Class-E Rectifier Capacitor Control for Thermal Runaway Prevention
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Solution Overview
Problem
Conventional class-E rectifier circuits experience a change in capacitance with temperature, leading to increased voltage peak values and decreased impedance, causing over temperature due to thermal runaway.
Innovation Solution
A power conversion device and method that regulate the AC wave input to a rectifier capacitor based on impedance changes, using a detector to monitor impedance and a controller to adjust the drive frequency of the switching element to maintain optimal impedance and prevent over temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the capacitance of the rectifier capacitor decreases due to temperature increase, then the peak value of the voltage waveform increases, but the impedance decreases leading to thermal runaway
Solution Approach 1:
The controller monitors the impedance of the rectifier capacitor and adjusts the drive frequency based on the detected impedance value, creating a closed-loop feedback system that maintains stable operation despite temperature variations
Solution Approach 2:
The controller changes the drive frequency parameter in response to impedance changes, thereby compensating for the capacitance variation caused by temperature increases and preventing thermal runaway
2Stability of the object's composition
If the drive frequency is increased to compensate for capacitance decrease, then the voltage peak can be controlled, but switching loss increases
Solution Approach 1:
The controller dynamically adjusts the drive frequency based on real-time impedance detection, optimizing the balance between voltage stability and switching loss by making frequency changes only when necessary
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
The solution effectively suppresses impedance changes in the rectifier capacitor, stabilizing input current, output voltage, and input impedance, thereby preventing over temperature in the rectifier capacitor.
Implementation Method 1
the capacitance value of the capacitor constituting the rectifier circuit changes depending on the temperature characteristics
Implementation Method 2
an alternating-current (AC) wave generation circuit for generating an AC wave
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
A method for controlling a power conversion device can prevent over temperature by suppressing a change in impedance of a capacitor included in a rectifier circuit. The power conversion device (1) includes an AC wave generation circuit (5) for generating an AC wave, and a rectifier circuit (7) for rectifying the AC wave generated by the AC wave generation circuit (5) with a configuration including a rectifier capacitor (73) and a diode (71) connected in parallel. The method for controlling the power conversion device (1) regulates the AC wave input to the rectifier capacitor (73) depending on a change in impedance of the rectifier capacitor (73) so as to suppress the change in the impedance of the rectifier capacitor (73).