help please

Discussion in 'The Projects Forum' started by muslim_eng, Mar 3, 2008.

  1. muslim_eng

    Thread Starter New Member

    Mar 3, 2008
    3
    0
    hi >>>>>>
    i am working in aproject of invertor and i have aproblem in transforming dc to ac ( from batrrey to output ) i use a555 isolator & invertor but i neet achip to make delay in the wave out of invertor to product asquare wave whats that chip ?
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You say you already have a 555 - those are usually timer ICs.

    555 timers can be used in astable mode (free-running oscillators) or monostable (timer) mode. You can connect them with a couple of resistors and capacitors to make square waves. They can output or sink up to 200mA of current.
     
  3. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Maybe he is making an inverter project with a center-tapped transformer and has two Mosfets driving it push-pull. The 555 drives one Mosfet and he wants a "delay" circuit to drive the other Mosfet with the opposite phase.
    He should use a logic inverter IC or another 555 connected as an inverter.

    I think a CD4047 IC is perfect for a simple square-wave inverter because it has an oscillator made with a single resistor and capacitor, a digital divider and two opposing outputs that are perfect square-waves. It even has its clock output at double the frequency that can be gated then makes a modified sine-wave waveform.
     
  4. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
    those two opposing outputs would have to have a little 'dead time' between them to avoid blowing up the supply.
     
  5. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    If it were an H-bridge or a push-pull, the dead time would be a requirement. But is dead time actually needed for a center-tapped primary set-up?
     
  6. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    Some Mosfets conduct a high current when each has a gate voltage of 6.5V when the square-wave is halfway through switching. But for only a moment if the drive has fast rise and fall times.
     
  7. S_lannan

    Active Member

    Jun 20, 2007
    247
    2
    i would definately consider dead-time in a push pull converter. those devices take time to switch off and i would very much like to avoid cross conduction.
     
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