Transcript Slajd 1 - Akademia Morska w Gdyni

PA
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THE ELECTROTHERMAL
ANALYSIS OF A SWITCHED
MODE VOLTAGE REGULATOR
Krzysztof Górecki and Janusz Zarębski
Department of Marine Electronics
Gdynia Maritime University, POLAND
S
Outline
 Introduction
 The electrothermal model of the PWM
controller (UC3842)
 The electrothermal SPICE hybrid models
(diode, MOS transistor)
 Results of investigations of SMPS
 Conclusions
2
Introduction
SMPS
Dc-dc converter
RLC elements
PWM controller
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 current mode PWM controller
 the diode
 the MOS transistor
dedicated for electrothermal analysis of SMPS in SPICE
 Measurements and calculations of nonisothermal
characteristics of SMPS
Why the new models are needed?
 the literature models are complicated
 the time duration of calculations with these models is
unacceptable long
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The ETM of the UC3842 controller
Ct/Rt
Rstan
OSC
OS
RQ1
Q
S
Ep2
VOSC
Estan
GOSC
Cstan
V3
Q1
R
V1
Vicq 2
ISUP
E1
EO2
EO1
VCC
ELIM
V2
Q
Vicq 1
Ep1
RQ2
Q2
FF
E2
IS
AB
COMP
REF
D1
REA
R1
ED1
R2
VX
EERR
EREF
D2
CEA
EERR1
ED2
D3
The electrical model
Tj
FB
Rth1
D10
EA
D11
V12
Rthn
T
V11
The power
model
Cth1
Gp
Cthn
Vta
The thermal
model
OUT
 The modified version
of the model from
[1]
 The changes in
description of the
error amplifier block
 In the model all
terminals of IC,
selfheating, nonlinear
characteristics of
semiconductor
devices are taken
into account
[1] Zarębski J., Górecki K.: Microelectronics Reliability, Vol. 47, No. 7, 2007, pp. 1145-1152.
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The ETMs of the diode and the MOSFET
• 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
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The ETMs of the diode and the MOSFET
(cont.)
iD
WMS
uD1
EG  u  Tj  T0 
ERS
i
A
ERD  iD  RD RD  Tj  T0 
D
u
K
D1
ERS  i  RS  RS  Tj  T0  E1  u  Tj  T0  pth  u  i G
EG
pth  uDS  iD
uDS
ERD
E1
WMS
S
4
10
1N5822
3,5
IRF640
iD [A]
2,5
i [A]
uGS = 12 V
Ta = 300 K
8
3
2
1,5
1
6
4
2
0,5
0
0
0
0,1
0,2
0,3
u [V]
0,4
0,5
0,6
0
0,25
0,5
0,75
1
uDS [V]
1,25
1,5
1,75
2
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Results of calculations and measurements
+Vcc
1 COMP
RT
R4
1
2
P1
R7
VFB
1
2
Q1
U
3 ISENSE
P2
2
4 RT/CT
R6
R5
C5
CT
UC 3842
C4
R8
Vin
L
R3
VREF 8
VCC
BOOST
converter
Vout
R2
7
D1
D2
OUT 6
Co
D3
C3
Ro
M1
C1
GND 5
R10
RS
R9
R11
Transient analysis till the steady-state
One non-physical thermal time constant – to short the time of
calculations
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Results - opened feedback loop
35
BOOST - opened feedback loop
30
R0 = 49.66 W
VISMAX = 0.31 V
Vin = 12.3 V
20
RS = 1.153 W
BOOST - opened feedback loop
45
40
Vout [V]
Vout [V]
25
50
VISMAX = 1.2V
VISMAX = 2.1 V
15
RS = 0.409 W
Vin = 6 V
VIS = 0.6 V
35
30
RS = 1.125 W
VFB = 3.06 V
25
20
15
10
10
5
5
0
0
0
1
2
3
4
5
6
VCOMP [V]
1
10
100
1000
R0 [W]
The calculations results
The measurements results
10
Results - closed feedback loop
14
BOOST - closed feedback loop
12
Vin = 5 V
Vout [V]
Vout [V]
10
RS = 0.397 W
8
RS = 1 W
6
4
2
0
1
10
100
1000
R0 [W]
20
18
16
14
12
10
8
6
4
2
0
BOOST -closed feedback loop
RS = 0.397 W
R0 = 49.67 W
R0 = 9.46 W
0
5
10
15
20
Vin [V]
The calculations results
The measurements results
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Conclusions
 The presented calculations and measurements results confirm the


correctness of the proposed by the authors electrothermal model
of the controller UC3842 and the hybrid electrothermal models
of the MOS transistor and of the diode.
The calculations and measurements results show the influence of
both the input signals of the controller and the values of the
boost converter elements on the output voltage.
The possibility of taking into account the phenomenon of
selfheating enabled, among others, determining from the
computer simulations the admissible values of load resistance
and the regulator input voltage, at which the voltage regulator
operates properly and the admissible temperature of its
component elements is not exceeded.
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