1. What is MOSFET Turn Off Time?

MOSFET Turn Off Time is the total time required for a MOSFET to transition from the ON state to the OFF state. It is the sum of the MOSFET OFF delay time and the fall time, representing the complete switching-off process of the device.

2. How Does the Calculator Work?

The calculator uses the MOSFET Turn Off Time formula:

Where:

• \( T_{off} \) — Total turn off time (seconds)
• \( T_{d-off} \) — MOSFET OFF delay time (seconds)
• \( T_f \) — Fall time (seconds)

Explanation: The OFF delay time is the time required for the gate-source capacitance to discharge, while the fall time is the time for the drain current to decrease from 90% to 10% of its maximum value.

3. Importance of Turn Off Time Calculation

Details: Accurate turn off time calculation is crucial for designing efficient switching circuits, minimizing switching losses, optimizing power conversion efficiency, and preventing shoot-through in bridge configurations.

4. Using the Calculator

Tips: Enter MOSFET OFF delay time and fall time in seconds. Both values must be non-negative numbers. The calculator will sum these values to provide the total turn off time.

5. Frequently Asked Questions (FAQ)

Q1: What factors affect MOSFET turn off time?
A: Gate driver capability, gate resistance, gate-source capacitance, drain current magnitude, and temperature all influence the turn off time.

Q2: Why is minimizing turn off time important?
A: Shorter turn off times reduce switching losses, improve efficiency, and allow for higher switching frequencies in power conversion applications.

Q3: How is turn off time measured experimentally?
A: Using an oscilloscope to measure the time between the gate drive signal falling edge and the drain current reaching 10% of its maximum value.

Q4: What is typical turn off time range for power MOSFETs?
A: Typically ranges from nanoseconds to microseconds, depending on the MOSFET type, size, and application conditions.

Q5: How does temperature affect turn off time?
A: Higher temperatures generally increase carrier mobility and can slightly reduce turn off time, but may also affect other parameters like threshold voltage.