Title: System and method for reducing external battery capacity requirement for a wireless card
Abstract: A system for providing power to a wireless card includes power interface that provides power to a compact flash card. A boost regulator boosts the power from the power interface. A battery provides power that is summed with the power from the power interface. Moreover, a buck regulator limits the voltage of the summed power. A compact flash card can be powered by the power interface while a wireless card can be powered by the summed power.
Patent Number: 6,998,816 Issued on 02/14/2006 to Wieck, et al.
| Inventors:
|
Wieck; Christopher Peter (San Diego, CA);
Clift; Graham Anthony (Poway, CA)
|
| Assignee:
|
Sony Electronics Inc. (Park Ridge, NJ)
|
| Appl. No.:
|
610779 |
| Filed:
|
June 30, 2003 |
| Current U.S. Class: |
320/107 |
| Current Intern'l Class: |
H01M 10/44 (20060101); H01M 10/46 (20060101) |
| Field of Search: |
320/107,110,112,114,115,137,138
|
References Cited [Referenced By]
U.S. Patent Documents
| 3696286 | Oct., 1972 | Ule.
| |
| 5451933 | Sep., 1995 | Stricklin et al.
| |
| 5463261 | Oct., 1995 | Skarda et al.
| |
| 5802379 | Sep., 1998 | Boatwright et al.
| |
| 5818207 | Oct., 1998 | Hwang.
| |
| 5870615 | Feb., 1999 | Bar-On et al.
| |
| 5914585 | Jun., 1999 | Grabon.
| |
| 5914980 | Jun., 1999 | Yokota et al.
| |
| 5946202 | Aug., 1999 | Balogh.
| |
| 5973475 | Oct., 1999 | Combaluzier.
| |
| 6157173 | Dec., 2000 | Baranowski et al.
| |
| 6292863 | Sep., 2001 | Terasaki et al.
| |
| 6327154 | Dec., 2001 | Gauld et al.
| |
| 6580258 | Jun., 2003 | Wilcox et al.
| |
| 2001/0033963 | Oct., 2001 | Yamazaki et al.
| |
| 2002/0083239 | Jun., 2002 | Lida et al.
| |
| 2002/0100809 | Aug., 2002 | Lu.
| |
| 2002/0121548 | Sep., 2002 | Lu.
| |
| 2002/0180277 | Dec., 2002 | Acharya et al.
| |
| 2003/0094924 | May., 2003 | Oh.
| |
Primary Examiner: Tso; Edward H.
Attorney, Agent or Firm: Rogitz; John L.
Claims
What is claimed is:
1. A power system, comprising:
a boost regulator;
a battery electrically connected to the boost regulator;
wherein the boost regulator charges the battery;
wherein the boost regulator provides a first power source; and
wherein the battery provides a second power source that is summed with the first
power source.
2. The system of claim 1, further comprising:
a buck regulator electrically connected to the boost regulator and the battery;
and
wherein the buck regulator provides an output voltage below a predetermined voltage.
3. The system of claim 2, further comprising:
a battery switch installed between the battery and the boost regulator.
4. The system of claim 3, wherein the switch comprises a field effect transistor switch.
5. The system of claim 3, further comprising:
a controller connected to at least one of: the boost regulator, the buck regulator
and the battery switch.
6. The system of claim 1, further comprising:
wireless circuitry connected to the boost regulator and the battery; and
wherein the wireless circuitry receives power from the boost regulator and the
battery.
7. The system of claim 6, wherein the wireless circuitry includes:
a power amplifier.
8. The system of claim 7, wherein the wireless circuitry further includes:
at least one low drop out voltage regulator.
9. The system of claim 2, wherein the first power source and the second power
source are summed within the buck regulator.
10. The system of claim 2, wherein the first power source and the second power
source are summed before the buck regulator.
11. A power system for a wireless card, comprising:
a power interface;
a battery connected parallel to the power interface;
a wireless card, the wireless card being powered by the power interface and the
battery; and
a compact flash card, the compact flash card being powered by the power interface
only.
12. The system of claim 11, further comprising:
a boost regulator electrically connected to the power interface, the boost regulator
increasing a voltage supplied by the power interface.
13. The system of claim 12, further comprising:
a buck regulator electrically connected to the boost regulator and the battery,
the buck regulator providing power to the wireless card and maintaining an output
voltage below a predetermined threshold.
14. The system of claim 13, further comprising:
a capacitor electrically connected between the boost regulator and the buck regulator.
15. A method for providing power to a wireless card and a compact flash card, comprising:
receiving power from a power interface;
receiving power from a battery;
summing the power from the power interface and the battery to yield a summed
power source;
powering the wireless card using the summed power source; and
powering the compact flash card using the power from the power interface.
16. The method of claim 15, further comprising:
boosting the power from the power interface to yield a boosted power source.
17. The method of claim 15, further comprising:
regulating the summed power below a predetermined threshold.
18. The method of claim 15, further comprising:
monitoring the voltage of the battery.
19. The method of claim 18, further comprising:
when the voltage of the battery falls below a predetermined minimum threshold,
trickle charging the battery at least partially using the boosted power until a
target voltage is reached.
20. The method of claim 19, further comprising:
when the target voltage is reached in the battery, opening a switch connected
to the battery to disrupt the flow of power to the battery.
21. The method of claim 18, further comprising:
when the voltage of the battery falls below a predetermined minimum threshold,
disabling the compact flash card.
22. The method of claim 18, further comprising:
when the voltage of the battery is greater than the boosted voltage, pulsing
a switch connected to the battery to allow the battery to discharge.
Description
FIELD OF THE INVENTION
The present invention relates generally to power supply systems for wireless cards.
BACKGROUND OF THE INVENTION
Compact flash cards (CF cards) are size compatible with the current state
of the art in wireless cards. Present technology allows integration in form factors
much smaller than the previous generation of PCMCIA cards. However, few compact
flash cards have been introduced to the market that are designed to work over Wireless
Wide Area Networks (WWAN). One of the main reasons is that the CF interface is
specified to allow only 500 mA maximum current to be drawn across a power interface
and CDMA, for example, requires up to 850 mA. Thus, a wireless card cannot operate
on the same power interface as the CF card.
It is possible to utilize an external battery to provide the additional power
required by a wireless card, but for a reasonable capacity, the size of the battery
can easily be larger than the size of the wireless card, defeating the purpose
of having a smaller CF form factor.
Accordingly, there is a need to provide a system and method for maintaining
a battery and sharing the stored charge with the supply from the CF card power
interface in order to provide power for a wireless card.
SUMMARY OF THE INVENTION
A power system for a wireless card includes a boost regulator. A battery is connected
to the output of the boost regulator via a means to share current, and an optional
buck regulator is electrically connected to the shared boost regulator/battery
configuration. The boost regulator charges the battery and provides a first power
source. The battery provides a second power source that is summed with the first
power source. Moreover, the buck regulator provides an output voltage below a predetermined voltage.
Preferably, a battery switch, e.g., a field effect transistor switch,
is installed between the battery and the boost regulator. Further, a controller
is connected to the boost regulator, the buck regulator and the battery switch.
The power supply input to the wireless card may be connected to a power amplifier
and multiple low drop out voltage regulators supplying various circuits of the
wireless card. The first power source and the second power source can be summed
within the buck regulator or before the buck regulator, before feeding the power
supply input to the wireless card.
In another aspect of the present invention, a power system for a wireless card
includes a power interface and a battery connected parallel to the power interface.
The system includes a wireless card that is powered by the power interface and
the battery. Additionally, the system includes a compact flash card interface that
is powered by the power interface only.
In yet another aspect of the present invention, a method for providing power
to
a compact flash wireless card includes receiving power from a power interface and
receiving power from a battery. The power from the power interface and the power
from the battery are summed to yield a summed power source. The wireless card is
powered using the summed power source and the compact flash card interface is powered
using power from the power interface only.
BRIEF DESCRIPTION OF THE DRAWINGS
The details of the present invention, both as to its structure and operation,
can best be understood in reference to the accompanying drawings, in which like
reference numerals refer to like parts, and in which:
FIG. 1 is a block diagram of a power system for a wireless card;
FIG. 2 is a flow chart of the operating logic according to the present invention;
FIG. 3 is a schematic diagram showing a circuit for a power system for a wireless
card; and
FIG. 4 is a schematic diagram showing a second circuit for a power system for
a wireless card.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to FIG. 1, a power system for a wireless card is shown
and is generally designated
10. As shown, the system
10 includes
a boost regulator
12 that is electrically connected to a buck regulator
14. A battery
16, e.g., a 220 mAH battery, is electrically connected
to the boost regulator
12 between the boost regulator
12 and the
buck regulator
14. As shown a battery switch
18, e.g., a field effect
transistor (FET) switch, can be installed between the boost regulator
12
and the battery
16. Moreover, the system
10 includes a controller
20 that communicates with the boost regulator
12, the buck regulator
14 and the battery switch
18. FIG. 1 further shows a capacitor
22,
e.g., a super capacitor having a relatively large storage capacity, that can be
installed in the system before the buck regulator
14.
As shown, the system
10 has an input
24 that is connected to the
boost regulator
12. Also, the system
10 has an output
26 that
is connected to the buck regulator
14. Further, wireless circuitry
28
providing power to a wireless card
30 is connected to the output
26
of the system
10. It is to be understood that the wireless circuitry
28
can include, e.g., a power amplifier and/or one or more low drop out voltage regulators
(LDO). Moreover, it is to be understood that typically the wireless circuitry
28
is incorporated into the wireless card
30. FIG. 1 also shows that a CF power
interface
32 can be connected to the system input
24. The CF power
interface
32 can also be connected to a CF card
34.
During operation, 3.3 volts are input to the boost regulator
12 from
the power interface
32. Preferably, the boost regulator
12 is designed
to limit the current to 500 mA and boost the voltage to 4.2 volts. The buck regulator
14 limits the voltage and outputs 3.2 volts to the wireless circuitry
28.
The controller
20 includes control logic that can, for example, control
the sharing of the charge between the boost
12 and battery
16, e.g.,
by opening and closing the switch
18.
Referring to FIG. 2, the control logic which resides in the controller
20 is shown and commences at block
50 with a do loop wherein during
operation the following steps are performed. At block
52, the battery voltage
is continuously monitored. Based on the battery voltage, one of three do loops
can be performed.
First, beginning at block
54 when the voltage drops below a predetermined
minimum threshold, the logic moves to block
56 where the battery
16
is trickle charged. At decision diamond
58, it is determined whether a target
voltage, e.g., 4.2 volts, is reached. If that target is not reached, the logic
returns to block
56 and the trickle charging continues. If the target voltage
is reached, the logic moves to block
60 where the switch
18 is opened
in order to prevent "floating" of the battery
16, which can decrease the
life of the battery
16. Thereafter, the logic returns to block
52
and the battery voltage continues to be monitored.
The second do loop that can be entered from block
52, commences at block
62 wherein when the battery voltage drops below a threshold to support the
buck regulator output voltage, e.g., 3.2 volts, the logic moves to block
64
and the CF card
34 is disabled. Thereafter, logic then returns to block
52 and the battery voltage continues to be monitored.
Proceeding to block
66, the third do loop that can be entered from
block
52 commences at block
66. At block
66, when the battery
voltage is greater than the boost voltage, the logic moves to block
68 and
the switch
18 is pulsed to allow current to flow from the battery
16.
It can be appreciated that the buck regulator
14 at the output of the system
10 provides a minimum voltage required by the CF card
30, which maximizes
efficiency and helps smooth transients. As an example, with a typical buck regulator
efficiency of 90%, a 4.2 to 3.2 voltage conversion reduces the peak current over
the boost regulator
14 and battery
16 by nearly 20%. It also happens
that power amplifiers used for CDMA also tend to draw less current at lower voltages
further trimming the peak current requirement.
Referring now to FIG. 3, a power circuit for a wireless card is shown and
is generally designated
100. As shown, the power circuit
100 includes
a boost regulator
102 connected to a buck regulator
104. A battery
106, e.g., a 220 mAH battery, is connected to the circuit
100 between
the boost regulator
102 and the buck regulator
104. A battery switch
108, e.g., a FET switch, and a first resistor
110 are connected in
parallel between the battery
106 and the circuit
100. A controller
112 is connected to the boost regulator
102, the buck regulator
104
and the battery switch
108.
As shown, an input
114 is connected to the boost regulator
102
and
an output
116 is connected to the buck regulator
104. Moreover, a
second resistor
116 is installed along the input
114 before the boost
regulator
102. The controller
112 senses the voltage across the second
resistor
116 and uses it to limit the current in the circuit
100.
FIG. 3 shows a first capacitor
118 installed in the circuit
100 before
the boost regulator
102. A second capacitor
120, e.g., a super capacitor
with a relatively large storage capacity, is installed before the buck regulator
104 between the battery
106 and the buck regulator
104. Further,
a third capacitor
122 is installed in the circuit
100 after the buck
regulator
104.
FIG. 3 shows that the boost regulator
102 includes an inductor
124
connected to the input
114. To prevent reverse current, a diode
126
is connected to the inductor
124 between the inductor
124 and the
buck regulator
104. Further, within the boost regulator
102, one
pole of a boost switch
128 is connected between the inductor
124
and the diode
126. The other pole of the boost switch
128 is connected
to ground. The boost switch
128 is connected to and controlled by the controller
112.
Still referring to FIG. 3, the buck regulator
104 includes a buck switch
130 at the input of the buck regulator
104 to control the flow of
electricity into the buck regulator
104. The buck switch
130 is connected
to and controlled by the controller
112. An inductor
132 is installed
in the buck regulator
104 at its output. A diode
134 is connected
to the buck regulator
104 between the buck switch
130 and the inductor
132. Specifically, the anode of the diode
134 is connected to ground
and the cathode of the diode is connected to the buck regulator
104 between
the buck switch
130 and the inductor
132.
It is to be understood that the logic described above in conjunction with FIG.
2 can be stored in the controller
112 of the circuit
100 shown in
FIG.
3. Accordingly, the controller
112 can utilize that logic to
control the charging of the battery, control a CF card connected to the circuit
100 and control the discharge of the battery
106. Moreover, the controller
112 can control the boost regulator
102 and the buck regulator
104
by controlling the operation of the boost switch
128 and the buck switch
130.
FIG. 4 shows an alternative embodiment of a power circuit for a wireless card,
generally designated
200. As shown, the power circuit
200 includes
a boost regulator
202 connected to a buck and sharing regulator
204.
A battery
206, e.g., a 150 mAH battery, is connected to the buck and sharing
regulator
204 parallel to the boost regulator
202. A controller
208
is connected to the boost regulator
202 and the buck and sharing regulator
204.
As shown, a circuit input
210 is connected to the boost regulator
202
and a circuit output
212 extends from the buck and sharing regulator
204.
FIG. 4 shows a first resistor
214 that can be installed along the input
210 before the boost regulator
202. Preferably, the controller
208
can be connected to the input
210 before and after the first resistor
214.
As such, the controller
208 can sense the voltage across the first resistor
214 and use it to limit the current in the circuit
200.
FIG. 4 further shows a first capacitor
216 installed in the circuit
200
before the boost regulator
202. A second capacitor
218, e.g., a super
capacitor with a relatively large capacitance, is installed between the boost regulator
202 and the buck and sharing regulator
204. It is to be understood
that the second capacitor
218 helps reduce ripple from the boost regulator
202 and it acts as a charge reservoir in order to provide instantaneous
currents to curb the magnitude of the current spikes. Moreover, the second capacitor
218 can act as an integrator for the boost regulator
202 in order
to improve efficiency in low current conditions. This can extend standby time for
a wireless device, e.g., a CF card, connected to the circuit
200. For example,
with a standby current of 2 mA and a fully charged battery
206, 2 mA is
the only boost required current. If the voltage of the second capacitor
218
varies from 4.2 volts to 3.4 volts and the capacitance is 1 mF, then the change
in charge is 0.8 milli-Coulombs. This amount of charge can source 2 mA for 0.4
seconds. The boost regulator
202 can re-supply this charge in 8 mA using
100 mA and operate in a 1/50 cycle mode. Accordingly, the efficiency of the boost
regulator
202 is greater when it is enabled.
As shown in FIG. 4, a third capacitor
220 can be installed in the circuit
200 between the battery
206 and the buck and sharing regulator
204.
A second resistor
222 can be installed in the circuit
200 between
the second capacitor
218 and the third capacitor
220. Further, as
shown in FIG. 4, a fourth capacitor
224 is connected after the buck and
sharing regulator
204 in the circuit output
212.
Still referring to FIG. 4, it is shown that the boost regulator
202
includes an inductor
226 that is connected to the circuit input
210.
A first switch
228 is connected after the inductor
226. Specifically,
one pole of the first switch
228 is connected after the inductor
226
and the other pole of the first switch
228 is connected to ground. The first
switch
228 can be used to control the operation of the boost regulator
202.
To prevent reverse current, a second switch
230 can be installed in the
boost regulator
202 after the first switch
228.
As further shown in FIG. 4, the buck and sharing regulator
204 includes
a third switch
232 that can be opened and closed to control the power supply
from the boost regulator
202. Moreover, a fourth switch
234 is installed
in the buck and sharing regulator
204 parallel the third switch
232.
The fourth switch
234 controls the power supply from the battery
206.
In a preferred embodiment, a second inductor
236 is installed in series
with the third switch
232 and the fourth switch
234 within the buck
and sharing regulator
232. To control the operation of the buck and sharing
regulator
204, a fifth switch
238 can be installed between the third
and fourth switches
232,
234 and the second inductor
236.
Specifically, one pole of the fifth switch
238 is connected to the buck
and sharing regulator
204 and the other pole of the fifth switch
238
is connected to ground.
It can be appreciated that the configuration of the third and fourth switches
232,
234 reduces the current and voltage drop across the third switch
232, which improves efficiency. Also, this configuration eliminates the
need for a relatively large FET switch to bypass the buck regulator
204.
Further the second inductor
236, i.e., the buck inductor, can have a lower
inductance than that of the second inductor
132 shown in FIG.
3.
This reduces the equivalent series resistance and the voltage drop across the buck
regulator
204. The second inductor
236 can be smaller because the
buck regulator
204 normally operates up to approximately 440 mA. Once the
current increases beyond 440 mA, the output of the boost regulator
202 begins
to sag due to the limiting of the input current, and there is a small window beyond
440 mA where the buck regulator
204 has a reduced input voltage. Beyond
that window, when the buck regulator
204 begins to drop out, the battery
206 is "bucked in" to keep the input voltage just high enough to maintain
3.2 volts at the output
212. As such, the fifth switch
238 is rarely
closed. Since that battery voltage is closer to the boost regulator voltage than
the boost regulator voltage is to the 0 volt ground potential across the fifth
switch
238, the fourth switch
234 is essentially bucking in more
current and the spikes across the second inductor
236 are reduced. The battery
206 can buck in 410 mA to combine with the 440 mA bucked in from the buck
regulator
204 to provide 850 mA.
Further, if the battery
206 is significantly charged, current can
flow through the second resistor
222, a charging resistor, and begin to
sum into the current from the boost regulator
202 before the boost voltage
sags significantly. In such a case, the boost regulator
204 can "ping-pong"
between the third and fourth switches
232,
234 to maintain the boost
voltage and the battery voltage about equal, so that the current flows through
the more efficient path of the fourth switch
234 from the battery
206.
Moreover, the buck regulator
204 can operate the fifth switch
236
to buck the voltage down to 3.2 volts. If the ripple due to this action becomes
too high, the buck output voltage can be allowed to rise above 3.2 volts. This
can occur when a PA connected to the output
212 is drawing maximum current
and the PA can benefit from a higher voltage and less ripple. The maximum voltage
from the boost regulator
202 and the battery
206 sharing is approximately
3.8 volts which is below the operating voltage of a typical PA, i.e., 4.2 volts
for direct battery operation.
It happens that some bucking can occur to improve efficiency if the ripple is
acceptable, but the ripple will likely be small since the buck is switching between
two nearly equivalent voltages across the third and fourth switches
232,
234. It is possible with a more complex controller that the second resistor
222, i.e., the charging resistor, can be eliminated and the battery can
be charged by tapping off of the buck regulator
204 in a pulsed mode through
the fourth switch
234.
It is to be understood that the logic described above in conjunction with FIG.
2 can be stored in the controller
208 of the circuit
200 shown in
FIG.
4. Accordingly, the controller
208 can utilize that logic to
control the charging of the battery, control a CF card connected to the circuit
200 and control the discharge of the battery
206. Moreover, the controller
208 can control the boost regulator
202 and the buck regulator
204
by controlling the operation of the switches
228,
230,
232,
234,
236.
While the particular SYSTEM AND METHOD FOR REDUCING EXTERNAL BATTERY CAPACITY
REQUIREMENT FOR A WIRELESS CARD as herein shown and described in detail is fully
capable of attaining the above-described objects of the invention, it is to be
understood that it is the presently preferred embodiment of the present invention
and is thus representative of the subject matter which is broadly contemplated
by the present invention, that the scope of the present invention fully encompasses
other embodiments which may become obvious to those skilled in the art, and that
the scope of the present invention is accordingly to be limited by nothing other
than the appended claims, in which reference to an element in the singular is not
intended to mean "one and only one" unless explicitly so stated, but rather "one
or more". All structural and functional equivalents to the elements of the above-described
preferred embodiment that are known or later come to be known to those of ordinary
skill in the art are expressly incorporated herein by reference and are intended
to be encompassed by the present claims. Moreover, it is not necessary for a device
or method to address each and every problem sought to be solved by the present
invention, for it to be encompassed by the present claims. Furthermore, no element,
component, or method step in the present disclosure is intended to be dedicated
to the public regardless of whether the element, component, or method step is explicitly
recited in the claims. No claim element herein is to be construed under the provisions
of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using
the phrase "means for" or, in the case of a method claim, the element is recited
as a "step" instead of an "act". Absent express definitions herein, claim terms
are to be given all ordinary and accustomed meanings that are not irreconcilable
with the present specification and file history.
*
