IR2214 IRF [International Rectifier], IR2214 Datasheet - Page 21

• Manufacturer Part Number: IR2214
• Description: HALF-BRIDGE GATE DRIVER IC
• Manufacturer: IRF [International Rectifier]

Bootstrap supply
The V
side driver circuitry of the IR2214. This supply
sits on top of the V
floating.
The bootstrap method to generate V
can be used with IR2214. The bootstrap supply
is formed by a diode and a capacitor connected
as in figure 19.
This method has the advantage of being simple
and low cost but may force some limitations on
duty-cycle and on-time since they are limited by
the requirement to refresh the charge in the boot-
strap capacitor.
Proper capacitor choice can reduce drastically
these limitations.
Bootstrap capacitor sizing
To size the bootstrap capacitor, the first step is
to establish the minimum voltage drop ( V
that we have to guarantee when the high side
IGBT is on.
www.irf.com
V
CC
Figure 19: bootstrap supply schematic
BS
VCC
voltage provides the supply to the high
bootstrap
resistor
R
boot
SSDH
HOP
HON
VB
VS
bootstrap
Sizing tips
diode
V
V
BS
F
S
voltage and so it must be
bootstrap
capacitor
V
ADVANCE DATA
CEon
V
GE
COM
DC+
BS
I
LOAD
supply
V
FP
motor
BS
)
If V
want to maintain, the voltage drop must be:
under the condition:
where V
strap diode forward voltage, V
lector voltage of low side IGBT and V
high-side supply undervoltage negative going
threshold.
Now we must consider the influencing factors
contributing V
I
capacitor and can be ignored if other types of
capacitors are used. It is strongly recommend
using at least one low ESR ceramic capacitor
(paralleling electrolytic and low ESR ceramic
may result in an efficient solution).
Then we have:
LK_CAP
Q
TOT
GEmin
I
- IGBT turn on required Gate charge (Q
- IGBT gate-source leakage current (I
- Floating section quiescent current (I
- Floating section leakage current (I
- Bootstrap diode leakage current (I
- Desat diode bias when on (I
- Charge required by the internal level shifters
- Bootstrap capacitor leakage current (I
- High side on time (T
LK
is only relevant when using an electrolytic
V
is the minimum gate emitter voltage we
(Q
CC
IR2214/IR22141(SS)
Q
BS
I
G
LS
is the IC voltage supply, V
LK
); typical 20nC
_
V
V
BS
DIODE
Q
GE
CC
to decrease:
LS
min
V
(
F
I
I
V
LK
LK
BSUV
V
HON
_
_
GE
GE
CAP
).
min
CEon
I
QBS
DS-
I
is emitter-col-
DS
V
)
CEon
BSUV-
F
)
LK_DIODE
LK
is boot-
T
LK_CAP
LK_GE
)
QBS
is the
HON
G
);
);
21
);
);
);