A Dual-Mode Wireless Power Transfer Using

Multi-Frequency Programmed

Pulse Width Modulation

Chongwen Zhao, Daniel Costinett

The University of Tennessee, Knoxville

Objective and Motivation • Simultaneously power multiple wireless devices

• Allow for different receiver standards (~100 kHz and 6.78 MHz)

• Use standard hardware developed for single-frequency applications WPT

Transmitter

DC/DCBattery Charger

Idc Ip Is1

DC/DCBattery Charger

Is2

Fig.1 Proposed system block diagram

Multi-frequency Programmed PWM

fspecturm

...

Fundamental kth

Harmonic

...

V

θ1 θ2θ3 θn

... ...

1. Purpose: Calculate solution sets of

switching instances: θ1, θ2,.. Θn

2. Method: Newton-Rasphon numeric

iteration algorithm

3. Modulation Scheme investigated:

Bipolar and Unipolar MFPW

4. Desired outputs: 101.2 kHz and 6.78 MHz

5. Total odd harmonics under control: 33

Vab VLF VHF

VLF

VHF

Desired Spectrum

Fourier Expansion

Modulation Solution

Dual-mode Operation

Q1 Q2

Q3 Q4

+

Vdc

-

Idc

+

Vab

-

a

b

CT100

LT100 LR100RLLF

RLHF

CR100

CT6.78

LT6.78

CR6.78

LR6.78

k1

k2

Voltage Gain @101. 2 kHz Voltage Gain @6.78 MHz

Fig.2 Circuit model of dual-mode operation

Fig.6 Cross interference reduction

101.2 kHz

Channel

6.78 MHz

ChannelGaN-Based

Inverter

Vab (10V/div)

Vload100 (5V/div)

Vload6.78 (12.5V/div)

2μs/div

Conclusion and future work Simultaneous 100kHz and 6.78MHz dual-mode operation

Verified on a 10 W GaN-based WPT prototype

Ability to regulate power to each load on simple full bridge power stage

Future investigations on hardware design and efficiency optimization

Reconstruction Result

Time domain result

Spectrum result

Fig.3 Bipolar MFPWM waveforms and spectrum(LF = 0.5,

HF = 0.9 normalized amplitude)

Fig.4 Dual-mode operation waveforms (top to bottom:

inverter output, 101.2 kHz receiver, 6.78 MHz receiver)

Fig.5 Unipolar MFPWM waveforms and spectrum

(LF = 0.6, HF=0.34, normalized amplitude)