TLE4726G Datasheet, PDF (19/23 Pages) Infineon Technologies AG – 2-Phase Stepper-Motor Driver

TLE 4726
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 (quiescent current times supply voltage) and
switching losses P_s (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.
P_tot = 2 × P_sat + P_q + 2 × P_s
where
P_sat ≅ I_N { V_satl × d + V_Fu (1 – d ) + V_satuC × d + V_satuD (1 – d ) }
P_q = I_q × V_S + I_L × V_L
P_S
≅
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
= 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
d
= duty cycle t_p/T
V_satl = saturation voltage of sink transistor (T3, T4)
V_satuC = saturation voltage of source transistor (T1, T2) during charge cycle
V_satuD = saturation voltage of source transistor (T1, T2) during discharge cycle
V_Fu = forward voltage of free-wheeling diode (D1, D2)
V_S = supply voltage
V_L = logic supply voltage
I_L = current from logic supply
Data Sheet
19
1999-09-15