POWER CONVERTER FOR AN ON-BOARD CHARGER FOR ELECTRIC VEHICLES

Abstract

An AC-DC converter for an onboard electric vehicle charger is described. The converter comprises a first circuit (102) with rectifier elements for rectifying input AC power into unregulated DC power, and the second circuit (104) comprises a common switching branch with at least one first switching element (S1) and one second switching element (S2), wherein the second circuit (104) is configured to convert the unregulated DC power into high-frequency AC power. The converter includes a third circuit (106) comprising an isolated DC-DC converter. Furthermore, the common switching branch forms a primary bridge of the isolated DC-DC converter. The third circuit (106) is configured to convert the high-frequency AC power into a target output DC voltage.The AC-DC converter uses the switch-sharing concept and operates in resonance mode to reduce switching losses and thereby achieve higher efficiencies.

Description

TECHNICAL AREA

[0001] The present subject matter relates generally to the field of onboard charging topology and in particular, but not exclusively, to an alternating current (AC) / direct current (DC) energy converter for an onboard charger for electric vehicles. BACKGROUND

[0002] The production and use of battery-powered electric vehicles, such as electric cars, including battery electric vehicles (BEVs) and plug-in hybrid electric vehicles (PHEVs), has increased recently with technological advancements. To use an AC charging station, these vehicles require onboard systems that convert the station's AC power to direct current (DC) to charge the batteries. These systems are often referred to as onboard chargers.

[0003] Onboard chargers typically consist of three stages. The first stage may include a diode bridge rectifier. The diode bridge rectifier converts an input alternating current into an unregulated direct current. The second stage may include a boost cell. The boost cell is used to correct the power factor and shapes the waveform of the input current to meet grid standards. The third stage may include an isolated DC-DC converter. The isolated DC-DC converter boosts the DC voltage to the requirements of the target vehicle's battery while providing galvanic isolation as required by safety standards such as the International Electrotechnical Commission (IEC) 61851-23. The boost cell, a crucial component in this architecture, typically comprises several components, which contribute to the complexity and cost of the overall system.Consequently, existing battery charging technologies attempt to simplify the onboard charger by reducing or eliminating the components of the charging cell, using active components such as an active rectifier instead of the diode bridge rectifier. However, the use of active components increases the overall cost.

[0004] One of the existing techniques, disclosed in patent publication number US20210399643, provides a single-stage power converter comprising an up-shifting segment and a blocking segment that share common switching devices to reduce the need for an additional switching stage.

[0005] Another existing technology, disclosed in patent publication no. CN201766508, relates to a single-phase full-bridge inverter in isolated form for power factor correction with soft-start charging circuit.

[0006] Another existing technique disclosed in patent publication JP2017163657 is a three-phase power converter for improving the power factor to balance the current of a single phase.

[0007] Another existing technique, disclosed in patent publication CN203233307, discloses a bridgeless forward correction of the power factor by controlling various switching tubes.

[0008] Another existing technique, disclosed in patent publication no. KR101776617, discloses a power factor corrector for converting electrical power from an alternating current source into direct current and for supplying a load with direct current.

[0009] Another existing technique, disclosed in patent publication USRE44136, discloses methods and devices for adaptively configuring an array of voltage converter modules.

[0010] However, there is still a need for an improved AC-DC converter for an onboard charger that reduces active switching components, cost, weight, space requirements and switching losses.

[0011] The information disclosed in this section concerning the background of the disclosure is provided solely for a better understanding of the general background of the disclosure and is not to be understood as an acknowledgment or an indication that this information is part of the prior art already known to the person skilled in the art. SUMMARY OF DISCLOSURE

[0012] The present disclosure overcomes one or more shortcomings of the prior art and offers additional advantages, which are explained herein. Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered part of the claimed disclosure.

[0013] The main purpose of this disclosure is to provide an AC-DC converter for an on-board electric vehicle charger that is capable of achieving soft switching with the fewest possible active switches.

[0014] Another purpose of the revelation is to reduce the number of components, weight and space requirements by reducing the switching losses of the charger.

[0015] Another task of the revelation is to utilize the switch-sharing concept to minimize the active switching components.

[0016] Another objective of the disclosure is to provide a converter topology for AC-DC conversion with power factor correction and galvanic isolation.

[0017] Another task of the revelation is to provide a converter topology that operates in resonance mode in order to reduce switching losses and thereby achieve higher efficiencies.

[0018] Another task of the revelation is to achieve high voltage on the output side and high efficiency compared to existing techniques.

[0019] Another objective of disclosure is to operate at a power factor of one across the entire operating range, keeping the total harmonic distortion (THD) below 5%.

[0020] In a non-limiting embodiment of the present disclosure, an AC-DC converter for an onboard charger is disclosed. The converter comprises a first circuit including a plurality of rectifier elements for rectifying an input AC power into unregulated DC power, and a second circuit electrically coupled to the first circuit and configured to convert the unregulated DC power into high-frequency AC power. The second circuit includes a common switching branch comprising at least one first switching element and one second switching element. Furthermore, the converter includes a third circuit electrically coupled to the second circuit and configured to convert the high-frequency AC power into a target output DC voltage.The third circuit comprises an isolated DC-DC converter with a primary bridge and a secondary bridge. In some embodiments, the common switching branch is located on one side of the primary bridge of the isolated DC-DC converter. In some embodiments, a voltage doubler circuit is located on the secondary side of the isolated DC-DC converter. The voltage doubler circuit enables the provision of a high output voltage and thus the fulfillment of the charging requirements of a high-voltage battery.

[0021] In another embodiment of the present disclosure, the two switches (the first switching element and the second switching element) in the shared switching branch are operated alternately to transfer the high-frequency AC power between the second circuit and the third circuit based on positive and negative half-cycles of the input AC power. According to one embodiment of the present disclosure, implementing a switch-sharing concept using the shared switching branch minimizes the number of active switching components required for implementing the onboard charging topology, while simultaneously reducing the line and switching losses with respect to the onboard charging topology.

[0022] In a further embodiment of the present disclosure, a method for operating an AC-DC converter is disclosed. The method for operating the converter comprises rectifying an input AC power into an unregulated DC power, converting the unregulated DC power into a high-frequency AC power based on alternating switching cycles associated with a common switching branch, and converting the high-frequency AC power into a target output DC voltage.

[0023] In a further embodiment of the present disclosure, the integrated charger can achieve smooth switching with the fewest possible active switches.

[0024] The foregoing summary serves only for illustration and is in no way intended to be limiting. In addition to the illustrative aspects, embodiments, and features described above, further aspects, embodiments, and features will become clear by reference to the drawings and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The accompanying drawings form part of the description and serve to further understand this disclosure. These accompanying drawings illustrate the embodiments of this disclosure, which are used to describe the principles of this disclosure. The embodiments are shown by way of example and are not limited to the illustrations in the accompanying drawings, where the same references denote similar elements. Fig. shows a circuit diagram of an AC-DC converter according to some embodiments of the present disclosure; Fig. 2a shows a circuit diagram of an AC-DC converter in a positive half-cycle of a first switching cycle of an input AC power according to some embodiments of the present disclosure; Fig. 2b shows a circuit diagram of an AC-DC converter in a positive half-cycle of a second switching cycle of the input alternating current according to some embodiments of the present disclosure; Fig. 3a shows a circuit diagram of an AC-DC converter in a negative half-cycle of the first switching cycle of the input AC current according to an embodiment of the present disclosure; Fig. 3b shows a circuit diagram of an AC-DC converter in a negative half-cycle of the second switching cycle of the input AC current according to an embodiment of the present disclosure; Fig. Figure 4a is a graphical representation of the average switching losses as a function of the power according to an embodiment of the present disclosure; Fig. 4b is a graphical representation of the average switching loss as a function of the voltage according to an embodiment of the present disclosure; Fig. Figure 4c is a graphical representation of the average switching loss as a function of the current according to an embodiment of the present disclosure; Fig. 5a is a graphical representation of the voltage and current of the resonance tank in conjunction with an AC-DC converter according to an embodiment of the present disclosure; Fig. 5b is a graphical representation of voltage and current in connection with a first switching element of an AC-DC converter according to an embodiment of the present disclosure; Fig. 5c is a graphical representation of voltage and current in connection with a second switching element of an AC-DC converter according to an embodiment of the present disclosure; Fig. Figure 6a is a graphical representation of an input voltage and a phase current in connection with an AC-DC converter according to an embodiment of the present disclosure; Fig. Figure 6b is a graphical representation of a Fast Fourier Transform (FFT) analysis of an input current connected to an AC-DC converter, according to an embodiment of the present disclosure; Fig. Figure 6c is a graphical representation of an output voltage of an AC-DC converter according to an embodiment of the present disclosure; and Fig. Figure 7 shows a flowchart of a method for operating an AC-DC converter in accordance with an embodiment of the present disclosure.

[0026] The illustrations show embodiments of the disclosure for illustrative purposes only. A person skilled in the art will readily recognize from the following description that alternative embodiments of the structures and methods presented here can be used without deviating from the principles of the disclosure described herein. DETAILED DESCRIPTION

[0027] It is understood that the present disclosure may encompass various alternative versions and sequences of steps, unless expressly stated otherwise. It is also understood that the specific devices and methods illustrated in the accompanying drawings and described in the following description represent only exemplary and non-limiting embodiments or aspects. Therefore, specific dimensions and other physical properties relating to the embodiments or aspects disclosed herein are not to be considered limiting.

[0028] Reference is now made to the exemplary embodiments of the disclosure shown in the accompanying drawings. Wherever possible, the same numerals are used to indicate identical or similar parts. Embodiments of the disclosure are described in the following sections with reference to the Fig. 1 to 7 described.

[0029] In one embodiment, an onboard charger for an electric vehicle comprises an AC-DC converter. The AC-DC converter further comprises a first circuit, a second circuit, and a third circuit. The first circuit may include a rectifier circuit that rectifies an input alternating current received from a wall outlet or mains power source into unregulated direct current. The second circuit is connected to the first circuit. The second circuit may include an amplifier circuit configured to receive the unregulated direct current power from the first circuit and convert the unregulated direct current power into high-frequency alternating current power. In some embodiments, the second circuit may include a common switching branch with at least two switching elements. The third circuit is coupled to the second circuit.The third circuit may include an isolated DC-DC converter (hereinafter also referred to as a DC-DC converter) configured to receive the high-frequency AC power from the second circuit and convert the high-frequency AC power into a target DC output voltage. The third circuit may also include the common switching branch. For example, the second and third circuits may share the common switching branch, based on their respective operating characteristics. The structural design and operating functions of various embodiments of the exemplary AC-DC converter are described in detail in the respective descriptions of the following figures.

[0030] Fig. Figure 1 shows a circuit diagram of an AC-DC power converter 100 according to some embodiments of the present disclosure. The AC-DC power converter may hereinafter also be referred to as converter 100. In one embodiment, the AC-DC converter 100 comprises a first circuit 102, a second circuit 104, and a third circuit 106. The first circuit 102 may comprise a plurality of rectifier elements to rectify an input AC power into unregulated DC power. The first circuit is, for example, a rectifier circuit. In some embodiments, the plurality of rectifier elements may comprise a plurality of diodes configured in various configurations to perform the rectification of the input AC power.

[0031] In one embodiment, the rectifier circuit may comprise four rectifier elements (e.g., D1, D2, D3, D4) connected in a bridge configuration to form a full-bridge rectifier. In another embodiment, the rectifier circuit may comprise two rectifier elements connected in a half-bridge configuration. A person skilled in the art will understand that a configuration of the rectifier circuit with a different number of rectifier elements than described in this disclosure may be used to rectify the input AC voltage or input AC power. In one example, the rectifier circuit may be configured to rectify a single-phase input AC voltage. In another example, the rectifier circuit may be configured to rectify a three-phase input AC voltage.In some embodiments, the rectifier elements can be integrated into a rectifier chip.

[0032] The second circuit 104 is electrically coupled to the first circuit. The second circuit 104 can include a series inductor (L3), a common switching branch with an upper sub-circuit and a lower sub-circuit. In some embodiments, the common switching branch includes a first switching element (S1), a second switching element (S2), and a first capacitor (C). P1 ) and a second capacitor (C P2 In some embodiments, the first switching element (S1) and the second switching element (S2) are bidirectional switches. In some embodiments, the upper partial circuit comprises the first switching element (S1) and the first capacitor (C). P1 In some embodiments, the lower partial circuit includes the second switching element (S2) and the second capacitor (C). P2In a preferred embodiment, the shared switching branch of the second circuit comprises a set of switching elements that are shared by the second circuit and the third circuit.

[0033] In one embodiment, the switches used in the common switching branch are configured to operate alternately to transfer the high-frequency AC power between the second circuit 104 and the third circuit 106 based on the respective positive and negative half-cycles of the input AC power. In one embodiment of the present disclosure, the upper partial circuit is electrically connected to the lower partial circuit to form a first connection. In a preferred embodiment of the present disclosure, as described in Fig. As shown in Figure 1, the first switching element (S1) and the second switching element (S2) comprise metal-oxide-semiconductor field-effect transistors (MOSFETs). In one embodiment, the source branch of the second switching element (e.g., MOSFET) and a second terminal of the second capacitor (C) are P2 ) electrically connected to ground.

[0034] In another embodiment of the present disclosure, the first switching element (S1) and the second switching element (S2) can comprise field-effect transistors (FETs). In a further embodiment, the first switching element (S1) can comprise a FET and the second switching element (S2) a MOSFET. In yet another embodiment, the first switching element (S1) can consist of a MOSFET and the second switching element (S2) of a FET. Those skilled in the art know that the switching elements (S1, S2) can also include other transistor types or combinations thereof besides FETs and MOSFETs, as described in the preceding sections.

[0035] In one embodiment, a first end of the series inductor (L3) is electrically connected to an output of the first circuit 102, and a second end of the series inductor (L3) is electrically connected to the first node. In another embodiment, the third circuit 106 is electrically connected to the second circuit 104. In an exemplary configuration, the third circuit 106 comprises an isolated DC-DC converter. The common switching branch forms a primary bridge of the isolated DC-DC converter on a primary side. In one embodiment, the primary bridge of the isolated DC-DC converter includes, for example, the common switching branch on a primary side of the third circuit 106. In another embodiment, the isolated DC-DC converter includes a secondary bridge that contains a voltage doubler circuit on a secondary side of the DC-DC converter.

[0036] In one embodiment of the present disclosure, the isolated DC-DC converter comprises a transformer with a primary winding (L1) and a secondary winding (L2). In another embodiment of the present disclosure, the isolated DC-DC converter is an integrated boost resonant converter. According to the exemplary embodiments of the present disclosure, the transformer provides sufficient voltage gain by taking into account the gain of a resonant tank circuit consisting of various components of the exemplary converter. In one embodiment, the voltage doubler comprises a plurality of diodes and a plurality of capacitors. For example, the voltage doubler comprises a first diode (D5), a second diode (D6), a third capacitor (C), and a third capacitor (C). S1 ) and a fourth capacitor (C S2 ).

[0037] In some embodiments, the secondary winding (L2) is electrically connected at one end to an anode of the first diode (D5) and a cathode of the second diode (D6). The secondary winding (L2) is electrically connected at the other end to a first terminal of the third capacitor (C). S1 ) and a first connection of the fourth capacitor (C S2 ). One cathode of the first diode (D5) is electrically connected to a second terminal of the third capacitor (C ). S1 ) connected, and an anode of the second diode (D6) and a second terminal of the fourth capacitor (C S2 ) are electrically connected to a ground.

[0038] In one embodiment of the present disclosure, the primary winding (L1) of the transformer is electrically connected to the common switching leg, and the secondary winding (L2) of the transformer is electromagnetically coupled to the primary winding (L1). The voltage doubler comprises the first diode (D5) connected to the secondary winding (L2). An anode of the first diode (D5) and a first end of the secondary winding (L2) are electrically connected to each other to form a second junction (J2). An anode of the second diode is electrically connected to ground, and a cathode of the second diode is electrically connected to the second junction. A first terminal of the third capacitor (C) S1 ) is electrically connected to a cathode of the first diode (D5). A second terminal of the third capacitor (C S1) and a second end of the secondary winding (L2) are electrically connected to form a third connection point (J3). A first connection of the fourth capacitor (C S2 ) is electrically connected to the third connection point (J3), and a second terminal of the fourth capacitor (C S2 ) is electrically connected to ground.

[0039] In some embodiments, the transformer includes a leakage inductance. In one embodiment of the present disclosure, the leakage inductance is an internal leakage inductance. In another embodiment, the leakage inductance is an external leakage inductance that is electrically connected to the transformer. One end of the leakage inductance (L k ) is electrically connected to the first junction (J1) and another end of the leakage inductance (L k ) is electrically connected to the first end of the primary winding (L1) of the transformer.

[0040] Fig. Figure 2a shows a circuit diagram of an AC-DC converter in a positive half-cycle of a first switching cycle of an input AC power in accordance with some embodiments of the present disclosure. For example, Fig. 2a show a first positive half-cycle of the first switching cycle of the input alternating voltage. Fig. 2a shows a 200A configuration of the 100 converter. Fig. 1. During the positive half-cycle of the first switching cycle of the AC input power, the first switching element (S1) is switched off and the second switching element (S2) is switched on during the first positive half-cycle of the AC input power. Furthermore, resonance is established between the lower sub-circuit and the secondary side of the isolated DC-DC converter based on the switch-on of the second switching element (S2). Additionally, the target output DC voltage is generated on the secondary side of the isolated DC-DC converter during the establishment of this resonance.

[0041] In one embodiment, the rectifier elements (D1, D4) are forward-biased during the first positive half-cycle. The first switching element (S1) is switched off, and the second switching element (S2) is switched on. The series inductor (L3) is charged by a current flowing through it. When the series inductor (L3) is charged, the voltage across the inductor is Vs (AC supply voltage), and the current flowing through the series inductor (L3) is, for example, Vs(t) = abs(Vs(t)).

[0042] Part of the lower circuit, including the second capacitor (C P2 ), is discharged via the transformer and the transformer's secondary winding (L2). The second capacitor (C P2 ) can, according to an associated switching operation of the inverter, together with a part that includes the third capacitor (C S1 ) and the fourth capacitor (C S2) includes the secondary side of the isolated DC-DC converter, forming a resonance. The associated switching process can, for example, be representative of the respective switching cycles of the converter. The first diode (D5) can be forward-biased to connect the third capacitor (C S1 ) and a fifth capacitor (C bulk ) to charge. A first connection of the fifth capacitor (C bulk ) is electrically connected to the first terminal of the third capacitor (C S1 ) connected and a second terminal of the fifth capacitor (C bulk The first diode (D5) is electrically connected to ground. It supplies the target output DC current to a resistor (R1) on the secondary side of the isolated DC-DC converter. The resistor (R1) can, for example, be connected to a load.

[0043] In one embodiment, as described in Fig. As shown in Figure 1, the ground connection between the second switching element (S2) and the second capacitor (C) can be P2 ) and the ground connection between the second terminal of the fourth capacitor (C S2 ) and the second terminal of the fifth capacitor (C bulk ) may differ on both sides. The first ground connection can be a primary ground and the second ground connection a secondary ground. In one embodiment, the sum of the current flowing through the series inductance (L3) and the current flowing through the leakage inductance (L) is k ) flowing current equal to the value of the current flowing through the second switching element (S2).

[0044] In some embodiments, during the first positive half-cycle and the first negative half-cycle of the input alternating current, the first switching element (S1) is switched off and the second switching element (S2) is switched on, and when the second switching element (S2) is switched on, the target output DC voltage is generated on the basis of a resonance generated by the lower sub-circuit and a secondary side of the isolated DC voltage converter.

[0045] In some embodiments, during a second positive half-cycle and a second negative half-cycle of the input alternating current: the first switching element (S1) is switched on and the second switching element (S2) is switched off, and when the first switching element (S1) is switched on, the desired output voltage is generated on the basis of a resonance generated by the upper sub-circuit, the lower sub-circuit and a secondary side of the isolated DC-DC converter.

[0046] Fig. Figure 2b shows a circuit diagram of an AC-DC converter in a positive half-cycle of a second switching cycle of the input AC power. For example, Fig. 3a show a second positive half-cycle of the input alternating voltage. Fig. 3b shows a configuration 300B of the converter 200 from Fig. 2. During the positive half-cycle of the second switching cycle of the input AC power, the first switching element (S1) is turned on and the second switching element (S2) is turned off. Furthermore, resonance is established through the upper circuit, the lower circuit, and the secondary side of the isolated DC-DC converter based on the turning-on of the first switching element (S1). During the establishment of resonance, the target output DC voltage is generated from a transformer output on the secondary side of the isolated DC-DC converter.

[0047] In one embodiment, during the second positive half-cycle, the series inductance (L3) is transferred to the first capacitor (C). P1 ) discharged. The second capacitor (C P2 ), the leakage inductance (L k ), the second capacitor (C P2 ) and the first capacitor (CP1 ) together with the third capacitor (C S1 ) and the fourth capacitor (C S2 ) a resonance corresponding to an associated switching operation with the leakage inductance (L k The second diode (D6) is forward-biased and charges the fourth capacitor (C). S2 ) and the fifth capacitor (C bulk ). The second diode (D6) supplies the target output DC voltage from the transformer to the resistor (R1).

[0048] In one embodiment, the difference between the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) k ) flows, equal to the value of the current flowing through the first switching element (S1).

[0049] Fig. Figure 3a shows a circuit diagram of an AC-DC converter in a negative half-cycle of the first switching cycle of the input AC power. For example, Fig. 3a represents a first negative half-cycle of the input AC power. Fig. Figure 4a shows a 300A configuration of the 100 converter. Fig. 1. During the negative half-cycle of the first switching cycle of the input AC power, the first switching element (S1) is switched off and the second switching element (S2) is switched on. The lower sub-circuit and one secondary side of the isolated DC-DC converter establish resonance when the second switching element (S2) is switched on. Furthermore, upon establishing resonance, the target output DC voltage is generated on the secondary side of the isolated DC-DC converter.

[0050] In one embodiment, the rectifier elements (D2, D3) are forward-biased during the first negative half-cycle. The series inductor (L3) is charged by a current flowing through it. When the series inductor (L3) is charged, the voltage across it is rectified. Vs(t) = abs (Vs(t)) The second capacitor (C S1 The voltage of the lower partial circuit is discharged via the transformer and the secondary winding (L2) of the transformer. The second capacitor (C P2 ) together with the third capacitor (C S1 ) and the fourth capacitor (C S2 ) a resonance corresponding to a related switching operation of the inverter. Furthermore, the first diode (D5) is forward-biased and charges the third capacitor (C). S1 ) and a fifth capacitor (C bulk). The first diode (D5) supplies the target output DC current to the load on the secondary side of the isolated DC-DC converter.

[0051] In one embodiment, the sum of the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) k ) flowing current equal to the value of the current flowing through the second switching element (S2).

[0052] Fig. Figure 3b shows a circuit diagram of an AC-DC converter in a negative half-cycle of the second switching cycle of the AC input power. For example, Fig. 3b represent a second negative half-cycle of the input AC power. Fig. 3b shows a configuration 300B of the converter 100 from Fig. 1. During the negative half-cycle of the second switching cycle of the AC input power, the first switching element (S1) is turned on and the second switching element (S2) is turned off. The upper sub-circuit, the lower sub-circuit, and the secondary side of the isolated DC-DC converter establish a resonance based on the turning on of the first switching element (S1). Furthermore, during the establishment of this resonance, the target output DC voltage is generated by an output of the transformer on the secondary side of the isolated DC-DC converter.

[0053] In one embodiment, during the second negative half-cycle of the input AC power, the series inductance (L3) is transferred to the first capacitor (C). P1 ), the second capacitor (C P2 ) and the leakage inductance (L k ) discharged. Furthermore, the second capacitor (C) forms P2) and the first capacitor (C P1 ) together with the third capacitor (C S1 ) and the fourth capacitor (C S2 ) a resonance corresponding to an associated switching operation of the converter with the leakage inductance (L k The second diode (D6) is forward-biased and charges the fourth capacitor (C). S2 ) and the fifth capacitor (C bulk The second diode (D6) supplies the desired output DC voltage from the transformer to the load. In one embodiment, the difference between the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) is kThe current flowing through the first switching element (S1) is equal to the value of the current flowing through it. In another embodiment of the present disclosure, the isolated DC-DC converter is configured to switch on the first switching element (S1) and the second switching element (S2) at zero voltage and to switch off the first switching element (S1) and the second switching element at zero current. In one embodiment, the switching loss is calculated based on the values ​​of voltage and current in relation to time.

[0054] Fig. Figure 4a is a graphical representation of an average switching loss as a function of power. Fig. Figure 4a shows the power delivered to the load and represents the time (in milliseconds) on the X-axis and the power values ​​(in watts) on the Y-axis. Fig. Figure 4b shows the voltage value (in volts) on the y-axis. The graph represents the voltage at the second switching element (S2). Fig. Figure 4c represents time (in milliseconds) on the x-axis and current values ​​(in amperes) on the y-axis. The graph shows the current through the second switching element (S2), through the switch, and the current through the antiparallel diode of the second switching element (S2).

[0055] In an exemplary embodiment of the present disclosure, the theoretical calculation of a generic topology is presented below. Since the input voltage is sinusoidal, the average voltage (Vds) and current (Id) load of the switch is 200 V and 30 A. The average switching loss per switch is 30 W, and the total switching loss is 60 W.

[0056] Theoretical calculations yield an average switching loss per switch of 30 W, while simulation results indicate a much lower value of 5 W. The switching loss is calculated based on the voltage and current values ​​as a function of time. From the values ​​in the Fig. The simulation results show that the average switching loss per switch is 5 W and the total switching loss is 10 W. Reducing the switching losses improves efficiency. Consistent with the topology and the simulation results, the switching loss is less than 10% compared to a hard-switching converter. The efficiency improvement is 0.5% compared to a hard-switching converter.

[0057] Fig. Figure 5a is a graphical representation 500A showing the resonant tank voltage and resonant tank current in conjunction with an AC-DC converter according to an embodiment of the present disclosure. The result shows the resonant tank current (Ixfmr) and voltage (Vxfmr). As shown, the diagram represents time (in milliseconds) on the x-axis and the values ​​of the transformer voltage (in volts) labeled 502A and the current (in amperes) labeled 504A. The diagram shows that the transformer voltage (Vxfmr) maintains a voltage-time equilibrium (volt-second) that prevents saturation of the transformer core. This equilibrium is critical for the transformer to provide adequate voltage gain to compensate for the gain of the resonant tank.

[0058] Fig. Figure 5b is a graphical representation 500B showing voltage and current associated with a first switching element (S1) of an AC-DC converter according to an embodiment of the present disclosure. The diagram illustrates the soft switching in the switch of the isolated DC-DC converter. As shown, the graph represents time (in milliseconds) on the x-axis and the values ​​of the voltage of the switch (S1), denoted as 502B, (in volts) and the values ​​of the current, denoted as 504B, (in amperes). The diagram shows that the first switching element is turned on at zero voltage and turned off at zero current. This operating mode offers several advantages, including lower switching losses, more efficient power transfer and power supply control, and thus higher efficiency.

[0059] Fig. Figure 5c is a graphical representation 500C showing voltage and current in connection with a second switching element (S2) of an AC-DC converter according to an embodiment of the present disclosure. As shown, the diagram represents time (in milliseconds) on the x-axis and the values ​​of the voltage of the switch (S2), designated 502C, (in volts) and the values ​​of the current, designated 504C, (in amperes). The diagram shows that the second switching element is turned on at zero voltage and turned off at zero current. This mode of operation offers several advantages, including lower switching losses, more efficient power transmission and power supply control, and thus improved efficiency.

[0060] Fig. Figure 6a is a graphical representation of Figure 600A, showing an input voltage and in-phase current in conjunction with an AC-DC converter according to an embodiment of the present disclosure. As shown, the diagram represents time (in milliseconds) on the x-axis and the values ​​of the input voltage, labeled 602A, (in volts) and the current, labeled 604A, (in amperes). This diagram shows that the voltage and current are in phase, which ensures that the power factor is corrected to approximately one. This power factor correction is crucial for reducing energy consumption.

[0061] Fig. Figure 6b is a graphical representation 600B showing a Fast Fourier Transform (FFT) analysis of an input current in conjunction with an AC-DC converter according to an embodiment of the present disclosure. As shown in Fig. As shown in Figure 7b, diagram 602B is represented by frequency values ​​(in Hz) on the x-axis and current values ​​(in amperes) on the y-axis. The FFT of the input current (Is) shows both the fundamental frequency (50 Hz) and its harmonic content. The Fast Fourier Transform (FFT) simulation results show that the total harmonic distortion (THD) is 4%, which is within the 5% limit specified in IEEE 1547:2020 (Institute of Electrical and Electronics Engineers). Total harmonic distortion (THD) is a measure of the harmonic content in a power grid. In grid-connected systems, achieving a THD value of 4% can offer various benefits, such as improved power quality, system efficiency, grid stability, regulatory compliance, and cost savings.

[0062] Fig. Figure 6c is a graphical representation 600C showing the output voltage of an AC-DC converter according to an embodiment of the present disclosure. As shown, the diagram 602C is illustrated by time values ​​(in seconds) on the x-axis and output voltage values ​​(in volts) on the y-axis. Furthermore, the converter is configured to maintain the requested output voltage of 800 V with a permissible ripple of less than 0.2%. A low ripple of less than 0.2% can offer several advantages, such as higher efficiency, improved electrical system performance, and compliance with safety standards and regulations.

[0063] Fig. Figure 7 shows a flowchart of method 700 for operating an AC-DC converter according to an embodiment of the present disclosure. For example, the AC-DC converter can be operated by Fig. 7. be similar to the AC-DC converter as it is in Fig. 1 is described. As in Fig. As shown in Figure 7, Procedure 700 can comprise one or more steps. Procedure 700 can be described in the general context of computer-executable instructions. In general, computer-executable instructions can include routines, programs, tasks, components, data structures, procedures, modules, and functions that perform specific functions or implement specific abstract data types.

[0064] The order in which Method 700 is described is not to be understood as a restriction, and any number of the described method blocks can be combined in any order to perform the method. Furthermore, individual blocks can be omitted from the method without affecting the scope of the subject matter described herein. In addition, the method can be implemented in any suitable hardware, software, firmware, or a combination thereof.

[0065] In block 702, an AC input power is rectified into an unregulated DC power. In one embodiment, the method for operating the AC-DC converter includes operating the converter in positive half-cycles and negative half-cycles. In some embodiments, the method for operating the converter includes operating the converter in a first cycle comprising a first positive half-cycle and a first negative half-cycle. Furthermore, in some embodiments, the method for operating the converter includes operating the converter in a second cycle comprising a second positive half-cycle and a second negative half-cycle.

[0066] In one embodiment, the method for operating the converter during the first positive half-cycle comprises switching off the first switching element (S1) and switching on the second switching element (S2). Furthermore, resonance is established through the lower sub-circuit and a secondary side of the isolated DC-DC converter based on the switching on of the second switching element (S2). Additionally, the target output DC voltage is generated on the secondary side of the isolated DC-DC converter once resonance is established.

[0067] In one embodiment, the method for operating the converter during the first positive half-cycle includes forward biasing the rectifier elements (D1, D4) of the first circuit. Furthermore, the first switching element (S1) can be switched off and the second switching element (S2) switched on. Additionally, the series inductor (L3) can be charged by a current flowing through it. Furthermore, a portion of the lower circuit, which connects to the second capacitor (C), is P2 ) contains, discharged via the transformer and the secondary winding (L2) of the transformer. Furthermore, it can be connected to the second capacitor (C P2 ) corresponding to an associated switching operation of the converter together with a part of the secondary side of the isolated DC-DC converter, which is the third capacitor (C S1 ) and the fourth capacitor (C S2) comprise, forming a resonance. In addition, the first diode (D5) can be forward-biased to charge the third capacitor (C). S1 ) and a fifth capacitor (C bulk ) to enable this. Afterwards, the target output DC current is supplied from the first diode (D5) to the resistor (R1) on a secondary side of the isolated DC-DC converter.

[0068] In block 704, the unregulated DC power is converted into high-frequency AC power based on alternating switching cycles connected to a common switching leg.

[0069] In block 706, the high-frequency alternating current is converted into a target output DC voltage.

[0070] In one embodiment, the sum of the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) kThe current flowing through the first switching element (S1) is equal to the value of the current flowing through the second switching element (S2). In one embodiment, the method for operating the converter during the second positive half-cycle of the input AC power comprises switching on the first switching element (S1) and switching off the second switching element (S2). Furthermore, resonance is established through the upper circuit, the lower circuit, and the secondary side of the isolated DC-DC converter based on the switching on of the first switching element (S1). Subsequently, the target output DC voltage is generated from a transformer output on the secondary side of the isolated DC-DC converter after resonance has been established.

[0071] In one embodiment, the method for operating the inverter during the second positive half-cycle comprises discharging the series choke (L3) into the first capacitor (C). P1Furthermore, a resonance with the second capacitor (C) is established. P2 ) and the leakage inductance (L k ), the second capacitor (C P2 ) and the first capacitor (C P1 ) and the third capacitor (C S1 ) and the fourth capacitor (C S2 ) corresponding to a related switching operation of the inverter with the leakage inductance (L k ). In addition, the second diode (D6) is forward-biased to connect the fourth capacitor (C). S2 ) and the fifth capacitor (C bulk ) to charge and to supply the target DC output voltage from the transformer to the load via the second diode (D6).

[0072] In one embodiment, the difference between the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) k ) flows, equal to the value of the current flowing through the first switching element (S1).

[0073] In one embodiment, the method for operating the converter during the first negative half-cycle of the input AC power comprises switching off the first switching element (S1) and switching on the second switching element (S2). Furthermore, resonance is established through the lower sub-circuit and a secondary side of the isolated DC-DC converter based on the switching on of the second switching element (S2). Subsequently, the target output DC voltage is generated on the secondary side of the isolated DC-DC converter once resonance is established.

[0074] In one embodiment, the method for operating the converter during the first negative half-cycle of the input AC power comprises forward biasing the rectifier elements (D2, D3) of the first circuit, switching off the first switching element (S1), and switching on the second switching element (S2). Furthermore, the series inductor (L3) is charged by a current flowing through it, and the second capacitor (C) P2 The current of the lower partial circuit is discharged via the transformer and the secondary winding (L2) of the transformer. Afterwards, resonance occurs with the second capacitor (C). P2 ) corresponding to a related switching operation of the inverter together with the third capacitor (C S1 ) and the fourth capacitor (C S2 ). Furthermore, the first diode (D5) is forward-biased to connect the third capacitor (C). S2 ) and a fifth capacitor (C bulk) to charge. In addition, the target output DC voltage is supplied from the first diode (D5) to the load on a secondary side of the isolated DC-DC converter.

[0075] In one embodiment, the sum of the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) k ) flowing current equal to the value of the current flowing through the second switching element (S2).

[0076] In one embodiment, the method for operating the converter during the second negative half-cycle of the input AC power comprises switching on the first switching element (S1) and switching off the second switching element (S2). Based on the switching on of the first switching element (S1), resonance is established through the upper circuit, the lower circuit, and the secondary side of the isolated DC-DC converter. Subsequently, the target output DC voltage is generated from a transformer output on the secondary side of the isolated DC-DC converter after resonance has been established.

[0077] In one embodiment, the method for operating the inverter during the second negative half-cycle of the input AC power comprises switching on the first switching element (S1) and switching off the second switching element (S2) as well as discharging the series inductance (L3) into the first capacitor (C).P1 ), the second capacitor (C P2 ) and the leakage inductance (L k Furthermore, the second capacitor (C) P2 ) and the first capacitor (C P1 ) together with the third capacitor (C S1 ) and the fourth capacitor (C S2 ) a resonance corresponding to an associated switching operation of the converter with the leakage inductance (L k Furthermore, the second diode (D6) is forward-biased and the fourth capacitor (C) S2 ) and the fifth capacitor (C bulk ) are charged. Then the target output DC voltage is supplied from the transformer and the second diode (D6) to the resistor (R1).

[0078] In one embodiment, the difference between the value of the current flowing through the series inductance (L3) and the value of the current flowing through the leakage inductance (L) kThe current flowing through the first switching element (S1) is equal to the current flowing through it. The AC-DC converter features power factor correction and galvanic isolation. The topology utilizes a switch-sharing concept to minimize active switching components, thereby reducing conduction and switching losses. The output voltage doubler meets the requirements for charging a high-voltage battery. The topology operates in a resonant mode to further reduce switching losses.

[0079] In an exemplary embodiment of the present disclosure, the values ​​of various parameters relating to the converter are given in the table below. Table 1 Netzspannung 230V Nennleistung 11kW Ausgangsspannung 800V Schaltfrequenz (Fsw) 100kHz Netzfrequenz 50 Hz

[0080] The existing implementation uses a flyback converter topology, which, due to core saturation limitations in the transformer, cannot be used for higher power applications (>500 W), whereas the onboard converter (OBC) has a power rating of over 3.3 kW. The converter can operate with two MOSFETs and achieve zero voltage on turn-on and zero current on turn-off through resonance. In contrast, the existing topology requires two IGBTs and one MOSFET to achieve zero voltage turn-off, but does not provide smooth turn-on. Some existing charger topologies may include three transformer windings, increasing losses and transformer design complexity. In contrast, the converter described in this document includes two transformer windings, compared to three in existing charger topologies.In an exemplary embodiment of the present disclosure, the efficiency is determined by the total loss. Existing topologies can only achieve an efficiency of 90% (measured at 220Vac, 48Vdc, 500W, 150kHz), whereas the converter described in the present disclosure can achieve an efficiency of 95.9%.

[0081] Furthermore, based on the aforementioned embodiment, the charger can achieve smooth switching with the fewest possible active switches. Moreover, according to the present invention, the charger is capable of operating with a power factor of one across its entire operating range, while maintaining total harmonic distortion (THD) below 5%. The charger's topology can be used in a three-phase configuration by connecting all three circuits in parallel.

[0082] The listing of points does not mean that some or all points are mutually exclusive, unless explicitly stated otherwise.

[0083] Finally, the language used in the description was chosen primarily for readability and guidance purposes, and not to delimit or define the subject matter of the invention. It is therefore intended that the scope of the disclosure is not limited by this detailed description, but rather by all claims arising from an application based thereon. Accordingly, the embodiments of the present disclosure are intended for illustration, but not to limit, the scope of the disclosure set forth in the following claims.

[0084] Although various aspects and embodiments have been disclosed here, other aspects and embodiments will be obvious to the person skilled in the art. The various aspects and embodiments disclosed here serve for illustration and are not to be understood as limiting, the true scope and spirit being specified by the following claims. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 20210399643

[0004] CN 201766508

[0005] JP 2017163657

[0006] CN 203233307

[0007] KR 101776617

[0008] USRE44136

[0009] Cited non-patent literature

[0000] IEC) 61851-23

[0003]

Claims

[1] Power converter for an on-board charger for electric vehicles, consisting of: a first circuit (102) containing a plurality of rectifier elements to rectify an input alternating current (AC) into an unregulated direct current (DC); a second circuit (104) electrically coupled to the first circuit (102), wherein the second circuit (104) comprises a common switching branch, the common switching branch comprising at least a first switching element (S1) and a second switching element (S2), wherein the second circuit (104) is configured to convert the unregulated DC power into high-frequency AC power; and a third circuit (106) which is electrically coupled to the second circuit (104), wherein the third circuit (106) comprises: an isolated DC-DC converter, wherein the common switching branch is formed on a primary bridge side of the isolated DC-DC converter, wherein the third circuit (106) is configured to convert the high-frequency AC power into a target DC output voltage. [2] Power converter according to claim 1, wherein the common switching branch is operated alternately to transfer the high-frequency AC power between the second circuit (104) and the third circuit (106) on the basis of positive half-cycles and negative half-cycles of the input AC power. [3] Power converter according to claim 1, wherein the second circuit (106, 204) further comprises: a series choke (L3) connected to the common switching branch, the common switching branch comprising an upper sub-circuit and a lower sub-circuit, the upper sub-circuit being electrically connected to the lower sub-circuit to form a first junction (J1), the upper sub-circuit comprising the first switching element (S1) and a first capacitor (C P1 ) comprises, and the lower sub-circuit includes the second switching element (S2) and a second capacitor (C) P2 ) comprising, wherein a first end of the series inductance (L3) is electrically connected to an output of the first circuit (104, 202) and a second end of the series inductance (L3) is electrically connected to the first junction (J1). [4] Power converter according to claim 1, wherein the isolated DC-DC converter comprises: a transformer with: a primary winding (L1) that is electrically connected to the common switching branch, and a secondary winding (L2) that is electromagnetically coupled to the primary winding (L1); and a secondary bridge configured as a voltage doubler, wherein the voltage doubler comprises: a first diode (D5), a second diode (D6), a third capacitor (C) S1 ) and a fourth capacitor (C S2 ), and where: The secondary winding (L2) is electrically connected at one end to an anode of the first diode (D5) and a cathode of the second diode (D6); the secondary winding (L2) is electrically connected at another end to a first terminal of the third capacitor (C) S1 ) and a first connection of the fourth capacitor (C S2 ) is connected; a cathode of the first diode (D5) electrically connected to a second terminal of the third capacitor (C S1) is connected; and an anode of the second diode (D6) and a second terminal of the fourth capacitor (C S2 ) are electrically connected to a ground. [5] Power converter according to claim 3, wherein: during a first positive half-cycle and a first negative half-cycle of the AC input power: the first switching element (S1) is switched off and the second switching element (S2) is switched on, and When the second switching element (S2) is switched on, the target output DC voltage is generated based on a resonance produced by the lower sub-circuit and a secondary side of the isolated DC-DC converter, and during a second positive half-cycle and a second negative half-cycle of the AC input power: the first switching element (S1) is switched on and the second switching element (S2) is switched off, and When the first switching element (S1) is switched on, the target output voltage is generated based on a resonance produced by the upper sub-circuit, the lower sub-circuit and a secondary side of the isolated DC-DC converter. [6] Power converter according to claim 1, wherein the isolated DC-DC converter is configured to switch on the first switching element (S1) and the second switching element (S2) at zero voltage and to switch off the first switching element (S1) and the second switching element at zero current. [7] Power converter according to claim 1, wherein the first circuit (102) is a rectifier circuit, the second circuit (104) is a boost converter and the isolated DC-DC converter is an integrated boost resonant converter. [8] Method for operating an AC-DC power converter, the method comprising: Rectification of an AC input power into an unregulated DC power; Conversion of unregulated direct current power into high-frequency alternating current power based on alternating switching cycles connected to a common switching branch; and converts the high-frequency alternating voltage into a target direct voltage, wherein the common switching leg comprises a first switching element (S1) and a second switching element (S2). [9] Method according to claim 8, wherein the common switching branch is operated alternately to transfer the high-frequency AC power between a second circuit (104) and a third circuit (106) on the basis of positive half-cycles and negative half-cycles of the input AC power. [10] Method according to claim 8, wherein: during a first positive half-cycle and a first negative half-cycle of the AC input power: Switching off the first switching element (S1) and switching on the second switching element (S2), and When the second switching element (S2) is switched on, the target output DC voltage is generated based on the creation of a resonance by a lower sub-circuit and a secondary side of an isolated DC-DC converter, and during a second positive half-cycle and a second negative half-cycle of the AC input power: Switching on the first switching element (S1) and switching off the second switching element (S2), and When the first switching element (S1) is switched on, the target output voltage is generated based on the creation of a resonance by a lower sub-circuit and a secondary side of an isolated DC-DC converter.

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