Dead Time Loss⚠ unverified
Electrical / Power Electronics · Compute the body-diode conduction loss during dead time
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| V | V | V | 1.0 | Body-diode forward voltage |
| I | I | A | 1.0 | Current through the body diode |
| tdead | tdead | s | 1.0 | Dead time per switching cycle |
| f | f | Hz | 1.0 | Switching frequency |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | P | W | Average dead-time power loss, in watts (W) |
The science & history
Understanding the Parameters
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$V$ — approximately the body-diode (or Schottky) forward voltage $V_F$ while current freewheels. Wide-bandgap devices often have higher $V_F$ body diodes, which is why external freewheel diodes or careful dead-time tuning matter.
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$I$ — current that must continue flowing (inductor current) while both FETs are off.
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$t_{dead}$ — intentional blanking so high-side and low-side never cross-conduct. Too short → shoot-through; too long → more diode loss and reverse-recovery stress.
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$f$ — more switching events per second mean more dead-time intervals per second, so loss scales linearly with $f$.
Derivation (Approaching a Proof)
While the body diode conducts, instantaneous power is $p \approx V_F\,I$ (constant-$V_F$ diode model). If each switching period $T = 1/f$ contains a total dead-time duration $t_{dead}$ (one or both edges, depending how you define the input), the energy lost per period is
$$E_{dead} \approx V\,I\,t_{dead},$$
and the average power is
$$P = E_{dead}\,f = V\,I\,t_{dead}\,f.$$
Equivalently, $P = V\,I\,d_{dead}$ where $d_{dead} = t_{dead}\,f$ is the dead-time duty. This is Watt's Law ($P = VI$) times the fraction of time the diode path is active — the dual of Diode Forward Loss applied only during blanking, not the whole conduction interval.
Caveats: real dead-time loss also includes reverse-recovery charge of the body diode and the extra hard-switching energy when the channel reclaims current; those terms are not in this formula.
History
Dead-time management became a first-class design topic with synchronous rectification and high-frequency half-bridges. Adaptive and predictive dead-time circuits in modern controllers exist largely to minimise this loss without risking shoot-through.
Related Concepts: Diode Forward Loss, Switching Loss, Synchronous Rectifier Loss, Conduction Loss, Watt's Law
Notes: Registry calculator dead-time-loss (unverified). Simple constant-$V$, constant-$I$ model.
Confirm whether your $t_{dead}$ is per edge or total per period so $t_{dead}\,f$ matches the true
blanking fraction.