With the rapid development of the building automation and lighting industry, the adoption of advanced energy-saving design and digital control will be an inevitable trend. To meet this need, a new DALI for modern lighting control was developed in collaboration with a number of luminaires, ballasts and fixture manufacturers. It is an open digital communication protocol that allows controllers and lighting tools such as fluorescent and incandescent lamps. Communication between.
Typical DALI uses include adjusting the brightness of day and night lighting, adjusting lighting for daytime events, and saving energy and remote control.
DALI makes room lighting easier to control to meet multiple requirements and supports pre-programming of lighting controls. The DALI network can be connected to the building management system through gateway and PC terminal control, innovating a variety of potential functions.
2 Digital Addressable Lighting Interface DALI is a new standard for communication between controllers and electronic control units (ECGs) and will be included as an appendix in the ffiC 929 standard. The DALI bus system model is shown.
2.1 Electrical standard 200kb/s, half-duplex transmission, dual-phase coding for error detection.
At least 4 parallel processes are allowed for each frame duration.
DALI uses two wires for bidirectional serial communication. When the voltage difference between wires is greater than 9.5V, it indicates a high level, and when it is less than 6.5V, it indicates a low level. The main control unit communicates with the ECG by setting the level of the level. When there is no information transmission, the main control unit will remain high, and the ECG responds to the main control unit by setting the level. A series of digital pulse signals are transmitted between the master and slave units, and all communication is controlled by the master unit. The information generated by the master unit includes a start bit, 16-bit data (8-bit address and 8-bit instruction) and 2 stop bits (see (a)); the response of the slave unit includes a start bit, 8-bit data. (response) and 2 stop bits (see (b)). Since there is only one pair of wires between the master and slave units, the transmission of information is asynchronous half-duplex.
The following parameters allow the user to configure the system very freely and protect the ECG: 1 voltage control operation. The power supply unit and control unit of the interface are spatially isolated; 2 asynchronous start and stop transmission protocol; 3 bidirectional transmission. Send to the ECG2byte frame, receive the 1 byte frame of the ECG response request; 4 control the overvoltage protection between the wires when the power supply voltage is abnormal.
2.2 Operating characteristics In order to minimize the cost of each interface, DALI specifies limited operating characteristics. Each ECG is equipped with a reasonably priced microcontroller that can handle all the specific tasks of the ballast and interface.
DALI allows both individual communication and group communication. DALI has the following addressing capabilities: Each ECG has a separate address called a short address and is capable of responding to broadcast commands, allowing up to 64 short addresses, each of which can be connected to up to 64 ECGs. ECGs can also be assigned to a group with corresponding group addresses, up to 16 groups, each of which can belong to several different groups. The ECG stores a large number of parameters that determine the operating state of the lamp in various situations. These parameters include: current brightness level, starting brightness level, system fault brightness level, minimum brightness level, maximum brightness level, attenuation rate. , decay time, short address, query address, random address, group, scene, status information, and version number.
DALI provides 256 brightness levels (see) that match the logarithmic law between the minimum and maximum adjustable brightness levels, which results in a large increase in brightness at high dimming levels and an increase in brightness at low dimming levels. Smaller. Since the human eye is much more sensitive to low brightness than to high brightness, this logarithmic law appears to be linear.
In the DALI bus system, the ECG responds only to the request, and each ECG will inform its status and version number in response to the request. The ballast cannot act as a master controller and cannot implement multiple masters and algorithms for collision detection and elimination. If a code violation is detected or the term expires, the ECG will ignore the instruction or interrupt the unfinished sequence. The maximum and minimum brightness levels can be determined programmatically within the physical performance limits of the ECG.
If the supply voltage of the interface is not detected, the ECG will be at the "system fault brightness level", ie a specific emergency brightness level. This feature is very important during the installation phase of the system, when the lamp is installed and connected to the power supply, but the system is controlled. Still not initialized or even installed, in this case, the default value of "System Fault Brightness Level" ensures 100% illumination.
The 3 digital addressable dimming ballast has a digital addressable dimming ballast (see) and passed the performance test. This is a highly efficient, high power factor digital dimmer electronic ballast for driving fast-start fluorescent lamps.
It mainly includes power factor correction integrated circuits for high power factor and low harmonic distortion; ballast control circuit using IR2159 for smooth dimming control of lamps; PIC16F628 microcontroller for digital control , plays the role of the interface between IR2159 and DALI. Data is transferred from DALI to a digitally addressable dimming ballast. The PIC16F628 collects and interprets the data through an isolation circuit and then sends the appropriate signal to the IR2159 or sends it back to DALI when necessary. The PIC16F628 also has a lamp fault detection. Features and can disable IR2159 in the event of a fault. The main advantages of this type of ballast are: a small number of components (only 92), which consumes less power and therefore saves energy due to an innovative method of shutting down and communicating.
The communication between the microcontroller and the IR2159 is achieved by four signals (see ). The digital dimming signal (RB3) is connected to the pin DIM of the IR2159. It is a pulse width modulated signal that is filtered by the RC network (R25 and Cn) and converted to an analog dimming voltage of 0.5 5V, where 0.5V corresponds to the logarithm The 1% brightness level in the dimming curve, and 5 V corresponds to the 100% brightness level. The microcontroller can change the dimming voltage to 0.55V by changing the duty cycle, providing the IR2159 with 256 logarithmic dimming voltage levels. The microcontroller can also change the attenuation by controlling the speed of the duty cycle. The relationship between time, illumination brightness and dimming voltage level can be adjusted according to specific needs.
IR2159 can be enabled or disabled. When the LED is high, the lamp is turned off, IR2159 is disabled and the current is minimum. When the LED is low, the lamp is turned on. The PIC16F628 has control over this line and can determine whether the light is switched or not based on the fault status obtained from DALI and the settings requested by the user.
When the lamp is removed, the lamp~out signal is raised to VDD by the varistor R17, the system forcibly turns off the IR2159, and when the lamp is replaced again, the lam-out signal goes low, and the microcontroller turns on the IR2159 again. Restart. Other fault conditions are represented by the fault signal, which indicates that the IR2159 is in a fault condition (IR2159 automatically shuts down in the fault state and remains in the fault state until the integrated circuit is reset).
There are some unique power states when the system is turned off. When the shutdown signal is low and the light is on, the PIC16F628 receives power from the IR2159's charge pump. During normal operation, the charge pump provides enough for the microcontroller. The current is allowed to operate at an internal frequency of 4 MHz. When the shutdown signal is active, the IR2159 is disabled and the charge pump is no longer active. During this period, to minimize current and power consumption, the microcontroller is put to sleep. When receiving data, the system temporarily wakes up the PIC16F628 and starts the IR2159's charge pump for a period of time (typically less than 25ms). This is enough time to handle the task, but not enough to illuminate the light. This unique management method makes the system The power consumed during shutdown is minimal.
4 Conclusion Digital addressable lighting is becoming one of the most popular lighting control methods in a variety of different applications. The individual control of each lamp allows the end user to precisely adjust the light as needed, anytime and anywhere. This lighting management method greatly reduces the energy consumed by the lighting and improves the quality of the lighting while saving energy.
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