Three-Level Inverter AC Switch Segmentation for Charge Discharge
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Solution Overview
Problem
Semiconductor devices in three-level power conversion circuits face damage during insulation tests and difficulty in evaluating individual elements due to charge accumulation and potential differences between collectors and emitters, particularly when using AC switches with shared collectors.
Innovation Solution
The semiconductor device incorporates an AC switch formed by connecting collectors of two IGBTs with reverse parallel diodes and an intermediate terminal, allowing for safe discharge of charges during insulation tests and enabling individual element evaluation by providing auxiliary emitters and arranging terminals to prevent interference with main current paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If AC switches with shared collectors are used to reduce device complexity, then the number of components is reduced, but charge accumulation causes potential differences that lead to device damage during insulation tests
Solution Approach 1:
The AC switch is segmented into two separate IGBT modules (first IGBT module and second IGBT module) instead of sharing a common collector. Each module has its own collector terminal, which allows independent charge discharge paths. This segmentation eliminates the charge accumulation problem while maintaining the compact structure benefit.
Solution Approach 2:
A discharge resistor is introduced as an intermediary component connected between the collector and emitter of each IGBT module. This discharge resistor provides a safe charge discharge path during insulation tests, preventing potential differences from causing device damage while not affecting normal operation.
2Device complexity
If collectors of two IGBTs are shared to simplify the circuit, then device complexity is reduced, but individual element evaluation becomes difficult due to charge accumulation
Solution Approach 1:
The IGBT modules are segmented into separate units with independent collector terminals. This allows each IGBT to be individually tested and evaluated without the interference of charge accumulation from shared collectors, enabling precise measurement of element characteristics while maintaining circuit simplicity.
Solution Approach 2:
The discharge resistor acts as an intermediary that enables individual element evaluation by providing a controlled discharge path. During insulation tests, the discharge resistor allows charges to be safely discharged from each IGBT module independently, facilitating accurate measurement of element characteristics without the complications of shared collector charge accumulation.
3Adaptability or versatility
If IGBTs are connected in series with reverse parallel diodes for AC switching, then AC switch functionality is achieved, but charge accumulation during insulation tests creates harmful potential differences
Solution Approach 1:
The AC switch functionality is maintained through separate IGBT modules instead of a single series connection with shared collector. Each module can independently perform AC switching while having its own charge discharge path, eliminating the harmful potential differences that would otherwise damage the devices during insulation tests.
Solution Approach 2:
The discharge resistor is introduced as an intermediary component that safely manages charge accumulation during insulation tests. It provides a controlled discharge path that prevents harmful potential differences from developing across the IGBT modules, protecting the devices while not affecting their AC switch functionality during normal operation.
Data Source
AI summary
A semiconductor device of a three-level inverter circuit with a reduced number of power supplies for driving IGBTs. The semiconductor device includes a series-connected circuit of IGBTs between P and N of a DC power supply and an AC switch element that is connected between a series connection point of the series-connected circuit and a neutral point of the DC power supply. The series-connected circuit and the AC switch element are integrated into one module. The AC switch element is formed by connecting a collector of a first IGBT to which a diode is connected in reverse parallel and a collector of a second IGBT to which a diode is connected in reverse parallel, and an intermediate terminal is provided at a connection point between the collectors.