5 ms·

> 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

> 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.

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.