Wide Bandgap Switching Element Gate Drive Surge Suppression
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Solution Overview
Problem
Existing surge voltage suppression methods for switching elements in large-capacity inverters require large and complex snubber capacitors, and existing techniques either fail to reduce surge voltage effectively or do not address the need for a countermeasure for large-capacity snubber capacitors.
Innovation Solution
An electric power conversion device using wide bandgap semiconductor switching elements and a drive circuit that controls the gate voltage to operate the elements in a non-linear region during turn-off, eliminating the need for large-capacity snubber capacitors and simplifying the circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a snubber capacitor is connected to each transistor in a large-capacity inverter to suppress surge voltage, then the surge voltage is suppressed, but the circuit size becomes large and the circuit becomes complex
Solution Approach 1:
The patent merges the surge suppression function into the existing gate drive circuit by adding a capacitor connected to the gate terminal, rather than requiring separate snubber capacitors for each transistor. This integration reduces circuit complexity while maintaining surge suppression capability.
Solution Approach 2:
The gate drive circuit is designed to serve multiple functions: both switching control and surge suppression. The capacitor connected to the gate terminal performs dual roles in controlling the switching timing and suppressing voltage surges, eliminating the need for dedicated snubber components.
2Reliability
If a large-capacity snubber capacitor is used to handle short-circuit current in the inverter, then the surge voltage suppression is improved, but the size of the snubber capacitor becomes considerably large
Solution Approach 1:
The patent applies local quality by concentrating the surge suppression capability at the gate terminal location rather than requiring large-capacity capacitors distributed throughout the circuit. The localized capacitor at the gate provides sufficient suppression for short-circuit conditions without requiring large overall capacitance.
Solution Approach 2:
The invention changes the operational parameters by utilizing the gate capacitance and drive circuit characteristics to achieve surge suppression. By optimizing the gate drive waveform and timing, the system handles short-circuit currents effectively with much smaller capacitor values than traditional approaches.
3Reliability
If the gate voltage is increased to prevent element breakage due to overcurrent, then the element protection is improved, but the surge voltage cannot be reduced at the time of turning off the element
Solution Approach 1:
The patent applies preliminary action by pre-charging the gate capacitor before the switching event. This pre-charged capacitor is ready to immediately suppress voltage surges when the transistor turns off, providing protection against both overcurrent and surge voltage without requiring high gate drive voltages.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively suppresses surge voltage using a small and simple circuit, suitable for high-temperature operations and reducing the risk of switching element breakage, while maintaining efficiency during output short-circuits.
Implementation Method 1
a voltage-driven wide bandgap switching element that uses a wide bandgap semiconductor
Data Source
AI summary
To provide an electric power conversion device that converts direct current power supplied from a direct-current power supply into alternating current power, the electric power conversion device includes six switching elements constituted by a voltage-driven transistor that uses a wide bandgap semiconductor and a diode, and a drive circuit that controls a voltage for driving the transistor at a time of turning off the switching elements based on a predetermined voltage profile specifying that the transistor is operated in a non-linear region.