Digitally Addressable DALI Dimming Ballast Cecilia Contenti and Tom Ribarich Applications Engineer, International Rectifier, Lighting Group, 101S Sepulveda Blv. El Segundo, CA, 90245-4382 tel. (310)726-8927, fax. (310)726-8846, email: [email protected] as presented at APEC 2002 Abstract: A digitally addressable digital dimming ballast has been developed. It conforms to DALI standard requiring very few parts and operates at very low power. Applications include building management or studio lighting where it is desired to control single or groups of lamps for conserving energy, performing lamp maintenance or creating prefect light quality. The design includes the digital dimming ballast, the code of the micro-controller and a platform to control the ballast by PC. ballast control, receiving status information from the ballast control and sending status information back to the user. This allows for complete and precise control of an entire lighting environment. A typical digital dimming solution includes an ASIC for sending and receiving instructions from the micro-controller and optocouplers for isolating the control input (Figure 3). The ASIC contains the necessary functions for controlling the lamp brightness as well as a digital interface for communicating with the micro-controller. I. INTRODUCTION Digitally addressable lighting is slowly emerging as a popular means for controlling complete lighting environments for a wide variety of different applications. Individual control of each lamp enables the end user to precisely deliver the correct amount of light when and where it is required. Managing the light in this manner allows for a massive reduction in global energy consumption due to lighting. Industrial environments can conserve the total energy required for lighting while actually increasing light quality in certain areas at given times. A complete digital dimming system includes the dimming ballasts and a digital control unit for converting information from an Ethernet connection to the communication protocol required by the micro-controller in each ballast (Figure 1). Applications for this system include building management or studio lighting where it is desired to control single or groups of lamps for conserving energy, performing lamp maintenance or creating precision lighting effects. Line Neutral Earth Ethernet Net-to-DALI Converter 64 Digital Dimming Ballasts Net-to-DALI Converter 64 Digital Dimming Ballasts Net-to-DALI Converter II. DIGITAL DIMMING 64 Digital Dimming Ballasts Digital dimming ballasts include an EMI filter, rectifier, power factor correction, and ballast output stage (Figure 2). The digital ballast also includes a micro-controller for sending and receiving information digitally. The microcontroller functions include storing the ballast address, receiving user instructions, setting the dim reference for the Figure 1, Typical digital dimming system. 1 Digital Dimmable Electronic Ballast Line Neutral Earth Digital Control Input EMI Filter Isolation Rectifier Power Factor Correction MicroController Ballast Output Stage Lamp Ballast Control Figure 2, Digital dimming ballast block diagram. This approach requires four primary ICs which include a power factor controller IC, a micro-controller IC, an ASIC and a driver IC for the output stage. 255 Digital Dimmable Electronic Ballast Line Neutral EMI Filter Power Factor Correction Rectifier Earth Digital Control Input OptoIsolator on/off, dim level and fade time. Various operating parameters can be changed and stored dynamically within the ballast memory. For example, scene levels can be set for different groups of ballasts. Also, maximum brightness, minimum brightness, power-on light level and failure light level and several other features can be set as desired. Another feature is the ability to diagnose problems such as lamp failures. The DALI provides 256 levels of brightness between the minimum and maximum dim levels and also includes a logarithmic dimming curve (Figure 5). This gives larger increments in brightness at high dim levels and smaller increments at low dim levels. The result is a dimming curve which appears linear to the human eye. MicroController Ballast Output Stage Lamp High/Low Side Driver ASIC Di m Val ue Figure 3, Typical digital dimming ASIC solution. A standard solution also exists that includes the IR2159 Dimming IC (Figure 4). With this approach the total number of ICs has been reduced to three as the IR2159 also includes the driver circuitry for the ballast output stage. 0 1 Lamp Brightness [%] 100 Digital Dimmable Electronic Ballast Line Neutral Earth Digital Control Input EMI Filter OptoIsolator Rectifier MicroController Power Factor Correction Figure 5, DALI logarithmic dimming curve with 256 brightness levels Ballast Output Stage Lamp IR2159 Figure 4, Digital dimming solution using the IR2159 Dimming IC. IV. IRPLDIM2 REFERENCE DESIGN KIT IR and Microchip Jointly developed a solution for digitally addressable digital dimming ballasts. It conforms to DALI standard. A fully-functional digitally addressable dimming ballast was designed (Figure 6), built and tested for performance. III. DALI A system known as the Digitally Addressable Lighting Interface (DALI) exists in Europe which has been widely adopted by several companies and is in the process of becoming a standard. This is a two-wire system with a defined digital communication protocol for sending and receiving instructions. The DALI includes a bitstream definition for both forward and backward going messages (standard prlEC929). The DALI allows for communication with all of the ballasts at once, groups of ballasts (16 maximum) or individual ballasts (64 maximum). The functions performed include Figure 6, IRPLDIM2: Digitally Addressable DALI Dimming Ballast 2 This reference design is a high efficiency, high power factor, digital dimming electronic ballast designed to drive a rapid start fluorescent lamp. The design contains an active power factor correction circuit for universal voltage input as well as a ballast control circuit using the IR2159. The design also includes a PIC16F628 micro-controller and an isolation circuit for connecting to a Digitally Addressable Lighting Interface (DALI). Other features include EMI filtering, transient protection and lamp fault protection (Figure 8). The input stage was designed for high power factor and low harmonic distortion using a generic PFC IC. The IR2159 Dimming Ballast IC was used to provide smooth dimming control of the lamp (phase control method, patented by IR). The IR2159 also includes a 0-to-5V analog dimming input, which is convenient for interfacing to a micro-controller. The PIC16F628 micro-controller was used for the digital control section. The PIC16F628 acts as an interface between the IR2159 ballast controller and the DALI. Data is transmitted to the ballast from the DALI and the PIC16F628 collects the data through an isolation circuit. The PIC16F628 then interprets the data and sends the appropriate signals to the IR2159 if necessary or sends information back to the DALI. The PIC16F628 also performs lamp fault detection and disables the IR2159 if a lamp fault is present. EMI Filter Rectifier PFC Output Stage • • • • • • • • Programmable Ignition High precision Digital Dimming Logarithmic Dimming Diagnostic and fault control Lamp Fault Protection Brownout Protection Phase control dimming Optically Isolated Communications This is a good example of merging digital technology (innovative software tricks) with high voltage analog technology (innovative hardware tricks) to face the modern market issue of energy saving, reducing complexity and cost and with an user-friendly design-development kit to reduce the design time for the customers adopting this solution. V. CONTROL BALLAST IC/ MICRO-CONTROLLER The communication between the micro-controller and the IR2159 is done with four signals (Figure 9). These signals are used for digital dimming (RB3), turning the ballast on or off (RB4), and fault detection (RB5 & RB6). The microcontroller controls the IR2159 by the following 3 pins: pin SD for shutdown of the IC (active high), pin FMIN used for fault detection (0 if the IC is in fault mode) and pin DIM to control the brightness. The micro-controller receives lamp information by the signal Lamp -out, connected to the lamp. Lamp Out VDD Line Input R17 PC Micro RA4 4 RA5 5 VSS 6 RB0 7 RB1 18 RA0 17 RA7 VDC HO 16 2 VCO VS 15 VB 14 VCC 13 C11 16 3 CPH RA6 15 4 DIM VDD 14 5 MAX RB7 13 6 MIN RB6 12 7 FMI N 8 RB2 RB5 11 9 RB3 RB4 10 Fault condition actual level light status ballast 8 IPH COM 1 2 LO 11 CS 10 SD 9 Lamp Dimming Feedback Preheat Feedback TR data signal from the network to the micro 1 RA2 RA118 2 RA3 RA017 3 RA4 4 RA5 5 6 Lamp Fault 7 Interface with Optos 8 RX data signal from the micro to the network Figure 8, IRPLDIM2 Digitally Addressable Dimming Ballast. VSS RB0 RB1 RB2 VDC HO 16 2 VCO VS 15 3 CPH VB 14 4 DIM 5 MAX 6 MIN 7 FMIN CS 10 8 IPH SD 9 RDIM RA716 RA615 If 0 IC OFF If 1 IC OK VDD14 VCC13 COM 12 L O 11 RB713 RB612 TURN ON IC RB511 TURN OFF IC 9 RB3 RB410 R25 Digital Signal CMOS DALI Signal C17 The main advantages of this solution are: 1) Low component count (only 92 components!) 2) Low power, low power standby due to an innovative Shut-down and communication method (this makes it possible to get 5V from the bus without an additional input) 3) Fast and easy design for customers adopting this solution (modifying the code for the micro and changing the ballast section with the new Ballast Designer software) Some others features are: • Interface DALI (2 wires) • High Power Factor/ Low THD • High Frequency Operation • Programmable Lamp Filament Preheating 1 R16 If 0 Lamo OK If 1 Lamp Fault Half Bridge Driver IR2159 3 RA1 1 PIC16F628 OptoIsolation RA3 Ballast Control IR2159 RS232-toDALI converter RA2 2 PIC16F62 Serial Port 1 light level Fade time Fade rate On/Off 1.25V 2.5V VSS 3.75V Figure 9, Micro-controller/IR2159 Communication The shutdown signal (RB4) enables or disables the IR2159. When high, the lamp is off and the IR2159 is disabled with minimal current flowing. When low, the lamp is on. The PIC16F628 has control of this line and determines if lamp should be on or off based on fault conditions and user requested settings from the DALI. There are two signals used for fault detection, lamp -out (RB6), and fault (RB5). The lamp-out signal indicates the presence of a lamp or lamp fault. When the lamp is removed the lamp -out signal is pulled up to VDD by the pull-up resistor R17 and the 3 software forces the IR2159 to shutdown. When the lamp is changed, this pin goes to 0 Volts, the micro-controller turns the IR2159 on again and the lamp re-starts automatically. Other fault conditions are indicated by the fault signal (pin FMIN of the IR2159). A low on the fault signal indicates that the IR2159 is in a fault state (the IR2159 turns off automatically in fault conditions such us VCC fault, overcurrent, failure to strike or low AC line and will remain in this FAULT state until the IC is reset. The IR2159 requires a 0.5-volt to 5-volt analog voltage (in pin DIM) to perform dimming, thus 0.5 volts corresponds to the 1% arc power level and 5 volts corresponds to the 100% arc power level. The PIC16F628 provides a pulse width modulated signal on pin RB3 that is filtered with a single RC network (R25 and C17). This provides an analog voltage for dimming. The micro can change the dim voltage from 0.5V to 5V by changing the duty cycle and therefore generate 256 different voltage levels for the IR2159. To conform to the digital dimming requirements, the output is logarithmic rather than linear. Since the human eye is much more sensitive to lower light levels than high levels, the logarithmic output appears to be linear. Therefore the PIC16F628 is programmed to produce a logarithmic voltage and the IR2159 drives the lamp arc power (Figure 10). VI. DALI INTERFACE/MICRO-CONTROLLER The Digitally Addressable Lighting Interface is optically isolated from the micro-controller. Figure 11 shows the connections between DALI and micro-controller. The two wires from the DALI are converted to four signals. Two of the four are the transmit signal (RB2) and receive signal (RX_DALI). The other two signals are the communications-enable (RB0) signal and the receive-drive (RB1) signal. The transmit signal and the receive signal directly correlate to the levels seen on the Digitally Addressable Lighting Interface. For receiving higher voltage logic on the DALI is translated to 5 volt logic at the microcontroller, and for transmission, the 5 volt logic is translated to the higher voltage logic on the DALI. RB0 ENABLE RB2 TX_DALI RB1 RECEIVE-DRIVE + DALI - RA1 RX_DALI RA2 Logarithmic Voltage Output MICRO-CONTROLLER Voltage Output 5 4 3 Figure 11, DALI/ Micro-controller communication. 2 1 0 85 115 145 175 205 235 Digital Input % Arc Power Output Logarithmic Arc Power Output 100 90 80 70 60 50 40 30 20 10 0 85 115 145 175 205 235 Digital Input Figure 10, Dimming Characteristics. The micro-controller can also change the fade time by controlling the speed in which the duty cycle changes. The relation between light level and dim level can be tuned according to specific needs. The minimum light level can be changed by adjusting RMIN, and the maximum level can be changed adjusting RMAX. RMIN sets the lower phase boundary corresponding to minimum lamp power when VDIM = 0.5V, and RMAX sets the upper phase boundary corresponding to maximum lamp power when VDIM = 5V. RMAX must be set after RMIN. The ballast achieves very low power by controlling the communications circuit with the communication-enable signal and the receive-drive signal. During normal operation the PIC16F628 enables the communication circuitry with the communication-enable signal. With this signal there is enough current, less than 100uA, to indicate when data is being sent to the ballast, but not enough current to accurately transfer the data. Upon detection (done by a S/H built into the PIC16F628) the receive-drive is asserted to raise the current above 500uA to achieve good signal transfer across the isolation. The receive-drive signal is only enabled long enough to transfer all the data; then it is disabled (waveforms in Figure 12). This method strongly reduces the power/current use. The comparator built into the PIC16F628 is used to set the thre shold for detection of the incoming data. The signal RA2 is used as threshold for the comparator. With shutdown there are some unique power conditions. With the shutdown line low and the lamp ignited, the PIC16F628 derives its power from the charge pump of the IR2159. The charge pump provides enough current for the micro-controller to run at its internal frequency of 4MHz during normal operation. When the shutdown line is asserted the IR2159 is disabled, and the charge pump is no longer functioning. Current is drawn directly from the high 4 voltage DC line through a high value resistor. The microcontroller is put to sleep during this time to minimize current draw and power dissipation. To receive data, which requires significant current, the PIC16F628 wakes up and starts the charge pump of the IR2159 long enough to process the command, typically less than 25ms, but not long enough to ignite the lamp (waveforms in Figure 12). Doing this unique management minimizes power dissipation during shutdown. Software was written for controlling the ballast from a PC. The software has a graphical user interface for performing all of the DALI functions (Figure 15). The PC sends commands via a serial cable to a RS232-to-DALI converter which then communicates with the ballast via a two-wire connection. Receive Receive-drive signal Communicationsenable Figure 15, Graphical user interface of the digital dimming software. Pin SD Pin LO Figure 13, Communication Signals between micro-controller/DALI VII. REFERENCE DESIGN KIT TOOLS The Reference Design Kit (Figure 14) consists of these following items: 1. IRPLDIM2 - DALI Ballast 2. RS232-DALI Bridge 3. DALI CD with software and design information The ballast and software system successfully performed all DALI functions while giving high-performance dimming as well. The CD encloses: Layout files, BOM and schematics, AN, Users manual, micro-controller code and software to drive the ballast by PC. To adapt the ballast to different lamp types and configurations you can use the BDA software on our WEB (www.irf.com) that will give you the new BOM, schematic and Layout files when selecting the kind of lamp, the number of lamps and the lamp configuration (Figure 16). Figure 16, Graphical user interface of the BDA software. VI. CONCLUSIONS A digitally addressable digital dimming ballast has been developed which conforms to the DALI standard. This reference design (IRPLDIM2) is a high efficiency, high power factor, digital dimming electronic ballast designed to drive rapid start fluorescent lamps. Some features are: 1) Low component count (only 92!) Figure 14, Reference Design Kit Setup. 5 2) Low power, due to an innovative communications and Shut-down method Fast and easy design for customers adopting this solution (modifying the code for the micro and adapting the ballast section with the new BDA software) 3) APPENDIX i: Schematics Reference BR1 C4, C5, CPH, CVDC C3 C1 C2, C13 C7, C8, C11, C18 C15 C6 C9 X1 L N GND X3 + - C19 F1 3 (-) T1 L1 C10 C16 C12 RV1 CY BR2 R33 C1 2 (+) BR1 C2 D9 R34 1 2 4 3 R28 U1 OPTO U2 OPTO R1 R2 R3 4 3 1 2 R5 R4 C3 R35 R12 C5 R11 R9 L2 C16 R31 R36 R30 R29 R32 1 2 3 4 R8 R10 IC1 1 2 IC3 3 4 5 6 7 8 PFC R20 TX 9 R25 RA2 RA3 RA4 8 7 6 5 VSS RA5 RB0 RB1 RB2 RB3 C4 PIC16F628 18 R6 17 R7 RA1 D1 RA0 16 13 RA7 12 15 RB7 11 RA6 RB6 VDD 14 RB5 10 C17 RB4 R16 R17 C11 D2 M1 +5V C15 C6 R22 RVDC CVDC CPH CVCO RDIM RMAX RMIN RIPH RFMIN R23 7 6 5 4 3 2 1 IPH FMIN MIN MAX DIM CPH VCO VDC IC2 8 HO 16 12 15 11 VS COM 10 14 LO VB CS VCC 13 SD C10 9 R24 IR2159 D6 R37 C18 C14 CVCO C17 CY D4, D7 D1, D8 D2, D3 D5 D9 D6 L1 L2 L3 M1, M2, M3 R15 R33 RFMIN R13 C7 C8 R26 R14 R15 R18 D3 C9 C19 RDIM, R12, R20, R35, R36 M2 M3 R27 R21 C12 D4 D8 D7 RIPH D5 R19 C13 C14 X2B X2C R34 L3 X2 X2A X2D RVDC RMIN RMAX APPENDIX ii: BOM IRPLDIM2E Bill of Materials Lamp Type: T8/36W, Line Input Voltage: 185 to 265 VAC R1, R2 R3 R6 Description Bridge Rectifier, 1A, 1000V Capacitor, 0.47uF, SMT 1206 Capacitor, 0.01uF, SMT 1206 Capacitor, 0.33uF, 275VAC Capacitor, 0.1uF, 400VDC Capacitor, 0.1uF, SMT1206 Capacitor, 0.22uF, SMT1206 Capacitor, 10uF, 450VDC,105C Capacitor, 4.7uF, 25VDC, 105C Capacitor, 10uF, 25VDC, 105C Capacitor, 220pF, SMT 1206 Capacitor, 1nF, SMT 1206 Capacitor, 1nF, 1KV, SMT 1812 Capacitor, 10nF, 1600VDC Capacitor, 47nF, SMT 1206 Capacitor, 1uF, SMT 1206 Y-Capacitor Diode, 1N4148, SMT DL35 Diode, 1N4148 Diode, 1A 600V SMB 12 V Zener SMT 5.1 V Zener SMT 5.6V Zener SMT EMI Inductor, 1x10mH, 0.7A PFC Inductor, 2.0mH, 2.0Apk Inductor, 2.0mH, 2.0Apk Transistor Mosfet Resistor, 1K Ohm, SMT 1206 Resistor, 470 Ohm, SMT 1206 Resistor, 39K Ohm, SMT 1206 Resistor, 10K Ohm, SMT 1206 Resistor, 18K Ohm, SMT 1206 Resistor, 5.1K Ohm, SMT 1206 Resistor, 27K Ohm, SMT 1206 Resistor, 28K Ohm, SMT 1206 Resistor, 32.4K Ohm,SMT1206 Resistor, 680KOhm, SMT 1206 Resistor, 7.5K Ohm, SMT 1206 Resistor, 22K Ohm, SMT1206 6 R7, R13, R14, R21, R24 R9, R16, R30 R10, R11 R17 R8 R18 R19 R4 R5 R26, R27 R22 R23 R31 R28 R29 R32 R25, R37 F1 IC1 IC2 U1, U2 U3 T1 BR2 X1 X2 X3 J1, J2, J3, J4, J5, J6, J7 R01, R02, R03, R04, R05, R06, R07, R08 Resistor, 22 Ohm, SMT 1206 Resistor, 100KOhm, SMT 1206 Resistor, 820KOhm, SMT 1206 Resistor, 1M Ohm, SMT1206 Resistor, 1 Ohm, ¼ Watt Resistor, 0.68 Ohm, ¼ Watt Resistor, 100K Ohm, ¼ Watt Resistor, 470 K Ohm Resistor, 1M Ohm Resistor, 10 Ohm, SMT1206 Resistor, 270 K Ohm, 0.5W Resistor, 470 KOhm, SMT1206 Resistor, 360KOhm, SMT1206 Resistor, 4.7 KOhm, SMT 1206 Resistor, 2.2 KOhm, SMT 1206 Resistor, 75K, SMT 1206 Resistor, 47 KOhm, SMT1206 Resistor, 0.5 Ohm, ½ Watt PFC IC for PWR FACTOR IC, Dimming Ballast Controller Mini-flat package Photo coupler Micro-controller PDIP SOT23 MP Transistor NPN .5A 200V Mini SM Bridge Rect Connector, 2 terminal Connector, 4 terminal Phone Connector RJ11 Jumper Resistor, 0 Ohm, SMT 1206 7