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Hot!Complementary Pwm without timer

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Frongach
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2020/05/29 09:49:56 (permalink)
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Complementary Pwm without timer

Hello,
I'm working on a synchronous 3 phase dc to dc converter controlled by a pic. My issue is that I have 6 switches to run and there are not enough ccp modules on the 16F pic I had been using. However, I am hoping to use a 28 pin dip package for the pcb design due to ease of soldering and changing out of chips. The only pics offering enough pwm outputs, along with some other features I need, are 24F chips with far more pins and only in a surface mount package, adding lots of complexity, cost etc to the pcb.
I was thinking that since the two switches on each regulator will be operated in inverted mode, it may be possible to time the pwm for one switch using the ccp module and to simply operate another arbitrary output pin 180 degrees out of phase, with a certain dead time added of course, for the other switch (ie, the 'diode') using the appropriate special function register.

Would this be feasible?
Sorry this is so long!
Thanks very much,
Brian
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5 Replies Related Threads

    coffee critic
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    Re: Complementary Pwm without timer 2020/06/02 14:23:52 (permalink)
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    Is this question still open?  If so a couple options the PIC16F177X family have 3 and 4 PWM options with assorted analog blocks for support.  If you are more brave the PIC16F178X family has the built in PSMC module that has a 3 phase module built in.

    n_*$
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    RISC
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    Re: Complementary Pwm without timer 2020/06/02 16:00:41 (permalink)
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    Hi,
    Did you try to use MAPS selector ?
    you can enter your specification (peripherals, pins, CCP, PWM,...) and it will list all devices which match :
    http://www.microchip.com/MAPS
    Maybe you want to check the PIC16F18856 or PIC18F26Q43 which have several PWM and many CCP modules in 28 pins
    Regards
     
     
    #3
    Bob White
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    Re: Complementary Pwm without timer 2020/06/02 18:48:26 (permalink)
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    Use 3 PWM outputs with a half-bridge gate driver IC for each pair of MOSFETs.
     
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    mpgmike
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    Re: Complementary Pwm without timer 2020/06/03 07:24:44 (permalink)
    +1 (1)
    The dsPIC33EV256GM102 is a 28-pin DIP part with advanced PWM functions.

    I don't need the world to know my name, but I want to live a life so all my great-grandchildren proudly remember me.
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    Frongach
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    Re: Complementary Pwm without timer 2020/06/03 09:46:02 (permalink)
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    Thanks for your suggestions, the psmc route has potential I think. I do use the parametric search, of course. Bob, this particular case requires separate drivers for each switch as output of buck boost is inverted, referencing system ground to the negative output voltage is not a good solution I think. Otherwise level shifting of the pwm control signal is needed if you want to drive both switches with a half bridge, or so it seems to me.
    I would still be interested in knowing if pwm can be used in the manner specified in the question, using a ccp module to time the pulses and inverting the on time for the other fet in software, or if there are hardware limitations to this.
    Thanks,
    Brian
    #6
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