PNP ?????

Discussion in 'General Electronics Chat' started by Burnit0017, Jan 24, 2012.

  1. Burnit0017

    Thread Starter Member

    Feb 15, 2010
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    Hi, will the PNP increase the discharge rate of the capacitor ?
    V out is 20 volts with a 1.5 ripple.
    Comments welcome.
     
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  2. Wendy

    Moderator

    Mar 24, 2008
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    You have the capacitor connected between power supply rails, there should be no ripple. Basically the capacitor and transistor are two separage circuits. The 1MΩ resistor is a 3rd separate circuit, as it is a load on the power supply.
     
  3. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, I am using a nand gate oscillator and voltage multiplier to charge the cap at point X and then I am trying oscillate a MOSFET for a buck converter to charge a battery bank using a permanent magnet alternator. This is a first attempt and I am trying to use discrete components. Thank you for any help received. Comments welcome.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    I don't think that's the power supply rail; merely some signal output.
    We don't know what is creating the ripple on the 20v.
    The capacitor tends to keep the voltage more constant.
    If you want the discharge rate of the cap to increase, why not simply substitute a smaller cap?

    [eta]
    I didn't see your reply before I posted. Ignore the above.

    I don't really know what you're trying to do. I can't read your schematic due to how far I am located from my monitor. I have no simulation tools available to me. Perhaps someone else will help you.
     
  5. Adjuster

    Well-Known Member

    Dec 26, 2010
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    This seems a very strange arrangement. With a 1μF capacitor from gate to ground, I would think that the MOSFET cannot switch quickly at all.

    Where did this circuit come from, and how is it supposed to work?
     
  6. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, I posted a better circuit drawing. I am using the battery bank to power the control circuit. The control circuit should be able to increase the 12 volts to 20 volts so the 20 volts can be used to drive the MOSFET. The problem I am trying to solve is the 20 volts is not oscillating so the MOSFET never turns off. I am searching for a circuit to oscillate the 20 volts.
     
  7. Wendy

    Moderator

    Mar 24, 2008
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    I have to say I think your circuit will not work as drawn. Your original drawing does not include the charge source for the cap, and it is required to put the rest into context.

    It looks automotive, which is not allowed on AAC. The only voltage multiplication is being feed into the gate of a MOSFET, and you do not have a buck boost on the output of the MOSFET.

    I have a sneaking suspicion this is some sort of HHO circuit, another subject not supported at AAC.

    I'll wait to see how it jells before I go further, but as it stands this circuit has some major flaws.
     
  8. t06afre

    AAC Fanatic!

    May 11, 2009
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    (VAWTs)Vertical-axis wind turbines, (MPPT) Maximum power point tracking. So it is basically a renewable energy project. So dear OP you have nothing to gain in being cryptic and holding back information, but all to loose! Just tell us what exactly the function of that circuit. And what you plan to do in your project.
     
  9. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, I constructed a vertical axis wind turbine. Then I fabricated a PMA. The wind spins the PMA, the PMA output is converted to DC and the battery is charged. The main problem with a PMA is the internal resistance of the stators. At higher RPMs a large part of the energy produced is wasted as heat in the PMA stator. I watch a video that demonstrated a PMA used with a MPPT controller and the PMA performance was improved. The core circuit of the MPPT is just a buck converter. It isolates the PMA from the battery bank by sending packets of energy when the MOSFET is turned on and off. The problem I am facing is generating a MOSFET gate signal for the buck circuit from the 12 volt battery bank. I apology to the forum if I am violating any rules, I am just searching for a solution to the gate trigger problem. Comments welcome.
     
    Last edited: Jan 24, 2012
    t06afre likes this.
  10. Wendy

    Moderator

    Mar 24, 2008
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    You are not violating any rules, but it is always better to give enough information up front then have people guess around it.
     
  11. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Why not use a standard buck converter IC? They have been developed to do the job and are probably in the long run cheaper to implement than the discrete version. They will be in a smaller package than using several discrete chips and the main development time for your project is already done for you.

    Your drawing says that this is an open source project. Any thing that makes it simpler for other builders, should be a focal point for something 'open source'.
     
  12. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, this is a first attempt and I have no experience with this type of circuit. Basically the circuit is a variable input DC - DC step down SMPS that operates at 12 volts. I have found a TC4420CPA gate driver IC but I am not sure if it will work with only a 12 volt supply. From the reading I have done, some articles say the gate driver signal should be 10 volts above the signal passing through the MOSFET. If I can get the circuit operational then I can test the system with a hand crank on the PMA to determine if it will beneficial and than post the results, good or bad. I have used the nand gate oscillator, voltage multiplier, and MOSFET for motor control circuit, but that did not require the MOSFET gate signal to oscillate. So the circuit does generate 20 volts at point X but I am searching for a way to oscillate the 20 volt as a square wave using only a 12 volt supply. Comments welcome.
     
  13. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Isn't a MPPT controller for a solar panel, not a wind generator? I was under the impression that wind generators used a 'shunt' type system to control it after batteries were full charged. Some people shunt the power in to water heating coils to supply hot water. With out a load or brake system won't your turbine just over speed when batteries are at full charge?
     
  14. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
  15. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, is it possible to have a transistor configuration to oscillate Vgs?

    When point “A” is enabled the voltage at point X will be 2 times the battery voltage.

    MOSFET source is always at the plus value of the battery voltage and is consider ground with respect to Vgs.

    The MOSFET requires 10 volts at the gate to turn on.

    Use a resistive voltage divider to create a high and low side of the voltage at point X.

    Configure a transistor circuit on the high side of the voltage divider to provide 10 volts to gate.

    I do not have a lot of experience with transistor circuits, comments are welcome.
     
  16. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Watching the video link, you may have missed something. That circuit is based on a micro controller. Doing it with discrete chips is going to take a lot more than the few that your trying to do it with. Did you notice the size of the board and all of the components on it? And thats with all the "logic" being done in a uC.

    While a PMA is easy to make, it is real hard to control. To me, a better type of alternator, even though harder to make, is one similar to a auto or emergency power alternator. With one built like that you control the rotor magnet to control out-put, not the stator.

    I know that everyone will say, "it has to turn too fast to get a usable amount of power". But thats where you modify it, to get more power at lower speed. The normal car alternator usually has six poles on the rotor, this is what makes it need to turn fast for the out-put. If you make the rotor have more poles, like in a PMA, the speed required would be the same as the speed for the PMA. And by controlling the voltage in the rotor you control the out-put of the alternator.
     
  17. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, I am just starting with a very buck converter. I plan on using a hand crank so I can observe the affects the circuit will have on the PMA output. After that I can move on to develop the algorithm for the MPPT. I believe I understand what high side and low side is, I just need a transistor configuration that well oscillate the voltage at point X so the MOSFET will turn on and off. Then I can test the circuit with the PMA. I am just solving one problem at a time. It is very easy to fabricate a PMA with high internal resistance, if I can get the circuit operational the benefit would be you are converting a voltage with low current to a low voltage with high current. Comments welcome.
     
  18. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    If you want to learn more about switch mode power circuits, have a look at this -
    http://www.ti.com/ww/en/simple_switcher_dc_dc_converters/index.html It is a way to enter your parameters into it and choose the best way to come up with components. It also has a circuit simulator.

    The video you linked to is really misleading. In the first part he has two of the coils short circuited with the light bulb, this makes the PMA hard to turn. This is how many DC motor controls do dynamic braking. So the PMA is doing what it should in this situation.

    Then he hooks up his board to the PMA and rectifies the out-put in the normal fashion and it's easier to turn, which it should be. Not because of his "micro controller algorithm" but because the PMA out-put is being used as its supposed to be.


    Good luck with your project.
     
  19. Burnit0017

    Thread Starter Member

    Feb 15, 2010
    101
    3
    Hi, thank you for your efforts. I redrew my circuit showing point X is 24 volts. The mosfet source is 12 volts. I am searching for a transistor circuit that will pulse from 12 to 24 volts to drive the mosfet gate. Thanks again. Comments are welcome.
     
    Last edited: Jan 27, 2012
  20. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Like the people told you in the beginning of the thread, your circuit does nothing. Mosfet gates don't normally get pulsed between 12 and 24 volts. In fact most are only rated to 20V, and there is no advantage to go much above 10V. A gate is pulsed from 0V to ~10V to turn it on and off.

    I or none of the others can figure out what it is your trying to accomplish with your circuit. If you could explain what you want it to do, maybe you could get some help. The way things are done with wind generators have to obey the simple principles and laws of electronics, just like all electrical things. Sorry.
     
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