Download Slajd 1

PA
DE
O
FM
RTMEN
ARINE
EL
T
N IC
O
R
T
C
E
SPICE-modelling
and the analysis of the self-excited
push-pull dc-dc converter with
selfheating taken into account
Krzysztof Górecki and Janusz Zarębski
Department of Marine Electronics
Gdynia Maritime University, POLAND
S
Outline
 Introduction
 The structure of the push-pull dc-dc converter
 The electrothermal hybrid models of the diode
and the BJT
 The electrothermal model of the transformer
 Results of investigations
 Conclusions
2
Introduction
Dc-dc converter
RLC elements
transformer
Semiconductor
devices
transistors
diodes
3
Introduction (cont.)
 Selfheating – results from changing the electrical

energy into the heat and non-ideal cooling
conditions
Due to selfheating
 Internal temperatures of semiconductor devices
increase
 Characteristics and parameters values of SMPS
change
 Electrothermal analysis – analysis with
selfheating taken into account
4
In the paper
 The new electrothermal models (ETM) of:
 the diode
 the BJT
 the pulse transformer
dedicated for electrothermal analysis of SMPS in SPICE
 Measurements and calculations of nonisothermal
characteristics of the self-excited push-pull dc-dc
converter
Why the new models are needed?
 the literature models are complicated
 the time duration of calculations with these models is
unacceptable long
5
The structure of the push-pull dc-dc converter
T1
Tr
R1
U11
Vin
U12
D
D1
T2
U21
C
Ro
Vout
U22 D2
RB1
RB2
• The transistors are switched alternativelly
• the core of the transformer operate with the saturation
• R1-D – the start circuit
6
The ETMs of the diode and the BJT
• The general conception
Electrothermal
hybrid model
SPICE
isothermal
built-in model
Controlled sources
modelling the
+
+
influence of selfheating
Thermal
model
• Only characteristics of the forward biased diode
and switched-on transistor operating in SMPS are important
7
The ETMs of the diode and the BJT (cont.)
v
C
iC
WMS
vD1
A
ERS
i
K
D1
E1
ERC
Cth
Tj
Tj
vB
B
Rth
Rth
WMS
iB
pth
pth
vBE
E
4
4,5
BY229
4
BD283
3,5
Ta = 300 K
3,5
Ta = 300 K
3
3
iB = 200 mA
2,5
iC [A]
i [A]
vCE
Cth
2,5
2
2
iB = 100 mA
1,5
1,5
1
1
0,5
0,5
0
0
0
0,2
0,4
0,6
0,8
1
1,2
1,4
0
1
1,5
2
uCE [V]
u [V]
nonisothermal calculations
0,5
isothermal calculations
measurements
8
The ETMs of the pulse transformer
Windings
I1
1A
VL1 = 0
EV1
RS1
GR1
Auxiliary circuits
B
Bsat H
ERS1
EBsat EH
EB
Re1
E11
EV2
RS2
GR2
Re2
ERS2
2B
C2
EDB
E2 R2
Thermal model
Ce2
VL3 = 0
EV3
RS3
ERS3
3B
RthU
GPU
EV4
RS4
EV5
RS5
ERS4
CthU
GPR1
4B
I5
TR
VL5 = 0
I6
6A
C1
TU
VL4 = 0
5A
D2
E1 R 1
I3
4A
ETS
In the model:
DB
E12
I4
Ec
D1
VL2 = 0
3A
TS
Ce1
I2
2A
c
1B
VL6 = 0
EV6
RS6
ERS5
ERS6
5B
RthR
6B
GPR
GPU1
Equations – see Proceedings
CthR
– The core without
histeresis
– Separated temperatures
of the core and the
windings
– The core characteristics
dependent on the core
temperature
– The skin effect in the
windings
– The mutual thermal
interaction between the
core and windings
9
Results of investigations
 Transient analysis till the steady-state
 One non-physical thermal time constant – to short the time
of calculations
90
80
R0 = 51.5 W
Ta = 20oC
70
70
60
50
h [%]
Vout [V]
60
R0 = 51.5 W
Ta = 20oC
80
40
30
50
40
30
20
20
10
10
0
0
2
4
6
8
10
12
14
Vin [V]
16
0
0
2
4
6
8
10
12
14
Vin [V]
results of calculations
results of measurements
10
16
Results of investigations (cont.)
50000
90
45000 R0 = 51.5 W
o
40000 Ta = 20 C
70
35000
60
30000
TR [oC]
f [Hz]
R0 = 51.5 W
o
Ta = 20 C
80
25000
20000
50
40
30
15000
10000
20
5000
10
0
0
0
2
4
6
8
10
12
14
Vin[V]
16
0
2
4
6
8
10
12
14
Vin [V]
results of calculations
results of measurements
11
16
Conclusions
• A very good agreement between the calculated and
•
measured non-isothermal characteristics of the selfexcited push-pull dc-dc converter is achieved within a
wide range of changes in the input voltage and the load
resistance.
From the authors’ investigations it results that even at
relatively high values of the load resistance the
transformer temperature can be high as a result of the
energy losses in the core. This temperature is the
increasing function of the frequency of the converter
operation.
12