WO2012029024A1

WO2012029024A1 - Electrical circuit for charging a battery

Info

Publication number: WO2012029024A1
Application number: PCT/IB2011/053793
Authority: WO
Inventors: Axel Krause
Original assignee: Brusa Elektronik AG
Current assignee: Brusa Elektronik AG
Priority date: 2010-08-31
Filing date: 2011-08-30
Publication date: 2012-03-08
Anticipated expiration: 2013-02-28

Abstract

The invention relates to an electrical circuit (1 ) for charging at least one battery (8), having a charging device (3) which comprises an input (2) for connecting to an AC voltage source and two battery-side output poles (4a, 4b) for providing a charging current, and having two connection poles (6a, 6b) for connecting to a battery (8), wherein a filter formed from a capacitor (C1 ) and an inductor (L) is provided between the output poles (4a, 4b) of the charging device (3) and the connection poles (6a, 6b) for a battery (8). To reduce the load on the battery and to extend the service life thereof, the capacitor (C1 ) is connected in parallel with the charging device output poles (4a, 4b) and the inductor (L) is connected between a battery connection pole (6a) and the equivalent pole of the capacitor (C1 ). Furthermore, a resonance capacitor (C2) is connected in parallel with the inductor (L).

Description

ELECTRICAL CIRCUIT FOR CHARGING A BATTERY

[0001 ] This application claims benefit of priority to prior U.S. provisional application no. 61/378,973 filed on September 1 , 2010, and as a non-provisional thereof; this application also claims benefit of priority to prior European application no.

EP10174714 filed on August 31 , 2010; the entirety of European application no. EP10174714 and of U.S. application no. 61/378,973 are expressly incorporated herein by reference in their entirety, for all intents and purposes, as if identically set forth herein.

[0002] The invention relates to an electrical circuit for charging at least one battery, having a charging device which comprises an input for connecting to an AC voltage source and two battery-side output poles for providing a charging current, and having two connection poles for connecting to a battery, wherein a filter formed from a capacitor and an inductor is provided between the output poles of the charging device and the connection poles for a battery and wherein the capacitor is connected in parallel with the charging device output poles and the inductor is connected between a battery connection pole and the equivalent pole of the capacitor.

[0003] The invention relates in particular also to an electric vehicle, in particular an electric car having at least one load such as an auxiliary motor, e.g. for a circulating pump, having a heater, a radio, an air conditioning unit, lights, electronics or similar, and having a battery for supplying the load.

[0004] Powerful voltage transformers which are run from the AC mains and generate a DC voltage at their output must satisfy a series of internationally standardised regulations, so that they do not disrupt the operation of other devices and do not adversely affect the quality of the mains voltage. Particularly at high power levels in the kW range, such as are necessary for example in charging devices for electric vehicles, the requirement for a low harmonic content of the mains input current is key. [0005] In the ideal case a voltage transformer on the main supply behaves like a resistance, i.e. the current drawn from the mains supply at any instant is

proportional to the input voltage. If this is sinusoidal, which is normally the case, then the current drawn is also purely sinusoidal and therefore contains no additional harmonics.

[0006] Standing in contrast to this is the case in which the charging of an electrical energy storage device (here a capacitor) takes place directly from a mains rectifier without a power-factor correction (PFC); the current is drawn in short pulses and therefore contains many harmonics.

[0007] In order to prevent this, a PFC-circuit is normally connected between the rectifier and the capacitor. This is a step-up converter, which is controlled such that the current drawn from the mains supply has the same shape as the mains voltage, that is, it is sinusoidal.

[0008] A consumer connected to the single-phase AC mains supply does not draw a continuous level of power, but a pulsating one at double the mains frequency. For a sinusoidal mains voltage, with an Ohmic consumer or a voltage transformer with PFC a sinusoidal mains current is produced at the input. The mains power is equal to the product of current and voltage: and therefore has the temporal profile of a sine-square function. This means that the power transmitted pulsates at twice the mains frequency. Further below, an example trace resulting from an Ohmic load is illustrated, which draws 16A_eff from the 230V mains.

[0009] For charging devices in electric vehicles additional requirements apply: they must be small, light and robust and nevertheless supply the energy drawn from the mains to the battery with the smallest possible losses. A potential isolation between mains and battery is strictly recommended for reasons of safety and

electromagnetic compatibility (EMC). In addition, as with all automobile components there is a very strong cost pressure and also a demand for operational safety in a large temperature range. [0010] On account of these conditions the charging device is configured as simply as possible. In particular, the power drawn from the mains is transmitted directly to the battery, and so there is normally no attenuation or filtering of the pulsed power described above. The battery is therefore charged with pulsed current.

Conventional batteries tolerate this pulsed charging, as long as the charging supplies energy continuously and no pulsating discharging occurs between the charging pulses.

[001 1 ] It can then happen that during the charging process of such a battery in a vehicle, a consumer is connected to the battery which draws a noticeable current but which is typically smaller than the charging current; thus the battery overall still becomes charged over time, namely with the output current of the charging device minus the consumer current. However, due to the current supply to the battery being only a pulsed one, this can result in a change in the current direction on the battery side and therefore in a pulsating discharge between the charging pulses.

[0012] It can now be the case that, due to these 100Hz-charging / discharging processes ("nano-cycles"), the battery ages more quickly. While in the prior art described below different charging devices are described, the problems inherent in the charging of a battery which is simultaneously loaded by a consumer, are not recognised or considered however, and in any case not mentioned.

[0013] FR2694144A1 discloses a charging device for a battery and its application for electric vehicles. An AC voltage is applied to the input of the charging device. The charging device further comprises a rectifier, a chopper and a transformer. An output filter has the form of a CL element. However, there is still considerable ripple expected at the output of the charging device. This ripple has a disadvantageous effect on the battery and its life-time. [0014] EP564726A1 discloses a charging circuit for charging a battery from an AC source. This document shows a similar CL element as the preceding document. However, this CL filter is also not appropriate to reduce ripple in a considerable manner. [0015] US20030102845A1 discloses a fast charger for high capacity batteries comprising a rectified AC input, an optional power factor corrected input and an output filter in the form of an LC element. In such chargers the ripple at the output has considerable values reducing the life-time of batteries.

[0016] US20070153560A1 discloses a portable charger with power factor correction capability for use with electric vehicles. As in the aforementioned document considerable ripple occurs at the output of the charging device. [0017] Document US 7,583,056 A relates to a circuit for balancing out the charging processes in multiple batteries and discloses (in the description of the prior art) charging devices for batteries consisting of a rectifier, a filter capacitance, a switching circuit, a transformer and a rectifier. A low-pass filter in the form of an LC element is connected upstream of the battery set to be charged. In Figures 4, 6 and 8, LC elements are also provided between the actual charging device and the battery.

[0018] This document however is not concerned with the problem of a DC load connected to the battery at the same time and possibly switched on during the charging process. Therefore this offers no solution either to the problem indicated above of the pulsating intermediate discharge due to the charging current on the battery side being only pulsed.

[0019] DE 19 534 174 A1 relates to a method and a device, in connection with electric vehicles, for charging a battery supplying the electric motor, which is charged up by means of a supply voltage. The special features of this are that this supply voltage is smoothed using an LC element and that the inductance of the LC element is formed by the exciter coil 3 of the electric motor. [0020] This document, similarly to the previous one, uses an LC element connected immediately upstream of the battery to smooth the charging current. However, the electric motor either must not or cannot be switched on during the charging. Switching between charging operation and motor operation takes place by means of directional contacts. [0021 ] DE 4 228 480 A1 does not relate to charging processes, but discloses a DC supply with a filter in combination with a mains supply unit for a tactical radio device. The DC supply device supplies DC voltages which are not affected by interference sources, such as for example the interference currents occurring in the switching frequency range of the DC voltage transformer. In fact, the part referred to as "LC filter" is simulated by means of a capacitively switched transistor and capacitors, that is, it is formed from coil-less means. The problem of a battery that is to be charged under simultaneous loading of the battery by a load is not discussed in this document either, however.

[0022] DE 69 421 408 T2 relates to the supply of current to battery operated devices, such as for example laptop computers, mobile telephones, pocket calculators, etc., and in this case primarily the conversion of the voltage output by the batteries into a voltage required by the circuit of the device. In this connection Fig. 2 shows a diagram of a DC -DC converter with pulse width modulation switching regulation. At the end of the diagram a low-pass filter is provided in the form of an LC element. [0023] Since this document does not relate to the charging of the battery itself, but to the supply of consumers by this battery, it cannot contribute to the solution of the present problem.

[0024] DE 20 2006 010 91 1 U1 discloses a switching power supply unit, in particular a wide-range power supply unit for supplying measurement transducers in slim construction modular housings This consists of a mains rectifier, an input filter, a switching controller and a potential isolation device. The input filter arrangement consists of two LC filters. [0025] These LC filters only affect the supply current indirectly, since they are located on the left-hand side (upstream) of the potential isolation device. The charging of batteries while simultaneously operating under load does not form part of the subject matter of this document either. [0026] The publication "Harmonics and Torque Ripple Minimization using L-C Filter for Brushless DC Motors", International Journal of Recent Trends in Engineering, Vol. 2, No. 5, 2009 discloses an LC filter at the interface between the motor and the drive unit in connection with brushless DC motors (BLDCM). The LC filter functions as a low-pass filter and minimises the harmonic content in the voltage supply of the motor and the inductor connected in series counteracts sudden changes in the current due to electrical switching and thereby reduces the torque ripple. [0027] This document however does not relate to charging processes of batteries either, so that no teaching can be taken from it that is relevant to this issue.

[0028] One idea that can be gathered from the first cited document is to provide an LC element before the supply to the battery for smoothing the charging current. This measure however, purely in view of the fact that one or more consumers are operated during the charging process of the battery, does not provide a satisfactory solution to the reduction of the ripple current.

[0029] This strongly pulsating power loads all subsequently connected consumers at this frequency and with the accordingly widely varying power, as long as the consumers are not operated by the battery in the same rhythm, so that the battery serves as an energy buffer for the consumers. It is precisely this buffer action however which loads the battery and reduces its service life. An already partially charged battery can buffer this effect in consumers. This buffering however, as already mentioned, leads to partial discharges of the battery at a rhythm that is twice the mains frequency, which is undesired and reduces the service life. This disadvantageous effect is the greater the lower the charge of the battery.

[0030] Put another way, the ripple-shaped charging current in the prior art does not deliver sufficient energy during the entire period to operate a DC consumer attached in parallel to the battery, with the result that - as already mentioned - during the power minima of the pulsating charging current, current is drawn from the battery. [0031 ] The object of the invention consists in overcoming these disadvantages and in providing an electrical circuit which eliminates the ripple current (also known as charging current ripple), or at least reduces it at the battery side, when a load is switched on, to the extent that when consumers are operated with powers below the charging power of the charging device, no change occurs in the direction of the current. This solution is also in particular intended to be applicable to simply constructed charging devices, the weight of which is small from the outset. The solution according to the invention itself is also intended to weight-saving, space- saving and inexpensive - requirements which are accorded the highest priority in automobile construction.

[0032] This objective is achieved with an electrical circuit of the type described above by connecting an additional capacitor (resonance capacitor) in parallel with the inductor.

[0033] This measure means that, with appropriate design of the capacitor and the inductor, the charging current available at the battery can be made largely ripple- free, so that the frequency of the mains voltage applied to the charging device has no negative effects on the battery itself, since the charging current is now - in general - above the value of the consumer current of the load for the whole time.

[0034] This measure enables the frequency which forms the main component of the ripple to be filtered out. The resonance filter formed by the additional

(resonance) capacitor and the inductor then has the effect that the frequency which represents the main component of the current ripple is prevented from reaching the battery. The combination of a resonance capacitor with the CL-filter gives an optimized solution for saving batteries during charging process.

[0035] The additional resonance capacitor forms together with the inductor a resonance filter. The resonance filter may be dimensioned such, that the main ripple in the output voltage of the charging device is reduced in a considerable manner. The dimension of the capacitor is adapted such, that the resonance frequency of the resonance filter matches the frequency of the main ripple component. [0036] Preferably, the resonance filter formed by the resonance capacitor and the inductor has a resonance frequency of essentially double the mains frequency at which the charging device is operated.

[0037] The essential advantage of the invention consists in the fact that consumers supplied by the battery can be switched on during the charging process without the charging current into the battery changing its sign or showing substantial rippling. This prevents a partial pulsating discharge of the battery from occurring.

[0038] Preferably, the circuit comprises load-connection poles for connecting a load. Here the load can be connected or coupled to the circuit at particular preferred points, which means both that the load can be supplied with DC current and the battery with correspondingly ripple-free charging current.

[0039] The advantageous effect of the additional resonance capacitor (in parallel to the inductor) has to be seen in connection with the special sequence of elements: charging device - capacitor - inductor - battery, so that here it is actually a case of a "CL element". Together with the additional resonance capacitor a CLC filter is formed. The reason for the special sequence of the capacitor C and inductor L is based on the reversed distribution of the impedance ratios: [0040] In most applications a low-impedance source that is subject to a ripple voltage (rectifier output) is connected to a consumer of high impedance (resistor, motor). The intermediate LC filter forms a voltage divider for the ripple frequency, so that only a small part of the ripple voltage gets through to the load. [0041 ] In the case of the invention by contrast, a high-impedance source subject to a ripple current (charging device output) is connected to a low-impedance consumer (battery). The intermediate CL filter forms a current divider for the ripple frequency, so that only a small part of the ripple current gets through to the battery. [0042] The essential feature of one embodiment of the invention consists in the fact that the capacitor with its two connection poles is directly connected to the charging device and at most one pole of the load is directly connected to the capacitor, while the other load pole is connected to the capacitor via an inductor (e.g. choke coil). This means that the resonance frequency of the LC combination is significantly less than double the mains frequency.

[0043] The charging device itself can have a potential isolation device or not, however a PFC function (as is always implemented also) is of great advantage. Furthermore, the charging device either contains no, or very low, energy storage; hence it transmits the supplied mains power directly and therefore supplies an output current which behaves according to a sin²- function at double the mains frequency (thus, 100Hz or 120Hz). The minimum requirement on the charging device is to provide a charging current, that is to say a current, which does not change its sign over time. [0044] The task of the filter then is to prepare the charging current coming from the charging device, in the above case to reduce this sin² function of the output current (CL filter) or practically to eliminate it (CLC filter), so that the load (battery) can be operated practically with pure (i.e. ripple-free) DC current. [0045] In the application in an electric vehicle, both the CL filters according to the invention and the charging device are integrated into the electric vehicle and preferably represent a constructional unit.

[0046] The "load" is an additional consumer in parallel to the battery (which of course for the charging device represents the main load). This "load" can be a motor (e.g. for driving a coolant compressor), a heater, a fan, radio, GPS device, computer, headlight, interior lights, etc..

[0047] The expression "connection pole" refers not only to a physical connection in the sense of a mating plug connection or the like, but as well as the meaning of joining together it also includes the meanings of input, output, pole, conductor, connection, etc. E.g., the item between the part referred to as a charging device and the filter formed from the inductor and capacitor can be a fixed connection or a constructional unit. [0048] Likewise, items considered to be included under the term "battery" are battery sets, consisting of multiple batteries connected together, accumulators and the like.

[0049] Preferably, the resonance filter formed by the resonance capacitor has a resonance frequency of essentially double the mains frequency at which the charging device is operated. For an application in Europe therefore, the result is a resonance frequency of essentially 100 Hz. This takes account of the fact that the European mains frequency of 50 Hz at the output of the charging device causes a ripple current at 100 Hz. In USA and parts of Japan the mains frequency is 60Hz, accordingly the resonance frequency is set to essentially 120Hz.

[0050] In one embodiment the battery connection poles also act as the load connection poles at the same time.

[0051 ] In one embodiment the load connection poles are linked to the poles of the capacitor, which means that the load current does not go through the filter. This means in particular that the filter inductor can be dimensioned smaller and lighter.

[0052] In one embodiment one of the load connection poles coincides with the equivalent battery connection pole and the other load connection pole is linked to the pole of the capacitor to which the inductor is connected. This prevents the load current from going through the filter.

[0053] As an extension of the preceding embodiment, a capacitor is connected in parallel to the load.

[0054] The charging device comprises a rectifier, so that a charging current is provided in a straightforward manner at the output poles without changes of sign. In one embodiment the output of the rectifier acts simultaneously as the input of the filter formed by the capacitor and the inductor. [0055] In one embodiment the charging device comprises a power-factor correction circuit.

[0056] In one embodiment the charging comprises a potential isolation device, preferably consisting of a PWM DC-AC converter, a transformer and a rectifier.

[0057] In one embodiment no branching is provided in parallel with the battery connection poles between the inductor and the battery connection pole connected to the inductor. Such an embodiment can then be used if the filter is hard-wired to the battery.

[0058] In one embodiment the inductor is a choke.

[0059] In one embodiment, the charging device and the filter formed from the capacitor or capacitors and the inductor represents a constructional unit, which simplifies installation and replacement and minimises weight.

[0060] In one embodiment a battery is connected to the battery connection poles and a load, such as for example a motor, a heater, a radio, an air conditioning unit, a computer controller, a light source or similar is connected to the load connection poles.

[0061 ] A vehicle according to the invention, in particular a car, is characterized in that the vehicle has an electrical circuit according to the invention, and that the battery is connected to the battery connection poles and the load to the load connection poles.

[0062] The invention is particularly suited to two-phase charging devices, since with three phases no ripple typically occurs. The circuit according to the invention eliminates the ripple current at the output of the charging devices; regardless of this, the regulations for the harmonics at the mains input must be observed.

However it is such that even for small charging devices requiring no PFC, the filter reduces the amplitude of the charging current ripple. [0063] Further embodiments of the invention are indicated in the Figures and in the dependent claims. The list of reference marks and the Claims form part of the disclosure.

[0064] Using the Figures the invention will now be explained in more detail by means of symbols and examples. The Figures will be described in combination and taken as a whole. Equivalent reference marks indicate identical components, and reference marks with different indices indicate functionally equivalent or similar components.

[0065] The drawings show:

[0066] Fig.1 - a voltage supply for a load consisting of a rectifier according to the prior art,

[0067] Fig.2 - a voltage supply as in Fig. 1 with an additional PFC circuit

[0068] Fig.3 - the trace of the mains voltage and the traces of the mains currents with and without PFC,

[0069] Fig.4 - a charging device for a battery according to the prior art,

[0070] Fig.5 - the trace of the mains power in a charging device according to the prior art,

[0071 ] Fig.6 - the trace of the charging current in a charging device according to the prior art,

[0072] Fig.7 - a circuit according to the invention with a CL filter,

[0073] Fig.8 - a variant of Fig. 7,

[0074] Fig.9 - a circuit according to the invention with a resonant CLC filter,

[0075] Fig.10 and 1 1 - variants of Fig. 9,

[0076] Fig.12 - the trace of the charging current of a circuit according to Fig. 7 with and without filter,

[0077] Fig.13 - the trace of the charging current of a circuit according to Fig. 9 with and without filter,

[0078] Fig.14 - the trace of the charging current of a circuit according to Fig. 10 before and after the filter, or with and without filter with no load at high charging current, [0079] Fig.15 - the trace of the charging current of a circuit according to Fig. 10 with and without filter at low charging current with load,

[0080] Fig.16 - the amplitude ratio and the phase angle of a 100 Hz filter as a function of the frequency of a circuit according to Fig. 7.

[0081 ] Fig. 17 - the frequency-dependent amplitude ratio in a comparison of two different circuits.

[0082] Fig.18 - a vehicle according to the invention.

[0083] In order to better understand the mode of functioning of the solutions according to the invention, in terms of the problems associated with the charging current ripple in the prior art, the previous situation found in the prior art is explained in further detail in Fig. 1 to 6.

[0084] Figure 1 shows a charging device according to the prior art consisting of a rectifier and a capacitor connected in parallel with the load. Figure 2 shows an improved charging device with a PFC-circuit. Fig. 3 shows the temporal trace of the mains voltage and the mains currents of both circuits. The PFC circuit causes the current drawn by the mains to have the same profile as the mains voltage, that is, it is sinusoidal. The short pulses, which contain many harmonics, have disappeared.

[0085] Figure 4 shows a further improved charging device, which in addition to the PFC circuit also comprises a potential isolation device. This consists of a PWM DC- AC converter, a transformer and a rectifier. [0086] Figure 5 shows the temporal trace of the mains voltage, the instantaneous power, the mean power and the mains current. Figure 6 shows the charging current obtained therefrom with a charging device according to the prior art, which displays a sin² function, hence a frequency of 100 Hz (at a mains voltage of 50 Hz). The charging current shown in Figure 6 is now the starting point for the invention and is to be further conditioned.

[0087] Figure 7 shows a possible circuit 1 to partially overcome the problems arising from the charging devices of Figs. 1 to 6, the circuit 1 having an input 2 for connecting an AC voltage source U_N, a charging device 3 with two battery-side output poles 4a, 4b for providing a charging current, a filter consisting of a capacitor or capacitance C1 and a choke coil or inductor L, and having connection poles for a battery 8, which serves to supply a consumer or load 9. The filter serves to condition the charging current coming from the charging device 3.

The capacitor C1 is connected in parallel with the charging device output poles 4a, 4b, i.e. when a charging device 3 is connected, the capacitor C1 is in parallel with the charging device 3. The inductor L is connected between a battery connection pole 6a and one pole of the capacitor C1 . The inductor L connects equivalent poles of battery 8 and capacitor C1 , and is thus connected serially between charging device 3 and battery 8, or battery connection poles. In the embodiment shown, apart from the inductor L there are no further electrical components located between the battery connection pole 6a and the pole of the capacitor C1 . The invention is characterized in particular by the special sequence of its components: charging device - capacitor - inductor - connection poles for the battery.

Furthermore, the circuit comprises load connection poles 7a, 7b for connecting to a consumer or load 9.

[0088] Preferably, no branching is provided in parallel with the battery connection poles 6a, 6b between the inductor L and the battery connection pole 6a connected to the inductor L.

[0089] With e.g. C1 = 2.24mF and L=5.75mH, only 25% of the original current ripple remains. [0090] Figure 12 shows the behaviour of such a circuit when a consumer is switched on at the same time. As a comparison the unfiltered current is shown, that is to say without the filter formed from the capacitor and the inductor. This can become negative when a consumer (load) is switched on at the same time, which leads to premature ageing of the battery. By installing a filter according to the invention, the charging current (in Figure 12 labelled as battery current) entering the battery obtains a profile with no changes of sign and with a sharply reduced ripple, and maintains this shape even when a consumer is switched on. [0091 ] Figure 16 illustrates the effect of a CL filter according to Figure 7.

Frequencies well below the resonance frequency (here 45Hz) are sharply reduced; at 100Hz the amplitude ratio between output and input current ripple is now 0.25; the current ripple at the battery is therefore only 25% of the value that is found at the output of the charging device.

Figure 8 shows another solution, in which the load 9 is applied directly to the poles of the capacitor C1 . This measure means that the filter (in particular the choke) is dimensioned for smaller currents, since the load current no longer goes through the filter.

[0092] Figure 9 shows a circuit according to the invention, in which a resonance capacitor C2 is connected in parallel with the inductor L. The ripple with is filtered by the CL filter according to Fig. 7 is further reduced by the resonance capacitor C2 of Fig. 9 forming - together with the inductor L - a specially dimensioned resonance filter. Preferably, the resonance filter has a resonance frequency corresponding to the double of the mains frequency of the AC source, since the main ripple component arises from that AC frequency. At a mains voltage frequency of 50 Hz the resonance filter formed by the resonance capacitor C2 preferably has a resonance frequency of essentially 100 Hz. This resonance filter then has the effect that the frequency which represents the main component of the current ripple is prevented from reaching the battery.

[0093] With e.g. C1 = 2.24mF, C2=0.44mF and L=5.75mH, the current ripple at 100Hz is practically eliminated.

[0094] Figure 13 shows the effect of such a filter, wherein the charging current here entering the battery (in Figure 13 labelled as battery current) is constant over time, regardless of whether a load 9 has just been switched on or not. [0095] Figure 17 shows the ripple current ratio between output and input for comparison of the two circuits of simple filter (CL filter, in which C2=0) and resonance filter (CLC filter). This comparison shows that in the case of the resonance filter a substantially higher component is suppressed by the filter at frequencies in the region of 100 Hz. Figure 17 clearly reveals the advantages of the invention. There is an enormous reduction in the ripple output/input ratio, particularly in the region of the resonance frequency of the inventive resonance filter. [0096] Figure 10 shows, as a continuation of Figure 9, a further variant of the invention in which it is not the case that both of the battery connection poles 6a, 6b coincide with the load connection poles 7a, 7b. Here it is such that one of the load connection poles 7b coincides with the equivalent battery connection pole 6b, while the other load connection pole 7a is attached to the pole of the capacitor C1 to which the inductor L is connected. This is a case, so to speak, of a filter with a tap for the load connection.

[0097] A great advantage of this circuit is the fact that the load current for the consumer is not passed through the filter. This means that the filter as a whole, but in particular the inductor L, can be dimensioned smaller. At high current (= smaller load current) the choke L does indeed reach saturation, but this does not result in a negative charging current.

[0098] The effect of such a circuit is illustrated in Figures 14 and 15. Figure 14 shows that at high values, the charging current entering the battery only has a reduced ripple, since the effect of the filter is reduced by the saturation of the choke. By contrast, at low values where no saturation of the choke occurs and the filter acts in an optimal way, the charging current is substantially constant. In neither case however does a change of the sign of the charging current take place.

[0099] Fig. 1 1 shows an extension of Fig. 10, by a capacitor C3 being connected in parallel with the load 9. This advantageously ensures a further smoothing of the load current. In particular, the capacitor C1 can be dimensioned correspondingly smaller, if it is guaranteed that the capacitor C3 (e.g. integrated in the load) is always connected.

[0100] Figure 18 shows the application of the invention in a vehicle, e.g. a car. Here, multiple consumers or loads 9 can be connected to a circuit 1 according to the invention, or to the battery 8. [0101 ] List of reference marks

1 - electrical circuit

2 - input

3 - charging device

4 - output poles

4a - output pole

4b - output pole

5 - filter

6a - battery connection pole

6b - battery connection pole

7a - load connection pole

7b - load connection pole

8 - battery

9 - load

10 - vehicle

C1 - capacitor

C2 - resonance capacitor

C3 - load capacitor

L - inductor

LI_N - mains voltage

Claims

1 . Electrical circuit (1 ) for charging at least one battery (8), having a charging device (3) which comprises an input (2) for connecting to an AC voltage source and two battery-side output poles (4a, 4b) for providing a charging current, and having two connection poles (6a, 6b) for connecting to a battery (8), wherein a filter formed from a capacitor (C1 ) and an inductor (L) is provided between the output poles (4a, 4b) of the charging device (3) and the connection poles (6a, 6b) for a battery (8), and wherein the capacitor (C1 ) is connected in parallel with the charging device output poles (4a, 4b) and the inductor (L) is connected between a battery connection pole (6a) and the equivalent pole of the capacitor (C1 ), characterized in that a resonance capacitor (C2) is connected in parallel with the inductor (L).

2. The electrical circuit according to Claim 1 , characterized in that the circuit (1 ) comprises load connection poles (7a, 7b) for connecting to a load (9).

3. The electrical circuit according to Claim 1 or 2, characterized in that the resonance filter formed by the resonance capacitor (C2) has a resonance frequency of essentially double the mains frequency at which the charging device is operated.

4. The electrical circuit according to one of Claims 2 to 3, characterized in that the battery connection poles (6a, 6b) simultaneously form the load connection poles (7a, 7b).

5. The electrical circuit according to one of Claims 2 to 3, characterized in that the load connection poles (7a, 7b) are attached to the poles of the capacitor (C1 ).

6. The electrical circuit according to one of Claims 2 to 3, characterized in that one of the load connection poles (7b) coincides with the equivalent battery connection pole (6b) and that the other load connection pole (7a) is attached to the pole of the capacitor (C1 ) to which the inductor (L) is connected.

7. The electrical circuit according to Claim 6, characterized in that a further capacitor (C3) is connected in parallel with the load (9).

8. The electrical circuit according to one of the preceding claims, characterized in that the charging device (3) comprises a rectifier.

9. The electrical circuit according to one of the preceding claims, characterized in that the charging device (3) comprises a power-factor correction circuit (PFC).

10. The electrical circuit according to one of the preceding claims, characterized in that the charging device (3) comprises a potential isolation device preferably consisting of a PWM DC-AC converter, a transformer and a rectifier.

1 1. The electrical circuit according to one of the preceding claims, characterized in that no branching is provided in parallel with the battery connection poles (6a, 6b) between the inductor (L) and the battery connection pole (6a) connected to the inductor (L).

12. The electrical circuit according to one of the preceding claims, characterized in that the inductor (L) is a choke.

13. The electrical circuit according to one of the preceding claims, characterized in that the charging device (3) and the filter formed from the capacitor (C1 ) and the inductor (L) and, where appropriate, from the resonance capacitor (C2), constitute a constructional unit.

14. The electrical circuit according to one of Claims 2 to 13, characterized in that a battery (8) is connected to the battery connection poles (6a, 6b) and at least one load (9), such as for example a motor, a heater, a radio, an air conditioning unit, a computer controller, lights or similar is/are connected to the load connection poles (7a, 7b).

15. A vehicle, in particular an electric vehicle, e.g. a car, having a load (9), such as an electric motor, a heater, a radio, an air conditioning unit, a computer controller, lights or similar, and a battery (8) for supplying the load (9), characterized in that the vehicle comprises an electrical circuit (1 ) according to one of Claims 1 to 14 and that the battery (8) is connected to the battery connection poles (6a, 6b) and the load (9) is connected to the load connection poles (7a, 7b).

16. A charging circuit comprising:

a charging unit, said charging unit having an AC-voltage input;

said charging unit having a first output pole;

said charging unit having a second output pole;

a first connection pole electrically communicating with said first output pole, said first connection pole electrically connected to a first battery pole;

a second connection pole electrically communicating with said second output pole, said second connection pole electrically connected to a second battery pole; a filter provided between said first and second output poles, said filter having a first capacitor connected across said first and second output poles, said filter having an inductor connected between said connection of said first capacitor to said first output pole and said first connection pole; and,

a resonance capacitor connected in parallel with said inductor.

17. A charging circuit as claimed in claim 16, further comprising:

a resonance filter formed by said resonance capacitor, said resonance filter having a resonance frequency essentially double the AC-voltage mains frequency input to said AC-voltage input of said charging unit.

18. A charging circuit as claimed in claim 16, further comprising:

a first load connection pole; and,

a second load connection pole.

The charging circuit as claimed in claim 18, wherein:

said first load connection pole is located at said first battery pole; and, said second load connection pole is located at said second battery pol

20. The charging circuit as claimed in claim 18, wherein:

said first load connection pole is located at said connection of said first capacitor to said first output pole; and,

said second load connection pole is located at said connection of said first 5 capacitor to said second output pole.

21. The charging circuit as claimed in claim 18, wherein:

said first load connection pole is in electrical communication with said connection of said first capacitor to said first output pole; and,

o said second load connection pole is located at said second battery pole.

22. A charging circuit as claimed in claim 21 , further comprising:

an electrical load connected between said first and second load connections poles; and,

5 a third capacitor connected in parallel with said electrical load.

23. A charging circuit as claimed in claim 16, further comprising:

said charging unit includes a rectifier.

24. A charging circuit as claimed in claim 16, further comprising:

said charging unit includes a power-factor correction circuit.

25. A charging circuit as claimed in claim 16, further comprising:

said charging unit includes a potential-isolation stage.

26. A charging circuit as claimed in claim 16, further comprising:

a pulse-width-modulated DC-AC converter included in said potential-isolation stage;

a transformer included in said potential-isolation stage; and,

a rectifier included in said potential-isolation stage.

27. A charging circuit as claimed in claim 16, further comprising:

said inductor being a choke.

28. A vehicular electrical assembly comprising:

a charging circuit, said charging circuit including a charging unit, said charging unit having an AC-voltage input;

said charging unit having a first output pole;

said charging unit having a second output pole;

a second connection pole electrically communicating with said second output pole, said second connection pole electrically connected to a second battery pole; a filter provided between said first and second output poles, said filter having a first capacitor connected across said first and second output poles, said filter having an inductor connected between said connection of said first capacitor to said first output pole and said first connection pole;

a resonance capacitor connected in parallel with said inductor;

said charging circuit having a first load connection pole;

said charging circuit having a second load connection pole; and,

a vehicle electrical load electrically connected across said first and second load connection poles.

29. The vehicular electrical assembly as claimed in claim 28, wherein:

said first load connection pole is located at said first battery pole; and, said second load connection pole is located at said second battery pole.

30. The vehicular electrical assembly as claimed in claim 28, wherein:

said second load connection pole is located at said connection of said first capacitor to said second output pole.

31 . The vehicular electrical assembly as claimed in claim 28, wherein:

said second load connection pole is located at said second battery pole.

32. A vehicular electrical assembly as claimed in claim 31 , further comprising: a third capacitor connected in parallel with said vehicle electrical load.

33. A vehicular electrical assembly as claimed in claim 28, further comprising: said charging unit includes a rectifier.

34. A vehicular electrical assembly as claimed in claim 28, further comprising: said charging unit includes a power-factor correction circuit.

35. A vehicular electrical assembly as claimed in claim 28, further comprising: a potential-isolation stage in said charging unit;

a transformer included in said potential-isolation stage; and,

a rectifier included in said potential-isolation stage.

36. A vehicular electrical assembly as claimed in claim 28, further comprising: said vehicle electrical load is selected from the group of vehicle electrical loads consisting of a motor, a heater, a radio, an air conditioning unit, a computer controller, and lighting.