MT6M15962a
© Fuji Electric Co., Ltd. All rights reserved.
2.4 Protection functions
The IPM has protection circuits that protects the IPM from abnormal modes. The IPM has four types
of protection functions; OC (over current protection), SC (short circuit protection), UV(control power
supply under voltage protection) and
T
jOH
(IGBT chips over heating protection).
When a protective function is activated, the MOSFET for alarm output is turned on, the alarm output
signal voltage changes from High to Low, and the alarm output terminal conducts to GND.
Furthermore, since a
1.3kΩ resistance is connected in series between the control IC and the alarm
output terminal, an optocoupler that is connected between the ALM terminal and the
V
CC
terminal can
be directly driven.
Alarm signal output function
If the abnormal mode is detect, the IGBT is slowly turn-off. The alarm signal is output from the
phase in which abnormal mode is detected. During the protection period, the IGBT is not turned on
even if the control input signal is in ON-state.
• After the elapse of
t
ALM
, if the alarm factor has been resolved, and the control input signal is OFF-
state, the protection operation is reset and normal operation is resumed.
• Even if the alarm factor is resolved within the alarm signal output period (
t
ALM
), the protection
operation continues during the alarm signal output period (
t
ALM
), and the IGBT will not turn on. If
the control input signal is OFF-state after the alarm signal output period (
t
ALM
) has elapsed, the
protection operation is reset and normal operation is resumed.
• On the upper arm side, the IGBT of the phase that detected the abnormal mode shutdown softly
and stops operation.
• On the lower arm side, when each phase of the inverter section goes into protection, all IGBTs of
the lower arm except the brake IGBT shutdown softly and stop operation. The brake IGBT can be
operated. Also, in the event of an abnormality in the brake section, all IGBTs in the lower arm and
brake IGBT will shutdown softly and stop operation.
* P629 and P639 package have protection functions on both of the upper arm and the lower
arm devices, but the upper arm devices do not have an alarm signal output function. The lower
arm devices have both the protective functions and alarm signal output function.
Alarm factor identification function
As the alarm signal output period (
t
ALM
) varies in correspondence to the failure mode, the failure
mode can be identified by measuring the alarm signal pulse width.
However, the pulse width of the alarm signal output through an optocoupler varies depending on the
delay time of the optocoupler and the influence of peripheral circuits. It is necessary to take these
influences into account in your design.
Alarm factor
Alarm signal output period (
t
ALM
)
Over current protection(OC)
Short-circuit protection(SC)
2ms(typ)
Control power supply under voltage protection(UV)
4ms(typ)
Chip temperature overheat protection(
T
jOH
)
8ms(typ)
3-5
