Half-Bridge Gate Drive for Turn-Off Surge and Loss Control
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Solution Overview
Problem
Existing gate drive devices for semiconductor switching elements in half bridge circuits face challenges in controlling turn-off surges without excessively increasing switching losses, as they often adjust gate resistance based on combined surge voltages including both turn-off and recovery surges, leading to inadequate control of turn-off surges.
Innovation Solution
A gate drive device with a detection unit to identify peak voltages and current directions, a determination unit to differentiate between forward and reverse energizations, and a calculation unit to set target instruction values for gate resistance or current to manage turn-off surges within permissible limits, ensuring the gate drive device only adjusts based on the turn-off surge magnitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gate resistance is adjusted based on combined surge voltages including both turn-off and recovery surges, then surge protection is provided, but turn-off surge control becomes inadequate
Solution Approach 1:
The patent segments the surge voltage measurement into separate components by introducing a current direction detection function. The surge measurement unit now independently measures turn-off surge voltage and recovery surge voltage based on current direction, allowing separate control of gate resistance for each surge type. This resolves the contradiction by providing precise turn-off surge control while maintaining overall surge protection.
Solution Approach 2:
The patent introduces a current direction detection unit as an intermediary between the surge measurement and gate resistance control. This intermediary function identifies whether the surge is a turn-off surge or recovery surge by detecting current direction, enabling selective adjustment of gate resistance. This resolves the contradiction by adding the necessary discrimination capability without compromising surge protection.
2Object-affected harmful factors
If gate resistance is increased to suppress turn-off surges, then surge magnitude is reduced, but switching losses increase excessively
Solution Approach 1:
The patent implements dynamic adjustment of gate resistance based on real-time detection of turn-off surge magnitude. The gate resistance control unit continuously monitors surge levels and adjusts resistance only when necessary to keep surges within permissible limits. This dynamic control suppresses turn-off surges effectively while minimizing unnecessary energy loss during normal switching operations.
Solution Approach 2:
The patent changes the gate resistance parameter dynamically based on detected surge conditions. When turn-off surge exceeds permissible values, gate resistance is increased to suppress the surge; when surge is within limits, gate resistance is reduced to minimize switching losses. This parameter change strategy resolves the contradiction by adapting resistance to actual surge conditions rather than using a fixed high value.
3Reliability
If gate resistance is adjusted based on combined surge voltages, then overall surge protection is maintained, but turn-off surge control precision is insufficient
Solution Approach 1:
The patent enhances the gate resistance control unit to perform multiple functions: it controls both turn-off surge suppression and recovery surge protection through a single unified control mechanism. By integrating current direction detection and selective gate resistance adjustment, the system achieves precise turn-off surge control while maintaining overall surge protection, avoiding the need for separate control circuits.
Data Source
AI summary
A gate drive device drives a gate of each of two semiconductor switching elements constituting upper and lower arms of a half bridge circuit. The gate drive device detects a peak value of an element voltage that is a voltage of a main terminal of one of the two semiconductor switching elements, as one semiconductor switching element, or a change rate of the element voltage during a change period in which the element voltage changes. The gate drive device determines whether an energization to the one semiconductor switching element during the change period is a forward energization in which a current flows in a forward direction or a reverse energization in which the current flows in a reverse direction.