TLE4729G datasheet(22/29 Pages) INFINEON

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TLE 4729 G

Data Sheet

V1.2, 2008-03-18

Calculation of Power Dissipation

The total power dissipation

Ptot is made up of

Saturation losses

Psat (transistor saturation voltage and diode forward voltages),

Quiescent losses

(quiescent current times supply voltage) and

Switching losses

(turn-ON / turn-OFF operations).

The following equations give the power dissipation for chopper operation without phase

reversal.

This is the worst case, because full current flows for the entire time and switching losses

occur in addition.

Ptot = 2 × Psat + Pq + 2 × Ps

where

Psat ≅ IN {VsatI × d + VFu (1 – d) + VsatuC × d + VsatuD (1 – d)}

Iq × VS

-------

DON

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

() t

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

-----

DOFF

OFF

()







≅

= Nominal current (mean value)

= Quiescent current

= Reverse current during turn-on delay

= Peak reverse current

= Conducting time of chopper transistor

tON

= Turn-ON time

tOFF = Turn-OFF time

tDON = Turn-ON delay

tDOFF = Turn-OFF delay

= Cycle duration

= Duty cycle

tp / T

Vsatl = Saturation voltage of sink transistor (TX3, TX4)

VsatuC= Saturation voltage of source transistor (TX1, TX2) during charge cycle

VsatuD= Saturation voltage of source transistor (TX1, TX2) during discharge cycle

VFu

= Forward voltage of free-wheeling diode (DX1, DX2)

= Supply voltage

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