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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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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1 answer
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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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ACF flyback clamp current issue

I study a paper. There is a paper named "Design Consideration of MHz Active Clamp Flyback Converter with GaN Devices for Low Power Adapter Application" I have a question about why changing ...
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ZVS Flyback - GaN / Si

I am reading a datasheet of a ZVS flyback controller. In it are written the following lines: These lines explain that the controller is looking at the switching node of the primary MOSFET (drain) and ...
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Active clamp flyback clamp voltage calculation

Does anyone know how to calculate the clamp voltage? I read some papers and documents. Some of them use \$n \times Vo\$ to calculate the voltage, but when I use simulation to verify it I find the ...
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ACF flyback leakage inductor current problem

I try to use Basso's Free SIMPLIS document to run the active clamp flyback, and I try to use math to build the leakage indcuctor current waveform, but I got some problems. please see the below ...
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Active clamp flyback control questions

Can I use an SR flip to control an active clamp flyback control? I am not very sure which method is a good choice to control the Qaux and Q1. Could you please provide some suggestions?
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Why does the signal and power supply in my custom ESC breadboard become so noisy when the motor is rotating?

I am building a custom ESC to drive my BLDC motor. The motor spins in open loop and I want to debug the back-EMF detection circuit, but as soon as the motor spins, the signal line of the MCU (MCU uses ...
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Over-power protection circuit

About NCP1342, there is a protection circuit which was called Overpower Protection (on page 14). I am confused about why this is over-power protection. There is no circuit to do the multiplication, I ...
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Leakage Inductance Delays the Secondary Current

I read Basso's seminar, on Page 30, it is talking about Leakage Inductance Delays the Secondary Current. From the formula, we can get the Δt, but I am curious about one thing if we don't add the RCD ...
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Flyback Converter Valley Switching and QR mode

I watched TI's basic flyback video about the different control methods. and I am confused about some things, please see mine below questions. 1.) Valley Switching and QR, last time I ask a question ...
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Why can't flyback work when the duty cycle is greater than 0.5?

I read this document talking about flyback design, and I am curious about why, when the duty cycle is greater than 0.5, do we need to adjust the VOR to make sure the duty cycle is less than 0.5? What'...
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Flyback Frequency Foldback Mode (FFM) and Skip Mode

I would like to know why flyback needs to use Frequency Foldback Mode (FFM) and Skip Mode. I did some research but I don't understand the details of what I've read. Below is a figure that I found in ...
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ZCD SIMPLIS function block questions

I find the figure which used to do the ZCD circuit. please see the below figure. Does anyone know what's name of U7? I can't find this module in SIMPLIS. I would like to use this way to do the ZCD, ...
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How does this high voltage device work? [closed]

In Ali express, I found the following high voltage small generator for fun. One transistor, one single coil, 2 caps and 2 resistors (not sure if the leds are an essential part of the circuit). The ...
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Why are the vertical deflection coils in a CRT deflection yoke so different from the horizontal coils?

Looking at a typical raster CRT deflection yoke, there appear to be two very different pairs of coils. There is the pair on the inside that curves outwards, and the pair on the outside, which are ...
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LM311 ZCD out to LM555 reset

I have no background in electrical engineering other than curiosity; I'm more of a copycat. I have been trying to reproduce this schematic: I have searched the forum but don't see anything remotely ...
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Flybuck converter at high power

It is said that the flybuck topologies are cheaper than the flyback topologies. This is due to the fact that there is no need to have an optocoupler, the regulation is said to be simpler and probably ...
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Issues Choosing Flyback Transformer Specs & General Direction Help

I'm working on trying to figure out how to wind transformers myself and picking values etc. I currently have PQ26/25 Bobbins with PC95PQ26/25Z-12 ferrite cores (N95). I have some smaller E cores ...
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Salvaged magnetic materials for low performance 1MHz boost converter

I am wondering if I could modify a MT3608 boost module by winding a custom inductor / transformer for it, to generate a kV range voltage (at sub mA current). I'm thinking of replacing the 22uH ...
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Sparking when touching terminal on valve

In an effort to protect my relay I have added a diode for flyback protection. However when I touch the second terminal with power from the circuit I see a small spark. The source voltage is 12 volts, ...
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Why does slow-decay mode increase torque of brushed DC motor under PWM?

I am working on a project requiring high torque operation of a brushed 12V DC motor at low speed, plus software speed control from a microcontroller. PWM is the obvious choice here. My driver supports ...
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Why does a flyback converter in DCM mode have a different oscillation waveform at start and end of MOSFET turn off?

As seen from the waveform, when the MOSFET turns off, it has some high-frequency oscillations (shown in red) whereas before MOSFET turns on it has low-frequency oscillations. I have found that the ...
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Flyback: opto/Zener feedback circuit

Could someone explain the difference between these two flyback feedback circuits, and how the second circuit works? Any application note available would be a favor for me.
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Flyback Cross-Regulation

The document "Under the Hood of Flyback SMPS Designs", talks about the cross-regulation (on page 8). I have some questions about that. 1.) In what condition the primary voltage will ...
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Flyback leakage inductance effect

The document "Under the Hood of Flyback SMPS Designs", talks about the leakage inductance effect (on page 6). I have some questions about that. The below questions are from fig 5. Why high ...
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Flyback CCM right-half-plane-zero and control question

The document Under the Hood of Flyback SMPS Designs, talks about the RHPZ effect. I have some questions about that. 1.) Why do we need to design in the low input voltage and maximum current? 2.) I don'...
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