U.S. patent application number 10/246513 was filed with the patent office on 2003-10-30 for electronic circuit breaker.
Invention is credited to Bittoni, Francesco, Canova, Antonio, Cincinelli, Lorenzo.
Application Number | 20030202304 10/246513 |
Document ID | / |
Family ID | 8184695 |
Filed Date | 2003-10-30 |
United States Patent
Application |
20030202304 |
Kind Code |
A1 |
Canova, Antonio ; et
al. |
October 30, 2003 |
Electronic circuit breaker
Abstract
The electronic circuit breaker comprises an input (A, B) for
connection to a power-supply network and an output (C, D) for
connection to a load (Z). Set between the input and the output are
a switch (7) and a limitation block (9) which controls the switch
(7) to cause at least partial inhibition thereof in the event of
overcurrent. Moreover provided is a microprocessor (13) connected
to the limitation block (9) to inhibit power supply to the load
(Z).
Inventors: |
Canova, Antonio; (Arezzo,
IT) ; Bittoni, Francesco; (Arezzo, IT) ;
Cincinelli, Lorenzo; (Arezzo, IT) |
Correspondence
Address: |
Mark J. Patterson
NationsBank Plaza
Suite 2020
414 Union Street
Nashville
TN
37219
US
|
Family ID: |
8184695 |
Appl. No.: |
10/246513 |
Filed: |
September 18, 2002 |
Current U.S.
Class: |
361/93.1 |
Current CPC
Class: |
H02H 3/006 20130101;
H02H 3/025 20130101; H02H 3/087 20130101; H02H 3/04 20130101 |
Class at
Publication: |
361/93.1 |
International
Class: |
H02H 003/08 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2001 |
EP |
01830592.0 |
Claims
1. An electronic circuit breaker with an input (A, B) for
connection to a power-supply network and an output (C, D) for
connection to a load (Z), comprising: between said input and said
output at least one switch (7) and a limitation block (9) which
controls said switch (7) to cause at least partial inhibition
thereof in the event of overcurrent; and a microprocessor (13)
connected to said limitation block (9) to cut off power supply to
the load (Z).
2. The circuit breaker according to claim 1, wherein said
limitation block (9) comprises an operational amplifier (11), to a
first input of which there is applied a signal proportional to the
current that traverses said circuit breaker, and to the second
input of which there is applied a reference voltage
(V.sub.ref).
3. The circuit breaker according to claim 2, wherein said reference
voltage is programmable by means of said microprocessor (13).
4. The circuit breaker according to claim 2 or 3, wherein said
microprocessor is connected to the inverting input of said
operational amplifier (11).
5. The circuit breaker according to claim 2, or 3 or 4, wherein
said switch (7) is connected to the output of said operational
amplifier.
6. The circuit breaker according claim 5, wherein a fuse is set
between the output of said operational amplifier and said
switch.
7. The circuit breaker according to one or more of the foregoing
claims, comprising at least one catastrophic-protection device (5)
between its input and its output.
8. The circuit breaker according to one or more of the foregoing
claims, comprising at least one read resistor for determining the
amount of current that flows through said circuit breaker.
9. The circuit breaker according to claim 7, wherein said at least
one catastrophic-protection device (5) is set in series to said at
least one switch.
10. The circuit breaker according to claim 8, wherein said at least
one read resistor is set in series to that at least one switch.
11. The circuit breaker according to one or more of the foregoing
claims, wherein said microprocessor is programmable for intervening
with a pre-set delay with respect to the partial inhibition of said
switch.
12. The circuit breaker according to one or more of the foregoing
claims, wherein said microprocessor is connected to a temperature
sensor and is programmed to cause opening of the circuit in the
event of overheating.
13. The circuit breaker according to one or more of the foregoing
claims, wherein said microprocessor (13) comprises an input/output
terminal (29) for programming and/or communication with the outside
world.
14. The circuit breaker according to one or more of the foregoing
claims, wherein said microprocessor is associated to a memory for
storing the parameters for operation of the circuit breaker.
15. The circuit breaker according to one or more of the foregoing
claims, comprising a plurality of switches (7), each of which is
associated to a corresponding limitation block (9), said switches
(7) being set in parallel with respect to one another.
16. The circuit breaker according to one or more of the foregoing
claims, wherein said microprocessor receives at input a signal
proportional to the voltage at input to the circuit breaker and is
programmed in such a way as to cause opening of the circuit by the
circuit breaker when said voltage exceeds a pre-determined value.
Description
[0001] The present invention relates to an electronic circuit
breaker for interrupting electric power supply to a user circuit
when the current exceeds a pre-set value, for instance in the case
of a short circuit.
[0002] There currently exist various types of circuit breakers for
protecting circuits from overcurrents. Some of these circuit
breakers are of a thermal type and are based on the use of
bimetallic strips, the deformation of which, on account of the
dissipation of heat by the Joule effect due to the passage of
current, causes opening of the circuit by a switch. In other
circuit breakers, those of the electromagnetic type, interruption
is caused by the movement of an armature under the effect of a
magnetic field generated by a coil traversed by the current. In
either case, an excessive current flowing through the strip (in the
case of a thermal circuit breaker) or through the coil (in the case
of a magnetic circuit breaker) causes tripping of the circuit
breaker.
[0003] Thermal circuit breakers present the drawback of having a
high tripping time and of being considerably unreliable owing to
the effect that ambient-temperature variations can have on their
operation even when appropriate measures are taken to offset the
effect of these variations.
[0004] Magnetic circuit breakers can be built in such a way that
they trip very fast, this being necessary for protecting
present-day circuits that comprise solid-state components. However,
their tripping speed is not altogether satisfactory. In addition,
their reliability is low in that they feel the effects of external
factors, such as variations in temperature, mechanical vibrations,
magnetic interference, etc. In addition, the presence of a mobile
armature sets limits to the freedom of choice of the position in
which these circuit breakers can be installed, on account of the
influence that the force of gravity may have on the tripping
characteristics of these devices.
[0005] There also exist electronic circuit breakers, for example of
the type described in U.S. Pat. No. 4,979,068. Also these circuit
breakers are not altogether satisfactory.
[0006] A purpose of the present invention is to provide an
electronic circuit breaker which overcomes the drawbacks presented
by traditional circuit breakers.
[0007] In particular, a purpose of the present invention is to
provide a reliable electronic circuit breaker that has
characteristics of high durability and very short tripping times
and enables limitation of peak current.
[0008] A further purpose of the present invention is to provide a
device that can be programmed.
[0009] These and further purposes and advantages, which will emerge
clearly to a person skilled in the art from the ensuing text, are
basically obtained with an electronic circuit breaker
comprising:
[0010] between the input and the output of the circuit breaker at
least one switch and one limitation block which controls said
switch to cause at least partial inhibition in the event of
overcurrent;
[0011] a microprocessor connected to said limitation block to cut
off power supply to the load connected to the circuit breaker.
[0012] In this way, an overcurrent causes tripping of the
limitation block and at least partial opening of the circuit by the
switch, for example a MOSFET. The tripping time is extremely short,
i.e., of the order of hundreds of microseconds. Within a delay time
that may be advantageously programmed by the microprocessor, the
latter sends the circuit breaker into a state of inhibition and
cuts off supply to the load. The circuit breaker can now be reset
by means of the reset signal of the microprocessor, once the cause
of its tripping has been determined.
[0013] The use of a microprocessor enables a plurality of functions
and advantages to be achieved. In particular, the delay in
intervention of the switch, which brings about complete inhibition
or interruption of the circuit breaker (the so-called "tripping"),
and the value of the current that causes opening of the circuit by
the circuit breaker are programmable and may possibly be modified
also remotely by means of an input/output terminal of the
microprocessor and a serial port. The operating parameters of the
circuit breaker (voltage at the terminals, current) can be stored
and then read whenever necessary by means of the same input/output
terminal and the same serial port that enable programming. The
circuit breaker can be remotely controlled.
[0014] The circuit breaker according to the invention presents
numerous advantages as compared to circuit breakers of the prior
art. In the first place, it is more reliable, with an MTBF up to
five times higher than that of other known circuit breakers. The
current is limited in extremely short time intervals, even during
the tripping time, i.e., the time interval up to complete opening
of the circuit. The programmability of the device renders it
extremely versatile. Furthermore, as will be clarified in what
follows, by using the microprocessor it is possible to provide
various functions without the need for auxiliary components. In
particular, it is possible to detect the input voltage of the
circuit breaker and program opening of the circuit by means of the
microprocessor when the voltage oversteps a given value, which is
programmable. This renders superfluous the use of other
electromechanical devices that are sensitive to overvoltages. The
current that flows through the circuit breaker can be determined by
the microprocessor itself and communicated to the outside world;
this fact eliminates the need for separate current sensors.
[0015] Further advantageous features and embodiments of the
invention are specified in the attached dependent claims.
[0016] A better understanding of the invention will be provided by
the ensuing description and the attached drawing, which illustrates
a possible, non-limiting, embodiment of the invention. In the
drawings:
[0017] FIG. 1 shows a block diagram of the circuit breaker
according to the invention;
[0018] FIG. 2 shows a more detailed diagram of an embodiment of the
invention; and
[0019] FIG. 3 shows the current-time characteristic of the circuit
breaker according to the invention.
[0020] With reference initially to the diagram in FIG. 1, the
circuit breaker, designated as a whole by 1, has an input
consisting of two terminals, A and B, and an output consisting of
two terminals, C and D. On the line A-C there is set a block 3
which contains a current-read resistor 4, by means of which the
current that traverses the circuit breaker and that supplies a load
circuit, or load, which is connected between the output terminals C
and D, is read. The block 3 moreover contains at least one fuse 5
and one electronic switch 7. The fuse 5 constitutes a so-called
"catastrophic protection"; i.e., it blows, so interrupting
definitively the passage of current, for example in the event of a
short circuit. In this case, the device must be replaced, or at
least the fuse must be replaced, whereas in other tripping
situations, as will be clarified in what follows, it is sufficient
to reset the circuit breaker that has tripped on account of an
overcurrent. The electronic switch 7, for example a MOSFET,
constitutes a protection against transient overcurrents, and opens
the circuit in the way described in what follows.
[0021] The reference number 9 designates a limitation block which
comprises an operational amplifier 11 and is connected both to the
block 3 and to a microprocessor 13. The limitation block 9 and the
microprocessor 13 are supplied by an auxiliary voltage generator
15.
[0022] In addition to being connected to the limitation block 9,
the microprocessor 13 is also connected to the block 3 and to a
resistor 17 that can vary with temperature, for example a PTC or an
NTC resistor, which is thermally coupled to the components of the
circuit breaker that are subject to overheating.
[0023] Operation of the device outlined above is as described in
what follows. In conditions of normal supply to the load Z (applied
to the terminals C, D of the device), a current I.sub.N is
supplied. The fuse 5 is intact, and the MOSFET 7 is in full
conduction.
[0024] In the case of a catastrophic event, such as a short
circuit, the fuse 5 causes the circuit breaker 1 to open the
circuit instantaneously and irreversibly, and power supply to the
load is thus interrupted.
[0025] In the event of overcurrent to the load Z, i.e., in the
event of the current exceeding a pre-set limit value I.sub.limit,
the limitation block 9, by means of the operational amplifier 11,
sends the MOSFET 7 of the block 3 into a condition of partial
inhibition. The time required for this inhibition to occur is very
short, i.e., in the region of 300 microseconds or even less. The
current that is now flowing through the circuit breaker is kept
below a value I.sub.limit for a delay time that can be programmed
by means of the microprocessor 13. Once this time interval has
elapsed, the microprocessor 13 causes complete inhibition of the
MOSFET 7 or other equivalent switching device, so bringing the
current on the load to a stand-by value I.sub.stand-by that is very
limited.
[0026] FIG. 3 shows the tripping characteristic of the circuit
breaker in these conditions. The time appears on the abscissa, and
the current values appear on the ordinate, as indicated above. The
graph shows the plots of the nominal or rated current I.sub.nom and
the maximum current I.sub.max for which the circuit breaker is
designed. The peak-current value is designated by I.sub.peak, this
value being reached in a very short time interval Ts, i.e., the
time needed for the limitation block 9 to go into action. The delay
time between intervention of the limitation block 9 and
intervention of the microprocessor 13 (tripping) is designated by
Td.
[0027] The resistor 17, which is variable according to the
temperature, constitutes a temperature sensor for the
microprocessor 13, said temperature sensor enabling interruption of
power supply in the event of overheating, by means of appropriate
programming of the microprocessor itself.
[0028] Since the microprocessor 13 is connected to the block 3, it
can determine, by means of the current-read resistor 4, the current
instantaneously flowing through the circuit breaker. A connection
between the terminals A and B moreover enables the instantaneous
voltage to be read, and hence enables opening of the circuit, which
is controlled by the microprocessor itself, also in the event of
overvoltage.
[0029] FIG. 2 presents a more detailed diagram of an embodiment of
the circuit breaker according to the invention, in which there are
shown only the components that are essential for enabling
understanding and reproduction of the invention. The same reference
numbers designate parts that are the same as or correspond to those
appearing in the block diagram of FIG. 1.
[0030] The circuit of FIG. 2 comprises three blocks, indicated by
3A, 3B, 3C, that are functionally equivalent to block 3 of FIG. 1,
the said blocks being connected in parallel together and being
basically the same as one another. The blocks 3 may vary in number
according to the maximum current for which the circuit breaker has
been sized. The larger the current for which the circuit breaker is
to be sized, the greater the number of blocks 3, 3A, 3B, 3C, . . .
, set in parallel, each being traversed by a fraction of the total
current supplied to the load Z.
[0031] Each block 3A, 3B, 3C comprises an operational amplifier 11,
the output of which is connected to the gate terminal of the MOSFET
7. The source terminal of the MOSFET 7 is connected to the terminal
A of the circuit breaker 1, whilst the drain terminal is connected
to the terminal C. The current-read resistor is designated by 4,
and the fuse is designated by 5, both of these being set between
the source terminal of the MOSFET 7 and the terminal A of the
circuit breaker 1. Set between the output of the operational
amplifier 11 and the gate terminal of the MOSFET 7 is a further
protection fuse 21, which is set in series to a parallel-RC
cell.
[0032] The inverting input of the operational amplifier 11 of each
block 3A, 3B, 3C is connected, by means of a resistor 22, between
the current-read resistor 4 and the fuse 5, whilst applied to the
non-inverting terminal of the amplifier itself is a reference
voltage V.sub.ref, which is generated by a circuit, designated as a
whole by 23, which is connected to the microprocessor 13 and is
described in greater detail in what follows.
[0033] The voltage across the current-read resistor 4 is applied to
the inputs of an operational amplifier 25, the output of which is
connected to the microprocessor 13, which thus receives a signal
that is proportional to the current flowing through the resistor 4.
The circuit arrangement described so far is envisaged only for the
block 3A, whereas it is absent in the blocks 3B and 3C. Since the
three blocks 3A, 3B, 3C are basically the same, the total current
supplied to the load Z is equal to three times the current read by
the microprocessor 13 by means of the current-read resistor 4
through the amplifier 25.
[0034] In the circuit diagram of FIG. 2, two terminals 27 are
shown, which are connected, by means of an interface 28, to an
input/output terminal 29, which constitutes a connection of the
microprocessor 13 with the outside world. By means of this
interface, the microprocessor 13 can be programmed and
interrogated, for example to check the operating conditions of the
device. Interrogation and programming can be carried out also
remotely.
[0035] The reference number 31 designates a reset terminal of the
microprocessor 13, whilst 33 designates a terminal via which the
microprocessor 13 is connected to the blocks 3A, 3B, 3C. More in
particular, the terminal 33 is connected to the inverting input of
each operational amplifier 11 of the various blocks 3A, 3B, 3C
through a transistor 35 and a corresponding diode 37. Connection
between each diode 37 and the corresponding inverting input of the
corresponding operational amplifier 11 is represented by the letter
X.
[0036] Also shown in the diagram of FIG. 2 are two LEDs, 41 and 43,
which are connected to corresponding pins of the microprocessor 13
and which enable display of the operating conditions of the circuit
breaker 1, and a storage block 45 connected to the microprocessor
13, in which the information regarding the operating conditions of
the circuit breaker 1 is stored, this information being readable by
means of the input/output terminal 29.
[0037] The circuit 23 comprises an operational amplifier 24, the
inverting input of which is connected to the microprocessor 13, and
on the output of which there is present the reference voltage
V.sub.ref. The value of the latter is programmable by means of the
microprocessor 13 according to the characteristics that the circuit
breaker 1 is to possess.
[0038] FIG. 2 is a schematic representation of the configuration,
in itself known, of the auxiliary voltage generator 15, connected
to the two terminals A and B of the circuit breaker 1. The
auxiliary voltage generator 15 generates two DC voltages, e.g., 12
V and 3 V, on the terminals designated by V.sub.cc and 3V. These
voltages are used to supply the various circuit components,
according to what is illustrated in the diagram of FIG. 2.
[0039] In line with what has been briefly described with reference
to the block diagram of FIG. 1, the circuit of FIG. 2 operates as
described in what follows. In normal operating conditions, the
current flows through the blocks 3A, 3B, 3C towards the load Z. The
MOSFETs 7 are in full conduction. In the event of overcurrent,
there is the intervention of each of the operational amplifiers 11.
The value at which the latter go into action is fixed by the
reference voltage V.sub.ref, which is determined by a corresponding
programming of the microprocessor 13. The time for intervention of
the individual operational amplifiers 11 is very limited (less than
300 microseconds), and they have the effect of reducing the current
flowing from the terminal A to the terminal C towards the load.
After a programmable delay time, the microprocessor 13 goes into
action, by means of the output voltage on the pin 33 sent to the
individual amplifiers 11 of the blocks 3A, 3B, 3C, and sends the
individual MOSFETs 7 into a state of inhibition, thus reducing the
current to the tripping value I.sub.stand-by. The microprocessor
can act on the blocks 3, causing inhibition of the switches 7 also
in the case of overheating, which is detected by the resistor 17,
which is temperature-variable.
[0040] It is understood that the drawings only illustrate a
possible exemplification of the invention, which may vary in its
embodiments and arrangements without thereby departing from the
scope of the underlying idea. The possible presence of reference
numbers in the attached claims has the purpose of facilitating
reading thereof in the light of the foregoing description and of
the attached drawings, and in no way limits the scope of protection
represented by the claims.
* * * * *