Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2000-05-22
2002-10-01
Wu, Daniel J. (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S639000, C340S644000
Reexamination Certificate
active
06459380
ABSTRACT:
BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a semiconductor apparatus incorporated in a power converting apparatus, such as an inverter, for variably controlling the speed of a motor. More specifically, the present invention relates to a so-called intelligent power module (hereinafter referred to as an “IPM”) that incorporates semiconductor switching devices for power conversion, driver circuits for driving the respective semiconductor switching devices and various protection circuits in a package.
FIG. 6
is a block diagram showing a main portion of a conventional inverter for variably controlling the speed of a motor including an intelligent power module (IPM). In the figure, there are shown an IPM
01
, a main DC power supply
02
formed of a rectifier circuit (not shown) in a main control board
05
of the inverter, a motor
03
, the speed thereof being variably controlled by the inverter, and a resistor
04
in the main control board
05
of the inverter for consuming regenerated electric power. The resistor
04
will be described later in detail.
The main control board
05
of the inverter includes the above described rectifier circuit that constitutes the main DC power supply
02
, and the control circuits which generate various control signals for controlling the IPM
01
.
The IPM
01
includes semiconductor switching devices which also work as sensing IGBTs
1
(
1
U through
1
Z and
1
DB), each having a sensing terminal SE for dividing the emitter current thereof and for detecting anomaly in the emitter current caused by a short circuit in the load and so on. In the following, the IGBTs
1
U through
1
Z will be sometimes referred to as the “inverter switches” and the IGBT
1
DB as a “braking switch”.
The IPM
01
includes free wheel diodes
2
(
2
U through
2
Z and
2
DB). Each of the free wheel diodes
2
U through
2
Z is connected in opposite parallel between the collector and the emitter of each of the IGBTs (inverter switches)
1
U through
1
Z. The free wheel diode
2
DB is connected in parallel to the resistor
04
in such a polarity that the cathode of the diode
2
DB is connected to the positive electrode P of the main DC power supply
02
.
The IPM
01
includes pre-drivers
3
(
3
U through
3
Z and
3
DB) disposed in one to one correspondence to the IGBTs
1
(
1
U through
1
Z and
1
DB). In
FIG. 6
, one pre-driver is used to drive one IGBT. Alternatively, one pre-driver may be used to drive all the inverter switches
1
U through
1
Z, two pre-drivers may be used to drive the inverter switches on the upper arm and the inverter switches on the lower arm respectively, or one pre-driver may be used to drive all the inverter switches
1
U through
1
Z and the braking switch
1
DB.
The IGBTs
1
U and
1
X are connected in series to each other and in forward between the positive electrode P and the negative electrode N of the main DC power supply
02
such that the IGBT
1
U is on the upper arm and the IGBT
1
X is on the lower arm of the inverter bridge. The IGBTs
1
V and
1
Y are connected in series to each other and in forward between the positive electrode P and the negative electrode N of the main DC power supply
02
such that the IGBT
1
V is on the upper arm and the IGBT
1
Y is on the lower arm. And, the IGBTs
1
W and
1
Z are connected in series to each other and in forward between the positive electrode P and the negative electrode N of the main DC power supply
02
such that the IGBT
1
W is on the upper arm and the IGBT
1
Z is on the lower arm.
Six inverter switches, i.e. IGBTs
1
U through
1
Z, constitute a three-phase inverter bridge circuit. The mutual connection point of the IGBTs
1
U and
1
X is connected to an output terminal U for the U phase of a three-phase alternating current. The mutual connection point of the IGBTs
1
V and
1
Y is connected to an output terminal V for the V phase of the three-phase alternating current. And, the mutual connection point of the IGBTs
1
W and
1
Z is connected to an output terminal W for the W phase of the three-phase alternating current. The output terminals U, V and W are connected to the motor (three-phase induction motor in
FIG. 6
)
03
.
The braking switch, i.e. IGBT
1
DB, is connected in series to the resistor
04
for consuming the regenerated electric power and in forward relative to the P and N electrodes of the main DC power supply
02
.
Each of the pre-drivers
3
U through
3
Z and
3
DB includes a circuit for driving the gate of the corresponding IGBT and a protection circuit. A driving power supply (DC 15 V in
FIG. 6
) is fed to the pre-drivers
3
U through
3
Z and
3
DB. Basically, each of the pre-drivers
3
U through
3
Z and
3
DB works as a driver circuit which feeds a gate signal, indicative of ON or OFF of the corresponding IGBT, between the gate and the emitter thereof, when an ON-signal or an OFF signal (hereinafter referred to as a “driver input”) is inputted from the main control board
05
of the inverter to the correspond one of the terminals VinU through VinZ and VinDB, to switch on or off the corresponding IGBT.
Usually, a three-phase AC voltage, wherein the voltage and the frequency thereof are variable, is generated through the IGBTs
1
U through
1
Z which convert the electric power from the main DC power supply
02
to control the speed of the motor
03
variably.
When the output frequency of the inverter is decreased to decelerate or stop the motor
03
while the motor
03
is driven, the energy of the motor
03
is regenerated to the main DC power supply
02
, and the voltage between the electrodes P and N of the DC power supply
02
rises. As the voltage rises too much, an over voltage exceeding the breakdown voltages of the IGBTs and the smoothing capacitor in the DC power supply
02
may be applied thereto.
To avoid this, the main control board
05
of the inverter monitors the voltage between the electrodes P and N of the DC power supply
02
. When the voltage between the electrodes P and N of the DC power supply
02
exceeds a predetermined value, the control circuit feeds ON and OFF signals to the input terminal VinDB of the pre-driver
3
DB for the braking switch, i.e. IGBT
1
DB, to intermittently switch the IGBT
1
DB. As the IGBT
1
DB is switched intermittently, the electric power regenerated from the motor
03
to the DC power supply
02
is bypassed to the resistor
04
to consume therein the regenerated electric power. Thus, the voltage between the electrodes of the main DC power supply
02
is prevented from increasing too much.
The pre-drivers
3
described above exhibit the function of driving of the IGBTs, and other various protection functions, such as (A) protection against short circuit, (B) protection against a low voltage, (C) protection against an overcurrent, and (D) protection against overheat of the IGBTs.
In the protection against short circuit (A), the pre-drivers
3
monitor the output currents from the sensing terminals SE of the IGBTs at a high speed. When any one of the monitored output currents exceeds a predetermined level, for example, at a value from 4 to 5 times greater than the rated current, the pertinent pre-driver
3
turns off the corresponding IGBT in a very short time by the so-called soft interruption that lowers the gate voltage at first and, then, turns off the IGBT, so that the pertinent IGBT may be protected.
The protection against the low voltage (B) is conducted to keep the gate voltages of the IGBTs at an optimum value. In the protection against the low voltage (B), the pre-drivers
3
monitor the driving voltages, to which the pre-drivers
3
feed. When any one of the monitored driving voltages is lower than a predetermined value, the pertinent pre-driver
3
turns off the corresponding IGBT so that the IGBT may be protected.
In the overcurrent protection (C), the pre-drivers
3
monitors the output currents from the sensing terminals SE of the IGBTs. When any one of the monitored output currents exceeds a predetermined level, for example, 1.5 to 2 times greater than
Kajiwara Tamao
Watanabe Manabu
Fuji Electric & Co., Ltd.
Huang Sihong
Kanesaka & Takeuchi
Wu Daniel J.
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