Snubber Rc⚠ unverified
Electrical / Power Electronics · Compute the energy dissipated in an RC snubber per cycle
Parameters
| Input | Symbol | Unit | Default | Description |
|---|---|---|---|---|
| R | R | — | 1.0 | Snubber resistance |
| C | C | F | 1.0 | Snubber capacitance |
| V | V | V | 1.0 | Voltage across the snubber capacitor |
| Output | Symbol | Unit | Description |
|---|---|---|---|
| result | E | J | Energy dissipated per switching cycle, in joules (J) |
The science & history
Understanding the Parameters
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$C$ — sized to absorb leakage / stray energy or to slow $dv/dt$ across a switch. Larger $C$ softens the spike but stores (and usually dissipates) more energy each cycle.
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$V$ — voltage the snubber cap reaches (often clamp level or peak switch voltage). Energy scales as $V^2$.
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$R$ — sets damping and discharge time constant $\tau = RC$. Important: the registry formula $E = \tfrac12 C V^2$ does not use $R$. The resistor still matters physically (damping, peak current, where heat appears) but does not change stored energy at a given $C$ and $V$. The live calculator accepts $R$ labelled
dimensionless(should be ohm) yet ignores it in the equation — Track B should either use $R$ in a richer model or drop the unused input. -
$E$ — joules per charge-up. At switching frequency $f$, average loss $\approx E f$ if the energy is resistively dumped each cycle.
Derivation (Approaching a Proof)
Capacitor energy follows from $i = C\,dv/dt$ and power $p = v i$:
$$E = \int_0^{V} C v\,dv = \frac{1}{2} C V^2$$
(see Capacitor Energy). In a classic RC snubber across a switch, when the switch opens the capacitor charges through the circuit impedance; when the switch closes (or via a discharge path) the stored energy is dissipated in $R$. Peak stored energy is still $\tfrac12 C V_{peak}^2$ regardless of $R$; $R$ only shapes the current pulse and thermal distribution.
Design notes: $R$ is often chosen so $\tau = RC$ is a fraction of the switching period and damping is near critical for the parasitic $L$–$C$ ring. Undamped $C$ alone can ring with leakage inductance.
History
RC and RCD snubbers were standard protection for bipolar and early MOSFET hard-switched converters. Soft-switching and clamp circuits reduced reliance on dissipative snubbers, but the $\tfrac12 C V^2 f$ loss estimate remains the first check on whether a snubber will overheat.
Related Concepts: Capacitor Energy, Switching Loss, Inductor Stored Energy, Conduction Loss
Notes: Registry calculator snubber-rc (unverified). Formula is pure capacitor energy; $R$ is an
unused input (registry defect / incomplete model). Unit bug: $R$ labelled dimensionless —
should be ohm. Average power requires multiplying by $f$ outside this calculator.