Gate Drive Timing Control for Turn-On Surge and Switching Loss
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Solution Overview
Problem
Conventional gate drive circuitries for semiconductor elements like IGBTs and MOSFETs require additional switches and gate resistors to manage surge voltages, leading to increased circuit size and switching loss.
Innovation Solution
A gate drive circuitry that connects two main switching elements in series, using a controller to maintain a high-impedance state at the gate terminal of one element during a prescribed period during the turn-on action, detected by a timing trigger, to suppress surge voltages and switching loss without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional switches and gate resistors are used to manage surge voltages, then surge voltage suppression is improved, but circuit size increases
Solution Approach 1:
The patent extracts the surge suppression function from the main gate drive circuit by introducing a separate auxiliary switch that operates independently during specific timing periods. This auxiliary switch is connected in parallel with the main switch and can be activated without affecting the main switching operation, thereby suppressing surge voltages without requiring additional gate resistors or complex circuit modifications.
Solution Approach 2:
The auxiliary switch is activated before the main switch turns off and remains on for a predetermined period after main switch activation. This preliminary and extended action ensures that the surge voltage is suppressed at the critical moment when the main switch transitions, preventing voltage spikes before they can occur while maintaining simple circuit architecture.
2Reliability
If additional switches and gate resistors are used to manage surge voltages, then surge voltage suppression is improved, but switching loss increases
Solution Approach 1:
The auxiliary switch operates only partially during the switching cycle - specifically during the transition period when surge suppression is needed - rather than being continuously on or off. By activating the auxiliary switch only for the predetermined period surrounding the main switch transition, energy losses are minimized while still providing effective surge suppression during the critical moments.
3Reliability
If switching speed is reduced to suppress surge voltage, then surge voltage is suppressed, but switching efficiency decreases
Solution Approach 1:
The auxiliary switch acts as an intermediary element that manages the surge voltage issue without requiring the main switch to operate more slowly. By introducing this intermediate component that handles the voltage transition separately, the main switch can maintain its high switching speed for efficiency while the auxiliary switch independently manages the surge suppression function during critical transition periods.
Data Source
AI summary
A gate drive circuitry for driving a main switching element connected in series with a main switching element includes: a controller that makes output to a gate terminal of the main switching element in a high-impedance state for a prescribed period when a drain-source voltage of the main switching element fluctuates during a turn-on action period, the turn-on action period being a period from a state change of the main switching element to completion of turning on of the main switching element, the state change being a change from a state in which the main switching element is kept turned off to a state in which the main switching element is in a turn-on state, the controller returning the output to the gate terminal of the main switching element to a turn-on action state; and a detector that detects a timing serving as a trigger to start the prescribed period.