U.S. patent application number 12/063460 was filed with the patent office on 2011-12-01 for multi-purpose battery charging circuit.
This patent application is currently assigned to NXP B.V.. Invention is credited to Guillaume De Cremoux.
Application Number | 20110291620 12/063460 |
Document ID | / |
Family ID | 37757949 |
Filed Date | 2011-12-01 |
United States Patent
Application |
20110291620 |
Kind Code |
A9 |
De Cremoux; Guillaume |
December 1, 2011 |
MULTI-PURPOSE BATTERY CHARGING CIRCUIT
Abstract
The present invention relates to a multi-purpose battery
charging circuit configuration able to be selectively in a simple
charge mode when intended for low-end solutions (option 3) or in a
charge-and-play mode when intended for medium- and high-end
solutions (options 1 and 2 respectively), while maintaining the
supply voltage of any portable and mobile electronic devices with
an acceptable noise level. The selection will be made possible by
the use of multiplexers (MUX1, MUX2). If the option 1 is chosen,
the bi-directional switching device (210) will be controlled by a
driver circuit (340) for allowing the current which flows through
it towards the battery (20) to strongly increase and thereby
maintaining the voltage across the circuitry (10) at a value
slightly greater than the voltage across the battery (20). If the
option 2 is chosen, the synchronous step-down voltage regulator
(310) comprising at least the driver circuit (350) and the
switching devices (200, 230) will track the voltages across the
circuitry (10) and the battery (20) for regulating the voltage
across the circuitry (10) at a value in the vicinity of the voltage
across the battery (20). If the option 3 is chosen, the battery
(20) which cannot be separated from the circuitry (10) will be in a
simple charge mode while being charged through the switching device
(210).
Inventors: |
De Cremoux; Guillaume;
(Edinburgh, GB) |
Assignee: |
NXP B.V.
Eindhoven
NL
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20100231171 A1 |
September 16, 2010 |
|
|
Family ID: |
37757949 |
Appl. No.: |
12/063460 |
Filed: |
August 7, 2006 |
PCT Filed: |
August 7, 2006 |
PCT NO: |
PCT/IB2006/052718 PCKC 00 |
371 Date: |
May 17, 2010 |
Current U.S.
Class: |
320/137 |
Current CPC
Class: |
H02J 7/0068
20130101 |
Class at
Publication: |
320/137 |
International
Class: |
H02J 7/00 20060101
H02J007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 17, 2005 |
EP |
05107451.4 |
Claims
1. A battery charging circuit configuration for operating a circuit
and simultaneously charging an associated battery separated from
said circuit, said battery charging circuit configuration
comprising: a voltage regulator means coupled between a first node
to which a power supply means is connected and a second node to
which said circuit is connected, for outputting a regulated voltage
at said second node at a value close to a voltage at a third node
to which said battery is connected, said value being higher than
said voltage at said third node; a bi-directional switching means,
coupled between said second node and said third node, for allowing
a current flowing from said second node towards said third node to
be reverted in order to flow from said third node towards said
second node, said bi-directional switching means being controlled
by a driver means.
2. A battery charging circuit configuration according to claim 1,
wherein said voltage regulator means is a DC-DC controller means
based on a switched operating mode, said DC-DC controller means
being a step-down DC-DC controller.
3. A battery charging circuit configuration according to claim 2,
wherein an external energy storage means is provided between said
voltage regulator means and said second node.
4. A battery charging circuit configuration according to claim 3,
wherein said external energy storage means is an inductor or a
coil.
5. A battery charging circuit configuration according to claim 1,
wherein said driver means is a digital and analog controller
means.
6. A battery charging circuit configuration according to claim 1,
wherein said battery charging circuit is an integrated circuit made
from a single silicon implementation.
7. A multi-purpose battery charging circuit configuration for being
selectively configurable in a charge-and-play mode for operating a
circuit separated from an associated battery and simultaneously
charging said battery or in a simple charge mode for charging a
battery connected to an associated circuit, said multi-purpose
battery charging circuit configuration comprising: a first
switching means, coupled between a first node and a fourth node; a
bi-directional switching means as claimed in claim 1, wherein said
driver means further allows said current flowing from said second
node towards said third node to be increased; a first multiplexing
means, for selecting a driver means amongst at least a first, a
second and a third driver means, said selected driver means
controlling said first switching means; a second multiplexing
means, for selecting said second driver means if said first
multiplexing means selects said second driver means, said second
driver means controlling a second switching means connected to said
fourth node, and for deactivating said second driver means if said
first multiplexing means selects said first driver means or said
third driver means; an external energy storage means if said first
multiplexing means selects said second driver means, or a
short-circuit means if said first multiplexing means selects said
first driver means or said third driver means, said external energy
storage means or said short-circuit means being connected between
said fourth node and said second node; a voltage regulator means,
wherein said voltage regulator means comprises at least said first
switching means, said second switching means and said second driver
means.
8. A multi-purpose battery charging circuit configuration according
to claim 7, wherein said selected first driver means has a first
input and a second input, said first input being coupled to said
first node and said second input being coupled to a first reference
voltage, said first switching means being switched off when said
first input has a voltage potential greater than said second
input.
9. A multi-purpose battery charging circuit configuration according
to claim 7, wherein said selected third driver means has a first
input and a second input, said first input being connected to said
second node and said second input being connected to a second
reference voltage, said first switching means being switched off
when said first input has a voltage potential greater than said
second input.
10. A multi-purpose battery charging circuit configuration
according to claim 7, wherein said voltage regulator means is a
DC-DC controller means based on a switched operating mode, said
DC-DC controller means being a step-down DC-DC controller.
11. A multi-purpose battery charging circuit configuration
according to claim 10, wherein said external energy storage means
is an inductor or a coil.
12. A multi-purpose battery charging circuit configuration
according to claim 7, wherein any one of said driver means is a
combined digital and analog controller means.
13. A multi-purpose battery charging circuit configuration
according to claim 7, wherein said first switching means is a power
metal oxide semiconductor field effect transistor or a bipolar
junction transistor or any other controllable semiconductor
switching device.
14. A multi-purpose battery charging circuit configuration
according to claim 7, wherein a second switching means controlled
by a driver means is connected in anti-series between said first
switching means and said fourth node.
15. A multi-purpose battery charging circuit configuration
according to claim 7, wherein said multi-purpose battery charging
circuit is an integrated circuit made from a single silicon
implementation.
Description
[0001] The present invention relates to a battery charging circuit,
and is more particularly directed to a multi-purpose integrated
battery charging circuit able to be selectively configured in a
simple charge mode or in a charge-and-play mode while maintaining
the supply voltage of any portable and mobile electronic devices
with an acceptable noise level.
[0002] Portable and mobile devices, such as a cellular phone,
personal digital assistant (PDA), portable personal computer,
camcorder, digital camera or MP3 player for example, need to have
their circuitry electrically supplied by an operational
rechargeable battery whenever no alternative electric power source
is available. When the battery is fully discharged and is therefore
no longer operational, it can nevertheless be charged again by
being electrically fed by a DC power source such as a wall plug
adapter. So two charging configuration modes can be obtained: the
simple charge mode which is commonly used in low-end solutions and
wherein the device can operate only from the battery to which it is
connected, and the charge-and-play mode which is commonly used in
medium- and high-end solutions and wherein the battery of the
device can be removable and is separated from the circuitry. In the
first case, the user must first wait for a while until the battery
is charged before using the device again, whereas in the second
case, the user can still continue using it in the same manner as a
portable computer while the battery is being charged, since the
wall-plug adapter simultaneously supplies the circuitry and the
battery of the device. Despite a larger flexibility through such
utilization, the charge-and-play mode can however generate large
ripple voltages on the terminal to which the circuitry is connected
and therefore become totally unsuitable for playing or operating
audio and RF devices.
[0003] Such a drawback can be explicitly illustrated by referring
to FIG. 1a wherein a conventional integrated battery charging
circuit in a charge-and-play mode is depicted, and to FIG. 1b
wherein the plots versus time of the voltage V.sub.SYS at the
terminal SYS connected to the circuitry and the corresponding
current I.sub.SYS are shown. In FIG. 1a, the wall plug adapter 100
connected at the terminal CHG charges the battery 20 of the
portable or mobile device at the terminal BAT, through two
switching devices 200 and 210 separated by the terminal SYS, while
simultaneously supplying the circuitry 10 disconnected from the
battery 20 with a voltage V.sub.SYS at the terminal SYS. The
capacitor C connected across the circuitry 10 at the terminal SYS
is an external output filter capacitor aiming to smooth the voltage
transitions. The first switching device 200 connected between the
terminals CHG and SYS will be supposed to act as an ideal switch
and will be hence considered as a short-circuit in a forward mode,
such that the voltage potentials at the terminals CHG and SYS will
be identical while satisfying the relation: V.sub.CHG=V.sub.SYS.
Its role is essentially to protect the circuitry 10 from over
voltage by decoupling it from the wall plug adapter 100 when
switching OFF. The second switching device 210 connected between
the terminals SYS and BAT is a bi-directional switch for allowing
the current to revert when the battery 20 must supply power to the
circuitry 10. It will be deemed to behave as an ideal diode when
the current flows from the terminal BAT towards the terminal SYS.
Referring to FIG. 1b, the wall plug adapter 100 has a limited
current capability (e.g. I.sub.(CHG)max=0.8 A) and a nominal
voltage V.sub.nom (e.g. 5 V) that it can maintain only if the total
sum of the currents which feed the circuitry 10 (refer to
I.sub.SYS) and the battery 20 is lower than the maximum current
I.sub.(CHG)max able to be delivered by the wall plug adapter 100.
If the circuitry 10 requires a current higher than I.sub.(CHG)max,
then the wall plug adapter voltage V.sub.CHG as well as V.sub.SYS
drop until to become lower than the battery voltage V.sub.BAT (e.g.
3 V if, at this instant, the battery has not yet reached its
nominal charging voltage of 3.6 V for example) in order to allow
the battery 20 to provide to the circuitry 10 the missing current
flowing through the second switching device 210 from the terminal
BAT towards the terminal SYS. The gap between V.sub.SYS and
V.sub.BAT will then correspond to the voltage drop .DELTA.
generated across the second switching device 210 (e.g. about 300 mV
if the second switching device 210 which behaves as an ideal diode
has a resistance of 0.3 .OMEGA. and is passed through by a current
of 1 A). This situation, which depends both on the importance of
the activity generated by the circuitry 10 and on its occurrence
frequency, may be encountered when, for example, a cellular phone
has a speaker which is sporadically activated to play music. Thus,
the terminal SYS to which the circuitry 10 is connected may be
subject to a large voltage variation (e.g. about 2 V if V.sub.nom=5
V and V.sub.BAT=3 V) which is totally at random, such that the
corresponding voltage V.sub.SYS can be sufficiently noisy compared
to the voltage V.sub.BAT supplied by the charged battery 20 to the
circuitry 10 when both are connected together and totally
unsuitable for supplying audio and RF devices.
[0004] A common way to overcome these deficiencies is to attempt as
often as possible to hold the voltage V.sub.SYS at a voltage
potential in the vicinity of V.sub.BAT in order to drastically
minimize the voltage variation at the terminal SYS to which the
circuitry 10 is connected. This can be realized by charging the
battery 20 with a very large current which flows through the second
switching device 210. Thus, even if the circuitry 10 has a low
activity which requires no current higher than I.sub.(CHG)max and
therefore no additional power supply from the battery 20, the total
sum of the currents charging the battery 20 and supplying the
circuitry 10 may already exceed the maximum current I.sub.(CHG)max
able to be delivered by the wall plug adapter 100. As a result, the
wall plug adapter voltage V.sub.CHG(=V.sub.SYS) decreases until a
voltage level slightly higher than the battery voltage V.sub.BAT,
such that the battery 20 is still operating in charging mode but
with a lower charge current in order to have the total sum of the
currents which feed the circuitry 10 and the battery 20 equal to
1.sub.(CHG)max. Therefore, any excess of activity of the circuitry
10 will result in a minor fluctuation of V.sub.SYS. Nevertheless,
this solution can no longer be considered as sufficient when, upon
charge completion, the wall plug adapter 100 switches to a trickle
charge mode for enabling the battery 20 to be kept fully charged
using a trickle charge rate low enough to avoid overcharging. Under
these conditions, the current injected to the battery 20 is
strongly reduced and cannot guarantee that the total sum of the
currents flowing through the battery 20 and the circuitry 10
exceeds the maximum current I.sub.(CHG)max outputting from the wall
plug adapter 100. It results that the wall plug adapter voltage
V.sub.CHG(=V.sub.SYS) may increase again and random ripples on
V.sub.SYS occur.
[0005] It is therefore an object of the present invention to
provide a battery charging circuit intended for high-end portable
and mobile electronic devices in order to minimize any ripples
which may arise on the voltage V.sub.SYS supplying the circuitry
when in a charge-and-play mode, as well as a multi-purpose battery
charging circuit capable to be selectively configured in a simple
charge mode or a charge-and-play mode in order to be compatible
with any low-, medium- or high-end portable and mobile electronic
devices.
[0006] This object is achieved by a battery charging circuit
configuration as claimed in claim 1 and a multi-purpose battery
charging circuit configuration as claimed in claim 7.
[0007] Accordingly, a battery charging circuit operating in a
charge-and-play mode comprises a voltage regulator tracking the
voltage V.sub.BAT at the terminal BAT to which a battery of a
portable or mobile electronic device is connected, and regulating
the voltage V.sub.SYS at the terminal SYS to which the circuitry of
this device is connected, at a value in the vicinity of V.sub.BAT
and slightly greater than V.sub.BAT. Thereby, the voltage variation
at the terminal SYS strongly diminishes such that the amplitude of
the ripples on V.sub.SYS is comparable to the one on V.sub.BAT when
the circuitry stays connected to the battery.
[0008] Furthermore, the battery charging circuit comprises a
bi-directional switching device connected between the battery and
the circuitry and through which a current flows. Thereby, the
battery may revert the current for supplying the circuitry with an
extra current if the current flowing through the circuitry exceeds
the maximum current to be delivered by a DC power source such as a
wall plug adapter.
[0009] The voltage regulator may be a DC-DC controller leading to
the use of an external coil. Thereby, heat dissipation can be
efficiently alleviated. Moreover, since such a coil is expensive in
terms of price and bulky in terms of area available on a printed
circuit board (PCB), this configuration will be thus affordable for
high-end solutions.
[0010] Additionally, a multi-purpose battery charging circuit,
partially built from the aforementioned battery charging circuit,
is selectively configurable owing to multiplexers for operating in
a simple charge mode intended for low-end solutions when the
circuitry is connected to the battery or in a charge-and-play mode
intended either for medium-end solutions when no coil associated
with a DC-DC controller is used or for high-end solutions when a
coil associated with a DC-DC controller is used. Being designed to
be an integrated circuit made from a single silicon implementation,
such a circuit thereby offers a high degree of flexibility, saving
a lot of development and adaptation time.
[0011] For medium-end solutions, the bi-directional switching
device, which is controlled by a driver means such as a digital and
analog controller means, allows the battery to be charged with a
much larger current using programming means for example such that
the total sum of the currents exceeds the maximum current able to
be delivered by the DC power source. Despite the fact that no DC-DC
controller is used, the voltage V.sub.SYS supplying the circuitry
can thereby be maintained at a voltage level in the vicinity of
V.sub.BAT even if the circuitry generates a low activity.
[0012] Further advantageous developments relating in particular to
the protection from thermal damage are also defined in the
dependent claims.
[0013] The present invention will be now described based on
preferred embodiments with reference to the accompanying drawings
in which:
[0014] FIG. 1a shows a conventional integrated battery charging
circuit in a charge-and-play mode, wherein the voltage V.sub.SYS is
not regulated;
[0015] FIG. 1b shows the plots versus time of the unregulated
voltage V.sub.SYS at the terminal SYS to be connected to the
circuitry and the corresponding current;
[0016] FIG. 2a shows an integrated battery charging circuit in a
charge-and-play mode according to the first preferred embodiment of
the invention, wherein V.sub.SYS is regulated at a value in the
vicinity of V.sub.BAT and slightly greater than V.sub.BAT;
[0017] FIG. 2b shows the plots versus time of the regulated voltage
V.sub.SYS at the terminal SYS to be connected to the circuitry and
the corresponding current;
[0018] FIG. 3 shows a multi-purpose integrated battery charging
circuit selectively configurable in a charge mode or in a
charge-and-play mode according to the second preferred embodiment
of the invention.
[0019] In the following, the first preferred embodiment will be
described in connection with an integrated battery charging circuit
in a charge-and-play mode which allows the voltage V.sub.SYS
connected to the circuitry to be regulated to a value close to the
voltage V.sub.BAT, such as depicted in FIGS. 2a and 2b.
[0020] In FIG. 2a, the integrated battery charging circuit in a
charge-and-play mode according to the first preferred embodiment of
the invention is based on the circuit from FIG. 1a wherein the
first switching device 200 (e.g. MOSFET, BJT or any other
controllable semiconductor switching device) is now part of a
voltage regulator 310 connected between the terminals CHG and SYS
and tracking the voltages V.sub.BAT at the terminal BAT and
V.sub.SYS at the terminal SYS. As depicted in FIG. 2b, this voltage
regulator 310 will regulate the voltage V.sub.SYS at the terminal
SYS at a value slightly greater than V.sub.BAT. Thus, all the
variations of V.sub.BAT will be tracked by the voltage regulator
310 in order to always maintain the voltage V.sub.SYS at a constant
level slightly higher (V.sub.BAT+.DELTA.) than V.sub.BAT, wherein
.DELTA. is a trade off between a value small enough so as to have
the noise level on V.sub.SYS (sum of .DELTA. and .DELTA.', wherein
.DELTA.' may be a predetermined value) small enough, and a value
large enough such that the second switching device 210 controlled
by a driver means 340 can properly charge the battery 20 from
V.sub.SYS. When the activity of the circuitry 10 connected at the
terminal SYS is increasing until the current capability of the wall
plug adapter 100 is reached, the voltage V.sub.SYS (=V.sub.CHG)
will slightly decrease under V.sub.BAT by the predetermined value
.DELTA.' so that the battery 20 can behave as a generator while
reverting the current which now flows from the terminal BAT towards
the terminal SYS through a bi-directional switch such as the second
switching device 210 controlled by a driver means 340. At the
terminal SYS, the voltage gap .DELTA.V which is equal to
.DELTA.+.DELTA.' will be therefore low enough in order to neglect
the disturbances generated by the ripples on V.sub.SYS. However,
the large shift from V.sub.CHG to V.sub.BAT-.DELTA.' at the
terminal CHG will cause the voltage regulator 310 to generate a too
high power dissipation
((V.sub.CHG-(V.sub.BAT-.DELTA.'')).times.I.sub.(CHG)max) able to
damage the die when heat sinks are missing. The presence of an
energy storage means such as an external coil L is thus widely
recommended and it is the reason why the voltage regulator 310 will
be preferably a step-down (buck) voltage regulator built, for
example, with a step-down DC-DC controller. To achieve a higher
efficiency, a technique called "synchronous rectification" will be
used in order to replace the common flywheel diode with an
additional switching device 230 (not represented here) having a
polarity different from the first switching device 200 and to
thereby remove its threshold voltage in conduction mode. A
synchronous step-down DC-DC controller will be then obtained.
[0021] Since the coil L is a costly and bulky component, this first
preferred embodiment will be however affordable in terms of price
and area on the printed Circuit Board (PCB) for high-end portable
and mobile electronic devices such as expensive mobile phones and
PDAs for example.
[0022] To address all types of market in terms of price, a second
preferred embodiment comprising the first preferred embodiment will
be described as follows. It consists in a multi-purpose integrated
battery charging circuit able to be selectively configured in a
simple charge mode for use by low-end solutions or in a
charge-and-play mode for medium- and high-end solutions, while
maintaining the supply voltage of the circuitry 10 with an
acceptable signal-to-noise ratio, such as depicted in FIG. 3. This
circuit includes driver circuits 300, 320, 330, 340, 350 such as
digital controllers to control switching devices 200, 210, 220,
230, 240, multiplexers MUX1, MUX2 to select the different
configuration options (opt.1, opt.2, opt.3) according to the type
of portable and mobile electronic devices used, a battery 20 to be
charged (opt.1, opt.2, opt.3) and, if removable and separated from
its battery (opt.1, opt.2), a circuitry 10 to be played at the same
time as the battery charge.
[0023] The circuit is powered by the wall plug adapter 100, but can
also be alternatively supplied by any DC power source such as an
USB power supply 110 for example, while being connected in parallel
from the terminal LX. In this case, the pair of switching devices
200 and 220 will be no longer used and will be replaced by the
switching device 240. The capacitor C connected in parallel to the
circuitry 10 is an external output filter capacitor aiming to
smooth the voltage transitions and to also play the role of a load
capacitor when a DC-DC controller is used (opt. 2). The switching
device 210 (e.g. a P-channel MOS transistor) will be a
bi-directional switch controlled by the driver circuit 340. The
latter 340 will enable a voltage V.sub.BAT or a current flowing
from the terminal SYS to the terminal BAT to be maintained
constant. If the circuitry 10 requires a current exceeding the
maximum current susceptible to be provided by the DC power source
100, 110, then the driver circuit 340 will allow the current to be
reverted and to flow from the terminal BAT to the terminal SYS
through the switching device 210. Due to the voltage drop across
the switching device 210, the voltage V.sub.SYS will become
slightly lower than V.sub.BAT. The switching devices 200, 220 will
have the same polarity as the switching device 240 (e.g. P-channel
MOS transistors) and will be connected in anti-series between the
terminals CHG and LX so as to prevent or control any casual reverse
mode operation in the event that the pin CHG is accidentally
grounded. Both switching devices 200, 220 will act as ideal
switches and will be hence considered as short-circuits in a
forward mode, such that the voltage potentials at the terminals CHG
and LX will be identical while satisfying the relation:
V.sub.CHG=V.sub.LX. Moreover, the switching devices 200, 240 will
be preferably power switching devices such as Power bipolar
transistors or Power MOSFETs able to withstand high voltages (e.g.
10 V, 20 V) at the terminal CHG. The circuit will be selectively
configured in a simple charge mode or in a charge-and-play mode
using the selection made by the multiplexers MUX1 and MUX2. Three
options will be selected according to the type of portable or
mobile devices to be used. Thus, the options 3, 1 and 2 will
respectively correspond to a low-end solution (not designed for
being used in a charge-and-play mode), medium-end solution (used in
a charge-and-play mode using no DC-DC converter and therefore no
external coil) and high-end solution (used in a charge-and-play
mode using external coil).
[0024] If the option 1 is chosen, then the portable or mobile
electronic device owns a rechargeable battery 20 which is removable
and separated from the circuitry 10 such as schematically depicted
in FIG. 3 using the ON-state switch SW. The selection of the
multiplexer MUX2 will result in deactivation of the switching
device 230 while grounding its gate for example if a N-channel MOS
transistor, whereas the switching device 220 that will have a
polarity different from the switching device 230 will be turned on
under the control of the driver circuit 330. The selection of the
multiplexer MUX1 will cause the switching device 200 to be
controlled by the driver circuit 300. The terminals SYS and LX will
be short-circuited on the PCB by being connected between them, such
that both terminals will be at the same voltage potential as the
terminal CHG through the ON-state of the switching devices 200 and
220. In order to strongly minimize any ripples on V.sub.SYS while
maintaining it at a voltage potential in the vicinity of V.sub.BAT
and improve the efficiency of this configuration, the driver
circuit 340 will be programmed for allowing the current which flows
through the switching device 210 to increase and saturating the
wall plug adapter current capability.
[0025] To offer secure protection from over voltage to the
circuitry 10, the driver circuit 300 may comprise a comparator with
a first input IN1 connected to the terminal CHG and a second input
IN2 set to a maximum voltage level (e.g. 5.5 V) able to be
withstood without damage by the circuitry 10 at the terminal SYS,
which will turn off the switching device 200 whenever the voltage
potential V.sub.CHG at the terminal CHG exceeds this voltage
threshold.
[0026] Finally, the option 1 which exhibits a supplemental
switching device 220 connected in anti-series with the switching
device 200 corresponds to the configuration such as depicted in
FIG. 1a and will be suited for medium-end solutions.
[0027] If the option 2 is chosen, then the portable or mobile
electronic device owns a rechargeable battery 20 which is removable
and separated from the circuitry 10 such as schematically depicted
in FIG. 3 using the ON-state switch SW. The selection of the
multiplexers MUX1 and MUX2 will cause the switching devices 200 and
230 to be driven by the same driver circuit 350 for determining an
appropriate ON-OFF switching sequence, whereas the switching device
220 will be turned on under the control of the driver circuit 330.
This driver circuit 350 will track the voltages V.sub.BAT and
V.sub.SYS for regulating V.sub.SYS at a value slightly greater than
V.sub.BAT. The terminal SYS will be connected to the terminal LX on
the PCB through an energy storage means such as an external coil L
in order to avoid any overheating. Thus, a synchronous step-down
DC-DC controller built with the switching devices 200, 220, 230,
the external coil L and the driver circuit 350 will be implemented.
The external filter capacitor C connected to the terminal SYS will
then play the role of a load capacitor.
[0028] Thus, the option 2 corresponds to the configuration such as
depicted in FIG. 2a and will be suited for high-end solutions.
[0029] If the option 3 is chosen, then the portable or mobile
electronic device owns a rechargeable battery 20 which is not
removable from the circuitry 10, such that the terminal SYS is no
longer connected to the circuitry 10 such as schematically depicted
in FIG. 3 using the OFF-state switch SW. The selection of the
multiplexer MUX2 will result in deactivation of the switching
device 230 while grounding its gate for example if a N-channel MOS
transistor, whereas the switching device 220 controlled by the
driver circuit 330 will be turned on. The selection of the
multiplexer MUX1 will cause the switching device 200 to be
controlled by the driver circuit 320. The terminals SYS and LX will
be short-circuited on the PCB by being connected between them, such
that both terminals will be at the same voltage potential as the
terminal CHG through the ON-state of the switching devices 200 and
220. Unlike the previous options, the option 3 authorizes a larger
heat dissipation and therefore a poorer efficiency while allowing
the switching device 200 to remain turned on even if the voltage
potential V.sub.CHG at the terminal CHG increases up to 10 or even
20 V. Thus, the driver circuit 320 may comprise an amplifier with a
first input in1 connected to the terminal SYS and not to the
terminal CHG as found in the option 1, and a second input in2 set
to a reference voltage (e.g. 5.5 V) which will regulate the
switching device 200 whenever the voltage potential V.sub.SYS at
the terminal SYS reaches this voltage threshold.
[0030] Unlike the previous options, the switching device 200 which
is a power switching device is no longer controlled by V.sub.CHG
but by a reference input voltage such that it must be able to
withstand high voltages at the terminal CHG while being maintained
in conduction mode and regulating V.sub.SYS at 5.5 V at maximum.
Due to a greater heat dissipation, a poorer efficiency will have to
be accepted by the user.
[0031] Therefore, the option 3 corresponds to the configuration of
a simple battery charge circuit and will be suited for low-end
solutions.
[0032] It is noted that the invention such as described according
to the preferred embodiments can be made from a single silicon
implementation while offering a high degree of flexibility. The
multiplexers MUX1 and MUX2 can be driven by a software, whereas the
terminals CHG, LX, SYS, BAT are part of the pin configuration
available on the PCB. Therefore, the multi-purpose integrated
battery charging circuit is configured such a manner as any one of
the three options can be chosen without the need of any change in
the Silicon Intellectual Property (IP).
[0033] As already quoted in the specification, it is noted that the
invention can be used by any electronic devices having a
rechargeable battery such as the mobile phones, the PDAs or the
portable computers for example.
[0034] In summary, a multi-purpose integrated battery charging
circuit configuration able to be selectively in a simple charge
mode when intended for low-end solutions (option 3) or in a
charge-and-play mode when intended for medium- and high-end
solutions (options 1 and 2 respectively), while maintaining the
supply voltage of any portable and mobile electronic devices with
an acceptable noise level, has been described. The selection will
be made possible by the use of multiplexers (MUX1, MUX2). If the
option 1 is chosen, the bi-directional switching device 210 will be
controlled by a driver circuit 340 for allowing the current which
flows through it towards the battery 20 to strongly increase and
thereby maintaining the voltage across the circuitry 10 at a value
in the vicinity of the voltage across the battery 20. If the option
2 is chosen, the synchronous step-down voltage regulator 310
comprising at least the driver circuit 350 and the switching
devices 200, 230 will track the voltages across the circuitry 10
and the battery 20 for regulating the voltage across the circuitry
10 at a value slightly greater than the voltage across the battery
20. If the option 3 is chosen, the battery 20 which cannot be
separated from the circuitry 10 will be in a simple charge mode
while being charged through the switching device 210.
[0035] Finally but yet importantly, it is noted that the term
"comprises" or "comprising" when used in the specification
including the claims is intended to specify the presence of stated
features, means, steps or components, but does not exclude the
presence or addition of one or more other features, means, steps,
components or group thereof. Further, the word "a" or "an"
preceding an element in a claim does not exclude the presence of a
plurality of such elements. Moreover, any reference sign does not
limit the scope of the claims.
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