Is DC-to-DC (24 V To 12 V) Buck Conversion Typically More Efficient ...

1. 1. Home
   2. Questions
   3. Tags
   4. Users
   5. Unanswered
2. Teams

   Ask questions, find answers and collaborate at work with Stack Overflow for Teams.

   Try Teams for free Explore Teams
3. Teams

4. Ask questions, find answers and collaborate at work with Stack Overflow for Teams. Explore Teams

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Learn more about Teams Is DC-to-DC (24 V to 12 V) buck conversion typically more efficient than AC-to-DC (110 V to 12 V) conversion? [closed] Ask Question Asked 5 years, 8 months ago Modified 5 years, 8 months ago Viewed 4k times 6 \$\begingroup\$ Closed. This question needs to be more focused. It is not currently accepting answers.

Want to improve this question? Update the question so it focuses on one problem only by editing this post.

Closed 5 years ago.

Improve this question

While building an online UPS system, I'm basing the choice to eliminate as many AC inverters from the system as possible because of the assumption that DC-to-DC conversion is more efficient than AC-to-DC conversion.

I'm not totally sure that this is the case though. I've read some articles stating that buck conversion might only be 85% efficient, yet many product offerings tout 97% efficiency. Also, one of the big selling points on AC is the efficiency of conversion. I am hoping to get some solid information on this specific efficiency comparison.

• dc-dc-converter
• buck
• inverter
• ac-dc
• comparison

Share Cite Follow edited Apr 28, 2019 at 11:49 Peter Mortensen 1,69333 gold badges1717 silver badges2323 bronze badges asked Apr 27, 2019 at 22:25 DoblerDobler 17911 silver badge55 bronze badges \$\endgroup\$ Add a comment |

4 Answers 4

Sorted by: Reset to default Highest score (default) Date modified (newest first) Date created (oldest first) 9 \$\begingroup\$

No general statements can be given.

Generally, the larger the input/output voltage ratio is, the smaller the efficiency for basically all converter topologies.

However, whether you end up with 70%, 85% or 99% efficiency depends on the actual converter and the load.

The reason installation wiring uses higher voltages like 120V or 230V is that the energy losses during transportation will be lower if you need less current to deliver the same power – so, the very standard way of having 120V to racks of equipment and then individual converters where you need your power makes a lot of sense.

AC/DC converters are technically so close to DC/DC converters that the difference between those is shadowed by other technical considerations, such as how much you need to "overdimension" your power supply, how much money you want to invest in copper, and whether you're going for constrained size etc.

Share Cite Follow answered Apr 27, 2019 at 22:38 Marcus MüllerMarcus Müller 101k55 gold badges141141 silver badges264264 bronze badges \$\endgroup\$ Add a comment | 5 \$\begingroup\$

There will be almost no difference in the conversion efficiency of an AC-DC versus a DC-DC convertor. For example if you used a PC power supply to convert 120/240 to 12VDC (I'll simply ignore the other voltages produced), most modern SMPS supplies are at least 85% efficient:

Here you can clearly see that the efficiency at some reasonable load range is much better than 85%, and up to 90% for some portion of the load managed.

A DC-DC convertor specifically designed for 24-12VDC conversion could be expected to achieve similar efficiencies at reasonable loads.

However, there are other differences that may impact your decision.

1. A task designed 24-12V convertor may run at a much higher frequency than a PC power supply and be more space efficient for the same power output.
2. For any given 12VDC load current the 24-12V convertor will have more input current flowing than the PC power supply. This may significantly impact the I^2R losses on the primary side.
3. The device cost (FETs voltage rating, isolation components, inductors) will be significantly higher in the PC supply.

You need to decide where your cost vs performance decisions are made.

Share Cite Follow edited Apr 27, 2019 at 23:29 answered Apr 27, 2019 at 23:14 Jack CreaseyJack Creasey 22k22 gold badges1616 silver badges2929 bronze badges \$\endgroup\$ Add a comment | 3 \$\begingroup\$

I would suggest, based on my own experience, the DC-to-DC route is better for low power situations like just a few watts. If you need kilowatts, you'd better go AC to DC.

In between the efficiency is unlikely to be regulated by this particular choice as pointed out by Marcus. I have used buck convertors with 90% or greater efficiency, and they are pretty well developed nowadays.

Share Cite Follow edited Apr 28, 2019 at 11:49 Peter Mortensen 1,69333 gold badges1717 silver badges2323 bronze badges answered Apr 28, 2019 at 0:57 PJ NoxonPJ Noxon 5344 bronze badges \$\endgroup\$ Add a comment | 1 \$\begingroup\$

You will be hard pressed to find any 120Vac to 12Vdc converter as efficient as the best 24V to 12V DC-DC converter in the mid 90% for a 120W range and up.

But then the energy must come from somewhere else besides 24V which will also have efficiency losses just as the AC to DC conversion does in the 1st stage.

Share Cite Follow answered Apr 28, 2019 at 13:37 Tony Stewart EE since 1975Tony Stewart EE since 1975 149k33 gold badges5656 silver badges190190 bronze badges \$\endgroup\$ 2

• \$\begingroup\$ Can you explain what the first stage is? \$\endgroup\$ – Dobler Commented Apr 29, 2019 at 19:02
• \$\begingroup\$ 1st stage is the pulsed charge pump from AC peak voltage to DC or in the case of Active PFC designs the switched sinusoidal boost current to some higher voltage DC so that the current follows voltage or PF=1... silverstonetek.com/techtalk_cont.php?area=en&tid=wh_pfc \$\endgroup\$ – Tony Stewart EE since 1975 Commented Apr 29, 2019 at 19:06

Add a comment |

Not the answer you're looking for? Browse other questions tagged

• dc-dc-converter
• buck
• inverter
• ac-dc
• comparison

or ask your own question.

• The Overflow Blog
• How AI apps are like Google Search
• Featured on Meta
• The December 2024 Community Asks Sprint has been moved to March 2025 (and...
• Stack Overflow Jobs is expanding to more countries

Related

2 Convert 320VDC to 220VAC or 48VDC voltage using 220VAC (UK) UPS? 4 Capacitor Powered Vehicle Project 0 Inverter Design - What DC input voltage for most efficient DC to 120VAC inverter 1 DC-to-DC conversion for solar, off the shelf or custom? 0 DC Buck Converter for more than 3A 0 How to deal with an inconsistent / noisy power signal? 6 Is the zeta DC-DC converter topology scalable to 50kW / hundreds of amps? 11 Is discontinuous conduction mode of a buck converter more efficient than continuous conduction mode? 5 Is a buck converter less efficient than 2 seperate PSUs? 1 For a high powered LED loads, is a buck or boost converter more efficient / simpler?

Hot Network Questions

• How was 煞 created from 殺?
• FindPeaks for sharp and broad peak
• Online Service Course in the era of ChatGPT
• Would a thermometer calibrated for water also be accurate for measuring the air temperature (or vice versa)?
• What is this FreeDOS kernel loader found on the “W3x4NTFS” disk image?
• determinant defining properties
• Ascon-128 cipher for 64-bits unique nonces
• What do people mean when they say "Everything is connected"?
• Algebraic equation to represent a triangle.
• What's left of wine or vodka after the water and alcohol is boiled off?
• Flat 2x4s as shims to raise and level a floor. Shorter better?
• Do we know when a cohomology theory "comes from a site"? In particular, is compactly supported cohomology a sheaf cohomology on a site?
• Why don't bicycles have the rear sprocket OUTSIDE of the frame spacing? (Single speed)
• Question regarding one modification of one inequality of Young type
• Image of the entire function
• Trying to find a middle grade book about a boy finding his way back to his reality/universe after he's taken away from it
• QGIS labeling: Why do we need a primary key for the auxiliary storage?
• \MakeLowercase in \section
• Why is pattern recognition not racism?
• Understanding the benefit of non principal repayment loan
• What builds a nest or storage structure in the shoe?
• Does gravity from a star go through a black hole's event horizon to affect objects on the other side?
• US Citizen Proposing to Foreigner
• Why does the engine prefer a5 (pass pawn) over axb5 (pass pawn+win a pawn)?

more hot questions