In order to ensure that the illumination-level white LED can not only get good application, but also can obtain high efficiency, firstly, it needs to meet certain application conditions, and secondly, it needs to adopt adaptive drive circuit to meet the parameter matching requirements of LDE work. .
First, application requirements
1. The drive circuit is a special Power Supply specially designed for LEDs. It has a simple circuit structure, a small footprint, and a high conversion efficiency.
2. The output electrical parameters (current, voltage) of the drive circuit should match the technical parameters of the driven LED to meet the requirements of the LED, and have a high precision constant current control and a suitable voltage limiting function. When multiple outputs are used, the output of each channel must be individually controllable.
3. It has a dimming function with good linearity to meet the requirements of LED illumination brightness adjustment for different applications.
4. In the abnormal state (LED open circuit, short circuit, drive circuit failure), the circuit can have corresponding protection for the circuit itself, LED and user.
5. When the drive circuit works, it has less interference to the normal operation of other circuits and meets the relevant electromagnetic compatibility requirements.
Second, linear drive applications
The linear drive application is one of the simplest and most direct drive applications. In the illumination-level white LED application, although there are problems such as low efficiency and poor adjustability, the circuit is simple and compact, and can meet general requirements, so it is widely used in some specific occasions.
1. Regulated power supply Vdd+ ballast resistor R mode Figure 1 shows the driving mode of the regulated power supply + ballast resistor. The advantage of the circuit is that the structure is simple and the cost is low. The additional loss on the resistor in series with the LED is large, and the power consumption of the linear regulated power supply Vdd itself is also large, so the overall efficiency of the two is superimposed (<50%), and the LED current The control precision is low and the brightness is not adjustable, so it is generally only used in occasions with low power and short time lighting, such as LED flashlights and emergency lighting.
2. Steady current power supply Vdd+ ballast resistor R+ electronic switch S mode: The driving mode shown in Fig. 2 is an improved way of the driving method of Fig. 3, the advantages of which not only improve the control precision of the LED current, but also the brightness of the LED can be changed. The on/off ratio of the electronic switch S is adjusted. However, since the series resistors and the linear steady current power supply have higher additional losses, the overall efficiency obtained is still low, and the specific application range is greatly limited.
1 2 Next Page
Customized Transformer and Reactors,Low Voltage Transformer,Others Low Voltage Transformer
Heyuan Electronic Technology Co., Ltd. , http://www.yqvoltagestabilizer.com