Inverter comprising a power device temperature estimation device
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Solution Overview
Problem
Existing methods for accurately estimating the temperature of switching elements in high-voltage inverters, such as those used in automobiles, face challenges due to the need to divide high voltages by a factor of 1/100, leading to difficulty in detecting minute voltage changes and resulting in inaccurate temperature estimation.
Innovation Solution
A power device temperature estimation device that uses a voltage divider circuit with a diode and resistor configuration to detect the forward voltage of a freewheel diode, allowing direct detection of voltage fluctuations associated with temperature changes without division, and incorporates a diode temperature estimation section with a dynamic thermal model and Kalman filter to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resistive voltage divider circuit is used to detect the forward voltage of the freewheel diode in a high-voltage inverter, then the voltage can be divided to a detectable level, but the detection accuracy deteriorates because the minute voltage change is divided along with the voltage
Solution Approach 1:
The patent introduces a capacitor as an intermediary element in the voltage divider circuit. The capacitor blocks the DC component while allowing the AC component (voltage change corresponding to temperature change) to pass through. This intermediary element enables the separation of the useful signal (voltage change) from the large DC voltage level, thereby improving detection accuracy without requiring direct detection of minute voltage changes against a high voltage background.
2Ease of operation
If a temperature sensor is attached to a board remotely from the power device, then the temperature can be detected, but the responsiveness and detection accuracy deteriorate due to the remote location
Solution Approach 1:
The patent employs the freewheel diode itself as the detection target rather than using a separate temperature sensor. By detecting the forward voltage of the freewheel diode, which has a known temperature-voltage characteristic, the system uses the diode's own electrical property to indicate its temperature. This self-service approach eliminates the need for separate sensors and ensures direct measurement at the power device location, improving both responsiveness and accuracy.
3Measurement precision
If the forward voltage of the freewheel diode is detected using a resistive voltage divider circuit, then the voltage can be measured, but the circuit complexity increases and detection accuracy decreases due to the need to detect minute voltage changes
Solution Approach 1:
The capacitor serves as a mediator that simplifies the detection circuit by automatically blocking the large DC voltage component and passing only the smaller AC voltage change component to the detection stage. This eliminates the need for complex high-precision amplifiers and signal conditioning circuits that would otherwise be required to detect minute voltage changes against a high DC voltage background, thereby reducing overall circuit complexity while improving detection accuracy.
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
Enables accurate temperature estimation of switching elements in high-voltage inverters, preventing thermal damage by improving responsiveness and reducing estimation errors.
Implementation Method 1
a voltage divider circuit that includes a first element and a second element connected in series with each other and is connected in parallel with the freewheel diode
Implementation Method 2
the temperature of the freewheel diode is determined on the basis of a relationship among the detected value, a current-voltage characteristic of the freewheel diode, and the temperature of the freewheel diode
Data Source
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AI summary
A device 30 is attached to an inverter 10 installed with a power device 40, and estimates a temperature of the power device 40 on the basis of a temperature of a freewheel diode 42. The device 30 includes: a voltage divider section 32 having a voltage divider circuit that includes a first element and a second element connected in series; a diode voltage detection section 33 detecting a forward voltage of the freewheel diode 42 on the basis of a divided voltage of the second element; a diode current detection section 31 detecting a forward current of the freewheel diode 42; and a diode temperature estimation section 34 estimating the temperature of the freewheel diode 42 on the basis of the detected forward voltage, the detected forward current, and characteristic data. The first element is a diode 32a arranged in forward parallel with the freewheel diode 42, and the second element is a resistor 32b.