Half-Bridge Gate Driver Circuit for Negative High-Side Bias
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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 in zener diode breakdown voltage and the need for insulated power supplies, which restricts the usable power-supply voltage range and requires additional components like FWDs to manage reverse power loss and noise.
Innovation Solution
A driver circuit configuration using a normally-on n-channel FET with a wide-gap semiconductor, where the high-voltage-side power-supply terminal is connected to a second power-supply voltage, and the on/off of switching elements is controlled via logical AND operations and delay signals, allowing the capacitor to charge and supply negative gate voltage without additional insulated power supplies, thereby reducing the need for FWDs and simplifying the structure.
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 usable 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 method. This eliminates the breakdown voltage limitation and reduces circuit complexity while maintaining the ability to supply negative gate voltage to the wide bandgap semiconductor switching elements
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 higher voltage than the zener diode could provide, the circuit can generate more negative voltage (e.g., -10V or lower) without being constrained by semiconductor breakdown voltage limits
2Reliability
If insulated power supplies are used to supply negative gate voltage, then the switching element can be turned off, but additional components like FWDs are required to manage reverse power loss and noise
Solution Approach 1:
The patent merges the negative voltage generation function with the existing capacitor in the half-bridge circuit. The same capacitor that is part of the switching circuit topology is used to generate the negative gate voltage, eliminating the need for separate insulated power supplies and associated protective components like FWDs
Solution Approach 2:
The capacitor serves multiple functions: it acts as part of the half-bridge circuit topology and simultaneously functions as the voltage storage element for generating negative gate voltage. This multi-functionality reduces the total component count while maintaining all necessary circuit functions
3Reliability
If additional components are added to manage reverse power loss and noise, then the switching element operation is improved, but the circuit size increases
Solution Approach 1:
The circuit uses the inherent voltage characteristics of the capacitor and the natural voltage drops during switching operations to generate the required negative gate voltage. This self-service approach eliminates the need for additional protective components, reducing circuit size while maintaining reliable switching element operation
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 configuration enables efficient supply of negative gate voltage to both high-side and low-side control circuits, reducing the reverse conducting on-set voltage and eliminating the need for FWDs, resulting in a compact, high-speed, and low-power consumption driver circuit capable of handling wide-gap semiconductor switching elements.
Implementation Method 1
a capacitor whose one end is connected to the low-voltage (negative voltage) side of the high-side power supply circuit is provided. The control circuit that controls on/off of the switching element is supplied with operating power supply from the control capacitor that is charged when the switching element is turned on.
Data Source
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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 1 is configured such that a half-bridge circuit in which a first transistor 21 and a second transistor are connected in series includes a capacitor 13 that supplies a negative gate voltage to a high-side first transistor 21 via a first control circuit 11, and a control circuit power supply 14 that supplies a negative gate voltage to a low-side second transistor 22 via a second control circuit 12, one end of the capacitor 13 being connected to a negative voltage VEE on a negative terminal side of the control circuit power supply 14 via a switching element 30, and the other end being connected to a voltage on an output terminal 4, wherein the switching element 30 is controlled to be on upon a timing when the second transistor 22 is turned on.