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What are Full Wave LED Christmas Lights?

What are Full Wave LED Christmas Lights?

LED Christmas lights become more popular every year.  They last longer and are less susceptible to vibrations or damage, but you may have noticed something odd (or had a friend who noticed) about the light given off by your new Christmas lights.  The bulbs may seem to flicker while you stare at them.  This is especially noticeable if the light string is moving in the breeze or on a display and can be very distracting or annoying.  The cause of this flicker is in how the LED string is designed:  Whether it uses full-wave or half-wave rectification.

Full-Wave vs Half-Wave

Part of the reason LEDs use so little power is that they aren’t actually on all the time; LEDs cycle on and off at either 60 or 120 Hz.  In simpler terms, half-wave LEDS cycle on and off 60 times per second, while full-wave LEDs turn on and off 120 times each second.  This off period decreases the amount of energy needed to run the light overall.  Unfortunately, our vision system tops out at 60 Hz, meaning some people can actually see this flicker between states (it’s the same flicker you might see in older TVs or fluorescents).  At 120 Hz, our brains can’t perceive the off state and we see a steady light.  It uses slightly more energy than a 60 Hz light string, but not by much (rather than a 90% energy savings over incandescent light strings, you’ll probably get 80%).

A More Technical Explanation

This on-off system is based on how AC current switches between positive and negative directions as a Sine wave.  The driver for an LED array or light string contains a very special bridge called a rectifier (from the French, meaning “to make straight”) which converts the AC signal into DC.  Half-wave rectifiers take only the voltage above the 0 voltage line (positive voltage) while full-wave rectifiers redirect all of the voltage into the positive bracket, as you can see in the images below.  The gap in half-wave rectification is where that flicker becomes visible, because whenever the Sine wave drops to 0, the bulb shuts off.  This happens 30 times each second in half-wave and 60 times in full-wave.

Image used courtesy of Wdwd
Image used courtesy of Wdwd
Image used courtesy of Wdwd
Image used courtesy of Wdwd

All of this is a very technical explanation.  The important thing to remember is that both methods allow LEDs to run on the voltage from your wall outlet and both help cut energy costs while running lights.  Half-wave rectifiers are a little cheaper (and are usually the type carried by big box stores) but if you can see the flickering, it can severely hamper your Christmas display.  For the record, all of the LED light strings on 1000bulbs.com, from wide angle to simple mini string lights, are full-wave rectified, so there’s no worry over flickering LEDs this holiday season!

Now that you know the difference, what do you think?  Can you see the flicker from a 60 Hz strand?  Have you already lit up your home with Christmas lights or are you planning on buying new LED strands to make things really stand out?  We’d love to hear what you’re plans are in the comments below.  Or if you have more questions (or fantastic holiday decoration pictures), share them with us through FacebookTwitterGoogle PlusLinkedInPinterest, or Instagram!

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