Smart lighting platform solution based on Renesas single MCU

This article mainly introduces the intelligent lighting platform solution developed by Shiqiang Telecom based on the high-performance 78K0/Ix2 series MCU designed by Renesas Electronics for lighting applications. This solution meets the needs of intelligent dimming control and networking of mid-to-high-end lighting products in terms of hardware and software, and has the advantages of high performance and low cost.

1. Current status of lighting technology

With the rapid development of the lighting industry, more and more lighting control solutions have emerged, and the power supply design, lamp drive circuit, safety protection, management interface and other aspects have become more flexible. At present, lighting technology mainly includes mainstream fluorescent lamps, LED lamps and HID technology, etc. Its wide application makes the topological structure of power drive very different. From the common Flyback, Buck, Boost and other extended structures are being used in large quantities. Whether the product design adopts advanced digital energy-saving control design, whether it supports the application of flexible topological structures such as flyback, Buck, Boost, etc., the length of R&D cycle and time to market will determine the success or failure of the product. However, traditional lighting solutions are often implemented with dedicated devices, which are difficult to meet the needs of rapid development.

Therefore, an excellent lighting platform solution undoubtedly needs to support flexible topology applications and meet the dimming and networking requirements of today's mainstream lighting control solutions such as DALI, DMX512, 0-10V, wireless, and infrared. In response to this situation, Shiqiang Telecom has developed an intelligent lighting platform solution with Renesas Electronics 78K0/Ix2 series MCU as the core, plus a wealth of reference designs, to provide effective guidance for lighting manufacturers' diverse lighting design solutions in hardware circuit and software development, helping manufacturers to more efficiently develop lighting systems with their own intellectual property rights.

2. Introduction to 78K0/Ix2 Series MCU

The 78K0/Ix2 series MCU is a high-performance 8-bit MCU designed by Renesas Electronics for lighting applications. As shown in Figure 1, this series of MCUs is positioned to meet the current lighting market's popular demands for high-resolution dimming control, abnormal detection protection, and intelligent energy-saving control. It relies on a single MCU to achieve a low-cost, high-performance green energy-saving lighting system.

Figure 1-78K0/Ix2 series MCU design concept

The 78K0/Ix2 series MCU has rich built-in hardware resources, providing excellent hardware support for flexible lighting power drive design and dimming control. Specifically:

1.16 bit PWM timer with maximum counting clock frequency of 40MHz, output and comparator linked to perform PFC control, with 2-way dead time controlled PWM output, suitable for driving half-bridge/full-bridge circuits to achieve variable frequency control;

2. Built-in operational amplifier, multi-channel high-speed 10-bit A/D and comparator and other analog circuits, simplifying the peripheral circuit;

3. The timer can trigger A/D sampling and capture the appropriate signal useful points;

4. The comparator/external interrupt can realize the hardware output prohibition function, with fast response and safety;

5. Timer remote control interface and UART function, for infrared and wireless remote control applications, communication module with DALI bus interface, suitable for intelligent lighting control;

6. Multiple protection modules: window watchdog, clock monitoring, low voltage alarm, etc., work reliably.

3. Shiqiang Intelligent Lighting Platform Solution

The intelligent lighting platform solution developed by Shiqiang Telecom is mainly based on the above-mentioned rich hardware functional resources of the 78K0/Ix2 series MCU, and is positioned at the design goal of high performance and low cost of lighting products. It provides customers with a variety of flexible reference designs in the fields of LED lighting, fluorescent lighting, HID lighting, etc.

Figure 2 is a reference solution for LED drive control applications. In this solution, three constant current controls can be performed independently by using only the comparator and PWM output linkage functions. Dimming can be achieved by changing the internal reference voltage or PWM output settings. In addition, the MCU supports various sensors and multiple communication interfaces such as DALI, DMX512, and analog input. The appropriate communication control solution can be selected according to the external environment to achieve optimal control.

Figure 2-78K0/Ix2 LED driver control

The following is an example of the Flyback circuit to illustrate the process of constant current control through a comparator.

Figure 3-Flyback circuit constant current control

For the switching power supply, the PWM duty cycle determines the output voltage, as shown in Figure 3. After the circuit starts working, the LED current is sampled and added to the MCU built-in comparator port, which is compared with the reference value to generate an interrupt signal to adjust the PWM duty cycle. The change process is shown in Figure 4. For example, when the current is greater than the reference value, the duty cycle is reduced; otherwise, the duty cycle is increased, and finally a state of dynamic stability of the load current is achieved.

For dimming, the 78K0/Ix2 series MCU has a variety of ways to achieve it, by changing the comparator reference voltage or using the timer TMH1 and PWM output linkage function. In addition, Shiqiang Telecom's solution can also use the powerful data processing and computing capabilities of this MCU to achieve constant current control through ADC function and embedded algorithm control, while providing sufficient resources for MCU function expansion.