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Elektronika 2010-11.pdf - Instytut Systemów Elektronicznych ...

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Using the measurement results for the considered transistor<br />

the following empirical dependence is proposed<br />

⎡<br />

⎛ p<br />

⎞ ⎛ ⎞⎤<br />

= ⋅ ⎢<br />

⋅<br />

⎜ −<br />

th<br />

p<br />

+<br />

⋅<br />

⎥ (6)<br />

⎣<br />

⎜ −<br />

th<br />

R<br />

⎟<br />

⎟<br />

th<br />

Rth<br />

max<br />

a1<br />

exp a2<br />

exp<br />

⎝ b1<br />

⎠ ⎝ b<br />

2<br />

⎠<br />

⎦<br />

where R thmax<br />

, a 1<br />

, a 2<br />

, b 1<br />

and b 2<br />

are the model parameters.<br />

In Table 2 the values of the parameters describing Eq. (6)<br />

for various cooling conditions of the investigated devices are<br />

collected. The investigations were carried out for the diode<br />

SDP10S30 and the transistor CRF24010F operating both<br />

without any heat-sink and situated on the small heat-sink.<br />

Measurements were performed with the electrical methods<br />

described in [14].<br />

The results of the measurements – points and the calculations<br />

according to Eq. (6) – lines of the dependence of the<br />

diode and the transistor thermal resistance on the dissipated<br />

power are presented in Fig. 6.<br />

As seen, the measured and calculated results differ from<br />

each other not more than 5%, which confirms well the proposed<br />

model.<br />

In the presented figures, decreasing of the thermal resistance<br />

of both the investigated devices operating at the various<br />

cooling conditions on increasing of the device dissipated<br />

power is observed. It is also seen, that the dependence<br />

R th<br />

(p th<br />

) is stronger for devices operating without any heat-sink.<br />

Z(t) [K/W]<br />

35<br />

30<br />

25<br />

20<br />

15<br />

10<br />

5<br />

SDP10S30<br />

p th = 3.3 W<br />

p th = 4.7 W<br />

p th = 1 W<br />

p th = 2.1 W<br />

p th = 5.7 W<br />

0<br />

0,0001 0,001 0,01 0,1 1 10 100 1000 10000<br />

t [s]<br />

Fig. 4. Measured (solid lines) and calculated (dotted lines) courses<br />

of Z(t) of the diode SDP10S30<br />

Rys. 4. Zmierzone (linie ciągłe) i obliczone (linie kreskowe) przebiegi<br />

Z(t) diody SDP10S30<br />

Z(t) [K/W]<br />

100<br />

80<br />

60<br />

40<br />

20<br />

CRF24010F<br />

T a = 20 o C<br />

p th = 0.51 W<br />

p th = 1.06 W<br />

p th = 1.5 W<br />

p th = 0.21 W<br />

p th = 2.03 W<br />

p th = 2.72 W<br />

0<br />

0,0001 0,001 0,01 0,1 1 10 100 1000 10000<br />

t [s]<br />

Fig. 5. Measured (solid lines) and calculated (dotted lines) courses<br />

of Z(t) of the transistor CRF24010F<br />

Rys. 5. Zmierzone (linie ciągłe) i obliczone (linie kreskowe) przebiegi<br />

Z(t) tranzystora CRF24010F<br />

Tabl. 2. Values of the parameters in Eq. (6) for the diode SDP10S30<br />

and the transistor CRF24010F<br />

Tab. 2. Wartości parametrów w równaniu (6) dla diody SDP10S30<br />

i tranzystora CRF24010F<br />

a)<br />

Parameters<br />

Rth [K/W]<br />

b)<br />

Rth [K/W]<br />

Diode without<br />

any heat-sink<br />

Diode on<br />

the<br />

heat-sink<br />

Transistor<br />

without any<br />

heat-sink<br />

Transistor<br />

on the<br />

heat-sink<br />

R thmax<br />

78 34 93 22.2<br />

80<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

10<br />

a 1<br />

0.88 0.9 0.85 0.92<br />

a 2<br />

18 25 18 45<br />

b 1<br />

0.12 0.1 0.15 0.08<br />

b 2<br />

1.5 1.5 0.7 1.5<br />

0<br />

0 1 2 3 4 5 6<br />

p th [W]<br />

Fig. 6. Calculated and measured dependences of the thermal resistance<br />

of the diode SDP10S30 (a) and the transistor CRF24010F<br />

(b) on the dissipated power<br />

Rys. 6. Obliczone i zmierzone zależności rezystancji termicznej<br />

diody SDP10S30 (a) oraz tranzystora CRF24010F (b) od mocy<br />

It probably results from the fact, that the influence of the heat<br />

conduction, radiation and convection is different in the devices<br />

situated on the heat-sink and operating without it.<br />

As it is seen, that in the considered range of device dissipated<br />

power the device thermal resistance can change even<br />

more than 20%.<br />

Conclusions<br />

SDP10S30<br />

device without any heat-sink<br />

device on the heat-sink<br />

100<br />

90<br />

CRF24010F<br />

80<br />

device without any heat-sink<br />

70<br />

60<br />

50<br />

40<br />

30<br />

20<br />

device on the heat-sink<br />

10<br />

0<br />

0 2 4 6 8 10<br />

p th [W]<br />

In the paper the compact nonlinear thermal model of two SiC<br />

semiconductor devices is proposed. The accuracy of this model<br />

is verified on the example of the power MESFET transistor<br />

CRF24010F and the Schottky diode SDP10S30. A good agreement<br />

between the measurements and the calculations with<br />

the use of the new model in the wide range of changes of the<br />

device dissipated power and for various conditions of theirs<br />

cooling is achieved.<br />

<strong>Elektronika</strong> 11/<strong>2010</strong> 11

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