another 1v to 5v dc-dc. please help

[teekay_tk]

dc voltage 1v to 5v

Hello
These have been discussed here before but my application is a bit different.
I want to generage 5V from 1V. However my source is a solarcell and th output is a few milliamps, usually between 1 and 5mA. I want to use this to top-up a rechargable battery, however due to size, space weight restriction, I cannot use bigger solarcell. Can some one help please.

Thanks

TK

 

[Prototyp_V1.0]

2 cell 5v step-up

Guess this one can be hard to solve.

There is very few (if any) ic's (opamps) that can operate under so low voltages.

Also a schmit-trigger will be hard to make.

Only solution I can think about is to make an regular astable multivibrator and apply output to a npn transistor with highest possible current gain. Then you connect the collector on the output transistor into an inductor.

If the 5V load current is near constant, then you can vary the resistors that leads charge current to the caps so that the pulse width to the output transistor makes the voltage out from the inductor 5 volts.

 

[M!k]

1 v naar 5v

How about using a step-up converter like MAX1674/1675/1676? It's running from an input voltage of 0.7V. Output can be 5V regulated.
Check datasheet here: **broken link removed**

 

[teekay_tk]

1v to 5v step up

I have setup a board with a similar device to that of MAX1674 from Linear Tech

Problem is that they require quite a large and variable input current which my tiny solar cell cannot provide and thus the device fails to start up.

for Prototyp_V1.0: can I use a 32khz squarewave oscillator that runs of 1.2 volts instead of the multivibrator. is that possible at all.

thanks

 

[Prototyp_V1.0]

1.v to 5v dc dc converter

for Prototyp_V1.0: can I use a 32khz squarewave oscillator that runs of 1.2 volts instead of the multivibrator. is that possible at all.. . .

Depends if the oscillator can run at all on 1 volt.

Also the oscillator must have the ability to provide different duty cycle output. If square wave with 50% dutycycle, then it's not sure yoy'll get as much as 5 volts.

 

[doraemon]

5vdc in,5v square wave out

Hello!

What I usually do:
Connect to digikey (or mouser or farnell, etc, well, usually digikey in my case).
See here.

1. Enter step-up in the search field. You'll notice that there are more than 4000
step-up converters, which is a good sign. Choose Voltage Regulators.
2. At the right of the results, you can set the voltage input filter. Choose all the
lines corresponding to less than 1V. Click apply filters. More than 700 devices
remain.
Then I guess you got it, apply other criteria. I would be surprised if you don't
find something close to what you are looking for. And if it doesn' work, it may
be because your solar cell is a bit too small, so you may consider to find a bigger
one.

Dora

I have setup a board with a similar device to that of MAX1674 from Linear Tech

Problem is that they require quite a large and variable input current which my tiny solar cell cannot provide and thus the device fails to start up.

for Prototyp_V1.0: can I use a 32khz squarewave oscillator that runs of 1.2 volts instead of the multivibrator. is that possible at all.

thanks