Which is better, constant voltage or constant current for designing a Tablet AC power adaper?

Friends, Should I make a constant voltage or current AC adapter for my huawei MediaPad M3 tablet?

I want to make an AC power adapter from a beefy 12vdc adapter and nine feet of 18ga two conductor wire.

I stream a lot of video on my tablet and the little phone charger that came with it isn't enough to charge and power the device simultaneously, especially with a four foot USB extension cable. Sincerely Jon

by xjohndoe001x
December 10, 2016

1 Answer

Answer by mikerogerswsm

Battery charging is best done by compatible chargers and maker supplied cables, usb charging cables have built-in coding resistors to identify the charge rate. The M3 supports use of a Qualcomm Quick Charge device.If you don't have one of these then charge at 5 volts using the maker supplied cable. In your case you might want to use your 12 volt supply, then the cable, then a 7805 regulator to drop the voltage to 5 volts near to the tablet, and then the maker supplied lead. Video streaming shouldn't take much out of the battery, one user reports only a 4 per cent battery drop after streaming a one hour thirty minute movie. This was at 30 per cent brightness.

+1 vote
by mikerogerswsm
December 14, 2016

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