ANP032g // 2018-01-19 // AnNa, CSo Page 1 of 25
A P P L I C A T I O N N O T E
High Power Wireless Power Transfer
for the Industrial Environment
ANP032 BY ANDREAS NADLER AND CEM SOM
1. Introduction_________________________________________________
As the presence of wireless power transfer technology increases in consumer electronics, the industrial and
medical industries are shifting focus towards this technology and its inherent advantages. As communication
interfaces are becoming increasingly wireless with technologies like WLAN and Bluetooth, wireless power
transfer has become a relevant option. Completely new approaches can be taken that not only offer obvious
technical advantages, but also open up possibilities for new industrial design. This technology offers new
concepts - especially in industrial sectors struggling with tough environmental conditions, aggressive cleaning
agents, heavy soiling and high mechanical stresses (e.g. ATEX, medicine, construction machines). For
instance, expensive and susceptible slip rings or contacts can be substituted. Another field of application is
with transformers, which have to satisfy special requirements, such as reinforced or doubled insulation.
The target of this Application Note is to demonstrate that easy-to-achieve solutions for wireless power transfer
of one hundred Watts or more are reachable using circuit technology, without the need of software or
controllers.
Figure 1: Wireless power coils from Würth Elektronik
ANP032g // 2018-01-19 // AnNa, CSo Page 2 of 25
A P P L I C A T I O N N O T E
High Power Wireless Power Transfer
for the Industrial Environment
2. ZVS Oscillator (Differential Mode Resonant Converter) ____________
A classical resonant converter is used as the clocking circuit in this Application Note.
This oscillator offers multiple benefits
It oscillates independently and only requires a DC source
The current and voltage profile is almost sinusoidal
No active components and no software are needed
It is scalable from 1 W – 200 W
The MOSFETs switch close to the zero crossover point
It is scalable for many different voltages/currents
2.1. Basic Circuit / Schematic:
Figure 2: Basic resonant converter circuit
The basic circuit shown here is the transmitter side incl. transmitter coil L
P
. The receiver side can be
constructed with the same basic circuit (see chapter 3.1).
2.2. Functionality
The resonant converter usually operates at a constant working frequency, which is determined by the resonant
frequency of the LC parallel resonant circuit. As soon as a DC voltage is applied to the circuit, it starts to
oscillate based on the MOSFETs component tolerances. Within a fraction of a second, one of the two
MOSFETs is slightly more conductive than the other. The positive feedback of the two MOSFET gates and the
opposite drain of the less conductive MOSFET gives rise to a 180° phase shift. The two MOSFETs are
therefore always driven out of phase and can never conduct simultaneously. The MOSFETs alternately
connect both ends of the parallel resonant circuit to ground allowing the resonant circuit to be periodically
recharged with energy.