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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 ...

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62 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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22 views

Flyback converter boosting operation failure

I have designed a 20W flyback converter, in the open loop operation, when the duty ratio is below 0.5 it works perfectly (hardware not simulation). But when I go above 0.5 , that is in boosting mode, ...
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3answers
87 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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2answers
48 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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24 views

Inductive spikes and noise in a hand prosthesis circuit

I am designing a circuit for a hand prosthesis. The main part of it is as follows (connections via pcb): Since it is meant to be as robust as possible, while keeping it low-cost and affordable (thus ...
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1answer
29 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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2answers
53 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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2answers
117 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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77 views

Flyback Transformer Output Voltage Testing

Recently, I purchased an electrostatic precipitator power supply as a means of providing a high voltage DC output (-5 - -40 kV DC). The power supply is rated to supply 60 kV DC at 600 W and can be ...
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87 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 Crockoft-Walton multiplier. I have actually tried several different drivers to drive a high-voltage ...
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2answers
54 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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4answers
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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303 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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43 views

Calculating capacitance for a ripple-smoothing device

I recently purchased a flyback-based power supply 1 with the claimed capability of supplying (-5) to (-60) kV DC and 10 mA (adjustable speed). However, the output seems to be relatively unstable for ...
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1answer
72 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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1answer
49 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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2answers
125 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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4answers
90 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 ...
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1answer
211 views

Are bypass caps reason why uC don't have flyback diode across ferrite bead in the sample schematics?

Often the IC datasheet recommends putting a ferrite bead before AVCC pin. First I started wondering if I don't need a flyback diode but than I realized that capacitor is probably able to absorb the ...
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1answer
40 views

Flyback from ignition transformer?

I'm using a 10kv ignition transformer for a jacob's ladder. It works great! Currently though I've only tested it on its own circuit. But I would like to have this thing running in my lab. (I know not ...
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3answers
80 views

Why Does Flyback Current Destroy Darlington Buffered Op-Amp?

I am working on a project where I'd like to deliver variable DC control voltages to a continuous solenoid motor in order to achieve different velocities of actuation. To buffer my DC control voltage ...
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4answers
1k views

Why don't flyback diodes in H-bridge damage power supply?

I'm currently learning about driving a small DC motor (~ 5V). My research so far indicated that a L298N might be a good choice to quickly get something up and running. However, I'm also trying to ...
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1answer
115 views

How to calculate secondary RMS current of each winding in multiplre output flyback converter?

As I am designing multiple output flyback converter and I have confusion in selection of wire gauge of the secondary winding. There are 4 secondary windings and one bias winding. Mode of operation is ...
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101 views

Fly-Back converter in Proteus

I have been having this problem since I started to design my Fly-Back type voltage converter, and it is that it is throwing me a time step too small error, and I tried to solve it by configuring the ...
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0answers
94 views

55-650V to 5V DC/DC convertor design

For an application I am building I need a custom DC/DC convertor that can convert a voltage ranging from 60V-600V to a contant voltage of around 5V. Using the TI Webench with the paramaters Vin_min = ...
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1answer
858 views

Flyback diode is acting weird

I have the following schematic: Vcc can vary from 12 to 15 volts, so the design was intended to switch on the relay through a MOSFET when the input voltage is over 13.4 volts. The actual Zener I've ...
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1answer
70 views

Flyback smps or floating buck converter?

I want to drive a 180V/1A string leds from 220VAC. Which topology should I use: flyback smps (with transformer) or, floating buck step down converter? I know that buck converter will be not ...
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127 views

Reflected voltage in DCM flyback

While designing converter I got to the point of calculating secondary coil. Most guides have these equations for it: Wait a second, didn't I calculate Nps already at the very beginning? Yes, I did! ...
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1answer
73 views

Correct formula for primary inductance

In just about every design guide I saw, the formula for primary inductance of flyback is: However in "SMPS Design" by Pressman/Billings the equation for CCM is: To bring second equation to the first ...
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1answer
232 views

Adjustable current limiting in flyback converter using TL431

I'm building a SMPS and I would like to have a current limiting feature on the output. I'm trying to make a feedback loop using TL431, shunt resistor, optocoupler and a potentiometer, but no luck this ...
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0answers
74 views

Designing flyback converter - Current ripple and turns ratio

This would be a long question, I apologize in advance. In the process of learning about flyback I've calculated same LT8302-based converter using five methods. Four from generic (as in: not related ...
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1answer
98 views

Designing flyback converter - DZ snubber

In many examples for DZ snubber zener voltage is calculated from maximum MOSFET rating and some arbitrary choosen voltage leakage (usually a percentage of Vin). They don't even use leakage inductance (...
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1answer
45 views

Designing flyback converter - wire selection

Some guides suggest using multiple very thin strands in parallel to "reduce the skin depth". Does this make any real difference? When I apply their formulas I end up with something like 14x31SWG, ...
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1answer
49 views

Designing flyback converter - minimum primary turns

Calculating minimum primary turns: when formulas provided they are based on transformer specs that are not always available, like permeability, air gap etc. In many cases, however, it is assumed that ...
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1answer
79 views

Designing flyback converter - multiple isolated outputs

Can I treat 2 secondary coils with dual voltage output as one with double voltage for the purpose of calculations? This seems to be OK for all formulas based on output power as technically the ...
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0answers
45 views

Designing flyback converter - Switch voltage drop

Switch voltage drop is often used in turn ratio calculations, however it is rarely specified in datasheets for converter ICs with built-in FETs. The closest I found is "Rds at Isw". Should I multiply ...
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66 views

Designing isolated flyback with multiple outputs

UPDATE: as suggested, I split this question into separate parts (links below). I left the last one here. It is so silly I am rather proud of it ;) UPDATE 2: it seems that breaking one post into ...
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1answer
104 views

Questions about Tesla coil (SGTC), spark gap and resonance

If I use a step up transformer (flyback for example) for primary to boost the voltage to 10 kV which (flyback) has a resonant frequency around 30-50 kHz, and the primary coil has a res. freq. of 500 ...
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0answers
60 views

Flyback Converter with multiple DC outputs

I am trying to understand how (step up) Flyback Converters work, since I need to design one myself. I am not at all new to electronics and I understand the fundamentals behind them, but I am totally ...
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2answers
333 views

Extremely high current in super simple SMPS Flyback

I'm building an SMPS in flyback topology. In order to do it, I use UC3845CB IC. In first step, I wanted to see if it even works at all with pulse transformer that I bought, made especially for flyback ...
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1answer
63 views

VNH5019A Flyback issue on custom PCB

I have a custom high power PCB I recently designed and am currently testing. It is designed to use 2 linear actuators link. I am using a VNH6019A H-bridge to control them. They operate simply as -12v ...
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1answer
95 views

flyback converter issue

When loading flyback converter with heavy load, waveforms are as expected. But with light load, waveforms are not as expected. What can be the reason ? Duty cycle is less than 50% so no slope ...
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0answers
53 views

Interfacing external high speed ADC techniques

I am designing a power converter for solar micro-inverter based on fly-back topology (step-up). I have to extract maximum power from the solar panel and for this I analyze voltage and current change ...
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2answers
171 views

Selecting a switching transistor for a 5V relay

I would like to use a STM32F microcontroller with 3.3V digital io pins which can deliver a max of 22mA to switch a transistor to then power a 5V relay which pulls 28mA. I'm not entirely sure what ...
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0answers
267 views

SMPS power calculation

I am planning to design smps power supply that using flyback topology. It will have 12V@5A output values. But it is not clear for me how to estimate input power. It will supply from 220 AC input port. ...
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0answers
61 views

Possibility of hybrid forward-flyback topology

Within the context of isolated converters, the flyback topology is nice in its simplicity as can be the forward topology, in spite of needing a second primary reset winding. However, both make poor ...
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3answers
552 views

On a relay coil, why use an MOV instead of flyback diode?

I briefly encountered a designer who wished to use an MOV instead of a flyback diode with a relay coil. I don't know much about the application, but why would you want to do that? The only reason I ...
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1answer
351 views

High voltage (2-6 kV), high frequency (20-50 kHz) power supply how to achive

I need to make a high voltage (2-6 kV), high frequency (20-50 kHz) power supply in order to generate cold plasma (in Ar gas). I use a fly back circuit (found in web) could allow me to to that. The ...
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1answer
167 views

Problems snubbing HF noise on flyback converter transistor

I am working on the design of a flyback converter based on the LT3751 capacitor charging circuit. My design is similar to the 42 A cap charger example on pg. 25 of the LT3751 datasheet. In my case, ...
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1answer
101 views

Two flyback diodes in parallel for higher current?

I'm trying to use a water pump that says 12V and 1200mA. I read somewhere that I need to put a flyback diode to handle current when it turns off, but looking around I only have 1N4001 diodes, which ...