Half-Bridge Gate Driver Circuit With Capacitor-Based Negative Bias
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing driver circuits for wide bandgap semiconductors, such as GaN or SiC, face challenges in supplying a negative gate voltage without increasing circuit size or complexity, particularly due to limitations with zener diodes and the need for insulated power supplies, which restrict the range of power-supply voltage and lead to increased cost and complexity.
Innovation Solution
A driver circuit design that includes a series connection of two transistors with different power-supply voltages, a control circuit for each transistor, and a capacitor to generate a power-supply voltage, allowing for the supply of a negative gate voltage without additional insulated power supplies, using wide-gap semiconductor transistors and a MOSFET as the switching element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a zener diode is used to generate negative voltage, then the negative gate voltage can be supplied, but the breakdown voltage limitation restricts the power-supply voltage range and increases circuit complexity
Solution Approach 1:
The patent extracts and removes the zener diode from the circuit, replacing it with a capacitor-based voltage generation approach. This eliminates the breakdown voltage limitation and reduces circuit complexity while maintaining the ability to supply negative gate voltage to the wide bandgap semiconductor device.
Solution Approach 2:
The patent changes the voltage generation mechanism from zener diode breakdown voltage to capacitor charging/discharging voltage. By using a capacitor charged to a specific voltage and then discharging it through a transistor, the circuit can generate negative voltage without being constrained by zener diode breakdown voltage limitations.
2Reliability
If an insulated power supply is used for the high-side circuit, then short-circuit prevention is achieved, but the circuit size and complexity increase
Solution Approach 1:
The patent merges the high-side and low-side power supply circuits into a single unified structure. By using a shared capacitor and transistor arrangement, both sides can be controlled without requiring separate insulated power supplies, thus reducing complexity while maintaining short-circuit prevention through proper timing control.
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage element that mediates between the power supply and the switching circuits. This capacitor serves as a temporary energy reservoir that enables voltage generation and switching control without requiring complex insulated power supply structures.
3Loss of energy
If a free-wheel diode is connected in parallel with the switching element, then reverse power loss and noise are suppressed, but the circuit structure becomes more complex
Solution Approach 1:
The patent enables the wide bandgap semiconductor device itself to provide the reverse conducting function that would otherwise require a separate free-wheel diode. By utilizing the device's inherent characteristics and controlling its switching timing, the circuit achieves reverse power loss suppression without adding external diode components.
4Speed
If wide bandgap semiconductor is used for high-speed switching, then switching speed is improved, but negative gate voltage is required to turn off the device
Solution Approach 1:
The patent implements a dynamic gate voltage control system that adapts to the switching state of the wide bandgap semiconductor device. The capacitor is charged during the off-state and discharged during the on-state, dynamically providing the necessary negative gate voltage only when needed for turn-off, thus maintaining high switching speed while managing voltage control complexity.
Data Source
AI summary
A gate driver circuit that can supply a negative gate voltage to a high-side circuit without being additionally provided with an insulated power supply is realized. A driver circuit is configured such that a half-bridge circuit in which a first transistor and a second transistor are connected in series includes a capacitor that supplies a negative gate voltage to a high-side first transistor via a first control circuit, and a control circuit power supply that supplies a negative gate voltage to a low-side second transistor via a second control circuit, one end of the capacitor being connected to a negative voltage VEE on a negative terminal side of the control circuit power supply via a switching element, and the other end being connected to a voltage on an output terminal, wherein the switching element is controlled to be on upon a timing when the second transistor is turned on.