[Solved] How to find voltage regulator for 3.3V or 5V at 3A to 5A

@ronalex4203

Solid state devices are much much simpler than the old power hungry tubes.

Bill has a tutorial/project on converting a computer power supply to a bench power supply.

There are voltage regulator ICs that can do the job.

I use this voltage regulator module for some experimenting.

You can set it to 5v or 3.3v and it has an on/off toggle button.

@robotbuilder Thanks, I have a 450W PSU coming in this week for my big supply, and I have 3 of those breadboard supplies. I want to build a laptop brick supply for medium duty with more than 3v3@800ma, say more like 3A to 5A and for 5V maybe 10V. This is in order to support maybe 6 devices at once.

My question remains, how do I do the research to find an acceptable voltage regulator for 3.3V at 3A to 5A. I think the LM1085 is 3A and the LM1084 is 5A but I don't know if I am missing a spec that makes this device a poor choice.

@ronalex4203 

Ok. Probably I would just have a regulator chip for each device but it is not an issue I have had to deal with.  I assume you have watched Bill's video on regulators and converters?

@robotbuilder I have, but I need to watch it quite a few times for it to sink in. Combination of being 'on the spectrum' and aging memory cells. Remember I am trying to learn how to make bread, not be given a loaf if that makes sense.

@ronalex4203 

Use a buck regulator, it's more efficient.

https://www.amazon.ca/Converter-1-25-36V-Voltage-Regulator-Display/dp/B085T73CSD/ref=sr_1_1?dchild=1&keywords=dc+5A+buck+regulator&qid=1635385042&sr=8-1

@will I will re-watch the video tomorrow when I have some time. I have a handful of those LM2596 but I thought they were the brute force solution and very inefficient. I just read the Wiki on that and see I was 180 degrees wrong. It does make me wonder though why Bill chose AMS1117's for the ESP32-CAM developers board which is where I started. I see now I asked my initial question wrong. Maybe I will re-post after watching the video unless that answers all my questions. Thanks for the pointer, that might be the better answer, time will tell.

Posted by: @ronalex4203

@will I will re-watch the video tomorrow when I have some time. I have a handful of those LM2596 but I thought they were the brute force solution and very inefficient. I just read the Wiki on that and see I was 180 degrees wrong. It does make me wonder though why Bill chose AMS1117's for the ESP32-CAM developers board which is where I started.

For relatively low-current applications, the linear regulators are simple and small by comparison to a switching regulator (buck/boost converter). The wasted power is also relatively easy to calculate (Vin-Vout)*Current. For small currents this is fine.

Another issue can be that switching regulators, by their nature, switch. This switching mechanism can introduce high frequency noise into the power system (on both the supply and output sides). This is the reason that pretty much all buck or boost converters you buy will specify the operating frequency.

Posted by: @jker FYI @ronalex4203

For relatively low-current applications, the linear regulators are simple and small by comparison to a switching regulator (buck/boost converter). The wasted power is also relatively easy to calculate (Vin-Vout)*Current. For small currents this is fine.

I agree, but he was talking about 10A at 5V. Assuming that he's using a 9V source (has to be >6 for the regulator drop), then we're talking (9-5) x 10 = 40 watts.

Another issue can be that switching regulators, by their nature, switch. This switching mechanism can introduce high frequency noise into the power system (on both the supply and output sides). This is the reason that pretty much all buck or boost converters you buy will specify the operating frequency.

Agreed, electronics is always a trade-off. Thanks for making the trade visible 🙂

@jker Thanks for explaining the cons of each approach. I kind of had that information in my head but did not know about the trivial calculation for the heat loss in the voltage regulators. Can you or anyone explain the impact of the 'noise'? What is the difference between 150kHz and 400kHz for instance. If the noise is a problem, are there not devices that can be added to the circuitry to reduce the noise?

@robotbuilder Watched the video and did pick up a valuable piece of information for battery operation. His meter was measuring the gate voltage and current, so finding a device with the lowest current consumption is a better choice for battery power. 

@will I have 3 of those plus a handful of LM2596. I think my original question should have been two questions and I certainly did a poor job of posing my root problem. The DROK's I have were bought a while ago and I don't foresee using them in any of the 3 power supplies I am building because to me it would be silly to bury a device with all that UI capability inside a case. Now the LM2596's are a different story, I am now planning on using them for my 3A supply. 

@will Perhaps I should have put in my profile that I am prone to 'thinking out loud' and I typically do any design work at least 5 times, code 3 times. My previous post had a typo that you compensated for, I meant to say 5V @ 10A. That is actually too high. Here is the latest design objectives.

1. BIG ATX style 450W mains powered. 12V @ 36A, 3.3 and 5 at 20A but total wattage is 110W

2. Medium laptop brick supply, 19V @ 4.74A in, 3.3 and 5 at 3A, 12V @ 5A

3. Light portable either 9V battery, same brick as above and now thinking of using my 20,000mAh Anker brick to produce 3.3, 5, and 12V @ 1A, more on the 12 if possible up to 3A.

I just got educated by Bill on Buck/Boost devices so using the high AH 5V power brick might work for driving at least 1A at 12V for about 90 minutes.

So how do I find the device that will work from 20V to 4V input and put out 12V?

I was hoping to hear that there is a web site that I plug in my knowns and it gives me a list of choices.

Posted by: @ronalex4203

@jker Thanks for explaining the cons of each approach. I kind of had that information in my head but did not know about the trivial calculation for the heat loss in the voltage regulators. Can you or anyone explain the impact of the 'noise'? What is the difference between 150kHz and 400kHz for instance. If the noise is a problem, are there not devices that can be added to the circuitry to reduce the noise?

The effect of the noise depends on exactly what you're using the rail for and the relative characteristics of the noise and your circuit. With sufficiently expensive measuring devices, you can determine that there is no such thing as completely eliminating noise. 🙂

You can measure the noise introduced by a LINEAR regulator's internal components, but it will generally be quite small (an AMS1117, for example, might have noise around 0.004% of Vout).

The simplest device to reduce noise on a power rail is simply to put a Low Dropout linear regulator after a switching power supply. By controlling the switching regulator output voltage, you can drastically reduce the linear regulator's input voltage to minimize the power loss in the "second stage".

But before you do that, you should consider the effect of the noise. Outside of the analog domain, _reasonable_ switching noise is usually not a problem. The most common effect is, as alluded to in my signature, unintentionally creating an antennae in your wiring.

@jker Sorry, I don't get it. What do you mean when you say 'unintentionally creating an antennae in your wiring.'?