Hot!How to generate 200KHz PWM with duty cycle resolution >12 bits

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aman111
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2018/07/11 14:15:33 (permalink)
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How to generate 200KHz PWM with duty cycle resolution >12 bits

Hi,
I am designing an MPPT circuit with a 2-phase Buck Converter.
The circuit contains 4 MOSFETs 
2 signals need to be 180 degrees phase shifted,
other two will be the complement of the first ones.
I need a 0.05% increase in the duty cycle for one increment cycle
Can somebody suggest how can I make this work???
Thank You for helping in Advance
#1

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    DarioG
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 14:27:19 (permalink)
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    any PIC in mind? use a dsPIC33 for motor control...

    PORCODIO DAMMI I SOLDI PORCAMADONNA!
    #2
    mbrowning
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 14:27:47 (permalink)
    +1 (1)
    Let's see, 200KHz with 12 bit resolution. Hmmm
    I know !! Just overclock your PIC to 819.2MHz  :)

    Can't remember. I've slept since then - Mark
    #3
    MBedder
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 14:32:32 (permalink)
    +1 (1)
    To achieve this resolution you need the PWM carrier frequency of 0.2 MHz x 2^12 = 819,2 MHz (or period of 1.22 ns). This is easily done with the GS series of dsPIC33 MCUs. The newest dsPIC33CH MCUs are able to provide 250 ps resolution PWM which equivalent to 4 GHz carrier frequency.
     
    #4
    NKurzman
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 14:41:09 (permalink)
    -1 (1)
    200,000 * 4096 = 819,200,000  so that is 819Mhz with 12 bits.   Plus the Dividers.
    No PIC Supports that.
    so >12 bits would be in the Gigahertz.
    #5
    MBedder
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 14:45:59 (permalink)
    +1 (1)
    NKurzmanNo PIC Supports that.
    RTFM. Start with the dsPIC33 GS series datasheet and discover their 1.05 ns PWM resolution, and end up with the dsPIC33CH MP series datasheet and discover their 0.25 ns PWM resolution.


    #6
    DarioG
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 15:10:50 (permalink)
    0 (2)
    oh, those russians grin

    PORCODIO DAMMI I SOLDI PORCAMADONNA!
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    NKurzman
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 15:40:34 (permalink)
    +1 (1)
    I stand Quite corrected.
    ( at least my math was correct)
    RTFM? There are a thousand of them.
    I wonder is the Part select would have helped here.
    now I have to look up the GS series.
     
    #8
    DarioG
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 15:48:59 (permalink)
    +1 (1)
    who's the idiot?

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    #9
    mbrowning
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 18:07:06 (permalink)
    +1 (1)
    But the forum is "8-Bit Microcontrollers" so dsPICs need not apply and the only way with an 8-bitter is to clock it at 819.2MHz :)   Probably need liquid helium cooling.

    Can't remember. I've slept since then - Mark
    #10
    NKurzman
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 18:39:24 (permalink)
    +1 (1)
    mbrowning
    But the forum is "8-Bit Microcontrollers" so dsPICs need not apply and the only way with an 8-bitter is to clock it at 819.2MHz :)   Probably need liquid helium cooling.


    If you can make 16 bitter do it They could make an 8 bit do it. ( not that they would).
    does any one have a Part number of one? I am wondering how they are doing it. Some hyper PLL?
    #11
    MBedder
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/11 23:56:19 (permalink)
    +1 (1)
    It is not done with that high PWM clock frequency - partial clock resolution is achieved using the gate delays. Some explanations can be found on the Texas Instrument site (look for High Resolution PWM) since they use a similar technique in some of their C2000 MCUs for a long time.
    #12
    n9wxu
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    Re: How to generate 200KHz PWM with duty cycle resolution >12 bits 2018/07/16 08:23:06 (permalink)
    +1 (1)
    This can be done by combining the NCO and a PWM using a CLC.  This will provide an AVERAGE resolution of 16-bits.
    The explanation is in AN1476.
    #13
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