Need Help , IR2110 half-bridge

Discussion in 'General Electronics Chat' started by yassser, Jul 28, 2011.

  1. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    Hi,

    first , I want to ask if this is the half bridge circuit , it's from the ir2110 application note

    http://imageshack.us/photo/my-images/585/unled2is.jpg/

    If it is , then how it would work , I have implemented it but the LO gives 0v and this is understandable in the full-bridge case because we need the high side mosfet to be on and the low side to be off or vice versa to be able to control the motor direction , but in half-bridge I imagine that I need both mosfets to be turned on simultaneously or off simultaneously to control the motor speed with the PWM signal.


    other than that , why do I need two mosfets , wouldn't one be sufficient to switch on and off and control the signal reaching the motor , and connect the other motor terminal directly to the mains.

    thanks in advance , and if this is not the right place for that question , please tell me.
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Interesting; they missed placing a junction between the drain of the upper, source of the lower, and the left end of the inductor.

    If LO isn't going high, are you certain that you have SD grounded, and that you're providing an adequate signal to LIN, and that Vdd and Vcc are correct?

    You need two MOSFETs. See the right side of the inductor? Where will the inductor current go otherwise? There is only a path for AC signals.
     
  3. yassser

    Thread Starter Member

    Jul 25, 2011
    91
    0
    thanks for the fast response.

    wouldn't placing a junction between between the drain of the upper , source of the lower , and the inductor left size , wouldn't that bypass the mosfets , could you offer further explanation .

    the two 50uF capacitors , what is their polarity ?

    and I can't see how will the current flow in the inductor , the right terminal of the inductor is connected to two capacitors that will block the dc current , how could that work?
     
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