U.S. patent application number 11/596642 was filed with the patent office on 2008-09-04 for multi-channel pulse modulator system.
Invention is credited to Lars Arknaes-Pedersen, Kim Rishoj Pedersen.
Application Number | 20080211594 11/596642 |
Document ID | / |
Family ID | 34957542 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080211594 |
Kind Code |
A1 |
Pedersen; Kim Rishoj ; et
al. |
September 4, 2008 |
Multi-Channel Pulse Modulator System
Abstract
The present invention relates to a multi-channel pulse modulator
system comprising a pulse modulator circuit, wherein said pulse
modulator circuit comprises an N-channel, wherein the modulator
output is output from the pulse modulator circuit by means of L
output connections of the pulse modulator circuit and where L is
less than the number of modulator channels N. The invention further
relates to a method of converting an N-channel pulse modulated
signal into an M-channel signal, where M is less than N.
Inventors: |
Pedersen; Kim Rishoj; (Ega,
DK) ; Arknaes-Pedersen; Lars; (Viby J, DK) |
Correspondence
Address: |
CANTOR COLBURN, LLP
20 Church Street, 22nd Floor
Hartford
CT
06103
US
|
Family ID: |
34957542 |
Appl. No.: |
11/596642 |
Filed: |
May 30, 2005 |
PCT Filed: |
May 30, 2005 |
PCT NO: |
PCT/DK2005/000358 |
371 Date: |
September 26, 2007 |
Current U.S.
Class: |
332/109 |
Current CPC
Class: |
H04L 25/4902 20130101;
H03F 1/32 20130101; H03F 2200/114 20130101; H03F 3/217 20130101;
H03F 2200/351 20130101 |
Class at
Publication: |
332/109 |
International
Class: |
H03K 7/08 20060101
H03K007/08 |
Foreign Application Data
Date |
Code |
Application Number |
May 28, 2004 |
DK |
PCT/DK2004/000376 |
Claims
1. A multi-channel pulse modulator system comprising a pulse
modulator circuit, wherein said pulse modulator circuit comprises
an N-channel pulse width modulator for modulating an N-channel
input signal, wherein modulator output is multiplexed and output
from the pulse modulator circuit by means of L output connections
of the pulse modulator circuit and where L is less than the number
of modulator channels N.
2. A multi-channel pulse modulator system according to claim 1,
wherein said multi-channel pulse modulator system further comprises
a switched output stage, wherein said pulse modulator circuit
comprises an N-channel pulse width modulator, wherein the modulator
output is interfaced from the pulse modulator circuit to the
switching output stage by means of L output connections, of the
modulator circuit and where L is less than the number of modulator
channels N.
3. A multi-channel pulse modulator system according to claim 1,
wherein the L output connections outputs an M-channel signal where
M is less than N, wherein said M-channel signal is established by a
pulse signal combiner, wherein said pulse signal combiner combines
at least one of said M-channel signals into a non-coincident pulse
modulated signal representing at least a subset of an N-channel
pulse modulated signal established by said N-channel pulse width
modulator.
4. A multi-channel pulse modulator system according to claim 2,
wherein the number of output channels of the switching output stage
is N.
5. A multi-channel pulse modulator system according to claim 3,
wherein said pulse signal combiner combines said N-channel pulse
modulated signal by an initial establishment of said N-channel
pulse signal of non-coincident pulses and whereby said
non-coincident pulses subsequently are combined into said M-channel
signal.
6. A multi-channel pulse modulator system according to claim 3,
whereby said M-channel output comprises a sequence of analog
pulses, and whereby said sequence of analog pulses defines the
pulses of an N-channel pulse modulated signal.
7. A multi-channel pulse modulator system according to claim 1,
wherein said pulse modulator circuit comprises a pulse modulator
chip.
8. A multi-channel pulse modulator system according to claim 1,
wherein said L connections comprises L output pins.
9. A multi-channel pulse modulator system according to claim 2,
wherein said switched output stage is comprised in one single
chip.
10. A multi-channel pulse modulator system according to claim 2,
wherein said switched output stage is distributed in two or more
chips.
11. A multi-channel pulse modulator system according to claim 1,
wherein said pulse modulation is a two-level modulation, a
three-level modulation or a higher-level modulation.
12. A multi-channel pulse modulator system according to claim 1,
wherein said multi-channel pulse modulator system comprises a pulse
width modulation system comprising a multi-channel pulse width
modulator comprised in said pulse modulator circuit.
13. A multi-channel pulse modulator system according to claim 1,
wherein said pulse modulator system is an audio converter
14. A multi-channel pulse modulator system according to claim 2,
wherein at least one of said L-output connections facilitate a
bi-directional communication between the modulation circuit and
said output stage.
15. A multi-channel pulse modulator system according to claim 2,
wherein said pulse modulator circuit comprises at least one
connection dedicated for receipt of information from the state of
the output stage.
16. A multi-channel pulse modulator system according to claim 2,
wherein said output stage comprises a pulse signal splitter.
17. A multi-channel pulse modulator system according to claim 16,
wherein said pulse signal splitter corrects modifications applied
in the pulse signal combiner.
18. A multi-channel pulse modulator system according to claim 1,
whereby the number L of output connections is one.
19. A multi-channel pulse modulator system according to claim 1,
whereby the number L of output connections is two.
20. A multi-channel pulse modulator system according to claim 3,
whereby at least one of said M-channels are bidirectional.
21. A multi-channel pulse modulator system according to claim 3,
whereby at least a subset of said M-channels are directed from the
pulse modulator circuit.
22. A multi-channel pulse modulator system according to claim 21,
whereby at least a further subset of said M-channels are directed
to the pulse modulator circuit.
23. A multi-channel pulse modulator system according to claim 3,
wherein said M-channel signal is converted into an N-channel signal
and distributed to N-channels of an output stage as pulse modulated
signals.
24. A multi-channel pulse modulator system according claim 23,
wherein said N-channel signal distributed to said output stage
corresponds to an N-channel signal established by an N-channel
pulse width modulator of said pulse modulator circuit.
25. Method of converting an N-channel pulse width modulated signal
established from an N-channel input signal into an M-channel
signal, where M is less than N, said method comprising: modifying
at least one of said M-channel signals into a non-coincident pulse
modulated signal representing at least a subset of said N-channel
pulse width modulated signal and where said subset of said
N-channel pulse width modulated signal comprises at least two
channels.
26. Method of converting an N-channel pulse width modulated signal
into an M-channel signal according to claim 25, whereby said
converting of said N-channel pulse width modulated signal comprises
an initial establishment of said N-channel pulse width modulated
signal of non-coincident pulses and whereby said non-coincident
pulses subsequently are combined into said M-channel signals.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a multi-channel pulse modulator
according to the provisions of claim 1.
SUMMARY OF THE INVENTION
[0002] The present invention relates to a multi-channel pulse
modulator system comprising a pulse modulator circuit PMC,
[0003] wherein said pulse modulator circuit PMC comprises an
N-channel modulator PWMS1, PWMS2, . . . PWMS6,
[0004] wherein the modulator output is output from the pulse
modulator circuit PMC by means of L output connections OP1, OPL of
the pulse modulator circuit PMC and where L is less than the number
of modulator channels N.
[0005] According to the invention an advantageous interfacing has
been established between the modulator circuit and the switching
stage in the sense that a multi-channel, e.g. N-channel signal, is
modulated into an N or N set of parallel signals by the modular of
the modulator circuit and the modulated signal may be encoded or
converted into a signal representation, which may be output from
the modulator circuit in a small-level signal by means of a number
of output connections L, e.g. L output pins, which is less than the
number of modulated channels. In this way, an advantageous export
of modulated signals may be obtained by a reduced number of pins of
the modulator circuit and by means of small-level signals. L is at
least one according to the invention. Thus, a complete
multi-channel pulse, e.g. an N-channel modulated signal may be
transmitted as a one channel by e.g. ultimately one single output
connection or e.g. as one channel by e.g. two output connections
forming a differential output connection of the circuit. Numerous
other configurations of the output connection may be applied within
the scope of the invention.
[0006] This advantage is in particular advantageous in relation to
a number of modulated small-level signal channels, which must be
fed to a switched high-level output stage.
[0007] When said multi-channel pulse modulation system further
comprises a switched output stage SWOS,
[0008] wherein said pulse modulator circuit PMC comprises an
N-channel modulator PWMS1, PWMS2, . . . PWMS6; PM,
[0009] wherein the modulator output is interfaced from the pulse
modulator circuit PMC to the switching output stage SWOS by means
of L output connections, e.g. output pins OP1, OPL, of the
modulator circuit PMC and where L is less than the number of
modulator channels N, an advantageous embodiment of the present
invention is obtained.
[0010] When the L output connections (OP1, OPL) outputs an
M-channel signal where M is less than N,
[0011] wherein said M-channel signal is established by a pulse
signal combiner (PSC),
[0012] wherein said pulse signal combiner (PSC) combines at least
one of said M-channel signals into a non-coincident pulse modulated
signal (202, 203) representing at least a subset of an N-channel
pulse modulated signal established by said N-channel modulator
(PWMS1, PWMS2, . . . PWMS6; PM), an advantageous embodiment of the
present invention is obtained.
[0013] When the number of output channels (OC1, OC2, OC3, . . .
OCN) of the switching output stage (SWOS) is N, an advantageous
embodiment of the present invention is obtained.
[0014] When said pulse signal combiner (PSC) combines said
N-channel pulse modulated signal by an initial establishment of
said N-channel pulse signal of non-coincident pulses and whereby
said non-coincident pulses subsequently are combined into said
M-channel signal, an advantageous embodiment of the present
invention is obtained.
[0015] A very interesting feature of the signal combining and
signal splitting according to the invention is that cross-talk in
the multi-channel output stage may be minimized due to the fact
that the pulses transmitted over each of the M-channels by nature
are non-coincident, thereby invoking that none of the output stages
addressed by the M-channel switches at the same time unless a
further signal processing occurs during the signal splitting and
distributing to the N-channels at the receiving end.
[0016] When said M-channel output comprises a sequence of analog
pulses, and whereby said sequence of analog pulses defines the
pulses of an N-channel pulse modulated signal, an advantageous
embodiment of the present invention is obtained.
[0017] When said pulse modulator circuit comprises a pulse
modulator chip (PMC), an advantageous embodiment of the present
invention is obtained.
[0018] According to a preferred embodiment of the invention the
pulse modulator circuit may comprise a single chip.
[0019] When said L connections comprises L output pins (OP1, OPL),
an advantageous embodiment of the present invention is
obtained.
[0020] When said switched output stage (SWOS) is comprised in one
single chip, an advantageous embodiment of the present invention is
obtained.
[0021] The switched output stage may e.g. be comprised in one
single chip, which may be advantageous in several different
applications where a multi-channel amplifier is applied.
[0022] When said switched output stage (SWOS) is distributed in two
or more chips, an advantageous embodiment of the present invention
is obtained.
[0023] When applying a multi-chip or multi-components switched
output stage an advantageous embodiment may be obtained with
respect to the single switching amplifiers and/or with respect to
the arranging of the amplifiers in relation to space, cooling,
topology in general, etc. When applying two or more chips, a
distribution method must be applied in order to distribute the
packed pulse modulated signal to the relevant channel amplifiers of
the output stage.
[0024] When said pulse modulation is a two-level modulation, a
three-level modulation or a higher-level modulation, an
advantageous embodiment of the present invention is obtained.
[0025] When said multi-channel pulse modulation system comprises a
pulse width modulation system comprising a multi-channel pulse
width modulator comprised in said pulse modulator circuit.
[0026] When said pulse modulation amplifier is an audio converter,
an advantageous embodiment of the present invention is
obtained.
[0027] When at least one of said L-output connections (OP1, OPL)
facilitate a bidirectional communication between the modulation
circuit (PMC) and said output stage, an advantageous embodiment of
the present invention is obtained.
[0028] A bi-directional communication established with respect to
each output or representation thereof facilitate that information
may be fed back from the output stage to the pulse modulator
circuit by means of few connections, e.g. pins. Such information
may e.g. be the actual switching times of the individual switched
channels may be fed back to the modulator circuit, thereby enabling
e.g. a desired compensation or modulation established responsive to
actual switching times of the individual output channels.
[0029] When said pulse modulator circuit (PMC) comprises at least
one connection dedicated for receipt of information from the state
of the output stage, an advantageous embodiment of the present
invention is obtained.
[0030] When said output stage comprises a pulse signal splitter
(PSS; 124), an advantageous embodiment of the present invention is
obtained.
[0031] When said pulse signal splitter (PSS; 124) corrects
modifications applied in the pulse signal combiner (PSC), an
advantageous embodiment of the present invention is obtained.
[0032] When correcting modifications applied to the N-channel pulse
modulated signal in the pulse signal combiner, errors may be
avoided in the final pulse modulated signal of the relevant channel
of the output stage.
[0033] It should of course be noted that such so-called errors may,
according to a preferred embodiment of the invention, relate to
deliberate modifications of the N-channel pulse modulated signal in
order to avoid simultaneous switching of the channels of the output
stage. Such deliberate errors should of course not be
corrected.
[0034] When the number L of output connections is one, an
advantageous embodiment of the present invention is obtained.
[0035] According to an embodiment of the invention, an M-channel
signal may be output as a single-ended signal. Thus, according to
an embodiment of the invention, a one-channel signal may be
transmitted by one output connection.
[0036] When the number L of output connections is two, an
advantageous embodiment of the present invention is obtained.
[0037] According to an embodiment of the invention, an M-channel
signal may be output as a differential signal.
[0038] When at least one of said M-channels are bidirectional, an
advantageous embodiment of the present invention is obtained.
[0039] The advantage of applying bidirectionality between the pulse
modulator circuit and the further switching circuitry is that e.g.
switch delay times of the switching stage(s) may vary dynamically
and may thereby be evaluated and compensated in the pulse modulator
circuit. According to an embodiment of the invention, each of the
applied M-channels are directional, thereby optimizing the signal
flow between the pulse modulator circuit and the switching
stage.
[0040] When at least a subset of said M-channels are directed from
the pulse modulator circuit (PMC), an advantageous embodiment of
the present invention is obtained.
[0041] When at least a further subset of said M-channels are
directed to the pulse modulator circuit (PMC), an advantageous
embodiment of the present invention is obtained.
[0042] An advantage of e.g. dedicating one or several channels as
return path(s) is that a relatively exhaustive information about
the actual switching stage(s) and the general state of these
stage(s) may be fed on a runtime basis back to the pulse modulator
circuit for monitoring, evaluation and/or compensation
purposes.
[0043] When said M-channel signal is converted into an N-channel
signal and distributed to N-channels of the output stage (AMP1, . .
. , AMP6) as pulse modulated signals, an advantageous embodiment of
the present invention is obtained.
[0044] When said N-channel signal distributed to said output stage
corresponds to an N-channel signal established by an N-channel
pulse modulator (N-PMS) of said pulse modulator circuit (PMC), an
advantageous embodiment of the present invention is obtained.
[0045] The present invention further relates to a method of
converting an N-channel pulse modulated signal into an M-channel
signal, where M is less than N,
[0046] whereby said converting involves that at least one of said
M-channel signals are modified into a non-coincident pulse
modulated signal representing at least a subset of said N-channel
pulse modulated signal and where said subset of said N-channel
pulse modulated signal comprises at least two channels.
[0047] When said converting of said N-channel pulse modulated
signal involves an initial establishment of said N-channel pulse
signal of non-coincident pulses and whereby said non-coincident
pulses subsequently are combined into said M-channel signals, an
advantageous embodiment of the present invention is obtained.
THE DRAWINGS
[0048] The invention will now be described with reference to
drawings where
[0049] FIG. 1 illustrates principles of signal combining and signal
splitting according to the invention in pulse modulator
multi-channel systems,
[0050] FIG. 2 illustrates some general principles of the
invention,
[0051] FIG. 3A-3C illustrate different properties of the individual
channels of the modulator applied in the specific embodiment of
FIGS. 4A and 4B,
[0052] FIG. 4A-4B illustrate specific multi-channel embodiments
applying the principles of the present invention,
[0053] FIG. 5A-5B illustrate possible combination signals of the
modulator output signals according to an embodiment of the present
invention, and where
[0054] FIG. 6 illustrates a more detailed view of a part of an
embodiment of the present invention.
DETAILED DESCRIPTION
[0055] FIG. 1 illustrates principles of signal combining and signal
splitting applied in an exemplary N-M-N pulse modulator
multi-channel system according to an embodiment of the
invention.
[0056] According to the invention, an N-channel pulse modulated
signal N-PMS, e.g. an N-channel pulse width modulated signal
modulated according to conventional pulse width modulation
principles is combined into an M-channel signal, preferably analog
pulse modulated signal, by means of a pulse signal combiner. The
M-channel signal is interfaced from the modulator circuit by means
of a number of L connections of the modulator circuit. The
modulator may e.g. be comprised in a chip. According to the
invention, the number of output connections, e.g. output pins, of
e.g. a 6-channel modulator chip may be as low as one.
[0057] The M-channel signal may then be transmitted to an output
stage and split into an N-channel pulse modulated signal by means
of a pulse signal splitter and thereby regenerated as intended and
corresponding to the principles applied when the N-channel pulse
modulated signal was established in the pulse modulator.
[0058] According to a very preferred embodiment of the invention,
the N-channel pulse modulated signal should be established as a
parallel sequence of N pulse modulated signal streams and where
none of the switching times of the complete sequence or at least
two of the N channels are coincident. Such a modulation technique
facilitates low cross-talk in the multi-channel output stage and a
relatively straightforward combining of the N-channels at the
modulator side by the pulse signal combiner PSC as all pulses may
be merged into one analog signal without conflicts arising from
e.g. two coincident pulse trigger signals in two parallel
N-channels.
[0059] FIG. 2 illustrates some general principles of the
invention.
[0060] The illustrated pulse modulator system according to the
invention comprises a pulse modulator circuit PMC receiving input
signals IS. The input signals may have any form and be established
internally in the modulator circuit PMC or they may be established
by interfacing the pulse modulator circuit with another signal
processing circuit. Input signals may comprise a single
fast-running stream of data or a parallel stream of data,
preferably one input line per channel.
[0061] The pulse modulator circuit may e.g. comprise a system of N
pulse modulator channels, e.g. six, where the input signal is
converted into a corresponding number of streams of pulse
modulation representations PMr. The pulse modulator combines the
pulse modulation representations PMr into a low number, e.g. one
differential coding of all channels of the pulse modulation
representations and interfaces the stream via L output connections
OP1, . . . ,OPL, e.g. two, of the circuit PMC as an output pulse
modulation representation OPMr.
[0062] In this way, a multi-channel pulse modulation representation
has been established in a small-signal environment and represented
as such, and the multi-channel output pulse modulation
representations OPMr have been interfaced with the environment by a
number of modulator circuit PMC output connections OP1, . . . ,OPL
which is lower than the number of channels N.
[0063] The output pulse modulation representations OPMr are then
interfaced with a multi-channel switched output stage SWOS by means
of input connections IP1, . . . IPL, e.g. pins, via L-communication
lines CL1, . . . CLL. The number of channels of the output stage
would typically correspond to the number of channels N of the pulse
modulator circuitry PMC. It should in this context be stressed that
the invention may apply even with only one communication line as
the sole communication line from the modulator to the output stage,
although two lines have been shown in the drawing.
[0064] The switched output stage may be arranged in one chip or in
a multi-chip arrangement as indicated by the dotted lines.
[0065] The multi-channel switched output stage SWOS receives the
output pulse modulation representations OPMr, and a pulse signal
splitter PSS decodes (splits) the signal into N channels of
reestablished pulse modulated signals RMS. The N channels of
reestablished pulse modulation representations are then fed to
switched output stages SOS and output by means of N-output channels
OC1, OCN.
[0066] In the illustrated embodiments, each of the outputs are fed
to demodulators and subsequently fed to loudspeakers LS.
[0067] According to a preferred embodiment of the invention, the
above described pulse modulator circuit PMC may advantageously
comprise a pulse modulator chip comprising a number of output
connections preferably constituted by output pin(s).
[0068] FIG. 3A-3C illustrate a few out of several different
principle topologies of PWM-amplifier system which may find use in
a multi-channel system of the invention,
[0069] FIG. 3A illustrates an embodiment of a pulse width modulator
system PWMS of an embodiment of the invention. It comprises a
modulator input MI receiving an input signal IS. The input signal
is preferably the utility signal to be pulse width modulated. An
amplitude distribution filter ADF processes the input signal IS in
order to adapt the input signal amplitude distribution to achieve
the best performance of subsequent stages. The amplitude
distribution filter ADF establishes an output signal OS, also
referred to as intermediate output signal, which is fed to a pulse
width modulator PMOD. The pulse width modulator PMOD establishes a
pulse width modulated representation of the output signal, and
outputs it via a modulator output MO as a modulator output signal
MOS. It is noted that the illustrated embodiment is merely an
example, and that several other pulse width modulator systems are
suitable for use with the present invention. In a preferred
alternative embodiment, the amplitude distribution filter ADF is,
e.g., integrated into the pulse width modulator PMOD in such a way
that it would render a simple illustration unclear with respect to
the present invention. A preferred embodiment is disclosed in
co-pending application PCT/DK2004/000376, hereby incorporated by
reference.
[0070] FIG. 3B illustrates a further embodiment of a pulse width
modulator system PWMS of the present invention, and a context for
its use. It comprises all elements of FIG. 1A coupled as described
above. It furthermore comprises an amplifier AMP receiving the
modulator output MOS. The amplifier is preferably of the power
switch type, but may be any amplifier suited for amplifying a
PWM-signal. The amplifier may comprise any number of switches and
couplings of these, in accordance with the type of PWM-modulation
scheme used by the PWM-modulator PMOD. The amplifier outputs a
modulator system output signal MSOS via an amplifier output AMPO.
The modulator system output signal MSOS being the output of the
pulse width modulator system PWMS of the present embodiment is
preferably demodulated by means of a demodulator DEM, typically a
low-loss, low-pass filter, and is fed to a loudspeaker LS.
According to the particular PWM-modulation scheme used, the
amplifier, demodulator and loudspeaker may be coupled in any way
suitable. This particularly applies for systems where the
PWM-signal is distributed over two or more simultaneous signal
parts, e.g. as typically used for three level PWM-signals.
[0071] FIG. 3C illustrates a further embodiment of a pulse width
modulator system PWMS of the present invention, and in particular
illustrates an example of an embodiment of the pulse width
modulator PMOD. The illustrated system comprises a
PWM-amplifier/audio system for use with a discrete time input
signal, e.g. a pulse code modulated (PCM) signal.
[0072] Like the embodiment of FIG. 1B the present embodiment
comprises a modulator system input MI feeding an input signal IS to
an amplitude distribution filter ADF. The intermediate output
signal OS of the amplitude distribution filter ADF is fed to the
pulse width modulator PMOD.
[0073] The modulator output MOS of the pulse width modulator PMOD,
i.e. a pulse width modulated signal, is amplified by means of an
amplifier AMP as described above and rendered into sound by means
of a demodulator DEM and a loudspeaker setup LS as also described
above.
[0074] FIG. 3C further illustrates an embodiment of a pulse width
modulator PMOD. It comprises an upsampling block 11 basically
transforming the intermediate output signal OS from one sampling
frequency representation into an N times higher sampling
representation.
[0075] The upsampled signal is then fed to an
intersection-computing block 12 adapted for determination of
intersections with a parallel reference signal representation 16
provided by a reference signal generator 15. The intersections may
e.g. be established in the block 12 according to the principles
disclosed in PCT/DK03/00334 hereby incorporated by reference, or in
PCT/DK2004/000361 hereby incorporated by reference. A consecutive
noise shaping and quantizing block 13 feeds the established
intersections to a pulse generator 14 which establishes the
modulator output signal MOS, i.e. a pulse width modulated signal.
In an alternative embodiment the amplitude distribution filter ADF,
or parts of it, may be integrated with the noise shaping and
quantizing block 13 of the pulse width modulator PMOD.
[0076] It is noted that the above-described embodiment of a pulse
width modulator PMOD is only one of several possible embodiments
suitable for use with the present invention. Also several different
kinds of pulse width modulation and encoding schemes may be used
for establishing the pulse width modulated signal MOS. This signal
may thus perfectly be distributed over several sub-signals, e.g.
when differential PWM-signals are established. In such cases also
the amplifier AMP may comprise several sub-amplifiers, typically
power switches, and the demodulator DEM may comprise several
demodulators. Also the loudspeaker setup may comprise several
signal inputs.
[0077] An example of a further pulse width modulator PMOD
embodiment that may be used with the present invention is disclosed
in PCT/DK03/00475, hereby incorporated by reference.
[0078] A further example of a pulse width modulator PMOD embodiment
that may be used with the present invention is disclosed in EP 1
178 388 A1, hereby incorporated by reference.
[0079] It is noted that the above-mentioned embodiment examples are
not exhaustive, and that the present invention may be used in any
context for any application and that the illustrations in FIGS. 3A,
3B and 3C are only examples for establishing a concept and context
for the following detailed description.
[0080] It is noted, with reference to the below explanation of FIG.
4A that a modification of the FIGS. 3B and 3C has to be made in
order to apply the principles of the invention in a multi-channel
system. Thus, when using e.g. N of the illustrated systems in
parallel in a multi-channel amplifier setup, modulator output
signals MOS of the pulse width modulator system of e.g. FIG. 3B or
FIG. 3C are merged or combined within the modulator chip to e.g.
two communication lines and interfaced to the switched output
stage, e.g. a chip.
[0081] FIG. 4A illustrates a principle embodiment of the
invention.
[0082] An example of an application where dynamically positioned
problematic amplitude ranges may be advantageously utilized is
given in FIG. 4A.
[0083] More details about the specific embodiment are given in the
co-pending PCT/DK2004/000376, hereby included by reference. This
application basically addresses the need for counteracting
undesired side effects due to limited slew rate when outputting
narrow pulses, resulting in a distortion of the pulse established
by the output stage. Such counteracting, i.e. the method and means
described in detail in PCT/DK2004/000376, may be applied
advantageously together with the principles of the present
invention in a multi-channel output stage as a modification of the
signal fed to the switching stage may advantageously by applied to
minimize cross-talk in the output stage by minimizing or removing
switching at the same time. Such compensation requires a mutual
control or interaction, as the switching or the intended switching
of one channel may result in a modified switching of another
channel.
[0084] It comprises an embodiment of a multi-channel PWM modulator
system MCS embodied in a pulse modulator chip PMC. Such a system
may e.g. be used for pulse width modulating several audio channels,
e.g. 6 channels, and may advantageously be implemented in a single
integrated circuit. One of several issues to consider when
implementing a system in an integrated circuit is the use of output
connectors, here output pins, as the number of these significantly
impacts the cost of the integrated circuit, i.e. production and
materials. A possible solution to this problem is to combine the
multiple audio channels into a fewer number of physical conductors.
When e.g. the system comprises 6 audio channels it may be possible
by means of a proper multiplexing algorithm, compression algorithm,
etc., to combine the information of these into e.g. 2 or 4 physical
wires. In FIG. 4 is shown two signals entering the multi-channel
PWM modulator system MCS. These signals may each require more than
one physical connector, but use together preferably less than 6
connectors. Within the multi-channel system MCS the combined
channels signal is split into a signal for each of the 6 individual
channels by a signal splitter 121. Alternatively, each of the 6
channels may enter the multi-channel system MCS by its own physical
connector. Each of the 6 channels are provided to a pulse width
modulating system PWMS1, PWMS2, . . . , PWMS6 as input signals,
whereof due to clarity in the drawing only a reference IS1 is given
for the first channel. The modulator output signals MOS1, etc.,
which are pulse width modulated representations for the input
signal IS1, etc. are again combined into less than 6 physically
wired signals by means of a signal combiner 123.
[0085] FIG. 4A further comprises a signal splitter 124 for dividing
the combined modulator output signal into a reestablished pulse
modulation signal RMS1, . . . , RMS6 for each channel outside the
integrated circuit comprising the multi-channel pulse width
modulator system MCS. The signal splitter 124 forms part of a pulse
signal splitter PSS as described and explained with reference to
FIG. 2. Each of these pulse width modulated output channels may
then be fed to, e.g., separate amplifiers AMP1, . . . , AMP6,
preferably switch-mode amplifiers. Alternatively the combined
modulator output signal may be fed directly to each of the
subsequent, e.g. amplifiers, by bypassing the signal splitter 124.
The subsequent stage, e.g. amplifier, should then be adapted to
retrieve from the combined signal only the relevant channel.
[0086] In order to most optimally combine multiple pulse width
modulated signals MOS1, etc., into a fewer physical signals by
means of signal combiner 123, it may be beneficial to assume that
none of the PWM-signals comprise concurrent pulse flanks. As the
input signal amplitudes determine the pulse widths, and thus the
flanks of the pulses, non-concurrent pulse flanks may be ensured by
ensuring that a pulse width modulator PMOD of one pulse width
modulator system PWMS1, . . . , PWM6 never receives the same
intermediate output signal OS amplitude at the same time as the
modulator of another system PWMS1, . . . , PWMS6, as this would
probably cause concurrent pulse flanks to be established.
[0087] A further reason for desiring non-concurrent pulse flanks is
the probability of establishing cross-talk when, e.g., the
amplifiers AMP1, . . . , AMP6 are operated from the same power
supply. By ensuring that the switches in different amplifiers are
never required to switch simultaneously, the problem of cross-talk
may be reduced.
[0088] Guaranteeing or at least increasing the probability of
non-concurrent flanks in a multi-channel system, e.g. a stereo
system or a 5.1 system, is thus desired, and one way in which this
may be ensured is, within the example embodiment of FIG. 4A, by
dynamically adapting the problematic amplitude ranges of some of
the pulse width modulator systems PWMS1, . . . , PWMS6 according to
the intermediate output signal amplitudes of other pulse width
modulator systems PWMS1, . . . , PWMS6.
[0089] Such dynamically adapting of the problematic amplitude
ranges may e.g. be performed by a pulse amplitude distribution
manager 122 connected with each pulse width modulator system PWMS1,
. . . , PWMS6 by means of two-way external control signals ECS1,
etc. Thereby the pulse amplitude distribution manager 122 may
continuously obtain information of the currently processed input
values or intermediate output values, and adaptively establish
control information accordingly. Within each pulse width modulator
system PWMS1, . . . , PWMS6 an amplitude distribution filter ADF as
mentioned above, or other suitable means, may communicate with the
pulse amplitude distribution manager 122 and on the basis of the
relevant input signal IS1 and external control signal ECS1 cause
establishment of non-concurrent flanks.
[0090] The signal combiner 123 and the pulse amplitude distribution
manager 122 thus forms a pulse signal combiner PSC as described and
explained with reference to FIG. 2.
[0091] Evidently, the invention may be applied in several other
technical concepts than the above-described.
[0092] FIG. 4B illustrates an alternative embodiment of an
application as described regarding FIG. 4A. FIG. 4B also comprises
a multi-channel pulse modulator system MCS as described above. The
multi-channel pulse modulator system also comprises a pulse signal
combiner PSC comprising a pulse amplitude distribution manager 122
and a signal combiner 123. The signal combiner 123 of FIG. 4B
establishes a data signal 202 and a channel code signal 203 on the
basis of the, e.g., six modulator output signals MOS1, . . . ,
MOS6. FIG. 4B further comprises a pulse signal splitter PSS, which
comprises a decoder 201 and parts of the output stages AMP1, . . .
, AMP6. The data signal 202 comprises a compressed representation
of the switching times for all channels, and is preferably
transferred by means of a single wire. The data signal 202 is
connected to all output stages AMP1, . . . , AMP6, which preferably
comprise latches, e.g. flip-flops, in order to be able to read the
data signal 202. The channel code signal 203 may, e.g., be a 3-bit
signal transferred over 3 wires, and thus able to address up to 8
channels by binary representation. For every switching time
comprised by the data signal 202, the channel code signal 203
preferably comprises a pointer to the channel to which the
switching time correspond. The decoder 201 decodes the channel code
signal 203 and is on this basis able to enable the latch of the
corresponding output stage.
[0093] FIG. 5A comprises a timing diagram illustrating possible
signal contents in order to clarify how the above-described
mechanism may work. FIG. 5A comprises the modulator output signal
MOS1, MOS2, MOS3, of three of the channels of FIG. 4B. Each signal
comprises a PWM pulse, but with no simultaneous edges. FIG. 5A
further comprises the data signal 202, i.e. a compressed
representation of the modulator output signals MOS1, MOS2, MOS3.
Each pulse in the data signal 202 represents an edge, either rising
or falling. The width of each pulse in the data signal 202 is
preferably as short as possible while still wide enough to be
detected by the latches of the output stages. As there are no
simultaneous edges, there is no problem in combining the edges of
the modulator output signals into a single data signal. In order
for the output stages to know which of the data signal pulses
correspond to which channels, a channel code signal 203 is
establish in correlation with the data signal 202. A possible
channel code signal 203 is shown in FIG. 5A. In a period from a
little before each pulse of the data signal 202 it is set to a
binary value representing the respective channel. Via the decoder
201 this causes the latch of the output stage corresponding to that
channel to be enabled in time for reading the pulse of the data
signal 202.
[0094] In FIG. 4B the data signal 202 is shown as a bi-directional
signal. In addition to the working mode describe above, the data
signal 202 may also be used for transmitting feedback from the
output stage AMP1, . . . , AMP6 to the pulse modulator circuit PMC.
Such feedback may, e.g., comprise the actual switch times
established by the output stages. As the output stages typically
comprise not only a fixed delay but also varying delays, e.g.
dependent on the input signal, such information may be used for
further pre-correction or compensation within the pulse modulator
circuit PMC. Other possible feedback may comprise information about
the state of the output stages, e.g. if an output stage is in an
illegal state, or otherwise malfunctioning, or information about
variations in the power supply voltage provided to switching output
stages. As the output stage delay is typically longer than the
necessary width of the data signal pulses, the feedback may be
established on the data signal wire during the period between the
end of a switch time representing pulse and until the next switch
time representing pulse. Such a data signal 202 comprising feedback
is illustrated in FIG. 5B. When the signal combiner 123 has
established a switch time representing pulse for some channel it
doesn't use the data signal wire until the next switch time
representing pulse has to be established. In the intervening time
the output stage may use the wire for feedback purposes. The
available feedback time slot may be pre-defined, or, e.g.,
controlled by the channel code signal, a further clock signal, or
any other suitable signal. In case of using the feedback feature,
the pulse modulator circuit PMC should evidently comprise a
circuitry for receiving, interpreting and using the feedback. This
may, e.g., be implemented by the pulse amplitude distribution
manager 122. For feedback interpretation purposes the channel code
203 or a separate control signal may further be provided to the
pulse modulator circuit PMC.
[0095] The data signal 202 may comprise adjusted switch time
representations or reference switch time representations. In the
first case the pulse modulator circuit PMC comprises correcting and
compensation logic for attempting to correct the errors in the
output stages. In the latter case the pulse modulator circuit PMC
merely transmits the correct reference switch time representations,
and lets the output stages correct or compensate their own errors.
In such case the output stages may comprise local, analog feedback.
Thereby, e.g., power supply errors or variations may be
compensated. In a further embodiment a combination is applied,
where local, analog feedback in the output stages establish error
information, which may be fed back to the pulse modulator circuit
PMC by means of the data signal 202 or a separate signal.
[0096] FIG. 6 illustrates a detailed view of an embodiment of the
connection between a pulse signal combiner PSC and a pulse signal
splitter PSS according to the present invention. The pulse signal
combiner PSC comprises N inputs, MOS1, . . . , MOS6, also referred
to as output pulse modulation representations OPMr. In the present
embodiment N is six. Each input represents an input channel of a
pulse modulator system PMC, e.g. audio channels. The pulse signal
combiner PSC establishes an M-channel communication signal 202,
203, which is transmitted to the pulse signal splitter PSS by means
of L output connections. In the embodiment of FIG. 6 M is two as
it, e.g., comprises a data signal 202 and a channel code 203. As
the channel code in the present embodiment uses 3 wires, L is 4 in
the present embodiment. The pulse signal splitter PSS establishes a
number of output channels RMS1, . . . , RMS6, preferably
corresponding to the N input channels.
[0097] It is noted that the embodiment of FIG. 6 is an example, and
that any values of N, M and L are within the present invention, as
long as N is greater than L, i.e. the communication between the
pulse signal combiner PSC and pulse signal splitter PSS uses less
connections from the pulse modulator circuit PMC than the number of
channel processed by the multi-channel pulse modulator system
MCS.
[0098] Hence connections between the signal combiner and signal
splitter may be uni- or bi-directional, may be a multilevel
signals, may comprise any number of connections less than N,
including 1 connection, may utilize any communication protocol and
data transfer technology, etc. Thus, in an alternative embodiment
only one wire connects the pulse modulator circuit PMC and the
pulse signal splitter PSS, that wire comprising a multilevel signal
where, e.g., the signal level is used for transmitting the channel
code information.
* * * * *