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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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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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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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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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1answer
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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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782 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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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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4answers
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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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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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2answers
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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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1answer
1k 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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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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1answer
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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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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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2answers
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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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2answers
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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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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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3answers
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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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1answer
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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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2answers
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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 ...
2
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1answer
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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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2answers
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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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1answer
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Flyback transformer

Recently, I posted a question about a flyback transformer schematic I was having. this http://www.eleccircuit.com/wp-content/uploads/2007/10/fly-drv2.gif If you didn't check the link, I was having ...
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3answers
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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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3answers
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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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2answers
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Flyback transformer - ambiguous schematics and other issues

I'm currently using this http://www.eleccircuit.com/wp-content/uploads/2007/10/fly-drv2.gif schematic for a flyback transformer. As you can see, there's a big problem - neither the schematic, nor the ...
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2answers
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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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2answers
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PIC32 intermittent resets - revisited

This is a follow-up on a previous question that I have asked before, after making some changes as suggested through valuable inputs by other members, but with the problem persisting. In a nutshell, ...
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2answers
247 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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2answers
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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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2answers
185 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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1answer
940 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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1answer
109 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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Designing isolated flyback with multiple outputs

UPDATE: as suggested, I split this question into separate parts (links below). I left the last one here. It is so silly I am rather proud of it ;) UPDATE 2: it seems that breaking one post into ...
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0answers
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Designing flyback converter - Switch voltage drop

Switch voltage drop is often used in turn ratio calculations, however it is rarely specified in datasheets for converter ICs with built-in FETs. The closest I found is "Rds at Isw". Should I multiply ...
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1answer
306 views

modify 30W LED driver for variable current output

I have a typical flyback converter for an LED chip rated at 30W output. My goal is to change the brightness of the LEDs using a microcontroller. If I am not mistaken (please correct me if I am wrong)...
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1answer
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Designing flyback converter - wire selection

Some guides suggest using multiple very thin strands in parallel to "reduce the skin depth". Does this make any real difference? When I apply their formulas I end up with something like 14x31SWG, ...
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1answer
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Designing flyback converter - minimum primary turns

Calculating minimum primary turns: when formulas provided they are based on transformer specs that are not always available, like permeability, air gap etc. In many cases, however, it is assumed that ...
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1answer
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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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1answer
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flyback converter issue

When loading flyback converter with heavy load, waveforms are as expected. But with light load, waveforms are not as expected. What can be the reason ? Duty cycle is less than 50% so no slope ...