DE102020007840A1 - Boost converter for charging an electrical energy store of an electrically powered vehicle, as well as vehicle and method - Google Patents

Abstract

The invention relates to a step-up converter (4) for charging an electrical energy store (2), with - an input side (5) for coupling to a DC voltage charging source (3), - an output side (6) for coupling to the electrical energy store (3), and - A first strand (7) and a second strand (8) which are connected between the input side (5) and the output side (6), the first strand (7) having a first inductance (9) for providing a first strand voltage (U1), - the second strand (8) has a series connection of a second inductance (10) and a first choke (L1) for providing a second strand voltage (U2), - the first inductance (9) with the second inductance ( 10) is magnetically coupled, depending on the first and second inductance (9, 10) as the charging current of the electrical energy store (2) being the sum of a charging current of the first strand (7) and a charging current of the second strand (8) to mount. The invention also relates to a vehicle (1) and a method.

Description

The invention relates to a step-up converter for charging an electrical energy store of an electrically driven vehicle with an input side of the step-up converter for coupling to a predetermined external DC voltage charging source which provides an input voltage. An output side of the boost converter is provided for coupling to an electrical energy store, the output side providing an output voltage higher than the input voltage, and a first strand and a second strand of the boost converter, which are connected between the input side and the output side.

The invention also relates to a vehicle with a corresponding step-up converter. The invention also relates to a method for charging an electrical energy store of an electrically powered vehicle with a step-up converter, an input voltage for a step-up converter being provided with an external DC voltage charging source and an output voltage higher than the input voltage being provided to the electrical energy store with the step-up converter.

Fast charging stations or fast charging columns can be used to charge electrically powered vehicles, such as electric vehicles, hybrid vehicles or plug-in vehicles. With the help of the fast charging stations, a direct voltage charging process with a higher charging capacity can be carried out. For example, today's fast charging stations only have a maximum voltage of 750 volts. In contrast, electric vehicles in particular have a voltage level of a maximum of 870 volts. This means that the voltage of the charging station also has to be stepped up in order to be able to charge the electric vehicle with a high charging power.

With the help of conventional galvanically coupled voltage converters, the charging voltage is stepped up by changing one of the two potentials (HV + or HV-). These converters require all power electronic components to be dimensioned accordingly for the charging currents required for the fast charging process. As a result, these galvanically coupled voltage converters are very large, very heavy and just as expensive. Voltage converters with capacitive energy stores, such as a charge pump, have the same problem.

In particular, galvanically isolated voltage converters have the negative property that they have a very low power density, so that they are unsuitable for rapid charging. Likewise, these show an extremely poor degree of efficiency when charging with low power. Likewise, not every type of charging station can be used with the galvanically isolated voltage converters. Since the galvanically isolated voltage converters have jumping HV potentials during the charging process, this can damage the charging stations.

For example, the DE 10 2017 009 355 A1 a method for operating a first vehicle electrical system to which a first electrical direct voltage is applied and a second vehicle electrical system to which a second electrical direct voltage is applied. This results in improved protection of on-board electrical systems.

In the DE 10 2017 009 352 A1 discloses an energy coupler for electrically coupling on-board electrical systems. This is a galvanically coupled voltage converter. This is also very large, very expensive and very space-consuming.

The object of the present invention is therefore to provide a compact voltage converter for a rapid charging process of an electric vehicle.

This object is achieved by an up converter, a vehicle and a method according to the independent claims. Meaningful further developments result from the subclaims.

• - einer Eingangsseite des Aufwärtswandlers zum Koppeln mit einer vorgegebenen externen Gleichspannungsladequelle, welche eine Eingangsspannung bereitstellt,
• - einer Ausgangsseite des Aufwärtswandlers zum Koppeln mit dem elektrischen Energiespeicher, wobei die Ausgangsseite eine zur Eingangsspannung höhere Ausgangsspannung bereitstellt, und
• - einen ersten Strang und einen zweiten Strang, welche zwischen der Eingangsseite und der Ausgangseite verschaltet sind, dadurch gekennzeichnet, dass
• - der erste Strang und der zweite Strang zueinander parallel verschaltet sind,
• - der erste Strang eine erste Induktivität zum Bereitstellen einer ersten Strangspannung aufweist,
• - der zweite Strang eine Reihenschaltung aus einer zweiten Induktivität und einer ersten Drossel zum Bereitstellen einer zweiten Strangspannung aufweist,
• - die erste Induktivität des ersten Strangs mit der zweiten Induktivität des zweiten Strangs magnetisch gekoppelt ist, wobei
• - der Aufwärtswandler dazu ausgebildet ist, in Abhängigkeit von der magnetischen Kopplung der ersten und zweiten Induktivität als Ladestrom des elektrischen Energiespeichers die Summe aus einem Ladestrom des ersten Strangs und einem Ladestrom des zweiten Strangs bereitzustellen.

One aspect of the invention relates to a step-up converter for charging an electrical energy store of an electrically driven vehicle

• - An input side of the boost converter for coupling to a predetermined external DC voltage charging source, which provides an input voltage,
• - An output side of the boost converter for coupling to the electrical energy store, the output side providing an output voltage that is higher than the input voltage, and
• - A first strand and a second strand, which are connected between the input side and the output side, characterized in that
• - the first line and the second line are connected in parallel to each other,
• - the first strand has a first inductance for providing a first strand voltage,
• - the second strand has a series connection of a second inductor and a first choke for providing a second strand voltage,
• - The first inductance of the first strand is magnetically coupled to the second inductance of the second strand, wherein
• the step-up converter is designed to provide the sum of a charging current of the first strand and a charging current of the second strand as the charging current of the electrical energy store as a function of the magnetic coupling of the first and second inductance.

In particular, with the proposed step-up converter, a voltage increase for a fast charging process of the electrically driven vehicle can be made more efficient. In particular, the proposed step-up converter enables a voltage increase even with high power requirements. In particular, the proposed step-up converter can be designed to be compact and space-saving. A compact, inexpensive and space-saving converter for converting, for example, 750 volts to 870 volts can thus be implemented with the aid of the proposed step-up converter.

In particular, the proposed step-up converter has the advantage over conventional galvanically coupled voltage converters that the proposed step-up converter does not have to be designed for the charging current to be transmitted. In the galvanically coupled voltage converter from the prior art, all power electronic components such as semiconductors, inductive components and capacitive components must therefore be designed or dimensioned accordingly. In contrast, the proposed boost converter provides considerable advantages. On the one hand, the proposed step-up converter has lower semiconductor costs and the first choke can be designed for a lower current deflection. The diodes of the voltage converter can also be designed for a smaller current path.

In particular, the proposed step-up converter is smaller, lighter and more cost-effective compared to the voltage converters in the prior art. Therefore, a weight reduction and space saving can be achieved in the electrically driven vehicle.

In particular, the boost converter is a boost converter with a magnetic coupling.

The electrically driven vehicle can in particular be an electric vehicle or a hybrid vehicle or a plug-in vehicle. The electrical energy store of the electrically driven vehicle is in particular a vehicle battery or a battery arrangement or a traction battery. In particular, the electrical energy store has a voltage level of a maximum of 750 volts. In contrast, the specified external DC voltage charging source has a maximum voltage of 750 volts. The external DC voltage charging source can be, for example, a DC voltage charging station or a charging infrastructure or a charging station. Since there is a voltage difference in particular between the DC voltage charging source and the electrical energy store, the proposed step-up converter is advantageously used. With the help of the proposed step-up converter, for example, the 750 volts of the charging station can be converted up to a voltage of 870 volts for the electrical energy storage device. Thus, in particular, a fast charging process with high charging power can be carried out.

In particular, the electrical energy store can be used to supply an electrical drive motor or a drive unit or a drive unit for moving the vehicle with energy.

In particular, the step-up converter is fixedly arranged in or on the electrically driven vehicle. In particular, the step-up converter is part of an on-board charger or an on-board network of the electrically powered vehicle. With the help of the magnetically coupled inductance, the electrical energy storage device (vehicle battery) can be charged with a corresponding voltage, although the DC voltage charging source provides a low voltage.

In an advantageous embodiment of the invention it is provided that the second strand between the first choke and a diode connected in series to the first choke has a center tap, a first switching element being connected to the center tap, whereby the second strand by means of the first switching element with a Potential of the electrical energy store is coupled. With the help of the center tap and the first switching element, a choke current can be built up in the first choke, as a result of which the electrical energy store can be charged with a higher voltage. In particular, the electrical energy store is charged directly via the first inductance with the aid of the first strand. Via the center tap and the first switching element of the second strand, the first throttle can be connected to a Choke current are impressed, which can be used in a subsequent freewheeling phase to charge the electrical energy store.

For example, the first choke is an inductance or an inductive component. The first switching element can be, for example, an electronic switch such as a diode or a thyristor or a field effect transistor or a bipolar transistor or a MOSFET or an IGBT.

In particular, the second strand is connected to a negative potential of the electrical energy store by means of the first switching element. In particular, with the help of the center tap, a branch is established between the second strand and the negative potentials of the DC voltage charging source and the electrical energy store.

In one embodiment of the invention it can be provided that the first strand has a series connection of the first inductance and a first diode, in particular a freewheeling diode, and the second strand has a series connection of the second inductance, the first choke and a second diode, in particular one Freewheeling diode. In particular, the diodes serve as protective diodes to protect against harmful overvoltages. When the first and second diodes are designed as freewheeling diodes, improved protection against overvoltage can be achieved when an inductive DC voltage load is switched off. In particular, the first and second diodes, which are designed as freewheeling diodes, prevent a voltage spike, which in particular adds up to the operating voltage and can damage or destroy the first and / or second strand. In particular, the two diodes each have a reverse direction with which only a current flow in the electrical energy store is possible.

For example, the first strand and the second strand can be an electrical branch or a switching path.

In one embodiment of the invention it is provided that a second choke for adapting a clock frequency of the first switching element is formed between the first inductance and the first diode of the first strand. With the aid of the additional second choke, which is designed in particular as an inductance, a leakage inductance can be provided for the step-up converter. In particular, a clock frequency of the first switching element can be set with the aid of the additional leakage inductance. In particular, the clock frequency of the first switching element is reduced.

In a further exemplary embodiment of the invention it is provided that the input side has an input capacitance and the output side has an output capacitance. The input capacitance and the output capacitance are, in particular, backup capacitors or buffer capacitors. In particular, the input capacitance and the output capacitance are capacitances for stabilizing the input voltage and the output voltage.

Furthermore, EMC filters can be used or interconnected on an output side and on an output side to filter interference.

In a further embodiment of the invention it is provided that the first inductance and the second inductance are designed as a coil, whereby the magnetically coupled inductances form a transformer, in particular the two inductances designed as a coil have opposite winding directions. The transformer formed allows the lower input voltage of the DC voltage charging source to be stepped up into the higher output voltage for charging the electrical energy store. In particular, the first inductance and the second inductance are coil windings or the windings of the transformer.

In a further exemplary embodiment of the invention it is provided that the first strand has a bypass line, with a bypass switch within the bypass line being able to divide a current flow in the first strand to the bypass line and to the first diode. In particular, the first diode can be bridged with the aid of the bypass line, so that the current flow is divided between the bypass line and the first diode. This results in a higher efficiency of the boost converter, since the forward losses of the first diode are reduced.

Since the first strand can have a high current flow, the first diode also experiences a current with a high current value. By adding the bypass line or a bypass circuit, the first choke and the first diode can be designed for a lower current value. In particular, the blocking capability of the first choke can be disregarded, since the charging current to be set can be set to essentially a current value of 0 amperes through the bypass line. It is particularly advantageous if the bypass switch is switched as a function of a current value of the first diode. For example, the bypass switch can be closed at a current threshold value of the first diode will. For example, if the diode current exceeds 50 amperes, the bypass switch can be closed. As soon as the diode current falls below a second threshold value, for example 30 amps, the bypass switch can be opened again. For example, the threshold values for opening and closing the bypass switch can be designed as a function of a current ripple in the first branch.

In particular, the voltage values shown are to be understood as target voltage values, since these can deviate by, for example, 5%, in particular 10%, due to measurement tolerances.

• - mit einer externen Gleichspannungsladequelle eine Eingangsspannung für den Aufwärtswandler bereitgestellt wird, und
• - mit dem Aufwärtswandler eine zur Eingangsspannung höhere Ausgangsspannung dem elektrischen Energiespeicher bereitgestellt wird, wobei
• - mit einem ersten Strang des Aufwärtswandlers, welcher eine erste Induktivität aufweist, eine ersten Strangspannung bereitgestellt wird,
• - mit einem zweiten Strang des Aufwärtswandlers, welcher eine Reihenschaltung aus einer zweiten Induktivität und einer ersten Drossel aufweist, eine zweite Strangspannung bereitgestellt wird, wobei
• - mit dem Aufwärtswandler in Abhängigkeit von einer magnetischen Kopplung der ersten und zweiten Induktivität als Ladestrom des elektrischen Energiespeichers die Summe aus einem Ladestrom des ersten Strangs und einem Ladestrom des zweiten Strangs bereitgestellt wird.

Another aspect of the invention relates to a method for charging an electrical energy store of an electrically driven vehicle with a boost converter, wherein

• - An input voltage for the boost converter is provided with an external DC voltage charging source, and
• - With the step-up converter, an output voltage higher than the input voltage is provided to the electrical energy store, wherein
• a first phase voltage is provided with a first phase of the step-up converter, which has a first inductance,
• - With a second strand of the step-up converter, which has a series connection of a second inductance and a first choke, a second phase voltage is provided, wherein
• - With the step-up converter depending on a magnetic coupling of the first and second inductance as the charging current of the electrical energy store, the sum of a charging current of the first strand and a charging current of the second strand is provided.

In particular, the proposed method enables efficient and uncomplicated charging or rapid charging of an electrically powered vehicle. In particular, the proposed method can be used to convert an input voltage of the DC voltage charging source into a higher output voltage for charging the electrical energy store of the electrically driven vehicle. For example, a voltage value of 750 volts of the direct voltage charging source can be stepped up to 870 volts for charging the electrical energy store (vehicle battery).

In a further exemplary embodiment, it is provided that a negative potential and / or a positive potential of an on-board electrical system of the electrically driven vehicle is adapted with the step-up converter. In particular, a negative HV potential and / or a positive HV potential of the on-board electrical system can be adapted or changed or varied with the aid of the boost converter.

Another aspect of the invention relates to a vehicle with an up converter according to one of the previous aspects or a development thereof.

Advantageous embodiments of the step-up converter are to be regarded as advantageous embodiments of the vehicle and of the method. For this purpose, the up-converter and the vehicle have objective features which enable the method or an advantageous embodiment thereof to be carried out.

Further advantages, features and details of the invention emerge from the following description of preferred exemplary embodiments and on the basis of the drawing (s). The features and combinations of features mentioned above in the description as well as the features and combinations of features mentioned below in the description of the figures and / or shown alone in the figures can be used not only in the combination specified, but also in other combinations or on their own, without the scope of the Invention to leave.

• 1 eine schematische Seitenansicht eines Elektrofahrzeugs bei einem DC-Ladevorgang;
• 2 ein schematisches Blockschaltbild eines Ausführungsbeispiels des erfindungsgemäßen Aufwärtswandlers;
• 3 einen schematischen Simulationsaufbau des Aufwärtswandlers aus 2;
• 4 beispielhafte Verläufe von Simulationsergebnissen des Simulationsausbaus aus 3;
• 5 ein schematisches Blockschaltbild eines weiteren Ausführungsbeispiels des erfindungsgemäßen Aufwärtswandlers;
• 6 ein schematisches Blockschaltbild eines weiteren Ausführungsbeispiels des erfindungsgemäßen Aufwärtswandlers;
• 7 ein schematisches Blockschaltbild eines weiteren Ausführungsbeispiels des erfindungsgemäßen Aufwärtswandlers; und
• 8 ein schematisches Blockschaltbild eines weiteren Ausführungsbeispiels des erfindungsgemäßen Aufwärtswandlers.

The following figures show in:

• 1 a schematic side view of an electric vehicle during a DC charging process;
• 2 a schematic block diagram of an embodiment of the boost converter according to the invention;
• 3 a schematic simulation setup of the boost converter 2 ;
• 4th exemplary courses of simulation results of the simulation expansion 3 ;
• 5 a schematic block diagram of a further embodiment of the boost converter according to the invention;
• 6th a schematic block diagram of a further embodiment of the boost converter according to the invention;
• 7th a schematic block diagram of a further embodiment of the boost converter according to the invention; and
• 8th a schematic block diagram of a further embodiment of the boost converter according to the invention.

In the figures, functionally identical elements are provided with the same reference symbols.

the 1 shows a schematic side view of a vehicle 1 . With the vehicle 1 it is in particular an electrically powered vehicle or an electrically powered vehicle or a fully electrically powered vehicle or an electric vehicle or a hybrid vehicle or a plug-in vehicle. The vehicle 1 furthermore has an electrical energy store 2 on. With the help of the electrical energy store 2 becomes in particular a drive unit of the vehicle 1 a voltage is provided. In particular, with the electrical energy store 2 a maximum voltage of 870 volts can be provided. With the electrical energy storage 2 it can be, for example, a traction battery or a battery arrangement or a vehicle battery. In particular, it is the electrical energy store 2 a high-voltage battery in the vehicle 1 .

To the electrical energy storage 2 of the vehicle 1 The vehicle will be able to supply or charge it with electrical energy 1 with a DC voltage charging source 3 coupled or connected. At the DC charging source 3 it is in particular one for the vehicle 1 external charging source. In particular, it is the DC voltage charging source 3 around a DC charging station or around a charging station or around a DC voltage source or around a charging infrastructure or around a charging system. In particular, the DC voltage charging source delivers 3 a voltage of maximum 750 volts.

the 2 shows a schematic block diagram of a boost converter according to the invention 4th . With the boost converter 4th it is in particular a boost converter. In particular, the boost converter is 4th designed as a galvanically coupled boost converter with magnetic coupling. The boost converter 4th has an entry side 5 for coupling with the DC voltage charging source 3 on. In particular, this creates an input voltage UE the DC voltage charging source 3 provided. Furthermore, the boost converter 4th an exit page 6th on which of the boost converter 4th with the electrical energy storage 2 is coupled. In particular, with the exit side 6th one to the input voltage UE higher output voltage UA to be provided. Between the entrance side 5 and the exit page 6th are a first strand 7th and a second strand 8th interconnected. In particular, the two strands 7th , 8th connected in parallel to each other. On the first strand 7th is in particular a first inductor 9 via a first diode D1 with the positive potential of the electrical energy store 2 tied together. In particular, the first strand 7th between the positive potential of the DC voltage charging source 3 and the positive potential of the electrical energy store 2 be interconnected. For example, the interconnection with the electrical energy store 2 via battery connection terminals.

In particular, the second strand 8th a second inductor 10 exhibit. The second strand can use the second inductance 10 , a first throttle L1 and a second diode D2 with the positive potential of the electrical energy store 2 get connected. In particular, the second inductance 10 , the first throttle L1 and the second diode D2 connected in series to each other. In particular, the second strand is 8th also connected to the battery terminals. In particular, are the first strand 7th and the second strand 8th via a common hub 11 with the positive potential of the electrical energy store 2 electrically connected.

For example, exhibit the first strand 7th and the second strand 8th one connection terminal each 12th on. The connection terminals 12th are in turn with the positive potential of the DC voltage charging source 3 interconnected. This results in a current flow between the DC voltage charging source 3 in the first strand 7th and in the second strand 8th .

For example, the entry page 5 an input capacitance C1 and the exit page 6th an output capacitance C2 exhibit. With the help of the two capacities C1 , C2 can smooth the input voltage UE and the output voltage UA be performed. In particular, it concerns the two capacities C1 , C2 to backup capacitors or buffer capacitors.

For example, the input capacitance C1 between the connection terminal 12th of the second strand 8th and the negative potential of the DC voltage charging source 3 be interconnected. The output capacitance C2 can between the node 11 and the negative potential of the electrical energy store 2 be interconnected.

In particular, the first inductance 9 and the second inductor 10 be designed as a coil or coil winding or winding. As a result, the two inductances in particular 9 , 10 be magnetically coupled, thus creating a transformer 13th can be formed. Thus, with the help of this formed transformer 13th the voltage increase from the input voltage UE on the output voltage UA will be realized. In particular, the two inductances 9 , 10 opposite winding sense of their coils.

In particular, the two diodes D1 , D2 be designed as free-wheeling diodes or protective diodes. With the help of the diodes D1 , D2 a dangerous overvoltage can be prevented. In particular, the two diodes prevent D1 , D2 a return flow of a current. In particular, the two diodes D1 , D2 the same blocking direction. The diodes D1 , D2 only allow current to flow from the terminals 12th to the node 11 .

In particular is the transformer 13th via the connection terminals 12th the strands 7th , 8th galvanically with the DC voltage charging source 3 coupled.

To now a voltage increase from the input voltage UE on the output voltage UA To be able to reach, the first throttle must be used L1 be charged with a throttle current. To achieve this, between the first throttle L1 and the second diode D2 a tap of funds 14th be trained. Between the center tap 14th and the negative potential of the electrical energy store 2 and the DC voltage charging source 3 is a first switching element S1 interconnected. Depending on how the switching element S1 is switched, a choke current can be in the first choke L1 be built up or dismantled. For example, it is the first switching element S1 around a transistor or around a MOSFET or around an IGBT.

In particular, the boost converter is 4th due to the magnetic coupling between the inductances 9 and 10 able to act as a charging current for the electrical energy storage device 2 the sum of a charging current of the first line 7th and a charging current of the second strand 8th provide.

Thus, in particular, the lower input voltage UE into the higher output voltage UA being transformed.

In the following, an exemplary embodiment for the mode of operation of the voltage converter is presented in particular 4th explained. The starting position at which the input voltage is present can optionally be present UE the DC voltage source 3 is the same as the voltage of the electrical energy store 2 of the electrically powered vehicle 1 . Voltage drops at internal resistances and other ohmic side effects, such as for supply lines, can be taken into account. Specifically, this starting position can be achieved by the vehicle 1 in a first charging process until the maximum output voltage of the DC voltage charging source is reached 3 is supplied. This can be done, for example, by a direct coupling between the electrical energy store 2 and the DC charge source 3 through a bypass of the voltage converter 4th can be achieved or by using the boost converter 4th is inactive and is designed for a corresponding charging current.

When the maximum output voltage (for example 750 volts) is reached, the boost converter begins 4th with its function or with its operation, by the required, essentially small, voltage increase for charging the electrical energy store 2 (High-voltage battery).

In particular, this takes place in two steps. In a first step, a choke current is built up in the first choke L1 . Using the mesh equation, we get the first inductance for the circuit 9 that the input voltage UE equal to the sum of the voltage across the first inductance 9 and the battery voltage of the electrical energy store 2 is. It can thus be seen that the voltage difference between the DC voltage charging source 3 and the electrical energy storage 2 about the inductance 9 or the first winding of the transformer 13th pending. On the basis of the mesh equation it results that the temporal voltage across the first inductance 9 is negative, so is the voltage across the first inductor 9 equal to the difference between the input voltage UE and the battery voltage of the electrical energy store 2 . Thus, with the help of a line current or the voltage U1 of the first strand 7th the electrical energy storage 2 loaded. At the same time, the choke current in the choke L1 built up. This is the first switching element S1 closed. In this case a mesh equation results when the switch is closed S1 that the input voltage UE equal to the sum of the temporal voltage of the second inductance 10 and the voltage across the choke L1 is. The voltage of the second inductor 10 can be determined by using the transformation ratio ü of the transformer 13th the voltage of the second inductor 10 via the voltage of the first inductance 9 multiplied times the transmission ratio ü can be determined. Above the first throttle L1 there is a voltage drop. This is the voltage across the second choke L1 equal to the difference between the input voltage UE and the voltage across the second inductor 10 . The voltage across the first choke is also the same L1 equal to the sum of the input voltage UE and the voltage of the first inductor 9 .

In a second subsequent step, the built-up inductor current is freewheeled. The first switching element is S1 opened, whereby the throttle current of the first throttle L1 is slowly degraded and also the electrical energy storage 2 loads. It flows in the first strand 7th the charging current from the DC voltage charging source remains unchanged 3 across the first inductor 9 to electrical energy storage 2 . At the two connection terminals 12th of the transformer 13th a voltage difference is generated in relation to the input voltage UE on the voltage level of the battery voltage of the electrical energy store 2 to raise. In particular, the charging current corresponds to the electrical energy store 2 equal to the sum of the string currents of the first string 7th and the second strand 8th .

A decision criterion for a voltage increase is the transformation ratio ü or the winding ratio of the transformer 13th . In particular, the transmission ratio ü is derived from the maximum voltage of the electrical energy store that can be achieved 2 and the voltage of the DC charging source 3 certainly. The transformation ratio ü is the sum of the maximum battery voltage and the input voltage UE divided by the input voltage UE certainly. For example, it can be the maximum voltage of the DC voltage charging source 3 act around a voltage level of 750 volts and at the maximum end-of-charge voltage of the electrical energy storage device 2 it can be 870 volts. This results in a gear ratio of -1 to 6.25. The opposite direction of winding is expressed here with the negative sign. The first thrush L1 can by the to be mentioned clock frequency of the first switching element S1 to be determined. This can be caused by the switching losses and the dissipatable waste heat of the first switching element 1 be decisively shaped. The first switching element is also S1 influenced by its current load by the transmission ratio ü, because the current through the first switching element S1 corresponds to 1: ü of the phase current of the first phase 7th . The larger the transmission ratio ü can be selected (that is, the smaller the voltage swing of the step-up converter 4th should be), the more compact the boost converter can be 4th be conceived.

In a further possible embodiment, the step-up converter can 4th have a function in which a voltage ratio between the electrical energy store 2 and the DC voltage charging source 3 exceeds the transformer ratio. This can be the case if the charging voltage is to be reached above 870 volts. For example, there is a battery voltage of the electrical energy store 2 , which is the result of a multiplication between the transformation ratio and the input voltage, the function of the first string 7th no longer given because the induced voltage increase across the inductances 9 , 10 of the transformer 13th not enough to keep up the voltage of the electrical energy store 2 to achieve or to surpass. The same would also be the case if, with a vehicle voltage, a voltage was applied to the DC voltage charging source 3 less than 750 volts would be present. This would be the first diode D1 lock to prevent uncontrolled discharging of the electrical energy store 2 to avoid. The resulting function of the boost converter 4th is reduced to the first strand S2 . This now corresponds to a circuit of a conventional boost converter. The charging current of this boost converter is now determined by the design of the first switching element S1 and the first throttle L1 (including leakage inductance of the transformer 13th ) certainly. In this case, a charging current flows through the second line 8th to the electrical energy storage 2 . The first switching element is in parallel S1 closed, so that in turn there is a throttle current in the throttle L1 forms. As soon as the choke current is sufficient, the first switching element S1 opened and the built-up choke current flows from the choke L1 in the electrical energy storage 2 and loads this.

In particular, the transformer 13th can be effectively produced despite high current requirements, since the number of windings in the first strand 7th by the factor of the transmission ratio ü smaller than that in the second strand 8th is. On the first strand 7th there are high charging currents (high conductor cross-section required) and in the second strand 8th lower currents prevail (smaller winding cross-section possible).

the 3 shows a schematic block diagram of the boost converter 4th , whereby a simulation setup is shown here in particular. In particular, the step-up converter 4th can be simulated. The electrical energy store is in this simulation setup 2 represented by a capacitance to the increasing voltage level of the electrical energy storage 2 to be able to represent. At the beginning of the simulation, the voltage of this capacitance of 750 volts is identical to the voltage of the DC charging source 3 . As the transformation ratio of the transformer 13th 1: -6.25 was chosen. In order to make the simulation more understandable, the value of the first throttle was initially used L1 with 0 Henry and also the internal resistances of the DC voltage charging source 3 and the electrical energy storage 2 set with 0 ohms. The input capacitance is also here C1 and the output capacitance C2 not provided.

the 4th shows in particular exemplary current and voltage curves over time of the simulation results of the simulation setup 3 . With the course a, the current is the DC voltage charging source 3 shown. The curve b is the voltage curve of the first switching element S1 shown. The curve c is the current of the first switching element S1 shown. The curve d is the state of the gate of the first switching element S1 shown. With the curve e is the throttle current of the first throttle L1 shown. The curve f is the voltage curve of the first choke L1 shown. In the case of curve g, the throttle current is the second throttle L2 shown and with h is the voltage curve of the second choke L2 shown. The curve i shows a transformer voltage of the transformer 13th . With the curve j is the voltage curve of the transformer 13th shown in the timing path. The curve k is the voltage curve of the electrical energy store 2 shown and the course I is the current course of the electrical energy store 2 shown.

In particular, the curves just described were taken into account with the up-converter 4th shown as a two-level boost converter. In particular, here is how the boost converter works 4th shown when the input voltage UE greater than twice the battery voltage of the electrical energy storage device 2 is. The voltage design of the components is in a "Continuous Current Mode" on both connection sides 5 , 6th shown.

By setting the first throttle L1 the previously described mesh equations can be traced to an inductive value of 0 Henry. Via the connection terminals 12th of the transformer 13th is on the first strand 7th to see how at any point in time there is a difference in the voltage of the DC charging source 3 and the battery voltage of the electrical energy store 2 is present. This can be seen in particular in curve i. The charging current (curve I) is regulated with a hysteresis to values between 80 and 120 amperes. The current through the second strand 8th has an essentially lower value, namely only the 1 / 6.25 level part. This corresponds exactly to the transmission ratio. The charging current ends automatically at 870 volts because the circuit is not able to generate a higher charging voltage with this design of the transmission ratio (this can be seen in curves j and k). For example, a maximum voltage increase of 120 volts can be achieved. It can also be seen here in the curves shown that in this mode of operation the charging current is on both the side of the DC voltage charging source 3 as well as on the side of the electrical energy storage 2 has intermittent operation. This makes it possible to use the boost converter with smaller capacitances in the input or output 4th to provide.

It can also be seen that the rise and fall phases of the currents in the first strand 7th and in the second strand 8th are synchronous (compare course e and g). While on the first strand 7th however, always the current from the DC voltage charger 3 to electrical energy storage 2 leads, the current of the second strand charges 8th only when the choke current is freewheeling (first switching element open) in the electrical energy store 2 .

If now the inductance of the choke L1 with the value 1 Microhenry is provided, the voltages at the ends of the transformer fluctuate 13th now in time with the first switching element S1 . This allows the clock frequency of the first switching element 1 can be reduced slightly, since there are more inductive energy stores in the boost converter 4th are engaged overall. However, the voltage range up to the maximum voltage of 870 volts is not affected.

Various possible embodiments of the boost converter shown above are shown in the following figures 4th shown. The respective functionalities and current curves are identical to those in 2 .

In the 5 is in particular a further embodiment of the boost converter 4th shown. A case is shown here, with which a higher efficiency of the boost converter 4th can be reached. This is particularly achieved through the use of a bypass switch S2 via the first diode D1 in the first strand 7th achieved. It is particularly between the node 11 and between the first inductor 9 and the first diode D1 interconnected a bypass line. In other words, becomes the first diode D1 bridged using the bypass line. It can thus be achieved that a current of the first strand 7th not completely over the first diode D1 flows, but to the diode D1 and the bypass line 15th is divided. Thus there can be losses in the first diode D1 can be reduced, thereby increasing the efficiency of the boost converter 4th can be increased. This enables a higher DC charging capacity of the boost converter 4th can be achieved by a low semiconductor expenditure and a lower winding quality (transformer 13th , Throttle L1 ) can be set. For this purpose, a higher charging current is required, which is passed through the first line 7th and the first diode D1 would flow, so in particular the first diode D1 would have to be designed for a higher current value. To remedy this, the bypass line is used 15th used. Thus, the first diode D1 are less loaded, which in particular the first throttle L1 must be designed for significantly smaller currents. This is due to the blocking ability of the throttle L1 at one himself setting charging current less than 0 amps is no longer necessary. In addition, as shown in the previous simulations, there is a non-intermittent current flow in the choke L1 available. However, it must be noted that at no time does the voltage across the first inductance 9 less than the differential voltage between the input voltage UE and the battery voltage of the electrical energy store 2 will. It is therefore advisable to use the bypass switch S2 to close only when a certain current threshold at D1 exceeded (for example 50 amps) and the bypass switch S2 to open again as soon as a second threshold value has been undershot again (for example 30 amps). The threshold values are based on the current ripple in the first strand 7th to interpret.

In particular, shows the 5 another modification of the boost converter 4th . This is done in the first strand 7th between the first inductor 9 and the first diode D1 a second throttle L2 interconnected. With the help of this second throttle L2 can be the clock frequency of the first switching element S1 adjusted, in particular reduced.

the 6th , 7th and 8th show further possible design variants or construction variants of the boost converter 4th .

the 6th shows in contrast to the 2 a possible variant of the boost converter 4th , at which a negative HV potential can be adjusted. In the 2 the voltage increase for charging the electrical energy storage device became to that effect 2 carried out in the positive HV potential. In the 6th the negative HV potential is lowered. Here are the strands 7th , 8th between the negative potential of the electrical energy store 2 and the DC voltage charging source 3 interconnected. However, this results in functions or functionalities that are analogous to those shown above.

the 7th shows in particular a further embodiment of the boost converter 4th . You can use the boost converter shown 4th both potentials (HV +, HV-) can be adjusted. One transformer is connected to a respective branch at the positive potential and one transformer is connected to two branches or two strings at the negative potential. Both transformers can be operated with the first switching element, i.e. with one switching element. Both HV potentials can be adjusted simultaneously and in the same ratio to one another.

the 8th shows in particular a further embodiment of the voltage converter 4th , whereby both HV potentials can also be adjusted here. Both HV potentials are adjusted using series switches with two semiconductor switches each and an internal intermediate circuit capacitor. Both HV potentials can be varied independently of one another.

List of reference symbols

1

vehicle

2

electrical energy storage

3

DC voltage charging source

4th

Boost converter

5

Entry page

6th

Exit page

7th

first strand

8th

second strand

9

first inductance

10

second inductance

11

Junction

12th

Terminals

13th

transformer

14th

Funding

15th

Bypass line

a-I

Voltage and current curves

C1

Input capacitance

C2

Output capacitance

D1

first diode

D2

second diode

L1

first throttle

L2

second throttle

S1

first switching element

S2

Bypass switch

UE

Input voltage

UA

Output voltage

U1

first string voltage

U2

second phase voltage

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102017009355 A1 [0006]
• DE 102017009352 A1 [0007]

Claims (10)

Step-up converter (4) for charging an electrical energy store (2) of an electrically powered vehicle (1), with - an input side (5) of the step-up converter (4) for coupling to a predetermined external DC voltage charging source (3) which provides an input voltage (UE) - An output side (6) of the boost converter (4) for coupling to the electrical energy store (3), the output side (6) providing an output voltage (UA) higher than the input voltage (UE), and - a first strand (7) and a second strand (8), which are interconnected between the input side (5) and the output side (6), characterized in that - the first strand (7) and the second strand (8) are interconnected in parallel, - the first strand (7) has a first inductance (9) for providing a first phase voltage (U1), - the second phase (8) has a series connection of a second inductance (10) and a first choke (L1) for making available a second phase voltage (U2), - the first inductance (9) of the first phase (7) is magnetically coupled to the second inductance (10) of the second phase (8), wherein - the step-up converter (4) is designed to, in Depending on the magnetic coupling of the first and second inductance (9, 10) as the charging current of the electrical energy store (2) to provide the sum of a charging current of the first strand (7) and a charging current of the second strand (8). Boost converter (4) according to Claim 1 , characterized in that the second strand (8) has a center tap (14) between the first choke (L1) and a diode (D2) connected in series to the first choke (L1), a first switching element (S1) with the center tap (14) is connected, whereby the second strand (8) is coupled to a potential of the electrical energy store (2) by means of the first switching element (S1). Step-up converter (4) according to one of the preceding claims, characterized in that the first strand (7) has a series connection of the first inductance (9) and a first diode (D1), in particular a freewheeling diode, and the second strand (8) has a Series connection of the second inductance (10), the first choke (L1) and a second diode (D2), in particular a freewheeling diode. Boost converter (4) according to Claim 2 and 3 , characterized in that a second choke (L2) for adapting a clock frequency of the first switching element (S1) is formed between the first inductance (9) and the first diode (D1) of the first strand (7). Up converter (4) according to one of the preceding claims, characterized in that the input side (5) has an input capacitance (C1) and the output side (6) has an output capacitance (C2). Step-up converter (4) according to one of the preceding claims, characterized in that the first inductance (9) and the second inductance (10) are designed as coils, whereby the magnetically coupled inductances (9, 10) form a transformer (13), in particular the two inductors (9, 10) designed as coils have opposite directions of winding. Boost converter (4) according to one of the preceding claims, characterized in that the first strand (7) has a bypass line (15), with a bypass switch (S2) within the bypass line (15) a current flow in the first strand (7) on the bypass line (15) and on the first diode (D1) can be divided. Vehicle (1) with a boost converter (4) according to one of the preceding Claims 1 until 7th . A method for charging an electrical energy store (2) of an electrically powered vehicle (1) with a step-up converter (4), wherein - an input voltage (UE) for the step-up converter (4) is provided with an external DC voltage charging source (3), and - with the Boost converter (4) an output voltage (UA) higher than the input voltage (UE) is provided to the electrical energy store (2), characterized in that - with a first strand (7) of the boost converter (4) which has a first inductance (9) , a first phase voltage (U1) is provided, - a second phase voltage (U2) is provided with a second phase (8) of the step-up converter (4), which has a series connection of a second inductor (9) and a first choke (L1) - with the step-up converter (4) depending on a magnetic coupling of the first and second inductance (9, 10) as the charging current of the electrical energy store (2) d The sum of a charging current of the first line (7) and a charging current of the second line (8) is provided. Procedure according to Claim 9 , characterized in that the step-up converter (4) has a negative potential and / or a positive potential an on-board electrical system of the electrically powered vehicle (1) is adapted.

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