1.5 to 3.3 volts efficiency

Thread Starter

zoom

Joined Jul 11, 2014
29
I am not quite familiar with boost converters. So, I have some questions;

Looking for this IC;
http://www.electroschematics.com/wp-content/uploads/2015/01/MCP1640-datasheet.pdf

It claims up to 96% efficiency.

Now, assume I have a 1.5 Volts alkaline 3000mAh battery. If I use this battery with a boost converter to get steady 3.3 volts output, I will for sure not be getting 3000mAh spec anymore. How can I calculate the new capacity with 3.3 volts output ?
 

dl324

Joined Mar 30, 2015
16,846
Without external components, you'll only get 150mA with 1.5V in and 3.3V out; from page 3 of the datasheet.
 

dl324

Joined Mar 30, 2015
16,846
Efficiency takes a nose dive past 100mA, max input current limited to 800mA; will take external components to get above 150mA.

From the datasheet:

Efficiency
33eff.jpg

Current ratings
33typI.jpg

33dcChar_.jpg

Vin=1.5V, Iout=200mA
33maxI.jpg
 
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Thread Starter

zoom

Joined Jul 11, 2014
29

dl324

Joined Mar 30, 2015
16,846
So, is the only thing I compromise is maximum current I get with the boosted 3.3 voltage ?
You can increase output current, but it will require external components to workaround limitations of the regulator.
Is my 3000mAh still there ?
Most of it. The regulator will be operating closer to 80% efficiency with a 1.5V input and the battery will still have self discharge.
 

Dr.killjoy

Joined Apr 28, 2013
1,196
With booster converter you have to remember the energy has to come from some where to make up the difference and it uses the current to make the difference in order for everything to work ..
 

dl324

Joined Mar 30, 2015
16,846
Look at post #3, you have about 1000 mAh from 3.3V output.
You're neglecting the fact that efficiency with an input of approx 1.5V varies from 65-85% and that the regulator will not provide more than a couple hundred mA with 1.5V input/3.3V output.

For this regulator, efficiency @ 1.2V in peaks at 85% @ 30mA and falls off rapidly @ 100mA. At max current supported by the regulator, efficiency falls to 65%.
 

jjw

Joined Dec 24, 2013
823
You're neglecting the fact that efficiency with an input of approx 1.5V varies from 65-85% and that the regulator will not provide more than a couple hundred mA with 1.5V input/3.3V output.

For this regulator, efficiency @ 1.2V in peaks at 85% @ 30mA and falls off rapidly @ 100mA. At max current supported by the regulator, efficiency falls to 65%.
I was not sure if op thinks he can get 3000mAh from 3.3V output, so just in rough figures 700 - 1000mAh from output depending on load current.
 

dl324

Joined Mar 30, 2015
16,846
I was not sure if op thinks he can get 3000mAh from 3.3V output, so just in rough figures 700 - 1000mAh from output depending on load current.
Except that without external components, it's going to be closer to 200mA due to regulator limitations.
 
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