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 👍🏻

  • @TechNerdWizard42English
    12•9 months ago

    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.

    • @[email protected]OPEnglish
      1•9 months ago

      Thanks is there a way to know if the voltage spikes are properly filtered out without a spectrum analyzer I only have a multimeter ( and It shows something around 5v )I also noticed the coils will randomly die, I have altrady bought 2 from china and now I’m wondering if it has something to do with me charging the headphones via USB c while the coil Is plugged in … I Will add photos of the circuit as soon as possibile thanks again for your help

      • @TechNerdWizard42English
        2•9 months ago

        You generally can’t just connect two power supplies together. Usually you’ll want some sort of power path style controller.

        You’d want to check the output with an oscilloscope.

          • @TechNerdWizard42English
            2•9 months ago

            Cheap power supplies being back-powered from the output will die. By connect together I mean put in the same circuit. Not use at the same time.

            You’re possibly powering the other power supply through the feedback resistors, ESD diodes, etc. You really want a controller that can share between the two sources or just 2 diodes if you can take the voltage drop

            • @[email protected]OPEnglish
              1•9 months ago

              Oh now its clear i dont have a special controller neither the space to fit It inside the headphones so i will go the diode rout, if i pay attention not to plug them both in at the same time could I use only one for the wireless circuit ? How do I know if I can take the voltage drop ?