4 ms·

I wonder where the losses are, and if GaN power transistors for switching would help with efficiency here. I like Seasonic's fanless series, but wouldn't mind

I wonder where the losses are, and if GaN power transistors for switching would help with efficiency here. I like Seasonic's fanless series, but wouldn't mind getting a bit more power out of the same size PSU.

londons_explore 5y ago
There are losses in every step, and power supply design is basically a big optimization problem to choose all the design parameters to minimize losses. The main components with losses: * The input capacitors are non-ideal and have some resistance. That resistance causes heat every time current flows in or out of them. * The MOSFET switch has an 'on resistance' which means it wastes energy when current flows through it. * The MOSFET takes a certain time to turn on or off. During that time it is partially on, which wastes a bunch of energy each switch. * The transformer has resistance in the coils. * The transformer has iron core hysteresis, which makes the steel of the transformer get warm as magnetic fields change in it. * The diode on the output side has voltage drop across it. * The capacitor on the output side has resistance.
- quercusa 5y ago
  It was a real learning experience moving from ideal transistors to real MOSFETs in an H-bridge driving a motor. Gate capacitance led to lots of expensive smokefests.
R0b0t1 5y ago
They do help. Since HN finds it interesting I can write some on the most modern designs. I am currently designing a FOSS power supply. One of the goals is to go for high efficiency. The end product will use GaN and SiC elements. The different chemistries give different switching characteristics. (Interesting aside is that some topologies can run forward as line conditioning AND backwards as a motor inverter.) There are also supply chain and security considerations, though. You can buy magic PSU chips but what if you can't?
- Scene_Cast2 5y ago
  Oh neat, sounds pretty cool. Is there a hackaday project page or similar? Is it an ATX PSU or something else? And I'm not up to date on modern electrical design, but a satellite-view on industry innovations & trends would be interesting.
  - R0b0t1 5y ago
    Goal is to make it [optionally] smart, compact, modular, and ATX compatible. Hopefully with just the newer 12V standard. My original motivation for the project was lack of SMBus/PMBus support on desktops (on a laptop, it's the battery controller that allows you to see power usage). I'll make a Hackaday page. So far I've got: https://www.patreon.com/sidspry https://www.patreon.com/sidspry https://opencollective.com/sidspryfoss https://opencollective.com/sidspryfoss I just started putting myself out there. I have material queued up that I need to edit and I need to pick out the good parts for blog posts. I've started acquiring components for the prototypes. Sadly it's slow going, HW prototyping is kind of expensive for me right now. My design progress is way ahead of what I've actually documented and I need to start documenting so it looks better.
    - daper 5y ago
      After some searching I've found that Supermicro is selling ATX power supplies with SMBus (hopefully PMBus really) connection in reasonable price but never had one and I'm not able to find any review. Example: https://store.supermicro.com/865w-atx-pws-865-pq.html https://store.supermicro.com/865w-atx-pws-865-pq.html
- zokier 5y ago
  I'm kinda surprised there would be still significant margin in improving efficiency, considering that modern top tier PSUs are already 90-95% efficient
  - R0b0t1 5y ago
    You are right, power supply improvements are asymptotic. It's not just about total efficiency, but also about how the heat is generated and where you can put it. A lot of the newer developments don't do a lot for total efficiency but produce smaller supplies by more efficiency managing heating. That said, most supplies for sale are based on old, fossilized designs created ~10 years ago, hovering at around 80%. If you spend more you can get the gold, titanium, etc. But then, even those tend to be below the maximum you can get, which is closer to 98% if you have information about your load. You can also design the system to have better efficiency at various loads. Typically half, but could be worth tracking newer CPU/mobo/GPU developments.
gautamcgoel 5y ago
Totally agree, Seasonic's fanless line is awesome.

londons_explore 5y ago

There are losses in every step, and power supply design is basically a big optimization problem to choose all the design parameters to minimize losses. The main components with losses: * The input capacitors are non-ideal and have some resistance. That resistance causes heat every time current flows in or out of them. * The MOSFET switch has an 'on resistance' which means it wastes energy when current flows through it. * The MOSFET takes a certain time to turn on or off. During that time it is partially on, which wastes a bunch of energy each switch. * The transformer has resistance in the coils. * The transformer has iron core hysteresis, which makes the steel of the transformer get warm as magnetic fields change in it. * The diode on the output side has voltage drop across it. * The capacitor on the output side has resistance.

quercusa 5y ago
It was a real learning experience moving from ideal transistors to real MOSFETs in an H-bridge driving a motor. Gate capacitance led to lots of expensive smokefests.

R0b0t1 5y ago

They do help. Since HN finds it interesting I can write some on the most modern designs. I am currently designing a FOSS power supply. One of the goals is to go for high efficiency. The end product will use GaN and SiC elements. The different chemistries give different switching characteristics. (Interesting aside is that some topologies can run forward as line conditioning AND backwards as a motor inverter.) There are also supply chain and security considerations, though. You can buy magic PSU chips but what if you can't?

Scene_Cast2 5y ago
Oh neat, sounds pretty cool. Is there a hackaday project page or similar? Is it an ATX PSU or something else? And I'm not up to date on modern electrical design, but a satellite-view on industry innovations & trends would be interesting.
- R0b0t1 5y ago
  Goal is to make it [optionally] smart, compact, modular, and ATX compatible. Hopefully with just the newer 12V standard. My original motivation for the project was lack of SMBus/PMBus support on desktops (on a laptop, it's the battery controller that allows you to see power usage). I'll make a Hackaday page. So far I've got: https://www.patreon.com/sidspry https://www.patreon.com/sidspry https://opencollective.com/sidspryfoss https://opencollective.com/sidspryfoss I just started putting myself out there. I have material queued up that I need to edit and I need to pick out the good parts for blog posts. I've started acquiring components for the prototypes. Sadly it's slow going, HW prototyping is kind of expensive for me right now. My design progress is way ahead of what I've actually documented and I need to start documenting so it looks better.
  - daper 5y ago
    After some searching I've found that Supermicro is selling ATX power supplies with SMBus (hopefully PMBus really) connection in reasonable price but never had one and I'm not able to find any review. Example: https://store.supermicro.com/865w-atx-pws-865-pq.html https://store.supermicro.com/865w-atx-pws-865-pq.html
zokier 5y ago
I'm kinda surprised there would be still significant margin in improving efficiency, considering that modern top tier PSUs are already 90-95% efficient
- R0b0t1 5y ago
  You are right, power supply improvements are asymptotic. It's not just about total efficiency, but also about how the heat is generated and where you can put it. A lot of the newer developments don't do a lot for total efficiency but produce smaller supplies by more efficiency managing heating. That said, most supplies for sale are based on old, fossilized designs created ~10 years ago, hovering at around 80%. If you spend more you can get the gold, titanium, etc. But then, even those tend to be below the maximum you can get, which is closer to 98% if you have information about your load. You can also design the system to have better efficiency at various loads. Typically half, but could be worth tracking newer CPU/mobo/GPU developments.

gautamcgoel 5y ago

Totally agree, Seasonic's fanless line is awesome.