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Spike Generation

Discussion in 'Power Electronics' started by Sagar Chandurkar, Sep 11, 2018.

  1. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    Does any 12V powered ckt generates spike?
     
  2. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Depends. Are there any switching elements/functions or any inductive components?
     
    Sagar Chandurkar likes this.
  3. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    There is 1 Inductor in 12V to 5V switching regulator ckt, of value 10uH, will it generate any spike, if yes what will be its Amplitude, can you help me with any calculations or Formula for that.
     
  4. kellys_eye

    kellys_eye

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    Jun 25, 2010
    What about the rest of the circuitry? What is the PSU driving?

    Have you looked at the data sheet for the regulator and checked the design characteristics and parameters?

    Why do you need to know these figures? What is your end purpose?
     
    Sagar Chandurkar likes this.
  5. Alec_t

    Alec_t

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    Jul 7, 2015
    Read up about Faraday's Law and Lenz's Law.
     
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  6. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    My unit is used in Generator application, PSU is driving Microcontroller, Relay Driver IC, optocoupler etc,

    and main problem is my relay driver IC MC33879 is getting Damaged and Supplier is saying its because of spikes, and want to get sure that my ckt is not generating any spike, so that I can ask my customer to look in other parts of Genset.

    Relay is Externally powered with 12V. and TVS Diode 5KP20CA Bi-Directional is already connected across relay driver ckt.
     
  7. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    Ok sir I will, thank you for your valuable reply.
     
  8. kellys_eye

    kellys_eye

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    Jun 25, 2010
    the TVS you've fitted still allows pulses of up to 20V to be generated/passed. Worse - it allows pulse of 20V in the WRONG DIRECTION to pass.

    Use a simple diode across the relay coil.
     
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  9. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    Relay Driver IC is used in Low Side Drive Configuration, and in this config it is immune till 45V pulses.
    1N4007 Diode is already present in ckt across relay coil still I am facing this problem.
     
    Last edited: Sep 15, 2018
  10. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Do you have the correct supply decoupling components situated around the circuit? i.e 100nF at each IC power pin, 10μF and/or 100μF across the supply lines?

    Show your schematic.
     
  11. Alec_t

    Alec_t

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    Jul 7, 2015
    That diode may not be fast enough to catch a sharp spike. If the relay coil current is less than ~150mA, try a 1N4148. Failing that, try a fast-recovery diode.
     
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  12. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    Sorry, Sir, I am not allowed to share Schematic but I can tell you that, to regulate power we have used ADP3050 to get regulated 5V supply from input 12V, Ckt is nearly same as suggested in Datasheet, and yes we have used Decoupling capacitors across power lines.

    this regulator is used only to power our internal ckt of a unit, and we are giving a negative drive to external realy though IC MC33879.
     
    Last edited: Sep 17, 2018
  13. kellys_eye

    kellys_eye

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    Jun 25, 2010
    Your difficulties may be as a result of a design issue so if you're not prepared to share the details then we've gone as far as we can with our assistance. You're on your own from here!
     
    Sagar Chandurkar likes this.
  14. Sagar Chandurkar

    Sagar Chandurkar

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    Sep 11, 2018
    ok Sir Thank you for your kind assistance I will try to get authority of sharing design and get back to you again.
     
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