Post by thread:[EE:] Shunt regulator? 317/337 solution

lm317 solution: input current to Vi pin, Vout pin connected to A pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, this is also output current. Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA Vasile On Wed, 24 Jan 2001, Roman Black wrote: {Quote hidden}> Harold M Hallikainen wrote: > > > > I have a project that involves a variable shunt regulator (10-15V, > > 200mA). It SEEMS that it should be possible to use an LM 317 or 337 wired > > in some manner to make this work, but I'm not seeing it. Anyone see how > > this might be done? > > > You can use one transistor and a zener, this works > very well as a shunt regulator as the zener is > driven from the regulated output and gives a > good precise regulation. > -Roman > > -- > http://www.piclist.com hint: The PICList is archived three different > ways. See http://www.piclist.com/#archives for details. > > -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spam_OUTlistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body

Vasile Surducan wrote: > > lm317 solution: input current to Vi pin, Vout pin connected to A > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, this > is also output current. > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > Vasile Hi Vasile, that is a series regulator? I think the person wanted a shunt regulator, and I don't think you can do it with a 317 as it uses negative feedback, not positive. :o) -Roman -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email .....listservKILLspam@spam@mitvma.mit.edu with SET PICList DIGEST in the body

On Thu, 25 Jan 2001, Roman Black wrote: > Vasile Surducan wrote: > > > > lm317 solution: input current to Vi pin, Vout pin connected to A > > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, this > > is also output current. > > > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > > > Vasile > > > Hi Vasile, that is a series regulator? I think the > person wanted a shunt regulator, and I don't think you > can do it with a 317 as it uses negative feedback, > not positive. :o) > -Roman > No, it's not. It's a current controlled source and can be used as shunt on positive supply. On the negative supply just the LM337. If on the negative or positive supply in series with this device ( 317 or 337) is placed a power resistor, the whole sistem becomes a shunt regulator. BTW, ANY and ALL linear stabiliser circuits use ONLY negative feedback ALSO becomes oscillators ! Cheers, Vasile -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

{Quote hidden}> -----Original Message----- > From: Roman Black [SMTP:.....fastvidKILLspam.....EZY.NET.AU] > Sent: Thursday, January 25, 2001 10:56 AM > To: EraseMEPICLISTspam_OUTTakeThisOuTMITVMA.MIT.EDU > Subject: Re: [EE:] Shunt regulator? 317/337 solution > > Vasile Surducan wrote: > > > > lm317 solution: input current to Vi pin, Vout pin connected to A > > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, > this > > is also output current. > > > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > > > Vasile > > > Hi Vasile, that is a series regulator? I think the > person wanted a shunt regulator, and I don't think you > can do it with a 317 as it uses negative feedback, > not positive. :o) > -Roman > It's actually a constant current source in that configuration. Been thinking about this and I can't see a simple solution. I reckon you could make it work with the addition of an opamp (to invert the sense of the feedback), but then you might as well stick with a 723 etc. Mike -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email listservspam_OUTmitvma.mit.edu with SET PICList DIGEST in the body

> > Hi Vasile, that is a series regulator? I think the > > person wanted a shunt regulator, and I don't think you > > can do it with a 317 as it uses negative feedback, > > not positive. :o) > > -Roman > > > It's actually a constant current source in that configuration. Been > thinking about this and I can't see a simple solution. I reckon you could > make it work with the addition of an opamp (to invert the sense of the > feedback), but then you might as well stick with a 723 etc. If you MUST make a shunt regukator with an LM317 try this. The 317 acts as the controller and the transistor as the dissipative shunt element. I haven't tried this circuit (but it will work :-) ) R1 feeds supply voltage to Vout line. NPN TO220 (or whatever) transistor Collector to Vout Emitter to ground Base via R1 to LM317 input. LM317 Input to Vout via R3 Input to transistor base via R2 as above Gnd to gnd Output to gnd via R4 Output to supply via R5 R4/R3 form divide. LM317 attempts to keep V across R4 at its standard value (1.25V I think it is) If Vout is too high LM317 shuts down and draws little.current Transistor is driven on via R2/R3 and shunts Vout to lower it. If Vout is too low LM317 turns on. This draws current through R3 thereby lowereing R2/R3 centre point and turning off transistor which deshunts supply as required. The advantage of this over a zener is that it would have a MUCH sharper control knee. A zener is a truly pathetic regulator by almost any standard. R2/R3 would need to be fiddled slightly to have transistor biased about right with the current drawn by R4/R5 but this should not be hard to achieve. I would try and use the LM317 as a series pass regulator as it was designed to be unless there was some really good reason to use a shunt regulator. regards Russell McMahon -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email @spam@listservKILLspammitvma.mit.edu with SET PICList DIGEST in the body

This is a current regulator, right? I'm looking for an "adjustable power zener", a shunt regulator. Thanks though! Harold On Thu, 25 Jan 2001 09:13:50 +0200 Vasile Surducan <KILLspamvasileKILLspamL30.ITIM-CJ.RO> writes: {Quote hidden}> lm317 solution: input current to Vi pin, Vout pin connected to A > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, > this > is also output current. > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > Vasile > > On Wed, 24 Jan 2001, Roman Black wrote: > > > Harold M Hallikainen wrote: > > > > > > I have a project that involves a variable shunt > regulator (10-15V, > > > 200mA). It SEEMS that it should be possible to use an LM 317 or > 337 wired > > > in some manner to make this work, but I'm not seeing it. Anyone > see how > > > this might be done? > > > > > > You can use one transistor and a zener, this works > > very well as a shunt regulator as the zener is > > driven from the regulated output and gives a > > good precise regulation. > > -Roman > > > > -- > > http://www.piclist.com hint: The PICList is archived three > different > > ways. See http://www.piclist.com/#archives for details. > > > > > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body > > FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: dl.http://www.juno.com/get/tagj. -- http://www.piclist.com#nomail Going offline? Don't AutoReply us! email spamBeGonelistservspamBeGonemitvma.mit.edu with SET PICList DIGEST in the body

This is an ajustable power zenner like you ask for. R may be a potentiometer but must dissipate an important power if you need large current as 0.5A. It's not a tipical shunt voltage regulator. If you need to keep at precise value a potential and to use it is not too good. But if you want only to minimise dissipation power on to a load ( like a serial power supply transistor or something else ) is perfect. Vasile On Thu, 25 Jan 2001, Harold M Hallikainen wrote: {Quote hidden}> This is a current regulator, right? I'm looking for an "adjustable power > zener", a shunt regulator. > > Thanks though! > > Harold > > > On Thu, 25 Jan 2001 09:13:50 +0200 Vasile Surducan > <TakeThisOuTvasileEraseMEspam_OUTL30.ITIM-CJ.RO> writes: > > lm317 solution: input current to Vi pin, Vout pin connected to A > > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, > > this > > is also output current. > > > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > > > Vasile > > > > On Wed, 24 Jan 2001, Roman Black wrote: > > > > > Harold M Hallikainen wrote: > > > > > > > > I have a project that involves a variable shunt > > regulator (10-15V, > > > > 200mA). It SEEMS that it should be possible to use an LM 317 or > > 337 wired > > > > in some manner to make this work, but I'm not seeing it. Anyone > > see how > > > > this might be done? > > > > > > > > > You can use one transistor and a zener, this works > > > very well as a shunt regulator as the zener is > > > driven from the regulated output and gives a > > > good precise regulation. > > > -Roman > > > > > > -- > > > http://www.piclist.com hint: The PICList is archived three > > different > > > ways. See http://www.piclist.com/#archives for details. > > > > > > > > > > -- > > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > > email RemoveMElistservTakeThisOuTmitvma.mit.edu with SET PICList DIGEST in the body > > > > > > FCC Rules Online at http://hallikainen.com/FccRules > Lighting control for theatre and television at http://www.dovesystems.com > > ________________________________________________________________ > GET INTERNET ACCESS FROM JUNO! > Juno offers FREE or PREMIUM Internet access for less! > Join Juno today! For your FREE software, visit: > dl.http://www.juno.com/get/tagj. > > -- > http://www.piclist.com#nomail Going offline? Don't AutoReply us! > email listservEraseME.....mitvma.mit.edu with SET PICList DIGEST in the body > > -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestmitvma.mit.edu

Michael Rigby-Jones wrote: {Quote hidden}> > > -----Original Message----- > > From: Roman Black [SMTP:RemoveMEfastvidEraseMEEraseMEEZY.NET.AU] > > Sent: Thursday, January 25, 2001 10:56 AM > > To: RemoveMEPICLISTspam_OUTKILLspamMITVMA.MIT.EDU > > Subject: Re: [EE:] Shunt regulator? 317/337 solution > > > > Vasile Surducan wrote: > > > > > > lm317 solution: input current to Vi pin, Vout pin connected to A > > > pin of a resistor, ADJ (adjustment) pin connected to B resistor pin, > > this > > > is also output current. > > > > > > Iout = Vref/R + Iadj where Vref = 1.2V, Iadj = 50uA > > > > > > Vasile > > > > > > Hi Vasile, that is a series regulator? I think the > > person wanted a shunt regulator, and I don't think you > > can do it with a 317 as it uses negative feedback, > > not positive. :o) > > -Roman > > > It's actually a constant current source in that configuration. Been > thinking about this and I can't see a simple solution. I reckon you could > make it work with the addition of an opamp (to invert the sense of the > feedback), but then you might as well stick with a 723 etc. > > Mike As I said, a shunt regulator needs positive feedback, ie; if voltage is too high, must turn on more. The actual inversion is provided by the nature of it being a shunt reg. I really don't think you can do it with a 317, but I already posted a one transistor solution that I have used for years that is cheaper and just as simple. You are not going to get short circuit protection from a shunt reg anyway so the extra cost of a regulator chip is not justified. :o) -Roman -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu

>You are not going to get short circuit >protection from a shunt reg anyway so the extra >cost of a regulator chip is not justified. :o) I always understood that shunt regulators were inherently short circuit protected by the series impedance they need to do the regulation. If you S/C the output the current flow is limited by the impedance, and if open circuit the shunt regulator needs to be able to sink the total design load current plus what it needs to maintain regulation. -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspamspamBeGonemitvma.mit.edu

{Quote hidden}> -----Original Message----- > From: Roman Black [SMTP:RemoveMEfastvidKILLspamEZY.NET.AU] > Sent: Friday, January 26, 2001 10:04 AM > To: PICLISTSTOPspamspam_OUTMITVMA.MIT.EDU > Subject: Re: [EE:] Shunt regulator? 317/337 solution > > > As I said, a shunt regulator needs positive feedback, > ie; if voltage is too high, must turn on more. > The actual inversion is provided by the nature > of it being a shunt reg. > > I really don't think you can do it with a 317, > but I already posted a one transistor solution that > I have used for years that is cheaper and just > as simple. You are not going to get short circuit > protection from a shunt reg anyway so the extra > cost of a regulator chip is not justified. :o) > > -Roman > Agreed, even the safe operating area protection that most 3 terminal regulators empliy is wasted, if the device overheats it will stop conducting and the voltage to your device will soar, probably toasting it. Mike -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestSTOPspamEraseMEmitvma.mit.edu

On Fri, 26 Jan 2001, Michael Rigby-Jones wrote: > > -----Original Message----- > > From: Roman Black [SMTP:KILLspamfastvidspamBeGoneEZY.NET.AU] > > Sent: Friday, January 26, 2001 10:04 AM > > To: EraseMEPICLISTEraseMEMITVMA.MIT.EDU > > Subject: Re: [EE:] Shunt regulator? 317/337 solution > > > > > > As I said, a shunt regulator needs positive feedback, > > ie; if voltage is too high, must turn on more. I'm agree with this only if "regulator" means for you the final transistor of a shunt regulator. But the effect of regulation comes because of the global negative feedback. If you have a NPN driven in base from an operational amplifier you must connect +in to feedback and -in to reference to achieve a shunt regulator. Colector of the npn conected to load and balast resistor to V+. But this is not a positive feedback. Increasing output voltage level will determine the amplifier to turn on more the transistor and the final effect is the output voltage will decrease at initial value ( assuming you have a good reference ) In any language we are talking about this is negative feedback ! > > The actual inversion is provided by the nature > > of it being a shunt reg. > > > > I really don't think you can do it with a 317, Well, the ideea was to do it with a 317. Of course is neither the cheapest nor the best methode. But can be done in some circumstances. Don't shut the piano player just because you don't like how it sing ! And if you don't think make first a try. Cheers, Vasile -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-request@spam@spam_OUTmitvma.mit.edu

Alan B. Pearce wrote: > > >You are not going to get short circuit > >protection from a shunt reg anyway so the extra > >cost of a regulator chip is not justified. :o) > > I always understood that shunt regulators were inherently short circuit > protected by the series impedance they need to do the regulation. If you S/C the > output the current flow is limited by the impedance, and if open circuit the > shunt regulator needs to be able to sink the total design load current plus what > it needs to maintain regulation. Hi Alan, you may be thinking of current regulation? A shunt regulator fixes the output voltage by drawing off excess current that the load does not require, with no series resistor etc needed. If the load becomes faulty, max current is limited only by the impedance of the psu, which probably has big caps!! Normally the regulator ICs like 317 etc are nice because of the current limiting, but using one as a shunt reg will not utilise this benefit, so you may as well use a transistor. :o) -Roman -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestKILLspammitvma.mit.edu

>Hi Alan, you may be thinking of current regulation? >A shunt regulator fixes the output voltage by >drawing off excess current that the load does not >require, with no series resistor etc needed. >If the load becomes faulty, max current is limited >only by the impedance of the psu, which probably >has big caps!! Normally the regulator ICs like >317 etc are nice because of the current limiting, >but using one as a shunt reg will not utilise this >benefit, so you may as well use a transistor. :o) >-Roman sheesh - can I have your contract for heat sinks? I would not want to do this. I always understood you used a shunt regulator zener diode style with a current limiting source, at minimum a resistor which can supply the full current that is needed in the load plus a tiny bit for the regulator. Then if part of the load is switched off the shunt regulator draws more current. I have never heard of people having current limiting within the shunt regulator before. If I was doing the sort of thing you describe above I would be looking at having some form of OVP to drop the input to the supply and shut it down. the only other situation I could see where one might do it is if a minimum current draw is required to keep the voltage from going too high, like what might happen with a wall wart supply, where the transformer is being pushed to its limits and has no low current regulation. But I would not class such a device as a real shunt regulator because I would not be designing it to have high stability - again it would be a OVP current sink, but not to the full current capability of the supply, just enough to maintain the peak voltage within limits. -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestspam_OUTmitvma.mit.edu

> > sheesh - can I have your contract for heat sinks? I would not want to do this. I > always understood you used a shunt regulator zener diode style with a current > limiting source, at minimum a resistor which can supply the full current that is > needed in the load plus a tiny bit for the regulator. Then if part of the load > is switched off the shunt regulator draws more current. I have never heard of > people having current limiting within the shunt regulator before. > > If I was doing the sort of thing you describe above I would be looking at having > some form of OVP to drop the input to the supply and shut it down. > > the only other situation I could see where one might do it is if a minimum > current draw is required to keep the voltage from going too high, like what > might happen with a wall wart supply, where the transformer is being pushed to > its limits and has no low current regulation. But I would not class such a > device as a real shunt regulator because I would not be designing it to have > high stability - again it would be a OVP current sink, but not to the full > current capability of the supply, just enough to maintain the peak voltage > within limits. Hi Alan, no, with high current supplies the main regulation concern is the transformer, and to keep efficiency high it is often better to use a linear shunt reg than a linear series reg. Especially for very high currents with a definite high-low range, that is not too far apart. Like a load that always draws between 15 and 20 amps, but needs a regulated voltage. :o) -Roman -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-request.....TakeThisOuTmitvma.mit.edu