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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Flyback diodes instead of a resistor in series with a capacitor in parallel with the inductor

Why do people use flyback diodes instead of a resistor in series with a capacitor in parallel with the inductor? Wouldn't it be just as good? It would also have the benefit of working with motors that ...
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63 views

How to drive flyback transformer with digital input?

I'm building a DSP PWM plasma speaker and using a push-pull to drive a TV flyback transformer: This circuit is not flyback but it works. However I'd like to properly drive the flyback transformer ...
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LT Spice simulation error: 'Time step too small'

Could someone get this up and running? Tried all the possibilities but it does not seem to work still. Here I am just trying to simulate the linked circuit here .. PMP7763 design reference
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high voltage isolated dc/dc converter watt selection problem

I am a beginner circuit developer. I used a TI WEBENCH POWER DESIGNER, to make all-in-one battery management system power design. POWER DESIGNER made a recommendation like the picture. Specifically, ...
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85 views

What are these soldering lines in following pcb?

I have a switch mode power supply (flyback) LED driver. I just wanted to extract its schematic but some straight parallel lines of soldering made me confused. Both layers of this pcb is presented in ...
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how this equation is obtained for calculating input capacitor of a fly back presented in UC3842 datasheet?

i know that it refers to stored energy formula for a capacitor according to voltage variations. but i dont have any idea about the specified part. where did this part come from? https://www.ti.com/lit/...
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input parallel capacitors for rectifier in flyback

When should we use multiple parallel capacitors instead of a single one in input rectifier topologies of switching converters such as flyback?? What are the advantages and disadvantages?? thankfully
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CCM flyback or DCM flyback

Recently, I have been working on a battery charger design based on a flyback DC-DC converter and I am curious about one thing: the flyback converter can work in CCM (continuous conduction mode) and ...
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controller for interleaved Flyback converter [closed]

I want to use the topology below and I want to know whether there is an IC for controlling it or not.
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Flyback power supply - 132 kHz radiated magnetic field issue

I request your expertise on a radiated magnetic field around 132 kHz (low frequency) on a Flyback power supply. I'm using the LNK3694 driver with a switching frequency around 66 kHz. Using a circular ...
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Schottky+Capacitor as flyback (snubber) diode

Since de-charged caps momentary act as short circuits, why not use schottky+capacitor (in series), as flywheel solution? don't they (at least theoretically) store fast energy transitions happening ...
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flyback compensation design

This is the control stage circuit of flyback, I want to use SIMPLIS to measure the bode plot to prove a theory is matched to simulation, I use Mathcad to draw the bode plot, the SIMPLIS result should ...
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Choosing the correct flyback diode

Is there a formula to figure out the appropriate flyback diode rating vs the current flowing through a relay? Maybe I'm asking the wrong question and it's only a voltage consideration.
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Self-Oscillating Flyback Converter

I am trying to design a self-oscillating flyback converter using the circuit below as a reference. I understand the ton time depends upon the values of Rst, Cf, and Rf and the switching mosfet, M1 ...
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What is the stuff hardened on an old flyback transformer?

I am restoring some vintage old Mac computers with the integrated CRT display. These have a flyback transformer on their analog board. Part of this device is some hardened brown/orange material at the ...
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Protection for arduino on two direction dc motor?

Basically I don't want to use an h bridge, I just want to protect my arduino when changing the direction of the motor. The code i use: ...
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optocoupler in flyback design

Recently, I am doing the flyback, when I design the control stage I have some questions: This is the optocoupler(PC817) I used and this figure is Current Transfer Ratio vs. Forward Current. There are ...
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34 views

Flyback Current Sense Resistor

Just want to make sure that I understand how the current sense resistor works in this circuit: Basically, we want to monitor the current through the primary side of the transformer, so we know when ...
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68 views

Calculating Efficiency of an SMPS

I was looking through previous posts and couldn't find anything that I was looking for on this topic. The waveform below is the input current to my system, which is also below. The question is, how do ...
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Flyback diode choice

I am curious about how to determine the turn ratio to get the minimum power loss. Assuming n=Np/Ns Vin=380, Vo=40, different turn ratios can get the same output because Vo =VinD/(n(1-D)). When the n ...
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164 views

flyback converter closed loop by using TL431

I have some things I can't understand when I use a TL431 to compensate for the flyback converter. This picture is from RICHTEK Feedback Control Design of Off-line Flyback Converter. According to this ...
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BJT Collector-Emitter Breakdown Voltage

I'm developing a flyback converter with the FT838NB1 IC, and I got some doubts about the Collector-Emitter breakdown voltage of the integrated NPN switching transistor. IC datasheet link: https://...
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SMPS Simulation Help

Finally bit the bullet and considered getting help with a simulation I'm looking to get right. Just a heads up, I have limited experience with SMPS simulation in both LTSpice and Multisim. The circuit ...
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31 views

Deviation in the switch current in a flyback converter

This is the current waveform of the switch and the Vds of the MOSFET. Ideally, the current should fall off in a normal fashion with the switch turns off. Here, the current fall stops and becomes flat ...
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Relay flyback protection

Is this the correct way to put a diode for flyback voltage protection to protect the infrared heater? And do I need to put a flyback protection for the Arduino pin or Vcc?
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Unused output of a flyback transformer

I have a flyback transformer. It has 2 outputs. I'm going to use one of them on a flyback converter. Should I leave the second output of the transformer unconnected or connect a load to it?
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How to calculate if flyback diode needs heatsink?

I'm designing a circuit for automotive use, where I control various kinds of inductive loads (motors, solenoids, etc) up to 20A (Máx). In the design i'm looking into using 2 SMD N channel MOSFET in ...
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57 views

How is the output voltage adjusted on this schematic?

This is a schematic of TI's reference design for a 65-W USB Type-C high density active clamp flyback with GaN (PMP21639), which can be found from this reference design page. The page claims that the ...
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flyback RCD design

the equation is used to calculate the power of RCD, I know this power is from leakage inductor the inductor energy can use 1/2Li^2 to express, but I don't know how to get this document equation. Can ...
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61 views

Inductor Polarity Reversal - Flyback Voltage

I have a question about how to intuitively think about the polarity reversal (flyback voltage) that occurs in an inductor when removed from a supply. Here is my understanding: When the switch is ...
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Transient Spice Simulation of Flyback Converter

I have created a simple model of a flyback converter using the PWM switch model by Vatche Vorperian. The simulation should be transient showing the switch events. In the picture below you see the ...
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Is there any problem if one of secondary windings is left floating in a flyback converter

Is there any problem if we leave one of the secondaries in a flyback converter floating? I have two secondaries: 24V & 18V. My application needs only 24V. What happens if the 18V winding is left ...
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JDS6600 signal generator - broken or normal?

I recently treated myself to a JDS6600-60M signal generator. It's a (very) cheap one but that's because electronics is just a hobby and not something I make money with or anything. The other day I ...
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DCM flyback converter

Recently,my research will focus on DCM flybck but I don't have any theory on DCM. I don't know how to start I want to model the small signal model. Do you guys can suggest me some paper or book let me ...
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61 views

Safely probing low voltage isolated DC/DC converter rails with an Oscilloscope

Lets say you have a flyback with a 20V dc input and 2 secondary side outputs, 5V and 12V. The 20V power in is provided by a benchtop power supply. What is the safe way to measure the input and output ...
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How do VAC ratings of flyback transformers translate to VDC ratings of flyback converters?

I am trying to design a 40-50W flyback converter but I am struggling to select an appropriately rated transformer. While most flyback transformers are rated in AC volts, plenty of flyback converters ...
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how to choose diode for PWM of high amperage solenoid?

I'm making a pulseable solenoid circuit via PWM at around 20 hz. THe solenoid is a heavy industrial type that pulls a whopping 18 amps. My snubber circuit gets hot and burns up as the current is too ...
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What could be the cause of high leakage inductance on my custom flyback transformer?

I've built a flyback transformer by hand for a circuit I am making and after shorting the secondary I have found my leakage inductance is very high. The primary inductance is around 2 mH, while the ...
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Can I use a back to back Zener as a flyback diode for an AC coil?

I am using the below AC electromagnet to switch on/off a pneumatic system. (It is a pneumatic actuator. I think that is what it is called.) The issue is, when I turn off (disconnect the switch) the ...
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61 views

DC solenoid overheat protection

I got 40 DC solenoids (12 V, 2 A) and each solenoid may be turned on for max. 5 seconds every couple of minutes or even more. Does this implementation require that an overheat protection should be ...
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No Current Flowing From 12v Solenoid Pins

I have recently designed my first PCB (forgive my poor understanding of electronics) and I'm having an issue with the pins that are supposed to be powering the 12v 2A solenoid. Everything works as ...
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63 views

Flyback transformer temperature rise - reasonable value

I had build an flyback converter based on UC3845 and some high voltage mosfet - it works fine, however I've got one problem with it. (but i'm not sure if that actually is a problem) The core for the ...
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Polarity independent flyback diode

I am currently building a controller for a slot car track. These work by placing a car on a track on two rails that supply the DC motor of the car with current. The track has an input of 20 V and has ...
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69 views

Energy of flyback with multiple outputs

Where does the additional energy for flyback with multiple outputs come from? It appears that I can add as many secondary outputs as I want, but the primary voltage is Vin, and the primary current can ...
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Trying to damp transformer output ringing of Flyback Converter when primary FET turns on

I have a flyback regulator with some output ringing spike problems. It is a 70-130V input with 6V regulated output and 75V unregulated output based on the LM5021 flyback IC. When going from no load to ...
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87 views

Simplest way to limit current from MCU pin

I'm trying to build a very simple flyback power supply capable of only about 1mA. The basis is to supply a PWM wave to a 1-1 sepic inductor (shielded coupled inductor). The problem is that it would ...
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Don't understand the current direction in a flyback diode circuit

I'm aware of that, in a circuit, inductive loads need to be protected with a flyback diode because if the circuit gets open the magnetic field will collapse forcing a current flow in the opposite ...
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Spark Gap Circuit Creating Unpredictable Current Spikes, What is Causing This?

I have recently been messing around with bug zapper / spark ignitor circuits as a way to learn more about high voltage electronics (This is my first foray into high voltage territory other than a few ...
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Secondary snubber in flyback converter

I am designing a flyback converter. Input = 180-240 Vac Output = 15 V, 0.4 A The secondary output seems to be oscillating when the diode is turns on. Oscillating frequency is around 27 MHz. I am using ...
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Voltage drop of free wheeling diode

I have two diodes one has an voltage drop of 0.2v while other has a drop of 0.55v in the same circuit. While I use the 0.55v drop diode for freewheeling (35 Amps diode) and the other diode remains in ...

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