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15
PIIPM25P12B008
I27147 01/03
phase short circuits. The only failure not covered
in this way is the shoot-through, where high
current levels cannot be detected from outside the
module rather internally between two IGBTs of
the same leg. In this case the protection is
implemented by means of the fourth sensing
element, with the same resistive value of the
other shunts present in the power module,
inserted in series to the DC bus minus. The
related dropout voltage is then filtered by a
15kHz passive filter to avoid false fault
detections due to unwanted induced voltage
spikes and finally applied to an operational
amplifier configured as a comparator. All data
referred to the OC protection are listed on page 9
of this datasheet.
4. Gate Drivers
Devices used to perform this task are the well-
known IR2213, capable of 2A sink and 2A
source maximum gate driving current, in a
SO16W package; on page 2 is shown also the
block schematic of the gate driving section of the
module.
The IGBTs used in the PI-IPM (genV NPT
1200V - 25A from IR) do not need any negative
gate drive voltage for their complete turn off, this
simplifies the flyback power supply design
avoiding the need of center tapped transformer
outputs or the use of zener diodes to create the
central common reference for the gate drivers
floating ground. Though the IR2213 do have +/-
2A of gate current capability, in the PI-
IPM25P12B008 we use different gate resistor
values for turn on and turn off as follows:
=
ohm
off
turn
ohm
22
on
turn
68
=
Commonly realized through a diode-resistor
series in parallel with a single resistor used in
turn on only. Observed rise and fall times are
around 250ns – 300ns depending on the output
current level, this values are considered as pretty
adequate for a 12.5A application at 16kHz
symmetric
PWM
carrier,
modulation.
space
vector
These gate drivers do provide levels shifting
without any galvanic isolation, that is no opto-
couplers are built inside. This turns out to be a
major benefit in this stage where the usual 1
μ
s
delay of optos impacts on the system control as a
systematic and fastidious delay.
5. DC bus and Input voltage feedback
The purpose of this block is to continuously
check the voltage of the two supply lines of the
system: Vin and DC bus. Vin is the only external
power supply needed for all electronics in the
EDB. The internal flyback regulator has its own
under-voltage lockout to prevent all electronics
from start working when an insufficient supply
voltage is present; minimum recommended
supply voltage is 12V. Low side gate drivers are
directly fed from the Vin line and there is no
further control to this voltage than their own
under-voltage lockout. This is typically set at
8.5V and this level could be not sufficient to
properly drive the IGBT gates, then it is
advisable to check with the DSP the input voltage
and impose that the system could start switching
only when the Vin voltage is between 10V and
18V thus providing also an over-voltage control.
The DC bus voltage is also important for the
system functioning and needs to be continuously
kept under control. A resistor divider provides a
partition coefficient of 2.44mV/V and a
maximum mapped voltage of around 1100V
As the block schematic shows, it has to be taken
into account that, to avoid false detections due to
voltage spikes inevitably present on the
partitioned voltage, a 1kHz passive filter has
been inserted between the divider and the voltage
follower buffer whose output is connected to one
of the ADC inputs.