THE ELECTROTHERMAL THE ELECTROTHERMAL ANALYSIS OF A SWITCHED ANALYSIS OF A SWITCHED

MODE VOLTAGE REGULATORMODE VOLTAGE REGULATOR Krzysztof Górecki and Janusz ZarębskiKrzysztof Górecki and Janusz Zarębski

Department of Marine Electronics Department of Marine Electronics

Gdynia Maritime University, POLANDGdynia Maritime University, POLAND

D E P A R T M E N T

F MARINE ELECTRONIC

22

OutlineOutline

IntroductionIntroduction The electrothermal model of the PWM The electrothermal model of the PWM

controller (UC3842)controller (UC3842) The electrothermal The electrothermal SPICE hybrid SPICE hybrid modelmodelss

((diodediode, MOS , MOS transistortransistor)) Results of Results of investigations of SMPS investigations of SMPS ConclusionsConclusions

33

IntroductionIntroduction

SMPS

Dc-dc converter PWM controller

RLC elements Semiconductor devices

transistors diodes

44

Introduction (cont.)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

55

In the paperIn 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

66

The ETM of the UC3842 controllerThe ETM of the UC3842 controller

[1] Zarębski J., Górecki K.: Microelectronics Reliability, Vol. 47, No. 7, 2007, pp. 1145-1152.

D11

V12

D10

OUT

VCC

Q1

Q2

ISUPE1

E2

Q

Q

Ct/Rt OSC

GOSC

EO1

V1

EO2

V2

V3

Rstan

Cstan

EERR EERR1

D1 D2 ED1R1

R2VX

ED2D3

ELIMEp1

Ep2

FF

S

REF

COMP

FB

Estan

IS

TRthn

Cth1 Cthn

Rth1

Gp VtaThe thermal

model

The power model

Tj

The electrical model

R

CEA

REA

V11

RQ1

RQ2

Vicq 1

Vicq 2

VOSC

EREF

OS

EA

AB

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

77

The The ETMsETMs of the diode of the diode and the MOSFET and the MOSFET

• The general conceptionThe general conception

+ ++ +

• Only characteristics of the forward biased diode and switched-on transistor operating in SMPS are important

Electrothermal hybrid model

SPICEisothermal

built-in model

Controlled sources modelling the

influence of selfheating

Thermal model

88

The The ETMsETMs of the diode of the diode and the MOSFET and the MOSFET (cont.)(cont.)

0TTRSiE jRSRS 01 TTE ju iupth

0TTRDiE jRDDRD

0TTE juG

DDSth iup

0

0,5

1

1,5

2

2,5

3

3,5

4

0 0,1 0,2 0,3 0,4 0,5 0,6

u [V]

i [A

]

1N5822

0

2

4

6

8

10

0 0,25 0,5 0,75 1 1,25 1,5 1,75 2

uDS [V]

i D [

A]

IRF640

uGS = 12 VTa = 300 K

99

Results of calculations Results of calculations and measurementsand measurements

Transient analysis till the steady-stateTransient analysis till the steady-stateOne non-physical thermal time constant – to short the time of One non-physical thermal time constant – to short the time of calculationscalculations

COMP

VFB

ISENSE

RT/CT GND

OUT

VCC

VREFU

UC

384

2

1

2

3

4 5

6

7

8L

RoCo

D1

M1

RS

Vin

+Vcc

C1

D2

R2

R3

C3D3

CT

R4

Q1

RT

R5R6

R7

R8

C4

R10

R9

P1

P2

R11

C5

1

1

2

2

Vout

BOOST converter

1010

Results - opened feedback loopResults - opened feedback loop

The calculations resultsThe calculations results

The measurements resultsThe measurements results

0

5

10

15

20

25

30

35

0 1 2 3 4 5 6

VCOMP [V]

Vou

t [V

]

VISMAX = 1.2V

R0 = 49.66 W

Vin = 12.3 V

RS = 1.153 W VISMAX = 2.1 V

VISMAX = 0.31 V

BOOST - opened feedback loop

0

5

10

15

20

25

30

35

40

45

50

1 10 100 1000

R0 [W]

Vou

t [V

]

VFB = 3.06 V

Vin = 6 VVIS = 0.6 V

RS = 1.125 W

RS = 0.409 WBOOST - opened feedback loop

1111

Results - closed feedback loopResults - closed feedback loop

The calculations resultsThe calculations results

The measurements resultsThe measurements results

0

24

6

8

1012

14

1618

20

0 5 10 15 20

Vin [V]

Vou

t [V

]

BOOST -closed feedback loop

RS = 0.397 W

R0 = 9.46 W

R0 = 49.67 W

0

2

4

6

8

10

12

14

1 10 100 1000

R0 [W]

Vou

t [V

]

Vin = 5 V

RS = 1 W

RS = 0.397 W

BOOST - closed feedback loop

1212

ConclusionsConclusions 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.