Wireless Charger

Overview

A wireless charger delivers power to a phone with no exposed contacts: it couples energy across a small air gap using a magnetic field. The pad takes USB-C power in, drives a flat coil under its surface, and the matching coil inside the phone picks the field back up and rectifies it to charge the battery. A ring of magnets snaps the phone into the one position where the two coils sit concentric, which is what makes the MagSafe-style profile reliable instead of fiddly.

The Housing Assembly sets the whole experience, a slim Top Pad keeps the coil close to the phone, and a Silicone Surface grips it so it does not slide off. Inside, the Main Board runs the Qi protocol, the TX Coil Assembly does the coupling, and a Cooling Fan carries away the heat that inductive transfer always wastes. Power arrives through the USB-C Input from the supplied USB-C Cable.

How it works

Wireless charging is a loosely coupled transformer split in half. The Qi Transmitter IC on the main board switches a Power MOSFET half-bridge to drive an alternating current through the transmitter coil, really the Copper Winding in the TX Coil Assembly, at a frequency between 110 and 205 kHz. That current creates an oscillating magnetic field. A Ferrite Shield sits behind the coil and steers that flux upward toward the phone instead of letting it leak into the electronics below.

When the phone's own coil enters the field, the changing flux induces a voltage in it, which the phone rectifies into DC to charge its battery. Alignment is everything: even a few millimeters of offset drops efficiency sharply, so the Alignment Magnet Ring uses a Neodymium Magnet array to pull the phone into concentric registration over the coil.

The two sides talk while they charge. The phone load-modulates its coil to send packets back to the Qi Transmitter IC, which uses them to ramp power up to 15 W, hold the target, and stop when the battery is full. The board's Microcontroller oversees this loop and watches the FOD Sensor: if power is disappearing into a coin or key rather than a phone, foreign-object detection trips and shuts the coil down before anything heats up. The Status LED reports power, active charging, and fault states throughout.