<Dual-In-Line Package Intelligent Power Module>
1200V Mini DIPIPM with BSD Series APPLICATION NOTE
Publication Date: September 2015
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3.2 Power Loss and Thermal Dissipation Calculation
3.2.1 Power Loss Calculation
Simple expressions for calculating average power loss are given below:
●
Scope
The power loss calculation intends to provide users a way of selecting a matched power device for their
VVVF inverter application. However, it is not expected to use for limit thermal dissipation design.
●
Assumptions
(1) PWM controlled VVVF inverter with sinusoidal output;
(2) PWM signals are generated by the comparison of sine waveform and triangular waveform.
(3) Duty amplitude of PWM signals varies between
2
1
2
1
D
D
～
(%/100), (D: modulation depth).
(4) Output current various with Icp
·
sinx and it does not include ripple.
(5) Power factor of load output current is cos
, ideal inductive load is used for switching.
●
Expressions Derivation
PWM signal duty is a function of phase angle
x
as
2
x
sin
D
1
which is equivalent to the output voltage
variation. From the power factor cos
, the output current and its corresponding PWM duty at any phase
angle
x
can be obtained as below:
2
)
sin(
1
sin
x
D
Duty
PWM
x
Icp
current
Output
Then, V
CE(sat)
and V
EC
at the phase
x
can be calculated by using a linear approximation:
)
sin
)(@
(
)
(
x
Icp
sat
Vce
sat
Vce
)
sin
)
(
(@
)
1
(
x
Icp
Iecp
Vec
Vec
Thus, the static loss of IGBT is given by:
dx
x
D
x
Icp
sat
Vce
x
Icp
2
)
sin(
1
)
sin
)(@
(
)
sin
(
2
1
0
Similarly, the static loss of free-wheeling diode is given by:
2
2
)
sin(
1
)
sin
(@
)
1
)((
sin
)
1
((
2
1
dx
x
D
x
Icp
Vec
x
Icp
On the other hand, the dynamic loss of IGBT, which does not depend on PWM duty, is given by:
dx
fc
x
Icp
off
Psw
x
Icp
on
Psw
0
))
sin
)(@
(
)
sin
)(@
(
(
2
1
