NXP Semiconductors MP-A11, WCT-15W1CFFPD User Manual
© 2019 NXP B.V.
WCT1012VLF/WCT1013VLH Consumer MPA11 (WCT-15W1CFFPD) V1.0 Wireless
Charging Application User’s Guide
1. Key features
The WCT1012VLF/WCT1013VLH Consumer MPA11_Rev1.0 (MP-A11_Rev1_SCH-32212_B, MPA11_Rev1_LAY-32212_B) wireless charging TX demo
(WCT-15W1CFFPD) is used to wirelessly transfer power
to a charged device. The charged device can be any
electronic device equipped with a dedicated Qi wireless
charging receiver.
The main parameters of the Wireless Charging
Transmitter (WCT) are:
• Support for QC 3.0 and USB PD 2.0/3.0 input.
The input voltage ranges from 5 to 19 V DC.
• The input voltage can drop down to 5 V DC
during the start-stop function.
• The nominal power delivered to the receiver is
15 W, up to 22 W (at the output of the receiver)
and compatible with a 5 W receiver.
• Designed to meet the Qi 1.2.4 specification.
• Operation frequency: 120 kHz ~ 130 kHz (the
default is 127.772 kHz) for Qi devices.
NXP Semiconductors
Document Number: WCT101XV10AUG
User’s Guide
Rev. 1
05/2019
1. Key features ....................................................................... 1
2. Hardware setup .................................................................. 2
3. Application operation ........................................................ 6
4. Hardware description ......................................................... 6
5. Application monitoring and control using FreeMASTER 15
6. Application monitoring using console ..............................20
7. Programming new software and calibration .....................22
8. Software description .........................................................46
9. System bring up ................................................................52
10. Revision history ................................................................ 56
Contents
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2. Hardware setup
2.1.
Package contents
1. WCT Consumer MP-A11 (WCT-15W1CFFPD) demo board.
Figure 1. MP-A11 (WCT-15W1CFFPD) demo board
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2.2.
Board description
The WCT board is powered through the on-board power connector.
The connectors on the upper-middle part of the board provides the JTAG connection for programming
and debugging and 1xUART for the FreeMASTER tool connection for the debug option and console
connection. The I2C connector is placed on the upper left-hand side of the board.
Figure 2 shows the device.
Coil
I2C
UARTJTAG
DSC
USB PD
Buck
FB
Invertor
Power
Figure 2. Device overview
2.3.
Powering the board on
To power the board on, perform these steps:
1. Plug the USB PD or QC adaptor.
2. Connect the board with the USB PD or QC adaptor by an USB type-C cable.
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Figure 3. Power supply components
2.4.
Hardware setup for FreeMASTER and console communication
To set up the hardware for the FreeMASTER and console communication, perform these steps:
1. Find the UART-to-USB adapter on the board and install the UART-to-USB device driver on the
computer. The virtual serial port on the computer should work well.
2. Plug the USB-UART converting board to the SCI connector according to the SCH signal pin
position.
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Figure 4. UART and JTAG connectors
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3. Application operation
Connect the demo to the USB PD or QC adaptor using a cable. The WCT starts to periodically send the
power ping to check whether a compatible Wireless Charging Receiver (WCR) is placed on the charging
surface.
When a Qi-compliant receiver is placed on the top of the TX coil area, the WCT starts the charging
process. If there is no correct Qi answer from the WCR side, the TX does not start the Qi charging
process.
If the WCR answers properly, the power transfer starts. The actual level of the transferred power is
controlled by the WCT in accordance with the WCR requirements. The receiver sends messages to the
WCT through the ASK on the coil resonance power signal and the transmitter sends the information to
the receiver using FSK, as per the Qi specification. The power transfer is terminated when the receiver is
removed from the WCT magnetic field.
The system supports all Qi WCR devices: Qi_Ver-1.0 compliance, Qi_Ver-1.1 compliance, and the Qi
EPP receiver. The system supports all the FOD features for different receivers. For the BPP receiver, the
power loss FOD is supported. For the EPP receiver, both the Q-value FOD method and the power loss
FOD method are supported.
4. Hardware description
Figure 5 shows the block diagram of the consumer wireless charger MP-A11 (WCT-15W1CFFPD).
Visit www.nxp.com to get the latest hardware design files.
The whole design consists of several blocks, which are described in the following sections.
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Figure 5. Block diagram of the consumer wireless charger MP-A11 (WCT-15W1CFFPD)
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4.1.
Input EMI filter
The input filter consists of the common-mode filter FL1 and filter capacitors C2, C3, C5, C7, and L1.
4.2.
USB power supply
A USB type-C cable can be plugged to the USB type-C connector J2. The PTN5110 USB PD PCTC
PHY is selected to support the type-C Configuration Channel (CC) interface and the USB PD physical
layer functions.
The MPA-11 design also supports the Qualcomm Quick Charge 2.0/3.0 technology. The WCT
controller manages the Qualcomm QC 2.0/3.0 protocol through the GPIOs and resistors connected to the
D+/D- data line.
Figure 6. USB PD power supply and QC circuits
4.3.
System voltage DCDC
The USB PD or QC adaptor input is connected to buck converter U12 (MP2314). Its output is 3.3 V.
This 3.3 V output is mainly for the WCT1012VLF/WCT1013VLH and other 3.3 V-powered
components. Generally, the DCDC load current is low. It is preferable to select a DCDC with a high
efficiency in the light-load condition.
The MP-A11 design can also support other customized-propriety power protocols.
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4.4.
Rail voltage generated by analog buck chip
The Qi specification for the MP-A11 topology requires the DC voltage control to control the power
transferred to the receiver. The buck converter is selected to get the regulated DC voltage ranging from
3 V DC to 18 V DC for the full-bridge inverter power supply. The buck is controlled by the individual
analog buck converter and the WCT chip only controls the output voltage feedback.
For the analog buck module, MP2229 (or a similar IC like SY8286) is selected to generate the rail
voltage. The WCT chip generates one analog signal from the PWM and controls the rail voltage using
this signal. This analog signal adjusts the analog buck converter feedback, and the system can get the
rail voltage as the system expects.
Figure 7. Analog buck-boost main circuits
4.5.
Full-bridge and resonant circuits
The full-bridge power stage consists of integrated power stage unit (U7 and U8). The MOSFETs and
their driver are integrated inside the power stage unit. The full-bridge power stage converts the variable
DC voltage VRAIL to the square-wave 50 % duty-cycle voltage with a default frequency of 127.772
kHz. The range of the frequency used (from 120 kHz to 130 kHz) is defined in the Qi specification for
the MP-A11 topology.
The resonant circuits consist of C81, C82, C83, C84, C85, and coils, all of which are fixed values
defined in the Qi specification for the MP-A11 topology. The snubber RC pairs connected in parallel to
the integrated power stages are used to lower the high frequency of the EMI products. The Vrail
discharge circuit (Q4 and R58) is switched ON while the system is terminated.
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Figure 8. Full bridge circuits
4.6.
Communication
There is bi-way communication between the EPP power transceiver and receiver. Communication from
RX to TX: The RX measures the received power and sends the information about the required power
level back to the transmitter. This message is Amplitude Modulated (AM) on the coil current and sensed
by the TX.
The RC circuits C87, R87, R88, and R92 (known as DDM) sample the signal from the coil, compress
the signal amplitude, and feed it to the ADC B-channel of the WCT1012VLF/WCT1013VLH. The
information about the current amplitude and modulated data are processed by the embedded software
routine.
Communication from TX to RX: The TX shall negotiate with the RX in the negotiation phase (if requested
by the RX). The TX uses the FSK modulation to communicate with the RX, and the communication
frequency is about 512 times the operating frequency.
4.7.
FOD based on power loss
The power loss
, which is defined as the difference between the Transmitted Power and the
Received Power , i.e.
, provides the power absorption in foreign objects, as shown
in Figure 9.
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Figure 9. Power loss illustrated
When the FO is implemented in the power transfer, the power loss increases accordingly, and the FO
can be detected based on the power loss method.
The power loss FOD method is divided into two types: FOD for the baseline power profile (TX and RX
can transfer no more than 5 W of power) and extensions power profile (TX and RX can transfer power
above 5 W).
Power-loss FOD baseline
The equation for the power-loss FOD baseline is
.
The Transmitted Power represents the amount of power that leaves the TX due to the magnetic field
of the TX, and
, where represents the input power of the TX and
is the
power dissipated inside the TX. can be measured by sampling the input voltage and input current,
and
can be estimated using the coil current.
The Received Power represents the amount of power that is dissipated within the RX due to the
magnetic field of the TX, and
. The power
is provided at the RX output and
is the power lost inside the RX.
When the NXP MP-A11 transmitter charges the baseline profile RX, the power-loss baseline is applied.
The TX continuously monitors
, and if it exceeds the threshold several times, the TX terminates
the power transfer.
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Power loss FOD extensions
Typically, the RX estimates the power loss inside itself to determine its received power. Similarly, the
TX estimates the power loss inside itself to determine its transmitted power. A systematic bias in these
estimates results in a difference between the transmitted power and the received power, even if there is
no Foreign Object (FO) present on the interface surface. To increase the effectiveness of the power-loss
method, the TX can remove the bias in the calculated power loss by calibration. For this purpose, the TX
and the power RX execute the calibration phase before the power transfer phase starts. The TX must
verify that there is no FO present on its interface surface before the calibration phase and FOD based on
the Q factor can work.
Because the bias in the estimates may depend on the power level, the TX and RX determine their
Transmitted Power and Received Power at two load conditions—a “light” load and a “connected” load.
The “light” load is close to the minimum expected output power, and the “connected” load is close to
the maximum expected output power. Based on the two load conditions, the power transmitter can
calibrate its transmitted power using linear interpolation. Alternatively, the power transmitter can
calibrate the reported received power.
Take the calibrated transmitted power as an example:
Therefore, the TX uses the calibrated transmitted power to determine the power loss as follows:
When the MP-A11 transmitter charges an RX baseline, only the power-loss FOD baseline works. If an
RX extension is placed on the MP-A11 transmitter, the Q factor is measured first to detect if there is an
FO present. If yes, the TX stops charging; otherwise, the TX can proceed to the calibration phase and
the power transfer phase, and the power-loss FOD extension works to detect if an FO is inserted during
the power transfer phase.
For more details about the FOD, see the WCT1012VLF /WCT1013VLH Consumer MP-A11 Run-Time
Debug User’s Guide (document WCT101XRTDUG).
4.8.
FOD based on Q factor change
A change in the environment of the TX coil typically causes its inductance to decrease or its equivalent
series resistance to increase. Both effects lead to a decrease of the TX coil’s Q factor. The RX sends a
packet including the reference Q factor for the TX to compare and determine if the FO exists, as shown
in Figure 10.
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The reference Q factor is defined as the Q factor of the test power transmitter #MP1’s primary coil at the
operating frequency of 100 kHz with RX positioned on the interface surface and no FO nearby. Due to
the differences between its design and that of the test power transmitter #MP1, the TX needs to convert
the Q factor it measured to that of the test power transmitter #MP1. NXP provides the conversion
method and must get the on-board parameters first. The TX performs the automatic calibration and gets
the parameters at the first powerup after a new image is flashed. These parameters are then written to the
flash memory. Therefore, it is necessary to ensure that there is no object on the TX surface during the
first powerup after flashing a new image.
Figure 10. Q factor threshold example
Free-resonance Q factor
The free-resonance Q factor detection detects the decay rate of the resonance signal, as shown in Figure
11. With the system’s high Q, just a few pulses near the resonant frequency are sufficient to serve as
impulses and start the system ringing. Collect the ADC data of the tank voltage (or coil current), and get
the decay rate of the signal.
Q=/(-ln(Rate))
Rate is the value of the decay rate of the resonance signal.
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Figure 11. Resonance signal
The circuit for the free-resonance Q measurement is as shown in the following figure, which samples the
signal on resonance capacitors.
Figure 12. Free-resonance Q measurement circuit
Pre-FOD based on the Q factor
The pre-FOD serves to detect foreign objects without an RX. The TX uses analog ping to detect objects.
If an object is detected, a digital ping is initiated to decide if it is an RX. If the object is a metal FO, it is
heated by a digital ping. The TX provides a pre-FOD method based on the Q factor to detect the foreign
object and prevent it from being heated before the transfer is initiated.
4.9.
Analog sensing
Some ports of the ADC A-channel of the WCT1012VLF/WCT1013VLH are used to sense analog
signals, such as the temperature, full-bridge input current, input voltage, and rail voltage.
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5. Application monitoring and control using FreeMASTER
FreeMASTER is a user-friendly real-time debug monitor and data visualization tool for application
development and information management. Supporting non-intrusive variable monitoring on a running
system, FreeMASTER allows the data from multiple variables to be viewed in an evolving
oscilloscope-like display or in a plain-text format. The application can also be monitored and operated
from the web-page-like control panel.
5.1.
Software setup
To set up the software, perform these steps:
1. Install FreeMASTER version 2.0.2 (or later) from the NXP website: www.nxp.com/freemaster.
2. Plug the USB-UART converting board to the SCI connector J4, and connect the FreeMASTER
Micro-USB port to your computer.
3. Open the Device Manager, and check the number of the COM port.
Figure 13. Device Manager
4. Unpack the embedded source code to your local disk.
5. Start the FreeMASTER application by opening:
• MWCT1013
<unpacked_files_location>/15W_MP/example/wct1013PD/ wct1013pd.pmp
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6. Choose “Project” –> “Options”.
Figure 14. Choosing “Options”
7. Ensure that the correct virtual port (according to Step 3) and speed are selected.
Figure 15. Setting port and speed
8. Ensure that the MAP file is correct. The default directories are:
• MWCT1013
<unpacked_files_location>/15W_MP/build/demo/wct1013PDdemo/demo_ldm_debug/wct1013P
Ddemo_debug.elf
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Figure 16. Setting the MAP file
9. Connect FreeMASTER.
Power the MP-A11 on and start the communication by clicking the “STOP” button in the
FreeMASTER GUI.
Figure 17. “STOP” button
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5.2.
Real-time application variables monitoring
FreeMASTER enables the monitoring and updating of all the application global variables. In this
application, several key variables are displayed in the scope windows. These variables are divided into
different blocks, as shown in the following figure.
Figure 18. Real-time application variables
• wct_debug
This block shows the variables used for the GUI command.
• Library
This block contains the power loss variables, timing variables, coil selection variables, working
parameters, system status, DDM variables, and RX information.
• HAL
This block contains the ADC raw data and DDM buffer values.
• NVM
This block lists all NVM parameters. The Q factor sub-block shows the Q factor calibration
constants. The RRQD sub-block shows the quick-removal calibration constants. The FOD
sub-block shows the FOD characterization calibration constants. The normalization sub-block
shows the FOD normalization constants. The analog sub-block shows the rail voltage calibration
constants.
• LIB PARAMS
This block lists all the parameters used for the WCT library.
• Command
The command variable is used to stop the WCT, start the WCT, and perform automatic
calibration.
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