Clean DC supply?

Hi,

I want to make a circuit that can take a simple 10-15V DC input and give me a multiple clean regulated 12V DC outputs. I want the output's to be isolated from the input and from each other to stop interference. The output's would only need to supply about 2-4 amps each maximum. That's the idea I have in my head anyway. I'm an electronics novice so I don't know how much of this is possible.

This is to supply power to several pieces of Hi-Fi equipment that require 12V DC supplies.

Could anyone point me in the direction of a suitable design for this?

May thanks,

David.
 
Google '12V buck boost'.

Thats what you want, a bunch of 12 volt buck/boost regulators. They'll be a switching regulators, so I don't know about 'clean DC' but it'll be regulated.

Or you could use a single boost regulator to say 18V and a bunch of linears to regulate back down. A 7812 will give you 12.6V if you connect the ground pin via a diode, then you can connect that to the bases of a bunch of (NPN) pass transistors all with their collectors connected to 18V and you'll get 12V at the emitters.

w
 
Since you want multiple isolated voltages, you must use a transformer-coupled converter. The maximum output power will determine the topology. At low power levels one might consider flyback, at higher power levels push-pull. Personally I would recommend using push-pull since the input voltage is very low. At low input voltage and high output power the input current will be large though.

But if you have never designed a switching converter or even studied related issues, I would say forget it. Or give the design task to someone who knows how to do it.

WBR
 
Thanks for the replies,

So far I've mainly looked into the buck boost regulators. These seem to fit the requirement for varying input voltage and constant output voltage. I've seen these called DC/DC converters which I've heard of before. Is a buck boost regulator the same as a DC/DC converter?

For example, I found THIS slightly expensive dual output DC/DC converter which can handle 9-36V DC input with a fixed 12V DC output at 6A. Would this do the job?

I'm not sure if this provides isolation between it's outputs though.
 
DavidJE said:
...Is a buck boost regulator the same as a DC/DC converter?...
A buck-boost converter is a type of DC-DC converter. There are various topologies that have different properties, with the main feature of the buck-boost topology being that it can both step up and step down the voltage.

Like Bootstrapper said, if you want isolation then you need a transformer. The simplest transformer-based topology is the flyback converter. However, as Bootstrapper also said, a DC-DC converter is not a good project for a novice.
 
You could possibly look at computer PSU's or commercial DC-DC convertors initialy, though the 10-15V input may be a problem. For the output power you require up to 48W, and multiple supplys, a custom built circuit is gonna be rather complex. To keep the transformers size down to a reasonable level will require a higher switching frequency, more noise. The capacitors will have to be good quality low ESR, not cheep. And the layout problems!!! I have worked on a similar spec commercial product and it took us 6 iterations of circuitry, layout, thermal anaysis etc to get it right. Dont forget a big mosfet for switching those sort of currents, that adds heat, and switching losses. Thats why most commercial SMPS at these currents come in an metal case , EMC shielding and somewhere to bolt active components to get rid of the heat.
If you realy did want to go the DIY route, a well used topology for your input output voltage is an initial boost section maybe to 20V, with reservoir capacitors, then a secondry flyback to give you your isolated 12V. The bigger the initial boost section determines the amount of power you are storing and could vary depending on how many 12V outputs you want. This can often be the cheeper option in component cost as the reservoir caps can be relatively cheap, as apposed to a single stage buck/boost design which would be more demanding.
 
Thanks for the replies everyone, there's some really interesting info here.

For clarification, the DC input into this PSU is from a 12V battery, hence the possibly fluctuation input voltage. I mainly need one regulated 12V DC output from this but I stated multiple outputs for future proofing. If this is going to seriously complicate things then I'll probably drop that requirement.

Also, the amount of current drawn from this PSU will probably be much less than 4A, especially if I only have one output. If I have one output it will probably not be above 1A. With two outputs probably no more than 2A.

If I do decide to have multiple outputs, I'm not sure if I need them to be isolated from each other. Would isolating them from each other provide any benefit to the sound quality of the connected devices?

Also, to provide isolation between the two outputs, could I just use two separate buck-boost converters? The DC/DC converter I linked to earlier states that it's output is isolated from it's input, so I would have thought that connecting two to the same input would provide isolation between the two outputs. Please excuse my ignorance if this is entirely wrong.

Many thanks,

David.
 
Clean DC and Clean AC

Dear friends,
I have an Intel NUC connected to a DAC and I have also a Preamp and an Amplifier.
I want to give the NUC (19V, 65W) clean CD and I've heard that there are modules that can do that.
Is there a module that can give PURE DC to the nuc from it's power supply (I don't want to buy a 1,000 USD linear power supply)?

I also want to clean my AC power from many interferences an I saw a filter at Aliexpress but I don't know if it's good.

Any suggestion?

Thank you very much.

Ilan.
 
ilan5555 look for an adjustable 24 volt power supply 120-240 depending on where you live. Some are 110-240 input so it should work any where.

here is onehttps://www.aliexpress.com/item/10000369192918.html?spm=a2g0o.productlist.0.0.7c9813f8PRRw6T&ad_pvid=202105180847364952386938348080041923456_2&s=p

I dont know why you want a quiet power supply, every mother board has a lot of switching regulators on it.

If you are worried about noise getting into your dac from you PC use an optical connection.
 
ilan5555 look for an adjustable 24 volt power supply 120-240 depending on where you live. Some are 110-240 input so it should work any where.

here is onehttps://www.aliexpress.com/item/10000369192918.html?spm=a2g0o.productlist.0.0.7c9813f8PRRw6T&ad_pvid=202105180847364952386938348080041923456_2&s=p

I dont know why you want a quiet power supply, every mother board has a lot of switching regulators on it.

If you are worried about noise getting into your dac from you PC use an optical connection.

Dear Multisync,
I have the NUC power supply and I read on some forums that clean DC is better for the sound.
The NUC doesn't have an optical connection as far as I know.

I also need to clean my AC power for my amplifier.

Thank you,

Ilan.
 
Google '12V buck boost'.

Thats what you want, a bunch of 12 volt buck/boost regulators. They'll be a switching regulators, so I don't know about 'clean DC' but it'll be regulated.

Or you could use a single boost regulator to say 18V and a bunch of linears to regulate back down. A 7812 will give you 12.6V if you connect the ground pin via a diode, then you can connect that to the bases of a bunch of (NPN) pass transistors all with their collectors connected to 18V and you'll get 12V at the emitters.

w

be aware of power dissipation. 18V to 12V under 2A (min). The regulator will dissipate 12W ;) a 7812 can provide suc a current ? (1.5A max in the datasheet)
 
Are you trying to fix a problem you don't have? You can buy a car or you can buy $$$$$$ filters, cables, interconnects etc. Virtually every comercial power supply has a line filter inside it. Sometimes it's just a surge suppressor or a couple of capacitors across the line. Sometimes you will see what looks like a tiny transformer which is a common mode choke.

If you are connecting your dac via usb you can get a galvanic isolator. Look for galvanic usb isolator.
 
I think best solution is to use a DC/DC with nominal 12V input (9-12V or 9-36V) and then have an output just above 12V to use LDO and limiting the dissipation. The DC/DC shall have a trim pin to tune the nominal 12V output to 12.5V for example. Then, many LDO to have many 12V clean DC. With a dropout of 0.5V the dissipation will be 1W to 2W for each regulator.

You cand try TDK Lambda DC/DC (some of them have a trim pin, some of them not), TRACO, XP POWER, CUI, MEANWELL -> search on mouser or directly on the website of above manufacturers.

For LDO, TI, Analog, Maxim, ....

What total power you need (how many 12V/2A or 12V/4A do you need) ? it will define the power of DC/DC. For LDO, you need a LDO with 2A or 4A of output current with a dropout of 0.5V max if you want to limite dissipation and avoid heatsink (if you configure the DC/DCoutput to 12.5V. If you find only a LDO with a dropout of 0.6V at 2A or 4A, then configure DC/DC outputs to 12.6V and so on)

However, for 2A you could find a LDO with a dropout less than 1V but for 4A output it is more difficult (one of the best, the classical LM1084/5A has 1.5V of dropout @ 5A so dissipation will be 7.5W. It is huge. Heatsink is mandatory).

Another solution is to use the DC/DC without the trim and an output of 12V then a diode (or better an eFuse) to distribute the voltages on many branches and for each branch a passive Pi Filter (maybe 2 Pi filters in Series would be better if you want a very very clean DC). The standard in ripple for DC/DC is 1% of output so 120mV for 12V output. A Pi filter could achieve at least 40dB (x100) of attenuation if right calculated so 1.2mV of ripple for load.
 
Open up an old desktop or dead laptop power supply. You will find inside an input line filter and an output filter, just like you want to buy. Open up your dac you will find lots of regulators and powersupply filtering, same with your amplifier. Many changes to your system may or may change the perceived sound better or worse.

A few years after I retired I took a part time job. There at work I met another fellow retired guy who also worked part time. Neither of us needed the money, just something to do. He told me a story of when he worked as a salesman in a high end stereo shop. The client wanted a super tweeter in addition to his multi $$$$$$ speakers. My buddy said sure no problem. My budy the salesman and a technician went to the clients home added the tweeters, new crossovers fancy cables etc. Before they did any measurements and setups they listened to some music. The client was amazed at the improved micro detail etc etc etc. The technician whispered to my buddy and said the tweeters arent hooked up yet.