Analog signal detecting circuit, and AC side current...

Details Analog signal detecting circuit, and AC side current... Analog signal detecting circuit, and AC side current...

2000-05-17

2001-01-30

Berhane, Adolf Deneke (Department: 2838)

Electric power conversion systems

Current conversion

With condition responsive means to control the output...

C363S132000

Reexamination Certificate

active

06181587

ABSTRACT:

BACKGROUND OF THE TNVENTTON
1. Field of the Invention
The present invention relates to an analog signal detecting circuit in which reference potentials at signal input/output terminals are different from each other, and an AC side current detector of a semiconductor power conversion device using the same, and particularly, to an analog signal detecting circuit using a HVIC (High Voltage Integrated Circuit) characterized by including a non-optical semiconductor element, and a dead time fixing method of input/output signals.
2. Description of the Related Art
A conventional analog signal detecting circuit will be described with reference to the drawings.
FIG. 6
is a view showing a structure of a conventional analog signal detecting circuit.
FIG. 6
shows an example of the conventionally used analog signal detecting circuit in which reference potentials at signal input/output terminals are different from each other.
In
FIG. 6
, reference numeral
1
designates an analog signal detecting circuit;
2
, a signal input terminal;
3
, a signal output terminal;
4
, a reference potential (GNDin) at the signal input terminal
2
;
5
, a reference potential (GNDout) at the signal output terminal
3
;
6
, a power supply (Vrefin) at the signal input terminal
2
;
7
, a power supply (Vrefout) at the signal output terminal
3
;
8
, a V/F converter;
9
, a F/V converter;
10
, a photocoupler;
11
, a power supply system with the Vrefin and GNDin; and
12
, a power supply system with the Vrefout and GNDout.
Next, the operation of the foregoing conventional analog signal detecting circuit will be described with reference to the drawing.
An analog signal is inputted to the V/F converter
8
through the signal input terminal
2
. This V/F converter
8
is operated through the same power supply system
11
as the signal input terminal
2
. The V/F converter
8
outputs a digital signal having a frequency uniquely corresponding to the signal level of the analog input signal.
The digital signal outputted from the V/F converter
8
is electrically insulated by the photocoupler
10
and is connected to the F/V converter
9
operating through the same power supply system
12
as the signal output terminal
3
. This F/V converter
9
outputs an analog signal of a level uniquely corresponding to the frequency of the inputted digital signal.
As described above, in this prior art, an analog signal is converted into a digital signal having a frequency uniquely corresponding to the level of the input analog signal, is electrically insulated by the photocoupler
10
, and is converted into an analog signal of a level uniquely corresponding to the frequency of the digital signal. In this way, even in the case where reference potentials at the input/output terminals are different from each other, the analog signal can be detected.
Subsequently, a conventional AC side current detector of a semiconductor power conversion device will be described with reference to the drawings.
FIG. 7
is a view showing a structure of a conventional AC side current detector of a semiconductor power conversion device using the analog signal detecting circuit of FIG.
6
.
In
FIG. 7
, reference character
1
a
designates a U-phase analog signal detecting circuit;
1
b,
a V-phase analog signal detecting circuit;
1
c,
a W-phase analog signal detecting circuit;
2
a
, a U-phase signal input terminal;
2
b
, a V-phase signal input terminal;
2
c
, a W-phase signal input terminal;
3
a
, a U-phase signal output terminal;
3
b
, a V-phase signal output terminal;
3
c
, a W-phase signal output terminal;
4
a
, a reference potential (GNDinu) at the U-phase signal input terminal
2
a
;
4
b
, a reference potential (GNDinv) at the V-phase signal input terminal
2
b
;
4
c
, a reference potential (GNDinw) at the W-phase signal input terminal
2
c
;
6
a
, a power supply (Vrefinu) at the U-phase input terminal
2
a
;
6
b
, a power supply (Vref inv) at the V-phase signal input terminal
2
b
; and
6
c
, a power supply (Vrefinw) at the W-phase signal input terminal
2
c.
Beside, in the drawing, reference character
8
a
designates a U-phase V/F converter;
8
b
, a V-phase V/F converter;
8
c
, a W-phase V/F converter;
9
a
, a U-phase F/V converter;
9
b
, a V-phase F/V converter;
9
c
, aW-phaseF/Vconverter;
10
a,
aU-phasephotocoupler;
10
b,
a V-phase photocoupler;
10
c,
a W-phase photocoupler;
11
a,
a power supply system with the Vrefinu and GNDinu;
11
b,
a power supply system with the Vrefinv and GNDinv; and
11
c,
a power supply system with the Vrefinw and GNDinw.
Beside, in the drawing, reference character
13
a
designates U-phase current voltage conversion means;
13
b
, V-phase current voltage conversion means;
13
c
, W-phase current voltage conversion means;
14
, a load; and
15
, a semiconductor power conversion device.
Furthermore, in the drawing, reference character
16
a
designates a U-phase P-side switching element;
16
b
, a V-phase P-side switching element;
16
c
, a W-phase P-side switching element;
16
d
, a U-phase N-side switching element;
16
e
, a V-phase N-side switching element;
16
f
, a W-phase N-side switching element;
17
a
, a U-phase P-side flywheel diode;
17
b
, a V-phase P-side flywheel diode;
17
c
, a W-phase P-side flywheel diode;
17
d
, a U-phase N-side flywheel diode;
17
e
, a V-phase N-side flywheel diode;
17
f
, a W-phase Nside flywheel diode; and
18
, an AC side current detector.
In
FIG. 7
, the semiconductor power conversion device
15
converts DC electric power from a not-shown power supply device into AC electric power, and supplies it to the load
14
. For example, the semiconductor power conversion device
15
is an inverter, and the load
14
is a three-phase AC electric motor.
At this time, the conversion from the DC electric power to the AC electric power is carried out by switching the switching elements constituting a power element of the semiconductor power conversion device
15
. Note that the power element is constituted by the switching elements
16
a
to
16
f
and the flywheel diodes
17
a
to
17
f
. In general, in the semiconductor power conversion device
15
, switching control of the switching elements and protection of the power element are carried out by detecting the U-phase, V-phase, and W-phase currents.
In the AC side current detector
18
, first, the U-phase, V-phase, and W-phase currents are converted into voltage signals by the current voltage conversion means
13
a
to
13
c
. For example, the current voltage conversion means
13
a
to
13
c
are shunt resistors. The voltage signals outputted from the respective U-phase, V-phase, and W-phase current voltage conversion means
13
a
to
13
c
are respectively operated on the electrically insulated power supply systems
11
a
to
11
c,
and are respectively converted into digital signals uniquely corresponding to the voltage signal levels by the V/F converters
8
a
to
8
c
operating on the respective power supply systems
11
a
to
11
c.
Any of the U-phase, V-phase, and W-phase signal output terminals
3
a
to
3
c
of the AC side current detector
18
operates on the same power supply system
12
. The digital signals outputted from the V/F converters
8
a
to
8
c
are electrically insulated by the photocouplers
10
a
to
10
c,
and are inputted to the F/V converters
9
a
to
9
c
. The F/V converters
9
a
to
9
c
convert the digital signals outputted from the photocouplers
10
a
to
10
c
into voltage signals of levels respectively uniquely corresponding to the frequencies of the digital signals.
As described above, in the conventional AC side current detector of the semiconductor power conversion device, AC side current detection of the semiconductor power conversion device is made possible by using the above conventional analog signal detecting circuit.
In the foregoing conventional analog signal detecting circuit, even in the case where potential references are different from each other at the input/output terminals, detection of the analog signal becomes possible. However, since the ph

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