INDUSTRY COMPONENT

Flyback Diode

A flyback diode is a protection component used in relay and contactor driver circuits to suppress voltage spikes from inductive loads.

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Component Specifications

Definition
A flyback diode, also known as a freewheeling diode, snubber diode, or suppression diode, is a semiconductor device connected in reverse polarity across an inductive load (such as a relay coil or contactor coil) in a driver circuit. Its primary function is to provide a safe discharge path for the inductive energy stored in the coil when the driving current is suddenly interrupted, thereby preventing damaging voltage spikes (back-EMF) that could harm switching transistors, microcontrollers, or other sensitive electronic components.
Working Principle
When current flows through an inductive coil, it stores energy in a magnetic field. When the driving switch (e.g., transistor) opens, the sudden collapse of this magnetic field induces a high reverse voltage (back-EMF) across the coil. The flyback diode, connected in parallel with the coil but in reverse bias during normal operation, becomes forward-biased by this induced voltage. This creates a low-resistance path for the current to circulate through the diode and coil, allowing the stored energy to dissipate safely as heat over a short period, clamping the voltage spike to approximately the diode's forward voltage drop (typically 0.7-1.2V for silicon diodes).
Materials
Typically silicon (Si) for general-purpose applications; may use fast-recovery or Schottky diodes (silicon or gallium arsenide) for high-speed switching. Encapsulation: DO-41, DO-15, SMA, SMB packages with epoxy molding compound. Lead material: tinned copper.
Technical Parameters
ParameterTypical rangeNotes & selection driver
PackageDO-41 axial lead, SMA/SMB surface mount
Forward Voltage (VF)0.7V to 1.2V at rated current
Operating Temperature-55°C to +150°C
Peak Reverse Voltage (VRRM)50V to 1000V
Reverse Recovery Time (trr)<200ns for standard; <35ns for fast-recovery
Average Forward Current (IF(AV))1A to 3A (common for relay drivers)

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards
IEC 60747, JEDEC JESD22, ISO 16750-2

Parent Products

This component is used in the following industrial products

Relay/Contactor Driver Circuit

Electronic circuit that controls the switching of relays or contactors by providing appropriate voltage and current signals.

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Valve Driver Circuit

Electronic circuit that controls and drives valve actuators by converting control signals into appropriate power outputs.

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Engineering Analysis

Risks & Mitigation
  • Overheating due to continuous high-current circulation
  • Incorrect polarity installation causing short circuits
  • Slow reverse recovery time leading to voltage overshoot in high-speed circuits
  • Inadequate voltage rating causing diode breakdown
FMEA Triads
Trigger: Diode open circuit due to thermal stress or manufacturing defect
Failure: No protection path; back-EMF spikes damage driver transistor or IC
Mitigation: Use diodes with sufficient current rating, implement thermal management, add redundant diode in parallel for critical applications
Trigger: Diode short circuit from overvoltage or reverse polarity
Failure: Continuous conduction prevents relay operation; may overheat and damage circuit
Mitigation: Select diode with VRRM exceeding worst-case spike voltage, include polarity protection in PCB design, use fuses or current-limiting resistors
Trigger: Slow reverse recovery time in high-frequency switching
Failure: Extended conduction during switch-on causes shoot-through current, reducing efficiency and heating components
Mitigation: Select fast-recovery or Schottky diodes for switching frequencies above 10kHz

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance
Forward voltage tolerance ±10%; reverse leakage current <10µA at rated voltage
Test Method
I-V characteristic testing per IEC 60747-1; surge current testing per IEC 61000-4-5; thermal cycling per JESD22-A104

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation
Request current drawings, revision history, and a signed specification sheet.
Manufacturing capability
Verify equipment lists, process limits, capacity, and representative production evidence.
Inspection readiness
Confirm test methods, calibrated equipment, sampling plans, and traceable reports.
Supplier transparency
Check the legal entity, factory address, ownership, certifications, and direct contacts.

CNFX does not score or rank suppliers. Buyers must verify all claims and documents with the legal manufacturer before ordering.

Manufacturers of Flyback Diode

Manufacturer profiles associated with Flyback Diode.

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Frequently Asked Questions

Why is a flyback diode necessary in a relay driver circuit?

It prevents high voltage spikes (back-EMF) generated by the relay coil when de-energized from damaging the driving transistor or microcontroller, ensuring circuit longevity and reliability.

What happens if a flyback diode is installed in the wrong orientation?

If reverse-biased incorrectly, it will conduct during normal operation, causing a short circuit that can burn out the diode, driver, or power supply, and the circuit will fail to switch the relay properly.

Can a standard rectifier diode be used as a flyback diode?

Yes, for low-frequency switching (e.g., relays under 100Hz), a standard silicon rectifier diode (e.g., 1N400x series) is often sufficient. For high-frequency applications, fast-recovery or Schottky diodes are recommended to minimize switching losses.

Data Basis

Editorial classification, named public sources where available, and source-reviewed manufacturer records. See the editorial policy.

Preliminary Technical Classification
This page supports structured research, RFQ preparation, and supplier evaluation. It does not replace buyer-led supplier qualification, standards review, or technical approval.

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