Notebook Circuit

Discussion in 'General Electronics Chat' started by Gsatel4306, Apr 30, 2008.

  1. Gsatel4306

    Thread Starter New Member

    Apr 30, 2008
    2
    0
    Hello. I have posted this question elsewhere and have not received a clear explanation of what is happening in this circuit. I have a notebook circuit which includes an IRF7811A Hexfet Mosfet and two SI4362DY mosfets. The IRF 7811 is used supposedly as the controller mosfet and the SI4362's are in parallel used as the synchronous rectifiers. At the drain of the controller mosfet there is supply voltage of 19.8 volts and 5.1 volts at both gates of the SI4362 mosfets in standby mode. When power is switched on, the controller mosfet turns on with 1.5 volts at the source and 1.8 volts at the gate. In addition, the SI4362 mosfets output 1.5 volts at the drain and the gate voltage changes to 4.5 volts. The only device that I can see that is driving the gates of these mosfets is a Maxim 1632 power IC. I know that this is a synchronous buck converter but I need to get the concept as to what each component is doing in each stage and how voltage is flowing and rectified.
     
  2. Norfindel

    Active Member

    Mar 6, 2008
    235
    9
    A notebook circuit? That's a pretty vague description...
    You mention a buck converter IC, are we talking about the power supply? Is this an external supply, or it's something inside the notebook?
    What's the problem with the notebook?
    You need to be a lot clearer, before someone can be able to help.
     
  3. Gsatel4306

    Thread Starter New Member

    Apr 30, 2008
    2
    0
    This circuit is in a notebook power supply and it is internal. I have one or two notebook mainboards that will not power up. Evidently this is a key circuit that steps down the voltage to be used by the cpu and these mosfets are known to short quite frequently. I thought that someone might be able to give me a theory of operation so I could understand this better.
     
  4. Norfindel

    Active Member

    Mar 6, 2008
    235
    9
    Do you checked the application notes for that IC in the Maxim site? There are good chances that they have notes about using the IC for power supplies. I remember seeing application notes regarding power supplies in the On Semiconductor site, with examples of buck, boost, flyback configurations for various of their IC's, Maxim wouldn't be the exception.
    On semiconductor have a "Linear & Switching Regulator Handbook" (document HB206/D). Maybe it can be of help to you, it talks about different switching power supply configurations and how they work.
     
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