93% Efficient DC to DC Converter

Introduction: 93% Efficient DC to DC Converter

About: Hello

I needed a better way to charge Super capacitors so I wired up this DC to DC converter. I was using a linear regulator which would have worked fine except I was regulating 12 volts (off a car battery) down to 2.5 volts. The regulator was getting frying hot and was very inefficient.

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Step 1:

This converter is one from the Murata OKR series. I used part number

OKR-T/3-W12-C. Here are some of the specifications:

Input voltage: 4.5 - 14

Output voltage: 0.591 - 6

Output amps: 0 - 3

Output watts: 15 max

93% efficient

Mean time before failure: Calculated to be over 5 million hours.

Short Circuit Duration: continuous, No damage.

Input reverse polarity protection (external fuse).

Step 2:

It works great. It does not even get a little bit warm in my application. I charge a 12 volt car battery in the garage with a 5 watt solar panel on the roof. I charge the super capacitors (400 farad and 2600 farad) using this dc to dc converter. In input and out put jacks are RCA type. I had to use 3 resistors to come up with the correct resistor value for 2.5 volts out.


400 Farad Super Capacitor Flashlight:




My only complaints about this converter are:

1. The lead spacing is smaller than 10th inch so I had to solder wires to the pins.

2. It would be helpful if Murata made one just like this one but with a higher input voltage like 24 volts so I could run it directly off a solar panel.

3.  When charging up a super capacitor for the first time or charging a super capacitor that has been discharged below about 0.4 volts. The chip does not operate at that low of a voltage. If you get no output due to these conditions you can charge up the capacitor with a D cell battery. I charged a 400 farad capacitor flashlight with a d cell when the capacitor was run down to about 0.3 volts. I had my flashlight switched on during charging and the LEDS turned back on in less than 30 seconds. I finished the rest of the charging with the dc to dc converter after that. I use the super capacitor flashlights all the time and I am charging up one of them at least once or twice a week. I have only needed to do the D cell jump start once in the last year. That was because I left it on all day by accident. The flashlights are good about letting you know it is time for a recharge because the start to get a little dim.


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    3 Discussions


    7 years ago on Introduction

    My bad. I did mention the car battery in the intructable.


    7 years ago on Introduction

    Hello Amandaghassaei,

    I think that what was missing was me saying in the instructable that the input to the DC to DC converter is connected to a car battery in my garage. Also in the picture of the inside of the converter ther are 3 resisitors. I had to use 3 to come up with the correct trim resistor for 2.5 volts. The schematic only shows one resistor since the schematic is intended to be generic. So the parts list for what is shown would be:
    2 RCA jacks
    Fuse holder
    Chassis / box
    Wires for internal connections
    Assorted shrink sleeve
    On / off switch
    Double stick foam tape and hot glue as needed.
    Perf board

    Yep. I think that is it. I included the link for the data sheet in my instructable. You can see on page one , figure 1, that I did what they did except I decided to cut power external to the chip rather than they way they show to do it so that when it is off it is really off. If I have missed anything let me know. By the way I charge the junk car battery (old one that used to be in my car) in my garage off of a 5 watt solar panel (regulated with an LM7814) on my roof. So I have really gone green on this project. But that will be for another instructable.