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Thread: Class D 200 Wrms with 2 mosfet cheap

  1. #371
    diysmps Senior Member
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    hi silivo ,thanks for the reply . which is better between the 2 circuits .
    i wanted to use ntc 10k but the 12volts i wanted to use +/-45vlts from the amps power supply .
    do you have or please draw a simplified schematic using 10k ntc and +/-45vlts for supplying the 12v fans power
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  2. #372
    .... Silvio's Avatar
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    Quote Originally Posted by stewin View Post
    hi silivo ,thanks for the reply . which is better between the 2 circuits .
    i wanted to use ntc 10k but the 12volts i wanted to use +/-45vlts from the amps power supply .
    do you have or please draw a simplified schematic using 10k ntc and +/-45vlts for supplying the 12v fans power
    If you intend to supply the 12v from a 45v supply there will surely be a lot of dissipation if you had to use the first circuit with 2 transistor. As you can clearly see the original supply voltage is 15v on the schematic.
    On the other hand the supply voltage of the second circuit is also 12v but I guess the NE555 is controlling the fan speed by pulse width modulation. This type will handle dissipation in the switching transistor more safely although I can see the voltage feeding it is still quite high.
    Using a dropper resistor still has to be quite large in wattage as it will get very hot due to the voltage difference is large.

    These are your options
    1) You either use a small iron core 12v transformer to supply the fan/s
    2) You can tread a couple of turns around the main transformer center core of your smps (if you have space) to provide the 12v-15v needed. I do not know the turns ratio of your transformer but they can be easily calculated according to the primary turns. The wire can be ECW or better still CAT5 solid core insulated wire. This you wind on top of everything and there will not be the need to tape it up, just twist the ends together with enough length to arrive to the place needed to feed the fan control circuit.

    Regarding the schematics I think they are copied from circuits of amplifiers and they are surely tested and work fine. I am adding a schematic which is a part of my 2KW smps. This was supplied from an auxiliary winding from the main trafo. It was tested with 3 X 80mm fan motors and can take them without any trouble. The darlington transistor was an old stock of mine but you can substitute it with TIP122 or similar.

    fan control for Steven.jpg

    Regards Silvio

  3. #373
    diysmps Senior Member
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    thanks silivio , now i am thinking to in cooperate it into the smps instead of the amp.
    but is it possible to use a fet like irf540 or tip41 instead of the darlington transistor?

  4. #374
    .... Silvio's Avatar
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    Well as you can see from all the schematics that the pass transistor controlling the fan speed need a lot of gain in the base/gate. I guess you can use a fet instead but I am not sure how it would behave. You see a fet needs more voltage in the gate to start saturation. You can use a small transistor like 2N2222 or any small NPN transistor and hook up the TIP41 in the darlington fashion. This will boost the gain at the base of the power transistor. You can build the circuit on a breadboard and try it out. It could be that you may need to change the value of some of the resistors to get the circuit working to your need. Be careful to monitor the temperature range and at what temperature the fan gets the maximum voltage (12v). I guess this should be around 45-50 degrees.

    Regards, Silvio

  5. #375
    diysmps Senior Member
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    Quote Originally Posted by Silvio View Post
    Well as you can see from all the schematics that the pass transistor controlling the fan speed need a lot of gain in the base/gate. I guess you can use a fet instead but I am not sure how it would behave. You see a fet needs more voltage in the gate to start saturation. You can use a small transistor like 2N2222 or any small NPN transistor and hook up the TIP41 in the darlington fashion. This will boost the gain at the base of the power transistor. You can build the circuit on a breadboard and try it out. It could be that you may need to change the value of some of the resistors to get the circuit working to your need. Be careful to monitor the temperature range and at what temperature the fan gets the maximum voltage (12v). I guess this should be around 45-50 degrees.

    Regards, Silvio
    hi silvio . meaning that the fan runs slow but at hotter temperatures the fan runs very fast?

  6. #376
    diysmps Senior Member
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    my new high efficiency class d amp using tl494 is ONLINE!!! https://www.facebook.com/harisd9401/...0334128753237/

  7. #377
    diysmps Senior Member
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    hi all . below is the original schematic of this project i managed to translate it . have fun all :

    switchingamp_189_Page_1.jpgswitchingamp_189.pdf

  8. #378
    diysmps Senior Member
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    hi all ,can i use irf6218 with irf540n , instead of irf9540n ?
    irf6218 seeems to have better parameters .
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    Last edited by stewin; 04-29-2020 at 05:59 PM.

  9. #379
    diysmps Senior Member
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    smd version

    hello all, the smd version of this amp with protection . the eagle file is for eagle 9 onward. old eagle will not open the pcb project , have fun all

    the files have refused to upload . but you can view them in the link below

    https://www.diyaudio.com/forums/clas...st6202805.html

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