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AN234970
Foreign object detection tuning guide for
wireless power transmitters
Applicable to WLC ICs
About this document
Scope and purpose
The wireless charger (WLC) power transmitter solution reference board is a highly integrated wireless solution
with Type-C power delivery (PD).
This application note is a guide to configure the foreign object detection (FOD) parameters required for custom
designs based on the WLC power transmitter reference design.
Intended audience
Experts who customize designs based on REF_WLC_TX15W_C1-based wireless power transmitters.
Application Note
Please read the Important Notice and Warnings at the end of this document
002-34970 Rev. **
www.infineon.com
page 1 of 36
2022-05-03
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Summary of Contents for Infineon AN234970
- Page 1 AN234970 Foreign object detection tuning guide for wireless power transmitters Applicable to WLC ICs About this document Scope and purpose The wireless charger (WLC) power transmitter solution reference board is a highly integrated wireless solution with Type-C power delivery (PD).
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Page 2: Table Of Contents
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Table of contents Table of contents Table of contents ..........................2 Acronyms/Abbreviations ......................... 3 Introduction .......................... 4 Document structure ..........................4 Getting started ........................5 FOD mechanism ............................5 2.1.1 FOD before power transfer ........................ -
Page 3: Acronyms/Abbreviations
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Acronyms/Abbreviations Acronyms/Abbreviations Acronyms/Abbreviations Table 1 Acronym/Abbreviation Definition USB PD Universal serial bus power delivery DUT/EUT Device under test/Equipment under test Transmitter Receiver Baseline power profile Extended power profile Test power receiver Amplitude shift keying Frequency shift keying... -
Page 4: Introduction
The Wireless Charging Configuration Utility enables the user to configure FOD parameters. Refer to for more details on the product reference design, referred to as “reference design” in this document. Please contact the Infineon sales team for any additional support. Document structure ▪... -
Page 5: Getting Started
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Getting started The WLC power transmitter provides Qi-compliant FOD features. Refer to the FOD chapter in the Qi Standard for further details (see and [4]). The following sections discuss the WLC power transmitter implementation of the FOD functionality. - Page 6 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Q FO detection threshold FOD mechanism based on Q factor Figure 1 Q factor: This involves measurement of the Q factor when an EPP TPR is placed on the interface surface of the transmitter.
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Page 7: Fod During Power Transfer
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Where F is the reported RF, F is the scaled RF, F is the threshold RF. Threshold_percent and scaled threshold ScalingFactor are configurable from the Wireless Charging Configuration Utility. Higher threshold of RF FO present... - Page 8 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Measured system power loss System Power Loss Curve CorrectedLosses 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000 -100 -150 PRx (mW) Typical power loss measurement with power delivery range Figure 3 System power loss: The FO is detected if the measured system power loss exceeds the system power loss threshold value.
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Page 9: Fod Using Pre- And In-Power Transfer Methods
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Case 1 represents the region and Case 2 represents the region Figure FOD mechanism based on system power loss Figure 4 The thresholds for FOD can be configured. Refer to Section 3.6 for tuning thresholds for power loss-based FOD. - Page 10 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started BPP and EPP devices Measure the open air Q-factor Receiver / FO arrival detection Is the measured Q less FO detected by than the Q-factor open Air FO threshold? Wait till the object...
- Page 11 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Figure 6 illustrates the FOD using Q factor mechanism: EPP device Continued from 1 Process the FOD/qf packet from receiver Is the NAK the FOD/qf measured Q less than packet indicating an FO...
- Page 12 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started Figure 7 illustrates FOD using the resonance frequency mechanism: EPP device Continued from 1 Process the FOD/rf packet from receiver Is the NAK the FOD/rf difference in RF packet indicating measurements...
- Page 13 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Getting started BPP and EPP devices In power transfer phase Is the load Wait for load stable (load to stabilize. transition)? Calculate the system power loss Is the loss exceeding the FO detected with threshold_...
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Page 14: Fod Parameter Tuning
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning FOD parameter tuning FOD parameter tuning is required when the reference design of the WLC power transmitter is changed. The following changes from the WLC power transmitter reference design will result in a need to retune the FOD: 1. -
Page 15: Required Tools
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning Required tools The following tools are required for the tuning process: Custom design power transmitter board. WPC-approved reference compliance tester Figure 9 WPC-approved compliance tester. The user may approach the WPC’s authorized test labs (ATLs) in case of unavailability of the compliance tester tools. -
Page 16: Hardware Setup
Applicable for WLC ICs FOD parameter tuning USB-UART device for capturing UART logs from WLC power transmitter board. Infineon USB to UART device Figure 10 4. Tera term or Putty or any serial communication-based PC tool for capturing UART logs from the WLC power transmitter board (ensure that the PC tool used for data logging is capable of processing UART data at 1,000,000 baud with minimal losses). -
Page 17: Q Factor Scaling Factor Tuning Process
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning UART connections with PC Figure 11 4. Open the serial communication terminal (such as Minicom/Tera Term/Putty) and set the baud rate to 1000000. 5. Leave the rest of the UART settings as default. 6. -
Page 18: Q Factor Scaling And Threshold Tuning Process
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning 3.4.1 Q factor scaling and threshold tuning process The Q factor scaling derives the reference Q factor for the WLC power transmitter from the receiver-reported reference Q factor. -
Page 19: Q Factor-Based Fod Tuning
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning 5. Enter the measured and reported Q factor values in the respective cells in the “QF Scaling Factor Calc” page. The scaling factor is calculated in this page. User input section in “QF Scaling Factor Calc”... -
Page 20: Resonance Frequency Scaling Factor And Threshold Tuning Process
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning S. no. Parameter Description Prepower Q FOD threshold (%) Q factor threshold for FO detection when there is no communication. Default value is 30. No response digital ping retry Object detected with no communication/response to count... - Page 21 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning UART logs for receiver reported and WLC power transmitter measured resonance Figure 16 frequency Follow these steps to tune the resonance frequency scaling factor and threshold values: 1.
- Page 22 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning 2. Capture the receiver reported reference resonance frequency for all the EPP TPRs in the “RF Scaling_Threshold Calc” page in FOD_TuningGuide_Calculator.xlsx. Enter the data in the row named “FOD/rf”.
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Page 23: Resonance Frequency-Based Fod Tuning
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning 3.5.2 Resonance frequency-based FOD tuning View of Q factor settings configuration tool Figure 19 Resonance frquency Q factor configuration setting parameters Table 3 S. no. Parameter Description Resonance frequency measurement... - Page 24 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning UI for signal strength, CE packets, Advanced mode, Electronic load selection on reference Figure 20 compliance tester 5. Set the load to the minimum load value. Refer to the “SystemPowerLoss_data” page in FOD_TuningGuide_Calculator.xlsx for load values.
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Page 25: Power Loss-Based Fod Tuning
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning User input section in “SystemPowerLoss_data” page Figure 22 11. This data is used in the next section for configuring the WLC power transmitter. 3.6.2 Power loss-based FOD tuning Power loss settings in the configuration tool Figure 23... - Page 26 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning The following table describes the parameters used for tuning the FOD using the power loss method. Power loss configuration setting parameters Table 4 S. no. Parameter Description Enable power loss FOD...
- Page 27 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning S. no. Parameter Description EPP 5W loss characterisation coefficient ‘b’ Coefficient b in Equation 6 for 5W EPP mode of power transfer. This value is auto-generated under the cell with t same name in SystemPowerLoss_data page.
- Page 28 Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD parameter tuning S. no. Parameter Description EPP power loss FOD threshold no retries Maximum power loss threshold for 15W EPP and power latch (mW) mode of operation. See Case 2. Default value is 2000mW.
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Page 29: Fod Functionality Verification
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs FOD functionality verification FOD functionality verification The following tests from the Qi compliance test suite can ensure an appropriate tuning of the FOD parameters for BPP devices: 1. -
Page 30: Checklist For Tuning Operation
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Checklist for tuning operation Checklist for tuning operation 1. Use caution while moving the TPR toward the interface surface of the transmitter. Ensure that the movement is subtle and does not lead to any mechanical or electrical damage to the transmitter or receiver. -
Page 31: Appendix I - Finding Signal Strength
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Appendix I – Finding signal strength Appendix I – Finding signal strength Note: This process is unique for every compliance tester. 1. Enable the Signal Strength Finder in the compliance tester tool. See Figure 2. -
Page 32: Appendix Ii - Received Power Offset
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Appendix II – Received power offset Appendix II – Received power offset Note: This section is compliance tester-specific and may be subject to change. Please contact sales support for more details. -
Page 33: Appendix Iii - Enabling Uart Logs Using Wireless Charging Configuration Utility
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Appendix III – Enabling UART logs using Wireless Charging Configuration Utility Appendix III – Enabling UART logs using Wireless Charging Configuration Utility Note: The UART logs are not enabled in the system. The user must disable the UART logs when not needed. The standard system behavior is tested with UART logs disabled. -
Page 34: References
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs References References Qi Standard Version 1.3.x Qi Standard (Version 1.3.1), Chapter “Foreign Object Detection” Two-point calibration – Section 11.4.3.1 of Part 12, Qi Standard Version 1.2.4 FOD based on calibrated power loss accounting – Section 11.4 of Part 12, Qi Standard Version 1.2.4 (External link) WPC’s list of ATLs Section 5.4.3.3... -
Page 35: Revision History
Foreign object detection tuning guide for wireless power transmitters Applicable for WLC ICs Revision history Revision history Document Date of release Description of changes version 2022-05-02 New application note Application Note 35 of 36 002-34970 Rev. ** 2022-05-03... - Page 36 Infineon Technologies hereby disclaims dangerous substances. For information on the types © 2022 Infineon Technologies AG. any and all warranties and liabilities of any kind in question please contact your nearest Infineon All Rights Reserved. (including without limitation warranties of non- Technologies office.