U.S. patent application number 11/427161 was filed with the patent office on 2008-01-03 for conveying temperature information in a controlled variable speed heating, ventilation, and air conditioning (hvac) system.
This patent application is currently assigned to Computime, Ltd.. Invention is credited to Chung Ming Cheng, Wai-Leung Ha, Kairy Kei Lei.
Application Number | 20080000246 11/427161 |
Document ID | / |
Family ID | 38846040 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080000246 |
Kind Code |
A1 |
Ha; Wai-Leung ; et
al. |
January 3, 2008 |
Conveying Temperature Information in a Controlled Variable Speed
Heating, Ventilation, and Air Conditioning (HVAC) System
Abstract
The present invention provides methods and apparatuses that
support the transfer of data from a thermostat unit to a controller
unit to control a variable speed heating, ventilation, and air
conditioning (HVAC) system. The duty cycle of a signal (that is
sent from a thermostat unit to a controller unit) is adjusted in
accordance with a temperature difference between the ambient
temperature of an environmentally controlled space and a set
temperature. The controller unit measures the duty cycle to
determine the temperature difference and adjusts the speed of a
blower motor or compressor in accordance with the temperature
difference. The signal is switched on and off, in which the AC
waveform is conducted and blocked by the thermostat unit and
received by the controller unit. The controller unit measures the
duty cycle of the received signal, determines the temperature from
the duty cycle, and adjusts the speed from a predetermined
relationship.
Inventors: |
Ha; Wai-Leung; (Hong Kong,
CN) ; Cheng; Chung Ming; (Hong Kong, CN) ;
Lei; Kairy Kei; (Shen Zhen City, CN) |
Correspondence
Address: |
BANNER & WITCOFF, LTD.
TEN SOUTH WACKER DRIVE, SUITE 3000
CHICAGO
IL
60606
US
|
Assignee: |
Computime, Ltd.
Kowloon
HK
|
Family ID: |
38846040 |
Appl. No.: |
11/427161 |
Filed: |
June 28, 2006 |
Current U.S.
Class: |
62/228.1 ;
236/49.1 |
Current CPC
Class: |
Y02B 30/70 20130101;
G05D 23/24 20130101; F25B 2600/0251 20130101; F25B 49/025 20130101;
Y02B 30/741 20130101; G05D 23/1913 20130101; F25B 2700/2104
20130101; F25B 2600/0253 20130101; F24F 11/83 20180101; F25B
2600/021 20130101 |
Class at
Publication: |
62/228.1 ;
236/49.1 |
International
Class: |
F24F 7/00 20060101
F24F007/00; F25B 49/00 20060101 F25B049/00 |
Claims
1. A system for controlling an air conditioning unit, the air
conditioning unit including a variable speed compressor, the system
comprising: a thermostat unit including: a temperature sensor
measuring an ambient temperature of an environmentally controlled
space; a switching module controlling conduction of a signal over a
controlled time interval; and a thermostat processing module
determining a temperature difference between the ambient
temperature and a set temperature, determines a duty cycle
corresponding to the temperature difference, and controlling the
switching module in accordance with the duty cycle, the signal
being electrically conducted during an activated time duration and
electrically blocked during an deactivated time duration over a
time period, the duty cycle specifying the activated time duration
and the deactivated time duration; and a compressor controller unit
including: a signal interface module monitoring the signal from the
thermostat unit; and a compressor controller processing module
determining the duty cycle from the signal, determining the
temperature difference from the duty cycle, and determining an
updated compressor speed from the temperature difference, and
instructing the variable speed compressor to function at the
updated compressor speed.
2. The system of claim 1, the switching module including an
electrical component that electrically closes during the activated
time duration and electrically opens during the deactivated time
duration.
3. The system of claim 1, the thermostat processing module
processing the temperature difference between a range between
T.sub.max and -T.sub.max.
4. The system of claim 3, thermostat processing module determining
the duty cycle from the temperature difference divided by said
T.sub.max times 50% plus 50%.
5. The system of claim 4, the thermostat processing module setting
the temperature difference to a positive limited value when the
temperature difference is greater than approximately T.sub.max and
setting the temperature difference to a negative limited value when
the temperature is less than approximately -T.sub.max.
6. The system of claim 3, the thermostat processing module sending
a pulse having a pulse duration less than a minimum value when
decoding the duty cycle as zero, the pulse being conveyed by the
signal.
7. The system of claim 6, the compressor controller processing
module decoding the signal corresponding to the duty cycle as being
zero when the pulse duration is less than the minimum value.
8. The system of claim 3, the thermostat processing module sending
a predetermined pulse pattern that designates an emergency stop,
the predetermined pulse pattern being conveyed on the signal.
9. The system of claim 8, the compressor controller processing
module decoding the signal corresponding to the emergency stop and
instructing the variable speed compressor to stop rotating.
10. The system of claim 1, the switching module controlling the
signal having a switched alternating current (AC) waveform.
11. The system of claim 1, the compressor controller processing
module determining the time period as a time value between raising
edges of consecutive time durations.
12. The system of claim 1, the thermostat unit sending
configuration information to the compressor controller unit.
13. The system of claim 12, the thermostat unit encoding a value of
T.sub.max in the configuration information.
14. The system of claim 1, the compressor controller unit further
including: a data structure that maps the temperature difference to
the updated compressor speed; and the compressor controller
processing module access the data structure to determine an updated
compressor speed.
15. A thermostat unit for controlling an air conditioning unit, the
air conditioning unit including a variable speed compressor, the
thermostat unit comprising: a temperature sensor measuring an
ambient temperature of an environmentally controlled space; a
switching module controlling conduction of a signal over a
controlled time interval, the signal having a switched alternating
current (AC) waveform; and a thermostat processing module
determining a temperature difference between the ambient
temperature and a set temperature, determines a duty cycle
corresponding to the temperature difference, and controlling the
switching module in accordance with the duty cycle, the signal
being electrically conducted during an activated time duration and
electrically blocked during an deactivated time duration over a
time period, the duty cycle specifying the activated time duration
and the deactivated time duration.
16. A thermostat unit of claim 15, the thermostat processing unit
determining the duty cycle from the temperature difference divided
by T.sub.max times 50% plus 50%.
17. A thermostat unit of claim 15, the switching module including
an electrical component that electrically closes during the
activated time duration and electrically opens during the
deactivated time duration.
18. A compressor controller unit for controlling an air
conditioning unit, the air conditioning unit including a variable
speed compressor, the compressor controller unit comprising: a
signal interface module monitoring a signal from a thermostat unit,
the signal having a switched alternating current (AC) waveform and
being characterized by a duty cycle; and a compressor controller
processing module determining the duty cycle from the signal,
determining the temperature difference from the duty cycle, and
determining an updated compressor speed from the temperature
difference, and instructing the variable speed compressor to
function at the updated compressor speed.
19. A compressor controller unit of claim 18, the compressor
controller processing module decoding the signal by determining
that the temperature difference equals the duty cycle minus 50%
divided by 50% times T.sub.max.
20. A compressor controller unit of claim 18, further comprising: a
pulse width modulation controller controlling a pulse width of at
least one control pulse in accordance with the temperature
difference and a feedback signal from the variable speed
compressor, the feedback signal being indicative of a difference
between a target compressor speed and an actual compressor speed;
and an array providing at least one control signal to the variable
speed compressor in accordance with the pulse width of the at least
one control pulse from the pulse width modulation controller.
21. A system for controlling a furnace, the furnace including a
variable speed blower motor, the system comprising: a thermostat
unit including: a temperature sensor measuring an ambient
temperature of an environmentally controlled space; a switching
module controlling conduction of a signal over a controlled time
interval; and a thermostat processing module determining a
temperature difference between the ambient temperature and a set
temperature, determines a duty cycle corresponding to the
temperature difference, and controlling the switching module in
accordance with the duty cycle, the signal being electrically
conducted during an activated time duration and electrically
blocked during an deactivated time duration over a time period, the
duty cycle specifying the activated time duration and the
deactivated time duration; and a furnace controller unit including:
a signal interface module monitoring the signal from the thermostat
unit; and a furnace controller processing module determining the
duty cycle from the signal, determining the temperature difference
from the duty cycle, and determining an updated speed of the
variable speed blower motor from the temperature difference, and
instructing the variable speed blower motor to function at the
updated compressor speed.
22. The system of claim 21, the thermostat processing module
processing the temperature difference between a range between
T.sub.max and -T.sub.max.
23. The system of claim 22, the thermostat processing module
determining the duty cycle from the temperature difference divided
by said T.sub.max times 50% plus 50%.
Description
FIELD OF THE INVENTION
[0001] The present invention relates generally to the field of
controlling a variable speed heating, ventilation, and air
conditioning (HVAC) system, and more particularly to sending a
signal that conveys a temperature difference from a thermostat unit
to a controller unit.
BACKGROUND OF THE INVENTION
[0002] With the price of energy steadily increasing, there is an
increasing need to enhance the efficiency of heating, ventilation,
and air conditioning (HVAC) systems. One approach to increase the
efficiency of a HVAC system is to incorporate a variable speed
controlled compressor in the system for the cooling function. The
latest technology typically employs a sophisticated microprocessor
controller unit (MCU) and a digital signal processor (DSP) to
support a high performance inverter type variable speed controlled
compressor. The speed (revolutions per unit time) of a variable
speed controlled compressor depends on the temperature difference
of the set temperature (typically set at a thermostat) and the
ambient temperature of the temperature-controlled room. In general
for the cooling function when the ambient temperature is higher
than the set temperature, the higher the temperature difference,
the faster the compressor should run.
[0003] A typical thermostat can provide only a simple ON/OFF
control of the 24V AC to a compressor controller that controls that
compressor. However, with this control mechanism, a variable speed
controlled compressor will not typically function at their maximum
efficiency. Consequently, there is a need for apparatuses and
methods that enable the typical thermostat to properly control a
variable speed controlled compressor.
SUMMARY OF THE INVENTION
[0004] The present invention provides methods and apparatuses that
support the transfer of data from a thermostat unit to a controller
unit to control the speed of a compressor of an air conditioner
unit or a blower motor of a furnace.
[0005] With an aspect of the invention, the duty cycle of a signal
that is sent from a thermostat unit to a compressor controller unit
is adjusted in accordance with a temperature difference between the
ambient temperature of an environmentally controlled space and a
set temperature. The compressor controller unit measures the duty
cycle to determine the temperature difference and adjusts the
compressor speed in accordance with the temperature difference.
[0006] With another aspect of the invention, the duty cycle of a
signal that is sent from a thermostat unit to a furnace controller
unit is adjusted in accordance with a temperature difference
between the ambient temperature of an environmentally controlled
space and a set temperature. The furnace controller unit measures
the duty cycle to determine the temperature difference and adjusts
the speed of a blower motor in accordance with the temperature
difference.
[0007] With another aspect of the invention, the change in hardware
at both the thermostat side and the compressor controller side is
minimized. An AC line (e.g., 24 volts) is used to transfer data in
a signal sent from the thermostat side to the compressor controller
side. The signal is switched on and off, in which the AC waveform
is conducted and blocked by the thermostat unit and received by the
compressor controller. Consequently, existing wiring can be used
without modifications.
[0008] With another aspect of the invention, a thermostat unit
instructs a compressor controller unit to stop operation
immediately in an emergency situation by sending a signal with a
pulse or pulses having a short time duration.
[0009] With another aspect of the invention, a compressor
controller unit measures the duty cycle of a received signal,
determines the temperature from the duty cycle, and adjusts the
compressor speed from a predetermined relationship. The compressor
speed is related to the temperature difference, in which the
compressor controller unit may access a lookup table using an
address determined by the temperature difference.
[0010] With another aspect of the invention, a pulse width
modulated (PWM) controller is instructed by a microprocessor
control unit to generate control pulses for the compressor so that
the compressor runs at a desired speed. The PWM controller
configures an IGBT (insulated-gate bipolar transistor) array so
that an appropriate pulse stream is provided to the compressor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The foregoing summary of the invention, as well as the
following detailed description of exemplary embodiments of the
invention, is better understood when read in conjunction with the
accompanying drawings, which are included by way of example, and
not by way of limitation with regard to the claimed invention.
[0012] FIG. 1 shows a thermostat unit for controlling a variable
speed compressor in accordance with an embodiment of the
invention.
[0013] FIG. 2 shows a signal that is sent from a thermostat unit to
a compressor controller unit for controlling a variable speed
compressor in accordance with an embodiment of the invention.
[0014] FIG. 3 shows a compressor controller unit for controlling a
variable speed compressor in accordance with an embodiment of the
invention.
[0015] FIG. 4 shows a relationship between a temperature
difference, referencing an ambient temperature to a set
temperature, and a duty cycle of a signal in accordance with an
embodiment of the invention.
[0016] FIG. 5 shows a relationship of a determined compression
speed and the temperature difference in accordance with an
embodiment of the invention.
[0017] FIG. 6 shows a flow diagram that is executed by the
thermostat unit in accordance with an embodiment of the
invention.
[0018] FIG. 7 shows a flow diagram that is executed by the
compressor controller unit to initiate processing of the signal, as
shown in FIG. 2.
[0019] FIG. 8 shows a flow diagram that is executed by the
compressor controller unit to process the signal, as shown in FIG.
2, during a time period.
[0020] FIG. 9 shows an exemplary configuration for controlling a
variable speed compressor.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0021] FIG. 1 shows a thermostat unit 100 for controlling a
variable speed compressor (not shown) in accordance with an
embodiment of the invention. Thermostat unit 100 includes
microprocessor control unit (MCU) 107 and switching module 105.
Switching module 105, which electrically turns on and off, may be
implemented with a relay, triac, or field effect transistor (FET).
Additionally, thermostat unit 100 may include keypad input 111 in
order for a user to input a set temperature or a profile of set
temperatures (as will be discussed) and display 113 to display the
ambient temperature of a controlled space (e.g., a room) and the
set temperature.
[0022] Microprocessor control unit 107 measures the ambient
temperature of the controlled space with thermistor 109, which is
situated in an appropriate point of the controlled space.
Microprocessor control unit 107 consequently determines a
difference temperature (T.sub.diff) by subtracting the set
temperature (T.sub.set) from the ambient temperature
(T.sub.amb):
T.sub.diff=T.sub.amb-T.sub.set (EQ. 1)
[0023] In the embodiment shown in FIG. 1, switching module 105 is
either in the "on" state or the "off" state. When in the "on"
state, electrical conductivity is completed from line 101 to line
103 and an AC waveform (typically 24 volts AC) is provided to a
compressor (for cooling) to a furnace control board (for heating).
When in the "off" state, electrical conductivity is blocked. In the
following discussion, the thermostat is supporting the cooling
function (i.e., by communicating with a compressor controller to
control a compressor as will be discussed).
[0024] Because switching module 105 is either on or off, only two
states are directly supported. However, in accordance with an
aspect of the invention, information that is indicative of
T.sub.diff is transmitted from thermostat unit 100 to compressor
controller unit 300 (as shown in FIG. 3 by varying the duty cycle
of a signal (e.g., signal 200 as shown in FIG. 2) that is conveyed
by lines 101, 103.
[0025] In an embodiment of an invention, thermostat unit 100 sends
a special signal that has a short pulse duration to notify a
furnace/air conditioner controller to immediately stop operation.
For example, the special signal can be four consecutive pulses with
1 second on and 1 second off.
[0026] FIG. 2 shows signal 200 that is sent from a thermostat unit
100 (as shown in FIG. 1) to a compressor controller unit 300 (as
shown in FIG. 3) for controlling a variable speed compressor 303
(as shown in FIG. 3) in accordance with an embodiment of the
invention. Signal 200, as shown in FIG. 2, spans a time duration
over time periods 201, 203, and 205.
[0027] During each time period 201, 203, 205, signal 200 is being
electrically conducted during an activated time duration (T.sub.on)
(e.g., activated time duration 201a for time period 201) and
electrically blocked during an deactivated time duration
(T.sub.off) (e.g., deactivated time duration 201b for time period
201). During activated time duration 201a, AC power (corresponding
to a 24 volts AC waveform) is conducted. During deactivated time
duration 201b, AC power is not conducted. The corresponding duty
cycle is determined by:
Duty_Cycle = T on T on + T off ( EQ . 2 ) ##EQU00001##
[0028] In an embodiment of the invention, thermostat unit 100
notifies compressor unit 300 the value of T.sub.max by sending a
configuration signal having a preamble followed by a number of
pulses, in which the number of pulses is indicative of the value of
T.sub.max. In an exemplary embodiment, the preamble comprises a
predetermined pulse sequence of two ON time periods followed by two
OFF time periods, each time period being one second. For each ON
time period, a pulse is generated for 0.5 second during an ON time
period and not generated during an OFF time period. The value of
T.sub.max (degrees Fahrenheit) is determined from the number of
pulses following the preamble by:
T.sub.max=2.sup.(number of pulses+5) (EQ. 3)
[0029] Referring to FIG. 1, microprocessor control unit 107
controls switching module 105 to turn on and turn off signal 200
based on any period of time. (In fact, as suggested by FIG. 2, the
time period may vary from one time period to another.) The time
period may be 5, 10 or 15 minutes or any other time period.
[0030] The duty cycle of signal 200 conveys information about the
temperature difference (T.sub.diff) as determined by microprocessor
control unit 107. As suggested by FIG. 2, the duty cycle typically
varies from one time period to another time period corresponding to
temperature difference variations.
[0031] In an embodiment of the invention, the temperature
difference (T.sub.diff) is encoded by the duty cycle as
follows:
Duty_Cycle=T.sub.diff/T.sub.max*50%+50% (EQ. 4)
Combining EQ. 4 and EQ. 2, one can determine the T.sub.on by:
[0032] T.sub.on=(T.sub.diff/T.sub.max*50%+50%)*T.sub.cycle (EQ.
5)
where T.sub.cycle=T.sub.on+T.sub.off
However, if the temperature difference if greater than
T.sub.max-.DELTA..sub.temp or less than
-T.sub.max+.DELTA..sub.temp, the temperature difference is limited
as follows:
T.sub.diff=T.sub.max-1 if T.sub.diff>=T.sub.max-.DELTA..sub.temp
(EQ. 6a)
T.sub.diff=-T.sub.max+1 if
T.sub.diff<=-T.sub.max+.DELTA..sub.temp (EQ. 6b)
T.sub.max-.DELTA..sub.temp corresponds to maximum value 409 of the
duty cycle and -T.sub.max+.DELTA..sub.temp corresponds to minimum
value 407 of the duty cycle as shown in FIG. 4. The limit of
|T.sub.diff| is reduced by one degree Fahrenheit in EQ. 6a and EQ.
6b so that the signal is not detected to be ON or OFF all of the
time by compressor controller unit 300 when thermostat unit 100 is
sending control information. (If signal 200 were ON or OFF all of
the time, no signal transitions could be detected.)
[0033] FIG. 3 shows compressor controller unit 300 for controlling
a variable speed compressor 303 in accordance with an embodiment of
the invention. Microprocessor control unit (MCU) 301 scans lines
101, 103 for signal 200 and detects a time between two rising
signal edges (e.g., signal edges 251 and 253 as shown in FIG. 2) to
determine the current time period of signal 200. Microprocessor
control unit 301 may be coupled with a digital signal processor in
order to facilitate calculations.
[0034] Referring to FIG. 2, when processing signal 200, compressor
controller unit 300 waits receives duty cycle information for an
entire time period before further processing the information. For
example, compressor controller unit 300 determines the duty cycle
for time period 201 from signal 200 after detecting signal edge
253. Compressor controller unit 300 consequently determines the
temperature difference T.sub.diff, as measured by thermostat unit
100, by decoding signal 200. (As will be discussed with FIG. 8,
compressor controller unit 300 utilizes flow diagram 800 to measure
the duty cycle.) Compressor controller unit 300 measures the duty
cycle of signal 200 of the previous time period in accordance with
EQ. 2 and determines:
T.sub.diff=(Measured_Duty_Cycle-50%)/50%*T.sub.max (EQ. 7)
If T.sub.diff is positive, variable speed compressor 303 should
turn faster based on a predetermined relationship, e.g.,
relationship 503 as shown in FIG. 5 as will be discussed. If
T.sub.diff is negative, variable speed compressor 303 should turn
slower based on an algorithm.
[0035] In an embodiment of the invention, compressor control unit
300 obtains T.sub.max by a user entering T.sub.max through keypad
309. While compressor controller unit 300 may obtain the value of
T.sub.max from a configuration signal sent by thermostat unit 100,
as previously discussed, the value of T.sub.max may be entered into
keypad 111 by the user. Other embodiments of the invention may
utilize a predetermined value of T.sub.max that is stored in
memory.
[0036] Microprocessor control unit 301 may access lookup data
structure 317 in order to determine the temperature difference
(T.sub.diff) and the compressor speed. (As will be discussed, the
compressor speed is determined as a function of the temperature
difference as shown in FIG. 5.) In order to obtain a desired
efficiency, compressor 303 typically runs at a higher speed as the
temperature difference becomes greater. When the compressor speed
has been determined, microprocessor control unit 301 instructs PWM
(pulse width modulated) controller 305 to drive IGBT
(insulated-gate bipolar transistor) array 307 (via bus 311) so that
compressor 303 runs at the desired compressor speed (over bus 313).
PWM controller 305 is provided an indication of the actual
compressor speed over feedback connection 315 in order to adjust
the compressor speed to obtain the desired compressor speed. An
exemplary embodiment will be further discussed with FIG. 9.
[0037] With the exemplary embodiment, compressor controller unit
300 functions with a traditional thermostat design but with
software modifications as will be discussed.
[0038] FIG. 4 shows relationship 405 between temperature difference
(T.sub.diff) 403, referencing an ambient temperature (of an
environmentally controlled space where thermistor 109 is located)
to a set temperature, and measured duty cycle 401 of a signal in
accordance with an embodiment of the invention. In the embodiment
shown in FIG. 4, relationship 405 is in accordance with EQ. 7,
although other embodiments may utilize a different relationship
between the temperature difference and the duty cycle. In the
example shown in FIG. 4, if measured duty cycle 401 equals 25%,
temperature difference 403 is determined to equal
-0.5T.sub.max.
[0039] As previously discussed, a duty cycle between minimum value
407 and maximum value 409 is utilized in order to facilitate the
detection of signal edges by microprocessor control unit 301. In an
embodiment of the invention, microprocessor control unit 301
analyzes signal 200 in a time-interrupt basis as shown in FIG. 8.
Depending on the value of the time interval between interrupts,
microprocessor control unit 301 may not detect a transition of
signal 200. (Between time-interrupts, microprocessor control unit
301 may be executing other tasks, e.g., diagnostics and executing
commands entered through keypad 309.) Consequently, the temperature
difference is limited between T.sub.max-.DELTA..sub.temp and
-T.sub.max+.DELTA..sub.temp so that signal transitions can be
detected. As the time durations between time-interrupts become
smaller, the value of |.DELTA..sub.temp| becomes smaller. If
microprocessor control unit 301 processes time-interrupts quickly
enough, .DELTA..sub.temp is essentially zero.
[0040] FIG. 5 shows relationship 503 of a determined compression
speed 501 and the temperature difference 403 in accordance with an
embodiment of the invention. Microprocessor control unit 301
measures duty cycle 401 and determines temperature difference 403
using relationship 405. In an embodiment of the invention,
microprocessor control unit 301 accesses lookup data structure 317
using an address determined by duty cycle 401 to obtain temperature
difference 403. Microprocessor control unit 301 subsequently
accesses lookup data structure 317 to determine compression speed
501 using an address determined by temperature difference 403 to
obtain compression speed 501. Because the temperature difference
typically varies from time period to time period, as suggested by
FIG. 2, compressor speed 501 consequently varies.
[0041] FIG. 6 shows flow diagram 600 that is executed by
microprocessor control unit 107 in accordance with an embodiment of
the invention. Microprocessor control unit 107 obtains the set
temperature T.sub.set, the time period (T.sub.cycle), and the
ambient temperature (T.sub.room) from thermistor 109 in step 601.
In step 603, microprocessor control unit 107 determines the
temperature difference (T.sub.diff) in accordance with EQ. 1. If
the temperature difference is larger than the maximum temperature
difference (T.sub.max), as determined by step 605, the temperature
difference is limited to T.sub.max-1 as determined by step 607.
Otherwise, step 611 determines whether the temperature difference
is less than the negative maximum temperature difference
(-T.sub.max) in step 611. If so, the temperature difference is
limited to -T.sub.max+1 in step 613. Otherwise, the activated time
duration (T.sub.on) is determined in accordance with EQ. 5 in step
609. Signal 200 is generated in accordance with T.sub.on and
T.sub.off as determined by flow diagram 600.
[0042] FIG. 7 shows flow diagram 700 that is executed by compressor
controller unit 300 to initiate processing of signal 200, as shown
in FIG. 2, during a time period. Microprocessor control unit 301
obtains T.sub.max and F.sub.def to initiate processing over the
current time period. Consequently, microprocessor control unit 301
resets T.sub.on, T.sub.off, and sets the compressor speed variable
F.sub.speed to F.sub.def in step 701. In step 702, microprocessor
control unit 301 determines whether signal 200 is present (i.e.,
whether any signal transitions have been detected.) In step 703,
interrupts are configured to occur periodically (every
T.sub.interrupt time interval) so that pulse edges can be detected.
For example, if the minimum pulse duration is 1 second
(corresponding to an emergency stop), interrupts are configured to
occur at least every 0.5 seconds. As will be discussed, procedure
800 (as shown in FIG. 8) is processed every T.sub.interrupt time
interval.
[0043] FIG. 8 shows flow diagram 800 that is executed by compressor
controller unit 300 to process signal 200, as shown in FIG. 2,
during a time period. In the following discussion, one should note
that flow diagram 800 determines whether there are signal edges
detected in signal 200. If not, compressor 303 is not active.
[0044] In step 801, microprocessor control unit 301 determines if
signal 200 is conducting AC power (typically 24 volts AC) during
T.sub.on. If not, the T.sub.off counter is incremented in step 817.
(In flow diagram 800, T.sub.off counter and T.sub.on counter are
appropriately incremented so that the duty cycle can be determined
when flow diagram is respectively executed during the current timer
period. Once the current time period is completed, the duty cycle
is determined by step 807 as will be discussed.) The process will
exit (i.e., flow diagram 800 determines that the air conditioner is
not active).
[0045] If microprocessor control unit 301 determines that signal
200 is conducting AC power during T.sub.on in step 801,
microprocessor control unit 301 determines if signal 200 was
previously in a non-conductive state (i.e., deactivated time
duration 201b for time period 201) in step 805. If not, the
T.sub.on counter is incremented in step 819, and process 800 is
exited. If so, a rising signal edge is detected and step 807 is
executed.
[0046] In step 807 (corresponding to a rising edge just being
detected), the temperature difference is determined in accordance
with EQ. 7 for the time period that has just completed. The
T.sub.on counter and the T.sub.off counter are then reset. In step
811, microprocessor control unit 301 determines the speed of
compressor 303 in accordance with a predetermined function
f(T.sub.diff), e.g., relationship 503 as shown in FIG. 5. In step
813, the compressor speed F.sub.speed is adjusted, in which
microprocessor control unit 301 provides the updated compressor
speed to PWM controller 305. Compressor 303 is consequently
instructed to change its speed through bus 311, IGBT array 307, and
bus 313.
[0047] FIG. 9 shows an exemplary configuration for controlling
variable speed compressor 303. In the exemplary embodiment,
compressor 303 comprises a three-phase motor; however, other
embodiments may support other types of motors, e.g., single-phase
induction motors, DC motors, and universal motors.
[0048] Compressor 303 is powered by AC power lines 905a, 905b
through rectifier bridge 907 and IGBT array 307. PWM controller 305
configures IGBT array 307 to control compressor 303 at the desired
compressor speed. PWM controller 305 includes microcontroller 901
and gate drivers 903a-903c. The speed of compressor 303 is
controlled by PWM controller 305, in which the voltage-to-frequency
ratio is adjusted with a speed feedback configuration.
[0049] Embodiments of the invention support a heating function in a
HVAC system. When supporting the heating function a controller
unit, in conjunction with a thermostat unit, couples with a
variable blower motor of a furnace. The speed of the variable
blower motor is varied in accordance with characteristics of the
motor and thermodynamics considerations.
[0050] As can be appreciated by one skilled in the art, a computer
system with an associated computer-readable medium containing
instructions for controlling the computer system can be utilized to
implement the exemplary embodiments that are disclosed herein. The
computer system may include at least one computer such as a
microprocessor, digital signal processor, and associated peripheral
electronic circuitry.
[0051] Although the subject matter has been described in language
specific to structural features and/or methodological acts, it is
to be understood that the subject matter defined in the appended
claims is not necessarily limited to the specific features or acts
described above. Rather, the specific features and acts described
above are disclosed as example forms of implementing the
claims.
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