PWM multiplier

Discussion in 'The Projects Forum' started by bfrigon, Nov 15, 2009.

  1. bfrigon

    Thread Starter New Member

    Dec 29, 2008
    3
    0
    Hi,

    I need to design a circuit that can multiply a PWM frequency by a factor of 4 while preserving the duty cycle..

    Input PWM frequency is 160Hz.

    I'm not looking for a complete ready-to-use circuit... Just need some ideas. I just don't know where to begin...

    Any help will be apreciated, thank you.
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    The approach I would use would be to build a pwm generator that ran at four times the frequency of your reference PWM signal. I would then convert the reference PWM signal back to the DC using an RC intergrator. I would then use this retrieved DC signal to control the PWM of the 4X frequency PWM generator.

    These signals would not be locked together. If they need to be locked together then you will need to use a Phase locked loop to generate the reference for the 4X frequency PWM generator.

    hgmjr
     
  3. bfrigon

    Thread Starter New Member

    Dec 29, 2008
    3
    0
    Thank you for your answer.

    Is there a way to transform the existing PWM signal without the need to use a second generator?
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Not that I know of.

    There is no straightforward way to multiply the frequency of a given squarewave by a constant. You need an F-to-V followed by a V-to-F with a gain stage in between or you need a PLL.

    hgmjr
     
  5. bfrigon

    Thread Starter New Member

    Dec 29, 2008
    3
    0
    I think i will go for the PLL solution...

    Thanks for your help hgmjr!
     
  6. russ_hensel

    Well-Known Member

    Jan 11, 2009
    818
    47
    You could use a microcontroller have it read and generate the signals.
     
  7. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    (edit) whoops just realised its 160Hz PWM not 160kHz...
    Which made my post irrelevant. :)
     
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