Author Topic: uc3844 flyback converter startup problem  (Read 3574 times)

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Offline electros6

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uc3844 flyback converter startup problem
« on: September 04, 2014, 02:41:03 pm »
Hi guys,
         I designed a flyback converter using uc3844. when I power up the circuit , the voltage at the Vcc pin swings between the threshold ie approximately between 12 and 16V like a sawtooth waveform. I increase the startup current by reducing the startup resister but result in same. Can somebody figure out the problem
  attached the schematics herewith
       
   
 

Offline bktemp

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Re: uc3844 flyback converter startup problem
« Reply #1 on: September 04, 2014, 03:12:33 pm »
Your feedback winding does not produce enough voltage for the uc3844 to keep running. So it stops until the startup resistor recharges the capacitor.
 

Offline T3sl4co1l

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Re: uc3844 flyback converter startup problem
« Reply #2 on: September 04, 2014, 03:27:21 pm »
Are you actually running it from 48V, and using the winding schedule specified for the transformer?
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Offline electros6

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Re: uc3844 flyback converter startup problem
« Reply #3 on: September 04, 2014, 04:04:42 pm »
No, I actually used my own designed transformer for 48V . not the one specified in the datasheet
 


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