How to convert ~mV dc voltage to ~3V voltage?

[jszair]

commercial dc-dc converters normally have input range ~1 to 2V. Is it possible to convert a small voltage into a ~3V voltage in applications like wireless sensor?

 

[jerkymotion]

is it a wireless conversion of millivolts to 3v..?

 

[FvM]

Startup of a DC/DC converter at mV input voltages is only possible with a special design, e.g. using depletion mode transistors, and difficult anyway.

Did you calculate the available power from your mV source?

 

[jerkymotion]

hi fvm
can you please explain how to use depletion mode transistors to convert mv to 3volt.....can't operational amp be used....??

 

[Sink0]

Is your mV a signal or a power source? If it is a signal, yea you should use some opamp or iamp. If it is a power source, just no! First becouse you must supply the am with some voltage... and second the output current is too low.

 

[Borber]

Precision low drift low noise OpA will do what you need. Asking about DC/DC converter after IanP answered your previous post and regarding your previous posts is simply another nonsens.

 

[FvM]

Asking about DC/DC converter after IanP answered your previous post and regarding your previous posts is simply another nonsens.

It's not obvious which previous post you're referring to.

Basically, the original poster should clarify it's intentention. I think, that dc-dc converter is clearly related to energy conversion, in contrast to signal amplification. In this case, the available source power respectively current and expectable voltage range is a key parameter in designing the converter.

 

[Borber]

This Thread:

https://www.edaboard.com/threads/190958/#post798960

I think that jszar understood what I was talking about.

 

[FvM]

Thank you. I agree, that reading both posts together gives an impression of certain confusion.

 

[jszair]

This Thread:

https://www.edaboard.com/threads/190958/#post798960

I think that jszar understood what I was talking about.

Em...I know in-amp needs power to operate.

This dc-dc conversion is just another different question...haha

---------- Post added at 22:10 ---------- Previous post was at 22:04 ----------

Precision low drift low noise OpA will do what you need. Asking about DC/DC converter after IanP answered your previous post and regarding your previous posts is simply another nonsens.

Yes, precision low drift low noise OpA can amplify dc voltage. I understand that.

But I'm talking about energy harvesting like application. For example convert small voltage generated by thermopiles and small solar cells to power circuits in wireless sensors.

Sorry about confusion.

 

[jszair]

Startup of a DC/DC converter at mV input voltages is only possible with a special design, e.g. using depletion mode transistors, and difficult anyway.

Did you calculate the available power from your mV source?

The only commercial DC/DC converter with startup at mV I can find is LTC3108 by linear technology (attached). @Page 8, looks like they used second coil in transformer and a capacitor to form an oscillator to startup.

Their design has low conversion efficiency (<50%). Is that because of low input voltage?

Is the depletion mode transistor you mentioned used as an switch?

Mod Kender: if the document is freely available on the web, don't upload it on EDAboard. Post a link instead. That saves EDAboard's resources.
Attachment deleted. Here's the link to the LTC3408 datasheet: http://cds.linear.com/docs/Datasheet/31081f.pdf
Nice find, BTW.

 

[Borber]

Hahaha...just ask LT how to design a better step-up than their LTC3108 is.

 

[FvM]

Is the depletion mode transistor you mentioned used as an switch?

Yes, it's basically a method to design a self-oscillating converter, that has a very low start-up voltage. LTC3108 is using this method.

On the other hand, it's apparently not easy to achieve high efficiency with low input voltage. I guess, it can be done better than with LTC3108. Most likely, a more sophisticated control of the power switch would be required.