1. PSpice For Power Electronics
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PSpice For Power Electronics
Nik Din Muhamad
Department of Encon,
Faculty of Electrical Engineering,
UTM.
11-12/8/04

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INTRODUCTION
Two types of simulators Used in Power Electronics:
CIRCUIT-ORIENTED SIMULATOR
e.g. SPICE
EQUATION-ORIENTED SIMULATOR
e.g. MATLAB:
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SPICE
Originally intended for analyzing IC.
Uses iterative Newton-Raphson Algorithm
to solve a set of nonlinear equations.
The AC analyses are linear and do not use
iterative algorithm
Digital devices are evaluated using Boolean
algebra.
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SPICE LIMITATIONS
The Newton-Raphson algorithm is guaranteed
to converge if the equations is continuous and
the initial approximation is close enough to
the solution.
The transient analysis has the additional
possibility of unable to converge because the
time step required too small due to something
in the circuit moving too fast.
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SPICE LIMITATIONS
Computer Hardware Limitation:
Voltage and currents are limited to +/-1e10.
Derivatives in Pspice are limited to 1e14.
The arithmetic used in Pspice is double
precision and has 15 digits of accuracy.
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PSPICE
A Three-step Process to use Pspice:
Open and draw circuit under Orcad Capture
Simulate
Plot results using Probe
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PSPICE
Four main types of analysis:
Bias point
DC Sweep
Transient
AC Sweep
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8. A General Procedure to Use Pspice:
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A General Procedure to Use Pspice:
Open the Orcad Capture
Create a new project
Load Libraries of parts
Choose parts for schematic
Specify attributes of the parts
Wire the schematic
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…Continue
7. Grounding the circuit
8. Create a New Simulation Profile
9. Run simulation and display the
the results
10. Analyze the results
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10. Where are we going today?
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Where are we going today?
Objective:
To develop skills of simulation of power
electronic systems using Pspice.
Emphasis on:
DC-DC Converter Systems using
averaged and Switched Models.
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11. Three Types of Models Commonly Used in Pspice:
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Three Types of Models Commonly Used in Pspice:
Switched Models
Large-signal Averaged Models
Small-signal models
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AVERAGING SCENARIO
Discrete + Continuous,
Nonlinear, Time Variant.
Switched Models
Averaging
Continuous,
Nonlinear,
Time Invariant.
Averaged Models
Linearization
Continuous,
Linear, Time Invariant.
DC Models
AC Small-signal Models
DC characteristics
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Switched Models
Used To simulate the time domain behavior
of the actual circuits.
Not easy to use in Pspice.
Carry too much information about the
waveforms.
Do not have a DC operating point.
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Averaged Models:
Tracks low frequency behavior, suppresses
switching ripples.
Still nonlinear but have a DC operating
point.
Used to predict converter steady-state
characteristics and small-signal dynamics.
Easy to use in Pspice.
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Averaged Models
Applications:
DC Transfer Functions
Transient (Large-signal, time domain)
phenomena.
AC (Small-signal, frequency domain)
Transfer Functions
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Small-signal Models
Linear Models.
Give analytical results of small-signals
dynamics.
Used to design controllers.
Easy to use in Pspice without any problem.
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17. DC-DC Converter Systems
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DC-DC Converter Systems
Discrete
Continuous
A Mixed System: Discrete Plus Continuous

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Continuous Approach
Make the discrete parts to be continuous
through averaging
Leave the continuous parts as-is
Can be Perturbed and linearized to obtain
small signal models.

19. Direct Circuit Averaging
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Direct Circuit Averaging
What is the function of the switch networks in terms of averaged values?
Buck
Boost
DC Transformer
Buck-Boost

20. Direct Circuit Averaging: CCM
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Direct Circuit Averaging: CCM
<I1>
<I2>
1: d
d’: 1 +
<V1> -
<V2>
d’: d d
<I1>=d<I2>
<V2>=d<V1>
<V1>=d’<V2>
<I2>=d’<I1>
<V1>=(d’/d)<V2>
<I2>=(d’/d)<I1>
Constraint Eqns.: .

21. Pspice Implementation: Buck
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Pspice Implementation: Buck
Evalue is used to implement the voltage equation
Gvalue is used to implement the current equation
Duty ratio d is coded into voltage
Large signal, nonlinear model suitable for DC, AC, or
Transient simulation.
Limitation: Topology dependent, valid for CCM only
Go To: Buck_Avg and Buck_Sw

22. Pspice Implementation
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Pspice Implementation
Boost
Buck-Boost

23. Buck Converter Example Averaged Vs. Switched Model
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Buck Converter Example Averaged Vs. Switched Model
Pspice Transient Analysis
LIVE SIMULATION
Go to: How to write equations in PSpice,1 2
Good Results, small DC offset due to device models

24. Boost Converter Example DC Characteristics
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Boost Converter Example DC Characteristics
Pspice DC Sweep analysis
LIVE SIMULATION
DC Transfer function and efficiency.

25. Buck-boost Converter Example Small-signal control-to-output response
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Buck-boost Converter Example Small-signal control-to-output response
Pspice AC Sweep analysis
LIVE SIMULATION
Will be very useful for controller design

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Comments
DC Transformer is implementation of a large signal,
nonlinear averaged model of the switch network.
Averaged circuit model of the converter is obtained
simply by replacing switching devices with DC Transformer.
Linearization and AC small-signal analysis are performed
by simulator.
DC Transfer Function and Efficiency, can be easily
generated for different operating points.
Small-signal dynamic responses can be easily generated for
different operating points or different sets of parameters.
Limitation: Topology dependent, valid for CCM.

27. Towards Topology Independent: Switch Averaged Model
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Towards Topology Independent: Switch Averaged Model
If we rearrange the constraint equations in such a way that
we can write the averaged current through diode and the
averaged voltage across Mosfet, we can obtain topology
independent of Switch Averaged Model. This is because certain
converters share the same constraint equations.
The constraint equation is what we have done for DC
transformer model of Buck-boost with no connection
between source (S) and cathode (K).
The model can be applied in any two-switch PWM converters
e.g. Buck, Boost, Buck-boost, Cuk, SEPIC

28. Pspice Implementation: Subcircuit Creation CCM1
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Pspice Implementation: Subcircuit Creation CCM1
*********************************************
* MODEL: ccm1
* Application: two-switch PWM converters
* Limitations: ideal switches, CCM only, no transformer
* Parameters: none
* Nodes: 1: transistor+ (D) 2: transistor- (S)
*3: diode cathode (K) 4: diode anode (A)
*5: duty ratio (duty)
.subckt ccm
Et 1 2 value={(1-v(5))*v(3,4)/v(5)}
Gd 4 3 value={(1-v(5))*i(Et)/v(5)}
.ends CCM1
**********************************************

29. Combined CCM/DCM: Averaged Switch Model
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Combined CCM/DCM: Averaged Switch Model
CCM/DCM Boundary:
u = equivalent switch duty ratio

30. Subcircuit Creation CCM-DCM1
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Subcircuit Creation CCM-DCM1
**********************************************************
* MODEL: ccm-dcm1
* Application: two-switch PWM converters, CCM or DCM
* Limitations: ideal switches, no transformer
* Parameters:
* L=equivalent inductance (relevant for DCM)
* fs=switching frequency
* Nodes:
* 1: transistor+ (D) 2: transistor- (S) 3: diode cathode (K)
* 4: diode anode (A) 5: duty ratio (duty)
.subckt ccm-dcm
+ params: L=1m fs=100k
Et 1 2 value={(1-v(u))*v(3,4)/v(u)}
Gd 4 3 value={(1-v(u))*i(Et)/v(u)}
Ga 0 a value={MAX(i(Et),0)}
Va a b
Rdummy b 0 1k
Eu u 0 table {MAX(v(5),
+ v(5)*v(5)/(v(5)*v(5)+2*L*fs*i(Et)/v(3,4)))} (0 0) (1 1)
.ends CCM-DCM1

31. Averaged Buck Converter with Feedback
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Averaged Buck Converter with Feedback
Averaged PWM
Averaged Switch
Error Amplifier (Linear)
LC Filter + Load (Linear)

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Averaged Model of PWM Vm Vp Vc
Linear Relation

33. Averaged PWM With Duty Cycle Limiter: Pspice Implementation
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Averaged PWM With Duty Cycle Limiter: Pspice Implementation
(0.01,0.01)
(0.99,0.99) Vc d Or
Etable and Gain Or
Etable Only.

34. Behavior Model of Comparator: Pspice Implementation
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Behavior Model of Comparator: Pspice Implementation
(0,0)
(200u,5)
V(+)-V(-)
V(out)
Ideal Equations:
IF V(+)>V(-) V(out)= High
IF V(+)<V(-) V(out)= Low
Can also be implemented to error amplifier.

35. Behavior Model of Error Amplifier: Pspice Implementation
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Behavior Model of Error Amplifier: Pspice Implementation
Error Amplifier and comparator share the same I/O
relationship.
Output
Input
Type-3 error amplifier: Commonly used for Buck, Boost, and
Buck-boost Converters.
Note that V(+) and V(-) was interchanged to make connection
easier.

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Buck Converter System: Switched Model Simulation (Pspice Transient analysis)
Load Disturbance

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Buck Converter System: Averaged Model Simulation (Pspice Transient analysis)
Load Disturbance

38. Buck Converter System: Closed loop Pspice AC analysis.
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Buck Converter System: Closed loop Pspice AC analysis.
controller
Plant
H(s)
A(s)
Zo(s) + -
vout
vref d vi io
C(s)
G(s)
The stability of the system is given by loop gain, LG.
The disturbance rejection performance of the system is
given by the closed loop output impedance, Zocl(s) and
the closed loop audio-susceptibility, Acl(s).

39. Buck Converter System: Averaged Model Simulation (Pspice AC analysis)
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Buck Converter System: Averaged Model Simulation (Pspice AC analysis)
Zocl(s)
Acl(s)
Loop gain
Place 1V AC Source
Closed loop system

40. Closed Loop Pspice AC Analysis
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Closed Loop Pspice AC Analysis
General Rules:
Locate AC source at particular locations
Set the AC source to any value (1V is fine)
Make sure that there are no other AC sources
in the system.
Check the bias point to make sure that All
operating points are OK.
Remember that the classical stability criteria
take into account the phase reversal (180°).

41. Closed Loop Pspice AC Analysis: Waveforms Analysis in Probe.
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Closed Loop Pspice AC Analysis: Waveforms Analysis in Probe.
Add Trace’s Equations:
Loopgain=dB(V(y)/V(x))
Loopphase=P(V(y)/V(x))-180
(Inject 1V AC source in any place in the loop and gives node a name as X at an inject point and Y at a return point )
ZoclGain=dB(V(out)) ; Inject 1A AC source at the output.
ZoclPhase=P(V(out))
AclGain=dB(V(out)) ; Apply 1V AC source at the input.
AclPhase=P(V(out))
Equations can be written as macros

42. Other Circuit Examples: Transient Simulation
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Other Circuit Examples: Transient Simulation
Sliding Mode Control of A Buck Converter
Problematic Part:
Hysteretic Comparator

43. Other Circuit Examples: Transient Simulation
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Other Circuit Examples: Transient Simulation
Power Factor Correction of Boost Converter With Hysteretic
Controller

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Simulation Results:
Inductor Current
Switching Function
Input Current

45. Hands on #1: Buck converter Averaged model
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Hands on #1: Buck converter Averaged model
Large signal time domain simulation
Parts: VDC, GVALUE, EVALUE, R, L, C
Analysis Type: Transient (time domain)
Note: Draw on the same page as Hands on #1 for comparison

46. Hands on # 2: Buck converter switched model
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Hands on # 2: Buck converter switched model
Large signal time domain simulation
Parts: VDC, VPULSE, IRF150, DBREAK, R, L, C
Analysis Type: Transient (time domain)
Run to time: 3m
Maximum step size: 0.1u

47. Hands on #3: Boost converter Averaged model
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Hands on #3: Boost converter Averaged model
DC Characteristics: Efficiency and DC Gain
New Parts: PARAM, ABM
Analysis: DC Sweep
Primary Sweep: d
Parametric sweep: Rind

48. Hands on #4: Buck-Boost converter Averaged model
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Hands on #4: Buck-Boost converter Averaged model
AC Small-signal:control-to-output TF
New Parts: NIL
Analysis: AC Sweep

49. Hands on #5: Buck converter Averaged model with FB
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Hands on #5: Buck converter Averaged model with FB
AC Small-signal Dynamics
Error Amplifier
Averaged PWM

50. Hands on # 6: Buck converter Averaged model
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Hands on # 6: Buck converter Averaged model
Large signal time domain simulation
Error Amplifier
Averaged PWM

51. Hands on #7: Buck converter Switched model with FB
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Hands on #7: Buck converter Switched model with FB
Large signal time domain simulation
Error Amplifier
Comparator

52. Simulation Setting: Hands on #1 and #2
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Simulation Setting: Hands on #1 and #2

53. Simulation Setting: Hands on #3
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Simulation Setting: Hands on #3
Primary sweep

54. Simulation Setting: Hands on #3
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Simulation Setting: Hands on #3
Parametric sweep

55. Simulation Setting: Hands on #4 and #5
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Simulation Setting: Hands on #4 and #5
AC Sweep

56. Simulation Setting: Hands on #6 and #7
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Simulation Setting: Hands on #6 and #7
Time Domain

57. How to write equations in PSpice ?
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How to write equations in PSpice ?

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In Pspice