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Technology / Technical guide
Diode Reverse Recovery: Stored Charge & Commutation
A diode’s transition from forward conduction toward reverse blocking can involve more than an ideal instantaneous change of state. Some structures contain stored minority-carrier charge, while capacitive charge can create another transient current. The distinction prevents every reverse-current pulse from being assigned one universal mechanism.
Separate carrier recovery from capacitive charge movement.
A recovery time or charge value belongs to a device, waveform definition and operating condition; it is not a universal converter loss.
01 / State transition
Reverse blocking can follow a finite charge-removal process.
In an applicable forward-conducting pn-junction structure, excess carriers contribute to conduction.
In an applicable forward-conducting pn-junction structure, excess carriers contribute to conduction. When the electrical conditions drive a transition toward reverse bias, removing that stored charge can require a finite interval. Reverse current can flow during part of that process.
Nexperia’s diode handbook explains stored-charge recovery for the relevant structures. The description does not mean every diode has identical charge storage, nor that a diode becomes an ideal open circuit precisely at the first forward-current zero crossing.
02 / Device differences
A Schottky structure has a different carrier mechanism.
A majority-carrier Schottky structure does not have the same ideal minority-carrier storage mechanism as a conducting pn structure.
A majority-carrier Schottky structure does not have the same ideal minority-carrier storage mechanism as a conducting pn structure. It can still exchange capacitive charge when terminal voltage changes. A transient reverse current is therefore not automatically evidence of minority-carrier recovery.
Practical structures can add complexities beyond a simple ideal label. Device material, construction and operating condition matter. The page does not rank every silicon or SiC device as universally superior, or infer an installed diode from a converter’s marketing description.
03 / Charge definition
Pulse area and pulse time measure different things.
A stated reverse-recovery charge is obtained from a defined part of the current waveform under its specified convention.
A stated reverse-recovery charge is obtained from a defined part of the current waveform under its specified convention. Duration, peak reverse current and integrated charge are different quantities. The endpoint criterion and included contributions must accompany the name.
For an invented triangular pulse of reverse-current magnitude with 1 A peak and 2 µs base duration, its area is 1 µC. This is purely a geometrical calculation. It does not identify a device’s Qrr definition, measured current, allowed pulse or recovery-time rating.
04 / Commutation path
Another device can experience the transition’s effects.
During commutation, current changes between paths in a switching circuit.
During commutation, current changes between paths in a switching circuit. A diode’s changing current can interact with another semiconductor and the interconnection, influencing their waveforms. The diode’s individual transition is therefore not isolated from the complete switching cell.
The parasitic-inductance guide explains why current slew can create a dynamic voltage contribution. That relationship and recovery charge describe different parts of the same possible event; neither alone predicts the full circuit peak or dissipation.
05 / Loss boundary
Charge is not energy without a voltage-time relationship.
Coulombs measure transferred charge, whereas joules measure energy.
Coulombs measure transferred charge, whereas joules measure energy. An event-energy calculation involves the relevant voltage and current over the defined interval. Multiplying one charge value by an unspecified voltage cannot establish a universally applicable recovery-loss result.
Temperature, prior current and the transition conditions can influence a given device’s behaviour. The switching-loss guide separates event energy from its repetition into average power. A recovery time alone is not a complete converter-efficiency metric.
06 / Model scope
Diode categories do not disclose actual topology.
The rectifier-type guide distinguishes device and control roles.
The rectifier-type guide distinguishes device and control roles. This page instead explains one dynamic device mechanism. Neither determines the actual current paths in an unconfirmed MARSTON rectifier or converter.
No MARSTON diode technology, Qrr, recovery time, commutation speed or loss figure is assigned. The guide gives no replacement choice, double-pulse test, live waveform measurement or gate timing change; its triangular example illustrates units and integration only.
Related technical guides: Parasitic Inductance, Current Slew & Switching Overshoot · Inverter Dead Time: Commutation Interval & Waveform Error · Converter Instantaneous Power, Storage & Dissipation.
General background: Nexperia: carrier recovery, capacitive charge and waveform-definition boundaries. These references explain industry concepts; they are separate from the applicable MARSTON product and project documents.
Key concepts and conditions.
Read each quantity with its reference, units and stated conditions. A general relation does not establish a model-specific value.
| Concept / quantity | Meaning / relation | Conditions / limits |
|---|---|---|
| Carrier recovery | Removal of excess stored carriers | Applicable pn-junction conduction history. |
| Capacitive current | Charge exchange as voltage changes | Distinct from minority-carrier storage. |
| Recovery duration | Time under a stated endpoint convention | Not interchangeable with integrated charge. |
| Pulse charge | Integral of defined current in C | Waveform portion and sign convention are explicit. |
| Event energy | Integral of applicable voltage × current | Charge alone does not establish the complete loss. |
Engineering questions.
Do all diodes have the same stored-charge mechanism?
No. Their structures and operating conditions differ.
Can a Schottky device show transient reverse current?
Yes. Capacitive charge exchange remains possible without the same minority-carrier mechanism.
Are peak current and Qrr the same quantity?
No. One is an amplitude and the other is integrated charge.
Does the triangular 1 µC example identify a component rating?
No. It is an invented waveform-area calculation.
Can recovery affect another switch?
Yes. Commutation connects the device behaviour with other paths in the switching circuit.
Does this specify MARSTON diode type or a replacement?
No actual topology, device or operational procedure is assigned.
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