Wireless Power Feed System Reactance Control for Overvoltage Prevention
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Solution Overview
Problem
Existing wireless power feed systems face inefficiencies and voltage increases when the power-receiving circuit is in a no-load state, particularly under poor radio wave conditions, leading to potential overvoltage issues.
Innovation Solution
The system employs a power transmission circuit with a resonance circuit having a non-zero reactance and a power-receiving circuit with zero reactance, allowing for efficient power transmission when loaded and reducing voltage increases when unloaded, by setting the absolute value of the power transmission resonance circuit's reactance to be greater than a threshold and the power-receiving resonance circuit's reactance to zero.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If wireless power transmission is performed with high output power, then power feeding efficiency is improved and power can be fed in a short time, but when the power-receiving circuit is in a no-load state, voltage increases excessively and exceeds allowance values
Solution Approach 1:
The patent implements a feedback mechanism where the power-receiving circuit wirelessly transmits information about its load state (loaded or no-load) to the power transmission circuit. Based on this feedback, the power transmission circuit automatically adjusts its transmission state - stopping transmission when no-load is detected to prevent overvoltage, and resuming when loaded. This closed-loop control resolves the contradiction by enabling high-power transmission when needed while preventing overvoltage during no-load conditions.
Solution Approach 2:
The patent makes the power transmission state dynamic rather than static. The transmission circuit transitions between different operational states (transmitting, stopping, resuming) based on real-time load conditions detected through wireless communication. This dynamic adaptation allows the system to optimize power feeding speed during loaded states while preventing overvoltage during no-load states, resolving the technical contradiction.
2Object-affected harmful factors
If a wireless communication mechanism is used to stop power transmission when no-load state is detected, then overvoltage can be prevented, but a time lag occurs from voltage increase detection to transmission stop instruction
Solution Approach 1:
The patent applies preliminary action by having the power-receiving circuit proactively transmit its load state information to the power transmission circuit before overvoltage occurs. Instead of waiting to detect voltage increase and then responding, the system continuously communicates the loaded/no-load state in advance, allowing the transmission circuit to stop transmission before overvoltage develops, thus eliminating the time lag.
Solution Approach 2:
The patent introduces wireless communication as an intermediary mechanism that enables real-time information exchange between the power-receiving and power-transmission circuits. This intermediary allows the receiving circuit to immediately notify the transmission circuit of its load state without time lag, enabling instantaneous response and preventing overvoltage before it occurs.
3Loss of energy
If the power-receiving circuit is in a no-load state, then power transmission efficiency decreases and voltage increases, but maintaining continuous transmission wastes energy
Solution Approach 1:
The patent uses feedback control where the power-receiving circuit continuously communicates its load state to the power transmission circuit. When no-load is detected, the transmission circuit stops transmission to prevent energy waste and voltage increase. When loaded, transmission resumes. This feedback mechanism resolves the contradiction by enabling energy-efficient operation during no-load states while preventing harmful voltage increases.
Solution Approach 2:
The patent implements periodic action by having the power transmission circuit operate in cycles - transmitting when loaded, stopping when no-load, and resuming when loaded again. This periodic on-off operation based on load conditions prevents continuous transmission during no-load states, thereby avoiding both energy waste and voltage increase, while maintaining readiness to transmit when power is needed.
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
This configuration ensures efficient power transmission when the power-receiving circuit is loaded and effectively restricts voltage increases when it is in a no-load state, thereby addressing the inefficiencies and overvoltage issues in existing systems.
Implementation Method 1
power is transmitted between a power transmission coil and a power-receiving coil that are arranged apart from one another
Implementation Method 2
a power transmission resonance circuit including an inductor having self-inductance L1 and a capacitor having capacity C1... a power-receiving resonance circuit including an inductor having self-inductance L2 and a capacitor having capacity C2
Data Source
Figure 1
Figure 2~3
Figure 4~5B
AI summary
A power feed system 1 includes a power-receiving circuit 6 and a power transmission circuit 3. The power transmission circuit 3 includes a power transmission resonance circuit 38 including an inductor having self-inductance L1 and a capacitor having capacity C1. The power-receiving circuit 6 includes a power-receiving resonance circuit 61 including an inductor having self-inductance L2 and a capacitor having capacity C2. The power transmission resonance circuit 38 is driven at a driving frequency ω and thereby performs power transmission from the power transmission circuit 3 to the power-receiving circuit 6. An absolute value of reactance X1 of the power transmission resonance circuit 38, which is determined by L1, C1, and ω, is set to be larger than a first threshold Th1 (Th1 ≥ 0) and reactance X2 of the power-receiving resonance circuit 61, which is determined by L2, C2, and ω, is set to be 0.