Dimmable LED (Light-Emitting Diode) driving circuit and driving method

Abstract

The invention provides a dimmable LED (Light-Emitting Diode) driving circuit and a driving method. An input current in a first power-level circuit is controlled as a square wave signal within a rectifier conducting time interval by an input current control circuit, the peak value of the input current is a constant value and meets the requirement of the minimum load current of an electronic transformer, and the valley value of the input current is zero; and the input current is kept at zero within a rectifier nonconducting time interval. The load current of the electronic transformer can be kept larger than the minimum load current, and thus, a normal working state can be kept in the working process, and the problem of LED load flicker caused by the switching off of the electronic transformer is avoided; in addition, information on the input current is detected through a dimmable signal generating circuit so that a dimmable signal for representing information on a conduction angle of a rectifier is obtained, an LED load is precisely dimmed, the dimming range is wide, and the dimming effect is good; and finally, constant-current control for the current of the LED load is realized by an output current control circuit, and therefore, the brightness stability of the LED load is ensured.

Description

technical field [0001] The present invention relates to the field of power electronics, more specifically, to a dimmable LED drive circuit and a drive method. Background technique [0002] In the field of lighting, it has become a development trend for LED lamps to replace traditional light sources (such as halogen lamps). In the process of replacing halogen lamps with LED lamps, on the one hand, it needs to match with the electronic transformer in the traditional circuit to ensure the normal operation of the electronic transformer. ; On the other hand, it is necessary to precisely adjust the light of the LED load to maximize the advantages of energy saving and high light efficiency of the LED light load. [0003] In the prior art, the dimming scheme of the thyristor is usually used to dim the LED lamp load. In the LED drive circuit with electronic transformer, the thyristor dimmer is generally placed at the front end of the electronic transformer. The basic principle of th...

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Problems solved by technology

However, the existing LED drive circuit generally contains a large filter capacitor, so that the LC resonance in the circuit will make the current through the thyristor uncontrollable, resulting in the thyristor not being able to maintain conduction, so the LED will flicker

In recent years, a variety of control schemes for LED dimming using thyristors have also been proposed. For example, the problem of uncontrollable current can be solved by adding a dummy load (such as a resistor), but the power consumption of the increased dummy load Undoubtedly, the efficiency of the whole machine will be low

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