Power Conversion Device Interline Capacitor Noise Suppression
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Solution Overview
Problem
Power conversion devices with semiconductor switching elements face challenges in suppressing switching surge and noise due to parasitic inductance in capacitors, which prevents effective reduction of conduction and radiation noise.
Innovation Solution
Incorporating a noise suppression capacitor with a smaller capacitance than the snubber capacitor, positioned closer to the power conversion portion, to create a parallel resonance that reduces series resonance noise, and optionally connecting a resistor in series or parallel with the capacitor to further attenuate noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a snubber capacitor is connected between the positive line and negative line to suppress switching surge, then the switching surge is reduced, but conduction noise and radiation noise increase due to series resonance caused by parasitic inductance
Solution Approach 1:
The patent divides the noise suppression function into multiple capacitors with different capacitance values positioned at different locations. A first capacitor is connected near the switching element, while a second capacitor with larger capacitance is connected farther from the switching element. This segmentation allows each capacitor to target specific frequency ranges and resonance modes, suppressing both switching surge and noise effectively without the harmful series resonance effect that occurs with a single capacitor.
Solution Approach 2:
The patent applies different capacitance values to capacitors based on their local position in the circuit. The capacitor closer to the switching element has a smaller capacitance value, while the capacitor farther away has a larger capacitance value. This local differentiation optimizes the suppression effect for each specific location's electrical characteristics, reducing both switching surge and noise simultaneously.
2Object-generated harmful factors
If a capacitor is connected parallel to the direct current power supply line to reduce noise, then conduction noise may be reduced, but switching surge worsens due to increased impedance
Solution Approach 1:
The patent segments the capacitor function into two distinct capacitors positioned at different locations with different capacitance values. The first capacitor (smaller capacitance) is positioned near the switching element where switching surge occurs, while the second capacitor (larger capacitance) is positioned farther away. This segmentation allows the first capacitor to suppress switching surge without significantly increasing line impedance, while the second capacitor addresses conduction noise.
Solution Approach 2:
The patent changes the capacitance parameter based on the position of the capacitor in the circuit. By using a smaller capacitance value for the capacitor near the switching element and a larger capacitance value for the capacitor farther away, the system optimizes both switching surge suppression and conduction noise reduction. This parameter differentiation prevents the impedance increase problem that would occur with a single large capacitor.
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 reduces conduction and radiation noise components by altering the impedance of the direct current power supply lines, effectively suppressing switching surge and noise without worsening the switching surge phenomenon.
Implementation Method 1
a snubber capacitor, connected between the positive line and negative line, that suppresses surge voltage generated when the power conversion portion switches
Implementation Method 2
at least one interline capacitor is connected between the positive line and negative line between the snubber capacitor and power conversion portion, the capacitance of the interline capacitor is of a value that becomes smaller the nearer to the power conversion portion the position in which the interline capacitor is connected
Data Source
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AI summary
In order to provide a power conversion device such that it is possible to realize both a suppression of switching surge and a countermeasure to noise in a power conversion device having a semiconductor switching element, a power conversion device including a voltage conversion portion that switches direct current voltage supplied by a positive line and negative line of a direct current power supply with a semiconductor switching element, and outputs converted voltage, is such that a plurality of interline capacitors are connected in parallel between the positive line and negative line, the capacitance of the plurality of interline capacitors is of a value that becomes smaller the nearer to the power conversion portion the position in which the interline capacitor is connected, and the interline capacitor with the smallest value of capacitance is set to a value greater than that of the capacitance between main electrodes when a direct current voltage is applied to the switching element used in the power conversion portion.