Contactless Power Transfer Bridge Circuit Zero-Crossing Control
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Solution Overview
Problem
Existing contactless power transfer systems face challenges in miniaturization and cost reduction due to large circuit size and high switching losses, leading to inefficiencies in power transfer.
Innovation Solution
A contactless power transfer system with a power receiving circuit configured as a bridge circuit including semiconductor switches and diodes, where capacitors are connected in parallel to the switches, and a control method that uses zero-crossing detection for switching actions to control the direct current output voltage without a constant voltage control circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the frequency of current supplied via the coil is increased to miniaturize the coil and core, then the coil size is reduced, but the switching loss of semiconductor switches increases and power transfer efficiency decreases
Solution Approach 1:
The patent employs periodic switching action synchronized with the zero-crossing points of the AC current. By detecting when the current passes through zero and timing the switching actions accordingly, the system performs power transfer in periodic cycles rather than continuous operation. This periodic action allows the use of higher frequency for miniaturization while managing switching losses through intelligent timing of the switching events at optimal moments in the AC cycle.
Solution Approach 2:
The patent changes the operating parameters by using zero-crossing detection to dynamically control the switching timing. Instead of fixed-frequency switching, the system adapts its switching moments to the actual current waveform characteristics. This parameter change approach allows optimization of both coil size (through higher frequency operation) and switching loss (through timing synchronization with current zero-crossings).
2Stability of the object's composition
If a constant voltage control circuit is used to maintain stable direct current output voltage, then voltage stability is improved, but the circuit size and complexity increase
Solution Approach 1:
The patent extracts and eliminates the constant voltage control circuit from the system. Instead of using a separate control circuit to regulate output voltage, the invention achieves voltage stability through the inherent characteristics of the bridge circuit configuration combined with zero-crossing detection and phase control. This extraction of the control circuit significantly reduces circuit complexity and size while maintaining the essential function of stable power delivery.
Solution Approach 2:
The system achieves self-regulation of output voltage through the phase control mechanism inherent in the bridge circuit. By controlling the phase angle of the switching relative to the AC input, the system automatically adjusts the output characteristics without requiring external constant voltage control. The circuit serves itself by using the AC waveform characteristics and switching timing to inherently stabilize the output.
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 simplifies and miniaturizes the circuit, reduces losses, and achieves stable, efficient power transfer by controlling the direct current output voltage through phase control of semiconductor switches.
Implementation Method 1
A contactless power transfer system supplies power to a load utilizing magnetic coupling between coils caused by electromagnetic induction
Data Source
AI summary
A contactless power transfer system, including a coil configured to supply or receive power contactlessly via magnetic coupling, a bridge circuit having two direct current (DC) terminals and two alternating current (AC) terminals, and a smoothing capacitor connected between the DC terminals. A load is connectable to either end of the smoothing capacitor. One of the AC terminals is connected to one end of the coil via a first capacitor. The other of the AC terminals is connected to the other end of the coil. The bridge circuit includes two serially-connected circuits each having upper and lower arms, each arm having a semiconductor switch and a diode in reverse parallel connection. A second capacitor is connected in parallel to the semiconductor switch of an upper arm, or of a lower arm, or to two semiconductor switches respectively of an upper arm and of a lower arms, of the bridge circuit.