U.S. patent application number 13/759834 was filed with the patent office on 2013-06-06 for motor with circuits for protecting motor from input power outages or surges.
The applicant listed for this patent is Young-Chun Jeung. Invention is credited to Young-Chun Jeung.
Application Number | 20130141026 13/759834 |
Document ID | / |
Family ID | 42543419 |
Filed Date | 2013-06-06 |
United States Patent
Application |
20130141026 |
Kind Code |
A1 |
Jeung; Young-Chun |
June 6, 2013 |
MOTOR WITH CIRCUITS FOR PROTECTING MOTOR FROM INPUT POWER OUTAGES
OR SURGES
Abstract
A DC motor is provided. The DC motor prevents rush or overload
of current in the DC motor during and/or after power input
irregularities to the DC motor. A control circuit of the DC motor
is configured to control current provided to the DC motor. When
power irregularities in the power input to the DC motor are
detected by the control circuit, the control circuit stops
generating PWM (Pulse Width Modulated) signals and stops the
current provided to the DC motor. After the stoppage of PWM
signals, the control circuit can perform a soft-start of the PWM
signals when the power irregularities are no longer detected. The
soft starting of the PWM signals generates gradual increase in
current to the DC motor, thus, preventing sudden rush of current
that cause malfunction of the DC motor.
Inventors: |
Jeung; Young-Chun; (Cypress,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Jeung; Young-Chun |
Cypress |
CA |
US |
|
|
Family ID: |
42543419 |
Appl. No.: |
13/759834 |
Filed: |
February 5, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13562126 |
Jul 30, 2012 |
8368333 |
|
|
13759834 |
|
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|
12417506 |
Apr 2, 2009 |
8232755 |
|
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13562126 |
|
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Current U.S.
Class: |
318/400.21 |
Current CPC
Class: |
H02H 7/09 20130101; H02P
6/28 20160201; H02P 6/20 20130101 |
Class at
Publication: |
318/400.21 |
International
Class: |
H02H 7/09 20060101
H02H007/09 |
Claims
1. A motor apparatus comprising: a DC motor comprising a stator and
a rotor; an AC to DC converter configured to receive an AC power
input and to convert the AC power input to a DC power; a switching
circuit configured to convert the DC power to a PWM switched power
for supplying to the DC motor; and at least one control circuit
configured to detect irregularities in the AC power input, wherein
upon detecting irregularities the at least one control circuit
causes the switching circuit to temporarily stop supplying the PWM
switched power to the DC motor and resume supplying the PWM
switched power.
Description
BACKGROUND
[0001] 1. Field
[0002] This application is a continuation application of U.S.
patent application Ser. No. 13/562,126 filed Jul. 30, 2012, which
is a continuation application of U.S. patent application Ser. No.
12/417,506, filed Apr. 2, 2009, now U.S. Pat. No. 8,232,755 B2, the
entire contents of which are hereby incorporated by reference.
[0003] 2. Description of Related Technology
[0004] A switch to start and stop an operation of an AC
(alternating current) motor has been widely used. However, in an
ECM (electronically commutated motor), more particularly, a
brushless DC (direct current) electric motor, instability can occur
when there are power input irregularities. The motor's control
circuit uses logic level voltages to control the operation of the
DC motor. When power input to the motor is irregular, the logic
level voltage become irregular and the control circuit may generate
incorrect control signals.
SUMMARY
[0005] One aspect of the invention provides a motor apparatus. The
motor apparatus comprises: a DC motor comprising a stator and a
rotor; an AC to DC converter configured to receive an AC power
input and to convert the AC power input to a DC power; a PWM signal
generator configured to generate PWM signals; a power switching
circuit configured to generate a PWM switched power using the DC
power and the PWM signals, and to supply the PWM switched power to
the DC motor; and an input power irregularity detector configured
to detect irregularities in the AC power input and to send a
control signal to the PWM signal generator, wherein upon receiving
the control signal the PWM signal generator is configured to stop
generating the PWM signals and then restart generating a new set of
PWM signals.
[0006] In the foregoing system, the input power irregularity
detector may comprise a surge detecting circuit configured to
detect surges in the AC power input, wherein the input power
irregularity detector is configured to send the control signal upon
detecting of at least one surge in the AC power input that is
greater than a predetermined value. The input power irregularity
detector may be configured to send the control signal upon
detecting of more than one surge during a predetermined time
period. The PWM signal generator may be configured to restart
generating the new set of PWM signals when no surges are detected
for a predetermined time period after stoppage of generating the
PWM signals. The predetermined time period may be 5 sec or
longer.
[0007] Still in the foregoing system, the input power irregularity
detector may comprise an outage detecting circuit configured to
detect an outage of the AC power input that is longer than a
predetermined time period, wherein the input power irregularity
detector is configured to send the control signal upon detecting of
an outage of the AC power input that is longer than the
predetermined time period. The predetermined time period may be 0.2
msec or longer. The outage detecting circuit may be configured to
detect an outage of the AC power input that is shorter than a
predetermined period, wherein the input power irregularity detector
is configured to send the control signal upon detecting of an
outage of the AC power input that is shorter than the predetermined
period. The input power irregularity detector may be configured to
send the control signal upon detecting of an outage of the AC power
input that is shorter than 10 sec. The input power irregularity
detector may comprise an outage detecting circuit configured to
detect low values in the AC power input that is lower than a
predetermined value or substantially zero, wherein the input power
irregularity detector is configured to send the control signal upon
detecting of low values in the AC power input that is lower than a
predetermined value. The AC power input and the DC power may be in
voltage. The system may further comprise a voltage dividing circuit
connected to the AC power input and configured to scale down the AC
power input to a logic circuit voltage level, wherein the input
power irregularity detector monitors the scale-down version of the
AC power input.
[0008] Another aspect of the invention provides a method of
operating a motor apparatus. The method comprises: providing a
motor apparatus comprising a DC motor comprising a stator and a
rotor, an AC to DC converter, an input power irregularity detector,
a PWM signal generator, and a power switching circuit; generating
PWM signals at the PWM signal generator; converting an AC power
input to a DC power at the AC to DC converter; generating a PWM
switched power using the DC power and the PWM signals at the power
switching circuit; supplying the PWM switched power to the DC
motor; detecting irregularities in the AC power input at the input
power irregularity detector; stopping to generate the PWM signals
upon detecting at least one irregularity in the AC power input; and
subsequent to stopping, restarting to generate a new set of PWM
signals.
[0009] In the foregoing method, the input power irregularity
detector may comprise a surge detecting circuit, wherein detecting
irregularities comprises detecting at least one surge in the AC
power input that is greater than a predetermined value. Stopping to
generate PWM signals may occur upon detecting of more than one
surge during a predetermined time period. Generating the new set of
PWM signals may be restarted when no surges are detected for a
predetermined time period after stoppage of generating the PWM
signals. The predetermined time period may be 5 sec or longer. The
input power irregularity detector may comprise an outage detecting
circuit, wherein detecting irregularities comprises detecting an
outage of the AC power input that is longer than a predetermined
time period. The predetermined time period may be 0.2 msec or
longer. The input power irregularity detector may monitor a
scale-down version of the AC power input in a logic circuit voltage
level.
[0010] Another aspect of the invention provides a motor apparatus,
which comprises: a DC motor comprising a stator and a rotor; an AC
to DC converter configured to receive an AC power input and to
convert the AC power input to a DC power; a switching circuit
configured to convert the DC power to a PWM switched power for
supplying to the DC motor; and at least one control circuit
configured to detect irregularities in the AC power input, wherein
upon detecting irregularities the at least one control circuit
causes the switching circuit to temporarily stop supplying the PWM
switched power to the DC motor and resume supplying the PWM
switched power.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing and other features of the present disclosure
will become more fully apparent from the following description and
appended claims, taken in conjunction with the accompanying
drawings. Understanding that these drawings depict only some
embodiments in accordance with the disclosure and are, therefore,
not to be considered limiting of its scope, the disclosure will be
described with additional specificity and detail through use of the
accompanying drawings.
[0012] FIG. 1 illustrates a block diagram of an embodiment of a DC
motor.
[0013] FIG. 2 illustrates a circuit diagram of an embodiment of a
DC motor.
[0014] FIGS. 3A-3G show graphs of voltage input, PWM signal, and
current generated by a DC motor according to an embodiment without
a soft-start.
[0015] FIGS. 4A-4F show graphs of voltage input, PWM signal, and
current generated by a power switching circuit in a DC motor
according to one embodiment with a soft-start.
DETAILED DESCRIPTION
[0016] In the following detailed description, reference is made to
the accompanying drawings, which form a part hereof. In the
drawings, similar symbols typically identify similar components,
unless context dictates otherwise. The illustrative embodiments
described in the detailed description, drawings, and claims are not
meant to be limiting. Other embodiments may be utilized, and other
changes may be made, without departing from the spirit or scope of
the subject matter presented here. It will be readily understood
that the aspects of the present disclosure, as generally described
herein, and illustrated in the Figures, can be arranged,
substituted, combined, and designed in a wide variety of different
configurations, all of which are explicitly contemplated and make
part of this disclosure.
DC Motor with Power Irregularities
[0017] In an embodiment, a DC motor is provided. The DC motor
prevents rush or overload of current during and/or after power
input irregularities to the DC motor. The power irregularities
include power outages and surges in the power input to the DC
motor. A control circuit of the motor is configured to control
current provided to the DC motor. When the power irregularities in
the power input to the DC motor are detected, generation of PWM
signals is stopped and the current supply to the DC motor is
stopped. After the stoppage of PWM signals, the control circuit can
perform a soft start of the PWM signals once the power
irregularities are no longer detected. The soft starting of the PWM
signals produces current to the DC motor that start from
substantially zero and gradually increases, thus, preventing sudden
rush of current. The soft start can reduce a rush of current in the
circuit and can consequently protect the circuit from damage.
DC Motor
[0018] FIGS. 1 and 2 illustrate components of a DC motor in one
embodiment. A DC motor 10 is connected to a power supply 11, an
AC-to-DC converter 51, a power irregularity detector 31, a PWM
generator 8, and a power switching circuit 9. Throughout the
disclosure, the term "DC motor" may refer to the motor 10 only.
Alternatively, the term refers to all the components as shown in
FIGS. 1 and 2 that are enclosed in motor a housing.
[0019] In the illustrated embodiment of FIGS. 1 and 2, the DC motor
10 receives current from the power switching circuit 9 and performs
work. Although not illustrated, the DC motor 10 includes a rotor
and a stator. In one embodiment, a plurality of position sensors
are included in the DC motor 10 to sense the position of the rotor.
The plurality of sensors are connected to the PWM generator and the
PWM generator 8 can be configured to monitor and control the speed
of rotation of the rotor. In some embodiments, the DC motor 10 can
be a brushless electric motor. The DC motor can perform work on a
load 101. In some embodiments, the DC motor 10 can perform work as
a blower or a fan of an HVAC (heating, ventilation, and air
conditioning) system.
Power Supply
[0020] In the illustrated embodiment of FIGS. 1 and 2, the power
supply 11 is configured to provide power to components of the DC
motor. Specifically, the power supply 11 provides power to the DC
motor 10 through the AC-to-DC converter 51 and the power switching
circuit 9. Referring to FIG. 2, the power supply 11 includes an AC
power source 1 and a switch 2. The power source 1 can be a
conventional electrical outlet or a portable power source, such as
a battery or a fuel cell but is not limited thereto. In one
embodiment, the switch 2 is an electrical switch configured to turn
on and off power provided by the power supply 11. The AC power
provided by the power supply 11 can be from about 5 volts to about
300 volts, such as about 110 volts and about 220 volts but is not
limited thereto.
AC-to-DC Converter
[0021] In the illustrated embodiment of FIGS. 1 and 2, the AC-to-DC
converter 51 is configured to convert AC power from the supply 11
into DC power. Referring to FIG. 1, the AC-to-DC converter 51
receives AC power from the power supply 11 and to converts the AC
power to DC power. Referring to FIG. 2, the AC-to-DC converter 51
includes a converter diode 4, a condenser 5, and a condenser
resistor 6. The AC power from the power supply 11 is provided to
the converter diode 4 via the AC power line 21. The converter diode
4 converts an AC power signal from the power supply 11 to a non-AC
power signal. The power signal from the converter diode 4 can
charge the condenser 5. When fully charged, the condenser 5
maintains a DC voltage that is substantially constant. The
condenser 5 can have a capacitance from about 100 mF to about 2000
mF, such as from about 250 mF to about 1000 mF although not limited
thereto. The condenser 5 discharges when no power is provided to
the condenser 5. When there is no power provided to the condenser
5, the condenser 5 can be completely discharged within a time
period from about 1 millisecond to about 10 seconds, such as from
about 10 milliseconds to about 5 seconds depending upon its
design.
Power Irregularity Detector
[0022] In the illustrated embodiment of FIGS. 1 and 2, the power
irregularity detector 31 receives the AC power from the power
supply 11 and converts the AC power into a logic level AC voltage.
The logic level AC voltage is used to detect voltage outage and/or
surge in the AC power from the power supply 11. The power
irregularity detector 31 includes a voltage dividing circuit 32, a
surge detecting circuit 33, and an outage detecting circuit 34.
Voltage Dividing Circuit
[0023] As shown in FIGS. 1 and 2, the voltage dividing circuit 32
receives the AC power from the power supply 11 and provides a
scaled-down version of the AC power. For example, the voltage
diving circuit 32 scales down the AC power at about 110 or 220
volts into logic level AC voltages with the amplitude of about 1,
about 1.5, about 2, about 2.5, about 3, about 3.5, about 4, about
4.5, about 5, about 5.5, about 6, about 6.5, about 7, about 7.5,
about 8, about 8.5, about 9, about 9.5, about 10, about 10.5, about
11, about 11.5, about 12, about 12.5, about 13, about 13.5, about
14, about 14.5, about 15, about 15.5, about 16, about 16.5, about
17, about 17.5, about 18, about 18.5, about 19, about 19.5, and
about 20 volts.
[0024] When zero power is provided to the voltage dividing circuit
32, the voltage dividing circuit 32 provides zero power or voltage.
As shown in FIG. 2, the voltage dividing circuit 32 includes a pair
of resistors 12 and 13. The resistors 12 and 13 are serially
connected and a voltage division line 14 is drawn out from between
the resistors 12 and 13. The logic level AC voltages are provided
to other components of the DC motor via the voltage division line
14. In some embodiments, a ratio of values of resistances for
resistors 12 and 13 can be between about 30 to 1 and about 40 to 1.
In some embodiments, the sum of the values of resistances of
resistors 12 and 13 can be from about 1 M (mega) ohm to about 100 M
ohm, such from about 2 M ohm to about 10 M ohm. However, the ratios
and the values of the resistors 12 and 13 can be designed in
various configurations to provide a desired log level voltage via
the voltage division line 14.
Outage Detecting Circuit
[0025] Referring to FIG. 1, the outage detecting circuit 34 detects
power outage or substantially zero power from the scaled-down
voltage at the voltage division line 14. When an outage of the
power is detected, the outage detecting circuit 34 sends a stop
signal to the PWM generator 8 to stop generating or outputting the
PWM signals from the PWM generator 8. In an embodiment, when the
outage detecting circuit 34 detects substantially non-zero power or
regular power from the voltage dividing circuit 32, the outage
detecting circuit 34 sends a soft-start signal to the PWM generator
8 for soft-starting PWM signals. In another embodiment, the outage
detecting circuit 34 can directly receive the AC power from the
power supply 11 and detect power outages. In one embodiment, the
soft-start signal is sent immediately after detecting non-zero or
regular power. In another embodiment, the soft-start signal is sent
some time after detecting non-zero or regular power.
[0026] In the embodiment of FIG. 2, the outage detecting circuit 34
is simply a wire 14 connecting between the voltage dividing circuit
32 and the PWM generator 8. In this embodiment, the logic level AC
voltage signals from the voltage diving circuit 32 constitute both
stop and soft-start signals to the PWM generator 8. The outage or
substantially zero voltage corresponds to the stop signal, and
resuming of the logic level AC voltage corresponds to the
soft-start signal.
Surge Detecting Circuit
[0027] As shown in FIGS. 1 and 2, the surge detecting circuit 33 is
connected to the voltage dividing circuit 32 and receives the logic
level AC voltage via the voltage division line 14. The surge
detecting circuit 33 is configured to generate a surge signal when
there is a surge in the logic level AC voltage from the voltage
dividing circuit 32. In another embodiment, the surge detecting
circuit 33 can directly receive the AC power from the power supply
11 and generate a surge signal for each surge in the AC power from
the power supply 11. In the illustrated embodiment of FIG. 2, the
surge detecting circuit 33 includes an operational amplifier (OP
amp) 140.
[0028] The OP amp 140 compares the voltage from the voltage diving
circuit 32 against a pre-determined threshold voltage value. The OP
amp 140 is configured to generate a surge signal if the voltage
from the voltage dividing circuit 32 exceeds the pre-determined
threshold voltage value. The pre-determined threshold voltage
values can be logic level voltages and provided in view of the
amplitude of the logic level voltage from the voltage dividing
circuit 32. For example, the pre-determined threshold voltage is
about 3, about 4, about 5, about 6, about 7, about 8, about 9,
about 10, about 11, about 12, about 13, about 14, about 15, about
16, about 17, about 18, about 19, and about 20 volts. The surge
signal from the surge detecting circuit 33 can be provided to the
PWM generator 8 via a surge signal line 141.
DC Transformer
[0029] In the illustrated embodiment of FIG. 2, the DC transformer
7 (which can be also referred as "DC/DC converter") receives the DC
power from the AC-to-DC converter 51 and scales it down for the PWM
generator 8. In some embodiments, the DC transformer 7 converts the
DC power at about 110 or 220 volts to logic level DC voltages, such
as about 3, about 4, about 5, about 6, about 7, about 8, about 9,
about 10, about 11, about 12, about 13, about 14, about 15, about
16, about 17, about 18, about 19, and about 20 volts.
PWM Generator
[0030] In the illustrated embodiment of FIG. 2, the PWM generator
receives logic level voltages from the transformer 7 and one or
more signals from the power irregularity detector 31, and generates
PWM (pulse-width-modulation) signals. Specifically, the PWM
generator 8 receives control signals from the voltage dividing
circuit 32 and the surge detecting circuit 33 and uses algorithms
to determine conditions to reset the PWM signals. The PWM signals
are provided to the power switching circuit 9. A skilled artisan
would well appreciate the construction of the PWM generator 8.
[0031] In some embodiments, algorithms to control operations of the
PWM generator 8 can be programmed into a firmware of the PWM
generator 8. The PWM generator 8 can include a microprocessor, or a
computing device.
Power Switching Circuit
[0032] In the illustrated embodiment of FIGS. 1 and 2, the power
switching circuit 9 receives the DC power from the AC-to-DC
converter 51 and switches it according to PWM signals from the PWM
generator 8. The pulses of the PWM signal controls amount of
current supplied to the DC motor 10 by the power switching circuit
9. When the pulses of the PWM signals are zero, the DC power
provided by the power switching circuit 9 is zero, as well. PWM
signals with narrow width pulses are configured to generate current
for shorter time interval than the wider width pulses. The amount
of current provided by the power switching circuit 9 is calculated
as average amount of current supplied over a certain time interval.
By producing gradually increasing width pulses of the PWM signals,
the average amount of current provided by the power switching
circuit 9 in a certain time interval is gradually increased.
[0033] When the PWM signal is stopped and soft-started by the
control circuit, the PWM switched current is also stopped and
soft-started. With the soft-starting of the PWM switched power a
current "rush" can be prevented. This prevention can prevent damage
and/or malfunction of the power switching circuit 9 and the DC
motor.
AC Power with Irregularities
[0034] FIGS. 3A and 4A illustrate exemplary AC voltage signals 21
supplied by the power supply 11. The interval 25 between "Off" and
"On" positions represents a time period of power outage. Position
"Off" refers to a power outage and no AC power being supplied by
the power supply 11. Position "On" refers to the AC power being
back on after the power outage. In FIGS. 3A and 4A, the AC voltage
signal 21 also includes power surges 22, 23, and 24 to the right of
the "on" position.
DC Power Converted from AC Power with Irregularities
[0035] FIG. 3B and 4B illustrate DC voltage signal 41 changes at
the condenser 5 of the AC-to-DC converter 51. When regular AC power
is provided to the AC-to-DC converter 51, the condenser 5 is fully
charged and maintains a substantially constant DC voltage level.
When there is an AC power outage, such as at the "Off" position,
the DC voltage 41 at the condenser 5 starts to decrease. Upon the
AC power being back on in the "On" position, the condenser 5 is
charged back to substantially same voltage level before the "Off"
position.
Logic Level DC Power Signals
[0036] FIGS. 3C and 4C illustrate a logic level DC voltage signal
71 that is outputted by the transformer 7 to power the logic
circuit of the PWM generator 8. The logic level DC voltage 71 is
maintained without decline for a period of time even after the
"Off" position. During this initial time period, the DC power input
41 to the transformer 7 decreases; however, the DC power 41 is
still high enough to maintain the logic level DC voltage 71. After
this initial period, the DC power 41 supplied to the transformer 7
becomes too low to maintain the logic level DC voltage 71 and
therefore the logic level DC voltage 71 starts to decline. As the
DC power input 41 falls further below, the logic level DC voltage
71 decreases below a threshold logic level DC voltage (V.sub.th)
for the PWM generator 8 to operate normally. The horizontal dashed
line of FIGS. 3C and 4C represents the threshold logic level DC
voltage (V.sub.th). When the power outage 21 in the AC power 21
becomes longer, the logic level DC voltage 71 falls below the
threshold value, as illustrated in these drawings.
PWM Signals Without Soft-Start
[0037] FIG. 3D illustrates PWM signal 81 outputted from the PWM
generator 8 in one embodiment without a soft-start. In the
illustrated embodiment, in response to the power outage, the PWM
generator 8 stops generating the PWM signal 81 when the logic level
DC voltage 71 falls below the threshold value. The hatched
rectangular window 85 of FIG. 3D represents a time period from when
the logic level DC voltage 71 falls below the threshold logic level
DC voltage value and to when the logic level DC voltage 71 comes
back above the threshold logic level DC voltage value. The PWM
generator 8 stops working during this time period.
[0038] After the time period, the PWM signal 81 from the PWM
generator 8 becomes unpredictable. Depending upon logic values
stored in the PWM generator 8 when the logic level DC voltage 71
falls below the threshold level, the PWM generator 8 may continue
the pulse 85 as if there was no power outage. In the illustrated
example of FIG. 3D, the PWM signal 81 stop as a high pulse and
start again as high a pulse before and after this time period. In
other situations, the PWM signal 8 may stop as a low pulse and
start again as a low pulse, stop as a low pulse and start as a high
pulse, or stop as a high pulse and start again as a low pulse. In
some situations, widths of the pulses of the PWM signal 81 can vary
before and after the time period as well.
Current Supplied to Motor without Soft-Start
[0039] FIG. 3E illustrates current 42 generated at the power
switching circuit 9 when the PWM signal 81 is provided to the power
switching circuit 9. As discussed above, the current 42 from the
power switching circuit 9 is outputted when the power switching
circuit 9 receives the DC power from the AC-to-DC converter 51 and
switches it according to PWM signals from the PWM generator 8. In
FIG. 3E, when there is a power outage, the current 42 starts to
decline as the DC voltage signal 41 of FIG. 3B starts to decline at
the "off" position. The current 42 continues to decline until after
the "On" position. When the DC voltage signal 41 comes back to
normal value after the "On" position, because the PWM signal 81 is
provided as a high pulse, the power switching circuit 9 outputs a
rush or overload of current 45. This is because the width of the
pulse of the PWM signal 81 is wide enough to generate a sudden
output of substantially high amount of current from the power
switching circuit 9. This rush current 45 can lead to damage or
malfunction of the DC motor.
Another Example of PWM Signals and Current Without Soft-Start
[0040] FIG. 3F illustrates another PWM signal 82 outputted from the
PWM generator 8. The hatched rectangular window 86 of FIG. 3F
represents a time period from when the logic level DC voltage 71
falls below the threshold logic level DC voltage value to when the
logic level DC voltage 71 comes back above the threshold logic
level DC voltage value. In this example, the PWM signals 82 stop as
a low pulse and start again as a low pulse in the time period. The
PWM signal 82 outputs a high pulse some time after the logic level
DC voltage 71 comes back above the threshold logic level DC voltage
value
[0041] FIG. 3G illustrates current 42 generated by the power
switching circuit 9 in response to the PWM signal 82. In this
example, current is outputted immediately after the "On" position
since the PWM signal 82 is a low pulse. However, a rush current 46
occurs when the DC voltage signal 41 is back to normal and the PWM
signal 82 becomes a high pulse sometime after the "On" position.
This is because the width of the first PWM pulse after the time
window 86 is wide enough to generate a sudden output of
substantially high amount of current from the power switching
circuit 9. This rush current 46 can lead to damage or malfunction
of the DC motor.
Logic Level AC Voltage
[0042] FIG. 4D illustrates scaled-down AC voltage signal 18
outputted by the voltage dividing circuit 32. The scaled-down AC
voltage signal 18 is scaled-down version of the AC voltage signal
from the power supply 11 to the voltage dividing circuit 32. The
scaled-down AC voltage signal 18 includes zero voltage signal
corresponding to the power outage 25 of FIG. 4A. The scaled-down AC
voltage signal 18 also includes surges 15, 16, and 17 corresponding
to surges 22, 23, and 24 of FIG. 4A.
PWM Signals with Soft-Start in Response Power Outage
[0043] FIG. 4E illustrates PWM signal 83 outputted from the PWM
generator 8 in one embodiment with a soft-start. In the illustrated
embodiment of FIG. 4E, if the scaled-down AC voltage signal 18
becomes zero or substantially zero, then the PWM generator 8 stops
generating or outputting PWM signals 83 as in "Stop 1" position. In
one embodiment where the power irregularity detector 31 (FIG. 1)
includes the outage detecting circuit 34, this circuit 34 sends a
stop signal to the PWM generator 8 to stop generating or outputting
the PWM signal 83.
[0044] In one embodiment, if the scaled-down AC voltage signal 18
becomes zero or substantially zero for longer than a predetermined
period, then the PWM generator 8 stops generating or outputting PWM
signals 83 after that predetermined time from first detecting the
power outage. In one embodiment, the outage detecting circuit 34
sends the stop signal in a predetermined time after first detecting
of the power outage. In another embodiment, the outage detecting
circuit 34 sends the stop signal only when the power outage becomes
longer than a predetermined time.
[0045] In embodiments, the predetermined time is about 0.05 msec.,
about 0.06 msec., about 0.07 msec., about 0.08 msec., about 0.09
msec., about 0.1 msec., 0.11 msec., about 0.12 msec., about 0.13
msec., about 0.14 msec., about 0.15 msec., about 0.16 msec., 0.17
msec., about 0.18 msec., about 0.19 msec., about 0.2 msec., 0.21
msec., about 0.22 msec., about 0.23 msec., about 0.24 msec., about
0.25 msec., about 0.26 msec., 0.27 msec., about 0.28 msec., about
0.29 msec., about 0.3 msec., 0.31 msec., about 0.32 msec., about
0.33 msec., about 0.34 msec., about 0.35 msec., about 0.36 msec.,
0.37 msec., about 0.38 msec., about 0.39 msec., about 0.4
msec..
[0046] In embodiments, when the PWM generator 8 receives a signal
that the power outage is over, the PWM generator is configured to
perform a soft-start of the PWM signals as in position "Soft-Start
1." In soft-starting, the PWM generator 8 sends a new set of PWM
signals to the power switching circuit 9. The new set of PWM
signals are pulse signals with pulse widths that start from
initially narrow widths to wider widths over time.
Current Supplied to Motor with Soft-Start in Response to Power
Outage
[0047] FIG. 4F illustrates current 43 supplied to the motor 10 from
the power switching circuit 9 in one embodiment with a soft start.
In FIG. 4E, the PWM signal 83 stops when there is an AC power
outage or when such power outage is longer than a predetermined
period. Then, when the power outage is over, the PWM signal 83
starts fresh or soft-started as shown in the "Soft-Start 1"
position. The soft-started PWM signal 83 begins with narrow width
pulses and gradually include wider width pulses. Thus, receiving
the DC power 41 and the PWM signal 83, the power switching circuit
9 generates current 43 that increases as if the motor 10 is turned
on fresh. By soft-starting the current 43 gradually increases
without substantial current rush as shown in FIGS. 3E and 3G.
[0048] PWM Signals with Soft-Start and Current in Response to Power
Surges
[0049] Further in the illustrated embodiment of FIG. 4E, the PWM
signal 83 soft-starts in response to certain level of surges. As
discussed above referring to FIGS. 1 and 2, the surge detecting
circuit 33 detects surges within the scaled-down AC voltage signal
18. When at least one surge 22, 23, 24 is detected, the surge
detecting circuit 33 sends a surge signal to the PWM generator 8,
which then stops generating or outputting PWM signals from the PWM
generator 8 as in "Stop 2" position. In some embodiments, the PWM
generator 8 reacts to soft-start PWM signals 83 at "Soft-Start 2"
when there is more than one surge signal from the surge detecting
circuit 33. Accordingly, referring to FIG. 4F, the current 43 also
includes a decline at "Stop 2" and a gradual increase after the
"Soft-Start 2" position.
[0050] In the illustrated embodiment of FIG. 4E, the PWM generator
8 soft-starts the PWM signals after detecting three surges, 15, 16,
and 17. In embodiments, the PWM generator 8 soft-starts after
detecting 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 surges. In some
embodiments, the PWM generator 8 soft-starts outputting PWM signal
83 when there is no surge for a predetermined period of time as in
"Soft-Start 2" position. In embodiments, the predetermined time
period is about 0.5 sec., about 1 sec., about 1.5 sec., about 2
sec., about 2.5 sec., about 3 sec., about 3.5 sec., about 4 sec.,
about 4.5 sec., about 5 sec., about 5.5 sec., about 6 sec., about
6.5 sec., about 7 sec., about 7.5 sec., about 8 sec., about 8.5
sec., about 9 sec., about 9.5 sec., about 10 sec., about 10.5 sec.,
about 11 sec., about 11.5 sec., about 12 sec., etc.
[0051] In embodiment, power surges are defined as those including
deviations of the voltage that are greater than about 1%, about 2%,
about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about
9%, about 10%, about 11%, about 12%, about 13%, about 14%, about
15%, about 16%, about 17%, about 18%, about 19%, about 20%, about
21%, about 22%, about 23%, about 24%, about 25%, about 26%, about
27%, about 28%, about 29%, and about 30% from the regular amplitude
of the logic level AC voltage.
* * * * *