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High efficiency low current low power supplies

Robert Dugour
Prodigy 50 points
Other Parts Discussed in Thread: UCC28911, UCC28910, UCC28710, UCC28700, UCC28880

the IOT trend asks for new solutions for power supply. While we try to decrease power consumption we will more and moer meet the limits of the power supply itself.

The efficiency of the available converters decreases dramatically if the output current decreases.

So if we limit the quiescent current to 4 mA the efficiency of the power supply will decrease to practically zero thus with a really bad overall efficiency.

Now the question: Are there new AC to DC or DC to DC converters that can offer high efficiencty at very low output currents? 

this could be for instance 60VDC in and 3.3VDC out at 2mA

Or 230VAC in and 3.3VDC out at 2mA

that still have an efficiency higher than 60%

best regards

Robert

  • 0
    TI__Mastermind 31580 points
    Hi Robert,

    Take a look at the UCC28910 and UCC28911 switcher controllers they have EVMs and reference designs that have very good efficiency at light loads. The UCC28700 and UCC28710 controllers are used with external mosfets and there are a range of EVMs and reference designs that have very low no-load power and good light load efficiency.

    Regards

    Peter
  • 0 in reply to Peter Meaney
    Prodigy 50 points

    Thanks for the advice,

    I studied the suggested parts , however there is nothing said over very low load conditions.

    Example the designed IOT device uses a buffer capacitor to store  just enough energy for a send burst. and a change over.

    Apart from loading this capacitor once in a while all parts are asleep that is 0,1mA or less currect at 3.3V

    After the send burst the buffer capacitor have to be reloaded, max current 10mA for a second or less thats all!

    Solution for now: I do use a very low quiescent current DCDC converter with 60V input voltage.

    As soon as the buffer capacitor reaches 55Volt the load current (AC 230V rectified and MOSFET controlled with serial resistor) As soon as the voltage on the buffer capacitor decreases below 15V the load current is switched on. The on and off switching circuit however consumes some energy which is all spoiled. therefore I can reach a maximum efficiency of 60%.

    Must be possible to do better aint that right?\

    Best regards

    Robert Dugour

    DEALOGIC

    Nederland

  • 0 in reply to Robert Dugour
    TI__Expert 7395 points
    Robert,
    Consider looking at ucc28880. This is typically used in very low power applications including <10 mA output designs for AFCI/GFCI circuit breakers.
    See the evm here where we do about 63% efficiencyat 10mA for 5v output from universal AC input. www.ti.com/.../sluub56c.pdf
    That board is designed for higher power so you might be able to get better if you designed it for even lower power.
    Additionally you may want to look at our blog discussing AC/DC solutions for IoT applications here: e2e.ti.com/.../powering-the-iot

    Regards
    John
  • 0
    Intellectual 540 points
    the UCC2863x family boasts potentially under 100mW in standby from a universal source