Bootstrap Gate Drive Circuit for Stable SiC Turn-Off Voltage
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Solution Overview
Problem
Third-generation semiconductor power devices, such as silicon carbide (SiC), require negative voltage to ensure reliable turn-off but experience voltage fluctuations, affecting the reliability of drive circuits in applications like electric vehicles.
Innovation Solution
A bootstrap drive circuit with a voltage stabilization unit that stabilizes the bootstrap voltage, reducing drive voltage fluctuations and enhancing reliability by generating a stable turn-off negative voltage for switch tubes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bootstrap drive circuit uses negative voltage to turn off SiC power devices, then the power device can be reliably turned off, but the negative voltage may exceed the allowed fluctuation range causing reliability issues
Solution Approach 1:
The patent introduces a bootstrap capacitor as an intermediary energy storage element between the power device and the drive circuit. This capacitor stores energy during the on-state and provides a stable negative voltage reference during the off-state, mediating the voltage fluctuations and preventing excessive negative voltage excursions that would compromise device reliability
Solution Approach 2:
The patent modifies the voltage parameters by introducing a stabilized bootstrap voltage (VBOOT) that references the negative voltage level. By changing the voltage reference parameter and using it to drive the gate, the circuit maintains the necessary negative voltage for turn-off while constraining the voltage within safe fluctuation ranges through the bootstrap capacitor's energy storage特性
2Reliability
If the bootstrap voltage is not stabilized, then the circuit structure remains simple, but the drive voltage fluctuates affecting reliability
Solution Approach 1:
The bootstrap capacitor serves as a compact intermediary component that provides voltage stabilization without requiring complex active regulation circuits. This single passive component mediates between the power supply and the drive circuit, reducing voltage fluctuations while maintaining structural simplicity
Solution Approach 2:
The bootstrap capacitor utilizes the natural switching operation of the power device to automatically charge and discharge, providing self-regulating voltage stabilization. During the on-state, the capacitor charges through the power device; during the off-state, it discharges to maintain the negative voltage reference, creating a self-service voltage regulation mechanism without external control
Data Source
AI summary
A bootstrap drive circuit, a motor controller, a compressor, and a vehicle are provided. The bootstrap drive circuit includes a bootstrap unit, a negative voltage unit, a drive unit, and a voltage stabilization unit. The bootstrap unit is configured to provide the voltage stabilization unit with a bootstrap voltage. The voltage stabilization unit is configured to perform a voltage stabilization processing on the bootstrap voltage to output a stable drive voltage to the drive unit. The drive unit is configured to drive, in response to receiving a turn-on control signal and based on the stable drive voltage, a switch tube corresponding to the drive unit to be turned on, and to control, in response to receiving a turn-off control signal, the negative voltage unit to drive the switch tube to be turned off by generating a stable turn-off negative voltage based on the stable drive voltage.