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Problem in LM2576 circuit

Discussion in 'General Electronics Discussion' started by shindehari, Oct 12, 2015.

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  1. shindehari

    shindehari

    14
    1
    May 19, 2014
    Dear all,

    I am using a LM2576 (5 Volt) switching regulator IC in my board, earlier it was working well for some time. When i switched on relays either small resistor type inductor is blowing or LM2576 is blowing up. To resolve it i have replaced diode 1N5822, 100uh inductor, LM2576, but still one of the two are blowing up. I have wasted couple of inductors and LM2576. My relay is connected to 24 volt power supply so no supply is going from the LM2576 regulator to the relay. I have tested capacitor also and it is in good condition.

    I cant find where is the exact problem. What is the main reason for blow up of inductor or lm2576.
     
  2. Colin Mitchell

    Colin Mitchell

    1,416
    314
    Aug 31, 2014
    What load have you got connected to the output of the IC?
     
  3. Martaine2005

    Martaine2005

    3,691
    1,006
    May 12, 2015
    Have you got a diode across the relay coil?

    Martin
     
  4. shindehari

    shindehari

    14
    1
    May 19, 2014
    Thanks for your attention

    I have connected ULN2003, so i hope no need of diode please specify if it requires.

    I have connected PIC16F877A, 5- 7 segment LEDs, 3 single LEDs, 5-BC547, 5-PC817 as load to 5 volt power supply.

    As per my knowledge resistor type inductor can support around 100mA. I think my load current is more than 500mA. Please help me to resolve this issue.
     
  5. Martaine2005

    Martaine2005

    3,691
    1,006
    May 12, 2015
    It may be better to upload a schematic of your circuit! with component values..
    And save people here from guessing.

    Martin
     
  6. shindehari

    shindehari

    14
    1
    May 19, 2014
    sorry sir,

    Please find the attached schematic for my circuit.

    Looking forward for your valuable suggetions
     

    Attached Files:

  7. eetech00

    eetech00

    95
    8
    Nov 17, 2014
    How about showing the LM2576 schematic?
     
  8. Arouse1973

    Arouse1973 Adam

    5,164
    1,087
    Dec 18, 2013
    Post the schematic you are having issues with and please highlight the area that is causing you issues.
    Adam
     
  9. Martaine2005

    Martaine2005

    3,691
    1,006
    May 12, 2015
    Is it by any chance U10? The text is not very clear at all.
    Also, I am having difficulty seeing how RL1, RL2 and RL3 are connected. What pins do they go to? Are they all parallel connected?

    Martin
     
  10. GPG

    GPG

    452
    66
    Sep 18, 2015
    This could be your problem.
     
  11. Harald Kapp

    Harald Kapp Moderator Moderator

    11,989
    2,809
    Nov 17, 2011
    Not only could, almost definitely is.

    When used with overcurrent, the inductor saturates and loses inductivity. It behaves as a resistor with comparatively low resistance. You neeed to use an inductor which is rated for at least the max. current that will flow through the inductor. Note that this is more than the average load current but the peak current which is higher!
     
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