IR2110 HO constant - pSpice simulation

Discussion in 'The Projects Forum' started by Roux, Jul 12, 2011.

  1. Roux

    Thread Starter New Member

    Jul 11, 2011
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    Hi there!

    I am busy with my final year project concerning a wireless power transfer device. I am using the NCP1200 to generate a pwm signal for the IR2110. I simulated the circuit in pSpice and are left with the following concerns:

    • HO output voltage is constant and LO is zero
    • Do I need to connect the ADJ pin to the load to adjust the pwm?
    Can anybody assist me in this problem please?

    Kind Regards
    Roux
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    You're trying to use a single IR2110 to drive both sides of an H-bridge. That's not going to work.

    You need an IR2110 for the left side, and another one for the right side.

    Also, until you can get the low-side MOSFET to turn on, you will not have a path to ground to charge the boost cap, so the high-side MOSFET won't turn on. Right now, you have the HO driving the low side MOSFET, so it can't turn on because the cap never had a ground path so that it could charge.
     
  3. Roux

    Thread Starter New Member

    Jul 11, 2011
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    I have reconsidered my design and realized that I do not need to drive four MOSFET's only two. I still cannot figure though why my HO pin are kept at a constant voltage? Does it have something to do with my input from the NCP1200 or is it the bootstrap capacitors that are connected incorrectly or their values? Please help me in this regard as I am still new and unexperienced in this field. Attached is the revised circuit diagram I am aiming to simulate.

    Thank you for the help in advance! It is really appriciated!
    Roux
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    You're using the HO output to drive the low-side MOSFET gate, and the LO output to drive the high-side MOSFET gate. That's just not going to work.
    The HO output needs to drive the high-side MOSFET
    The LO output needs to drive the low-side MOSFET

    You also have Vb (pin 7) connected directly to +15v, which also is not going to work.
    Only C4 and the diode in parallel with it should be connected to Vb.

    I don't know why you are trying to turn on both the high and low side MOSFETs simultaneously, but that's not good either.
    Vs needs to be connected to the junction of the high-side MOSFET source terminal, which it is, but also to the low-side MOSFET drain, which it is not; as R13 is between the two. So, R13 is in the charge path for C4, the boost cap. However, since you are trying to turn on both MOSFETs simultaneously, I have my doubts about C4 attaining/maintaining a proper state of charge.

    Unless the low-side MOSFET is on by itself for some period of time, the boost cap won't get charged/recharged.
     
    Last edited: Jul 15, 2011
  5. Roux

    Thread Starter New Member

    Jul 11, 2011
    4
    0
    Thank you so much for the reply SgtWookie, it is greatly appreciated. I have fixed the circuit diagram and I FINALLY got the HO driven for the high side MOSFET thanks to you advice. I now need to apply an inverting pwm signal to Lin (Pin 4) to get the low-side MOSFET driven as I only grounded it in the attached circuit diagram right? How will I do this? I have searched for methods to invert the signal in the NCP1200 but nothing successful came from it. Would I have to use an opamp or something to do this? Sorry for all the questions once again...... Thank you for your patience! I really appreciate it!

    Thank you in advance!
    Roux
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    Well, you are trying to use the NCP1200, which is a flyback current-mode PWM controller that is only designed to control a single low-side switch.

    Why don't you look at a more appropriate controller for your application?

    If you are "stuck" with the NCP1200, you need to stay with a single low-side switch.

    [eta]
    I really don't know where you are going with this; you have a single 100 Ohm resistor acting as a load. If you intend to reverse the direction of the current, you will need to use a full H-bridge, and a different controller.
    If you are going to use a transformer with a center-tapped primary, then you might use something like an SG3524, UC3825, etc. There are a LOT of controllers out there.
     
    Last edited: Jul 15, 2011
  7. Roux

    Thread Starter New Member

    Jul 11, 2011
    4
    0
    The 100 ohm resistor is only used for simulation purposes to get the h-bridge on the go. I have looked into other types of controllers such as the UC3825 but the problem that I found there was that unmodelled pins occur in this IC and therefor I won't be able to simulate the circuit before buiding it which is a problem as I am still new in this field (as you have seen in my previous circuit diagrams) and would like to minimize all possible problems before I develop the circuit on PCB. Will it be possible to use a 555-timer to suffiently supply the IR2110 with a PWM signal and its inverse? Am I at least aiming in thr right direction if I say that HO and LO should drive a load in such a way that HO is on when LO is off and the other way around and that when a full-H-bridge is used that the frequency at which this process takes place is the same as the frequency of the pwm signal? Thank you so much once again for all the help and replies, I really appreciate it.

    Regards
     
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