CROSS-REFERENCE TO RELATED APPLICATIONS

This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 202010455009.7 filed in P.R. China on May 26, 2020, the entire contents of which are hereby incorporated by reference.

Some references, if any, which may include patents, patent applications and various publications, may be cited and discussed in the description of this invention. The citation and/or discussion of such references, if any, is provided merely to clarify the description of the present invention and is not an admission that any such reference is “Prior Art” to the present invention described herein. All references listed, cited and/or discussed in this specification are incorporated herein by reference in their entireties and to the same extent as if each reference was individually incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the field of lighting, and particularly to a dimming control method.

2. Related Art

Intelligent lighting has become the key point of the development of future industries. More and more intelligent lighting is controlled by digital control. Digitization enables LED lighting products to be miniaturized and integrated. Moreover, digital control has the following advantages: (1) easy to realize stepless dimming and color temperature control, (1) digital control is more flexible and applicable, and can enjoy high performance with low cost. Since light can produce a special visual effect on people which can adjust people's circadian rhythm, more and more lighting products are aiming at creating comfortable scene lighting, and providing more interactive experience and enjoyment to users. To redefining life with light and improve people's quality of life, a higher requirement is proposed for lighting control.

In applications with a higher requirement of lighting so that dimming and color modulation are needed, multiple channels of LED with different colors are often required for deep dimming and color control, so every channel of LED needs dimming with a wider range and a higher accuracy, such as, between 0.1% and 100%, or even between 0.01% and 100%. In such a way, a conventional dimming driving circuit cannot meet the requirement, and a LED dimming driving circuit having a higher accuracy shall be developed.

Based on digital lighting, the present applicant has proposed a LED driving circuit and a control method thereof (publication No.: CN 107347222 B) having a high accuracy dimming function. In order to avoid the problem of insufficient dimming accuracy caused by the direct sampling of the output current, the control method calculates the turn-on time by detecting the input and output voltages, and controls the LED driver to work in discontinuous conduction mode or chopping mode. High-precision dimming can be achieved. Since the LED driving circuit is only operated in the DCM mode and the chopping mode, the solution applies to limited situations with a high output voltage and a low output current. Moreover, over-current protection of the circuit can be realized only by adding additional circuits, which results in a complicated structure and increased costs of the circuit.

SUMMARY OF THE INVENTION

An object of the invention is to provide a dimming control method, which can expand a dimming range greatly and realize over-current protection conveniently while ensuring a high dimming accuracy by controlling a LED driving power to operate in different modes according to the output current.

To realize the above object, the invention provides a dimming control method applied to a dimming circuit for controlling the brightness of a light emitting diode. The dimming circuit includes a power conversion unit having an input end, an output end, an inductor, and a switch. The power conversion unit receives an input voltage from the input end, and converts the input voltage into an output voltage output from the output end by operation of the switch. Wherein the dimming control method includes:

generating an input voltage sampling signal by detecting the input voltage of the power conversion unit;

generating an output voltage sampling signal by detecting the output voltage of the power conversion unit;

generating a current sampling signal by detecting a current flowing through the switch in the power conversion unit;

receiving a dimming signal to calculate and generate a dimming current signal; and

outputting a control signal to a driving circuit to drive and control the switch to turn on or turn off according to the input voltage sampling signal, the output voltage sampling signal, the current sampling signal, and the dimming current signal; wherein,the dimming current signal is compared with a first current threshold and a second current threshold,when the dimming current signal is higher than or equal to the first current threshold, the switch is controlled such that the power conversion unit operates in a continuous conduction mode or a boundary conduction mode;when the dimming current signal is lower than the first current threshold, the switch is controlled such that the power conversion unit operates in a discontinuous conduction mode, wherein when the dimming current signal is lower than the second current threshold, the switch is controlled such that the power conversion unit operates in a chopping control mode.

The additional aspects and advantages of the invention are partially explained in the below description, and partially becoming apparent from the description, or can be obtained through the practice of the invention.

