Cheap Qi Charger

Written by  on May 23, 2015

Wireless charging is cool. Because anything wireless is cool. Next best thing to not having to do it at all.

So, people have tried to do wireless power for over a century. Think Tesla – the man, not the car. He wanted to send electricity across distances without any wires. At the moment we’d settle for charging the phone by putting it on a special pad, and avoiding three seconds of fiddling with plugging in the cable.

The Qi standard, of which we’ll talk further later, is built into the latest Google Nexus 6. And, there is a whole bunch of cheapo pads offered on eBay, one branded TechMatte. Having invested $11, I had a pleasure of taking it apart.

The top pops open without any tools, thanks! Here comes the Coil. Tesla would be happy, initially at least. The square piece of plastic that the coil is resting on is stuck onto the back of the case with two-sided tape, which one pry off to see the interesting part of the PCB.

The main ASIC is labeled GPMQ8005A, and it comes from a Shenzhen company Generalplus Technology. A QI Compliant Wireless Power Transmitter (no surprise there). I could not find an official quote on it, but on Alibaba there was an offer for $2.80.  There are two TI (ON Semi) LM324 Quad Opamps, at $0.10 these days. Two Michrochip TC4427 MOSFETS, at $0.90, Alpha & Omega Semi AO4606 30V complementary MOSFET, say $0.20. Or maybe I got them all wrong. Will microscope them again at work.

On the back of the unit is says: Input 5V – 1.5A, Output 5V – 1A. In the context of a wireless charger, the Output labeling is wrong in so many ways.

Oh, the dang thing does not work. Have to take the phone out of the case. Finding the one spot on top of the pad where the green LED goes on is a game that grows old quickly. And, if you find it, by using an App that monitors charging you will discover that it does not charge worth a damn. Cannot even keep-up with the power consumption of the screen being on.