This is one I was initially going to mention later, but a Craig’s list post piqued my interest and changed some of the direction of my initial intentions. For various reasons, using an alternative backlighting scheme for an LCD display is something to consider for a low voltage system. While they are inherently loaw voltage with a built in inverter for the backlighting, the backlighting consumes by far the most energy of the LCD display.
Additionally there are some people who are sensitive to light in a manner most people do not understand. There may be several reasons why this can occur which I will expand on in moment. Suffice it to say, bypassing the CCFL lighting system for testing purposes is one thing, totally removing the CCFL system is quite another. It is this latter approach that I will pursue. In principle it sounds easy enough to do. Finding a practical method of description that covers many models is another matter altogether.
The CCFL system usually uses a 24 volt supply which is then applied to at least one oscillator circuit, essentially nothing more than a basic transistor logic “Flip Flop”. each basic transformer will have 2 switching transistors for low and moderate power systems, with 4 windings. The voltage for the output secondary winding is usually between 750 volts up to about 2500 volts depending on tube. The transistors toggle on and off at a rate upwards of 10 Kilohertz. This is the same principle used for conventional flourescent emergency ballasts and is also the principle of the energy efficient lighting ballasts for T12, T8 and T5 flourescent ballasts, although configured slightly differently and using a different control IC/scheme. Compact Flourescents also use similar ballast controllers, and some made by Zetex (now a subsidiary of Avago, and who knows who will own Avago next week except the inside traders of Wall Street.) were tested to operate on a supply voltage of only 32 volts, and the Application note mentioned they believed it could operate on an even lower voltage.
Why the health issues? There can be many reasons. Western medicine does not have all the answers, and light has an incredible influence on all of us in the same or similar way no matter who we are. The health effects of not enough UV light are known to be a deficiency of Vitamin D3. Seasonal Affective Disorder is treated by hy intensity broad spectrum light exposure. Migrane sufferes sometimes have the onset of headaches after being under flourescent lighting, some from the “Newton Rings” that appear in some assemblies which are those bands of brighter light that move back and forth in the tube, and some from just the flicker rate, which most people normally do not see due to persistance of vision- it is why movies move, yet is merely a projection of sequential still images. Some people are sensitive to the color quality or spectrum of light.
Some of the things that go on with a CCFL specifically, but also apply to regular flourescent tubes. First is they produce a significant amount of UV light in addition to the visible portion of the spectrum- including the sickly colored “warm white” flourescent tubes. Conventional T series tubes produce a green hue which most people do not notice, but they know if they have cured ham sliced on a plate, that it looks pretty disgusting under flourescent lighting. This is why.
CCFL, CFL, and high efficiency ballasted lighting also produce RF energy. You can hear for yourself with a battery powered AM/MW radio held nearby. Switch mode supplies also give off an RF signal as well, it is how all of these achieve the efficiency they do. Modified Sine inverters, PWM motor and light controls, including the Class D audio amplifiers all use a PWM modulation circuit, each with it’s own optimal frequency. Class D audio amplifiers are also NOT rated with RMS power, they are rated with “Peak” ratings, which are deceptive, but you can get away with it with adequate marketing.
Why the PWM? For lighting, it allows for optimal energy transfer from the inductive reactance of the CCFL transformer and associated capacitors. It is also how LCD displays, be it TV or computer monitor are able to dim. Lighting dimmers for LED and flourescent dimmable ballasts use this principle. The amount of “ON time” relative to the mains supply frequency is the duty cycle. They are also in use for motor speed controls, and for pulse charging. This noise will radiate through the structural wiring of the domicile too. Adding Ferrite cores will help reduce this noise radiating to and from the mains wiring.
There is also information that is relevent here concerning mind control. If you doubt this, take some flashing marquee lights into a classroom full of kids- depending on the flashing speed and whether the kids are paying attention to the flashing lights or not- as long as the flashing is peripherally visible- that rate determines if you have a roomful of well behaved kids, or a roomful of little noisy monsters. A good book on the subject is one written By Nick Beggich: “Controlling the Human Mind.” Others have written extensively on this matter, there is not much I can add to what he and others have published on the subject.
For a little bit history to explain why I mention this is while MK Ultra and MK Searh were exposed in congressional testimony in the 1970′s (Church Committee) the research became difuse and did not really garner great interest, discussion or exposure until the opening of this century with DARPA being in the lead of such research currently. I only post this additional information to give you starting points for youe own research. Like it or not, it is being used subtly to shape your perceptions.
Ever have the urge for a cup of coffee shortly after you see and hear one being poured “on screen?” There are other methods at work too- you see people often with disarming props, such as an ice cream cone to soften your impression of them. Just look analytically at your local or national news broadcasts and you will see things you never saw before- sound effects to introduce a story, or moving nonsense images to distract part of your brain while something serious is being discussed- often to try program you how to think about a certain topic. Something to consider in light of mainstream news reporting on “Electric Calming methods” being employed in a recent major hurricane. But do not simply take my word for it- do your own research and follow up on the numerous footnotes you will find with most articles.
Another factor that may contribute to headaches even with a different lighting source is due to the flicker of the screen. What you percieve as a screen background as you read this, is actually a series of sequential dots and lines illuminated sequentially across the screen in a matrix and when the end of the scan matrix is reached, a “black screen” is created for an equal interval and the scan begins again. Typically at a frame rate on TV sets of half the mains power, which translates to 30 illuminated screens to 30 black screens for those with 60Hertz electric mains, and 25 illuminated and 25 black in areas where the mains is 50 hertz. In computers however, it can be twice that, give or take depending what your screen settings are for the monitor you are using and video chipsets.
With TV’s another factor is a “progressive scan”. At it’s most simplistic description it just means every other line is illuminated first, with a subsequent scan frame being interlaced with that first on the originally non-iluminated scan lines. In other words, frame 1 is partially scanned onto the screen, followed by part of frame 2 to make a full image, then comes the black frame, and then the part of the frame 2 that was not initially scanned is now scanned and part of frame 3 completes the scan, and this continues while the set is on.
Sometimes such interlacing is beneficial to the percieved image quality, and sometimes not. 20 years ago due to limitations of the hardware, an interlaced image was used to compensate. With those systems it was not portions of 2 frames, it was merely each frame by itself drawn in 2 passes. For many people this caused headaches, and in some nausea.
By backlighting with an alternate light source such as incandescent light source or other LEDs, this might not resolve the potential health issues created by the scanning, but it will alleviate the most power consuming portion of the monitor or TV; and the RF hash it’s power source creates. Utilizing a tricolor white LED allows you to adjustt the color balance for artistic applications as well.
But I am diverging from my point. Essentially, the project I plan to pursue with this is to eliminate the CCFL lighting circuit entirely and replace it with either Power LEDs, Tri-Color Power LEDs, or incandescent, or even daylight. Mainly the motivation is to see how much effort will be needed, or if it is in fact incredibly simple- I am inclined to believe it falls somewhere in between, but more to the simple end of that spectrum.
Looking at some approaches on the web- those that I could find, all have left the 24 volt supply intact. My approach will eliminate most, if not all of it.
The Power LEDs would best be powered with straight DC. While the application notes for LED lighitng suggest using constant current supplies and PWM for dimming, as opposed to just using a variable voltage or variable resistance; it is largely one of perceptions. The reality is a linear decrease in voltage does not yield a linear decrease in light output, whereas a linear decrease of the duty cycle will produce the appearance of linearity in the light dimming.
When one applies the concept of percieved linearity to audio this is no surprise. If you were to replace the volume controls on you Class A, B, C amplifier or permutation of those- the result is most of your adjustability from loud to soft occurs in a very narrow angle of rotation of the control. The Audio taper potentiometer is a logarithmic taper. If you plot the resistance on a linear graph, it is not a straight line if the graduations of the graph are linear.
Why a Tricolor power LED? Because you can color balance the light emitted from the face of the LCD. You can do it to a greater extent even than what can be adjusted from the LCD panel itself. It harkens a little bit back to the days of analog color TV where you had the ability for 2 sets of controls in the back of the set for color rendering in addition to the color level and tint controls on the front of the set. For those people who may have a mystery headache trigger that is more pronounced with one of the primary projected colors, they can reduce that amount to zero from the LED.
The other detail about “White” LEDs, is regardless of balance, their spectral emission for single phoshor/single chip LED’s, no matter who makes them- they still have a high blue spike in spectral response leading into ultraviolet light.
I personally prefer the daylight balanced LEDs because color rendering is closer to real daylight, but it works for me largely because the power supplies I use output a filtered straight DC with no dimmers. I do also recognize where some people may not like so much blue, and for some there is a health reason for it- usually manifests as headaches, fatigue and nausea. For some, the RF hash from PWM circuits can trigger it, for some- just unrealistic color rendering from what they are used to can manifest it. Cerulian Blue carrots for example may sound colorful, and Syngenta might come up with some- they arlready produced the GMO form of Cauliflower by making it orange. But I do not think too many people would want to eat Cerulian blue carrots, after all, there is no naturally ocurring blue food. Blueberries and grapes are a shade of purple.
So to sum up, My goal is to bypass and eliminate the CCFL circuit of an LCD monitor/display, and describe the basics as they should apply to other displays so they can be lit with other means, such as a kerosene lantern (for the Steam Punk crowd) or candle, to an incandescent light source to an LED source. I might even look into setting something up as an art display.
I shall post progress and action photos here in subsequent follow up posts. I just need to find some potential monitors for this project. The largest hurdle is to bypass the shutdown feature built into most monitors.
While this post may seem a bit fractured, it is largely the result of inter laced concepts. I do plan to get back to a few more regulators, and panel construction, as well as few other details, so please stay tuned.