User Guide
9 of 25
002-35126 Rev. **
2022-05-10
WLC1115 MP-A11 15-W wireless power transmitter
(REF_WLC_TX15W_C1) user guide
WLC1115 wireless power transmitter system design
3.
Inverter stage
–
The full-bridge inverter (Q1 to Q4) is operated at a fixed frequency of 127.7-kHz to drive the
resonant tank formed by the transmitter coil (Lr) and resonant capacitors (Cr). The coil voltage feedback
(COIL-SNS) is used for Q-factor estimation and ASK demodulator circuits
4.
Transmitter coil assembly
–
The transmitter coil is MP-A11 type with specifications per Qi standards. The
coil is mounted on a separate coil PCB. An acrylic sheet forms the interface surface of the transmitter. The
coil mounting adhesive, spacers, and acrylic thickness are selected such that the distance between coil top
surface to interface surface is approximately 3.35-mm (Qi specification
–
3.5 ± 1 mm). See
for coil
assembly details
.
dz
PCB
Spacer
Acrylic
Coil assembly
Adhesive
PCB thickness
–
1.6mm
Acrylic thickness
–
1.78mm
Spacer height
–
4.8mm
PCB + ad Coil assembly
–
4.9mm
Dz gap
–
3.35mm
Figure 5
MP A11 transmitter coil assembly
5.
WLC1115-68LQXQ
–
The WLC1115 is a single controller unit to control the transmitter coil and USB-PD
interface. The WLC1115 simplifies the transmitter board architecture with inbuilt gate drivers for buck and
inverter stage, inbuilt LDO for logic and core power, and more features. With an on-chip 32-bit Arm® Cortex®-
M0 processor, 128-kB flash, 16-kB RAM, and 32-kB ROM, the firmware supporting the complete Qi and USB
PD state machine logic can be programmed onto WLC1115
6.
ASK demodulator
–
The ASK demodulator is based on coil voltage and bridge current. The demodulated
signal from both paths is processed through a dual opamp-based gain stage and a comparator (U1) and
decoded by the WLC1115 controller
7.
SLS32AIA020U3USON10
–
The authentication requirements for the Qi 1.3.2 is realized using a security
controller from Infineon.
The OPTIGA™ Trust c
omes with full system integration for the cost-effective and
seamless authentication deployment, and it is interfaced to WLC1115 over I2C
8.
Q-factor estimation
–
The Q-factor estimation from coil voltage is performed by WLC1115 through the
signal at Q_COMP. The coil voltage is processed through a blocking capacitor, voltage divider, and clamping
diode to feed to the WLC1115 controller for Q-factor estimation
9.
Status indication
–
The firmware indicates the various system states or events using the dual-color (red
and blue) status LED (LED1). See Reference board operation to understand more details
