LED linear constant current driving circuit in active valley fill circuit mode

Abstract

The invention discloses an LED linear constant current driving circuit in an active valley fill circuit mode. The LED linear constant current driving circuit comprises a rectifier bridge, a capacitor C1, a diode D1, a diode D2, a diode D3, a diode D4, an LED light string, and a constant current module. The constant current module comprises an NMOS tube N1, a first operational amplifier, an NMOS tube N2, and a second operational amplifier. In a power frequency period, the LED light string is used for the charging and the energy storage of the capacitor C1 by the constant current, and the energy stored in the capacitor C1 is used for discharging the current to the LED light string by the constant current, and therefore under a condition of large voltage differences between a direct current input voltage and the voltages of the two ends of the LED light string, the efficiency of the whole linear constant current driving circuit is improved, and the current flowing through the LED light string has smaller power frequency ripples.

Description

technical field [0001] The invention relates to an LED driving circuit, in particular to an LED linear constant current driving circuit in an active valley filling circuit mode. Background technique [0002] LED linear constant current drive circuit is more and more widely used due to its simple scheme, low cost, no high-frequency transformer and no EMC problems. [0003] At present, the existing LED linear constant current drive circuit such as figure 1 As shown, the input AC source is connected to the input terminal of the rectifier bridge 101, the positive output terminal of the rectifier bridge 101 is connected to the input terminal of the LED light string 102, and the negative output terminal of the rectifier bridge 101 is grounded. The constant current module 103 is composed of an operational amplifier 104 and an NMOS transistor 105 . The output terminal of the LED light string 102 is connected to the drain of the NMOS tube 105, the grid of the NMOS tube 105 is conne...

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Problems solved by technology

[0007] If the number of LED lights in the LED light string 102 is increased, the voltage difference between the input voltage Vin and the voltage Vled at both ends of the LED light string 102 will be reduced, but increasing the number of LED lights in the LED light string 102 will increase the cost. So this is not a good way to increase efficiency

[0008] Therefore, the problem existing in the prior art is how to improve the efficiency of the entire LED linear constant current drive circuit when the voltage difference between the input voltage Vin and the voltage Vled at both ends of the LED light string 102 is large.

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