Specifications

25
Dec. 20
Mitsubishi IPM-series Application Note
The inside of the control input terminal is connected to the comparator and is with high impedance.
When IPM (IGBT) is turn-off , the output impedance of the photo-coupler becomes high. Total impedance of the
circuit which connect the interface circuit is equal to a resistance of about 20KΩ.
The most important consideration in interface circuit design is layout. Shielding and careful routing of printed
circuit wiring is necessary in order to avoid coupling of dv/dt noise into control circuits. Parasitic capacitance
between high side interface circuits, high and low side interface circuits, or primary and secondary sides of the
isolating devices can cause noise problems. Careful layout of control power supply and isolating circuit wiring is
necessary. In layout, it is important not to make wiring of the photo-coupler primary side and secondly side cross
each other. Also, pattern should be made shortest and not to be crowded around and the magnetic field make the
inside of the current-loop not cross. Place condenser with good frequency response between the power - GND of
the photo coupler.
Depending on the pattern layout, sometimes a ringing as shown below occurs. In this case, the output current
of the photo-coupler doesn't change so much than the corrugation at normal.
However, the ringing problem increases the IPM switching loss, results possibly the IPM heat destruction. It is
necessary to check in design.
㩷
Off On On
Off
threshold voltage
The extraordinary oscillation
㩷
㩷
㩷
㩷
Control input terminal
Vcin
(secondary-side of
photo-coupler)
5V/div㩷
㩷
㩷
㪦㫌㫋㫇㫌㫋㩷㫍㫆㫃㫋㪸㪾㪼㩷㫆㪽㩷㪠㪧㪤㩷
㪭㪚㪜㩷
㩷 㩷 㩷 㪈㪇㪇㪭㪆㪻㫀㫍㩷
㩷
㫋㫀㫄㪼㩷㪑㩷㪈㫌㫊㪆㪻㫀㫍㩷
㪝㫀㪾㪅㪐㪅㪈㩷㪫㪿㪼㩷㪼㫏㪸㫄㫇㫃㪼㩷㫆㪽㩷㫋㪿㪼㩷㫆㫊㪺㫀㫃㫃㪸㫋㫀㫆㫅㩷㫎㪸㫍㪼㪽㫆㫉㫄㩷㪘㩷㫆㪽㩷㫋㪿㪼㩷㫇㪿㫆㫋㫆㪄㪺㫆㫌㫇㫃㪼㫉㩷
㩷
In the following example, the oscillation happens at the timing of both after on and off. When the oscillation after
turn off continues over the dead time, it falls in the period when the opposite arm becomes on then cause an arm
short failure. The protection circuit works and IPM outputs Fo. This phenomenon sometimes happens under the
condition of no-load. It is easily confused with the malfunction on the side of IPM and the cause investigation takes
time. As a countermeasure, reducing the power supply impedance of the photo-coupler and the photo-coupler use
by IPM compatible is effective.
㩷
㩷
Control input terminal
Vcin
(secondary-side of
photo-coupler)
5V/div
time : 10us/div㩷
㩷
㪝㫀㪾㪅㪐㪅㪉㩷㪫㪿㪼㩷㪼㫏㪸㫄㫇㫃㪼㩷㫆㪽㩷㫋㪿㪼㩷㫆㫊㪺㫀㫃㫃㪸㫋㫀㫆㫅㩷㫎㪸㫍㪼㪽㫆㫉㫄㩷㪙㩷㫆㪽㩷㫋㪿㪼㩷㫇㪿㫆㫋㫆㪄㪺㫆㫌㫇㫃㪼㫉㩷
Threshold voltage
Using IPM