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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Why is the air gap important in a flyback transformer?
Why is the air gap important in a flyback transformer?
How should we consider the equivalent circuit of a standard flyback transformer?
If we are going to wrap all the windings of transformer to the ...
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Why does this circuit stop breaking down with a stronger flyback diode?
On a PCBA, I am using a LED driver to drive a high-power LED. Here is the schematics:
V_IN = 16 V
R_OSC is set so that the gate of the MOSFET is controlled at 150 kHz
R_CS is set so that the current ...
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Flyback Synchronous rectification voltage-second balance control
Below figure is a flyback with Synchronous rectification.
there is a control method call voltage-second balance to use to control the Q2 switch.
I see this picture from internet, but I can't find it ...
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Choose right capacitors for flyback design
Would like to build an flyback inverter from 12V to 100V power 250W.
The 12V source is a rectified generator.
I'm struggeling with the right primary capacitor selection.
I calculated a ripple current ...
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Accurate output of Flyback converter
I am currently designing a isolated power supply based on a flyback converter with the MAX17690. I am using this ic because I cannot add feedback for my application. However, in the design the voltage ...
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Flyback transformer design process review
I was hoping I could get some verification on my flyback design process, and some questions answered.
The document I was following is from Fairchild, AN4137, and the steps below essentially outline ...
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Problem with flyback converter simulation
I am simulating a flyback converter working in CCM and I don't understand the results. According to volt-second balance, there's this well-known equation regarding flyback converters:
$$V_{\mathrm{in}}...
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DC-DC flyback transformer (SMT)
I am building a flyback DC-DC converter for a school project and am new to soldering and power electronics. I want to prototype the design on a breadboard first, now that I have the design equations ...
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Do all relays need a diode in parallel with the coil?
I often see circuits with relays and diodes like this:
Note the diode D1 in parallel with RLY1, at reverse polarity to the driving voltage V1. Per my research, the reason is that the relay coil is ...
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Reading voltage on flyback diode's anode
So I have this motor driver that I've already asked a couple dozen questions about that I have finally got around to building.
Here's the final schematic that I'm using:
It uses only N channel ...
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What are these four diodes doing?
I am working with a MC33186DH1 5A H-bridge IC.
It seems to simplify things quite a lot. The data sheet shows this simple schematic:
I found a break out board that mostly follows that design:
My ...
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What is the most used bi-polar output SMPS topology in gate driver isolation?
I have some questions concerning this schematic:
What is the topology used here? I am guessing flyback without feedback circuitry.
Why is the TPS40211 utilized here? Is it to provide more current? ...
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Could a vacuum-tube diode be used to snub a relay's coil?
I recently asked a question about inductor flyback in relay computers on Retrocomputing.SE. The preferred modern way to snub the inductive kick of a relay's coil is to add a flyback diode across the ...
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Driving an ignition coil with an IGBT circuit
I'm trying to drive an automotive wasted-spark ignition coil pack using the following circuit which is being driven by a high-side driver at 12 V at the input for a 3 ms dwell duration (IN1 & IN2)....
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Can flyback diodes damage DC brushed treadmill motors?
I am confused again. I just watched a recent YouTube video today where the host claims a flyback diode is not only unnecessary, but a bad idea for treadmill DC motors. He "demonstrates" it ...
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Is back-EMF an issue in a push-pull converter when both driving transistors are off?
For reference, I am talking about a conventional push-pull converter topology as discussed e.g. in this question.
Wikipedia has the following to say about transistor timing in the push-pull converter (...
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Pulse transformer for two switch flyback converter
I would like to design a pulse transformer for a two-switch flyback converter, with a 1:1:1 turn ratio (1 input 2 outputs).
I have troubles choosing the correct Volt-second and inductance.
My MOSFETs ...
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Can you change the polarity of a flyback transformer by swapping the output pins?
I am using the following flyback transformer from Pulse electronics:
I am typically used to seeing the dots reversed on the diagram. For this transformer, would current be flowing out of pins 5, 9 ...
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Controller design for a flyback converter for continuous and discontinuous modes of conduction
I am designing a flyback converter that has to operate in both continuous and discontinuous modes of operations.
I am stuck with the design of the controller design part.
Since the transfer functions ...
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Why doesn't SMPS controller VCC capacitor get fully charged to 310 V?
Most SMPS circuits have a startup circuit like the one in the schematic below:
The rectified 310 V goes through Rstartup1 and Rstartup2 to fill Cvcc to UVLO limit and the controller IC starts working....
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Forward recovery time - Which diodes are the fastest?
I am trying to design an RCD clamp of a flyback. In order to limit the overshoot attributed to the time the diode takes to conduct, I need a fast diode. (That information comes from Switching-Mode ...
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Check if flyback transformers are working
I recently got 3 flyback transformers for $21 at a store which are all different. They were most likely harvested from old TVs. However I am not sure if they are still functioning. I tried to test by ...
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MCU heating up in high-voltage circuit
I have been facing a major issue on my board. The board is about Vin that is 4.5 V, and Vout is 100 V using a flyback converter, H-bridge inverter high-voltage mux.
STM32 is used for multiple MOSFET ...
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Is a snubber diode the correct solution? Preventing overload protection faults
I have been troubleshooting a strange problem for a while now and I think I've settled on the right solution.
I have an off-the-shelf 12v lithium-ion battery (12v 10A max output) with integrated over-...
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Question about PM brushed DC motor freewheeling
As a hobby project, I want to mount a permanent magnet brushed DC motor on a bike.
I've already asked a question about the PWM and half-bridge driving circuit for the motor and got a very useful reply....
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PWM converters: operation over and under 50% duty cycle
I have a DC/DC Flyback converter based on the UC2844 regulator and I would like to use other regulators of the same UCx84x family.
Reading the datasheet, I found that there are regulators that can ...
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Understanding back EMF current in DC
I am trying to make a kicker solenoid. My circuit is:
12 V battery connected to DC step-up booster 300 V
diode A10A. The diode is rated for 10 A and 1000 V.
thyristor BTW69-1200 with external ...
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Controlling a solenoid valve with a relay and a 18650 battery
I have a 12 V 18 W (1.5 A) solenoid valve that I want to control valve with an RF relay.
I use a Sony 18650 li-on battery to power this system. A 1S 10 A BMS unit is protecting the battery.
Even ...
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Trying to protect MOSFET from motor flyback
I am trying to protect a MOSFET from motor flyback with two Schottky diodes. There is a DPDT reversal switch to reverse the direction of the motor. Is the included circuit accurate?
MOSFET: 55 V, 49 ...
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What's Blanking time in Flyback
I read some documents (see below) about the blanking time of flyback. Both are talking about it, but I don't know exactly what this function does. I also tried to get an explanation from the datasheet,...
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TVS diode across motor leads failing short. How to protect MOSFET from motor back EMF?
I am having an issue with a TVS diode failing short on 3 out of 7 units. The intended purpose of putting this diode across the motor leads was to protect the MOSFET and relay from the motor's back EMF....
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No output voltage on flyback power supply transformer
I'm attempting to repair (with not much success) a flyback power supply circuit. The circuit takes input of 240v AC and has output rails, from a flyback transformer, for 5v and 12v DC. I have traced ...
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Determining \$Z_N \$ and \$Z_D \$ for a flyback converter
According to page 448 of "Fundamentals of Power Electronics" (pdf) the small signal model of a flyback converter is
In my case \$R_\text{on} = 0 \: \Omega\$ so it should be ignored. Now, to ...
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How should I wire the flyback diode on this relay?
Is the diode soldered facing to the left or to the right? (The same image is found on page 3 of the datasheet linked below.)
Some information:
The relay is part of a "soft-start" circuit; ...
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Lead-acid battery + MOSFET-based spot welder keeps frying MOSFETs and drivers
Here is an imgur link with relevant pictures and schematics.
Here is a link to an example on YouTube of one of the spot welders I'm trying to emulate.
I'm trying to build a spot welder following some ...
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What is the frequency at the input of the bulk capacitor in a flyback?
I am under the impression that the output frequency of the bulk capacitor will be the same as the switching frequency of the PWM chip. The input however I am a bit confused about, because if it is ...
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Do pumps and motors also need flyback diodes?
So my question is simple, we know that its good practice to use flyback diodes in solenoid valves and relays, but do pumps and motors also need them as they also have coils?
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How pick/calculate flyback diode current value?
Say I have a design that switches a 5A coil using a MOSFET.
In order to protect the MOSFET, I place a flyback diode parallel over the coil.
If the coil is switched off, a back EMF current will flow ...
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Driving a motor with a high-side PMOS switch. Does it need a flyback diode?
I'm looking to use a high-side PMOS switch to control a brushed DC motor. Is it necessary to add a flyback diode for this implementation? And if so, how/where exactly should it be added?
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Is this the correct way to use a relay and diode in this system?
I've no experience with electrical work so everything I've learned about this circuit has been cobbled together from youtube videos and subreddits.
I have a water pump in my back garden to pump water ...
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EMI standards just for power on/off
I know the FCC has EMI/EMC maximums for connected emissions into the AC power cable while electronics are on.
But, are there FCC requirements on the brief connected emissions/bursts when the ...
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How do I clean up the static in this musical flyback transformer?
So I built this musical flyback transformer off of Franzoli Electrctronics schematic,
https://franzolielectronics.com/easy-flyback-i/.
I had to go the through hole method and it works. However, the ...
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Two different topologies for flyback
I heard someone say the QR (quasi-resonant) flyback has a smaller primary side current than an ACF (active-clamp flyback) under the same circumstances. Is this correct?
I tried to search for ...
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Why do you need the bottom flyback diodes in a BLDC motor circuit?
In a BLDC motor drive circuit:
What is the point of the bottom three flyback diodes on each of these MOSFETs?
This is how I imagine the current is flowing when the MOSFETs are on:
Once the inductors ...
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Why does the arc stop few seconds of running?
I am running a CRT Flyback transformer using a 36W/40W Philips Ballast. My primary winding is of 20 turns. I do get a nice arc. But it stops after a few seconds. To strike the arc again I have to ...
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Reflected output voltage (VOR) in a transformer
What, exactly, does VOR mean, and how does it affect the number of turns, output voltage and controlling circuit in a flyback transformer?
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Appropriate flyback transformer to boost 5V to 140 V
I have an LED string that requires 140V that I plan to use in a circuit that has a 5V power supply (capable of up to 4A of current.) The LEDS glow at an acceptable brightness with as little as 50mA. ...
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DK1203 Flyback SMPS - How does it work?
Has anyone come across a DK1203 SMPS like this? I've come across ICs like the FSGN300N that have a startup pin and aux coil to supply the IC. How would the self-supply circuit in the DK1203 work? In ...
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Driving flyback transformer with variable frequency
Is it good idea/practice to drive a flyback transformer using two MOSFETs, similar to common ZVS drivers, but instead by controlling the gates without depending on resonance and LC tank calculations?
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QR flyback ZCD detect circuit question
About QR flyback document from Onsemi, please see page 5.
there is a circuit called ZCD detect.
and I have one questions about this circuit.
Please see the red sign, why the waveform will be shifted ...
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