Active Gate Drive Circuit for Surge Voltage and Switching Loss
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Solution Overview
Problem
Existing drive circuits for switching elements face challenges in managing the collector-emitter voltage and switching loss due to varying collector currents, leading to increased surge voltage and reduced switching speed, as the gate discharging rate is not adequately adjusted in response to changing operating conditions.
Innovation Solution
A drive circuit that incorporates active gate control and a determination mechanism to adjust the gate charging/discharging rate based on terminal voltage, current, and temperature, allowing for dynamic control of the gate discharging process to suppress surge voltage and switching loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the gate is discharged through the first charge/discharge paths having low resistance, then the switching speed is improved, but the surge voltage increases
Solution Approach 1:
The patent applies dynamics by making the gate discharge path resistance variable rather than fixed. The control circuit dynamically switches between low resistance (first paths) and high resistance (second paths) based on real-time detection of collector current changes, allowing the system to optimize between switching speed and surge voltage suppression adaptively
Solution Approach 2:
The patent changes the resistance parameter of the gate discharge path based on operating conditions. By detecting when collector current starts to decrease and subsequently changing the discharge path resistance, the system adjusts the electrical parameters to balance switching performance and voltage suppression
2Reliability
If the gate discharging rate is reduced to suppress surge voltage, then the reliability is improved, but the switching loss increases
Solution Approach 1:
The system dynamically adjusts the gate discharging rate based on real-time operating conditions. By detecting collector current changes and adaptively switching between high and low resistance discharge paths, the system maintains high switching speed when safe, thereby reducing switching loss while still suppressing surge voltage when necessary
3Loss of energy
If the active gate control is applied without considering collector-emitter voltage margin, then the switching loss is reduced, but the switching element may be damaged
Solution Approach 1:
The patent implements feedback by continuously monitoring collector current and using this information to control the gate discharging process. The control circuit detects when collector current starts to decrease and adjusts the discharge path accordingly, creating a closed-loop control system that adapts to actual operating conditions
Solution Approach 2:
The system takes preliminary action by detecting collector current changes before the collector-emitter voltage reaches dangerous levels. By proactively adjusting the gate discharge rate based on current detection, the system prevents excessive voltage buildup while optimizing switching performance
Data Source
AI summary
The drive circuit is for turning on and off a switching element having an open/close control terminal, an input terminal and an output terminal by moving electrical charge in the open/close control terminal in accordance with an on-manipulation command and an off-manipulation command received from outside. The drive circuit includes an active gate control means for changing a moving speed of the electrical charge midway between when movement of the electrical charge is started and when the movement is completed, and a determination means for making at least one of a determination on a change timing to change the moving speed and a determination on whether or not a change of the moving speed by the active gate control means should be made.