MOSFET Body Diode Loss
P = Vf × If × (1 − D)
Quick answer
This calculator solves P = V_f × I_f × (1 − D) for Body Diode Loss. With Diode Forward Voltage 12 V, Diode Current 2 A, Duty Cycle 50 %, the result is 12 W. It solves in 4 directions, so you can enter the values you have and get the one you need.
Calculator
Formula
Description
The MOSFET body diode conducts during dead time in half-bridge and full-bridge circuits when the inductor current forces through the antiparallel diode before the complementary switch turns on. The loss depends on the diode forward voltage drop (typically 0.7-1.2 V for silicon MOSFETs), the current magnitude, and the fraction of the switching period spent in diode conduction (approximately 1 − D for the low-side switch, or proportional to dead time). Body diode losses are significant in synchronous rectifiers and motor drives, especially at low duty cycles.
Variables
- P — Body diode conduction loss (W)
- V_f — Body diode forward voltage (V)
- I_f — Current through the body diode (A)
- D — Duty cycle of the MOSFET channel conduction (0 to 1)
Practical Notes
GaN FETs do not have a true body diode but have a reverse conduction mode with higher voltage drop (2-3 V) and zero reverse recovery charge. Schottky diodes placed in parallel with the body diode can reduce the forward voltage and eliminate reverse recovery loss in silicon MOSFETs. In synchronous buck converters, the body diode conducts only during dead time (typically < 1% of the period), so this loss is usually small.
Symbols and units
| Symbol | Meaning | Default unit | Accepted units |
|---|---|---|---|
| P | Body Diode Loss | W | µW, mW, W, kW |
| Vf | Diode Forward Voltage | V | pV, nV, µV, mV, V, kV |
| If | Diode Current | A | pA, nA, µA, mA, A, kA |
| D | Duty Cycle | — | —, % |
Step by step
- 1. What you know: Diode Forward Voltage 12 V, Diode Current 2 A, Duty Cycle 50 %
- 2. The relation: P = V_f × I_f × (1 − D)
- 3. Substitute: Vf = 12 V, If = 2 A, D = 50 %
- 4. Result: Body Diode Loss = 12 W
Related quantities from the same inputs
- P = V × I = 24 W
Worked examples
Minimum range
Given: Diode Forward Voltage 0.33 V, Diode Current 2 mA, Duty Cycle 2.5 %
Result: Body Diode Loss = 0.6435 mW
Low range
Given: Diode Forward Voltage 3.3 V, Diode Current 20 mA, Duty Cycle 25 %
Result: Body Diode Loss = 49.5 mW
Typical
Given: Diode Forward Voltage 12 V, Diode Current 2 A, Duty Cycle 50 %
Result: Body Diode Loss = 12 W
High range
Given: Diode Forward Voltage 0.23 kV, Diode Current 100 A, Duty Cycle 0.8
Result: Body Diode Loss = 4.6 kW
Maximum range
Given: Diode Forward Voltage 2.3 V, Diode Current 1 A, Duty Cycle 0.8 %
Result: Body Diode Loss = 2.282 W
Solving for each variable
Solve for Body Diode Loss
Diode Forward Voltage 0.33 V, Diode Current 2 mA, Duty Cycle 2.5 % → 0.6435 mW
Solve for Diode Forward Voltage
Body Diode Loss 10 mW, Diode Current 2 mA, Duty Cycle 2.5 % → 5.128 V
Solve for Diode Current
Body Diode Loss 10 mW, Diode Forward Voltage 0.33 V, Duty Cycle 2.5 % → 31.08 mA
Solve for Duty Cycle
Body Diode Loss 10 mW, Diode Forward Voltage 0.33 V, Diode Current 2 mA → -14.15
How Body Diode Loss changes with Diode Forward Voltage
| Diode Forward Voltage (input) | Body Diode Loss (result) |
|---|---|
| 1.2 V | 1.2 W |
| 3 V | 3 W |
| 6 V | 6 W |
| 9 V | 9 W |
| 12 V | 12 W |
| 18 V | 18 W |
| 24 V | 24 W |
| 48 V | 48 W |
| 84 V | 84 W |
| 120 V | 120 W |
The same result in other units
| Unit | Value |
|---|---|
| mW | 12000 |
| W | 12 |
| kW | 0.012 |
Embed this calculator
Paste this into any page. It keeps working when this page updates, and credits the source.
<iframe src="https://vbatpower.com/embed/mosfet-body-diode/" width="100%" height="460" style="border:1px solid #1f2a37;border-radius:12px" loading="lazy" title="MOSFET Body Diode Loss"></iframe>
<p><a href="https://vbatpower.com/formulas/mosfet-body-diode/">MOSFET Body Diode Loss</a> Calculator by vbatpower.com</p>Frequently asked questions
How do you calculate MOSFET Body Diode Loss?
Use P = V_f × I_f × (1 − D). With Diode Forward Voltage 12 V, Diode Current 2 A, Duty Cycle 50 %, Body Diode Loss works out to 12 W.
How to calculate body-diode forward current of mosfet?
Rearrange for Body Diode Loss: with Diode Forward Voltage 3.3 V, Diode Current 20 mA, Duty Cycle 25 %, Body Diode Loss is 49.5 mW.
What is the formula for MOSFET Body Diode Loss?
The formula is P = V_f × I_f × (1 − D). The MOSFET body diode conducts during dead time in half-bridge and full-bridge circuits when the inductor current forces through the antiparallel diode before the complementary switch turns on.
How do you find Diode Forward Voltage when you know the other values?
Rearrange for Diode Forward Voltage: with Body Diode Loss 10 mW, Diode Current 2 mA, Duty Cycle 2.5 %, Diode Forward Voltage is 5.128 V.
How do you find Diode Current when you know the other values?
Rearrange for Diode Current: with Body Diode Loss 10 mW, Diode Forward Voltage 0.33 V, Duty Cycle 2.5 %, Diode Current is 31.08 mA.
What units does MOSFET Body Diode Loss use?
Body Diode Loss is shown in mW, W, kW. Values are held in SI base units internally, so you can mix prefixes without converting by hand.
Related Concepts
All Semiconductors formulas →Need more features?
Save calculations, import telemetry data, simulate battery discharge, and collaborate with your team.
Try the App