Charging and discharging capacitors 6

[cjl222]

I am looking for an intergrated circuit that would charge a bank of 4 capacitors in parallel and then discharge them in series. I have a 1 volt dc source.

 

[Skogsgurra]

I am afraid that you have to look for a long time for that IC. One volt is not something you can even start affecting a transfer gate or switch with. Unless it is a BJT switch. And that will not work in such an application.

You need to create a higher voltage from 1 V? There is a possibility that a fly-back switcher could do the job.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[logbook]

I agree with Skogs. Low voltage CMOS switches seem to run out of steam at around 1.8V. A single transistor blocking oscillator using a small transformer or pot core would probably do the job, but the efficiency would probably be poor (40%).

 

[BobbyNewmark]

I doubt you will find a ready-made chip. Advanced Linear Devices does make some nift zero-threshold MOSFETs that would be useful building blocks for your own design.

 

[Skogsgurra]

That's good news Bobby!

Never heard about them before. But, if you look at the characteristics, you will have a hard time making it work if 1.0 V is all you have available.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[IRstuff]

Zero threshold is great for turning on, but basically not possible to turn off.

The 0.2V or 0.4 V threshold devices are probably more practical.

TTFN

 

[zeitghost]

I vaguely recall a Maxim device that boosted a single cell to about 9V or so.

Can't remember the part number, but if it still exists, it should be on their website.

 

[jimkirk]

Yeah, you're probably not going to find a single chip that does what you want. The Maxim MAX660 will double a voltage (or generate an inverse) with a 100 mA load but is only specified down to 1.2 volts, not quite what you want. If that's good enough, and you only need 50 mA or so, you can cascade a couple of them.

What level of current are you dealing with? Size of capacitor?

There are plenty of circuits that can boost from 1 volt to several volts, but they generally use discrete parts.

If you really need to charge 4 caps in parallel and then connect them in series, I suggest using a low power boost circuit to generate enough voltage to power some MOS devices to do the switching. That way, you can tailor the devices to the power level you require.

 

[Compositepro]

A standard voltage mulitplier circuit does what you want to do - sort of. An electromechanical chopper would have less switching losses at one volt.

 

[itsmoked]

How about a few analog muxes? They pass voltages down to ground and handle up to ~6V. I didn't see any mention of doing this in any particular hurry.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[IRstuff]

Maxim:

http://para.maxim-ic.com/cache/en/results/4637.html

2x appears to be the limit of the Maxim parts


TTFN

 

[ScottyUK]

Googling [blue]single cell "boost converter"[/blue] gives a number of hits. The highest power I noticed was 5V @ 1A from a single cell using the Linear's LT1308B. 1.0V is right at the bottom of its operating range.


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Sometimes I only open my mouth to swap feet...

 

[Skogsgurra]

I am not so sure that we are answering the OP's question any more. I was just guessing that he needed to go from 1 V to a higher voltage. But all he asked for was an IC that could charge four capacitor in parallel and then connect them in series. We seem to have lost him.We haven't had any comments from him so far.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[cjl222]

Thank You all for your input on this issue. My main objective is to boost the level to 3 volts but have exhausted all resources here at work. we are looking to charge a battery and figured the only possibility would be a pulsed type of a charge by charging the caps in parallel and discharging in series. The power level of the source is in the microwatt range. We have experimented by charging 3 10,000 uf caps in parallel and hitting a switch to series them. I was hoping to do it electronicly.

 

[ScottyUK]

3.0 / 3.3V are standard voltages for microprocessors. There are numerous ICs which are specifically designed to produce a stable 3.0 or 3.3V from a single cell.


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Sometimes I only open my mouth to swap feet...

 

[itsmoked]

Here's two:

http://www.micrel.com/_PDF/mic2571.pdf

http://www.micrel.com/_PDF/mic2570.pdf

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[Comcokid]

I was sorting out articles I've removed from magazines when one made me recall this eng-tips post for charging capacitors from less than a 1 volt supply.

EDN designs ideas for May 25, 2006 pp 91-92 has a DC-to-DC converter that can operate from voltages as low as 300mV to 1.6 volts. With 475mV input it can suppy 2ma at 5 volts.

 

[logbook]

>The power level of the source is in the microwatt range
That is 1µA at 1V.

The best option is to give up now, if possible.

1µA operating current is a big thing to ask and would require specialist development if it is actually possible.

 

[Skogsgurra]

Yes,

And, besides, self-discharge of a rechargable battry is around this current - often higher. Charging time will be close to eternity.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[Comcokid]

Oops, missed that "source is in the microwatt range. Must be some parasitic power sensor application where the source is a flea bouncing on a piezo.

Even powering a DC-DC from 300mv is pretty exteme.