march 2009 rev 3 1/10 AN1756 application note choosing a dali implementation strategy with st7dalif2 introduction this application note describes how to choose a dali (digital addressable lighting interface) implementation strategy using the st7dalif2 microcontroller. as well as presenting topology options, this document also gives an introduction to the dali standard with a description of the protocol and a list of advantages. please refer to section 4 for a list of additional documents referenced in this application note. www.st.com
contents AN1756 2/10 contents 1 high-frequency tube lamp ball ast applications . . . . . . . . . . . . . . . . . . . 3 2 choosing an implementation strat egy . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3 dali standard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2 dali standard protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3 dali system advantages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4 references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
AN1756 high-frequency tube lamp ballast applications 3/10 1 high-frequency tube lamp ballast applications basically, a hf-tl ballast converts the 50-60 hz ac line input or a dc voltage to a high frequency output, usually in the range of 25-125 khz. a rectifier block and a dc to high frequency inverter usually make up a ballast (please refer to 1 in section 4: references ). voltage fed series resonant half bridge inverters are currently used for fluorescent lamps. this topology allows to eas ily operate in zero voltage switching (zvs) resonant mode, reducing the transistor switching losses and the electromagnetic interference (please refer to 2 in section 4: references ). the half bridge of the inverter can be controlled in different ways with different ics: half-bridge controller lik e, for example, the l6574 . figure 1. typical topology with a half-bridge controller half-bridge driver like, for example, the l6384 + some kind of control. figure 2. typical topology with a half-bridge driver what is the difference between a half-bridge driver and a half-bridge controller? a driver is ?just? able to drive the floating (high side) transistor of a symmetric half bridge inverter, from a pulse width modulation (pwm) signal. the controller also includes some form of oscillator, usually tunable by using a few external components (resistor, capacitor). varying the switching frequency is the mainly us ed control principle. this allows the current in the lamp, and therefore the output power to be modulated (please refer to 2 in section 4: references ). so the lamp can be dimmed and input voltage variations can be compensated. to know more about high frequency tube lamp ballast applications, please refer to 2 in section 4: references .
choosing an implementation strategy AN1756 4/10 2 choosing an implementation strategy in order to have a centralized control of each dimmable ballast of a room, a communication protocol is needed. dali is an economic solu tion that is more an d more widely possibility becoming popular in the lighting market. to find out the benefits of dali, please refer to document 3 referenced in section 4 since dali is a digital protocol, it needs to handled by a microcontroller like st7dalif2. various topologies can be used to integrate this digital communication. it can work together with a ballast controller, just for dali communication as shown in figure 3 : figure 3. micro handles only communication or it can do the dali communication and take the place of the driver control, like in figure 4 : figure 4. micro handles communication and control the choice is up to the designer. whatever solu tion is chosen, st is the first semiconductor manufacturer able to provide both the right high-voltage driver or controller, as well as a microcontroller with an on-chip decoder for the dali protocol. to get more information on the first topology and its advantages, please refer to application note an1900 ?hardware implementation for st7dali-eval? or order the st7dali-eval evaluation kit.
AN1756 choosing an implementation strategy 5/10 figure 5. st7dali-eval kit
dali standard AN1756 6/10 3 dali standard 3.1 introduction dali is an acronym for digital addressable lighting interface, standardized as iec 929. dali is the new interface standard for lighting controls solutions defined by the lighting industry. ag-dali is the ?digital addressable lighting interface working group? established for joint promotion and application of the dali standard by leading manufacturers and institutions in the field of digital addressing of lamps and/or luminaires. for more information, refer to document 3 referenced in section 4 . 3.2 dali standard protocol the dali protocol uses the bi-phase manchester asynchronous serial data format. all the bits of the frame are bi-phase encoded except the two stop bits. the transmission rate is about 1.2 khz. the bi-phase bit period is 833.33us 10%. a forward frame consists of 19 bi-phase encoded bits: ? 1 start bit (0->1: logical ?1?) ? 1 address byte (8-bit address) ? 1 data byte (8-bit data) ? 2 high level stop bits (no change of phase) a backward frame consists of 11 bi-phase encoded bits: ? 1 start bit (0->1: logical ?1?) ? 1 data byte (8-bit data) ? 2 high level stop bits (no change of phase) a forward frame consists of 19 bi-phase encoded bits: 1 start bit (logical ?1?), 1 address byte and 1 data byte. the frame is terminated by 2 stop bits (idle). the stop bits do not contain any change of phase. a backward frame consists of 11 bi-phase enc oded bits: 1 start bit (logical ?1?) and 1 data byte. the frame is terminated by 2 stop bits (idle). the stop bits do not contain any change of phase. the transmission rate, expressed as a bandwidth, is specified at 1.2 khz for the forward channel and for the backward channel. the settling time between two subsequent forward frames is 9.17 ms (minimum). the settling time between forward and backward frames is between 2.92 ms and 9.17 ms. if a backward frame has not been started after 9.17 ms, this is interpreted as ?no answer?. in the event of code violation, the frame is ignored. after a code violation has occurred, the system is ready again for data reception.
AN1756 dali standard 7/10 figure 6. dali standard frame only the st7dalif2 microcontroller has a dedicated peripheral for handling the dali protocol! for more details, please refer to document 4 referenced in section 4 . 3.3 dali system advantages figure 7. dali cable here are the main advantages of the dali system: simple wiring: all of the units in the system are interconnected using a simple five-core cable (see figure 7 ). no mains switching required: lamps can be dimmed or switched on and off using control system commands without any need for mains switching. easy system re-configuration: the operation of the system can be changed quickly without any modification to the hardware. easy system modification: if the lighting system needs to be enlarged, new components can be added anywhere on the dali cable. it is possible to define light scenes. scene means: a particular light level intensity. a maximum of 16 scenes can be defined. please refer to document 3 in section 4 to find out more details of what are the other benefits of the dali standard for the end user and for specifiers and architects.
references AN1756 8/10 4 references 1. an1320: l6574 & microcontroller in ballast applications 2. an993: electronic ballast with pfc using l6574 and l6561 3. ag dali internet site: http://www.dali-ag.org 4. st7dalif2 datasheet
AN1756 revision history 9/10 5 revision history table 1. document revision history date revision changes 30-nov-2003 1 initial release. 31-may-2004 2 added introduction chapter. updated references. 17-mar-2009 3 changed product referenc es from st7dali to st7dalif2.
AN1756 10/10 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a parti cular purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. unless expressly approved in writing by an authorized st representative, st products are not recommended, authorized or warranted for use in milita ry, air craft, space, life saving, or life sustaining applications, nor in products or systems where failure or malfunction may result in personal injury, death, or severe property or environmental damage. st products which are not specified as "automotive grade" may only be used in automotive applications at user?s own risk. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2009 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com
|
