FR3090243A1 - Electric circuit for charging a DC voltage source - Google Patents

Abstract

Electric circuit for charging a DC voltage source from an AC voltage network, the circuit comprising: a) an input receiving an AC voltage, b) a first output connected to the DC voltage source, and c) a transformer capacitive formed using several capacitors, arranged so as to electrically isolate the input from the first output of the circuit. Figure for the abstract: Figure 1

Description

Description

Title of the invention: Electric circuit for charging a DC voltage source

The present invention relates to an electrical circuit for charging a DC voltage source using an AC network. The invention applies in particular, but not exclusively, to charging a source of direct voltage used for the electrical supply of a propulsion engine of an electric or hybrid vehicle.

For various reasons such as safety, or the non-referencing between two voltage sources, it may be desirable to have electrical insulation between the AC electrical network and the DC voltage source charged by this electrical network. . For this purpose, it is known to use a magnetic transformer. Such a transformer has the disadvantage of having to use a magnetic core. The use of such a magnetic core generates bulk, an increase in weight, a significant cost and can be difficult to integrate into the electrical circuit.

There is a need to remedy the drawbacks associated with the use of a magnetic transformer.

The invention aims to meet this need and it achieves this, according to one of its aspects, using an electric circuit for charging a first source of DC voltage from a network of alternating voltage, the circuit comprising:

- an input receiving an alternating voltage,

a first output connected to the first DC voltage source, and

- a capacitive transformer formed using several capacitors, arranged so as to electrically isolate the input from the first output of the circuit.

Thanks to the invention as defined above, electrical insulation is produced between the input and the first output of the electrical circuit via capacitors.

It is thus possible to benefit from the advantages of non-referencing of the voltage or safety sources mentioned above without the need to have recourse to a magnetic core.

The circuit input can be connected to a connector, single-phase or multi-phase, allowing connection to the alternative network, the latter being for example an industrial electrical network managed by an operator. This alternative network can supply a voltage greater than 100V. It can be a single-phase or multi-phase network, for example three-phase.

The first DC voltage source has for example a voltage of value equal to 48V, or a voltage of value greater than 300V.

The capacitive transformer can be arranged in a single-phase part of the electrical circuit, the capacitive transformer then comprising a first and a second capacitor, the first capacitor being disposed on the phase and the second capacitor being disposed on the neutral.

Alternatively, the capacitive transformer can be arranged in a polyphase part of the circuit, in particular a three-phase part of the circuit, the capacitive transformer then comprising a plurality of capacitors so that each capacitor is respectively arranged on one phase or on the neutral. The capacitive transformer can then include a number of capacitors equal to the number of phases of this part traversed by alternating current incremented by 1.

According to a first example of implementation, the capacitive transformer can be arranged in a part of the circuit traversed by an alternating current at the frequency of the alternating network. The alternative network is for example at a frequency of 50Hz or 60Hz. According to a particular case of this first example of implementation, the capacitive transformer can be connected to the input of the circuit without the intermediary of a voltage converter.

In this particular case, the circuit may include a rectifier, possibly being an inverter / rectifier, and the capacitive transformer can be mounted between the input of the circuit and this rectifier. The rectifier is for example a voltage doubler. As a variant, the rectifier could be produced otherwise, for example via a Graetz bridge or an H-bridge.

In this particular case, the circuit may include a common mode filter. The rectifier can be mounted between the capacitive transformer and the common mode filter.

In this particular case, the circuit may include a differential mode filter. The common mode filter can be mounted between the rectifier and the differential mode filter. Alternatively, the relative positioning of these two filters can be reversed.

In this particular case, the differential mode filter can be directly connected to the first output of the circuit. As a variant, a DC / DC voltage converter can be fitted between the differential mode filter and the first output of the circuit. The DC / DC voltage converter is for example a series chopper or a parallel chopper. The DC / DC voltage converter uses, for example, switching cells, each being for example a switch which is controllable and bidirectional in current or not. Each switching cell is for example formed by a transistor such as a MOSEET or IGBT transistor, with an anti-parallel diode, which is or is not the intrinsic diode of this transistor.

According to a second example of implementation, the capacitive transformer can be arranged in a part of the circuit traversed by an alternating current at a frequency higher than that of the alternating network. The ratio between the frequency of the current flowing through this part of the circuit and the frequency of the alternating network can be greater than 5. The positioning of the capacitive transformer in a part of the circuit traversed by an alternating current at higher frequency can allow using to realize this capacitive transformer capacitors of reduced size and / or lower cost. The resonant inductor (s) associated with these capacitors can also be of reduced size and / or of lower cost.

According to this second example, the capacitive transformer can be connected to the input of the circuit by means of at least one rectifier, in particular an inverter / rectifier rectifying the alternating voltage applied to the input of the circuit. The rectifier uses, for example, switching cells, for example each being a switch that can be controlled and bidirectionally with current or not. Each switching cell is for example formed by a transistor such as a MOSFET or IGBT transistor, with an anti-parallel diode, which is or is not the intrinsic diode of this transistor.

In the second example, the circuit may include a common mode filter mounted between the input of the circuit and the aforementioned rectifier.

According to the second example, the rectifier is for example a lifting rectifier without bridge ("boost bridgeless converter" in English) This rectifier for example implements the power factor correction function ("Power Factor Corrector" in English ).

According to the second example, the circuit may include a second inverter, in particular a second inverter / rectifier. This second inverter can be mounted between the aforementioned rectifier and the capacitive transformer. The second inverter is for example controlled at a switching frequency between 200Hz and 100MHz.

According to the second example, the circuit can include a third rectifier, being in particular a third inverter / rectifier, and this third rectifier can be mounted between the capacitive transformer and the first output of the circuit. This third rectifier is for example a voltage doubler. If necessary, a DC / DC voltage converter can be mounted between the third rectifier and the first output of the circuit, for example to regulate the load current of the DC voltage source. This converter is for example a series or parallel chopper.

According to the second example, the circuit can allow the switching in the first rectifier and in the second inverter to be done at zero current, which eliminates the switching losses.

The invention is not limited to a circuit for charging a single source of DC voltage from the AC network, as explained below.

In combination with all of the above, the circuit can also allow the charging of a second DC voltage source, the circuit comprising: a second output connected to the second DC voltage source, and another capacitive transformer formed at using several capacitors, arranged so as to electrically isolate the input from the second output of the circuit.

This other capacitive transformer can be functionally mounted in parallel with that previously described. No capacitor belonging to this other capacitive transformer for example also belongs to the capacitive transformer previously described for the electrical isolation of the input and the first output.

The other capacitive transformer can be associated with components (inverter, rectifier, filter ...) as described with reference to the first example of implementation above or with components (inverter, rectifier, filter. ..) as described with reference to the second example of implementation above.

When the AC network allows two separate DC voltage sources to be charged, these two DC voltage sources may or may not have the same voltage value, for example 48V or a value greater than 300V. As a variant, these two sources of direct voltage can have different voltage values.

In all of the above, each capacitive transformer can be obtained using at least two layers of a printed circuit. This printed circuit can be used exclusively to make the capacitive transformer or also carry other electronic components. Each of these layers comprises for example a first electrically conductive area and a second electrically conductive area, the first electrically conductive area being electrically isolated from the second electrically conductive area, the two layers being arranged relative to each other, being especially superimposed, so that a capacitor is formed between the first electrically conductive area of a layer and the first electrically conductive area of the other layer and so that another capacitor is formed between the second electrically conductive area of one layer and the second electrically conductive zone of the other layer. It is thus possible to use existing components to produce the capacitive transformer, which is advantageous in terms of space. Between the two layers of the printed circuit is disposed a dielectric, for example epoxy resin.

At least one of the first electrically conductive areas, or even each second electrically conductive area, may have a spiral shape so as to define an inductance.

Each of the layers of the printed circuit can be planar.

As a variant, when the layers of a printed circuit are used to form the capacitive transformer, several first layers can be electrically connected to each other and several second layers can be electrically connected to each other, and these first and second layers are arranged with respect to each other so that between two first, respectively second, layers, is arranged a second, respectively first, layer so that a capacitor is formed between each first, respectively second, layer and the second, respectively first, layer. The global capacitor modeling all the capacitors thus formed in parallel between the first and second layers then defines a capacitor of the capacitive transformer. Each of the first and second layers may have a first electrically conductive area and a second electrically conductive area, as mentioned above, so that the relative arrangements of the first layers and of the second layers then make it possible to obtain two capacitors from the capacitive transformer.

In all of the above, the electrical circuit may or may not be reversible, a reversible circuit allowing the DC voltage source (s) to transfer electrical energy to the AC network.

The invention can be better understood on reading the description which follows of nonlimiting examples of implementation thereof and on examining the appended drawing in which:

• [Lig 1] is a schematic view of an electrical circuit according to a first example of implementation of the invention, • [Lig 2] is a schematic view of an electrical circuit according to a variant of the first example of implementation work of the invention, • [Lig 3] is a schematic view of an electrical circuit according to a second example of implementation of the invention, • [Lig 4] is an electrical circuit according to a third example of implementation of the invention, • [Lig 5] is a schematic view of an exemplary embodiment of a capacitive transformer, • [Lig 6] corresponds to the equivalent electrical diagram of the example of [Ligure 5], • [Lig 7] represents a variant of [Ligure 5] and, • [Lig 8] corresponds to the equivalent electrical diagram of the example of [Ligure

7].

There is shown in Ligure 1 an electrical circuit 1 according to a first example of implementation of the invention. This circuit 1 allows here the charging of a first source of direct voltage from an alternating network. The alternative network is for example an industrial electrical network managed by an operator and supplying a single-phase or polyphase voltage and frequency equal to 50Hz or 60Hz. In the example considered, the electrical network is single-phase and it is connected to an input 3 of the electrical circuit 1 by means of a connector not shown.

According to this first example, the circuit 1 comprises a rectifier 5 which is here a voltage doubler. This rectifier 5 comprises two diodes 8 and 9, the diode 8 being mounted between a connection point to a terminal of the input 3 and the positive terminal of the continuous output of the rectifier 5, while the diode 9 is mounted between the point above connection and the negative terminal of the continuous output of the rectifier 5. The rectifier 5 also comprises in the example described two capacitors 10 and 11, the capacitor 10 being mounted between a connection point to the other terminal of the input 3 and the positive terminal of the continuous output of the rectifier 5, while the capacitor 11 is mounted between the aforementioned connection point to the other terminal of the input 3 and the negative terminal of the continuous output of the rectifier 5. As a variant , the rectifier 5 could be made otherwise, for example via a Graetz bridge.

Still in the example of FIG. 1, the circuit 1 comprises a common mode filter 12 implementing capacitors 13, 14, 15 and 16 as well as coupled inductors 17 and 18. This common mode filter is connected to a differential mode filter 20 which includes an inductor 22 and a capacitor 23.

In the example of Figure 1, a series chopper 25 is mounted between the differential mode filter 20 and the first output 4 of the circuit 1, the latter being connected to the terminals of the first DC voltage source.

According to this first example of implementation, and in accordance with the invention, a capacitive transformer is provided. This capacitive transformer is here connected to the input 3 of the circuit 1 without the intermediary of a voltage converter. The capacitive transformer is thus traversed in this example by current which is at the frequency of the alternating network. The network being here single phase, the capacitive transformer is here formed by two capacitors 30 and 31, the capacitor 30 being disposed on the phase and the capacitor 31 being disposed on the neutral.

2 shows, very schematically a variant of Figure 1 in which the capacitive transformer is always disposed in a part of the circuit 1 traversed by an alternating current whose frequency is that of the alternating network. In the case of FIG. 2, the capacitive transformer is arranged in a part of the circuit which is three phase. It can be seen here that the capacitive transformer comprises four capacitors 30, 31, 32 and 33, the capacitors 30, 32 and 33 each being positioned on a phase of this part of the circuit while the capacitor 31 is positioned on the neutral of this part of the circuit 1.

We will now describe with reference to Figure 3 an electrical circuit 1 according to a second example of implementation of the invention. This electrical circuit 1 differs essentially from that which has just been described in that the capacitive transformer is no longer disposed in a part of the circuit in which a current flows at the frequency of the AC network. According to this second example of implementation, the capacitive transformer is mounted in a part of the circuit traversed by an electric current whose frequency is between 200Hz and 100MHz.

We see in the example of Figure 3 that several components are interposed between the input 3 of the circuit and the capacitive transformer.

Thus, a common mode filter 39 implementing two coupled inductors 40 and two capacitors 41 for connection to earth is directly connected to the input 3. A first inverter / rectifier 42 is connected at the output of this filter common mode, to rectify the alternating voltage applied to input 3 after filtering by the common mode filter 39. This first inverter / rectifier implements in this example switching cells 45, each being here formed by a transistor such that a MOSFET or IGBT transistor, with an anti-parallel diode, which is or is not the intrinsic diode of this transistor. This first inverter / rectifier is here a lifting rectifier without bridge implementing the power factor correction function (“PFC boost bridgeless converter” in English) and is mounted in parallel with a capacitor 48. A second inverter / rectifier 50 cuts the voltage rectified by the first inverter / rectifier 42. This second inverter / rectifier 50 works for example at a switching frequency between 200Hz and 100MHz. This second inverter / rectifier is for example a simple switching arm formed by two switching cells 51 which can be similar in construction to the above-mentioned switching cells 45. The two switching cells 51 are connected in series between the positive potential and the negative potential of the voltage across the capacitor 48.

In series between these two switching cells 51, a connection to the phase of the part of the circuit in which the capacitive transformer is located exists. This part of the circuit being single phase, the capacitive transformer is formed by two capacitors 30 and 31, the capacitor 30 being positioned on the phase of this part of the circuit while the capacitor 31 is positioned on the neutral of this part of the circuit.

A third inverter / rectifier 53 is arranged at the output of the capacitive transformer. This third inverter / rectifier 53 is here a voltage doubler, implementing two switching cells 54 of similar construction to those of the aforementioned switching cells 45. These switching cells 54 are connected in series between the positive potential and the negative potential of the voltage rectified by this third inverter / rectifier 53. The voltage doubler 53 further comprises two capacitors 56 and 57 in the example considered, being both connected in series between the positive potential and the negative potential of the voltage rectified by voltage doubler 53. Between these two capacitors 56 and 57 is connected the neutral of the part of the circuit in which the capacitive transformer is placed.

In the example of Figure 3, the circuit 1 also includes a DC / DC voltage converter 60, which is here a series chopper mounted between the third inverter / rectifier 53 and the first output 4 of the circuit.

We will describe with reference to Figure 4 a third example of implementation which differs from those described with reference to Figures 1 to 3 in that the circuit 1 not only allows the charging of a first voltage source continues on the first output 4 but also the charge of a second DC voltage source on a second output 100 of the electrical circuit 1.

According to this third example, a first capacitive transformer is mounted between a rectifier, in particular an inverter / rectifier, and the first output 4 of the electrical circuit and a second capacitive transformer is mounted between a rectifier, in particular an inverter / rectifier, and the second output 100 of the electrical circuit. In the example described, each capacitive transformer has its capacitors arranged in parts of the circuit 1 traversed by an electric current at the frequency of the alternating network but arrangements similar to what is described with reference to FIG. 2 allowing that one at least capacitive transformers is arranged in a part of the circuit traversed by current of higher frequency than that of the alternating network is possible.

We will now describe with reference to Figures 5 and 6 a particular embodiment of a capacitive transformer according to the invention. This capacitive transformer is produced here by using two layers 61 and 62 of a printed circuit carrying or not other components such as capacitors.

As can be seen in Figure 5, the first layer 61 comprises a first electrically conductive area 63 and a second electrically conductive area 64, these areas being electrically isolated from each other. It can be seen that the first electrically conductive zone 63 has a spiral shape. The second layer 62 also includes a first electrically conductive area 65 and a second electrically conductive area 66, these areas being electrically isolated from each other. Again, the first electrically conductive area 65 has a spiral shape. The first electrically conductive zones 63 and 65 can be exactly superimposed.

In the example of Figure 5, the distance between the two layers 61 and 62 of the printed circuit is such that capacitors are defined between these layers. The equivalent electrical circuit is shown in FIG. 6. It can be seen that the shape of the first electrically conductive area 63 and that of the first electrically conductive area 65 are such that an inductance is defined. Each of the first 61 and the second 62 layer of the printed circuit is here flat.

As a variant of what has just been described with reference to FIGS. 5 and 6, the formation of the capacitors of the capacitive transformer may involve the cooperation of several first layers of printed circuit electrically connected together, and of several second layers of printed circuit electrically connected to each other. In the example considered, two first layers 70 and 71 are electrically connected to each other and two second layers 72 and 73 are electrically connected to each other. As can be seen in Figure 7, between two first layers 70 and 71 is disposed a second layer 72, so that a capacitor is formed between the first layer 70 and the second layer 72 on the one hand and between the first layer 71 and the second layer 72 on the other hand. The meeting of these capacitors in parallel defines a capacitor of the capacitive transformer, as shown in FIG. 8. When each layer 70 to 73 has a first electrically conductive area and a second electrically conductive area insulated from each other, for example as described with reference to FIGS. 5 and 7, the cooperation between the different layers 70 to 73 of FIG. 7 makes it possible to obtain two capacitors of the capacitive transformer

In the example described with reference to Figure 7, two first layers 70 and 71 are used, and two second layers 72 and 73 are used, but the invention is not limited to a particular number of first layers electrically connected to each other and second electrically connected layers. Another number, for example three first layers and three second layers is possible, as well as an arrangement in which the number of first layers electrically connected to each other differs from the number of second layers electrically connected to each other.

The invention is not limited to the examples which have just been described.

The invention can also be used in other applications. We can for example use a capacitive transformer as described above to achieve isolation of a communication signal between two devices connected by a network, for example a CAN, SPI RS485, RS232 data network ...

Claims (1)

Claims [Claim 1] Electric circuit (1) for charging a DC voltage source from an AC voltage network, the circuit comprising: an input (3) receiving an AC voltage, a first output (4) connected to the DC voltage source, and a capacitive transformer formed using several capacitors (30, 31, 32, 33), arranged so as to electrically isolate the input (3) from the first output (4) of the circuit. [Claim 2] Electrical circuit according to claim 1, the capacitive transformer being arranged in a single-phase part of the electrical circuit, the capacitive transformer comprising a first (30) and a second (31) capacitor, the first capacitor being disposed on the phase and the second capacitor being arranged on neutral. [Claim 3] Circuit according to claim 1, the capacitive transformer being arranged in a polyphase part of the circuit, in particular a three-phase part of the circuit, and the capacitive transformer comprising a plurality of capacitors (30, 31, 32, 33) so that each capacitor is respectively arranged on a phase or on the neutral [Claim 4] Circuit according to any one of the preceding claims, the capacitive transformer being arranged in a part of the circuit traversed by an alternating current at the frequency of the alternating network. [Claim 5] Circuit according to the preceding claim, the capacitive transformer being connected to the input of the circuit without the intermediary of a voltage converter. [Claim 6] Circuit according to any one of claims 1 to 3, the capacitive transformer being arranged in a part of the circuit traversed by an alternating current at a frequency higher than that of the alternating network. [Claim 7] Circuit according to the preceding claim, the capacitive transformer being connected to the input of the circuit by means of at least one inverter / rectifier (42, 50) [Claim 8] A circuit according to any one of the preceding claims, also allowing the charging of a second DC voltage source, the circuit comprising: a second output (100) connected to the second DC voltage source, and another capacitive transformer formed at using several capacitors, arranged so as to electrically isolate the input (3) from the second output (100) of the circuit. [Claim 9] Circuit according to any one of the preceding claims, the capacitive transformer being obtained using at least two layers (34, 37) of a printed circuit, each of these layers (34, 37) comprising a first region electrically conductive (35, 38) and a second electrically conductive area (36, 39), the first electrically conductive area (35, 38) being electrically isolated from the second electrically conductive area (36, 39), the two layers (34, 37 ) being arranged relative to each other so that a capacitor is formed between the first electrically conductive area (35) of a layer (34) and the first electrically conductive area (38) of the another layer (37) and that another capacitor is formed between the second electrically conductive area (36) of one layer (34) and the second electrically conductive area (39) of the other layer (37). [Claim 10] Circuit according to the preceding claim, at least one of the first electrically conductive zones (35, 38) having a spiral shape, so as to define an inductance. [Claim 11] Circuit according to claim 9 or 10, the capacitive transformer being obtained by means of several layers (70, 71, 72, 73) of a printed circuit, several first layers (70, 71) being electrically connected together and several second layers (72, 73) being electrically interconnected, and these first and second layers being arranged relative to each other so that between two first (70, 71), respectively second (72, 73), layers , is arranged a second (72, 73), respectively first (70, 71), layer so that a capacitor is formed between each first, respectively second, layer and the second, respectively first, layer so that the overall capacitor modeling all the capacitors thus formed in parallel between the first and second layers define a capacitor of the capacitive transformer. 1/4