Initial Charging In Bootstrap Circuit - Mitsubishi Electric PSSxxMC1Fx Manual

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DIPIPM+ Series Application note
Table 4-3-2 Electric characteristics of built-in bootstrap diode
Item
Bootstrap Di forward voltage
Built-in limiting resistance

4.4 Initial charging in bootstrap circuit

In case of applying bootstrap circuit, it is necessary to charge to the BSC initially because voltage of BSC is 0V
at initial state or it may drop down to the trip level of under voltage protection after long suspending period (even
1s). BSC charging is performed by turning on all N-side IGBT normally. When outer load (e.g. motor) is connected
to the DIPIPM, BSC charging may be performed by turning on only one phase N-side IGBT since potential of all
output terminals will go down to GND level through the wiring in the motor. But its charging efficiency might
become lower due to some cause. (e.g. wiring resistance of motor)
There are mainly two procedures for BSC charging. One is performed by one long pulse, and another is
conducted by multiple short pulses. Multi pulse method is used when there are some restriction like control supply
capability and etc.
BSD
VFB
V
P1
V
PC
VFS
HVIC
15V V
N1
V
NC
LVIC
Fig.4-4-1 Initial charging root
Initial charging needs to be performed until voltage of BSC exceeds 13V, recommended minimum supply
voltage. (It is recommended to charge higher than 13V with consideration for voltage drop from the end of
charging to start time of inverter operation.)
After BSC was charged, it is recommended to input one ON pulse to the P-side input for reset of internal IC
state before starting system. Input pulse width is needed to be longer than allowable minimum input pulse width
PWIN(on). (1.5μs or more for DIPIPM+. Please refer the datasheet for each product in detail.)
Publication Date: September 2016
Symbol
I =10mA including voltage drop
F
V
F
R
P(Vcc)
P-side
IGBT
+
V
DB
U,V,W
N-side
IGBT N-side
FWDi
ON
N(GND)
Condition
by limiting resistor
Included in bootstrap Di
15V
V
D
0V
N-side
input
0V
Charge
current
0
Voltage of
BSC V
DB
0
Fig .4-4-2 Example of waveform by one charging pulse
52
Min. Typ. Max.
－
0.9 1.3
16 20 24
Unit
V
Ω