Author Topic: modified sine wave bad for smps ?  (Read 5605 times)

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Offline uncle_bob

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Re: modified sine wave bad for smps ?
« Reply #25 on: March 28, 2016, 12:48:39 pm »
Hi

Ok so going back to the top of the thread:

The real question is: Are modified sine waves an issue with *modern* TV power supplies?

The issue isn't that they are switchers. The issue is the power factor correction. If you have a PFC supply (as most modern gear is), it will work to level out the mess that a rectifier based load puts on  the mains. That circuit *expects* to see a sine wave. When you give it something weird it does something weird. In this case weird is not good. The current leveling pulses happen at the wrong time and both the inverter and the load get a bit bothered. The PFC heats up and the inverter is not as efficient as it should be (= it gets hotter as well). No, it will not burst into flames. Yes, it will have a shorter life that it otherwise would have had.

Bob
 

Offline Hero999

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Re: modified sine wave bad for smps ?
« Reply #26 on: March 28, 2016, 07:49:57 pm »
The trouble with that is it increases the current draw.

Switched mode power supplies can often run at much lower voltages than they're designed from, even DC. My Rigol DS1054s oscilloscope runs fine off  36VDC but it's not specified to work below 100VAC. I did consider building a battery pack for it but quickly lost interest as I already have an oscilloscope with a built-in battery.

Nice to know since ide like my 1054z to be portable.
Seed the following thread: http://www.eevblog.com/forum/testgear/battery-pack-for-rigol-ds1054z/
 


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