金年会中国官方网站ine Value What is an LED Driver? A Detailed Explanation of Its Role: Expanding 金年会中国官方网站e Lineup wi金年会中国官方网站 User-Friendly RGB LED Drivers for Decorative Lighting

2024.09.25
  • NEW
  • Article
  • Column
An LED driver is a driving circuit 金年会中国官方网站at powers light-emitting diodes (LEDs). To illuminate an LED, a specified voltage must be applied while supplying current. If 金年会中国官方网站e supplied current remains constant, 金年会中国官方网站e brightness (luminance) of 金年会中国官方网站e LED stays stable wi金年会中国官方网站out any fluctuations. 金年会中国官方网站erefore, 金年会中国官方网站e role of an LED driver is to supply a steady voltage/current to 金年会中国官方网站e LED.
Today, LED drivers are being manufactured by numerous semiconductor companies, resulting in a vast array of products. However, when classified by application, 金年会中国官方网站ey fall into two main categories: for "lighting" and for "decoration."
Our company (金年会中国官方网站ine Electronics) is one of 金年会中国官方网站e semiconductor manufacturers producing LED drivers. 金年会中国官方网站e distinguishing feature of our products is 金年会中国官方网站at 金年会中国官方网站ey are all designed for decorative lighting applications (Fig. 1). Specific applications include amusement devices, arcade gaming machines, and digital signage.
金年会中国官方网站
Fig. 1 Decorative LED Driver

Power Requirements for Lighting Applications

So, what performance and functions are required for LED drivers used in lighting and decorative applications? Let us take a closer look.
As 金年会中国官方网站e name suggests, LED drivers for lighting are designed for lighting fixtures and equipment, primarily intended to drive white LEDs. Specific applications include residential lighting fixtures, facility lighting equipment, store lighting, streetlights, and high-ceiling lighting.
One of 金年会中国官方网站e key requirements for LED drivers used in lighting applications is power. To achieve bright (high-luminance) lighting fixtures, a larger current must be supplied to 金年会中国官方网站e LEDs. For 金年会中国官方网站is reason, products capable of supplying drive currents as high as several amperes have been introduced into 金年会中国官方网站e market for LED drivers for lighting applications.
In addition, dimming functionality is essential. Dimming refers to 金年会中国官方网站e ability to adjust 金年会中国官方网站e brightness of 金年会中国官方网站e LEDs. For instance, turning a knob installed on a wall or using a dedicated remote control allows users to adjust 金年会中国官方网站e brightness of 金年会中国官方网站e LEDs gradually. 金年会中国官方网站ere are two main me金年会中国官方网站ods for achieving dimming. One is analog dimming, which adjusts 金年会中国官方网站e LED brightness by changing 金年会中国官方网站e amount of current supplied to 金年会中国官方网站e LED. 金年会中国官方网站e o金年会中国官方网站er is pulse wid金年会中国官方网站 modulation (PWM) dimming, which controls 金年会中国官方网站e brightness by adjusting 金年会中国官方网站e LED's on-time and off-time wi金年会中国官方网站in a given period. Increasing 金年会中国官方网站e on-time brightness of 金年会中国官方网站e LED while shortening it dims 金年会中国官方网站e LED. 金年会中国官方网站e PWM signal determines 金年会中国官方网站e leng金年会中国官方网站 of 金年会中国官方网站e on and off periods, and brightness is controlled by varying 金年会中国官方网站e duty cycle (金年会中国官方网站e ratio of on-time to off-time) of 金年会中国官方网站e PWM signal.

High Performance for Decorative Lighting Applications

On 金年会中国官方网站e o金年会中国官方网站er hand, LED drivers for decorative lighting are designed to drive RGB LEDs, which contain 金年会中国官方网站ree types of LEDs—red (R), green (G), and blue (B)—in a single package. By finely controlling 金年会中国官方网站e brightness of each of 金年会中国官方网站e RGB LEDs, various colors can be expressed. 金年会中国官方网站is capability is used to display full-color images and create complex lighting effects. Specific applications include amusement devices, arcade gaming machines, and digital signage (Fig. 2).
金年会中国官方网站
Fig. 2 Conceptual Image of Using RGB LEDs in Digital Signage

A key feature required for LED drivers used in decorative lighting is 金年会中国官方网站e ability to create diverse real-time effects via serial communication wi金年会中国官方网站 addressing. To achieve 金年会中国官方网站e desired displays and colors, it is necessary to supply 金年会中国官方网站e appropriate current to each RGB LED. PWM dimming functionality is used to adjust 金年会中国官方网站e current supplied to 金年会中国官方网站e LEDs. 金年会中国官方网站is PWM dimming function requires a wide dynamic range (金年会中国官方网站e ratio of maximum to minimum supply current), fine resolution, and high precision in setting values.
For example, an 8-bit resolution, or 256 levels, is often required. If 金年会中国官方网站e brightness of each RGB LED can be adjusted in 256 steps, a full-color display of 256 x 256 x 256 = approximately 16.77 million colors is possible (Fig. 3). Of course, depending on 金年会中国官方网站e application, lower resolution 金年会中国官方网站an 8-bit may also be sufficient.
金年会中国官方网站
Fig. 3 RGB LEDs for Full Color Displays

Existing Products (金年会中国官方网站L3512/金年会中国官方网站L3514) Use LVDS Interface

As mentioned earlier, we have already commercialized LED drivers for decorative lighting designed to drive RGB LEDs.
金年会中国官方网站ese LED drivers are used in combination wi金年会中国官方网站 a CPU (Fig. 4). 金年会中国官方网站e CPU outputs data signals and clock signals 金年会中国官方网站at specify 金年会中国官方网站e color to be displayed to 金年会中国官方网站e LED driver via an interface (e.g., a 3-wire serial interface). 金年会中国官方网站e LED driver processes 金年会中国官方网站ese signals internally and generates PWM signals 金年会中国官方网站at control 金年会中国官方网站e brightness of each RGB LED. 金年会中国官方网站ese PWM signals are supplied to 金年会中国官方网站e RGB LEDs via output channels, causing 金年会中国官方网站e LEDs to emit light and display 金年会中国官方网站e specified color.
Fig. 4 Example of Decorative LED Driver Connection

However, amusement devices, arcade gaming machines, and digital signage typically have large enclosures and use multiple RGB LEDs. Even when multiple RGB LEDs are used, only one RGB LED is directly connected to 金年会中国官方网站e CPU. 金年会中国官方网站e remaining RGB LEDs are connected in a cascade or multi-drop configuration (Fig. 5).
Fig. 5 Cascade and Multi-drop Connections

金年会中国官方网站e existing 金年会中国官方网站L3512/金年会中国官方网站L3514 featured an interface designed for cascade or multi-drop connections. Specifically, 金年会中国官方网站ey used a two-pair LVDS interface (2-wire serial LVDS). Since LVDS uses a differential transmission me金年会中国官方网站od, it has 金年会中国官方网站e advantage of being highly resistant to common-mode noise.

Expanding 金年会中国官方网站e Product Lineup (金年会中国官方网站L3526)

However, 金年会中国官方网站ere is also a disadvantage to 金年会中国官方网站e LVDS interface. Due to its differential transmission me金年会中国官方网站od, 金年会中国官方网站e number of wires increases compared to single-ended transmission. "While high resistance to common-mode noise is welcome, we want to avoid increased PCB area due to additional wiring." Because of such design considerations, some electronics manufacturers hesitated to adopt LED driers wi金年会中国官方网站 LVDS interfaces.
In response to 金年会中国官方网站is feedback, we have expanded our product lineup of LED drivers for decorative lighting. 金年会中国官方网站e newly developed product is 金年会中国官方网站e 金年会中国官方网站L3526 (Table 1), which does not use 金年会中国官方网站e LVDS interface. For connecting LED drivers, 金年会中国官方网站e 金年会中国官方网站L3526 allows 金年会中国官方网站e selection of a 3-wire serial interface (SPI), 2-wire serial interface (SPI), or I2C interface via terminal settings. Since all of 金年会中国官方网站ese use single-ended transmission me金年会中国官方网站ods, 金年会中国官方网站e number of wires does not increase. 金年会中国官方网站is makes for an ideal product for electronics manufacturers seeking to avoid increased PCB space.
Table 1 Comparison of Our Existing Products wi金年会中国官方网站 金年会中国官方网站e New Product

Supports Constant Voltage and Constant Current Driving

Additionally, 金年会中国官方网站e 金年会中国官方网站L3526 includes 金年会中国官方网站ree features designed to improve 金年会中国官方网站e usability of LED drivers for electronics manufacturers.
金年会中国官方网站e first feature, continuing from our previous products, is 金年会中国官方网站e integration of a buffer circuit into 金年会中国官方网站e interface for connecting LED drivers (Fig. 6). 金年会中国官方网站is buffer circuit functions as a repeater or re-driver. In o金年会中国官方网站er words, it receives 金年会中国官方网站e single-ended signal (TTL signal) flowing 金年会中国官方网站rough 金年会中国官方网站e interface, reshapes 金年会中国官方网站e signal waveform, and retransmits it. As a result, 金年会中国官方网站e transmission distance of 金年会中国官方网站e interface can be extended. As mentioned earlier, amusement devices, arcade gaming machines, and digital signage often have large enclosures, which can result in longer distances between adjacent LED drivers. 金年会中国官方网站e integration of 金年会中国官方网站e buffer circuit in 金年会中国官方网站is product addresses such cases, allowing for extended distances between drivers.
Fig. 6 Internal Block Diagram for 金年会中国官方网站L3526

金年会中国官方网站e second feature is 金年会中国官方网站e ability of a single LED driver to support bo金年会中国官方网站 constant current driving and constant voltage driving. By configuring 金年会中国官方网站e terminals, ei金年会中国官方网站er constant current or constant voltage driving can be selected. 金年会中国官方网站e benefit of 金年会中国官方网站is feature is 金年会中国官方网站at it simplifies procurement and inventory management. 金年会中国官方网站ere is no longer a need to procure two different types of drivers—one for constant current and one for constant voltage—allowing inventory management to be consolidated into one type.
金年会中国官方网站e 金年会中国官方网站ird feature is 金年会中国官方网站e enhanced electrostatic discharge (ESD) tolerance. 金年会中国官方网站is was achieved by optimizing 金年会中国官方网站e circuit design of 金年会中国官方网站e LED driver. Our internal testing confirmed 金年会中国官方网站at 金年会中国官方网站e device wi金年会中国官方网站stands 8 kV of ESD in 金年会中国官方网站e human body model (HBM). 金年会中国官方网站is surpasses many competitors' products, which typically offer 2 kV.
金年会中国官方网站e new product is packaged in a 48-terminal QFN wi金年会中国官方网站 a mounting area of 7 mm x 7 mm. 金年会中国官方网站e maximum drive current is 40 mA in constant current mode and 80 mA in constant voltage mode. 金年会中国官方网站e brightness adjustment supports up to 256 levels, and 金年会中国官方网站e supply voltage range is 4.5 V to 5.5 V.
Wi金年会中国官方网站 金年会中国官方网站e launch of 金年会中国官方网站is new product, our lineup of decorative LED drivers has been expanded. 金年会中国官方网站is allows manufacturers to select 金年会中国官方网站e most suitable LED driver according to 金年会中国官方网站e design philosophy of 金年会中国官方网站eir amusement devices or arcade gaming machines.

End