sliding mode control of smps - goniv
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Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 16
SLIDING MODE CONTROL OF SMPS
Ms. A. Jonisha, Mrs. V. Devi Maheswaran, Dr. V. T. Sreedevi Department of Power Electronics and Drives
Rajalakshmi Engineering College Chennai, India
[email protected] , [email protected]
ABSTRACT
Digital control technique is a technique for high frequency switching mode power supply (SMPS). The regulation requirement for high frequency integrated DC-DC switching mode power supply becomes more demanding in industry and portable Communication systems at very high frequency beyond 10 Mega Hertz range. Analysis and experimental study of buck converter and the boost converter is presented to achieve desired output voltage. The SMPS are emerging in terms of higher dynamic response performances, less output ripple, smaller size and weight. The sliding mode controller is associated with a digital pulse width modulation (DPWM) block instead of conventional PWM to operate at high switching frequency. Sliding mode control (SMC) can reduce the voltage ripple voltage ripple of SMPS. Sliding mode controller will be used by means of analog to digital conversion (ADC) and Digital pulse width modulation (DPWM). Keywords-Analog to Digital converter(ADC);Sliding mode control; Digital pulse width modulation(DPWM)
1. INTRODUCTION
Switching mode power supplies provide high efficiency, easy integration small weight and dimension. SMPS used in the portable personal communication system, cell phones, telephones, MP3 players and the other PDA products, have grown explosively in recent years. They are also used in a various applications including computer systems, wireless communication systems, medical instrumentations, motor drives, lighting and consumer electronics. Especially the miniaturization is always a critical consideration for the portable devices. Even now in some portable application, the size of the DC-DC power converters is becoming the primary focus in the overall design. Therefore the technology for high switching frequency operation to reduce size of passive components like inductors and capacitors to obtain miniaturization is urgently needed. Advanced semiconductor integrated technology over the last decade has resulted in a noticeable reduction in the size and weight of electronic components. 2. ANALOG SLIDING MODE CONTROL
SMPS has simplicity and low cost which are operated with analog controllers applications. The analog controlled SMPS operates as follows:The output voltage Vo and the reference voltage Vref are compared, and obtained the error signal e=Vref-Vo.
The closed loop operation offers large performance in keeping the output voltage constant and restraining the overshoot during the input voltage or external load changes. The error signal constitutes the input of the controller. The controller can be realized by using an operational amplifier and the network of passive components such as capacitors and resistors. The output of the controller is the control signal is u. The pulse width modulator (PWM) is used to transform the control signal u.
The analog components are sensitive to the
environment influence, such as temperature, noise, tolerance of fabrication, which results in lack of flexibility, low reliability .It is difficult to apply sophisticated control algorithm with an analog approach implementation. In addition, to meet the size miniaturizations demand the high switching frequency is unavoidable. However in higher switching frequency operation the analog controller signal transmission through the process will suffer from the limitation of band width and the large gain variation. The variability of the integration technology is more critical with higher switching frequency. The sliding surface is
S = K (V − V ) + Kddt
(V − V ) +
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 17
K ∫(V − V )dt (1)
The control signal of the switched mode power supply with buck converter is
= , ( ) > 0 , ( ) < 0
(2)
The control signal of the boost converter is U = V = −k i + k (V − βV ) + β(V −
V ) (3) Where,
k = αα
− (4)
k = LC αα
(5)
3. DIGITAL SLIDING MODE CONTROL
In order to reduce size and improve the system performance, the digital controllers are used. The digital controller consists of three blocks: analog to digital converter (ADC), digital control law and digital PWM (DPWM), and all these blocks should be integrated in one chip. In conventional PWM control schemes, the control signal is compared to the ramp waveform to generate a discrete gate pulse signal. The advantage of PWM based SMC are that it does not need additional hardware circuitries since the switching function is performed by the PWM modulator, which can be implemented inside the digital controller.
However in order to preserve the original sliding
mode control laws, the practical implementation of PWM based SMC is little importance, when both current and voltage state variable are involved. The digital controller SMPS operates similarly as the analog controller as follows: The output voltage Vo subtracted from the reference voltage Vref results in the voltage error. The ADC transfers the analog error to discrete in digital signals. During each switching period, the error value is sent to the control law block, where the controller makes algorithm calculation to regulate the output by new digital control duty of PWM ratio. Through the DPWM block, the digital duty value is converted into time analog signal to drive MOSFET switches.
.
Figure .1Block diagram of Sliding mode control.
The algorithm of control law can be implemented with internal structure of logic circuits, without any external analog component. Thus the digital controller should be less sensitive to environment than analog counterpart. Also digital control law offers possibility to implement more sophisticated control strategies and other intelligent interface functions that are impractical in analog. 4. SIMULATION CIRCUITS OF CONVENTIONAL METHODS
The simulation circuits of the control techniques are simulated with the help of MATLAB/ SIMULINK software.
A. Open loop Buck Converter
Fig.2 shows the circuit diagram of buck converter. It consists of MOSFET, inductance, DC source and load. The external triggering pulse is given to each MOSFET. This converter is used to decrease the output voltage. It converts high voltage DC supply to low voltage DC supply.
Figure 2. Simulation circuit diagram of open loop
buck converter.
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 18
B. Closed loop Buck Converter using Pulse Width Modulation Control The closed loop buck converter with pulse width
modulation control is simulated with the output voltage and the reference voltage. These voltages are added. The error signal is produced, which is compared with the external repeating sequence. The compared pulse is given to the MOSFET switch. It controlled the buck converter of switched mode power supply.
Figure 3. Simulation circuit of closed loop buck
converter using pulse width modulation
C. Closed loop buck converter with Sliding Mode Control The control circuit consists of a liner part;
usually for simplicity it is represented with integrator and gain part; usually for simplicity it is represented with integrator and gain part. The second part is the non linear control. The non linear part represented by the hysterisis block could be implemented as the switch off and switch on points, here it is represented with current ripple.
Figure.4 Simulation circuit of closed loop buck
converter with Sliding mode control.
D. Open loop boost converter Fig.5 shows the simulation circuit of open loop
boost converter. It consists of MOSFET, inductance, DC source and load. The external triggering pulse is given to each MOSFET. This converter is used to increase the output voltage. It converts low voltage to high voltage. The output voltage is controlled by controlling the firing angle of the MOSFET.
Figure.5 Simulation circuit of open loop boost
converter.
E. Closed loop boost converter with Pulse Width Modulation Control The closed loop boost converter with pulse width
modulation control is simulated with the output voltage and the reference voltage. These voltages are added. The error signal is produced, which is compared with the external repeating sequence. The compared pulse is given to the MOSFET switch. It controlled the boost converter of switched mode power supply.
Figure 6. Simulation circuit of closed loop boost
converter using pulse width modulation.
F. Closed loop boost converter with Sliding Mode Control Using control voltage equation, the sliding mode
controller for boost converter can be modeled as shown in fig.7. The pulse is generated and triggered the MOSFET.
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 19
Figure 7. Simulation circuit of boost converter with sliding mode control.
5. SIMULATION CIRCUITS OF PROPOSED METHOD
The simulation circuit of the proposed method is simulated with the help of ORCAD PSPICE
software.
Figure 8. Simulation circuit of Digital sliding mode control
The simulation circuit of the digital sliding mode
control of switched mode power supply consists of analog to digital converter (ADC), control of switched mode power supply consists of analog to digital converter(ADC), control and digital pulse width modulation(DPWM). The analog to digital converter is a flash type analog to digital converter. The conversion involves quantization of the input, so it introduces a small amount of error. Instead of doing a single conversion, an ADC often performs the conversion of samples periodically. The result is a sequence of digital values that have converted continuous amplitude and continuous time analog signal to discrete amplitude and discrete time signal. The output voltage of the DC-DC converter and
reference voltage are the input of the analog to digital converter gives three bit output they are B0, B1, B2.
Figure 9. Simulation circuit of analog to digital
converter In classical PWM control schemes, the control
signal is compared to the ramp waveform to generate a discrete gate pulse signal. The advantages of the PWM based SMC are that it does not need a additional hardware circuits. A high resolution, high frequency digital pulse width modulator (DPWM) can be constructed using a fast clocked counter and digital comparator. To achieve n bit resolution at the switching frequency Fs takes the digital value d of the duty ratio and produces the pulsating waveform that controls the power MOSFETs in the power converter. The inputs of the ADC are sensed output voltage and the reference voltage and the outputs are 3 bit digital output the ADC having encoder part to converter the 8 bit analog signal to digital signal. The DPWM having digital circuits like flip flops, multiplexers, digital compactors. The switching pulse generated by these digital pulse width modulators. The pulse is given to the switching voltage of the MOSFETs.
U1
ADC
B01
B12
B23
GND4
VO5
VREF6
U2
DPWM1
B01
B12
B23
PWM04
PWM15
M1IRF140
M2
IRF9133
V13 C1
2u
10
0
U16E
7404
11 10
U17F7404
1312
L1
4.7u
0
V17TD = 0TF = .1nsPW = .5usPER = 1usV1 = 0TR = .1nsV2 = 1.5
0
R1
30k
R2
20k
R3
20k
R4
20k
R5
20k
R6
20k
R7
20k
R8
10k
R910 R10
10R1110 R12
10
R1310
R1410
R1510
+-+-
SbreakS1
+-+-
SbreakS2
+-+-
SbreakS3
+-+-
SbreakS4
+-+-
SbreakS5
+-+-
SbreakS6
+-+-
SbreakS7
U1A
7408
1
23
U2B
7408
4
56
U2C
7408
9
108
U3A
7427
12
1312
U3B
7427
345
6
U4A
7402
2
31
U4B
7402
5
64
U4C
7402
8
910
U4D
7402
11
1213
U5A
7404
1 2
U5B
7404
3 4
U5C
7404
5 6
U5D
7404
9 8
V25
V35 V4
5
V55
V65 V7
5
V85
B1
B0
B2
000
0
0
0
0
Vo
0
Vref
B0B1
B2
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 20
Figure 10..Simulation circuit of digital pulse width modulator.
6. SIMULATION RESULTS
The simulation results of conventional techniques and digital sliding mode control of buck converter shows the result of output voltage and the output current. The simulation results of boost converter control techniques also shown.
A. Open loop buck converter
Fig.11 depicts the input dc source of magnitude 3V. This voltage is fed to the buck converter, reduce the input source voltage into 1.4V.
Figure 11.Simulation result of open loop buck
converter.
B. Closed loop Buck Converter with Pulse Width Modulation Control Fig.12 depicts the input dc source of magnitude
3V. This voltage is fed to the buck converter, reduces the input source voltage. The output waveforms of output voltage, output current depends the pulse width in PWM control.
Figure 12.Closed loop buck converter with Pulse
width modulation Fig.13 depicts the input dc source of magnitude
3V. This voltage fed to the buck converter, which reduce the input source voltage. The ripple of the circuit is 0.3V
Figure 13.Simulation result of closed loop buck
converter with pulse width modulation
V65
U11A
7404
12
0
0
0
0
0LO
CLKDSTM4OFFTIME = .5uS
ONTIME = .5uSDELAY = 0STARTVAL = 0OPPVAL = 1
CLKDSTM5OFFTIME = .5uS
ONTIME = .5uSDELAY = 0STARTVAL = 0OPPVAL = 1
S1DSTM6
S1DSTM7
CLKDSTM8OFFTIME = .5uS
ONTIME = . 5uSDELAY = 0STARTVAL = 0OPPVAL = 1
V7
TD = 0
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = .1ns
V2 = 5
0
U12A
74100
C23
D12
D23
D322
D421
Q15
Q24
Q319
Q420
pwm0
pwm2
V8
TD = .02us
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = .1ns
V2 = 5
0
U1A
74100
C23
D12
D23
D322
D421
Q15
Q24
Q319
Q420
U5A
74LS393
A1
QA3
QB4
QC5
QD6
CLR
2
U6
7485
B31
A315
B214
A213
B111
A112
B09
A010
A<B_IN2
A=B_IN3
A>B_IN4
A<B7
A=B6
A>B5
U7
7485
B31
A315
B214
A213
B111
A112
B09
A010
A<B_IN2
A=B_IN3
A>B_IN4
A<B7
A=B6
A>B5
U8
74F153
A14
B2
1G1
1C06
1C15
1C24
1C33
2G15
2C010
2C111
2C212
2C313
1Y7
2Y9
U9A
74ALS08
1
23
U10B
74ALS08
4
56
CL KDSTM1OF FTIME = . 5uS
ONTIME = .5uSDELAY = 0STARTVAL = 0OPPVAL = 1
V2
TD = 0
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = .1ns
V2 = 5
V3
TD = .01us
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = .1ns
V2 = 5
V4
TD = . 05us
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = . 1ns
V2 = 5
V5
TD = . 015us
TF = .1nsPW = .5usPER = 1us
V1 = 0
TR = . 1ns
V2 = 5
Q3Q2
Q4
Q1
B1B0B2
pwm0
pwm2
0 1 2
x 10-4
0
0.1
0.2
Time (sec)
Out
put
Cur
rent
(A)
0 1 2
x 10-4
0
1
2
3
Time (sec)
Out
put V
olta
ge (V
)
0 1 2
x 10-4
0
0.5
1
Time (sec)
Sw
itchi
ng P
ulse
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 21
C. Closed loop buck converter with Sliding Mode Control Fig.14 depicts the input dc source of magnitude
3V. This voltage feed to the buck converter, reduce the input source voltage. The overshoot also reduced.
Figure 14.Closed loop buck converter with sliding
mode control Fig.15 depicts the input dc source of magnitude
3V. This voltage feed to the buck converter, which reduce the input source voltage. The ripple voltage is 0.01V
Figure 15.. Simulation result of closed loop buck converter with sliding mode control
D. Open loop boost converter Fig.16 depicts the input dc source of magnitude
24V. This voltage fed to the boost converter, which increase the input source voltage to 47.15V.
Figure 16. Simulation result of open loop boost
converter.
E. Closed loop boost converter with Pulse Width Modulation Control Fig.17 depicts the input dc source of magnitude
24V. This voltage fed to the boost converter, which increase the input source voltage.
Figure 17.Closed loop boost converter with pulse
width modulation. Fig.18 depicts the input dc source of magnitude
24V. This voltage fed to the boost converter increase
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.020
0.2
0.4
Indu
ctan
ce c
urre
nt(A
)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.020
0.1
0.2
Io (A
)
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.020
1
2
Vo
( V )
0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018 0.020
0.5
1
Time (sec)Sw
itchi
ng P
ulse
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
0.1
0.2
Time(sec)
Out
put C
urre
nt(A
) Output Current
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
20
40
Time(sec)Out
put V
olta
ge(V
)
0 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10
0.5
1
Time
Sw
itchi
ng P
ulls
e
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 22
the voltage to 29.8V. The ripple voltage of the boost converter is 0.5V.
Figure 18.Simulatiion result of closed loop boost
converter with pulse with modulation
F. Closed loop boost converter with Sliding Mode Control Fig.19 depicts the input dc source of magnitude
24V. This voltage is fed to the boost converter increase the input source voltage. The output waveforms of output voltage, depends the sliding mode
Figure 19. Closed loop boost converter with
sliding mode control.
Fig.20 depicts the input dc source of magnitude 24V. This voltage fed to the boost converter. The output voltage increased to 30.4V. The output ripple voltage is 0.1V
Figure 20.Simulation result of closed loop boost
converter with sliding mode control
G. Simulation circuit result of the proposed method:Digital Sliding Mode Control Fig.21 depicts the input dc source of magnitude
3V. This voltage fed to the buck converter, reduce the input source voltage. The output waveforms of output voltage is reduced to 1.36V with very low ripple voltage 0.2mV.
Figure 21.Simulation result of Digital sliding
mode control. 7. CONCLUSION
The simulation circuit of sliding mode control and PWM control of SMPS was explained. Simultaneous output voltage, output current and ripple voltage were observed with respect to input.
0 0.05 0.1 0.15 0.2 0.25 0.30
0.5
1
Sw
itchi
ng P
ulse
0 0.05 0.1 0.15 0.2 0.25 0.30
2
5
Cap
acito
r cur
rent
(A)
0 0.05 0.1 0.15 0.2 0.25 0.30
20
4050
Time
Out
put V
olta
ge(V
)
Indian Journal of Electronics and Electrical Engineering(IJEEE) Vol1.No.1 2013 pp 16-23.
available at: www.goniv.com Paper Received :17-12-2012 Paper Accepted:24-02-2013
Paper Reviewed by: 1. John Arhter 2. S.K.Raman Editor : Prof. P.Muthukumar
goniv publications Page 23
Table I shows the comparsion of output voltage, output currenta and the ripple voltage of control techniques. Table.1Output comparison of control techniques
Conver
ter Control Technique
Input
Voltage
(V)
Output
Current (A)
Output
Voltage (V)
Ripple
Voltage
(V)
Buck Conver
ter
PWM control
3 0.18 1.8 0.3
Sliding mode
control
3 0.15 1.505 0.01
Digital Sliding mode
control
3 0.11 1.36 0.0002
Boost
Converter
PWM control
24 0.125 29.5 0.5
Sliding mode
control
24 0.126 30.4 0.1
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