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My experience with power supplies so far is limited to linear regulators. I am looking to build a 5V charger capable of charging a smart-phone from a variety of battery sources. I'd like the allowable input voltage range to be ~3-15V, a maximum output current of >=1A, and a reasonable efficiency (i.e. not a critical requirement). I'm having trouble finding a part including a reference design that will meet these requirements. I have looked at several boost/buck converters with datasheets showing circuits for either boost or buck, but not both together.

Except, I did find a mention of this one part that seems to do what I want, but I'm not sure this is the best solution: http://www.ti.com/product/lm25118 I also have not been able to figure out how to search for similar parts- i.e. keywords / parameters to use.

I found this thread, How to adjust the voltage of this SMPS? which shows one method. Someone in that thread pointed out that a SEPIC would be a better choice than using two regulators. I found that Linear has a line of SEPICs. This one looked promising http://www.linear.com/product/LT1935 but the datasheet seems to indicate that while the max switching current is 2A, in a SEPIC configuration it can only provide 5V at 550mA off of four AA batteries.

Anyway, I'm guessing this is a mostly solved problem and I was wondering if anyone could point me toward a part, app note, reference circuit, or some search terms that I might be able to work from.

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  • \$\begingroup\$ Welcome to EE.SE! Your question is very broad and it sounds a bit like you are asking for help shopping for a particular part. Can you try to do a little more research and come back with questions about electronics design? \$\endgroup\$ – Joe Hass Jan 12 '14 at 22:11
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I'd suggest the LM3488 current mode controller in a SEPIC configuration.

It utilizes an external FET switch so provided your support components are selected with suitable ratings then you can supply as much current as you like if your source is up to it.

I've used this particular part for a 6A/24V SEPIC converter from a 10-30V battery (Car/Truck) voltage input range.

There are many applications notes and design guides for this part.

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  • \$\begingroup\$ The datasheet for this part has a typical application circuit that does exactly what I described. TI also has free samples for this part and the FET. \$\endgroup\$ – imjosh Jan 12 '14 at 23:06
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You might just about be able to get 3V in and 5V 1A out with this: -

enter image description here

If you look at the PWM graph on the right, they are implying a 5V output with 2.7 volts in at about 800mA load current. It's close but worth a try I think.

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