U.S. patent application number 15/901530 was filed with the patent office on 2018-11-01 for adaptive common mode dimmer.
This patent application is currently assigned to Microchip Technology Incorporated. The applicant listed for this patent is Microchip Technology Incorporated. Invention is credited to Maarten Kuijk, Tony Susanto.
Application Number | 20180314285 15/901530 |
Document ID | / |
Family ID | 63916619 |
Filed Date | 2018-11-01 |
United States Patent
Application |
20180314285 |
Kind Code |
A1 |
Susanto; Tony ; et
al. |
November 1, 2018 |
Adaptive Common Mode Dimmer
Abstract
An adaptive mode has been added in a common mode (CM) dimmer
circuit to increase output current capability only when needed.
Without having an adaptive mode in the CM dimmer, the output
current drivers must operate with large quiescent current to handle
a bulk current injection (BCI) event. Therefore, a CM dimmer
without the adaptive mode will consume a significant amount of
power even when there is no BCI event occurring. With the adaptive
mode, the CM dimmer can be used effectively to suppress the BCI
event, e.g., in a transformer-less physical layer (PHY) connection,
while consuming minimal power during normal circuit operation.
Inventors: |
Susanto; Tony; (Austin,
TX) ; Kuijk; Maarten; (Antwerp, BE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Microchip Technology Incorporated |
Chandler |
AZ |
US |
|
|
Assignee: |
Microchip Technology
Incorporated
Chandler
AZ
|
Family ID: |
63916619 |
Appl. No.: |
15/901530 |
Filed: |
February 21, 2018 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62491049 |
Apr 27, 2017 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 3/28 20130101; H04L
7/0087 20130101; G05F 3/262 20130101; H04B 1/58 20130101; H03K
17/162 20130101; H04L 25/085 20130101; H04L 25/0276 20130101; H04L
25/028 20130101; H04B 3/50 20130101; H03K 19/018564 20130101 |
International
Class: |
G05F 3/26 20060101
G05F003/26 |
Claims
1. An adaptive common mode dimmer, comprising: a common mode dimmer
having a low operating quiescent current first mode and a higher
operating quiescent current second mode; and the common mode dimmer
is adapted for coupling to a two-wire transmission line and
maintaining a common mode voltage thereon at a desired common mode
reference voltage, wherein the two-wire transmission line carries
differential signals; wherein the common mode dimmer is in the
first mode when the common mode voltage on the two-wire
transmission line is between a high common mode reference voltage
and a low common mode reference voltage, and is in the second mode
otherwise.
2. The adaptive common mode dimmer according to claim 1, wherein:
the high common mode reference voltage is less than a power supply
voltage; the desired common mode reference voltage is less than the
high common mode reference voltage; and the low common mode
reference voltage is less than the desired common mode reference
voltage and greater than a ground or power supply common.
3. The adaptive common mode dimmer according to claim 2, wherein
the desired common mode reference voltage is about one-half of the
power supply voltage.
4. The adaptive common mode dimmer according to claim 1, wherein a
bulk current injection (BCI) event causes the common mode voltage
to be above the high common mode reference voltage or below the low
common mode reference voltage, wherein the common mode dimmer is in
the second mode.
5. The adaptive common mode dimmer according to claim 4, wherein
the BCI event causes at least 200 milliamperes of common mode
current on the two-wire transmission line and the common mode
dimmer is in the second mode when the common mode voltage is
greater than the high common mode reference voltage or less than
the low common mode reference voltage.
6. The adaptive common mode dimmer according to claim 1, wherein
the common mode dimmer causes the common mode voltage to return to
between the high and low common mode reference voltages before
changing from the second mode to the first mode.
7. The adaptive common mode dimmer according to claim 1, wherein
when the common mode voltage is above the desired common mode
reference voltage the common mode dimmer sinks current from the
two-wire transmission line to a ground or power supply common.
8. The adaptive common mode dimmer according to claim 1, wherein
when the common mode voltage is below the desired common mode
reference voltage the common mode dimmer sources current to the
two-wire transmission line from the power supply voltage.
9. A method for reducing common mode voltage on a differential
signal transmission line by using an adaptive common mode dimmer
having low and high operating quiescent current modes, said method
comprising the steps of: providing a common mode dimmer having a
low operating quiescent current first mode and a higher operating
quiescent current second mode; coupling the common mode dimmer to a
two-wire transmission line for maintaining a common mode voltage
thereon at a desired common mode reference voltage, wherein the
two-wire transmission line carries differential signals; operating
the common mode dimmer in the first mode when the common mode
voltage on the two-wire transmission line is between a high common
mode reference voltage and a low common mode reference voltage; and
operating the common mode dimmer in the second mode when the common
mode voltage on the two-wire transmission line is greater than the
high common mode reference voltage or lower than the low common
mode reference voltage.
10. The method according to claim 9, wherein: the high common mode
reference voltage is less than a power supply voltage; the desired
common mode reference voltage is less than the high common mode
reference voltage; and the low common mode reference voltage is
less than the desired common mode reference voltage and greater
than a ground or power supply common.
11. The method according to claim 10, wherein the desired common
mode reference voltage is about one-half of the power supply
voltage.
12. The method according to claim 9, comprises the step of causing
the common mode dimmer to be in the second mode during a bulk
current injection (BCI) event when the common mode voltage is above
the high common mode reference voltage or below the low common mode
reference voltage.
13. The method according to claim 9, comprises the step of
returning the common mode voltage to between the high and low
common mode reference voltages when the common mode dimmer is in
the second mode.
14. The method according to claim 9, comprises the step of sinking
current from the two-wire transmission line to ground or power
supply common when the common mode voltage is above the desired
common mode reference voltage.
15. The method according to claim 9, comprises the step of sourcing
current to the two-wire transmission line from a power supply
voltage when the common mode voltage is below the desired common
mode reference voltage.
16. A system for transmission of signals over a differential
transmission line and having adaptive common mode dimmers with low
and high operating quiescent current modes, said system comprising:
a differential signal transmitter having a first adaptive common
mode dimmer coupled thereto; a differential signal receiver having
a second adaptive common mode dimmer coupled thereto; and a
differential signal transmission line coupling the differential
signal transmitter and the differential signal receiver; the first
and second adaptive common mode dimmers each have a low operating
quiescent current first mode and a higher operating quiescent
current second mode; wherein the first and second adaptive common
mode dimmers are in the first mode when a common mode voltage on
the two-wire transmission line is between a high common mode
reference voltage and a low common mode reference voltage, and are
in the second mode otherwise.
17. An adaptive common mode dimmer, comprising: a first set of
current drivers coupled between a power supply voltage and a
two-wire transmission line; a second set of current drivers coupled
between a ground or power supply common and the two-wire
transmission line; first and second voltage comparators having
outputs coupled to and controlling the first and second sets of
current drivers, respectively, first inputs coupled to the two-wire
transmission line, and second inputs coupled to a first reference
voltage, wherein the first reference voltage is less than the power
supply voltage and greater than the ground or power supply common;
wherein when a common mode voltage on the two-wire transmission
line is greater than the first reference voltage the second set of
current drivers will sink more current than the first set of
current drivers will source, and when the common mode voltage on
the two-wire transmission line is less than the first reference
voltage the first set of current drivers will source more current
than the second set of current drivers will sink; a third voltage
comparator having a first input coupled to a second reference
voltage, a second input coupled to the two-wire transmission line,
and an output coupled to the second set of current drivers for
increasing their operating quiescent current when the common mode
voltage is greater than the second reference voltage, wherein the
second reference voltage is greater than the first reference
voltage; and a fourth voltage comparator having a first input
coupled to a third reference voltage, a second input coupled to the
two-wire transmission line, and an output coupled to the first set
of current drivers for increasing their operating quiescent current
when the common mode voltage is less than the third reference
voltage, wherein the third reference voltage is less than the first
reference voltage.
18. The adaptive common mode dimmer according to claim 17, wherein
the first reference voltage is about one-half the power supply
voltage.
19. The adaptive common mode dimmer according to claim 17, further
comprising a first buffer transistor between the output of the
fourth voltage comparator and the first set of current drivers.
20. The adaptive common mode dimmer according to claim 17, further
comprising a second buffer transistor between the output of the
third voltage comparator and the second set of current drivers.
Description
RELATED PATENT APPLICATION
[0001] This application claims priority to commonly owned U.S.
Provisional Patent Application No. 62/491,049; filed Apr. 27, 2017;
which is hereby incorporated by reference herein for all
purposes.
TECHNICAL FIELD
[0002] The present disclosure relates to power technology and, in
particular, to an adaptive common mode dimmer.
BACKGROUND
[0003] Common-mode (CM) currents may be caused by a bulk current
injection (BCI) event by capacitive coupling from a noise source,
electromagnetic interference (EMI), and/or magnetic coupling. CM
currents can cause cables to act as unintentional
radiators/receptors in electrical systems. CM radiation has been
shown to be proportional to cable length and signal frequency.
Reduction of CM radiation generally requires minimizing the CM
current or CM signal frequency. A way to reduce CM current is to
use CM dimmer circuit(s) coupled to differential drivers and
receivers communicating over a two-wire differential signal
transmission line. This requires differential driver circuits in
the CM dimmer circuit having sufficient drive/sink current capacity
to overcome BCI events. However, to guarantee sufficient drive/sink
current capacity the CM dimmer differential driver circuits must
operate at a high quiescent current. This is a significant power
drain for the overall system.
SUMMARY
[0004] Hence, there is a need for a CM dimmer circuit having lower
power consumption during normal operation when no BCI events are
occurring but be able to handle high current CM BCI events when
they do occur.
[0005] According to an embodiment, an adaptive common mode dimmer
may comprise: a common mode dimmer having a low operating quiescent
current first mode and a higher operating quiescent current second
mode; and the common mode dimmer may be adapted for coupling to a
two-wire transmission line and maintaining a common mode voltage
thereon at a desired common mode reference voltage, wherein the
two-wire transmission line may carry differential signals; wherein
the common mode dimmer may be in the first mode when the common
mode voltage on the two-wire transmission line may be between a
high common mode reference voltage and a low common mode reference
voltage, and may be in the second mode otherwise.
[0006] According to a further embodiment, the high common mode
reference voltage is less than a power supply voltage; the desired
common mode reference voltage is less than the high common mode
reference voltage; and the low common mode reference voltage is
less than the desired common mode reference voltage and greater
than a ground or power supply common. According to a further
embodiment, the desired common mode reference voltage may be about
one-half of a power supply voltage. According to a further
embodiment, a bulk current injection (BCI) event may cause the
common mode voltage to be above the high common mode reference
voltage or may be below the low common mode reference voltage,
wherein the common mode dimmer may be in the second mode. According
to a further embodiment, the common mode dimmer may cause the
common mode voltage to return to between the high and low common
mode reference voltages before changing from the second mode to the
first mode.
[0007] According to a further embodiment, when the common mode
voltage may be above the desired common mode reference voltage the
common mode dimmer may sink current from the two-wire transmission
line to a ground or power supply common. According to a further
embodiment, when the common mode voltage may be below the desired
common mode reference voltage the common mode dimmer may source
current to the two-wire transmission line from the power supply
voltage. According to a further embodiment, the BCI event may cause
at least 200 milliamperes of common mode current on the two-wire
transmission line and the common mode dimmer may be in the second
mode when the common mode voltage may be greater than the high
common mode reference voltage or less than the low common mode
reference voltage.
[0008] According to another embodiment, a method for reducing
common mode voltage on a differential signal transmission line by
using an adaptive common mode dimmer having low and high operating
quiescent current modes may comprise the steps of: providing a
common mode dimmer having a low operating quiescent current first
mode and a higher operating quiescent current second mode; coupling
the common mode dimmer to a two-wire transmission line for
maintaining a common mode voltage thereon at a desired common mode
reference voltage, wherein the two-wire transmission line carries
differential signals; operating the common mode dimmer in the first
mode when the common mode voltage on the two-wire transmission line
may be between a high common mode reference voltage and a low
common mode reference voltage; and operating the common mode dimmer
in the second mode when the common mode voltage on the two-wire
transmission line may be greater than the high common mode
reference voltage or lower than the low common mode reference
voltage.
[0009] According to a further embodiment of the method, the high
common mode reference voltage may be less than a power supply
voltage; the desired common mode reference voltage may be less than
the high common mode reference voltage; and the low common mode
reference voltage may be less than the desired common mode
reference voltage and greater than a ground or power supply common.
According to a further embodiment of the method, the desired common
mode reference voltage may be about one-half of the power supply
voltage. According to a further embodiment of the method, may
comprise the step of causing the common mode dimmer to be in the
second mode during a bulk current injection (BCI) event when the
common mode voltage may be above the high common mode reference
voltage or below the low common mode reference voltage. According
to a further embodiment of the method, may comprise the step of
returning the common mode voltage to between the high and low
common mode reference voltages when the common mode dimmer may be
in the second mode. According to a further embodiment of the
method, may comprise the step of sinking current from the two-wire
transmission line to ground or power supply common when the common
mode voltage may be above the desired common mode reference
voltage. According to a further embodiment of the method, may
comprise the step of sourcing current to the two-wire transmission
line from a power supply voltage when the common mode voltage may
be below the desired common mode reference voltage.
[0010] According to yet another embodiment, a system for
transmission of signals over a differential transmission line and
having adaptive common mode dimmers with low and high operating
quiescent current modes may comprise: a differential signal
transmitter having a first adaptive common mode dimmer coupled
thereto; a differential signal receiver having a second adaptive
common mode dimmer coupled thereto; and a differential signal
transmission line coupling the differential signal transmitter and
the differential signal receiver; the first and second adaptive
common mode dimmers each have a low operating quiescent current
first mode and a higher operating quiescent current second mode;
wherein the first and second adaptive common mode dimmers may be in
the first mode when a common mode voltage on the two-wire
transmission line may be between a high common mode reference
voltage and a low common mode reference voltage, and may be in the
second mode otherwise.
[0011] According to still another embodiment, an adaptive common
mode dimmer may comprise: a first set of current drivers coupled
between a power supply voltage and a two-wire transmission line; a
second set of current drivers coupled between a ground or power
supply common and the two-wire transmission line; first and second
voltage comparators having outputs coupled to and controlling the
first and second sets of current drivers, respectively, first
inputs coupled to the two-wire transmission line, and second inputs
coupled to a first reference voltage, wherein the first reference
voltage may be less than the power supply voltage and greater than
the ground or power supply common; wherein when a common mode
voltage on the two-wire transmission line may be greater than the
first reference voltage the second set of current drivers will sink
more current than the first set of current drivers will source, and
when the common mode voltage on the two-wire transmission line may
be less than the first reference voltage the first set of current
drivers will source more current than the second set of current
drivers will sink; a third voltage comparator having a first input
coupled to a second reference voltage, a second input coupled to
the two-wire transmission line, and an output coupled to the second
set of current drivers for increasing their operating quiescent
current when the common mode voltage may be greater than the second
reference voltage, wherein the second reference voltage may be
greater than the first reference voltage; and a fourth voltage
comparator having a first input coupled to a third reference
voltage, a second input coupled to the two-wire transmission line,
and an output coupled to the first set of current drivers for
increasing their operating quiescent current when the common mode
voltage may be less than the third reference voltage, wherein the
third reference voltage may be less than the first reference
voltage.
[0012] According to a further embodiment, the first reference
voltage may be about one-half the power supply voltage. According
to a further embodiment, a first buffer transistor may be between
the output of the fourth voltage comparator and the first set of
current drivers. According to a further embodiment, a second buffer
transistor may be between the output of the third voltage
comparator and the second set of current drivers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] A more complete understanding of the present disclosure may
be acquired by referring to the following description taken in
conjunction with the accompanying drawings wherein:
[0014] FIG. 1 illustrates a schematic block diagram of a
differential transmitter and receiver pair each having common mode
dimmers coupled thereto, according to the teachings of this
disclosure;
[0015] FIG. 2 illustrates a schematic diagram of a common mode
dimmer, according to the teachings of this disclosure;
[0016] FIG. 3 illustrates a schematic diagram of an adaptive common
mode dimmer, according to a specific example embodiment of this
disclosure; and
[0017] FIG. 4 illustrates a schematic block diagram of a
differential transceiver pair each having common mode dimmers
coupled thereto, according to the teachings of this disclosure.
[0018] While the present disclosure is susceptible to various
modifications and alternative forms, specific example embodiments
thereof have been shown in the drawings and are herein described in
detail. It should be understood, however, that the description
herein of specific example embodiments is not intended to limit the
disclosure to the forms disclosed herein.
DETAILED DESCRIPTION
[0019] An adaptive mode has been added in a common mode (CM) dimmer
circuit to increase output current capability only when needed.
Without having an adaptive mode in the CM dimmer, the output
current drivers must operate with large quiescent current to handle
a bulk current injection (BCI) event. Therefore, a CM dimmer
without the adaptive mode will consume a significant amount of
power even when there is no BCI event occurring. With the adaptive
mode, the CM dimmer can be used effectively to suppress the BCI
event, e.g., in a transformer-less physical layer (PHY) connection,
while consuming minimal power during normal circuit operation.
[0020] Referring now to the drawings, the details of example
embodiments are schematically illustrated. Like elements in the
drawings will be represented by like numbers, and similar elements
will be represented by like numbers with a different lower-case
letter suffix.
[0021] Referring to FIG. 1, depicted is a schematic block diagram
of a differential transmitter and receiver pair each having common
mode dimmers coupled thereto, according to the teachings of this
disclosure. FIG. 1 shows a simplified typical connection between a
transmitter 114 having a differential output and a receiver 116
having a differential input, with each having a common mode (CM)
dimmer circuit 104, 108 coupled thereto respectively. The
electrical signal connection between the differential transmitter
114 and differential receiver 116 may be with a pair of wires
forming a transmission line 110, e.g., unshielded twisted pair
(UTP) wires or coaxial (shielded) cables.
[0022] Common mode current I.sub.BCI (represented by a current
source 112) from any external interference may be injected through
capacitive coupling, electromagnetic interference and/or
magnetically induced onto the transmission line 110. This
phenomenon is commonly called "Bulk Current Injection" (BCI).
During this BCI event, the common mode voltage (voltage between
wires and ground of the differentially connected pair of wires
(OUTP, OUTN, INP, INN) forming the transmission line 110) will
increase when the injected CM current I.sub.BCI is positive and
decrease when it is negative. The CM dimmer circuits 104, 108 will
then source or sink currents onto the differentially connected pair
of wires 110 to counteract the externally induced common mode
current I.sub.BCI from a BCI event.
[0023] Referring to FIG. 4, depicted is a schematic block diagram
of a differential transceiver pair each having common mode dimmers
coupled thereto, according to the teachings of this disclosure.
Transceivers 414 and 416 are coupled together with and communicate
over a differential transmission line 110. Operation of the
Transceivers 414 and 416 are functionally the same as the
differential transmitter 102 and receiver 106 pair shown in FIG. 1
but capable of communicating in a half-duplex mode. For a full
duplex mode of communications, a second differential transmission
line may be provided (not shown) and coupled directly between the
receiver 406 and transmitter 402, however in this configuration
additional CM dimmers would have to be provided for and coupled to
the second differential transmission line.
[0024] Referring to FIG. 2, depicted is a schematic diagram of a
common mode dimmer, according to the teachings of this disclosure.
Each of the CM dimmer circuits 104, 108 may comprise voltage
comparators 224, 226; resistors 220, 222, 236, 238; and transistors
228, 230, 232, 234, 240, 242, 244, 246. Additional resistors and
capacitors not numbered are not relevant to the discussion herein
but have been included for circuit completeness. The CM dimmer
circuit 104, 108 shown in FIG. 2 measures the common mode voltage,
Vcm, of a differential signal pair SIGP, SIGN and adjusts it to be
substantially the same as a common mode voltage reference, Vmid
(Vmid=VDD/2, the values of resistors 220 and 222 are the same). The
CM dimmer circuit 104, 108 increases or decreases the gate voltages
and thus the currents of the transistors 240 and 242 (similarly
transistors 244 and 246) through the comparators 224 and 226, and
the mirror transistors 228 and 234. When Vcm is greater than Vmid,
comparator 224 turns off transistor 230 and comparator 226 turns on
transistor 232. When Vcm is less than Vmid, comparator 224 turns on
transistor 230 and comparator 226 turns off transistor 232. For
example, when Vcm is higher than Vmid, the comparators 224 and 226
will increase the gate voltages of transistors 228 and 234. Because
of this current mirroring, transistors 240 and 244 will source less
current, and transistors 242 and 246 will sink more current, and
consequently, the common mode voltage Vcm will be reduced through
this feedback operation.
[0025] The amount of CM current caused by a BCI event can be very
large, thus transistors 240, 242, 244, 246 are designed to source
and sink some of the CM current caused by the BCI event that may
generate hundreds of milliamperes of CM current. To source and sink
this much CM current these transistors 240, 242, 244, 246 must
operate (be biased) at a high quiescent current. However, during
normal operation, when a BCI event is not occurring, a reduction of
quiescent current is desired to minimize circuit power consumption
while keeping the transistors 240, 242, 244, 246 in their
saturation region (hard ON) when appropriate.
[0026] For example, for the transistors 240, 242, 244, 246 to have
200 milliampere CM current capabilities during a BCI event, and
assuming a 20 times current ratio, the circuit for the transistors
228 and 234 may be designed to conduct a maximum of 10
milliamperes. Under normal operation, however, the transistors 228
and 234 will consume approximately half of this maximum current, or
5 milliampere, which means that the transistors 240, 242, 244, 246
will have a quiescent current of 100 milliamperes. 100 milliamperes
is an enormous power consumption for just one CM dimmer circuit,
and considering that a plurality of CM dimmers will be used in a
data transmission system a large power consumption penalty is
created.
[0027] Referring to FIG. 3, depicted is a schematic diagram of an
adaptive common mode dimmer, according to a specific example
embodiment of this disclosure. The CM dimmers 104a, 108a comprise
similar circuitry to the CM dimmers 104, 108 shown in FIG. 2 with
the addition of resistors 320, 348, 350 and 322; voltage
comparators 352 and 354, and transistors 356 and 358. The resistors
320, 348, 350 and 322 are configured as a resistance ladder network
to provide reference voltages Vhi, Vmid and Vlo, where
Vhi>Vmid>Vlo. The CM dimmers 104a, 108a shown in FIG. 3
provide both lower power consumption under normal operating
conditions and high current capacity during a BCI event.
[0028] Comparators 352, 354 and transistors 356, 358 provide
additional currents on the transistors 228, 234 only when the
common mode voltage Vcm is higher or lower than Vhi or Vlo,
respectively. Under normal operation, without a BCI event
occurring, transistors 228 and 234 consume very little current
which are then replicated by the transistors 240, 244, 242 and 246.
But when a BCI event occurs, the common mode voltage Vcm could be
higher than Vhi or lower than Vlo depending upon the amount of the
current injected into the SIGP and SIGN signal lines. When this
occurs, transistors 228 and 234 and therefore transistors 240, 244,
242 and 246 will source and sink more current due to the additional
voltage comparators 352 and 354, and the transistors 356 and
358.
[0029] Referring to the previous examples, preferably transistors
228 and 234 will have a maximum current of 10 milliamperes, whereby
with a 20.times. current ratio, transistors 240, 244, 242 and 246
will be able to handle a 200 milliampere BCI event. For
illustration purposes but without limitation, the maximum current
flowing through transistors 230 and 356 can be divided into one (1)
milliampere and nine (9) milliamperes, respectively. In normal
operation, the voltage Vcm will be close to Vmid, therefore, the
comparators 352 and 354 will be turned off. Thus, no current will
be flowing through the transistors 356 and 358. The current flowing
through transistors 230 and 232 will be approximately 0.5
milliampere which is the same amount of current flowing through
transistors 228 and 234. There, the quiescent current flowing
through transistors 240 and 242 will be approximately 10
milliamperes, a significant savings of power during normal
operation.
[0030] The adaptive mode performed by the voltage comparators 352
and 354 in combination with the transistors 356 and 358 may be used
to increase the output current capability only when it is needed,
e.g., during a BCI event. Without the voltage comparators 352 and
354 and the transistors 356 and 358, the output current drivers,
implemented by the transistors 240, 244, 242 and 246 would have to
operate at a large quiescent current all the time in order to
handle a BCI event.
* * * * *