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网上看见一篇关于场效应管（MOSFET），双极型管（BJT）和绝缘栅双极型管（IGBT）做功率放大器时的优缺点分析的好文章，而且很简短，简单读了一遍，很受益，我会把它全部翻译出来给像我这样的外行高烧参考。
Power_Semiconductors__12-12-04_.pdf
(65.72 KB, 下载次数: 475)
1
Abstract—Although insulated gate bipolar transistors (IGBTs)
are now the most common type of power semiconductors, they
have inherent advantages and disadvantages over other such
devices as bipolar junction transistors (BJTs) and metal oxide
field-effect transistors (FETs).
Index Terms—Insulated gate bipolar transistors, Power
bipolar transistors, Power MOSFETs, Power semiconductor
devices.
I. INTRODUCTION
LTHOUGH power semiconductors were first developed
in the late 1940s, they have matured significantly in sixty
years. In today’s society, power semiconductors can be found
everywhere. They are essentially the solid-state version of the
mechanical relay or the vacuum tube. Some of most common
applications include motor drives, uninterruptible power
supplies, audio amplifiers, and fluorescent lighting. For the
best device suited for the job, it has become a competition
between the bipolar junction transistor (BJT), the metal oxide
field-effect transistor (MOSFET), and the insulated gate
bipolar transistor (IGBT). Each has inherent advantages over
the others, but the IGBT has seemed to dominate the industry
in recent years.
II. THE BIPOLAR JUNCTION TRANSISTOR (BJT)
A. Physical Characteristics
One of the first types of power semiconductors, the BJT is a
three layered semiconductor consisting of a sandwich of p-n-p
or n-p-n materials. In addition, it has three terminals: the
emitter, the collector, and the base. The base is lightly doped,
whereas the emitter is heavily doped and wider. The emitter-
Manuscript received December 12, 2004.
Reid L. Sprite is an undergraduate student with the Department of
Electrical and Computer Engineering, University of Rochester, Rochester, NY
14627-5982 USA (phone: 517-372-2348; email: reid@reidsprite.com).
base region is forward biased so that majority carriers will
flow across the junction. On the other hand, the collectorbase
region is reverse biased, which results in a small minority
carrier flow.
B. Operational Advantages and Disadvantages
When used in a common emitter mode, as it is most often,
the BJT acts as a current-controlled switch. The base current
is in the input and the collector current is the output. Because
it is current-controlled, it has a fairly low saturation voltage,
which is desirable. In addition, BJTs are able to handle high
voltages and currents with few problems.
Of course, there are many drawbacks. The BJT has low
gain at high frequencies, so it is not useful for amplification
under those conditions. Additionally, it does not have a very
high surge rating—the peak current is only about twice the
maximum continuous current rating. Unlike MOSFETs, BJTs
also have a relatively slow switching speed because it takes
time to charge the emitter and collector depletion
capacitances, which consequently slows the turn-on time.
There are also two breakdown areas associated with the BJT
that reduce its safe operating area. The first is the avalanche
breakdown, which causes a rapid rise in current, and a second
breakdown can be brought on by inductive loads, which can
overheat and destroy the transistor.
III. THE METAL OXIDE SEMICONDUCTOR FIELD EFFECT
TRANSISTOR (MOSFET)
A. Physical Characteristics
The MOSFET was introduced in the 1970s and, unlike the
BJT, is a voltage controlled device. It also has three
terminals, though they differ from the BJT: the source, the
gate, and the drain. The source and drain diffusions are
separated by the gate. The MOSFET has a p or n channel and
can operate in depletion or enhancement mode. In
enhancement, no current flows when the gate voltage is zero.
In depletion mode, however, a narrow n channel is formed
under the gate such that current will still flow when the gate
voltage is zero.
B. Operational Advantages and Disadvantages
In comparison to the BJT, the MOSFET is far superior. It
has a high input impedance, reducing complexity and cost,
and a low input current drive. At low currents, it also has a
higher gain than the BJT. To handle higher currents, it is
Power Semiconductors:
The BJT, MOSFET, and IGBT
Reid L. Sprite, Member, IEEE
A
Fig. 1. Schematic diagram and circuit symbol of the BJT
2
sufficient to simply put several MOSFETs in parallel, and
because there is only one breakdown region, the safe
operating region is larger. Additionally, because they are free
from minority carrier storage times, MOSFETs are faster at
switching than the BJTs.
Despite its advantages, the MOSFET has low gain at
high currents. Moreover, it was slow to catch on and had an
overall greater cost than a BJT of the same power rating.
However, in recent years, the prices have come down and
MOSFETs have gained in popularity [2].
IV. THE INSULATED GATE BIPOLAR TRANSISTOR (IGBT)
A. Physical Characteristics
The IGBT is the most popular power semiconductor
currently used today. It combines the MOS gate structure
with the bipolar current conduction to create a device that is
the best of both the MOSFET and the BJT. For terminals, it is
a hybrid between the BJT and the MOSFET. It has three
terminals: the collector, the gate, and the emitter.
Schematically, the IGBT is basically a p-n-p BJT powered by
an n-channel MOSFET.
B. Operational Advantages and Disadvantages
The IGBT brings together the advantages of a BJT and
MOSFET. It has high input impedance, a low power
consumption, and a large safe operating area. It also has a
remarkably high power handling capability for a given chip
size. And, because it is a minority carrier device on a p+
substrate, it has superior conduction to a standard MOSFET.
When used in combination with power integrated circuits, one
can expect a cost reduction by a factor of ten [2].
The only disadvantage comes in switching speed. While
the IGBT can compete with the speed of the BJT, it cannot
beat the MOSFET. The faster the switching, the greater the
forward voltage drop, and it has a relatively high turn-off time
due to the long lifetime of minority carriers. However, these
problems recently have been overcome [4], allowing the IGBT
to dominate in industrial applications.
V. APPLICATIONS
. Because power semiconductors have very wide-ranging
applications, the most desirable type for a given application
comes down to several factors: the amplification, the
switching speed, and the power class. Trends in particular
types can be seen in applications in industry, the consumer
market, and transportation.
A. Industrial Applications
Within industry, the two main uses for power
semiconductors are for motor control and power supplies. For
motor drives, power semiconductors can control all sizes of
motors from those found in large mills to simple machine
tools. The trend in the method of controlling of these motors
has been toward IGBTs. Likewise, due to their versatility, the
use of the IGBT has become the trend in constructing power
supplies for such applications as battery charging, welding,
and induction heating.
B. Consumer Applications
In the consumer market, power semiconductors can be found
in audio amplifiers, heat controls, light dimmers, and again in
motor controls. Because of the low cost and high
amplification of MOSFETs, they have become the preference
in audio amplifier construction. On the other hand, the IGBT
is dominating in heat controls, dimmers, and motor drives.
An example consumer application of the IGBT can be seen
in Figure 4. Here, and IGBT modules is used to control an
induction coil that is used to heat a pan for cooking. In this
particular case, the IGBT acts as a switch; when voltage is
applied to the gate, the current will flow through the induction
coil, otherwise no current will flow. Because the IGBT can
Fig. 2. Power MOSFET schematic [1]
Fig. 3. IGBT schematic [3].
Fig. 4. Basic circuit example of IGBT power module used with an induction
heating coil for cooking [6].
3
handle high currents, there is little concern that the
semiconductor will overheat and/or be destroyed with the high
currents that are necessary for induction heating.
C. Transportation Applications
Within transportation, motor control with the IGBT is again
most prevalent. IGBTs are utilized in drives for electric cars
and trains. However, BJTs can be found in simpler
applications such as electronic ignition and vehicle voltage
regulation.
VI. CONCLUSION
Whereas all of the mentioned devices have certain
advantages, the IGBT has proven to make the best use of all
of these advantages while minimizing the disadvantages. As
such, IGBTs have taken over in popularity and are now being
even further optimized to suit the needs of an ideal power
semiconductor.
REFERENCES
[1] Vrej Barkhordarian, “Power MOSFET Basics”, (International Rectifier,
2004), http://www.irf.com/technical-info/appnotes/mosfet.pdf.
[2] B. Jayant Baliga, Modern Power Devices (Krieger Publishing, Malabar,
Florida, 1987), Chap. 1.
[3] “IGBT Fundamentals,” (Seimens Semiconductor Group, 2004),
http://www.infineon.com/cmc_upload/migrated_files/document_files/Ap
plication_Notes/lh_ap_18.pdf.
[4] Fraidoon Mazda, Power Electronics Handbook (Newnes, Oxford, 1997),
Chap. 1.
[5] D.A. Grant, “Power semiconductors-innovation and improvement
continue to challenge the designer,” in New Developments in Power
Semiconductor Devices, IEE Colloquium on, May 1991.
[6] “Main Applications for Power Modules,” (Mitsubishi Electronics, Sept.
1998), http://www.mitsubishichips.com/webfiles/pdf/powermos2_0.pdf.
[ 本帖最后由 今夜星光 于 2010-8-12 14:58 编辑 ] |
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