Community Translation: MOSFET/GaNFET/SiCFET:スパイスモデルを用いた 配線/寄生インダクタンスの求め方- KBA236693
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Due to very high-speed switching transients, practical power electronic switches are subjected to high dV/dt and di/dt. As the slopes of these transients increase, the voltage and current induced across the parasitic inductance/capacitance increase, which can sometimes damage the device and affect its performance.
Since these devices have a very short switching time and; therefore, faster voltage transition (dV/dt), it may result in induced voltage spikes. The voltage induced across the parasitic inductors will be . The influence of parasitic parameters on these power electronic switches is more serious due to the switching transients. For example, if the induced turn-on spike exceeds the Vth of the device, then the device will partially turn on for a brief period of time before the high-side MOSFET has fully turned off. With both the devices partially on, a high current can flow through the half-bridge, which can violate SOA limits and destroy one or both devices.
Figure 1 Representation of a MOSFET along with its parasitic lead inductance
See the device datasheet for more information. If it is not present in the datasheet, you can determine the lead inductance values from the device Spice Model:
- Search for your device on the Infineon website using the product part number.
- If you do not have the exact part number, go to Home > Product > Power > Products, and choose the required part from the available part numbers as shown in Figure 2.
Figure 2 Searching the product part number in Infineon website
- Go to the product page and scroll down for the design files, or click Design Support.
- Click Simulation Models and download the respective simulation model - MOSFET OptiMOS™ 40V N-Channel Spice (.lib file, Ex- StrongIRFET_40V_LTSpice.lib) as shown in Figure 3.
Figure 3 Searching for the Spice Model on the product page
- Open the downloaded file in any text editor tool (for example, WordPad or Notepad).
- Go to the sub circuit definition of the part number (L0, L1, or L3) and find the values for Ls (Source Inductance), Ld (Drain Inductance), and Lg (Gate Inductance) in the circuit definition. Press Ctrl+F and choose from the available inductance values.
Figure 4 Searching for inductance value
Figure 5 Finding the lead inductance value
In the simulation model, while defining Ls, Ld, and Lg values, the effect of PCB tracks is also considered up to a certain extent, which depends on the length and width of the PCB track defined.