Capacitor Model Parameter Calculation via DC-DC Converter
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Solution Overview
Problem
Existing methods for modeling capacitors, such as those using LCR meters, are inadequate for accurately measuring capacitors under non-sine wave conditions with high currents and voltages, as they fail to account for parasitic inductance and provide inaccurate model parameters.
Innovation Solution
A method involving a DC to DC converter with switching elements and a resistive load, where the capacitor is modeled by varying input voltage, frequency, and duty cycle to measure current and voltage across the capacitor, allowing for the calculation of capacitance, parasitic inductance, resistance, and loss power, effectively characterizing the capacitor's behavior in a realistic operating environment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If an LCR meter with sine wave signal is used to measure capacitor parameters, then the measurement process is simple, but the measurement precision deteriorates under non-sine wave conditions with high currents and voltages
Solution Approach 1:
The patent changes the measurement parameters by using a DC-to-DC converter to generate variable voltage and current waveforms (including non-sine waves, high currents, and high voltages) instead of a simple sine wave. This allows the capacitor to be measured under realistic operating conditions, improving the accuracy of model parameters while maintaining a relatively simple measurement setup.
2Device complexity
If a simple LCR meter is used for capacitor measurement, then the device complexity is low, but the measurement precision deteriorates due to inability to account for parasitic inductance
Solution Approach 1:
The patent introduces a DC-to-DC converter as an intermediary device between the measurement system and the capacitor. This converter enables the measurement of parasitic inductance by creating controlled voltage and current conditions, thereby improving measurement precision without significantly increasing the overall device complexity.
3Device complexity
If a measurement circuit adapted from coil modeling is used for capacitor modeling, then the device complexity is reduced, but the measurement precision deteriorates due to parasitic inductance in the measurement circuit
Solution Approach 1:
The patent extracts and separately measures the parasitic inductance component from the overall measurement system. By using the DC-to-DC converter to independently determine parasitic inductance values, the method eliminates the interference that would otherwise occur if a coil-modeling circuit were directly adapted for capacitor measurement, thereby improving precision while keeping the circuit design relatively simple.
Data Source
AI summary
Method for calculating model parameters for a capacitor to be modelled, the method comprising the following steps of: incorporating the capacitor to be modelled into a DC to DC converter with at least a first switching element; connecting a resistive load between the output terminals; applying an input voltage to the input terminals of the converter; controlling the first switching element in accordance with a frequency and duty cycle in order to obtain a current varying periodically in time through the capacitor to be modelled; measuring at least a first quantity representative of the current through the capacitor and at least a second quantity representative of the voltage across the capacitor; determining on the basis of the measured first and second quantities at least one current value for the current through the capacitor and at least one voltage value for the voltage across the capacitor.