Efficient voltage stabilization

[Sigmoid]

Hey,

I'm quite familiar with the voltage stabilizer designs based on Zener diodes, but I'm a bit confused by their power implications...

Say, I have a voltage source (battery), which will provide me with "something around 12V". The battery charge degrades over time, and I need stable 5 Volts for sensitive stuff.

So I implement a voltage regulator with a 5V Zener. Now, this involves adding a resistor to the positive terminal of the battery, in order to limit the Zener current, and create the voltage divider... but this seems like an issue.
If I make the resistance too low, I'll be bleeding Watt-hours from my ass (sorry), and have a bad heat problem to boot. If I make the resistance too high, I won't have enough current for the actual load!

Is there a more efficient way of regulating voltage?

[mariush]

Yes, use a low quiescent current low drop linear regulator if your sensitive stuff only needs a few mA.
Use a high efficiency switching regulator if you need more current.

[IanB]

What mariush said, but why are you even considering a zener diode for this application? The immediate thought should be "voltage regulator" and then look up a part like the 7805 or equivalent...

[awallin]

don't mix these two:
a) voltage regulator: reasonably stable voltage, meant for supplying current to a device
b) voltage reference: very stable voltage, but almost no current sourcing capacity

a Zener might sometimes be OKish for use b) but very seldom for a)

[edavid]

Yes, use a low quiescent current low drop linear regulator if your sensitive stuff only needs a few mA.
Use a high efficiency switching regulator if you need more current.

Aren't those kind of expensive?  A zener is a simple and cheap solution if your load is in the 1-20mA range.  That's especially true if you need to create a split supply from a single supply... just stack 2 zeners.

[c4757p]

On one hand, I'm squarely of the belief that Zeners are hugely underrated. They're quite good little regulators when you have a small-ish, constant-ish load, and they're cheap as, well¸ diodes. "Small-ish, constant-ish loads" are common in analog applications.

On the other hand, this is a battery application, perhaps a low quiescent current series regulator would be better.

On the gripping hand, we don't know what kind of battery this is, perhaps a quiescent handful of milliamps through the diode is nothing at all.

5V to me suggests digital, though. Consider a low quiescent current buck converter.

[Sigmoid]

Use a series regulator. The type of regulator you are talking about is called a shunt regulator. Shunt regulators are good when you know the load as well as the line voltage inefficent for varying line or load. Shunt regulators will dissapate any power not consumed by the load.

http://electriciantraining.tpub.com/14179/css/14179_207.htm

Thanks, this design seems quite adequate, as in not bleeding power all over the place, and being reasonably cheap as well: http://electriciantraining.tpub.com/14179/css/14179_210.htm

There's a lot of these practical cookbook designs that I don't know.

[madires]

Thanks, this design seems quite adequate, as in not bleeding power all over the place, and being reasonably cheap as well: http://electriciantraining.tpub.com/14179/css/14179_210.htm

Adding a cap in parallel to CR1 would improve the regulation.

[sleemanj]

Is there a more efficient way of regulating voltage?

A buck converter (step down DC-DC converter). 

Search eBay for LM2596 you'll find very cheap modules (like this one, just the first one that came up: http://www.ebay.com/itm/1pcs-DC-DC-Buck-Converter-Step-Down-Module-LM2596-Power-Supply-Output-1-23V-30V-/251066005460 ), your 12v goes in one end, twiddle the pot until you get 5v out the other. 

Far far FAR more efficient than a linear regulator (or zener shunt), which is quite important if you're running off battery.

[txescientist]

Hi,

Why don't you use low dropout regulator like LF50CV. It is much better than 7805 in battery operated circuits in case you don't want switching regulator. http://www.datasheetcatalog.com/datasheets_pdf/L/F/5/0/LF50CV.shtml