Relay Coil Resonance for Load-Stable Contactless Power Feed
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Solution Overview
Problem
Existing contactless power feed technologies face efficiency deterioration when the load connected to the power reception device changes, due to challenges in maintaining Zero-Voltage-Switching (ZVS) and Zero-Voltage-Derivative-Switching (ZDS) conditions.
Innovation Solution
A contactless power feed apparatus is designed with a relay circuit that includes a first coil electromagnetically coupled with the transmission coil, a second coil for transmitting power to the reception device, and a resonant capacitor. This configuration allows for efficient power transmission by achieving ZVS and minimizing switching losses even with changing loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If power feed is performed through electromagnetic induction using a Class-E amplifier configuration, then power transmission efficiency is improved, but the conditions for maintaining ZVS and ZDS become difficult to satisfy when the load changes
Solution Approach 1:
The control circuit monitors the load conditions and dynamically adjusts the switching timing and frequency of the switching element to maintain ZVS and ZDS conditions across varying load scenarios, enabling both high efficiency and load adaptability
Solution Approach 2:
The system transitions from a fixed-frequency Class-E amplifier to a dynamically adjustable switching circuit that can modify its operating parameters in real-time based on load changes, allowing the maintenance of optimal switching conditions under varying conditions
2Power
If the switching frequency is increased to 6.78 MHz using Class-E amplifier, then power transmission capability is improved, but the complexity of maintaining ZVS and ZDS conditions increases
Solution Approach 1:
The circuit is designed to self-regulate the switching timing and frequency through inherent resonant characteristics and control circuit feedback, automatically maintaining ZVS and ZDS conditions without requiring complex external control mechanisms
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The apparatus effectively suppresses the deterioration of power transmission efficiency when the load changes, by ensuring ZVS and reducing switching losses, thereby maintaining reliable power delivery.
Implementation Method 1
power feed through electromagnetic induction is known. In the power feed through electromagnetic induction, in general, by driving an inverter provided at a device on the power transmission side at a switching frequency lower than 1 MHz, AC power is supplied to a coil on the power transmission side to generate electromagnetic induction with a coil on the power reception side
Implementation Method 2
a resonant capacitor, resonating with the AC power supplied to the transmission coil together with the first coil and the second coil
Implementation Method 3
a resonant circuit, having a reception coil receiving the AC power from the second coil by being electromagnetically coupled with the second coil of the relay circuit
Data Source
AI summary
A contactless power feed apparatus 1 has a relay circuit 4 relaying power transmitted from a power transmission device 2 to a power reception device 3 in a contactless manner. The power transmission device 2 has: a transmission coil 12 transmitting AC power to the relay circuit 4. The relay circuit 4 has: a first coil 31, electromagnetically coupled with the transmission coil 12 and receiving the AC power from the transmission coil 12; a second coil 32, transmitting the AC power to the power reception device 3; and a resonant capacitor 33, resonating with the AC power supplied to the transmission coil 12 together with the first and second coils 31, 32. The power reception device 3 has: a resonant circuit 20, having a reception coil 21 receiving AC power from the second coil 32 by being electromagnetically coupled with the second coil 32 of the relay circuit 4.