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voltage booster needed

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kad

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I need a small circuit to boost variable input voltage of 0.3 - 2.3 v to a constant voltage of 3.6v .could someone please help?
 
Well..i have a solar panel which gives me a min voltage of .3v and a max voltage of 2.3v, depending on the light intensity..but i need to use this for an application which needs exactly 3.6v ..so, can i get a small circuit or is there any IC which can do this job..please help :)
 
kad said:
Well..i have a solar panel which gives me a min voltage of .3v and a max voltage of 2.3v, depending on the light intensity..but i need to use this for an application which needs exactly 3.6v ..so, can i get a small circuit or is there any IC which can do this job..please help :)

This is FAR from a trivial project, I would suggest getting another panel and putting them in series to give 4.6V, and perhaps using a 3.6V rechargable battery, or shunt regulator, to give your 3.6V - however, it won't boost low voltages.

Your requirements are still very vague though, what current can the panel provide?, what current does the load need?, why does it need exactly 3.6V?, what actually is the load?.
 
kad said:
Well..i have a solar panel which gives me a min voltage of .3v and a max voltage of 2.3v, depending on the light intensity..but i need to use this for an application which needs exactly 3.6v ..so, can i get a small circuit or is there any IC which can do this job..please help :)

1) You'll want a high efficiency switchmode coneverter of somekind very likely.

2) Traditional solutions will not work down to 0.3V so, you have to stack cells to get the voltage up as Nigel suggested. After that, you'll have more choices of converter topology.

3) If you _must_ deal with 0.3V to 2.3V, my only thought would be some kind of charge pump / switched capacitor circuit where you charge up several capacitors in parallel to 0.3V and then switch them in series to deliver a multiple of 0.3V to a switchmode stage that will regulate to 3.6V
but this is more of a custome design and will take more effort to get working.

As Nigel asked, you have to tell us the load. If your solar cells cannot generate enough _power_ to drive your load, then no solution exists - in that case, the solar cell would be an inappropriate choice of energy source.
 
A solar cell is virtually a constant voltage device. On the high end it's basically open circuit and you're not drawing any current. On the low end you're basically shorting it out.

The max power point is a fairly narrow voltage range. The trick is to adjust the current so the output voltage is at its max power voltage. The max power voltage varies little with the intensity of the light. Unfortunately unless you're charging a battery the job doesn't usually allow you to adjust the current. But the point is, loading so it drags the voltage below the max power point means the power output will only go down.

It sounds like you've got 4 cells there, so the max power voltage should be around 2v. So consider your source voltage to be 2v. If the cell can't produce the current to run your circuit at a particular light level, it will drag down the voltage to 0.3v, but at that point making a boost converter is pointless; there's no power available. Google for a "solar cell IV curve" to see how loading affects the voltage and current you can pull.

The circuit to convert this effectively is called a "max power point tracker", but it's a bit tricky.
 
well..my load is a cell phone battery(Li battery)..
my idea is to charge the li battery using a solar cell..but i don't know whether that is possible or not..so i just wanted to give a trial..
 
Well you've got a problem there. Li-ion does NOT tolerate overcharge, nor is there a really simple, direct way to see when the charge is done.

Now powering the normal charger with a solar power source is possible. 2 problems though. The cell must be able to put out what the charger requires or the charger will malfunction or shut down.

The other part that troubles me is the charger DOES have a "charge done" detection algorithm, but it may be confused if the charger keeps turning on and off resulting in repeated bits of overcharge.
 
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