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  • First there was PFC, now it's PWM!


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    A few years ago, America was behind the curve in requiring power supplies to have PFC - Power Factor Control - essentially builtin protection from brown outs, lower fluctuations in power that would stomp on your components and make them die.  The EU had this for several years, before the US reviewers caught on, and started slamming the US versions of the same PSUs EU folks had with PFC, but the US did not.  Today we have it.

    PWM is something similar, but it has to do with your laptop.  Pulse-width Modulation!  PWM is used to regulate the brightness of LCD and LED displays. How does that concern us? The pulsations can be bad for your health and more specifically for the users’ eyesight. They can lead to migraines, headaches or other forms of discomfort after long-term usage. In most cases those pulsations have a frequency somewhere around 200Hz. They cause multiple contractions and expansions of the pupils, which bears down negatively on your health. They are especially harmful in models with LED backlight because the colors of the emitted light are not as inert as the colors of the CCFL backlight and so they reach high amplitudes and rapid luminance changes. Basically, the problem comes from the flickering light, not from the crystals of the LCD monitors.

    You can read more here - http://laptopmedia.com/highlights/what-is-pwm-why-is-it-important-and-why-did-we-add-this-test-to-our-reviews/

    and see laptop ratings for it here:  http://laptopmedia.com/top-laptop-pwm-ranking-rated-by-negative-impact-on-eyesight/

    I had not heard about this, the government didn't come out and stop laptop makers from destroying our eyesight, they didn't even test for it - which is why the US really needs to raise taxes, pay for tech inspections, their health effects, and save us billions in health care expenses.

    More directly, I am looking at getting one of the top 10 gaming laptops out there from CostCo.  I had seen the Lenovo Y720, a better model over the previous 520, and a low cost leader.  But I declined to buy from the Chinese, and instead stick with Taiwanese ASUS, as they have been very good for many years, where Lenovo had been bad, until they purchased IBMs laptop business.

    Reading reviews from people who purchase them are essentially useless, feel-good, posts.  I located a good article here: http://laptopmedia.com/review/lenovo-legion-y720-review-lenovos-premium-15-inch-gaming-solution-is-all-about-features/  and noted their testing and discussion of PWM.  Shocking, eye-opening, eye-saving stuff.  

    Where is this on the box?  Cigarettes cause cancer, bad PWM causes blindness.  They should be equally warned to all consumers, but they are not.

    Luckily, Laptopmedia took their studies, and created a list of all the laptops they have reviewed with PWM.

    This directly affected my choices - Lenovo was junk at a 5.2 rating.  ASUS is a 10, not using PWM at all.  I recommend you check all your monitors, anything using PWM needs to be replaced right away.  Good Luck, and good night.  8-)

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    • 2 months later...

    Check your monitors and laptops display specifications before buying them.  If they contain / use PWM, avoid them.

    Here is the more technical article on PWM, from there they have a list of laptops with PWM scores.


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