Resonance-Type Contactless Power Supply Tuning Circuit
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional resonance-type contactless power supplies face efficiency issues due to detuning caused by variations in inductance values of transmitting and receiving coils, which are not effectively addressed by existing zero-crossing detection methods, especially at high resonance frequencies.
Innovation Solution
A tuning circuit and method that compares sampling values of inductor current across cycles to adjust the frequency of the control signal for the inverter circuit, allowing for precise tuning without the need for zero-crossing detection, using a sampling circuit, adjustment instruction circuit, and control signal adjusting circuit to regulate the inverter frequency based on the comparison of sampling signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If zero-crossing detection method is used for tuning, then tuning can be achieved, but tuning precision is insufficient especially at high resonance frequencies due to delays in the detecting circuit
Solution Approach 1:
The patent extracts the tuning function from the zero-crossing detection circuit by using a separate sampling circuit that measures inductor current at specific intervals. This separates the tuning measurement function from the main power conversion circuit, eliminating the delay issues inherent in zero-crossing detection while maintaining circuit simplicity.
Solution Approach 2:
The patent replaces the electrical zero-crossing detection mechanism with a sampling-based measurement approach. Instead of detecting voltage zero-crossings electrically, the system samples the inductor current at controlled intervals and uses this sampled data for tuning decisions, achieving higher precision without circuit complexity.
2Loss of energy
If inductance values of coils are adjusted to maintain resonance frequency, then energy transfer efficiency is improved, but this requires complex real-time detection and adjustment mechanisms
Solution Approach 1:
The patent implements a feedback mechanism where the sampling circuit continuously monitors inductor current and feeds this information to the control circuit. The control circuit adjusts the switching frequency based on the sampled current values, creating a closed-loop system that maintains resonance and maximizes energy transfer efficiency without requiring complex real-time detection.
Solution Approach 2:
The patent uses periodic sampling of the inductor current at specific intervals during each switching cycle. This periodic measurement approach allows the system to track changes in coil inductance and adjust the operating frequency accordingly, maintaining efficient energy transfer through regular, simple measurements rather than continuous complex detection.
3Speed
If high resonance frequency is used for power transfer, then power transfer speed is improved, but tuning precision deteriorates due to delays in zero-crossing detecting circuit
Solution Approach 1:
The patent performs preliminary sampling of the inductor current at predetermined intervals during the switching cycle, before the current reaches its peak or zero-crossing points. This preliminary sampling approach provides advance information about the current state, allowing the control circuit to make accurate tuning decisions at high frequencies without being limited by detection delays.
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 approach enhances tuning precision and reduces circuit costs by maintaining efficient energy transfer across varying conditions, ensuring the inductor current reaches peak values at resonance frequencies without requiring zero-crossing detection.
Implementation Method 1
a sampling circuit configured to obtain a sampling value of an inductor current from a resonance-type contactless power supply in each cycle
Implementation Method 2
transfers energy from transmitting terminal to receiving terminal by coupling of magnetic field between primary and secondary coils of the transformer
Implementation Method 3
a resonance circuit configured to receive the high-frequency AC current... and configured to receive electric energy from the transmitting coil
Data Source
AI summary
A resonance-type contactless power supply has the characteristic that an inductor current has a maximum value when it operates at a resonance frequency. Sampling values of the inductor current in two successive cycles are compared with each other. A frequency of an inverter circuit is adjusted in a manner the same as that in a previous cycle in a case that the inductor current increases, and is adjusted in a manner opposite to that in the previous cycle in a case that the inductor current decreases. Thus, the resonance-type contactless power supply can be properly tuned without the need for zero-crossing detection.