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.