U.S. patent application number 12/806053 was filed with the patent office on 2012-01-12 for method and apparatus for determining battery capacity in a defibrillator.
Invention is credited to Kyle R. Bowers.
Application Number | 20120010673 12/806053 |
Document ID | / |
Family ID | 35731380 |
Filed Date | 2012-01-12 |
United States Patent
Application |
20120010673 |
Kind Code |
A1 |
Bowers; Kyle R. |
January 12, 2012 |
Method and apparatus for determining battery capacity in a
defibrillator
Abstract
A defibrillator system and associated methodology for
determining capacity of a battery and/or a number of battery cells
contained in a pack. The system measures and stores the battery or
battery pack voltage signal data and uses an algorithm to determine
the remaining capacity. The algorithm takes into account the
operating mode of the device, historical information of the device
including, but not limited to, how long it has been since the
device has been used, how the device has been used (e.g. shocking
mode or idle mode), how many times the device has been used with
its installed battery or battery pack, how many charging cycles
and/or shocks have been delivered etc. The output from the system
is fed back to the user to inform the user when the battery is low,
needs to be replaced and/or how many remaining shocks are left the
battery.
Inventors: |
Bowers; Kyle R.;
(Boxborough, MA) |
Family ID: |
35731380 |
Appl. No.: |
12/806053 |
Filed: |
August 4, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11193940 |
Jul 29, 2005 |
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12806053 |
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60592788 |
Jul 30, 2004 |
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Current U.S.
Class: |
607/8 ;
702/63 |
Current CPC
Class: |
G01R 31/367 20190101;
H02J 7/0047 20130101; A61N 1/3925 20130101; G01R 31/3646 20190101;
A61N 1/3993 20130101; H02J 7/0048 20200101; H02J 7/342 20200101;
H02J 7/00034 20200101; A61N 1/3975 20130101; H02J 7/345
20130101 |
Class at
Publication: |
607/8 ;
702/63 |
International
Class: |
A61N 1/39 20060101
A61N001/39; G01R 31/36 20060101 G01R031/36; G06F 19/00 20110101
G06F019/00 |
Claims
1. A method for determining the remaining battery capacity of a
battery in a defibrillator, the method comprising: applying an
algorithm that calculates remaining battery capacity of a battery
using measured battery voltage value in conjunction with historical
information previously stored in the defibrillator.
2. The method according to claim 1 wherein the algorithm uses a
predetermined voltage value threshold for defibrillator in idle
mode and at least one other threshold when the defibrillator is
charging to deliver at least one shock.
3. The method according to claim 1 wherein the algorithm uses the
battery voltage value and time period of how long the device has
not been used.
4. The method according to claim 1 wherein the algorithm uses the
battery voltage value and the number of times the device has been
used with its installed battery.
5. The method of claim 1 wherein the algorithm uses the battery
voltage and how many times the device has been used to charge its
internal capacitors with its installed battery to determine the
remaining capacity of the battery.
6. The method of claim 1 wherein the algorithm uses the battery
voltage and how many times the device has been used to deliver a
biphasic shock to a patient with its installed battery.
7. The method of claim 1 wherein the algorithm uses the battery
voltage and how long the device has been used to monitor a patient
with its installed battery.
8. The method of claim 1 wherein the algorithm uses the data to
determine the remaining capacity of the battery and informs the
user that the battery is low.
9. The method of claim 1 wherein the algorithm uses the data to
determine the remaining capacity of the battery and informs the
user that the battery needs to be replaced.
10. The method of claim 1 wherein the algorithm uses the data to
determine the remaining capacity of the battery or battery pack and
informs the user of the number of shocks left.
11. The method of claim 1 wherein the algorithm uses the data to
determine the remaining capacity of the battery or battery pack and
informs the user of the remaining monitor time.
12. The method of claim 1 wherein the algorithm uses the data to
determine the remaining capacity of the battery or battery pack and
informs the user of the general battery capacity as it relates to
typical use.
13. A defibrillator comprising: at least one battery; at least one
capacitor; a circuit to charge the at least one capacitor from at
least one battery; a circuit to deliver a biphasic waveform from at
least one capacitor to the patient; user notification apparatus for
notifying the user of events during defibrillator operation; and a
data acquisition circuit that measures the terminal voltage of the
at least one battery, digitizes the signal and stores the data in
memory for analysis.
14. A defibrillator according to claim 13 wherein at least one
battery comprises at least one cell, and further wherein the supply
voltage is at least 3V.
15. A defibrillator according to claim 13 further comprising at
least one Lithium Manganese Dioxide type cell.
16. A defibrillator according to claim 13 wherein the data
acquisition circuit comprises: a microprocessor for executing
instructions to sample data, store the data into memory and process
the data to determine the remaining battery capacity; a
programmable logic device; and an analog-to-digital converter.
17. A defibrillator according to claim 16 wherein the programmable
logic device is configured to (i) control the interface to the
analog-to-digital converter, (ii) store the sampled data into a
local memory buffer, and (iii) interrupt the microprocessor to
sample the data contained in the buffer.
18. A defibrillator according to claim 16 wherein the
microprocessor directly interfaces with the analog-to-digital
converter and uses internal timing to interrupt the microprocessor
for sampling the data.
19. A defibrillator according to claim 16 wherein the
microprocessor comprises a microcontroller with memory, an
analog-to-digital converter and other peripherals on a single
chip.
20. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to sample battery voltage value
and store the data into memory.
21. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to sample battery voltage value
and store it onto a removable multi-media flash card for post
incident review.
22. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to sample battery voltage value
and store it into EEPROM or Flash.
23. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal voltage value and its associated operational mode in
memory.
24. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal or voltage value and how long it has been since the device
was last used.
25. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal voltage value and how many times the device has been used
with its installed battery.
26. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal voltage value and how many times the device has been used
to charge its internal capacitors with its installed battery.
27. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal voltage value and how many times the device has been used
to deliver a biphasic shock to a patient with its installed
battery.
28. A defibrillator according to claim 13 wherein the data
acquisition circuit is configured to store the measured battery
terminal voltage value and how long the device has been used to
monitor a patient with its installed battery.
29. A defibrillator according to claim 23 wherein the data is
stored into random access memory.
30. A defibrillator system according to claim 23 where in the data
is stored onto a removable multi-media flash card, EEPROM and or
Flash.
31. A method for determining battery capacity in a defibrillator
comprising: recording historical data comprising at least one from
the group consisting of: how long it has been since the battery was
last charged; how the defibrillator has been used since the battery
was last charged, including a record of when the defibrillator was
in idle mode and when the defibrillator was in shocking mode; how
many shocks have been delivered since the battery was last
recharged; how long has it been since the defibrillator was last
used in shocking mode; and how many times the battery has been
recharged over its lifetime; measuring the current battery voltage;
and applying an algorithm to calculate remaining battery capacity,
using the measured battery voltage and the recorded historical
data.
32. A method according to claim 31, further comprising notifying
the user when the calculated remaining battery capacity is below a
selected level.
33. A method according to claim 32, wherein the user is notified if
the number of shocks delivered since the battery was last charged
exceeds a selected number.
34. A method according to claim 32, wherein the user is notified if
the number of shocks delivered since the battery was last charged
exceeds a selected number and the current battery voltage is less
than a selected voltage.
35. A method according to claim 32, wherein the user is notified if
the number of shocks delivered since the battery was last charged
is within a selected range and the current battery voltage is less
than a selected voltage.
36. A method according to claim 32, wherein the user is notified if
the total monitoring time since the battery was last charged is
within a selected range and the current battery voltage is less
than a selected voltage.
37. A method according to claim 32, wherein the user is notified if
the number of shocks delivered since the battery was last charged
is below a selected number and the current battery voltage is less
than a selected voltage.
38. A method according to claim 32, wherein the user is notified if
the total monitoring time since the battery was last charged is
below a selected number and the current battery voltage is less
than a selected voltage.
39. A method according to claim 32, wherein the user is notified if
the time since the battery was last charged exceeds a selected
amount.
40. Apparatus for determining the battery capacity in a
defibrillator comprising: apparatus for recording historical data
comprising at least one from the group consisting of: how long it
has been since the battery was last charged; how the defibrillator
has been used since the battery was last charged, including a
record of when the defibrillator was in idle mode and when the
defibrillator was in shocking mode; how many shocks have been
delivered since the battery was last recharged; how long has it
been since the defibrillator was last used in shocking mode; and
how many times the battery has been recharged over its lifetime;
apparatus for measuring the current battery voltage; and apparatus
for applying an algorithm to calculate remaining battery capacity,
using the measured battery voltage and the recorded historical
data.
Description
REFERENCE TO PENDING PRIOR PATENT APPLICATIONS
[0001] This patent application claims benefit of pending prior U.S.
Provisional Patent Application Ser. No. 60/592,788, filed
07/30/2004 by Kyle R. Bowers for METHOD AND SYSTEM FOR DETERMINING
DEFIBRILLATOR BATTERY CAPACITY (Attorney Docket No. ACCESS-5 PROV),
which patent application is hereby incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates generally to the measurement
of battery capacity. More particularly, the present invention
relates to the measurement and determination of the remaining
capacity of a battery or battery pack in a defibrillator
system.
BACKGROUND OF THE INVENTION
[0003] Approximately 350,000 deaths occur each year in the United
States, due to sudden cardiac arrest (SCA). Many of these deaths
can be prevented if effective defibrillation is administered within
3-5 minutes of SCA.
[0004] Sudden cardiac arrest is the onset of an abnormal heart
rhythm, lack of pulse and absence of breath, leading to a loss of
consciousness. If a pulse is not restored within a few minutes,
death occurs. Most often, SCA is due to ventricular fibrillation, a
chaotic heart rhythm that causes an uncoordinated quivering of the
heart muscle. The lack of coordinated heart muscle contractions
results in insufficient blood flow to the brain and other organs.
Unless this chaotic rhythm is terminated, allowing the heart to
restore its own normal rhythm and thus normal blood flow to the
brain and other organs, death ensues.
[0005] Rapid defibrillation is the only known means to restore the
normal heart rhythm and prevent death after SCA due to ventricular
fibrillation. For each minute that passes after the onset of SCA,
the mortality rate increases by 10%. If defibrillated within 1-2
minutes, a patient's survival rate can be as high as 90% or more.
At 7-10 minutes, the patient's survival rate drops below 10%.
Therefore, the only way to increase the survival chances for an SCA
victim is through early defibrillation.
[0006] Automatic External Defibrillators (AEDs) can provide early
access to defibrillation, but they must be portable so they can be
easily carried to a victim of SCA, easy-to-use so that they can be
properly utilized when SCA occurs, and easily maintained. In
addition, AEDs must be inexpensive, so that they can be broadly
deployed.
[0007] Additionally, AEDs require a portable energy source to
enable the device to be deployed quickly to treat a victim of SCA.
Often, the victim may be in a remote or difficult-to-reach area,
making compact and portable AEDs attractive to police, EMT,
Search-And-Rescue and other rescue or emergency services.
[0008] AEDs must remain in a standby mode for extended periods of
time. Most current AEDs are rated for two years of standby and must
be able to complete a sufficient number of shocks at the end of
this period. However, during this two-year standby period, the
battery pack may discharge significantly and thus may not have
sufficient capacity to provide therapy, especially in situations
which may require many defibrillation shocks and an extended period
of monitoring time.
[0009] Currently, many AEDs use a battery monitoring circuit, also
known as a "smart battery", to provide a "fuel gauge" for remaining
capacity. This technique requires the use of low power analog and
digital circuitry within the battery pack or the device to
constantly monitor battery capacity. Most of these devices also
monitor battery temperature in order to accurately gauge capacity.
As those skilled in the art can appreciate, the disadvantage of
this technique is that the additional circuitry, components and
connections needed to monitor battery capacity may add significant
cost to the battery pack and/or the AED itself. As is well known to
those skilled in the art, this technique has been historically
problematic and has been an issue with portable AEDs that use
either disposable or rechargeable battery packs.
SUMMARY OF THE INVENTION
[0010] The present invention addresses the deficiencies described
above by providing a novel method and apparatus for determining the
capacity of a battery and/or a number of battery cells contained in
a battery pack.
[0011] In accordance with the present invention, the defibrillation
system contains a battery or battery pack, a circuit to charge the
defibrillation capacitor or capacitors, and a circuit to deliver a
biphasic waveform.
[0012] In accordance with the present invention, the defibrillation
system contains an LCD display and voice playback circuitry, an
audio amplifier and a speaker to notify the user of events during
device operation.
[0013] In accordance with the present invention, the defibrillation
system contains a microprocessor and circuitry that measures the
battery terminal or battery pack terminal voltage, digitizes the
signal and stores the data in local memory for analysis.
[0014] In another aspect of the present invention, the
defibrillation system stores the battery data in flash memory for
post-incident analysis.
[0015] In another aspect of the present invention, the
defibrillation system applies filtering techniques before and/or
after storing the measured battery voltage signal data.
[0016] In another aspect of the invention, the defibrillation
system uses an algorithm to determine the remaining capacity of the
battery or battery pack.
[0017] In another aspect of the present invention, the
defibrillation system stores in memory the measured battery
terminal or battery pack terminal voltage and its associated
operational mode. The different operating modes draw various levels
of current from the battery or battery pack. The algorithm then
uses this stored data to determine the remaining capacity of the
battery or battery pack.
[0018] In another aspect of the present invention, the
defibrillation system stores in memory how long the device has been
used. The algorithm then uses this stored data to determine the
remaining capacity of the battery or battery pack.
[0019] In another aspect of the present invention, the
defibrillation system stores in memory the measured battery
terminal or battery pack terminal voltage and how long the device
has been used. The algorithm then uses this stored data to
determine the remaining capacity of the battery or battery
pack.
[0020] In another aspect of the present invention, the
defibrillation system stores in memory the measured battery
terminal or battery pack terminal voltage and how many times the
device has been used with its installed battery or battery pack.
The algorithm then uses this stored data to determine the remaining
capacity of the battery or battery pack.
[0021] In another aspect of the present invention, the
defibrillation system stores in memory the measured battery
terminal or battery pack terminal voltage and how many times the
device has been used to charge its internal capacitors with its
installed battery or battery pack. The algorithm then uses this
stored data to determine the remaining capacity of the battery or
battery pack.
[0022] In another aspect of the present invention, the
defibrillation system stores in memory how many times the device
has been used to deliver a biphasic shock to a patient with its
installed battery or battery pack. The algorithm then uses this
stored data to determine the remaining capacity of the battery or
battery pack.
[0023] In another aspect of the present invention, the
defibrillation system stores in memory the measured battery
terminal or battery pack terminal voltage and how many times the
device has been used to deliver a biphasic shock to a patient with
its installed battery or battery pack. The algorithm then uses this
stored data to determine the remaining capacity of the battery or
battery pack.
[0024] In another aspect the present invention, the algorithm uses
the stored data to determine the remaining capacity of the battery
or battery pack and informs the user audibly and/or visually that
the battery or battery pack is low.
[0025] In another aspect the present invention, the algorithm uses
the stored data to determine the remaining capacity of the battery
or battery pack and informs the user that the battery or battery
pack needs to be replaced.
[0026] In another aspect the present invention, the algorithm uses
the data to determine the remaining capacity of the battery or
battery pack and informs the user of the number of shocks left.
[0027] In another aspect the present invention, the algorithm uses
the data to determine the remaining capacity of the battery or
battery pack and informs the user of the remaining monitor
time.
[0028] In another aspect the present invention, the algorithm uses
the data to determine the remaining capacity of the battery or
battery pack and informs the user of the general battery capacity
as it relates to typical use, as for example, by displaying a "fuel
gauge".
[0029] In one form of the invention, there is provided a method for
determining the remaining battery capacity of a battery in a
defibrillator, the method comprising:
[0030] applying an algorithm that calculates remaining battery
capacity of a battery using measured battery voltage value in
conjunction with historical information previously stored in the
defibrillator.
[0031] In another form of the invention, there is provided a
defibrillator comprising:
[0032] at least one battery;
[0033] at least one capacitor;
[0034] a circuit to charge the at least one capacitor from the at
least one battery;
[0035] a circuit to deliver a biphasic waveform from the at least
one capacitor to the patient;
[0036] user notification apparatus for notifying the user of events
during defibrillator operation; and
[0037] a data acquisition circuit that measures the terminal
voltage of the at least one battery, digitizes the signal and
stores the data in memory for analysis.
[0038] In another form of the invention, there is provided a method
for determining battery capacity in a defibrillator comprising:
[0039] recording historical data comprising at least one from the
group consisting of: [0040] how long it has been since the battery
was last charged; [0041] how the defibrillator has been used since
the battery was last charged, including a record of when the
defibrillator was in idle mode and when the defibrillator was in
shocking mode; [0042] how many shocks have been delivered since the
battery was last recharged; [0043] how long has it been since the
defibrillator was last used in shocking mode; and [0044] how many
times the battery has been recharged over its lifetime;
[0045] measuring the current battery voltage; and
[0046] applying an algorithm to calculate remaining battery
capacity, using the measured battery voltage and the recorded
historical data.
[0047] In another form of the invention, there is provided
apparatus for determining the battery capacity in a defibrillator
comprising:
[0048] apparatus for recording historical data comprising at least
one from the group consisting of: [0049] how long it has been since
the battery was last charged; [0050] how the defibrillator has been
used since the battery was last charged, including a record of when
the defibrillator was in idle mode and when the defibrillator was
in shocking mode; [0051] how many shocks have been delivered since
the battery was last recharged; [0052] how long has it been since
the defibrillator was last used in shocking mode; and [0053] how
many times the battery has been recharged over its lifetime;
[0054] apparatus for measuring the current battery voltage; and
[0055] apparatus for applying an algorithm to calculate remaining
battery capacity, using the measured battery voltage and the
recorded historical data.
BRIEF DESCRIPTION OF THE DRAWINGS
[0056] These and other objects and features of the present
invention will be more fully disclosed or rendered obvious by the
following detailed description of the preferred embodiments of the
invention, which is to be considered together with the accompanying
drawings wherein like numbers refer to like parts and further
wherein:
[0057] FIG. 1 is an illustration of a battery pack containing
battery cells;
[0058] FIG. 2 shows how the battery pack is inserted into the
defibrillator;
[0059] FIG. 3 is a schematic drawing showing the cell arrangement
of the battery pack;
[0060] FIG. 4 is block diagram of the defibrillator components;
[0061] FIG. 5 is a profile of a new battery pack run in the
defibrillator for a number of continuous shock cycles, wherein two
voltages, i.e., the minimum voltage during charging (Vchg(min)) and
the recovered voltage in between shocks (Vrecover), are
measured;
[0062] FIG. 6 is a profile of a used battery pack run in the
defibrillator for a number of continuous shock cycles, wherein two
voltages, i.e., the minimum voltage during charging (Vchg(min)) and
the recovered voltage in between shocks (Vrecover), are
measured;
[0063] FIG. 7 is a profile of a depleted battery pack run in the
defibrillator for a number of continuous shock cycles, wherein two
voltages, i.e., the minimum voltage during charging (Vchg(min)) and
the recovered voltage in between shocks (Vrecover), are
measured;
[0064] FIG. 8 is an oscilloscope display showing the battery
voltage drop during a defibrillator charge cycle; and
[0065] FIG. 9 is a flow diagram showing a preferred algorithm for
determining battery capacity.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0066] The present invention discloses a system and method for
determining the remaining capacity in the battery pack of a
defibrillator.
[0067] Looking first at FIGS. 1 and 2, there is shown the battery
pack 5 of a defibrillator 15. It should be appreciated that the
present invention may be applied the entire battery pack 15 or to
individual cells of the battery pack.
[0068] In current defibrillator systems, it is difficult to
determine the remaining capacity of the battery cells of a
defibrillator. The battery pack voltage during idle mode (i.e.,
during the monitoring mode) yields little information about the
remaining battery capacity due to the lack of cell load. In
addition, as the batteries become depleted over time, the internal
impedance of the cell increases. When the defibrillator begins
charging the capacitors to deliver a shock, the battery load is
significantly increased, thereby lowering the cell voltage. In
cases where the battery is depleted, the battery cell impedance is
high and the voltage may decrease to a level insufficient to charge
the capacitors and provide defibrillation therapy.
[0069] The varying capacities of battery cells are illustrated in
FIGS. 5-7.
[0070] FIG. 5 is the profile of a new battery pack measured while
the defibrillator is running in AED mode for a number of continuous
shock cycles. AED mode is defined as three shocks per minute
followed by one minute of rest. The battery profile in FIG. 5 shows
two voltage measurements. The first measured voltage, Vchg(min) 80,
is the minimum voltage reached during the charge cycle (i.e., while
the defibrillator is delivering shocks). The second measured
voltage, (Vrecover) 85, is the battery voltage present when the
battery has recovered after a charging cycle (i.e., while the
battery is "resting" between shocks). As can be seen in the profile
of FIG. 5, the measured Vchg(min) 80 is relatively flat with a
slight increase in voltage over the first thirty shocks, followed
by a slight decrease in approximately the last twelve shocks before
the voltage decreases sharply after the last shock (approximately
shock number 43 in FIG. 5). This decrease is due to a rise in cell
temperature as the defibrillator is delivering shocks. However, the
measured Vrecover 85 shows little indication that the battery is
depleting at any point measured.
[0071] FIG. 6 shows the profile of a used battery pack, also
measured while the battery pack is run in a defibrillator for a
number of continuous shock cycles. As can be seen, the two voltages
measured (Vchg(min) 80 and Vrecover 85) exhibit characteristics
similar to that of a new battery, with the exception that Vchg(min)
80 has a lower baseline voltage and the used battery pack has a
smaller shock capacity than the new battery pack.
[0072] FIG. 7 shows the profile of a depleted battery pack. While
the depleted battery pack is capable of delivering several shocks,
both voltages (Vchg(min) 80 and Vrecover 85) are gradually
decreasing. The depleted battery pack has a much lower shock
capacity than both the new and used battery packs (FIGS. 5 and 6,
respectively). It should be appreciated that the depleted battery
in this case should not be confused with a deeply discharged
battery. A deeply discharged battery is unable to sustain a voltage
even under a nominal load.
[0073] As can be seen in FIG. 7, a depleted battery pack, does not
provide the defibrillator with a reliable source of power. Yet, it
is critical in life saving situations that the device reliably
notify the user that the battery is low. Many current AED units use
a battery monitoring circuit, also known as a "smart battery", to
provide a "fuel gauge" for remaining battery capacity. This
technique requires the use of low power analog and digital
circuitry within the battery pack, or within the device, to
constantly monitor battery capacity. Many current devices also
monitor battery cell temperature to accurately gauge capacity. The
disadvantage of this technique is that the additional circuitry,
components and connections which are needed for battery monitoring
add significant cost to the battery pack and/or the AED unit
itself. Therefore, this "fuel gauge" technique has been
historically problematic and has been an issue with portable AEDs
with both disposable and rechargeable battery packs.
[0074] To overcome these issues, the AED of the present invention
uses a data acquisition system that measures the current battery
voltage and stores the data, along with historical information, for
analysis, thereby eliminating the need for using additional
circuitry, components and connections.
[0075] Looking again at FIGS. 1 and 2, there is shown the battery
pack 5 of the defibrillator 15. Battery pack 5 preferably comprises
Lithium Manganese Dioxide type cells, however, the method and
apparatus of the present invention may be applied to other cell
chemistries as well including, but not limited to, Alkaline
Manganese Dioxide or rechargeable types, Nickel-Metal Hydride types
or Lithium Ion types, etc. A preferred embodiment of the battery
pack uses five battery cells, however, the battery pack may easily
implement a different number of battery cells. The voltage of each
of the five single battery cells is 3V, therefore, the
defibrillator supply voltage is 15V. The present invention could
also be utilized with more or less battery cells and/or other
supply voltages.
[0076] Battery pack 5, preferably placed in a plastic housing, is
inserted into defibrillator 15 as shown in FIG. 2.
[0077] A schematic of the five-cell arrangement 20, comprising five
individual cells 10, each with a supply voltage of 3V, is shown in
FIG. 3.
[0078] A block diagram of the defibrillator components is shown in
FIG. 4. Defibrillator 15 contains a data acquisition system
including, but not limited to, microprocessor 25, programmable
logic device (PLD) 30, memory (not shown) and analog-to-digital
converter 40.
[0079] The preferred embodiment of the invention uses
microprocessor 25 to execute instructions to (i) sample data, (ii)
store the data into memory, and (iii) process the data to determine
the remaining battery capacity. In a preferred embodiment,
programmable logic device 30 controls the interface to
analog-to-digital converter 40 and stores the sampled data into a
local memory buffer. Programmable logic device 30 then interrupts
microprocessor 25 to sample the data contained in the buffer, via
data-bus 45 connected between microprocessor 25 and PLD 30.
Microprocessor 25 may also directly interface to analog-to-digital
converter 40 and use internal timing to interrupt microprocessor 25
for sampling frequency. Additionally, microprocessor 25 may be a
microcontroller and have memory, analog-to-digital converter 40 and
other peripherals on a single chip.
[0080] The defibrillator also contains LCD screen 50, as well as a
voice synthesizer and speaker for instructing the rescuer.
Defibrillator 15 also contains all the necessary components for
defibrillation including, but not limited to, charger circuit 60,
battery pack 10, capacitors 65 and an H-bridge circuit 70.
[0081] The defibrillator data acquisition system samples the
battery voltage once every 45 mS (22.22 Hz) and stores the data
into random access memory (RAM). The data acquisition system may
also store the battery data onto a removable multi-media flash card
for post-incident review. Defibrillator 15 is also capable of
storing the battery data into EEPROM, Flash or other types of
memory well known in the art.
[0082] Defibrillator 15 does not need to implement a digital
filter, however, a digital filter, such as, but not limited to, an
averaging filter (smoothing filter), low-pass filter or other
filters well known in the art, may easily be implemented.
[0083] Defibrillator 15 may also store historical information into
RAM. Such data may contain information about the period of time
since the device was last used, the number of times the device has
been used, the operational mode of the device and the number of
shocks that have been delivered. The device may additionally store
its historical information onto a removable multi-media flash card
for post-incident review. Defibrillator 15 is also capable of
storing its historical information into EEPROM, Flash or other
types of memory well known in the art.
[0084] In one embodiment of the present invention, the method for
determining the remaining battery capacity of defibrillator 15 may
apply an algorithm that uses battery voltage values in conjunction
with the device's historical information. Different thresholds for
different modes of the defibrillator operation may be used when
applying the algorithm to determine the remaining battery capacity
of defibrillator 15. As shown in FIG. 8, for example, voltage 100
drops significantly when the defibrillator begins to charge. The
method of the present invention uses a predetermined threshold for
when the defibrillator is in idle mode (monitor mode) and applies
an algorithm using multiple thresholds for when the defibrillator
is in charge mode (charging the capacitors in preparation to
provide a shock). The algorithm takes into account, among other
things, how long it has been since the defibrillator was last used,
how many times the capacitors have been charged and how many times
the defibrillator has delivered a shock.
[0085] As shown in the flow diagram of FIG. 9, the defibrillator
uses three predetermined thresholds based, on the number of shocks
delivered, to determine the charge remaining in the battery pack.
The method of the present invention preferably uses a threshold of
7.39 volts for one to three shocks, a threshold of 7.87 volts for
three to six shocks, and a threshold of 9.03 volts for more than
six shocks. When in idle (i.e., monitoring) mode, the method of the
present invention uses a single threshold of 10 volts. When the
defibrillator battery cell's voltage falls below the predetermined
threshold, the algorithm will determine that a battery capacity
remaining is capable of, for example, a minimum of six shocks,
although in some cases may be able to deliver up to a maximum of
twelve shocks. The rescuer is notified to replace the battery by
means of visual and audible messages.
[0086] It should be appreciated that the method for determining the
remaining battery capacity of defibrillator 15 uses delays between
modes to allow the battery voltage to recover. As can be seen in
FIG. 8, it can take several hundred milliseconds for the battery to
recover after charge mode.
[0087] The algorithm used in the method for determining remaining
battery capacity also takes into account the total number of shocks
delivered. When the device has reached a predetermined threshold
for the number of shocks delivered, the device proceeds to notify
the user to replace the battery. In one embodiment of the present
invention, the defibrillator may use a twenty-shock count
threshold.
[0088] In addition, the algorithm used in the method of the present
invention for determining remaining battery capacity also takes
into account the total time the device has been used. When the
device has reached a predetermined threshold for the total time of
use, the device proceeds to notify the user to replace the battery.
In one embodiment of the present invention, the defibrillator may
use a two-hour time threshold.
MODIFICATIONS
[0089] It is to be understood that the present invention is by no
means limited to the particular constructions herein disclosed
and/or shown in the drawings, but also comprises any modifications
or equivalents within the scope of the invention.
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