 Open Access
 Total Downloads : 491
 Authors : S. Shiva Kumar, P. Prasanth Kumar
 Paper ID : IJERTV2IS80112
 Volume & Issue : Volume 02, Issue 08 (August 2013)
 Published (First Online): 07082013
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
Development and Testing of NonIsolated Boost Converter
S. Shiva Kumar, P. Prasanth Kumar
M.Tech (Power Electronics) GRIET(JNTU)
Hyderabad,AP
Abstract NonIsolated Boost Converter is designed using standard topology and a commercially available application specified integrated circuits (ASIC). Compensator Design has been done. Methodology of
change of current, and not to the original charging voltage, thus allowing different input and output voltages.
choosing components, selection of values, and design of magnetic like Inductors has been expanded. Design is simulated on MATLAB software and tested.
Key wordsNonisolated Boost converter, Application integrated specific circuit(ASIC), Compensator.

INTRODUCTION
Over the years as the portable electronics industry progressed, different requirements evolved such as increased battery lifetime, small and cheap systems, brighter, fullcolor displays and a demand for increased talktime in cellular
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phones. An ever increasing demand from power systems has placed power consumption at a premium. To keep up with these demands engineers have worked towards developing efficient conversion techniques and also have resulted in the subsequent formal growth of an interdisciplinary field of Power Electronics.
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A DCtoDC converter is an electronic circuit which converts a source of direct current (DC) from one voltage level to another. It is also called as Chopper. It is a class of power converter. DC DC converters are the power supply that output a fixed voltage efficiently, converting the input voltage. There are three types of DC DC converters [1]
The nonisolated converter usually employs an inductor, and there is no dc voltage isolation between the input and the output. The vast majority of applications do not require dc isolation between input and output voltages. The nonisolated dcdc converter has a dc path between its input and output. Batterybased systems that dont use the ac power line represent a major application for nonisolated dcdc converters.

BOOST CONVERTER
Operating Principle:
The key principle that drives the boost converter is the tendency of an inductor to resist changes in current. When
being charged it acts as a load and absorbs energy, when being discharged, it acts as an energy source. The voltage it produces during the discharge phase is related to the rate of
Figure 1: Boost converter when switch is ON and OFF
The above figures are the two configurations of a boost converter, depending on the state of the switch S.
The basic principle of a Boost converter consists of 2 distinct states:

In the Onstate, the switch S (see figure 1) is closed, resulting in an increase in the inductor current.

In the Offstate, the switch S (see figure 1) is open and the only path offered to inductor current is through the D, the capacitor C and the load R. This result in transferring the energy accumulated during the Onstate into the capacitor.
During the Onstate, the switch S is closed, which makes the input voltage (Vi) appear across the inductor, which causes a change in current (IL) flowing through the inductor during a time period (t) by the formula:
IL Vi
t L
Figure 2: Waveforms of current and voltage in a boost converter
The final equation of the two modes is: V0 = 1
Vi 1D
From the above expression it can be seen that the output voltage is always higher than the input voltage (as the duty cycle goes from 0 to 1), and that it increases with D, theoretically to infinity as D approaches 1. This is why this converter is sometimes referred to as a stepup converter.


BLOCK DIAGRAM OF BOOST CONVERTER

DUTY RATIO CONTROLLED DC DC CONVERTER
Figure 4 Duty ratio controlled dcdc converter
The block diagram is a duty ratio controlled converter where output voltage is taken as feedback and compared with ramp voltage which gives pulses to the mosfet and gives required output.

DESIGN OF COMPONENTS OF POWER CIRCUIT POWER CIRCUIT:
L 410uF
Vin 8V to12V
C 220uF
RL 3.3K
Figure 5 : Boost Converter
The designing components of power circuit are inductor Lo, Capacitor C and Diode (MUR110) and a MOSFET.
TABLE I
Necessary Parameter
Value
Input Voltage
8V to 12V
Output Voltage
15V
Ouput Current
0.5A
Output Power
7.5W
Switching Frequency
100Khz
Necessary Parameter
Value
Input Voltage
8V to 12V
Output Voltage
15V
Ouput Current
0.5A
Output Power
7.5W
Switching Frequency
100Khz
NECESSARY PARAMETERS OF POWER STAGE
Figure 3: Block diagram of Boost converter

The voltage source provides the input DC voltage to the switch control, and to the magnetic field storage element.

The switch control directs the action of the switching element, while the output rectifier and filter deliver an acceptable DC voltage to the output.
From above parameters we can find Duty cycle, Inductor and capacitor values.
SELECTION OF MOSFET:The power MOSFET has to carry about 1A and block about 20V. The device chosen is IRFZ44.
DESIGN OF INDUCTOR Lo:
g
g
V L0 * I
Ton
L0
Vg * Ton
I
I=20% of rated current
Figure 6 Practical Implementation of Boost converter
The rated current is 0.5 A. The ripple current is chosen as

A. With maximum on time of 5.3Âµs, at input voltage of 8V, this gives an inductor value of approximately 400 ÂµH.
DESIGN OF CAPACITOR Co:
I * T
The Power circuit provides the dead time control to the fourth pin of the IC controller (UC494C). This dead time control maintains the minimum off time of the circuit. The input voltage given to the circuit is 10V. The diode used here is to avoid the reverse voltage. The input voltage given will be maintained across the capacitor and this voltage is given to the
C0
rated off
V
potential divider which provides the dead time control. The minimum ON time is decided by the dead time control circuit
V 1% Of output voltage
Vo=17V;
I rated=0.5A; Toff=5Âµs;
The output capacitor required has to limit the voltage ripple to about 1 %( 0.017V).This capacitor is selected to be 220ÂµF (an order of magnitude higher than the desired value).
According to [2] these filter components design equations have been derived.
SELECTION OF DIODE: The diode carries about 0.5 A average current and blocks about 20 V and suitable for 100 kHz switching. MUR110 is selected. (MUR110) [2]
The figure (6) represents whole connection diagram of the nonisolated power circuit. This circuit consists of all the circuits which are explained above

Power circuit.

Startup circuit.

Feedback circuit.

Maximumpulse width circuit.

IC controller circuit (UC494C).
R1 (10k) and R2 (220).
The Maximum Pulse Width circuit consists of two transistors Q1 (2N2222) and Q2 (2N2907). The main purpose of this circuit is to limit the voltage [6]
Controller circuit of boost converter:
Figure 7: Control Circuit TL494C
The above circuit represents the control circuit (TL494C) of the nonisolated boost converter. R8 (4.7k) and C2 (2.2 nF) are the resistor and capacitor used to determine
F 1.11 100KHz
F 1.11 100KHz
t t
t t
the switching frequency. An inbuilt oscillator is present which has two pins Rt & Ct opened. By connecting R8 & C2 ramp voltage signal is produced and its magnitude is decided by dtc (dead time control) Pin no 4. The switching frequency is given by
s
R C
s
R C
The control circuit IC TL494C consists of two error amplifiers of which only one is used i.e. pin no1 & pin no2. Pin no15 & pin no16 forms another error amplifier which is grounded. Pin no 14 i.e. VREF is divided by a potential divider by resistors R10 (10K) and R11 (10K) to 2.5V is fed to noninverting terminal of error amplifier i.e. pin no1.The
The important rule that is used here is that, if the loop gain crosses 0 dB (unity gain) with a single slope (20dB/decade), then the closed loop system will be stable. The reason is that the phase gain of a function crossing 0dB with a single slope at a frequency of c is approximately the same as the function K/c(s) and is equal to 900. This argument is valid only when the loop gain is a minimum phase function. The actual phase angle will depend on the poles and zeroes nearest to the crossover frequency. With the above simple rule in mind, the compensator function H1(s) is selected to be simple leadlag compensator [46].
1 s
feedback voltage is connected to inverting terminal i.e. pin no2. The voltage gets subtracted and compared with ramp voltage. There are two inbuilt transistors in which emitters are
H1 ( S ) K1
z1
1 s
p1
grounded, the collector C1 is connected with pullup resistor and C2 with pulldown resistor. An inbuilt PWM comparator is present which is connected to base b2 and pulses are taken out by pin no 11.OutC i.e. pin no 13 is grounded. When error amplifier voltage exceeds 2.7V pin no3 i.e. compensation pin gets enabled and maximum pulse width modulation circuit operates.



COMPENSATOR DESIGN
Closed Loop Control: Control Requirements:
The control specification of the converter will be in two parts.

Steady state accuracy

Settling time and allowed transient overshoot in the event of disturbances or command changes.
The approximate transient overshoot is related to the phase margin (m) of the loop gain according to the Table (below) for acceptable transient overshoot, the phase margin may be taken as 45o .
The first design step in closed loop controller design is to convert the control specification to the following.
The purpose of is to make the slope of crossover section of
the loop gain to 20 dB/decade near the desired crossover frequency, and to improve the phase margin.

If G(s) is a first order system in the vicinity of c, then H1 may be just K1.

If G(s) is a second order system in the vicinity of c, then select z1 and p1 such that z1<c < p1

If G(s) is a second order system with a complex pole pair o then z1 may be taken as o, p1 is usually as ten times z1.

Now K1 may be selected to meet the requirements of c and m.
The next part of the compensator H2(s) is needed to meet the steady state error specification. If G(0)H1(0) is already compatible with the steady state error, then H2(s) is 1. However, if G(0)H1(0) is not compatible with the desired steady state error, H2(s) is different from unity. The conditions on H2(s) are
G(0)H1(0)H2(0) = T(0).

H2(s) must not affect the gain & phase margin already designed. Or in the other words, phase and magnitude gain of H2(s) in the vicinity of c must be 0 and 0dB respectively.

Desired T(0) [to meet the steady state error]

Desired c [to meet the settling time]

Desired phase margin m [to meet the transient

A PI controller of the form H ( S )
1 s
z2 satisfies the
s
2
2
overshoot]
Table II:
z2
above requirements. The overall compensator is
Phase margin vs transient overshoot
H( s )
1 s
z 2 K
s 1
1 s
z 2
Phase Margin(Degrees) 
30 
35 
40 
45 
50 
55 
60 
Transient Overshoot(%) 
37 
30% 
35% 
16% 
9% 
5% 
1% 
Phase Margin(Degrees) 
30 
35 
40 
45 
50 
55 
60 
Transient Overshoot(%) 
37 
30% 
35% 
16% 
9% 
5% 
1% 
s
1
z 2 p1
Compensator Structure:
And can be realized using operational amplifiers.
Theoretical Compensator Design: Consider one pole and one zero compensation.
Considering Openloop Transfer Function
( 1 k )
G( s ) LC
Figure 8: Structure of a closed loop controller
S 2 1
( 1 k )2
S
Design of Compensator:
RC LC
Here duty cycle k is taken as 0.3.
Load resistance R=3300. Inductor L=400ÂµH. Capacitor C=220ÂµF.
Substituting the above values in G(S), we get from bodeplot of G(S) shown in figure we can obtained the values of n, GainMargin (Gm), Phasemargin (Pm), Gain crossover frequency (gc) and Phasecrossover Frequency (pc)
Therefore,
n = 2359.69 rad/sec Gm = Inf
Pm = 0.2502 dB
gc = Inf
pc= 2.5226e+003 rad/sec
Bode Diagram
9336.81s2 28473676570s 60276144300000
s4 6971.337s3 567108627s2 41657372130s 602761442300000
From bodeplot of Closedloop transfer function shown in figure (30) we can obtained the values of GainMargin (Gm), Phasemargin (Pm), Gaincrossover frequency (gc) and Phasecrossover Frequency (pc).[3]
Bode Diagram
50
Magnitude (dB)
Magnitude (dB)
0
50
100
150
200
0
Phase (deg)
Phase (deg)
45
Magnitude (dB)
Magnitude (dB)
50
0
50
90
135
180
225
103
104
105
106
107
100
0
Phase (deg)
Phase (deg)
45
90
135
180
2
10
3 4
10 10
Frequency (rad/sec)
Frequency (rad/sec)
Figure 10: Bode plot of ClosedLoop Transfer Function
Therefore,
Gm = 0.3571 dB Pm = 50.1342 dB
gc = 0 rad/sec
10
10
5 pc= 5.6165e+003 rad/sec
The Closedloop transfer function of above system is stable.
Figure 9: Bode plot of Openloop Transfer Function G(S)
Step 1: Let z1= 1.2842 n
P1= 2.9537 n
P1 and z1 are chosen as per the stability requirement.
From bodeplot of GH1(S) shown in figure we can obtained the values of GainMargin (Gm), Phasemargin (Pm), Gaincrossover frequency (gc) and Phasecrossover Frequency (pc)
Step 2:
To meet the SteadyState Error specificatio we choose a PI Controller of form
Let z2 2131.8 rad / sec
Practical Compensator Design:
Figure 11:Practical compensator
1 s
R4 1
H ( S ) z 2
R 5.6
2 s 3
z2
Therefore Closedloop Transfer Function of the System is
GH1 H2 * 0.17
1 GH1 H2 * 0.17
Therefore, ClosedLoop Transfer function (CLTF)
VII. SIMULATION RESULTS
Output current(Amps)
Output current(Amps)
0.6
3
Inductor current(amps)
Inductor current(amps)
2.5
0.4
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Time(Secs)
Output Voltage(volts)
Output Voltage(volts)
Iout Vs Time
15
10
5
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Time(secs)
Vout Vs time
1
Gate Pulses(volts)
Gate Pulses(volts)
0.8
0.6
0.4
0.2
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Time(secs)
Gate voltage Vs time
2
1.5
1
0.5
0
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
Time(secs)
Inductor current Vs time CONCLUSION:
NONISOLATED BOOST Converter is an efficient step up DCDC converter used in numerous electronics devices. It is modeled and simulated using Matlab. A closed loop model is developed and used successfully for simulation. This converter has advantages like reduced hardware, high performance, less weight and accuracy. The simulation results are in line with the predictions.
The same was implemented as a hardware project and an output voltage of 15V was obtained with an input of 8V12V DC supply.
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Power Electronics: Converters, Applications and Design. Mohan/undeland/Robbins.

M. Pedram and Q. Wu, Design considerations for batterypowered electronics, DAC, 1999

Mathematical modeling for power dcdc converters, in Proc. IEEE Int. Conf. POWERCON04, Singapore, Nov. 2124, 2004, pp.323328

M. K. Kazimierczuk and R. Cravens, II, Open and closedloop dc and smallsignal characteristics of PWM buckboost converter for CCM,J. Circuits, Syst. Comput., vol. 5, no. 3, pp. 2613003, Sep. 1995.

R. W. Erickson and D. Maksimovic, Fundamentals of Power Electronics, 2nd ed. Norwell, MA: Kluwer, 2001.

Raju.N ,Laxminarasamma.N ,Ramnarayan.VA doityourself (DIY) switched mode power conversion laboratoryin Proc IEEE Int.IICPE2006,Bangalore,Dec. 1921 ,2006,pp.289292