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Is square wave inverter harmful to electronic devices? - Answers

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Depends on the device. For instance almost all laptop power supplies use a international (aka universal) switch mode power supply. They don't care about modified sine wave output at all! Almost all low-cost inverters use a step-wave output that approximates a RMS sine wave (like wall voltage). This is a double square wave with a gap between the negative going and positive going squares. The inverter companies call this "modified sine" which is kind of a misnomer used as a marketing term. The more expensive inverters use a high-frequency Class-D amplifier to produce a more accurate approximation of a sine wave. It's usually not "pure", as it has some amount of harmonic distortion, but for marketing reasons they try to distinguish their product from the "modified-sine" by using the "pure sine" misnomer. The front end of all switch-mode power supplies rectify the incoming AC into DC as a first step in conversion. Step wave rectifies just as well as a normal sine wave! The ONLY reason to run "pure sine" inverters is if you are running sensitive audio gear with linear power supplies, as step-wave will induce a buzzing noise in the audio signals whereas the smoother approximation will not. Don't believe the hype that the "pure sine" inverter companies promote, it simply isn't true. The only things that are dangerous to run on step-wave are things with triac devices or capacitor-based power supplies. This includes things like Dewalt power tool chargers, light dimmers, etc. If it's extremely light (feels like there's nothing in it), and/or it has a 120V rating only, then it's probably not safe for step-wave use. Dewalt chargers have been known to fail and overheat on step-wave! If your power supply has a wide input voltage, such as almost all laptop supplies (100-240v), it is a universal switch mode supply and therefore safe. This includes most small electronics chargers, like for phones, iPods and cameras. If the voltage requirement reads only 120V and it's NOT a heavy "wall-wart" type supply, it's probably not safe. Check your nameplates! If your device has sound such as a TV or Stereo and it emits a buzzing sound out of it's speaker when you run it on step-wave, then that's not harmful, but is an annoying side-effect. You can buy the more expensive "pure-sine" model if this is undesirable.

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