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International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 Constant Power SMD LED Tube light with Variable Input Voltage Saurabh Gandhe#1 ,Pooja Bora#2, Avinash K. Dwivedi#3 #1 Dept. of Electronic & Tele Communication,Pimpri chinchwad college of engineering Pune, India . #2 Dept. of Electronic & Tele Communication,Pimpri chinchwad college of engineering Pune, India, #2 Dept. of Electronic & Tele Communication,Pimpri chinchwad college of engineering Pune, India. ABSTRACT A transit vehicle lighting system has a plurality of LED-based lighting fixtures for providing interior illumination. A control network comprises a plurality of slave nodes for controlling the LED-based lighting fixtures, and a master node for controlling the slave nodes Many of today’s portable electronics require backlight LED-driver solutions with the following features: direct control of current, high efficiency, PWM dimming, overvoltage protection, load disconnect, small size, and ease of use. Intensity of SMD LED are controlled by a controller which is based on IC TPS926920/9001Q. Key words: PWM dimming; overvoltage protection; TPS926920/9001Q Corresponding Author: Saurabh Gandhe INTRODUCTION A. SMD LED It consists of a lead frame which is embedded in a white thermo. The reflector inside this package is filled with a mixture of epoxy and TAG phosphor. The TAG phosphor converts the blue emission partially to yellow, which mixes with the remaining blue to give white. This is a fine 3 W Pure white LED, it is very painfully bright; It is recommended not looking directly at CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 22 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 these LEDs when they are lit up. This SMD LED should be contacted to a larger heat sink to prevent overheating of the LED element. appears in the Figure 1 B. About Boost Integrated Circuit IC TPS9260 is buck-boost IC. The TPS92690/90Q1 is a high voltage, low-side NFET controller with an adjustable output current sense resistor voltage. Ideal for LED drivers, it contains all of the features needed to implement current regulators based on boost, SEPIC, flyback, and buck topologies. Output current regulation is based on peak current mode control supervised by a control loop. This methodology eases the design of loop compensation while providing inherent input voltage feed-forward compensation. The TPS92690/90Q1 includes a high voltage start-up regulator that operates over a wide input range of 4.5V to 75V. The PWM controller is designed for high speed capability including an oscillator frequency range up to 2.0 MHz. The TPS92690/90Q1 includes an error amplifier, precision reference, cycle-by-cycle current limit, and thermal shutdown. C. About PWM Wave The NE555 is a highly stable device for generating accurate time delays or oscillation. Additional terminals are provided for triggering or resetting if desired. In the time delay mode of operation, the time is precisely controlled by one external resistor and capacitor. For astable operation as an oscillator, the free running frequency and duty cycle are accurately controlled with two external resistors and one capacitor. The circuit may be triggered and reset on falling waveforms, and the output circuit can source x°C or sink up to 200mA or drive TTL circuits. CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 23 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 BLOCK DIAGRAM A. Description Fig. 2 Block Diagram The Intensity Control Block gives voltage input to the PWM Controller Circuit. PWM controller circuit triggers the constant current boost IC (TPS926920) then it is given to the constant current IC via Mosfet Circuit. Mosfet is a voltage controlled device. Finally, the output of the constant current IC is used to control the intensity and power of SMD LED Tube light. B. Working and calculation Forward voltage of SMD led is 3.3V approximately. Lumens range is from 180 to 200 so average lumens is 190 and we want 8 SMD led to mount on strip SMD led PCB so total lumens is 190*8=1520 lumens of the circuit should be near to 1600 and total wattage used is 4 watt-12 watt. The current flow through the SMD led is 840mA so 12 watt is power consumption. Using working principle of LDR circuit , control the value of the resistance . Pulse width modulation of timer IC 555 increased the life time of the tube light. Cost of the circuit is expensive due to use of SMD led but its long life time and its efficiency is more so its better to use than simple tube light and the arrangement of SMD leds as shown in diagram, it is seen that if one led damages there is no effect to other leds, they are not damage due to short circuit. For maximum forward voltage buck-boost IC is used. Here we can also use LM317 but its forward voltage rating is maximum 2 V, and we have 3.7 V. Maximum voltage range of the circuit is 24-30V.And current flowing through the SMD led is 1A,power consumption of the circuit by using ohms law is 1A*12 ohm=12 watt. The current range is approximately 280mA so power consumption of the circuit is 280mA*12ohm=3.36 watt. It is near to forward cut off voltage .The efficiency of the tube light having more lumens and less power rating of the led tube . B. PCB design of constant power SMD LED tubelight using TPS92690 IC. It is a multilayer PCB designed in Diptrace. CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 24 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 Fig. 3a Front View and Fig.3b Rear View COMPARISON BASED ON CURRENT CONTROLLED CIRCUITS There are many ways available to control or limit the current rather to use current boost IC. Comparison is given below with advantages and disadvantages. A. Resistor For LED Current Limitations The only advantage of using this circuit is it provides simplest solution to current control. But it has high power loss across the RLED. Resistor needs to be defined for maximum supply voltage conditions. For typical supply voltage conditions the LED current is much lower, which leads to a visible decrease of brightness e.g. during start stop operation. LED nominal current range cannot be used for nominal operation conditions, because current has to be fixed for maximum supply voltage. No intrinsic overvoltage protection (during supply voltage spikes the LEDs are stressed significantly, because of exceeding the LEDs maximum ratings) ,degradation of LEDs No simple temperature protection of the LEDs possible. Reduced LED lifetime. Any diagnosis functions needs to be realized by additional circuits. Only limited LED chain length, dependent on the LED forward voltage VF and minimum supply voltage. Fig.4.1 Resistor For LED Current Limitations Fig. 4.2 Constant Current IC CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 25 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 B. Constant Current IC In the constant current IC circuit LED can be used in the nominal operation condition at full brightness. Stable brightness during start and stop. This circuit also provides intrinsic overvoltage protection and thus no LED degradation, high temperature protection of LEDs is also possible. It has an additional feature of integrated diagnosis functions (optional). However it has high power loss across the constant current source and increased components count. Only limited LED chain length, dependent on the LED forward voltage VF and minimum supply voltage to increase the efficiency of the total system a so called Matrix setup could be used asdescribed later in this application note. C.DC/DC convertor in constant current mode Fig.4.3. DC/DC convertor in constant current mode This circuit has the highest efficiency. LED can be used in the nominal operation condition at full brightness. Stable brightness even during start stop. This converter is capable of handling high brightness LEDs. Various topologies are possible. It also provides intrinsic overvoltage protection and no LED degradation. High temperature protection of LEDs is also possible. Integrated diagnosis functions is optional. But the drawback is increased components count and PCB layout needs to be optimized regarding EMC performance. D. Current Boost IC The TPS92690 is an N-channel MOSFET (NFET) controller for boost, SEPIC, buck, and flyback current regulators which are ideal for driving LED loads. The controller has wide input voltage range allowing for regulation of a variety of LED loads. The low-side current sense, with low adjustable threshold voltage, provides an excellent method for regulating output current while maintaining high system efficiency. The TPS92690 uses peak current mode control providing good noise immunity and an inherent cycle-by-cycle current limit. The adjustable current sense threshold provides a way to analog dim the LED current, which can also be used to implement thermal foldback. The dual function n DIM pin provides a PWM dimming input that controls the main GATE output for PWM dimming the LED current also. When designing, the maximum attainable LED current is not internally limited because the TPS92690 is a controller. Instead it is a function of the system operating point, component choices, and switching frequency allowing CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 26 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 the TPS92690 to easily provide constant currents up to 5A. This simple controller contains all the features necessary to implement a high efficiency versatile LED driver. CIRCUIT SIMULATED DESIGNED IN MULTISIM A. PWM wave generation circuit Timer IC 555 is used to generate the PWM wave. This PWM circuit is used to trigger the TPS926920 IC which is used to control the intensity and maintain constant power of SMD LED Tubelight. When the circuit powers up, the trigger pin is LOW as capacitor C1 is discharged. This begins Figure 5.1 The output is seen on the CRO. the oscillator cycle, causing the output to go HIGH. When the output goes HIGH, capacitor C1 begins to charge through the right side of R4 and diode D2. When the voltage on C1 reaches 2/3 of +V, the threshold (pin 6) is activated, which in turn causes the output (pin 3), and discharge (pin 7) to go LOW. When the output (pin 3) goes LOW, capacitor C1 starts to discharge through the left side of R4 and D1. When the voltage on C1 falls below 1/3 of +V, the output (pin 3) and discharge (pin 7) pins go HIGH, and the cycle repeats. Note the configuration of R4, D1, and D2. Capacitor C1 charges through one side of R4 and discharges through the other side. The sum of the charge and discharge resistance is always the same, therefore the wavelength of the output signal is constant. Only the duty cycle varies with R4. The overall frequency of the PWM signal in this circuit is determined by the values of R4 and C1. In the schematic above, this has been set to 144 Hz. To compute the component values for other frequencies, use the formula: Frequency = 1.44 / (R4 * C1) In this circuit, the output pin is used to charge and discharge C1, rather than the discharge pin. This is done because the output pin has a "totem pole" configuration. It can source and sink current, while the discharge pin only sinks current. Note that the output and discharge pins go HIGH and LOW at the same time in the oscillator cycle. CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 27 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 B. Output of PWM wave As you can see from the diagram, a 90% duty cycle signal is on for 90% and off for 10%. These signals are sent to the TPS926920 ICat a high enough frequency that the pulsing has no effect on the motor. The end result of the PWM process is that the overall power sent to the motor can be adjusted from off (0% duty cycle) to full on (100% duty cycle) with good efficiency and stable control. Figure 5.2 Table 1 Output Frequency Cahnnel A 166.6Hz 221.180mv C. Hardware implementation Channel B 3.749V Fig 5.3 RESULT AND DISCUSSION The arrangement of SMD led circuits is as shown in figure. If one of the led are short circuited due to some over flow of current and voltage then also the circuit works properly, there is no effect to other SMD leds’.They are more efficient so high lumens power exists. The efficiency of SMD led is more because of less power rating and less power consumption. Only. Limited LED chain length is allowed, depending on the LED forward voltage Vf and minimum supply voltage to increase efficiency.There is a requirement to work our circuit between the range of 3V to 24V CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 28 International Journal of Computer Application (Special issue- Issue 5, Volume 2 (January 2015) Available online on http://www.rspublication.com/ijca/ijca_index.htm ISSN: 2250-1797 and using this IC TPS92690 we achieve the target upto 27V.We get upto 90% efficiency at linear constant source. Also life time of LED is increased. The arrangement of SMD led circuits is as shown in figure. If one of the led are short circuited due to some over flow of current and voltage then also the circuit works properly, there is no effect to other SMD leds. REFERENCES [1] Diego Gonzalez Lamar, Javier Sebastian Zuniga, Alberto Rodriguez Alonso, Miguel RodriguezGonzalez, Marta Maria Hernando Alvarez. A Very Simple Control Strategy for Power Factor Correctors Driving High-Brightness LEDs. IEEE Transactions on Power Electronics, 2009; 24(8):2032-2042. [2] Dongsheng Ma, Janet Wang, Minkyu Song. Adaptive On-Chip Power Supply With Robust One-CycleControl Technique. IEEE Transactions on Very Large Scale Integration (VLSI) Systems. 2008; 16(9): 1240-1243. [3] Huang-Jen Chiu, Yu-Kang Lo, Jun-Ting Chen, Shih-Jen Cheng, Chung-Yi Lin, Shann-Chyi Mou, AHigh-Efficiency Dimmable LED Driver for [4] Low-Power Lighting Applications. IEEE Transactions on Industrial Electronics. 2010; 57(2): 735-743. [5] Hongbo Ma, Jih-Sheng Lai, Quanyuan Feng, Wensong Yu, Cong Zheng, Zheng Zhao. A Novel Valley-Fill SEPIC-derived Power Supply without Electrolytic Capacitors for LED Lighting Application. IEEE Transactions On Power Electronics. 2012; 27(6): 3057-3071. [6] KV Hari Prasad, CH Uma Maheswar Rao, A Sri Hari. Design and Simulation of A Fuzzy LogicController for Buck & Boost Converters. International Journal Advanced Technology& Engineering Research. 2012; 2(3): 218-224. [7] Hari S, Balamurugan R. A valley-fill SEPIC-derived power factor correction topology for LED lightingapplications using one cycle control technique, International Conference on Computer Communication and Informatics (ICCCI). 2013: 1-4. [8] E.S.Kim,C.J.Kim, "A Constant Current Controller Design for Power Transactions on KIEE, Vol.59, No.3, 2010. LED Drive", [9] Baixiong Kuang, Jerry Lin, Yongchang Wang, Chin Seong Khor Control network for LEDbased lighting system in a transit vehicle,US8786191B2 CONFERENCE PAPER National level conference on "Advances in Networking, Embedded System and Telecommunication 2015(ANEC-2015)" On 6-8 Jan 2015 organized by " G.H.Raisoni College of Engg. & Management, Wagholi, Pune, Maharashtra, India." Page 29