GaN-HEMT Gate Drive Waveform Shaping Circuit
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Solution Overview
Problem
Existing control ICs designed for silicon MOSFETs struggle to drive GaN-HEMTs, which require negative gate voltages, leading to increased circuit complexity due to the need for a negative power supply to generate these voltages.
Innovation Solution
A waveform shaping circuit that includes parallel circuits with capacitors and resistors, Zener diodes, and rectifier circuits, allowing for the generation of negative voltages without an external negative power supply by utilizing a positive pulse voltage and Zener diodes to regulate and interrupt current flow, thereby producing a stable negative output voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a negative power supply is added to generate negative gate voltage for GaN-HEMT, then the gate voltage requirement is met, but the circuit scale increases
Solution Approach 1:
A waveform shaping circuit is introduced as an intermediary component between the control IC and the GaN-HEMT. This circuit converts the positive gate voltage from the control IC into the required negative gate voltage, eliminating the need for a separate negative power supply while meeting the voltage requirements of the normally-on GaN-HEMT
Solution Approach 2:
The waveform shaping circuit generates the negative voltage needed by the GaN-HEMT using only the positive power supply already available in the system. The circuit utilizes the existing positive gate voltage signal and transforms it through RC networks and diodes to produce the required negative voltage, making the system self-sufficient without external negative power supply
2Ease of operation
If a control IC designed for Si-MOSFET is used, then the control function is provided, but it cannot drive GaN-HEMT requiring negative voltage
Solution Approach 1:
The waveform shaping circuit serves multiple functions: it acts as a voltage converter to generate negative voltage, serves as an interface adapter between control IC and GaN-HEMT, and provides waveform conditioning. This enables a single control IC to effectively drive both Si-MOSFET and GaN-HEMT devices through the same control interface
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
The proposed solution reduces circuit complexity by eliminating the need for a negative power supply, enabling the generation of a stable negative voltage from a positive pulse input, suitable for driving GaN-HEMTs without increasing the circuit scale.
Implementation Method 1
a Zener diode disposed between a point of coupling between a seventh terminal of the second capacitance element and an eighth terminal of the second resistance element and the point of coupling between the third terminal and the fourth terminal, the Zener diode interrupting a current flowing in a direction from the seventh terminal and the eighth terminal to the third terminal and the fourth terminal at a time of application of a voltage equal to or higher than a Zener voltage
Implementation Method 2
the first rectifier circuit interrupting a current flowing in a direction from the third terminal and the fourth terminal to the output terminal
Data Source
AI summary
A waveform shaping circuit includes a first parallel circuit including a first capacitance element and a first resistance element coupled in parallel with each other, a positive pulse voltage being applied to a first terminal of the first capacitance element and a second terminal of the first resistance element, a first rectifier circuit disposed between a point of coupling between a third terminal of the first capacitance element and a fourth terminal of the first resistance element and an output terminal.