Solution of low power and high power LED lighting system

In the meantime, the challenge for LED lighting designers is how to ensure that the new design is compatible with the existing controller and wiring architecture originally developed for incandescent lighting. This paper presents a solution that can be applied to both low power and high power LED lighting systems. The LED bulb is constructed of a LED lamp that contains one or more LED chips, which are usually connected in series.

LED lighting will replace the mainstream incandescent lighting and other lighting technology, occupy the dominant position in the market. But it will take years to move from old technology to new technology. In the meantime, the challenge for LED lighting designers is how to ensure that the new design is compatible with the existing controller and wiring architecture originally developed for incandescent lighting. This paper presents a solution that can be applied to both low power and high power LED lighting systems.

The LED bulb is constructed of a LED lamp that contains one or more LED chips, which are usually connected in series. The brightness of each chip is determined by the magnitude of the current. Because of the series connection, each LED chip will automatically pass the same current, but the voltage on each chip is different. The forward voltage drop of LED is usually 3.4V, but it will change between 2.8V and 4.2V.

LED can be classified to limit the magnitude of the voltage change, but this will increase the cost, and the forward voltage drop will continue to change with temperature and time. In order to provide uniform light output, LED lamp must be strictly regulated by the constant current source driver. As a substitute for LED incandescent lamp, the power supply must be integrated in the shell. A typical integrated LED lamp includes a drive circuit, a LED cluster, and a housing that provides both mechanical and thermal protection for the driver and the LED chip.

LED drive requirements are very strict. It must be energy efficient, must meet strict EMI and power factor specifications, and be able to safely tolerate a variety of fault conditions. One of the most difficult requirements is the dimming function. Due to the characteristics of the LED lamp and the design of the light controller for the incandescent lamp does not match, so it is easy to cause poor performance. The problem may be slow to start, flicker, uneven illumination, or flicker when adjusting the brightness.

In addition, there are problems in the performance of each unit and the LED lamp can emit audible noise. These negative conditions are usually caused by the false trigger or premature shutdown of the controller and LED current control and other factors. Dimming controller lighting controller to line dimming or PWM dimming mode of work. The simplest way to adjust the line is the front of the silicon controller. This is the most commonly used lighting control mode, but unfortunately, the use of SCR controller for LED lamp dimming will produce a lot of problems. The more advanced line dimmer is the electronic front or rear side dimmer.

PWM dimmer for professional lighting system. With the use of a leading silicon modulator, the dimming control is achieved by changing the phase angle of each half cycle of the silicon controlled rectifier. The input power of the bulb and the phase angle of the dimming signal have a certain functional relationship, and the phase angle varies from 0 to 180 degrees. One of the important parameters of SCR is to maintain current (IH). This is the minimum load required to maintain the conduction of the thyristor in the absence of a gate drive.

In order to maintain the stability of SCR, the current can not be zero, the typical value of IH is between 8mA and 40mA. Therefore, the incandescent phase angle dimmer usually has a specified minimum load, 230V rated AC voltage is usually 40W. This is to ensure that the current flowing through the internal silicon controlled rectifier is always higher than the current threshold. Due to the low power consumption of LED lighting, maintaining the current will become a problem.