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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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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Difference between equivalent output current & secondary RMS output current for flyback

What is difference between equivalent output current & secondary RMS output current for flyback? Assume Vout = 24V, Output power = 50W If we divide 50W/24V = 2.08A, this is called as ...
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High Voltage Generation With PWM

I am trying to design 20W output power supply with about 1KV output with 20mA current. Designs I am working on are, 1: But with this configuration ampere comes from the 12V DC supply goes too high ...
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Feedback diode question

In the following circuit the explanation of D1 says: “D1 connected across the input to output terminals is for protection and prevents the regulator from being reverse biased when the input supply ...
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28 views

SPICE model for Current PWM Controller

Is it possible if we run AC analysis using general current PMW controller & not the actual PWM controller specified by the vendor? Reason is because I asked the chip maker regarding their SPICE ...
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71 views

Understanding a chinese Ringing Choke Converter

I got a Chinese torch with a charger supposedly needed to charge the (removable) Li-Ion cell in it. The connection is direct to the unprotected cell, but the charger shows a spec of 4.2V +/- 0.5V. ...
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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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48 views

Misunderstanding document about leakage inductance in a flyback converter

I am currently reading a document about leakage inductance in a flyback converter from ON SEMICONDUCTOR . Here it is : https://pdfs.semanticscholar.org/c061/313303ee8c231b069be4f0d67d9e4cddcbf0.pdf (...
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37 views

How to calculate the power rating of zener diode for flyback protection?

I'm trying to calculate the power rating for the zener diode I'm using on my circuit for flyback protection. For example, if a flyback event occurs, the cathode of the zener diode is having a 30V ...
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62 views

Flyback converter role of diode in parallel to primary windings

I am trying hard to remember the role of the Diode labeled "D1" and marked with a red circle in the following schematic of the flyback converter below: Why do we need a diode there? I know the RLC ...
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48 views

FAN6754 flyback converter-overcurrent problem

I have a design 193V output voltage and 700mA current, but when the current drawn from output, the auxilary winding voltage fall down, and IC shut down PWM gate signal as you can see in the attachment ...
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22 views

Switching Frequency for Flyback Quasi Resonant Converter

As I know, the major difference between normal flyback converter & flyback quasi resonant converter is for flyback quasi resonant converter, the switching frequency is variable. This means that ...
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88 views

MOSFET Fails After Few Uses

I am attempting to use a N-Channel Logic Level MOSFET as a switch for a phone charger that runs on a 42V battery. I have a resistor circuit with an LDR that currently outputs 3.3v when LIT with a ...
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71 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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137 views

Inductive energy when 12V relay coil is released

Maybe this question is non-sense. If I have a commom 12V relay (12V, 400 ohms coil) WITHOUT having a flyback diode connected to it, and driven by a low-side protected transistor/IC like ZXMS6004FF (...
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Measure leakage inductance of flyback transformer with multiple secondary windings

I have a transformer consisting of one primary winding and 3 secondary windings. Now I want to measure the leakage inductance at the primary side, so I need to short the secondary windings. Most of ...
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42 views

Transformer auxiliary winding

I'm designing an AC-DC based on the UCC28780 active clamp flyback controller . I have a question about the primary auxiliary winding that is supposed to power the UCC28780 and the gate driver. My ...
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140 views

Flyback Transformer Connection & Construction

I don't understand how the coils are wound in a flyback transformer. Can someone post an image or explain. Basically I can understand all the calculation needed to design the flyback transformer. ...
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Trouble shooting ZVS driver

I've posted a few question on this forum about ZVF drivers and you all have been a big help and I'm hoping you can help me again. Forgive me if this is a bit long, I just want to be through.   Above ...
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124 views

Peak Power Vs Rated Power

I wish to understand more on power parameter needed to design the power supply of audio amplifier. Which power parameter should we use when designing the SMPS? Is it peak power or rated power? Lets ...
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How to control output voltage of DC to DC Step Up Fly Back?

I need to control the output voltage of Isolated Flyback Step-Up power supply using an MCU may be using DAC or PWM or via a digital pot, how to do this? spec Vin 5V - 8V Iout 40mA Vout max 100V ...
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54 views

Relay back emf cauisng my micro controller reset

I have a 5V 30A relay in my circuit. I made a PCB with all the connections to microcontroller and relay. At present I am using M7 smd diode as flyback diode. But problem is occuring if I switch on/off ...
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Simple Synchronous Rectification of Unidirectional Motor?

I'm trying to drive a high current, low voltage motor (24V 100A cont.). It previously used a very large and overpowered H-Bridge (16 FETs). The system only can rotate 1 direction, and is required to ...
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72 views

Flyback converter with dual outputs (12V / 5V)

I came across the following flyback converter circuit, which has a dual output (12V and 5V), but I am unable to figure out why the secondary windings are connected in series. Based on the datasheet ...
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51 views

Resistor ratings for inductor fly-back suppression

I am building a circuit for user to interface with relays, and I am trying to build a protection to the circuit against fly-back from the inductor coil of the relay. Since there is no specific relay ...
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What´s the purpose of this diode?

I'm trying to build my own relay board to use with a 3.3V controller. I found the schematic of the board, so I'll try to replicate it. I'm only having trouble understanding what's the purpose of the ...
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Help with flyback driver

I have been thinking of making a one 2n3055 transistor flyback driver. I have a question: can I substitute that transistor with the one I found in the same CRT TV which I got the transformer from? It'...
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Decrease Noise from DC motor?

I have a 9v battery pack and a small dc motor connected according to the diagram above. When the motor is disconnected my battery terminals have a peak-to-peak voltage of 800mv: However, during ...
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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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Line and load regulation testing of flyback converter

I have designed a flyback converter with dual outputs. I have the following queries for performing line & load regulation tests for the same. 1)To perform line regulation on 25 V rail, should I ...
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3answers
2k views

What the purpose of a diode in parallel with a power switch

I've come across a circuit that has a diode in parallel with a power switch that's controlling a BLDC motor circuit. I was told that it's a flyback diode to prevent voltage spikes from an inductive ...
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88 views

Series diode instead of a flyback one

My question is can I use a diode in series with a MOSFET, instead of pusing it as a flyback diode. simulate this circuit – Schematic created using CircuitLab
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92 views

Flyback Converter - Low Voltage High Current Output Problem

I have designed a digitally-adjustable 22W Flyback LED driver using FSL136MR which has a built-in 650V MOSFET. Here's the simplified schematic (Auxilliary supply regulators and some other components (...
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Using schottky diode near reverse breakdown region

I am currently using a 1N7070 schottky diode as the output rectifier for a flyback converter. The designed reverse blocking voltage is 70V. However, due to leakage elements I am seeing a transient ...
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flyback diode across the relay coil

so my question is regarding the diode used across the relay coil. My A level textbook (the section from the textbook is given below) says that its purpose is to protect the op-amp from a back emf ...
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68 views

Fly back converter- No output voltage at secondary winding

IC controller datasheet From my preliminary examination, I found that the VDD is fluctuating from 12 to 5v, My inference from the datasheet is that the High voltage current source is helping till it ...
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134 views

Transformer construction diagram

Contoller 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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MOSFET broke after attaching capacitor bank

I have a solenoid that has a coil resistance of \$0.3\Omega\$ and accelerates a steel projectile here. I've posted the schematics below. Normal Version that acts as a control The GPIO8 goes to 5V to ...
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560 views

Can the inductive kick be discharged without a freewheeling diode, in this example?

In literature we commonly see the use of a freewheel diode to protect the circuit against the inductive kick when the switch goes from closed to open (Fig 1). However, what would be the pros/cons of ...
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58 views

How to use a MOSFET driver directly to drive DC motors with PWM?

I need to control a DC motor runs at 9v with PWM signal 3.3V vpeak. I found MOSFET driver noninverting MCP1401. Can this MOSFET be used directly with a Back EMF diode (diode as usual across the ...
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What is the effect of doubling the airgap in a flyback converter?

If I understand correctly it would flatten the hysteresis curve. So it would allow to store more energy and it would also decrease the permeability of the core. Would it have another effect or will ...
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Are the topology of these flyback transformer for PoE the same?

I am looking for a transformer with the topology like 750310059 as shown below unfortunately the winding ratio and L value will not work with the PoE controller (MP8007) I am using for my design since ...
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64 views

Flyback Isolation Transformer Alternative

I am using the mEZS84801A as a reference design as shown below. It uses the MP8007 PoE chip. I have modified and tested this PoE system successfully and my camera be powered and it can run at 1 ...
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27 views

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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28 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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205 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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46 views

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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55 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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94 views

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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64 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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