The Design Of LED Drive Circuit With Multiple Protection Circuits

LED(Light Emitting Diode) is widely used in various fields because of its high efficiency:low power consumption, long life, low pollution and other characteristics. In the Lighting field, they have the trend of replacing the traditional lighting lamps to become the mainstream lighting lamps. Now,the countries of the world want to slow nervous energy by developing the LED industry.But due to the electrical characteristics of LED, if we want to make the LED work steadily and normally, they must be equipped with corresponding driver power. However,there are many disadvantages in the driver chips of the high-power LED, like low efficiency, poor stability and single protection function and so on. Low efficiency means it will consume more energy, and poor stability meas the LED working life will be shorted, single protect function means the drive circuit are unable to cope with emergency of the outside world, then the drive circuits are prone to failure. These problems have become the main factors which restrict the development of the LED to further.In this paper, according to the current deficiency of some drive circuits, a new type Buck LED drive circuit with multiple protection circuits is designed.The main contents of this paper as follows:(1) The development status of the LED and its application prospect are simply described in the article. Then the content of the LED light-emitting mechanism and luminescence properties and electrical characteristics are described, and several types of LED driver circuits and its protection circuits are descripted detailedly in the paper.(2) In order to improve the efficiency of the circuit, the LED drive circuit designed in this paper is adopted the Buck switching circuit, the Buck switch circuit is one of the LED driver circuits with high efficiency, its efficiency can reach above 90%. But because the electrolytic capacitors is joined in the circuit, its working life is shortened. In this paper,the electrolytic capacitor is removed from the Buck drive circuit, and a current compensation circuit is integrated into the drive circuit to reduce current ripple to ensure the stability of the circuit.(3) In this paper, a variety of protection circuits are integrated into the LED drive circuit, including over-voltage protection circuit, over-current protection circuit, temperature adaptive circuit and under-voltage protection circuit, so as to make the performance of the drive circuit be better. The temperature adaptive circuit includes thermal shut off circuit and temperature adaptive circuit,the principle of the temperature adaptive circuit is that it make the temperature change of the circuit into the current change through taking use of the negative temperature characteristics of MOS pipe trench way carrier mobility mu,then the detection of the drive circuit temperature is realized by it. It is no longer the simple feature that circuit is shut off when the circuit temperature is high, but there is a temperature buffer area, so the efficiency of temperature protection circuit is improved, and it also has a temperature hysteresis interval, so that we can prevent the circuit oscillation phenomenon.