5v PWM to 10v PWM

Discussion in 'General Electronics Chat' started by SoundUser, May 9, 2012.

  1. SoundUser

    Thread Starter New Member

    May 9, 2012
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    Okay. So I want to convert 5v PWM to 10v.
    5 volts from an Arduino to dim LEDs off of 10 volt Meanwell.

    Can I used the 5 volt from the Arduino to the gate of an N-channel MOSFET and then use a 10v DC supply into the Meanwell??

    Or is that too simple?? :)
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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    With some caveats, yes.

    You should use a logic-level MOSFET; these are MOSFETs that have Rds(on) specified at 4.5v or lower. Very generally, International Rectifier and Vishay MOSFETs that start with IRF are standard level, and those that begin with IRL are logic level.

    You should use a resistor to connect your I/O pin with the MOSFET for a couple of reasons; 1) Reduces the tendency of the gate to "ring" due to parasitic L of the trace and C of the gate, and 2) helps to protect your I/O pin from overcurrent in case the MOSFET fails shorted from drain to gate (a very common failure mode).

    You should post a schematic of your proposed circuit.
     
    strantor and #12 like this.
  3. SoundUser

    Thread Starter New Member

    May 9, 2012
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    This is with an N-Channel MOSFET. Should i be looking at using a P-Channel MOSFET and having it on the + side of the 10 Volts DC?

    [​IMG]
     
  4. crutschow

    Expert

    Mar 14, 2008
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    From the data sheet for the LPF-40D series of LED drivers it would appear that the inputs are isolated and thus can be driven from either a high-side or low-side driver, so your circuit should work.

    I don't see any need for the resistor you show in the 10V circuit unless you want to limit the maximum brightness.

    Edit: It might work without a 10V supply by just connecting the MOSFET directly across the control terminals to simulate a varying resistance, which is one option they show for dimming the lights. I'd give it a try before I added the 10V supply (unless the supply is already available). Note that will give the opposite polarity of dimming, e.g. 100% duty-cycle would act like minimum resistance and give minimum brightness.
     
    Last edited: May 10, 2012
  5. SoundUser

    Thread Starter New Member

    May 9, 2012
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  6. crutschow

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    Mar 14, 2008
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    OK, that unit only accepts 10V PWM so you need the 10V supply.

    And since the diagram on the second page shows the PWM negative signal point connected to the V- output, I believe you probably need a P-MOSFET or PNP transistor as a high side driver. That would require an NPN or N-MOSFET stage to provide the 10V need to drive the P driver.

    You could perhaps just use a single N-MOSFET or NPN with a resistor load to give a grounded signal, but I couldn't find a spec in the data sheet for the control input impedance so I can't determine what resistor value would be needed. Perhaps you could contact them about that.
     
  7. SoundUser

    Thread Starter New Member

    May 9, 2012
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    Cheers. Ill order some and have a play :)
     
  8. crutschow

    Expert

    Mar 14, 2008
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    Order some what?
     
  9. SoundUser

    Thread Starter New Member

    May 9, 2012
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    P-Channel Mosfets
     
  10. SgtWookie

    Expert

    Jul 17, 2007
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    You need to post up a schematic, or you may wind up with something that doesn't work at all.

    If you're going to PWM the Meanwell with a P-ch MOSFET, you won't be able to drive it directly from a microcontroller; you'll need a driver circuit. You would not have that problem with an N-ch logic level MOSFET.
     
  11. crutschow

    Expert

    Mar 14, 2008
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    The problem is that the input apparently needs a grounded source. So that means an N-MOSFET with a resistor load or a P-MOSFET high-side driver.

    Since the input impedance of the circuit is not given, the proper value of the resistor for an N-MOSFET circuit is unknown. Of course we could take a guess and just use a relatively low value such as 1kΩ and see if it works.
     
  12. SoundUser

    Thread Starter New Member

    May 9, 2012
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    Could you recommend one of me to try?
     
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