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About Supply Input To Power IC

By on July 21, 2010

 Voltage testing is one of the fastest way to determine if a particular section or a component have problem or not. Whenever there was a complaint of no power in an equipment, the first thing i check was the fuse. Next i can either check the supply input to  power IC or the output voltages from the SMPS. If there is zero voltage at the output then most probably the primary section is the cause of the problem. For your information, have supply input (VCC) to the power IC does not guarantee that the IC is working. It could be the internal part of the IC have open circuit or something external that had caused the power IC not to produce output thus causing no power symptom.

In your case you can either direct replace the power IC and retest or check all the components in the primary side (assuming you have check the secondary output diodes and found all to be okay) and then only you replace the power IC assuming you found no bad components in the primary section.  You may use the method i just explained to troubleshoot any consumer electronics SMPS.




  1. Waleed

    July 21, 2010 at 2:34 pm

    I could relate to that because today, I saw and experience what you have mentioned in this article.
    I was working on a sat. receiver and there was problem with the power supply. the output voltages were fluctuating. the main voltage was reaching the ic but the voltages out, not stabel. eventually it stopped working. I replaced the ic and the receiver worked like a charm.

  2. admin

    July 21, 2010 at 10:14 pm

    Hi Waleed,

    That was a good sharing-thanks!


  3. Sam C

    September 20, 2010 at 10:27 pm


    I am working on an IP (inverter power) board with a shorted primary section. Series bulb flashes brightly twice and all output dead except 5VSB. Voltages are about 10% below spec (SB is 4.8V versus 5.3V). DC at the main filter capacitor shoots up to 380V from 166V, Vcc is 13.9V and HV is 380V. No noticeable voltage spikes at other legs of the Infineon ICE2QS01 PWM IC during power on. I suspect a faulty IC and other primary components seem OK.

    This PWM IC can run in standby (Infineon calls it Active Burst) mode whereby it generates just enough gate output to trigger a 1 watt 5V SB circuit. It also has built-in startup cell and there is no need for external startup resistor. Here is its Datasheet
    and Application
    Note. More and more manufacturers are switching to this type of power IC’s.

    I am curious what is your opinion on this and why would the filter capacitor voltage shoot up ?

  4. admin

    September 22, 2010 at 2:33 am

    HI Sam,

    Thanks for the link and yes this is indeed a new type of design in smps circuit. It does not need start up resistor. Since i have not repair such power supply before thus i do not know why the dc voltage could shoot up to 380vdc. I suggest that you remove the power ic and retest to see if the voltage will go down to 165 vdc. If it is 165 volt then i guess you need to replace the power ic and retest.


  5. rupinder

    August 10, 2011 at 2:55 am

    good job you done

  6. George Agsamosam

    December 5, 2011 at 1:33 pm

    Sir jestine,

    Good day sir, is it ok to replace a 220 ohms 1/4 watts resistor with
    220 ohms 2watts resistor?


  7. admin

    December 5, 2011 at 2:00 pm

    HI George,

    Yes you can use but the best replacement is still the nearest wattage which is 1/2 watt.


  8. Big P

    July 16, 2012 at 5:33 am

    I wouldlike to change an ICE2QS01 IC for a DVD player power supply.What can I substitute it with(including other brands) as we dont have them in stock in our area.

    • Jestine Yong

      July 16, 2012 at 9:35 pm

      Hi Big,

      I suggest that you get the original part number as there is no substitute for this ic.



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