Motor Drive Power Module Protection Switch for Short-Circuit Withstand
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Solution Overview
Problem
IGBTs in Intelligent Power Modules (IPMs) have short-circuit withstand times that are insufficient for high current motor applications, limiting their performance and requiring a trade-off between short-circuit withstand time and on-state conduction losses.
Innovation Solution
Incorporating a protection switch with a higher short-circuit withstand time and lower short-circuit current level in series with the high-side power switch, along with a driver circuit to manage its operation, allowing the IGBTs to be optimized for better performance without the constraint of short-circuit withstand time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If IGBT gain is increased to reduce on-state conduction losses, then on-state performance is improved, but short-circuit withstand time decreases
Solution Approach 1:
The power switch function is segmented into two separate components: the IGBT optimized for low on-state losses and the protection switch optimized for short-circuit withstand. This segmentation allows each component to be independently optimized for its specific function, resolving the contradiction between on-state performance and short-circuit durability.
Solution Approach 2:
The protection switch acts as an intermediary component between the power source and the IGBT. It absorbs the short-circuit stress and protects the IGBT from damage, allowing the IGBT to operate at higher gain levels without compromising short-circuit withstand capability.
2Reliability
If IGBT short-circuit withstand time is increased to protect against motor short circuits, then reliability is improved, but on-state conduction losses increase
Solution Approach 1:
The system segments the protective function from the power switching function. The protection switch handles short-circuit protection while the IGBT handles efficient power conversion, eliminating the need for IGBTs to be oversized for short-circuit durability.
Solution Approach 2:
The protection switch is designed as a sacrificial component that can be easily replaced if damaged during a short circuit event. This allows the use of highly efficient, high-gain IGBTs that would otherwise be vulnerable to short-circuit damage, resolving the reliability-loss contradiction.
Data Source
AI summary
A power module for driving a motor includes: a positive bus input voltage terminal; a phase terminal for each motor phase; an inverter including a half bridge for each motor phase, each half bridge including a high-side power switch electrically coupled between the positive bus input voltage terminal and respective phase terminal, and a low-side power switch electrically coupled between the respective phase terminal and ground; a first driver circuit for driving a gate terminal of each power switch; a protection switch electrically coupled in series between the positive bus input voltage terminal and each high-side power switch, and having a greater short-circuit withstand time and a lower short-circuit current level compared to each inverter power switch; and a second driver circuit for turning on the protection switch during normal operation and turning off the protection switch in response to a detected short circuit condition.