In developed countries, efficiency is promoted. In the process of pursuing efficiency, a field that is undergoing major changes is lighting. Solid state lighting is mainly in the form of a semiconductor (although the organic LED and the polymer LED are constantly emerging), it continues to replace traditional and more energy-saving illumination forms such as incandescent lamps, compact fluorescent lamps and gas discharge lamps.
Although LED lighting provides an inherent energy-saving effect, it may be at the expense of design complexity. The control circuitry required to drive the LED light is only an AC-DC converter, but usually includes some degree of intelligent control. Although this increased complexity may increase cost, after careful design, a LED lighting solution that provides great value in an appropriate price can be produced.
The ultimate application of LED lighting is almost unlimited, from low level consumption to high shed industries, kitchen cabinets, and then go to street lighting. Prospects including intelligent dimming, connectivity, and remote management have made the transition to LED lighting into a very persuasive point of view that continues to win decision makers.
Develop a complete set of LED lighting solutions involve integration of multiple functions, including AC rectification, DC-DC conversion, and LED control with power factor correction (PFC). If connectivity is added to this range to provide a more forward-looking solution, the design challenge will further increase.
Although the LED is essentially more efficient than other forms of lighting, in order to maintain this advantage, every stage of the solution must provide optimum efficiency. This is very different from developing traditional lighting solutions, but it is necessary. Another important trend affecting LED lighting is to transition to digitally control power conversion. By including digital power supplies in the overall topology, a more efficient and flexible solution can be achieved. If a full digital method is used during the design, you can integrate a large number of functions into a smaller number of devices. Microcontrollers are ideal for providing this level of functionality and flexibility.
Although AC conversion is the main part of the solution, running multiple independent LED lighting circuits from a single DC power supply is fully feasible, just use an AC conversion level to optimize overall design. In this case, you need to consider the rest of the solution, create more possibilities for cost optimization by value-added characteristics.
Adding control and connectivity to lighting devices is a major development because it can integrate lighting systems into the Building Management System (BMS) or as part of a smart home. One advantage of LED lighting is that there is a robustness: the light can be dimmed, or it can be opened / closed more frequently without affecting its life or a surge current. The LED lamp also provides greater location flexibility to achieve more distributed installation and wider working conditions. All of these features increase the attraction of LED lighting, but requires higher control levels.
In order to solve this design challenge, the reference design is constantly emerging. Texas Instruments developed DC-DC LED driver subsystem reference design although it can not be purchased as an assembled PCB, but has been thoroughly tested and provide all documentation (BOM, schematics, PCB Gerber). Figure 1 shows a block diagram of the reference design.
TIDA-01096 TI is energy efficient, adjustable white LED DC-DC drive, a Bluetooth connection with a smart design reference, provides a complete hardware and software platform for intelligent lighting solutions engineers.
By using warm white light and cooling LED strings in a luminaire, a sunlight of indoor lighting in a residential and retail environment can be simulated. TIDA-01096 is dedicated to this application area and uses several advanced components to achieve 98% efficiency under extensive working conditions.
This reference design is intended to be used as an interconnected LED driver, one of which is its connection, which uses intelligent Bluetooth form. This feature is fully integrated into the MCU selected by the design, supported by the software resource developed by TI. This feature provides a series of "intelligent" features along other main components in the design, such as dimming, color temperature adjustment, and daylight collection. Since the design is intended to control the LED string to simulate daylight, it can also be used to create a day and night rhythm that has proven health care advantage.
For LEDs, different levels of output are generated, which requires an integrated solution. Wherein a product is TPS92513 / HV 1.5 A buck LED driver with an integrated analog current modulation - one of the main components of the reference design. When used in conjunction with SimpleLink CC2650 MCU multi-standard, which can provide a perfect platform from a regulated DC power supply operation for the development of intelligent LED lighting systems. A complete schematic is formed after adding other components in the design, as described below.
The TPS92513 / HV LED driver is developed for a range of high-power lighting (including street lights, emergency lighting, and industrial and retail lighting), but also suitable for small appliances. In addition to providing inputs for analog and PWM control signals, it also has an integrated N-channel high voltage side MOSFET. Figure 2 shows how to use the simplified schematic diagram of the device.
In the reference design, two devices are used to drive two LED strings. In this topology, the inner oscillator of each device can be supercured by using an external oscillator to implement synchronization of the device. Using the same clock source to operate multiple devices to avoid adverse effects (such as frequency hop) between LEDs on different light strings, can also help minimize design overall EMI. Functional block diagram is shown in Figure 3.
Synchronization is achieved by applying a square wave between 300 kHz and 2 MHz by applying an RT / CLK pin (pin 5). The source of the internal MOSFET is on the pin 10, which is marked as pH. Its rising edge is synchronized with the falling edge of the RT / CLK signal.
In the reference design, dimming can be achieved in three ways: by changing analog input on the IADJ pin (pin 6); use digital mode to apply a PWM signal to the PDIM pin (pin 4); or both Combination. All control signals are generated by the SimpleLink CC2650 MCU (see Figure 4).
Since the analog dimming is more efficient, the reference design generates an analog signal by transmitting a PWM signal using a low-pass filter, and then applies it as an analog average of the PWM signal to the IADJ pin. This reference design also supports the simulation / PWM dimming control combination, and supports both simulation and PWM methods without flash low LED current dimming.
SimpleLink CC2650 Wireless MCU is closely collaborated with LED drivers, providing two key features: the control signal of the drive, and the function of affecting these signals in wireless mode. In this way, the light output or color temperature can be adjusted from the application running on the smartphone, or allow the BMS to turn the light to close, open, lighten, or dimmed - may use the voice command.
This possibility is limited to imagination when using an interconnected system. Since the SIMPLINK CC2650 is a multi-standard wireless MCU, Bluetooth, Zigbee, and 6LowPan can be supported. A powerful and efficient ARM® Cortex®-M3 kernel can accommodate the high-level selected protocol stack (when using CC2650, Bluetooth and Zigbee Stacks are provided free of charge by TI). The radio portion of the device also integrates an ARM Cortex-M0 core used to handle most stacks, as well as interfaces between baseband and analog front ends. It uses API to connect to the main CPU to further simplify design.
In addition to the LED driver and a wireless MCU, further comprising a reference design OPT3001 digital ambient light sensor, which is an optical sensor for the spectral response of the human eye to match the height. In the reference design, this sensor is included in the following instances: Adjust the light output to provide an environment that is suitable for human visual. Design contains LMT84 analog output temperature sensor connected to the LED heat sink, the thermal runaway can be avoided.
Figure 5 shows how TIDA-01096 and SimpleLink CC2650 LaunchPad pair to configure the hardware reference design for an LED-based lighting solutions. The firmware of the project is developed by TI as a code debugger project, and can be provided as required.
Summarize
Solid lighting may thoroughly change our lighting in the family, office, factory, transportation hub and public places. Compared to existing lighting technologies, it provides significant cost advantages.
Semiconductor manufacturers have a large investment in this, and now there are many products to help engineers design optimized solutions to maximize the potential of LED lighting. To this end, the practice of adding connection functions in the form of wired or wireless communications is increasingly popular.
Develop a full-featured, adjustable LED lighting solution involves two design challenges that may be difficult to deal with, but with the emergence of related development platforms and reference design (as described herein), it is now possible to respond to these challenges. It's easier.
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