2011 Issue

28 ginal. Was there a better way? Yes, an L-charge pulse circuit did the job! That was the prelude to use of the phosphor screen for lighting, but that was not then viable business. Later, at work in other companies and in my own for 20-plus years, LCC HV circuits were used – and without a hint of use anywhere else until both polarity transistors and switch mode came along. As to DC transmission, it’s not been much in my purview, but seems to have had a slow and tortuous path. Has it really emerged yet? Where does LCC fit in? Although the energized Aluminized Phosphor Screen (APS) light should be simpler, less expensive and more efficient, like LCC’s L-charge circuit, it has been thoroughly ignored. Fluorescents have come to the fore, seemingly because they were already there and the pressure for high efficiency has pushed them ahead. They have now achieved both the low size and price to directly compete with incandescent. Over eighty percent of my lighting is fluorescent. With the looming promise of the light emitting diode (LED), pursuit of LCC APS lighting seemed pointless – until? A recent article in IEEE Spectrum seems to have turned the above outlook upside down. The problem: the essential white LED could not achieve adequate brightness. Progress would require a break- through. Everyone should know that such come only at the time and pleasure of the Gods! The article was not very clear, at least to me, as to just what applications would be impacted, but it seemed to include some residential. That brought the LCC APS alternative back into my consideration. So let’s take a close look. Fig. 1, with its negative transistor, is an inverse equivalent of Fig. 4.84a of the RL excerpt. The ALC is at ground and an electron emissive cold cathode is pulsed negatively by the L-charge circuit at a relatively high (10 – 30 kHz) frequency controlled by DO, a drive pulse oscillator. The HV is all in the vacuum and input is 110V through a standard screw base. Thus the bulb replaces standard incandescent or fluorescent bulbs. Its cost should be lower than LED and fluorescent . It has no mercury to impose an environ- mental hazard. The screen can be shaped to directly provide from 300- to180-degree general illumination, or to give from a wide flood to a sharp spot. A wide choice of colors are also available. So, let’s take a look at efficiencies. The modern ver- sion of Edison’s i nc ande s cen t bulb is the stan- dard measure of luminous effica- cy! It comes in with much heat at a typical 15 lumens per watt. The fluorescent has been finally beaten into the equivalent incandescent size. Its price and efficiency make it a wise buy. Its typical rating is 60-90 lumen/watt – four-six times higher than incandescent. As to the LED– it ismaking great progress in specialized application such as projection and in LCD panel TV’s. A few at astronomical prices are appearing to replace standard screw base bulbs. But general application is nowhere in sight. It would seem that a better first choice step would be replacing all those expensive and inef- ficient small-screw-base and candelabra units. Information Display, Vol. 26, No. 1 of Jan. 2010 is on The Transition to Solid State Light- ing. Compared to the above, current LEDs can provide 90 lumens per watt. That is expected (optimistically?) to go to 150 lm/W in a few years. It should be noted that LED’s require special optical treatment to make them suitable for residential application – thus raising the question of efficacy/efficiency of actual use. Nothing seems to have been said about the adaptation of low DC voltage LEDs to the 120 volt AC power line. Before LCC, I used its equivalent, the Capacitive Charge Converter (CCC) circuit, to energize VR tubes direct from a convenient AC voltage. There were other similar applications. At RL I spent substantial time helping other members with their problems The circuit would have become familiar. I have also used CCC in product applica- tions ever since. But, as with LCC, CCC seems to have become unknown. It is shown in Fig. 2 applied to an LED light. The C voltage drop can be large, and on L-loaded transmission lines it improves power factor. The question then is: how does our LCC–APS light stack up? LCC is very efficient and it runs cool. It is simple and should be less expensive than a fluorescent bulb drive. P4, the first white CRT faceplate phosphor, is listed at a nominal 20 lm/W and later one of the best white screens at 25 lm/W. But in order to reduce ambient reflections, the CRT faceplate transmission is reduced to 46%. APC has no such limitation. That raises efficacy for white to 54 lm/W. Neither the phosphor response time nor constraints of R, G and B primaries are imposed on APS. That leaves substantial room for improvement. Best phosphor efficiencies are in the range of 90 lum/w – on par with current LEDs. In summary, it can be stated that the LCC-APS light will outper- form the fluorescent in all respects. It uses old technology that can be implemented quickly. In contrast to all others, it can put all of the output exactly where it is wanted – high efficacy; and with removal of the CRT display restraints, adaptation of phosphors to improve efficiency should not be difficult. It is more rugged and with life equal to or above that of the fluorescent. APS lighting uses no mercury. Its startup is fast with no flicker and it can be efficiently dimmed over full range. It works at low temperature. It can provide the color spectrum to meet a wide range of demand. The same basic comparison with respect to implementation and adaptation can be made regarding the LED. Its cost will be much higher than APS for a long time. In the short term, expected improvement in efficacy will be no better than for the phosphor screen. It would seem then that the final question as to the com- petitive permanence of APS boils down to the question of when the cost vs. efficacy and the adaptability of LED lighting thoroughly surpasses that of ALC. In this writer’s view, ALC can provide a reasonably long and useful life at a time when reducing energy use is said to be critical and alternatives are worse or uncertain. Mr. Washburn received the B.S.E.E degree, communications major (honors) in 1939 from the University of Utah. His work has been on the development of electronic engineering and its Cathode Ray Tube technology – circuits, components, and systems – beginning with microwave radar indicators at the Radiation Laboratory, M I T. Mr. Washburn founded and was president of Washburn Laboratory Inc. which specialized in high resolution and high precision CRT systems. He holds 20 US patents. Washburn