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    IC for adding turn ON delay but zero turn off delay

    Have anyone seen an IC that can add turn on delay for a PWM but zero turn OFF delay

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    Re: IC for adding turn ON delay but zero turn off delay

    Hi,

    I'd say "zero" is not possible.
    Even a piece of wire causes a delay.

    --> give values for expected turn ON delay (range, values with units)
    --> give value for acceptable turn OFF delay (value with unit, no phrase like "as short as possible")
    Maybe even useful information: logic family and voltages, PWM frequency, a brief description of your application..

    Klaus
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  3. #3
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    Re: IC for adding turn ON delay but zero turn off delay

    Hi,

    At the risk of looking stupid because I'm not sure what sort of thing you're looking for, a dual MOSFET and a few passive components could be used for an ON delay, especially if it is just to control an enable pin or similar rather than a power path. This simulation looks promising to create a delay, if it's reliably accurate. Sharper turn on after the delay would need something like a comparator added.

    Click image for larger version. 

Name:	ON DELAY NO OFF DELAY.JPG 
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ID:	150678


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    Re: IC for adding turn ON delay but zero turn off delay

    Useful pwm dead times are in the range of a few ns for GaN or SiC power stages up to us for IGBT. A popular method to implement it in the analog domain are RCD circuits. Also a combination of symmetrical RC delays and logic gates. Monoflops can work too, but I didn't yet feel a need to use it. Digital pwm controllers (uC or PLD) will use timers.


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