Hey guys i cant find any usefull guide on how USB c charging works in depth. In particular i have bought a pair of Sony headphones which i would like to make wireless change so I also bought a crappy wireless coil meant to convert a phone into wireless charging. i opened the headphones, located the ground and 5v pin coming from the USB connected the circuit and surprise the charging led doesn’t light … The charging board is separated from the main board so I checked the flat cable that connects them, found the 5v and gnd ,spliced into it, and the led light lit as if it was charging. the next morning the led was of signaling the headphones are full, unfortunately after powering them on the battery status indicated was still 20% as the evening before … Have I done anything wrong ? What about that phase when they negotiate the power output with a magic resistor ? What should I try next? Thanks in advance 👍🏻
That looks like a really simple USB C port in legacy A (with DP/DM charge signals) configuration. The single IC most likely does the USB negotiation and the CC/CV charge of the battery.
Often these devices are tightly coupled with the USB state machine. Just applying 5v without terminating the sense resistors won’t do anything.
Also be very careful with Qi chargers. The resonant circuit produces voltage spikes in the tens of volts. It is usually regulated and smoothed to 5v out. But it’s also very bursty. Make sure your output circuit after the coil is fully regulated 5v voltage. I’ve seen them be varying voltages and even current mode outputs.