SiC MOSFET Gate Turn-Off Voltage Range to Prevent False Turn-On
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Solution Overview
Problem
Silicon-carbide Metal Oxide Semiconductor (MOS) transistors used in vehicle compressor inverter systems are prone to mistaken turn-on due to high input voltages, leading to efficiency losses and reduced service life.
Innovation Solution
A method and apparatus for determining a turn-off negative voltage interval of a switching transistor, which involves using first and second turn-off negative voltage models to accurately calculate the upper and lower limits of this interval, thereby preventing mistaken turn-on and protecting the transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If silicon-carbide MOS transistor is used in high input voltage inverter system, then loss is reduced and efficiency is improved, but the transistor is easily turned on mistakenly
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the gate voltage parameters of the silicon-carbide MOS transistor. Specifically, it changes the gate voltage from positive to negative to ensure reliable turn-off state. The control method adjusts the gate voltage parameter based on the switching state requirements, preventing mistaken turn-on while maintaining the transistor's efficient operation in high voltage applications.
Solution Approach 2:
The patent implements feedback control by continuously monitoring the gate voltage and adjusting it to maintain the transistor in the desired state. The control circuit uses feedback to detect potential mistaken turn-on conditions and applies corrective negative voltage to the gate terminal to ensure the transistor remains properly turned off, thereby improving reliability without sacrificing efficiency.
2Reliability
If negative voltage turn-off control is performed using turn-off negative voltage interval, then mistaken turn-on is prevented and transistor is protected, but the complexity of control circuit increases
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the turn-off negative voltage interval before actual switching operations. The control circuit prepares the appropriate negative voltage levels in advance based on the transistor's characteristics and operating conditions. This preliminary preparation allows the control circuit to quickly and reliably apply the correct negative voltage without complex real-time calculations, reducing control complexity while maintaining protection effectiveness.
Data Source
AI summary
A method and an apparatus for determining a turn-off negative voltage of a switching transistor are provided. The method includes: determining first and second turn-off negative voltage models; inputting acquired turn-off and turn-on gate resistances of the switching transistor, an acquired bus voltage, and an acquired minimum turn-on voltage of the switching transistor into the first model to obtain a turn-off negative voltage upper limit absolute value of the switching transistor; inputting the acquired turn-off and turn-on gate resistances of the switching transistor, the acquired bus voltage, and an acquired maximum bearable negative voltage absolute value of the switching transistor into the second model to obtain a turn-off negative voltage lower limit absolute value of the switching transistor; and determining a turn-off negative voltage interval of the switching transistor based on the turn-off negative voltage upper limit absolute value and the turn-off negative voltage lower limit absolute value.