TLE4728G Datasheet, PDF (21/25 Pages) Infineon Technologies AG – 2-Phase Stepper-Motor Driver

TLE 4728 G
Calculation of Power Dissipation
The total power dissipation P_tot is made up of
saturation losses P_sat
(transistor saturation voltage and diode forward
voltages),
quiescent losses P_q
switching losses P_s
(quiescent current times supply voltage) and
(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.
where
P_tot = 2 × P_sat + P_q + 2 × P_s
P_sat ≅ I_N { V_satI × d + V_Fu (1 – d ) + V_satuC × d + V_satuD ( 1 – d ) }
P_q = I_q × V_S
P_q
≅
V_-----S-
T



i_--D-----×_----t_{--D----O---N-}
2
+
-⁽--ⁱ--^D----+-----ⁱ--^R---⁾---^×-----^t--^O----^N-
4
+
I_---N-
2
(
t_DOFF
+
t_OFF)



I_N
I_q
i_D
i_R
t_p
t_ON
t_OFF
t_DON
t_DOFF
T
d
V_satl
V_satuC
V_satuD
V_Fu
V_S
= nominal current (mean value)
= quiescent current
= reverse current during turn-on delay
= peak reverse current
= conducting time of chopper transistor
= turn-ON time
= turn-OFF time
= turn-ON delay
= turn-OFF delay
= cycle duration
= duty cycle t_p / T
= saturation voltage of sink transistor (TX3, TX4)
= saturation voltage of source transistor (TX1, TX2) during charge cycle
= saturation voltage of source transistor (TX1, TX2) during discharge cycle
= forward voltage of free-wheeling diode (DX1, DX2)
= supply voltage
Data Sheet
21
2004-03-01