Linear Technology DC2132A CV&CC Adj. Bench Power Supply Board - Page 1
Forum section: electronics / projects

author: BravoV
author_rank: Super Contributor
timestamp: September 22, 2014, 04:04:04 am
content: Spotted at Linear Technology Journal, the DC2132A Adjustable bench psu board released in May 2014, I think size wise is quite nice, and also it has switching pre-regulator with linear front end of course.Efficiency wise stated in their spec sheet with Vin = 36 Volt & Vout = 3.3 Volt @ 3 Amp is at 60%, not bad at all isn't it ? While with Vin = 12 Volt & Vout = 5 Volt @ 3 Amp is reaching 70% with approx < 7 Watt of power loss.All details like the schematic, manual, performance tests like transient responses (overload included) and etc with claimed ripple < 20 mV at 60 uF Cout.Details of DC2132A product page here ->Linear Technology DC2132A - 24V 3A Constant Voltage, Constant Current Bench Supplyordirectly at the details & performance page (PDF) ->High Performance Portable DC Bench PS : Save Money and Free Up Bench Real Estate by Building Your OwnPrice ? $200 a pop.Obviously they had to use all LT's made chips, its just really like to hear our resident experts here about this circuit design or a discussion about it.

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 22, 2014, 08:09:19 am
content: Looks very nice.I have used the lower power LT8614 in a design and that one really preforms well.If u add two simple voltage displays to the output and Imon u can even monitor your settings. Very nice.Add a transformer (or a black box input), a output on/off/set switch and u can make a nice little kit. Let me now if u need someone to design the board.

author: nowlan
author_rank: Frequent Contributor
timestamp: September 22, 2014, 09:27:47 am
content: I would say spin up some boards, $200 too rich. I think the soldering is not very fun for a kit.I always wonder why no one has cloned the older HP power supplies.

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 22, 2014, 09:38:03 am
content: Quote from: nowlan on September 22, 2014, 09:27:47 amTrue, I meant a kit as in a custom assembled pcb with a housing etc.

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 10:25:31 am
content: Hmm, this looks nice. I'm thinking it would be easy to get uC control by adding a dual OpAmp and dual DAC. Use that in place of the pots on SET and ILM.In the schematic they show an INTVCC rail but don't provide a source for it. I guess you need to have a seprrate converter to power everything?Sent from my Smartphone

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 22, 2014, 10:29:51 am
content: Quote from: timb on September 22, 2014, 10:25:31 amIntVCC is generated from the LT8614

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 11:13:51 am
content: Quote from: DutchGert on September 22, 2014, 10:29:51 amAh, okay, good catch!Sent from my Smartphone

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 11:47:15 am
content: Those LT3081's look pretty neat!It looks like the Vset pin sources 50uA of current and is typically set by a single resistor.So I'm trying to figure out the best way to put this under MCU control. The issue I see is that this current + resistor is used to set a voltage on the non-inverting input of the internal error amplifier. It seems this set voltage is equivalent to the desired output voltage, I.e. If you want 5V, you'd use a 100k resistor (50uA * 100k = 5V).If you had a current DAC that could sink or source current, I'm thinking you could set it up so that when it's supplying 0uA the output voltage would be 12V (based on the regulators internal 50uA source, so you'd use a 240k resistor), then you'd use the DAC to inject or absorb more or less current to change the voltage from 0 to 24 volts.It's late and I'm most likely over thinking this, I'm sure. Would love to hear ideas though.Sent from my Smartphone

author: pelud
author_rank: Regular Contributor
timestamp: September 22, 2014, 09:07:41 pm
content: Quote from: timb on September 22, 2014, 11:47:15 amI'm not sure how well it would work, but what about just having an op-amp drive a transistor with the voltage at the set point as the feedback?

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 09:36:14 pm
content: Interesting. Where is the 1.2V, 50V and 12V coming from?

author: pelud
author_rank: Regular Contributor
timestamp: September 22, 2014, 09:45:21 pm
content: Quote from: timb on September 22, 2014, 09:36:14 pmThe 50V would be the unregulated input going to the LT3081, the 1.2V is an example set-point voltage coming from the micro (via a DAC or maybe PWM + RC filter?), and the 12V is the voltage going to the SET pin. If you load the .txt file into thefalstadcircuit simulator you can play around with the set-point via the voltage slider on the right. The 50uA current source is of course the one built into the regulator between the input and the SET pin.

author: rdl
author_rank: Super Contributor
timestamp: September 22, 2014, 10:33:34 pm
content: I'm not saying this isn't a nice board and I'm probably wrong about this, but it seems like it's way over-priced.I see just 5 ICs and a handful of passive components, and the ICs are made by the same company selling the board. They sure aren't paying retail price for them.I've bought a number of other dev boards and such of equal or higher component quantity for 1/3 to 1/2 the price of this one, and I'm not talking about from China either. Obviously I must be missing something here.

author: dannyf
author_rank: Super Contributor
timestamp: September 22, 2014, 11:15:35 pm
content: Nothing unusual.The switching regulator is configured to drop a constant voltage over the regulators, vs. the ground. I mentioned this as one efficient way to deal with heat dissipation in one of the power supply threads.

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 11:50:39 pm
content: It’s basically a Dev Board, and like all Dev Boards (TI’s LaunchPad’s aside), there’s an arbitrarily high cost associated with it. I’ve found you can get these type of things for free if you just ask a lot of times.Anyway, the benefit here is that the schematic and BOM is available, so recreating it won’t be hard. I wish Gerbers or CAD files were provided though. (That’s one thing I *LOVE* about TI. They provide CAD, Gerber, PDFs, Source Code, pretty much everything for a large number of their boards.)Edit: Wait, here we go:http://www.linear.com/docs/44898Full Schematics, PCB, Gerbers… Nice!

author: timb
author_rank: Super Contributor
timestamp: September 22, 2014, 11:53:37 pm
content: Quote from: pelud on September 22, 2014, 09:45:21 pmAh I see now. The image was loading at low resolution for me (it’s fine now) so it made it hard to see exactly what was going on.Seems like a very sane approach. I’ll do some more advanced simulations with it on the full circuit.The other issue I see for a bench top version is that if you’re simply using a transformer and rectifier on the front end to power it (120VAC to 36VAC @ 3A), that’s going to be a pretty big transformer I imagine…I wonder how well this would run with a boost converter in place of the buck. Might be a good option for a battery powered portable supply.

author: timb
author_rank: Super Contributor
timestamp: September 23, 2014, 12:39:52 am
content: Quote from: AcHmed99 on September 23, 2014, 12:32:24 amYeah, after my post I started looking. At $35 for that transformer,you’d be better off just getting one of these.It’s hard to find laptop bricks at that voltage/current rating it seems like. I did manage to find one, but it’s only 36V@2A.Something else they mention in the manual is that you can add a third linear regulator to bump the output to 4.5A; but I’m finding that when you get past 150W or so with those Chinese AC to DC supplies, they start getting very big and have fans, which defeats the purpose entirely.Anyway, that 120W supply I linked above looks like the ticket. I’d have to change the capacitors out and verify the clearance was okay, but it’s not putting out a tremendous amount of power, so I don’t think *that much* can go wrong, so long as it’s safe.

author: dannyf
author_rank: Super Contributor
timestamp: September 23, 2014, 12:45:56 am
content: QuoteThat's why having the pre-regulator referenced to the output is so incredibly important: in this case, the voltage the linear regulators are dropping is just 1.7v, regardless of the output voltage.Jung has the same concept in his regulators.

author: timb
author_rank: Super Contributor
timestamp: September 23, 2014, 01:38:24 am
content: Quote from: dannyf on September 23, 2014, 12:45:56 amEither way though, *something* has to power the pre-regulator. Now, what might interesting is to use the AC/DC SMPS itself as the pre-regulator. Normally they use a TL431 or other shunt based reference to do the regulation, so you’d just have to inject in to that and you could stay in regulation and 1.7V above your output.The issue I can see with this, however, is that fact that most of these AC/DC SMPS designs are using an isolation transfer with a turn ratio that’s specific to the output (obviously). As you start lowering the voltage, the output side rectification diodes are going to be blocking more and more energy, which means they’re going to heat up pretty quickly. You’ll also be lowering your duty cycle, which means a bigger output capacitor will be required, which means worse load regulation… You also might have flux issues in your transformer at very low duty cycles. Synchronous rectification could solve some of this. Combine that with a multi-tapped transformer and a very smart SMPS controller and it could work I suppose.

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 23, 2014, 06:11:22 am
content: These boards are never meant to go into big production. Just a way for Linear to show of there components.Btw, they not always cost a lot, after showing interest in one to my local Linear rep he just told me one is coming my way free of charge. I love Linear for that.

author: BravoV
author_rank: Super Contributor
timestamp: September 23, 2014, 06:35:11 am
content: Quote from: DutchGert on September 23, 2014, 06:11:22 amYep, this is intended as sales & promotional item for their customer for free, I guess LT deliberately put that kind of price tag just to piss off potential retail buyers.Please do some torture review once you have it in your hand.

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 23, 2014, 06:42:02 am
content: Quote from: BravoV on September 23, 2014, 06:35:11 amWill do

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 23, 2014, 07:51:34 am
content: I am thinking of brewing up a schematic combining this with some proper SET and OUTPUT ON/OFF circuitry and combining it with a ideal diode bridge (LT4320), a nice torroid transformer (80VA 2x12V Transformer) and some proper input protection to make a nice 'Green' linear PSU (as far as u can call a linear psu green ofc).

author: kt315
author_rank: Regular Contributor
timestamp: September 24, 2014, 04:29:22 am
content: I was quite curious about this schematic as well. I have no doubt LT does not pay nearly close to $200 for the boards, but ...I loaded the BOM into digi-key. There are quite a few costly components on the list aside from the LT parts + 4 layer board. I was in fact quite surprised by the cost of some passives they are using.I probably will try to build one of these for entertaining/educational purposes, I'd be surprised if it would be less than $100 in cost for single quantities.The switcher chip seem to be PITA to solder (at least at my level of experience).

author: DutchGert
author_rank: Frequent Contributor
timestamp: September 24, 2014, 07:42:45 am
content: Quote from: kt315 on September 24, 2014, 04:29:22 amTrue, they use quite a bit of odd-valued/rare components. It clearly was design't as a show-off of there parts.That said, I like the design as they present it so perhaps it can be made into something rela nice. Especialy if u add another 3081 so u have 4,5A output which makes it more useful in the lower voltage ranges.

author: DutchGert
author_rank: Frequent Contributor
timestamp: October 08, 2014, 02:19:41 pm
content: It took a bit longer than expected but I had a go at testing the board.So far it performs really nice.Power consumptionIdle load @ 35VIN, no output connected = 17mAPowerIn @ 35VIN, 3V3 3A Out = 35V x 470mA = 16,45WPowerOut @ 35VIN, 3V3 3A Out = 3,3V x 3A = 9,9WPloss = 16,45W - 9,9W = 6,55Wn = ~60%Temperature LT3080 @ 25C Amb@ 35VIN, 3V3 3A Out:Temp 1 = 0,63VTemp 2 = 0,65VLoad regulation (on output terminals)@ 35VIN, 3V3 3A Out :Vout no load = 3,30VVout full load = 3,28VNoise and transient responseNoise no load: ~10mVNoise 3A load: ~28mV0-3A Transient response overshoot: ~160mV3-0A Transient response undershoot: ~316mV

author: szolusha
author_rank: Newbie
timestamp: April 30, 2015, 05:06:41 pm
content: Hi folks,This is a demonstration circuit meant to show off the ability of the parts. It is not meant to be mass produced and sold by LTC.We provide the files, schematic, etc. to you so that you can go and produce your own. BOM cost for somebody doing this might be sub $50.We are not making money off of these boards since we put a lot of engineering time and gathering of small number of components (as well as assembly and testing).Instead, these boards are provided as demonstration of what you can build on your own. If we set the price as low as the BOM, then some places come in and sweep up 50 boards and we run out of stock, forcing us to remanufacture small amount of boards, making it hard for those interested in producing their own to get his/her own demo.If you want samples of this, get in touch with your local sales office. Thanks for looking at the board.LTC parts traditionally are very high performance.I wrote the LT Journal article on the bench supply demo to give you as much information as possible.On the schematic, INTVcc is generated by the LT8612. It does not need an extra supply to get this rail. I am sorry if you did not catch that in the schematic.K Szolusha

author: prasimix
author_rank: Unknown
timestamp: April 30, 2015, 09:49:36 pm
content: Quote from: DutchGert on October 08, 2014, 02:19:41 pmThanks DutchGert for sharing. Is it possible to provide how Vout looks like during power up and power down in CV mode with and without load, and in CC mode?

author: dadler
author_rank: Unknown
timestamp: July 17, 2016, 07:41:05 pm
content: Sorry to bump an old thread-I'm trying to fully understand this circuit. It seems that the LTC3632 is configured as a constant current load that can pull the output below ground--to satisfy the minimum load requirements of the LT3081s.Is this correct? If so, is there a simpler way of doing this and still maintaining 0v output? It seems complex to introduce an entire additional switching regulator just to satisfy the minimum load.Thanks

author: parasole
author_rank: Contributor
timestamp: July 17, 2016, 09:26:42 pm
content: In my understanding you still need to have negative supply, regardless how do you provide it...

author: dadler
author_rank: Unknown
timestamp: July 18, 2016, 12:11:31 am
content: Quote from: parasole on July 17, 2016, 09:26:42 pmThanks. I suspect you are right, I missed this part of the datasheet (which makes sense):QuoteI was hoping there was some way to achieve 0v output without a negative supply, but I suspect that is not possible.

author: parasole
author_rank: Contributor
timestamp: March 09, 2021, 04:13:11 am
content: Hi folks,I just received DC2132A ref design PCBs, I found the design in Circuit maker and ordered them as is, good enough for lab power supply.If anyone is interested, I have 3 spare PCB that may sell out for fabrication cost (4USD each) + shipping, if interested pls PM me...BR//

author: parasole
author_rank: Contributor
timestamp: March 15, 2021, 02:35:04 pm
content: PCB

author: dobsonr741
author_rank: Frequent Contributor
timestamp: January 13, 2023, 08:45:26 am
content: Where did you find available stock of the Linear parts?

author: dobsonr741
author_rank: Frequent Contributor
timestamp: January 13, 2023, 02:56:55 pm
content: Where did you find available stock of the Linear parts?