Gate Circuit Segmentation for Power Device Surge Prevention
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Solution Overview
Problem
Existing gate circuits for power devices face challenges in quickly reducing excessive current while avoiding surge voltages, as they often use low resistance elements that result in rapid current decrease rates (di/dt), leading to device turn-off issues.
Innovation Solution
A gate circuit design incorporating a combination of resistive elements and switching devices, where a low resistance element is used to rapidly reduce excessive current and a higher resistance element for gradual turn-off, with a controller integrated circuit managing the switching to maintain a slow current decrease rate and prevent surge voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a low resistance value element is used to quickly reduce excessive current, then the excessive current reduction speed is improved, but the current decrease rate (di/dt) becomes too rapid causing surge voltage
Solution Approach 1:
The gate circuit is segmented into multiple resistive elements (first gate resistive element with lower resistance and second gate resistive element with higher resistance) that are selectively activated. The first resistive element quickly reduces excessive current, then the second resistive element takes over to slowly turn off the power device, preventing surge voltage. This segmentation allows different resistance values to be used at different stages of current reduction.
Solution Approach 2:
The gate circuit dynamically switches between different resistance configurations based on the operating state. During excessive current conditions, the first gate resistive element is activated for rapid current reduction. During normal turn-off, the second gate resistive element is used for controlled current decrease. This dynamic switching optimizes both current reduction speed and surge prevention.
2Productivity
If a low resistance value element is used to quickly reduce excessive current, then the excessive current reduction speed is improved, but the power device turn-off control becomes difficult
Solution Approach 1:
The gate control function is segmented between first and second gate resistive elements. The first element handles excessive current suppression, while the second element handles normal turn-off control. This segmentation allows each element to be optimized for its specific function, improving both productivity and ease of operation.
Solution Approach 2:
The gate circuit changes resistance parameters dynamically by switching between different gate resistive elements. When excessive current is detected, the circuit switches to the lower resistance value for rapid current reduction. During normal operation, it uses the higher resistance value for controlled turn-off, optimizing both efficiency and control.
Data Source
AI summary
A gate circuit includes a gate resistive element connected at one end to the gate of a power device, an on-switching device connected between a power supply and the other end of the gate resistive element, a first resistive element whose connection to the gate is controlled by a first switching device, a second resistive element whose connection to the gate is controlled by a second switching device, and having a higher resistance value than the first resistive element, excessive current suppression means for turning on the first switching device just when the current in the power device reaches a predetermined value, and turn-off delay means for, after the excessive current suppression means turns on the first switching device, turning off the on-switching device and the first switching device and turning on the second switching device to turn off the power device.