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.
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.
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.
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