2012 will be a year of full and large-scale LED entry into the home. The E26 type incandescent lamp is mainly used in American households. However, in urban households in China, few people still use incandescent lamps, and most of them use ceiling lamps with curved fluorescent tubes. How to produce low-cost, good-performance LED ceiling lamps will be a great challenge for LED practitioners. In order to do this alternative work, we must first have a full understanding of ordinary ceiling lamps in order to be able to know ourselves and know each other.
First, ordinary ceiling lamp
1.1 The shape of the ceiling lamp
Although there are many types of ordinary ceiling lamps (Fig. 1), the most common ones are round or square, and the more complex ones have various odd-shaped crystal ceiling lamps:
Figure 1. Ceiling lights of various shapes
1.2 ceiling lamp tube
Most of its lamps are T5 fluorescent lamps after bending (Fig. 2). There are many kinds of specifications, mainly the following.
(a) Annular (b) U-shaped (c) 2D-shaped Figure 2. Fluorescent lamp for ceiling lamps
1.3 The power of the ceiling lamp is not clearly defined.
The most commonly used powers are 10W, 16W, 21W, 28W, 32W, 38W, 40W and so on.
two. Common ceiling lamps' problems and shortcomings
2.1 Low luminous efficiency
The overall lighting efficiency with ballast energy-saving lamps is only 55lm/W, and the highest high-power U-shape is only 80lm/W. And because most of these ceiling lamps are mostly T5-type lamps, they are bent into various shapes. But no matter what shape it is finally bent into, it is 360-degree light, and the upward 180 degrees of light must be reflected back to become useful light, and this reflection process will lose a lot of light. Therefore, at least 70% discount will be applied to the light effect after the lamp is made. That is to say, the above light effect is multiplied by 0.7. Moreover, in actual use, its brightness decays rapidly with time. For example, a Philips 32W ring T5 tricolor lamp YH32RR16 has a color temperature of 6500oK, a luminous efficiency of 67lm/W, and a total lumen of 2150lm. In fact, only 70% of the light can be used. That is only 1500lm.
2.2 Containing mercury
Mercury has a very low boiling point and can evaporate at normal temperatures. After a waste discarded fluorescent lamp is broken, it immediately emits mercury vapor to the surrounding area, which instantly makes the concentration of mercury in the surrounding air reach 10-20 mg/m3, exceeding the maximum allowable concentration of mercury in the air (0.01 mg/cubic). 1000 to 2000 times the amount of rice, the human body inhaled 2.5 grams of mercury vapor is life-threatening. Moreover, the liquid mercury has a very high permeability and will immediately penetrate into the underground polluted groundwater when it falls to the ground. 1 milligram of mercury is enough to contaminate 5454.5 kilograms of drinking water, making it impossible to meet safe drinking standards. Nowadays, the promotion of energy-saving lamps is actually an irresponsible approach to our children and grandchildren.
2.3 Low life
Energy-saving lamps are classified according to phosphors: mixed powder, halogen powder, and three primary colors. The life of the halogen powder is 3000-4000 hours; the life of the mixed powder is 4000-6000 hours; the three primary colors are more than 8000 hours.
2.4 ballast quality is low
Most of the ballasts used in fluorescent lamps do not give enough power. For example, the authors measured the ballast used in a 32W fluorescent lamp with an output of only 16W, which is only 50% of the rated power. Moreover, the life of all fluorescent lamps is short, mainly because the life of the ballast is very short, and once the fluorescent lamp is damaged, the ballast is usually followed. Almost everyone's experience is that the ballast or lamp should be replaced once a year. Most of the time it is less than a year, and both must be changed.
2.5 The price is not cheap
The price of general ceiling lamps ranges from tens to hundreds of dollars. The ceiling lamps of foreign brands should cost more than 600 yuan. As for some ceiling lamps with crystal ornaments, the price is as high as several thousand yuan, and the light source is only But at most it is a 40W shaped fluorescent lamp. Therefore, ceiling lamps are not as cheap as ordinary energy-saving lamps.
Rectifier Diode A semiconductor device used to convert alternating current into direct current. The most important characteristic of a diode is its unidirectional conductivity. In the circuit, current can only flow from the positive pole of the diode and the negative pole flows out. Usually it contains a PN junction with two terminals, positive and negative. Its structure is shown in the figure. The carriers in the P region are holes, and the carriers in the N region are electrons, forming a certain barrier in the P region and the N region. When the applied voltage makes the P region positive with respect to the N region, the barrier is lowered, and the storage carriers are generated near the two sides of the barrier, which can pass a large current and have a low voltage drop (typically 0.7V), which is called positive. Wizard status. If the opposite voltage is applied, the barrier is increased to withstand a high reverse voltage, and a small reverse current (called reverse leakage current) is called a reverse blocking state. The rectifier diode has significant unidirectional conductivity. The rectifier diode can be fabricated from materials such as semiconductor germanium or silicon. The silicon rectifier diode has a high breakdown voltage, a small reverse leakage current, and good high temperature performance. Usually high-voltage and high-power rectifier diodes are made of high-purity single crystal silicon (it is easy to reverse breakdown when doping more). This device has a large junction area and can pass a large current (up to thousands of amps), but the operating frequency is not high, generally below several tens of kilohertz. Rectifier diodes are mainly used in various low-frequency half-wave rectification circuits. If full-wave rectification is required, they must be connected to a Rectifier Bridge.
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