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 estimate NMOS Cds+Cdb capacitance from VDMOS Pspice/LTSpice model?

I'm designing a fly-back converter and in order to calculate the switching frequency I want to know a method or formula of how estimate the Cds+Cdb capacitance of NMOS switch using the Pspice ...
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23 views

Isolation voltage of a flyback transformer

How to calculate the isolation voltage of a planar flyback transformer? Or if there are any standards about it? I am designing a planar flyback transformer that need an isolation voltage of 1000V, ...
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117 views

Can a flyback diode work on the “ground” side of a transistor?

In every flyback diode setup I see, the relay coils are on the drain side of the transistor (if my terminology is wrong, I mean the top), so the flyback diode sends current back toward the power ...
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Flyback Converter Transformer Leakage Inductance

We are in the process of designing an inverter , in which designing a step up flyback converter is crucial. The problem, we initially faced was there were more step down transformers available than ...
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50 views

Sending flyback current to another inductor using crossed diodes

So, here is the context. We have two electromagnets (modeled as R1 and L1, and R2 and L2), their state is dictated by a microcontroller which sends PWM to Q1 and Q2. The signal sent to Q1 and Q2 is a ...
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My push-pull converter uses a flyback transformer with an air gap. How does changing air gap size affect the secondary output voltage?

My push-pull converter circuit uses a flyback transformer with an air gap. If that air gap is changed (increased), the primary inductance is decreased. How should I expect the secondary voltage and ...
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50 views

A flyback diode selection problem?

I have a motor that constantly rotates in reverse, the current is measured at 5-8A, and the selenium rectifier (Fwd: 1.2A Rev: 150V) is used.But it didn't take long to burn, what should I replace it ...
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Charger for a CDI ignition system [duplicate]

Maybe my first question Dc-Dc converter from 12v Input 400v Output was too broad for what I was actually trying to solve, which is why I am reformating my question. I want to charge a capacitor (C=0....
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110 views

Dc-Dc converter from 12v Input 400v Output

Maybe my first question Dc-Dc converter from 12v Input 400v Output was too broad for what I was actually trying to solve, which is why I am reformating my question. I want to charge a capacitor (C=0....
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42 views

One single fly-back diode or individual diodes for multiple relays?

Please see my crude drawing: My question is this. If I was to have multiple relays powered from the same rail, but have each one sinking via whatever to respective MCU pins, could I use option B as ...
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63 views

Understanding flyback transformer datasheet

Please see the below image of a flyback transformer I found. I see voltage/current outputs at each secondary winding. My question however is, how are these determined? I thought the output levels are ...
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71 views

P-Channel MOSFET reverse polarity protection on NMOS array chip

I'm trying to achieve reverse polarity protection for the TPL7404LADR chip which is basically an updated version of the ULN2003 darling transistor array. To do this I want to use a P Channel MOSFET ...
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21 views

power supply management IC switching transistor - flyback converter

I have a very simple question : is it better to have the switch (transistor) of the flyback converter, Inside the power supply management IC or outside it? or it depend on the application? Thank you ...
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58 views

Flyback Converter Switching MOSFET Breakdown

I am using a UC1845A to control the switching element MOSFET (FCB20N60F) which is used for a typical Flyback Converter circuit. MOSFET's drain is connected to transformer. Rarely MOSFET is not working ...
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55 views

Digital DC DC Converter for Power Control

I want to find a way to control a power device from a microcontroller. I must control a power device from the microcontroller, making the voltage to vary betwen 0 and 28 VDC, knowing that the power ...
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67 views

Topology choice for wide-output-voltage-range SMPS

I'm intending on building a off line (230VAC), 50W, isolated, constant-current switch mode power supply. This by itself is not a big challenge with the plethora of application notes and examples ...
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49 views

Increasing output current from ZVS driver

I bought the ZVS driver as shown in the picture below: After connecting a flyback transformer, I tried measuring the voltage and current at the output. The open circuit voltage is about 12KV. To ...
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103 views

Why would Discontinuous Conduction Mode be desirable for an LED driver?

I saw this press release where DCM was listed as a feature for a new Infineon driver chip. Source: led-professional.com I'm involved in LED driver design for Horticulture where DCM is undesirable....
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83 views

Sizing Flyback Diode

I'm working on a project to run a 12 volt 12 amp DC gearmotor via PWM output from a controller. I am using a Crydom solid state relay to power and motor and trying to figure out what diode is correct ...
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109 views

TV flyback transformer replacement without RC snubber?

I need to replace the flyback transformer on my Atari SC1224 CRT monitor. The flyback I removed from this monitor has a model number of Kf4825G, and has an RC snubber attached to it, which does not ...
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30 views

Flyback, primary inductance selection for wide output current changes

I would build my first flyback converter. Converter would be designed for 2A max and load device would draw about 100-200mA for most of the time with 1.8A peaks. Peaks would take a little longer so I ...
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70 views

Coupled inductor/pulse transformer for very tiny power supply

I need an isolated 24V 3mA supply to activate some optocoupler that will be read by some microcontroller. Its power supply will be the microcontroller's 5V. My first instinct was to use a flyback ...
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33 views

SMPS Transformer - Different Current Densities for Primary and Secondary

I've seen a design sheet of an isolated off-line 5V/2A flyback converter. In the "Calculating Wire Sizes" step the designer uses 4A/mm2 for primary and 10A/mm2 for secondary. This seems quite ...
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50 views

What is the purpose of a schottky/zener couple on an isolated flyback topology?

This isolated flyback topology has been generated by TI's webench. It's a classic schematics with a feedback going through an optoisolator. There are, however, two diodes connecting the switching ...
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119 views

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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82 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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126 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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244 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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41 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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137 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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61 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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44 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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148 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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88 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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107 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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231 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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166 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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662 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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93 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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139 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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81 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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185 views

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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262 views

Mazzilli flyback driver mosfets keep failing

I've been trying to build a high voltage generator consisting of a high-voltage transformer and a Cockroft-Walton multiplier. I have actually tried several different drivers to drive a high-voltage ...
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2answers
89 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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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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948 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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140 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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82 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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200 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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238 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 ...