Performance test and review of 20W DC-DC Step Down Voltage Regulator - Page 1
Forum section: electronics / projects

author: HKJ
author_rank: Super Contributor
timestamp: August 17, 2015, 07:47:14 am
content: I needed this converter for some of my projects and decided to do some tests on it first.The full result can be seen here (It includes more input/output voltages):http://lygte-info.dk/review/Power%20Adjustable%20buck%20converter%20LM2596%20UK.htmlFirst curve is with 5 volt input and 3.3 volt output.12V input 3.3 volt output.Unloaded current consumption when adjusted to 3.3 voltConstant 1A load, input voltage is swept from 0 to 30 volt.Temperature at 12 volt input, 3.3 volt output and 2A load.Ripple.

author: Neverther
author_rank: Regular Contributor
timestamp: August 17, 2015, 08:35:24 am
content: Cheapest board and seems to be a fake lm2596.150Khz switching frequency? Nope.Good sized ceramics on output? Nope.But it seems to be matching the efficency on the datasheet pretty close.Atleast it has 3A diode as I've seen those sold with SS14 diodes.I got pile of those as Im not even sure if any of those have real chips.

author: HKJ
author_rank: Super Contributor
timestamp: August 17, 2015, 11:55:05 am
content: Quote from: AcHmed99 on August 17, 2015, 11:43:52 amIt is not the output power that is interesting for that, but the loss in the controller and 3 watt is too much. With 1 watt loss it is much better.

author: HKJ
author_rank: Super Contributor
timestamp: August 17, 2015, 12:33:26 pm
content: Quote from: AcHmed99 on August 17, 2015, 12:24:05 pmWith controller I meant the pcb, not only the switcher chip. All the other components would not remain at ambient anyway, heat is conducted to them (As is obvious to see on the trimpot).Quote from: AcHmed99 on August 17, 2015, 12:24:05 pmI believe they mean you need heatsink above 2A, up to a maximum of 3A, but I would prefer to use heatsink at lower current also. The 1A thermo photo looks fairly acceptable without heatsink, but again it is not the output current, but the loss and you can see that on most of my curves.

author: HKJ
author_rank: Super Contributor
timestamp: August 17, 2015, 01:00:09 pm
content: Quote from: AcHmed99 on August 17, 2015, 12:55:46 pmWhat is very interesting is the jump in power loss when using higher output voltages:

author: HKJ
author_rank: Super Contributor
timestamp: August 17, 2015, 01:26:01 pm
content: Quote from: AcHmed99 on August 17, 2015, 01:18:36 pmYes, but here it is very abruptly just above 20 volt.

author: eneuro
author_rank: Super Contributor
timestamp: August 17, 2015, 07:04:53 pm
content: Quote from: HKJ on August 17, 2015, 07:47:14 amThat is interesting they says about 65kHz switching frequency, butLM2596 datasheetsays 150kHzQuoteAnyway, using ATTiny85 and 2 x IRFZ44N in parallel in lead acid battery charger project at 5A those mosfets are maybe only slightly above room temperature, since its RDSON at low temperatures is 18m Ohm, so 5A^2*(0.018/2)= 0.225 W power loses in those two TO-220 rated at 49A IDSometimes custom solutions perform much better and we know where elements were sourced-from reliable supplier-no fake ICs means successfull home made projects

author: nctnico
author_rank: Super Contributor
timestamp: August 18, 2015, 12:09:17 am
content: This is pretty crappy. With efficiencies around 70% I'd choose something else. A converter with synchronous rectification for example.

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 12:51:04 am
content: ImpressiveWhat equipment did you use?What graph(s) do you think the most interesting? What test (graph) would you recommend to someone who does not have your equipment?Any chance you could do these tests on some other buck modules?Did this module pass your requirements for your project(s)? Is the ripple acceptable for your needs?thanks

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 03:04:14 am
content: How about run the tests with these attached?http://www.aliexpress.com/item/Free-Shipping-100Pcs-Lot-14-14-6-mm-Extruded-Aluminum-Radiator-Extrusion-Aluminium-Heatsink-For-LM2596/1359566154.htmlCan I ask how long did it take you to do these tests? Do you know how many graphs you have? I stopped counting at 50.

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2015, 05:36:34 am
content: Quote from: ez24 on August 18, 2015, 12:51:04 amA Keithley 2280S power supply and a Itech IT8512+ load, both controlled from a computer.Quote from: ez24 on August 18, 2015, 12:51:04 amDepends on what you want to use the module for, with varying input voltage and stable load the charts where I sweep the input voltage is interesting. If you have fairly stable input voltage and varying load the one where I sweep the load current are the most interesting.In both cases only at the voltage/currents you need.Quote from: ez24 on August 18, 2015, 12:51:04 amDepending on time I may do a few more of the cheap modules.Quote from: ez24 on August 18, 2015, 12:51:04 amProbably, I do not have the final requirements yet, but it do tell me not to except 2A from this module.

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2015, 05:44:16 am
content: Quote from: ez24 on August 18, 2015, 03:04:14 amI am not going to do any tests with heat sink at the current time.Quote from: ez24 on August 18, 2015, 03:04:14 amProbably around a day, most of the time was testing time where the equipment worked alone. Due to the adjustable output voltage I did get many charts, I have not counted them. I just listed the tests I wanted done and worked at something else while the equipment made the charts.

author: sleemanj
author_rank: Super Contributor
timestamp: August 18, 2015, 09:50:35 am
content: Quote from: HKJ on August 17, 2015, 07:47:14 am"20W" - only if you heatsink it well, which is something that the chinese vendors on eBay etc usually forget to mention :-/Luckily the underside of the board is all one big ground plane usually, which is quite amenable to having a heatsink attached with double-sided thermal transfer tape, scrape off the soldermask for better conduction. Even just putting a small 1cm x 1cm heatsink on top of the IC and another directly under it can help sufficiently.

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2015, 09:56:51 am
content: Quote from: sleemanj on August 18, 2015, 09:50:35 amMaybe you can get 20W at higher voltage, but 12V output was not enough.Quote from: sleemanj on August 18, 2015, 09:50:35 amThere is a slight problem with the trimpot, it is leaded (There is some more pictures (included hires) of the module in the linked review).

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 06:50:19 pm
content: HiCould you summarize the measured specs against the product specs:Input voltage:3V-40VOutput voltage:1.5V-35VOutput current:Rated current is 2A,maximum 3A (Additional heatsink is required)Conversion efficiency:92% (highest).Switching frequency:65KHzOutput ripple:30mV (maximum)Load regulation:±0.5%Voltage regulation:± 2.5%For ripple can I say that you measured : 186 to 280 mV (maximum) ?If the ripple is too high for your application, have you thought about putting a 317 on the output? A lot of sources say to do this (including AofE) but I have not seen any test results from anyone doing this (putting a linear on the output of a buck). Sure would be interesting to see some good tests like you are doing. If you are into YT there is a lack of good testing on YT on buck regulators.What country do you live in (Denmark ?)? I have some spare bucks to test if you live in the US.Oh --- I just put 2 and 2 together. You are the battery and charger guy that I followLast week I bought a Panasonic charger from Costco and then read your report, then decided I wanted another one and went back and they were sold out. I just wonder how many people read your reports (a lot I bet). So I assume you are looking into making battery chargers (and do not care about ripple), if anyone can it is you.If you are on YT - what is you YT name? If not think about signing up for a commercial account and make some money on your tests, a lot of people make a living from YT including Dave. You could even get a student intern to help you or someone to work on commission.Sure would like to see a picture of your work shop. What do you do with all that equipment?Thanks for all your good work.

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2015, 07:44:27 pm
content: Quote from: ez24 on August 18, 2015, 06:50:19 pmThat is not really a good idea, it always depends on the conditions. My test are done to get an idea about performance under different conditions and without trying to improve anything.Quote from: ez24 on August 18, 2015, 06:50:19 pmFirst try would be a capacitor. The LM317 is very useful, but you need a lot of voltage across it, a LDO regulator would probably be better.Quote from: ez24 on August 18, 2015, 06:50:19 pmI have enough chargers, I do not want to build any. This is just a couple of hobby projects.Quote from: ez24 on August 18, 2015, 06:50:19 pmNo, I am not on YouTube, I do not speak English good enough for that and if I did it in Danish there would probably only be 5 people watching it.Quote from: ez24 on August 18, 2015, 06:50:19 pmI do not share pictures of my workshop, it is way to messy. I do have electronic as hobby, but lately most of my free time has been spent testing and writing about chargers and batteries, both things require use of my equipment.

author: ez24
author_rank: Super Contributor
timestamp: August 18, 2015, 09:04:28 pm
content: QuoteEveryone wants to see other workshops to see if it is possible someone can have one more messy than their own.A while back someone died and pictures of his workbench were posted and it would be very hard to have a more messy shop than him and from what I gather, he was very respected.ie more messy more respect

author: HKJ
author_rank: Super Contributor
timestamp: August 18, 2015, 09:13:22 pm
content: Quote from: ez24 on August 18, 2015, 09:04:28 pmSorry, but no.You can see some of my lap equipment here:http://lygte-info.dk/info/myLabSetup%20UK.html(It is not up to date).

author: eneuro
author_rank: Super Contributor
timestamp: August 19, 2015, 01:16:19 am
content: Quote from: HKJ on August 18, 2015, 09:13:22 pmis it?Anyway, I can't see any good... scientific programmable calculator which is my most important equipmentThis is mine, which helps me in successfull engineering projects:Osciloscopes and other stuff can be helpfull, but the most important is good design and theory behind, so calculate first, than...

author: HKJ
author_rank: Super Contributor
timestamp: August 19, 2015, 06:23:17 am
content: Quote from: eneuro on August 19, 2015, 01:16:19 amA photo diode with a couple of switch selectable parallel resistors, very useful for seeing PWM on flashlights. The pcb also makes it possible to clamp it down to get a fixed distance to the led when testing different modes.Quote from: eneuro on August 19, 2015, 01:16:19 amI wrote my own for use on a PC.