23/39

AN1625 APPLICATION NOTE

Figure 24. Power Dissipation formulae and results.

Result

PowerDMOS

Commutation Time

Tcom = 9.60E-08

[s]

Vs / (250V/

µs)

Electrical frequency

Fel = 1.67E+02 [Hz]

n*sp/60

Rise Time

Trise =

5.65E-5

[s]

Fall Time

Tfall = 5.13E-05

[s]

Duty Cycle

D = 6.08E-01

-

Vb+I(2*Ron+Rm))/(Vs -I*Rs)

Switching

Frequency

fSW = 4.90E+04 [Hz]

(1-D) / tOFF

Current Ripple

∆I = 3.19E-01 [A]

2.1*((2Ron+Rm)*Ipk+Vb)*toff/Lm

Period

T = 6.00E-03

[s]

1 / fel

Load Time

Tload = 5.66E-03

[s]

T-6Trise

Average Current

during Load

Time

I = 1.34E+00

[A]

r.m.s. Current

during Load

Time

Irms = 1.34E+00

[A]

Rise Time

Dissipating

power

Prise = 1.58E-02

[W]

Fall Time

Dissipating

power

Pfall = 3.00E-02

[W]

Load Time

Diss. Power

Pload = 1.91E-00

[W]

Commutation

Dissipating Pw

Pcom = 2.86E-01

[W]

(2Vs · I · Tcom · Tload · fSW) / T

Quiescent

Dissipating Pw

Pq = 1.32E-01

[W]

Vs · Iq

Total Dissipat-

ing Power

P = 2.37E+00

[W]

Pq + Pcom + Pload + Pfall + Prise

Ipk Rm

2 2Ipk Ron

Ipk R s

V s

+

⋅

–

⋅

⋅

–

⋅

–

()

Vs

-------------------------------------------------------------------------------------------------------------------

Lm

Rm

Rs

2Ron

++

----------------------------------------------

⋅

ln

–

Vs

2 Vd

⋅

–

Ipk Rm

Ipk

+

Rs

Vs

2 Vd

⋅

()

–

+

⋅⋅

()

------------------------------------------------------------------------------------------------

Lm

Rm

Rs

+

()

----------------------------

⋅

ln

–

Ipk

∆I

2

-----

–

Ipk

Ipk

I

∆

–

()

I

2

∆

3

--------

+

⋅

2Ron Ipk

2

Trise

3

---------------

⋅⋅



 2

T

---

⋅

2

T

--- 2 V d Tfall

Vs

–

2Vd

⋅

+

()

Rm

Rs

+

()

--------------------------------------

Lm

Ipk Rm

Ipk Rs

Vs

2 Vd

⋅

–

+

⋅

+

⋅

()

⋅

1

T

– fall

Lm

----------------

Rm

Rs

+

()

⋅

exp

–

Rm

Rs

+

()

2

---------------------------------------------------------------------------------

⋅

+

⋅

⋅⋅