Wireless power transfer feedback circuit (Wireless charger)

[Bebe]

Hello, i'm trying to design a smartphone wireless charger and i encountered a problem. I want to add a feature to detect when a device is placed on the charging pad to improve efficiency. For this i think i have to monitor the output waveform somehow, so i bought a few chinese wireless chargers to experiment with this. I noticed that when placing a device on the charging pad the waveform changed shape in every case (it becomes more like a triangular wave). All the chargers i bought have this feature so i tried to reverse engineer the feedback circuit to try to understand how to implement this. I did this with two different chargers and they both seem to have the same feedback circuit. My problem is that i can't quite understant it so i was thinking that maybe i made some mistakes when reverse engineering. From what i see they have a diode envelope detector of witch output is connected to a mcu pin through a voltage divider. The envelope detector's output is also connected to an op-amp circuit that i'm still trying to understand. I will atach the schematic i reverse engineered from the chinese wireless chargers. For the first op-amp part (The A instance) i see that the "+" input is ac coupled then it ads a ~2V DC offset with the  (100/75K) voltage divider and i think the capacitor in series with the 10k resistor from the feedback loop is there so only the AC component is amplified (but i'm not sure about this). The B instance i don't understand at all, it doesn't make sense to me so i thought that i might missed something. Both op-amps (it's a LM358) outputs and the voltage divider (from the envelope detector) output are each connected to one of the mcu pins. I would apreciate if someone with more experience could help me understand this circuit or give me some ideas on how to implement it. I'm using an atmega328 MCU and a H-bridge to drive the LC resonant circuit. Thank you!