solution:
Isolated and non-isolated design
The controller used can perform power factor correction
LED brightness light-emitting angle of the LED is now there is a certain relationship, the smaller the angle the higher the LED brightness it did not have any bright not bright, it is a lie to children, if they are good quality LED No matter what home LED manufacturers of everyone's brightness are similar, but the production process is not the same, life is slightly different, because we are using is that several foreign LED chip. If the brightness of the white LED180 5MM angle of only a few hundred MCD, if the luminance is 15 degrees going to more than ten thousand to twenty thousand MCD brightness, the brightness difference of several times, if it is used in the illumination Use, in the outdoor is best to use high-power LED, the brightness is even higher, a single power has 1W, 3W, 5W, and some use a combination of multiple high power into a high-power LED, power to hundreds There are.
Power factor is a very important factor because high power factor can reduce the loss of the distribution network. The most effective way to reduce the environmental impact of electricity use is to reduce waste, and therefore regulatory agencies around the world are further their stringent power factor specification. An example of this is the Energy Star Solid State Lighting Energy Efficiency Specification (09/12/07), which states that the power factor (PF) for residential lighting products should be greater than 0.7 and the power factor (PF) for commercial lighting products should be greater than 0.9.
Figure 1 LED bulb construction diagram
LED bulbs and lamps manufacturers are responding to these demands, they want their product versatility as high as possible. Therefore, they are in great need of LED driver circuits compatible with various dimmers to achieve high efficiency and power factor of 0.9 or higher. The LED is made of a III-IV compound such as GaAs (gallium arsenide), GaP ( gallium phosphide), GaAsP (phosphorus gallium arsenide) and the like, and its core is a PN junction. Therefore, it has the IN characteristic of a general PN junction, that is, forward conduction, reverse cutoff, and breakdown characteristics. In addition, it has luminescent properties under certain conditions . At the forward voltage, electrons are injected into the P region from the N region, and holes are injected into the N region from the P region. A part of the minority carriers (small children) entering the other area is combined with the majority carriers (multiple sub-) to emit light. There are called long-life LED light source lamp. It is a solid cold light source, epoxy resin package, and there is no loose part in the lamp body. There are no shortcomings such as filament light-emitting , heat deposition, light decay, etc. Under the proper current and voltage, the service life can reach 60,000 to 10 Ten thousand hours , more than 10 times longer than traditional light sources.
Dimming controller
The lighting controller operates in either line dimming or secondary side dimming. The simplest line dimming method is the leading edge thyristor controller. This is the most commonly used lighting control, and unfortunately, many problems occur when using an SCR control dimming of the LED lamp. Flexible programmable control function may control the amplitude of the pressure limiting buck, switch lamp time arbitrarily set. The control mode is sometimes control, light control, manual control, remote control and root PC automatically controlled according to the latitude and longitude of the point of use. Soft start, soft transition, soft shut-off function, prevent over-voltage and cold start large current impact on the luminaire, greatly reducing the damage rate of the luminaire. For sodium lamps, mercury lamps and other lamps with adjustable full- pressure preheating start-up time, the lamps can be fully preheated and smoothly transition to normal working conditions. It can realize all-night light and midnight light control, and has the function of step-down and current adjustment in the middle of the night, and the energy-saving effect is more ideal. The perfect restart function can automatically re-ignite the lamp when the load is faulty and the external power supply is over. The control mode is sometimes controlled, light control, manual control, remote control of the upper computer and automatic control of latitude and longitude according to the place of use (optional). The three-phase switch lamp time and output voltage can be adjusted independently, and can be connected to unbalanced and different types of loads. Programmable maintenance mode, then the lighting system overhaul, maintenance and lamp replacement. A set of clocked normally open contacts is reserved for special control . The contact capacity is 7A/250VAC.
The performance of thyristor controllers in incandescent lamps is impeccable, but there are various negative effects in LED lamps, including flicker, uneven illumination, audible noise, and flicker. To understand the reason, we must first understand the working principle of controllable silicon dimmer.
Figure 2 Front edge thyristor dimmer
Dimming control is achieved by changing the phase angle of each half cycle of the thyristor conduction. Lamp filament current is closely related to the phase angle of the dimmer signal, a phase angle range between 0 ° (nearly 0 °) to 180 ° between the. This is the minimum load that the thyristor must maintain to remain conductive without the use of a gate drive. In order to maintain stable operation of the thyristor, the current cannot be zero, and the typical value of IH is between 8 mA and 40 mA. Maintaining current is not a problem when driving incandescent lamps .
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