laptop with inverter


I have a 300W square wave inverter. Is it safe to use it with my laptop that
uses a switchmode power supply?
I have tried it with a lower power 1A 12V switchmode power supply and there
is a notiseable buzz coming from the switchmode power supply when it is on
the square wave. It is silent when used on a sine wave.
I don't want to damage the laptop or power supply. As I will be using it
only for 1 day, I don't want to buy extra equipment if I don't have to.
-H
Reply to
Heywood Jablome
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The are also called computer grade UPSes - because they can output square waves (modified sine waves) with so much harmonics as to even damage some small electric motors. But since computers are so resilient, then that 'dirty' UPS output (only when in battery backup mode) will not harm properly constructed electronics.
As noted elsewhere, those square waves simply recharge front end electrolytic capacitors typically to 320 volts DC. Then the power supply sips electricity from those capacitors to operate the computer. Those electrolytic capacitors will remain charged whether the incoming AC is a sine wave or a square wave.
In addition, minimally sufficient power supplies will also contain line filters. Although intended to keep RF interference inside the machine, those filters also make that square wave more sine like - just another layer between electronics and the 'dirty' UPS output.
Meanwhile, a UPS may output 'dirty' square waves only during battery backup mode. Most of the time, the UPS connects cleaner sine waves, direct from the AC mains, into the load. Those square waves only exist during rare battery backup mode.
Some third party power supplies are so inferior as to be easily damaged. IOW essential features such as the line filter, sufficiently sized electrolytic capacitors, and other 'cost cutting' measures could mean dirty UPS electricity causes power supply failure. Its not a problem created by the UPS. Its a problem created by bean counting computer assemblers who don't even have basic electrical knowledge; who purchase inferior power supplies only on price.
Again, they are called computer grade UPSes for good reason. Electricity so dirty that it can even harm a power strip surge protector attached to its output. Called 'computer grade' because computers must be a most resilient appliance connected to AC mains.
An example: this plug-in UPS creates a modified 120 VAC sine wave. IOW it creates two 200 volt square waves with a spike of up to 270 volts between those square waves. Output not destructive to computers as even required by Intel specs and other industry standards. Just don't power other less resilient appliances (ie small electric motor) with this UPS when in battery backup mode.
Meanwhile some laptops have another problem with that so dirty UPS output. Laptops monitor AC input and switch over to internal batteries if AC power does not measure sufficient. IOW some laptops running on a computer grade UPS will remain powered from batteries and not recharge laptop's internal batteries. This because of how AC voltage is monitored AND because that UPS (in battery backup mode) outputs square waves.
Heywood Jablome wrote:
Reply to
w_tom
There is quite a debate about this going in the aus.computers forum. I suspect a square wave will be fine, unless someone could give me an exact reason why any particular component would fail under a square wave. I'll give it a go anyway.
-H
Reply to
Heywood Jablome
The switching power supply in the computer generates square waves, rectifies and filters them. You are using a low frequency square wave to drive the power supply. The engineers on news:sci.electronics.design and other sci.electronics newsgroups routinely tell people to use an inverter to provide power to devices with switching power supplies.
--
Former professional electron wrangler.

Michael A. Terrell
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Reply to
Michael A. Terrell
How to read that hogpog discussion in aus.computers. Many are just posting claims without providing technical reasons why and without providing numbers. Heavily discount those posts. Go back to that discussion and weed out the myths: no supporting technical facts and no numbers. That entire discussion will break down into only a few useful posts.
Heywood Jablome wrote:
Reply to
w_tom
I went through this a few months ago on behalf of a friend - he ended up using a Jaycar square wave inverter. He used it to power an Apple powerbook for about 10 hours continuously (it was doing time-lapse capture) with no ill effects.
Reply to
Poxy
This is an example of the point I last posted. Provided was an example that by itself does not constitute a fact. Alone, it tells us nothing useful. However combined with underlying concepts and numbers, only then would the post have provided definitive information. For example, what was the inverter output voltage? AND what does the Apple power supply claim as its input voltage limits? Those numbers must be printed on each appliances. What is its AC input voltage rating?
A Powerbook powered by a 120 volt inverter. The Powerbook input voltage rating is what? 90 VAC to 265 VAC? That is the point. Numbers are missing in so many posts in that other newsgroup; making those posts useless. Numbers from that Powerbook would make Poxy's post so more useful.
Poxy does provide one useful number. 10 hours without failure. If ten hours from a UPS, then it tells us nothing because the UPS only acts as an inverter when disconnected from AC mains. However 10 hours from an inverter powered by DC battery power does provide a useful number. Again, underlying numbers AND the underlying concepts - the theory behind the example - create useful facts. To know something, one must have both fundamental theory and experimental evidence. Poxy only provided one experiment that demonstrated little due to missing facts and numbers.
However, previously posted was an example of a 120 VAC inverter rated for computer use (computer grade). Two 200 volt square waves with a spike of up to 270 volts between those square waves. A 120 volt computer should be powered by this modified sine wave without damage. That 120 volt computer rated to operate anywhere from 90 to 130 VAC. Without these numbers, then my previous post provided little useful information.
Poxy wrote:
Reply to
w_tom

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