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.

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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 ...
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17 votes
3 answers
13k views

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 ...
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25 votes
7 answers
44k views

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 ...
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14 votes
4 answers
3k views

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 ...
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3 votes
2 answers
10k views

How to use a flyback diode on a +/-12V motor

I've got a motor hooked up to +12V on one side and -12V on the other, being driven in both directions by a Motor controller (link). We were getting voltage spikes in the common ground after sending ...
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15 votes
4 answers
12k views

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 ...
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4 votes
2 answers
10k views

Do I need a Schottky diode as a flyback diode with PWM @ 30khz?

I use a regular diode (1N4007) as a flyback diode for a 250ma 5v fan. My transistor is a <...
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4 votes
2 answers
2k views

The flyback diode and its applications

So in an application like this: The coil of the motor will, by Lenz's Law, induce a very large negative voltage across its terminals (without the diode in place). Would this voltage be very negative ...
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2 votes
3 answers
904 views

Transformer for Flyback power supply

I am designing an isolated DC-DC converter with an input of 12V and an output of 5V@12A, at the moment, a flyback seems like the best option. I have read several books regarding the subject and I am ...
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9 votes
3 answers
4k views

Practical way to generate 1500V?

Designing the power supply for an radiation detector, need to supply up to 1500V at 2 mA from mains (170 Vdc). I've largely considered a flyback converter, but cannot find a flyback transformer with ...
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9 votes
1 answer
4k views

Use of Flyback Diodes

A flyback diode is commonly use to eliminate sudden voltage spike when current drop across an inductive load. These kind of diode can be found close to relay, motor or sometime MOSFET. simulate this ...
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0 votes
2 answers
19k views

SMPS schematic - transformer calculator

I found this schematic for a simple SMPS. I want to use it to build a 24V/2-3A power supply for a soldering station. How are the turns on the transformer calculated? For the primary I can use $$...
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10 votes
2 answers
8k views

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'...
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4 votes
1 answer
2k views

Flyback transformer core heating up

I am designing a discontinous conduction mode flyback converter, 100kHz using UC3844 IC with the spec. 220V,50Hz to 5V 5A. The issue is that after testing it for an hour, the transformer starts ...
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3 votes
1 answer
839 views

RMS Current & Average Current Questions

I understand that: For purely DC current with fixed DC voltage, the DC & RMS current value will be the same, means that the total power RMS & DC will be the same using Pdc = Idc x Vdc For ...
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2 votes
4 answers
6k views

On a relay coil, why use an MOV instead of flyback diode?

I briefly encountered a designer who wished to use an MOV instead of a flyback diode with a relay coil. I don't know much about the application, but why would you want to do that? The only reason I ...
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1 vote
2 answers
144 views

How can I make my flyback converter discharge immediately?

I'm using a flyback converter (220-100V to 19vdc) to power an electronics unit. But it doesn't discharge fast enough, this causes some relays to stay energised for a second or two after power supply ...
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6 votes
3 answers
827 views

Intermittent MCLR reset on PIC32 - involves switching electromagnets

I am working on a project that involves a lot of switching of electromagnets. The switching is controlled by a PIC32MX6xx-series microcontroller, which determines the required states of 80x 12 VDC ...
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2 votes
1 answer
304 views

Derive Parameters for Unknown Flyback Transformer

I am designing a 1.7 kV @ 6 mA flyback power supply. The issue I have is that it seems to be extremely difficult to find any type of high voltage flyback transformers for the design. I bought a cheap ...
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2 votes
0 answers
110 views

ESC (flyback diode)

i bulid ESC circuit based on TLP250 gate driver and IRF3205 MOSFET ,My motor works with 5V and consume about between 6 A and 8 A. the ESC circuit works well over month with software PWM frequency = ...
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1 vote
2 answers
215 views

Is a current transformer appropriate for a voltage step up flyback converter?

I am designing a flyback converter, input 170V output 1200V at 2mA. I am having trouble finding an appropriate transformer, most do not have a high enough N. Current transformers seem to have ranges ...
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0 votes
1 answer
718 views

Designing flyback converter - DZ snubber

In many examples for DZ snubber zener voltage is calculated from maximum MOSFET rating and some arbitrary choosen voltage leakage (usually a percentage of Vin). They don't even use leakage inductance (...
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16 votes
2 answers
3k views

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 ...
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5 votes
3 answers
4k views

Determine adequate speed of flyback diode for a relay

I have already looked at this question which looked like it would provide the answer: How to choose a flyback diode for a relay? But it didn't, so I also checked out these: https://electronics....
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10 votes
4 answers
4k views

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 "...
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2 votes
3 answers
5k views

How do flyback diodes (on an H-bridge) affect the motion of the motor?

I'm designing an H-bridge and one of the features I'd like to have is to allow the motor to keep it's momentum even when the H-bridge is off. Obviously flyback diodes are used in H-bridge designs to ...
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12 votes
2 answers
2k views

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 ...
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1 vote
3 answers
7k views

Selecting Flyback Diode for Inductive Load

I intend to run a 48V DC water pump which uses this motor (http://www.leeson.com/leeson/searchproduct.do?invoke=viewProductDetails&motorNo=098382.00&productType=0) through a solid-state relay ...
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11 votes
4 answers
2k views

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 ...
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3 votes
1 answer
3k views

H-Bridge freewheeling current

I'm building an H-Bridge to drive some motors I have around. I'd like to have a bridge that can be powered by different power sources, for example batteries or atx power supplies interchangeably. I'...
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3 votes
2 answers
2k views

How does a flyback diode work?

In a previous question I posted to the exchange I asked for some instructions on trying to variable speed control a motor. Someone suggested utilizing PWM from my Arduino to open and close a ...
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2 votes
1 answer
5k views

Flyback transformer pin connections

I took a flyback transformer out of an old CRT television. This is how it looks like on the top: And this is how it looks like on the bottom: http://i.imgur.com/8QYwPhQ.png W1 is a thick red wire ...
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1 vote
1 answer
5k views

Flyback transformer

Recently, I posted a question about a flyback transformer schematic I was having. (source: eleccircuit.com) If you didn't check the link, I was having problems with the frequency of the 555 timer as ...
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1 vote
2 answers
126 views

Voltage Mode Control

Since i started my training about design of DCDC I'm really confuse with control part. At school i learned that DutyDycle=Vout/Vin for Buck, and that's it. But now, i see that, Duty cycle is set ...
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1 vote
2 answers
3k views

H-Bridge flyback diode selection?

I am wanting to make a motor driver using a SN754410 Quadruple Half-H Driver IC. The SN754410 requires external flyback diodes. Here is an example circuit: My question is, how do I choose which ...
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0 votes
1 answer
362 views

Designing flyback converter - multiple isolated outputs

Can I treat 2 secondary coils with dual voltage output as one with double voltage for the purpose of calculations? This seems to be OK for all formulas based on output power as technically the ...
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9 votes
3 answers
7k views

Protecting microcontroller from inductive loads

I'm working on a project where I will be controlling a variety of loads (relay, solenoid, motor) from an Arduino and I'd like to make sure I build in enough protection for the microcontroller and ...
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7 votes
3 answers
2k views

In a flyback transformer with multiple windings, how are voltages controlled for different current loads?

This is the flyback transformer I will be referring to: Wurth 760871543 There are three output windings as follows, 24 V at 0.30 A, 5 V at 1.15 A, 14 V (unspecified but in mA range aux winding). ...
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3 votes
2 answers
6k views

What is the use of the capacitor in this relay circuit?

In the schematic below there is a relay coil driven by a 24V DC battery. In parallel to the coil there is a flyback diode and also a ceramic capacitor. What is the purpose of the capacitor in this ...
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3 votes
2 answers
2k views

Flyback transformer - ambiguous schematics and other issues

I'm currently using this schematic for a flyback transformer: (source: eleccircuit.com) As you can see, there's a big problem - neither the schematic, nor the website describing it, give the value ...
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2 votes
2 answers
2k views

Selecting a switching transistor for a 5V relay

I would like to use a STM32F microcontroller with 3.3V digital io pins which can deliver a max of 22mA to switch a transistor to then power a 5V relay which pulls 28mA. I'm not entirely sure what ...
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2 votes
2 answers
881 views

Flyback diode with 5V relay

I am having trouble choosing a flyback diode for my 5v relay. The switching current of the relay for 83Ohm is ~60mA. Goind through the parameter list of the RS catalog I selected: Maximum Continous ...
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2 votes
4 answers
854 views

Minimum specs before a flyback diode is needed for a relay?

Given a low power signal relay, 3V 140mW coil, controlled by a 2n3904 npn transistor, is a flyback diode required? At what point is a flyback diode needed for any given inductor? Is it total power, ...
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2 votes
1 answer
87 views

Misunderstanding document about leakage inductance in a flyback converter V2

I m back again on this document ! :D The document teaches me a lot of things and I think it will help me to better understand the losses across the switching components. I really appreciate if someone ...
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1 vote
1 answer
383 views

Transformer construction diagram

Controller datasheet Can anyone explain how the actual winding happens? The transformer is a shell type transformer used in a flyback circuit. The circuit is not working, and I'm suspecting the ...
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1 vote
2 answers
692 views

Atmega328p resets and crashes when powering up solenoids

I'm having problems with my PCB board based on atmega328p microcontroller (very similar to an Arduino standalone board). This is my current PCB schematics and Eagle board. SCHEMATICS UPDATED! I use ...
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1 vote
4 answers
541 views

Flyback Diodes For Inductive Loads With Long Wire Runs

I have a project that uses several high power DC solenoids (50 VDC) that will have ~10 feet of wire between them and the driver board. This is for pinball machines. These solenoids typically come with ...
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1 vote
2 answers
447 views

Can every voltage source accept fly-back diode's current?

A diode is used parallel to the motor (or inductive load) in order to prevent damage to the switch because of back-emf voltage. Now, that back-emf voltage actually produces a current and by using a ...
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0 votes
2 answers
140 views

Inductor Back EMF Direction Relative to Changing Current

I have spent a lot of time thinking about Faraday's law and common explanation as given on wikipedia does not sit well with me. I may be confused. My concern is entirely with the wording of this ...
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0 votes
1 answer
2k views

Flyback converter losses

i have been designing flyback converter of a 5Volt 5 ampere specifications output deriving from 220v ac mains. But i have been stuck at one point and can't seem to get out it. Efficiency is ...
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