Questions tagged [flyback]

A flyback 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. A flyback transformer, also called a line output transformer, is a special type of electrical transformer designed to generate high voltage sawtooth signals at a relatively high frequency.

A flyback diode (sometimes called a snubber 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.

A flyback transformer (FBT), also called a line output transformer (LOPT), is a special type of electrical transformer. It was initially designed to generate high-voltage sawtooth signals at a relatively high frequency. In modern applications it is used extensively in switched-mode power supplies for both low-voltage (3 V) and high-voltage (over 10 kV) supplies.

664 questions
66
votes
4 answers

How to choose a flyback diode for a relay?

A diode is put in parallel with a relay coil (with opposite polarity) to prevent damage to other components when the relay is turned off. Here's an example schematic I found online: I'm planning on using a relay with a coil voltage of 5V and…
Nate
  • 4,496
  • 11
  • 56
  • 75
25
votes
7 answers

Correct use of Flyback or Snubber diode across Motor or Transistor?

From seeing a few schematics where the flyback or snubber diode has been placed across the transistor C-E terminals (Right Configuration), instead of what I typically seen as the the flyback being placed across the coil terminals (Left…
Passerby
  • 72,580
  • 7
  • 90
  • 202
18
votes
2 answers

How to calculate air gap in flyback transformer?

I’m designing (or at least trying to design) a flyback converter on LM3478. I chose the EFD20/10/7-3F3 core [1]. Using a PDF from Infineon [2] I calculated that I need a primary winding inductance of about 56µH and a turns ratio of 1:22.125. I have…
urhen
  • 411
  • 4
  • 8
17
votes
3 answers

Can a Zener diode that protects a switch against inductance when the switch opens, affect turn on speed of the valve when you close it again?

As you probably know, in the applications that the turn off speed of the solenoid valves are crucial, the simple flyback diode is not effective. Some people put a resistor in series with the flyback diode to alleviate the problem, but for real fast…
arudino.tyro
  • 694
  • 2
  • 10
  • 22
15
votes
4 answers

What are the effective power limitations of the flyback converter topology, and why?

Looking at several different isolated converter topologies, flyback looks like it's the simplest at first glance. There's only one switch, so there's only one driver, which (all other things being equal) should reduce the cost. However, at high…
Stephen Collings
  • 17,373
  • 17
  • 92
  • 180
15
votes
4 answers

Why is flyback air gap needed for energy storage?

Why do so many sources say something along the lines "since a flyback transformer stores energy, an air gap is needed"? I have seen this reasoning in textbooks and app notes. I thought air gaps cannot store energy and I thought also a flyback…
14
votes
4 answers

H-Bridge Fly-Back

Sorry if this question is a little long, but I though it prudent here to discuss the state-of-the art as I know it before asking the question. ISSUE When using an H-bridge to drive a bidirectional coil of a motor etc, I have always had my concerns…
Trevor_G
  • 46,364
  • 8
  • 68
  • 151
13
votes
4 answers

Why don't flyback diodes in H-bridge damage power supply?

I'm currently learning about driving a small DC motor (~ 5V). My research so far indicated that a L298N might be a good choice to quickly get something up and running. However, I'm also trying to understand what is exactly happening (i.e. the…
s1m0n
  • 231
  • 2
  • 5
12
votes
2 answers

Why do most flyback converters / LED drivers operate under 100 kHz?

Most of the LED drivers and flyback converters I have come across operate in the 60-100 kHz range. Is there any particular reason behind this - example - ferrite cores not being able to handle higher frequencies, etc.? Regular buck converters go up…
Whiskeyjack
  • 7,946
  • 8
  • 53
  • 91
12
votes
4 answers

What keeps the kickback voltage from reaching an infinite voltage?

We know that the voltage over an inductor is defined by the formula: \$V = L * \frac {di}{dt} \$ So in the case where the current flow is suddenly interrupted (like when a mechanical contact is opened), voltage spikes occur in real life. However,…
C K
  • 942
  • 8
  • 23
11
votes
5 answers

MOSFET broke after attaching capacitor bank

I have a solenoid that has a coil resistance of \$0.3\Omega\$ and accelerates a steel projectile here. I've posted the schematics below. Normal Version that acts as a control The GPIO8 goes to 5V to switch on the MOSFET and turn it off when the…
user229515
11
votes
2 answers

Flyback diodes issues and pull-in & hold current issues in this Relay circuit

Although this may be a basic question but I'm still struggling with it. In this schematic, two zener diodes D1 and D2 are connected back-to back across relay coil L1. The BVds = -30V for Q1. Can I use 15V(Vz = 15V) zeners for D1 and D2 instead of…
jacks
  • 363
  • 1
  • 4
  • 12
10
votes
2 answers

Is a balancing diode really necessary for the Balanced Boost converter?

Please pardon all of the information that precedes the question -- I didn't want you to actually have to go read the paper itself. This question is in two parts, but they are really equivalent, so it's really just one question. This question refers…
10
votes
2 answers

Do I need a flyback diode?

I have some experience using automotive relays and triggering them using the output from a two-way radio aux pin so I am aware of the need to add a diode in parallel with the coil to protect the radio's internal transitor when it is turned…
Chef Flambe
  • 1,011
  • 11
  • 22
10
votes
4 answers

What is a flyback?

Trying to find this answer is so difficult that I can't even tell whether What is the difference between a transformer and a coupled inductor? is asking the same thing. Some reading suggests that a "flyback" element (which may be called a "flyback…
feetwet
  • 2,322
  • 9
  • 31
  • 55
1
2 3
44 45