Note: Descriptions are shown in the official language in which they were submitted.
CA 02777387 2012-05-16
Portable Battery Charger
FIELD OF THE INVENTION
The invention relates to battery chargers for portable devices.
BACKGROUND
Since their inception portable electronic devices like cell phones have used
AC/DC adapters to charge
their batteries from household AC power. USB connections are also used to
charge portable devices
using a DC current of approximately 5V, as well the USB can be used to
exchange data between the USB
source and the portable device.
US Patent No. 7,688,026 discloses a mobile charging adapter The charger uses a
first input conversion to
the battery voltage (perhaps on the order of 4.2V) and then in outputting,
converts again from the
battery voltage of 4.2 to the output voltage of 5V, reducing efficiency by the
two conversions of one
power. The input power cannot be output directly without conversion to the
nature of the circuit, where
the battery is connected directly to the input/output circuit, necessitating
the multiple conversions
outlined above, and thereby increasing complexity and reducing efficiency.
Further, the charger will not
work if the battery is damaged or near the end of its life.
Therefore there is a need in the art for a battery-powered charger which can
output the input power
directly, without the inefficiency of the battery connected between the input
and the output.
SUMMARY OF THE INVENTION
A portable device charger is disclosed, which is able to charge portable
devices whether it is connected
to an external power supply or not. The charger connects to household AC power
as well as USB DC
power, and further has a photovoltaic (PV) cell. it manages the input power
from these three sources to
charge a portable device and/or recharge the charger's battery, by
supplementing the input power with
battery power if the device demands more power than the input source, and
charging the battery with
remaining power if the device demands less power than is provided by the input
source. The charger
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turns off the AC/DC converter and draws no power from the AC source if the
battery is full and there is
no attached device.
The portable charger for charging a device comprises a housing, a battery
contained within the
housing and having a battery voltage, a battery charger between the input
power source and the battery
for controlling the current and voltage provided to the battery, an output
power connector for providing
output power to a device, an input source for providing power at a system
voltage, comprising a DC
power input at the system voltage; and an AC power input having an AC/DC
converter to convert AC to
DC power at the system voltage, a power path controller between the input
source and the output
power connector for directing the power from the input source to the output
power connector and the
battery simultaneously, which controller directs some or all of the power from
the input source to the
output power connector when a device is connected to the output power
connector, and directs the
power from the input source to charge the battery when no device is connected
to the power output.
An embodiment of the charger has an input source further comprising a PV
panel. Another embodiment
further comprises a power point controller between the PV panel and the
battery, wherein the power
point controller directs power from the PV panel to the battery unless a
device is connected to the
output power connector wherein the power point controller directs the power
from the PV panel to the
device.
Another embodiment has an auxiliary PV panel and connected through the USB
power input. The
charger may further comprise a DC/DC converter between the battery and the
output power connector
for converting the battery voltage to the system voltage, wherein when a
device is connected to the
output power connector and the device demands further output power than is
provided by the input
source the output power is supplemented by the battery. In an embodiment, if
the input source
provides more power than the device demands, remaining power is directed by
the power path
controller to charge the battery. In a further embodiment, if a current draw
from the AC/DC converter is
above a threshold, the AC/DC converter produces an overcurrent signal for the
battery charger to
reduce a current draw of the battery charger.
In another embodiment the charger further comprises a USB controller for
transmitting data between
the charger and an input source. Also the charger may further comprise a USB
controller for transmitting
data between the charger and the device. If the battery cannot receive any
charge and no device is
connected, the AC/DC converter is turned off to save power from an AC source.
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A method of charging a device battery is disclosed, comprising the steps of
connecting a DC input source
or an AC input source or both to a charger for providing input power;
connecting a device to the
charger; charging the device battery with output power from the charger; and
supplementing the
output power by power from a charger battery when the device demands further
output power than is
provided by the input source.
A method of charging a device using a charger is disclosed, comprising the
steps of determining if an
input source comprising an AC source or a DC source is connected; receiving
power in a charger battery
when the input source is connected, unless a device is also connected to an
output power connector;
directing power from the input source to the device when the device is
connected; supplementing an
output power with power from the charger battery when the device demands more
power than is
provided by the input source; and receiving excess power in the charger
battery when the device
demands less power than is provided by the input source.
The method may further comprise the steps of receiving power from a PV panel;
directing the PV panel
power to the device when the device is connected; and directing the PV panel
power to charge the
battery when no device is connected. Also, the PV panel may be an auxiliary PV
panel connected to the
USB input.
In an embodiment, the method may comprise one or more of the further steps of
transmitting data
between the charger and the input source, transmitting data between the
charger and the device,
directing remaining power to charge the battery when the input source provides
more power than the
device demands, producing an overcurrent signal for the battery charger to
reduce the current draw of
the battery charger when the current draw is above a threshold, and turning
off an AC/DC converter
when the battery cannot receive a charge and no device is connected to an
output power connector.
Description of Figures
Figure la is a isometric view of the external features of the portable battery
charger;
Figure lb is a plan view of the internal features of the portable battery
charger;
Figure 2 is a system function diagram of the portable battery charger;
Figure 3 is a circuit diagram of the portable battery charger; and
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Figure 4 is a circuit diagram of the portable battery charger in a further
embodiment.
DETAILED DESCRIPTION
While this invention is susceptible of embodiment in many different forms,
there are shown in the
drawings, and will be described herein in detail, specific embodiments thereof
with the understanding
that the present disclosure is to be considered as an exemplification of the
principles of the invention
and is not intended to limit the invention to the specific embodiments
illustrated.
With reference to Figure la, the portable battery charger 2 is shown in a
perspective view and has a
housing 10, a photovoltaic (PV) panel 54, AC input prongs 14 connected to an
AC input 52 described
below, a button 87, a USB input connector 56, and a display 85 for showing
battery conditions and other
information. Screws 18 or other fasteners in the art are used to hold the
housing 10 together.
With reference to Figure 1b, one half of the housing 10 is removed to show the
interior of the charger 2.
The main feature of the interior is the battery 70, the AC input prongs 14,
the USB input connector 56, a
AC/DC converter 58, and a PCB assembly 22 which includes a microcontroller 80,
battery charging and
protection circuits, battery fuel gauge and output DC/DC converter (none of
which are shown in this
Figure). The battery charger 2 also has an output connector 65, in one
embodiment in the form of a USB
connector, however one skilled in the art would appreciate that one charger
may have several outputs,
possibly each of a different format. If the voltage requirements are the same
for each output, the
outputs can be set up in parallel. If the outputs voltages are different, then
each output will have its own
DC/DC converter to regulate the output voltage for that output. While USB v.1,
2 and 3 present a useful
standard that may be used in one embodiment, other connectors may be used in
other embodiments,
the connectors known to one skilled in the art, for example, FireWireTM 400
and 800 and eSATA, and will
be referred to inclusively in the specification as USB. The acronym "USB" in
the specification refers to
any DC source.
With reference to Figures 2 and 3, the portable battery charger has three
input sources, an AC power
input 52, a USB input 56, and a photovoltaic (PV) panel 54. The AC input 52
receives power from a
household socket, for example at 120V alternating current (AC) power, and this
is converted to direct
current (DC) power through the AC/DC power conversion module 58, DC power is
provided in this way
to the power path controller 60. DC power may also be received from the USB
input 56, which receives
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standard USB power and voltage when connected to a IJSB source, which voltage
is 5V in some
embodiments. The USB input 56 may be any DC source, not limited to USB, and
may include FirewireTM
and other sources. These two power inputs, the AC input 52 converted to DC by
the AC/DC converter 58,
also SV in some embodiments, and the DC power received from the USB input 56,
are inputs to the
power path controller 60. Therefore, the portable charger receives SV input
from the USB input 56 and
5V input from the AC/DC converter 58, and can directly output these voltages,
without further
conversion, to the output connector 65 (through the power path controller 60
and power MUX 64).
Whether the power is received from the AC input 52 or the USB input 56, the
power path controller 60
can either send the power received to the battery charger 62 to charge the
battery, or to the power
multiplexer (MUX) 64, for output through the output power connector 65.
The PV panel 54 receives sunlight and transforms it into DC electricity. The
DC electricity is transmitted
through the power point controller 55 to the junction 63. The PV panel 54
provides a "trickle" charge
into the system of 50 - 100mA if mounted to the case and limited by the case
size, and a higher charge
current if auxiliary and not limited to a certain size. In an embodiment where
an auxiliary PV panel 88
(shown in Fig. 4) is used, it may be connected by wire to the USB input 56 or
to a further dedicated input
(not shown). When the microcontroller 80 knows that the auxiliary PV panel 88
is plugged into the USB
input 56, it will turn off battery charger 62 and turn on power switch 92,
such that the PV input power is
connected to power point controller 55 for conversion and output to junction
63. The auxiliary PV panel
88 is connected to the power path controller as an input to be selected
between, or connected to the
current location of the PV panel 54. The flow of the power received from the
PV panel 54 is transmitted
in the same direction as the junction 63. If the battery 70 is charging a
load, such as a portable device,
then current from the PV panel 54 will go to charge the load as well,
otherwise it will go to the battery
70. The power point controller 55, in communication with and operated by the
microcontroller 80, then
transmits the power to the junction 63.
If there is a load, such as a portable device, connected to the output power
connector 65, then the
priority of the power path controller 60 is to charge the load, so all or some
of the power from the input
sources 52, 56, if there is remaining power, is sent to the output power
connector 65 by means of the
power MUX 64. If input power remains after the necessary power is delivered to
the load, the remaining
input power is diverted by the power path controller to the battery charger 62
to charge the battery.
The charger 62 sends an interrupt to the microcontroller 80 with which it is
connected, and the
microcontroller 80 verifies the charge of the battery. If it is not charged,
the charge control switch 66 is
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turned on and current enters the battery. The load simultaneously receives the
maximum amount of
current it can receive. As the load is charged, the current demanded will
diminish and the current
diverted to the battery grows.
If the load demands further power to that received from the input sources 52,
56, then the output
power can be supplemented by the battery70. If the load requires a greater
current, the power MUX 64
gives an overcurrent signal to the microcontroller 80, which signals the DC/DC
converter to output
battery power. If the battery is empty, despite the overcurrent signal the
microcontroller 80 will check
the battery power. Once it determines there is no power available in the
battery it decides not to open
the DC/DC converter to provide battery power. Once power is provided by the
DC/DC converter 68,
current flows from the charge control switch 66 through the DC/DC converter
68, power MUX 64 to the
output connector 65. As the device is charged, the current demand will become
less and the battery
output will also be diminished, as the battery 70 conserves energy. A constant
amount is drawn from
the input sources 52, 56. The power MUX 64 can be set for multiple inputs
simultaneously, or individual
inputs. The output power can be further supplemented by the PV panel 54 which
provides additional
power to the junction 63, for output by means of the DC/DC converter. If the
load demands an output
power that is greater than can be delivered by the input sources 52, 56 and
the battery 70 has no
power, the power MUX 64 will operate in overcurrent mode with a lower voltage.
The addition of power
by the battery 70 is typically the case where the input source S6 is USB 2.0
input, where the input source
56 does not provide sufficient power for the load (not shown), which power is
then supplemented by
the battery 70 to charge the load as quickly as possible.
If the AC/DC converter 58 has an overcurrent condition, then voltage is
decreased to a threshold (4.7V in
some embodiments) forming an overcurrent signal, and the charger 62 knows from
the overcurrent
signal to decrease its current draw so output voltage from the power source
doesn't further decrease.
If there is no input source 52, 56, and a load is connected, once the load is
connected or the button 87
pushed, the microcontroller 80 checks the battery. if there is available power
in the battery, the
microcontroller 80 signals the DC/DC converter 68 to open and the current
flows from the battery
through the DC/DC converter 68 (where the voltage is increased to 5V) and out
the output connector
65.
If there is no load on the output power connector 65, input power is instead
sent by the power path
controller 60 to the battery charger 62. The charge control switch 66 is
informed by the microcontroller
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80 to which it is connected whether the battery 70 can receive power, which
depends on whether the
battery 70 is fully charged, or damaged, for example. if the microcontroller
indicates the battery 70 can
receive further power, then the charge control switch 66 sends power to the
battery pack to charge it.
The charger 62 determines the charging current and the battery's 70 condition.
If the battery is full
charged and cannot receive further power, the power is sent to the DC/DC
converter 68, and then on
the power MUX and the output power connector 65 for output, if a load such as
a portable device (not
shown) is connected. In no load is connected, the charger 62 provides a
trickle charge (SOmA -100mA)
to the battery to maintain it.
If the battery 70 is damaged, or old, this will typically result in a lower
capacity and a high internal
resistance for the battery 70, and so considering the voltage drop on the
internal resistance more power
is needed the more aged or damaged the battery. When the microcontroller 80
determines that a
battery 70 is damaged, it may use a trickle charge only to charge it, as
damage can reduce the input
current of the battery in addition to its capacity.
The power path controller 60 has no input from the microcontroller. It
receives power from the AC
power input 52 and the USB input 56. In one embodiment, it receives power from
either the AC power
input 52 or the USB input 56, not both simultaneously, and has a one-way
circuit 57, consisting of
Schottky diodes that have a 0.3V voltage drop, or ideal diodes that have less
than 20mV voltage drop for
high efficiency applications, such that there is no reversal of power flow
from the input sources. Due to
the one-way circuit 57, power cannot enter via the AC power input 52 and exit
by the USB input 56, for
example. In another embodiment, the input sources are on separate circuits so
their input power may
be combined. Therefore the portable charger can receive power from both AC and
USB sources
individually or, in some embodiments, simultaneously.
When the power is sent from the battery charger 62 or the power point
controller 55 into the junction
63, the microcontroller determines if there is a load on the output power
connector 65. If the output
power connector is connected to a load (not shown) which is drawing power, the
microcontroller
commands the junction 63 to route the power through the DC/DC converter 68,
which adjusts the
varying voltage of the battery 70 to a fixed output voltage for the load (not
shown) connected to the
output power connector 65. The power having adjusted voltage is then directed
to the power MUX
which outputs it through the output power connector 65.
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If the battery 70 cannot receive a charge, as it is fully charged, and there
is no load connected to the
output connector 65, then no power is drawn from the input sources. The
microcontroller 80 turns off
the charger 62 and there is no power path to the battery, and the
microcontroller 80 will turn off the
AC/DC converter 58 in order to save energy from AC line. In one embodiment the
PV panel 54 is
constantly on so as to provide a trickle charge to the battery 70. If the
battery cannot receive the charge
from the PV panel 54 the excess energy is dissipated as heat.
In one embodiment, the USB input connector 56 has a signal connection to a USB
controller 74, which
controls data flow with a USB port through the USB input. The USB controller
74 may instead be a
controller for data from another DC input, like FirewireT"" for example. The
output connector 65 may
also communicate with the USB controller 74, such that a load may transmit
data to the USB controller
74. In other embodiments there is no connection between the output connector
65 and the USB
controller 74. The USB controller 74 is connected to flash memory 76, which is
capable of storing and
retrieving data transmitted to and from the USB controller, and the
microcontroller 80. The USB
controller 74 has a USB port detector 77 that communicates to the
microcontroller 80 the current that
can be provided by the USB port (not shown). For example, USB 2.0 produces
500mA while USB 3.0 can
deliver a current of 1.5A. The USB controller 74 is also connected to the
microcontroller 80, which
determines whether the USB receiving machine is connected to the USB input 56
is a dumb port (i.e.
power only port or an auxiliary PV panel) or a smart port, having memory and
data transmission
capability. In another embodiment the flash memory is a removable memory, such
as an SDTM card or
microSDTM card. Power from the USB input 56 powers the USB controller 74 as
well.
The battery 70 is monitored by a fuel gauge 82, which is able to determine
battery conditions, for
example, battery voltage, current through battery, battery temperature and
battery health, the
remaining power, the estimated time remaining at current draw levels. The fuel
gauge 82 consists of
sensors for determining the battery voltage, current and temperature. The fuel
gauge 82 communicates
with the microcontroller 80 which receives data from the fuel gauge 82 and
makes a determination
regarding the condition of the battery 70, and the microcontroller 80
determines which conditions to
show on the display 85. For example, in one embodiment the microcontroller 80
calculates the amount
of power remaining in the battery relative to a full charge and displays that
information.
There are two protection layers for the battery 70. The first protection layer
is governed by the battery
charger 62 which senses the battery voltage, battery current and battery
temperature (there is a
temperature probe in the battery that is attached to the charger 62) and
protects the battery 70 from
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over-voltage, over-current and over-temperature conditions, by turning off
current from the battery
charger 62. Based on the voltage level of the battery 70, the charger decides
whether to use a trickle
charge, a constant current charge or a constant voltage charge to the battery
70.
The following example assumes a 4.2V battery. The thresholds may be calculated
differently for
batteries of different voltages. When the battery is lower than 3V, a small
current of typically fewer than
200mA, representing a trickle charge, is used by the charger 62. When the
battery voltage is greater
than 3V but smaller than 4.2V, the charger 62 uses a constant current charge,
providing the highest
current that the battery 70 will accept. When the battery voltage is 4.2V, the
charger outputs a constant
voltage of 4.2V. The internal resistance reduces the battery voltage to
slightly less than 4.2V, and the
charger 62 provides the current the battery will accept. When the battery is
nearly full, the charger 62
will provide a trickle charge current (approximately 5-10% of the battery
capacity). In order to effect the
appropriate thresholds the battery current is also monitored. The charger 62
has a temperature
monitor, and when the battery temperature is out of the normal range, the
charger stops charging. The
normal charging temperature range is 0 to 45'C.
The microcontroller 80 is the next level of protection, wherein the
microcontroller 80 receives signals on
the battery's condition from the fuel gauge 82, and is able to monitor the
voltage, current and
temperature of the battery 70 and turn off or adjust the charge control switch
66 if the battery 70
experiences a voltage, current, or temperature outside a predefined range on
charging. The
microcontroller 80 acts to protect the battery based on the sensor input from
the fuel gauge, and is able
to turn off the charger 62 as necessary to protect the battery 70. For
example, if the voltage is above
4.2V (for a 4.2V battery) or if the temperature is out of the acceptable range
for charging (0' - 45 C), the
microcontroller 80 turns the charger 62 off.
On discharging, if the battery voltage is too low (in one embodiment below 3V)
then the microcontroller
80 will turn off the charge control switch 66. If an overcurrent signal is
raised from fuel gauge 82 during
the discharge, the charge control switch 66 is also turned off. If the
temperature is out of the acceptable
range (in one embodiment -15' to 65' C) then the microcontroller 80 will turn
the charge control switch
66 off.
The DC/DC converter 68 is in communication with the microcontroller 80, which
determines the voltage
at the battery output and controls the DC/DC converter 68 so as to provide a
standard voltage to the
power MUX 64. In one embodiment the output of the DC/DC converter 68 is always
at SV, unless it is in
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overcurrent mode where the power MUX reduces the voltage accordingly (perhaps
to 4.7V), so the
output current is the maximum the system can provide. This is due to the
standardization of input
voltages on ports, which is typically 5V. The portable charger is also useful
for higher voltage devices
such as laptops, where the output voltage may be standardized at a higher
value.
The microcontroller 80 is connected with each of the units by serial bus, and
is able to communicate
with individual units as each has a unique address to identify its signals to
the microcontroller 80.
With reference to the circuit diagram in Figure 3, the PV panel 54 mounted
within the case produces a
trickle charge which may be sent directly to the battery or output, as
described above. In a further
embodiment, the charger contains circuitry to maximize the utility of the
power received from the PV
panel 54, including a DC/DC converter located within the power point
controller. While efficient in their
recommended operating ranges, the efficiency of DC/DC converters falls off
dramatically at low
voltages, such that there is a "threshold" to overcome before the DC/DC
converter is within its most-
efficient operating range. To maximize the power received from the PV panel 54
in view of the DC/DC
converter's threshold, the low power output of the PV panel can be stored in a
supercapacitor (not
shown) first, to collect and rise above the DC/DC converter's threshold
voltage. The microcontroller 80
selectively engages the DC/DC converter when the voltage and current of the
supercapacitor is
sufficiently high to overcome the efficiency threshold of the DC/DC converter,
and charges the battery
70.
With reference to Figure 4, in a further embodiment the charger is shown with
a larger auxiliary PV
panel 88 that connects through the USB input 56 by means of a USB plug (not
shown). As discussed
above, the auxiliary PV panel 88 is larger and can produce much more power
than the PV panel 54
mounted on the case, since it is not limited to the size of the case. The
higher power cannot simply be
transferred to the battery as is the case with the PV panel 54. Instead, the
power enters through the
USB input 56, where the USB port detector 77 determines that the auxiliary PV
panel is not a USB
source. The external PV panel can be designed in such way that it outputs a
special voltage ID through D-
and D+ pins to the USB port detector 77, which transfers the voltage ID to the
microcontroller 80. The
microcontroller 80 reads this voltage ID and realizes the input source through
USB input is an auxiliary
PV panel 88. The microcontroller 80 then turns on the power switch 92 and
turns off the battery
charger 62 so the power from the auxiliary PV panel 88 is fed to the input of
the power point controller
55.
CA 02777387 2012-05-16
EXAM PLES
In one embodiment, the battery is 5700 mAh. An empty battery can be charged
within 8 hours by means
of the AC power input, while charging by USB input takes more than 12 hours.
Performance may be
enhanced by increasing the AC/DC converter 58 from a 3.5W to a 7.5W rating,
and to insert a battery
charger 62 that is more efficient, for example moving from a linear charger to
a switching charger. To
illustrate the example, the linear charger, while its input and output current
are same (1.OA), the voltage
difference between input voltage (5V) and the output voltage (battery voltage
3-4.2V) will be on the
linear charger and wasted as heat. The average charging efficiency is only
about 70%. The switching
charger has an efficiency of more than 90%, and is able to vary the voltage
and current. If the input to
the charger is 5V and 1A, and the battery is at 3V, then 3V and 1.5A may be
provided to the battery 70
by the switching charger, resulting in faster charging than the linear
charger.
As an example, in an embodiment where the PV panel is mounted on the case of
the charger, and is
therefore limited in size to 2" X 2" for example, the PV panel outputs 100 -
500 mW in bright light, a
trickle charge of 5OmA at 4.5V. Where an auxiliary PV panel is used, which may
be of any conceivable
size, the power output may be in the range of 3-5W, for a current of 0.6-1A at
5V.
From the foregoing, it will be observed that numerous variations and
modifications 20 may be effected
without departing from the spirit and scope of the invention. It is to be
understood that no limitation
with respect to the specific apparatus illustrated herein is intended or
should be inferred. It is intended
to cover by the appended claims all such modifications as fall within the
scope of the claims.
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