Connect with us

nanowatt switch

Discussion in 'General Electronics Discussion' started by EnergyScavenger, Feb 24, 2013.

Scroll to continue with content
  1. EnergyScavenger

    EnergyScavenger

    7
    0
    Feb 14, 2013
    Greetings,
    I am looking for equivalent of relay or optocoupler but in nanowatts range if there is any.
    I looked into a MOSFET however gate switch cannot be isolated and there is Id drop when conducting. Relay is cool because there is no current drop or voltage drop when switch is on. Timing is in millisecond range.

    ----- ------- switch
    ---------

    ---=====----- trigger input

    however trigger input has coil which has consumes lots of watts.
    Optoisolator has losses in both ways (switch and trigger input).
    Voltages are of 0.4V minimum to 2V maximum. Currents are in low mAmps.
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    You could look at something like the LH1262 to switch a pair of mosfets.

    I'm not sure where you want the nanowatts to be though?

    Are you switching a very tiny signal, or do you want the switching to be very low power.
     
  3. Harald Kapp

    Harald Kapp Moderator Moderator

    11,513
    2,651
    Nov 17, 2011
    That gives mW, not nW.

    Tell us more about your application.
     
  4. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    If you don't have very frequent switching cycles, I am sure the most energy saving alternative is a bi-stable (latching) relay.
    That's anyway the way I am doing such projects (you should even be able to go into the nW region).
     
  5. EnergyScavenger

    EnergyScavenger

    7
    0
    Feb 14, 2013
    thats interesting concept

    Thanks everyone for reply.
    My frequency of switching cycles is between 2Hz and 10Hz with a 20 percent duty cycle.
    The critical parts are that
    1) Activating signal side is in microwatts range, less the better.
    2) Switch itself (the bus or rail) does not introduce power losses like optoisolator's transistor etc. (nanowatts losses is okay), that is why relay looks better because it is just a contact.

    I will look into LH1262 and bi-stable latching relay.
     
  6. Electrobrains

    Electrobrains

    259
    5
    Jan 2, 2012
    Hmm, with that switching speed whatever relay is out of question!
    Optocouplers or Photovoltaic Couplers will not be nW.

    Let's try another path:
    Question: Do you really need isolation?
    I think the only component that would be able to do your work well would be a modern power MOSFET. If it could be switched directly without isolation, you could reach your goal.
    Maybe through level shifting or some other form of isolation (for instance capacitive coupling).
     
  7. EnergyScavenger

    EnergyScavenger

    7
    0
    Feb 14, 2013
    Found analog switch in microwatt range

    Yes, you are correct. Optocoupler and Relays will not do the job.
    I looked for alternative and right now I am looking for one to one analog switch like circuit. I am reviewing at TI.com the TS5A12301E chip. It gives power consumptions in small microwatts range (less than 20uW) which I can accept. I recommend others to look into it. Its cool. Unless someone got something better than that. If you do, please surprise me.
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    An analog switch is going to have a relatively high resistance and you're not going to be able to isolate it from the voltage used to drive it.

    Perhaps you need to tell us more about your application so we can assist you.
     
  9. EnergyScavenger

    EnergyScavenger

    7
    0
    Feb 14, 2013
    the purpose of low watt switch

    I need switch1 to temporarily connect source/microgenerator to capacitor to charge it up. Then open that switch1 and close switch2 connecting that same capacitor to battery. I am using timer to activate switches accordingly. That is why switch activation power requirement to be as low as possible in microwatt range acceptable, and the switch itself at low resistance as possible like relay type switch. I still believe that analog switch I mentioned is an option, unless someone points out to me on its datasheet. I will order some analog switches to experiment with it. I've already played with optoisolators and mosfets and they take a lot of current.
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

    25,496
    2,837
    Jan 21, 2010
    From the sound of it a mosfet would be the easiest option. It doesn't appear that you really need any isolation.
     
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.
Similar Threads
There are no similar threads yet.
Loading...
Electronics Point Logo
Continue to site
Quote of the day

-