Slew rate control

Discussion in 'General Electronics Chat' started by nepdeep, Sep 5, 2012.

  1. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    I am developing a fast transient repsonse testing system. I have to make a circuit to control the slew rate. Need some advice form experts in the forum.
     
  2. crutschow

    Expert

    Mar 14, 2008
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    What are the requirements for the transient signal?

    Edit: In general you can generate a specific slew-rate by using an integrator.
     
  3. ramancini8

    Member

    Jul 18, 2012
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    A good question gets a good answer. What range of slew rates are you interested in? What voltage limits do you need? What power is available? Describe everything you can and maybe we can help.
     
  4. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    these are the requirements for my project :

    if possible detailed answers please. I am engineering student. It is my graduation project.

    Voltages < 20V
    Current > 10A
    Thermal overload protection
    Overcurrent protection
    Max current setting
    Current measurement output (to omit current probe)
    Decent very low inductance wire connection. (what connector?)
    Pulse control (dutycycle and frequency and count?) thumbwheel?
    Voltage and current measurement points (SMB?)
    Addtional requirements
    · Dissipate up to ~20W
    · Frequency in range of 100Hz to 1kHz
    · Slew rate control
    · Powered with single labsupply
    · 2 adjustable loads, one continuous typical load, other to ‘step’ to max load.
    · The current step should not react on the voltage ringing caused by the step
     
  5. crutschow

    Expert

    Mar 14, 2008
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    So, the answer to your original question is, for those frequency ranges, you can use an op amp integrator for the variable slew rate. Depending upon the range you need, you may need to switch in different integrator capacitor feedback values as well as use a variable input resistance to cover the slew-rate range you need.
     
  6. Ron H

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    Apr 14, 2005
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    Current>10A is unlimited on the upper end. No one can design to that spec.
     
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  7. nepdeep

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    Sep 14, 2011
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    some more insights from everyone please.
     
  8. Ron H

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    If you can't put an upper bound on current, I don't think you'll get much help.:(
     
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  9. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    What could be the reasonable upper bound ? If you assume some max. upper bound , can you help me with rest of them.I need overview of construction of the circuit please. Thanks in advance.
     
  10. crutschow

    Expert

    Mar 14, 2008
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    I would think it would be Current < 10A, not Current > 10A.
     
  11. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    current upper bound ....is 20[A]...

    P.S. while starting this project I was in total darkness...now getting somewhere...I can understand how general my question were..and how could i expect good answer then...
    help needed ....
    and I am using the circuit almost similar to the appnote from linear...
    I am in the phase of design....what could be equivalent block diagram...if i have to include the overcurrrent and overvoltage protection....my block diagram is as follows:

    Block diagram.jpg

    http://cds.linear.com/docs/Application%20Note/an104f.pdf
     
  12. bountyhunter

    Well-Known Member

    Sep 7, 2009
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    Yeah, in my former career I had to design around impossible specs all the time. The very first step of any project is to get the person requesting it to tell you what they actually need.

    Amazing how many people think that designers have the capability of mind reading in their skill set.:p
     
  13. bountyhunter

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    Sep 7, 2009
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    see page 5 for transient tester with adjustable slew rate

    http://www.ti.com/lit/an/snoa507/snoa507.pdf
     
  14. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    They donot mention high current..eg 22 A here on texas appnote....
    That is the reason ...I want to implement the circuit similar to linear appnote...any suggesitons and comments on my previoius question.!!
     
  15. bountyhunter

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    Sep 7, 2009
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    The current is supplied by the power supply under test, peak value is determined by the voltage and ohmic value of the load resistance.

    I think you need to read the app notes, you don't seem to understand how it works. In the Linear Tech note they are referred to as "RLOAD" and "REGULATOR UNDER TEST".
     
  16. bountyhunter

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    Sep 7, 2009
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    My only suggestion is that the block diagram is basically meaningless, I don't know how to respond to it because it doesn't convey any information to me.
     
  17. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    What range of slew rate control do you need?
    Answer should be in amps/second, or amps/μs, etc.
     
  18. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    slew rate of 5[A/us]

    Thanks in advance
     
  19. Ron H

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    It doesn't need to be variable?

    EDIT: Is 5A/us the minimum, or does it need to be controlled? In other words, is faster OK?
     
    Last edited: Nov 2, 2012
  20. nepdeep

    Thread Starter Member

    Sep 14, 2011
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    Faster is better ...minimum is the slew rate...is faster possible?? :)
    please let me know...m getting really curious...

    yes and slew rate is controllable via...external controller
     
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