GaN Gate Drive Circuit for Normally-Off Control Under VDD Transitions
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Solution Overview
Problem
Converting GaN power devices from normally-on to normally-off type poses challenges, including the inability to adjust gate drive capability, requiring dedicated negative power supplies and gate drivers, and a trade-off between preventing erroneous ON states and standby power consumption.
Innovation Solution
A semiconductor device configuration that includes a first and second circuitry and a diode, allowing the first transistor to operate normally-off without external input signals, by controlling voltages applied to the gate, drain, and source of transistors, using a p-type MOSFET in series with the first transistor to manage power supply voltage fluctuations and prevent simultaneous turn-on of transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a circuit converts GaN power devices from normally-on to 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 conversion circuit automatically detects the power supply voltage level and self-adjusts the gate drive capability without requiring external control signals. The circuit monitors VDD and autonomously determines whether to output a positive or negative gate voltage based on the detected voltage state, enabling the GaN transistor to switch between normally-on and normally-off modes adaptively.
Solution Approach 2:
The conversion circuit incorporates a feedback mechanism that continuously monitors the power supply voltage and uses this information to control the gate drive output. The circuit detects the voltage level and adjusts its output accordingly, creating a closed-loop control system that maintains proper transistor operation under varying supply conditions.
2Reliability
If a dedicated negative power supply circuit and gate driver are used to achieve normally-off operation, then the transistor can be controlled to turn off, but the device complexity increases
Solution Approach 1:
The conversion circuit performs multiple functions using a single integrated structure. It simultaneously acts as a voltage detector, a level shifter, and a gate driver, eliminating the need for separate negative power supply circuits and dedicated gate drivers. The same circuit components handle both the detection of power supply voltage and the generation of appropriate gate drive signals.
Solution Approach 2:
The patent combines the functions of voltage detection, signal processing, and gate drive generation into a single integrated conversion circuit. By merging these previously separate functions into one compact unit, the overall device complexity is reduced while maintaining full normally-off control capability.
3Use of energy by stationary object
If the gate driver power supply is turned off to reduce standby power consumption, then power efficiency improves, but erroneous ON prevention becomes difficult
Solution Approach 1:
The conversion circuit is designed to detect power supply voltage fluctuations and prepare the gate drive output in advance before any erroneous turn-on can occur. When voltage fluctuations are detected, the circuit proactively adjusts the gate voltage to prevent unintended transistor activation, ensuring reliability even during power supply transitions.
Solution Approach 2:
The circuit implements preliminary protective action by monitoring power supply voltage and preemptively counteracting conditions that could cause erroneous turn-on. The conversion circuit detects potential problematic voltage states and applies countermeasures through appropriate gate voltage control, preventing erroneous activation before it can occur.
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.