half-bridge circuit with dual supply

Discussion in 'The Projects Forum' started by EEE86, Apr 21, 2011.

  1. EEE86

    Thread Starter New Member

    Apr 21, 2011
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    Hi all,

    I would like to design a half-bridge circuit that can switch between psoitive and negative power rails. basically, I want to apply positive voltage to the load for a period of time then apply negative voltage. I have built a half bridge circuit using n-channel MOSFETS and IR2103 driver but the output switches between positive power rail and GND.

    I attached to this thread the datasheet of IR2103

    Any ideas?

    regards,
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    You would need to have the IR2103 "ground" connected to the negative rail instead of ground, along with whatever logic you were using to control the half-H bridge - basically ignoring the ground for the input side of the IR2103.

    If your negative rail were -20v, then you'd need a -15v or -10v for your Vcc, depending on the mosfets you were using. If you were using a microcontroller to generate the input signals, you'd need a -15v supply for the uC's Vdd.
     
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  3. EEE86

    Thread Starter New Member

    Apr 21, 2011
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    Thanks a lot. I am using a microcontroller to generate the input signals for the half-bridge. Do you mean to connect uC's Vdd to -5V?
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    I do not know what voltages you are using for your supply rails.

    However, Vdd should be 5v more positive than the negative rail that you are using instead of ground.
     
  5. EEE86

    Thread Starter New Member

    Apr 21, 2011
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    my power rails are 20V and -20V. 2103 chip was connected to 15V so will connect it to -15v and uC's Vdd was connected to 5V so will connect it to -5V.
     
  6. SgtWookie

    Expert

    Jul 17, 2007
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    No, you will fry your uC.

    I am not sure what you have now. You need to post a schematic.

    You say your power rails are 20v and -20v, but you were using 15v for the 2103, and 5v for Vdd.

    You need to move all of your connections to ground to -20v. Then you need a -15v supply to use for Vdd, as -15v is 5v higher than -20v.

    Then you need a -5v supply to power the 2103 IC, as -5v is 15v higher than -20v.
     
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