LED drive device and control circuit and control method of LED drive device

Abstract

The invention discloses an LED drive device and a control circuit and a control method of the LED drive device. The control circuit of the LED drive device comprises a conduction time control circuit, an average current value obtaining circuit, a proportion superposition circuit, a comparison circuit, an OR gate, a set signal generation circuit and an RS trigger, wherein the conduction time control circuit is used for generating a first control signal according to a sawtooth wave signal and first reference voltage; the average current value obtaining circuit is used for generating an average current signal of reflecting an average output current value according to a current sampling signal; the proportion superposition circuit is used for superposing the average current signal and the sawtooth wave signal according to the ratio to generate a superposed signal; the comparison circuit is used for comparing the superposed signal with second reference voltage to generate a second control signal; the OR gate is used for generating a set signal according to the first control signal and the second control signal; the set signal generation circuit is used for generating the set signal; and the RS trigger is used for generating a switching control signal according to a reset signal and the set signal. By the control circuit of the LED drive device, a compensation network of a regulating ring can be omitted; a relatively high power factor is achieved; and a leakage circuit is not needed when applied to dimming of a silicon controlled rectifier.

Description

technical field [0001] The invention relates to an LED driving device, a control circuit and a control method thereof. Background technique [0002] As we all know, LED is a current-mode device. In order to keep the luminous flux output by the LED constant, the prior art generally adopts a closed-loop control control circuit to realize the constant output current of the LED driving device. In addition, in order to reduce the harmonic pollution of the drive device to the grid, the control circuit also needs to achieve a high power factor. [0003] figure 1 Shown is a simplified schematic diagram of a prior art LED drive control circuit. figure 1 The circuit shown is a floating buck type high power factor LED driver. Such as figure 1 As shown, the input AC voltage Vac is rectified by the rectifier bridge B1 and filtered by the capacitor Cin to obtain a rectified bus voltage Vin. The bus voltage Vin is a half-sine wave signal. The LED drive control circuit 100 includes a...

AI Technical Summary

Problems solved by technology

[0008] The technical problem to be solved by the present invention is to provide a new type of LED drive device and its control circuit and control method to overcome the shortcomings of the existing LED drive control circuit, such as high cost, complicated control and dimming with thyristor

Images