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Design Help --- Bubba Oscillator

Discussion in 'Homework Help' started by ismith1984, Oct 5, 2009.

  1. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The CD4047 IC can probably drive the Mosfets directly without the opamps.
    The Mosfets need 100 ohm resistors in series with their gates to prevent VHF oscillation and the resistors must be mounted very close to the gate pins.

    Which part number Mosfets did you get?

    Voltage regulation is very complicated. You must rectify and filter the output to be used as a reference. Then you must make a complicated Pulse-Width-Modulation oscillator circuit that has the pulse width controlled by the amount of reference voltage.
    The transformer voltage must be selected to be too high so that the PWM can reduce and regulate it.

    A protection circuit must detect, rectify and filter the output current then shut down the oscillator if the current is too high. It might react too slowly then the circuit will blow up.
     
  2. ismith1984

    ismith1984 New Member

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    the mosfets i ordered were the MTP75N03HDL.

    i would like a point out in the direction as to go about designing the regulator for the inverter. i need to know where i should start.

    the other question is, the protection circuit; are you referring to a new inverter circuit to be designed from scratch or can it be incorporated into the current 100W inverter design.
     
  3. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The 25V voltage rating of your Mosfets is too low. The battery is 13.8V or more when it is fully charged and the transformer causes each drain to swing to double the battery voltage or more which is at least 27.6V.

    I told you how to make a voltage regulator by using PWM. The PWM can also make a modified sine-wave inverter or a pure sine-wave inverter.

    A protection circuit might not be fast enough to stop the circuit from blowing up if it is overloaded.

    Yes, I am talking about a completely different design from the current extremely simple square-wave one that does not have voltage regulation and does not have overload protection.
     
  4. dave

    Dave New Member

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  5. ismith1984

    ismith1984 New Member

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    Hi again guys. i need a little information on the process of battery charging. what is required of the voltage charging with reference to the battery being charged and the current needed. what exactly happens during the charging process......... and are there any formulas go know that charging time and stuff like that . a link if any would help.
     
  6. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The Battery University on the web has details about every type of battery.

    An ordinary lead-acid car battery is designed to provide a high current for a short duration. An inverter should use a "deep discharge' battery that is used on motor homes and fork lift trucks.

    The charging should use current-limiting and have a regulated max voltage of 13.8V to 14.4V as determined by the battery manufacturer. Since the battery will self-discharge by itself then it should be trickle-charged all the time.
     
  7. ismith1984

    ismith1984 New Member

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    Ok I get the trickle charged aspect of it but what is the recommended current and is there anything that you have to keep in mind when applying a current to it.
     
  8. audioguru

    audioguru Well-Known Member Most Helpful Member

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    The battery manufacturer should have a detailed datasheet or have the charging information printed on the battery.
     
  9. tsveti

    tsveti New Member

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    >Hello "ismith1984", the lead-acid battery are charged normaly with 1/10 of the battery capacity. You may charge the battery to 13.8V in standby mode.
    >If you are interested, I could publish a charger schematic, I have been using successsully for 15 years. It includes IC LM723 , 2N3055, transformer and some more components. The schematic provides 13.8V with current limit 10A. Charging the battery to higher voltage will cause water evapuration in standby mode.
     
  10. michaellowe3001

    michaellowe3001 New Member

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    Hey BrownOut,
    I built this circuit but where your green trace oscillates mine just steadily rises and settles at the same value as the pulse. Could you tell me what ltspice op amp you are using?
     
  11. JoeJester

    JoeJester Active Member

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    deleted post as the thread was too old
     

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