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Comments for Shunt Regulation Part 3

Current Discussion: Main discussion

  1.   #1
    iko's Avatar
    iko is offline
    diyAudio Moderator Emeritus
    Higher current through v1.2 will easily lead to instability because of the higher gain at higher frequency (you can blame the buffer which extends the bandwidth). v1 does not suffer of this problem. That's what I think, although I haven't built v1.2 yet.
     
  2.   #2
    iko's Avatar
    iko is offline
    diyAudio Moderator Emeritus
    However, I haven't thought of the compensation which I'm told brings the regulator to stability. So I retract my previous comment.
     
  3.   #3
    Salas's Avatar
    diyAudio Chief Moderator
    Here are two simulation indications. Run on V1.2 TO-220 IRF9610 & 9540 46Vo with 10uF film cap for the Norton Vref decoupling and 4u7 film cap with 1R locally across reg's output. There is a lead-lag step network compensating the error amplifier. To the left at 200mA. To the right at 1A. 10 degrees of PM loss. Its not meant to run on amps due to the heat inefficiency, thus the lighter/faster CCS Mosfet, but I checked it out on the sim just for the sake of argument. If a heavy duty application comes to mind, the gate stoppers and the comp can always be centered around large current and TO-247 Mosfets. I would not think that the signal levels on a power amp will justify more than a V1.0 if a shunt is wished to power it though.
    [image]1V2@970mA.gif|thumb[/image][image]46V1V2LMCb.jpg|thumb[/image][image]1V2@200mA.gif|thumb[/image]
     
  4.   #4
    RCruz's Avatar
    diyAudio Member
    Would you elaborate a little bit more on the sense wire connections ?

    Theoretically I know why we need it and I can confirm the benefits ( I have built more than 20 V12R), but would like to have a clearer idea on how it works.
    __________________
    RC
     
  5.   #5
    Salas's Avatar
    diyAudio Chief Moderator
    We want the reg's error amplifier to measure correctly the impedance at the actual load's nodes. It's exactly like when we want to do precise resistance measurements with a multimeter. We should take the probe wires resistance out of the picture. See this video, its easy to grasp Kelvin's principle:
    [url=http://www.youtube.com/watch?v=m9YBOwVMos4]Digital Multimeter Tutorial, Making Resistance Measurements, Understanding 4-Wire Ohm Measurement - YouTube[/url]
     
  6.   #6
    JonSnell Electronic's Avatar
    diyAudio Member
    I would say that any resistance measured below 47R won't see any appreciable difference. This system is for Low Ohms Meters only.
    __________________
    Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
     
  7.   #7
    Salas's Avatar
    diyAudio Chief Moderator
    In the case of the reg the principle is the same, but we are interested in the tiny dynamic fluctuations. So if the voltage we look to hold constant will play with signal for say 10mV at a load circuit's nodes that runs at DC bias of 100mA we are talking a 0.1 Ohm impedance change.
     
  8.   #8
    JonSnell Electronic's Avatar
    diyAudio Member
    Do you mean that you want to measure a voltage across the load with the aim of calculating the current drawn or dissipated in the circuit? Maybe too simple a question.
    If you use a feedback loop to regulate a power supply, that is very similar to an analogue amplifier feed back loop but if there is too much feedback, it may 'take off' and oscillate. Current feedback is subtly differen to voltage feedback.
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  9.   #9
    Salas's Avatar
    diyAudio Chief Moderator
    The error voltage amplifier in the reg (the "sense" wires connected part) constantly compares the voltage at the load's nodes to its reference at the reg and counteracts differences by pumping or drawing current via the shunt current amplifier it controls. That part is connected to the load via the "force" wires.
     
  10.   #10
    JonSnell Electronic's Avatar
    diyAudio Member
    [QUOTE=Salas;3560573]The error voltage amplifier in the reg (the "sense" wires connected part) constantly compares the voltage at the load's nodes to its reference at the reg and counteracts differences by pumping or drawing current via the shunt current amplifier it controls. That part is connected to the load via the "force" wires.[/QUOTE]

    Yes, that is correct but we are discussing, I thought, a voltage regulator?
    I have just scrolled down and find all sorts of writings that I have not seen before.
    How confusing!
    Is this a continuation of another blog?
    __________________
    Support for Fender, Marshall and all Valve Equipment; Audio Innovations, Audiorama FU29, Quad and Leak. www.jonsnell.co.uk
     
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