DE102020121952A1 - Resonance transformer with additional coupled inductance for OBC - Google Patents

Abstract

The invention relates to an on-board charging device (OBC) 1 for an electric motor vehicle 2, having a housing G with at least one electrical input connection 7 for an external supply voltage source and at least one output connection 8 to a traction battery 9 and power electronics arranged in the housing G, which have at least one voltage converter has, the voltage converter being preceded by a choke L as an inductor, a further choke 17 being arranged in a return line 21 of a primary side 15 of the voltage converter, the two chokes L, 17 being coupled to one another.

Description

The present invention relates to on-board charging electronics according to the features in the preamble of claim 1.

It is known from the prior art to use electrical energy to move motor vehicles. Such motor vehicles are driven purely electrically as an electric vehicle. However, there are also hybrid variants in which energy is also generated with an internal combustion engine or a fuel cell. What both vehicles have in common is that the electrical energy is stored in a traction battery, also referred to below as a rechargeable battery, accumulator or battery.

This traction battery is charged when the electric vehicle is idle by connecting it to an external voltage source.

Depending on the local conditions and also depending on the country in which the electric vehicle is to be charged, different connection options and supply voltages are available for carrying out the charging process. Usually the supply voltage is 100V - 500V with a frequency of 50 - 60 Hz.

For this purpose, power electronics are used, which transform the different supply voltages to a charging voltage, so that the traction battery in the electric vehicle can be charged.

So that the electric vehicle can now be used as flexibly as possible for different supply voltages, there is power electronics with charging communication in the motor vehicle, which is also referred to as an on-board charger (OBC). Such on-board charging electronics can generally be operated with single-phase networks (typically PL ₁ and N conductors) or three-phase networks (PL ₁ - PL ₂ - PL ₃ conductors, with/without N conductor). . The OBC essentially transforms the 50 Hz sinusoidal AC voltage (supply voltage) into a DC voltage. The OBC can also create potential-free conditions between the vehicle and the supply network with the help of an integrated transformer.

So that the 50 Hz alternating voltage (supply voltage) can be converted into a direct current voltage (charging voltage), active front ends (AFE) or power factor correction (PFC) are used in the prior art. PFCs are used when the flow of energy is only directed from the supply voltage to the load. So-called bidirectional PFCs are also known. Conversely, if the battery is discharged in order to feed the battery voltage into the supply network, this is referred to as an AFE, which can also be referred to as a bidirectional PFC.

It is known from the prior art that a PFC choke is formed from an inductance, and therefore a wound coil. Such a coil also has a winding core.

A resonant transformer is usually used as a voltage converter in such an on-board charger. The resonant transformer can also be called LLC converter. In this case, a capacitor and a filter in the form of a choke, which is preferably in the form of an inductance, are connected in series on a primary side of the transformer. There is a parasitic leakage inductance in the area of the transformer. However, the choke as an inductance itself is an additional component.

On the secondary side there is, for example, a diode and/or transistor circuit which is used to rectify a charging voltage which is then passed on to the traction battery of the electric vehicle.

If a DC voltage is now generated on the primary side by means of PFC/AFE, a common-mode voltage is also generated in relation to the protective conductor PE or the housing of the OBC. This creates a common-mode interference current.

It is therefore the object of the present invention, based on the prior art, to show a possibility of reducing the common-mode interference current and thus improving the charging performance with the most cost-effective production and small installation space of an on-board charger.

The aforementioned object is achieved according to the invention with an on-board charging device according to the features in claim 1 .

Advantageous design variants are the subject matter of the dependent claims.

The on-board charging device is therefore suitable for an electric motor vehicle or a hybrid vehicle. It has a housing. The housing has at least one electrical input connection for an external supply voltage source and at least one electrical output connection for coupling to a traction battery. Furthermore, the power electronics of the on-board charging device are arranged in the housing. This includes at least one voltage converter. Optionally, a filter can also be installed on a primary side of the voltage converter, in particular an EMI filter and a rectifier can be provided.

A choke is connected upstream of the voltage converter as an inductor on the primary side. The choke can also be preceded by a series-connected capacitor in the primary circuit of the transformer.

According to the invention, a further choke is arranged in a return line of the primary side of the voltage converter, with the two chokes being coupled to one another. Particularly preferably, a capacitor can also be connected upstream of the second inductor coupled to the first inductor.

Alternatively or optionally in addition, this coupled choke can also be arranged on the secondary side. This means that the inductance is then arranged on the secondary side of the voltage converter, in particular in the form of the transformer. A capacitor can optionally be assigned to this. The second choke is then arranged in a line on the secondary side, in particular a return line on the secondary side, and is coupled to the first choke. Optionally, a second capacitor can also be arranged here. The arrangement of the coupled choke according to the invention on the secondary side is particularly advantageous when the battery voltage is higher than the supply voltage, and therefore the voltage present on the primary side. If the voltage on the primary side is 400 V, for example, and the supply voltage is 400 V and the battery voltage on the secondary side is 1000 V, so that the charging voltage must also be 1000 V, a lower current flows with the same power (P=U x I). the secondary side. As a result, the lines can be designed thinner on the secondary side. This in turn saves installation space, is less error-prone and lighter in relation to its own weight.

The other choke is also designed as an inductance. In the context of the invention, coupling with one another means that the two chokes are physically arranged directly next to one another with the incorporation of an air gap. For this purpose, each choke is formed from a winding core, in particular an E-shaped winding core. The two winding cores are then arranged directly next to one another with the incorporation of an air gap. In particular, the openings of the respective E-shape of both throttles are designed to point towards one another.

The windings of each inductor are particularly preferably designed to be complementary to one another, which means that they have the same number of windings and the same winding diameter.

In particular, in the case of an E-shaped winding core, only the inner web of the E is wrapped with a winding wire.

A preferred development of the invention provides that the two coupled chokes are coupled directly to the voltage converter in the form of a transformer. In particular, the chokes are glued to the winding core or the housing of the transformer. As a result, the space can be reduced.

According to the invention, the coupled chokes thus have two functions together. On the one hand, as a common-mode inductance, they form an additional filter, as a result of which a common-mode interference current that would flow through the entire voltage converter, in particular as a return line via the housing, is reduced.

Another advantage is that the two coupled chokes form an oscillating circuit with the capacitor and the leakage inductance of the transformer, which means that the leakage inductance of the transformer can be designed to be lower.

The installation space of the coupled choke can also be reduced, so that the actual choke connected upstream of the voltage converter can also be designed to be smaller in terms of installation space.

The direct arrangement of the chokes on one another and the optional coupling with the transformer itself leads to greater mechanical stability, which is important in on-board charging electronics in a motor vehicle, since these are exposed to vibrations when the electric motor vehicle is in operation. Malfunctions or internal damage to the power electronics over the period of use of such an electric motor vehicle can thus be reliably avoided.

The respective second capacitor has the advantage that greater symmetry of the circuit arrangement is achieved. In this way, additional differential currents that occur are avoided or reduced, so that there is less differential interference.

• 1 ein Blockschaltbild eines On-Board Chargers in einem Elektrokraftfahrzeug,
• 2 ein Schaltbild eines Resonanztransformators,
• 3 und 4 ein Schaltbild der Leistungselektronik innerhalb eines On-Board Chargers,
• 5 das Schaltbild mit einer erfindungsgemäß gekoppelten Drossel,
• 6 die erste und zweite Drossel, physisch miteinander gekoppelt und elektrisch an den Transformator angeschlossen,
• 7 eine Ausgestaltungsvariante, bei welcher beide Drosseln unmittelbar an den Transformator gekoppelt sind.
• 8 eine Anordnung zweier gekoppelter Drosseln.
• 9 eine Schaltungsanordnung gemäß 5 mit zusätzlichem Kondensator,
• 10 eine Schaltungsanordnung analog zu 5, wobei die Drosseln auf der Sekundärseite angeordnet sind und
• 11 eine Schaltungsanordnung analog zu 10, wobei hier ein ebenfalls zweiter Kondensator angeordnet ist.

Further advantages, features, properties and aspects of the present invention are the subject of the following description. Preferred embodiment variants are shown in the following figures. These serve to make the invention easier to understand. Show it:

• 1 a block diagram of an on-board charger in an electric vehicle,
• 2 a circuit diagram of a resonant transformer,
• 3 and 4 a circuit diagram of the power electronics within an on-board charger,
• 5 the circuit diagram with a choke coupled according to the invention,
• 6 the first and second chokes physically coupled together and electrically connected to the transformer,
• 7 a design variant in which both chokes are coupled directly to the transformer.
• 8th an arrangement of two coupled chokes.
• 9 a circuit arrangement according to 5 with additional condenser,
• 10 a circuit arrangement analogous to 5 , wherein the chokes are arranged on the secondary side and
• 11 a circuit arrangement analogous to 10 , whereby a second capacitor is also arranged here.

In the figures, the same reference numbers are used for the same or similar components, even if a repeated description is omitted for reasons of simplification.

1 shows the arrangement of an on-board charging device 1 according to the invention in an electric vehicle 2. For this purpose, the electric vehicle 2 is connected with an on-board socket 3 to an external charging socket 4 with a charging cable 5. The external charging socket 4 provides a supply voltage 6 ready. The on-board socket 3 is electrically connected to the on-board charging device 1 . For this purpose, the on-board charging device 1 has at least one electrical input connection 7 . Furthermore, the on-board charging device 1 has an electrical output connection 8 which is coupled to a traction battery 9 of the electric motor vehicle 2 . Further electrical input connections or output connections 10 can be present, for example an input connection of the vehicle battery, in particular with regard to a communication connected thereto. In addition, a communication network of the electric motor vehicle 2, for example a CAN bus, can also be connected. This can also be cooling connections.

A mains filter 11 is then arranged in particular in the on-board charging device 1, for example in the form of an EMI filter. This is then followed by a PFC choke 12, in turn followed by a voltage converter in the form of a transformer 13, in particular a resonant transformer, for converting the supply voltage 6 into a charging voltage and an optional rectifier 14, which is then electrically coupled to the actual traction battery 9.

2 shows a circuit arrangement for a voltage converter in an on-board charger, the voltage converter being designed as a resonant transformer. Referring to the image plane, there is therefore a primary side 15 on the left and a secondary side 16 on the right of the transformer 13. On the primary side 15, in addition to a voltage source and various switches S ₁ and S ₂ , there is a capacitor C and a choke in the form of an inductance L in series switched arranged. A parasitic leakage inductance L _ST in the area of the transformer 13 is also shown, which is caused by the structure of the transformer 13 itself. The switches S ₁ and S ₂ generate a square-wave voltage with a mark-to-space ratio of approximately 50%. The frequency of the square wave voltage is chosen to be close to the resonant frequency formed by the capacitor C and the inductances L and L _ST . A diode and/or transistor combination for rectification is shown on the secondary side 16 . A charging voltage is then delivered to the traction battery 9 .

3 and 4 now show the housing G of an on-board charging device 1 or on-board charger. A mains filter 11 is additionally arranged inside the housing G, for example a mains filter and a PFC or AFE designed as a PFC choke. The capacitances Ck1 and Ck2 are also shown. The capacitance Ck1 is the winding capacitance between the primary and secondary windings of the voltage converter in the form of the resonant transformer. The capacitance Ck2 is the total capacitance that arises from the structure of the secondary side 16 in relation to the housing G and the output filter. The common-mode voltage that is generated in the AFE or PFC causes an interference current that is shown as a dot-dash line in 4 is shown. The interference current flows through the intermediate circuit, the transformer 13, the rectifier 14, the housing G and the Y capacitor and the EMI filter in the circuit. This interference current means that impermissible interference voltages are generated both in the output circuit at the connection of the traction battery 9 and on the mains side, which is not shown in detail. This results in additional voltage drops across CY and Ck2.

Here, the present invention according to 5 at. Analogous to the representation 4 however, the inductor L is arranged a second inductor in the form of a coupled choke 17, wel che is electrically connected in series with the primary winding on the primary side. The inductor L and the coupled inductor 17 are thus physically coupled to one another by incorporating an air gap 19 . A second throttle 17 is thus used in the return line of the primary side 15 . This second choke 17 has the function that the common-mode inductance forms an additional filter, as a result of which the common-mode interference current is reduced. On the other hand, it forms an additional inductance for the required oscillating circuit together with the capacitor C and the parasitic leakage inductance L _ST .

The coupled choke 17 can also be used in reverse as a so-called common-mode choke. The difference and common-mode inductance then change, which must be taken into account when designing the resonant circuit frequency and the transformer 13 .

6 shows the schematic structure of the coupled inductor 17 and electrically connected to the voltage converter in the form of a transformer.

The first choke L and the second choke 17 coupled thereto are thus formed as one component. They each have a winding core 18, which is designed here in the form of an E-shaped winding core. The respective openings of the E are arranged facing each other. An air gap 19 is formed between the two winding cores 18 so that they are physically coupled to one another with the incorporation of the air gap 19 as a built-in part. An insulating material, not shown in detail, can also be arranged here, for example. Both the choke L and the coupled choke 17 each have windings 20 . The windings 20 are designed to run in opposite directions to one another if the two chokes L and 17 are arranged pointing towards one another, as in FIG 6 shown.

Alternatively, it is also conceivable for the windings 20 to run in the same direction. The two coupled chokes together have a common-mode filter effect and at the same time also a differential-mode filter effect, but in each case with different parameter levels. The unit for this is Henry. This means the common-mode filter effect, but the differential-mode filter effect can also be set by the orientation of the winding (opposite or co-rotating) of the two chokes L and 17. This depends on the desired filter performance, in particular on the voltage converter or transformer used.

The choke L and the coupled choke 17 are then electrically connected to the transformer 13 on the primary side. The windings 20 of the transformer 13 are also coupled via a respective line 22, so that the coupled choke 17 can be fed into the electrical return line 21 on the primary side 15 is integrated.

7 shows a development according to the invention. In this case, the choke L and the choke 17 coupled thereto, and consequently the two coupled inductances are physically arranged with the incorporation of the air gap 19 with one another. These are then physically coupled to the transformer 13 itself, for example glued onto the transformer 13 . Schematically indicated, the windings 20 can thus be routed both through the transformer 13 and the two chokes L, 17 coupled to one another, so that overall there is less installation space in addition to the advantages of the electronic circuit described above.

8th shows the coupled chokes L and 17 in a preferred embodiment. Here, the choke L and the choke 17 coupled thereto are shown, which rest directly against one another at the ends of the outer webs 23 of the winding cores 18 . The central webs 24, on the other hand, are shortened or spaced apart from one another in such a way that an air gap 19 results. The air gap preferably has a size of 100 μm to 3 mm. In particular, the ends of the webs 23 can be glued together. The windings 20 are electrically insulated from the respective winding core 18 itself. A magnetic field then flows through the winding core 18 . However, there is no electrical short circuit at the ends of the outer webs 23 . The windings 20 are shown only schematically.

9 shows a circuit arrangement analogous to 5 . A second capacitor C2 is arranged in the return line 21 on the primary side 15 . In this circuit, the circuit is thus constructed “more symmetrically” with regard to the capacitor, the first coil L, the second coil 17 coupled thereto, and the second capacitor C2. Additional residual currents that occur are reduced as a result.

10 shows a structure analogous to 5 . However, the clear difference here is that the inductor L and the inductor 17 coupled thereto and the capacitor C are arranged on the secondary side 16 of the transformer 13 . This circuit arrangement is particularly advantageous when a significantly higher voltage is present as charging voltage on the secondary side 16 to the traction battery 9 than on the primary side and thus as the in-house supply voltage.

11 shows an analog structure, with a second capacitor C2 also being arranged in a line 25, in particular a return line, on the secondary side.

Reference List

1

onboard charger

2

electric vehicle

3

board socket

4

external charging socket

5

charging cable

6

supply voltage

7

electrical input connection

8th

electrical output connection

9

traction battery

10

further electrical input connections or output connections

11

line filter

12

PFC choke

13

transformer

14

rectifier

15

primary side

16

secondary side

17

coupled throttle

18

winding core

19

air gap

20

winding

21

return line

22

management

23

outer ridges

24

inner webs

25

management

C

capacitor

C2

capacitor

Ck1

capacity

Ck2

capacity

G

housing

L

inductance/choke

LST

leakage inductance

S1

counter

S2

counter

Claims (10)

On-board charging device (OBC) (1) for an electric motor vehicle (2), having a housing (G) with at least one electrical input connection (7) for an external supply voltage source and at least one output connection (8) to a traction battery (9) and in the housing (G) arranged power electronics, which has at least one voltage converter, with the voltage converter being assigned a choke (L) as inductance, characterized in that in a return line (21) of a primary side (15) or a secondary side of the voltage converter, a further choke (17 ) is arranged, wherein the two chokes (L, 17) are coupled to each other. On-board charging device (1) according to claim 1 , characterized in that the chokes (L, 17) are physically coupled together incorporating an air gap (19). On-board charging device (1) according to claim 1 or 2 , characterized in that each choke (L, 17) is designed as a wound coil or inductor (L). On-board loading device (1) according to one of the preceding Claims 1 until 3 , characterized in that the chokes (L, 17) are electrically connected in series with one another on the primary side (15) of the voltage converter with the latter, the first choke (L) being followed by the primary winding of the voltage converter, followed in turn by the second choke (17) or that the chokes (L, 17) are electrically connected in series with one another on the secondary side of the voltage converter. On-board loading device (1) according to one of the preceding Claims 1 until 4 , characterized in that both chokes (L, 17) are arranged directly on the voltage converter, in particular are glued to it. On-board loading device (1) according to one of the preceding Claims 1 until 5 , characterized in that the windings (20) of the first choke (L) and the windings (20) of the second choke (17) in the assembled state are designed to run in opposite directions or in the same direction as one another. On-board loading device (1) according to one of the preceding Claims 1 until 6 , characterized in that the first choke (L) is formed by a winding core (18), in particular an E-shaped winding core (18) and the second choke (17) by a winding core (18), in particular an E-shaped winding core ( 18) is formed and the winding cores (18) are in direct contact with one another with the incorporation of an air gap (19), in particular the openings of the E-shape point towards one another. On-board loading device (1) according to one of the preceding Claims 1 until 7 , characterized in that the coupled two chokes (L, 17) act as a common-mode interference current filter. On-board loading device (1) according to one of the preceding Claims 1 until 8th , characterized in that the coupled second choke (17) forms an oscillating circuit with a capacitor (C) arranged on the primary side (15) and the first choke (L), such that the leakage inductance (L _ST ) of the transformer (13) is designed lower, optionally with a second capacitor is arranged. On-board loading device (1) according to one of the preceding Claims 1 until 8th , characterized in that the coupled second choke (17) with a capacitor arranged on the secondary side and the first choke (L) forms an oscillating circuit such that the leakage inductance (L _ST ) of the transformer (13) is designed to be lower, with optional a second capacitor is also arranged.

Images