• EEVblog #971 – Zero Standby Power TV – BUSTED!

    Bristol University have a neat new “zero power sensing” chip that takes energy harvested signals and switches an open drain output, the UB20M Voltage Detector.
    But the marketing has gone too far when they demo a TV that supposedly has zero standby power. Dave busts this smoke and mirrors demo.
    Forum HERE
    Datasheet HERE

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      • ScottK

        Their chip needs 0.65V minimum input signal to operate. That precludes the use of quite a few passive sensor technologies (no need to discuss active, they need power to run). Photovoltaic and piezoelectric sensors can produce such high voltages, but what else? I doubt you’d get 0.65V from a passive seismic detector until something falls on it.

        Never mind the quiescent power consumption of the power brick, I can probably design an IR receiver with power consumption lower than the energy loss in a 6ft 230V power cord (just measured: 140pF hot to neutral, Rp = 110Mohm, half a milliwatt of loss @ 230Vrms). It’s easy to forget how hard it is to achieve zero power consumption in AC circuits due to parasitic capacitance.

        And, as you have observed, the standby power consumption of many battery powered devices is already so low that battery shelf life is the limiting factor. The low current draw and (presumably) glitch free operation of their device as it powers up is impressive, but of questionable use in a lot of products and of no use in their demonstration scenarios.

      • tlhIngan

        If anyone is curious, European regulations dictate that if your device does NOT have an LED, in standby you can draw… 0.5W. If you DO have an LED, you can use 1W in standby state (where you’re off but waiting for an IR turn on signal).

        The power supply draws about half that power, so you really have about 250mW or 500mW to play with. In the TV SoCs we used, they used most of that (and that was with the SoC entering standby mode, too), leaving you with maybe 50-100mW to your IR or other remote control sensor (e.g., if you use Bluetooth) hardware.

        And yes, the power budget is very tight – which is why people put LEDs, because at 1W, your power supply drawing 500mW is not such a big deal anymore.

        This chip might be useful if we wanted to meet the 500mW requirement because the power supply will be consuming practically all of that.

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