NGTG12N60TF1G Application Note

NGTG12N60TF1G
Application Note
How to Use IGBT
http://onsemi.com
(Application in part switching PFC circuit)
1. Beginning
IGBT is the abbreviation for Insulated Gate Bipolar Transistor, which operates like MOSFET, applying voltage
between gate and emitter and controlling collector-emitter current. The table below summarized the similarities
and differences in structure and operation compared with Power MOSFET.
The point is, in comparatively high voltage (V>400V) and large current application, IGBT has a less conduction
loss because of its low RDS(on). By contrast, in small current area, its conduction loss may be higher than
MOSFET because it has PN junction on collector structurally, which results in a forward voltage(VF) of the
diode. Furthermore, in high-frequency application, switching loss of IGBT will be higher than that of MOSFET
because when switching off, the accumulated carries injected from collector’s P layer into N layer do not cease
to exist immediately and subsequently tf tailing occurs. Therefore, IGBT is recommended to be used in
comparatively low frequency (30kHz).
IGBT
*Voltage
Assume ≥400V
MOSFET
E
G
G
N+
N+
P
P
e
e: electronic current
h: hole current
S
N‐
e
N‐
h
P+
N+
D
C
P layer is formed on collector,
because of the holes injected
from this P layer (conductivity
modulation), ON resistance is
reduced.
For all the paths current flows, if you
want to increase N-type voltage, you
will have to increase N-layer
resistance. High-volt. MOSFET has a
disadvantage in ON resistance
compared with IGBT.
Current controlling
method
Gate-emitter voltage, which is
applied to switch on C-E current.
8~15V is common.
Gate-source voltage, which is
applied to switch on D-S current.
10~15V is common.
Conduction loss
For high current, lower than
MOSFET
RDS(on) will also increase as you
increase the voltage
Switching loss
Will be higher than MOSFET due
to tf tailing
Recommended
frequency
30kHz or below
20~100kHz
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NGTG12N60TF1G
Application Note
2. How to see the specifications (especially the major items) and the design point
2-1) Absolute maximum rating
Take NGTG12N60TF1G as an example as shown in Table 1. The important items are explained as follows.
VCES: in this instance, the maximum voltage applicable to VCE is 600V. When using in L load switching, you
should pay attention to VCE voltage as to whether or not exceed the absolute maximum rating because of a
steep VCE increase that may occur due to the circuit floating inductance when input signal is OFF and the
occurrence of ringing voltage.
Ic: because Ic is subject to Tc, when Tc changes, Ic also changes (refer to *1). The higher the temperature rises,
the smaller the current that can be flowed. It is roughly considered that when the temperature rises by ∆75deg
the current will become half.
PD(Power Dissipation): because NGTG12N60TF1G is a full-molded TO-3P package, PD is calculated low
compared with TO-3PB. In case of NGTG12N60TF1G, PD is 54W. Compared with full-molded package, Ic
rating description of the backside metal package is large. But in actual use, because the backside is insulated
with heat sink or PCB, the actual PD of TO-3PB will be rarely different from that of TO3-PF, sometimes even
smaller.
Table 1
The Absolute Maximum Ratings (Example: NGTG12N60TF1G)
Absolute Maximum Ratings at Ta = 25C, Unless otherwise specified
Parameter
Collector to Emitter Voltage
Gate to Emitter Voltage
Symbol
Conditions
VCES
VGES
1
Collector Current (DC)
IC*
Collector Current (Pulse)
Allowable Power Dissipation
ICP
PD
Junction Temperature
Tj
Storage Temperature
Tstg
Limited by
Tjmax
@ Tc=25 C * 2
@ Tc=100 C * 2
y
Tjmax(Ref :ASO graph)
(
dissipation condition) * 2
Ratings
Unit
600
 20
V
V
24
A
12
A
88
54
A
W
150
- 55 to
+150
C
C
2-2) Electrical characteristics (Table 2)
Gate to Emitter cutoff voltage-VGE(off): in order to prevent malfunctions due to noises, VGE(off) should be
lower than minimum value at the time of OFF. Because the temperature-dependency is negative, special
attention should be paid to the OFF voltage at high temperature. On the other hand, when flowing Ic,
VGE=15V±1V is recommended in order to obtain low enough VCE(sat). Sometimes, the Gate is put in minus
potential in order to speed turn-off, but the absolute maximum rating of VGE is ±20V. So, this range should be
used for design.
Collector to Emitter voltage- VCE(sat): very important when comparing devices. Ic rating varies according to
package, but VCE(sat) depends on the chip’s characteristic. So, VCE(sat) does not change even if the
package is different (When temperature is the same). Therefore, VCE(sat) is especially useful to evaluate
IGBT’s conduction loss. Temperature-dependency of VCE(sat) is positive when Ic flows sufficiently, it is
necessary to pay attention to heat dissipation design.
2/10
NGTG12N60TF1G
Table 2
Application Note
Electrical Characteristics (major items)
Electrical Characteristics at Ta = 25C, Unless otherwise specified
Ratings
Parameter
Collector to Emitter Breakdown
Voltage
Symbol
Conditions
V(BR)CES IC=500A, VGE=0V
Tc=25C
VCE=600V
Collector to Emitter Cut off Current ICES
, VGE=0V
Gate to Emitter Leakage Current
IGES
VGE= 20V, VCE =0V
Gate to Emitter Threshold Voltage
min
typ
600
V
10
A
1
mA
 100
nA
Tc=125C
VGE(th)
VCE =20V, IC=250A
Collector to Emitter Saturation
Voltage
Input Capacitance
VCE (sat)
VGE=15V,
IC=12A
Output Capacitance
Coes
Reverse Transfer Capacitance
Cres
Tc=25C
Tc=125C
Cies
VCE =20V,f=1MHz
Unit
max
4.5
1.4
1.6
6.5
V
1.6
V
V
2000
pF
60
pF
50
pF
Input capacitance Cies: when turning on/off gate-emitter, this capacitance will influence in case switching time
and/or Eon/Eoff is made smaller. The smaller they are, the faster the switching speed tends to be. Depending
on the value of Cies, in order to make Eon/Eoff smaller, the output of drive IC is not added directly to the gate of
IGBT, instead a Buffer Tr is used sometimes. In this way, an interface circuit of the gate becomes important in
order to drive IGBT efficiently.
Next, we will introduce the optimal driving method in consideration of making IGBT’s Eon/Eoff smaller.
3. IGBT’s gate drive characteristic
As shown in below fig.2, taking NGTG12N60TF1G’s Rg (Gate Resistance) as X-axis, switching loss
(measured at IGBT’s L load: fig.1) is positively correlated with Rg (fig.2). If you put weight on reducing
switching loss, you should select a small Rg preferably in consideration of the impact of operation noise (47Ω
or below is recommended).
Additionally, when control IC output is insufficient, Buffer Tr needs to be added between control IC and the
IGBT. In that case, resistance in OFF direction can be made smaller than in ON direction for improving toff
performance.
Switching measurement circuit (basic circuit)
fig.1
Measuring circuit
fig.2
Switching loss (characteristic)
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NGTG12N60TF1G
fig.3
Circuit with an added Buffer
fig.4
Application Note
Comparison of Switching loss
Drive circuit design example:
Spec. of Buffer Tr and drive current:
IG=(VBB+|VEE|)/Rg(total)
For emitter-common, usually separate paths are set for
IGON and IGOFF (refer to fig.5),
so Rg is considered as R1 and R2 in parallel:
IGp‘= (15+5)/(22×4.7÷(22+4.7))=5.17A.
In this case, a buffer tr that meets Icp>5.2A is needed.
fig.5 Driving example
4. Losses calculation
Losses occur to IGBT when used in inverter circuit, switching circuit and etc. The losses are roughly divided
into ON loss and switching (turn-on/turn-off) loss. The sum of the two types is almost the total loss. Additionally,
a radiator is installed in order to achieve enough heat radiation in use.
4-1) Calculation of switching loss
Assume a basic switching waveform of continuous operation like in fig.6.
[IGBT]
ON loss: VCE(sat) is assumed constant during ON period.
PVCE(sat)=(Ic1 + Ic2) ÷ 2 × VCE(sat) × Ton/T
Regarding turn-on/turn-off, calculate by using the measured Eon & Eoff of each device at the value of Ic2.
Pon=Eon×f f: operating frequency
Poff=Eoff×f
So, P(IGBT total) = PVCE(sat) + Pon + Poff
However, because Eon, Eoff varies according Rg and Ic, use the data in the near distance for calculation.
4/10
NGTG12N60TF1G Application Note
T
Ton
VGE
VCE
Ic
Ic2
Ic1
Eon
fig.6
VCE
VCE(sat)
conduction loss
Eoff
Switching continuous operation waveform
5. Application circuit centering with part SWPFC
NGTG12N60TF1G and NGTG20N60L2TF1G are the types without freewheel diode built in. As typical
application circuit, there are part SW PFC circuits, inverter’s brake circuits.
5-1) part SW PFC circuit
AC
FILTER
DRIVER
ZERO CROSS
DETECT
fig.7
CONTROLLER
part switching circuit
In order to improve Power Factor, current is flowed into the inductance forcibly, and used as a switch that
expands the angle of input current flow.
*However, in such cases for PFC where multiple times of switching are performed in 1 cycle or full switching
method, VCE ringing occurs at the time of Ic cutoff, which may result in minus-direction voltage(emitter side is
plus), so you need to add a freewheel diode between C-E in parallel or use some device with built-in FRD like
NGTB20N60L2TF1G.
Image of input voltage and current:
Take AC input voltage as “V”, current as “i”.
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NGTG12N60TF1G Application Note
Waveform seen from AC input when operating part SW circuit
is shown as fig.8 (a). Power Factor can be improved by having
v
i
input current waveform approach input voltage waveform by
(a)
operating on the PFC IGBT within certain period and flowing
input current i.
Ic
Power factor is estimated to be 0.9~0.97.
(b)
Twice the commercial frequency is used. (That is, operate at
VGE
100Hz when commercial freq. is 50Hz)
(c)
Waveform of Ic is triangle wave starting at zero cross.
See WP.1 (operate with IGBT) for your reference.
fig.8
WP.1
part switching operation
IGBT part switching operation waveform
5-2) Other IGBT application circuit example…Inverter brake circuit
Break
Inverter
fig.9 Brake circuit
Used as switch of resistance circuit in order to suppress Vcc line voltage rise in regenerative operation in
applications such as AC servo.
6/10
NGTG12N60TF1G Application Note
6. Calculation of Losses in PFC circuit (part switching method)
IGBT is used for improving the Power Factor of the applications such as air-conditioner. We explained part
switching PFC circuit in 5-1) as an example of low-frequency switching circuit.
The loss when IGBT is used in the part switching PFC circuit is calculated based on the waveform.
Part switching Ic waveform is a triangle waveform. Therefore, the losses may be considered as the sum of
conduction loss [VCE(sat) loss] and Poff loss. Calculation is done by assuming f=100~120Hz.
Because the frequency is low, Poff loss is small compared with VCE(sat) loss. VCE(sat) loss is calculated as
the main loss.
Ic starts from 0A and reaches Icp, so assume VCE(sat) linear from 0[A] to Icp[A], calculate by approximating
VCE(sat) and Ic as straight line. For Poff, use Eoff at Icp, and calculate by Poff=Eoff×f.
For conduction loss P(VCE(sat)), assume 0.6V as start (because the current begins to rise at approx. 0.6V).
Take the current as Ax and the voltage as Bx+0.6, then integrate Ax×(Bx+0.6) of TON segment.
However, because the segment is 0~Ton, A=Icp/TON & B=(VCEsat(@Icp)-0.6))/TON. The formula becomes:
TON
TON
∫f(x)dx=∫(Icp/Ton×Icp×([email protected])×x2+0.6×Icp/Ton×x)dX
0
0
Ton
3
2
= [1/(3×Ton)×Icp(VCEsat@Icp×Icp-0.6)×x +1/(2×Ton)×0.6×Icp×x ]
0
=1/6×(2×Icp×VCEsat@Icp+0.6×Icp)×Ton
…(1)
Regard the period as T, then conduction loss PVCE(sat) is
PVCE(sat) = formula (1)/T …(2)
Ic triangle wave
Furthermore, Ptotal becomes:
Ptotal= PVCE(sat)+Poff …(3)
Take NGTG12N60TF1G as example, in case of 20A (Tc=100deg),
VCE(sat)=1.8V based on Ic-VCE(sat) dependency(fig.10-2).
Wave pattern approximation of VCE(sat)
VCE (sat) = 0.6V that Ic is zero. And you read VCE (sat) in Ic=30A on the catalogue. It links those VCE (sat) by a straight line.
Given TON=1.33mS, T=8.33mS(120Hz).
Assign the above TON and T in formula (2):
PVCE(sat) = Ton/T ×1/6×Icp(2×VCEsat+0.6)=2.24[W]
fig.10-1 Loss equivalent waveform
And because Poff is: Eoff=825μJ at Icp=20A (see fig.7-2),
Poff=120×825×10-6=0.099[W].
Therefore, Ptotal= PVCE(sat)+Poff=2.34[W]
Above is an example when regarding Icp=20A. Pay attention that Ton changes when Icp changes(assume
inclination as constant), and the loss will also change. fig.10-3 shows how Pc changes when Icp changes.
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NGTG12N60TF1G Application Note
Eoff VS Ic
NGTG12N60TF1G
1600 Vcc=300V
L=200µH
Rg=47O
Tc=100℃
1400 1200 1000 J]
[µ
ff 800 Eo
Eoff
600 400 200 0 0
5
10
15
20
25
30
35
Ic [A]
fig.10-2
Ic-VCE(sat) when Tc=100deg
fig.10-3
Eoff when Icp changes
PVCE(sat) VS Icp
Ex) Loss alculation of parcial SW circuit 7
NGTG12N60TF1G
parcial SW
T=8.33mS
Degree of leaning of Ic =15A/mS
VCE（sat）@100℃
6
]5
W
)[t 4
as
(E
C3
V
P
2
Pc｢W]
1
0
5
10
15
20
25
30
35
Icp[A]
fig.10-4 Calculation of VCE(sat) loss when Icp
changes
7. Heat sink design (centering with NGTG12N60TF1G)
NGTG12N60TF1G’s Tjmax is 150 degrees Celsius, heat sink should be designed so as not exceed 150deg
even in the worst case. Furthermore, when taking high reliability of switching operation into account, Tc(Case
Temperature) is recommended to be 100~110 degrees Celsius.
In part SW operation Icp=30A, PVCE(sat)=5.8W(fig.7-4), Eoff=1460μJ when Icp=30A(fig.7-3),
Based on formula (3), Ptotal=5.8+120×1460×10-6=5.98W
In order to hold Tc=100deg,
suppose Tamax=60deg, the heat sink becomes:
Θh=(100-60)÷5.98=6.6 deg/W.
For the above device, Tj becomes Rth(j-c)=2.33deg/W rather than the specification sheet,
So, Tj = 5.8×2.33+100=113.5 degrees Celsius
(against Tjmax=150deg)
8. ASO (or SOA) (Area of Safe Operation)
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NGTG12N60TF1G Application Note
ASO(SOA*) is critical parameter that assure the device to be used in circuits safely, especially for
high-voltage high-current power device used in switching circuit. ASO is divided into two areas:
FB(Forward Bias) and RB(Reverse Bias). Which ASO is used for evaluation depends on gate input
condition. *Generally SOA is called, but in accordance with NGTG12N60TF1G’s specification sheet, ASO
is used hereinafter.
8-1) FB/ASO (Forward-biased Area of Safe Operation)
FB/ASO is a parameter used to evaluate 2-dimentional locus of the voltage/current between collector and
emitter when gate voltage exceeds Vth and forward collector current flows.
This ASO depends on the powered time (PT).
The area is composed of the following:
□
□ Icp-restricted area
○ Tjmax-restricted area
○
○
△ secondary breakdown restricted area
○
◇ VCESmax-restricted area
△
For NGTG12N60TF1G, it is shown as in fig.11
◇
ᇞ
fig.11 Example of FB・ASO
for NGTG12N60TF1G
FB/ASO is also dependent on temperature. The higher the temperature is, the narrower the ASO becomes.
So attention should be paid when temperature rises. Please consult FB/ASO when temperature rises
separately.
8-2) RB/ASO (Reverse Bias Area of Safe Operation)
RB/ASO is a parameter used to evaluate the locus between collector and emitter in the area where gate
voltage is less than Vth. In switching operation at L load, although gate voltage is usually made to be 0V or
negative in order to OFF the operation, the current decreases behind time as the collector voltage rises, this
makes a unique locus.
9/10
NGTG12N60TF1G Application Note
Especially in case of L-load SW, RB/ASO becomes critical. Graph of RB/ASO is shown in fig.12.
RB/ASO is usually described by two areas: one restricted by peak collector current and the other restricted by
collector-emitter voltage(VCES).
For example, if you plot ASO locus of the
operation as WP.1 around the RB/ASO graph,
(fig.12)
Worst
case
You can see this operation is within the area.
We recommend you conduct verification
actually in the worst case (both current and
voltage are max.) to check whether RB/ASO
is exceeded or not.
fig. 12 RB・ASO and operation locus (NGTG12N60TF1G)
9. Short-circuit capacity Safe Operating Area (SC SOA)
It is a parameter to show how long the device can operate without being destructed when C-E is shorted. In
protection circuit, it is necessary to have the protection circuit operate earlier than the time SC SOA is reached
and completely turn-off the gate voltage.
Please pay attention that SC SOA will become
smaller(shorter) when the device temperature
or VGE becomes higher, plus when the voltage of
the collector side power line becomes higher.
In case of NGTG12N60TF1G,
under Tc=100 degrees Celsius,
VGE=15V and Vcc=300V,
VGE-5V/div
VCE-100V/div
Ic-100A/div
5μS is the design guarantee.
VCE、Ic
GND
WP.2 SC SOA operation waveform example
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