High frequency sine wave invertor

Discussion in 'Power Electronics' started by Motanache, Dec 4, 2017.

  1. Motanache

    Thread Starter Member

    Mar 2, 2015
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    I realized a 50Hz sine inverter and I found it too havy.

    Now I have an SMPS that gives a maximum voltage high enough to light a bulb in the room.

    But how do I get to have 50Hz?

    How do I made from the continue voltage a sinusoidal voltage?

    My idea was to use a class D amplifier but it seems a waste of components.
     
  2. wayneh

    Expert

    Sep 9, 2010
    16,099
    6,209
    It is a waste for most applications, because most things don't need a sine wave. My cheap inverter puts out a "modified sine wave", which is really just a square wave with a brief interval at zero volts at each zero crossing. I've never had a problem with anything malfunctioning on that.

    If I really wanted a 50Hz sine wave with significant power, I'd use a modern audio amplifier fed a 50Hz tone. I'm glad I don't need any such thing.
     
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  3. Motanache

    Thread Starter Member

    Mar 2, 2015
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    Thanks a lot for encouragement.
    I can change the polarity of the output(with MOSFETs). This gives at output a rectangular signal.

    Now I wonder if I could do somehow round this rectangular output signal with LC filters.

    But the positive half wave is just sources.I can not use that:
    [​IMG]

    Because when Vs changes its polarity the diode becomes directly polarized.
     
  4. Motanache

    Thread Starter Member

    Mar 2, 2015
    474
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    I would like to know how this signal looks like?
    Looks like this?:*(middle)
    [​IMG]
    Is OFF time a falf of ON time?


    I tried to create such a signal (Figure2). The result was that I broke a microcntroller.
    Better I make it simpler but to work.
    http://www.industrial-electronics.c...rter/23_Pulse-Width_Modulation_Inverters.html
    [​IMG]
    Figure2
     
  5. Motanache

    Thread Starter Member

    Mar 2, 2015
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    The first step will try with the rectangular signal that I think it is. That until I get the answer to this:

    Then, as an idea of the future, I would like to know how you filter such a PWM:
    [​IMG]
    Note that above 0V is just current sources and below is just current sinks.
     
  6. tcmtech

    Distinguished Member

    Nov 4, 2013
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    A basic LC tank filter will clean it up to where it's more than acceptable for powering most anything.
     
  7. Motanache

    Thread Starter Member

    Mar 2, 2015
    474
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    It's a little weird, because at the opening of the switch there is no diode D.
    When the switch opens, theoretical, the voltage on L should increase so much to burn the transistor.(Switch is a transistor)
    But maybe too much theory is bad and has to works so


    [​IMG]

    Then this circuit must consider the load R. It sischarging the capacitor.

    If R is too big the capacitor remains charged at maximum voltage when the output voltage should have been zero.

    I want to power from this inverter either a 1W LED bulb or a 100W incandescent bulb or other.
     
  8. tcmtech

    Distinguished Member

    Nov 4, 2013
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    A 100 watt incandescent doesn't care what type of current it gets so regardless of whether it's AC, DC or PWM of some sort it doesn't matter.

    As for a LED's or CFL's they have tiny inverter or like power converters in them that rectify the incoming current so they too don't really care what current form they get so long as it doesn't have a base frequency that is higher than the input diodes can work with which given their relatively small size most will handle any input frequency below a few kilohertz without issue.
     
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