Introduction: DC-to-DC Converter

Picture of DC-to-DC Converter

I built this DC-to-DC converter for my 48V electric bike because I wanted to be able to plug-in some common 12V accessories, e.g. my cell-phone charger, or a GPS unit.

Step 1: Schematic

Picture of Schematic

Here's the schematic. The cap values are somewhat flexible depending on how much ripple you can tolerate. Be sure to observe the correct polarity for the electrolytic caps. I do not have a list of Digikey part numbers because I found many of the parts I needed at a local electronics surplus store. But all these parts (or something close) are available from Digikey.

Step 2:

Picture of

Since I found many of the parts I needed at a local electronics surplus store, I don't have Digikey part numbers for everything, but I have attempted to find Digikey part numbers or substitutes where possible. The connectors are up to the builder's discretion, broken PC power supplies are a good source for connectors and wires.

Step 3: Layout

Picture of Layout

This is a hypothetical layout for a single-sided circuit board. I did not follow this exactly when I built my protoytpe.

Step 4: Prototype Component Placement

Picture of Prototype Component Placement

This shows the components placed on a perf board (from Radio Shack). I just used point-to-point wiring on the back of the perf board to connect the circuit. The case is from a discarded cell phone charger. It's not shown in this picture, but I later bolted on a small copper heat sink to U1 to help keep it cool. For my purposes (cell-phone and GPS battery charging) I do not expect any heat problems from the converter. Be sure to use some thermal grease when attaching any heat sink.

Step 5: Ready to Charge That Cell Phone

Picture of Ready to Charge That Cell Phone

This shows the finished converter with a 12V cigarette-lighter dongle that is suitable for plugging-in a cell-phone charger or other 12V car accessory. I purchased the dongle at a local auto-parts store. The orange connectors are one-off connector types I found at a local electronics surplus store, but almost any 2-pin electrical connector will work. Salvaging connectors from a broken PC power supply is a good source of connectors and wire. I went a little connector crazy here; I don't really need any connectors on the 12V side since the cigarette-lighter dongle could be wired directly to the converter.

Note that the case does not close completely and I used 4 nylon standoffs (epoxied in place) to secure the top. I see this as a feature because it allows for airflow to the regulator :-)


dogukann (author)2017-01-26

Hi, I want to run a radio with your circuit. I have a 48volt power supply and my radio's values are;

supply voltage : 48V
speaker impedance : 4-8 ohm

I think that it will be ok, what is your opinion? Thanks.

scd (author)dogukann2017-01-26

What are the voltage and current requirements of your radio?

mohamadmahdi (author)2016-05-24


5v in to 19v uot



Jimmy Bravo (author)mohamadmahdi2016-10-07

This circuit is a DC-DC Step down Converter. You want to look for a Step up converter.

scd (author)mohamadmahdi2016-05-24

AnaM55 (author)2015-11-05

Hi! I'm a complete newbie to electronics and started studying for myself but short days are coming sooner than I can learn enough to wire my weirdo solar panel system! is there any chance you could give me some tips or direct me to someone who could?

I got this huge amorphous solar panel on sale that can work with very little light (good for stormy winter), but the thing outputs 319V at peak performance and over 400V in open circuit! Most solar panel chargers for 12V batteries can only handle about 48VDC input, and I can't find a DC-DC converter that can work within these in-out ranges.

So I ordered this TDK Densei-Lambda PH300F 280-15 converter that supposedly does the trick. However, it's supposed to be attached to external components for operation. I can do the heatsink part, but I understand nothing about choosing fuses, capacitators and the sort!

My charger can handle:
Max V input: 40VDC
Max A input: 20A

My solar panel outputs:
Open circuit voltage: 400VDC

Closed circuit voltage: 319VDC max

Max output current: 0.29A

Lamda converter I got:

Max V output: 15VDC
Max A output: 20A
Input voltage range: 200-400VDC

Input current max: 1.25A

Is there any chance I could get this setup to work with my limited knolage?

AbassM (author)2015-10-15

That's very interesting project. I am building a hybrid car and need to convert 240V to 12V. Any suesstions?

scd (author)AbassM2015-10-15

I do not have any specific suggestions. There are some online tools for exploring converter designs. For example:

olee5 (author)2015-07-13

Hi, thank you for a nice instructable.
I need your help plz. I need to use this converter with my diy 18650 li-ion battery pack and is about 57.6v 70A discharge(max). I checked the datasheet of the regulator ic but still wondering if I can apply it to my battery pack because of the ampare . Can you give me an advice plz?

olee5 (author)olee52015-07-13

Actually I'm using 50A Bms so the max current would be 50A

scd (author)olee52015-07-13

What are you planning to connect to the output of the converter?
What is the expected load current from the output of the converter?

olee5 (author)scd2015-07-13

Actually I'm planning to connect Arduino and IRS2104 using this kind of converter. I checked Digikey yesterday and found out LTC3637 would be great dor me. The datasheet even showed me a application ex for 12v output and I think input current is not that important for this chip(I'm not sure). Oh and one mistake I asked yesterday is, if I use the BMS, the 'continuous' discharge current would be 50A and it would be the input of the buck converter.

olee5 (author)olee52015-07-13

How do you think about using LTC3637?

scd (author)olee52015-07-13

The LTC3637 is only rated for 1A load current. Is this enough for your Arduino and IRS2104?

olee5 (author)scd2015-07-14

Yes. I searched yesterday and I concluded it would be fine :)

scd (author)olee52015-07-13

The 50A spec is a maximum rating for your BMS. The buck converter will only use a small fraction of this as its input current.

scd (author)olee52015-07-13

The LM2576HV-12 buck converter chip is rated at 60V, so yes, I think it should work, although 57.6V is pushing it a bit. It can handle up to 3A@12V (36W), but you may need some extra heat sinking if you plan to source that much current over a long period of time.

You can do a search on the Digikey site to find other buck converters that can handle higher voltages and higher currents. The circuit for any buck converter will look very similar to this one.

olee5 (author)scd2015-07-13

Really thank you for the help!!!

RickyD4 (author)2015-05-21

Your parts list includes a ferrite bead but the part number you have listed is a 10 microH inductor. What is the correct part number for the ferrite bead that would be similar to what you used?

scd (author)RickyD42015-05-21

Thanks for finding the error. I will fix the parts list.
You could try this one: 240-2296-ND

WaqarA2 (author)2014-12-10

Sir what, if we want to make 48V to 5V DC converter , changes we have to in this circuit.?? we need 5V to power controller in E-bike kit

scd (author)WaqarA22014-12-10

You could substitute an LM2576HV-5 for the LM2576HV-12

There are also many other buck converter chips available from other manufacturers that you could compare to decide which one would be best for your application.

Regards and Best of luck with your project :)

imark77 (author)2013-11-13

so this is such an interesting thing to run across as I am pondering something similar in voltage but different in requirements. I'm looking at something that has 48V in and 12V out, and looking at an output of approximately 500mA. the input current on the other hand is the tight spot as it varies and is vague and unclear as to what the maximum device draw capability is. and the rated output, is well never listed and varies between products.

so here's the idea.
wireless microphone receiver, requires 12V at Roughly 500mA (+/- 200mA).
XLR Cable
Mixer XLR microphone input, with 48V phantom power.

The Peace of mind of never having to dig out that darned power brick! = priceless!.
( On top of never having to find an outlet! ).
I call it a "phantom powered wireless microphone receiver" adapter ( But that's not what Google thinks! ).

More info on phantom power, what little there is.

Mikerwr (author)2013-10-01

How about 25v dc 200 amp to 16v dc 200amp any ideas?

scd (author)Mikerwr2013-10-01

That would take a custom designed DC-to-DC buck converter. I don't think it would be that difficult to design .. but the devil is in the details. What is the application?

cam1128 (author)2011-04-14

How would you make a 90V to 50V converter (with low amp levels)?

frank_w12 (author)2010-01-20

is there a way to go from 15 to 12

scd (author)frank_w122010-01-20

That's probably easiest to accomplish with a simple linear regulator such as a  7812 .. I found a 7812 datasheet here:

fatboyslim (author)2009-12-08

Is there a way of having in input of between 9-15 volts and achieving a ouput of 48-60volts?

scd (author)fatboyslim2009-12-09

Yes, but not with this circuit.  What you are looking for is called a boost converter.

kentdream (author)2009-07-23

LM2576HVT - 12 should do the job, however 2576HVT-12 only provide 3A output.

thz author SCD. I was also searching for a 48dc to 12dc for my electric bike.

maybe we can share more ideas about e-bike =)

BobS (author)2009-04-24

Not visible, no components list. This way it cannot be built. How about formulas to calculate different in and outputs; or make it variable/ adjustable? How about current?

atombomb1945 (author)BobS2009-04-24

Agreed, I would love to find out how to build this and step it down for a 24v system (Military Vehicles)

scd (author)atombomb19452009-04-24

This would work as-is with a 24V input voltage.

mykelpogi (author)scd2009-07-06

can you pls give more specific details on materials like voltage on capacitor , what kind of diode is shottky,inductor.. plss plss. can i use LM2575 instead of LM27576 more details pls.. because i real like to try ur work many thanks

scd (author)BobS2009-04-24

This particular switcher is not adjustable. It is 12V only. There are other similar switching regulators that do provide adjustability. The components are listed on the schematic and the output current capability is 3A (listed as a note in step 3)

silencekilla (author)2009-04-26

can you give us a list of the electronics components please?

scd (author)silencekilla2009-04-26

Since I found many of the parts I needed locally, I don't have Digikey part numbers for everything, but I have updated the Instructable with a parts list including Digikey part numbers or substitutes where possible.

kelseymh (author)2009-04-24
Very nice idea! To make it easier to reproduce by others (not everyone is familiar with building circuits or wiring connectors), could you consider showing some additional steps or details?

  • Provide a list of the necessary components, and sources (e.g., RS part numbers) if possible.
  • How are the Molex (? hard to tell from the pix) connectors pinned out?
  • What does the back of the perf board look like?
  • Use image notes to call out each component (on both sides of the board)
  • How did you make the car-lighter dongle?
  • It looks like you had to drill a clearance hole in the case for one of the caps.
  • You're using nylon standoffs because the case won't close?
scd (author)kelseymh2009-04-24

The car-lighter dongle came from my local auto-parts store. The connectors are one-off types from my local electronics surplus store but almost any 2-pin connector would work. Yes I had to drill a clearance hole for the larger cap. Yes, the nylon standoffs were needed because the case wouldn't close but I see that as a feature because it allows for airflow to the regulator :-) I will try to improve the Instructable with more info. Thanks, Scott

NachoMahma (author)scd2009-04-24

. kelseymh makes some excellent points on how to make your iBle better, but, if one assumes that the reader has just a little bit of experience, it gives all the info needed. As is, I'd rate it 2½-3; with his suggestions incorporated and a few more details on assembly (eg, how the components are connected), possibly a 4. More info on theory of operation and how to adapt for other uses will give it a slight boost. . If the unit will be used for anything close to the rated 3A, a heatsink would be a good idea. Probably not an issue for cell phones and GPSs (?½A max?).

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