Charging device and method for operating a charging device

Abstract

The invention relates to a charging device (100) having a first connection (110_1, 110_2) on the input side for connection to an electrical energy source (200), a second connection (190_1, 190_2) on the output side for connection to a battery (300) to be charged, and a transformer (150), a primary winding (150_1) of which is electrically connected to the first connection (110_1, 110_2) by means of a primary circuit (400) and a secondary winding (150_2) of which is electrically connected to the second connection (190_1, 190_2) by means of a secondary circuit (500).

Description

Technical Field

[0001] This invention relates to a charging device and a method for operating the charging device. Furthermore, this invention relates to a powertrain having a charging device, a vehicle having a powertrain, a computer program, and a machine-readable storage medium. Background Technology

[0002] For example, charging equipment in vehicles with electric drive systems, electric vehicles, or hybrid vehicles is used to recharge batteries, preferably storage batteries, or traction batteries from an electrical energy source, preferably an AC power source, or a public AC power grid. For this purpose, the charging equipment converts the sinusoidal AC power from the energy source into direct current. For single-phase AC power, the power pulsates at twice the frequency of the AC power.

[0003] The charging equipment preferably has a two-stage power electronics system. The first stage shapes the sinusoidal input current from the AC grid, a so-called power factor correction (PFC) stage. The second stage consists of a DC / DC converter that ensures electrical isolation via a transformer and regulates the voltage level, preferably by means of circuitry and a regulating mechanism, to adjust the output voltage or current. An intermediate circuit capacitor is arranged between the two stages to buffer power pulses at twice the frequency of the AC current with the energy source. Typically, this intermediate circuit is implemented using an electrolytic capacitor. These topologies allow for maintaining a near-sinusoidal input current on the grid side to meet grid-side standards, electrical isolation between the grid and the vehicle to meet safety requirements, and a constant output DC current on the battery side to minimize the load on the battery during charging operation.

[0004] Based on this two-level circuit topology and its characteristics, there is a need for a simplified circuit topology for compact and lighter charging devices, preferably for electric vehicles. Summary of the Invention

[0005] A charging device is provided, the charging device having a first connector on the input side for connection to an electrical energy source, a second connector on the output side for connection to a battery to be charged, and a transformer, wherein the primary winding of the transformer is electrically connected to the first connector via a primary circuit and the secondary winding of the transformer is electrically connected to the second connector via a secondary circuit.

[0006] The primary circuit includes a rectifier circuit and two parallel branches, each branch having a high-side element and a low-side element. The first branch includes a first capacitor and a second capacitor connected in series, and a first intermediate tap located between the capacitors, which is connected to the first terminal of the primary winding. The second branch includes a first low-side switching element connected in series and a second high-side switching element connected in series, along with a second intermediate tap located between the switching elements, which is connected to the second terminal of the primary winding.

[0007] The intrinsic diodes of the first and second switching elements are oriented in such a way that current from the low side to the high side of the second branch is allowed.

[0008] The secondary circuit includes a parallel circuit consisting of two branches, namely the third and fourth branches, each branch having a high-side element and a low-side element.

[0009] The third branch includes a series circuit of a first high-side diode and a third low-side switching element, the series circuit having a third intermediate tap between the first diode and the third switching element, the third intermediate tap being connected to a second connection terminal of the secondary winding, wherein the intrinsic diodes of the first diode and the third switching element are oriented to allow current from the low side to the high side of the third branch. The fourth branch includes a series circuit of a second high-side diode and a fourth low-side switching element, the series circuit having a fourth intermediate tap between the second diode and the fourth switching element, the fourth intermediate tap being connected to a first connection terminal of the secondary winding, wherein the intrinsic diodes of the second diode and the fourth switching element are oriented to allow current from the low side to the high side of the fourth branch. The first connection terminal of the second connector is connected to the cathodes of the first and second diodes, and the second connection terminal of the second connector is connected to the third and fourth switching elements located at the ends of the third and fourth branches.

[0010] The power source is preferably a single-phase AC power grid, and more preferably a public low-voltage power grid. The battery to be charged is preferably a storage battery or traction battery, which powers the electric drive system of the vehicle. The rectifier circuit is preferably a rectifier for converting AC current to DC current. The branch of the parallel circuit with high-side and low-side components is preferably a half-bridge with two electrical, passive and / or active components and a center tap between the components. Power is supplied to the center tap of the half-bridge through the components, wherein the first component on the first side of the center tap is called the high-side component, and the second component on the other side of the center tap is called the low-side component. The switching element is preferably a power semiconductor switch including intrinsic diodes, and more preferably IGBTs or MOSFETs. The expression "for example, connection between the center tap and the terminal" means that the components are connected, contacted, or linked by means of conductive lines or electrical connections.

[0011] Advantageously, a simplified circuit arrangement for a charging device is provided, capable of achieving a near-sinusoidal input current on the grid side, electrical isolation between the grid and the vehicle, and a constant output DC current. This is achieved with a minimal number of components, enabling low-cost manufacturing of the charging device based on this topology. Only four switching elements are used, preferably active semiconductor switches, which preferably operate as zero-voltage switching (ZVS) and / or zero-current switching (ZCS). This results in low switching losses, enabling a high switching frequency. This allows the use of small passive components. Preferably, the control overhead (drivers, logic circuits, processors) is significantly reduced by using a small number of switching components. Preferably, only one inductor component is used: the topology preferably uses only one coupling reactor not only as a transformer but also as a PFC inductor. Preferably, the transformer is used as a component for electrical isolation and as a PFC inductor for the charging device. This results in a reduction in the size of the charging device.

[0012] In another embodiment of the invention, the rectifier circuit includes a third high-side diode and a fourth low-side diode connected in series, together with a fifth intermediate tap between the diodes, the fifth intermediate tap being connected to a first terminal of a first connector, wherein the third high-side diode and the fourth low-side diode are connected in parallel with first and second capacitors, and wherein the third and fourth diodes are oriented such that current can flow from the low side to the high side, and wherein the first intermediate tap between the capacitors is connected to a second terminal of the first connector.

[0013] The simple series circuit of the diode only allows current to flow from the energy source into the primary circuit in the desired direction.

[0014] Advantageously, a simple rectifier circuit is provided for the simplified circuitry of charging devices, which enables a nearly sinusoidal input current on the grid side, electrical isolation between the grid and the vehicle, and a constant output DC current.

[0015] In another design of the present invention, the rectifier circuit includes a bridge rectifier with four diodes, the bridge rectifier being connected to the first and second terminals of the first connector on the input side and in parallel with the second capacitor on the output side.

[0016] The bridge rectifier allows current to flow from the energy source to the primary circuit, regardless of the direction of the current flow. Due to bidirectional rectification, the half-wave of the (AC) energy source is uniformly polarized in the DC circuit of the primary circuit.

[0017] Advantageously, a rectifier circuit is provided as an alternative to the simplified circuitry of charging devices, which can achieve a nearly sinusoidal input current on the grid side, electrical isolation between the grid and the vehicle, and a constant output DC current.

[0018] In another design of the invention, a fifth branch, including a third capacitor, is connected in parallel with the primary circuit. Preferably, this third capacitor is an electrolytic capacitor, which buffers the pulsating power (double the grid frequency) in the primary circuit. This advantageously provides an optimized primary circuit for a simplified charging device.

[0019] In another embodiment of the invention, a fourth capacitor is connected between the fourth intermediate tap and the first connection terminal of the secondary winding. Preferably, this fourth capacitor is a film capacitor or a ceramic capacitor, designed to compensate for voltage components at the mains frequency.

[0020] It advantageously provides an optimized secondary circuit for simplified charging devices.

[0021] Furthermore, the present invention relates to a powertrain for a vehicle, comprising an inverter and a motor, wherein the powertrain includes at least one charging device as described above. Advantageously, a powertrain for an electric vehicle is provided, having a charging device with a simplified circuit topology.

[0022] Furthermore, the present invention relates to a vehicle having a power transmission system as described above.

[0023] Advantageously, a means of transportation is provided which has a charging device with a simplified circuit topology.

[0024] Furthermore, the present invention relates to a method for operating the charging device described above, the method comprising the steps of: alternately switching on and off a second and a first switching element, wherein a fourth switching element is switched on and off at least once while the first switching element is switched on, and wherein a third switching element is switched on and off at least once while the second switching element is switched on.

[0025] By alternating switching on and off of the second and first switching elements, the primary winding or main inductor and the third capacitor or electrolytic capacitor are alternately charged when the voltage of the energy source is positive. When the mains voltage is negative, the components switch roles, thereby charging the primary winding and the third capacitor in the same way. A boost chopper is in operation. The pre-defined switching frequencies of the first and second switching elements are significantly greater than the AC frequency of the energy source, thereby switching the first and second switching elements S1 and S2 on and off multiple times during a phase of positive or negative mains voltage. To avoid short circuits, the first and second switching elements S1 and S2 are never switched on simultaneously, and a settling time is preferably observed after one switching element is switched off and before the other is switched on. The input current is regulated by varying the duty cycle of the first and / or second switching elements. During the period when the first switching element is switched on, the secondary coil absorbs energy by at least a single switching on and off of the fourth switching element. During the period when the second switching element is turned on, energy from the secondary coil is supplied to the output terminal by means of at least a single turn-on and turn-off of the third switching element. A boost chopper is also in operation. The output current and / or output voltage are regulated by means of changes in the duty cycle of the third and / or fourth switching elements.

[0026] The main inductor of the transformer serves as a PFC reactor. Four switching states must be distinguished. The first and second switching elements S1 and S2 always switch alternately with a defined duty cycle. A settling time is provided between the off-state of the first and second switching elements S1 or S2 and the on-state of the second and first switching elements S2 or S1 to allow passive current commutation or to reliably prevent bridge short circuits. The third high-side diode conducts continuously during this phase, operating only at the grid frequency, as long as the grid voltage is positive. Therefore, the grid voltage is also applied to the first capacitor or upper capacitor of the capacitor half-bridge. The second switching element S2 is first turned on. The grid voltage is applied through the main inductor of the transformer, generating a rising current flowing through the transformer. The second switching element S2 is then turned off. The current passively commutates to the backward-conducting intrinsic diode of the first switching element S1, allowing this switching element to be turned on at ZVS after the settling time. The main inductor then preferably drives the current into the third capacitor or electrolytic capacitor. This involves the operation of a boost chopper. Here, energy is stored in the third capacitor. After a certain period of time, the first switching element S1 is turned off and the second switching element S2 is turned on again. Thus, the described cycle restarts. For a negative grid voltage, the operation functions in a very similar way. Here, all components exchange their roles. The fourth low-side diode is now turned on. When the first switching element S1 is turned on, current is again flowing through the transformer (in the same direction as before). After the first switching element S1 is turned off, the second switching element S2 is turned on with ZVS and energy is supplied to the third capacitor. This is also the operation of the boost chopper. With the second switching element S2 turned off and the first switching element S1 turned on, the cycle restarts.

[0027] With the first switching element S1 turned on, the fourth switching element S4 is turned on for voltage conversion. This creates a raised current in the leakage inductance of the transformer. Preferably, the fourth capacitor or the series capacitor on the secondary side of the converter is used as a DC block and is designed to be so large that no significant voltage change occurs over a switching cycle. After the fourth switching element is turned off, the current autonomously commutates to the second high-side diode in this branch and thus supplies current to the connected battery. Once the first switching element S1 is turned off and the second switching element S2 is turned on after a rest period, the current returns from the secondary side to the primary side at a steep rate. The third switching element S3 is now turned on. The current on the secondary side changes sign and now flows in reverse through the third switching element S3 and the fourth switching element S4. After a certain duration, the third switching element S3 is turned off and the current commutates to the corresponding first high-side diode and supplies current to the battery. With the first switching element S1 and the fourth switching element S4 turned on, the cycle restarts.

[0028] The converter is preferably operated in a continuous operating mode, meaning that the current in the leakage inductance on the secondary side of the transformer does not have a phase in which the current is zero. All switching elements are turned on with particularly low-loss ZVS. If the converter is operated in an intermittent operating mode, the transformer current on the secondary side has a distinct phase in which the transformer current is zero. This involves intermittent operation on the secondary side of the converter. At this operating point, the first, second, and fourth switching elements S1, S2, and S4 are switched with ZVS. The third switching element S3 is turned on with ZCS against a decreasing voltage. This operating point also has low switching losses and therefore allows for high switching frequencies.

[0029] In order to deliver a constant power to the battery at all times, the duty cycles of the first and second switching elements S1 and S2 are not allowed to fall below or exceed certain minimum and maximum limits. Consequently, the converter can only receive current from the grid up to the minimum input voltage. Therefore, the current obtained from the energy source has a region in the zero-crossing region of the energy source voltage where the current is zero and the third and fourth diodes of the diode half-bridge are simultaneously turned off.

[0030] Advantageously, a method is provided in which the switching elements of the charging device are manipulated such that energy transfer occurs through the charging device from the connected energy source to the connected battery.

[0031] Furthermore, the present invention relates to a computer program configured to perform the described method.

[0032] Furthermore, the present invention relates to a machine-readable storage medium on which the described computer program is stored.

[0033] It goes without saying that the features, characteristics, and advantages of the charging equipment are accordingly applicable to or can be applied to the method, powertrain, and vehicles, and vice versa.

[0034] Other features and advantages of embodiments of the present invention will become apparent from the following description with reference to the accompanying drawings. Attached Figure Description

[0035] The invention will now be explained in detail with the aid of some accompanying drawings, for which:

[0036] Figure 1 A schematic diagram of a first embodiment of a circuit topology for a charging device is shown.

[0037] Figure 2 A schematic diagram of a second embodiment of the circuit topology for a charging device is shown.

[0038] Figure 3 A schematic diagram of a third embodiment of a circuit topology for a charging device is shown.

[0039] Figure 4 A schematic representation of a vehicle with a powertrain equipped with a charging device is shown.

[0040] Figure 5 A schematic flowchart illustrating a method for operating a charging device is shown. Detailed Implementation

[0041] Figure 1A charging device 100 is shown, which, during operation, is electrically connected to an energy source 200 at first connectors 110_1, 110_2 on the input side and to a battery 300 to be charged at second connectors 190_1, 190_2 on the output side. The energy source 200 is preferably a single-phase AC power source, such as a public power grid, from which the battery is charged. The charging device includes a primary circuit 400 on the input side and a secondary circuit 500 on the output side. The primary and secondary circuits are preferably inductively connected to each other, but electrically isolated, via the primary winding 150_1 and secondary coil 150_2 of a transformer 150. The primary circuit includes a rectifier circuit 405 and a parallel circuit consisting of two branches, each branch having a high-side element (preferably an electrical component) arranged on the high-side of a half-bridge and a low-side element (preferably an electrical component) arranged on the low-side of the half-bridge. The first branch includes first and second capacitors 422 and 424 connected in series, and a first intermediate tap 426 between the capacitors. The first intermediate tap 426 is connected to the first terminal 152 of the primary winding 150_1 of the transformer. The second branch includes a first low-side switching element S1 and a second high-side switching element S2 connected in series, together with a second intermediate tap 436 between the switching elements S1 and S2. The second intermediate tap 436 is connected to the second terminal 154 of the primary winding 150_1. The intrinsic diodes of the first and second switching elements S1 and S2 are oriented in such a way that current flows from the low side to the high side in the second branch. The secondary circuit 500 includes a parallel circuit consisting of two branches, each having a high-side element and a low-side element. One of these branches, the third branch, includes a series circuit of a first high-side diode 512 and a third low-side switching element S3, with a third intermediate tap 516 between the first diode and the third switching element. The third intermediate tap 516 is connected to the second connection terminal 158 of the secondary winding 150_2 of the transformer 150. The intrinsic diodes of the first diode 512 and the third switching element S3 are oriented in such a way that current flows from the low side to the high side in the third branch. The other branch of the secondary circuit, the fourth branch, comprises a series circuit of the second high-side diode 522 and the fourth low-side switching element S4, which has a fourth intermediate tap 526 located between the second diode 522 and the fourth switching element S4. The fourth intermediate tap 526 is connected to the first connection terminal 156 of the secondary winding 150_2 of the transformer 150. The intrinsic diodes of the second diode 522 and the fourth switching element S4 are oriented in such a way that current flows from the low side to the high side in the fourth branch.The first connection electrode 190_1 of the second connector 190 is connected to the cathodes of the first and second diodes 512 and 522, and the second connection electrode 190_2 of the second connector 190 is connected to the third and fourth switching elements S3 and S4 located at the ends of the third and fourth branches. (According to...) Figure 1 The rectifier circuit 405 includes a third high-side diode 412 and a fourth low-side diode 414 connected in series, along with a fifth intermediate tap 416 located between the third and fourth diodes 412 and 414. The fifth intermediate tap is connected to the first terminal 110_1 of the first connector. The third high-side diode 412 and the fourth low-side diode 414 are connected in parallel with first and second capacitors 422 and 424. The third and fourth diodes are oriented to allow current to flow from the low side to the high side. The first intermediate tap 426 between the capacitors is connected to the second terminal 110_2 of the first connector. Preferably, the primary circuit 400 is connected in parallel with another fifth branch including the third capacitor 425. Furthermore, it is preferable that a fourth capacitor 525 is connected between the fourth intermediate tap 526 and the first terminal 156 of the secondary winding of the transformer 150.

[0042] Figure 2 A schematic diagram of a second embodiment of a circuit topology for a charging device is shown. The circuit topology and reference numerals largely correspond to... Figure 1 The circuit topology shown is illustrated below. The following discussion focuses only on the circuit topology relative to... Figure 1 The differences in circuit topology shown are illustrated. The rectifier circuit 405 includes a bridge rectifier with four diodes. This bridge rectifier is connected on the input side to the first connection 110_1 and the second connection 110_2 of the first terminal and on the output side in parallel with the second capacitor 424. Preferably, the secondary circuit 500 is connected in parallel with another sixth branch including a fifth capacitor 536. In particular, it is connected according to... Figure 1 The topology is different from that of the two grid half-waves, which are only electrically connected to the second capacitor 424.

[0043] Figure 3 A schematic diagram of a third embodiment of a circuit topology for a charging device is shown. The circuit topology and reference numerals largely correspond to... Figure 2 The circuit topology shown is illustrated below. The following discussion focuses only on the circuit topology relative to... Figure 2The differences in circuit topologies shown are illustrated. The secondary circuit 500 of the charging device 100 includes a parallel circuit consisting of two branches, each having a high-side element and a low-side element. One of these branches, the third branch, includes a series circuit of a first high-side diode 512 and a third low-side switching element S3, with a third intermediate tap 516 between the first diode and the third switching element. The third intermediate tap 516 is connected to the second terminal 158 of the secondary winding 150_2 of the transformer 150. The intrinsic diodes of the first diode 512 and the third switching element S3 are oriented in such a way that current can flow from the low side to the high side in the third branch. The other branch of the secondary circuit, the fourth branch, includes a series circuit of a sixth capacitor 532 and a seventh capacitor 534, with a fourth intermediate tap 526 between the sixth and seventh capacitors 532 and 534. The fourth intermediate tap 526 is connected to the first connection pole 156 of the secondary winding 150_2 of the transformer 150. The first connection pole 190_1 of the second connector 190 is connected to the cathode of the first diode 512, and the second connection pole 190_2 of the second connector 190 is connected to the third switching element S3 at the end of the third and fourth branches.

[0044] Figure 4 A vehicle 600 is shown schematically, having a powertrain 650 with a charging device 100. The vehicle 600 is shown here only exemplary with four wheels, but the invention can also be used in any land, water, and air vehicle with any number of wheels. The exemplary powertrain 650 includes at least one charging device 100. Furthermore, the powertrain preferably includes a battery 300, an inverter 640, and a motor 630.

[0045] Figure 5 A schematic flowchart illustrating a method 700 for operating a charging device 100 is shown. The method 700 begins at step 705. In step 710, the second and first switching elements are alternately switched on and off. With the first switching element (720) switched on, the fourth switching element is switched on and off at least once. With the second switching element (730) switched on, the third switching element is switched on and off once. The method ends at step 740.

Claims

1. Charging device (100) having a first connection (110_1, 110_2) at the input side for connection to an electrical energy source (200), a second connection (190_1, 190_2) at the output side for connection to a battery (300) to be charged, a transformer (150) whose primary winding (150_1) is electrically connected to the first connection (110_1, 110_2) by means of a primary circuit (400) and whose secondary winding (150_2) is electrically connected to the second connection (190_1, 190_2) by means of a secondary circuit (500), wherein the primary circuit (400) comprises a rectifier circuit (405) and a parallel circuit consisting of two branches each having a high-side element and a low-side element, the parallel circuit having a first branch comprising a first and a second capacitor (422, 424) connected in series together with a first intermediate tap (426) between these capacitors, the first intermediate tap being connected to a first connection pole (152) of the primary winding (150_1), a second branch comprising a first low-side switching element (S1) connected in series and a second high-side switching element (S2) connected in series together with a second intermediate tap (436) between these switching elements, the second intermediate tap being connected to a second connection pole (154) of the primary winding (150_1), wherein the intrinsic diodes of the first and second switching elements (S1, S2) are oriented so as to allow a current flow from low side to high side, wherein the secondary circuit (500) comprises a parallel circuit consisting of two branches each having a high-side element and a low-side element, the parallel circuit having a third branch comprising a first high-side diode (512) and a third low-side switching element (S3) in series circuit with a third intermediate tap (516) between the first diode and the third switching element, the third intermediate tap being connected to a second connection pole (158) of the secondary winding (150_2), wherein the intrinsic diodes of the first diode (512) and the third switching element (S3) are oriented so as to allow a current flow from low side to high side, a fourth branch comprising a second high-side diode (522) and a fourth low-side switching element (S4) in series circuit with a fourth intermediate tap (526) between the second diode (522) and the fourth switching element (S4), the fourth intermediate tap being connected to a first connection pole (156) of the secondary winding (150_2), wherein the intrinsic diodes of the second diode (522) and the fourth switching element (S4) are oriented so as to allow a current flow from low side to high side, wherein a first connection pole (190_1) of the second connection (190_1, 190_2) is connected to the cathodes of the first and second diodes (512, 522) and a second connection pole (190_2) of the second connection (190_1, 190_2) is connected to the third and fourth switching elements (S3, S4) at the ends of the third and fourth branches.

2. The charging device (100) according to claim 1, wherein the rectifier circuit (405) comprises a third high-side diode (412) and a fourth low-side diode (414) connected in series together with a fifth intermediate tap (416) between these diodes (412, 414), which fifth intermediate tap is connected to the first connection pole (110_1) of the first connection, wherein the third and fourth diodes are oriented such that a current from low side to high side is allowed, and wherein a first intermediate tap (426) between the capacitors is connected to the second connection pole (110_2) of the first connection.

3. The charging device (100) according to claim 1, wherein the rectifier circuit (405) comprises a bridge rectifier with four diodes, which bridge rectifier is connected on the input side to the first connection pole (110_1) and to the second connection pole (110_2) of the first connection and on the output side in parallel to the second capacitor (424).

4. The charging device (100) according to any one of claims 1 to 3, wherein the primary circuit (400) is connected in parallel to a further fifth branch comprising a third capacitor (425).

5. The charging device (100) according to any one of claims 1 to 3, wherein a fourth capacitor (525) is connected between the fourth intermediate tap (526) and the first connection pole (156) of the secondary winding.

6. A powertrain (650) of a vehicle (600) having an inverter (640) and an electric machine (630), wherein the powertrain comprises at least one charging device (100) according to any one of claims 1 to 5.

7. A vehicle (600) having a powertrain (650) according to claim 6.

8. A method (700) for operating a charging device (100) according to any one of claims 1 to 3, with the following steps: alternately switching on and off (710) the second and first switching elements (S2, S1), wherein the fourth switching element (S4) is switched on and off at least once in case the first switching element (S1) is switched on (720), and wherein the third switching element (S3) is switched on and off at least once in case the second switching element (S2) is switched on (730).

9. The method (700) according to claim 8, wherein the first switching element (S1) is switched on (720) and the second switching element (S2) is switched off (730) for a first time period, and wherein the second switching element (S2) is switched on (730) and the first switching element (S1) is switched off (720) for a second time period.

9. Computer program, which is set up to carry out the method (700) according to claim 8.

10. Machine-readable storage medium, on which the computer program according to claim 9 is stored.

Images