Power Device Current Sensing With Thermal Impedance Correction
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Solution Overview
Problem
Existing current detection methods for power devices face challenges in accurately estimating the main current due to errors in loss measurement, particularly switching loss, and require extensive data acquisition for various temperature, voltage, and current conditions, increasing development complexity and inflexibility.
Innovation Solution
A current detection device that includes a sense element temperature estimation unit, a reference temperature acquisition unit, a main element temperature estimation unit, and a main current estimation unit, which estimates the sense element and main element temperatures using thermal impedance ratios and calculates the main current based on the sense current, sense element temperature, and main element temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If loss data is acquired for various temperature, voltage, and current conditions, then current estimation accuracy is improved, but device complexity increases due to extensive data acquisition requirements
Solution Approach 1:
The patent extracts only the essential parameter needed for correction - the temperature difference between main element and sense element - by using a temperature sensitive element. This eliminates the need to acquire comprehensive loss data across multiple conditions (temperature, voltage, current), reducing device complexity while maintaining current estimation accuracy through targeted temperature-based correction
2Measurement precision
If comprehensive loss measurement is performed, then temperature difference estimation can be achieved, but loss of time increases due to extensive measurement and data processing
Solution Approach 1:
The patent extracts only the temperature difference information needed for correction by using a temperature sensitive element, eliminating the time-consuming process of comprehensive loss measurement and data acquisition across multiple conditions. The temperature sensitive element provides direct temperature information that can be used immediately for sense ratio correction
Solution Approach 2:
The temperature sensitive element serves itself by providing temperature information that directly enables the correction process. The element's own temperature characteristics are utilized to measure the temperature difference, eliminating the need for external loss measurement systems and extensive data processing
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 solution enables accurate estimation of the main current flowing through the power device, reduces the number of development steps for loss data acquisition, shortens the development period, and allows for flexible changes in design according to different use conditions.
Implementation Method 1
PTL 2 discloses a method of using the temperature characteristics of the body resistance of a power semiconductor as a temperature sensitive element
Implementation Method 2
converting a magnetic field generated by a current into a voltage, and detecting the voltage
Data Source
AI summary
The present invention improves a problem associated with the acquisition of loss data and accurately estimates, from a sense current, main current flowing through a power device. This power device current detection device is characterized in that a circuit for detecting the current of a power device mounted with a power semiconductor having a main element, a current detection sense element, and a temperature detection temperature-sensitive element comprises: a sense element temperature estimation unit for estimating, on the basis of the output of the temperature-sensitive element, a sense element temperature that is the temperature of the sense element; a reference temperature acquiring unit for acquiring the reference temperature of the power device; a main element temperature estimation unit for estimating, on the basis of the sense element temperature and the reference temperature, a main element temperature that is the temperature of the main element; and a main current estimation unit for estimating, on the basis of a sense current value detected by the sense element, the sense element temperature, and the main element temperature, a main current value flowing through the main element. The main element temperature estimation unit uses a thermal impedance ratio that is the ratio between the mutual thermal impedance of the sense element with respect to the heat generation of the main element and the self-thermal impedance of the main element to estimate the main element temperature.