10A 1.2-45V power supply schematic - Page 1
Forum section: electronics / general

author: uranium235
author_rank: Contributor
timestamp: June 14, 2010, 04:39:08 pm
content: guys im looking for 1.2-45V 10A linear regulated power supply with current limit and short circuit protection schematic tnx

author: Unknown
author_rank: Unknown
timestamp: June 14, 2010, 05:27:46 pm
content: Take any good linear bench supply schematic, make sure the power transistors and other related components can withstand the 55V or so input voltage, and put a bunch of power transistors in parallel (might have to increase the base current). Note you will need some serious cooling (1.2V at 10A is more than 500W of dissipation!). Using a 2x20V transformer and switching the second winding off below 20V or so will halve that, but ~270W is still a lot).

author: sigxcpu
author_rank: Regular Contributor
timestamp: June 14, 2010, 08:26:57 pm
content: Hm, I don't understand.First, 1.2V@10A cannot be >500W. Maybe 45V@10A comes closer.Second, why do you consider that the power dissipatedequalsthe power created? Then what is left for your consumer, this being the first reason for building a supply?

author: Unknown
author_rank: Unknown
timestamp: June 14, 2010, 08:37:59 pm
content: I was talking about a linear supply (which was the original question). A linear supply decreases the voltage by converting the rest to heat. So a 50V input with a 25V output means 50% of the energy is converted to heat. With 55V input (estimate for 45V output, depends on the voltage drop over the power transistors) and 1.2V output at 10A, this would mean (55V-1.2V) * 10A is converted to heat. So in the worst case scenario (10A in a dead short), dissipation is almost equal to the maximum power (minus a few hundred mV or so over the short times the current).

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: June 14, 2010, 09:04:18 pm
content: Lets see some real facts ..This is an 35V 10A ... check out the Fuse rates VS input voltage , so to realize that this devices are not cheap toys.

author: saturation
author_rank: Super Contributor
timestamp: June 14, 2010, 10:05:03 pm
content: Those Kenwood PSU are all Japanese good supplies. Expensive to get here, used to be the 'cheapo' PSU in Asia before China and when the US dominated the test equipment market.Updated model still made today.http://www.tequipment.net/KenwoodPD36-10A.htmlQuote from: Kiriakos-GR on June 14, 2010, 09:04:18 pm

author: Unknown
author_rank: Unknown
timestamp: June 14, 2010, 10:09:53 pm
content: Yep, that's some real cooling. Something like that (with a really powerful fan) would probably suffice.

author: uranium235
author_rank: Contributor
timestamp: June 15, 2010, 07:15:00 am
content: i know that it would produce much heat when dropping the voltage im designing the entire case as a heatsink and high power fans 12v @ 0.9Aim currently looking into switching regulators as my other option and the availability of the parts localy

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: June 15, 2010, 07:17:37 pm
content: Quote from: saturation on June 14, 2010, 10:05:03 pmI think that you over reacting ...The only place that the American test equipment, have some acceptance , are in the U.S.A. continent ..I think that you are an over passioned with your flag ..And even if the Americans like to believe that they got first on the Moon , all the planet are aware of,that the Russians did it first ..About the Kenwood PSU , its one indestructible monster , very heavy even to lift ,every five years or so , I open it up and just blow the dust away ..The specific model , as it looks at the back of it , it has extra outputs , and extra connectors ,so to operate it remotely , or by external potentiometer .Its called as specialized for laboratories , because its made for 24/24 365X what ever .. operationIf you build a bulb , you can test it for how many thousands of hours it will keep working , with this PSU.With all this facts in mind , the 1.500$ , its a fair price for it.

author: kc1980
author_rank: Regular Contributor
timestamp: June 15, 2010, 08:03:30 pm
content: I'm no circuit design expert, but I was in the middle of designing a linear power supply for myself with those specs. I'm planning to use a variac transformer to limit the power dissipation during low voltage / high current situations. It does make the unit somewhat bulky and inconvenient to handle but I think it's worth it.

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: June 15, 2010, 08:54:39 pm
content: Quote from: kc1980 on June 15, 2010, 08:03:30 pmYour main enemy are the ripple , and the stability.If you deal somehow with that , the rest part has lower difficulty .

author: Zad
author_rank: Super Contributor
timestamp: June 15, 2010, 09:08:43 pm
content: Many linear-only PSUs use a transformer with a multi-tap output winding (say 5v, 10v, 15....) which is usually switched in by relay. This clearly reduces the maximum amount you have to dissipate from the regulator transistor. Another increasingly popular method is to use a switched mode PSU to pre-regulate it, then follow up with a linear regulator.

author: saturation
author_rank: Super Contributor
timestamp: June 15, 2010, 09:35:56 pm
content: In 1980s Kenwood was a well known superb brand but low cost when it was known by its older name Trio, then Trio-Kenwood. After it became Kenwood, all their test equipment prices just flew. Trio was very popular in the Pacific, great quality, low cost.http://www.fundinguniverse.com/company-histories/Kenwood-Corporation-Company-History.htmlIn the 1980s, a number of at least, I recall, BK Precision gear was rebadged Trios.http://www.picbasic.co.uk/forum/showthread.php?t=7019&s=8bb42a46c747e65f3dde96e42b571426&p=43307#post43307Today, they are a big name, some of their budget gear could be rebranded Mastech while the true made in Japan ones are the top of the line.Quote from: Kiriakos-GR on June 15, 2010, 07:17:37 pm

author: Kiriakos-GR
author_rank: Super Contributor
timestamp: June 15, 2010, 10:34:03 pm
content: Quote from: saturation on June 15, 2010, 09:35:56 pmDo not ever , travel me that far back ... I loose my orientation, and I became unstable

author: Zero999
author_rank: Super Contributor
timestamp: June 16, 2010, 10:04:43 pm
content: If you use a transformer with a centre tap, you can draw the power from the centre tap when the output voltage is low which will save power dissipation in the power transistors.For example, for 45V, use a transformer with twin 18V secondaries connected in series, when the output voltage is set below 18V draw the power from the centre tap and when the output voltage is set above 19V (there needs to be some hysteresis to avoid oscillation) draw the power from both windings.If you're able to wind your own transformer, you could use many voltage taps to save even more power, for example if you have a tap every 9V you can limit the voltage drop across the transistors to 12v.

author: uranium235
author_rank: Contributor
timestamp: June 17, 2010, 04:03:57 am
content: so i would be very hard to drop the votlage at 45v to 1.2v and would waste alot of heat dropping the voltage?

author: Unknown
author_rank: Unknown
timestamp: June 17, 2010, 05:20:04 am
content: Dropping the voltage isn't that hard, but the current means you need a bunch of power transistors in parallel, and it will generate lots of heat.

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2010, 11:23:11 am
content: Quote from: uranium235 on June 17, 2010, 04:03:57 amYes it wastes a lot of heat but you shouldn't need to drop 45V down to 1.2V.

author: uranium235
author_rank: Contributor
timestamp: June 17, 2010, 02:18:19 pm
content: Quote from: Hero999 on June 17, 2010, 11:23:11 ami think it wont heat to much if your load @ 1.2v required is minimal peferably 0.5A to 1A

author: Unknown
author_rank: Unknown
timestamp: June 17, 2010, 10:47:57 pm
content: Sure, if you limit the current at lower voltages (combined with the trick of multiple transformer windings), you can limit dissipation. I would want some sort of limit, so you can't accidentally set it too high at low voltage.

author: uranium235
author_rank: Contributor
timestamp: July 08, 2010, 05:43:55 pm
content: since i cant find a schematic i decided to design one based on the typical aplication figure 2. on the datasheeti aready done it in simulation using proteus it work finethe problem is LM723 R4, RV1 R5 heats upim thinking on R4, RV1, and R5 ive use low wattage resistor and too much current at LM723the voltage at lm723 is at 33-34v ive change 1N4751 to 1N4752im still thinking other possible problemif anyone notice any problem on the circuit please postheres the data sheethttp://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS008563.PDFschem

author: Zero999
author_rank: Super Contributor
timestamp: July 08, 2010, 06:04:35 pm
content: Q1 to Q6 don't have any emitter resistors which are required to ensure good current sharing.

author: NiHaoMike
author_rank: Super Contributor
timestamp: July 08, 2010, 10:46:51 pm
content: Use a buck converter, either by itself or as a preregulator.

author: uranium235
author_rank: Contributor
timestamp: July 09, 2010, 04:02:53 am
content: Quote from: Hero999 on July 08, 2010, 06:04:35 pmi already done that when i build the circuit i just forgot to put it in the diagram ive use 1 ohm 5watt per emitterQuote from: NiHaoMike on July 08, 2010, 10:46:51 pmits a good idea but im minimizing the use of components

author: Zero999
author_rank: Super Contributor
timestamp: July 09, 2010, 08:24:06 am
content: A buck converter would probably be smaller and possibly cheaper when the size of the heat sink is taken into account.Modern SMPS controllers also require minimum components, even less than the above circuit.

author: RayJones
author_rank: Frequent Contributor
timestamp: July 09, 2010, 10:17:22 am
content: If you're pushing 10A @ 1.2V the only sensible approach is a buck regulator.Otherwise your dumping 450W+ into the heatsinksI'm actually playing with a MPPT circuit at the moment, and I keep getting the supply going into thermal shutdown at a lowly 2A (40V capable unit).I'd Love a switcher right now(other than the one I'm working upon within the MPPT)

author: uranium235
author_rank: Contributor
timestamp: July 09, 2010, 10:18:41 am
content: although SMPS has alot of advantages over linear type but the parts are not available locally that makes parts much expensive buying it online, probably twice the price of each component in my circuit and i don't have much knowledge about SMPSs.