MSK4803 M. S Kennedy, MSK4803 Datasheet - Page 3

• Manufacturer Part Number: MSK4803
• Description: 600v/600a Half Bridge Pem
• Manufacturer: M. S Kennedy

THERMAL CALCULATIONS
P W M dut y c y cle and s w itching frequenc y all factor into po w er dissipation. D C losses or " O N-TIM E " losses are simply
duty cycle of 3 0 % , D C losses equal 5 2 2 w atts. S w itching losses vary proportionally w ith s w itching frequency. The M SK
4 8 0 3 t ypical s w itching losses at V
s w itching loss and the turn-off s w itching loss. Multiplying the s w itching frequency times the s w itching losses w ill result in
a po w er dissipation number for s w itching. The MSK 4 8 0 3, at 5 KHz, w ill exhibit s w itching po w er dissipation of 3 9 0 w atts.
The total losses are the sum of D C losses plus s w itching losses, or in this case, 9 1 2 w atts total.
Subtracting 6 4 ° C from the ma ximum junction temperature of 1 5 0 ° C equals 8 6 ° C ma ximum case temperature for this
example.
V
CE
9 1 2 w atts x 0 . 0 7 ° C / W thermal resistance equals 6 4 degrees of temperature rise bet w een the case and the junction.
Po w er dissipation and maximum allo w able temperature rise involve many variables w orking together. Collector current,
V
Turn-on s w itching loss + Turn-off s w itching loss = Total s w itching losses = 1 7.5 + 6 0 = 7 7.5 mJ
Total s w itching loss x PW M frequency = Total s w itching po w er dissipation = 7 8 mJ x 5 K Hz = 3 9 0 w atts
Total po w er dissipation = D C losses + s w itching losses = 5 2 2 + 3 9 0 = 9 1 2 w atts
Junction temperature rise above case = Total po w er dissipation x thermal resistance
M aximum junction temperature - junction temperature rise = maximum baseplate temperature
APPLICATION NOTES
(S A T) x Collector Current x PW M duty cycle. For the MSK 4 8 0 3, V
C E
1 5 0 ° C - 6 4 ° C = 8 6 ° C
9 1 2 w atts x 0 . 0 7 ° C / W = 6 3 . 8 ° C temperature rise abov e case
(S A T) x IC x P W M dut y c y cle = 2 . 9 V x 6 0 0 amps x 3 0 % = 5 2 2 w atts D C losses
C E
= 3 0 0 V and I
C E
= 6 0 0 A are about 7 8 m J, w hich is simply the sum of the turn-on
3
C E
(S A T) = 2.9 V max., and at 6 0 0 amps and a PW M
Re v. -
1 1/0 9