LED lighting as a new lighting technology, the world's attention, known as the third revolution in the history of mankind lighting. Compared with a relatively traditional halogen low voltage lighting, high brightness LED interior lights, landscape lighting, automotive lighting has many advantages. The high brightness led driver 30w to provide greater brightness, the smaller the power consumption with energy saving, environmental protection, seismic, long life and quick connect.
In today's mobile phone, one of the most popular feature is the built-in digital camera can capture high-resolution photos and images. With the emergence of broadband 3G networks, demand for high photo resolution, and such video conferencing and other new applications, continue to improve the performance of the integrated camera. The camera performance enhancement also created a demand for the use of high-power white light source of the camera indoors or in dark environment.
The white led power 50w is not only widely used in rear projection lighting color display, has become one of the primary light source of the camera phone. White LED has the ideal characteristics required of the mobile phone designer integration, such as small size, high brightness output and "Flash" and the continuity of the "Video" object illumination. High output power LED Flood light has been developed especially suitable for the purposes of the integrated camera light, its can be quite competent to the task of lighting objects, the camera LED indicates another important demand for battery-powered.
There are three focus to drive high-current white LED
Drive high-current white LED Power 100W from the system designer's point of view, there are three main problems: 1. To provide an efficient power supply; adjust the LED current; when the camera lights turned off to ensure that the LED is completely cut off from the power supply terminal . Power operation of high-current white LED as a general diode, but with a 3.4V Shun transmitted to the voltage, or a "typical" 350mA forward current operation (Table 1).
LED current ("Flash" mode, 500mA-700mA +) lead to a higher forward voltage, low current ("Torch" or "Video" mode, 100mA-350mA) produce lower forward voltage. Forward voltage inversely change with temperature, operating temperature range as the other diode, its forward voltage will be generated as the temperature rises hundreds of millivolts of drift. Therefore, an efficient power supply for LED is quite challenging, because the LED forward voltage will be based on the operating condition of high or lower than the lithium battery voltage.
If two or more LED camera light to use two or more parallel LEDs, additional supply will be accurate current matching become a must - because of the forward pressure between any two LED can vary widely, including most obvious way to strain series led driver 120w connected to this as a boost converter to be able to cope well, however, if a parallel connection is a must, this program shall be provided independent of each LED current control, whether in what kind of situation, the current control circuit should be as much as possible across the current sense resistor voltage drop control to a minimum, the camera lighting applications Another complicating factor is the presence of visible light, which is a forward current drops when the micro-ampere series high current LED. In the case of the lack of an existing LED and cut off the connection, a separate switch in series with the LED must be shutdown to ensure that no current flows through this LED.