Higher efficiency PSUs?

Belgarion · Post by **Belgarion** » Sun Jan 19, 2003 8:36 pm

It's been mentioned here that a signficant amount of the heat a typical PSU has to vent comes from inefficiency in power conversion in the PSU itself. E.g., a PSU operating at 70% efficiency while delivering 100W DC is consuming about 143W of AC power and therefore "wasting" about 43 watts, which goes to extra heat that needs to be exhausted (in addition to heat from internal components).

Are there any PSUs with significantly higher efficiencies? I don't know much at all about power electronics (I stuck with DSP/comms in my EE courses), but I seem to recall reading that switching power supplies can theoretically reach very high efficiency ratings. For example, the 2000 VA and 2500 VA models of Xantrex Sun Tie inverters (for PV solar electric systems) have a rated peak efficiency of 94%. I presume this implies that they operate with 90+% (or least 85+%) efficiency over a decent range of their power curve. But typical computer PSUs tend to max out in the 70-75% range.

Is there any reason, other than design/manufacturing cost, that PSUs aren't made to be more efficient? I know the inverter example above isn't entirely fair since those things cost MUCH more than a commodity computer PSU, but are there any technical reasons? I suppose the inverter has a relatively easy job converting between 120V AC and 24V or 48V DC. A PSU, on the other hand, needs to supply a range of DC voltages with varying currents (including time-varying currents!) from the AC input. Is this really too hard to do with high efficiency? Or would it just cost too much to design one?

It seems to me that a "niche" market for higher-efficiency (and hence quieter?) PSUs exists now that computer noise is becoming more of an issue. I'd certainly consider (and probably buy) a PSU with, say, 85+% efficiency for a reasonable price premium over a generic model. I suspect a decent number of SPCR readers might also. I'd think a high-end PC (e.g. dual-CPU video editing workstation) that needs a high-end PSU would benefit even more.

Am I off my rocker here?

jojo4u · Post by **jojo4u** » Mon Jan 20, 2003 5:04 am

I would also be interested if these notebook psu have a higher efficiency than common atx ones.

powergyoza · Post by **powergyoza** » Mon Jan 20, 2003 8:28 am

I was interested to see who makes such a thing and found this: http://www.n2power.com/. They offer 81-90% efficiency, but not quite all the voltages that we need - like 3.3V.