NOISE FILTERING IN A BATTERY MODULE

Abstract

A circuit is provided, including first and second input terminals (110, 112) an output terminal (114), a DC-to-DC converter (120), and a trifilar choke (130) including a first inductor (140) connected between the first input terminal (110) and a first input terminal (150) of the converter (120), a second inductor (142) connected between the second input terminal (112) and a second input terminal (152) of the converter (120), and a third inductor (144) connected between the output terminal (114) and an output terminal (154) of the converter (120). The converter (120) is configured to convert a first voltage (V.sub.1) received at its first and second input terminals (150, 152) to a second voltage (V.sub.2) at its output terminal (154) higher than the first voltage (V.sub.1). The first, second and third inductors (140, 142, 144) are wound on a same core, mutually coupled and arranged such that currents common to the first and second inductors (140, 142) and currents common to the second and third inductors (142, 144) are blocked or attenuated. A current-limiting device, battery modules and a method of noise filtering are also provided.

Claims

1. A battery module, comprising: a battery cell arrangement including a first terminal and a second terminal, a first charging terminal and a second charging terminal, wherein the first charging terminal is connected to the first terminal of the battery cell arrangement; and a current limit device, including: a first input terminal and a second input terminal connectable to a charger; a first out put terminal and a second output terminal connectable to the battery cell arrangement, and; a circuit including: a first input terminal, a second input terminal and an output terminal; a direct current to direct current converter; and a trifilar choke including a first inductor connected between the first input terminal of the circuit and a first input terminal of the converter, a second inductor connected between the second input terminal of the circuit and a second input terminal of the converter, and a third inductor connected between the output terminal of the circuit and an output terminal of the converter, and wherein the output terminal of the circuit is connected to the first input terminal and the first output terminal of the device, wherein the first input terminal of the circuit is connected to the second input terminal of the device, and wherein the second input terminal of the circuit is connected to the second output terminal of the device wherein the converter is configured to convert a first voltage (V.sub.1) received at its first input terminal and second input terminal to a second voltage (V.sub.2) at its output terminal, the second voltage (V.sub.2) being higher than the first voltage (V.sub.1), and wherein the first inductor, the second inductor and the third inductor of the trifilar choke are wound on a same core, mutually coupled and arranged such that currents common to the first inductor and the second inductor and currents common to the second inductor and the third inductor are blocked or attenuated.

2. The battery module of claim 1, wherein the converter includes: an inductance connected between the second input terminal of the converter and a first node; a diode connected between the first node and the output terminal of the converter; a switching element connected between the first node and the first input terminal of the converter; and a modulation section configured to alternately operate the switching element between at least an open state and a closed state.

3. (canceled)

4. The battery module of claim 1, further comprising a first capacitor connected between the first input terminal and the second input terminal of the converter, a second capacitor connected between the second input terminal and the output terminal of the converter, a third capacitor connected between the first input terminal and the second input terminal of the circuit, and a fourth capacitor connected between the second input terminal and the output terminal of the circuit.

5. (canceled)

6. The battery module of claim 1, further comprising a switching device connected between the first input terminal and the second input terminal of the circuit.

7. The battery module of claim 1, wherein, using the circuit, the device is configured to limit a charge current (I.sub.charge) to the battery cell arrangement when a charge voltage (V.sub.charge) is applied by the charger at the first input terminal and the second input terminal of the device.

8. (canceled)

9. The battery module of claim 1, further comprising a further switching device connected between the second terminal of the battery cell arrangement and the second output terminal of the circuit.

10. (canceled)

11. (canceled)

12. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Exemplifying embodiments will be described below with reference to the accompanying drawings, in which:

[0030] FIG. 1a illustrates schematically an embodiment of a circuit according to the present disclosure;

[0031] FIG. 1b illustrates schematically an embodiment of a circuit according to the present disclosure;

[0032] FIG. 1c illustrates schematically an embodiment of a converter according to the present disclosure;

[0033] FIG. 2 illustrates schematically an embodiment of a current-limiting device according to the present disclosure;

[0034] FIG. 3 illustrates schematically an embodiment of a battery module according to the present disclosure; and

[0035] FIG. 4 illustrates schematically an embodiment of a battery module according to the present disclosure.

[0036] In the drawings, like reference numerals will be used for like elements unless stated otherwise. Unless explicitly stated to the contrary, the drawings show only such elements that are necessary to illustrate the example embodiments, while other elements, in the interest of clarity, may be omitted or merely suggested. As illustrated in the figures, the sizes of elements and regions may not necessarily be drawn to scale and may e.g. be exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of the embodiments.

DETAILED DESCRIPTION

[0037] Exemplifying embodiments will now be described more fully hereinafter with reference to the accompanying drawings. The drawings show currently preferred embodiments, but the invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the present disclosure to the skilled person.

[0038] With reference to FIGS. 1a and 1b, embodiments of a circuit according to the present disclosure will now be described in more detail.

[0039] FIG. 1a illustrates schematically an embodiment of a circuit 100. The circuit 100 has a first input terminal 110, a second input terminal 112 and an output terminal 114. The circuit 100 also includes a DC-to-DC converter 120 which has a first input terminal 150, a second input terminal 152 and an output terminal 154. The circuit 100 further includes a trifilar choke 130 which includes a first inductor 140, a second inductor 142, and a third inductor 144. The first inductor 140, the second inductor 142 and the third inductor 144 are wound on a same core (as illustrated in FIG. 1a by the dashed lines below each inductor) and mutually coupled (such as indicated in FIG. 1a by the dots above each inductor). The first inductor 140 is connected between the first input terminal 110 of the circuit 100 and the first input terminal 150 of the converter 120. The second inductor 142 is connected between the second input terminal 112 of the circuit 100 and the second input terminal 152 of the converter 120. The third inductor 144 is connected between the output terminal 114 of the circuit 100 and the output terminal 154 of the converter 120.

[0040] The converter 120 may be e.g. a boost convert, a step-up converter, or similar, and takes an input voltage V.sub.1 on the input terminals 150 and 152 and outputs an output voltage V.sub.2 on the output terminal 154 (e.g. between the output terminal 154 and the second input terminal 152). Although referred to as “second input terminals”, as will be described below, the terminals 112 and 152 function as combined input/output terminals in that both a power supply (from which the converter 120 receives power) and a load (to which the converter 120 provides power) may be connected to the terminal 112 and to the terminal 152 via the second inductor 142.

[0041] During operation of the circuit 100, the power supply (not shown) may be connected to the first input terminal 150 and the second input terminal 152 of the converter 120, and a load (also not shown) may be connected to the output terminal 114 and the second input/output terminal 112 of the circuit 100. An input voltage (e.g. a DC input voltage) provided by the power supply across the input terminals 110 and 112 of the circuit 100 may be provided as a voltage V.sub.1 across the terminals 150 and 152 of the converter 120, and the converter 120 may transform the voltage V.sub.1 into a higher voltage V.sub.2 at the output terminal 154 of the converter (e.g. between the output terminal 154 and the second input/output terminal 152 of the converter 120). The voltage V.sub.2 may be provided as an output voltage to the load across the output terminal 114 and the second input/output terminal 112 of the circuit 100.

[0042] In particular, an input current I.sub.1 may pass from the power supply to the converter 120 via the second inductor 142, and back to the power supply via the first inductor 140. Likewise, an output current I.sub.2 may pass from the converter 120 to the load via the third inductor 144, and back to the converter via the second inductor 142. During normal operation, current in the second inductor 142 will move in a direction different from current in the first inductor 140 and the third inductor 144, and the inductors will present a low impedance to such normal currents. However, due to the inductors 140, 142, 144 being mutually coupled and arranged as indicated by the dots in FIG. 1a, noise currents which travels in a same direction in both the first inductor 140 and the second inductor 142, and/or in a same direction in both the second inductor 142 and the third inductor 144, will generate equal and in-phase magnetic fields which add together, and the inductors 140, 142, 144 will present a high impedance to such “common-mode” noise currents. By the configuration of the converter 120 as described herein, current will always flow in the second inductor 142, while current will alternately flow in the first inductor 140 and in the third inductor 144 depending on whether the switching element in the converter 120 is in the opened or closed state.

[0043] As a result, the configuration of the converter 120 with the shared input/output terminal 152 allows the trifilar choke 130 to function as a filter for common-mode noise currents. The filter reduces the effects of EMI due to e.g. switching within the converter 120, and improves the EMC of the circuit 100. In addition, the use of a single choke, instead of e.g. separate bifilar chokes arranged both on the input terminals and the output terminals of the converter, allows for a reduced footprint and cost of circuit including the converter and filter.

[0044] FIG. 1b illustrates schematically another embodiment of a circuit 101 according to the present disclosure. In the circuit 101, a first capacitor 160 is connected between the first input terminal 150 and the second input/output terminal 152 of the converter 120; a second capacitor 162 is connected between the second input/output terminal 152 and the output terminal 154 of the converter 120; a third capacitor 164 is connected between the first input terminal 110 and the second input/output terminal 112 of the circuit 101; and a fourth capacitor 166 is connected between the second input/output terminal 112 and the output terminal 114 of the circuit 101. In the circuit 101 as illustrated in FIG. 1b, the capacitors 160-166 form part of the trifilar choke 131. It is envisaged also that the capacitors 160-166, if included, may instead be located outside of the choke 131. In such an embodiment of the circuit 101, the trifilar choke 131 may be identical to the trifilar choke 130 described with reference to the circuit 100 illustrated in FIG. 1a. The various capacitors 160-166 may for example help to prevent also differential-mode noise currents to reach/emerge from the circuit 101, and/or for example help to reduce voltage ripple at the output of the converter 120. It is envisaged also that in addition to the trifilar choke 130, the filter may include other components not shown in the Figures.

[0045] With reference to FIG. 1c, the DC-to-DC converter 120 as used in some embodiments of the circuits 100,101 will now be described in more detail.

[0046] FIG. 1c illustrates schematically a DC-to-DC converter 120. The converter 120 has a first input terminal 150, a second input/output terminal 152 and an output terminal 154. The converter 120 includes an inductance, i.e. a storage inductance, 122 which is connected between the second input/output terminal 152 and a first node 124. The converter 120 includes a diode 126 which is connected between the first node 124 and the output terminal 154 and oriented such that current is kept from passing from the output terminal 154, through the diode 126 and towards the first node 124. The converter 120 also includes a switching element 128 which is connected between the first node 124 and the first input terminal 150. Also, the converter 120 includes a modulation section (not shown) which is connected to the switching element 128, and which may alternately operate the switching element 128 between at least an open state (in which the switching element 128 disconnects the first node 124 from the first input terminal 150) and a closed state (in which the switching element 128 connects the first node 124 to the first input terminal 150).

[0047] When the switching element 128 is operated in the opened state, a voltage V.sub.1 provided across the first input terminal 150 and the second input/output terminal 152 will force a current I.sub.1 to pass into the second input/output terminal 152, through the inductor 122 and out via the first input terminal 150. It is assumed that, at this stage, no or very little current flows through the diode 126 due to the higher impedance of such an alternative current path. The polarity across the inductor 122 may be assumed to be such that the polarity on the side of the inductor 122 closest to the second input/output terminal 152 is positive. When the current I.sub.1 flows through the inductor 122, the inductor 122 may store some energy by generating a magnetic field.

[0048] In a next stage, the modulation section operates the switching element 128 to the open state, such that current may no longer flow through the switching element 128. The current will instead flow through the diode 126 and out at the output terminal 154. Due to the increased impedance of the current path through the diode, compared with the current path through the closed switching element 128, the current I.sub.2 flowing through the diode 126 will be smaller than the current I.sub.1. However, as the inductor 122 will attempt to oppose any change in current flowing through it, the magnetic field previously created will be destroyed in order to keep the current flowing. As a consequence, the polarity across the inductor 122 will change, resulting in a higher voltage at the first node 124 due to both the input voltage across the input terminals 152 and 150 and the voltage across the inductor 122 now being connected in series. A voltage V.sub.2 output across e.g. the output terminal 154 and the second input/output terminal 152 (which now serves as an output) will thus be higher than the input voltage V.sub.1. If the switching of the switching element 128 between the open and closed state is repeated quick enough, the inductor 122 will not discharge fully between each cycle and the output voltage V.sub.2 experienced by the load connected across the output terminal 154 and the second input/output terminal 152 will always be higher than the input voltage V.sub.1. The ratio between the input voltage V.sub.1 and the output voltage V.sub.2 may be controlled by e.g. the duty cycle of the switching.

[0049] In this and other embodiments, it is envisaged also to include e.g. one or more capacitors connected between the output terminal 154 and the second input/output terminal 152. Such one or more capacitors may be charged by the current I.sub.2 when the switching element 128 is in the opened state, and the one or more capacitors may then be able to provide energy to the load also during the next stage when the switching element 128 is in the closed state. This may provide e.g. a smoother voltage output to the load.

[0050] It is envisaged that the skilled person would know how to properly select the sizes of the various inductors and capacitances, and how to modulate the switching element 128 accordingly to obtain a desired ratio between input voltage and output voltage when using the converter 120.

[0051] With reference to FIG. 2, an embodiment of a current-limiting device according to the present disclosure will now be described in more detail.

[0052] FIG. 2 illustrates schematically an embodiment of a current-limiting device 200. The device 200 includes a first input terminal 210 and a second input terminal 212. The first and second input terminals 210, 212 may serve as charging terminals and be connected e.g. to a charger (not shown). The device 200 includes a first output terminal 220 and a second output terminal 222. The first and second output terminals 220, 222 may be connected e.g. to a battery cell arrangement (not shown) which is to be charged by the charger. The device 200 also includes a circuit 100. The circuit 100 may be the circuit as described earlier herein, for example the circuit 100 as described with reference to FIG. 1a or the circuit 101 as described with reference to FIG. 1b.

[0053] The output terminal 114 of the circuit 100 is connected to the first input terminal 210 of the device 200. The first input terminal 110 of the circuit 100 is connected to the second input terminal 212 of the device 200. The second input terminal 112 of the circuit 100 is connected to the second output terminal 222 of the device 200.

[0054] If the input terminals 210, 212 of the device 200 are connected to a charger (not shown), and if the output terminals 220, 222 of the device 200 are connected to a battery cell arrangement (not shown) which is to be charged by the charger, the operation of the device 200 may be illustrated by the following example:

[0055] Assume that the charger provides a charging voltage V.sub.charge across the input terminals 210, 212. When the battery cell arrangement is fully charged, the voltage V.sub.2 across the terminals 220, 222 will also be V.sub.charge or at least close to V.sub.charge. However, as long as the battery cell arrangement is not fully charged, the voltage V.sub.2 will be less than V.sub.charge, and the voltage V.sub.1 across the input terminals of the circuit 100 will be finite and equal to V.sub.1=V.sub.charge V.sub.2. As long as the voltage across the input terminals of the converter in the circuit 100 is kept above a certain threshold, the converter may be adapted to maintain a constant power level of P.sub.input at its input terminals (and i.e. at the input terminals 110 and 112 of the circuit 100), and the current I.sub.1 flowing into the circuit 100 will be I.sub.1=P.sub.input/V.sub.1. With a conversion efficiency of X % (where X=[0-100]), the power level P.sub.output at the output of the converter (and i.e. at the output terminal 114 and e.g. the second input/output terminal 112) of the circuit 100 will be P.sub.output=(X/100)*P.sub.input. The current I.sub.2 flowing out of the output terminal 114 of the circuit will be P.sub.output/V.sub.2, and it may be seen in FIG. 2 that the charge current I.sub.charge to the battery will equal I.sub.charge=I.sub.1+I.sub.2=P.sub.input/V.sub.1+P.sub.output/V.sub.2=P.sub.input*(1/(V.sub.charge−V.sub.2) (X/100)/V.sub.2).

[0056] If, for example, V.sub.charge=60 V, P.sub.input=60 W, X=50, and V.sub.2=30 V (i.e., the battery cell arrangement is not close to being fully charged), the circuit 100 will regulate the charge current to the battery such that I.sub.charge=4 A, with a corresponding power P.sub.battery=V.sub.2*I.sub.charge=120 W provided to the battery. Meanwhile, the input power P.sub.charge provided by the charger to the device 200 is given by P.sub.charge=V.sub.charge*I.sub.1=(V.sub.charge/(V.sub.charge V.sub.2))*P.sub.input=150 W. Comparing the input power P.sub.charge provided by the charger to the power P.sub.battery provided to the battery, one finds that the total charging efficiency in the above example is 80%.

[0057] If, instead, V.sub.2=45 V (i.e. the battery cell arrangement is close to being fully charged), one finds that I.sub.charge=12.67 A, P.sub.battery=570 W and P.sub.charge=600 W, leading to a total charging efficiency of 95%. In summary, the device 200 allows to efficiently regulate the charge current to the battery, and provides a high total charging efficiency even if the efficiency of the converter itself (in the above example 50%) is low. Increasing the efficiency of the converter would further improve the total charging efficiency.

[0058] Once the battery cell arrangement gets close to being fully charged, the voltage V.sub.1 across the input terminals 110, 112 of the circuit 100 is reduced, and may eventually fall below a threshold value under which the converter can no longer maintain the constant input power P.sub.input and/or its conversion efficiency. However, when the battery cell arrangement is close to being fully charged, it may be assumed that the battery cells within the battery cell arrangement is less sensitive to high charge currents, and the need for the converter is then reduced or eliminated. By e.g. detecting the voltage across the battery (i.e. the voltage V.sub.2), the charging level of the battery cell arrangement may be determined, and the switching device 230 may be operated such that it is closed (and thereby shorting the inputs to the circuit 100) once the battery is determined to be close to fully charged or fully charged. Likewise, if it is determined that the battery is not close to being fully charged, the switching device 230 may be operated such that it is opened, allowing the circuit 100 to regulate the charge current to the battery cell arrangement as described above.

[0059] With reference to FIG. 3, an embodiment of a battery module according to the present disclosure will now be described in more detail.

[0060] FIG. 3 illustrates schematically a battery module 300, including a current-limiting device 200 as described above with reference to FIG. 2, and a battery cell arrangement 310. The battery cell arrangement 310 has a first terminal 320 which is connected to the first output terminal 220 of the device 200, and a second terminal 322 which is connected to the second output terminal 222 of the device 200. The battery module 300 may further be connected to a charger 340, using the first input terminal 210 and the second input terminal 220 of the device 200. The charger 340 may provide the voltage V.sub.charge across the input terminals 220, 222 of the device. The battery cell arrangement 310 includes one or more battery cells 330, which may for example include lithium or lithium-ions. The one or more battery cells 330 may for example be Lithium cells, but it is envisaged also that other battery technologies may be used for the battery cells 330 of the battery cell arrangement 310.

[0061] With reference to FIG. 4, an embodiment of a battery module according to the present disclosure will now be described in more detail.

[0062] FIG. 4 illustrates schematically a battery module 400. The module 400 includes a first input/charging terminal 210 and a second input/charging terminal 212, and the input/charging terminals 210, 212 may for example be connected to a charger in order to provide a charging voltage V.sub.charge across the terminals 210, 212.

[0063] The module 400 includes a battery cell arrangement 310, wherein a first terminal 320 of the arrangement 310 is connected to the first input terminal 210 of the module 400, and wherein the battery cell arrangement 310 includes one or more battery cells 330 as discussed above in relation to the module 300 described with reference to FIG. 3.

[0064] The module 400 includes a DC-to-DC converter 120, which as described earlier herein may for example be a boost-converter, a step-up converter, or similar, such as the converter 120 described with reference to FIG. 1c. The converter 120 has a first input terminal 150, a second input terminal 152 and an output terminal 154. As described earlier herein, the second input terminal 152 may also serve as an output terminal, making the terminal 152 a combined input/output terminal. The converter 120 is configured to transform an input voltage provided at the input terminals 150 and 152 to an output voltage at the output terminal 154, where the output voltage is higher than the input voltage.

[0065] In particular, an EMC/EMI filter in form of a trifilar choke 130 is arranged such that it connects the converter 120 to the rest of the module 400. As e.g. discussed in relation to the embodiments of the circuits 100, 101 described with reference to FIGS. 1a and 1c, the trifilar choke 130 includes a first inductor 140, a second inductor 142 and a third inductor 144, all wound on a same core (as indicated by the dashed lines under each inductor) and mutually coupled (as indicated by the dots at each inductor) such that a magnetic field induced by a current passing through one inductor effects a current passing through one or more of the other inductors, and vice versa. As further indicated by the location of the dots above each inductor, the trifilar choke 130 is arranged in a common-mode rejection fashion, such that equally large currents passing through e.g. the first inductor 140 and the second inductor 142, and/or e.g. in the second inductor 142 and the third inductor 144, in a same direction will induce equal and in-phase magnetic fields which will add up, and result in a high impedance of the trifilar choke 130 for such currents. Phrased differently, the trifilar choke 130 will allow currents to flow in opposite directions in e.g. the first inductor 140 and the second inductor 142, and/or in the second inductor 142 and the third inductor 144, and the trifilar choke 130 will block corresponding currents which flows in a same direction, leading to a common-mode rejection filtering which reduces EMI otherwise caused by the converter 120 and which thereby improves the EMC of the module 400.

[0066] The converter 120 is connected to the first terminal 320 of the battery cell arrangement 310 via the third inductor 144. A switching device 230 is provided between the ends of the inductors 140 and 142 not connected to a respective input terminal 150 and 152 of the converter, and the respective ends of the inductors 140 and 142 are also connected to the second input terminal 212 of the module 400 and the second terminal 322 of the battery 310, respectively (as illustrated in FIG. 4).

[0067] It should be noted that the battery module 400 as described with reference to FIG. 4 is the same as e.g. the battery module 300 described with reference to FIG. 3, but where the various components/constituents are shown directly instead of being implicitly included in objects such as “the circuit 100/101” and/or “the charge-limiting device 200”.

[0068] The battery module 400 may also be provided with a further switching device 430, which may be operated such that it is open (blocking) while the battery cell arrangement 310 is being charged (e.g. when a charger is connected to the input terminals 210, 212 of the module 400), and e.g. such that it is closed (conducting) when the battery cell arrangement 310 is not being charged and e.g. instead connected to a load through which the battery cell arrangement 310 is to be discharged. It is envisaged, also, that the module 400 may be simultaneously connected to both a charger and a load (e.g. such that the charger and the load are connected in parallel). The further switching device 430 may then for example be used to control whether the battery cell arrangement 310 is to be charged or discharged. The further switching device 430 may be optional.

[0069] The present disclosure also provides a method of noise filtering when regulating a charge current in a battery module using a DC-to-DC converter. The method includes the steps taken to provide the connection of the trifilar coil at the converter as described e.g. with reference to FIGS. 1a, 1b, 2, 3 and 4, and includes also providing the charging voltage at the input/charging terminals of the battery module.

[0070] Although not illustrated in any of Figures, it is envisaged that in the embodiments of the various circuits, current-limiting devices, battery modules and methods as disclosed herein, additional circuitry may be provided for controlling the various switching elements, switching devices and modulation sections as needed.

[0071] While referring to the embodiments shown in FIGS. 1a, 1b, 1c, 2, 3 and 4, further details and alternatives about the DC-DC converter 120, its possible connections in e.g. the battery module 300, 400 and its functionality may be of the type described in the International patent application PCT/EP2016/063144 by the same applicant. The same applies also to the charging functionality of the charge-limiting device 200 and the battery modules 300, 400, where further details and alternatives are also to be found in the above referred to International patent application. Accordingly, the content of International patent application PCT/EP2016/063144 is herein incorporated in its entirety.

[0072] However, the present disclosure improves on previous teachings by introducing the trifilar choke. In particular, the placement of the trifilar choke directly at the terminals of the converter results in currents always flowing only in one direction in each inductor during normal operation of the battery module. This introduces balanced currents in the inductors of the choke during normal operation, and provides common-mode rejection filtering in order to reduce unwanted EMI from e.g. the switching within the converter. This enhances the EMC of the battery module. In addition, the placement of the trifilar choke directly at the converter terminals, and not e.g. at the input terminals of the battery module, avoids having to run/pass the full charge current (e.g. the current provided by the charger) to the battery through all or some parts of the choke. This reduces the rating requirements of the choke, prevents a saturation of the core of the choke and allows the choke to be made more cost and area effective.

[0073] The person skilled in the art realizes that the present disclosure is by no means limited to the embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

[0074] Although features and elements are described above in particular combinations, each feature or element may be used alone without the other features and elements or in various combinations with or without other features and elements.

[0075] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain features are recited in mutually different dependent claims does not indicate that a combination of these features cannot be used to advantage.