IGBT Overcurrent Detection Self-Diagnosis via Simulated Sense Current
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Solution Overview
Problem
In power conversion apparatuses, the detection of sense current using shunt resistors and comparators is unreliable, leading to inadequate overcurrent detection and potential damage to power semiconductor elements.
Innovation Solution
Incorporating an overcurrent detecting circuit and an overcurrent simulating circuit that utilize an emitter sensing terminal to accurately diagnose the overcurrent condition, allowing for the simulation of overcurrent scenarios to verify the functionality of the overcurrent detection system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shunt resistor and comparator circuits are used to detect sense current, then overcurrent detection can be implemented, but the detection reliability deteriorates when these circuits are broken
Solution Approach 1:
The patent creates a virtual copy of the overcurrent condition by generating a simulated sense current that mirrors what would be produced during an actual overcurrent event. This simulation allows the system to test the detection circuit's response without requiring actual fault conditions, thereby improving reliability while avoiding the need for complex physical test setups.
Solution Approach 2:
The patent introduces an intermediate testing mechanism that injects a simulated sense current into the detection circuit. This intermediary signal serves as a mediator between the test controller and the detection circuit, enabling verification of detection functionality without directly manipulating the power semiconductor element or creating actual overcurrent conditions.
2Reliability
If conventional overcurrent detection circuits are used, then overcurrent can be detected, but the system cannot diagnose whether the detection function itself is normal
Solution Approach 1:
The patent enables the detection system to self-diagnose by incorporating a self-test capability. The test controller generates a simulated sense current and monitors the detection circuit's response, allowing the system to automatically verify its own detection functionality. This self-service approach improves reliability by enabling continuous health monitoring without external intervention.
Solution Approach 2:
The patent performs preliminary testing of the detection circuit by simulating overcurrent conditions before actual operation or fault occurrence. By proactively testing the detection function using simulated sense current, the system can identify potential issues in advance, ensuring reliable operation during normal and fault conditions.
3Measurement precision
If the detection circuit components are simplified, then device complexity is reduced, but measurement precision of sense current deteriorates
Solution Approach 1:
The patent uses a simulation approach that creates a virtual test signal copying the characteristics of an actual overcurrent event. This simulated sense current allows precise testing of the detection circuit's measurement capability without requiring complex physical test equipment, maintaining measurement precision while avoiding increased device complexity.
Data Source
AI summary
An object of the invention is to diagnose whether an overcurrent detecting function with respect to a power semiconductor element of a power conversion apparatus is normal. The power conversion apparatus of the invention is provided with IGBTs as the power semiconductor element which performs a switching operation to convert DC power supplied from a DC power source into AC power, an overcurrent detecting circuit, and an overcurrent simulating circuit. The IGBTs include an emitter sensing terminal which outputs a sense current according to a current flowing to an emitter electrode. The overcurrent detecting circuit detects the overcurrent flowing to the IGBTs on the basis of the sense current output from the emitter sensing terminal. The overcurrent simulating circuit outputs a simulation signal which simulates the overcurrent flowing to the IGBTs and toward the overcurrent detecting circuit.