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i need a 0,5V to 3.3V converter

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diegor747

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i need a converter:

Vin: 0,5Vdc

Vout: 3,3Vdc 150~300mA

thanks!!
 

biff44

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I am not aware of any way to do that. There are switched capacitor arrangements that can double or tripple the voltage, but they need some sort of oscillator running to turn on/off the analog switches to reconfigure the capacitors. With 0.5 V, there is not enough voltage to run the oscillator, or turn on/off fet switches.

Do you have any other higher voltage available, even just a few microamps?
 

dick_freebird

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I am curious what kind of system provides 0.5V and
2A output. Maybe a single solar cell, but max power
point there is liable to be an even lower voltage (esp.
when hot).

It might be that you have to use a transformer, maybe
a JFET pair self-oscillating a center tapped primary and
a 7:1 turns ratio? Depletion mode RF devices could be
efficient in this application, though you'd want to run
them at a much lower than 50-ohm output impedance.

Getting a controlled output voltage would be more work.
 

389iaB4Yg6Xn

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TI and ST have chips for exactly this purpose and support such low input voltage boost conversion.

Added after 22 minutes:

TI:
TPS61200
TPS61201
TPS61202

ST:
L6920
 

SimonB

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AS1322 from Austria Microsystems also works down to 0.5V too
 

389iaB4Yg6Xn

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biff44 said:
Wow, I am impressed! How do those chips work at .5V in?
Quite well, cause I tested one TI type and ST type as well. You can use one 1,2V cell supplied by solar power and boost it to power LED or whatever.

I don't know how it works, I guess they use BJT transistor instead of MOSFET and latest low voltage technology...Datasheets should tell more.
 

dick_freebird

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I looked at the chips mentioned earlier and all of the ones
I saw, have 0.8 - 1.0V undervoltage lockouts.

A low-threshold CMOS could be used for flyback / boost.

A pretty old-school setup is a center-tapped transformer
with cross-coupled NPNs at the ends and supply at the
center. This will self-oscillate (presuming it starts) and
the turns ratio to a secondary defines the step-up. You
can sometimes find suitable transformers in battery operated
audio devices (final stage to speaker).
 

FvM

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A pretty old-school setup is a center-tapped transformer
with cross-coupled NPNs at the ends and supply at the
center.
The original requirement is 0.5V operation. Si BJT can't reliably work at 0.5 V (at least not work at lower temperatures). Ge BJT or depeletion mode FET would be required. The said TPS612xx and similar have a switched cap startup circuitry and thus can work at lower supply voltages. Unfortunately, the output current at Vi = 0.5V isn't sufficient.
 

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