Download PSpice Simulations using .CIR - FER-a

20V
AVG(V(control))
10V
SEL>>
0V
V(control)
V(control)
AVG (V(control))
20V
AVG (V(error))
0V
V(error)
-20V
V(error)
AVG (V(error))
40V
V(out)
20V
AVG (V(out))
0V
0s
1ms
2ms
V(out)
AVG (V(out))
3ms
4ms
5ms
6ms
7ms
8ms
9ms
10ms
Chapter 9
Time
Simulation
of
Switching Converters
Overview

PSpice









PSpice Simulations using .CIR
PSpice Simulations using schematics entry
PSpice Simulations Using Behavioral Modeling
PSpice simulations using vendor models
Small-signal analysis of switching converters
Creating capture symbols for PSpice simulation
Solving convergence problems
Matlab
Simulink
Power switching converters
Simulation of switching converters
2
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
Open-loop buck converter simulation
* SWITCHING FREQUENCY = 1 KHZ ; DUTY CYCLE = 50%
VPWM 1 0 PULSE(0 10 0 1US 1US 0.5MS 1MS)
* PULSE PWM SOURCE: PULSED VOLTAGE = 10 V, RISE TIME = 1 US,
* FALL TIME = 1 US, PULSE WIDTH = 500 US, PERIOD = 1 MS.
L0 1 2 10M
C0 2 0 100U
LO
2
1
RL 2 0 5
10mH
.TRAN 50US 20MS
+
CO
.OPTION ITL5=0
VPWM
100µF
.PROBE
.END
R
5O
0
Power switching converters
Simulation of switching converters
3
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
8.0
V1(RL)
4.0
I(L0)
0
I(C0)
-4.0
0s
V1(RL)
5ms
I(C0)
I(L0)
10ms
15ms
20ms
Time
Power switching converters
Simulation of switching converters
4
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
6.0
V(2)
L = 50 mH
4.0
2.0
I(LO)
I(CO)
0
-2.0
0s
I(C0)
Power switching converters
5ms
I(L0)
10ms
V(2)
15ms
20ms
25ms
30ms
35ms
40ms
45ms
50ms
Time
Simulation of switching converters
5
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
L = 5 mH
Power switching converters
Simulation of switching converters
6
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
10
L = 1.25 mH
8
V(2)
6
4
I(LO)
2
0
I(CO)
-2
0s
5ms
V(2)
I(LO)
10ms
15ms
20ms
I(CO)
Time
Power switching converters
Simulation of switching converters
7
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
8.0
V(2)
6.0
L = 10 mH
and
C = 500 uF
4.0
2.0
I(LO)
I(CO)
0
-2.0
0s
5ms
V(2)
Power switching converters
I(LO)
I(CO)
Simulation of switching converters
10ms
15ms
20ms
Time
8
PSpice Simulations using .CIR
An Ideal Open-Loop Buck Converter
10
L = 1.25 mH
and
C = 500 uF
V(2)
5
I(LO)
0
I(CO)
-5
0s
5ms
V(2)
Power switching converters
I(LO)
I(CO)
Simulation of switching converters
10ms
15ms
20ms
Time
9
PSpice Simulations using .CIR
N+
Voltage-controlled switch
Nc+
Ron
S
Nc-
N-
S<name> N+ N- NC+ NC- SNAME
.MODEL SNAME VSWITCH (RON=0.01 ROFF=1E+7 VON=0.7 VOFF=0)
Power switching converters
Simulation of switching converters
10
PSpice Simulations using .CIR
N+
Current-controlled switch
Ron
VN
W
N-
W<name> N+ N- VN WNAME
.MODEL WNAME ISWITCH (RON=0.01 ROFF=1E+7 ION=0.1 IOFF=0)
Power switching converters
Simulation of switching converters
11
PSpice Simulations using .CIR
Buck Converter with an Ideal Switch
OPEN-LOOP BUCK CONVERTER WITH AN IDEAL SWITCH
* SWITCHING FREQUENCY = 1 KHZ ; DUTY CYCLE = 50%
VS 1 0 10.0
VPWM 100 101 PULSE(0 1 0 1US 1US 500US 1MS)
S1 1 2 100 101 SX
S1
RSX 100 0 10G
1
DFW 0 2 D1
L0 2 3 10M
10V
VS
C0 3 0 100U
RL 3 0 5
RSX
LO
2
3
10mH
DFW
CO
100uf
R
5ohms
VPWM
0
.MODEL SX VSWITCH (RON=0.01 ROFF=1E+7 VON=1 VOFF=0)
.MODEL D1 D
.TRAN 0.05MS 20MS
.PROBE
.END
Power switching converters
Simulation of switching converters
12
PSpice Simulations using .CIR
Buck Converter with an Ideal Switch
6.0
V(3)
4.0
2.0
I(LO)
I(CO)
0
-1.0
0s
5ms
V(3)
I(LO)
10ms
15ms
20ms
I(CO)
Time
Power switching converters
Simulation of switching converters
13
PSpice Simulations using .CIR
Buck Converter with an Ideal Switch
5.0
V(3)
I(CO)*20
0
-3.0
15.0ms
V(3)
15.5ms
20* I(CO)
16.0ms
16.5ms
17.0ms
17.5ms
18.0ms
Time
Power switching converters
Simulation of switching converters
14
PSpice Simulations using .CIR
Using Initial Conditions IC
6.0
V(3)
4.0
2.0
I(LO)
I(CO)
0
-1.0
0s
L0 2 3 100U IC=1
C0 3 0 IC=5
.TRAN 2NS 200NS UIC
Power switching converters
5ms
V(3)
I(LO)
10ms
15ms
20ms
I(CO)
Time
Simulation of switching converters
15
PSpice Simulations using
schematics entry
Boost converter
L1
pwm
10mH
+
V1
10Vdc
-
V1 = 0
V2 = 1
TD = 0
TR = 1n
TF = 1n
PW = 0.5m
PER = 1m
V2
S1
++
- S
D1
out
Dbreak
VOFF = 0.0V
VON = 1.0V
ROFF = 1e6
RON = 1.0
C1
100µF
R1
20O
0
Power switching converters
Simulation of switching converters
16
PSpice Simulations using
schematics entry
25V
20V
15V
10V
5V
0s
5ms
V(out)
Power switching converters
10ms
15ms
20ms
25ms
30ms
Time
Simulation of switching converters
17
PSpice Simulations using
schematics entry
3.0A
I(L1)
2.0A
1.0A
0A
-1.0A
I(C1)
-2.0A
0s
I(L1)
Power switching converters
5ms
I(C1)
10ms
15ms
20ms
25ms
30ms
Time
Simulation of switching converters
18
PSpice Simulations Using
Behavioral Modeling

ABM.OLB part library

Control system parts
Power switching converters
Simulation of switching converters
19
Control system parts
Power switching converters
Simulation of switching converters
20
Control system parts
Power switching converters
Simulation of switching converters
21
Control system parts
Power switching converters
Simulation of switching converters
22
Control system parts
Power switching converters
Simulation of switching converters
23
Control system parts
Power switching converters
Simulation of switching converters
24
PSpice-equivalent parts
Power switching converters
Simulation of switching converters
25
PSpice-equivalent parts
Power switching converters
Simulation of switching converters
26
Operators in ABM expressions
Power switching converters
Simulation of switching converters
27
Operators in ABM expressions
Power switching converters
Simulation of switching converters
28
Functions in arithmetic
expressions
Power switching converters
Simulation of switching converters
29
Functions in arithmetic
expressions
Power switching converters
Simulation of switching converters
30
Examples of ABM blocks use
PARAMETERS:
PI = 3.141592654
freq = 1k
3*sin (2*PI*freq*TIME)
sine
ABM and PARAM
Power switching converters
Simulation of switching converters
31
Examples of ABM blocks use
3*V (sine)
control
Node voltages can be accessed from ABM blocks
Power switching converters
Simulation of switching converters
32
Examples of ABM blocks use
sine
rms
If (TIME<=0,0,SQRT(SDT(PWR(V(%IN),2))/TIME))
RMS meter
If(argument,then,else)
If (TIME<=0, 0, SQRT(SDT(PWR(V(%IN),2))/TIME))
Power switching converters
Simulation of switching converters
33
Examples of ABM blocks use
If (V(%IN1) > V(%IN2),1,0)
control
triangular
V1 = -10
V2 = 10
TD = 0
TR = 1u
TF = 1u
PW = 1n
PER = 2u
pwm
V4
0
PWM modulator
Power switching converters
Simulation of switching converters
34
Examples of ABM blocks use
Sin (2*PI*100k*ABS(V(%IN)) * TIME)
triangular
VCO
VCO implementation with ABM1
Power switching converters
Simulation of switching converters
35
PSpice Simulations Using Control
Blocks
control
10
triangular
V1 = -10
V2 = 10
TD = 0
TR = 0.5m
TF = 0.5m
PW = 1n
PER = 1m
100k
pwm
0
V4
0
PWM modulator with control blocks
Power switching converters
Simulation of switching converters
36
PSpice Simulations Using Control
Blocks
In-
PARAMETERS:
R2
10Meg
Vcc = +12
VEE = 0
{Vcc}
0
In+
0
50
100k
IN
R1
10Meg
1Vac
0Vdc
V4
OpAmp
50 + s OUT
{VEE}
0
0
Model of an operational amplifier
Power switching converters
Simulation of switching converters
37
PSpice Simulations Using Control
Blocks
100
50
0
SEL>>
-50
0d
DB(V(OPAMP))
-50d
-100d
1.0mHz 10mHz
P(V(OPAMP))
1.0Hz
100Hz
10KHz
1.0MHz
100MHz
Frequency
Open loop frequency response
Power switching converters
Simulation of switching converters
38
PSpice Simulations Using Control
Blocks
R3
10k
InR4
1k
R2
10Meg
0
In+
0
R1
10Meg
1Vac
0Vdc
V4
PARAMETERS:
Vcc = +12
VEE = 0
{Vcc}
100k
IN
50
50 + s OUT
OpAmp
{VEE}
0
0
Closed loop amplifier
Power switching converters
Simulation of switching converters
39
PSpice Simulations Using Control
Blocks
50
0
-50
0d
DB(V(OPAMP))
-50d
SEL>>
-100d
1.0mHz 10mHz
P(V(OPAMP))
1.0Hz
100Hz
10KHz
1.0MHz
100MHz
Frequency
Closed loop frequency response
Power switching converters
Simulation of switching converters
40
Voltage –mode PWM boost converter
R2
1
L1
10mH
pwm
D1
S1
Dbreak
++
- S
+
V1
10Vdc
-
0
out
VOFF = 0.0V
VON = 1.0V
ROFF = 1e6
RON = 0.05
C1
100µF
R1
20
E1
++
- E
If (V(%IN1) > V (%IN2),1,0)
control
pwm_out
PWM
modulator saw
V1 = 0
V2 = 10
V4
TD = 0
TR = 999u
TF = 1n
PW = 1n 0
PER = 1m
Power switching converters
GAIN = 0.25
sense
0
error
12
1Meg
-12
1Meg+s
3
5
Vref
Error amplifier
Simulation of switching converters
41
Voltage –mode PWM boost converter
20V
AVG(V(control))
10V
SEL>>
0V
V(control)
V(control)
AVG (V(control))
20V
AVG (V(error))
0V
V(error)
-20V
V(error)
AVG (V(error))
40V
V(out)
20V
AVG (V(out))
0V
0s
1ms
2ms
V(out)
AVG (V(out))
3ms
4ms
5ms
6ms
7ms
8ms
9ms
10ms
Time
Power switching converters
Simulation of switching converters
42
PSpice simulations using vendor
models
R7
L1
1
10mH
IC = 0
100uF
ESR
10m
20
R3
100k
R5
+15
0
V-
G
-
0
-15
PWM modulator
R4
V-
control
3k
V1 = 0
V2 = 10
TD = 0
TR = 999u
TF = 1n
PW = 1n
PER = 1m
Simulation of switching converters
1k
TL084
saw
V4
V+
+
LM311
pwm_out
.TRAN 0 30m 0 0.1u
.OPTIONS STEPGMIN
.OPTIONS ABSTOL= 10p
.OPTIONS ITL1= 400
.OPTIONS ITL4= 500
.OPTIONS RELTOL= 0.01
.OPTIONS VNTOL= 10u
V+
B/S
B
-15
R8
300
Power switching converters
300k
R1
sense
MTP15N05E/MC
-
R2
C1
X2
100
V1
10Vdc
out
MUR420
R6
+
D1
pwm
+
5
Vref
Error amplifier
+15
0
43
PSpice simulations using vendor
models
4.0A
2.0A
0A
I(L1)
5.2V
5.0V
4.8V
V(control)
20V
10V
SEL>>
0V
0s
5ms
10ms
15ms
20ms
25ms
30ms
V(out)
Time
Power switching converters
Simulation of switching converters
44
Vorperian models for PSpice
Power switching converters
Simulation of switching converters
45
Vorperian models for PSpice
Power switching converters
Simulation of switching converters
46
Vorperian models for PSpice
Power switching converters
Simulation of switching converters
47
Vorperian models for PSpice
**** VMSSCCM ****
* Small signal continuous conduction voltage mode model
* Params: RMPHITE --> External ramp height
*
D
--> Duty cycle
*
Ic --> Current flowing from terminal C
*
Vap
--> Voltage across terminal A P
*
Rsw
--> Switch on resistance
*
Rd
--> diode on resistance
*
Rm
--> which models the base storage effects
*
Re
--> models ripple across esr of cap
* Pins control voltage -*
common -------- |
*
passive----- | |
*
active -- | | |
.subckt VMSSCCM A P C VC Params: RMPHITE=2 D=0.4 IC=1 VAP=20
+
Rsw=1e-6 Rd=1e-6 Re=1e-6 Rm=1e-6
efm 4 0 value ={v(Vc)/rmphite}
e2 A 6 value={v(0,4)*Vap/d}
g1 A P value={v(4)*IC}
gxfr 6 P VALUE={I(vms)*D}
exfr 9 P VALUE={V(6,P)*D}
vms 9 8 0
rd 8 C {d*rd+(1-d)*rsw+d*(1-d)*re+rm}
rope 4 0 1g
rgnd 0 P 1g
.ends
Power switching converters
Simulation of switching converters
48
Small-signal analysis of switching
converters
3
10mH
IC = 0
1
A
+
10Vdc
VMSSCCM
C
1
U7
VC
L1
P
V1
-
2
out
D = 0.5
IC = -1.84
RMPHITE = 10
4
Rs
RD = 1e-6
RM = 1e-6
RE = 10m
0
1Vac
0Vdc
V4
RSW = 10m
VAP = -17.6
Cout
100uF
IC = 0
Resr
10m
R
20
Rs1
300k
sense
Rs2
100k
0
Small-signal AC analysis
Power switching converters
Simulation of switching converters
49
Small-signal analysis of switching
converters
3.0A
2.0A
1.0A
0A
20V
I(L1)
10V
SEL>>
0V
0s
5ms
10ms
15ms
20ms
25ms
30ms
V(OUT)
Time
Power switching converters
Simulation of switching converters
50
Small-signal analysis of switching
converters
Open-loop transfer function
40
0
-40
SEL>>
-80
-0d
DB(V(OUT))
-100d
-200d
-300d
1.0Hz
P(V(OUT))
10Hz
100Hz
1.0KHz
10KHz
100KHz
1.0MHz
Frequency
Power switching converters
Simulation of switching converters
51
L1
1
10mH
IC = 0
1 A
4
Rs
3
VC C
Small-signal analysis of switching
converters
1Vac
10Vdc
V4
0
U7
VMSSCCM
P 2
D = 0.5
IC = -1.84
RMPHITE = 10
RD = 1e-6
RM = 1e-6
RE = 10m
RSW = 10m
VAP = -17.6
out
Cout
100uF
IC = 0
Resr
10m
R
20
R s1
300k
sense
R s2
100k
0
Input impedance
Power switching converters
Simulation of switching converters
52
Small-signal analysis of switching
converters
100
80
60
40
20
0
1.0Hz
10Hz
DB(V(V4:+)/I(V4))
100Hz
1.0KHz
10KHz
100KHz
1.0MHz
Frequency
Input impedance
Power switching converters
Simulation of switching converters
53
1
10mH
IC = 0
1A
VC
L1
4
Rs
C 3
Small-signal analysis of switching
converters
+
10Vdc
V5
-
0
U7
VMSSCCM
out
P 2
D = 0.5
IC = -1.84
RMPHITE = 10
RD = 1e-6
RM = 1e-6
RE = 10m
RSW = 10m
VAP = -17.6
Cout
100uF
IC = 0
Resr
10m
R
20
Rs1
300k
sense
1Vac
10Vdc
V4
Rs2
100k
0
Output impedance
Power switching converters
Simulation of switching converters
54
Small-signal analysis of switching
converters
40
20
0
-20
-40
1.0Hz
10Hz
DB(V(V4:+)/I(V4))
100Hz
1.0KHz
10KHz
100KHz
1.0MHz
Frequency
Output impedance
Power switching converters
Simulation of switching converters
55
Small-signal analysis of switching
converters
3
10mH
IC = 0
1
C
1
U7
VMSSCCM
A
VC
L1
P
2
+
10Vdc
V1
-
0
V1 = 1.2
V2 = 1.5
TD = 20m
TR = 1n
TF = 1n
PW = 50m
PER = 50m
out
D = 0.5
IC = -1.84
RMPHITE = 10
4
Rs
RD = 1e-6
RM = 1e-6
RE = 10m
V4
RSW = 10m
VAP = -17.6
Rs1
Cout
100uF
IC = 0
Resr
10m
R
300k
sense
20
Rs2
100k
0
Small-signal transient analysis
Power switching converters
Simulation of switching converters
56
Small-signal analysis of switching
converters
25V
20V
10V
SEL>>
0V
3.0A
V(OUT)
2.0A
1.0A
0A
0s
5ms
I(L1)
10ms
15ms
20ms
25ms
30ms
Time
Small-signal transient analysis
Power switching converters
Simulation of switching converters
57
Averaged-inductor model for a
voltage-mode boost converter
U7 BOOSTVM
R3
out
OUT
IN
DON GND
1
0.5
Rs = 1
FS = 1k
L = 10m
R1
10m
R2
20
+
V1
10
C1
100u
IC = 0
0
Power switching converters
Simulation of switching converters
58
Output voltage obtained with the
averaged-inductor model
30V
25V
20V
15V
10V
5V
0V
0s
5ms
10ms
15ms
20ms
25ms
30ms
V(OUT)
Time
Power switching converters
Simulation of switching converters
59
Measuring the loop gain
1
A
0
+
10Vdc
3
10mH
IC = 0
U7
VMSSCCM
C
1
VC
L1
P
Vg
-
1Vac
0Vdc
2
out
D = 0.5
IC = -1.84
RMPHITE = 10
4
Rs
V1
RD = 1e-6
RM = 1e-6
RE = 10m
RSW = 10m
VAP = -17.6
Cout
100uF
IC = 0
R
20
Resr
GAIN = 0.25
E1
+ +
- E
10m
0
0
Power switching converters
Vf
0
0
Simulation of switching converters
60
Measuring the loop gain
20
(100.000,-1.2488)
0
-40
-80
90
DB(V(VF))
0
(100.000,-163.029)
-90
-180
-270
SEL>>
-360
1.0mHz
10mHz
P(V(VF))
100mHz
1.0Hz
10Hz
100Hz
1.0KHz
10KHz
100KHz
1.0MHz 10MHz
Frequency
Power switching converters
Simulation of switching converters
61
Frequency compensation
choose f1 = 100 Hz for a switching frequency of 1 kHz
PID compensation
 f1 
 f1 
1

2
tan
 

f
 z
 fp 
 comp ( f1 )  90  2 tan 1 
2 
2 






f
f
M comp ( f1 )  20 Log10 (2 f1 )  40 Log10  1   1    40 Log10  1   1  
 f  


fz  

 p 




 f1  
1
  comp  90  2 tan   
f1

 fp  
f1z   tan 

fz
2






2 



f
M comp ( f1 )  20 Log10 (2 f1 )  40 Log10 1  f1z 2  40 Log10  1   1  
 f  

 p 


Power switching converters

Simulation of switching converters
62
PID compensation
f p1 =
1
2 R 3C 3
( C1 + C 2 )
=
f p2
2 R 2C 1C 2
1
=
f z1
2 R 2C 1
1
=
f z2
2 ( R1 + R 3 )C 3
Power switching converters
R2
=
K1
R1
R 2( R 1 + R 3 )
=
K2
R1R 3
R 3 = C 1C 2 .
C3
C1 + C 2
R2
Simulation of switching converters
Mag_comp_f1 = -7.0985
Ph_comp = 32
k1_db = -24.6094
k1 = 0.0588
k2_db = -5.0259
k2 = 0.5607
R2 = 588.2076
R3 = 269.7258
C1 = 5.0034e-005
C2 = 1.3496e-006
C3 = 2.8658e-006
63
Boost switching converter with
PID compensator
+
V1
10Vdc
-
D1
pwm
10mH
IC = 4
R6
MUR420
V
X2
out
Cout
100uF
IC = 20
ESR
10m
100
MTP15N05E/MC
R
20
Rs2
3k
Rs3
1k
+15
V+
C2
0
V-
B
R8
B/S
+
300
LM311
pwm_out
G
0
-15
-15
PWM
V3 modulator
+15
`15
V2
-15
control
R2
saw
V1 = 0
V2 = 10
V4
TD = 0
TR = 999u
TF = 1n
0
PW = 1n
PER = 1m
R4
10meg
173.0498 2.5483e-006
R 3 C3
1.1461e-006
C1
518.3291 5.0014e-005
-15
0
Power switching converters
sense
V-
1
L1
R1
10k
-
TL084
+
V+
Rs
5
Vref
Error amplifier
+15
Simulation of switching converters
64
Simulation results with a PID
compensator
5.0A
4.5A
4.0A
I(L1)
10.0V
7.5V
SEL>>
5.0V
V(control)
40V
20V
0V
0s
V(out)
5ms
10ms
15ms
20ms
25ms
30ms
Time
Power switching converters
Simulation of switching converters
65
PI compensation
L1
3
1
C
10mH
IC = 0
A
0
+
10Vdc
P
2
out
D = 0.5
IC = -1.84
RMPHITE = 10
4
1
U7
VMSSCCM
VC
Rs
Vg
Cout
200uF
IC = 0
RD = 1e-6
RM = 1e-6
RE = 10m
-
20
Resr
RSW = 10m
VAP = -17.6
1Vac
0Vdc
R
10m
GAIN = 0.25
E1
+ +
- E
V1
0
Vf
0
0
0
10k
R1
TF 
s C1 R1  1
s C1 R2
10
-10
Vf
500n
1k
EAO
R2
C1
10
error
10 + s
100k
Small-signal model of the boost converter with PI
compensation
Power switching converters
Simulation of switching converters
0
66
PI compensation
100
Compensated loop gain
Uncompensated loop gain
0
-100
SEL>>
-200
DB(V(VF))
DB(V(EAO))
180
Compensated loop gain
90
Uncompensated loop gain
0
-90
-180
-270
-360
1.0mHz
10mHz
P(V(VF))
Power switching converters
100mHz
P(V(EAO))
1.0Hz
10Hz
100Hz
1.0KHz
10KHz
100KHz 1.0MHz
Frequency
Simulation of switching converters
67
PI compensation using ABM
blocks
C2
R3 1n
Rs
0.1
+
10Vdc
V1
-
1
L1
2 pwm
D1
100k
10mH
Dbreak
IC = 1.8
S1
gate
++
- S
0 VOFF = 0.0V
VON = 1.0V
out
Cout
R
100u
IC = 20 20
Resr
10m
0.25
0
0
if( V(%IN1) < V(%IN2),1,0)
control
2
3
1 saw
V1 = 0
V2 = 10
TD = 0
TR = 99.9u
TF = 0.05u
PW = 0.05u
PER = 100u
Power switching converters
C1
R1
1k
10k
500n
10
V2
R2
-10
1
1+s
100k
ref
5
0
Simulation of switching converters
68
Simulation results of the PI
compensation using ABM blocks
4.0A
2.0A
0A
I(L1)
30V
20V
10V
SEL>>
0V
10V
V(OUT)
5V
0V
0s
V(CONTROL)
5ms
10ms
15ms
20ms
25ms
30ms
Time
Power switching converters
Simulation of switching converters
69
PI compensation using vendor
models
Rs
0.1
L1
2 pwm
10mH
R3
X1
1
IC = 1.8
gate
MUR420
10
Cout
100u
IC = 20
Resr
10m
R5
R
3k
20
R6
1k
+15
B
R4 B/S
300
0
-15
+15
-15
V3
-15Vdc
0
Power switching converters
+
control
V4
R2
C1
-15
saw
V1 = 0
V2 = 10
TD = 0
TR = 99.9u
TF = 0.05u
PW = 0.05u
PER = 100u
10k
500n
V-
-
R1
1k
LM311
G
0
0
-
TL084
V2
+15
V+
0
V+
-
+15Vdc
MTP15N05E/MC
out
V1
V-
10Vdc
+
D2
+
ref
5
0
0
Simulation of switching converters
70
Simulation results of the PI
compensation using vendor
models
4.0A
2.0A
0A
40V
I(L1)
20V
0V
10V
V(OUT)
5V
SEL>>
0V
0s
2ms
V(CONTROL)
Power switching converters
4ms
6ms
8ms
10ms
12ms
14ms
16ms
18ms
20ms
Time
Simulation of switching converters
71
PI compensation using vendor
models
*Analysis directives:
.TRAN 0 30m 0 10n SKIPBP
.OPTIONS STEPGMIN
.OPTIONS PREORDER
.OPTIONS ABSTOL= 10.0p
.OPTIONS CHGTOL= 0.1p
.OPTIONS ITL2= 200
.OPTIONS ITL4= 400
.OPTIONS RELTOL= 0.01
.OPTIONS VNTOL= 10.0u
I/O ERROR -- Probe file size exceeds 2000000000
JOB ABORTED
TOTAL JOB TIME
912.11
Power switching converters
Simulation of switching converters
72
Creating capture symbols for PSpice
simulation
•Vendors often provide PSpice models for their circuit
components. They are normally provided in a text file with
extension .LIB; if the file has a different extension, it should be
changed to .LIB
•Start the PSpice Model Editor and from the File menu, choose
Create Parts
•Browse to find the input model library (.LIB file) and click
OK to start
•This step creates an .OBL file with a schematic symbol linked
to your model
•To place the new part into the schematic, open Capture, and
from the Place menu choose Part. Click Add library, then find
and add the new “.OLB” file
Power switching converters
Simulation of switching converters
73
Solving convergence
problems

PSpice uses the Newton-Raphson algorithm to
solve the nonlinear equations in these analyses

The algorithm is guaranteed to converge only if the
analysis is started close to the solution

If the initial guess is far away from the solution, this
may cause a convergence failure or even a false
convergence

If the node voltages do not settle down within a
certain number of iterations, an error message will
be issued
Power switching converters
Simulation of switching converters
74
DC analysis error messages

The DC Analysis calculates the small-signal bias
points before starting the AC analysis or the initial
transient solution for the transient analysis

Solutions to the DC analysis may fail to converge
because of incorrect initial voltage guesses, model
discontinuities, unstable or bistable operation, or
unrealistic circuit impedances

When an error is found during the DC analysis,
SPICE will then terminate the run because both the
AC and transient analyses require an initial stable
operating point in order to start
Power switching converters
Simulation of switching converters
75
DC analysis error messages

No convergence in DC analysis

PIVTOL Error

Singular Matrix

Gmin/Source Stepping Failed

No Convergence in DC analysis at Step = xxx
Power switching converters
Simulation of switching converters
76
Transient analysis error messages

If the node voltages do not settle down, the time
step is reduced and SPICE tries again to determine
the node voltages

If the time step is reduced beyond a certain fraction
of the total analysis time, the transient analysis will
issue an error message “Time step too small” and
the analysis will be halted

Transient analysis failures are usually due to model
discontinuities or unrealistic circuit, source, or
parasitic modeling
Power switching converters
Simulation of switching converters
77
Solutions to convergence
problems

There are two ways to solve convergence problems
 the first only tries to fix the symptoms by adjusting the
simulator options
 while the other attacks the root cause of the
convergence problems

Once the circuit is properly modeled, many of the
modifications of the "options" parameters will no
longer be required

It should be noted that solutions involving simulation
options may simply mask the underlying circuit
instabilities
Power switching converters
Simulation of switching converters
78
Bias point (DC) convergence

Checking circuit topology and connectivity

Modeling of circuit components

PSpice options are checked to ensure that
they are properly defined
Power switching converters
Simulation of switching converters
79
Checking circuit topology and
connectivity

Make sure that all of the circuit connections are valid

Check for incorrect node numbering or dangling
nodes

Verify component polarity

Check for syntax mistakes

Make sure that the correct PSpice units (i.e. MEG
for 1E6, not M, which means mili in simulations) are
used
Power switching converters
Simulation of switching converters
80

Make sure that there is a DC path from every
node to ground

Make sure that there are at least two connections
at every node

Make sure that capacitors and/or current sources
are not connected in series

Make sure that no (groups of) nodes are isolated
from ground by current sources and/or capacitors

Make sure that there are no loops of inductors
and/or voltage sources only
Power switching converters
Simulation of switching converters
81




Place the ground (node 0) somewhere in the
circuit
Be careful when floating grounds (e.g., chassis
ground) are used; a large resistor should be
connected from the floating node to ground. All
nodes will be reported as floating if "0 ground" is
not used
Make sure that voltage/current generators use
realistic values, and verify that the syntax is
correct
Make sure that dependent source gains are
correct, and that E/G element expressions are
reasonable
Power switching converters
Simulation of switching converters
82

Verify that division by zero or LOG(0) cannot
occur

Voltages and currents in PSpice are limited to the
range +/- 1e10

Avoid using digital components, unless really
necessary

Initialize the digital nodes with valid digital values

Avoid situations where an ideal current source
delivers current into a reverse-biased p-n junction
without a shunt resistance
Power switching converters
Simulation of switching converters
83
Setting up the options for the
analog simulation








Increase ITL1 to 400
Use NODESETs to set node voltages to the nearest
reasonable guess at their DC values
Enable the GMIN stepping algorithm
Set PREORDER in Simulation Profiles options
Setting the value of ABSTOL to 1 µ
PSpice does not always converge when relaxed
tolerances are used
Setting GMIN to a value between 1n and 10n will often
solve convergence problems
Setting GMIN to a value, which is greater than 10n,
may cause convergence problems
Power switching converters
Simulation of switching converters
84
Transient convergence

The transient analysis can fail to complete if
the time step becomes too small

This can be due to either


(a) the Newton-Raphson iterations would not
converge even for the smallest time step size
(b) something in the circuit is moving faster than
can be accommodated by the minimum step size
Power switching converters
Simulation of switching converters
85
Transient convergence

The circuit topology and connectivity should
first be checked

Followed by the PSpice options
Power switching converters
Simulation of switching converters
86
Circuit topology and
connectivity

Avoid using digital components, unless really
necessary

Initialize the nodes with valid digital value to ensure
there are no ambiguous states

Use RC snubbers around diodes

Add Capacitance for all semiconductor junctions
Power switching converters
Simulation of switching converters
87
Circuit topology and
connectivity

Add realistic circuit and element parasitics

It is important that switching times be
nonzero

It is recommended that all inductors have a
parallel resistor

Look for waveforms that transition vertically
(up or down) at the point during which the
analysis halts
Power switching converters
Simulation of switching converters
88
Circuit topology and
connectivity


Increase the rise/fall times of the PULSE
sources
Ensure that there is no unreasonably large
capacitor or inductor
Power switching converters
Simulation of switching converters
89
PSpice options

Set RELTOL=.01

Reduce the accuracy of ABSTOL/VNTOL if
current/voltage levels allow it

ABSTOL and VNTOL should be set to about 8
orders of magnitude below the level of the maximum
voltage and current

Increase ITL4, but no more than 100
Power switching converters
Simulation of switching converters
90
PSpice options

Skipping the bias point is not recommended

Any applicable .IC and IC= initial conditions
statements should be added to assist in the
initial stages of the transient analysis
Power switching converters
Simulation of switching converters
91
Switching converter simulation using
Matlab
Working with transfer functions
Consider a buck converter designed to operate in the continuous conduction
mode having the following parameters: R = 4Ω, L = 1.330 mH, C = 94 µf, Vs =
42 V, Va = 12 V

s 
s 
1

1




sz1  sz 2 
vo ( s)

 Kd
s
s2
d ( s)
1

0 Q 0 2
sz 2 
Kd 
s z1 
Vs
(1  D) 2
1
RESR C
R
(1  D)
( R  RESR || R)  ind
L
L
2
Power switching converters
Simulation of switching converters
0 
1
LC
Rind  re D (1  D)
RESR  R
re  RESR || R
Q
0
Rind  re (1  D)
1

L
C ( RESR  R )
92
Switching converter simulation using
Matlab
% this is a comment
% parameters
R= 4;
L = 1.330 e-3;
Rind = 100 e-3;
C = 94 e-6;
Resr = 10 e-3
Vs = 42;
Va = 12;
D=Va/Vs;
Kd= Vs/(1-D)^2;
Sz1=1/(Resr*C);
Req = R-(Resr*R/(Resr+R));
Sz2 = (1/L)*(1-D)^2* Req – Rind/L;
Re=(Resr*R)/( Resr+R);
Wo = (1/sqrt(L*C)) * sqrt((Rind+re*D*(1-D))/(Resr+R));
Q = Wo/(((Rind+re*(1-D))/L)+(1/(C*(Resr+R))));
Power switching converters
Simulation of switching converters
93
Switching converter simulation using
Matlab
% polynomials are entered in descending order of S.
n1=[1/Sz1 1]
n2=[-1/Sz2 1]
NUM=conv(n1,n2)
% the convolution realizes the product of 2 polynomials
% define denumerator
DEN = [1/(Wo^2) 1/(Wo*Q) 1]
% create TF variable
sysTF = Kd * tf(NUM,DEN)
which returns
Transfer function:
sysTF 
-5.317e-008 s^2 - 0.05648 s + 82.32
4.913e-006 s^2 + 0.01343 s + 1
Power switching converters
Simulation of switching converters
94
Switching converter simulation using
Matlab
Bode Diagram
20
0
-20
-40
0
-45
Phase (deg)
The location of the poles can be
found using
poles = roots(DEN)
and the frequency response can be
plotted using
bode(sysTF)
Magnitude (dB)
40
-90
-135
-180
-225
-270
10
1
10
2
3
10
4
10
5
10
10
6
7
10
Frequency (rad/sec)
Power switching converters
Simulation of switching converters
95
Switching converter simulation using
Matlab
The small signal transient step response can be plotted using
Figure
% this command opens a new figure window
step(sysTF)
Step Response
90
80
70
60
Amplitude
50
40
30
20
10
0
-10
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
Time (sec)
Power switching converters
Simulation of switching converters
96
Switching converter simulation using
Matlab
Working with matrices
Consider a buck converter designed to operate in the continuous conduction mode
having the following parameters: R = 4Ω, L = 1.330 mH, C = 94 µf, Vs = 42 V, Va
= 12 V.
% state-space averaged model of a Buck converter
Rload= 4;% load resistance
L= 1.330e-3;
% inductance
cap=94.e-6;
% capacitance
Ts=1.e-4; % switching period
Vs=42; % input DC voltage
Vref=12; % desired output voltage
The average duty cycle is:
D=Vref/(Vs); % ideal duty cycle
Power switching converters
Simulation of switching converters
97
Switching converter simulation using
Matlab
 0
x
1
 C

^
A=[
B1=[
0
1/cap
1/L
0];
1
  x^   D  ^ Vs  ^
L  1  
 L u L d
^
 
1     
x
0
2
RC     
0
-1/L
-1/(Rload*cap)]
%during Ton
B2=[
0
0];
%during Toff
B=B1*D+B2*(1-D)
C=[0 1];
Power switching converters
Simulation of switching converters
98
Switching converter simulation using
Matlab
Step Response
From: U (1)
0.35
OLpoles = eig(A)
0.3
sysOL=ss(A,B,C,0)
step(sysOL)
To: Y (1)
Amplitude
0.25
0.2
0.15
0.1
0.05
0
0
0.5
1
1.5
2
Time (sec.)
Power switching converters
Simulation of switching converters
2.5
3
3.5
4
4.5
x 10 -3
99
Switching converter simulation using
Matlab
gamma=[
0];
Vs/L
closed-loop poles:
P=1e3*[-0.3298 + 0.10i -0.3298 - 0.10i]';
Bf= gamma*(D/Vref);
F=place(A,Bf ,P)
Power switching converters
Simulation of switching converters
100
Switching converter simulation using
Simulink
90
sysTF 
-5.317e-8 s^2 - 0.05648 s + 82.32
4.913e-6 s^2 + 0.01343 s + 1
80
70
[NUM,DEN] = TFDATA(sysTF,’v’)
60
Output
50
40
30
-5.317e-8s 2 -0.0565s+82.32
20
2
4.913e-6s +0.0134s+1.0
Step
Scope
Transfer Fcn
10
0
output
time
Clock
-10
To Workspace
0
0.005
To Workspace1
Power switching converters
Simulation of switching converters
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0.045
Time (s)
101
0.05
Switching converter simulation using
Simulink
sysZPK = zpk(sysTF)
sysZPK 
-0.010821 (s+1.064e006) (s-1455)
(s+2657) (s+76.6)
-0.010821(s+1.0638e+006)(s-1455)
(s+2657)(s+76.6)
Step
Scope
Zero-Pole
zeroes: [-1.0638e+006 +1455]
poles: [-2657 -76.6]
gain: [-0.010821]
Power switching converters
output
time
Clock
To Workspace
To Workspace1
Simulation of switching converters
102
Switching converter simulation using
Simulink
752 
 0
A

10638 2660 
B   214.82 0 '
x' = Ax+Bu
y = Cx+Du
Step
Scope
State-Space
C   0 1 '
output
D0
time
Clock
Power switching converters
To Workspace
To Workspace1
Simulation of switching converters
103