ACPL-W456 Просмотр технического описания (PDF) - Avago Technologies
Номер в каталоге
Компоненты Описание
производитель
ACPL-W456 Datasheet PDF : 12 Pages
| |||
IPM Dead Time and Propagation Delay Specifications
The ACPL-P456/W456 includes a Propagation Delay
Difference specification intended to help designers
minimize “dead time” in their power inverter designs.
Dead time is the time period during which both the high
and low side power transistors (Q1 and Q2 in Figure 21)
are off. Any overlap in Q1 and Q2 conduction will result
in large currents flowing through the power devices
between the high and low voltage motor rails.
To minimize dead time the designer must consider
the propagation delay characteristics of the optocou-
pler as well as the characteristics of the IPM IGBT gate
drive circuit. Considering only the delay characteristics
of the optocoupler (the characteristics of the IPM IGBT
gate drive circuit can be analyzed in the same way) it is
important to know the minimum and maximum turn on
(tPHL) and turn-off (tPLH) propagation delay specifications,
preferably over the desired operating temperature range.
The limiting case of zero dead time occurs when the input
to Q1 turns off at the same time that the input to Q2 turns
on. This case determines the minimum delay between
LED1 turn-off and LED2 turn-on, which is related to the
worst case optocoupler propagation delay waveforms,
as shown in Figure 22. A minimum dead time of zero is
achieved in Figure 22 when the signal to turn on LED2
is delayed by (tPLH max - tPHL min) from the LED1 turn
off. Note that the propagation delays used to calculate
PDD are taken at equal temperatures since the optocou-
plers under consideration are typically mounted in close
proximity to each other. (Specifically, previous equation
are not the same as the tPLH max and tPHL min, over the
full operating temperature range, specified in the data
sheet.) This delay is the maximum value for the propaga-
tion delay difference specification which is specified at
450 ns for the ACPL-P456/W456 over an operating tem-
perature range of -40°C to 100°C.
Delaying the LED signal by the maximum propagation
delay difference ensures that the minimum dead time is
zero, but it does not tell a designer what the maximum
dead time will be. The maximum dead time occurs in
the highly unlikely case where one optocoupler with
the fastest tPLH and another with the slowest tPHL are in
the same inverter leg. The maximum dead time in this
case becomes the sum of the spread in the tPLH and tPHL
propagation delays as shown in Figure 23. The maximum
dead time is also equivalent to the difference between
the maximum and minimum propagation delay differ-
ence specifications. The maximum dead time (due to the
optocouplers) for the ACPL-P456/W456 are 600 ns (= 450
ns - (-150 ns)) over an operating temperature range of -
40°C to 100°C.
IPM
ILED1
+5 V
1
2
310 Ω
3
CMOS
ILED2
+5 V
1
2
310 Ω
3
CMOS
SHIELD
SHIELD
6
0.1 μF
5
4
VCC1
20 kΩ VOUT1
6
0.1 μF
5
VCC2
20 kΩ VOUT2
4
ACPL-P/W456
ACPL-P/W456
ACPL-P/W456
ACPL-P/W456
ACPL-P/W456
+HV
M
-HV
Figure 21. Typical Application Circuit.
11
Share Link: 