White Light Illuminator In order to ensure that the lighting level white LED can not only get a good application, but also get a high efficiency, first of all need to make it meet certain application conditions, followed by the need to use the appropriate drive circuit to meet the LDE work parameters with the requirements The
Drive circuit is a special power supply for the LED, White Light Illuminator to have a simple circuit structure, a smaller footprint, and higher conversion efficiency.
B. The output electrical parameters (current, voltage) of the drive circuit are matched with 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. Multi-output, White Light Illuminator each way the output should be able to separate control.
C. With a good degree of linear dimming function to meet the different applications on the LED light brightness adjustment requirements.
D. In the abnormal state (LED open circuit, White Light Illuminator short circuit, drive circuit failure), the circuit can circuit itself, LED and the user has a corresponding protective effect.
E. Drive circuit work, the other circuit of the normal work of less interference to meet the relevant electromagnetic compatibility requirements.
Linear drive applications
Linear drive applications are one of the simplest and most direct driver applications. In the lighting-grade white LED applications, although there is a low efficiency,White Light Illuminator poor regulation and other issues, but because of its simple circuit, small size, to meet the general requirements, so in some specific occasions, more applications.
A. Power supply Vdd + ballast resistance R way for the regulator power supply + ballast resistance drive mode, the circuit has the advantage of simple structure, low cost. White Light Illuminator The additional losses on the resistors in series with the LEDs are large and the power consumption of the linearly regulated power supply Vdd itself is large, so that the overall efficiency of the two is superimposed (<50%) and the LED current Control accuracy is low, brightness can not be adjusted, it is generally only used in smaller power, White Light Illuminator short time lighting occasions, such as LED flashlight, emergency lights.
B. Steady flow power supply Vdd + ballast resistance R + electronic switch S mode: its advantages not only improve the LED current control accuracy, and LED brightness can also change the electronic switch S to adjust the ratio. However, due to the higher resistance of series resistance and linear steady current power supply, White Light Illuminator the overall efficiency obtained is still very low, and the specific application range is limited.
A. Step-down switch drive: step-down switch driver is for the power supply voltage is higher than the LED terminal voltage or multiple LEDs in parallel drive applications.
The main principle of the circuit is to use the cut-off current obtained by the on-off electronic switch S to get the current lf value required to meet the LED operation, White Light Illuminator and the current feedback by the current (current sampling by R0) Of the current If stable in a certain range, White Light Illuminator and can also have a certain dimming function. The role of the inductor L is to play S when the energy storage and S off after the freewheeling action to reduce the flow through the LED current If.
B. Step-up switch drive: Boost switch driver is for the power supply voltage is lower than the LED terminal voltage or multiple LEDs in series drive applications.
The working principle of the circuit is to use the on-off function of the electronic switch S according to the requirements. When S is turned on, the power supply Vdd is stored in the inductor L, White Light Illuminator and the voltage polarity reversal on the L after S is turned on and the power supply voltage Vf is superimposed to obtain the current value If and the voltage value Vr required to meet the LED operation, (By R0 current sampling), so that the current flow through the LED If the stability of a certain range, White Light Illuminator and can also have a range of dimming function.