Regulator - High Efficiency

BCJKiwi

Senior Member
#1
There was recent thread (which I can no longer find) in which these regulators were mentioned but the cost was high.

Just noted the RECOM site where the prices are much less than was discussed then.

See
<A href='http://www.recom-international.com/switching_regulator_R-78xx.html' Target=_Blank>External Web Link</a>
and
<A href='http://www.recom-power.com/pages/highseller.php' Target=_Blank>External Web Link</a>

These are claimed at up to 97% efficiency so could be the answer to that high volt drop DC - DC regulator issue.

BCJ

Edited by - BCJKiwi on 01/09/2007 07:14:17
 
#2
Incidentally, it is often cheaper to make a LDO out of discrete components, eg my circuit in Silicon Chip, May 2007 (you don't really need a fet, by the way!). I'm currently working on a bi-mode (linear and switching) regulator for a picaxe that uses the picaxe itself to do the switch-mode part of the job (how, you might ask, do I get the picaxe to regulate its own power supply??).
 
#4
Looks very interesting BCJ.
For UK customers it seems that the distributor is PIV Technology in Bracknell.

I read an article suggesting a bit of extra filtering on O/P so I guess we're looking at &gt; &#163;6 for regulator. Probably a bit more expensive than a sw/mode controller plus discretes if you factor in board+assembly.

Get a sample and do some tests with a scope and meter and let us know. I'm quite a fan of sw/mode for battery stuff. But I don't tell that to people down the pub.
 

BCJKiwi

Senior Member
#5
Maitchy - interesting.

I was simply intending to update those interested in the previous post with new pricing they may have missed.

There appears to be as many ways to build a power supply as there are ways to skin the proverbial cat.

It may be a simple and cheap solution for you if you have the knowledge, resources and components to hand. But for those of us who are more interested in the other end of the process - i.e. the programming and problem solving to get a picaxe to accomplish the task(s) required, then there can be merit in sourcing a tried and tested component to do the job of supply.

I however, as also would many others I am sure, be interested in how you achieve what appears to be the nirvana of the electronic equivalent of perpetual motion - to get a picaxe to regulate its own supply voltage while at the same time having sufficient program space and resources left over to do the work you wanted the picaxe for in the first place (while handling all the saftey issues etc etc) and all for less than it costs for the standard part.

So please - enlighten us.

BCJ

Edited by - BCJKiwi on 01/09/2007 13:58:59
 
#6
LV power supplies are becoming something of an obsession with me, so please bear with the rant...

I can see how you might use a picaxe to control its supply with some diode isolation, am I getting warm? (US idiomatic expression &quot;am I getting close?&quot;)

The downside as I see it; you still have to meet the minimum start voltage unless you take advantage of that slow oscillation that the picaxe goes into with low battery voltage? (in the old days that was called &quot;motor-boating&quot; and occurred in audio amps when the output caused the power supply to dip below the bias points of the toobs or transistors)

Another downside, is if it is self regulating and working to boost voltage you might be burning more power than saving - keeping the voltage as low as possible saves power, but it depends on a lot of variables and circuit considerations.

I would like to see what you are doing along those lines since I'm working at 3V power and having to isolate the picaxe with a germanium diode and cap to keep it working when the loads pull current.

Both Maxim and Analog Devices make a range of regulated buck-boost converters that work at voltages from 2.2 to 5+V (out) (~1.1 - 1.8V in). The parts are in the $2-4 price range and they sell sample lots directly to the consumer. One has a .4 amp 8 pin dip package, and the other a 1.7 amp 8pd package but requires an external diode, logic level mosfet, and cap.

Actually there are tons of great buck-boost converters available - I'm limiting my searches to 8 pin dip devices since my eyesight isn't as great as it was. The slew of cell phones, digital cameras, mp3 players,some usb toys,laptops, etc.. use them.

Efficiencies in the 97% range. Efficiency is usually dependent on the temperature, load and supply voltage, so saying 97% is not accurate - one needs a graph.
 
#7
Nice component from Revcon. Unfortunately a bit pricy ~10 US. Worth a look though, for special applicatios.

Obsolete cell phone chargers are a great source of self contained 5 volt power supplies.

Myc

Edited by - mycroft2152 on 01/09/2007 16:37:52
 

boriz

Senior Member
#8
Dippy. &#8220;I'm quite a fan of sw/mode for battery stuff. But I don't tell that to people down the pub.&#8221;

LOL. I sometimes try to discuss electronics with friends. It&#8217;s nice to have someone to chat with about my hobby. But the glazed looks get me down.
 
#11
BCJ: Honest mate, if you're going to correct all typos and smelling mistakes on this Forum then you'll have a full-time job.
;-)

Anyway, bottom line, it's hores-for-courses innit. If you want small or you want to have a production run then you buy ready-made. If you want to save a couple of pennies and size isn't an issue(!) then you'll buy an i.c. and discretes.
But, if it's educational or you like the challenge or you're tight or insane then you build it from scratch.
If it's the last one then well done, I've done it myself. But don't come back here saying there's a bit of a problem on transients.

Smell you later.
 
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