Talk:Flyback diode

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Initial Comments[edit]

First page created in wikipedia! (Done some minor edits and corrections before, though)

Not great with diagrams. Stuck these in here (I think they're right) in the hopes that someone might come up with something better down the road.

This isn't a complete definition either, just one that can act as a starting point for a more elaborate treatment.

Hello Ryansturmer, I hav created an new drawing, which eliminates some errors in the former diagrams. Unfortunately it is an jpg. Feel free to create a better one (svg, png) from it to add it to your good explanation.--Ulfbastel 09:40, 5 September 2007 (UTC)
Dear Ulfbastel, thank you very much for improving this article.
Would it help (or just make things more confusing?) to graph *both* the voltage across the switch, *and* the voltage across the inductor? The 2 voltage graphs are very different from each other, causing many people to jump to the incorrect conclusion that one or the other "has errors". Perhaps it would be educational to point out that both are right.
The voltage spike across the switch (not the voltage spike across inductor) is usually the biggest problem in real circuits. So if you decide to draw only one voltage graph, this is the one I would prefer. Many transistor switches come with a built-in diode. Too often people incorrectly believe that diode can be used as the flyback diode in this kind of circuit. The "voltage across the switch" graph is the only one that clearly shows why they need *another* diode.
The graph of the voltage across the switch, on the other hand, is always positive.
-- (talk) 02:18, 17 January 2008 (UTC)

The figures in this article are wrong. when the switch opens, the voltage at point B will go largely positive, which means that the voltage in your chart should go largely negative! --Gabe Brisson —Preceding unsigned comment added by (talk) 23:54, 17 April 2008 (UTC)

I will be removing the images in this article and replacing them with actual digital oscilloscope waveforms. It's far simpler to look at the waveform and say "yeah the voltage across the inductor (solenoid) spiked to -300 V" and "with the diode it only spiked to -1 V". Voltage across the switch is irrelevant in my opinion since we only care when it's being switched. (talk) 17:25, 6 July 2010 (UTC)

Merge with Free Wheeling Diode[edit]

I think those articles are just about the same thing, whereas this one is a little bit more elaborate. --sdschulze (talk) 16:32, 12 May 2008 (UTC)

pls tell me the function of diode in series with inductor and switch like..[edit]

diode D in series with Induct. L then switch S? —Preceding unsigned comment added by (talk) 13:32, 12 February 2009 (UTC)

Wikipedia is not a message board for basic electronics questions, please use more appropriate means to obtain the answer to your question. --ArticCynda (talk) 22:23, 17 March 2010 (UTC)

Derivation section of article.[edit]

The derivation section of this article refers to a circuit and components that are never shown and identified. Someone who thoroughly understands the subject would have no problem imagining the circuit and component locations. But presumably the article is written for someone without thorough understanding. —Preceding unsigned comment added by WithGLEE (talkcontribs) 16:26, 18 August 2010 (UTC)

No infinite voltage[edit]

Flyback without a resistive path cannot create an infinite voltage. Radiation losses take over. — Preceding unsigned comment added by (talk) 21:49, 6 August 2012 (UTC)

Figure 2 diagram[edit]

The green arrow illustrating flow from the inductive kick is going in the wrong direction.

Purplephlogiston (talk) 01:56, 17 February 2014 (UTC)Purplephlogiston

Origin of "Flyback" term[edit]

I am fairly sure that the term "flyback" comes from the appearance of the phenomenon in cathode ray tube driver circuits. In the horizontal deflection circuit, as it commands the rapid "fly back" of the electron beam to start a new scan line, the magnetic deflection coils must quickly reverse their magnetic field. The energy from the coils, produces a large current pulse that is used in the high voltage "flyback" transformer to generate the anode voltage for the CRT.

Am I wrong on this origin?

Gwideman (talk) 17:15, 11 May 2014 (UTC)


The lead currently states:

A flyback diode (sometimes called a snubber diode, commutating diode, freewheeling diode, suppressor diode, suppression diode, clamp diode or catch diode) is a diode used to eliminate flyback, which is the sudden voltage spike seen across an inductive load when its supply voltage is suddenly reduced or removed.

The definition is too simple and the various names oven imply subtle differences.

A fluxed inductor will exhibit a flyback voltage spike when the current is interrupted. Diodes are often used in the presence of these spikes, but those diodes can have different purposes.

Some diode circuits are placed across the inductor; other circuits are placed across the switch. Some circuits are designed to quickly dissipate the inductive energy, some intend to keep the inductor current flowing, and others are designed to recover the stored energy. In still other circuits, the diode's function is not to suppress the flyback but rather isolate the capacitor which collected the inductive energy.

Snubbers and suppressors are usually focussed on protecting the switch. For mechanical contacts, their purpose is to prevent arcing. They often consist of more than just a diode.

Clamp diodes are usually associated more with setting a voltage rather than tackling the inductive spike. Clamp diodes are used with capacitors in logic switching circuits. In the flyback regulator context, the clamp diode can be used on the primary side to set the secondary output voltage. The low efficiency version uses a zener diode as a shunt regulator. The high efficiency version uses a clamp winding and returns the energy to the power supply. In the flyback switcher, the flyback is desired; the goal is not to snub or suppress or eliminate the flyback.

The typical reverse-biased diode across inductor can suppress the flyback, but it keeps the current flowing with little loss. The circuit is a problem when trying to turn the magnetic field off quickly. A zener or a diode-resistor combination will speed the field collapse.

Zener diodes can be used as suppressor diodes. In that circumstance, the energy is being removed quickly by dissipation.

Freewheeling diodes provide reverse current paths to keep the current going. In simple applications, it can be viewed as the same a flyback protection diode, but there are more subtle uses.[1] (See figure 5 where unidirectional IGBT with freewheel diode looks like bidirectional short.)

Glrx (talk) 03:16, 25 March 2016 (UTC)

Reference for catch diode.[edit]

@Glrx: The reference supplied was never offered to be a reference for all the terms offered in the article. It was clearly identified as an example of the use of 'catch doide' and in that it succeeded. I agree that references supporting the other terms are required. --Elektrik Fanne 13:49, 25 March 2016 (UTC)

My edit comment also stated that the reference was not authoritative.[2] It is just a text reference, there are no diagrams, and the statements cannot be verified. Some statements are also wrong: "Usually, a 'catch' diode would be placed across the inductive solenoid to safely dump power from the spike into the power supply’s ground return."[3] The issue is energy rather than power. The energy gets converted to heat in the diode and the solenoid rather than being dumped into the supply's ground return. There are other confusing remarks. Glrx (talk) 18:23, 25 March 2016 (UTC)

Incorrect information in article relating to direction of current flow[edit]

Current is the flow of electrons. Voltage is a difference of electrical charge, and is the reason that current flows in a specific direction (if at all). In DC current, the negative side of the battery has an abundance of electrons, giving it a negative charge, while the positive side of a battery has a lack of electrons, giving it a positive charge. When connected to a circuit, electrons flow from the negative side of the battery through the circuit to the positive side of the battery.

In the article, it says "Current is flowing "down" from the positive terminal of the voltage source to its negative terminal, through the inductor.", which is incorrect.[1]

Additionally, the green arrows in the illustrations indicating the direction of current flow are pointing in the wrong direction.

Regarding a diode, here is how I remember which direction a diode will allow current to flow: Current can flow in the opposite direction of the arrow, but current attempting to flow in the same direction as the arrow hits a wall and is stopped. (talk) 19:46, 15 December 2017 (UTC)


  1. ^ Louis E. Frenzel (July 2002). "WHICH WAY DOES CURRENT REALLY FLOW?". Nuts & Volts Magazine. Retrieved 15 December 2017. 

Yes, but the standard convention in electronics is to talk about current flowing from positive to negative regardless of which way the charged particles are actually flowing. (talk) 08:49, 11 July 2018 (UTC)