EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Rapidice on January 31, 2021, 12:45:40 pm
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Hello,
I am currently working on a project, which I want to power with 4 rechargeable AA batteries. The max voltage of those is about 1.4V. For my project, I would need a constant 6V at about 2A. On the internet, I have found a voltage booster circuit, for which I have ordered a PCB and all the parts.
The first time I tried to use it, I have noticed a significant voltage drop and a quiet high-pitch noise. The circuit is based on an MT3608. I have read that it should be able to output 2 amps. Did I use the wrong inductor?
https://lcsc.com/product-detail/Power-Inductors_SXN-Shun-Xiang-Nuo-Elec-SMMS0630-220M_C128694.html.
Or is it something else?
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With larger output currents usually a smaller inductor value is used with switchers. There should be a formula in the datasheet for L vs. output current calculation. Also 4x 1.2V to 6V conversion may lead to a low efficiency (the voltage difference is rather small)..
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With 2A output you have to push a lot of current into the L. The frequency is fixed - 1.2MHz - and pwm is used with that chip. I would start with that 4.7uH they mention there, or even smaller (like 2.2uH, 3.3uH) with larger saturation current.
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The inductor's current rating should be higher.
Also 4x 1.2V to 6V conversion may lead to a low efficiency (the voltage difference is rather small)..
Actually the reverse is true: the smaller the voltage difference between the input and output, the higher the efficiency. The problem with the small voltage difference could be instability, if the controller doesn't work well with low duty cycles, but I did skim the data sheet and no mention of that was made.
https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf (https://www.olimex.com/Products/Breadboarding/BB-PWR-3608/resources/MT3608.pdf)