LED drive circuit and method based on voltage memory and segmented current limiting

Abstract

The invention discloses an LED drive circuit and method based on voltage memory and segmented current limiting. The circuit comprises a rectifying circuit, a voltage division circuit, a voltage increasing and reducing detection module, a voltage memory module, a comparator set, a control logic module, a high-voltage switch circuit, a detection resistor, a current detection comparator and an LED lamp string. According to the drive method of the circuit, according to the increasing and reducing characteristics of the directly-rectified direct-current ripple voltages, the segmented type lightening control mode is adopted in the load of the LED lamp string. The drive circuit solves the problem of the influence of the difference of voltage current characteristics of an LED chip adopted by the lamp string in the actual application on drive currents, the work current of the LED lamp string in the whole work period is limited within the designed largest current value Imax, the problems of lower brightness caused by undercurrents and damage, caused by overcurrents, to the LED chip are solved, the light-emitting efficiency of the LED lamp is improved, and meanwhile overcurrent protection can be carried out on an LED device well.

Description

technical field [0001] The present invention relates to an LED drive circuit and method, in particular to an LED drive circuit and method that utilizes DC pulsating voltage directly rectified by AC mains for power supply, uses voltage memory and section current limiting, and belongs to the technical field of LED drive . Background technique [0002] The LED lighting drive circuit is the power supply circuit required to enable the lighting equipment using LEDs as light-emitting devices to work normally, and can provide the required voltage and current for the normal operation of the LED device. LED lighting drive circuit structure framework such as figure 1 As shown, it is mainly composed of a rectifier circuit, an auxiliary power supply circuit, a power conversion circuit and a feedback loop. The input AC power is transformed into DC high voltage by the rectifier circuit, and the DC high voltage is generated by the auxiliary power supply circuit to generate a stable DC low...

AI Technical Summary

Problems solved by technology

[0004] The segmented LED drive circuit described above does not require electrolytic capacitors for voltage energy storage, the power factor is high, and the life of the entire lamp will not be limited by capacitors. However, this driving method also has shortcomings, which can be seen from the volt-ampere characteristics of LED devices. Under its normal working voltage condition, small differences in voltage will lead to obvious fluctuations in current, and the light intensity of LED is mainly related to the current flowing through LED; in practical applications, even if the LED chips produced by the same manufacturer in the same batch, There will also be differences in the volt-ampere characteristic curve, so the segmented driving method based on the fixed voltage division ratio, due to the reference voltage accuracy used for comparison and the difference in the volt-ampere characteristic of the LED chip, the working current of the LED in the light string cannot be determined. Accurate prediction and design, under-current or over-current driving status

Undercurrent will cause the brightness of the light string to be dim, while overcurrent will cause damage to the LED chip

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