Connect with us

Interesting PFC Control IC (for PS gurus only)

Discussion in 'Electronic Design' started by Harry Dellamano, Mar 9, 2005.

Scroll to continue with content
  1. IRF has introduced the IR1150S control IC. It contains a proprietary "one
    cycle control" for CCM PFC with no line voltage sense required. Pretty
    neat!
    But, can't we also use it in any DC/DC CCM loop, be it forward, flyback or
    boost as a voltage feedforward control loop without actually looking at the
    input voltage. Even better, will this controller not cure the dreaded
    Harmonic Oscillation in peak current controlled CCM loops operated at >50%
    duty?
    OMG, I just wet my pants.
    What say you, you power supply gurus?
    Cheers,
    Harry
     
  2. Harry Dellamano wrote...
    http://www.irf.com/whats-new/nr050307.html
    http://www.irf.com/product-info/datasheets/data/ir1150.pdf
    http://www.irf.com/technical-info/refdesigns/irac1150-300w.pdf

    "Pricing is US $1.05 each for the IR1150S/IR1150SPbF and
    US $1.38 each for the IR1150IS/IR1150ISPbF..."

    "The One Cycle Control method used in the IR1150 controller does not have
    an analog multiplier, input voltage sensing, or fixed oscillator ramp,
    simplifying circuitry and reducing component count. Instead, IR's OCC
    uses a proprietary integrator with a reset circuit: The output of the
    error amplifier is integrated over each clock cycle to generate a variable-
    slope ramp. This variable ramp is compared with the error voltage and
    subtracted from the current sense signal to generate the PWM gate drive."
     
  3. Joerg

    Joerg Guest

    Hello Harry,
    Well, what does it cost? That is what it boils down to in the end. RHP
    problems could be handled with regular chips, too. But even those were
    too expensive in some of my designs so it ended up being all discrete or
    logic chips.

    Regards, Joerg
     
  4. Joerg

    Joerg Guest

    Hello Winfield,
    Thanks for the information. That is better than I thought, certainly a
    good deal for large PFC circuits. Regular switchers, maybe not. I am
    still holding out for something like the LM3478 but around 30 cents.

    Regards, Joerg
     
  5. Joerg wrote...
    That level of pricing is only obtained with legacy parts produced at
    paid-for yester-year backwater fabs. Not that there's anything wrong
    with those parts or fab lines; we depend upon them for ICs, etc., for
    lots of jelly-bean electronics products, such as PC power supplies.
     
  6. Joerg

    Joerg Guest

    Hello Winfield,
    Maybe that's why my designs contain legacy parts almost exclusively.
    Sometimes though I have the feeling that some mfgs want to front load
    the amortization, trying to squish out whatever the market gives in the
    first couple years. Not the IR1150S, that one seems fair in price.

    Front loading can really hinder market entrance. I have looked at
    several opportunities to swing a design to uC (MSP430). No chance, the
    jelly bean concoctions beat it all the time. At least they need to come
    out with a real bare bones version. It is amazing how cheap discrete SMT
    designs are these days. And when, for example, a switcher or PFC can be
    designed with CMOS logic then it's done that way.

    Regards, Joerg
     
  7. Terry Given

    Terry Given Guest

    Keyue Smedley has written dozens of papers on one-cycle control; Dragan
    Maksimovic wrote a really nice paper on an OCC boost converter about 10
    years ago. I figured out how it works once, but carefully forgot most of
    it. Basically its a non-linear modulating ramp, whose non-linearity is
    carefully chosen to automagically achieve (in this case) UPF. Heck, I've
    even seen an OCC paper by Slobodan Cuk.

    The problem with OCC is that it requires integrators that get reset
    every cycle. Thats not so bad, but (until now) you have had to DIY these
    integrators. I have never built one to prove it, but I expect that
    making a practical device work is a lot trickier than it appears from
    the papers I have read (none of which give any detail of the resettable
    integrators). I imagine that IR have done a nice job though.

    Cheers
    Terry
     
  8. Terry Given

    Terry Given Guest

    Their PF isnt too good at low load, high line though, its about 0.828
    for 30W = 10% rated load at 230V (cf 0.985 at 115V). Although they have
    made little or no effort at controlling them, emissions are not bad.

    I suspect the PF could be improved with peak input voltage feed-forward
    of some description, but that might prove tricky as there is no access
    to the on-chip integrators.

    Cheers
    Terry
     
  9. Genome

    Genome Guest

    Fairchild FAN4803, PFC and OFFLINE current mode controller in an 8 pin
    package.

    Internally synchronized PFC and PWM in one 8-pin IC
    Patented one-pin voltage error amplifier with advanced input current shaping
    technique
    Peak or average current, continuous boost, leading edge PFC (Input Current
    Shaping Technology)
    High efficiency trailing-edge current mode PWM
    Low supply currents; start-up: 150µA typ., operating: 2mA typ.
    Synchronized leading and trailing edge modulation
    Reduces ripple current in the storage capacitor between the PFC and PWM
    sections
    Overvoltage, UVLO, and brownout protection
    PFC VCCOVP with PFC Soft Start

    $1.24

    DNA
     
  10. I like your "even....S.Cuk"
    So Terry, will this controller cure sub harmonic oscillation in CCM >50%
    duty??
    What about using it's voltage feedforward ability in DC/DC loops?

    Regards,
    Harry
     
  11. legg

    legg Guest

    Previously known as the ML4803.

    RL
     
  12. legg

    legg Guest

    Which voltage?

    Read and enjoy.

    http://www.eng.uci.edu/faculty/smedley/occ.pdf
    http://www.eng.uci.edu/~pelwww/ocamp.pdf
    http://www.eng.uci.edu/~smedley/IPEMC-A185.PDF
    http://ece-www.colorado.edu/~rwe/papers/PESC95.pdf
    http://www.irf.com/technical-info/whitepaper/pcimeur03sccpfc.pdf

    others
    http://www.eng.uci.edu/faculty/smedley/index.html#sel
    http://ece-www.colorado.edu/~pwrelect/publications.html

    RL
     
  13. Terry Given

    Terry Given Guest

    Hey, if Dr Cuk writes papers on it, it probably works. Unlike much of
    the crap published in some professional comics :), which look something
    like this:

    1. design a topology have way too many magnetic components, switches,
    diodes and capacitors than necessary. If possible, ensure > 3
    semiconductors in power path at all times.

    2. write the NLTV equations for the system.

    3. run thru maths package and draw pretty pictures

    4. spice circuit - ie enter graphically, then let spice numerically
    extract & solve much the same equations as (2), and draw some more
    pretty pictures

    5. Compare and contrast the pretty pictures. If they are very similar,
    pat self on back and proudly announce "it works" (or in other words the
    analytic solution mathced the numeric one)

    6. Add to list of published papers, lean back at desk and sigh
    contentedly. Outside, the real world rushes madly by.
    I think in general it will do so, but you can perhaps design one that
    doesnt.

    OCC is by definition a non-linear controller, so there is no need to
    "linearize" (read as: pretend it is something it is not) the system
    before designing the controller. Quite the opposite in fact.

    You design a One-Cycle Controller by developing a non-linear
    time-varying mathematical description of the converter to be controlled.
    We do this anyway when designing a conventional linear controller.

    After adopting a suitable pose and expression, stare long and hard at
    the mathematical description, and voila - the desired OCC control law
    comes leaping out at you.

    This is basically a kind of feedback linearization controller (eg
    Applied Nonlinear Control, Slotine, pp207-271). The idea is to cancel
    the nonlinearities in a nonlinear system so that the closed-loop
    dynamics are in a linear form. Traditional LTI system theory can then be
    used to design the controller, and assuming there are no model
    uncertainties the controller behaves as predicted, for large as well as
    small signals.

    [linearisation is actually "do a taylor/maclaurin series expansion and
    throw almost all of it away". Often the bits you discard are important,
    which is why linearised controllers dont necessarily work so well for
    say large signals]

    A simple example of this concept is a boost PFC. When designing the
    voltage control loop, if you use square of the DC bus voltage and
    compare it with the square of the setpoint voltage (trivial in s/w) - in
    other words implement a DC bus energy controller - then analysis shows
    the closed loop behaviour is in fact linear (assuming the current
    controller is fast enough to reach setpoint faster than the voltage loop
    sample time).

    Its interesting that one method of nonlinear stability analysis,
    Lyapunovs 1st (or is it 2nd? someone will correct me im sure) method
    uses suitable "lyapunov functions" to check asymptotic stability. Common
    functions are the so-called "energy functions" that mathematically are
    similar to physics equations for energy like 0.5CV^2 etc. Oops,
    rambling...its because of the 2nd law of thermodynamics, real systems
    are always asymptotically stable (if not they would be perpetual motion
    or free energy machines) blurble.

    that control systems label isnt necessarily right either - I suspect
    some OCC designs may look more like a straight nonlinear controller
    rather than the aforementioned feedback linearisation. who cares, its
    only a label, but the techniques are interesting.

    A significant drawback with non-linear control is the lack of a
    handle-cranking mechanism for, say, proving stability, or even choosing
    a controller. Its a big nasty world out there....time to go shelter
    behing whats left of Maclaurin....

    as usual, *it depends*. Each OCC strategy is (or can be) unique - define
    your system, design the controller. A literature search will save you a
    fair chunk of work here, but in practice if you're gonna design a loop
    you might as well analyse the entire thing. Or at least load up the last
    mathcad file, save as and twiddle the numbers....

    One potential problem with feedback linearisation is its robustness to
    parameter variations. Some implementations may be very sensitive, others
    may not. The published results I've read for many OCC converters look
    pretty good, probably because the integration smooths over any errors.
    But I betcha you could come up with really lousy OCC's if you tried :)

    I (hopefully) have a project coming up where I will implement a whole
    raft of feedback linearisation controllers. Maybe they will even
    work.....the idea is to implement non-linear controllers to enable the
    system to maintain control (not saturate) for large setpoint & load
    changes, along with a high closed-loop bandwidth for relatively low
    sampling rates. This stuff (in some respects) is quite easy in a DSP,
    whereas a lot of it is a pig in hardware (until IR, ST etc. make nice
    cheap chips)

    Cheers
    Terry
     
  14. Joerg

    Joerg Guest

    Hello Terry,
    Or follow the route of the new age "instant design":

    1. Key your parameters into a web interface and click.

    2. Wait.

    3. Wait some more.

    4. Upon the message "parameters are outside the scope of this web design
    program", "design cannot be completed with entered parameters" or
    something like that, rip sheet off anger management pad on office wall.

    3. Crumple anger management sheet and throw into corner of office. For
    maximum relief, do so with gusto.

    4. Roll your own design. Heck, maybe you don't even need any fancy
    controller chip.

    Regards, Joerg
     
  15. Terry Given

    Terry Given Guest

    ROTFLMAO!

    Cheers
    Terry
     
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day

-