495W server power supply teardown (with schematic)

What's inside a Dell 495W server switching power supply, including the simplified schematic and how does it work. This is a less common topology, a double boost circuit (active PFC and a pre-regulator) followed by a synchronously rectified isolated halfbridge converter with no output inductor (probably non-PWM).

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[rfmerrill]

I worked at Arista Networks from 2013-2016 or so and was qualifying power supplies with basically the same form factor as this, possibly same interface but hard to tell since they cut the end off (probably to harvest the gold plating). The ones we had were made by Artesyn/Emerson and Delta, exact same power rating 495W (although we also had bigger ones up to 750W and higher I think) and same +12V and 12Vsb. There are probably just the two power outputs, some control GPIOs, an analog current sharing signal that connects to the other power supply, and a PMBus interface (which is basically built on SMBus which is similar to I2C). I believe these power supplies can be configured for automatic fan control, but you can also read the temp sensor and control the fan via PMBus, which is desirable because you don't want the PSU fan doing its own thing separate from the main chassis fans, otherwise you can end up with reversed air flow when one is pushing harder than the other.

[Novus_Ordo_Conditor]

Even though he drew the schematic by hand, I have never seen anyone else draw such a good schematic. It's a great video, thank you.

[WagTsX]

I really wanted to see you trying to power it. Seems in a very good shape, most of server PSUs that I got, were covered in dust so hard that I could barely read the components. This one seems brand new or used in a very well regulated environment.

[KeritechElectronics]

Nice supply. Packing lots of power in such a small size is quite an engineering achievement! I use a similar supply, albeit it's HP rather than Dell, as a central 12VDC supply for my lab.

[alexloktionoff]

Can you make a video about double boost PSU? What is efficiency of each stage? What are the strong and weak points? Why don't we see such architecture in PCs?

[mahdyfouad]

12:23 this cute creature is more intelligent than a lot of engineers i know.

[_________________]

I barely understand anything about the electrical components but love watching it as always.

[EdwinSteiner]

Nice schematic and explanations! Seeing some measurements and waveforms of this thing in operation would be nice.

[pcrepairshop]

nice video. its platinum rated power supply(92% efficient at half load) and server too not like dekstop like fan alone 2/3 of its volume, no wonder it bloody complex

[MiguelBaalm]

0:15
80 Plus Platinum actually means it must be over 90% efficient :)
(90% at 20% load, 94% at 50% load, 91% at 100% load).

[markp]

What an awesome video. I have learned so much about switch mode PSUs and electronics because of you and your videos, thank you 😃😃😃

[callmefoxie]

These power supplies in Dell R620 like to blow up with a large blast. Something on the bottom goes up in smoke and shorts live to neutral killing circuit breakers. However output still works and the other power supply in the server keeps the server up & running :D

[rfmerrill]

12:06 did you notice your old power supply is the same brand? :) Both made by Flextronics

[wurgervomlichtenmoor]

It could be a fixed frequency resonant topology. Usually they are frequency controlled, but this can also work with the variable input voltage... I think. I've read that the diodes across the possible resonant capacitors limit the power and prevent capacitive operation. I've never seen a setup like this before...

[andrewbowden]

Awesome video, Thanks for sharing!
I wouldn't mind seeing you get your hands on a Hewlett Packard HSTNS-PL48-B, Specs are 100-120vac 7a/200-240vac 5a or 240vdc 4.5a In and 400vdc 2.4aMax out 550w or 960w depending on input volts.
I plan to use it for charging batteries (solar setup).
Unfortunately I have not been able to get it out of idle mode into standby mode as of yet.

[phenome]

Great video thansk for the great explanation. I've not seen the double boost topology unti watching your video 👍

[jaguarbog]

Secondary boost converter which is bypassed a diode is likely meant for AC dropout immunity. TI calls them "baby boost", they are only active when AC disappears and they recover most of the energy from the bigger 270 uF capacitor, keeping the server alive for additional few ms.

[airmann]

Very neat psu, so much control circuitry. Would love to find a full schematic and really figure it out.

[DuroLabs]

I think it might still work, just the card edge connector seems to have broke off when sliding it in the server or maybe servicing which may explain why it was in a such good condition from inside ??

[Alexelectricalengineering]

This one would be really hard to modify for a different output voltage, 2 years ago I modified 2 ATX PSU to go up to 20V!