Monday, 8 August 2016

power supply - How does such an USB step-up 5V-12V work?



I just bought a cheap USB 5V to 12V step up converter:



enter image description here


Surprisingly, it works very well. There is few place for electronic components (maybe in the USB connector?), how can we do a 5V to 12V conversion with such a small size / few components?



Answer



As mentioned in a comment, here is an interesting video giving details about the internals of a step up converter.


I bought this item, and here are more details:


enter image description here


Internal:


enter image description here


Apart from some resistors and capacitors, there are:






I also bought this item ("MT3608 DC-DC Step Up Boost Converter Power Supply Module 2V-24V to 5V-28V 2A"):


enter image description here


I tried to power it with:



  • 1 AA battery (1,35V) : non working, the output stayed always at 1.21V

  • 2 AA battery (2.7V) : working great, the output can go up to 27.4V !

  • 3 AA battery (4V) : working as well


During my test, there was a cool feature (I don't know if it's common or not, or which chip is responsible for this): no matter the input voltage (2.7V or 4V), the output voltage only depended on the position of the potentiometer. Ex: I set the out voltage to 9.00V when using two AA batteries. Then I plugged 3 AA batteries without moving the potentiometer. The out voltage stayed at 9.01V, this is interesting!



I wonder if there exists step up converters able to convert 1 AA battery (let's say 1.4V) to 9V, I haven't found any in the same micro-size PCB.




Interesting reading: https://www.analog.com/media/en/technical-documentation/application-notes/an19fc.pdf


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