ST STDES-50W2CWBC - User Manual

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Introduction

The STDES-50W2CWBC dual-coil reference design is based on the STWBC2-HP Qi-compliant, inductive wireless charger

transmitter. It supports two coils, which could work alternatively to increase the Rx positioning freedom. The solution supports

Qi EPP-compliant mode up to 15 W, featuring an ST proprietary protocol. It can also support 50 W or an even higher wireless

power transfer.

The embedded STWBC2-HP integrates the following main components:

• three pairs of half-bridge gate drivers

• a dedicated DC-DC controller that supports buck, boost, and buck-boost topologies

• high-performance Q-factor detection hardware

• a high-resolution main PWM controller

• a dedicated Qi communication modulator and demodulator

• a USB-PD controller

• a buck DC-DC

• a charge-pump

The

STDES-50W2CWBC

is a fully assembled reference design developed for performance evaluation only, not available for

sale.

To achieve the best performance, carry out some procedures before finalizing the application.

This document summarizes the following fundamental steps:

• power supply test

• firmware downloading test

• power-on LED status check

• parameter setting test

• presence detection test

• power transfer switching test

• ST super charger (STSC) protocol test

• ASK demodulation test

• Q-factor accuracy test

STDES-50W2CWBC test report

TN1399

Technical note

TN1399 - Rev 1 - March 2022

For further information contact your local STMicroelectronics sales office.

www.st.com

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The STDES-50W2CWBC is a dual-coil reference design for wireless power transfer, adhering to the WPC MP-A2 topology. This device is designed to automatically detect and charge a receiver (PX) using either of its two coils. It is suitable for evaluation in laboratory and development environments by electronics experts.

Function Description

The core function of the STDES-50W2CWBC is to provide wireless power transfer. It supports two coils, which can work alternatively to increase the Rx positioning freedom. The solution supports Qi EPP, providing up to 50 W to the PX, and can also support 60 W or even higher wireless power transfer using a proprietary protocol. The device incorporates an embedded STWBC2-HP, which integrates several key components:

Three pairs of half-bridge gate drivers: These drivers manage the power switching for the coils.
A dedicated DC-DC controller: This controller supports buck, boost, and buck-boost topologies for efficient power conversion.
High-performance Q-factor detection hardware: This feature allows for accurate measurement of the Q-factor, which is crucial for efficient power transfer.
A high-resolution main PWM controller: This controller generates the pulse-width modulation signals for power control.
A dedicated Qi communication modulator and demodulator: This enables communication with Qi-compatible receivers.
A USB-PD controller: Supports USB Power Delivery.
A buck DC-DC: For voltage step-down.
A charge-pump: Used for specific voltage generation.

The reference design is capable of detecting the presence of a receiver and initiating power transfer. It also supports a proprietary ST Super Charge (STSC) protocol, which allows for higher power transfer than the standard Qi EPP. The firmware can route demodulation results (voltage and current) to a GPIO, providing insight into the Rx modulation waveform.

Important Technical Specifications

Input Power: The boost DC-DC supports 60 W (20 V/3 A) input.
Output Voltage: The boost DC-DC provides 30 V+ output. The Rx output can range from 5 V to 20 V when using the STSC proprietary protocol.
AC Voltage Support: The full bridge converter supports an AC voltage of ≤ ±100 V.
Coil Switching: The coil switcher alternatively switches the two LC tanks for coils into high voltage.
Q-factor Accuracy: The Q-factor measurement accuracy is designed to be close to that of an LCR meter.
LED Indicators: Three LEDs (D209 Green, D202 Red, D203 Green) indicate the STWBC2-HP power-on status. D209 is always on, D202 blinks once long and once short, and D203 blinks once long.
Presence Detection: The presence detection on both coils typically shows a level of ~6 V, a duration of ~80 ms, and a cycle of ~1900 ms.
STSC Power Supplies:
- Presence detection: 5 V input, 12 V VDCDC.
- Digital ping: 9 V input, 12 V VDCDC.
- STSC 5 V: 9 V input, 12 V VDCDC.
- STSC 9 V: 9 V input, 9 V VDCDC.
- STSC 12 V: 12 V input, 12 V VDCDC.
- STSC 15 V: 15 V input, 15 V VDCDC.
- STSC 18 V: 15 V input, 16.5-18 V VDCDC.
- STSC 20 V: 20 V input, 20 V VDCDC.
Q-factor Accuracy Test (with RMB coins):
- LCR: 11.7 (One Yuan), 18.1 (50 cents), 29.4 (10 cents).
- Coil 1: 11.3 (One Yuan), 18.4 (50 cents), 31.5 (10 cents).
- Coil 2: 11.4 (One Yuan), 18.3 (50 cents), 31.1 (10 cents).

Usage Features

Flexible Positioning: The dual-coil design allows for greater freedom in positioning the receiver.
Qi EPP Compatibility: Supports the Qi Extended Power Profile for standard wireless charging up to 50 W.
Proprietary Protocol Support: Capable of higher power transfer (up to 60 W or more) using the ST Super Charge (STSC) protocol.
USB-C Interface: Provides a USB-C interface for connectivity.
STLINK-V3MINI Interface: Includes an STLINK-V3MINI interface with SWD for firmware debugging and UART for demo GUI.
I²C Interface: Supports external daughter boards, such as STSAFE-A110 for authentication, via an I²C interface.
GUI Control: Parameters for board initialization and features like FOD (Foreign Object Detection) and protection can be set via the STWBC2_GUI.

Maintenance Features

Firmware Updates: The device supports firmware updates, which can be performed using the STLINK-V3MINI.
Diagnostic Tools: The STWBC2_GUI provides tools to check board behavior, perform tuning, and collect logs in case of failure.
LED Status Indicators: Power-on LEDs provide visual feedback on the STWBC2-HP's operational status.
Test Points: Various test points are available for monitoring different aspects of the system, such as power supply levels, oscillation waveforms, and demodulation results, facilitating troubleshooting and evaluation.
Q-factor Measurement: The integrated Q-factor detection hardware allows for verification of the coil's quality, which is important for maintaining efficient power transfer.