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[SOLVED] Efficiency issue in offline Flyback Converter

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sabu31

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Dear All,

I am testing a Flyback converter with input 230V ac and output of 12 V at 3.4A.
When I am calculating efficiency from RMS values the efficiency is coming around 40%. I am attaching the waveforms of the same. The switching frequency is 100kHz.

I am noticing that there is excessive heating of output diode. I am assuming this is due to the smaller heat sink (13degree/W coefficient) and heat sink temperature is going upto 90 degree after running for 5minutes after which I switched off the system. Input side I am not observing any heating of Mosfet, snubber etc.

What could be the issue with the design for causing lower efficiency.
 

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KlausST

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Hi,

Truepower is NOT V_RMS x I_RMS.
Thus it´s impossible to do efficiency calcualtions.

...and for the rest we need schematic and exact part types and values .. or even better (links to) the datasheets.

Klaus
 

danadakk

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Consider using a SIC diode ?



Regards, Dana.
 

sabu31

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Consider using a SIC diode ?



Regards, Dana.
Its low cost supply and its available off the shelf also so there is no question of using SiC diode. Mostly they use Ultra fast diodes
--- Updated ---

Hi,

Truepower is NOT V_RMS x I_RMS.
Thus it´s impossible to do efficiency calcualtions.

...and for the rest we need schematic and exact part types and values .. or even better (links to) the datasheets.

Klaus
Then what parameters should be measured for obtaining efficiency
 

danadakk

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    sabu31

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sabu31

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Setup to do the measurements -



40% seems quite low....


Regards, Dana.
Thanks Dana. The link solved my problem. I made mistake of using Apparent Power for Calculations instead of real power. As per the power analysis software. Real power input is around 50 W. My output is 39.8 W. So it should be sufficient efficiency (75% to 80%) of typical off-line flyback converter
 

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FvM

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What you label reactive power is mostly harmonic power. We also see a DC offset in current measurement, but it has no effect on real power measurement as long as it's averaged over full cycles.
 

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