Gate Modulation for Wide Bandgap Semiconductor Ringing
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Solution Overview
Problem
Wide band gap semiconductor devices experience high frequency ringing during switching, leading to electromagnetic interference and performance issues, which existing solutions like improved packaging or external passive components fail to adequately address due to increased cost, size, and reduced reliability.
Innovation Solution
Implementing gate modulation techniques that create a period of operational overlap between semiconductor devices to reduce lumped stray capacitance and increase lumped loop resistance, utilizing inherent device characteristics without additional hardware, allowing for adjustable control of ringing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If improved packaging is used to reduce stray inductance, then parasitic inductance is minimized, but packaging cost and manufacturing difficulty increase significantly
Solution Approach 1:
The patent applies self-service by utilizing the inherent body diode of the WBG semiconductor device to provide the desired function of reducing parasitic inductance effects. The body diode naturally conducts during reverse recovery, creating a low-inductance path without requiring external packaging modifications or additional components.
Solution Approach 2:
The patent converts the typically harmful body diode (which causes reverse recovery issues) into a beneficial element by intentionally allowing it to conduct during specific switching transitions. This transforms the harmful reverse recovery effect into a useful mechanism for reducing parasitic inductance and minimizing ringing.
2Object-affected harmful factors
If external passive components (R/C snubber circuits) are added to minimize ringing, then oscillations are reduced, but device complexity and packaging size increase
Solution Approach 1:
The patent eliminates the need for external R/C snubber circuits by using the inherent characteristics of the WBG device itself. The body diode and device capacitance work together to provide natural damping of oscillations without requiring additional passive components.
Solution Approach 2:
The patent extracts and eliminates the need for external passive damping components by incorporating the damping function directly into the semiconductor device operation. The harmful oscillations are suppressed using only the device's intrinsic properties.
3Object-affected harmful factors
If external resistors and passive components are introduced to reduce ringing, then oscillations are minimized, but dv/dt and di/dt speeds are reduced, increasing switching loss
Solution Approach 1:
The patent converts the typically harmful body diode conduction into a beneficial mechanism that provides oscillation damping without the energy losses associated with external resistors. The natural resistance of the body diode during conduction provides sufficient damping while maintaining fast switching speeds.
Solution Approach 2:
The patent changes the operating parameters by controlling the timing and voltage levels during switching transitions. By carefully managing the gate voltage and switching timing, the device exploits the body diode's characteristics to achieve both low loss and oscillation suppression.
4Object-affected harmful factors
If gate voltage is reduced to intermediate value during switching overlap, then ringing is minimized by reducing lumped stray capacitance, but device switching speed is temporarily reduced
Solution Approach 1:
The patent applies periodic action by using pulsed gate voltage modulation during specific switching intervals. The gate voltage is temporarily reduced to an intermediate level only during the critical overlap period when both switches are conducting, then quickly restored to full level, creating a periodic control pattern that minimizes capacitance effects without sustained speed reduction.
Solution Approach 2:
The patent employs dynamic gate voltage control that adapts the switching characteristics in real-time. The gate voltage is dynamically adjusted to an intermediate level during the overlap period and then rapidly transitioned back, creating a dynamic response that minimizes ringing while maintaining overall fast switching performance.
Data Source
AI summary
Embodiments include a power conversion circuit comprising first and second semiconductor switches, and a drive circuit configured to create a period of operational overlap for the first and second switches by setting a gate voltage of the first switch to an intermediate value above a threshold voltage of the first switch, during turn-on and turn-off operations of the second switch. Embodiments also include a method of operating first and second semiconductor devices, comprising: reducing a gate voltage of the first device to an intermediate value above a threshold voltage while the second device is off; turning off the first device after the second device is on; increasing the gate voltage of the first device to the intermediate value while the second device is on; and fully turning on the first device after the second device is off.