Active Gate Driver With di/dt Feedback for Low-EMI WBG Switching
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Solution Overview
Problem
Wide band gap (WBG) power semiconductor devices face challenges with electromagnetic interference (EMI) and potential false turn-ons due to fast switching transients, which are not effectively addressed by conventional gate driver designs, especially in high voltage and high current electrical systems used in hybrid-electric and all-electric aircraft.
Innovation Solution
A gate drive circuit for WBG power devices, specifically an insulated gate bipolar transistor (IGBT), incorporating a buffer, di/dt sensing network, turn-on circuit, and turn-off circuit, which uses feedback control signals to manage parasitic inductance and capacitance, ensuring safe switching and reducing EMI by controlling current paths during turn-on and turn-off transients.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fast switching transients are used in WBG power devices, then switching losses are reduced, but electromagnetic interference (EMI) and false turn-ons are introduced
Solution Approach 1:
The patent employs a di/dt sensing network that provides feedback control by monitoring the rate of current change and using this information to control the gate driver circuit. This feedback mechanism allows the system to maintain fast switching for low losses while actively managing EMI by adjusting gate signals based on real-time di/dt measurements
Solution Approach 2:
The gate driver circuit dynamically adjusts its operation based on real-time conditions. The circuit transitions from static gate resistance to dynamic control where the gate resistance and drive signals are continuously adjusted based on di/dt feedback, enabling the system to optimize switching performance while managing EMI on-the-fly
2Speed
If fast switching transients are used in WBG power devices, then switching speed is improved, but false turn-ons become possible
Solution Approach 1:
The di/dt sensing network provides real-time feedback that enables the gate driver to detect and respond to conditions that could cause false turn-ons. By monitoring the actual current change rate, the system can distinguish between legitimate switching events and spurious signals, maintaining high switching speed while preventing false operations
Solution Approach 2:
The circuit takes preliminary anti-action by proactively managing gate signals before false turn-ons can occur. The feedback control mechanism anticipates potential false turn-on conditions and applies countermeasures through controlled gate drive signals, preventing the issue before it manifests
3Device complexity
If conventional gate driver designs are used, then device simplicity is maintained, but EMI and false turn-ons are not effectively addressed
Solution Approach 1:
The patent transforms the conventional open-loop gate driver into a closed-loop system by introducing di/dt sensing and feedback control. This feedback mechanism adds the capability to effectively address EMI and false turn-ons while maintaining reasonable device complexity through efficient circuit implementation
Data Source
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AI summary
A gate drive circuit of a wide band gap power device (IGBT) includes a buffer, a di/dt sensing network, a turn-on circuit portion and turn-off circuit portion. The buffer, responsive to turn-on, supplies a first current via the first current path to the gate of the IGBT, and responsive to turn-off ceases the supply of the first current. The di/dt sensing network receives a feedback control signal representative of a voltage measurement across a parasitic inductance that exists between a Kelvin emitter and a power emitter of the IGBT. The turn-on circuit portion, responsive to turn-on and a parasitic inductance of zero volts, supplies a second current via a second current path to the gate of the IGBT. The turn-off circuit portion, responsive to turn-off and a parasitic inductance of zero volts, discharges a gate capacitance of the IGBT through both the first current path and a third current path.