pdf Ratio Adaptive Gated Oscillator Based, DC DC Boost Converter-Low Vin, Low Ripple, General Purpose. ---------------------------------------------------------- The LM2623 is a high efficiency, general purpose, step-up DC-DC switching regulator for battery-powered and low input voltage systems. It accepts an input voltage between 0.8 and 14 volts and converts it into a regulated output voltage. The LM2623 can be used to generate up to 14 volts using an inductor and almost any positive voltage using a transformer. It has an internal .17§Ù N-Channel MOSFET power switch. Efficiencies up to 90% are achievable with the LM2623. In order to adapt to a number of applications, the LM2623 allows the designer to vary the output voltage, the operating frequency (300kHz to 2 MHz) and duty cycle (17% to 90%) to optimize the part¡¯s performance. The selected values can be fixed or can vary with battery voltage or input to output voltage ratio. Using these techniques according to the design guidelines may improve efficiency or reduce parts cost or both. The LM2623 is a gated oscillator and uses a very simple, on/off regulation mode to produce good efficiency and stable operation over a wide operating range. It normally regulates by skipping switching cycles when it reaches the regulation limit (Pulse Frequency Modulation). In some applications, with the proper selection of external feedback components, it can also regulate cycle to cycle, similar to Pulse Width Modulated parts. It does this by adjusting the off time between switching cycles, while maintaining continuous current through the coil. This cycle to cycle type of PFM results in very low ripple on the output voltage and/or minimum sized output capacitors, similar to PWM parts. This mode also typically maximizes efficiency. >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> Perhaps LM2623 would be better? I wanted to see what I could do with off the shelf cheap jellybean parts. Note that the cheapest LM2623 from DigiKey is $1.72 each for 25. Then you still have to buy the inductor and a few other parts. My whole circuit with inductor costs less than an LM2632, and can probably be cost reduced further. One possibility is use a little more current in the oscillator, make less pessimistic assumptions about the gain (but still within repeatable limits), maybe use higher gain transistors (2N5087/5088 real cheap at Jameco) for all but the last driver, and get rid of a couple of gain stages. ***************************************************************** Embed Inc, embedded system specialists in Littleton Massachusetts (978) 742-9014, http://www.embedinc.com -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistserv.....TakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Olin Lathrop wrote: > Perhaps LM2623 would be better? > > I wanted to see what I could do with off the shelf cheap > jellybean parts. Note that the cheapest LM2623 from DigiKey > is $1.72 each for 25. Then you still have to buy the > inductor and a few other parts. My whole circuit with > inductor costs less than an LM2632, and can probably be > cost reduced further. One possibility is use a little > more current in the oscillator, make less pessimistic > assumptions about the gain (but still within repeatable > limits), maybe use higher gain transistors (2N5087/5088 > real cheap at Jameco) for all but the last driver, and > get rid of a couple of gain stages. Perhaps you are right, but I'd rather add to calcs: - the cost of assembling your extra parts; - the cost of extra PCB space; - the cost of your time (did you tell us 110 $/h?) - the cost of reliability issues of you big discrete orchestra compared to approved few parts ensemble. Heck, whom do I tell all these obvious things? You were joking, I'm sure. Mike. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email TakeThisOuTlistservKILLspamspammitvma.mit.edu with SET PICList DIGEST in the body