Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2003-02-13
2004-11-02
Zweizig, Jeffrey (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
Reexamination Certificate
active
06812749
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control circuit for current converter valves. More specifically, the present invention relates to a control circuit including at least a request unit having at least one digital processor, a digital transmission unit, and a control unit. The control unit includes at least one digital interface, a control circuit, a digital processor and analog components for directly controlling the at least one current converter valve.
2. Description of the Related Art
The invention relates to a control circuit for current converter valves of a type used, for example, in several classes of current converters. Examples of related types of control circuits are shown in “Application Handbook IGBT and MOSFET power modules” by U. Nicolai, ISBN 30932633-24-5, pages 192 to 196.
Commonly, control circuits for known current converters consist of a “user-specific” request unit and a “system-specific” control unit for the power semiconductor module.
“User-specific” request units are those units individually designed for a specific application range of current converter valves or current converters. “System-specific” control units are those control units individually designed for, or as a component of, the current converter valves or valve elements, such as current converters in the form of power semiconductor modules.
Referring now to
FIG. 1
, a control circuit
1
for a current converter
36
employing current converter valves
37
includes a request unit
10
and a control unit
30
joined by a conventional multi-wire cable
20
. This type of conventional current converter
36
consists of one or more power semiconductor modules (not shown). In this case, a three-phase current converter is used to drive
40
(as shown in a motor
40
as will be described).
Request unit
10
includes a digital processor
11
, and a downstream analog signal processor or signal generator
12
which generates analog control signals for the three TOP and three BOT switches (not shown) of conventional current converter
36
(described later). These control signals are then applied as 0/15 V analog values to an interface
13
as an output signal.
Multi-wire cable
20
transmits the output signals as continuous analog values from request unit
10
to control unit
30
, in a point-to-point connection.
An analog interface
31
, in control unit
30
, receives the continuous analog values from interface
13
and continually transmits them directly to analog components
35
for the direct control of current converter valves
37
of current converter
36
. In this manner, control unit
30
controls a drive in the form of motor
40
.
Unfortunately, to control the current converter valves
37
in current converter
36
, each valve must remain switched on for as long as the corresponding output signal is applied, and consequently the control signal for each of the six (6) current converter valves must be continuously applied to a contact in interface
13
.
Conventionally, interface
13
of request unit
10
also receives at least one analog input signal. Conventionally, analog input signals include the following:
temperature monitoring of the current converter valves
over-current monitoring of the current converter valves
current output of the corresponding half-bridge
voltage of the intermediate circuit.
Conventionally, control unit
30
functions by relaying the multiple analog control signals generated by request unit
10
to the drivers of current converter valves
37
. Additionally, control unit
30
attempts to serve multiple protective functions, including spike suppression and short-circuit recognition. Finally, control unit
30
attempts to report errors and individual measured values such as temperature or current output as analog signals back to request unit
10
providing a rudimentary feed back.
As noted above, the user-specific request circuit
10
generates systemspecific analog control signals, i.e. control signals at the time and for the duration when current converter valves
37
are intended to be switched on. These control signals are relayed as a continuous analog signal to control unit
30
. Consequently, the analog signals generated by request unit
10
control current converter valves
37
directly.
One disadvantage of the conventional design is that it is possible to unintentionally interrupt the continuous data transmission between request unit
10
and control unit
30
(see below). Where interruption occurs, not all of the input signals in request unit
10
can be correctly evaluated and converted into the appropriately altered control pulses sent to control unit
30
and control circuit
1
cannot function.
Another disadvantage of the conventional art is that since request unit
10
must generate “system-specific” signals, request unit
10
must be adapted to the new “system-specific” control signals whenever current converter
36
is changed or modified. This need often arises when a new generation of current converters
36
is introduced by a manufacturer. Further, depending upon the new generation of current converter
36
used, it may be necessary to additionally reconfiguration of signals sent to request unit
10
and require the re-adaptation of the “user-specific” request unit to the “system-specific” signals.
As noted above, request unit
30
contains analog interface
31
for continuous communication with request unit
10
. Analog interface
31
receives the analog control signals from request unit
10
and continuously transmits the above mentioned feedback signals, such as temperature monitoring signals for current converter valves
37
, over-current monitoring for current converter valves
37
, or current output of the corresponding half-bridge and voltage of the intermediate circuit.
For feedback purposes, either control unit
30
or current converter
36
include the requisite conventional sensors (not shown). Based on values from these sensors, control unit
30
, which also includes internal protective functions (not shown) for current converter valves
37
, can for example, turn current converter
36
off and prevent destruction from over heating.
Unfortunately, due to the conventional design, for internal protective functions the only basic data that can be evaluated are the own sensor values and the control signals presently applied by the request unit
10
. Due to the lack of values for the future control of the current converter valves
37
, a preventive protective function is possible only to an extremely limited extent.
As a further difficulty of the present design, since each conventional user-specific request unit
10
generates its own control pulses, conventional system-specific control unit
30
is also unable to recognize principal or systematic false controls of request unit
10
, since only an instantaneous value is available in each case, and the future control pulses cannot be electrically predicted. Consequently, current converter
36
cannot be completely protected by the system-specific control unit
30
against malfunctions of the user-specific request unit
10
. There is also no assurance in the conventional control circuit
1
that all error messages to user-specific request unit
10
were evaluated correctly by that unit and converted into appropriately changed control pulses.
It is also possible that conventional control circuit
1
can pick up interference (recognized as signals), or specific transmitted signals containing incident interference which may not be recognized as such. Consequently, conventional control circuit
1
fails to prevent a danger of undesirable control of current converter
36
with the associated risk of malfunction or failure.
As noted above, all signals between request unit
10
and control unit
30
are transmitted as continuous analog values via conventional multi-wire cable
20
designed as a point-to-point connection. Since the control signal of each current converter valve
37
requires its own load, i.e. six wires are necessary in total, since t
Bode Rüdiger
Katzenberger Günther
Semikron Elektronik GmbH
Young, P.C. Andrew F.
Zweizig Jeffrey
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