MOSFET Body Diode Loss Calculator
Calculate body-diode conduction and reverse-recovery losses in synchronous rectifiers. For buck converters and motor-drive inverters where dead-time forces body-diode conduction.
How to Use
- Enter Vf (body diode forward voltage), dead-time duration, load current, and switching frequency.
- Enter Qrr (reverse recovery charge from datasheet) and DC bus voltage.
- Tool computes conduction loss + recovery loss.
Show Work
Formulas
History of Body-Diode Conduction
The parasitic body diode in DMOS power transistors - formed by the junction between source/body and drain - became a performance limitation when power MOSFETs displaced bipolar transistors in switching supplies in the late 1970s. Early MOSFETs had slow body diodes (trr > 500 ns) that caused shoot-through and EMI. Modern trench-gate MOSFETs reduce Qrr 5-10x. SiC and GaN devices eliminate body-diode reverse recovery entirely - a major efficiency gain driving their adoption in high-frequency converters.
About This Calculator
Enter Vf body diode (typical 0.7-1.2 V, datasheet), dead-time t_d (gate-driver spec, 10-200 ns), load current, switching frequency, Qrr (reverse recovery charge), and DC bus voltage. The tool computes conduction loss during dead-time and recovery loss per switching cycle.
To reduce body-diode losses: choose low-Qrr MOSFETs (trench or super-junction), add Schottky in parallel, or use adaptive dead-time gate drivers. Everything runs client-side.
About the MOSFET Body Diode Loss Calculator
The MOSFET Body Diode Loss Calculator gives you a fast, free answer for electronics and circuit design without sending anything off your device. Calculate body-diode conduction and reverse-recovery losses in synchronous rectifiers. For buck converters and motor-drive inverters where dead-time forces body-diode conduction.
How it works
Enter your figures and the result appears instantly, updating the moment you change anything. There is no submit button and nothing to wait for, so it is easy to try a few what-if numbers and compare the results. Just check each box holds the kind of value it expects.
Want the deeper story? The Knowledge Base explains the ideas behind the tools in more detail.
Frequently Asked Questions
Why body diode?
In a synchronous rectifier (e.g., buck low-side MOSFET), during dead-time the body diode conducts instead of the channel. High Vf (~1 V vs ~0.1 V channel) causes extra loss.
Recovery loss?
When the high-side turns on, the low-side body diode must recover — the Qrr charge flows through the high-side MOSFET as shoot-through, dissipating Qrr·V_bus·f each switching cycle.
Schottky in parallel?
Adding an external Schottky across the MOSFET body diode reduces Vf during dead-time and bypasses much of the recovery charge. Common in motor drives where body-diode losses are a significant % of total.
How do I use the MOSFET Body Diode Loss Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Does it cost anything or need an account?
No. The tool is completely free, there is no account to create, and it keeps working offline after the page first loads.
Is anything I type uploaded?
No. The tool works entirely on your device, so the values you enter never leave your browser.
Common Use Cases
Buck Converter
Low-side MOSFET body diode conducts during dead-time; typical 1-3% efficiency loss at high current.
Motor Drive Inverter
Body diode conducts commutation current; Qrr loss dominates above 10 kHz.
Flyback Sync Rect
Replace Schottky output diode with synchronous MOSFET for +2-3% efficiency.
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