SIM689XM datasheet(31/55 Pages) SANKEN

31 / 55 page

SIM689xM Series

SIM689xM-DSE Rev.3.4

SANKEN ELECTRIC CO., LTD.

Mar. 05, 2024

https://www.sanken-ele.co.jp/en

14.1.3

Estimating Junction Temperature

of IGBT

The junction temperature of all IGBTs operating, TJ,

can be estimated with Equation (6):

TJ = R(J−C)Q × {(PON + PSW) × 6} + TC .

(6)

Where:

R(J-C)Q is the junction-to-case thermal resistance

(°C/W) of all the IGBTs operating, and

TC is the case temperature (°C), measured at the point

defined in Figure 3-1.

14.2 Power MOSFET

Total power loss in a power MOSFET can be

obtained by taking the sum of the following losses:

steady-state loss, PRON; switching loss, PSW; the steady-

state loss of a body diode, PSD. In the calculation

procedure we offer, the recovery loss of a body diode,

PRR, is considered negligibly small compared with the

ratios of other losses.

The following subsections contain the mathematical

procedures to calculate these losses (PRON, PSW, and PSD)

and the junction temperature of all power MOSFETs

operating.

14.2.1

Power MOSFET Steady-state Loss,

PRON

Steady-state loss in a power MOSFET can be

computed by using the RDS(ON) vs. ID curves, listed in

Section 15.3.1. As expressed by the curves in Figure

14-2, a linear approximation at a range the ID is actually

used is obtained by: RDS(ON) = α × ID + β. The values

gained by the above calculation are then applied as

parameters in Equation (7), below. Hence, the equation

to obtain the power MOSFET steady-state loss, PRON, is:

PRON =

2π

∫ ID (φ)2 × RDS(ON)(φ) × DT × dφ

= 2√2α (

3π

M × cos θ) IM

+2β (

3π

M × cos θ) IM

2 .

(7)

Where:

ID is the drain current of the power MOSFET (A),

RDS(ON) is the drain-to-source on-resistance of the

power MOSFET (Ω),

DT is the duty cycle, which is given by

DT =

1 + M × sin(φ + θ)

M is the modulation index (0 to 1),

cosθ is the motor power factor (0 to 1),

IM is the effective motor current (A),

α is the slope of the linear approximation in the RDS(ON)

vs. ID curve, and

β is the intercept of the linear approximation in the

RDS(ON) vs. ID curve.

Figure 14-2.

Linear Approximate Equation of

RDS(ON) vs. ID

14.2.2

Power MOSFET Switching Loss,

PSW

Switching loss in a power MOSFET can be calculated

by Equation (8), letting IM be the effective current value

of the motor:

PSW =

√2

× fC × αE × IM ×

VDC

300

(8)

Where:

fC is the PWM carrier frequency (Hz),

VDC is the main power supply voltage (V), i.e., the

VBB pin input voltage, and

αE is the slope of the switching loss curve (see Section

14.2.2).

y = 0.56x + 3.7

0.0

1.0

2.0

3.0

4.0

5.0

6.0

0.0

0.5

1.0

1.5

2.0

2.5

D (A)

VCCx = 15 V

25°C

75°C

125°C

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