U.S. patent application number 13/434735 was filed with the patent office on 2012-07-19 for digital signal transfer method and apparatus.
Invention is credited to Bernhard STRZALKOWSKI.
Application Number | 20120183024 13/434735 |
Document ID | / |
Family ID | 32009837 |
Filed Date | 2012-07-19 |
United States Patent
Application |
20120183024 |
Kind Code |
A1 |
STRZALKOWSKI; Bernhard |
July 19, 2012 |
DIGITAL SIGNAL TRANSFER METHOD AND APPARATUS
Abstract
The invention relates to a digital signal transfer method and
apparatus in which signals are transferred between first and second
electrically isolated circuits. An announcement signal is
transferred from the first circuit to the second circuit and a data
signal is transferred from the first circuit to the second circuit
within a data signal time window associated with the announcement
signal.
Inventors: |
STRZALKOWSKI; Bernhard;
(Muenchen, DE) |
Family ID: |
32009837 |
Appl. No.: |
13/434735 |
Filed: |
March 29, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12570082 |
Sep 30, 2009 |
8189693 |
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13434735 |
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11776390 |
Jul 11, 2007 |
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12570082 |
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10666221 |
Sep 18, 2003 |
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11776390 |
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Current U.S.
Class: |
375/220 |
Current CPC
Class: |
H04B 3/00 20130101; H04L
25/00 20130101; H04L 25/085 20130101 |
Class at
Publication: |
375/220 |
International
Class: |
H04B 1/38 20060101
H04B001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 18, 2002 |
DE |
10243197.3 |
Claims
1. A method for transferring at least a signal between isolated
circuits, comprising: transferring an announcement signal from a
first circuit to a second circuit, the first and second circuits
being electrically isolated from each other; commencing a signal
time window subsequent to the transferring of the announcement
signal from the first circuit to the second circuit; and
transferring one of a pulse, a plurality of pulses or no pulse
during the signal time window depending on a state of an input
signal supplied to the first circuit.
2. The method of claim 1, wherein the signal time window is for a
prescribed period of time.
3. The method of claim 1, wherein the signal time window commences
after a prescribed time interval following receipt of the
announcement signal by the second circuit.
4. The method of claim 1, wherein the announcement signal is
transferred over a first transfer channel associated with a planar
transformer.
5. The method of claim 4, wherein the act of transferring one of a
pulse, a plurality of pulses or no pulse during the signal time
window depending on a state of an input signal supplied to the
first circuit is facilitated by a second transfer channel.
6. The method of claim 1, wherein the act of transferring an
announcement signal is repeated at regular intervals.
7. The method of claim 1, wherein the act of transferring an
announcement signal is repeated at irregular intervals.
8. The method of claim 1, wherein the act of transferring one of a
pulse, a plurality of pulses or no pulse during the signal time
window comprises transferring a pulse or a plurality of pulses when
the input signal is in a first state and transferring no pulse when
the input signal is in a second state.
9. The method of claim 8, wherein the first state is a high level
of the input signal and the second state is a low level of the
input signal.
10. The method of claim 1, further comprising receiving the input
signal at the first circuit.
11. An apparatus, comprising: a first circuit configured to receive
an input signal and transmit an announcement signal, the
announcement signal to trigger a signal time window; and a second
circuit electrically isolated from the first circuit, the second
circuit configured to receive the announcement signal, the second
circuit further configured to receive one of a pulse, a plurality
of pulses or no pulse during the signal time window depending on a
state of the input signal.
12. The apparatus of claim 11, wherein signal time window lasts for
a prescribed period of time.
13. The apparatus of claim 11, wherein the signal time window
begins after a prescribed time interval following receipt of the
announcement signal by the second circuit.
14. The apparatus of claim 11, further comprising first and second
transfer channels, the first transfer channel to communicate the
announcement signal to the second circuit and the second transfer
channel to communicate one or more pulses to the second circuit
during the signal time window.
15. The apparatus of claim 14, wherein each of the first and second
transfer channels comprises a planar transformer.
16. The apparatus of claim 11, wherein the first circuit comprises
a coder configured to encode at least a portion of the input
signal, and the second circuit comprises a decoder to decode
signals encoded by the first circuit.
17. The apparatus of claim 11, wherein the second circuit receives
a pulse or a plurality of pulses when the input signal is in a
first state and receives no pulse when the input signal is in a
second state.
18. An apparatus, comprising: a first circuit configured to receive
an input signal and transmit an announcement signal, the
announcement signal to trigger a signal time window; and a second
circuit electrically isolated from the first circuit by a
transformer, the second circuit configured to receive the
announcement signal, the second circuit further configured to
receive one of a pulse, a plurality of pulses or no pulse during
the signal time window depending on a state of the input signal,
wherein at least no pulse is to be received at some point during a
logic level low state of the input signal.
19. The apparatus of claim 18, further comprising a first transfer
link coupled to the first and second circuits, the first circuit is
configured to transmit the announcement signal to the second
circuit using the first transfer link.
20. The apparatus of claim 19, further comprising a second transfer
link coupled to the first and second circuits and the transformer,
the second transfer link to carry data from the first circuit to
the second circuit.
21. The apparatus of claim 18, further comprising a transfer link
coupled to the first and second circuits, the first circuit is
configured to transmit the announcement signal and data to the
second circuit using the first transfer link.
Description
RELATED U.S. APPLICATION DATA
[0001] This application is a continuation of U.S. application Ser.
No. 12/570,082 filed on Sep. 30, 2009, which in turn is a
divisional application of U.S. application Ser. No. 11/776,390
filed Jul. 11, 2007, which in turn is a continuation of U.S.
application Ser. No. 10/666,221, filed Sep. 18, 2003, now
abandoned. Each of the prior filed applications is hereby fully
incorporated herein by reference.
FOREIGN APPLICATION PRIORITY DATA
[0002] The present application claims priority to German patent
application no. DE10243197.3, filed Sep. 18, 2002, the disclosure
of which is hereby incorporated by reference.
FIELD OF THE INVENTION
[0003] The present invention relates to a digital signal transfer
method, particularly for transferring a digital signal via a
potential barrier.
BACKGROUND
[0004] The transfer of digital control signals and data signals via
a potential barrier is frequently necessary in electrical
installations in order to electrically isolate different circuits,
for example, a circuit which produces a control signal and a
circuit which processes the control signal, from one another. To
reduce the number of coupling points between such circuits, which
are to be electrically isolated, and data lines, serial transfer
methods are frequently used. Thus, by way of example,
microcontrollers (IC) use interfaces of the RS-485 type or use SPI
(Serial Parallel Interface) interfaces to communicate with circuit
components that are to be actuated. In this context, it is
desirable to transfer data at a high transfer rate and to isolate
potentials between the microcontroller and the circuits that are to
be actuated. In addition, the transfer method needs to be highly
immune to interference.
[0005] For data transfer with electrical isolation between a
transmitter circuit and a receiver circuit, it is known practice to
use transformers, particularly planar transformers integrated on an
IC, as described in Published German Patent Application 101 00 282
A1, for example, as data couplers. To transfer signals using such
transformers, it is necessary to convert the signals into pulse
trains that are suitable for transfer, and it is known practice,
for example, to produce cyclic pulse trains from a binary control
signal and to transfer them, as described in U.S. Pat. Nos.
4,027,152, 4,748,419, 5,952,849 and 6,262,600, for example.
[0006] Planar transformers integrated in an integrated circuit,
which are also called coreless transformers, are capable of
transferring data at a speed of up to 1 Gbaud, where not just the
high data transfer speed, but also the low power consumption with
good immunity to interference make such transformers attractive as
coupling modules in data transfer links.
SUMMARY
[0007] It is accordingly an object of the invention to provide a
digital signal transfer method that overcomes the above-mentioned
disadvantages of the prior art methods of this general type. In
particular, it is an object of the invention to provide a fast and
secure data transfer method, particularly a transfer method that is
suitable for data transfer using integrated transformers as
coupling modules.
[0008] With the foregoing and other objects in view there is
provided, in accordance with the invention, an embodiment of the
inventive digital signal transfer method in which a first and a
second transfer channel are provided. The first transfer channel is
used as an "announcement channel" for data transfer and the second
transfer channel is used as an actual data channel. To transfer a
data signal, an announcement signal including at least one pulse is
first transferred via the first transfer channel. The data signal
is subsequently transferred via the second transfer channel within
a data signal time window lasting for a prescribed period after the
announcement signal.
[0009] The inventive method involves the announcement signal and
the data signal being transferred at different times via separate
transfer channels, which ensures a very high level of immunity to
interference. The likelihood of an interference signal which
appears on the data channel being incorrectly identified as a
useful signal is low in the case of the inventive method, because
the receiver accepts only such signals that are received within the
data signal time window after the announcement signal.
[0010] Preferably, the transfer channels each include a magnetic
coupling element, particularly a transformer integrated in an
integrated circuit. The use of two transfer channels, with
announcement signals being transferred on the first transfer
channel and the data signal being transferred on the second
transfer channel, at different times from one another, also reduces
immunity to interference, when transformers are used as coupling
elements, because electromagnetic interference appears in the two
transformers in common mode, i.e., the interference brings about
signals which occur simultaneously and whose signal profiles are
the same. Such interference signals are easy to detect in a
receiver circuit and are correspondingly easy to isolate from the
useful signal.
[0011] Preferably, the data signal time window within which data
signals are transferred starts after a period which is greater than
zero after the announcement signal. By way of example, the
announcement signal includes just a single pulse, and the data
signal time window does not start until after the end of this
announcement pulse.
[0012] In one embodiment of the invention, a further transfer
channel is provided which is used to transfer control information.
Such control information includes a parity check signal or a
transfer check signal, for example. Preferably, the data signal is
transferred within the respective data signal time window in coded
form in order to increase redundancy and hence to increase immunity
to interference further, and any coding methods which increase
redundancy can be used for this. In the simplest case, a data pulse
or a data pulse train is repeated within the data signal time
window, that is to say is transferred a plurality of times at
successive times.
[0013] The inventive method is also suitable for transferring a
binary signal that has a first or a second signal level. Such
signal profiles, in which a signal assumes a first signal level or
a second signal level over a comparatively long period, which is
much longer than the data signal time window, are typical of
control signals, for example turn-on and turn-off signals for
loads, which need to be transferred in electrical installations
with isolation of potentials. In one embodiment of the inventive
method for transferring such control signals, provision is made for
announcement pulses to be transferred at regular intervals of time
and for respective pulse trains that represent the first or the
second signal level to be transferred during the data signal time
windows which follow the announcement signals. In the simplest
case, a pulse is transferred during the data signal time window
when the control signal assumes a first signal level, and no pulse
is transferred when the control signal assumes a second signal
level. The transfer, repeated at cyclic intervals of time, of pulse
trains which represent the signal level of the control signal helps
to increase immunity to interference during the transfer of such
control signals, since even if interference arises during a data
signal time window and makes data transfer impossible, the data
signal is transferred during one of the subsequent data signal time
windows, after the interference has declined.
[0014] With the foregoing and other objects in view there is also
provided, in accordance with the invention, a digital signal
transfer method that includes providing a transfer channel. An
announcement signal including at least one pulse is transmitted via
the transfer channel. A data signal is also transmitted via the
transfer channel within a data signal time window lasting for a
prescribed period after the announcement signal.
[0015] Other features which are considered as characteristic for
the invention are set forth in the appended claims.
[0016] Although the invention is illustrated and described herein
as embodied in a digital signal transfer method, it is nevertheless
not intended to be limited to the details shown, since various
modifications and structural changes may be made therein without
departing from the spirit of the invention and within the scope and
range of equivalents of the claims.
[0017] The construction and method of operation of the invention,
however, together with additional objects and advantages thereof
will be best understood from the following description of specific
embodiments when read in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a block diagram of a data transfer link having two
transfer channels that each include a coupling element for
isolating potentials in a transmitter circuit and a receiver
circuit.
[0019] FIG. 2 is a diagram showing exemplary signal profiles of
signals on the first and second transfer channels.
[0020] FIG. 3A is a diagram showing exemplary signal profiles of
signals, on the first and second transfer channels and also time
profiles for selected internal signals in a transmitter circuit and
a receiver circuit, which occur in one embodiment of a transfer
method.
[0021] FIG. 3B is a diagram showing exemplary signal profiles of
signals, on the first and second transfer channels and also on a
third channel that is used as control information channel, which
occur in a modification of the method.
[0022] FIG. 4 is a diagram showing selected signal profiles for a
method for transferring a binary control signal with regular
announcement pulses.
[0023] FIG. 5 is a diagram showing selected signal profiles for a
method for transferring a binary control signal with
event-controlled announcement pulses.
[0024] FIG. 6 is a block diagram of a data transfer link having a
single transfer channel that includes a coupling element for
isolating potentials in a transmitter circuit and a receiver
circuit.
DETAILED DESCRIPTION
[0025] Unless otherwise indicated, the same reference symbols
denote the same circuit components and signals having the same
meaning in the figures.
[0026] Referring now to the figures of the drawing in detail and
first, particularly, to FIG. 1 thereof, there is schematically
shown a data transfer link with a transmitter circuit 10, to which
an input signal Sin is supplied, and a receiver circuit 20 which
provides an output signal Sout which is dependent on the input
signal Sin. The data transfer link also includes a first transfer
channel with a coupling element TR1 and a second transfer channel
with a second coupling element TR2. The coupling elements TR1, TR2
preferably each include an integrated transformer for isolating the
potentials of the transmitter circuit 10 and the receiver circuit
20.
[0027] In the case of the transfer link shown, the first transfer
channel is used as an announcement channel to transfer an
announcement signal S1 when data transfer needs to take place. The
second transfer channel is used as the actual data channel to
transfer the actual data signal containing the useful information
to the receiver. Both the announcement signal S1 and the data
signal S2 are individual pulses or pulse trains that are generated
by the transmitter circuit 10. The length of the individual pulses
is matched to the transfer properties of the coupling elements TR1,
TR2 in order for these pulses to be transferred optimally on
interference-free channels. As is sufficiently well known, each of
the transformers TR1, TR2 includes a primary coil which is excited
by the signal S1 or S2 generated by the transmitter circuit 10. The
magnetic coupling of the primary coil and the secondary coil mean
that the transmitter-end pulse trains result in corresponding
receiver-end pulse trains that are detected by the receiver circuit
20.
[0028] FIG. 2 fundamentally shows the signal profiles for the
announcement signal S1 and the data signal S2 in the inventive
method. The method provides for the first transfer channel, which
serves as the announcement channel, to be used to transfer an
announcement signal S1. The method also includes transferring a
pulse or a pulse train for the data signal within a respective time
window lasting for a prescribed period after a pulse or a pulse
train for the announcement signal. In the example shown in FIG. 1,
the announcement signal transferred via the announcement channel is
a respective individual announcement pulse. A period td after the
start of the announcement pulse is followed by the start of a time
window, lasting for a period tf, within which the data signal is
transferred. The data signal includes just one data pulse per time
window in the example shown in FIG. 2. The period td after which
the data signal time window starts is longer in this case than the
pulse length of the announcement pulse, which means that the time
window does not start until after the end of the announcement
pulse, as a result of which the announcement pulses and the data
pulses following the announcement pulses within the time windows
are transferred at different times from one another, resulting in
immunity to interference when using the method.
[0029] The data pulse train transferred during the data signal time
window can contain the information that is to be transferred in
virtually any manner. Thus, by way of example, just one pulse can
be transferred during a data signal time window such that the
information which is to be transferred is held in the period, for
example, by which this pulse is additionally shifted with respect
to the start of the data signal time window. In addition, a
plurality of, for example n, pulses representing that single bits
of a data word of a length of n bits to be transferred, can be
transferred during a data signal time window.
[0030] The transmitter and the receiver are synchronized in the
inventive method by virtue of the shape of the announcement signal
generated by the transmitter, the period for which the data signal
time window lasts, and also because the interval of time between
the announcement signal and the data signal time window is known at
the receiver. Whenever an announcement signal is received, this
results in the receiver taking the known information about the
period for which the data signal time window lasts and the latter's
distance from the announcement signal as a basis for producing a
time window within which pulses which are received on the data
channel at the receiver are accepted as a data signal.
[0031] If the transmitter circuit 10 contains a coder which codes
the signal transferred within the data signal time windows, the
receiver circuit contains a corresponding decoder which provides
the output signal Sout from the signals received via the data
channel within the data signal time windows.
[0032] FIGS. 3A and 3B illustrate an exemplary embodiment of the
inventive method, in which announcement pulses in the announcement
signal S1 are generated cyclically in time with a clock signal Ts
having a clock period tc. In time with this clock signal, an input
signal Sin is also available which is shown by way of example as a
binary signal whose level can change in time with the clock signal
Ts. Such signals appear at the outputs of shift registers, for
example. The information about the current level of the input
signal Sin is transferred in data signal time windows of length tf.
The start of these data signal time windows respectively come a
period td after the start of an announcement pulse. The signal
level of the input signal Sin is converted into the pulses
transferred during the data signal time window by virtue of
transferring two pulses at successive times in the data signal time
window for a first level, for example, an upper level, of the input
signal Sin, while no pulses are generated and transferred during
the time window for a second level, for example, a lower level, of
the input signal Sin. The transfer of two successive pulses serves
for redundancy and hence to increase the immunity to
interference.
[0033] The receiver circuit 20 contains a shift register. The
content of this shift register is shown in FIG. 3A. This shift
register has a logic one written to it whenever two pulses are
detected during the data signal time window. In the case of the
fourth data signal time window shown in FIGS. 3A and 3B, there is a
transfer error, because only one pulse is being transferred instead
of two pulses. This one pulse is not sufficient for a logic one to
be written to the shift register. If no pulses are transferred
during a data signal time window after an announcement pulse, a
logic zero is written to the shift register.
[0034] In the method shown in FIG. 3A, provision is also made for a
parity signal announcement pulse to be transferred via the
announcement channel and for the associated parity signal to be
transferred via the data channel within a data signal time window
lasting for the period tf. This method involves the stipulation
that every nth pulse of the announcement signal 51 is an
announcement pulse for a parity signal or that a parity signal is
transferred during every nth data signal time window. For the data
transfer of 8-bit data words, every ninth announcement pulse is an
announcement pulse for a parity signal.
[0035] In the case of the method shown in FIG. 3A, the receiver 20
generates an internal transfer signal after a period is after the
parity signal announcement pulse. The internal transfer signal
governs the reading of the shift register described above for the
purpose of generating the output signal Sout, provided that the
parity check performed on the basis of the parity signal delivers a
correct result.
[0036] FIG. 3B shows a modification of the method shown in FIG. 3A
in which a third transfer channel is provided, which is shown in
dashes in FIG. 1 and which likewise has a coupling element,
preferably a magnetic coupling element, used to transfer a parity
signal announcement pulse whenever the transfer of a data word has
ended. Additionally, a parity signal is transferred via the data
channel during a data signal time window lasting for the period tf
after this parity signal announcement pulse. The provision of a
separate channel for the parity signal announcement pulse reduces
the systems susceptibility to interference and also makes the
system more flexible for transferring data words of different
length. Hence, a parity check is not performed until a parity
signal announcement pulse is received on the further channel.
[0037] The method shown in FIG. 3B also has provision for the
further channel to be used to transfer a stop pulse which governs
the generation of the internal transfer signal, which in turn
governs the reading of the shift register to which the data from
the data channel have previously been written. To increase immunity
to interference, a pulse is transferred on the announcement
channel, preferably simultaneously with the stop pulse. An internal
transfer signal for reading the shift register and for outputting
the output signal Sout is produced at the output of the receiver 20
only when the receiver receives the stop pulse and the pulse on the
announcement channel.
[0038] FIG. 4 illustrates an exemplary embodiment of a method for
transferring the information contained in a control signal Sin. The
control signal Sin is a binary signal which assumes an upper or a
lower level. The respective level is present for a period which is
normally much longer than the period for which a data signal time
window lasts. For transferring such a signal, provision is made for
the announcement channel to be used to transfer announcement pulses
at regular intervals of time and to transfer at least one pulse
containing information about the current signal level of the
control signal Sin within data signal time windows, lasting for the
period tf, the start of which respectively comes a period td after
the start of an announcement pulse. In the exemplary embodiment
shown in FIG. 4, a pulse is transferred within the time window tf
when the input signal Sin assumes an upper signal level, and no
pulse is transferred within the data signal time window when the
input signal Sin assumes a lower signal level.
[0039] The inventive method thus involves transferring pulses that
indicate the current level of the input signal Sin at regular
intervals of time. The result of this is a high level of immunity
to interference, since even if interference arises during one or
more data signal time windows, a correct pulse is transferred
sooner or later.
[0040] In the signal profile shown in FIG. 4, the input signal Sin
changes from a lower level to an upper level at a time t1. The
information about this level change is transferred with a time
delay after a period tdp in the method. This period tdp results
from the interval of time td between the announcement pulse and the
data signal time window and from the interval of time between the
level change in the input signal Sin and the announcement pulse.
Accordingly, a delay tdn is produced when the signal level changes
from an upper level to a lower level of the input signal Sin, which
accordingly results from a delay time between the time t2 at which
the level change takes place and the time of the next announcement
pulse and from the interval of time td between the announcement
pulse and the data signal time window to which the information
about the level change which has taken place is transferred.
[0041] FIG. 5 illustrates a modification to the method for
transferring a binary signal Sin which is explained with reference
to FIG. 4. This method involves first generating the announcement
pulses cyclically, as can be seen, in particular, from the first
time period, during which the signal assumes a high level. In
addition, the announcement pulses are generated on an
event-controlled basis when there is a level change in the input
signal Sin, in order to reduce the delay time between the level
change and the data signal's pulse which represents this level
change as compared with the method in FIG. 4. From the time profile
for the announcement signal S1 in FIG. 5, it becomes clear that,
besides the cyclically recurring announcement pulses, further
announcement pulses are present whose appearance is dependent on a
level change in the input signal Sin. The delay time which elapses
during this method in line with FIG. 5 between a rising edge of the
input signal Sin and the transmission of a useful pulse which
represents this edge corresponds essentially to the period td,
provided that the useful pulse is transferred immediately at the
start of the data signal time window. The maximum time delay
between a level change in the input signal Sin and the output
signal Sout is tdn=tp+tf, where tp is again the period between the
start of an announcement pulse and a data signal time window, and
tf is the length of the data signal time window. This delay time
arises when the signal level of the input signal changes from an
upper signal level to a lower signal level. This information is
transferred by not transferring a pulse during the data signal time
window, which means that it is necessary to wait the length of this
time window until the output signal Sout changes its level.
[0042] In the method explained up to now, announcement pulses S1
announcing a data transfer and data pulses S2 are transferred via
physically separate channels TR1, TR2 in order to increase immunity
to interference. If a reduction in the immunity to interference is
acceptable, then one modification to the method explained up to now
has provision for the announcement pulses S1 and the data pulses S2
to be transferred via just one common channel 30 as depicted in
FIG. 6 instead of via separate channels. In this case, the data
pulses S2 are each transferred within a data signal time window of
prescribed length which comes after an announcement pulse S1 in
time, with, as in the case of the method explained previously, the
receiver "accepting" only such data pulses that are transferred
within the data signal time window after an announcement signal or
announcement pulse.
[0043] In the case of this modification of the method, just one
transformer TR1 is required, which means that the chip area
required for implementing the transfer link and the associated
transmitter and receiver circuits is reduced by up to 50% as
compared with the method with two transfer channels.
* * * * *