SiC Power Device｜Application
Conventional MOSFET Driving Method
2023.12.27
Points of this article
・In order to understand the effective of the driver source terminal, one must understand the method for driving conventional MOSFETs, as well as current flows and parasitic components.
Conventional MOSFET Driving Method
Before explaining driver source terminals, we first review the driving method for conventional MOSFETs.
MOSFETs are generally voltage-driven devices; switching operation is controlled by turning on and off the voltage applied to the gate terminal (pin). Below is shown an example of a general gate driving circuit for a conventional MOSFET in a TO-247N package (3 pins).
An external resistor RG_EXT is connected between the driving power supply VG and the MOSFET gate terminal (Gate) to control the switching speed, but the driving circuit includes the inductance LTRACE of the PCB traces as well as a package inductance LSOURCE that is present in the MOSFET source terminal (Source). It is very important that these parameters be considered. The package inductance of the gate terminal is included in LTRACE, but the inductance LDRAIN of the drain terminal Drain is not included in the gate driving circuit, and so is here omitted.
The action of this driving circuit is basic and generally known, and so is not discussed here; but one phenomenon that tends not to be noticed at normal switching speeds is the emf VLSOURCE in the inductance LSOURCE due to changes in the drain current ID flowing between drain and source. Below are shown the voltages applied during switching action in the driving circuit.
When VG is applied and the MOSFET turns on, ID increases, and a voltage VLSOURCE appears in LSOURCE, in the direction shown in the diagram (I). On the other hand, because the current IG flows into the gate terminal, a voltage drop VRG_EXT(I) occurs across RG_EXT. These voltages are included in the driving circuitry at turn-on, and reduce the voltage VGS_INT necessary for turn-on action of the MOSFET, as indicated by equation (1), and consequently tend to reduce the turn-on speed. An emf also appears in LTRACE, but it is small and is here omitted.
For similar reasons, upon turn-off, IG and dID/dt in equation (1) are negative, so that voltage rises (II) occur in RG_EXT and LSOURCE, and the increase in VGS_INT causes a decrease in turn-off speed.
In general, the value of LSOURCE in power switching devices ranges a few nH to a dozen nH, and when dID/dt reaches several A/ns, a VLSOURCE voltage of 10 V or higher may occur, greatly affecting switching operation.
A driver source terminal eliminates the influence of VLSOURCE and improves switching speed.
【Download Documents】 Basics of SiC Power Devices
This handbook explains the physical properties and advantages of SiC, the differences in characteristics and usage of SiC Schottky barrier diodes and SiC MOSFETs with a comparison to Si devices, and includes a description of full SiC modules with various advantages.
SiC Power Device
Basic
- What are SiC Schottky barrier diodes? ? Introduction
- What are SiC-MOSFETs? – SiC-MOSFET Features
- What are Full-SiC Power Modules?
- Summary
- Introduction
- What is silicon carbide?
Application
-
Introduction
- SiC MOSFET Bridge Configuration
- SiC MOSFET Gate Driving Circuit and Turn-On/Turn-Off Operation
- Currents and Voltages Occurring Due to Switching in Bridge Circuits
- Behavior of the Gate-Source Voltage During Low-side Switch Turn-on
- Behavior of the Gate-Source Voltage During Low-side Switch Turn-off
- Summary
- SiC MOSFETs: Method for Determining Losses from Switching Waveforms
-
SiC MOSFETs： Snubber Circuit Designs ーIntroductionー
- Non-Discharge RCD Snubber Circuit Design
- Surges Occurring between Drain and Source
- Types and Selection of Snubber Circuits
- C Snubber Circuit Design
- RC Snubber Circuit Design
- Discharge RCD Snubber Circuit Design
- Non-Discharge RCD Snubber Circuit Design
- Differences in Surge Occurrence Depending on Package
- SiC MOSFETs： Snubber Circuit Designs ーSummaryー
- Points to Note When Measuring SiC MOSFET Gate-Source Voltages: General Measurement Methods
-
Conventional MOSFET Driving Method
- Packages Provided with Driver Source Terminals
- Differences Made by and Benefits of a Driver Source Pin
- Benefits of a Driver Source Terminal: Comparisons Using Double Pulse Tests
- Behavior of Gate-Source Voltages when in a Bridge Configuration: Behavior at Turn-on
- Behavior of Gate-Source Voltages when in a Bridge Configuration: Behavior at Turn-off
- Points to be Noted Relating to Board Wiring Layout Key Points of This Article
- Verification of Loss Reduction Using Latest-Generation SiC MOSFETs
- About Surges in Gate-Source Voltages
Product Information
- SiC Schottky Barrier Diodes
- SiC MOSFET
- SiC Power Modules
- SiC Schottky barrier diode Bare Die
- SiC MOSFET Bare Die
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