MC34063API Step Up Converter To Charge A Usb Device from A 3.7 Lion Battery - Page 1
Forum section: electronics / projects

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: August 15, 2015, 10:42:59 am
content: Hello i would like your help on my little project... i have the MC34063API and 2 3.7 volt Lion Batteries and i would like to create a portable charger for my phone (not Iphone a regular android device). I could not find a schematic and i am not even sure if the MC34063API can work with 3.7V.My problem is that i cannot find a way to power the thing and to get a reasonable current from it ( i would like about 800 - 1000 mA )Any suggestions as were to begin would be useful thank you.

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 15, 2015, 12:42:36 pm
content: Just to clarify, you want to use the two Li-ion cells to make a 5V/1A power supply with a micro-USB output connector, correct?

author: ChrisGreece52
author_rank: Frequent Contributor
timestamp: August 15, 2015, 12:48:44 pm
content: exactly but the output will be a regular usb port not a micro usb one...but the rest is exactly my idea i dont know if the capacities of the batteries matter but if its needed ill post them

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 15, 2015, 01:17:52 pm
content: Ok, then you want to make a buck converter that can operate over an input voltage range of ~6V to 8.4V while delivering an output of 5V and 1A max. Depending on how low the input voltage is allowed to go you might not be able to use the MC34063 due to its relatively switch voltage drop (1.3V max in Darlington configuration). That said, if you run the MC34063 at its default frequency of 33kHz and want to use an off-the-shelf inductor pick one with a value of 150uH to 220uH and with a DC current rating of at least 1.8A. Oh, and make sure it is "shielded" - I like the Bourns SRR1210 series for this kind of application (note, however, that they are surface-mount only).You should protect the cells from over-discharge, over-current (and over-charge if they will not be removed for recharging); the easiest way to do all of that is to use a dedicated battery protection or monitor IC (TI and LT both make many such ICs).

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 15, 2015, 01:47:17 pm
content: http://www.ebay.com.au/itm/DC-DC-Boost-Converter-3V-Up-5V-to-9V-2A-USB-Output-Voltage-Step-up-Module-HOT-/281731886071every other day of the week I would say build it, buy at $2 buy the whole thing

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 15, 2015, 02:16:12 pm
content: Quote from: TheElectricChicken on August 15, 2015, 01:47:17 pmI assumed - perhaps incorrectly - that the OP was taking this project on at least in part for the educational value, seeing as his profiles says this,"Electronics Engineering Freshman".

author: TheElectricChicken
author_rank: Frequent Contributor
timestamp: August 15, 2015, 02:24:32 pm
content: Quote from: MagicSmoker on August 15, 2015, 02:16:12 pmIndeed, an easy mistake to make. But just ask anyone who has taught a class full of them and they'll curse the day they took up teaching and swear like a sailor about how components go missing and then eventually they work out what they are doing with all that stuff, they are using it at home to watch porn on their smartphone until the batteries die. I think he said something about batteries dying from watching porn in the original message, lets have a look.Quote from: ChrisGreece52 on August 15, 2015, 10:42:59 amHmmm very suspicious, all traces of porn have been erased from my imagination since it was first written. Suspicious indeed. It still mentions the charger, that plus humorous innuendo is unfortunately not enough to allow us to call the police, but be warned, I'm watching carefully -(o)-(o)-