Wide Input Voltage Range, 350mA Constant Current LED Driver Micro-Module’s Design

Nowadays, economic development has an increasing demand for energy. Human are looking for new energy and renewable energy, at the same time, also develop low carbon economy and improve the use efficiency of energy through various technical means. The appearance of the LED is a typical embodiment of the pursuit of high efficiency and energy saving ideas in the field of lighting.As a new kind of light-emitting devices, LED will work properly and provide the corresponding product function only when it’s under the condition of specific electrical which is required by its electrical and optical properties. LED driver circuit is the core of the LED products technology and the guarantee of quality. Developing LED driver circuit to provide higher efficiency, more reliable product is the unremitting pursuit.This paper embarks from the LED itself, explores the important role of LED in modern lighting filed, as well as the importance of the development of the LED driver chip. With the development of some companies as an example, there is a summary about the development situation at home and aboard and our country’s emphasis on semiconductor integrated circuit.Then the principle of LED driver circuit design is elaborated based on the theoretical analysis. According to the basic electrical and optical characteristic of LED, the basic requirements of driver circuit for LED work properly is summarized. Include the constancy of the current, security, reliability, simplicity. Compared the different mechanisms of LED constant current circuit topologies design, like resistance-limit, linear regulator and switch regulator, and analyse the advantages and disadvantages for each of them. Illustrated the structures of Buck, Boost, Buck-Boost of switch regulator, especially the floating Buck-based LED driver. The necessity of several kinds of protection mechanism is talked about, also the design ideas and principle, like UVLO, OVP, OTP, OCP, SCP, some of which designed a hysteresis characteristics. Several kinds of dimming mechanisms wared compared, e.g. the PWM dimming and linear dimming. Expound the clear advantages and necessity of uModule for LED power supply by showing the complexity of usage of the LED driver IC and the problems followed.Based on the previous sufficient analysis, a Buck-based constant current LED driver circuit is designed under a standard 0.5μm BCD process, input voltage range 6V~60V, typical output current 350 mA, the output current is adjustable, with UVLO, OVP, OTP, OCP and SCP functions. In addition, both linear and PWM dimming functions are achieved.It has been verified by the simulation that the desired design goal.