P9412 Datasheet

R35DS0011EU0120 Rev.1.2

Jul.6.21

Page 12

3.

Functional Description

3.1

Wireless Power Charging System

A wireless power charging system has a base station with one or more transmitters (Tx) that make power

available via DC-to-AC inverter(s) and transmit the power over a strongly-coupled inductor pair (magnetic

induction), or over a loosely-coupled inductor pair (magnetic resonance) to a receiver (Rx) in a mobile device. A

Wireless Power Consortium (WPC)1 system uses near field magnetic induction between coils and can be a free-

positioning or magnetically-guided type of system.

In WPC systems the amount of power transferred to the mobile device is controlled by the receiver. The receiver

sends communication packets to the transmitter to increase power, decrease power, or maintain the power level.

The Rx-to-Tx communication uses the existing power links (in-band communication) with Amplitude Shift Key

(ASK) at 2kbps data rate.

Base Station

Transmitter

Transmitter

Mobile Device

Receiver

Transmitter

Power

PowerConversion

Power Pick

-up

Control

Control

Messages

Comm

Comm

Reflected Load

Mod

DeMod

Figure 3. Block Diagram of a WPC System

3.2

Theory of Operation

3.2.1.

Overview

The P9412 is a highly-integrated wireless power transmitter/receiver (TRx) IC for mobile applications. As a

wireless power receiver (Rx), the device can deliver up to 30W wirelessly using near-field magnetic induction,

and it operates in compliance with WPC specification in all modes. The P9412 also employs higher power

protocols enabling the extension of power delivery beyond the WPC EPP standard.

Figure 3 shows the simplified block diagram of the P9412. External Rx coil(s) and CS capacitor(s) transfer

energy wirelessly using the P9412 AC1 and AC2 pins to be full-wave-rectified (AC-to-DC).

The wireless power is stored on a capacitor(s) connected to VRECT. Until the voltage across the VRECT

capacitor exceeds the UVLO threshold, the rectification is performed by the body diodes of the synchronous full

bridge rectifier FETs. After the internal biasing circuit is enabled, the driver and control block operates the

MOSFET switches of the rectifier in various modes to maintain reliable connections at optimal efficiency. An

internal ADC monitors the voltage at VRECT and the load current, the P9412 sends instructions to the wireless

power transmitter to increase or decrease the amount of power transferred or to terminate power transmission

based on these readings. The voltage at the output of the P9412 Main Low-Drop-Out (LDO) regulator (VOUT) is

programmed from 5V to 20V using I2C commands. The internal temperature is continuously monitored to ensure

safe operation.

1 For the most current information, see the WPC specification at http://www.wirelesspowerconsortium.com/.