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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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Advice on choosing components for a flyback arrangement, for switching inductive loads fast

I have a bank of x6 MOSFETs (SUG90090E) connected in parallel, which I am using to switch a current of maximum 30A through a coil (resistance 1R and inductance 1mH), and am looking for some general ...
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55 views

Relay coil suppression

I am following this application note for relay coil suppression. It suggests a diode and zener in series to be used for better contact life. I am using Panasonic ADW1212HLW relay. It's a 2 coil ...
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38 views

Choosing the right (flyback) diode to stop contacts (points) arcing (sparking) on solenoid (relay)

Clock with a simple electric remontoire, consisting of a solenoid, with an arm, that kicks back the main spring, rewinding it. Solenoid coil data: operating voltage: 12V-15V measured resistance: ...
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56 views

Buck-Boost Controller Arduino Nano vs STM32

I have 900W (150W*6Panels) solar panels and 12V inverter (1000VA) which have inbuilt PWM solar charge controller. The distance between pannels and inverter is around >10m and the wires are 6 sq mm ...
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24 views

SMPS topology for combination of current controlled rail and fixed voltage rail

I'm looking at designing a LED driving power supply that can interface with a universal AC main input (~90VAC-260VAC) and produce 2 rails at the output; one a current controlled rail, and the other a ...
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52 views

Reducing AC/DC adapter (SMPS) output voltage

I have a AC/DC adapter P-1650-22 (used to power a notebook) laying around. I would like to use it for other purposes, i.e. as a constant voltage source for LEDs. The problem is, that the output ...
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55 views

Row Column Matrix Problem with Flyback Diodes

So I had a simple row column matrix which I am driving with mosfets to power solenoid locks like this: GC is ground via 1.5k resistor C is 24V via 1.5k resistor And these are the connectors: ...
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36 views

Coil causing spike and circuit reset?

I built a circuit that pulses a 50-ohm electromagnet when a 'trigger' magnet passes over a hall-effect sensor. This circuit swings a pendulum and simultaneously plays an audio clip as long as the 555 ...
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40 views

SMPS Flyback transformer selection

I am trying to design a SMPS for a project (I have to make a custom one for integration purpose). This SMPS have universal input (85-265V AC at 50 or 60 Hz) and an output of ideally 53V (but it can ...
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52 views

Hybrid Boost-Flyback Stability Issue

I tried to design a step up SMPS to create ~200-300v from a 24V input with an expected power of ~12W max. Since the project is for a hobby, I chose to attempt a hybrid boost-flyback converter to get ...
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74 views

Flyback discontinuous mode, double voltage over the switch

Considering the following simplified flyback schematic. Which has the following voltage current graphs Why is there 2*Vin over the switch when the switch is turned off? And why is that change to Vin ...
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185 views

How to safely generate 200V from low voltage supply

Unfortunately, this post requires quite a bit of background if it's going to be useful to anybody (including me). I have been trying to build a relatively high voltage power converter for part of my ...
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79 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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226 views

Best way to protect a MOSFET from overcurrent

I'm trying to build the circuit in picture above. unfortunately the load on high side of the step up transformer is unpredictable and the input impedance of transformer is very low so I'm guessing the ...
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2answers
63 views

Diode package selection in flyback circuit for a relay

I intend to use the following flyback circuit for my relays (third circuit circled in red): Here are my relay specs: 1) G6DN - 5 A 250 VAC contact rating Coil voltage = 5VDC Coil resistance = 227 ...
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62 views

Flyback converter primary and secondary sides power calculation

The problem is as below. Input DC voltage is at 12V, transformer inductances are: Lp = 60uH, Ls = 240uH, switching behaviour is controlled by a single NMOS with switching frequency at 60kHz. For ...
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65 views

Rectifier, Flyback vs Transformer, Rectifier, Buck

I've just finished doing my first off-line flyback, which proved a success. A simple block diagram is as follows: I know this topology seems common now, for example it is used in Apple USB Charger ...
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flyback spike elimination

I have a circuit that is switching a transformer primary winding from 15 volts to ground, through an N-channel MOSFET at 50 kHz. I was seeing occasional field failures and found that every time the ...
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Mazzilli flyback driver mosfets keep failing

I've been trying to build a high voltage generator consisting of a high-voltage transformer and a Crockoft-Walton multiplier. I have actually tried several different drivers to drive a high-voltage ...
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61 views

How does flyback converter with two MOSFETs work?

This is the schematic. Both switches are in phase (On and Off at the same times). When both SW are On, current flows through primary transformer coil, entering from the top side of it, and leaving ...
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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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551 views

Process for Making a Flyback Transformer

I am looking to make my own flyback transformer that can put out a DC voltage from 0 to -40 kV DC and a power of 400 watts, as most commercial flybacks do not go up to the specified power and ...
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91 views

Maximum voltage and current input of this circuit?

I am looking to assemble a power supply with an output of roughly 600 watts. One of the components required for such an apparatus is a 40 kVDC, 20 mA flyback transformer that I managed to find and ...
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57 views

Proper Flyback Current Protection Circuit for Variable Voltage Solenoid Driver

I am using a darlington buffered op-amp to drive a solenoid motor at variable voltages (for variable speeds of actuation). Here is my circuit as it is now: I am wondering which of the two flyback ...
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157 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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126 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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222 views

Are bypass caps reason why uC don't have flyback diode across ferrite bead in the sample schematics?

Often the IC datasheet recommends putting a ferrite bead before AVCC pin. First I started wondering if I don't need a flyback diode but than I realized that capacitor is probably able to absorb the ...
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47 views

Flyback from ignition transformer?

I'm using a 10kv ignition transformer for a jacob's ladder. It works great! Currently though I've only tested it on its own circuit. But I would like to have this thing running in my lab. (I know not ...
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101 views

Why Does Flyback Current Destroy Darlington Buffered Op-Amp?

I am working on a project where I'd like to deliver variable DC control voltages to a continuous solenoid motor in order to achieve different velocities of actuation. To buffer my DC control voltage ...
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4answers
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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 ...
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1answer
178 views

How to calculate secondary RMS current of each winding in multiplre output flyback converter?

As I am designing multiple output flyback converter and I have confusion in selection of wire gauge of the secondary winding. There are 4 secondary windings and one bias winding. Mode of operation is ...
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190 views

Fly-Back converter in Proteus

I have been having this problem since I started to design my Fly-Back type voltage converter, and it is that it is throwing me a time step too small error, and I tried to solve it by configuring the ...
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103 views

55-650V to 5V DC/DC convertor design

For an application I am building I need a custom DC/DC convertor that can convert a voltage ranging from 60V-600V to a contant voltage of around 5V. Using the TI Webench with the paramaters Vin_min = ...
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1answer
871 views

Flyback diode is acting weird

I have the following schematic: Vcc can vary from 12 to 15 volts, so the design was intended to switch on the relay through a MOSFET when the input voltage is over 13.4 volts. The actual Zener I've ...
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81 views

Flyback smps or floating buck converter?

I want to drive a 180V/1A string leds from 220VAC. Which topology should I use: flyback smps (with transformer) or, floating buck step down converter? I know that buck converter will be not ...
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210 views

Reflected voltage in DCM flyback

While designing converter I got to the point of calculating secondary coil. Most guides have these equations for it: Wait a second, didn't I calculate Nps already at the very beginning? Yes, I did! ...
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1answer
76 views

Correct formula for primary inductance

In just about every design guide I saw, the formula for primary inductance of flyback is: However in "SMPS Design" by Pressman/Billings the equation for CCM is: To bring second equation to the first ...
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327 views

Adjustable current limiting in flyback converter using TL431

I'm building a SMPS and I would like to have a current limiting feature on the output. I'm trying to make a feedback loop using TL431, shunt resistor, optocoupler and a potentiometer, but no luck this ...
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82 views

Designing flyback converter - Current ripple and turns ratio

This would be a long question, I apologize in advance. In the process of learning about flyback I've calculated same LT8302-based converter using five methods. Four from generic (as in: not related ...
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1answer
122 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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1answer
50 views

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
52 views

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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92 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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46 views

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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67 views

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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1answer
161 views

Questions about Tesla coil (SGTC), spark gap and resonance

If I use a step up transformer (flyback for example) for primary to boost the voltage to 10 kV which (flyback) has a resonant frequency around 30-50 kHz, and the primary coil has a res. freq. of 500 ...
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Flyback Converter with multiple DC outputs

I am trying to understand how (step up) Flyback Converters work, since I need to design one myself. I am not at all new to electronics and I understand the fundamentals behind them, but I am totally ...
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425 views

Extremely high current in super simple SMPS Flyback

I'm building an SMPS in flyback topology. In order to do it, I use UC3845CB IC. In first step, I wanted to see if it even works at all with pulse transformer that I bought, made especially for flyback ...
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1answer
65 views

VNH5019A Flyback issue on custom PCB

I have a custom high power PCB I recently designed and am currently testing. It is designed to use 2 linear actuators link. I am using a VNH6019A H-bridge to control them. They operate simply as -12v ...
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113 views

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 ...