SiC MOSFET Gate Driver With UVLO-Regulated Bipolar Voltage
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Solution Overview
Problem
Silicon carbide MOSFETs require distinct gate drive requirements due to varying on-resistance with gate source voltage and temperature, necessitating regulated gate voltage and negative gate voltage to prevent parasitic oscillations, which complicates converter design and leads to excessive heat dissipation and conflicts with Under Voltage Lock Out (UVLO) requirements.
Innovation Solution
A gate driving device using an operational amplifier, multiplexer, and UVLO circuit generates regulated gate voltage from a single unregulated power source, providing both positive and negative voltages, and includes a transformer for isolation, ensuring efficient power delivery and preventing false triggering, thus simplifying the converter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If regulated gate voltage is applied to SiC MOSFET, then on-resistance is reduced and performance is improved, but device complexity and design difficulty increase due to feedback requirements
Solution Approach 1:
The patent combines the voltage regulation function and gate drive function into a single integrated circuit. The operational amplifier simultaneously regulates the gate voltage and provides the gate drive signal, eliminating the need for separate regulation and drive circuits. This merging approach maintains the performance benefits of regulated voltage while reducing overall system complexity.
Solution Approach 2:
The operational amplifier serves multiple functions: it acts as a voltage regulator, a buffer amplifier, and a gate driver. The single power supply configuration further enhances multi-functionality by providing both positive and negative gate voltages through the same power source, reducing the number of required power supplies and simplifying the overall design.
2Reliability
If negative gate voltage is applied to prevent parasitic oscillations, then reliability is improved, but power supply complexity increases due to requirement for both positive and negative voltages
Solution Approach 1:
The patent merges the positive and negative power supply functions into a single power supply configuration. The operational amplifier uses a single power supply but generates both positive and negative output voltages through its feedback network and multiplexer configuration, eliminating the need for separate positive and negative power supplies while maintaining the reliability benefits of negative gate voltage for preventing parasitic oscillations.
3Device complexity
If single unregulated power source is used, then device complexity is reduced, but voltage regulation becomes more challenging
Solution Approach 1:
The patent employs feedback through the operational amplifier to precisely regulate the gate voltage from an unregulated power source. The feedback network continuously monitors the output voltage and adjusts the operational amplifier output to maintain the desired gate voltage level, achieving precise voltage regulation despite using a simple unregulated power source. This feedback mechanism compensates for variations in the unregulated input voltage and maintains accurate gate voltage control.
Data Source
AI summary
A gate driving device includes an operational amplifier, two impedances, a multiplexer, and an UVLO circuit. The operational amplifier has an output coupled to the gate of the SiC MOSFET, a positive power terminal coupled to a positive power rail, and a negative power terminal coupled to a negative power rail. The impedances are coupled in series and coupled between the output of the amplifier and a low-voltage terminal. The UVLO circuit is coupled to the multiplexer and the positive power rail and coupled to the positive power voltage of the positive power rail, a driving voltage, and an UVLO voltage. The UVLO circuit controls the multiplexer to transmit an off voltage or an on voltage to the positive input of the operational amplifier based on the positive power voltage, the driving voltage, and the UVLO voltage, thereby turning on or off the SiC MOSFET.