Power conversion device

Abstract

A power conversion device according to an embodiment of the present invention includes a power conversion unit that converts AC power into DC power to charge a battery when connected to an AC power source, and an initial charging unit that is connected to the secondary output side of the power conversion unit and initially charges a load-side capacitor. An output terminal of the power conversion unit is connected to the battery and the load-side capacitor.

Description

Technical Field

[0001] The present invention relates to a power conversion device, and more specifically, to a power conversion device capable of initial charging and a vehicle battery system including the same.

Background Art

[0002] In order to convert the battery power into a power suitable for the loads inside the vehicle, the voltage has to be converted. The battery voltage can be 400V to 800V, and the rated voltage of the loads inside the vehicle can be 12V.

[0003] When operating a switch to connect the battery and the load, if there is a voltage difference across the switch, surge voltage and current may be generated due to the parasitic inductor components of the load-side capacitor and the connection wire, which may cause burnout of internal components etc. To solve this, a relay and a resistor are connected to initially charge the load-side capacitor.

[0004] At this time, since separate relays and resistors are required, there is a problem that the cost and area increase.

Summary of the Invention

Problems to be Solved by the Invention

[0005] The technical problem to be solved by the present invention is to provide a power conversion device capable of initial charging and a vehicle battery system including the same.

Means for Solving the Problems

[0006] In order to solve the above technical problem, a power conversion device according to an embodiment of the present invention includes a power conversion unit that converts AC power into DC power to charge a battery when connected to an AC power source, and an initial charging unit that is connected to the secondary output side of the power conversion unit and initially charges a load-side capacitor, and an output terminal of the power conversion unit is connected to the battery and the load-side capacitor.

[0007] Further, it includes a first output terminal connected to the (+) terminal of the battery, a second output terminal connected to the (-) terminal of the battery, and a third output terminal connected to the load-side capacitor. The first output terminal and the third output terminal are connected by a first switch. The AC power supply is a three-phase four-wire AC power supply. The power conversion unit includes three power conversion units connected to each of the three phases to convert power. The initial charging unit can be connected to the first output terminal of the first power conversion unit, which is one of the three power conversion units.

[0008] Also, with the first switch turned off, the first output terminal and the third output terminal can be connected inside the power conversion unit to initially charge the load-side capacitor.

[0009] Further, the power conversion unit includes a primary side to which the AC power is input, a transformer that converts the power on the primary side, and a secondary side connected to the output of the transformer. The secondary side of the power conversion unit includes a full-bridge circuit connected to the output terminal of the transformer, a first upper switch and a first lower switch connected in parallel with the full-bridge circuit, and an LC circuit connected to a node to which the first upper switch and the first lower switch are connected. The first output terminal is connected to the (+) terminal of the full-bridge circuit, the second output terminal is connected to the (-) terminal of the full-bridge circuit, and the third output terminal can be connected to a node connecting the first inductor and the first capacitor of the LC circuit.

[0010] Also, the initial charging unit can include a second switch connected in series with the first capacitor and a first diode connected in parallel with the first capacitor.

[0011] Also, a third switch and a fourth switch with different connection directions can be connected in series to each of the first output terminals of the three power conversion units.

[0012] Also, it can include a first capacitor unit connected in parallel to the node to which the first output terminals of the three power conversion units are connected.

[0013] Further, the first capacitor section, the fourth switch, the first diode, the first inductor, the first upper switch, and the second lower switch can form an H-bridge circuit.

[0014] Also, when initially charging the load-side capacitor, the first switch is off, the fourth switch connecting the first output end in the input direction is on, the second switch is off, the first upper switch is on, the voltage of the battery is input via the first output end, and can be output to the second output end to initially charge the load-side capacitor.

[0015] Also, when a DC power supply is connected to the battery, the battery is charged via the DC power supply, and after the battery is charged, the load-side capacitor can be initially charged.

[0016] When the voltage of the battery is lower than the initial charging voltage of the load-side capacitor, the second switch is off, the third switch and the fourth switch of the first power conversion unit are on, the third switch and the fourth switch of the second power conversion unit are off, the third switch and the fourth switch of the third power conversion unit are off, and each first upper switch of the first power conversion unit, the second power conversion unit, and the third power conversion unit is on. In this state, the load-side capacitor is charged with a first voltage that is the battery voltage. The first capacitor of the second power conversion unit and the first capacitor of the third power conversion unit are charged with the first voltage. Thereafter, the second switch is on, the third switch and the fourth switch of the first power conversion unit are off, the third switch and the fourth switch of the second power conversion unit are on, the third switch and the fourth switch of the third power conversion unit are on, and each first upper switch of the first power conversion unit, the second power conversion unit, and the third power conversion unit is on. In this state, the load-side capacitor is charged with a second voltage obtained by adding the battery voltage to the first voltage, and the first capacitor is charged with the first voltage. Thereafter, the second switch is off, the third switch and the fourth switch of the first power conversion unit are on, the third switch and the fourth switch of the second power conversion unit are on, the third switch and the fourth switch of the third power conversion unit are on, and each first upper switch of the first power conversion unit, the second power conversion unit, and the third power conversion unit is on. In this state, the load-side capacitor can be charged with the second voltage.

[0017] The vehicle battery system according to an embodiment of the present invention can include one of the power conversion devices.

Advantages of the Invention

[0018] According to an embodiment of the present invention, by adding a simple element to an on-board charger (OBC), initial charging is possible without a separate relay and resistor for initial charging.

Brief Description of the Drawings

[0019]

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Best Mode for Carrying Out the Invention

[0020] Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention will be described in detail.

[0021] However, the technical idea of the present invention is not limited to some of the embodiments described, and can be embodied in various different forms. As long as it is within the scope of the technical idea of the present invention, one or more of the constituent elements among the embodiments can be selectively combined or replaced and used.

[0022] In addition, the terms (including technical and scientific terms) used in the embodiments of the present invention can be interpreted in a meaning generally understood by those having ordinary knowledge in the technical field to which the present invention pertains, unless otherwise specifically defined and described. Terms generally used like those defined in a dictionary can have their meanings interpreted in consideration of the meaning in the context of the related art.

[0023] Also, the terms used in the embodiments of the present invention are for explaining the embodiments and are not intended to limit the present invention.

[0024] In this specification, the singular form can include the plural form unless otherwise particularly mentioned in the text. When described as "at least one (or one or more) of A and (or) B, C", it can include one or more of all combinations possible with A, B, and C.

[0025] In addition, when explaining the constituent elements of the embodiments of the present invention, terms such as first, second, A, B, (a), (b), etc. can be used. Such terms are merely for distinguishing the constituent elements from other constituent elements, and the essence, order, or sequence of the constituent elements is not limited by such terms.

[0026] When a component is described as being "coupled", "joined", or "connected" to another component, the component can include not only the case where it is directly "coupled", "joined", or "connected" to the other component, but also the case where it is "coupled", "joined", or "connected" by still other components intervening between the component and the other component.

[0027] Also, when it is described that something is formed or disposed "above (on top of)" or "below (beneath)" each component, "above (on top of)" or "below (beneath)" includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or disposed between the two components. Also, when expressed as "above (on top of)" or "below (beneath)", it can include the meaning not only in the upward direction but also in the downward direction with respect to one component as a reference.

[0028] The modification examples according to this embodiment can include some configurations in each embodiment and some configurations in other embodiments together. That is, the modification example includes one of the various embodiments, but some configurations are omitted and can include some configurations of the corresponding other embodiments. Or, vice versa may also be possible. The features, structures, effects, etc. described in the embodiments are included in at least one embodiment and are not necessarily limited to only one embodiment. Furthermore, the features, structures, effects, etc. exemplified in each embodiment can be combined or modified and implemented for other embodiments by those having ordinary knowledge in the field to which the embodiments belong. Therefore, the content related to such combinations and modifications should be construed as being included in the scope of the embodiments.

[0029] FIG. 1 is a block diagram of a power conversion device according to an embodiment of the present invention. FIG. 2 is a block diagram of a power conversion device according to an embodiment of the present invention, FIG. 3 is a diagram showing the environment of a vehicle battery system to which the power conversion device according to an embodiment of the present invention is applied, FIGS. 4 to 6 are circuit diagrams of the power conversion device according to an embodiment of the present invention, and FIGS. 7 to 18 are diagrams for explaining the power conversion device according to an embodiment of the present invention.

[0030] The power conversion device 100 according to an embodiment of the present invention includes a power conversion unit 110 and an initial charging unit 120, and may include a control unit 130.

[0031] The power conversion device 100 according to an embodiment of the present invention may be a power conversion device applied to a vehicle battery system, and may be an on-board charger (OBC) that charges a battery using the power of an AC power source when connected to the AC power source.

[0032] When connected to the AC power source 210, the power conversion unit 110 converts AC power into DC power to charge the battery. When AC power is input from the AC power source 210, the power conversion unit 110 converts it into DC power for charging the battery. The power conversion unit 110 may include an input terminal connected to the AC power source 210 and an output terminal from which the converted power is output. The output terminal of the power conversion unit 110 may be connected to the battery 220 and may be connected to the load-side capacitor 230. Here, the battery 220 may be a vehicle battery, and the load-side capacitor 230 may be a capacitor located at the load terminal to which a load inside the vehicle is connected. The load-side capacitor 230 can serve to enable the battery 220 and the load to be stably connected.

[0033] The initial charging unit 120 is connected to the secondary output side of the power conversion unit 110 and can initially charge the load-side capacitor 230. The initial charging unit 120 is connected to the secondary output side of the power conversion unit 110 to form a circuit for initial charging, and can initially charge the load-side capacitor 230 according to the connection state of the power conversion unit 110 and the initial charging unit 120.

[0034] The power conversion device 100 according to an embodiment of the present invention can be connected to a vehicle battery system as shown in FIG. 3. The battery may be composed of one battery or, as shown in FIG. 3, a plurality of batteries, and the battery voltage can be variously implemented depending on the connection state. For example, as shown in FIG. 3, for two 400V batteries, if BC1 is on and BC2 and BC3 are off, the two batteries can be connected in series to form an 800V battery. Also, if BC1 is off and BC2 and BC3 are on, the two batteries can be connected in parallel to form a 400V battery. If BC1 is off and either one of BC2 and BC3 is on and the other is off, a 400V battery can be formed.

[0035] When charging the battery, a DC charger can be connected, and FC1 and FC2 can be turned on when the DC charger is connected. Not only the DC charger, but also when an AC, which is an AC power source like a grid, is connected to the power conversion device 100 according to an embodiment of the present invention, the AC can be converted to DC to charge the battery. The power stored in the battery 220 can be output to the load via the load-side capacitor (C_L). The load-side capacitor 230 can be connected to the high-voltage bus terminal (HV Bus). The power conversion device 100 can include three output terminals. Two output terminals are respectively connected to HV(+) and HV(-) of the high-voltage bus terminal, and one output terminal (Non-native) can be connected to the battery.

[0036] The power conversion unit 110 can include a plurality of output terminals. The power conversion unit 110 can include a first output terminal 111 connected to the (+) terminal of the battery 220, a second output terminal 112 connected to the (-) terminal of the battery 220, and a third output terminal 113 connected to the load-side capacitor 230. The first output terminal 111 and the third output terminal 113 are connected by a switch MC1, and the second output terminal can be connected to the (-) terminal of the battery by a switch MC2. The switches MC1 and MC2 may be relays or MOSFETs and can include body diodes.

[0037] The input terminal of the power conversion unit 110 can be connected to the AC power supply 210. Here, the AC power supply 210 may be a three-phase four-wire AC power supply or a single-phase AC power supply. When the AC power supply 210 is a three-phase four-wire AC power supply, the power conversion unit 110 can include three power conversion units connected to each of the three phases to convert power. The initial charging unit 120 can be connected to the first output terminal of the first power conversion unit, which is one of the three power conversion units.

[0038] Each of the power conversion units can include a primary side to which the AC power of the AC power supply 210 is input, a transformer 410 that converts the power on the primary side, and a secondary side connected to the output of the transformer 410. That is, the AC power supply 210 can be connected to the primary side of the transformer 410, and the output terminal can be connected to the secondary side of the transformer 410. An input terminal connected to the AC power supply 210 can include an EMI filter as shown in FIG. 6, and can include a primary side switch unit, a transformer, and a secondary side switch unit for converting each phase of the AC power supply 210.

[0039] The secondary side of the power conversion unit may include a full-bridge circuit 420, a first upper switch and a first lower switch 430, and an LC circuit 440. The full-bridge circuit 420 may be connected to the output terminal of the transformer 410. The first upper switch S1 and the first lower switch S2 are connected in parallel with the full-bridge circuit 420. The LC circuit 440 may be connected to the node to which the first upper switch S1 and the first lower switch S2 are connected.

[0040] The full-bridge circuit 420 includes two upper switches and two lower switches. Although the upper switch and the lower switch are connected in series with each other, the two nodes connecting the upper switch and the lower switch may be respectively connected to both ends of the secondary side of the transformer of the power conversion unit. The upper switch and the lower switch connected in series can conduct complementarily with each other. A first upper switch S1 and a first lower switch S2 are connected to the output terminal side of the full-bridge circuit 420, and an inductor L1 and a capacitor C1 may be connected to the node to which the first upper switch S1 and the first lower switch S2 are connected. Here, each switch may be a MOSFET and may include a body diode.

[0041] Here, the first output terminal 111 is connected to the (+) terminal of the full-bridge circuit 420, the second output terminal 112 is connected to the (-) terminal of the full-bridge circuit 420, and the third output terminal 113 may be connected to the node connecting the first inductor L1 and the first capacitor C1 of the LC circuit 440.

[0042] The initial charging unit 120 can include a switch S3 connected in series with the first capacitor C1 and a first diode D1 connected in parallel with the first capacitor C1. Switches S4 and S5 with different connection directions can be connected in series to each of the first output ends of the three power conversion units. Each switch may be a MOSFET and can include a body diode. The switches S4 and S5 with different connection directions can have their sources connected to each other, and depending on the type of MOSFET, their drains may be connected to each other. The directions of the body diodes can also be connected in opposite directions to each other.

[0043] A capacitor unit can be included and connected in parallel to the node to which the first output end 111 is connected. Here, the capacitor unit can include a plurality of capacitors connected in series and can include two capacitors C2 and C3.

[0044] The capacitor unit, switch S5, first diode D1, first inductor L1, first upper switch S1, and second lower switch S2 can form an H-bridge circuit 500. The battery 220 and the load-side capacitor 230 can be connected via the H-bridge circuit 500 as shown in FIG. 5, and the H-bridge circuit 500 can operate as a buck-boost converter. That is, the voltage of the battery 220 can be stepped up or down so that the load-side capacitor 230 can be initially charged according to the magnitude of the voltage of the battery 220. Through this, the load-side capacitor 230 can be initially charged using the voltage of the battery 220.

[0045] When performing initial charging with a boost circuit, an inrush current may occur on the output side at the moment when duty is applied. Since an inrush current can occur at the initial stage of initial charging and the inrush current is not generated until the output-side capacitor C1 is sufficiently charged, it must be operated with an H-bridge. Since the capacitor section, switch S5, first diode D1, first inductor L1, first upper switch S1, and second lower switch S2 can form the H-bridge circuit 500, the inrush current can be resolved.

[0046] By adding only the switch S3, diode D1, switches S4, S5, and capacitors C2, C3 to the configuration of the power conversion unit 110 that converts the AC power of the AC power supply 210 into DC power, the load-side capacitor 230 can be initially charged.

[0047] With the switch MC1 turned off, the first output terminal 111 and the third output terminal 113 can be connected inside the power conversion unit 110 to initially charge the load-side capacitor 230.

[0048] When initially charging the load-side capacitor 230, the switch MC1 is off, the switch S5 connected to the first output terminal 111 in the input direction is on, the switch S3 is off, and the first upper switch S1 is on. At this time, the voltage of the battery 220 is input via the first output terminal 111 and output to the second output terminal 112, and the load-side capacitor 230 can be initially charged.

[0049] In order to prevent burnout that may occur due to a voltage difference when directly connecting the voltage of the battery 220 to the load-side capacitor 230, it is necessary to initially charge the load-side capacitor 230 with the required voltage. For this purpose, by connecting the battery 220 and the load-side capacitor 230 via the initial charging unit 120 and the power conversion unit 110, before directly connecting the battery 220 to the load-side capacitor 230, the load-side capacitor 230 can be initially charged through the voltage of the battery 220. For this purpose, the (+) terminal of the battery 220 must be connected to the first output terminal 111 instead of being directly connected to the load-side capacitor 230. At this time, MC1 is turned off, and MC2 is turned on. Among the switches S4 and S5, S5 is turned on, S4 is turned off, S2 and S3 are turned off, and S1 is turned on. Along the path connecting the first output terminal 111, the body diodes of S5 and S4, the first inductor L1, S1, and the third output terminal 113, the battery 220 and the load-side capacitor 230 are connected, and the load-side capacitor 230 can be initially charged.

[0050] At this time, as described above, the capacitor unit, the switch S5, the first diode D1, the first inductor L1, the first upper switch S1, and the second lower switch S2 can form an H-bridge circuit 500, and the voltage of the battery 220 can be boosted or pressurized to initially charge the load-side capacitor 230. By forming a simple circuit with elements for initial charging in the power conversion unit 110, the load-side capacitor 230 can be initially charged without a separate relay and resistor for initial charging.

[0051] When initially charging the load-side capacitor 230 using the battery 220, depending on the situation, the control unit 130 can control the switch to initially charge the load-side capacitor 230. For example, when charging the battery 220 with a DC charger, when charging during vehicle operation, when charging the battery 220 with an AC power supply 210, when the voltage of the battery 220 is low, etc., the operation sequence may vary depending on each situation.

[0052] When a DC power supply is connected to the battery 220, the battery 220 is charged via the DC power supply, and after the battery 220 is charged, the load-side capacitor 230 can be initially charged.

[0053] When a DC charger is connected and the battery 220 is charged, the load-side capacitor can be initially charged with the power of the battery 220 via the OBC which is the power conversion device 100. For example, as shown in FIGS. 7 to 9, after the DC charger charges the battery 220 at 800V and the load-side capacitor 230 is initially charged at 800V, the battery 220 and the load-side capacitor 230 can be connected. For this purpose, first, when the plug of the 800V DC charger is connected (S101) to the vehicle, the DC charging voltage is sensed (S102), and it is confirmed (S103) whether the DC charging voltage matches the battery voltage of 800V. When the battery voltage and the DC charging voltage do not match, FC1 and FC2 are maintained off (S104), and safety can be maintained by preventing the DC charger from being connected to the battery 220. When the battery voltage and the DC charging voltage match, the battery constitutes an 800V battery pack, and FC1 and FC2 are turned on to charge the battery (S105). When the battery is charged, MC2 is turned on (S106), and the high-voltage bus (HV Bus) is tested (S107) by the OBC. When the test of the high-voltage bus fails, an error of the high-voltage bus is transmitted to an external MCU or the like, and the test circuit is turned off (S108). When the test of the high-voltage bus passes, the high-voltage bus capacitor which is the load-side capacitor is initially charged (S109). It is confirmed (S110) whether the initial charge of the high-voltage bus capacitor is at the target voltage for initial charging. When the initial charging is completed, MC1 is turned on (S111), the initial charging of the OBC is turned off (S112), and the battery 220 and the high-voltage bus can be directly connected to supply the battery voltage to the load (S113). As shown in FIG. 9, with MC1 off and MC2 on, the battery 220 and the load-side capacitor 230 are connected through a path formed inside the OBC to test the high-voltage bus. After initially charging the load-side capacitor, MC1 is turned on, and the battery 220 can be directly connected to the high-voltage bus to supply the battery voltage to the load.

[0054] Without a connection for charging the battery 220, like when the vehicle is in operation, the load side capacitor can be initially charged with the power of the battery 220 through the OBC which is the power conversion device 100 in the current state of the battery 220. For example, as shown in FIGS. 10 to 12, after the load side capacitor 230 is initially charged at 800V with the voltage of the battery 220 being 800V, the battery 220 and the load side capacitor 230 can be connected. For this purpose, when the vehicle start is detected (S201), MC2 is turned on (S202), and the high voltage bus (HV Bus) is tested by the OBC (S203). When the test of the high voltage bus fails, an error of the high voltage bus is transmitted to an external MCU or the like, and the test circuit is turned off (S204). When the test of the high voltage bus passes, the high voltage bus capacitor which is the load side capacitor is initially charged (S205). It is confirmed (S206) whether the initial charge of the high voltage bus capacitor is at the target voltage and the initial charge is performed. When the initial charge is completed, MC1 is turned on (S207), the initial charge of the OBC is turned off (S208), and the battery 220 and the high voltage bus can be directly connected to supply the battery voltage to the load (S209). As shown in FIG. 12, MC1 is turned off and MC2 is turned on, the battery 220 and the load side capacitor 230 are connected through the path formed inside the OBC to test the high voltage bus, and after the load side capacitor is initially charged, MC1 is turned on, and the battery 220 can be directly connected to the high voltage bus to supply the battery voltage to the load.

[0055] When an AC power source is connected to the OBC and the battery 220 is charged via the OBC, the load-side capacitor can be initially charged with the power of the battery 220 via the OBC which is the power conversion device 100. For example, as shown in FIGS. 13 to 15, when the AC power source 210 is connected, after the load-side capacitor 230 is initially charged at 800V, the battery 220 and the load-side capacitor 230 are connected, and the battery 220 can be charged at 800V. For this purpose, first, when the AC power plug is connected (S301) to the vehicle, MC2 is turned on (S302), and the high-voltage bus (HV Bus) is tested (S303) with the OBC. When the test of the high-voltage bus fails, the error of the high-voltage bus is transmitted to an external MCU or the like, and the test circuit is turned off (S304). When the test of the high-voltage bus passes, the high-voltage bus capacitor which is the load-side capacitor is initially charged (S305). It is confirmed (S306) whether the initial charge of the high-voltage bus capacitor is at the target voltage and the initial charge is performed. When the initial charge is completed, MC1 is turned on (S307), the initial charge of the OBC is turned off (S308), the battery 220 and the high-voltage bus are directly connected to supply the battery voltage to the load (S311), the primary-side clamp capacitor of the OBC is initially charged (S309), and the OBC is turned on (S310) to charge the battery. As shown in FIG. 15, after testing the high-voltage bus with the AC power source connected to the OBC and initially charging the load-side capacitor 230, MC1 can be turned on and the battery 220 can be directly connected to the high-voltage bus to supply the battery voltage to the load.

[0056] When the voltage of the battery 220 is lower than the initial charging voltage of the load-side capacitor 230, it is necessary to boost the voltage of the battery 220 to initially charge the load-side capacitor 230. For this purpose, first, switch S3 is off, switches S4 and S5 of the first power conversion unit (Block C) are on, switches S4 and S5 of the second power conversion unit (Block A) and the third power conversion unit (Block B) are off, and with each upper switch S1 of the first power conversion unit, the second power conversion unit, and the third power conversion unit being on, the load-side capacitor 230 is charged with a first voltage that is the battery voltage, and the first capacitor C1 of the second power conversion unit (Block A) and the third power conversion unit (Block B) can be charged with the first voltage.

[0057] After that, switch S3 is on, switches S4 and S5 of the first power conversion unit (Block C) are off, switches S4 and S5 of the second power conversion unit (Block A) and the third power conversion unit (Block B) are on, and with each upper switch S1 of the first power conversion unit, the second power conversion unit, and the third power conversion unit being on, the load-side capacitor is charged with a second voltage obtained by adding the battery voltage to the first voltage, and the first capacitor C1 can be charged with the first voltage.

[0058] After that, switch S3 is off, switches S4 and S5 of the first power conversion unit (Block C) are on, switches S4 and S5 of the second power conversion unit (Block A) and the third power conversion unit (Block B) are on, and with each upper switch S1 of the first power conversion unit, the second power conversion unit, and the third power conversion unit being on, the load-side capacitor can be charged with the second voltage.

[0059] When the voltage of the battery 220 is lower than the initial charging voltage of the load-side capacitor 230, for example, as shown in FIGS. 16 to 18, the DC charger is a 400V charger, the battery is charged at 400V, but the load-side capacitor must be initially charged at 800V, the initial charging can be performed as follows. In this case, since the battery voltage and the voltage of the load-side capacitor are different, power can be supplied to the load by connecting them via the OBC without directly connecting the battery and the load-side capacitor.

[0060] For this purpose, first, when the plug of the DC charger is connected (S401) to the vehicle, the DC charging voltage is sensed (S402), and it is confirmed (S403) whether the DC charging voltage is 400V. If the DC charging voltage is not 400V, FC1 and FC2 are maintained off (S404), and safety can be maintained by preventing the DC charger and the battery 220 from being connected. If the DC charging voltage is 400V, the battery constitutes a 400V battery pack, and FC1 and FC2 are turned on to charge the battery (S405). When the battery is charged, MC2 is turned on (S406), and the high-voltage bus (HV Bus) is tested (S407) with the OBC. When the test of the high-voltage bus fails, an error of the high-voltage bus is transmitted to an external MCU or the like, and the test circuit is turned off (S408). When the test of the high-voltage bus passes, the high-voltage bus capacitor, which is the load-side capacitor, is initially charged (S409). It is confirmed (S410) whether the initial charging of the high-voltage bus capacitor is at the target voltage to perform the initial charging. When the initial charging is completed, the initial charging of the OBC is turned off (S411), and the OBC non-Native mode is turned on (S412) so that the battery 220 and the high-voltage bus are not directly connected, and they are connected to the load via the OBC, and the battery voltage can be supplied to the load (S413).

[0061] As shown in Fig. 18, when the voltage of the battery 220 is lower than the initial charging voltage of the load-side capacitor 230, first, MC1 is turned off and MC2 is turned on. Through the path formed by Block C, which is the first power conversion unit inside the OBC, the load-side capacitor, the output-side capacitors of the second and third power conversion units (Block A and Block B), are initially charged with the first voltage, which is the battery voltage. At this time, Block C can operate as an H-bridge circuit. The B2B switches A and B of Block A and Block B, which are the second and third power conversion units, are turned off, the upper-side switches (High-side MOSFETs) are turned on, and the Auxiliary MOSFET, which is switch S3 of Block C, the first power conversion unit, is turned off to initially charge the load-side capacitor with 400V, which is the first voltage.

[0062] After that, the B2B switches A and B of Block A and Block B, which are the second and third power conversion units, are turned on, and the B2B switch C of Block C, which is the first power conversion unit, is turned off. Although the load-side capacitor is charged through the path formed by Block A and Block B, which are the second and third power conversion units, the first voltage of 400V, which is the battery voltage, is added to the first voltage of 400V initially charged to the output-side capacitors of Block A and Block B, which are the second and third power conversion units, in the previous step, and the load-side capacitor is initially charged with 800V, which is the second voltage. At this time, Block A and Block B can operate as Boost circuits. At this time, the Auxiliary MOSFET, which is switch S3 of Block C, the first power conversion unit, is turned on to initially charge the output-side capacitor of Block C, which is the first power conversion unit, with 400V, which is the first voltage. At this time, Block C, which is the first power conversion unit, can operate as a Buck circuit.

[0063] After that, turn on the B2B switch C of Block C, which is the first power conversion unit, and the load-side capacitor can be charged through the path formed by Blocks A, B, and C, which are the first to third power conversion units. At this time, Block C, which is the first power conversion unit, can also operate as a Boost circuit, similar to Blocks A and B. Through this, the battery voltage of 400V can be boosted to 800V, and an 800V voltage can be supplied to the load-side capacitor 230. At this time, MC1 can be maintained off so that the battery 220 is not directly connected to the load-side capacitor 230.

[0064] The vehicle battery system according to an embodiment of the present invention may include an OBC, which is a power conversion device according to an embodiment of the present invention. The detailed description of the power conversion device of the vehicle battery system corresponds to the detailed description of the power conversion device in FIGS. 1 to 18, and the overlapping description will be omitted below. The vehicle battery system includes a battery and a power conversion device that converts the power source of the battery and outputs it to a load, or is connected to an AC power source and converts it according to the power source for charging the battery and outputs it to the battery.

[0065] To solve the above technical problem, a power conversion device according to an embodiment of the present invention includes a power conversion unit that converts AC power into DC power to charge a battery when connected to an AC power source, and an initial charging unit that is connected to the secondary output side of the power conversion unit and initially charges a load-side capacitor. An output terminal of the power conversion unit is connected to the battery and the load-side capacitor. Further, it includes a first output terminal connected to the (+) end of the battery, a second output terminal connected to the (-) end of the battery, and a third output terminal connected to the load-side capacitor. The first output terminal and the third output terminal are connected by a switch. The AC power source is a three-phase four-wire AC power source. The power conversion unit includes three power conversion units connected to each of the three phases to convert power. The initial charging unit may be connected to the first output terminal of a first power conversion unit, which is one of the three power conversion units. With the switch turned off, the first output terminal and the third output terminal can be connected inside the power conversion unit to initially charge the load-side capacitor.

[0066] Those with ordinary knowledge in the technical field related to this embodiment will understand that it can be implemented in a modified form without departing from the essential characteristics described above. Therefore, the disclosed method should be considered from an illustrative rather than a limiting perspective. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the equivalent scope thereof should be construed as being included in the present invention.

Claims

1. A power conversion device including a power conversion unit that converts AC power to DC power to charge a battery when connected to an AC power source, and an initial charging unit connected to the secondary output side of the power conversion unit to initially charge a load-side capacitor, wherein an output terminal of the power conversion unit is connected to the battery and the load-side capacitor.

2. The power conversion unit includes a first output terminal connected to the (+) terminal of the battery, a second output terminal connected to the (-) terminal of the battery, and a third output terminal connected to the load-side capacitor, wherein the first output terminal and the third output terminal are connected by a first switch, the AC power source is a three-phase four-wire AC power source, the power conversion unit includes three power conversion units connected to each of the three phases to convert power, and the initial charging unit is connected to the first output terminal of a first power conversion unit which is one of the three power conversion units. The power conversion device according to claim 1.

3. The power conversion device according to claim 2, wherein in a state where the first switch is turned off, the first output terminal and the third output terminal are connected inside the power conversion unit to initially charge the load-side capacitor.

4. The power conversion unit includes a primary side to which the AC power is input, a transformer that converts the power on the primary side, and a secondary side connected to the output of the transformer, wherein the secondary side of the power conversion unit includes a full-bridge circuit connected to the output terminal of the transformer, a first upper switch and a first lower switch connected in parallel with the full-bridge circuit, and an LC circuit connected to a node to which the first upper switch and the first lower switch are connected, the first output terminal is connected to the (+) terminal of the full-bridge circuit, the second output terminal is connected to the (-) terminal of the full-bridge circuit, and the third output terminal is connected to a node connecting a first inductor and a first capacitor of the LC circuit. The power conversion device according to claim 2.

5. The initial charging unit includes a second switch connected in series with the first capacitor, and a first diode connected in parallel with the first capacitor. The power conversion device according to claim 4.

6. A third switch and a fourth switch with different connection directions are connected in series to each of the first output terminals of the three power conversion units. The power conversion device according to claim 5.

7. ​ The power conversion device according to claim 6, comprising a first capacitor unit connected in parallel to a node to which the first output ends of the three power conversion units are connected.

8. The power conversion device according to claim 7, wherein the first capacitor unit, the fourth switch, the first diode, the first inductor, the first upper switch, and the second lower switch form an H-bridge circuit.

9. When the load-side capacitor is initially charged, the first switch is off, the fourth switch connected to the first output end in the input direction is on, the second switch is off, and the first upper switch is on. The power conversion device according to claim 7, wherein the voltage of the battery is input through the first output end and output to the second output end to initially charge the load-side capacitor.

10. When a DC power supply is connected to the battery, the battery is charged through the DC power supply. The power conversion device according to claim 9, wherein after the battery is charged, the load-side capacitor is initially charged.

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