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I live in an area where power cuts are common. In order to protect my TV from the sudden power loss from a power cut, I am planning to buy a uninterruptible power supply (UPS). Most of the cost effective UPSs have a modified sine wave. Will this damage the OLED TV in the long run?

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  • How does a power cut damage a TV? It sounds to me like either you really want a surge protectior.... or your real motivation is you want to watch TV during power outages. UPSs are not surge protectors. They have no surge protecting ability at all, they just pass the utility power straight through until there's an outage. Unless they have a surge protector stuck on, but it won't be very good. Commented Dec 29, 2022 at 23:32
  • @Harper-ReinstateMonica - Pricier UPS systems fully isolate the input ac from the output ac through the dc battery, always providing power through the inverter. More used in, e.g., data centers. Sometimes called double-conversion.
    – Jon Custer
    Commented Dec 29, 2022 at 23:51
  • @JonCuster yeah, but it's way out of OP's price range. Commented Dec 29, 2022 at 23:56
  • SOME UPS units also provide surge suppression ... but I agree that if that's the function you want, a $10 surge-suppressing power strip is a better choice than a much more expensive UPS.
    – keshlam
    Commented Dec 30, 2022 at 4:13

3 Answers 3

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If you have a particularly expensive TV then consider spending more on a better UPS; albeit I'm seeing 600 watt models for only $200.

Anyways:

It’s important to understand that both types of UPS system produce true sine wave output more than 99% of the time. It is only during a power failure, when the UPS is producing power from its battery reserves, the output waveform is a concern. Also keep in mind that typical applications for pure sine wave UPS systems involve the protection of critical server, network, medical and telecommunications equipment or electronic equipment that is particularly sensitive to input power, such as lab test equipment. Modified sine wave UPS systems typically protect PCs, home entertainment systems, A/V components and media centers.

https://blog.tripplite.com/pure-sine-wave-vs-modified-sine-wave-explained

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A surge protector is not a UPS

A surge suppressor has some electronics kit inside to try to suppress the kind of surges that damage equipment. It has one job. Now when power is cut and when it's turned back on, there can be considerable surges, so there's a sensible role for a surge suppressor there.

A UPS has a completely different job.

When AC power fails, the UPS has a battery, inverter and transfer switch to create replacement AC power from the battery using the inverter. That will keep your PC running long enough to do a controlled and orderly shutdown of databases, disk caches, and the operating system. So, you know, 20 minutes of power.

You seem to be expecting that the UPS will create replacement AC power off the battery at all times, and so the thing on UPS will never experience power surges from the utility. No, only a few "Double Conversion" or "Online" type UPSs work that way, and you've already said you don't want to pay for those.

Affordable UPS's actually connect your loads directly to utility power whenever utility power is available. There is no filtering. The load simply gets utility power directly. Only when power fails does a switch inside go "snap" and connect the load to the battery+inverter. However, the disconnect surge has already happened at that point.

If you want surge protection, get a surge suppressor and that's it. They're cheap compared to UPSs but get a good one. Tripp-Lite is top shelf.

If you want both a surge suppressor and a UPS, buy one of each and connect the surge suppressor after the UPS.

If you want to watch TV when the power fails

... for more than 20 minutes, then a UPS is the wrong thing. You need a Jackery or other so-called "solar generator" or "solar/portable power station" which is simply a battery+inverter in a pretty box. You won't like the price of those, though. I don't like it either.

UPS's are only for orderly shutdown of PCs. You should not be using a UPS as a cheap substitute for a Jackery or other "portable power station". The lead-acid battery in the UPS should only be drawn down 30% or so (leaving 70% unused) if you're doing it on a regular basis. If you ignore this and run it down anyway, it will greatly shorten the usable life of the battery and you will find yourself having to buy another UPS every 1-6 months depending on abuse level.

The key difference with a Portable Power Station is that it has lithium batteries, which do not have the "discharging below 70% damages the battery" problem. They do explode if disrespected, but any competent installation will have a Battery Management System that prevents that from happening. That adds very little cost.

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It can do. It probably won't instantly destroy the TV, but it will stress the components in the power supply. This can reduce its life.

A "modified sine wave" isn't really much like a sine wave at all. It's a slight improvement on the old square wave inverters. The waveform has sudden step edges, and these cause current surges in an appliance's power supplies that don't happen with a true sine wave. In the long run, this can destroy the capacitors or diodes that make up the power supply.

Given that true sine wave inverters are now available, the best place for a modified sine wave inverter is your local electricals recycling centre.

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    The switching mode supply in the TV really doesn’t care what the input looks like to a great extent.
    – Jon Custer
    Commented Dec 29, 2022 at 23:52

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