EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: nsled on May 01, 2024, 04:25:32 pm
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A transformer primary is driven with a pulsed DC square wave source. Can I use a diode to prevent any EMF from returning to the driving circuit? Should it just be placed in series with the positive line input or in parallel with the coil?
Is there any negative effect to doing this?
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In flyback topology all energy from primary side transferred to secondary, so no EMF on primary side (in ideal case). In real transformer there is a leakage inductance that prevent ideal energy transfer. To deal with energy excess used primary side snubber circuit. This is RC or TVS, placed across primary side of transformer.
Just diode will not work.
https://ez.analog.com/cfs-file/__key/telligent-evolution-components-attachments/00-330-01-00-00-06-34-74/FlybackSnubberDesign.pdf&ved=2ahUKEwiH3Pnt3O-FAxX0S0EAHbiVDjwQFnoECBIQAQ&usg=AOvVaw3ODNdk6a17dTEQepZh68zl (https://ez.analog.com/cfs-file/__key/telligent-evolution-components-attachments/00-330-01-00-00-06-34-74/FlybackSnubberDesign.pdf&ved=2ahUKEwiH3Pnt3O-FAxX0S0EAHbiVDjwQFnoECBIQAQ&usg=AOvVaw3ODNdk6a17dTEQepZh68zl)
https://www.analog.com/en/resources/technical-articles/snubber-circuits-suppress-voltage-transient-spikes.html (https://www.analog.com/en/resources/technical-articles/snubber-circuits-suppress-voltage-transient-spikes.html)
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A transformer primary is driven with a pulsed DC square wave source. Can I use a diode to prevent any EMF from returning to the driving circuit? Should it just be placed in series with the positive line input or in parallel with the coil?
Is there any negative effect to doing this?
Won't work.
You're storing energy in an inductor, and when your driving signal (your square wave) is turned off, that energy has to go somewhere.
As xvr suggests, you can dissipate it in a TVS.
You can also dissipate it in the load on the secondary side of the transformer (if there is a load). Or you can send it back on the power supply line by having a second primary winding connected through a diode to the main DC power input.
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A snubber is a more suitable remedy
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A snubber is a more suitable remedy
Doesn't really solve the problem, does it?
From your PDF:
· Reduce or eliminate voltage or current spikes
· Limit dI/dt or dV/dt
· Shape the load line to keep it within the safe operating area (SOA)
· Transfer power dissipation from the switch to a resistor or a useful load
· Reduce total losses due to switching
· Reduce EMI by damping voltage and current ringing
I see nothing about dissipating the energy stored in the inductor. Try again.