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TOPIC: A Look at Switching DC-DC Converters

Re: A Look at Switching DC-DC Converters 6 years 2 months ago #16541

  • Jon Chandler
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HEAT.  A nightlight bulb is 4 watts for comparison and that's more than enough to burn your fingers, so 18 watts is a huge waste!  It would take a large heat sink to dissipate this much heany to keep a linear regulator at a safe temperate.

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Re: A Look at Switching DC-DC Converters 6 years 1 month ago #13376

  • Jon Chandler
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I hope you find this comparison interesting.

Re: A Look at Switching DC-DC Converters 6 years 1 month ago #13374

  • Baldor
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Thanks for the cristal clear explanation.

I'm planing to use one of these for an small project: http://www.ebay.com/itm/400358408922

9V(batery) to 5V, less than 300mA needed, but is the cheapest one I found in ebay.

I think this regulator also fits your needs.

(I was planing to build it myself in the circuit board, but is more expensive, and also the complete circuit exceeds the 50x50mm size for the cheapest ones)
Aprendiz de mucho, maestro de casi nada.

Re: A Look at Switching DC-DC Converters 6 years 1 month ago #13375

  • Jon Chandler
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Those look like great modules. I like the adjustable output voltage.

It's amazing what ou can find on eBay sometimes. To buy the parts would cost more than these modules.

Re: A Look at Switching DC-DC Converters 6 years 1 month ago #13384

  • Baldor
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One question: For batery operated circuits, what wold be beter, from an eficiency point of view? Buck, or boost? For example, 2AA bateries (3V alcalines, 2.4V NiMH) and boost to 5V, or a 9V batery and buck to 5V. ¿How I will squeeze more energy, asuming the same energy stored in the bateries?
Aprendiz de mucho, maestro de casi nada.

Re: A Look at Switching DC-DC Converters 6 years 1 month ago #13385

  • Jon Chandler
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I'm probably not the right guy to ask, but I'll take a stab at this. Look at the efficiency of various designs. I think they're pretty close between step-up and step-down.

So the next consideration is the energy available in the batteries available. An AA alkaline battery capacity is shown below.



At a current drain of 100 mA, a single AA cell will supply about 2500 mA-Hr. Two cells, with about the same volume as a 9-volt battery, will supply 5000 mA-Hr. Remember, with a switching supply, the power remains about the same over the working range, so supplying twice the voltage cuts the current in half.

Compare this to an alkaline 9-volt battery.



At the same draw of 100 mA, this battery only provides about 500 mA-Hr, about 10x less than a pair of AA batteries. Another consideration is the cost of a 9-volt battery – usually a lot more than AA batteries.

Looks like AA batteries with a step-up would be the best option.
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