This is progress, but in a small part of the power supply. It looks like they have a charge-pump type power supply, and they turn off the charge-level checking circuit except during polls. They also adjust the polling rate down when not much is happening. The question is how fast they can respond to a sudden demand for output power. Can a sudden load drain the capacitor before the input side notices and pumps it up again?<p>Excessive standby power consumption is a big problem. There are lots of devices, especially TVs, which consume far too much power when supposedly off. (Of course, some of them are constantly listening to you, phoning home, and possibly spying on you.)<p>One of the more important recent developments in switching power supplies is the elimination of electrolytic capacitors. They're the biggest point of failure. This is already happening in LED lightbulbs.[1][2] Electrolytic caps inside LED lamp units are the primary cause of failure. They only last about 10,000 to 20,000 hours, while high-output LEDs are good for 40,000 hours. If a power supply can be built with lower capacitance, ceramic capacitors can be used. That makes it possible to get the lifetime of all the power components above 100,000 hours, so the LEDs will burn out first.<p>[1] <a href="https://hub.hku.hk/bitstream/10722/164083/1/Content.pdf" rel="nofollow">https://hub.hku.hk/bitstream/10722/164083/1/Content.pdf</a>
[2] www.rle.mit.edu/per/wp-content/uploads/2014/10/Chen-Electrolytic-Free.pdf
Quote: “In the low-power regime, the way these power converters work, it’s not based on a continuous flow of energy,” Paidimarri says. “It’s based on these packets of energy. You have these switches, and an inductor, and a capacitor in the power converter, and you basically turn on and off these switches.”<p>To me that's a failed attempt to create a layperson-accessible explanation. In my NASA Space Shuttle work in decades past I also created efficient power supplies and I used similar methods -- but I think I can explain it more effectively.<p>The trick to making a modern power supply efficient is to control the phase relationship between voltage and current. This is normally performed in reactive elements like an inductor, a capacitor, or both.<p>Put another way, instead of changing a voltage level with a resistance (which would waste power), you need only manipulate a reactive element so the phase angle between voltage and current is something other than zero degrees. For example, at a phase angle of 90 degrees, you can have substantial voltage as well as current, but no power dissipation (except where it's needed).<p>That's the secret to power supply efficiency -- change the voltage without using any power-dissipating elements.
Would it be more efficient to have a secondary bus in the home that provides lower voltage and current for IoT type devices? Something like the USB ports built in to the power outlet but that actually has a single converter in the home with more efficiency.
Short story they measure the output voltage every once in a while, depending on the load, instead of always measuring it.<p>> If no device is drawing current from the converter, or if the current is going only to a simple, local circuit, the controllers might release between 1 and a couple hundred packets per second.<p>> .. To accommodate that range of outputs, a typical converter — even a low-power one — will simply perform 1 million voltage measurements a second; on that basis, it will release anywhere from 1 to 1 million packets.<p>^ Normal switched-mode converter, though a million is not realistic and they don't always work like that<p>Considering that today's computers power supplies work at 70kHz, a megahertz is probably too much. (granted PSUs do PWM so i may be wrong, but it depends on the size of the capacitor at the output; then again chemical capacitors are bad for efficiency and block capacitors are huge compared to their capacity so block capacitors would have to be filled more often meaning more pulses meaning more losses on the FETs but then again transistors now have much lower capacitance and resistance then ever before but .. ramble ramble ramble etc)<p>> Paidimarri and Chandrakasan’s converter thus features a variable clock, which can run the switch controllers at a wide range of rates.<p>Theirs just varies the rate of (in programmers terms) pool()ing. Like clocking down a cpu when there is no load.<p>(note: "packets" means pulses, see switched-mode power supply on wikipedia)
Lets look at this practically: <a href="http://www.ti.com/product/tps62240/description" rel="nofollow">http://www.ti.com/product/tps62240/description</a><p>This TPS62240 has an efficiency of 95% across any load above 1mA. Below 0.1mA, its 15uA quiescent current kills its efficiency... but it still has over 70% efficiency at 0.1mA. That is, the converter uses say... 0.13mA while outputting only 0.1mA. (I mean, it really should be in terms of Watts. But since P = VxI, the mA estimation is a good enough indicator).<p>A single NiMH AA battery has 2000mAh of energy storage capacity, Eneloops actually are closer 2500mAh. <a href="https://www.amazon.com/Panasonic-BK-3HCCA4BA-Eneloop-Pre-Charged-Rechargeable/dp/B00JHKSL28" rel="nofollow">https://www.amazon.com/Panasonic-BK-3HCCA4BA-Eneloop-Pre-Cha...</a><p>So in effect, a SINGLE AA NiMH batteries can run at 0.13mA for around 2 <i></i>years<i></i>. In practice, the self-leakage of these batteries are the major problem on those time periods.<p>At some point, reducing quiescent power consumption isn't a major problem anymore. I think the ridiculously efficient 500pA draw is unlikely to be used in any design where a AA battery is sufficient.<p>Smaller coin-batteries have issues ramping up to the ~50mA to transmit a radio signal. So I'd bet that in practice, AA batteries (or larger 18650 cells) will continue to be used... and therefore a hugely power-efficient design from these researchers won't have a major competitive edge.<p>-------<p>As an FYI: These efficient power converters enter "sleep" modes while the voltage output is above 1% of the voltage. Once the voltage drops to the nominal voltage, the TPS62240 "wakes up" and starts injecting charge into the capacitor / inductors... before entering another sleep cycle.<p>Furthermore, at higher currents, I have my doubts that a charge-pump design would be superior to the capacitor/inductor design of a typical buck (or boost) converter. So sure... this charge-pump design might be more efficient at 0.1mA, but I bet you that the capacitor/inductor is more efficient at 50mA. (The TPS62240 hitting 95% efficiency in the >1mA range)<p>> new power converter that maintains its efficiency at currents ranging from 500 picoamps to 1 milliamp<p>Hmmm... so this design really is designed for below 1mA currents. I really wonder what applications they are trying to use. Below 1mA, I say... just be wasteful. If it takes two months for a AA battery to run out of charge... is there really an issue?
Maybe this is relevant:<p><a href="https://youtu.be/1vYJq4GeXPM" rel="nofollow">https://youtu.be/1vYJq4GeXPM</a><p>Dave has recently busted another device claiming 0 standby power consumption.
I recently powered an old Acer laptop on that I didn't use for a while. It informed me that "/dev/sda2 has gone 941 days without being checked", after it finished that and booting fully up (a quick affair, even on that machine with no SSD), the i3 status bar further informed me, that the battery still holds a 57 % charge :)