LED drive circuit capable of adjusting light and light adjusting method thereof

Abstract

The present disclosure relates to dimming circuit and method for LEDs. The dimming circuit obtains a DC voltage from an external AC power supply by using a TRIAC, an electronic transformer, and a rectifier bridge sequentially. The dimming circuit comprises a first power stage circuit, a second power stage, a first control circuit, and a second control circuit. The first power stage circuit has an input terminal configured to receive the DC voltage. The second power stage has an input terminal coupled to an output terminal of the first power stage and an output terminal coupled to an LED load. The first control circuit is configured to generate a first control signal in accordance with a first output voltage generated at the output terminal of the first power stage circuit, a first reference voltage and an upper threshold voltage to maintain an average value of the first output voltage to be consistent with the first reference voltage. The second control circuit is configured to generate a dimming signal in accordance with a first current and the first output voltage to control an operation of the second power stage circuit to maintain an output current of the second power stage circuit to be consistent with an expected driving current represented by the dimming signal. The first current is no less than a holding current of the electronic transformer. An input current of the first power stage circuit is maintained to be consistent with the first current by the first control signal when the first output voltage is in a continuously increasing state and is lower than the upper threshold voltage. The first output voltage decreases continuously and the input current is maintained to be consistent with a second current after the first output voltage reaches the upper threshold voltage.

Description

technical field [0001] The invention relates to the field of power electronics, more specifically, to a dimmable LED driving circuit and a dimming method thereof. Background technique [0002] For the field of lighting, since the thyristor phase control (chopper method) dimming method has the advantages of small size, reasonable price and wide range of dimming power, the thyristor phase control dimming method is currently the most widely used The dimming method is widely used in the fields of stage lighting and ambient lighting. By applying the SCR phase-controlled working principle, by controlling the conduction angle of the SCR rectifier element, a part of the sine wave voltage input by the AC power grid is cut off to reduce the average value of the output voltage, thereby controlling the power supply voltage of the lamp circuit and realizing Dimming function for lamp load. [0003] refer to Figure 1A , shows a schematic block diagram of an existing dimming circuit usin...

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