Segmented linear constant current led drive circuit

Abstract

The invention provides a segmented linear constant current light emitting diode (LED) driving circuit which is high in efficiency, high in power factor and small in size, and an electrolytic capacitor and an inductor are not needed. The segmented linear constant current LED driving circuit is used for carrying out constant current control on at least two segments of LED strings and comprises a rectifier bridge circuit and constant current control circuits in one-to-one correspondence with the LED strings, wherein the rectifier bridge circuit is used for receiving alternating-current input voltage and rectifying the alternating-current input voltage into direct-current voltage, and the constant current control circuits are used for carrying out the constant current control on the LED strings.

Description

technical field [0001] The invention relates to the technical field of power electronics, in particular to a segmented linear constant current LED drive circuit. Background technique [0002] For the application of low-power light-emitting diode LED lighting drive circuit, according to the working nature of the drive circuit, it can be divided into: linear constant current drive circuit and switch drive circuit, the adjustment tube of the drive circuit in the linear constant current drive circuit works in a continuous state, and the switch drive circuit The MOS tube in it works in a high-frequency switching state. In these circuits, electrolytic capacitors are commonly used to smooth the voltage. The life of electrolytic capacitors is exponentially related to their operating temperature. At 75 degrees, the capacitance will gradually decrease due to the evaporation of the electrolyte, and its life is only 5000-10000 Hour. There is a huge gap between the short life of electr...

AI Technical Summary

Problems solved by technology

Since the power consumed by the adjustment tube is equal to the product of the voltage across the adjustment tube and the current flowing through it, the efficiency is generally not very high, much lower than the conversion efficiency of the switching circuit

And due to the heat caused by power consumption, a heat sink needs to be installed on the adjustment tube, which affects the cost and increases the occupied volume

The conversion efficiency of the switching power supply circuit can be as high as 90%, but its disadvantage is that the MOS tube working in the high-frequency switching state will generate serious electromagnetic interference, and an additional electromagnetic filter circuit needs to be added, and the cost of the inductor to eliminate common mode noise Higher, which increases the cost and volume of the circuit, and the additional EMC circuit reduces the efficiency of the conversion circuit. In actual use, the efficiency of the flyback switching power supply is about 85%.

Both circuits require the use of electrolytic capacitors, which have become a hidden danger to the life of the drive circuit

[0006] To sum up, among the existing LED drive circuits, the ordinary linear constant current drive circuit has the advantages of simple circuit and no electromagnetic radiation, but has the disadvantages of low conversion efficiency, large-area radiator and electrolytic capacitor

However, switching power supply drives have high conversion efficiency, and at the same time, there are problems such as electromagnetic radiation, complex circuits, and the need for electrolytic capacitors.

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