A Constant current constant Voltage output mode of LED Drive. ZhiJun Guo

Transcription

1 nternational Conference on Civil, Transortation and Environment (CCTE 06 A Constant current constant oltage outut mode of ED Drive ZhiJun Guo Zhejiang niversity of Water esources and Electric Power, Hangzhou,Zhejiang,Cha @qq.com Keywords: The ED driver, DC/DC converter, constant current + constant ressure Abstract. n this aer, we design a ED driver, ower factor correction circuit toology used + quasi resonant flyback tye two level structure, the quasi resonant flyback tye DC/DC transform art of the small signal model, design the system feedback loo arameters, to achieve the constant current drive + constant voltage outut mode. ntroduction Energy and environment roblem is becomg more and more serious, become a toic of common concern to eole, energy savg and emission reduction electricity consumtion, the world about lightg electricity accounts for roughly 9% of the total generatg caacity. eds as energy savg, environmental rotection, long service life new green light source, the ED lams and lanterns to relace traditional lightg lams and lanterns can save at least 40% of the energy consumtion, the current environment deterioration and energy shortage, ED lightg has a good sace for develoment and broad market rosect. ED belongs to low voltage driver cold light source, its erformance the restriction of the drive ower erformance and thermal environment, the need of high efficiency and reliable secial ED constant current drive ower to match. For different ower ED lams and lanterns, driven by different toological circuit [] [] : 3 w to 0 w leds ower scoe, SES the rimary side adjustment (PS flyback tye toological structure, save the secondary feedback circuit, can achieve high efficiency, reduce cost, simlify the design and save PCB sace; With 0 w ~ 50 w a sgle-stage ower factor correction (PFC flyback tye toological structure, with the limited sace to achieve high ower factor, and higher efficiency and reliability; With 0 w ~ 00 w a ower factor correction (PFC + quasi resonant flyback tye (Q toology structure, with high efficiency, high reliability; ore than 00 w a ower factor correction (PFC + C half-bridge resonance toology structure, with high efficiency, high reliability and low cost. Accordg to different alications, different ower is suitable for ball stee light, ED lam, fluorescent lam, late lam, dustrial lam, stage lam, wall lam, sign lights, street lightg and other alications. The workg rcile of the quasi resonant flyback tye transformation A. workg rcile Quasi resonant flyback. the flyback converter with the traditional similar form, as shown figure. The difference is that quasi resonant flyback converter is much more than traditional flyback trough a certa voltage sequence detection circuit. Transformer the rocess of magnetic reset, due to the excitation ductance and stray caacitance on ower tube, makes the switch tube voltage oscillation exists, as shown figure, A ot the voltage oscillation curve, is the first mimum dra-source voltage switch tube (valley, if the OSFET tube oeng, the conduction current sike would be mimal, under certa conditions, even can achieve zero voltage switchg (ZS. No matter how much or le voltage when load is by adjustg the workg frequency of change ower suly, switch tube always stay at the bottom moment conduction. The flyback converter with discrete and contuous workg mode, comared to reduce the loss of its oeng, quasi resonant switch can imrove efficiency and reduce the device temerature, reduce the electromagnetic terference. 06. The authors - Published by Atlantis Press 033

2 lk m s o K DC C OSS DC Figure quasi resonant rcile diagram B. transformer design For quasi resonant mode, workg frequency is changg, when the design, should work with the mimum frequency to determe the related arameters. The flyback transformer outut ower: he workg rcile of the quasi resonant flyback tye transformationsection Headgs. Po fs η ( Through the flyback transformer rimary wdg is the maximum current: P (max Ton ( (m + (m The rimary wdg ductance value: f η P o (max s(m When the design order to use smaller size of the transformer, on the other hand order to reduce switchg loss and E noise, frequency values 50 khz to 00 khz. Converter, when the ut voltage must be ower creasg, the converter switchg cycle; educe the outut ower and frequency creases, when the maximum ower is still more than settg the ower, the conduction time become smaller, to DC work mode. Outut ower is constant, the ut voltage is reduced, cycle of change creases, the mimum ut voltage for the same ower transmission, OSFET turn-on time needs to change, when workg under the lowest frequency. That is the ductance value is one of the biggest ductance value, if the ductance is too large, order to obta the same ower to a lower frequency. n this article the values: fs(m 60KHz, (m 0, 00. Accordg to the formula ( (3, mh (3 The loo design Design the driver of the excellent erformance, after determe the toological structure and drive C, loo arameters otimization calculation should also be considered. ED to constant current drive + constant voltage outut mode, the voltage control loo and current loo contas two arts, the control loo changes the ut voltage, load, constant voltage and constant current regulation and stability. A. converter small signal model Drive at light load work constant voltage mode, workg rcile is: the system outut voltage is artial ressure samlg and reference voltage After the error amlifier is amlified by the lear change, as with the ut of the comarator, while the current samlg signal from the switch tube as a comarator to the vertg ut signal, when the hase of the signal amlitude exceeds the -hase end, reset by S fli-flo, through drivg circuit shut off switch tube, make the origal wdg current is zero, the energy transferred to the deuty wdg, current began to decle. When zero crossg detection circuit detected vice wdg voltage to the bottom of resonance, by the S fli-flo outut a high level, and through the drive circuit oen switch tube, the origal wdg current rise, its 034

3 rcile block diagram as shown figure, the system loo structure diagram is shown figure 3. Drive when overloaded work constant current mode, rcile of work. This design choose the control chi TEA75 NXP. m Co o Z i k Z f Z i FBCT EF e Z f K EF Figure quasi resonant flyback rcile block diagram ZCD ear Block G(s e + - PW odulator k Power Stage G3(s o G(s FBCT Feedback H(s Figure 3 system loo structure e ear module transfer functiong ( s : G ( s K FBCT k Contas the current loo PW ga is simlified as: G( s Power level transfer function: K r e N N ( +, GC( s + o f, Kr + Among them: ω, ω zc Co( rc( Kr + + Corc Dc converter voltage control loo ga: Dc converter current control loo ga A C :, K 0.66 (4 e (5 s + K ω (6 s Kr + + ω o e zc k K e N, + N N AC G( s G( s G3( s K A C η + η + η (7 A (8 C B The feedback loo design Feedback network has different structure, with the required tolerance and adjust the outut voltage. n this aer, the voltage control loo feedback comensation adots double ole of sgle zero comensation method, as shown figure 4. Feedback comensation current control loo SES uniolar order zero comensation mode, as shown figure 5. se light coulg PC87 as rimary and secondary electrical isolation, AP430 double o-am comlete error with reference voltage signal amlification. 035

4 D g C P CZ B C B C ref Figure 4 voltage feedback control loo comensation circuit rcile diagram oltage feedback network transfer function H ( s : H ( s FBCT o + S C g CT B S C S C + S ( + D z g ~ [ + S( + C ] + S( C B B B C z D F C ref B C B 3 C 5 4 s Figure 5 current feedback control loo comensation circuit rcile diagram Current feedback network transfer function H ( s : H ( s o FBCT + S C F CT B S S C 5 D + S ~ [ + S( + C ] + S( C B B B C Parameter design and the test results By the above theoretical analysis, design the voltage control loo feedback comensation arameters are: 5K, 4.K, C 56 F, C 8nF, 50K, 5.K, 39K, C 330nF, CB 0nF. Current control loo feedback comensation arameters is designed as follows: S 0., 3 00K, K, 5 50, C 470nF, F 0K. Drive when the ut voltage 0 v, the ower factor is 0.975, the efficiency is 88.%. Acknowledgements National high technology research and develoment rogram (863 rogram roject number 04 AA05005 eferences [] iu Yu, Jmg Yang, The Toologies of White ED ams' Power Drivers, Power Electronics Systems and Alications, 009. PESA.. -6, ay. 009 z g D 036

5 [] ianghui Xu, Hulong Zeng, Junmg Zhang and Zhaomg Qian, A rimary side controlled WED driver comatible with Triac dimmer, EEE Alied Power Electronics Conf. (APEC , arch