Hello,
We use the two products together for a Qi Transmitter (SWTBC86) and Qi Receiver (STWLC38) solution for a single product and it's accompanying charger board. The eval kits of both boards perform much better than our production design, particularly our TX board, and we're wondering why that is the case.
Our designs were based off of the reference schematic of both ST products. The coils are the same.
Some remarks:
1) The transmitter overheats to > 100C in about 15 minutes
2) Efficiency nears 45% even at a nominal distance of 2.5mm
3) We send about 5.5W across the link and receive 2.1W (desired receive)
4) Operational TX voltage is 12v (to try and meet our distance requirement - up to 6mm). Receive voltage is set to 5.0v, that goes into a 3.8v nominal (4.35v charged) li-ion battery charger
5) Stock firmware for both
Because this is for a consumer wearable, the efficiency needs to be better than a run of the mill desktop charger. It also need to keep cool. We've reached neither goal.
Transmitter design
Receiver Design
