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How can I stabilize a 12V input to a 12V stabilized output voltage?

I have a battery that supplies 12V but not regulated and a device that uses 12V regulated, how can I supply power to that device using thus battery?

EDIT

I just searched on the subject a bit more and found a part called a "zener diode" it seems from a quick reading on Wikipedia to do what I want, make an unclean 12V to a regulated 12V. but I'm not sure. Can someone please clarify if this is in fact what I want?

My "needs":

12V @1A from a ~12V lead acid battery - can go down to 8V - to an XBOX Kinect.

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  • \$\begingroup\$ Does the device have to be treated as one big load? Or is it possible that some of the device internals need precise 12V, whereas other parts can run off unregulated voltage? If the parts that need exact voltage have a low current draw, you can take advantage of that. \$\endgroup\$
    – Kaz
    Oct 7, 2013 at 18:59
  • \$\begingroup\$ Is this for a robot that has a 12V accu and 12V motors, and the motors must always have an accurate 12V? Ditch your system designer! Instead use an accu with a higher voltage than the motors, and use a PWM to get constant motor power. \$\endgroup\$
    – Wouter van Ooijen
    Oct 7, 2013 at 19:07
  • \$\begingroup\$ Batteries are very well self-regulated. Their voltage will only change according to the load, and will steadily decline as power is removed. Are you sure you need to "regulate" the voltage at all? What are your exact requirements? What sort of load(s) will be connected? Does the supply voltage need to remain at 12V over the entire useful lifespan of the battery? Are you expecting large current draws that you need to keep from reducing the voltage momentarily? \$\endgroup\$
    – Peter Bierman
    Oct 7, 2013 at 19:19
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    \$\begingroup\$ You want to check the current rating for the XBOX device. I think that will rule out couple of the answers below. A simple zerer for example won't help you here. \$\endgroup\$
    – jippie
    Oct 8, 2013 at 5:16
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    \$\begingroup\$ Your spec is self contradictory. Apparently re minimum allowed Vin to Kinect you say in one place "can go down to 8V" and in another "and the device need precise 12V all the time". What is the complete actual spec please. Vin min allowed, Power, ... . If Vbattery_min - Vload_allowed_min is > about 0.5 V you can use a linear LDO regulator. If Vbatmin < 12V and Vloadmin = 12V a boost converter is in order. It may be simpler and effective to use an inverter which is either pass through or boost followed by an LDO linear regulator. \$\endgroup\$
    – Russell McMahon ♦
    Oct 8, 2013 at 9:36

5 Answers 5

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This looks like a good target for a SEPIC or Buck boost converter, which can allow an output voltage higher, lower or the same as the input voltage

Zener diode only limits the voltage. If the output is 11.6V, the zener diode will not do anything.

You didn't specify your current requirement, so its hard to give you a part as a starting point.

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  • \$\begingroup\$ Yep, buck-boost or sepic. Boost won't help unless the voltage drops to less than 12V. \$\endgroup\$
    – gsills
    Oct 7, 2013 at 19:00
  • \$\begingroup\$ I can't find SEPICs on eBay, so if you can link me to one that'll be great. I found this Buck Boost Converter (basically a stabilizer) would this fit my needs? (12V @2A from a ~12V battery - can go down to 8V - to an XBOX Kinect.) ebay.com/itm/… thanks for all the help :-) \$\endgroup\$
    – Dan Barzilay
    Oct 7, 2013 at 20:08
  • \$\begingroup\$ @DanBarzilay: It looks good. A bit unclear on output voltage specs but if it is 12V out, it should be good for what you need as long as form factor isn't an issue. I'd test it thoroughly before using it in anything long term though. \$\endgroup\$
    – Gustavo Litovsky
    Oct 7, 2013 at 20:18
  • \$\begingroup\$ How would you suggest to test it \$\endgroup\$
    – Dan Barzilay
    Oct 7, 2013 at 20:24
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    \$\begingroup\$ @DanBarzilay: Well its mainly testing the specs. So I would apply 8V to it, then draw 3A and run it making sure that it works. Then Apply more than 12 V(40V if you have but perhaps its over kill), then draw 3A and make sure it works. If it fails, then it won't meet spec. If you are using it in any kind of harsh environment, also test over temperature. \$\endgroup\$
    – Gustavo Litovsky
    Oct 7, 2013 at 20:28
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A boost switching regulator can increase the battery voltage high enough for a buck switching regulator to bring it back down to a regulated 12V. It won't have the efficiency of, say, just a large capacitor, but it will be regulated as closely as part specs allow.

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  • \$\begingroup\$ That's what I'd do. \$\endgroup\$
    – Andy aka
    Oct 7, 2013 at 18:41
  • \$\begingroup\$ Efficiency is quite important actually, the battery and device are placed on a robot which I want to have the longest battery-life possible. That is why I canceled this idea, Thanks a lot for answering though :) \$\endgroup\$
    – Dan Barzilay
    Oct 7, 2013 at 18:41
  • \$\begingroup\$ Then start with a higher voltage battery and use the buck regulator alone. \$\endgroup\$
    – Ignacio Vazquez-Abrams
    Oct 7, 2013 at 18:42
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    \$\begingroup\$ A buck-boost converter is NOT two converters in one package, it is a 'combined topology'. The main disadvantage is that it inverts polarity. That might not be a problem here. \$\endgroup\$
    – Wouter van Ooijen
    Oct 7, 2013 at 19:05
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    \$\begingroup\$ No. Two converters means two steps, each with power loss. A buck-boost converter is a single step: one switch, one inductor, one diode. \$\endgroup\$
    – Wouter van Ooijen
    Oct 7, 2013 at 19:16
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There is two simple options. The first is checking to see if that 12v regulated part actually uses or needs 12v. If it regulates down inside and only uses the 12v into a regulator, modify that, or figure out the tolerances/dropout it needs and work around it.

Otherwise, you can use a boost converter. Assuming the 12v battery never goes beyond 12.7v (typical max charge of a 12v battery), the only way to go is down. A Boost converter with passthrough region or feature is your best bet. If the VIN voltage is at 12v, it simply allows it to pass through without regulation. Once the voltage drops, it starts to regulate it up to 12v.

Update: Since you are going for a Kinect, as shown here the Kinect can still work from an input voltage lower than 12v. So you would not need to have a steady regulated 12v rail unless you need it for something else.

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  • \$\begingroup\$ In many cases, people will be charging the battery at the same time as they are placing a load on it - so the voltage reaching 14 volts is plausible. \$\endgroup\$
    – frodeborli
    May 27, 2017 at 14:19
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Yes, you are right!

Because of the low difference of voltage between the input and output, you can't use a ic for to regulate the voltage like the 7812. But maybe you can use a Low-dropout regulator.

So you can use a zener diode to control the voltage. But it will only regulate the overvoltage, so if the voltage drops 12V you will need a big capacitor to mantain the voltage.

A batery normally the voltage will be under 12V not, over 12V, so this probably its not a good idea to stabilize the output voltage.

Vin > Vz -> Vout = Vz

Vin < Vz -> Vout = Vin

schematic

simulate this circuit – Schematic created using CircuitLab

Vz = 12V

R1 = (Vin - Vz) / I

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    \$\begingroup\$ Your answer only applies if battery voltage is above 12V. This may/may not be the case. \$\endgroup\$
    – Gustavo Litovsky
    Oct 7, 2013 at 18:54
  • \$\begingroup\$ There are three-terminal voltage regulators which can work with a lower voltage difference than the 7812. They are called low drop-out regulators, or LDO. \$\endgroup\$
    – Kaz
    Oct 7, 2013 at 18:58
  • \$\begingroup\$ @GustavoLitovsky Yes, I know, but its what Dan Barzilay asked. And I explained in the answer about this. \$\endgroup\$
    – Butzke
    Oct 7, 2013 at 19:02
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I found something rather affordable that can do the trick if I didn't screw up. It's a stock built Buck stabilizer. Maybe it can help you?

https://www.amazon.com/Yeeco-Regulator-Converter-Converters-Adjustable/dp/B00XM8SM66/ref=sr_1_11?s=electronics&ie=UTF8&qid=1492180208&sr=1-11&keywords=dc+power+regulator

Just be sure NOT to plug any standard USB device into the USB outlet when you have it set for anything other than 5V. The USB port voltage is the same as the voltage at the output wire coupler.

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