Inverter Control System Soft Turn-Off IGBT Protection

The patent applies beforehand cushioning by introducing a filter circuit that delays the forcible turn-off control current signal. This delay allows the IGBT to remain conducting for a brief period longer, cushioning against the sudden voltage spike that would otherwise occur during immediate forcible turn-off. The filter acts as a protective buffer that softens the turn-off process, preventing excessive voltage generation while still protecting the IGBT from damage.

The patent applies partial action by implementing a filter that provides only a partial delay to the turn-off control current, rather than a complete or excessive delay. The filter is designed to delay the signal just enough to prevent excessive voltage spikes during turn-off, but not so much that it significantly impacts the overall response time. This partial delay achieves the necessary protection while minimizing the impact on switching speed.

The patent applies beforehand cushioning by using the filter to delay the turn-off control signal, which prevents excessive voltage spikes during IGBT switching. This cushioning effect allows the system to operate with high DC link voltage without subjecting the IGBT to voltage stresses beyond its rated capability. The filter protects the IGBT from voltage over-shoot, enabling the use of higher DC link voltages to increase inverter power output while maintaining IGBT safety within its voltage ratings.