MT6M15962a
© Fuji Electric Co., Ltd. All rights reserved.
4-8
Fig.4-5 IPM input circuit and constant current operation timing
2.10 Snubber
Directly connect a snubber circuit to the P/N terminals as close as possible. For P631 package which
has two P/N terminals, it is effective to connect snubber circuits to both P1-N1 and P2-N2 terminals to
reduce surge voltage. Do not connect snubber circuits across the two terminals such as P1-N2 and P2-
N1 as it may cause a malfunction.
2.11 Grounding capacitor
Connect grounding capacitors between each AC input line and its ground to prevent noise from
flowing in the system.
.
2.12 Input circuit of IPM
There are constant current circuits in the input circuit of IPMs as shown in Figure 4-5(a).
The constant current of
l
in
= 0.15 mA or
l
in
= 0.65 mA flows at that timing shown in Figure 4-5(b).
The current of the secondary side of optocoupler is the sum of the constant current
l
in
and the current
through a pull-up resistor
I
R
. Therefore, it is necessary to determine the current of the primary side of
optocoupler
I
F
so that sufficient current can flow in the secondary side of optocoupler. If
I
F
is insufficient,
the secondary side may a malfunction.
* The operating time of the constant current circuit (0.65 mA) is the period until
V
in
reaches
V
CC
.
It is about 5
μs at maximum.
(b) constant current operation timing
(a) IPM input circuit
