LED drive circuit with controllable current ripples

Abstract

The invention provides an LED drive circuit with controllable current ripples. The LED drive circuit with the controllable current ripples comprises a voltage reduction type converting circuit and a PWM signal generating circuit, wherein the voltage reduction type converting circuit is used for generating currents needed for lightening an LED, and the PWM signal generating circuit is used for generating PWM signals needed for controlling a switch transistor contained in the voltage reduction type converting circuit. The LED drive circuit further comprises a lowpass filtering circuit and a ripple control circuit, wherein the lowpass filtering circuit is used for converting PWM dimming signals into direct current electrical levels, the amplitude of the direct current electrical levels is proportional to the pulse width or the electrical level amplitude of the PWM dimming signals, the ripple control circuit is used for providing the cut-off time of the switch transistor in proportion with the amplitude of the direct current levels, and thus the ripples of the currents passing through the LED are controlled through the PWM signal generating circuit. According to the LED drive circuit with the controllable current ripples, the changes of the LED current ripples are in proportional with the changes of TRIAC conduction angles or the width of the PWM, and thus the current ripples are made to be controllable, and be free of the influence of the voltage fluctuation or the changes of the switching frequency duty ratio.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to an LED drive circuit with controllable current ripple. Background technique [0002] In recent years, more and more LEDs (Light Emitting Diode, Light Emitting Diode) are used in household lighting, commercial lighting and public lighting and other fields. Because LED is more efficient and energy-saving than traditional incandescent lamps and fluorescent lamps, and the unit lumen is stronger, it has been widely promoted and applied. [0003] The traditional dimming lighting equipment is the structure of TRIAC (triac triac) plus incandescent lamp. After replacing the incandescent lamp with LED, in order to make the traditional TRIAC dimming system achieve the purpose of adjusting the intensity of LED light, At present, the most common solution is the BUCK (step-down conversion) architecture solution. This solution is to replace the PWM wave or low-frequency PWM (pulse width mo...

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Problems solved by technology

[0005] The disadvantage of this method is that the OFF-TIME (cut-off time) of the power switching transistor is variable and not constant. Any change in LED current caused by any factor will cause OFF-TIME to change, so the current ripple will also vary with It changes with the change of OFF-TIME, and the direct consequence of ripple change is the reduction of efficiency and the reduction of LED life

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