1 Introduction
The luminous flux of white LEDs can now easily reach 80 lumens per watt, making the LED lighting industry, especially LED streetlights, more feasible.
However, in the application of LED street lamps, most of the current drive circuits of various manufacturers adopt Switching Power Supply schemes. The voltage is generally between 24 and 48 volts. Because the power of street lamps is relatively large, generally more than 120W, it is necessary to use multiple sets of switches at the same time. The power supply is not only costly, but the average power consumption loss of the switching power supply itself is between 15% and 20%. This makes the LED street light that was originally energy-saving and wasteful, which wastes 15~20% of energy consumption, which is worthless. At the same time, due to the switching power supply used by each household, the voltages are not the same, which makes the use unit face different standards in the future, and the cost is too high. In addition, the switching power supply generally only provides constant voltage, but the LED is long-term at high temperature. After the work, the problem of the voltage drop and the current rise is faced, which causes problems in the stability and reliability of the LED street lamp. In view of this, how to develop a LED driver circuit with low power loss (should be within 5~10%), low cost, long service life, and constant voltage and constant current function is already in the LED application field. A major topic.
On November 29, 2008, the China Lighting Association Outdoor Lighting Professional Committee and the Transportation Lighting and Optical Signal Committee and China Lighting Network held a debate on the status quo of high-power LED street lamps in Guangzhou, where Guangzhou and Shanghai street lamps were held. It is recommended that the power supply circuit of the LED street lamp should be standardized to facilitate user maintenance, and the author will provide the reference for the LED street lamp solution developed by our company with Chinese intellectual property rights.
2, LED street light circuit design essentials
Because the current common metal sodium lamp power is about 250W each. If the LED street lamp is to become a competitive street lamp alternative, it should basically play an advantage in the power-saving function. Since the LED is unidirectional, in the case of the same light effect, the lamp has four-side illumination than the metal sodium. The lighting effect is much stronger, so as an alternative to the 250W metal sodium lamp, the power of the LED street light should be between 120~160W.
At present, the commonly used light sources on the market are generally 1W chips, that is, the general street lamps have 120~160 chips, and the on-voltage of each chip is between 3.3~3.6V. Even, the voltage across the chip will be close to 400V or more.
Since the power of each street lamp is above 120W, the power factor correction problem must be considered in the power supply design.