參數(shù)資料
型號： HCPL-M454
英文描述： Ultra High CMR, Small Outline,5 Lead, High Speed Optocoupler(超高CMR，小型，5引線，高速光耦合器)
中文描述： 超高CMR，小外形，5鉛，高速光耦（超高公路貨運，小型，5引線，高速光耦合器）
文件頁數(shù)： 10/12頁
文件大?。?/td> 272K
代理商： HCPL-M454
10
Power Inverter Dead
Time and Propagation
Delay Specifications
The HCPL-M454 includes a
specification intended to help
designers minimize “dead time” in
their power inverter designs. The
new “propagation delay
difference” specification (t
PLH
-
t
PHL
) is useful for determining not
only how much optocoupler
switching delay is needed to
prevent “shoot-through” current,
but also for determining the best
achievable wort-case dead time
for a given design.
When inverter power transistors
switch (Q1 and Q2 in Figure 15),
it is essential that they never
conduct at the same time.
Extremely large currents will flow
if there is any overlap in their
conduction during switching
transitions, potentially damaging
the transistor and even the
surrounding circuitry. This
“shoot-through” current is
eliminated by delaying the turn-on
of one transistor (Q2) long
enough to ensure that the
opposing transistor (Q1) has
completely turned off. This delay
introduces a small amount of
“dead time” at the output of the
inverter during which both
transistors are off during
switching transitions. Minimizing
this dead time is an important
design goal for an inverter
designer.
The amount of turn-on delay
needed depends on the propa-
gation delay characteristics of the
optocoupler, as well as the
characteristics of the transistor
base/gate drive circuit. Consider-
ing only the delay characteristics
of the optocoupler (the
characteristics of the base/gate
drive circuit can be analyzed in
the same way), it is important to
know the minimum and maximum
turn-on (t
PHL
) and turn-off (t
PLH
)
propagation delay specifications,
preferably over the desired
operating temperature range. The
importance of these specifications
is illustrated in Figure 16. The
waveforms labeled “LED1”,
“LED2”, “OUT1”, and “OUT2” are
the input and output voltages of
the optocoupler circuits driving
Q1 and Q2 respectively. Most
inverters are designed such that
the power transistor turns on
when the optocoupler LED turns
on; this ensures that both power
transistors will be off in the event
of a power loss in the control
circuit. Inverters can also be
designed such that the power
transistor turns off when the
optocoupler LED turns on; this
type of design, however, requires
additional fail-safe circuitry to
turn off the power transistor if an
over-current condition is
detected. The timing illustrated in
Figure 16 assumes that the power
transistor turns on when the
optocoupler LED turns on.
The LED signal to turn on Q2
should be delayed enough so that
an optocoupler with the very
fastest turn-on propagation delay
(t
PHLmin
) will never turn on before
an optocoupler with the very
slowest turn-off propagation delay
(t
PLHmax
) turns off. To ensure this,
the turn-on of the optocoupler
should be delayed by an amount
no less than (t
PLHmax
- t
PHLmin
),
which also happens to be the
maximum data sheet value for the
propagation delay difference
specification, (t
PLH
- t
PHL
). The
HCPL-M454 specifies a maximum
(t
PLH
- t
PHL
) of 1.3
μ
s over an
operating temperature range of 0-
70
°
C.
Although (t
PLH
- t
PHL
)
max
tells the
designer how much delay is
needed to prevent shoot-through
current, it is insufficient to tell the
designer how much dead time a
design will have. Assuming that
the optocoupler turn-on delay is
exactly equal to (t
PLH
- t
PHL
)
max
,
the minimum dead time is zero
(i.e., there is zero time between
the turn-off of the very slowest
optocoupler and the turn-on of
the very fastest optocoupler).
Calculating the maximum dead
time is slightly more complicated.
Assuming that the LED turn-on
delay is still exactly equal to (t
PLH
- t
PHL
)
max
, it can be seen in Figure
16 that the maximum dead time is
the sum of the maximum
difference in turn-on delay plus
the maximum difference in turn-
off delay,
[(t
PLHmax
-t
PLHmin
) + (t
PHLmax
-
t
PHLmin
)],
This expression can be
rearranged to obtain
[(t
PLHmax
-t
PHLmin
) - (t
PHLmin
-
t
PHLmax
)],
and further rearranged to obtain
[(t
PLH
-t
PHL
)
max
- (t
PLH
-t
PHL
)
min
],
which is the maximum minus the
minimum data sheet values of
(t
PLH
- t
PHL
). The difference
between the maximum and
minimum values depends directly
on the total spread of
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參數(shù)描述
HCPL-M454#500 功能描述:高速光耦合器 1MBd 3750Vdc RoHS:否 制造商:Avago Technologies 電流傳遞比: 最大波特率: 最大正向二極管電壓:1.75 V 最大反向二極管電壓:5 V 最大功率耗散:40 mW 最大工作溫度:+125 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-5 封裝:Tube
HCPL-M454-000E 功能描述:高速光耦合器 1MBd 3750Vdc RoHS:否 制造商:Avago Technologies 電流傳遞比: 最大波特率: 最大正向二極管電壓:1.75 V 最大反向二極管電壓:5 V 最大功率耗散:40 mW 最大工作溫度:+125 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-5 封裝:Tube
HCPL-M454-500E 功能描述:高速光耦合器 1MBd 3750Vdc RoHS:否 制造商:Avago Technologies 電流傳遞比: 最大波特率: 最大正向二極管電壓:1.75 V 最大反向二極管電壓:5 V 最大功率耗散:40 mW 最大工作溫度:+125 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-5 封裝:Tube
HCPL-M454-560 功能描述:高速光耦合器 1MBd 3750Vdc RoHS:否 制造商:Avago Technologies 電流傳遞比: 最大波特率: 最大正向二極管電壓:1.75 V 最大反向二極管電壓:5 V 最大功率耗散:40 mW 最大工作溫度:+125 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-5 封裝:Tube
HCPL-M454-560E 功能描述:高速光耦合器 1MBd 3750Vdc RoHS:否 制造商:Avago Technologies 電流傳遞比: 最大波特率: 最大正向二極管電壓:1.75 V 最大反向二極管電壓:5 V 最大功率耗散:40 mW 最大工作溫度:+125 C 最小工作溫度:- 40 C 封裝 / 箱體:SOIC-5 封裝:Tube
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