3 ms·

It was bound to happen eventually, there has been a long trend towards point-of-use regulation displacing multiple output supplies. I'm just surprised they went

by vifya 7y ago

It was bound to happen eventually, there has been a long trend towards point-of-use regulation displacing multiple output supplies. I'm just surprised they went with 12V, and not 19V which has lower rectification losses, less power loss to wire/trace resistance, and a large existing design ecosystem from laptops where 19V has been the norm for years.

jacob019 7y ago
Or 24V or 36V, but alas 12V is the existing standard for legacy reasons so it's the path of least resistance for an overhaul of the PSU spec.
- deleted 7y ago
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- dev_tty01 7y ago
  "path of least resistance" -- Ha, I see what you did there.
thehobgoblin 7y ago
To me it seems like the ATX12VO specification is more of an endorsement of the direction PC power supplies seem to be moving in rather than a from-scratch redesign. It would be nice to have higher voltage (19V, 24V or perhaps higher) for a single voltage supply, but it would be a far bigger change to the overall PC ecosystem.
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numpad0 7y ago
Why is it 19V for laptops? I had suspected it’s to compensate for voltage drop at linear regulators. Batteries are either 11.1(3.7v 4 cells) or 14.8(3.7v 3 cells 1-3 parallel) and these voltages doesn’t seem immediately consistent with ATX12V to me.
- guerrilla 7y ago
  I don't think we'd want to put those in our laps if they were dropping that much over linear regulators... Roughly (Dropped Voltage)*(Current through regulator)=(Power Dissipated)
- thehobgoblin 7y ago
  The nominal voltage of a battery isn't the maximum voltage, 3.7V lithium cells are typically charged to around 4.2V. A 4S battery (or equivalent) will have a nominal voltage of 14.8V and a maximum voltage of 16.8V, which leaves 2.2V extra, probably to account for losses. Why 19V ended up being the typical voltage rather than rounding it up to something like 20V or 24V is beyond me (probably a matter of compliance, try checking IEC 60950-1 or related standards).
  - cesarb 7y ago
    I have seen many laptops where the charger sticker says the output voltage is 19.5V. And the nearest USB-C standard voltage is 20V, so that's probably what most newer laptops which charge through a USB-C socket use.
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by vifya 7y ago

jacob019 7y ago

Or 24V or 36V, but alas 12V is the existing standard for legacy reasons so it's the path of least resistance for an overhaul of the PSU spec.

deleted 7y ago
[deleted]
dev_tty01 7y ago
"path of least resistance" -- Ha, I see what you did there.

thehobgoblin 7y ago

To me it seems like the ATX12VO specification is more of an endorsement of the direction PC power supplies seem to be moving in rather than a from-scratch redesign. It would be nice to have higher voltage (19V, 24V or perhaps higher) for a single voltage supply, but it would be a far bigger change to the overall PC ecosystem.

deleted 7y ago
[deleted]

numpad0 7y ago

Why is it 19V for laptops? I had suspected it’s to compensate for voltage drop at linear regulators. Batteries are either 11.1(3.7v 4 cells) or 14.8(3.7v 3 cells 1-3 parallel) and these voltages doesn’t seem immediately consistent with ATX12V to me.

guerrilla 7y ago
I don't think we'd want to put those in our laps if they were dropping that much over linear regulators... Roughly (Dropped Voltage)*(Current through regulator)=(Power Dissipated)
thehobgoblin 7y ago
The nominal voltage of a battery isn't the maximum voltage, 3.7V lithium cells are typically charged to around 4.2V. A 4S battery (or equivalent) will have a nominal voltage of 14.8V and a maximum voltage of 16.8V, which leaves 2.2V extra, probably to account for losses. Why 19V ended up being the typical voltage rather than rounding it up to something like 20V or 24V is beyond me (probably a matter of compliance, try checking IEC 60950-1 or related standards).
- cesarb 7y ago
  I have seen many laptops where the charger sticker says the output voltage is 19.5V. And the nearest USB-C standard voltage is 20V, so that's probably what most newer laptops which charge through a USB-C socket use.
deleted 7y ago
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