Difference in "PWM" controllers

garlic Solar Expert Posts: 43
I had read somewhere yesterday someone stating that the Xantrex
C series controllers were not "true" PWM controllers.I was wondering
then If someone could please explain the difference in technology (if any)
between say a C35 and a Prostar 30 as far as how they apply current?
Are there any substantial advantages or just a different way to get to
the same destination?Not that this has any major bearing on what my
system plans are.I'm just curious as to how they might be different.




  • niel
    niel Solar Expert Posts: 10,300 ✭✭✭✭
    Re: Difference in "PWM" controllers

    they are pwm controllers. i don't know of any basic differences. if you think of what was really said about it and where please tell us as i'd certainly be curious who said what.
  • garlic
    garlic Solar Expert Posts: 43
    Re: Difference in "PWM" controllers

    I hope I wasn't taking it out of context,though I don't believe I was:

    An FYI

    the Xantrex C40/C60 is not a true pwm contoller , it lacks the inductor part for that. It is really an On/OFF controller.

    I just wanted to make sure I understood the technology correctly


  • mike95490
    mike95490 Solar Expert Posts: 9,583 ✭✭✭✭✭
    Re: Difference in "PWM" controllers

    I think there was a typo in that message.

    A simple FET can perform PWM control (Pulse width modulation) and needs no inductor.

    A MPPT controller needs inductors, so it can perform the voltage downconversion.

    The C-xx series is all PWM controlers
    Powerfab top of pole PV mount | Listeroid 6/1 w/st5 gen head | XW6048 inverter/chgr | Iota 48V/15A charger | Morningstar 60A MPPT | 48V, 800A NiFe Battery (in series)| 15, Evergreen 205w "12V" PV array on pole | Midnight ePanel | Grundfos 10 SO5-9 with 3 wire Franklin Electric motor (1/2hp 240V 1ph ) on a timer for 3 hr noontime run - Runs off PV ||
    || Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
    || VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A

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  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    Re: Difference in "PWM" controllers

    That was about 9 years ago... Not answering for Solar Guppy, but today, as Mike says, we call PWM as "on/off" controllers.

    And controllers that use inductors are MPPT (Maximum Power Point Tracking) which, usually inside have a switch mode power supply that is Buck type down converter. Which has the inductors to allow the MPPT/Buck Mode type charge controllers to efficiently take high voltage / low current and down convert to lower voltage / higher current for the battery bank.

    Buck Converter

    Without the inverters, the CXX family is just a PWM (pulse width modulation) On/Off switch...

    Buck converters also use PWM internally to control their operation--Probably the root of the confusion...

    A MPPT type charge controller costs about 3-5x more than a PWM / On-Off controller. And typically MPPT are used with larger systems (say more than 400-600+ watts)

    PWM's tend to be used for smaller systems (~200 watts and under).

    The MPPT is a more flexible controller that can allow you to place the solar panels much farther away from controller/battery shed because you can use a higher voltage solar panel array...

    They are nice--but not cheap.

    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
  • garlic
    garlic Solar Expert Posts: 43
    Re: Difference in "PWM" controllers

    Thank you folks for ironing out this wrinkle.

    I knew the difference between mppt and pwm.I thought maybe
    I had missed some disparity between the Cxx CC's and other pwm types and
    that motivated me to ask what they might be.

    Thank you again,