IGBT Sense Current Estimation for Stable Inverter Current Control
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Solution Overview
Problem
Existing power conversion devices using IGBTs face inaccuracies in current estimation due to varying ratios between main and sense currents, influenced by peripheral current components and wiring resistance, leading to unstable inverter current control and vehicle acceleration.
Innovation Solution
A power conversion device with a main IGBT and a current sense IGBT on the same semiconductor chip, utilizing a measurement device to select calculation methods based on sense current values, optimizing current range divisions to accurately estimate main current across different operation regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sense IGBT is used to detect main current, then the size and manufacturing cost are reduced, but the measurement precision deteriorates due to varying current ratios
Solution Approach 1:
The patent applies dynamics by making the current ratio dynamic rather than fixed. It divides the operation range into multiple current regions (first current region with higher ratio, second current region with lower ratio) and dynamically selects different ratio values based on the detected current magnitude. This resolves the contradiction by adapting the measurement approach to different operating conditions, maintaining precision across the full range while keeping the simple sense IGBT structure.
Solution Approach 2:
The patent changes the parameter of current ratio based on operating conditions. By detecting the magnitude of main current and selecting different ratio parameters (first ratio for higher currents, second ratio for lower currents), the system maintains accurate measurement across varying load conditions. This parameter adaptation resolves the precision issue while preserving the cost-effective sense IGBT approach.
2Device complexity
If a fixed current ratio is assumed for calculation, then the calculation is simplified, but the measurement precision deteriorates in varying current regions
Solution Approach 1:
The patent segments the continuous current operation range into discrete current regions (first current region and second current region). Each region has its own optimized current ratio parameter. This segmentation allows the system to use simple fixed-ratio calculations within each region while maintaining overall accuracy across the full range, resolving the contradiction between calculation simplicity and measurement precision.
Solution Approach 2:
The system dynamically selects the appropriate current ratio based on the detected current magnitude. The control unit determines which current region the operation is in and applies the corresponding ratio (first ratio or second ratio). This dynamic adaptation maintains high measurement precision across varying conditions while keeping each individual calculation simple.
3Area of moving object
If the sense IGBT area is reduced to minimize chip size, then the device size is reduced, but the measurement precision deteriorates due to increased peripheral current component ratio
Solution Approach 1:
The patent compensates for the increased peripheral current effect in small sense IGBTs by changing the current ratio parameter based on operating conditions. By using different ratios for different current regions and magnitudes, the system accounts for the non-linear current distribution effects that are more pronounced in smaller devices, thereby maintaining measurement precision despite the reduced chip area.
Solution Approach 2:
The patent applies different measurement parameters (current ratios) to different operating conditions (current regions and magnitudes). This local optimization ensures that the measurement approach is tailored to the specific operating state, compensating for the geometric effects of the small sense IGBT size and maintaining accuracy across all operating conditions.
Data Source
AI summary
Provided is a power conversion device on which an IGBT power module that includes a main IGBT and a current sense IGBT in the same semiconductor chip is mounted, wherein the power conversion device is a high-performance and highly reliable power conversion device capable of accurately estimating a main current flowing through the main IGBT using a sense current in an entire operation region of the power conversion device. A power conversion device includes: a first IGBT through which a main current flows; a second IGBT which is disposed on the same semiconductor substrate as the first IGBT and through which a sense current flows; and a measurement device which calculates the main current based on the sense current, wherein the measurement device selects a method of calculating the main current corresponding to a current value of the sense current.