GaN Transistor Gate Drive Circuit for Normally-Off Switching
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Solution Overview
Problem
GaN-based power devices face challenges in transitioning to a normally-off type due to issues with gate drive capability, requiring dedicated circuits and long gate current loops, and a trade-off between erroneous ON prevention and standby power when the gate driver power supply is turned off.
Innovation Solution
A semiconductor device that includes a first circuitry and a second circuitry, along with a diode, to detect power supply voltage fluctuations and drive a series-connected second transistor, enabling a normally-off operation without external input signals, using GaN transistors in conjunction with p-type MOSFETs to control gate voltages and prevent simultaneous switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conversion circuit is used to make GaN transistors normally-off type, then the transistor can operate in normally-off mode, but the gate drive capability cannot be adjusted by the conversion circuit
Solution Approach 1:
The circuit uses the power supply voltage itself to generate the gate drive signal through the first circuitry that detects power supply voltage and outputs a transition state, eliminating the need for external control signals while maintaining adjustable gate drive capability through the second circuitry
2Reliability
If a dedicated negative power supply circuit and gate driver are used, then normally-off operation is achieved, but device complexity increases
Solution Approach 1:
The first circuitry that detects power supply voltage and the second circuitry that outputs drive voltage are merged into a single integrated structure that works together with the GaN transistor, eliminating the need for separate dedicated negative power supply circuits and gate drivers
Solution Approach 2:
The first circuitry serves multiple functions by detecting power supply voltage transitions and generating control signals, while the second circuitry provides both voltage level shifting and drive signal generation, making the overall structure more universal and less complex
3Use of energy by stationary object
If the gate driver power supply is turned off, then standby power is reduced, but the trade-off between erroneous ON prevention and standby power becomes large
Solution Approach 1:
The first circuitry automatically detects power supply voltage transitions and generates appropriate drive signals without requiring external control, enabling the gate driver to remain reliable even when the power supply is turned off to reduce standby power
Solution Approach 2:
The first circuitry provides feedback by detecting the power supply voltage state and using this information to control the second circuitry, which in turn controls the GaN transistor, creating a closed-loop system that prevents erroneous ON states while minimizing standby power
4Reliability
If passive circuits are used to manage gate voltages, then simultaneous switching is prevented, but circuit complexity increases
Solution Approach 1:
The control function is segmented into two distinct circuitries: the first circuitry detects power supply voltage transitions, and the second circuitry generates the actual drive signal for the GaN transistor. This segmentation prevents simultaneous switching by ensuring proper sequencing of voltage transitions
Data Source
AI summary
A semiconductor device that normally-off drives a first transistor that normally-on drives, the semiconductor device includes a first circuitry, a second circuitry, and a first diode. The first circuitry that is connected with a power supply voltage and a ground voltage, detects the power supply voltage, and outputs a transition state of the power supply voltage. The second circuitry that is connected with the power supply voltage, the ground voltage, the first circuitry, and a second transistor, and outputs a drive voltage of a second transistor connected in series with the first transistor, based on an output of the first circuitry. The first diode having an anode connected with a drive terminal of the first transistor and a cathode connected with an output terminal of the second transistor.