Dynamic IGBT Gate Drive for Switching Loss Reduction
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Solution Overview
Problem
Conventional gate drivers for IGBTs in hybrid-electric powertrains have limited control over switching delay time, current slope, and voltage slope, leading to suboptimal switching performance and excessive switching losses across various operating conditions.
Innovation Solution
A smart gate driving strategy involving a two-step current source profile with adaptive timing based on operating conditions, transitioning from a high current pulse to a low current pulse to minimize switching losses and prevent voltage overshoot, is implemented.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional gate driver with fixed current control is used, then the device complexity is low, but the switching loss is excessive and switching performance is suboptimal
Solution Approach 1:
The gate driver transitions from fixed current control to dynamic two-level current control, where the gate current can switch between a first level and a second level based on the time integral of collector-emitter voltage, enabling adaptive optimization of switching performance across different operating conditions
Solution Approach 2:
The invention changes the gate current parameter dynamically by implementing a two-level current source that switches between different current magnitudes, allowing optimization of turn-on delay and switching speed while minimizing switching losses under varying operating conditions
2Speed
If a high gate current is applied continuously, then the turn-on delay is reduced and switching speed is increased, but the switching loss increases
Solution Approach 1:
The gate current waveform is segmented into two distinct levels: a first level applied during the initial charging phase to achieve fast turn-on, and a second level applied after the time integral threshold is exceeded to maintain switching speed while reducing power loss during the remainder of the switching transition
Solution Approach 2:
The gate driver implements periodic switching between two current levels based on the time integral of collector-emitter voltage, creating an optimized current profile that alternates between high current for fast switching and lower current for loss reduction
3Loss of energy
If the gate current is reduced to minimize switching loss, then the energy efficiency improves, but the turn-on delay increases and switching speed decreases
Solution Approach 1:
The gate driver applies a preliminary high current level to rapidly charge the gate and achieve fast turn-on within a critical initial period, then transitions to a lower current level after the time integral threshold is exceeded, thereby minimizing both turn-on delay and subsequent switching losses
Data Source
AI summary
A vehicle includes an electric machine, an IGBT, and a gate driver. The IGBT has a gate, an emitter, and a collector and is configured to flow an electric charge through a phase of the electric machine. The gate driver is configured to flow current onto the gate at a first level, and in response to a time integral of a voltage across the phase exceeding a predetermined level, transition from the first level to a second level less than the first level.