Three dimmable LED fluorescent lamps
Shanghai Longmao Microelectronics Co., Ltd. recently launched several dimmable LED fluorescent lamps. Although the fluorescent lamps in the past had relatively high luminous efficiency, they contained a highly toxic substance-mercury, and they could not be dimmed. Now the luminous efficiency of LED has caught up with and surpassed that of ordinary fluorescent lamp. Under the same brightness, the input power of LED fluorescent lamp can be reduced by half, and it does not contain toxic substances. It is a green and environmentally friendly new light source. Not only that, LED is a very easy to change the brightness of the device, as long as input a pulse width modulation (PWM) signal, it can be dimmed, so Longmao has introduced three dimmable LED fluorescent lamps.
The first is the manual dimming LED fluorescent lamp. In many occasions, it is necessary to manually adjust the brightness of the LED fluorescent lamp. This manual dimming fluorescent lamp uses the same knob installed at the light switch as the ordinary incandescent lamp dimming, but it is not like an incandescent lamp. SCR is used, so it will not cause interference in the power cord. It is just a low-level PWM signal generator. Generate the required dimming signal, send it to the dimmable boost constant current drive source SLM2842SD, and then send it to the LED fluorescent lamp for dimming. The block diagram is as follows:
The second type is photosensitive dimming LED fluorescent lamp
In many occasions, the light changes at any time. For example, in an office near the window, it will be very bright in sunny weather. At this time, the brightness of the fluorescent lamp does not need to be so bright. After adopting the photosensitive auto-dimming LED fluorescent lamp , It can be dimmed in sunny days and brighter in rainy weather, which can further save energy. In addition, fluorescent lights in subway cars have a similar situation. In urban areas, subways usually run underground, and at this time, the interior of the cars needs greater brightness. In the suburbs, the subway usually runs to the ground. At this time, the outside brightness is very bright, and there is no need for internal lighting. If photosensitive automatic dimming is used, the brightness in the carriage can be automatically adjusted.
Its construction principle is similar to manual dimming, except that the manual dimming knob is changed to a photosensitive element, and the PWM signal generator is changed to use a single-chip microcomputer to generate the PWM dimming signal.
The third type of dimmable LED lamps is not necessarily in the form of fluorescent lamps, but can be any kind of high-power LED lamps, which are mainly used in tunnel lamps. In the application of tunnel lights, it is also necessary to adjust the brightness of LED lamps according to day and night, sunny or cloudy and rainy days, which requires a device that can dim the light at a long distance (several kilometers to tens of kilometers). Shanghai Longmao Company also successfully solved this problem and proposed a very reliable long-distance dimming system.
Now these three dimming devices have applied for patents.
The LED fluorescent lamps used in the design of led fluorescent lamps are all high-brightness SMD LEDs with a thermal resistance of only 45℃/W, and use a tube with a semi-aluminum radiator. Because the drive power is external, it can be used without built-in The aluminum alloy tube with full heat sink in the space improves the heat dissipation efficiency and avoids the light decay of some LEDs caused by the heat of the built-in power supply, thus reducing the LED junction temperature and prolonging the LED life, which can be 50,000 hours Service life. Moreover, the AC power supply adopts an isolated switching power supply, which can completely CE hit high voltage, which also eliminates the possibility of electric shock for users. This kind of fluorescent lamp has been produced in small batches to meet the needs of the majority of users.
