Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter

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1 Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter Mr.S.Naganjaneyulu M-Tech Student Scholar Department of Electrical & Electronics Engineering, VRS&YRN College of engineering & technology, Chirala; Prakasam (Dt); Andhra pradesh, India. Dr.S.SATYANARAYANA PROFESSOR Department of Electrical & Electronics Engineering, VRS&YRN College of engineering & technology, Chirala; Prakasam (Dt); Andhra pradesh, India. Abstract This project presents a non-inverting buck-boost based power-factor-correction (PFC) converter operating in the boundary-conduction-mode (BCM) for the wide input -voltage range applications. Unlike other conventional PFC converters, the proposed non-inverting buck-boost based PFC converter has both step-up and step-down conversion functionalities to provide positive DC output-voltage. In order to reduce the turn-on switching-loss in high frequency applications, the BCM current control is employed to achieve zero current turn-on for the power switches. In this paper linear peak current Mode Control (LPCM) for dc-dc converters is proposed to achieve high step-up voltage gain without an extremely high duty ratio. Proposed converter is controlled with linear peak current mode controller as a linear controller and results are compared with sliding mode current controller. Index Terms About four key words or phrases in alphabetical order, separated by commas. I. INTRODUCTION Conventional series-regulated linear power supplies maintain a constant voltage by varying their resistance to cope with input voltage changes or load current demand changes. The linear regulator can, therefore, tend to be very inefficient. Due to high efficiency and high power density as well as reduced costs, switched mode power supplies (SMPS) are now becoming more popular compared to the linear power supplies. A switched-mode power supply is a power supply that provides the power supply function through low loss components such as capacitors, inductors, and transformers and the use of switches that are in one of two states, on or off. The advantage is that the switch dissipates very little power in either of these two states and power conversion can be accomplished with minimal power loss, which equates to high efficiency. SMPS is a power source which utilizes the energy stored during one portion of its operating cycle to supply power during the remaining segment of its operating cycle. SMPS operates on the chopper principle. SMPS is used to get regulated dc output voltages. SMPS can be used to step-down a supply voltage, just as linear supplies do. Unlike a linear regulator, however, an SMPS can also provide a step-up function and an inverted output function. In SMPS, MOSFET is used as switching element( as MOSFET has low switching loss compared to Transistor at high switching frequency of around 200kHz).At Such High Frequency Ferrite core is used. Fig 1.Block diagram of SMPS The AC Voltage is rectified, smoothed and supplied to the electronic chopper, which operates at a frequency above the audible range to prevent noise. The filter shown on the left of the diagram is necessary to prevent the supply from causing interference from the mains. It can also help to protect the SMPS circuitry from voltage spikes (or power surges) on the mains supply. The unregulated dc is fed directly to the central block of the supply, the high frequency power switching section. Fast Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 14

2 switching power semiconductor devices such as MOSFETs and Bipolars are driven on and off, and switch the input voltage across the primary of the power transformer. The unregulated DC voltage is converted into high frequency AC to get various voltage outputs. The drive pulses are normally fixed frequency (20 to 200 khz) and variable duty cycle. Hence, a voltage pulse train of suitable magnitude and duty ratio appears on the transformer secondary s. This voltage pulse train is appropriately rectified, and then smoothed by the output filter, which is either a capacitor or capacitor / inductor arrangement, depending upon the topology used. This transfer of power has to be carried out with the lowest losses possible, to maintain efficiency. Thus, optimum design of the passive and magnetic components, and selection of the correct power semiconductors is critical. The high frequency AC Voltages are then filtered to get DC which is supplied to PC. II. BUCK-BOOST CONVERTER Fig. 2. schematic for buck-boost converter With continuous conduction for the Buck-Boost converter Vx =Vin when the transistor is ON and Vx=Vo when the transistor is OFF. For zero net current change over a period the average voltage across the inductor is zero Fig. 3 Inductor voltage and Inductor current waveforms (1) which gives the voltage ratio (2) Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 15

3 and the corresponding current Since the duty ratio "D" is between 0 and 1 the output voltage can vary between lower or higher than the input voltage in magnitude. The negative sign indicates a reversal of sense of the output voltage. III. LINEAR PEAK CURRENT MODE CONTROL Unity power factor and tight output voltage regulation are achieved by active power factor correction techniques. The primary tasks of a controller for PFC circuits are to Achieve high power factor during steady-state operation with a constant load; Maintain an output voltage waveform v o (t) around a specified average value V o (t)with low ripple; The above both control goals can be achieved, if the controller forces the input current wave i g to have the same shape as the input voltage v g so that input impedance appears to be resistive, that rectifier is called a resistor emulator. The resistor emulator not only requires a near-unity power factor, but also low harmonic contents in the line current. There are two traditional approaches to control a resistor emulator, namely, the voltage follower approach and the multiplier approach. The voltage follower approach realizes a resistor emulator with the constant-duty-ratio or the constant-on-time control, such as a flyback or a Cuk converter operating at discontinuous conduction mode (DCM), or a boost converter at the boundary of DCM and CCM. The control circuit is simply a voltage-mode pulse-width-modulation (PWM) chip does not required a current sensor. However, the DCM or the boundary operation causes a large current stress on semiconductors and demands more effort to attenuate the current ripple so as to have a satisfactory low electromagnetic interference (EMI) to the line. The multiplier approach requires relatively complicated control circuitry. This approach needs a multiplier, current sensor, sensor of the input voltage v g. The control method is based on the current mode control. The current reference is rectified line voltage with its amplitude modulated by the modulation voltage v m, the output of the feedback compensator. In contrast to the voltage-follower approach, resistor emulator with the multiplier approach operates in CCM. The shortcoming of this technique is the variable switching frequency.the above shortcoming is overcome by using PWM Active Power factor corr ection techniques under Current mode control. In this approach, an additional inner control loop is used as shown in Fig.4. Where the control voltage v m directly controls the boost inductor current that feeds the output stage and thus output voltage the fact that the current feeding the output stage is controlled directly in current mode control has profound effect on a dynamic behavior of the negative feed back control loop. (3) Fig 4 Current Mode Control Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 16

4 Linear Peak Current Mode Control (LPCMC)-enables CCM operated rectifiers to be controlled using a much simpler controller Fig.5 LPCMC offers the following advantages: Elimination of the controller multiplier and input voltages sensing circuits, unconditional stability of the current loop, and ease of implementation using low standard PWM control IC s.the control technique is based on designing a current loop whose static gain is linearly dependent upon the off-duty cycle of the switch Fig 5 Linear Peak Current Mode Controller The peak inductor current is expressed as (4) Where Ve is the voltage error amplifier output signal, and RS is the current sensing resistor, the peak inductor current becomes mc is the slope of the compensating ramp, Ts is the switching period,and D is the duty cycle. Consider re-writing equation (16) in terms of D =1-D By rearranging equation (45),we can express the static gain of current loop as Equation (7) shows a positive dependence of the static current loop gain of the off-duty cycle D. III. DESIGN PARAMETERS (5) (6) (7) Specifications Output power Value 70w Expected Efficiency 0.9 Input power Input voltage range 78w 90 to 264 Output voltage 220 Maximum output voltage ripple 10 Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 17

5 Source Frequency 60HZ IV. SIMULATION RESULTS A Linear peak current mode control (LPCM) proposed dc dc converters with high step-up voltage gain has been simulated using MATLAB/Simulink. The proposed converter components are selected as Vin = 90 to 264 V, Vo = 220V, fs = 60 khz, Po = 70 W, L1 = L2 = 0.1 mh, and Co =48 μf. The simulink model and the output voltage, load current, source voltage & source current linear current controller waveforms for a step change in load is as shown in the below figures Discrete 1st-Order Discrete Filter1 S1 g m.05 Gain3 Scope D S i + - i + - i + - I Diode Diode3 I1 L D2 Current Measurement Scope1 V + - v v Co Rl1 + - v Volt Scope3 D1 g D Rl S2 g m S Gain4 -K- 1 Diode1 Diode4 Step I2 m 2 Gain2.1 Continuous powergui LPCMarier Q IL PI Controller Scope Ve Gain1 Constant Fig.8.Simulation diagram of LPCM Controller for proposed Dc Dc Converter with High Step-Up Voltage Gain 1 Q Pu2 S Q R SRLatch 1 IL 2 Scope >= R carrier1 Vc pulse 2 Fig 9 subsystem of LPCM controller Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 18

6 Fig 10 Output voltage waveform for step change in load from 0.2A to 0.6A At time t= 1 msec Fig 11 Output current waveform for a step change in load from 0.3A to 0.6A at t=1 msec V CONCLUSION Fig 12 source voltage and source current waveform The Buck-Boost converter is simulated with linear peak mode to verify dynamic performance using Matlab/simulink from the results it can be concluded LPCM superior dynamic. The power factor at input side of the converter is around 0.9. VI REFERENCES Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 19

7 [1] IEC International Standard Limites for Harmonic Current Emissions, Third Edition [2] T.Nussbaumer, k.raggl, J.W.Kolar, Design Guidelines for Interleaved Single-phase Boost PFC Circuits IEEE Trans.on Industrial Electronics, vol.56, no.7, July 2009, pp [3] S.Busquest-Monge, J-C.Crebier, S.Ragon, E.Hertz, D.Boroyevich, Z.Guradal, M.Arpilliere, D.K.Lindner, Design of a Boost power factor correction converter using optimization techniques,ieee Trans.on power Electronics,vol.19, no.6,november 2004,pp [4] C.A. Canesin and F.A.S. Goncalves, Single-phase High Power-Factor Boost ZCS Pre-regulator operating in critical conduction mode in proc. IEEE ISIE, June 9-11, 2003, pp [5] F.Tao, and F.C Lee, A Critical-conduction-mode single-stage power-factor-correction Electronic Ballast, in proc.ieee APEC, February 6-10, 2000, pp [6] M. A. Co, D.S.L Simonetti, and J. L. Fretites Vieira, High Power Factor Electronic Ballast Operating at Critical Conduction Mode in Proc IEEE PESC, June 23-27, 1996, pp [7] M. M. Jovanovic, D.M.C. Tsang, and F.C Lee Reduction of Voltage Stress in Integrated High-quality Rectifier-regulators by Variable-frequency Control, in Proc IEEE APEC, February 13-17, 1994, pp [8] K.H. Liu and Y. L. Lin, Current Waveform distortion in power factor correction circuits employing discontinuous-mode boost converters, in Proc IEEE PESC 89,1989, pp [9] Design Equations of High-Power-Factor Fly back Converters Based on the L6561, Appl.Note 1059, pp [10] Y.Zhao, single phase power Factor Correction Circuit with Wide Output Voltage Range, M.S. thesis, University of Virginia, Virginia, EE, Linear Peak Current Mode Controlled Non-inverting Buck-Boost Power-Factor-Correction Converter 20