Electricity: motive power systems – Induction motor systems – Primary circuit control
Reexamination Certificate
1996-12-31
2003-02-18
Martin, David (Department: 2841)
Electricity: motive power systems
Induction motor systems
Primary circuit control
C318S811000, C361S709000, C363S123000, C363S141000
Reexamination Certificate
active
06522098
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a controller for power devices and, more particularly, to a controller for power devices employing high-breakdown-voltage semiconductor elements.
2. Description of the Background Art
FIG. 26
is a circuit diagram of a drive circuit for an AC input three-phase motor which is an example of background art controllers for power devices employing high-breakdown-voltage semiconductor elements. As shown in
FIG. 26
, an AC three-phase power supply APW serving as a power supply for an AC input three-phase motor M is connected to a converter circuit CC
1
between lines P and N, and the respective phases of the AC input three-phase motor M are connected to inverter circuits I
1
, I
2
,
13
for controlling the phases, respectively.
The inverter circuit I
1
(I
2
, I
3
) includes a pair of transistors Q
1
and Q
2
(Q
3
and Q
4
; Q
5
and Q
6
) which are power devices, such as IGBTs (insulated gate bipolar transistors), totem-pole connected between the lines P and N, and a control block SB
1
(SB
2
, SB
3
). Inputs of the respective phases of the motor M are connected to connection points U, V, W of the totem-pole connected transistors, respectively. Free-wheeling diodes D
1
to D
6
are connected in inverse-parallel with the transistors Q
1
to Q
6
, respectively. Between the lines P and N are connected a smoothing capacitor C and a brake circuit BK for use in applying electrical brakes to the AC input three-phase motor M and including a diode D
7
and a transistor Q
7
connected in series. A brake resistor BR exteriorly attached is connected in parallel with the diode D
7
in the brake circuit BK A control block SB
4
is connected to the gate electrode of the transistor Q
7
.
The control blocks SB
1
, SB
2
, SB
3
forming the inverter circuits I
1
, I
2
, I
3
and the control block SB
4
are connected to an external controller
6
employing a microcomputer and the like. A DC power supply DPW for operating the control blocks SB
1
, SB
2
, SB
3
is a power supply receiving a single-phase output from the AC three-phase power supply APW. The single-phase output from the AC three-phase power supply APW is connected to primary coils of an isolation transformer TR through a converter circuit CC
2
. Two DC outputs from secondary coils of the isolation transformer TR are applied to the control blocks SB
1
, SB
2
, SB
3
through converter circuits. For instance, DC outputs X and Y are applied to the inverter circuit I
1
.
The arrangement of the control block SB
1
of the inverter circuit I
1
is shown in FIG.
27
. Referring to
FIG. 27
, control circuits LS
1
and LS
2
employing LVICs (low-voltage ICs) are connected to the gate electrodes of the transistors Q
1
and Q
2
, respectively. Insulation circuits Z
1
and Z
2
are connected to the control circuits LS
1
and LS
2
, respectively. Reference potentials G
1
and G
2
for the control circuits LS
1
and LS
2
are based on different potentials.
Operation will be discussed with reference to
FIGS. 26 and 27
. Referring to
FIG. 26
, the converter circuit CC
1
converts a 400 V AC input voltage to a voltage of about 600 V DC which is applied between the lines P and N. Then the smoothing capacitor C between the lines P and N is charged, and ripple on the power supply line is suppressed. The voltage of about 600 V DC is provided as main power supplies for the inverter circuits I
1
, I
2
, I
3
.
Referring to
FIG. 27
, since the connection point U serving as an output of the inverter circuit I
1
is provided between the totem-pole connected transistors Q
1
and Q
2
, the reference potential G
1
for the control circuit LS
1
is, for example, the 600 V main power supply voltage when the transistor Q
1
is ON. In such a construction, a voltage as high as 600 V is applied to the control circuit LS
1
if the reference potential G
1
for the control circuit LS
1
is a ground potential of 0 V.
The LVIC forming the control circuit LS
1
normally has an operating voltage of not more than 30 V and is not constructed to withstand the voltage as high as 600 V. Hence, the control circuit LS
1
is designed such that the reference potential G
1
for the control circuit LS
1
is held floating from the ground potential and the main power supply voltage of 600 V becomes the reference potential G
1
when the transistor Q
1
is ON. A portion in which the main power supply potential is the reference potential is referred to hereinafter as a high potential portion, and a portion in which the ground potential is the reference potential, such as the control circuit LS
2
, as a low potential portion. It should be noted that the control circuit LS
2
in the low potential portion is held floating in the same manner as the control circuit LS
1
.
To that end, the DC power supplies X and Y insulated through the isolation transformer TR and then rectified by the converter circuit are applied to the control circuits LS
1
and LS
2
for driving thereof. Further, a control signal from the external controller
6
is applied to the control circuits LS
1
and LS
2
through the insulation circuits Z
1
and Z
2
including insulating means such as photocouplers. The DC power supplies X and Y are fed to drive the insulation circuits Z
1
, Z
2
and the control circuits LS
1
, LS
2
.
Each of the inverter circuits I
2
and I
3
includes circuits similar to the insulation circuits Z
1
, Z
2
and the control circuits LS
1
, LS
2
and requires power supplies similar to the DC power supplies X and Y. The drive circuit for the AC input three-phase motor requires at least four DC power supplies since separate DC power supplies are connected respectively to the control circuits in the high potential portions such as the control circuit LS
1
and a DC power supply is commonly connected to the control circuits in the low potential portions similar to the control circuit LS
2
.
The brake circuit BK applies electrical brakes to the motor M which tends to keep rotating after receiving a stop signal from the external controller
6
. The circuit arrangement of the control block SB
4
for controlling the transistor Q
7
is similar to that of the circuits for controlling the low potential transistors in the control blocks SB
1
to SB
3
, and is connected to the external controller
6
.
The inverter circuits I
1
, I
2
, I
3
are well known in the art, and the description of the detailed circuit arrangements thereof will be omitted herein.
As above stated, the conventional controller for the power devices has required particular insulating elements such as photocouplers for insulation of the control signal. In particular, insulation of high-frequency noises has necessitated an advanced insulation technique and costly insulating elements.
The control signal is given from the external controller
6
through the insulating means, resulting in the power devices being less responsive to the control signal and being difficult to integrate.
Further, it has been necessary to individually apply the drive power supply to the control circuits positioned in the high and low potential portions through the isolation transformer TR, which causes an increased size of the power supply portion and a large amount of power consumption. The need for the particular insulating elements, such as photocouplers, as insulating means results in an increased size of a module (Intelligent Power Module; referred to as an IPM hereinafter) designed such that an integrated controller for power devices including a protective circuit, the power devices, and a control power supply are encapsulated in a single package.
SUMMARY OF THE INVENTION
For a power device including in-series connected first and second semiconductor circuits between first and second main power supply potentials, the conduction of at least the first semiconductor circuit being controllable by a control signal, the first and second semiconductor circuits providing an output at their connection node, the present invention is intended for a controller for controlling the power device in r
Fukunaga Masanori
Hatae Shinji
Majumdar Gourab
Oota Tatsuo
Martin David
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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