3 ms·

I'd also point to Google's Little Box Challenge[1] as an interesting data-point of yore. Little Box Challenge went the other direction: instead of taking AC an

I'd also point to Google's Little Box Challenge[1] as an interesting data-point of yore. Little Box Challenge went the other direction: instead of taking AC and producing DC power, it was an inverter that took DC power and produced AC output. It had to output 2kW and be smaller than 655 cubic centimeters (cc's). The winning Red Electrical Devil's team got 3x more dense than this[2]! 240 cc's! While inverting 2kW of juice. Second place was 340ccs. I don't know whether we'd argue this DC->AC is harder/easier than an ATX supply (AC->DC) (probably not?) but this was quite an impressive competition, almost a decade ago, that resulted in probably some of the most power-dense, highest-efficiency power conversions that humanity has ever gotten up to. For compare, this 250W unit is 212cc's. 8x less power conversion, 88% the size. The Little Box Challenge designs were published, so there's a ton of great reading. Alas, Google frakking let the damned site bitrot off the net?! Sooo, head to archive.org[3] to read the team's writeups. From the winning CET Red Electric Devils writeup: > GaN transistors have many very interesting electrical characteristics (low Rds_on, low Qgate and Cds, ultra low Qrr); these create technological advantages over current MOSFET and IGBT devices (small size and low production costs). Unfortunately, they also have serious drawbacks due to their very fast switching characteristics: they are challenging to drive and require sensitive electromagnetic noise management. Another pitfall is the high voltage drop due to the reverse current when the GaN is turned off. The solution selected to overcome these difficulties is to control all the GaN transistors using soft switching for the entire operation range. [1] https://news.ycombinator.com/item?id=8070215 https://news.ycombinator.com/item?id=8070215 (271 points, 8 years ago, 138 comments) [2] https://ai.googleblog.com/2016/02/and-winner-of-1-million-little-box.html https://ai.googleblog.com/2016/02/and-winner-of-1-million-li... [3] http://web.archive.org/web/20171006105655/https://littleboxchallenge.com/ http://web.archive.org/web/20171006105655/https://littleboxc...

elihu 4y ago
I'm doing an EV conversion, and have trouble wrapping my head around the idea that a motor controller that weighs about ten pounds or so and isn't much bigger than a loaf of bread can handle about 100 kilowatts of power, converting DC at around 140-180 volts from the battery to 3-phase AC. And that's a relatively low-end inverter.
- virginiadoolf 4y ago
  the answer is liquid cooling. these Little Box and ATX power supplies have to rely on passive cooling (radiative, conductive, and convective) which is generally proportional to surface area == physical size ^ 3. if you halve the size, then, you lose 87.5% of the surface area! that's why these things can't shrink as much. but ultimately the silicon involved is miniscule.
  - MauranKilom 4y ago
    Not to detract from your point, but surface area scales with size ^ 2.
  - elihu 4y ago
    Technically my motor controller can be passively cooled too, it's just not recommended. (It automatically goes into a low-power "limp" mode rather than burn itself out.) I'm not sure how much power it can handle continuously in a pure passive-cooling mode.
  - wolrah 4y ago
    It would also be worth noting that a typical EV doesn't have to run at anything close to 100% load for extended periods of time. What sort of power an electric drivetrain can handle for a burst of acceleration lasting a few seconds versus what that same drivetrain can handle as a continuous load are two very different things. The same even applies with combustion powered cars too, if you look at the pickup truck market you'll see massive power numbers on every manufacturer's diesel pickups. If you look at their chassis-cab commercial trucks those same diesel engines are often derated by 30-50% compared to the pickups even while being equipped with larger cooling systems. That's because the commercial variants are rated to perform to spec all day every day where the pickup version just needs to put a grin on the owner's face when they floor it off the line and then occasionally tow a boat or something.
Ballas 4y ago
> I don't know whether we'd argue this DC->AC is harder/easier than an ATX supply (AC->DC) The little box challenge was significantly harder, primarily due to the ripple requirements on the DC side. This is not an issue in the same sense in the AC->DC case, because you don't have that problem there (you have other ripple considerations that might look similar, but are not (PFC and ripple on the output)). Usually you would require a lot of capacitance to solve the ripple issue for DC->AC and the winning team had a very interesting way of solving it without the use of very large capacitors.
brandmeyer 4y ago
> I don't know whether we'd argue this DC->AC is harder/easier than an ATX supply (AC->DC) (probably not?) but this was quite an impressive competition, almost a decade ago, that resulted in probably some of the most power-dense, highest-efficiency power conversions that humanity has ever gotten up to. The LBC was misshapen because they had an odd requirement: Be single-phase. A three-phase inverter (or rectifier) naturally has low DC ripple and is both more compact and more efficient than a single-phase inverter at all power levels. All of the winning solutions had extra energy storage elements which added inefficiency and bulk which a three-phase inverter would not have needed. With that in mind, the LBC was a little silly. A three-phase machine at the same power level would have been much smaller than any of the "winning" designs. A high-efficiency ATX power supply has additional requirements that the LBC didn't need to meet: Isolation. This implies the use of a transformer to protect the low-voltage DC side from the AC side. They typically accomplish this by rectifing AC, using a transformer-isolated unidirectionally optimized DC/DC supply to 12V, and then provide a handful of lower-power DC/DC converters to derive the other voltage levels used by ATX. A modern unisolated DC->AC machine is effectively symmetric in its power flow, and also functions as an AC->DC machine.
- spookthesunset 4y ago
  One of the things I only recently learned is modern power supply’s aren’t using the transformer to knock down “raw mains” 60hz AC. Modern switch mode PSU’s in-fact rectify the AC to DC and then chop it up at a much higher frequency. By using a higher frequency, the transformer can be much smaller and more efficient. If they were doing mains 60hz AC the transformer would be substantially larger. I forget if they also step the supply side DC voltage up too…
  - brandmeyer 4y ago
    > I forget if they also step the supply side DC voltage up too… They do, but they don't have to. The front-end rectifier boosts the voltage up to 400-450 VDC. This way, most of the components can be optimized for a single world-wide compatible machine that is capable of rectifying 230VAC. In principle, you could squeeze out a bit of efficiency (or cost) by producing a North American market machine that was optimized for 120V and a separate machine optimized for 208/230V. In practice, supply chain simplification reduces overall per-unit costs, so just about everything is designed as a single machine for world-wide markets. Only the plugs change. For ATX, only the cord shipping in the box changes.
chasil 4y ago
The interesting thing about gallium nitride is its use in blue LEDs (light-emitting diodes), which was discovered in 1972 and perfected in 1993, resulting in a Nobel prize. https://en.wikipedia.org/wiki/Light-emitting_diode#Blue_LED https://en.wikipedia.org/wiki/Light-emitting_diode#Blue_LED I wonder what new engineering knowledge has emerged about gallium nitride that allowed it to become such a recent force in power supply electronics. I didn't know that gallium nitride is transparent. https://en.wikipedia.org/wiki/Gallium_nitride https://en.wikipedia.org/wiki/Gallium_nitride
- Kirby64 4y ago
  It's effectively process technology improvements that allow gallium nitride devices to become less defect prone. It's been known for some time that GaN has a superior electron mobility number (which, effectively means you can get a better/smaller/lower impedance/faster switching device depending on which tradeoff you want). Problem is, getting reasonably good process control has been challenging. It appears some folks in the industry have been overcoming that challenge, therefore we're seeing the results of that.

elihu 4y ago

I'm doing an EV conversion, and have trouble wrapping my head around the idea that a motor controller that weighs about ten pounds or so and isn't much bigger than a loaf of bread can handle about 100 kilowatts of power, converting DC at around 140-180 volts from the battery to 3-phase AC. And that's a relatively low-end inverter.

virginiadoolf 4y ago
the answer is liquid cooling. these Little Box and ATX power supplies have to rely on passive cooling (radiative, conductive, and convective) which is generally proportional to surface area == physical size ^ 3. if you halve the size, then, you lose 87.5% of the surface area! that's why these things can't shrink as much. but ultimately the silicon involved is miniscule.
- MauranKilom 4y ago
  Not to detract from your point, but surface area scales with size ^ 2.
- elihu 4y ago
  Technically my motor controller can be passively cooled too, it's just not recommended. (It automatically goes into a low-power "limp" mode rather than burn itself out.) I'm not sure how much power it can handle continuously in a pure passive-cooling mode.
- wolrah 4y ago
  It would also be worth noting that a typical EV doesn't have to run at anything close to 100% load for extended periods of time. What sort of power an electric drivetrain can handle for a burst of acceleration lasting a few seconds versus what that same drivetrain can handle as a continuous load are two very different things. The same even applies with combustion powered cars too, if you look at the pickup truck market you'll see massive power numbers on every manufacturer's diesel pickups. If you look at their chassis-cab commercial trucks those same diesel engines are often derated by 30-50% compared to the pickups even while being equipped with larger cooling systems. That's because the commercial variants are rated to perform to spec all day every day where the pickup version just needs to put a grin on the owner's face when they floor it off the line and then occasionally tow a boat or something.

Ballas 4y ago

> I don't know whether we'd argue this DC->AC is harder/easier than an ATX supply (AC->DC) The little box challenge was significantly harder, primarily due to the ripple requirements on the DC side. This is not an issue in the same sense in the AC->DC case, because you don't have that problem there (you have other ripple considerations that might look similar, but are not (PFC and ripple on the output)). Usually you would require a lot of capacitance to solve the ripple issue for DC->AC and the winning team had a very interesting way of solving it without the use of very large capacitors.

brandmeyer 4y ago

> I don't know whether we'd argue this DC->AC is harder/easier than an ATX supply (AC->DC) (probably not?) but this was quite an impressive competition, almost a decade ago, that resulted in probably some of the most power-dense, highest-efficiency power conversions that humanity has ever gotten up to. The LBC was misshapen because they had an odd requirement: Be single-phase. A three-phase inverter (or rectifier) naturally has low DC ripple and is both more compact and more efficient than a single-phase inverter at all power levels. All of the winning solutions had extra energy storage elements which added inefficiency and bulk which a three-phase inverter would not have needed. With that in mind, the LBC was a little silly. A three-phase machine at the same power level would have been much smaller than any of the "winning" designs. A high-efficiency ATX power supply has additional requirements that the LBC didn't need to meet: Isolation. This implies the use of a transformer to protect the low-voltage DC side from the AC side. They typically accomplish this by rectifing AC, using a transformer-isolated unidirectionally optimized DC/DC supply to 12V, and then provide a handful of lower-power DC/DC converters to derive the other voltage levels used by ATX. A modern unisolated DC->AC machine is effectively symmetric in its power flow, and also functions as an AC->DC machine.

spookthesunset 4y ago
One of the things I only recently learned is modern power supply’s aren’t using the transformer to knock down “raw mains” 60hz AC. Modern switch mode PSU’s in-fact rectify the AC to DC and then chop it up at a much higher frequency. By using a higher frequency, the transformer can be much smaller and more efficient. If they were doing mains 60hz AC the transformer would be substantially larger. I forget if they also step the supply side DC voltage up too…
- brandmeyer 4y ago
  > I forget if they also step the supply side DC voltage up too… They do, but they don't have to. The front-end rectifier boosts the voltage up to 400-450 VDC. This way, most of the components can be optimized for a single world-wide compatible machine that is capable of rectifying 230VAC. In principle, you could squeeze out a bit of efficiency (or cost) by producing a North American market machine that was optimized for 120V and a separate machine optimized for 208/230V. In practice, supply chain simplification reduces overall per-unit costs, so just about everything is designed as a single machine for world-wide markets. Only the plugs change. For ATX, only the cord shipping in the box changes.

chasil 4y ago

The interesting thing about gallium nitride is its use in blue LEDs (light-emitting diodes), which was discovered in 1972 and perfected in 1993, resulting in a Nobel prize. https://en.wikipedia.org/wiki/Light-emitting_diode#Blue_LED https://en.wikipedia.org/wiki/Light-emitting_diode#Blue_LED I wonder what new engineering knowledge has emerged about gallium nitride that allowed it to become such a recent force in power supply electronics. I didn't know that gallium nitride is transparent. https://en.wikipedia.org/wiki/Gallium_nitride https://en.wikipedia.org/wiki/Gallium_nitride

Kirby64 4y ago
It's effectively process technology improvements that allow gallium nitride devices to become less defect prone. It's been known for some time that GaN has a superior electron mobility number (which, effectively means you can get a better/smaller/lower impedance/faster switching device depending on which tradeoff you want). Problem is, getting reasonably good process control has been challenging. It appears some folks in the industry have been overcoming that challenge, therefore we're seeing the results of that.