Analysis and Simulation of AC to DC Boost Converter by Using IC Uc3854a

Transcription

1 IJCTA ol.8, No., Jan-June 205, Pp International Sciences Press, India Analysis and Simulation o AC to DC Boost Converter by Using IC Uc3854a G. Kishor, T. Sudha Rani 2 and P. ijaya 2 Associate Proessor, Department o EEE, GPREC, Kurnool. 2 UG students, Department o EEE, GPREC, Kurnool ABSTRACT This paper presents the analysis and simulation o ac to dc boost converter by using IC UC3854A.This paper covers the important speciications or boost converter power circuit design, power actor correction and the UC3854A integrated circuit which controls the boost converter PWM to 0.99 power actor. In this, the input voltage to the power circuit is in the range o 220 to 300,that results the output voltage which is controlled at 450. The simulation results prove the veriication o converter design in PSIM. Key words: Boost converter, Power Factor Correction (PFC), Pulse Width Modulation (PWM). INTRODUCTION The attention devoted to the quality o the currents absorbed rom the utility line by electronic equipment is increasing due to the evolution o growing in computers, laptops, uninterrupted power supplies, telecom and biomedical equipment. In act, a low power actor reduces the power available rom the utility grid, while a high harmonic distortion o the line current causes EMI problems and cross-intererences, through the line impedance, between dierent systems connected to the same grid. From this point o view, the standard rectiier employing a diode bridge ollowed by a ilter capacitor gives unacceptable perormances. Thus, many eorts are being done to develop interace systems which improve the power actor o standard electronic loads. An ideal power actor corrector (PFC) should emulate a resistor on the supply side while maintaining a airly regulated output voltage []. In the case o sinusoidal line voltage, this means that the converter must draw a sinusoidal current rom the utility; in order to do that, a suitable sinusoidalreerence is generally needed and the control objective is to orce the input current to ollow, as close as possible, this current reerence. The most popular topology in PFC applications is certainly the boost topology[2]. PFC converters are good choice or oline power supply and other AC DC power conversion applications as increasingconcerns about power quality and also to meet the need o power quality terms and standards. Severalcontrol techniques are evaluated and developed to meet the targetapplications. These control techniques evaluation o a system without huge investment and eorts or developing and testing o actual boost converter. These simulation is used to check and any ault condition and

2 278 operating mode. One can understand the interaction o dierent components and inluence o the overall act o the system [3]-[4]. 2. AC TO DC BOOST CONERTER A boost converter is a non-linear load device. A load is considered non-linear i its impedance changes with the applied voltage. The changing impedance means that the current drawn by the non-linear load will not be sinusoidal even when it is connected to a sinusoidal voltage. These non-sinusoidal currents contain harmonic currents that interact with the impedance o the power distribution system to create voltage distortion that can aect both the distribution system equipment and the loads connected to it. Active PFC technique is used to regulate power actor o boost converter [5]-[6]. In conventional AC-DC conversion, a capacitor ollowing a bridge rectiier is used to derive DC voltage rom the AC power source. With this capacitor, however, the input current pulsates. This pulsating current increases the input current harmonics and results in a low power actor less than 0.64[7]. To reduce the input current harmonics and increase the power actor, a high power actor technique is desired. Power actor correction is to make the input to a power supply look like a simple resistor. AC to DC converter cascaded with boost converter generates stable dc voltage as output or the given input ac voltage in which the output voltage must always be higher than the input voltage in magnitude. Thereore, an AC-DC converter based on power stage o boost coniguration i.e., AC to DC boost converter which is as shown in Fig.[8]has been studied as a high power actor pre-regulation circuit [9]. As shown in Fig., according to the current o in-ductor L, the operation modes can be speciied as: CCM (continuous conduction mode), DCM (discontinuous conduction mode and CRM (critical conduction mode). The critical conduction mode operates at the boundary o CCM and DCM [0]. The input current in these converters lows through the inductor and thereorecan easily be activelywave shaped with appropriate current mode control. Moreover, boost converters provide regulated dc output voltage at unity input power actor and reduced THD o input ac current. These converters have ound wide spread use in various applications due to the advantages o high eiciency, high power density and inherent power quality improvement at ac input and dc output. The preerred power circuit coniguration o single-phase boost converter is the most popular and economical PFC converter consisting o diode bridge rectiier with step up chopper. This paper provides a study o single phase boost converter topology. Complete mathematical modelling o PFC converters is carried out []. Simulation results are provided or evaluation o converter perormance under steady state and dynamic conditions and perormance o single-phase boost converter is then experimentally veriied. PFC converter topology considered in this work is described in this section.

3 279 L D i i S S C L d Diode Bridge Fig.. Ac to Dc Boost Converter 3. IC UC3854A The UC854 provides active power actor correction or power systems that otherwise would draw non-sinusoidal current rom sinusoidal power lines in which it controls the boost PWM where its power actor is near to unity.this device implements all the control unctions necessary to build a power supply capable o optimally using available power-line current while minimizing line-current distortion to <3%. The block diagram o IC UC3854A is as shown in the Fig.2. The power section is a "boost" converter, with the inductor operating in the continuous mode[]. In this mode, the duty cycle is dependent on the ratio between input and output voltages; also, the input current has low switching requency ripple, which means that the line noise is low. Furthermore, the output voltage must be higher than the peak value o the highest expected AC line voltage.the UC854 s high reerence voltage and high oscillator amplitude minimize noise sensitivity while ast PWM elements permit chopping requencies above 200KHz. Fig.2. Block Diagram O Ic Uc3854a

4 DESIGN OF BOOST CONERTER USING IC UC3854A Design o single phase AC-DC boost converter using IC UC3854A with power actor corrector is listed below: Speciications: Maximum power output (Po): 500W Input voltage range : ac Line requency range (o) : 50Hz Output oltage (o) : 450dc Switching Frequency (s) : 22 KHz. Inductor Selection: i. Maximum peak line current: I pk 2 * P in in (min) Consider the input current ( P in ) 700W (with losses) ( 2 *700W ) I pk 220 I pk 0.89A ii. Ripple Current:- L 0.2*I PK 0.2* A ( peak to peak) iii. Duty Factor: in(pk) is the peak o rectiied line voltage at low line where we are inding the duty actor at Ipk is as ollows: D in( pk ) in ( 2 * 220)

5 28 iv. Calculation o the Inductance: L in s * D * l 2 * 220 * KHz * mH R load calculation: R LOAD 2 ( ) OUT P ( 450*450) Ω OUT 2. Output Capacitor Selection: Typical values or Co are microarad to 2 microarad per watt. So, here in this case we consider 2 microarad per watt and thereore output capacitor value is as ollows C 2*500W 3000µ F 0 3. Select Current Sensing Resistor: I Current Transormers are used then that include turns ratio and decide whether the output will be positive or negative relative to circuit common. Keep peak voltage across resistor low i.e.,.0 is a typical value or rs. i. Find Ipk(Max): I PK (max) I A PK l ii. Find Current Sense Resistor: Rs I rs pk (max)

6 Ω iii. Find Actual Peak Sense oltage: rs ( peak ) I pk (max) * Rs.979* Oscillator Frequency: Rset is a oscillator charging current and multiplier limit and its value is 0.35KΩ C t.25 R * set KΩ * 22KHz 5.6nF s 5. Current Error Ampliier Compensation: i. Current Error Ampliier Gain at s: rs 0 * RS L * 450* mH * 22KHz s This voltage must equal the peak to peak amplitude o s, the voltage on the timing capacitor and its value is considered as 5.2. G ca S ii. Feed Back Resistors: rs Rci Rmo KΩ

7 283 R R * G cz ci ca 3027K * K iii. Crossover Frequency: ci 0 * Rs * Rcz * 2*3.4* L * R s 450* *8.43k 5.2* 2 *3.4* 2mH *3.027k 3.5KHz ci The cross over requency ci value should be (/6) th to (/0) th o switching requency s iv. Ccz and Ccp Selection: a. Ccz Selection:- Ccz ci * 2 *3.4 * Rcz 3.5KHz * 2*3.4*8. 43KΩ 2466 pf b. Ccp Selection: C cp s * 2 *3.4 * 22KHz * 2*3.4*8. 43KΩ pf R cz 6. oltage Error Ampliier Compensation: i. Output ripples voltage:- The output ripple voltage is given by the ollowing equation where r is the second harmonic ripple requency 0 pk r P in * 2*3.4* C * 0 0 Where Co 3000µF, o 450, r 00Hz, Pin700W

8 * 2 *3. 4 * 450 *300 uf 2 ii. oltage Error Ampliier Gain: Gva iii. Set gain o voltage error ampliier: R iv. Set DC output voltage: R vao ( 5.5) vi vd 303. K * r R 23.4KΩ * * 2* *3.4*C v * Gva vi 0 * * % Ripple re re 0 pk 00 * 2 *3. 4 * µ * KΩ 5. SIMULATION RESULTS The circuit shown in Fig.3.is simulated using PSIM. The simulation results are as shown Fig. 4 and Fig,5. Fig.3. Simulation circuit o AC-DC boost converter using UC3854A IC.

9 285 In Fig.4. consist o waveorms or input voltage(in)424,input current (Iin) 5A (peak to peak), input current and voltage(both are in phase), inductor current(iind)7.5a, pulses to the gate terminal o the switch, output voltage(o)450 and output power (Po)500W at min220, s22khz, Po500W. Fig.4. simulation results or in 220 Fig.5. simulation results or in 300

10 286 In Fig.5. consist o waveorms or input voltage(in)424, input current (Iin) 22A (peak to peak), input current and voltage(both are in phase), inductor current(iind)a, pulses to the gate terminal o the switch, output voltage(o)450 and output power (Po)500W at max300, s22khz, Po500W. Both the iguresfig.4. and Fig.5shows the same output voltage(o)450 and output power (Po) o 500W. The input current and input voltage arein phase i.e., having good power actor at the input side or the voltages min220 and max CONCLUSION AC to DC boost corrector using IC UC3854A with power actor converter controls input current o load in such a way that input current wave-orm is in proportional to the mains input voltage waveorm. Hence, the power actor o boost converter will become nearer to unity, which can be clearly seen rom the simulation results. IC UC3854A has better power limiting eature and distortion is limited to less than 3 %. Even though the input voltage is under certain variations i.e., rom the range o 220 to 300, the boost converter provides ixed DC voltage as 450and output power as 500KW. Thus it s an optimal converter in terms o perormance, eiciency and provides unidirectional (dc) power low in application such as power supplies, electronic ballast and low power drive applications. REFERENCES [] S. D. Freeland, Input Current Shaping or Single-Phase ac/dc Power Converters, Phd Thesis,Part II, CalTech, 988. [2] L. Rossetto, G. Spiazzi, P. Tenti, control techniques or power actor correction Converters. [3] Jugnu Patel, SwapnilArya, Power Factor Corrector or AC to DC Boost Converter. [4] C. Silva, Power Factor Correction with the UC3854, Application Note Unitrode IC. [5] Suresh Kumar.K.S., Active power actor correction in AC-DC Converters- I [6] J. Lai, D. Chen, "Design consideration or power actor correction boost converter, operating at the Boundary o continuous conduction and discontinuous conduction mode', APEC Con, proc., 993, pp [7] Sanjay L. Kurkute, Pradeep M. Patil, Kakasaheb C. Mohite, Mathematical Modelling o Single Phase Unity Power Factor Boost Converter [8] X. W. Mao and D. W. Zhu, The Control IC, Principles and Applications o PFC, 2007, st edition, China Elec-tric Power PRESS

11 287 [9] R. Keller and G. Baker, Unity Power Factor o-line Switching Power Supply, in IEEE INTELEC record, 984, pp [0] Weiping Zhang, Wei Zhang, Jianbo Yang,Faris Al-Naemi Comparisons between CRM and CCM PFC. [] Datasheet or High Power Factor Preregulator IC UC 3854A. [2] B.Andreycak, "Optimizing Perormance in UC3854 power actor correction application, Unitrode, products and application handbook in, 993/94. [3] C.Zhou, Design and Analysis o an Active Power Factor Correction Circuit, M.S.Thesis, irginia Polytechnic Institute and State University, Sept.989. [4] Denis Graham, European Applications, Advanced Power Technology, F Nontron, improved power mosets boost eiciency in a 3.5kw single phase pc [5] Siu-Chung Wong, Chi K. Tse, Mohamed Orabi, and Tamotsu Ninomiya, The Method o Double Averaging: An Approach or Modeling Power-Factor- Correction Switching Converters IEEE transactions on circuits and systems- I: regular papers, vol. 53, no. 2, February [6] P.S. Bimbhra(200), Power Electronics, 4 th Edition, Khanna publishers. [7] M.D.Singh and K.B. Khanchandani (2002), power Electronics, 2 nd Edition, Tata McGraw Hill Publishers.