Post by thread:[EE]: Best way to get +- Supply from Car battery

I have an application where ideally I'd like to get +18V and -18V regulated power from a standard car battery (unregulated ~11.5-14+) .. I can't seem to figure out anything to get me there. The current requirements are pretty small (certainly less than 50mA probably more like 10mA) I've tracked down a MAX743 chip that can give me +-15 from a +6 supply but it costs about $4 in Qty of 1000. I'm not much of a circuit designer but I can follow one :) so if anyone has any ideas or suggestions I'd appreciate it. Thanks, Damon Hopkins -- /-=-=-=-=-=-=-=-=-=-=-=-=-\ | http://www.openpic.com | | New OpenSource Pic site | \-=-=-=-=-=-=-=-==-=-==-=-/ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use spam_OUTlistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST>

Not trivial. Look closely at what you are trying to power first, you seem to be concerned with cost so can I presume this is a volume application. If this is a 1-off and you just want it to work then look at buying a DC-DC converter. If you really want to build your own then work out what power you need and whether both supplies need full regulation or not. Also decide whether the demand is spread across both supply rails or whether one supply is trivial eg <10ma. Decide whether you are prepared to wind your own transformer. A simple supply design involves an IC 'Boost Regulator' with a three winding inductor. Two output windings supply the positive and negative outputs. The National Semiconductor 'Simple Switcher' design software will design this type of converter but there are cheaper controller ICs about. In the sub10mA region I would recomend a charge pump followed by a conventional regulator, since this is trivial to design. {Original Message removed}

Oliver Broad wrote: {Quote hidden}> Not trivial. > > Look closely at what you are trying to power first, you seem to be concerned > with cost so can I presume this is a volume application. If this is a 1-off > and you just want it to work then look at buying a DC-DC converter. > > If you really want to build your own then work out what power you need and > whether both supplies need full regulation or not. Also decide whether the > demand is spread across both supply rails or whether one supply is trivial > eg <10ma. > > Decide whether you are prepared to wind your own transformer. > > A simple supply design involves an IC 'Boost Regulator' with a three winding > inductor. Two output windings supply the positive and negative outputs. The > National Semiconductor 'Simple Switcher' design software will design this > type of converter but there are cheaper controller ICs about. > > In the sub10mA region I would recomend a charge pump followed by a > conventional regulator, since this is trivial to design. > > {Original Message removed}

Mike Eggleston wrote: {Quote hidden}> Oliver Broad wrote: > > > Not trivial. > > > > Look closely at what you are trying to power first, you seem to be concerned > > with cost so can I presume this is a volume application. If this is a 1-off > > and you just want it to work then look at buying a DC-DC converter. > > > > If you really want to build your own then work out what power you need and > > whether both supplies need full regulation or not. Also decide whether the > > demand is spread across both supply rails or whether one supply is trivial > > eg <10ma. > > > > Decide whether you are prepared to wind your own transformer. > > > > A simple supply design involves an IC 'Boost Regulator' with a three winding > > inductor. Two output windings supply the positive and negative outputs. The > > National Semiconductor 'Simple Switcher' design software will design this > > type of converter but there are cheaper controller ICs about. > > > > In the sub10mA region I would recomend a charge pump followed by a > > conventional regulator, since this is trivial to design. > > > > {Original Message removed}

On 28 Aug 2000, at 0:50, Damon Hopkins wrote: > I have an application where ideally I'd like to get +18V and -18V > regulated power from a standard car battery (unregulated ~11.5-14+) .. I > can't seem to figure out anything to get me there. The current > requirements are pretty small (certainly less than 50mA probably more > like 10mA) I've tracked down a MAX743 chip that can give me +-15 from a > +6 supply but it costs about $4 in Qty of 1000. I'm not much of a > circuit designer but I can follow one :) so if anyone has any ideas or > suggestions I'd appreciate it. > This is a very big subject with an array of options (learnt by experience... usually making all the wrong choices first off). It is important to exactly define what you want. If you want the +/-18 supply for low level audio then a switcher will need to be high freq (300kHz+...sub-harmonics bite) and then well post conversion filtered. And yes.. they usually are not cheap. Maxim have quite a library of engineering examples as do many other manufacturers. For the lowest cost, easiest to implement option (in low power apps like this) I would investigate charge pumps. Double the nominal +12 to around 23 (1 volt lost to diodes) and then linear regulate to +18, the -ve rail operates off the +23 and is also regulated accordingly. All you need is a nice PWM square wave (adjusted for best efficiency.. i.e. lowest duty cycle that will support the output) and 4 diodes(fast recovery types), 4 capacitors and a +ve 18 regulator and a -ve 18 volt regulator. If the frequency is say 300kHz to 500kHz the caps can be in the 100s of nanofarads range but the driver stage from the PWM will need mosfets(one to pull up, one to pull down) capable a few amps. Beware power mosfets have gate capacitance of in the low nanofarads, so at 500kHz it will look like a 100 ohms or so to the predriver. Bulky compared to the nice little Maxim chips and not as efficient but cheaper. Check out the myriads of articles, projects and postings on the subject. With swithchers the terms cheap, simple, small, low noise and efficient are somewhat mutually exclusive in most combinations. _____________________________ Lance Allen Technical Officer Uni of Auckland Psych Dept New Zealand http://www.psych.auckland.ac.nz _____________________________ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use .....listservKILLspam@spam@mitvma.mit.edu?body=SET%20PICList%20DIGEST>

Tell us more about your application - is it completely isolated from the vehicle? If so you can use one of these solutions - 2 voltage doublers in series to get 0 to +48V, then create an artificial, floating 0V somewhere in the middle with 2 large, equal resistors to get your +-18V. This is a >$10 solution, most of the cost in 64V capacitors for the charge pump voltage doublers. Oliver's suggestion (below) sounds like the right sort of advice. You create a chopped AC with a simple oscillator and a power transistor to feed the input to a custom built centre tapped transformer to get +-24V AC which you then rectify and regulate. This is a <$10 solution so long as you wind your own transformers. Bye. {Original Message removed}

Damon, Oliver, Lance and the others are right. Not trivial. Relatively straightforward solutions do exist but you do need to determine fairly closely what you need out of the power supply before you start designing it. Minimally, you need to know the range of input voltages (possibly including noise), the output voltages, output currents, dc regulation, and tolerance for ripple on the output. Additionally, you will be making the obvious tradeoffs between size, cost, efficiency and complexity. Personally, I like inductor based switchers (even for the small stuff) but your requirements seem to be in the range of what is reasonable with charge pumps. None of the single chip charge pumps that I am aware of will operate with either the input voltage range or output voltage range that you specify so you will have to roll your own. Without the output regulation, I would guess you could beat $4 per unit in quantity but you will have to work for it. Tell us more about your application. Perhaps we can do a better job steering you in the right direction. Best regards, Dave Minkler Damon Hopkins wrote: {Quote hidden}> > I have an application where ideally I'd like to get +18V and -18V > regulated power from a standard car battery (unregulated ~11.5-14+) .. I > can't seem to figure out anything to get me there. The current > requirements are pretty small (certainly less than 50mA probably more > like 10mA) I've tracked down a MAX743 chip that can give me +-15 from a > +6 supply but it costs about $4 in Qty of 1000. I'm not much of a > circuit designer but I can follow one :) so if anyone has any ideas or > suggestions I'd appreciate it. > > Thanks, > > Damon Hopkins > -- > /-=-=-=-=-=-=-=-=-=-=-=-=-\ > | http://www.openpic.com | > | New OpenSource Pic site | > \-=-=-=-=-=-=-=-==-=-==-=-/ > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > use listservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use .....listservKILLspam.....mitvma.mit.edu?body=SET%20PICList%20DIGEST>

----- Original Message ----- From: "Damon Hopkins" <EraseMEmdhopkinspam_OUTTakeThisOuTUNITY.NCSU.EDU> To: <PICLISTspam_OUTMITVMA.MIT.EDU> Sent: Monday, August 28, 2000 5:50 AM Subject: [EE]: Best way to get +- Supply from Car battery > I have an application where ideally I'd like to get +18V and -18V > regulated power from a standard car battery (unregulated ~11.5-14+) .. I > can't seem to figure out anything to get me there. The current > requirements are pretty small (certainly less than 50mA probably more > like 10mA) I've tracked down a MAX743 chip that can give me +-15 from a > +6 supply but it costs about $4 in Qty of 1000. I'm not much of a > circuit designer but I can follow one :) so if anyone has any ideas or > suggestions I'd appreciate it. For around UKP5 (~USD8) (Qty-1 price) you can get a minature 2W encapulated dual-output DC-DC convertor from Newport Components http://www.dc-dc.com. I've not seen any 18V ones but they come in quite a variety of input and output voltages. 5,9,12,15V are values I currently have in the workshop. They are dual output so you could regulate your car supply down to something that won't drop out e.g. when cranking the engine and then follow it with one of these to give both rails. They claim a 2:1 input voltage range but it's a good idea to put some spike suppression on anything taking car power. You can buy them from Farnell http://www.farnell.co.uk. According to the website Mouser also stock them. I don't see any 18V versions listed but they do say in several places that they do many custom versions so they may have 18V on the shelf if someone else has needed it. . -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use @spam@listservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST>

At 02:14 AM 8/29/00 +0100, you wrote: >For around UKP5 (~USD8) (Qty-1 price) you can get a minature 2W encapulated >dual-output DC-DC convertor from Newport Components http://www.dc-dc.com. Where did you get that price? Mouser 1-9 price is USD 21.07 Farnell 1-9 price is GBP 12.77 Their press release states a price of USD 14.37 for >2500 pieces. I'd love to find DC-DC converters available in small quantities for more like US$5, I know where to get them in big quantities. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" KILLspamspeffKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST>

----- Original Message ----- From: "Spehro Pefhany" <spamBeGonespeffspamBeGoneINTERLOG.COM> To: <TakeThisOuTPICLISTEraseMEspam_OUTMITVMA.MIT.EDU> Sent: Tuesday, August 29, 2000 2:38 AM Subject: Re: [EE]: Best way to get +- Supply from Car battery > At 02:14 AM 8/29/00 +0100, you wrote: > > >For around UKP5 (~USD8) (Qty-1 price) you can get a minature 2W encapulated {Quote hidden}> >dual-output DC-DC convertor from Newport Components http://www.dc-dc.com. > > Where did you get that price? > > Mouser 1-9 price is USD 21.07 > Farnell 1-9 price is GBP 12.77 > Their press release states a price of USD 14.37 for >2500 pieces. > > I'd love to find DC-DC converters available in small quantities for more > like US$5, I know where to get them in big quantities. The one I use most of is Farnell part no. 305-7902 and costs UKP 5.32 in single quantities (ordered in the UK), 4.75 in 25s and 4.15 in 100s. It's the 1W part rather than the 2W, but the 2W version is listed here as only 8.21 UKP. http://www.farnell.co.uk/Search/search-frame1.jhtml?CATID1=24 takes you to the dc-dc convertors. http://www.farnell.co.uk/Search/level_5.jhtml?PRODID=25629&SKUID=23614 is the one mentioned. Maybe Farnell charge excessively for orders originating outside the UK (assuming you are outside the UK of course). Anyway, hope this helps. They're extremely handy little devices and very small (they take marginally less PCB than an 'F84). Highly recommended. . -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservTakeThisOuTmitvma.mit.edu?body=SET%20PICList%20DIGEST>

At 03:10 AM 8/29/00 +0100, you wrote: >The one I use most of is Farnell part no. 305-7902 and costs UKP 5.32 in >single quantities (ordered in the UK), 4.75 in 25s and 4.15 in 100s. It's >the 1W part rather than the 2W, but the 2W version is listed here as only >8.21 UKP. Thanks! these ones are not available in 24V input, unfortunately, but the price agrees with what you gave. Not bad for an *isolated* converter. The NME and NMA at GBP7.75/7.24 (1W) isn't too too bad. I was looking at the NDL 2W series (new product), they have a *lot* of series. Farnell is actually OK for orders outside UK, I've used them in a pinch when their local guys (Newark) didn't stock the line. Shipping cost is a bit more, of course. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" speffEraseME.....interlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use EraseMElistservmitvma.mit.edu?body=SET%20PICList%20DIGEST>

Damon Hopkins wrote: > > I have an application where ideally I'd like to get +18V and -18V > regulated power from a standard car battery (unregulated ~11.5-14+) .. I > can't seem to figure out anything to get me there. The current > requirements are pretty small (certainly less than 50mA probably more > like 10mA) I've tracked down a MAX743 chip that can give me +-15 from a > +6 supply but it costs about $4 in Qty of 1000. I'm not much of a > circuit designer but I can follow one :) so if anyone has any ideas or > suggestions I'd appreciate it. > > Thanks, > > Damon Hopkins > -- > /-=-=-=-=-=-=-=-=-=-=-=-=-\ > | http://www.openpic.com | > | New OpenSource Pic site | > \-=-=-=-=-=-=-=-==-=-==-=-/ It would be ALOT easier to get +/- 10V regulated wouldn't it? The application is for a stereo (2 channel) Line driver for a car and The specs on the parts (the IC's) call for between +-4 to +-18V I'd like to get as high as possible BUT I don't want to incur unnecessary costs. 10V would be plenty and is found on currently existing devices already. Probably due to the added costs and design complexity that +-12 or greater incurs. a list of IC's if anyone care are Burr Brown OPA2134, DRV134, and INA134. I can provide a link to the data sheets if needed. What I want to do is take an unbalanced RCA output (from a head unit), convert it to a balanced signal (DRV134), run it down a length of cable ,shielded 4 pair twisted (cat 5 cable), and then convert it back to an unbalanced RCA output jack (INA134). the OPA134 (actually a dual chip version OPA2134) will be used in there somewhere for basically a gain setting, probably just before the long cable run. What I envision is a small case w/ inputs: 2 RCA line inputs (50mv-10v depends on source unit) 1 power wire +12 unregulated from the car power system 1 ground wire (chassis automotive Ground) 1 remote turn on wire (from source unit) in this case I'd have: the unit's power supply ( up to +-18V regulated) the DRV134 chip (the Line Driver chip) the OPA2134 OP amp to boost the signal for transit down the wire an output to an 8 position mini-DIN jack down the wire (8 conductor) I'd like to run Common Ground + system power - system power Channel 1 + Channel 1 - Channel 2 + Channel 2 - remote turn on wire at the other end another small case with: a 8 pin mini-DIN connector the INA134 Chip (unbalancer chip) and 2 RCA outputs for connections to external amps right now on parts alone in single quantities my 2 channel line balancer/unbalancer is $14.20 for the IC's and a few needed capacitors, no connectors, jacks, power supply, hence my need to keep the costs down.. I hope to keep the total cost on parts (including case and connectors) to under $25. as far as ripple currents on the voltage regulation go.. I'm at a complete loss.. designing simple fuzz pedals w/ my dad growing up it didn't come into consideration. :).. shouldn't I be paying for this kind of help?? j/k don't ask I can't afford it right now :) You guys are great, Damon Hopkins -- /-=-=-=-=-=-=-=-=-=-=-=-=-\ | http://www.openpic.com | | New OpenSource Pic site | \-=-=-=-=-=-=-=-==-=-==-=-/ -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! use RemoveMElistservEraseMEEraseMEmitvma.mit.edu?body=SET%20PICList%20DIGEST>

As someone else already suggested a charge pump would probably fit the bill here. Maybe use one element of standard hex cmos inverter as the oscillator and the other five elements paralleled up through 10 ohm resistors (or whatever) to drive your diode (1n4148 would be fine) / capacitor networks. This will give you a rough n* multiplication of the voltage. If you need to regulate that then you could use a standard 78xx 79xx pair or zeners or just an output capacitor and tweak the 'paralleling' resistors to give you the output you want. Then again.... I am assuming that the 'long cable run' you are talking about is to an amp at the back of the car from your head unit ? and the problem is you get hum / buzz / noise with your current setup so you very sensibly thought that going balanced would fix it ? (if not then this won't be much use) you may be able to solve the problem simply by playing around with the grounding of your system. try disconnecting the ground wire from the signal cables at one end this might solve your problem immediately (the noise is actually still there, just a lot less loud) or even... don't bother running the circuit at +-18 volts - just use large series caps on the inputs and outputs of the circuit and run it off 0 and vbat. Regards, Simon -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu>

If you can tolerate the reduced swing I think you should try to go single supply, for Audio it can work very well (for DC applications it is a pain). Filter your incoming DC with a reasonably high wattage resistor maybe 10 to 100 ohm, then a filter cap. A zener diode could be fitted to protect against excessive overvoltage. Derive a 1/2 supply reference using a resistor voltage divider and a large C to ground. Bias your electronics from this so the audio swings about this point rather than about ground. At the recieving end you now have a definite proof that the line is connected which could be valuable, two LEDs to indicate OK or an analog SW to mute it if open circuit?. Oliver. {Quote hidden}> > It would be ALOT easier to get +/- 10V regulated wouldn't it? > > The application is for a stereo (2 channel) Line driver for a car and > The specs on the parts (the IC's) call for between +-4 to +-18V I'd like > to get as high as possible BUT I don't want to incur unnecessary costs. > 10V would be plenty and is found on currently existing devices already. > Probably due to the added costs and design complexity that +-12 or > greater incurs. > > a list of IC's if anyone care are Burr Brown OPA2134, DRV134, and > INA134. I can provide a link to the data sheets if needed. > > What I want to do is take an unbalanced RCA output (from a head unit), > convert it to a balanced signal (DRV134), run it down a length of cable > ,shielded 4 pair twisted (cat 5 cable), and then convert it back to an > unbalanced RCA output jack (INA134). the OPA134 (actually a dual chip > version OPA2134) will be used in there somewhere for basically a gain > setting, probably just before the long cable run. What I envision is a > small case w/ inputs: > 2 RCA line inputs (50mv-10v depends on source unit) > 1 power wire +12 unregulated from the car power system > 1 ground wire (chassis automotive Ground) > 1 remote turn on wire (from source unit) > > in this case I'd have: > the unit's power supply ( up to +-18V regulated) > the DRV134 chip (the Line Driver chip) > the OPA2134 OP amp to boost the signal for transit down the wire > an output to an 8 position mini-DIN jack > > down the wire (8 conductor) I'd like to run > Common Ground > + system power > - system power > Channel 1 + > Channel 1 - > Channel 2 + > Channel 2 - > remote turn on wire > > at the other end another small case with: > a 8 pin mini-DIN connector > the INA134 Chip (unbalancer chip) > and 2 RCA outputs for connections to external amps > > right now on parts alone in single quantities my 2 channel line > balancer/unbalancer is $14.20 for the IC's and a few needed capacitors, > no connectors, jacks, power supply, hence my need to keep the costs > down.. I hope to keep the total cost on parts (including case and > connectors) to under $25. > > as far as ripple currents on the voltage regulation go.. I'm at a > complete loss.. designing simple fuzz pedals w/ my dad growing up it > didn't come into consideration. :).. shouldn't I be paying for this kind > of help?? j/k don't ask I can't afford it right now :) > > You guys are great, > > Damon Hopkins > -- > /-=-=-=-=-=-=-=-=-=-=-=-=-\ > | http://www.openpic.com | > | New OpenSource Pic site | > \-=-=-=-=-=-=-=-==-=-==-=-/ > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > use RemoveMElistservKILLspammitvma.mit.edu?body=SET%20PICList%20DIGEST > -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestSTOPspamspam_OUTmitvma.mit.edu>

----- Original Message ----- From: "Spehro Pefhany" <spamBeGonespeffSTOPspamEraseMEINTERLOG.COM> To: <KILLspamPICLISTspamBeGoneMITVMA.MIT.EDU> Sent: Tuesday, August 29, 2000 3:49 AM Subject: Re: [EE]: Best way to get +- Supply from Car battery > At 03:10 AM 8/29/00 +0100, you wrote: > > >The one I use most of is Farnell part no. 305-7902 and costs UKP 5.32 in > >single quantities (ordered in the UK), 4.75 in 25s and 4.15 in 100s. It's > >the 1W part rather than the 2W, but the 2W version is listed here as only > >8.21 UKP. > > Thanks! these ones are not available in 24V input, unfortunately, Ah, 24V. If you're looking for a downconvertor then maybe something like ST's L4962 would do the trick, they're much cheaper too, though not fully isolated. http://www.st.com/stonline/books/pdf/docs/1357.pdf -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's