IR21141SSPBF_09 IRF [International Rectifier], IR21141SSPBF_09 Datasheet - Page 17

• Manufacturer Part Number: IR21141SSPBF_09
• Description: HALF-BRIDGE GATE DRIVER IC
• Manufacturer: IRF [International Rectifier]

www.irf.com
2.1 Bootstrap Supply
The V
driver circuitry of the gate driver. This supply sits on top
of the V
bootstrap method is used to generate the V
and can be used with any of the IR211(4,41)/
IR221(4,41) drivers. The bootstrap supply is formed by
a diode and a capacitor as connected in Fig. 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 bootstrap capacitor. Proper
capacitor
limitations.
2.2 Bootstrap Capacitor Sizing
To size the bootstrap capacitor, the first step is to
establish the minimum voltage drop ( ∆V
have to guarantee when the high side IGBT is on.
If V
to maintain, the voltage drop must be:
under the condition,
where V
diode forward voltage, V
of low side IGBT, and V
undervoltage negative going threshold.
Now
contributing V
V
CC
GEmin
− 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
Figure 19: Bootstrap Supply Schematic
BS
we must
CC
∆
S
is the minimum gate emitter voltage we want
voltage provides the supply to the high side
VCC
V
bootstrap
resistor
voltage and so it must be floating. The
R
choice
is the IC voltage supply, V
boot
BS
BS
≤
SSDH
to decrease:
HOP
HON
VB
VS
2 Sizing Tips
V
V
bootstrap
consider
CC
diode
V
V
GE
BS
can
F
−
min
BSUV-
CEon
V
F
>
bootstrap
capacitor
reduce
is emitter-collector voltage
−
is the high-side supply
V
the
V
BSUV
GE
DS
min
−
influencing
),
drastically
V
CEon
−
V
GE
LK
LK_DIODE
V
F
QBS
CEon
LK_GE
),
COM
DC+
is bootstrap
BS
G
),
),
) that we
BS
I
LOAD
),
),
V
FP
factors
supply
these
motor
17
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:
The minimum size of bootstrap capacitor is:
An example follows using IR2214SS or IR22141SS:
a) using a 25 A @ 125 ° C 1200 V IGBT
(IRGP30B120KD):
And:
the maximum voltage drop ∆V
And the bootstrap capacitor is:
NOTICE: V
IGBTs may require a higher supply to work correctly
with the bootstrap technique. Also V
must be accounted in the above formulas.
Q
∆
LK_CAP
V
TOT
• I
• I
• Q
• Q
• I
• I
• I
• I
• T
•
•
•
•
BS
− Charge required by the internal level shifters
− Bootstrap capacitor leakage current ( I
− High side on time ( T
QBS
LK
LK_GE
LK_DIODE
LK_CAP
DS-
HON
LS
G
( Q
=
≤
= 50 µA
+
V
V
V
V
is only relevant when using an electrolytic
= 160 nC
= 150 µA (see Static Electrical Characteristics);
Q
V
= 20 nC
LS
= 800 µA
CC
F
CEonmax
GEmin
I
= 100 µs.
CC
G
= 100 nA
); typical 20 nC,
= 1 V
LK
= 0
CC
= 15 V
+
= 100 µA
C
−
+
= 10.5 V
Q
has been chosen to be 15 V. Some
IR21141/IR22141SSPbF
V
BOOT
= 3.1 V
I
LS
F
C
(see Static Electrical Characteristics);
LK
−
BOOT
+
_
V
≥
(neglected for ceramic capacitor);
DIODE
(
GE
I
290
LK
min
0
min
4 .
(datasheet IRGP30B120KD);
(datasheet IRGP30B120KD);
HON
_
(reverse recovery <100 ns);
GE
+
−
=
nC
V
© 2009 International Rectifier
).
BS
I
V
+
∆
Q
LK
CEon
becomes
V
=
I
TOT
_
QBS
BS
(datasheet IR2214);
CAP
725
=
+
CC
+
nF
I
variations
DS
LK_CAP
−
)
⋅
T
),
HON