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What's in a power supply.....your design ideas

colporteur — Sun, 31 May 2026 20:42:59 GMT

What do you include in your power supply design? For years, I use a LM7805 regulator with an input and output capacitor as my simple 5V power supply on PCB's. (top drawing) Itypically plug in a 12VDC wall wart as a source. I use the same 12V to feed the Arduino. No AC design needed.

I discovered after my Spring Clean project, it would be nice to have power supply indicators. I seem to recall Shabaz had some nifty things he did with zenor diodes on power supplies. Great protection, little cost. I can't find my notes on that idea. A search for power supplies in the community I came across this. [mention:0246f71516444919a690f367645308de:f7d226abd59f475c9d224a79e3f0ec07] From the post I added the indicators and the protection diodes to mine. (bottom drawing)

I've seen designs with an LM317 regulator, looks cool. I have a bag of LM7805 components I have to use up so regulator changes are not a high priority. I find it hard to walk away from components that are bought and sitting on the shelf.

I recalled when I worked in Engineering during the 80's, new Electrical Engineers assigned to a project would always start trying to improve the power supply. Our derogatory comment, there is a new power supply born for every Engineering graduate. As an Engineering Technologist I never understood why you would design something you could buy off the shelf.

For a few buck you can get a DC to DC power supply with indicators and other bells and whistles. Why build your own. I just like a 5V supply on my designs.

My goal is to enhance my current power supply design with some bells and whistles. Identify the parts and then perfect a PCB layout I can replicate in the future. My first step in any KiCAD project is copy the power supply. With that done I can start step 2. If you have insight to share that would be great. If you have a KiCAD drawing to share that is even greater. I'm no above begging to get ahead.

RE: What's in a power supply.....your design ideas

colporteur — Tue, 02 Jun 2026 22:40:08 GMT

Yeah that ain't going to work. The indicator diodes are reversed. Working the schematic in KiCAD and found the oops.

RE: What's in a power supply.....your design ideas

colporteur — Mon, 01 Jun 2026 16:22:59 GMT

At one point in my electronics lifecycle I could do those goes-into calculations. Now I use resources of digi-key when I think about it. You mention 1.5A. I need to look at the wall warts ( collection of phone chargers) I'me using. I think they are less than 0.5amps.

RE: What's in a power supply.....your design ideas

michaelkellett — Mon, 01 Jun 2026 14:02:02 GMT

If you do a pcb for it I suggest that you add the 2 RCs across the rectifier - if they don't do any good then you don't need to fit them.

Referring to your circuit above, 10uF on the input looks very small.

I think the LM317 can manage 1.5A. At 50Hz you might expect to see 750V ripple (assuming a conduction time of 5ms).

4V ripple at 1.5 A sounds more reasonable so C1 = 1.5 / 4 * 0.005 = 1875uF - use 2000, 2200 or maybe 1800.

You can scale with current - so if the max current you will draw = 500mA then a 680uF will be fine for C1.

RE: What's in a power supply.....your design ideas

colporteur — Mon, 01 Jun 2026 13:25:10 GMT

Power supply design is an electronics art on itself. The supplies found in rack servers blow me away. A little overkill for a simple Arduino project.

I've just started chapter 9 in the book you mentioned. It has contributed to this redesign motivation. My son-in-law pokes fun at me because the book is my go to bathroom reading material.

I included the protection diode ideas from the second drawing in my upgrade.

I found an LM317 circuit drawing that holds some promise. Changing two resistor to get a different O/P voltage. This redesign is to create the ubiquitous P.S. for projects. I can't recall the last time I used an O/P other than 5V. It would be nice to have a 3.3V option. Maybe this circuit with the protection diodes from your second drawing is an option. Humm wonder how it layouts on a PCB?

RE: What's in a power supply.....your design ideas

michaelkellett — Mon, 01 Jun 2026 08:23:16 GMT

What you put in a power supply must surely depend on the specification.

Input voltage range

Output voltage (range if adjustable)

Output current

Input transient protection

Output over-voltage protection

Noise

Max inrush current

Efficiency

Cost

and many others.

I very often end up with an LD1117 in a SOT223 package and aluminium electrolytic caps on input and output but quite recently I did this:

It's a 5V internal supply which is part of a much more complex power supply. It can get input power from three different sources. When running from super-caps it needs very low current drain and may need to work with an input as low as 6V and up to 30V, from the external PSU it may get anything from 24 to 48V and from POE anything from 24 - 70V with 80V surges)

I couldn't find a switcher that could do everything including the 80V input so I had to use the Q11 pre-regulator on that power source.

A more general purpose tip that I can offer is that when you are using a mains supply with a transformer, bridge rectifier and big capacitor followed by a ciruit like your standard one then a common source of noise is ringing where the transformer inductance interacts with the rectifier diodes switching. An easy fix is to put snubber caps across the rectifier.

(See Art of Electronics 3, The X chapters, chapter 9x.6 page 410)

I try to remember this whenever I design a mains powered supply.

This PSU was designed to power some current sense buffer amplifiers which needed an isolated low noise supply.

RE: What's in a power supply.....your design ideas

ralphjy — Mon, 01 Jun 2026 04:22:28 GMT

You need to flip the LEDs over in your schematic so they are forward biased.

RE: Triple Output Bench-top power supply - Any requests?

beacon_dave — Sat, 23 May 2026 09:01:23 GMT

Sounds familiar... 🙂

USB to Banana Plug Adapter

https://community.element14.com/products/pcbprototyping/b/pcb-blogs/posts/usb-to-banana-plug-adapter

Triple Output Bench-top power supply - Any requests?

Magnethicc — Wed, 20 May 2026 07:28:08 GMT

Hi Everyone,

I will be designing a high performance triple-output bench power supply and I was wondering if any of you have any information regarding your current benchtop power supply:

1. what do you like about it?

2. what do you don't like about it?

3. what kind of features is missing as of today and wish were available?

feel free to go nuts, any help is greatly appreciated!

RE: Triple Output Bench-top power supply - Any requests?

dougw — Sat, 23 May 2026 07:01:36 GMT

It is handy to have a USB connector that can supply USB voltage and display how much current the load is consuming.

RE: Triple Output Bench-top power supply - Any requests?

geralds — Thu, 21 May 2026 10:32:41 GMT

Please read michaelkellett 's information and arguments again carefully.

I agree with him; I think similarly.

BUT --- What is YOUR wish?

You haven't answered any of the questions so far. 😉

The real point is: what do you need for yourself? The thoughts and wishes of others are rather irrelevant.

You have to choose what's right for YOU, what functions it should have, and then you have to calculate YOUR costs accordingly.

..."" 😎 ""...feel free to go nuts, any help is greatly appreciated! ..."

RE: Triple Output Bench-top power supply - Any requests?

michaelkellett — Thu, 21 May 2026 09:09:34 GMT

As is common with questions such as yours I find that replies (including mine) focus on the current project. One of my current projects is a switching supply for precision motor control - its a buck regulator designed for very high efficiency and fast dynamic control of the output voltage.

It works with anything from 10 - 60V input and may draw up to 10A from its supply, it is capable of 8.5 to 60V outputs at 6A (8A for short periods). The efficiency is between 90 and 96% for any combination of input and load above 0.5A. It has built in pull down for fast output voltage change with low or zero load.

Now you can see the form of my PSU requirement - currently I'm using the AimTTi MX180 for the supply but it cant provide enough current at 60V. I'm using a Rigol DL3031A electronic load and a Keysight DAQ970A for data acquisition with a custom interconnecting box for current measurement.

It's all controlled by a PC via Ethernet.

If I want to test at full input power I have to use a brute of a supply which has only manual or analogue control and can do 100V @ 28A.

I want a load which can simulate a motor type load and feed power back into the supply.

A typical source meter can do all this but only at low power.

Analogue modulation allows you to connect an existing programmable waveform generator. A built in one would be fine but all to often these are poor second cousins to a decent signal generator. (You need triggering, slew rate control etc).

A single box solution to this problem would great, but unlikely. I think Keysight can do it (just about) with multiple boxes but very expensive.

So in the end I'll do the motor load testing with a motor !

Could you explain you project a little - is it commerical, marketing, fun or something else.

RE: Triple Output Bench-top power supply - Any requests?

Magnethicc — Thu, 21 May 2026 08:24:09 GMT

What do you like about the E36313A that you can't find in other bench power supplies?

What does it miss?

Thank you.

RE: Triple Output Bench-top power supply - Any requests?

Magnethicc — Thu, 21 May 2026 08:01:08 GMT

I do not know how you came to the conclusion that I am not knowledgeable about electronics 🙂

RE: Triple Output Bench-top power supply - Any requests?

Magnethicc — Thu, 21 May 2026 07:59:47 GMT

Thank you Doug.

What do you mean by USB output that can monitor or limit current? can you please elaborate?

RE: Triple Output Bench-top power supply - Any requests?

Magnethicc — Thu, 21 May 2026 07:58:48 GMT

Thank you so much! a few questions:

1. why would you want the analog modulation?

2. would a 200W source, 20W sink will be good enough as a 2 quadrant or 20W is too little?

3. Would you wish for an arbitrary waveform generator? if Yes what kind of specs would be necessary (what bandwidth for example?)

RE: Triple Output Bench-top power supply - Any requests?

robogary — Wed, 20 May 2026 20:47:18 GMT

I sure would be nice to have an array of usb jacks so I can use standard cables instead of breakout cables.

RE: Triple Output Bench-top power supply - Any requests?

geralds — Wed, 20 May 2026 20:38:24 GMT

It's not so easy to "do"... "it" ... "yourself" (yes, I phrased it that way deliberately).
I have many circuit diagrams and assembly drawings.

I also have service manuals for older Keysight bench power supplies with detailed circuit diagrams and measurement descriptions. I've repaired such devices.

In analog times, that would have been somewhat cheaper, but his question shows that he is looking for a microcontroller-controlled laboratory power supply.

That's not so simple.

His question also reveals that he's not particularly knowledgeable about electronics.

Hmm, how can we help him? With a good recommendation. I think it would be best for him if he bought one.

RE: Triple Output Bench-top power supply - Any requests?

michaelkellett — Wed, 20 May 2026 16:40:54 GMT

It will be a lot of work to match the specs of that one with a home brew !

RE: Triple Output Bench-top power supply - Any requests?

geralds — Wed, 20 May 2026 16:02:43 GMT

I've always wanted to build a really great desktop power supply.

Due to lack of time, I postponed it and am now using the Keysight E36313A.

https://www.keysight.com/us/en/product/E36313A/160w-triple-output-power-supply-6v-10a-2x-25v-2a.html

RE: Triple Output Bench-top power supply - Any requests?

dougw — Wed, 20 May 2026 14:31:38 GMT

I have a triple output supply that I use extensively. It has one high current output but that output only goes to 6V. The two 30V outputs only go to 2A. The only combination I miss is an output capable of 24V at 3A. (My supply can do this by using 2 outputs in parallel) but then I only have 2 outputs. It would be nice to have a USB output that monitors current or can limit current.

RE: Triple Output Bench-top power supply - Any requests?

michaelkellett — Wed, 20 May 2026 08:52:31 GMT

I have two preferred bench power supplies:

AimTTi QL564TP, Linear supply, 2 main outputs, switchable ranges 0-25V, 4A and 0-56V, 2A, full LAN control.

Used almost all the time, there are few days when it isn't switched on.

AimTTi MX180TP

also with full LAN control

Used less often but good when higher power is needed.

Both of these supplies are quite easy to use under manual control and easy to programme via Ethernet or serial port.

The metering (especially on the QL564) is quite accurate. The ergonomics could be a little better on both supplies - a rotary control per channel would be good and the QL564 would benefit from a better display.

I have other supplies (many) for more specialised things.

When you say high performance I wonder what you actually mean - putting everything in one box would be possible but absurdly expensive.

Perhaps you could explain the idea behind your project.

Just for fun this is what I would like:

+/-60V @ 10A full 4 quadrant operation , noise less than 0.5mV p-p 20MHz bandwidth, settling time < 100us, constant voltage, current and power modes, full LAN control, analogue modulation supported, 6.5 digit metering, 2U 19" format. Built in battery emulation mode. 3 identical channels fully isolated from each other, simultaneous 6 channel current/voltage metering at > 10ks/s

(Effectively 3 high power source meters in one box)

Price under £10k ☺

MOSFET recomendation for LTC4008 Li-ion Charger (5 cells pack)

e14 Contributor — Mon, 04 Feb 2013 10:01:33 GMT

Hi,

I´m currently designing a 5 cell pack Li-ion charger with LTC4008 chip (discussion posted in Sep 2011 in this thread)

In page 15 of LTC4008 datasheet you can find the topic about the MOSFET selection.

I´m certainly lost in the proper selection. I know that logic-level MOSFETS must be used (gate voltage around (5.6V-6V), but is the first time for me designing with mosfets.

One important point is the output voltage of the carger, datasheet says that if Vout>20V then the RDSon should be little more high for reducing the ripple...

The charge voltage will be 20.5V and maximum Output Current 1.5A

I was thinking on use the mosfets that appear in the schematics of the datasheet, but has anyone any recommendation?, I mean, do I have to go deep in the mosfets area or can I use one recommended by anyone who has be involved in similar scenarios?

The only important thing in this design is the proper selection for minimum ripple current, at cost of something (as always). Efficiency for example is not a problem cause it´s a battery charger (I prefer to lost energy efficency if that means reduce ripple current in the output). I´m thinking to use a slightly high Inductor (around 40 microH) and two low ESR tantalum capacitors "surge robust" in parallel in the output of the mosfets.

Any comments are appreciated

PS: I need reference values. (What means high ... what means low... 0.001 - 0.01 ? (in mosfet parameters)

RE: MOSFET recomendation for LTC4008 Li-ion Charger (5 cells pack)

Pradipsinh — Fri, 24 Apr 2026 05:22:08 GMT

Which use mosfet

RE: MOSFET recomendation for LTC4008 Li-ion Charger (5 cells pack)

Pradipsinh — Fri, 24 Apr 2026 05:20:30 GMT

7.2 ah battery charger use Ltc4008 which mosfet runnig