Inverter Diode Junction Temperature Characterization Under Load
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Solution Overview
Problem
Existing methods for characterizing junction temperatures of power diodes in voltage source inverters are inadequate, particularly for multiple diodes connected in antiparallel, and lack techniques for real-time estimation during operational conditions, leading to inefficiencies and safety margins.
Innovation Solution
A method and system for characterizing junction temperatures of power diodes in voltage source inverters that allows direct commissioning on the inverter in its final form, using on-board sensors and controlled current pulses to measure junction temperatures accurately and efficiently, even in operational conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical methods (infrared camera) are used to measure junction temperature, then measurement precision is improved, but device complexity and ease of manufacture deteriorate due to special laboratory equipment requirements and non-reversible modification
Solution Approach 1:
The patent replaces optical measurement methods (infrared camera) with electrical measurement methods using voltage drop across the semiconductor device. This substitution eliminates the need for special laboratory equipment and complex optical systems, while maintaining measurement capability through electrical parameters that can be measured with standard voltmeters.
Solution Approach 2:
The patent introduces voltage drop as an intermediary parameter to indirectly measure junction temperature. Instead of directly measuring temperature with complex optical equipment, the voltage drop across the device serves as a mediator that correlates with temperature, enabling measurement through simpler electrical means.
2Measurement precision
If physical contact methods (thermocouples) are used to measure junction temperature, then measurement precision is improved, but ease of operation deteriorates due to mechanical access requirements to the die inside power semiconductor devices
Solution Approach 1:
The patent replaces physical contact mechanical measurement methods (thermocouples requiring mechanical access to the die) with electrical measurement methods. By measuring voltage drop across the device terminals, the system eliminates the need for mechanical disassembly or direct physical contact with the semiconductor die, significantly improving ease of operation.
3Reliability
If converter is designed for worst-case operating conditions with safety margin, then reliability is improved, but productivity deteriorates due to current limiting at low frequency
Solution Approach 1:
The patent implements real-time feedback by continuously measuring junction temperature through voltage drop measurements and using this information to dynamically adjust operating conditions. This feedback mechanism replaces static worst-case design margins with adaptive temperature-based control, allowing the converter to operate at optimal power levels while maintaining safety.
Solution Approach 2:
The patent transitions from static safety margin design to dynamic temperature-based control. By continuously monitoring junction temperature and adapting operating parameters in real-time, the system optimizes productivity while ensuring safe operation, rather than being constrained by fixed worst-case assumptions.
4Measurement precision
If lookup table or program for computing thermal characteristic is used to estimate temperature, then measurement precision is improved, but difficulty of detecting and measuring worsens due to lack of specification on how to obtain such data
Solution Approach 1:
The patent performs preliminary characterization by measuring voltage drop and current under known operating conditions to establish the relationship between these parameters and junction temperature. This preliminary data collection creates the basis for subsequent temperature estimation without requiring complex pre-programmed lookup tables, simplifying the measurement process.
Solution Approach 2:
The system uses its own operating data (voltage drop and current measurements) to self-determine junction temperature through the established voltage-current-temperature relationship. This self-service approach eliminates the need for external thermal characteristic data or complex lookup tables, as the system generates its own characterization data during normal operation.
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
Enhances the accuracy and dynamic response of junction temperature estimation, reducing errors to about 5°C from 20°C and improving operational efficiency by adapting switching actions based on precise temperature data.
Implementation Method 1
at each current pulse of the current pulses train the processing means command the power semiconductor switching devices to switch on and off in such a way that current pulses are allowed to flow through the power semiconductor diode devices
Implementation Method 2
said thermic sensors being thermally coupled to said direct bonded copper element and/or to said heatsink
Data Source
AI summary
A method is provided for characterizing junction temperatures of power diodes devices, each of the diode devices being one-to-one connected in antiparallel to each power semiconductor switching devices of a voltage source inverter having processing and measuring capability, the method including: an initialization stage, wherein a heater is thermally coupled with a heatsink and/or with a direct bonded copper element of the voltage source inverter; a temperature setting stage, wherein the temperature of the direct bonded copper element and/or the heatsink is increased up to a maximum operative temperature; a commissioning stage, wherein at each current pulse of a current pulses train sampled data are collected in a sampling period wherein the corresponding power semiconductor switching device connected with at least one of the power semiconductor diode devices is turned-off; an output stage, wherein the processor generates, from the sampled data, processed data for at least one of the power semiconductor diode devices.