Laptop Power Supply Hums When Connected To Inverter

**PaulF** · 01-15-2008, 06:41 PM

Today I was in a hurry and my laptop battery was dead so I plugged my laptop into my power inverter. When I plugged it in, the laptop's power supply made a constant humming noise. It doesn't do this when plugged into an AC outlet. What could be the cause of this?

Thanks,
Paul

**2k1Toaster** · 01-15-2008, 06:52 PM

Noisy inverter. This is why we regard inverters as a bad solution. The cheap ones are really really cheap! For that to not happen you need to use a true sine wave inverter which is really really expensive.

**PaulF** · 01-15-2008, 06:55 PM

Would using a "cheap" inverter damage the equipment connected to it?

**jontz** · 01-15-2008, 06:55 PM

An inverter doesn't supply a true AC sine wave like the outlet in your house does, it supplies a modified or "stair step" sine wave. This can cause certain electronics to behave differently than they do in the house.

Unless your power supply is running hot, smoking, or doing something else alarming, I wouldn't worry about it.

**2k1Toaster** · 01-15-2008, 06:58 PM

Originally Posted by PaulF

Would using a "cheap" inverter damage the equipment connected to it?

Originally Posted by jontz

An inverter doesn't supply a true AC sine wave like the outlet in your house does, it supplies a modified or "stair step" sine wave. This can cause certain electronics to behave differently than they do in the house.

Unless your power supply is running hot, smoking, or doing something else alarming, I wouldn't worry about it.

I doubt it will damage anything.

But if you want to see some really funny stuff, take an old old alarm clock. They use the 60hz signal from the wall to time their clock pulses. So for isntance if you hooked it up in a 50hz environment it would be (50/60)% slower. Hook that up to a cheap inverter in your car, and all hell breaks loose! it will start to randomly fling time. Hours pass in no time.

**cazorp** · 01-15-2008, 07:01 PM

Originally Posted by 2k1Toaster

I doubt it will damage anything.

But if you want to see some really funny stuff, take an old old alarm clock. They use the 60hz signal from the wall to time their clock pulses. So for isntance if you hooked it up in a 50hz environment it would be (50/60)% slower. Hook that up to a cheap inverter in your car, and all hell breaks loose! it will start to randomly fling time. Hours pass in no time.

AHHHH .... so thats what they do to cab meters on new years eve??? No wonder my cab fees were $200 for 6 miles

**PaulF** · 01-15-2008, 07:03 PM

Alright, as long as I'm not doing damage, I'm happy. Just out of question though... if I were to hook up a computer UPS to the inverter, would it change the modified sine wave to a true sine wave?

**jontz** · 01-15-2008, 07:05 PM

Nope

**PaulF** · 01-15-2008, 07:09 PM

See now I was planning on hooking up a home stereo self-powered sub woofer to this thing for a few months before I get my new system. I'm guessing that I'll get a nice little hum there too, correct?