Mains transformer power supply - backend for Riden RD6012 - Page 1
Forum section: electronics / projects

author: badgerthing
author_rank: Contributor
timestamp: September 15, 2020, 03:21:43 pm
content: Hello! Skip to the end if you don't need my life storyI am in need of a good bench power supply.I have some particular preferences based on my circumstances.1) Not huge, and not vertical. It can be deep. Will be good to stack stuff on top.2) No fan noise unless needed. So many power supplies have a needlessly high minimum fan noise floor. I power projects that use less than a watt, up to some serious LED systems and amplifiers.3) Plenty of current. I power all kinds of weird things, mostly in repair attempts.4) Good controls. I like the idea of separate voltage and current knobs, reducing the number of steps needed to change things. Some of those Keysight power supplies looked nice, but they're over $2000 and are packed with features I don't see myself needing.After looking about, I figured the Riden RD6012 would be suitable for me.After learning about it on YouTube, I noticed Jerry Walker got better performance using a transformer instead of a SMPS with the RD6006.I imagined it would cost a lot more than a good SMPS, but turns out it doesn't cost too much more. $145 vs $110.I'm not going to use the $56 USD 800W off-brand SMPS. It will need fan modding too.The S12A case you can bundle with the Riden looks nice. I think I'll use that. Comes with a semi-passive fan controller that accepts a 70V input from what I can see.Some observations:- Jerry Walker's results were comparing to a Chinese SMPS as the backend. A better SMPS should provide better results, but it's not something I can know without trying.- A quality, fanless SMPS - Mean Well UHP-500-48 - 500W - about 42V max output from the RD6012 at worst case scenario.- The proposed transformer backend project - 800W - about 48V max output from the RD6012 in my calculated worst case scenario. Up near 60V at low loads with my normal 240V mains voltage, taking into account the RD6012's dropout.- It looks like I'll get about 5V p-p ripple with the RD6012 at full load, with the 20mF cap.- Huge scary toroidal needs inrush limiting and NTCs are lame. The inrush resistors are not sized to survive if the relay fails. What's the failure mode for the ceramic brick resistors?I come here seeking a second set of eyes, in case I've come a gutser somewhere.Here is my schematic thus far:

author: ptluis
author_rank: Frequent Contributor
timestamp: October 01, 2020, 02:04:00 pm
content: Quote from: badgerthing on September 15, 2020, 03:21:43 pmwith transformer you must take into account the AC power line fluctuations and the effect it has on transformer secondary output to avoid burning input of the RD6012. In my country AC line can fluctuate from 230-240v (during day-night). in my case I wind my own transformer and adjust it to 46v secondary output when primary at 240v. This way I get between 62-64V DC (after rectification) that stays below the input 70v limit of RD6006 (that's the unit I got). I will be adding later some sort of voltage monitor and a relay to shutoff input power if it exceeds 66v (it happened one time AC reach 245V).Ripple is lower now, before I had a cheap 65v SMPS and noise were higher (besides I'm not a big fan of SMPS when I have to touch output lines, I prefer isolation transformer). On my other PS RD6006 I turn it into a portable power supply and used LI-ion batteries as source of power, of course weight is higher but noise is just from the RD6006 unit. I use it only for low voltage electronic projects or some tests. But for more sensitive things when noise should be avoided, like transceivers, I still use analog PS.Have a nice day

author: badgerthing
author_rank: Contributor
timestamp: October 01, 2020, 02:11:06 pm
content: Thanks for the reply!The RD6012 (and now the new RD6018) can come with a PSU that outputs exactly 70V. 70V seems like quite an arbitrary number also, I don't imagine 73V will cause problems.I calculated the peak unloaded voltage will be just over 72V when the mains is at its highest allowed level here in NZ (253V).I have never seen it that high. It is 230V always where I live, and 240V at my previous residence.With 230V, I imagine I will lose regulation at 60V output, but I don't use 60V often, let alone at 12A.I am still working on the fan controller circuit. The previous one with a TC648B isn't ideal as not all fans play well with PWM's supply. I will use linear fan regulation, or directly adjusting the XL7005A SMPS (80V SMPS controller IC I use for generating fan 12V).Also, I believe I will need to derate the transformer. 800VA isn't 800W, as I imagine the Riden will have a terrible power factor. We will see when I get the transformer.We will also see what the inrush current is like. I imagine 20 ohm 10W wirewound resistor for less than 1 second should do it?What kind of noise specs do you get?I tested powering the RD6012 from a 48V server PSU, and with 30V 12A load. The noise specs is within the advertised levels. Perhaps with a lower quality mains SMPS as the backend it would be worse. The server PSU is decent quality.

author: ptluis
author_rank: Frequent Contributor
timestamp: October 01, 2020, 04:08:24 pm
content: Quote from: badgerthing on October 01, 2020, 02:11:06 pmI have a silent fan running 90% speed so didn't bother to much in adding a digital controller fan. I didn't bought RD6012 because according to specs ripple will be about 250mv at 6A and from what I've seen on youtube videos at 12A some got 500mv+ that's no no for me. I don't need more than 6A so RD6006 is enough. In my RD6006 with isolation transformer ripple is about 75-80mv at full 6A load, so a little below specs. The other one with li-ion, as input, about the same but a little less spikes, more clean. with SMTP ripple is between 100-120mv but much more spikes. Values reading in my old GWinstek oscilloscope. But normally never above 100mv as stated. That's why I like this cheap PS module.about inrush current, I have a relay installed with 3 sec delay, before connecting to RD6006 module.Filtering capacitor it's a 15000μF, so when I turn it on you will "hear" the surge

author: badgerthing
author_rank: Contributor
timestamp: October 02, 2020, 01:02:43 am
content: Shouldn't you be using the inrush limiting and relay on the primary side?Here's my noise result with the RD6012 powered from a loud 48V 1200W server PSU.Output set to 30VKP184 electronic loadmV p-p0A: 150 (spikes?)1A: 1002A: 1254A: 1508A: 18512A: 225All noise seems to be 70kHzHere are some scope captures:

author: ptluis
author_rank: Frequent Contributor
timestamp: October 03, 2020, 01:16:19 am
content: Quote from: badgerthing on October 02, 2020, 01:02:43 amThe relay only activate after the big capacitor is charged, meaning DC is stable. 3 secs is enough. Only then the relay clicks and send power to RD6006. This means, before I can use RD6006 I need to wait 3sec+boot time of RD6006. 15000μF is a huge capacitor. I could add some sort of circuit to alow it to charge slow to avoid that initial "bong", using the same anti-spark trick when connecting ebike battery packs with cheap bms boards, or even without bms, but for this large capacity I certainly have to wait more than 3 secs.At 30v why are you measuring using 1x probe? why not 10x? on 1X you'll catch much more noise. On my oscilloscope I always get the same type of waveform, with spikes increasing with AMPS, doesn't matter if 0A or 6A. Never like your 2-3 screenshot. I'm sorry but I don't have any knowledge on your oscilloscope to comment on 2-3 screenshots.

author: badgerthing
author_rank: Contributor
timestamp: October 03, 2020, 01:19:55 am
content: Quote from: ptluis on October 03, 2020, 01:16:19 amI will measure again with 10X - I am not well versed in scope techniques sorry.So why don't you put the inrush resistor and relay on the primary side? I could be wrong but I imagine this should prevent both transformer inrush and capacitor charge inrush - no bong sound or component stress.

author: badgerthing
author_rank: Contributor
timestamp: October 03, 2020, 02:19:21 am
content: I tested with X10 probe, and researched why I should do that, especially in this scenario.I am learning.Results:33V 12A: 1V p-p5V 12A: 930mV p-p33V 1A: 450mV p-p5V 0.1A: 270mV p-p (bad)33V 0A: 370mV p-p

author: ptluis
author_rank: Frequent Contributor
timestamp: October 03, 2020, 11:52:31 pm
content: Quote from: badgerthing on October 03, 2020, 02:19:21 amDon't worry, we all learn with each otherinruch is better controlled on the secondary (low voltage) side using the same anti-spark trick when we use such large capacitance . See the picture I attach to better undertand how it works. Don't forget that the capacitor acts like a short in it's initial state. With a good old NE555, and a relay you can control it. Don't worry, isolation transformers, proper built, stand quite well the half sec inrush. The transformer won't burn, copper wire has enough tolerance to support this. I like the bump sound, it's like having a Ferraripower!About your screenshots they look ok, I think the first is noise from something you have on your lab, the other seem ok, in specs.

author: badgerthing
author_rank: Contributor
timestamp: October 04, 2020, 12:00:34 am
content: Would the primary resistance not kind of "transfer" to the secondary and prevent inrush?Also, an 800VA toroidal transformer may be pushing it for household breakers no?

author: ptluis
author_rank: Frequent Contributor
timestamp: October 04, 2020, 01:14:13 am
content: Quote from: badgerthing on October 04, 2020, 12:00:34 amI think you should study a little more about transformers and how they are build to understand better what's really involved, resistance, inductance, magnetic field, core, losses, copper wire diameter, isolation, and so on. and BTW never but never fix you toroidal transformer with metal screw/plate in a metal box in a way that you create a short turn, you will destroy it if not proper fused. check here:https://www.edn.com/audio-amplifier-power-supply-design-part-1-power-supply-types-transformer-considerations/I don't know the specs of household breakers in your country, but in mine 800VA it's perfectly fine.

author: tcz
author_rank: Contributor
timestamp: November 18, 2020, 07:25:13 am
content: Can I connect this thing (RD6012) to an ATX power supply?I have a nice Corsair TX850W with a built in fan controller that ramps it up slowly starting at 50% load.It's good for 840W on the +12V rail

author: badgerthing
author_rank: Contributor
timestamp: November 18, 2020, 07:27:29 am
content: Quote from: tcz on November 18, 2020, 07:25:13 amNo. 12V isn't enough, and even if it was, a bench power supply that only goes up to about 8V isn't super useful.You need a power supply of at least 30V to make the RD60xx useful. Preferably over 50V.You can get decent quality 500W Mean Well power supplies that output 56V for under $100 from Mouser etc.

author: badgerthing
author_rank: Contributor
timestamp: November 22, 2020, 01:38:29 am
content: Quote from: ptluis on October 04, 2020, 01:14:13 amWhen you say 800VA is fine with your breakers, do you mean an EI transformer or a Toroidal?Here are the results of my tests. I haven't tested with fuse bypassed, as resetting the breakers here is inconvenient.The fuse could be replaced with another type, but this seems adequate, and will tolerate finite-length overload conditions which is one of the advantages of this linear backend vs a SMPS backend.

author: Pawelr98
author_rank: Regular Contributor
timestamp: November 22, 2020, 03:33:59 am
content: Quote from: badgerthing on October 01, 2020, 02:11:06 pmAC input line fluctuation can be mitigated by using another small auxilary transformer, with secondary connected in series with mains.Depending on phase you can either add or subtract the voltage from mains.As for derating, most use 1.6x, so for 800W you would need a 1.3kVA.That's a nice chunk of a transformer, with insane inrush even without the filter caps at the secondary side.If only for short periods then you may get away with less derating if the windings are thick enough to handle the peak currents.Myself I have my own design linear power supply with 300VA toroid and it does make the lights dim for a second.Won't pop the fuse (no soft-start) but still.Toroids have larger inrush than EI and that should be taken into account.Fan controller ? Just use a 494 with a PTC for simplicty and buy a fan that accepts PWM input (computers have these, they come with a 4pin connector).It will generate adequate PWM signal.Or a comparator with hysteresis if only 0/1 operation is fine.

author: badgerthing
author_rank: Contributor
timestamp: November 22, 2020, 03:59:03 am
content: Quote from: Pawelr98 on November 22, 2020, 03:33:59 amHelloI designed an inrush circuit to reduce peak inrush currents from 50A+ to about 12A. (1st attachment)I have designed a fan controller circuit that has the desired fan curve, a fan-off mode with hysteresis, and quiet voltage-control. (2nd attachment). I am in the process of replacing some resistors with trimpots so the design is more flexible, as not every fan can start at 4.5V like the one I selected.I made a 2.8 ohm resistor by winding some 0.8mm aluminium wire around a brick. I was then able to test for long periods, determine the transformer temp rise, and therefore, the maximum overload allowed.I took the resistance of the transformer windings when cold, and when hot, and determined how much hotter the inside of the transformer is compared to the temp I take from the outside with IR thermometer. The difference was zero - the temp was roughly uniform, so I was confident I could rely on external temp as a good indication.The heatsinks for those efficient diodes are overkill (and there's nothing wrong with that). With any amount of airflow from the adjacent fan, they run cool at all loads.Measuring at the mains input, with 800W load on the RD6018, there is 1150VA on the transformer primary, 84% regulation, and a temp rise of 72C with my cooling solution.I believe this means I can run this overload indefinitely if it's a cool day (<20C). If it's a hot day, I can only run this overload for a finite time.So a rough figure of what I can draw from the RD6018 on a very hot day (40C), is 650W. I will do more testing.My transformer is rated for 55C temp rise. 105C (A) temp class. It doesn't specify ambient temp, only rise. Online sources suggested 35 as an ambient temp to base the temp rise off, and get max temp from.Efficiency of the entire unit was around 87% with 800W load, if I remember correctly.

author: badgerthing
author_rank: Contributor
timestamp: November 22, 2020, 04:04:17 am
content: Oh, and here is photos of the current finished version that I am taking measurements from.There will be one more PCB revision with a more adjustable fan controller and some bodges fixed.https://imgur.com/a/f4WbrPy

author: AJ3G
author_rank: Regular Contributor
timestamp: December 19, 2020, 07:42:05 pm
content: While I do not have the 6012, I did build a supply which has two 6018's. Its a Quasi Two Channel Supply, with the hope that I can work in the Software to make one controller master, and the other a slave, so I can achieve tracking. My backend is not the SMPS supplies with the kit that is offered, but instead a Farnell A1500 Powermag SMPS. I am supplying both controllers 65.75Vdc.Last night I just completed some voltage ripple testing and I am getting 11.2mVp-p with the Supply at 50V @ 5A. I was shocked by this, as this is far below the specification of RIDEN. I assumed they must assuming the use of the SMPS they sell with their "kit"..Here are the measurements, and for the record, its entirely possible I have measured wrong. I do note that the HF Noise, but noticed this had subsided when I turned off a LED Lamp I use on my desk for reading.Rich Miller

author: badgerthing
author_rank: Contributor
timestamp: December 19, 2020, 07:49:50 pm
content: I am not too sure of the best way to measure either, but will work that out when my second RD6018 arrives.I am making two supplies, and will likely sell one.One is an RD6018 in their S12D enclosure, with a 500W 56V mean-well crammed inside and controlled active cooling.The other is the linear backend, which will achieve about 500W also, on a hot summer's day, or 900W+ for finite periods.I can't tell what volt/div setting is on your scope. Try zooming out on the timebase and see if the spike in the middle, is repetitive.1x or 10x probe? Have you enabled 20MHz BW limit?

author: AJ3G
author_rank: Regular Contributor
timestamp: December 19, 2020, 07:58:34 pm
content: Badgerthing:It's been a long time since I have done ripple measurements. Last time I did it was with a analog scope.The measurement is at 20mV/DIV at 20MHz BW. I am using a X10 Probe, which I know is not ideal. If I recall correctly, RIDEN Spec quotes 250mVp-p. I suspect this is using their SMPS for the kit. I was using a DC Electronic Load and was getting close to the limit. I am terminating some of the binding post at the moment, but will revisit the measurement later. I too want to see what story is on the HF Noise.Rich

author: badgerthing
author_rank: Contributor
timestamp: December 19, 2020, 08:02:37 pm
content: Quote from: AJ3G on December 19, 2020, 07:58:34 pmWhy's 1X probe recommended again? I forgot the reason.Zoom out and see how often that 90mV p-p spike repeats. Maybe it's 50/60 Hz.

author: AJ3G
author_rank: Regular Contributor
timestamp: December 19, 2020, 08:10:39 pm
content: I think by taking out the divider of the probe you get a better reproduction of the signal you are analyzing. I am not sure how much of an impact going to 1X will make. The ideal way is to go to Differential Probing, but those are expensive. Maybe Santa will bring me one for Christmas.Rich

author: badgerthing
author_rank: Contributor
timestamp: December 19, 2020, 08:13:27 pm
content: Quote from: AJ3G on December 19, 2020, 08:10:39 pmOn 10X, I get more ripple. I believe 1X is presenting a lower impedance to the DUT, and so isn't showing noise components with a high impedance, which may or may not be what we want when measuring PSU output - I am not sure.

author: AJ3G
author_rank: Regular Contributor
timestamp: December 19, 2020, 08:31:07 pm
content: I will have to try it. I do have some X1 Probes which have the B/W for the job. The LeCroy Scope I am using is not ideal for the measurement, but it's not too bad either. I have enclosed some pictures of what I am working on at the moment. All of those binding posts have to be terminated. I just received the ring terminals I need for the job yesterday, so I am working to terminate all of them. Since I have it apart, I might be able to get some photos of the inside too.Rich

author: AJ3G
author_rank: Regular Contributor
timestamp: December 20, 2020, 05:01:46 am
content: Hello Badgerthing:It's getting late here, but I did try with a X1 Probe. I used a configuration I saw on YouTube earlier today of another person who ran similar test with the RIDEN. I used a capacitor on the output and a snap on ferrite core on the ground strap. My results are different. My Ripple looks to have increased to 83.3mVp-p. This is still a great number for my application.I also took some pictures showing the switching frequency, loaded, unloaded, and then compared to a clamp on current probe on Channel 2, which is set for 10mV/1A.Picture 1 - PSU unloaded, and Voltage set to 50VDCPicture 2 - PSU Loaded at 50VDC @ 5APicture 3 - Same configuration as above, but with a Current Probe Attached to Channel 2.Picture 3 - Picture of one of the RIDEN front EndsPicture 4 - DC Electronic Load Readings. I know, I need better cables!Rich

author: rlohmann
author_rank: Contributor
timestamp: December 30, 2020, 02:28:59 pm
content: Hi,I have a RD6012 with a blown TO-263? buck converter (next to the wifi module cutout), on which I can't read the making anymore.Hopefully someone has a open/working unit and could share the labeling.UPDATE: I assume it's a XL7015 ...Thanks,Rene

author: AJ3G
author_rank: Regular Contributor
timestamp: January 03, 2021, 01:54:48 am
content: That is in fact the Buck Converter. The XL7015’s can be had very cheap from distributors in China. I wonder how that happened?

author: badgerthing
author_rank: Contributor
timestamp: January 03, 2021, 01:56:33 am
content: Here is XL7015, if that's what it is:https://lcsc.com/product-detail/DC-DC-Converters_XL7015E1_C73013.html

author: rlohmann
author_rank: Contributor
timestamp: January 03, 2021, 09:58:35 am
content: Thanks @AJ3G @badgerthng for the confirmation.In fact I'm also wondering what happend to the unit. (got it broken)I've meanwhile figured out that the step-up converter (I assume SX1308) after the XL7015 was shorted to ground.Just ordered both and hope I get the unit fixed by replacing both.Btw, does anybody know if there is a schematic available for the RD6012 (or RD6006)?

author: AJ3G
author_rank: Regular Contributor
timestamp: January 03, 2021, 03:00:01 pm
content: I am not aware of one. I have looked mostly for a 6018, without much luck.Rich

author: Thermionix
author_rank: Newbie
timestamp: January 10, 2021, 04:55:30 am
content: Quote from: badgerthing on November 22, 2020, 04:04:17 amI'm planning to build a linear supply for my RD6012How are you finding the ripple?V pp = I / ((2f) C)V pp = 12 / ((2x50)x0.024)24mFD gives 5 V Ripple @ 12AmpsSeems extremeI was looking at your schematic and I believe powering the soft-start off VDC isn't recommended - the circuit won't reset quickly enough if there's a short power loss as the filtering caps will retain a charge - keeping the relay active, the relay will stay latched until <10vI then did some reading -https://sound-au.com/articles/soft-start.htm"Many fail to ensure that the circuitry resets itself quickly, so a rapid on-off-on cycle (whether by design or accident) provides protection after a brief interruption. In general, any circuit that does not reset in under 500ms should be considered a fail. A full reset ensures that when the power is restored (after perhaps 1/2 second or so), the ballast resistors are in circuit again, and the soft start is performed just as it would if the equipment were turned on after being turned off overnight"I think I'm going to build a seperate inrush controller based on Figure 6A on that page.

author: Everbrave
author_rank: Regular Contributor
timestamp: March 21, 2021, 11:40:46 am
content: I have done quite a number of experiments comparing the linear back-end with a MeanWell NRD-240-48 with a specified 150mv Rippe&Noise.The conclusion is, the final, regulated, noise & ripple at the switching freq. (not the line 50Hz) is dominated by my RD6018 itself. With the linear back-end, I gain only few mv of (less) ripple. e.g. 20mv rms @20V, 4A for the linear BE instead of 24mv rms with the MeanWell switching power supply.I am still planning to build a larger linear back-end with a 400VA toroid Transformer to test further but the published results seem to support my observations (200-300mvpp) no matter how well you reduce the input ripple at the line freq.