Power Transmission Device FET Zero-Voltage Switching Control
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Solution Overview
Problem
Non-contact power transmission devices face challenges in maintaining an ideal waveform for switching FETs, leading to heat generation and deterioration when the load exceeds the rating, due to potential non-zero voltage at FET terminals during state switching.
Innovation Solution
Incorporating a control circuit that determines whether the load of the power reception device is excessive by monitoring the output voltage and notifying the device to adjust its load, thereby preventing through current and heat generation in the FET.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the power transmission device transmits power to a load exceeding its rating, then the power transmission capability is improved, but the FET generates heat and deteriorates due to non-zero voltage at terminals during switching
Solution Approach 1:
The control circuit monitors the voltage at the FET terminal and adjusts the switching timing accordingly. When the voltage does not reach zero at the expected switching moment, the control circuit delays the turn-on timing until the voltage becomes zero, preventing excessive current and heat generation while maintaining power transmission capability.
Solution Approach 2:
The switching timing of the FET is made dynamic rather than fixed. The control circuit continuously adjusts the turn-on timing based on the real-time voltage waveform at the FET terminal, allowing the system to adapt to varying load conditions and maintain zero-voltage switching even when the load exceeds the rated capacity.
2Temperature
If the FET switching timing is controlled to achieve zero voltage switching, then the heat generation is reduced, but the ideal waveform cannot be obtained when the load exceeds the rating
Solution Approach 1:
The control circuit uses feedback from the voltage waveform monitoring to dynamically adjust the switching timing. This ensures that even when the load exceeds the rating and the waveform distorts, the FET still switches at the optimal moment when the voltage is zero, maintaining low heat generation while adapting to the actual waveform conditions.
3Productivity
If the switching element is turned on when voltage is non-zero, then the power transmission is continuous, but excessive current flows and heat is generated
Solution Approach 1:
The system employs periodic zero-voltage switching by waiting for the voltage to naturally oscillate to zero before turning on the FET again. This periodic action maintains continuous power transmission through repeated on-off cycles while ensuring energy-efficient switching at each cycle, preventing excessive current and heat generation.
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
Prevents excessive current flow and heat generation in the FET by ensuring the load is within the appropriate range, enhancing the reliability and longevity of the power transmission device.
Implementation Method 1
The non-contact power transmission device and the non-contact power reception device respectively transmit and receive the electric power using the power transmission coil and the power reception coil according to principles such as electromagnetic induction or magnetic field resonance
Implementation Method 2
The non-contact power transmission device and the non-contact power reception device respectively transmit and receive the electric power using the power transmission coil and the power reception coil according to principles such as electromagnetic induction or magnetic field resonance
Implementation Method 3
The power transmission circuit turns on or off the FET to apply an alternating current to the power transmission coil to transmit the electric power to the power reception coil
Data Source
AI summary
A power transmission device for use with a power reception device having a power reception coil includes a power transmission coil, a power transmission circuit, a communication circuit, and a control circuit. The power transmission coil is configured to be magnetically coupled to a power reception coil of a power reception device. The power transmission circuit includes a switching element and is configured to switch the switching element to apply alternating current to the power transmission coil. The communication circuit is configured to establish communication with the power reception device. The control circuit is configured to control switching of the power transmission circuit, determine whether or not a load of the power reception device is greater than a threshold based on an output voltage from the switching element and a determination criterion, and provide a notification to the power reception device from the communication circuit.