High Current AWG using Power Supply - Page 1
Forum section: electronics / testgear

author: mawyatt
author_rank: Super Contributor
timestamp: September 21, 2025, 05:33:24 pm
content: On another thread there was a discussion on how to create low frequency sinewave high currents using all sorts of various schemes, including injecting the waveform in the Power Supply feedback and feedforward circuits.This got us thinking could we create high current waveforms with a simple power supply without modification utilizing the sense terminals? Here's the back-of-the-envelope concept we came up with on theback of an envelope!!We utilized our Korad KWR102 30V/30A power supply (because it has sense terminals) and SDG2042X AWG. Load resistor is a 100mΩ precision power resistor, and R in the sketch is1K10K to protect the AWG just-in-case!! At first we were going to "inject" the waveform on the PS High Side Sense Terminal, but realized we could do this on the Low Sense side and be closer to ground reference. Then set up the DSO to show voltage across the load resistor scaled in Amps as shown.PS settings were V at 0.5V and I at 15 Amps, with rear terminal sensing enabled. AWG was set to ~1.5Vpp thur the1K10K resistor to the PS Sense Low Side.First waveform was a sinewave at 100Hz which shows this configuration capability and can extend to higher frequencies if desired, and note the current levels in all the plots!! We also include some Arbitrary Waveforms just for fun!! Note last (PNG22), this is with a 10mΩ current sense shunt and we used ERES to show a cleaner waveform (acts a LPF).Anyway, this High Current AWG configuration was created without any additional equipment or custom 'tronics other than some cables, a load, and a resistorHope some folks find this interestingBTW be careful, this might cause some issues with other supplies and AWGs, we just employed what we have on hand for this!!Best

author: temperance
author_rank: Super Contributor
timestamp: September 21, 2025, 07:19:42 pm
content: Darn, a class A amplifier.

author: mawyatt
author_rank: Super Contributor
timestamp: September 21, 2025, 07:39:20 pm
content: Quote from: temperance on September 21, 2025, 07:19:42 pmNope, it just "looks" like a Class A amp, it's actually a Switch-Mode ampActually capable of delivering 300wattsBest

author: mawyatt
author_rank: Super Contributor
timestamp: September 21, 2025, 07:51:27 pm
content: To follow up, we decided to take a look at the Bode plot of this configuration. Here we're using the SDS800X HD Bode function with CH3 set as the Input and CH1 set as the Output. The AWG is set to provide a 1.2Vpp signal with a 0.6V DC bias in the Bode Configuration, which "swings" 12App across the 100mΩ load.The overall scale factor is 1V Input produces 10Amps Output or 20dB as shown, and this shows some "useable" bandwidth past 100Hz and stable operation with forcing a Dynamic Signal thru the PS - Sense Terminal.Best

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2025, 08:21:03 pm
content: some old supplies had a spec for frequency response on the control screws

author: joeqsmith
author_rank: Super Contributor
timestamp: September 21, 2025, 08:45:16 pm
content: Quote from: coppercone2 on September 21, 2025, 08:21:03 pmI used some old large Lamda supplies that provided the step response.I can understand wanting to have a supply that could be programmed remotely but nothing at 100Hz. What would you ever use it for? Being single ended, I can't think of a good case.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2025, 08:53:40 pm
content: It could be used with a balun of some kind, for AC signals. That might be a interesting transformer100MHz is alot, but single ended pulse signals could be used to test things like noise filters for power supplies (so you don't actually need the power supply). But it would probobly still need some kind of impedance match to have a similar output impedance to the thing you are simulating, unless it happens to be close enough. Or just testing the rectifier portionActually that is interesting for a power supply, if you can get rid of the 'high side' of things and just test the low side rectifier/filter end. Such equipment might make some stuff easier to fix. Not sure how you would get the feedback in there, but at least it might be able to test portions for proper operation. A switching supply is... rather difficult to test in order to determine where a repair is needed. The more isolated sub circuits that can be properly tested (at proper current levels) the less unknowns you have).It might require sync with other equipment for things that are more complicated, like synchronous designsThe idea would be to test what you can at the transformer output, with the transformer disconnected.

author: Smokey
author_rank: Super Contributor
timestamp: September 21, 2025, 08:59:36 pm
content: cool! do I get credit for this? I think I was the first one to suggest this might work in the other thread.Thanks for validating it.[]https://www.eevblog.com/forum/projects/low-freq-psu-012-v-sine-(dc-offset)-up-to-10-a-externally-driven/msg6041003/#msg6041003

author: joeqsmith
author_rank: Super Contributor
timestamp: September 21, 2025, 09:16:32 pm
content: Quote from: coppercone2 on September 21, 2025, 08:53:40 pm100Hz is a bit slower than 100MHz. I wonder what the fastest supplies are.Shown is a very old switching load I designed. I doubt I could put more than a few Amps through it and it may have been even slower than the 100Hz shown.

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2025, 09:31:31 pm
content: I think you could look at the filter/rectifier circuit to find out where the limitations are. I wonder how much you can mess with a SMPSU output filter characteristics. And feedback filters.some mega riced out meanwell (honda civic) comes to mindIt might get alot more noisy but its possible it would still work at increased bandwidth if care is taken

author: coppercone2
author_rank: Super Contributor
timestamp: September 21, 2025, 09:36:47 pm
content: At lower frequencies, it might have a use for some kind of magnetic thing too.=

author: Hydron
author_rank: Super Contributor
timestamp: September 21, 2025, 10:14:54 pm
content: My PSW 80-40 (80V/40A/1080W switching bench supply) can do current/voltage/both(!) modulation (though it is a little annoying to enable, and I'm not sure if there is a spec as to how fast it can modulate). Also Keithley 228(A) up to IIRC 600Hz, though that is a bit unusual in that it's a 4-quadrant supply (very annoyingly the modulation does NOT seem to work between quadrants, which would have made it much more useful!)

author: joeqsmith
author_rank: Super Contributor
timestamp: September 21, 2025, 11:17:47 pm
content: My switcher's 3dB is about 1kHz is all. Lot's of ripple from the switching and very distorted.

author: mawyatt
author_rank: Super Contributor
timestamp: September 22, 2025, 12:04:08 am
content: Quote from: Smokey on September 21, 2025, 08:59:36 pmIf you mentioned this then you get creditHonestly, surprised this inexpensive Korad 30A 300W switcher works this well, figured there would be some "glitches" somewhere, apparently notDon't think it was ever intended to be used this way.Best

author: Smokey
author_rank: Super Contributor
timestamp: September 22, 2025, 03:44:23 am
content: Makes me want to try it out with my 6632B. Has both sense terminals and downprogramming/load capabilities. And it's linear.

author: mawyatt
author_rank: Super Contributor
timestamp: September 22, 2025, 01:21:13 pm
content: Quote from: Smokey on September 22, 2025, 03:44:23 amGive the linear 6632B PS at try, curious to see how it behaves, also try a Bode plot on the Sense Control channel.We don't have a linear supply that has sense terminalsBest

author: joeqsmith
author_rank: Super Contributor
timestamp: September 22, 2025, 11:04:01 pm
content: Another custom DC-DC using a more modern controller from this decade. At 1kHz its starting to roll off and is a bit non-linear. At 1.7kHz, it's fairly distorted.

author: joeqsmith
author_rank: Super Contributor
timestamp: September 23, 2025, 02:16:01 am
content: Even at 10Hz, we are past 3dB with a lot of distortion.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: September 23, 2025, 02:35:33 am
content: Neat trick, but quite limited in its use since you are really programming a voltage and the current conversion requires a constant resistance.Also, as mentioned it operates only in a single quadrant.Kepco has a whole series (BOP) of four quadrant power supplies / amplifiers that cover a huge range of voltages and currents.Sometimes you can get them for cheap like in this listing:https://www.ebay.com/itm/127385967592

author: joeqsmith
author_rank: Super Contributor
timestamp: September 23, 2025, 11:44:45 am
content: Quote from: KrudyZ on September 23, 2025, 02:35:33 amSome supplies also offer current control with a voltage input.I can't think of a use for it.

author: mawyatt
author_rank: Super Contributor
timestamp: September 23, 2025, 04:29:37 pm
content: After some help fromhflemingin finding out how to enable the External Sense Capability on the SDL1020X-E Electronic Load (see manual pg 65 and 80, enableExternal Senseis calledVrmt), we decided to see if this AWG modulation of the Sense Terminals would also work on an Electronic Load.The setup is similar to the PS setup shown above except the Load is now the Electronic Load rather than a resistor and the PS is fixed. The Load is setup for Constant Resistance Mode and a current sense resistor is used for monitoring the Load Current with DSO. This works similar to modulating the PS except now the load resistance is modulated by the AWG.Ause casemight employ this setup in investigating how a given PS behaves wrt to various dynamic load characteristics which can be dictated by the AWG, either as built-in waveforms or custom arbitrary waveforms.Here's an example with EL set to 1Ω and modulated to produce a load current of ~3App at 100Hz and a Bode plot of the Sense Channel Response.Best

author: joeqsmith
author_rank: Super Contributor
timestamp: September 23, 2025, 05:05:34 pm
content: Quote from: mawyatt on September 23, 2025, 04:29:37 pmWe have a BK load that has inputs allowing external control from an analog source. You can also run it from the front panel or with a serial interface. It has a pulse mode and has a setting for the slew rate. They spec a 2.5A/us with the fast slew rate selected.We also have a controller made by California Instruments for running flicker and other similar tests. Basically its an Arb with power output stage.

author: KrudyZ
author_rank: Frequent Contributor
timestamp: September 24, 2025, 03:13:36 am
content: Quote from: joeqsmith on September 23, 2025, 11:44:45 amIsn't that exactly what the OP was trying to do, generate a current proportionate to the AWG voltage?The BOP series does both V->V and V->A

author: joeqsmith
author_rank: Super Contributor
timestamp: September 24, 2025, 04:01:02 am
content: I am not sure. There was no link provided to what started the discussion and from the starting post, it was not clear to me. That BK load I mentioned will sink, not source. It can run constant current, voltage, resistance, or power I think. I only mentioned it as OP brought up power supply testing as a use case.

author: mawyatt
author_rank: Super Contributor
timestamp: September 24, 2025, 02:12:34 pm
content: This thread was precipitated by the discussion Smokey mentioned above in post #7.Our interest was we don't have a supply of any kind with external control capability, and using a SMPS (KWR102) was the only supply we had withExternal Sense Terminals, so decided to give it a tryBest

author: joeqsmith
author_rank: Super Contributor
timestamp: September 24, 2025, 06:34:09 pm
content: When I read their post, I thought it was some insider discussion and the link was their signature so I never checked it.Now that I have some context, it makes much more sense.With them only looking for 10A and 10Hz, voltage control, plus they can run it from a car battery so really just a simple DC-DC. They didn't seem to mention distortion so requirements must be fairly relaxed. 10Hz is so slow, the type of load shouldn't pose a problem.They mentioned needing it fast. Maybe they have parts laying in the scrap bin to pull it off. 10A@12V drop, could just burn it up in heat. 317 regulator and a pass transistor with a big heatsink...

author: ali_asadzadeh
author_rank: Super Contributor
timestamp: September 24, 2025, 06:39:00 pm
content: I Wonder if this set up can be used to inject sine wave currents into smart grid toys like protection relays to calibrate their CT. Actually I'm designing a new over current relay and I need this toy to be a precise sin wave current source!