What are your expectations from an adjustable power supply? - Page 1
Forum section: electronics / general

author: rcnkk
author_rank: Newbie
timestamp: April 09, 2023, 10:50:25 pm
content: Hello, I want to make an portable adjustable power supply that works with usb pd like mdp xp.I'd like to get your thoughts on what you can expect from a variable power supply.Max VoltageMax CurrentConnectivity (e.g. Phone or desktop app)-Max priceAnd any other features you can think of.

author: nctnico
author_rank: Super Contributor
timestamp: April 09, 2023, 11:30:24 pm
content: Some minimum requirements:- Not having power on / power off overshoots is extremely important where it comes to adjustable power supplies. You should be able to pull the plug without getting an overshoot on the output. Same for plugging in: when the output is supposed to be disabled, it should not show anything- Output enable / disable button- Programmable power-up setting (voltage, current limit and output state) so it can be used in a more permanent test setup.Nice to have: high & low current measurement range. It is very handy to have single digit uA accuracy for currents below -say 20mA-.

author: Brumby
author_rank: Unknown
timestamp: April 10, 2023, 12:28:14 am
content: You might get some ideas from Dave's own efforts along these lines:https://www.eevblog.com/projects/usupply/

author: Karel
author_rank: Super Contributor
timestamp: April 10, 2023, 02:39:42 pm
content: Must withstand reverse current & voltage (e.g. from a connected battery), no matter the output is enabled or not.At home I have a Peaktech 6225A that blows up immediately if you connect a battery with the output disabled

author: mendip_discovery
author_rank: Super Contributor
timestamp: April 10, 2023, 03:06:12 pm
content: Max Voltage = 5 kV ACMax Current = 100 AConnectivity (e.g. Phone or desktop app) - Connect to a phone and access via a cloud-based website.Max price = £20And any other features you can think of. = Use connectors that nobody else uses. Sod thermal EMF.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2023, 03:17:35 pm
content: Binding posts is another good point. It would be nice to have quality binding posts from Hirschman so people don't need to replace the usual Chinese crap binding posts.

author: TopQuark
author_rank: Frequent Contributor
timestamp: April 10, 2023, 04:38:42 pm
content: One thing I would be quite concerned about is leakage current, especially in what is supposed to be a lab supply.Usually consumer grade Type-C chargers are optimised for efficiency and size, but rarely for leakage current. I have a very nice GaN USB-PD charger (good efficiency, 100W output, small-ish size) that works very well for charging my laptop, but I would not use it to power any sensitive circuits with its ~150uA of leakage current.If your power supply design is non-isolated and you use a consumer grade 2-prong charger, there's not much you can do in regards to leakage current. If you design your power supply to be isolated and take great care handling the leakage current (e.g. reducing transformer inter-winding capacitance, reducing voltage slew rates etc.), you can get something that works well for sensitive electronics.Or maybe you are not powering anything sensitive, or maybe you are using a battery power bank to power your supply, in which case you don't really have to careSome good discussions here:https://www.eevblog.com/forum/beginners/ac-leakage-does-it-matter/

author: Rick Law
author_rank: Super Contributor
timestamp: April 10, 2023, 05:04:40 pm
content: I am not sure why, but from the photo, the look of the OP's device doesn't give me confidence.I would not mind using it like any other phone charger power-brick, but something in the look makes me feel uncomfortable using it as a "lab power supply."Lack of fan? Lack of bunch of plugs and connection post? No visible opening for fuse replacement? ... Those may be part of it but I am not sure exactly what. The looks make me think it is just a light weight phone charger type power-brick.

author: nctnico
author_rank: Super Contributor
timestamp: April 10, 2023, 05:46:44 pm
content: Quote from: TopQuark on April 10, 2023, 04:38:42 pmThis is a very good point!In the past I have destroyed some circuits because of the mains leakage current from an adapter.

author: jonpaul
author_rank: Super Contributor
timestamp: April 13, 2023, 02:44:02 am
content: Doing design, debugg and production test since 1970s, we use HP and Lambda vintage analog lab supplies.Have three HP 6237B120/240 V mains powertriple output 5V, 1A logic, 0..+/- 20V 400 ma analogAdjustable current limitAnalog metersReverse voltage and reverse power protectionsafety rated mains isolation

author: AndyC_772
author_rank: Super Contributor
timestamp: April 13, 2023, 11:02:08 am
content: Quote from: nctnico on April 09, 2023, 11:30:24 pmI'll second this; if it's a lab supply, then by definition it's suitable to be connected directly to low voltage semiconductors, which may have little or no protection against overvoltage. I did once destroy a couple of low voltage, low power DSPs because a PSU had poorly controlled behaviour on light loads.The start-up behaviour in particular must be monotonic with zero overshoot. It should also be able to deliver a controlled amount of energy to supply the load's start-up surge before its current limiter kicks in.I use an HP 6632B as my bench supply for this very reason; its performance is exemplary, so I have no worries at all about connecting it to whatever I happen to be working on at the time.

author: thm_w
author_rank: Super Contributor
timestamp: April 13, 2023, 09:52:03 pm
content: Quote from: Brumby on April 10, 2023, 12:28:14 amYeah UI wise this is a better place to look.The miniware UI is not great. Its cool and compact, but I don't know how many people want that.Quote from: TopQuark on April 10, 2023, 04:38:42 pmMiniware doesn't come with an external PSU. Up to you to plug in a barrel jack or USB PD supply.So going to be similar here, either purchase a low leakage supply or earth the output or whatever.

author: armandine2
author_rank: Frequent Contributor
timestamp: April 14, 2023, 12:51:25 pm
content: I got myself various single model power supplies rather than dual power supplies, I don't therefore have tracking

author: heygeorge
author_rank: Contributor
timestamp: May 12, 2023, 09:58:41 am
content: Input voltage: 220V/110V 50HzOutput current : 0-8ACollecting precision: 0.1mAFast charge protocols: PD, QC fast chargeFor example ~ AiXun P3208https://www.aixuntech.com/product/p3208-320w-smart-regulated-power-supply-32v8a-one-key-boot-power-box-/

author: ejeffrey
author_rank: Super Contributor
timestamp: May 13, 2023, 06:42:30 pm
content: Quote from: armandine2 on April 14, 2023, 12:51:25 pmI've never found tracking that important of a feature. It's slightly convenient if you are doing opamp split supplies or trying to parallel for large loads but nothing that I miss when it's gone.

author: nctnico
author_rank: Super Contributor
timestamp: May 13, 2023, 06:49:43 pm
content: Quote from: ejeffrey on May 13, 2023, 06:42:30 pmI use series operation regulary. And being able to switch on / off several outputs at the same time helps with power sequencing circuits. But that doesn't mean a simple, single output PSU doesn't serve any purpose.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 13, 2023, 06:55:24 pm
content: Does not blow up for whatever reason, including the user connecting a battery, capacitor etc. pre-biased load on output while the thing is powered off.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 13, 2023, 09:45:31 pm
content: But can it connect to ChatGPT?

author: hans
author_rank: Super Contributor
timestamp: May 14, 2023, 08:59:20 am
content: From must have to nice to have...- Constant Voltage setting can be set down to 0V.- Constant Current setting can be set down to 0mA.- Low output capacitance to avoid a dump of charge when switching from CV to CC mode.- Multiple outputs should be floating so they can be chained in series or parallelized at will.- Preferably, readbacks should have low offset. Plenty of cheap PSUs that will display 0.000A even though the load is drawing 3mA. At 1A calibration, I don't care if its 0.997A because of that negative offset. But near zero load I like it to be accurate..- Power on/off button- Ability to lock UI for accidental changes. However, power on/off button should always stay operational (atleast in turning off).- Nice to have: two quadrant supply for constant voltage. Or at least not blow up. There could be projects where a DUT will raise the supply voltage. So survival of that is good. However if you design a power supply with both current load and current sink supported in constant voltage, it should pull the output down by sinking current via some crowbar circuit.Don't have to go full SMU route with four quadrant supply though. Although this is already getting on the fancy side..- Price: I don't know. Do you want to compete with 50$ 30V/5A digital supplies, or go into the programmable supply market? The latter is competitive on different aspects, like programmability feature set, for example sequencing profiles, accurate readback or logging. I'm not a product expert on PSU's, so I have no clue what a fair price for what feature set would be.