Common Applications of High Power Wireless Power Transfer for the Industrial Industry

As we discussed in our previous post, the industrial industry has begun to embrace high power wireless power transfer because of its many benefits for industrial applications.

But what exactly are those applications? In this post, we’ll cover the most common uses for high power wireless power transfer in the industrial environment.

1. Simple Receiver Circuit

Figure 14: Bridge rectifier circuit with Schottky diodes and ripple current resistant aluminum polymer SMD capacitors. Output power of this receiver circuit is approx. 20 W depending on the cooling surface.*

Ua = (2 · Ue · √2) - (2 · Udiode)

TVS Power Diode to protect against transient over-voltages (bidirectional; max. operating voltage 60 V).

2. Standard Resonant Converter

Figure 15: Example of simple transmitter/receiver resonator circuitry for use up to 10 W. An input current monitoring should be implemented for all transmitters. This protects the power FETs from thermal overload. If the oscillation does not start properly or breaks down during operation, one of the power FETs would be permanently controlled by GND and thus thermally destroyed. Logic level FETs must be used for supply voltages below 9 V.*

3. Modified Receiver Circuit

Figure 16: Replacing the filter inductors with power Schottky diodes allows higher output voltages by double rectification at the receiver; output filter (C7 / C8 / L1) required; to feed the gates, a small voltage can be generated from the high DC voltage at L1 with the help of an LDO/buck converter, whereby the voltage dividers and ten diodes can be removed from the design. This circuit can only be used on the receiver side for up to 50 W. If no logic level FETs are used, at least 9 V gate source voltage is required for a safe and reliable transmission.*

4. Push-Pull Gate Control

Figure 17: Control of the power MOSFET gates via push-pull switching of the gates instead of half sine; this circuit can be used on the transmitter and receiver side. The 8 - 10 V auxiliary voltage can be generated from the operating voltage by means of an LDO or WE Power Module ( 171 012 401). An overcurrent cut-off at the input should always be used. If the oscillation does not start properly or breaks down during operation, one of the power FETs will be permanently connected to GND and thus thermally destroyed. Logic level FETs must be used for supply voltages below 9 V.*

5. Double Resonant Converter

Figure 20: Transmitter and receiver for approx. 100W (up to 20 V / 8 A max.).*

6. Resonant Converter with Center Tap

Figure 21: Resonance converter for coils with center tap. The advantage of the circuit is that you only need one filter coil. Due to the center tapping, the frequency is twice as high and the voltage swing is reduced. This allows smaller filter coils to be used. In addition, an array with two overlapping coils can be easily controlled. The 8 - 10 V auxiliary voltage can be generated from the operating voltage using an LDO or WE Magic Power Module ( 171 012 401).*

Summary of High Power Wireless Power for Industrial Applications

This resonant converter is very flexible and can be adapted to the requirements of many different applications.

This circuit currently represents the most effective wireless transfer of energy of up to several hundred Watts. If the demands of the application grows in terms of safety, On/Off, charging state detection, and so forth, this circuit can serve as the basis and be extended by the hardware developer. A classical H bridge circuit with active regulation can also be taken as the basis rather than the resonant converter topology. In any case, EMC measurements should be performed on the first prototypes at an early stage during development.

High efficiency, the most compact package, and good EMC properties essentially depend on the clocking circuit, as well as the transmitter and receiver coils. Besides the widest product range, Würth Elektronik also offers coils with the highest Q factors in their respective packages. This allows higher inductance values to be attained and results in smaller packages for the capacitors.

In addition, Würth Elektronik uses HF litz (stranded) wire exclusively for high power (lower AC losses) with high quality ferrite material (high permeability). This means the maximum efficiency and best possible EMC performance for the end product.

To learn more, view our solutions for wireless power transfer for the industrial environment.

*Please note: Observe precautionary measures and touch protection with voltages above 50 VAC / 120 VDC!

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