Capacitive Voltage Sensing for Resonant Contactless Power Transfer
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Solution Overview
Problem
Existing contactless power transmission systems face challenges in accurately detecting voltage and controlling power due to the influence of capacitors and parasitic inductance, making it difficult to maintain consistent voltage output to loads with varying states.
Innovation Solution
A power transmission device and system that includes a DC power supply, a power converter, a power transmission electrode, a voltage detection unit with a separate voltage detection electrode for capacitive coupling, and a control unit to adjust power based on detected voltage, allowing for accurate voltage detection and control without disrupting the resonance condition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a capacitor is interposed to detect voltage between power transmission electrodes, then voltage detection is enabled, but the resonance condition in the power transmission circuit is influenced and changed
Solution Approach 1:
A voltage detection electrode is introduced as an intermediary element to detect voltage between the power transmission electrodes. This detection electrode forms a capacitive coupling with the power transmission electrodes, enabling voltage detection through the capacitive divider formed by the coupling capacitance and the detection electrode's self-capacitance, without requiring direct connection of capacitors that would disrupt the resonance condition.
2Measurement precision
If voltage division is performed by a series capacitor, then voltage detection is achieved, but parasitic inductance and capacitor variation affect detection accuracy
Solution Approach 1:
The patent replaces the traditional capacitor-based voltage division method with a capacitive coupling-based detection method. Instead of using a series capacitor that introduces parasitic inductance and component variation issues, the voltage detection electrode utilizes capacitive coupling with the power transmission electrodes to achieve voltage division through purely capacitive elements, eliminating the harmful parasitic effects.
3Productivity
If capacitive voltage division is used to recognize load state, then power transmission efficiency control is improved, but accurate voltage detection becomes difficult due to capacitor influences
Solution Approach 1:
The voltage detection electrode serves as an intermediary that enables accurate voltage detection through capacitive coupling. By forming a capacitive divider with the coupling capacitance between the power transmission electrodes and the detection electrode's self-capacitance to ground, it provides an accurate voltage signal for load state recognition without being affected by parasitic inductance or capacitor variations present in traditional methods.
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
Enables precise control of power supplied to the load, maintaining consistent voltage output despite varying load states without affecting the power transmission circuit's resonance condition, and reduces device size by eliminating the need for voltage division circuits.
Implementation Method 1
the voltage detection unit has a voltage detection electrode and detects the voltage of the power transmission electrode through capacitive coupling between the power transmission electrode and the voltage detection electrode
Implementation Method 2
Power is supplied to the power reception device through capacitive coupling between the power transmission electrode and the power reception electrode
Implementation Method 3
capacitive coupling present between power transmission electrodes and an inductor connected in series to the power transmission electrode are resonated to generate high voltage at the power transmission electrode
Data Source
AI summary
A contactless power feeding system includes: a power converter which converts DC power from a DC power supply, to AC power; a power transmission electrode to which AC power converted by the power converter is applied; a power reception device having a power reception electrode, receiving power through capacitive coupling between the power transmission and reception electrodes, and feeding power to a load; a voltage detection unit which detects voltage of the power transmission electrode; and a control unit which controls the DC power supply or the power converter using voltage detected by the voltage detection unit. The voltage detection unit has a voltage detection electrode and detects voltage of the power transmission electrode through capacitive coupling between the power transmission electrode and the voltage detection electrode.