Enermax Platimax 750W - 80 Plus Platinum Arrives
by Martin Kaffei on February 10, 2012 6:00 PM EST- Posted in
- Cases/Cooling/PSUs
- PSUs
- 80Plus
- 750W
- Enermax
- 80Plus Platinum
Switching Circuits and Components
The 750W Platimax PSU uses a multi-layer PCB design similar to the Modu87+ series, as well as similar components. The biggest difference is in the transistors, which have a slightly lower turn-on resistance. Enermax still relies on the resonant converter with Zero Voltage Switching (ZVS). Its core is the resonant circuit consisting of a capacitor and a coil; these have specific loading characteristics that make the voltage waveform nearly sinusoidal. The transistors switch at the zero-crossing, which greatly reduces power dissipation. This compensates for the slightly higher losses during saturation (which is no problem with a low resistance between drain and source).
With the improvement in efficiency, manufacturers can also reduce the heatsink size(s). However, even on the secondary side Enermax still uses through-hole components for synchronous rectification instead of SMDs (Surface Mounted Devices). The efficient MOSFETs there could even be cooled by the conductor path. With THT (Through Hole Technology) Enermax is playing it safe, but it also means the fan should be able to run at lower RPMs.
Note that the inductive components get very hot in a switching power supply, which requires additional cooling. The temperature of the chokes can heat all the neighboring components. Enermax seems to know this is a potential problem, which is one reason why they're not making this a passively or semi-passively cooled PSU.
Most of the capacitors are of Japanese make, which is nice to see. Enermax uses a buck converter for -12V, an interesting development. Not long ago -12V was regulated by a linear regulator with large voltage drops. Usually the power dissipation is not a problem on this rail, since the current is low, but even so this is an improvement.
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ssj3gohan - Sunday, February 12, 2012 - link
In this sentence:"(...) This compensates for the slightly higher losses during turn-on (which is no problem with a low resistance between drain and source). (...)"
you imply that the drain-source resistance has something to do with the switching losses. This is not the case! Let me explain: there are two types of losses associated with power transistors: on-state losses and switching losses. On-state losses are incurred when the transistor is fully on and conducting current; it's simply the drain-source on-state resistance (R(DS, on)) times current squared. Then there's losses associated with the transition from off to on, or from on to off. At this moment, the transistor doesn't instantaneously turn on or off, but enters its linear region. At this time, both high voltage and current exist simultaneously over and through the device, which means P=I*U=high losses. You can't fix this with lower on-state resistance because the transistor is not in its on-state, it is in some state in between. This transient period is only very short (tens of nanoseconds) but if you switch really fast, e.g. 200kHz+ which is what happens in some power supplies, the losses add up quickly. The only way to combat these losses is:
- Making either I, or U, or both zero at switching time (zero current, zero voltage switching [ZVS, ZCS])
- Making the transient period as short as possible (which in practice means reducing gate charge or if possible using better drivers)
That last bit is pretty much a no-go for modern supplies because it causes noise spikes, hence the advent of ZCS and ZVS.
Martin Kaffei - Sunday, February 12, 2012 - link
I know. This might be a translation failure.The previous sentence is already about turn-on ("switching"), so this one was about the next phase.
In this case I meant saturation (no sure if this is the correct word in English).
kenyee - Sunday, February 12, 2012 - link
I.e., is it small enough to fit in actual HTPC cases?86% efficiency at 10% load makes it enticing... :-)
Lithium466 - Monday, February 13, 2012 - link
It seems that the 5Vsb rail is not protected, and that overloading it (with more than 4A) will permanently destroy the power supply...Have you tried it ? Is is true ?
ShieTar - Monday, February 13, 2012 - link
Apparently 20% are specified to be 20% on each rail, for each voltage, (see the qualification test report here: http://www.plugloadsolutions.com/psu_reports/ENERM... ).To me, this seems to be a bit less than realistic. In normal day usage, I would expect the 12V rail to be the one that really changes between idle and load cases, with the other voltages remaining at a relatively constant, and rather low, load.
Would it be possible to test efficiency at a few realistic load cases on top of the ones used by the specification? This would be really interesting to see.
86waterpumper - Monday, February 13, 2012 - link
I agree that alot here run higher end gaming rigs and may use 750 watts of power or even more. I also say that alot here are more likely to have htpcs, servers, and secondary systems somewhere in their house they themselves have built. Then you have the times when a friend or family member wants you to build a system for them to do light tasks. It doesn't always make sense to use a pico type supply for these and there is a gap between say 200 watts and 400/450 watt psus. For all these reasons it is past due time that we get some more efficient lower watt supplies. Right now my main system is a 2500k using the onboard hd3000 video I can play games fine since I have dual older 4:3 monitors still. I currently am using a x-400 seasonic and it's great but I really wish there had been a x-200, 250 or 300 instead.There will be a need for high end video cards for those that want to run huge monitors, but as onboard graphics get better and better we will see a shift where people who don't game all the time or want to blow 500 bucks on a video card are content with using onboard. It would be like if chevrolet decided to ONLY make the camaro and corvette fuel efficient and did not care about the compact cars it just does not make sense. I think psu manufacturers are missing the boat in a way but I'm also sure they are afraid that people will not pay a premium for a psu unless it has big watt numbers...
Iketh - Monday, February 13, 2012 - link
My thoughts exactly. I'm sick of using 400w power supplies to power 50-100w. I've even thought of the possibility of tapping into the wires or finding splitters for every plug so I can run 2-3 systems off one power supply.