Output voltage variable ev charger based on bidirectional power semiconductor and charging method thereof

Abstract

The present invention relates to an output voltage variable electric vehicle (EV) charger based on a bidirectional power semiconductor and a charging method thereof. The charger comprises: an input converter unit for converting input voltage (Vin) into high-frequency AC signals by means of H-bridge switches (SP1, SP2, SP3, SP4); a power transmission unit for outputting AC voltage-transformed signals by inputting the high frequency AC signals to first and second transformers (Lm1, Lm2); an output voltage switch unit for controlling a path of a battery charging / discharging current by means of first and second multi-stage switching networks (Ss1-Ss8) and first and second common connection nodes that connect the first and second multi-stage switching networks (Ss1-Ss8); an output voltage smoothing unit including a common capacitor node connecting the first and second common connection nodes, a first capacitor (C1) connecting the first multi-stage switching network and the common capacitor node at a first path node, and a second capacitor (C2) connecting the second multi-stage switching network and the common capacitor node at a second path node; and a battery charging and discharging unit including a first relay switch (RLY1) for controlling a connection between the first and second path nodes and a second relay switch (RLY2) connecting an input terminal or an output terminal of the battery to the common connection node or the second path node.

Description

Bidirectional power semiconductor-based variable output voltage EV charger and charging method

[0001] The present invention relates to electric vehicle (EV) charger technology, and more specifically, to a bidirectional power semiconductor-based output voltage variable EV charger and charging method that can expand the output voltage range and perform bidirectional battery charging and discharging by applying a bidirectional power semiconductor.

[0002]

[0003] There is a trend of shifting from internal combustion engine vehicles, which generate driving energy using fossil fuels such as gasoline and diesel, to electric vehicles that utilize power conversion systems and batteries.

[0004] The battery voltage of electric vehicles is continuously increasing to improve charging efficiency and facilitate system operation. As a result, the number of vehicles with diverse battery voltage ranges has increased. Accordingly, there is a growing need for the development of on-board chargers capable of a wide output voltage range.

[0005] Conventionally, a wide range of outputs was achieved by utilizing multiple relays based on a circuit structure employing unidirectional switching elements. However, since unidirectional switching elements are used, there may be limitations on circuit operation (current direction) when considering switching patterns and dead time. Due to these limitations, the converter cannot perform bidirectional power transfer, and this operational limitation can act as one of the causes limiting the output voltage range.

[0006] To overcome these limitations, the output range has been expanded by applying multiple relays and modifying the circuit structure. However, this may result in relatively high costs during charger manufacturing. Components such as relays may require a large volume and additional circuitry to control them.

[0007]

[0008] [Prior Art Literature]

[0009] [Patent Literature]

[0010] Korean Registered Patent No. 10-1207716 (2012.11.27)

[0011] Korean Published Patent No. 10-2023-0114732 (2023.08.01)

[0012] Korean Published Patent No. 10-2023-0015171 (2023.01.31)

[0013]

[0014] One embodiment of the present invention aims to provide a bidirectional power semiconductor-based output voltage variable EV charger and charging method that can expand the output voltage range and perform bidirectional battery charging and discharging by applying a bidirectional power semiconductor.

[0015] One embodiment of the present invention aims to provide a bidirectional power semiconductor-based output voltage variable EV charger and charging method that can overcome the current flow limit of the secondary circuit by applying a bidirectional switch to the secondary switching part.

[0016] One embodiment of the present invention aims to provide a bidirectional power semiconductor-based output voltage variable EV charger and charging method that can be operated as a series or parallel circuit using equivalent states of a bidirectional switch.

[0017]

[0018] Among the embodiments, a bidirectional power semiconductor-based output voltage variable EV (Electric Vehicle) charger comprises: an input converter unit that converts an input power source (Vin) into a high-frequency AC signal through H-bridge switches (Sp1, Sp2, Sp3, Sp4); a power transmission unit that inputs the high-frequency AC signal to first and second transformers (Lm1, Lm2) to output an AC voltage transformation signal; an output voltage switch unit that controls the path of a battery charge / discharge current through first and second multi-stage switching networks (Ss1~Ss8) and first and second common connection nodes connecting the first and second multi-stage switching networks (Ss1~Ss8); and an output voltage smoothing unit including a common capacitor node connecting the first and second common connection nodes, a first capacitor (C1) connecting the first multi-stage switching network and the common capacitor node at a first path node, and a second capacitor (C2) connecting the second multi-stage switching network and the common capacitor node at a second path node. The battery charging and discharging unit includes a first relay switch (RLY1) that controls the connection between the first and second path nodes, and a second relay switch (RLY2) that connects the input or output terminal of the battery to the common connection node or the second path node.

[0019] The above input converter unit can transmit the high-frequency alternating current signal to the first and second transformers (Lm1, Lm2) by forming a primary transformer unit including a first inductor (Lr1) connected to the input terminal of the first transformer (Lm1) and a second inductor (Lr2) connected to the input terminal of the second transformer (Lm2).

[0020] The above input converter unit can commonly connect the first and second inductors (Lr1, Lr2) to a first switch node located between the H-bridge switches (Sp1, Sp2), and commonly connect the first and second transformers (Lm1, Lm2) to a second switch node located between the H-bridge switches (Sp3, Sp4).

[0021] The above power transmission unit can receive the high-frequency AC signal through the first and second transformers (Lm1, Lm2) and output the AC voltage transformation signal by considering the target output voltage.

[0022] The output voltage switch unit can control the AC voltage transformation signal into a positive sequence or a negative sequence through the first multi-stage switching network (Ss1~Ss4).

[0023] The output voltage switch unit can determine the path of the battery charging and discharging current by controlling the AC voltage transformation signal through the second multi-stage switching network (Ss5~Ss8) into the positive sequence or the negative sequence.

[0024] The output voltage switch unit above can implement each of the first and second multi-stage switching networks (Ss1~Ss8) as a bidirectional switch element.

[0025] The output voltage smoothing unit can smooth and filter the output voltage associated with the battery charge / discharge current through the series connection of the first and second capacitors.

[0026] The battery charging / discharging unit can operate the secondary transformer as an equivalent series circuit by opening the first relay switch (RLY1) and connecting the second relay switch (RLY2) to the second path node to induce a flow path of the battery charging / discharging current.

[0027] The battery charging / discharging unit can operate the secondary transformer as an equivalent parallel circuit by short-circuiting the first relay switch (RLY1) and connecting the second relay switch (RLY2) to the common connection node to induce a flow path of the battery charging / discharging current.

[0028] Among the embodiments, a bidirectional power semiconductor-based output voltage variable EV (Electric Vehicle) charging method comprises: an input converter step that converts an input power source (Vin) into a high-frequency AC signal through an H-bridge switch (Sp1, Sp2, Sp3, Sp4); a power transmission step that inputs the high-frequency AC signal to first and second transformers (Lm1, Lm2) to output an AC voltage transformation signal; an output voltage switch step that controls the path of a battery charge / discharge current through first and second multi-stage switching networks (Ss1~Ss8) and first and second common connection nodes that connect the first and second multi-stage switching networks (Ss1~Ss8); and an output voltage smoothing step comprising a common capacitor node connecting the first and second common connection nodes, a first capacitor (C1) that connects the first multi-stage switching network and the common capacitor node at a first path node, and a second capacitor (C2) that connects the second multi-stage switching network and the common capacitor node at a second path node. The battery charging and discharging step includes a first relay switch (RLY1) that controls the connection between the first and second path nodes, and a second relay switch (RLY2) that connects the input or output terminal of the battery to the common connection node or the second path node.

[0029]

[0030] The disclosed technology may have the following effects. However, this does not mean that a specific embodiment must include all of the following effects or only the following effects; therefore, the scope of the rights of the disclosed technology should not be understood as being limited by this.

[0031] An output voltage variable EV charger and charging method based on a bidirectional power semiconductor according to one embodiment of the present invention can expand the output voltage range and perform bidirectional battery charging and discharging by applying a bidirectional power semiconductor.

[0032] An output voltage variable EV charger and charging method based on a bidirectional power semiconductor according to one embodiment of the present invention can overcome the current flow limit of the secondary circuit by applying a bidirectional switch to the secondary switching part.

[0033] An output voltage variable EV charger and charging method based on a bidirectional power semiconductor according to one embodiment of the present invention can be operated as a series or parallel circuit by utilizing equivalent states of a bidirectional switch.

[0034] Therefore, the present invention can reduce the number of relays, thereby reducing costs and the required space for the charger. Additionally, by forming many equivalent circuit states through the control of bidirectional switching elements, there are fewer limitations required to generate a wide range of output voltages. This increases the degree of freedom during charger design and manufacturing, thereby enabling optimal design and improved charger performance.

[0035]

[0036] FIG. 1 is a circuit diagram showing a bidirectional power semiconductor-based output voltage variable EV charger according to the present invention.

[0037] Figures 2a-2b are diagrams showing the current flow according to the equivalent series circuit operation of the secondary transformer section in the EV charger of Figure 1.

[0038] Figures 3a-3b are diagrams showing the current flow according to the equivalent parallel circuit operation of the secondary transformer section in the EV charger of Figure 1.

[0039] FIG. 4 is a flowchart illustrating a bidirectional power semiconductor-based variable output voltage EV charging method performed in an EV charger according to the present invention.

[0040]

[0041] The description of the present invention is merely an example for structural or functional explanation, and therefore the scope of the present invention should not be interpreted as being limited by the examples described in the text. That is, since the examples are subject to various modifications and may take various forms, the scope of the present invention should be understood to include equivalents capable of realizing the technical concept. Furthermore, the objectives or effects presented in the present invention do not imply that a specific example must include all of them or only such effects; therefore, the scope of the present invention should not be understood as being limited by them.

[0042] Meanwhile, the meaning of the terms described in this application should be understood as follows.

[0043] Terms such as "first," "second," etc., are intended to distinguish one component from another, and the scope of rights shall not be limited by these terms. For example, the first component may be named the second component, and similarly, the second component may be named the first component.

[0044] When it is stated that one component is "connected" to another component, it should be understood that it may be directly connected to that other component, or that there may be other components in between. Conversely, when it is stated that one component is "directly connected" to another component, it should be understood that there are no other components in between. Meanwhile, other expressions describing the relationships between components, such as "between" and "exactly between," or "adjacent to" and "directly adjacent to," should be interpreted in the same way.

[0045] A singular expression should be understood to include a plural expression unless the context clearly indicates otherwise, and terms such as "include" or "have" are intended to specify the existence of the implemented features, numbers, steps, actions, components, parts, or combinations thereof, and should be understood not to preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0046] In each step, identifiers (e.g., a, b, c, etc.) are used for convenience of explanation and do not describe the order of the steps; the steps may occur differently from the specified order unless a specific order is clearly indicated in the context. That is, the steps may occur in the same order as specified, may be performed substantially simultaneously, or may be performed in the reverse order.

[0047] Unless otherwise defined, all terms used herein have the same meaning as generally understood by those skilled in the art to which this invention pertains. Terms defined in commonly used dictionaries should be interpreted as having meanings consistent with the context of the relevant technology and should not be interpreted as having an ideal or overly formal meaning unless explicitly defined in this application.

[0048]

[0049] FIG. 1 is a circuit diagram showing a bidirectional power semiconductor-based output voltage variable EV charger according to the present invention.

[0050] Referring to FIG. 1, the EV charger (100) may include an input converter section (110), a power transmission section (130), an output voltage switch section (150), an output voltage smoothing section (170), and a battery charging / discharging section (190).

[0051] The input converter unit (110) can convert the input power (Vin) into a high-frequency AC signal through H-bridge switches (Sp1, Sp2, Sp3, Sp4). The input converter unit (110) plays the role of converting the input power (Vin) from the EV charger (100) into a high-frequency AC signal and transmitting it to the transformer and the downstream circuit. This enables power conversion and output voltage adjustment. Here, the H-bridge switches (Sp1, Sp2, Sp3, Sp4) convert the input DC power (Vin) into a high-frequency AC signal by having two switches (Sp1, Sp4) and (Sp2, Sp3) form a diagonal pair and operate in a cross pattern. The H-bridge switches (Sp1, Sp2, Sp3, Sp4) can be implemented as semiconductor switches such as IGBTs or MOSFETs. The H-bridge switches (Sp1, Sp2, Sp3, Sp4) can minimize switching losses and maximize power conversion efficiency.

[0052] In one embodiment, the input converter unit (110) can transmit a high-frequency AC signal to the first and second transformers (Lm1, Lm2) by forming a primary transformer unit including a first inductor (Lr1) connected to the input terminal of the first transformer (Lm1) and a second inductor (Lr2) connected to the input terminal of the second transformer (Lm2). The first and second inductors (Lr1, Lr2) are elements that transmit power and may correspond to one of the elements that determine the magnitude of the power transmitted by the input converter unit (110). That is, the first and second inductors (Lr1, Lr2) can determine the magnitude of the current flowing through the first and second transformers (Lm1, Lm2). The input converter section (110) can transfer power to the first and second transformers (Lm1, Lm2) when charging the battery through the first and second inductors (Lr1, Lr2) or receive power when discharging the battery.

[0053] The H-bridge switches (Sp1, Sp2, Sp3, Sp4) may contain current ripple and high-frequency noise during the switching process of converting the input power (Vin) into a high-frequency AC signal. At this time, the input converter section (110) can reduce the current ripple by utilizing the electromagnetic characteristics of the first and second inductors (Lr1, Lr2).

[0054] The input converter section (110) can commonly connect the first and second inductors (Lr1, Lr2) to a first switch node (111) located between H-bridge switches (Sp1, Sp2), and can commonly connect the first and second transformers (Lm1, Lm2) to a second switch node (112) located between H-bridge switches (Sp3, Sp4). The first and second switch nodes (111, 112) can transmit signals to the input terminals of the first and second transformers (Lm1, Lm2) through the first and second inductors (Lr1, Lr2). Here, the first and second inductors (Lr1, Lr2) can regulate the flow of current and improve power conversion efficiency when the input converter section (110) generates a high-frequency AC signal. The inductance values ​​of the first and second inductors (Lr1, Lr2) control the rising and falling speeds of the current to stabilize the magnitude of the current flowing on the primary side of the first and second transformers (Lm1, Lm2), thereby enabling the desired output voltage to be obtained on the secondary side. In one embodiment, the input converter unit (110) can transmit AC power to the first and second transformers (Lm1, Lm2) through the first and second inductors (Lr1, Lr2) according to the switching operation of the H-bridge switches (Sp1, Sp2, Sp3, Sp4) when charging the battery, and when discharging the battery, the power transmitted from the secondary side of the first and second transformers (Lm1, Lm2) to the input converter unit (110) through the first and second inductors (Lr1, Lr2) to invert the power and output it. The first and second inductors (Lr1, Lr2) can be made to minimize losses by using ferrite cores suitable for high-frequency operation.

[0055] The power transmission unit (130) can input a high-frequency AC signal to the first and second transformers (Lm1, Lm2) to output an AC voltage transformation signal. The power transmission unit (130) can input the high-frequency AC signal generated in the input converter unit (110) to the first and second transformers (Lm1, Lm2) to generate an AC voltage transformation signal that can be used at the output terminal. Here, the first transformer (Lm1) can receive the high-frequency AC signal transmitted through the first inductor (Lr1), convert the voltage (boost or step down), and transmit the transformed AC signal to the output voltage switch unit (150). The second transformer (Lm2) can receive the high-frequency AC signal transmitted through the second inductor (Lr2), and transmit the AC signal transformed in the same way as the first transformer (Lm1) to the output voltage switch unit (150) to provide a second output channel that satisfies the multi-stage output voltage requirement.

[0056] In one embodiment, the power transmission unit (130) receives a high-frequency AC signal through the first and second transformers (Lm1, Lm2) and outputs an AC voltage transformation signal considering the target output voltage. By generating an AC voltage transformation signal that matches the received high-frequency AC signal to the target output voltage, the power transmission unit (130) can maximize power conversion efficiency, ensure the stability of the output voltage of the EV charger (100), and respond to various battery voltage requirements. The first and second transformers (Lm1, Lm2) each transmit the high-frequency AC signal input to the primary winding to the secondary winding through the principle of magnetic induction, and the voltage in the secondary winding is adjusted (stepped up or stepped down) according to the winding ratio to generate an AC voltage transformation signal at the target output voltage level. The power transmission unit (130) can support various output voltages required by the charger by adjusting the winding ratio and input signal characteristics of the first and second transformers (Lm1, Lm2). That is, the winding ratio of the first and second transformers (Lm1, Lm2) can be determined by considering the battery voltage range and charging requirements. Here, the first and second transformers (Lm1, Lm2) operate independently to ensure power isolation, multi-stage output voltage support, and the flexibility and stability of the charger system, and enable high-efficiency power transmission capable of responding to various battery conditions.

[0057] The output voltage switch unit (150) can control the path of the battery charging and discharging current through the first and second multi-stage switching networks (Ss1 to Ss8) and the first and second common connection nodes (151, 152) connecting the first and second multi-stage switching networks (Ss1 to Ss8). The output voltage switch unit (150) can efficiently manage the power flow during charging and discharging and enable flexible control of the output voltage. Specifically, the output voltage switch unit (150) can control the AC voltage transformation signal into a positive sequence or a negative sequence through the first multi-stage switching network (Ss1 to Ss4). The first multi-stage switching network (Ss1 to Ss4) controls the AC voltage transformation signal output from the first transformer (Lm1) into a positive sequence or a negative sequence, thereby flexibly adjusting the direction of the output current and the power flow during battery charging and discharging. Here, the output voltage switch unit (150) can set a current path by combining the ON / OFF state of each switch of the first multi-stage switching network (Ss1~Ss4). Positive sequence control can set a positive polarity path of the AC voltage transformation signal by activating (ON state) the first multi-stage switching network (Ss1, Ss4) so ​​that current is output from the first transformer (Lm1) and flows along the battery charging path. Negative sequence control can set a negative polarity path of the AC voltage transformation signal by activating (ON state) the first multi-stage switching network (Ss2, Ss3) so that current flows along the battery discharging path in the opposite direction.

[0058] The output voltage switch unit (150) can determine the path of the battery charging and discharging current by controlling the AC voltage transformation signal through the second multi-stage switching network (Ss5~Ss8) into a positive sequence or a negative sequence. Here, the second multi-stage switching network (Ss5~Ss8) performs the same role as the first multi-stage switching network (Ss1~Ss4) and can set the current path according to charging and discharging conditions. The output voltage switch unit (150) can selectively control the positive and negative sequences by combining the ON / OFF states of each switching of the second multi-stage switching network (Ss5~Ss8).

[0059] The output voltage switch unit (150) can implement each of the first and second multi-stage switching networks (Ss1 to Ss8) as a bidirectional switch element. The output voltage switch unit (150) can control the direction of current flow during charging and discharging through the bidirectional switch element. The bidirectional switch element is designed to operate a power semiconductor device, such as a MOSFET or IGBT, in a serial bidirectional, parallel bidirectional, or single bidirectional manner to support bidirectional current flow and to perform positive and negative sequence switching. The output voltage switch unit (150) can overcome the current flow limit of the secondary circuit by implementing the first and second multi-stage switching networks (Ss1 to Ss8) as bidirectional switch elements. The bidirectional switch element can create four equivalent states, such as short, forward diode operation, reverse diode operation, open, or two diode operation, depending on the signal applied to the element. The EV charger (100) can form equivalent circuit structures that cannot be formed in conventional converters by utilizing the equivalent states of bidirectional switch elements, thereby having more degrees of freedom than conventional converters.

[0060] The output voltage smoothing unit (170) may include a common capacitor node (171) connecting the first and second common connection nodes (151, 152), a first capacitor (C1) connecting the common capacitor node (171) to the first multi-stage switching network (Ss1~Ss4) at the first path node, and a second capacitor (C2) connecting the common capacitor node (171) to the second multi-stage switching network (Ss5~Ss8) at the second path node. The output voltage smoothing unit (170) can smooth and filter the output voltage associated with the battery charge / discharge current through the series connection of the first and second capacitors (C1, C2). By connecting the first and second capacitors (C1, C2) in series, the output voltage smoothing unit (170) can reduce the ripple of the output voltage associated with the battery charge / discharge current and stabilize the signal, thereby improving the output voltage quality of the EV charger (100) and ensuring a stable power supply. Here, the first capacitor (C1) can reduce the ripple of the output voltage and filter high-frequency components. The second capacitor (C2) is connected in series with the first capacitor (C1) to further ensure the stability of the output voltage. That is, through the series connection of the first and second capacitors (C1, C2), fluctuations in the output voltage due to the charging and discharging current can be mitigated, and reliability in high-voltage circuits can be increased.

[0061] The battery charging / discharging unit (190) may include a first relay switch (RLY1) that controls the connection between the first and second path nodes, and a second relay switch (RLY2) that connects the input or output terminal of the battery (210) to a common connection node or a second path node. The battery charging / discharging unit (190) can control the flow path of the battery charging / discharging current through the operation of the first and second relay switches (RLY1, RLY2). In one embodiment, the battery charging / discharging unit (190) can operate the secondary transformer as an equivalent series circuit by opening the first relay switch (RLY1) and connecting the second relay switch (RLY2) to the second path node to induce the flow path of the battery charging / discharging current. The first relay switch (RLY1) controls the operating state in the battery charging / discharging path and blocks the current flow when in an open state, thereby enabling the configuration of the series circuit of the secondary transformer. At this time, the second relay switch (RLY2) controls the connection state between the battery (210) and the second path node, and when in the closed state, it can complete the series circuit configuration by connecting the current path between the battery (210) and the transformer. Here, the secondary transformer operates as part of a circuit including the first and second multi-stage switching networks (Ss1~Ss8) and the battery charging / discharging unit (190), and can operate as an equivalent series or parallel circuit depending on the state of the first and second relay switches (RLY1, RLY2). In one embodiment, the battery charging / discharging unit (190) can operate the secondary transformer as an equivalent parallel circuit by short-circuiting the first relay switch (RLY1) and connecting the second relay switch (RLY2) to a common connection node to induce a flow path for the battery charging / discharging current. The second path node can be connected to the battery (210) through the second relay switch (RLY2) to form a charging / discharging current path.

[0062]

[0063] FIGS. 2a and 2b are diagrams showing the current flow according to the equivalent series circuit operation of the secondary transformer in the EV charger of FIG. 1, where FIG. 2a shows the operation when controlled in a positive sequence and FIG. 2b shows the operation when controlled in a negative sequence.

[0064] First, referring to FIG. 2a, the input converter unit (110) operates such that the H-bridge switches (Sp1, Sp4) are in an “ON” state and the H-bridge switches (Sp2, Sp3) are in an “OFF” state, converting the input power (Vin) into a high-frequency AC signal through the H-bridge switches (Sp1, Sp4) in the “ON” state, and transmitting the high-frequency AC signal to the power transmission unit (130) through each of the first and second inductors (Lr1, Lr2). The power transmission unit (130) can transform the high-frequency AC signal input to the primary side of the first and second transformers (Lm1, Lm2) and transmit it to the secondary side. The output voltage switch unit (150) can be controlled in a positive sequence such that among the first and second multi-stage switching networks (Ss1~Ss8), the first multi-stage switching network (Ss1, Ss4) operates in an “ON” state and the first multi-stage switching network (Ss2, Ss3) operates in an “OFF” state, the second multi-stage switching network (Ss5, Ss8) operates in an “ON” state and the second multi-stage switching network (Ss6, Ss7) operates in an “OFF” state, thereby forming a path to transmit the output of the first and second transformers (Lm1, Lm2) to the battery through the first and second multi-stage switching networks (Ss1, Ss4) (Ss5, Ss8) in an “ON” state. At this time, current flow through unnecessary paths can be blocked through the first and second multi-stage switching networks (Ss2, Ss3) (Ss6, Ss7) in the “OFF” state. When the battery charging / discharging unit (190) opens the first relay switch (RYL1) and connects the second relay switch (RLY2) to the lower contact, it can induce a current flow as shown in FIG. 2a, thereby operating the secondary transformer unit as an equivalent series circuit.

[0065] Next, referring to FIG. 2b, the input converter unit (110) operates such that the H-bridge switches (Sp2, Sp3) are in an “ON” state and the H-bridge switches (Sp1, Sp4) are in an “OFF” state, converting the input power (Vin) into a high-frequency AC signal through the H-bridge switches (Sp2, Sp3) in the “ON” state, and transmitting the high-frequency AC signal to the power transmission unit (130) through each of the first and second inductors (Lr1, Lr2). The power transmission unit (130) can transform the high-frequency AC signal input to the primary side of the first and second transformers (Lm1, Lm2) and transmit it to the secondary side. The output voltage switch unit (150) can form a negative sequence path that transmits the output of the first and second transformers (Lm1, Lm2) to the battery (210) through the first and second multi-stage switching networks (Ss2, Ss3) (Ss6, Ss7) in the "ON" state, the first multi-stage switching network (Ss1, Ss3) among the first and second multi-stage switching networks (Ss1~Ss8) in the "ON" state, the first multi-stage switching network (Ss1, Ss4) in the "OFF" state, the second multi-stage switching network (Ss6, Ss7) in the "ON" state, and the second multi-stage switching network (Ss5, Ss8) in the "OFF" state. At this time, current flow through unnecessary paths can be blocked through the first and second multi-stage switching networks (Ss1, Ss4) (Ss5, Ss8) in the “OFF” state. The battery charging / discharging unit (190) can block the path between the common connection node and the battery (210) by opening the first relay switch (RYL1) and induce current flow by connecting the second relay switch (RLY2) to the lower contact, thereby operating the secondary transformer unit as an equivalent series circuit.Here, when charging the battery, the current flow can form a path in the order of first and second transformers (Lm1, Lm2), first multi-stage switching network (Ss2, Ss3), first capacitor (C1), common capacitor node (171), second capacitor (C2), second multi-stage switching network (Ss6, Ss7), second relay switch (RYL2), and battery (210). When discharging the battery (210), the current flow can form a path in the order of battery (210), second relay switch (RYL2), second multi-stage switching network (Ss7, Ss6), second capacitor (C2), first capacitor (C1), first multi-stage switching network (Ss3, Ss2), and first and second transformers (Lm1, Lm2).

[0066] In the equivalent series operation of FIGS. 2a and 2b, the output voltage switch unit (150) can perform positive sequence control and negative sequence control according to the switch operation, which can be defined in Table 1 below.

[0067] [Table 1]

[0068]

[0069] In the case of Figures 2a and 2b, only the reverse diode state of the bidirectional switch was used for convenience of explanation, but all states of the bidirectional switch can be used depending on the operation sequence.

[0070]

[0071] FIGS. 3a and 3b are diagrams showing the current flow according to the equivalent parallel circuit operation of the secondary transformer section of the EV charger of FIG. 1, where FIG. 3a shows the operation when controlled in a positive sequence and FIG. 3b shows the operation when controlled in a negative sequence.

[0072] First, referring to FIG. 3a, the input converter unit (110) operates such that the H-bridge switches (Sp1, Sp4) are in an “ON” state and the H-bridge switches (Sp2, Sp3) are in an “OFF” state, converting the input power (Vin) into a high-frequency AC signal through the H-bridge switches (Sp1, Sp4) in the “ON” state, and transmitting the high-frequency AC signal to the power transmission unit (130) through each of the first and second inductors (Lr1, Lr2). The power transmission unit (130) can transform the high-frequency AC signal input to the primary side of the first and second transformers (Lm1, Lm2) and transmit it to the secondary side. The output voltage switch unit (150) can be controlled in a positive sequence such that among the first and second multi-stage switching networks (Ss1~Ss8), the first multi-stage switching network (Ss1, Ss4) operates in an “ON” state and the first multi-stage switching network (Ss2, Ss3) operates in an “OFF” state, the second multi-stage switching network (Ss5, Ss8) operates in an “OFF” state and the second multi-stage switching network (Ss6, Ss7) operates in an “ON” state, thereby forming a path to transmit the output of the first and second transformers (Lm1, Lm2) to the battery through the first and second multi-stage switching networks (Ss1, Ss4) (Ss6, Ss7) in the “ON” state. At this time, current flow through unnecessary paths can be blocked through the first and second multi-stage switching networks (Ss2, Ss3) (Ss5, Ss8) in the “OFF” state. When the battery charging / discharging unit (190) shorts the first relay switch (RYL1) and connects the second relay switch (RLY2) to the upper contact, it can induce a current flow as shown in FIG. 3a, thereby operating the secondary transformer unit as an equivalent parallel circuit.Here, the battery charging current flow may form a first path in the order of the first transformer (Lm1), the first multi-stage switching network (Ss1, Ss4), the first capacitor (C1), the common capacitor node (171), and the battery, and a second path may form in the order of the second transformer (Lm2), the second multi-stage switching network (Ss6, Ss7), the second capacitor (C2), the common capacitor node (171), and the battery. The two paths operate in parallel so that current can be stably delivered to the battery. That is, the outputs of the first and second transformers (Lm1, Lm2) are combined in parallel and delivered to the battery, thereby improving the charging speed and efficiency.

[0073] Next, referring to FIG. 3b, the input converter unit (110) operates such that the H-bridge switches (Sp2, Sp3) are in an “ON” state and the H-bridge switches (Sp1, Sp4) are in an “OFF” state, converting the input power (Vin) into a high-frequency AC signal through the “ON” H-bridge switches (Sp2, Sp3), and transmitting the high-frequency AC signal to the power transmission unit (130) through each of the first and second inductors (Lr1, Lr2). The power transmission unit (130) can transform the high-frequency AC signal input to the primary side of the first and second transformers (Lm1, Lm2) and transmit it to the secondary side. The output voltage switch unit (150) can form a negative sequence path that transmits the output of the first and second transformers (Lm1, Lm2) to the battery through the first and second multi-stage switching networks (Ss2, Ss3) (Ss5, Ss8) in the "ON" state, the first multi-stage switching network (Ss2, Ss3) among the first and second multi-stage switching networks (Ss1~Ss8) in the "ON" state, the first multi-stage switching network (Ss1, Ss4) in the "OFF" state, the second multi-stage switching network (Ss5, Ss8) in the "ON" state, and the second multi-stage switching network (Ss6, Ss7) in the "OFF" state. At this time, current flow through unnecessary paths can be blocked through the first and second multi-stage switching networks (Ss1, Ss4) (Ss6, Ss7) in the “OFF” state. When the battery charging / discharging unit (190) shorts the first relay switch (RYL1) and connects the second relay switch (RLY2) to the upper contact, it can induce a current flow as shown in FIG. 3b to operate the secondary transformer unit as an equivalent parallel circuit.Here, when charging the battery, the current flow can form a first path in the order of the first multi-stage switching network (Ss2, Ss3), the first capacitor (C1), the common capacitor node (171), and the battery, and a second path in the order of the second multi-stage switching network (Ss5, Ss8), the second capacitor (C2), the common capacitor node (171), and the battery from the second transformer (Lm2). The two paths operate in parallel so that current can be stably delivered to the battery.

[0074] In the equivalent parallel operation of FIGS. 3a and 3b, the output voltage switch unit (150) can perform positive sequence control and negative sequence control according to the switch operation, which can be defined in Table 2 below.

[0075] [Table 2]

[0076]

[0077] In the case of Figures 3a and 3b, only the reverse diode state of the bidirectional switch was used for convenience of explanation, but all states of the bidirectional switch can be used depending on the operation sequence.

[0078] The EV charger (100) can control the first and second multi-stage switching networks (Ss1~Ss8) implemented with bidirectional switching elements and two relay switches (RYL1, RYL2) to operate the secondary transformer as an equivalent series circuit or an equivalent parallel circuit, and accordingly, can have a wide output voltage range.

[0079]

[0080] FIG. 4 is a flowchart illustrating a bidirectional power semiconductor-based variable output voltage EV charging method performed in an EV charger according to the present invention.

[0081] Referring to FIG. 4, the EV charger (100) can convert the input power (Vin) into a high-frequency AC signal through H-bridge switches (Sp1, Sp2, Sp3, Sp4) in the input converter section (110) (step S410). The EV charger (100) can input the high-frequency AC signal to the first and second transformers (Lm1, Lm2) in the power transmission section (130) to output an AC voltage transformation signal (step S430).

[0082] Additionally, the EV charger (100) can control the path of the battery charging and discharging current through the first and second multi-stage switching networks (Ss1~Ss8) and the first and second common connection nodes connecting the first and second multi-stage switching networks (Ss1~Ss8) in the output voltage switch section (150) (step S450). The EV charger (100) includes, in the output voltage smoothing section (170), a common capacitor node (171) connecting the first and second common connection nodes, a first capacitor (C1) connecting the common capacitor node (171) to the first multi-stage switching network (Ss1~Ss4) at the first path node, and a second capacitor (C2) connecting the common capacitor node (171) to the second multi-stage switching network (Ss5~Ss8) at the second path node, and can smooth and filter the output voltage associated with the battery charging / discharging current through the series connection of the first and second capacitors (C1, C2) (step S470).

[0083] Additionally, the EV charger (100) includes a first relay switch (RYL1) that controls the connection between the first and second path nodes in the battery charging / discharging section (190), and a second relay switch (RYL2) that connects the input or output terminal of the battery to a common connection node or a second path node. By opening the first relay switch (RYL1) and connecting the second relay switch (RYL2) to the second path node to induce a flow path for the battery charging / discharging current, the secondary transformer can be operated as an equivalent series circuit. By short-circuiting the first relay switch (RYL1) and connecting the second relay switch (RYL2) to the common connection node to induce a flow path for the battery charging / discharging current, the secondary transformer can be operated as an equivalent parallel circuit (step S490).

[0084]

[0085] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art will understand that various modifications and changes can be made to the invention without departing from the spirit and scope of the invention as described in the following claims.

[0086]

[0087] [National R&D projects that supported this invention]

[0088] [Project ID] 2410000575

[0089] [Assignment No.] G01004027271

[0090] [Ministry Name] Ministry of Trade, Industry and Energy

[0091] [Name of Project Management (Specialized) Agency] Korea Institute of Industrial Technology Planning and Evaluation

[0092] [Research Project Name] Automotive Industry Technology Development

[0093] [Research Project Title] Submodule-based 3kW / L or higher compatible by country / capacity

[0094] Development of High Power Density EV ICCU Technology (Korea Institute of Industrial Technology Planning and Evaluation)

[0095] [Name of Project Performing Organization] Konkuk University Industry-Academic Cooperation Foundation

[0096] [Research Period] 2024.04.01 ~ 2024.12.31

[0097]

[0098] [Explanation of the symbol]

[0099] 100: EV (Electric Vehicle) charger

[0100] 110: Input converter section

[0101] 111: 1st Switch Node 112: 2nd Switch Node

[0102] 130: Power transmission unit 150: Output voltage switch unit

[0103] 151,152: 1st and 2nd common connected nodes

[0104] 170: Output voltage smoothing section

[0105] 171: Common capacitor node

[0106] 190: Battery charging / discharging section 210: Battery

[0107] Sp1, Sp2, Sp3, Sp4: H-bridge switch

[0108] Lm1, Lm2: First and second transformers

[0109] Ss1~Ss8: 1st and 2nd multistage switching networks

[0110] C1: First capacitor C2: Second capacitor

[0111] RYL1: 1st relay switch RYL2: 2nd relay switch

Claims

1. An input converter section that converts the input power (Vin) into a high-frequency AC signal through H-bridge switches (Sp1, Sp2, Sp3, Sp4); A power transmission unit that inputs the above high-frequency AC signal to first and second transformers (Lm1, Lm2) and outputs an AC voltage transformation signal; An output voltage switch unit that controls the path of battery charging and discharging current through first and second multi-stage switching networks (Ss1 to Ss8) and first and second common connection nodes connecting the first and second multi-stage switching networks (Ss1 to Ss8); An output voltage smoothing unit comprising a common capacitor node connecting the first and second common connection nodes, a first capacitor (C1) connecting the first multi-stage switching network and the common capacitor node at a first path node, and a second capacitor (C2) connecting the second multi-stage switching network and the common capacitor node at a second path node; and A bidirectional power semiconductor-based output voltage variable EV (Electric Vehicle) charger comprising a battery charging / discharging unit including a first relay switch (RLY1) that controls the connection between the first and second path nodes and a second relay switch (RLY2) that connects the input or output terminal of the battery to the common connection node or the second path node.

2. In paragraph 1, the input converter A bidirectional power semiconductor-based output voltage variable EV charger characterized by transmitting the high-frequency AC signal to the first and second transformers (Lm1, Lm2) by forming a primary transformer section including a first inductor (Lr1) connected to the input terminal of the first transformer (Lm1) and a second inductor (Lr2) connected to the input terminal of the second transformer (Lm2).

3. In paragraph 2, the input converter A bidirectional power semiconductor-based variable output voltage EV charger characterized by connecting the first and second inductors (Lr1, Lr2) in common with a first switch node located between H-bridge switches (Sp1, Sp2), and connecting the first and second transformers (Lm1, Lm2) in common with a second switch node located between H-bridge switches (Sp3, Sp4).

4. In paragraph 1, the power transmission unit A bidirectional power semiconductor-based variable output voltage EV charger characterized by receiving the high-frequency AC signal through the first and second transformers (Lm1, Lm2) and outputting the AC voltage transformation signal considering the target output voltage.

5. In paragraph 1, the output voltage switch portion A bidirectional power semiconductor-based output voltage variable EV charger characterized by controlling the AC voltage transformation signal into a positive sequence or a negative sequence through the first multi-stage switching network (Ss1 to Ss4).

6. In paragraph 5, the output voltage switch part A bidirectional power semiconductor-based output voltage variable EV charger characterized by determining the path of the battery charging / discharging current by controlling the AC voltage transformation signal through the second multi-stage switching network (Ss5 to Ss8) into the positive sequence or the negative sequence.

7. In paragraph 6, the output voltage switch part A bidirectional power semiconductor-based output voltage variable EV charger characterized by implementing each of the first and second multi-stage switching networks (Ss1 to Ss8) as a bidirectional switching element.

8. In paragraph 1, the output voltage smoothing part A bidirectional power semiconductor-based output voltage variable EV charger characterized by smoothing and filtering the output voltage associated with the battery charge / discharge current through the series connection of the first and second capacitors.

9. In paragraph 1, the battery charging and discharging unit A bidirectional power semiconductor-based output voltage variable EV charger characterized by opening the first relay switch (RLY1) and connecting the second relay switch (RLY2) to the second path node to induce a flow path of the battery charging / discharging current, thereby operating the secondary transformer as an equivalent series circuit.

10. In paragraph 1, the battery charging and discharging unit A bidirectional power semiconductor-based output voltage variable EV charger characterized by short-circuiting the first relay switch (RLY1) and connecting the second relay switch (RLY2) to the common connection node to induce a flow path of the battery charging / discharging current, thereby operating the secondary transformer as an equivalent parallel circuit.

11. Input converter step that converts the input power (Vin) into a high-frequency AC signal through H-bridge switches (Sp1, Sp2, Sp3, Sp4); A power transmission step of inputting the above high-frequency AC signal to first and second transformers (Lm1, Lm2) to output an AC voltage transformation signal; An output voltage switch step for controlling the path of battery charging and discharging current through first and second multi-stage switching networks (Ss1 to Ss8) and first and second common connection nodes connecting the first and second multi-stage switching networks (Ss1 to Ss8); An output voltage smoothing step comprising a common capacitor node connecting the first and second common connection nodes, a first capacitor (C1) connecting the first multi-stage switching network and the common capacitor node at a first path node, and a second capacitor (C2) connecting the second multi-stage switching network and the common capacitor node at a second path node; and A bidirectional power semiconductor-based output voltage variable EV (Electric Vehicle) charging method comprising a battery charging / discharging step including a first relay switch (RLY1) that controls the connection between the first and second path nodes and a second relay switch (RLY2) that connects the input or output terminal of the battery to the common connection node or the second path node.

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