DC-to-DC Converter





Introduction: 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

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:

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

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

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

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 :-)



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    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.


    What are the voltage and current requirements of your radio?

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



    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?

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


    I do not have any specific suggestions. There are some online tools for exploring converter designs. For example: http://www.coilcraft.com/dcdc.cfm

    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?

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