Power conversion device

Abstract

The present disclosure relates to a power conversion device. The power conversion device according to an embodiment of the present disclosure comprises: a first capacitor connected to a first battery; a second capacitor connected to a second battery; a transformer; a first full-bridge switching unit, which includes a plurality of switching elements and is arranged between the first capacitor and the input side of the transformer; a second full-bridge switching unit, which includes a plurality of switching elements and is arranged between the second capacitor and the output side of the transformer, wherein, in the pre-charge mode, turn-off points of some switching elements in the second full-bridge switching unit are delayed during operation of the first full-bridge switching unit and the second full-bridge switching unit. Therefore, the capacitor can be stably pre-charged.

Description

power conversion device

[0001] The present disclosure relates to a power conversion device, and more particularly, to a power conversion device capable of stably pre-charging a capacitor.

[0002] Electric vehicles that run on electricity, or hybrid vehicles that combine internal combustion engines and these, generate their output using motors and batteries.

[0003] Meanwhile, to drive the motor, an inverter is required to convert DC voltage into AC voltage, and the inverter uses the DC voltage of the battery and converts it into AC voltage.

[0004] Meanwhile, a capacitor is used in the inverter, and the capacitor stores the DC voltage from the battery.

[0005] Meanwhile, when the power conversion device starts operating, a momentary inrush current flows from the battery to the capacitor. The higher the inrush current, the greater the risk of capacitor damage.

[0006] The technical problem of the present disclosure is to provide a power conversion device capable of stably pre-charging a capacitor.

[0007] Another technical problem of the present disclosure is to provide a power conversion device capable of preventing damage to a capacitor.

[0008] A power conversion device according to an embodiment of the present disclosure for solving the above technical problem comprises a first capacitor connected to a first battery, a second capacitor connected to a second battery, a transformer, and a plurality of switching elements, and includes a first full bridge switching unit between an input side of the first capacitor and the transformer, and a second full bridge switching unit between the second capacitor and an output side of the transformer, wherein in a pre-charge mode, during operations of the first full bridge switching unit and the second full bridge switching unit, the turn-off timing of some switching elements of the second full bridge switching unit is delayed.

[0009] Meanwhile, in the pre-charge mode, the turn-off timing of some of the switching elements of the second full bridge switching unit is delayed, so that the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-off timing of some of the other switching elements may be smaller than the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-on timing of some of the other switching elements.

[0010] Meanwhile, in the pre-charge mode, during the turn-off delay period in which the turn-off timing of some switching elements of the second full bridge switching unit is delayed, other some switching elements of the second full bridge switching unit may be turned on, and switching elements within the first full bridge switching unit may be turned on.

[0011] Meanwhile, after the turn-off delay period, some of the switching elements of the second full bridge switching unit are turned off, and during the turn-off period in which some of the switching elements of the second full bridge switching unit are turned off, other some of the switching elements of the second full bridge switching unit are turned on, and the switching elements in the first full bridge switching unit can be turned on.

[0012] Meanwhile, after the turn-off section, during the turn-on section in which another part of the switching elements of the second full bridge switching section is turned on, another part of the switching elements of the second full bridge switching section may be turned on, and the switching elements in the first full bridge switching section may be turned on.

[0013] Meanwhile, after the turn-on section, some other switching elements of the second full bridge switching unit may remain turned on, some other switching elements of the second full bridge switching unit may be turned off, some switching elements within the first full bridge switching unit may be turned off, and some other switching elements within the first full bridge switching unit may be turned on.

[0014] Meanwhile, the power conversion device according to the embodiment of the present disclosure may further include a control unit that controls the first full bridge switching unit and the second full bridge switching unit.

[0015] Meanwhile, the control unit can control the turn-off timing of some switching elements of the second full bridge switching unit to be delayed during the operation of the first full bridge switching unit and the second full bridge switching unit in the pre-charge mode.

[0016] Meanwhile, the control unit can control the delay to decrease as the difference between the first battery voltage and the second battery voltage increases in the pre-charge mode.

[0017] Meanwhile, the control unit can control the delay to become smaller when the voltage of the second capacitor increases in the pre-charge mode.

[0018] Meanwhile, a power conversion device according to an embodiment of the present disclosure further includes an inductor connected between a first capacitor and a first full bridge switching unit, and a first current detection unit that detects a current flowing in the inductor, and a control unit that can control the delay to be reduced when the current flowing in the inductor is reduced in the pre-charge mode.

[0019] Meanwhile, the power conversion device according to the embodiment of the present disclosure may further include a second current detection unit disposed between the second full bridge switching unit and the second capacitor, and a third current detection unit disposed between the second capacitor and the second battery.

[0020] Meanwhile, the control unit can control current to flow from the first capacitor in the direction of the second capacitor in the pre-charge mode, and after the pre-charge mode ends, control current to flow from the second capacitor in the direction of the first capacitor.

[0021] Meanwhile, the power conversion device according to the embodiment of the present disclosure further includes a battery switching element connected between the second capacitor and the second battery, and the control unit can control the battery switching element to be turned off in the pre-charge mode.

[0022] Meanwhile, the control unit can control the battery switching element to be turned on after the pre-charge mode.

[0023] Meanwhile, the power conversion device according to the embodiment of the present disclosure further includes an inverter connected to both ends of the second capacitor, and the control unit can control the voltage from the second battery to be stored in the second capacitor after the pre-charge mode, and control the inverter to operate based on the voltage stored in the second capacitor.

[0024] Meanwhile, the power conversion device according to the embodiment of the present disclosure further includes a converter that converts an input AC voltage into a DC voltage, and a second battery may be placed between the converter and the inverter.

[0025] Meanwhile, the first full bridge switching unit may include a first switching element and a second switching element that correspond to the first leg and are connected in series with each other, and a third switching element and a fourth switching element that correspond to the second leg that is connected in parallel with the first leg and are connected in series with each other.

[0026] Meanwhile, the second full bridge switching unit may include a fifth switching element and a sixth switching element that correspond to the third leg and are connected in series with each other, and a seventh switching element and an eighth switching element that correspond to the fourth leg that is connected in parallel with the third leg and are connected in series with each other.

[0027] Meanwhile, the second full bridge switching unit may further include a first diode element and a second diode element that are connected in parallel to the third and fourth legs and are connected in series with each other.

[0028] A power conversion device according to another embodiment of the present disclosure includes a first capacitor connected to a first battery, a second capacitor connected to a second battery, a transformer, and a plurality of switching elements, and includes a first full bridge switching unit between an input side of the first capacitor and the transformer, and a second full bridge switching unit between a second capacitor and an output side of the transformer, and a plurality of switching elements, wherein in a pre-charge mode, an interval between a turn-off point of some switching elements of the second full bridge switching unit and a turn-off point of some other switching elements is smaller than an interval between a turn-off point of some switching elements of the second full bridge switching unit and a turn-on point of some other switching elements.

[0029] A power conversion device according to an embodiment of the present disclosure comprises a first capacitor connected to a first battery, a second capacitor connected to a second battery, a transformer, and a plurality of switching elements, and includes a first full bridge switching unit between an input side of the first capacitor and the transformer, and a second full bridge switching unit between the second capacitor and an output side of the transformer, wherein in a pre-charge mode, during the operation of the first full bridge switching unit and the second full bridge switching unit, the turn-off timing of some of the switching elements of the second full bridge switching unit is delayed. Accordingly, the capacitor can be stably pre-charged. In particular, damage to the capacitor can be prevented.

[0030] Meanwhile, in the pre-charge mode, the turn-off timing of some of the switching elements of the second full bridge switching unit is delayed, so that the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-off timing of some of the other switching elements may be smaller than the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-on timing of some of the other switching elements. Accordingly, the capacitor can be stably pre-charged.

[0031] Meanwhile, in the pre-charge mode, during the turn-off delay period in which the turn-off timing of some switching elements of the second full bridge switching unit is delayed, other switching elements of the second full bridge switching unit may be turned on, and switching elements within the first full bridge switching unit may be turned on. Accordingly, the capacitor can be stably pre-charged.

[0032] Meanwhile, after the turn-off delay period, some of the switching elements of the second full bridge switching unit are turned off, and during the turn-off period in which some of the switching elements of the second full bridge switching unit are turned off, other some of the switching elements of the second full bridge switching unit are turned on, and the switching elements within the first full bridge switching unit can be turned on. Accordingly, the capacitor can be stably pre-charged.

[0033] Meanwhile, after the turn-off period, during the turn-on period in which some other switching elements of the second full bridge switching unit are turned on, some other switching elements of the second full bridge switching unit are turned on, and the switching elements within the first full bridge switching unit can be turned on. Accordingly, the capacitor can be stably pre-charged.

[0034] Meanwhile, after the turn-on section, some other switching elements of the second full bridge switching unit remain turned on, some other switching elements of the second full bridge switching unit are turned off, some switching elements within the first full bridge switching unit are turned off, and some other switching elements within the first full bridge switching unit are turned on. Accordingly, the capacitor can be stably pre-charged.

[0035] Meanwhile, the power conversion device according to the embodiment of the present disclosure may further include a control unit that controls the first full bridge switching unit and the second full bridge switching unit. Accordingly, the capacitor can be stably precharged.

[0036] Meanwhile, the control unit can control the turn-off timing of some switching elements of the second full bridge switching unit to be delayed during the operation of the first full bridge switching unit and the second full bridge switching unit in the pre-charge mode. Accordingly, the capacitor can be stably pre-charged.

[0037] Meanwhile, the control unit can control the delay to decrease as the difference between the first and second battery voltages increases in pre-charge mode. Accordingly, the capacitor can be efficiently pre-charged.

[0038] Meanwhile, the control unit can control the delay to be reduced when the voltage of the second capacitor increases in the pre-charge mode. Accordingly, the capacitor can be efficiently pre-charged.

[0039] Meanwhile, a power conversion device according to an embodiment of the present disclosure further includes an inductor connected between a first capacitor and a first full bridge switching unit, and a first current detection unit that detects a current flowing in the inductor, and the control unit can control the delay to be reduced when the current flowing in the inductor decreases in the pre-charge mode. Accordingly, the capacitor can be efficiently pre-charged.

[0040] Meanwhile, the power conversion device according to an embodiment of the present disclosure may further include a second current detection unit positioned between the second full bridge switching unit and the second capacitor, and a third current detection unit positioned between the second capacitor and the second battery. Accordingly, the capacitor can be efficiently precharged.

[0041] Meanwhile, the control unit can control current to flow from the first capacitor toward the second capacitor in the pre-charge mode, and after the pre-charge mode ends, control current to flow from the second capacitor toward the first capacitor. Accordingly, after the pre-charge mode, the first battery can be stably charged.

[0042] Meanwhile, the power conversion device according to an embodiment of the present disclosure further includes a battery switching element connected between a second capacitor and a second battery, and the control unit can control the battery switching element to be turned off in the pre-charge mode. Accordingly, the capacitor can be efficiently pre-charged.

[0043] Meanwhile, the control unit can control the battery switching element to turn on after the pre-charge mode. Accordingly, the first battery can be stably charged after the pre-charge mode.

[0044] Meanwhile, the power conversion device according to the embodiment of the present disclosure further includes an inverter connected to both ends of the second capacitor, and the control unit controls, after the pre-charge mode, the voltage from the second battery to be stored in the second capacitor, and controls the inverter to operate based on the voltage stored in the second capacitor. Accordingly, the motor operation mode can be stably performed.

[0045] Meanwhile, the power conversion device according to the embodiment of the present disclosure further includes a converter that converts input AC voltage into DC voltage, and a second battery may be placed between the converter and the inverter. Accordingly, the second battery can be stably charged.

[0046] Meanwhile, the first full bridge switching unit may include a first switching element and a second switching element that correspond to the first leg and are connected in series with each other, and a third switching element and a fourth switching element that correspond to the second leg that is connected in parallel with the first leg and are connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0047] Meanwhile, the second full bridge switching unit may include a fifth switching element and a sixth switching element that correspond to the third leg and are connected in series with each other, and a seventh switching element and an eighth switching element that correspond to the fourth leg that is connected in parallel with the third leg and are connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0048] Meanwhile, the second full bridge switching unit may further include a first diode element and a second diode element that are connected in parallel to the third and fourth legs and connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0049] According to another embodiment of the present disclosure, a power conversion device includes a first capacitor connected to a first battery, a second capacitor connected to a second battery, a transformer, and a plurality of switching elements, and includes a first full bridge switching unit between an input side of the first capacitor and the transformer, and a second full bridge switching unit between an output side of the second capacitor and the transformer, and a plurality of switching elements, wherein in a pre-charge mode, an interval between the turn-off points of some of the switching elements of the second full bridge switching unit and the turn-off points of other switching elements is smaller than an interval between the turn-off points of some of the switching elements of the second full bridge switching unit and the turn-on points of other switching elements. Accordingly, the capacitor can be stably pre-charged. In particular, damage to the capacitor can be prevented.

[0050] FIG. 1 is a schematic drawing showing a body of a vehicle according to one embodiment of the present disclosure.

[0051] FIG. 2 is an example of a motor drive system according to one embodiment of the present disclosure.

[0052] Figure 3 illustrates an example of an internal block diagram of the motor driving device of Figure 2.

[0053] Fig. 4 is an example of an internal circuit diagram of the motor driving device of Fig. 3.

[0054] Fig. 5 is an example of an internal block diagram of the inverter control unit of Fig. 4.

[0055] FIG. 6 is a diagram illustrating the operation of a battery and an inverter related to the present disclosure.

[0056] FIG. 7 is a block diagram illustrating a power conversion device according to an embodiment of the present disclosure.

[0057] Fig. 8 is a drawing illustrating an example of the operation of the power conversion device of Fig. 7.

[0058] Fig. 9 is a diagram illustrating the dc / dc converter of Fig. 7.

[0059] Figures 10a to 11f are drawings referenced in the operation description of Figure 9.

[0060] Hereinafter, the present disclosure will be described in more detail with reference to the drawings.

[0061] The suffixes "module" and "part" used in the following description are given solely for the convenience of writing this specification and do not impart any particularly significant meaning or role to the components themselves. Therefore, the terms "module" and "part" may be used interchangeably.

[0062] FIG. 1 is a schematic drawing showing a body of a vehicle according to one embodiment of the present disclosure.

[0063] Referring to the drawings, a vehicle (100) according to an embodiment of the present disclosure may include a battery (205) that supplies voltage, a motor driving device (200) that receives voltage from the battery (205), a motor (250) that is driven and rotates by the motor driving device (200), front wheels (150) and rear wheels (155) that are rotated by the motor (250), a front suspension device (160) and a rear suspension device (165) that block vibrations of the road surface from being transmitted to the vehicle body, and an inclination detection unit (190) that detects an inclination angle of the vehicle body. Meanwhile, a driving gear (not shown) that converts the rotational speed of the motor (250) based on a gear ratio may be additionally provided.

[0064] The battery (205) supplies voltage to the motor drive device (200). In particular, it supplies direct current voltage to the capacitor (C) in the motor drive device (200).

[0065] Such a battery (205) may be formed by a set of multiple unit cells. The multiple unit cells may be managed by a battery management system (BMS) to maintain a constant voltage, and may discharge a constant voltage by the battery management system.

[0066] For example, the battery management system can detect the voltage (Vbat) of the battery (205) and transmit it to an electronic control unit (not shown) or an inverter control unit (250) within the motor drive device (200), and when the battery voltage (Vbat) falls below a lower limit, the battery can supply a DC voltage stored in a capacitor (C) within the motor drive device (200). In addition, when the battery voltage (Vbat) rises above an upper limit, the battery management system can also supply a DC voltage to the capacitor (C) within the motor drive device (200).

[0067] The battery (205) is preferably composed of a secondary battery that can be charged and discharged, but is not limited thereto.

[0068] The motor drive device (200) receives a direct current voltage from the battery (205) through a voltage input cable (120). The motor drive device (200) converts the direct current voltage received from the battery (205) into an alternating current voltage and supplies it to the motor (250). The converted alternating current voltage is preferably a three-phase alternating current voltage. The motor drive device (200) supplies a three-phase alternating current voltage to the motor (250) through a three-phase output cable (125) provided in the motor drive device (200).

[0069] The motor drive device (200) of Fig. 1 illustrates a three-phase output cable (125) composed of three cables, but three cables may be provided within a single cable.

[0070] Meanwhile, the motor driving device (200) according to the embodiment of the present disclosure is described below in FIG. 3.

[0071] The motor (250) includes a stator (131) that is fixed and does not rotate, and a rotor (135) that rotates. The motor (250) is provided with an input cable (140) and receives an AC voltage supplied from a motor driving device (200). The motor (250) may be, for example, a three-phase motor, and when a voltage-variable / frequency-variable AC voltage of each phase is applied to the coils of each phase's stator, the rotational speed of the rotor varies based on the applied frequency.

[0072] The motor (250) can take various forms, such as an induction motor, a BLDC motor (blushless DC motor), and a reluctance motor.

[0073] Meanwhile, a drive gear (not shown) may be provided on one side of the motor (250). The drive gear converts the rotational energy of the motor (250) based on a gear ratio. The rotational energy output from the drive gear is transmitted to the front wheels (150) and / or the rear wheels (155) to move the vehicle (100).

[0074] The front suspension (160) and rear suspension (165) support the front wheels (150) and rear wheels (155) respectively with respect to the vehicle body. The vertical directions of the front suspension (160) and rear suspension (165) are supported by springs or damping mechanisms to prevent road vibrations from reaching the vehicle body.

[0075] The front wheels (150) may further be equipped with a steering device (not shown). The steering device is a device that controls the direction of the front wheels (150) to drive the vehicle (100) in the direction intended by the driver.

[0076] Meanwhile, although not shown in the drawing, the vehicle (100) may further include an electronic controller for controlling electronic devices throughout the vehicle. The electronic controller (not shown) controls each device so that it can operate, display, etc. In addition, it may also control the battery management system described above.

[0077] In addition, the control unit (170 in FIG. 2) can generate driving command values ​​according to various driving modes (driving mode, reverse mode, neutral mode, parking mode, etc.) based on detection signals from an inclination detection unit (not shown) that detects an inclination angle of the vehicle (100), a speed detection unit (not shown) that detects a speed of the vehicle (100), a brake detection unit (not shown) according to the operation of the brake pedal, an accelerator detection unit (not shown) according to the operation of the accelerator pedal, etc. The driving command value at this time can be, for example, a torque command value or a torque command value.

[0078] Meanwhile, the vehicle (100) according to the embodiment of the present disclosure may be a concept that includes a pure electric vehicle using a battery and a motor, as well as a hybrid electric vehicle using a battery and a motor while using an engine.

[0079] At this time, the hybrid electric vehicle may further be equipped with a switching means capable of selecting at least one of a battery and an engine, and a transmission.

[0080] Meanwhile, hybrid electric vehicles can be divided into a series method that converts mechanical energy output from the engine into electrical energy to drive the motor, a parallel method that simultaneously uses mechanical energy output from the engine and electrical energy from the battery, and a series-parallel method that combines the two.

[0081] FIG. 2 is an example of a motor drive system according to one embodiment of the present disclosure.

[0082] Referring to the drawings, a motor driving system according to one embodiment of the present disclosure may include a vehicle (100) and a server (500).

[0083] Here, the server (500) may be a server operated by the manufacturer of the motor drive device (200) or the vehicle (100), or may correspond to a mobile terminal of the driver of the motor drive device (200) or the vehicle (100).

[0084] Meanwhile, the vehicle (100) may be equipped with an input unit (120), a communication unit (130), a memory (140), a control unit (170), and a motor driving device (200).

[0085] The input unit (120) is equipped with operation buttons, keys, etc., and can output input signals for turning the voltage on / off, setting the operation, etc. of the vehicle (100).

[0086] The communication unit (130) can exchange data with peripheral devices, such as a server (500), wired or wirelessly, or wirelessly with a remote server, etc. For example, it can perform mobile communication such as 4G or 5G, infrared (IR) communication, RF communication, Bluetooth communication, Zigbee communication, WiFi communication, etc.

[0087] Meanwhile, the memory (140) of the vehicle (100) can store data necessary for the operation of the vehicle (100). For example, data regarding the operating time and operating mode of the motor driving device (200) can be stored.

[0088] Additionally, the memory (140) of the vehicle (100) can store management data including power consumption information of the vehicle, recommended driving information, current driving information, and management information.

[0089] Additionally, the memory (140) of the vehicle (100) can store diagnostic data including vehicle operation information, driving information, and error information.

[0090] The control unit (170) can control each unit within the vehicle (100). For example, the control unit (170) can control the input unit (120), the communication unit (130), the memory (140), the motor driving device (200), etc.

[0091] The motor driving device (200) may be referred to as a motor driving unit as a driving unit for driving the motor (250).

[0092] Meanwhile, the motor driving device (200) includes a plurality of inverter switching elements, an inverter (420) that outputs an AC voltage to the motor (250), an output current detection unit (E) that detects the output current (io) flowing in the motor (250), and current information (id, iq) and a torque command value (T) based on the output current (io) detected by the output current detection unit (E). * ), it may include an inverter control unit (430) that outputs a switching control signal to the inverter (420).

[0093] Meanwhile, current information (id, iq) and torque command (T) based on the output current (io) * ) can be transmitted to an external server (500), and the current command value (i) from the server (500) * d,i * q) may be received. And, based on the current command value received from the communication unit (130), the inverter control unit (430) may output a switching control signal to the inverter (420).

[0094] Accordingly, the motor (250) can be driven based on a current command value corresponding to the maximum torque calculated in real time by the server (500). Therefore, maximum torque driving of the motor (250) becomes possible.

[0095] Meanwhile, the communication unit (130) in the motor drive device (200) transmits current information (id, iq), torque command value (T * ), and voltage information regarding the detected DC voltage (Vdc) can be transmitted to the server (500). Accordingly, maximum torque operation of the motor (250) under various conditions becomes possible.

[0096] Meanwhile, the detailed operation of the motor driving device (200) is described with reference to FIG. 3.

[0097] Figure 3 illustrates an example of an internal block diagram of the motor driving device of Figure 2.

[0098] Referring to the drawings, a motor driving device (200) according to an embodiment of the present disclosure is a driving device for driving a motor (250), and may include a plurality of inverter switching elements (Sa to Sc, S'a to S'c), an inverter (420) for outputting an AC voltage to the motor (250), and an inverter control unit (430) for controlling the inverter (420). In addition, the motor driving device (200) may include a memory (270) for providing various stored data to the inverter control unit (430).

[0099] Meanwhile, the motor driving device (200) according to the embodiment of the present disclosure may further include a capacitor (C) that stores the dc voltage (Vdc) that is the input terminal of the inverter (420), a dc voltage detection unit (B) that detects the dc voltage (Vdc), an output current detection unit (E) that detects the output current flowing to the motor (250), and a position detection sensor (105).

[0100] According to an embodiment of the present disclosure, the motor (250) may be a three-phase motor driven by an inverter (420).

[0101] Meanwhile, the inverter control unit (430) sets the current command value (i) corresponding to the calculated maximum torque. * d,i * Based on q), a switching control signal (Sic) can be output to the inverter (420). Accordingly, maximum torque driving of the motor (250) becomes possible.

[0102] The inverter control unit (430) according to the embodiment of the present disclosure provides current information (id, iq) and torque command value (T) in real time. * ) and calculate the torque command value (T * ), the current command value (i * d,i * q) and calculate the current command value (i * d,i * q) is used to drive the motor (250). Accordingly, the accuracy for high-efficiency driving is improved.

[0103] Meanwhile, the motor driving device (200) may further include a capacitor (C) that stores the dc voltage (Vdc) of the input terminal of the inverter (420), and a dc voltage detection unit (B) that detects the dc voltage (Vdc).

[0104] The inverter control unit (430) provides current information (id, iq), torque command value (T * ), and based on the detected dc terminal voltage (Vdc), the current command value (i * d,i * q) and calculate the current command value (i * d,i * q) is used to drive the motor (250). Accordingly, the accuracy for high-efficiency driving is improved.

[0105] Fig. 4 is an example of an internal circuit diagram of the motor driving device of Fig. 3.

[0106] Referring to the drawings, a motor driving device (200) according to an embodiment of the present disclosure may include an inverter (420), an inverter control unit (430), an output current detection unit (E), a dc voltage detection unit (Vdc), and a position detection sensor (105).

[0107] Meanwhile, the motor driving device (200) converts power to drive the motor, so it can also be called a power conversion device.

[0108] The dc capacitor (C) stores the voltage input to the dc terminal (ab terminal). In the drawing, one dc capacitor (C) is illustrated as an element, but multiple capacitors may be provided to ensure element stability.

[0109] Meanwhile, the input voltage supplied to the dc capacitor (C) may be a voltage stored in the battery (205) or a voltage level-converted by a converter (not shown).

[0110] Meanwhile, since both ends of the dc capacitor (C) store direct current voltage, they can also be called dc terminals or dc link terminals.

[0111] The DC voltage detection unit (B) can detect the DC voltage (Vdc) at both ends of the DC capacitor (C). To this end, the DC voltage detection unit (B) can include a resistance element, an amplifier, etc. The detected DC voltage (Vdc) can be input to the inverter control unit (430) as a discrete signal in the form of a pulse.

[0112] The inverter (420) has a plurality of inverter switching elements (Sa to Sc, S'a to S'c), and can convert a direct current voltage (Vdc) into a three-phase alternating current voltage (Va, Vb, Vc) of a predetermined frequency by the on / off operation of the switching elements (Sa to Sc, S'a to S'c), and output it to a three-phase synchronous motor (250).

[0113] The inverter (420) is composed of a pair of upper-arm switching elements (Sa, Sb, Sc) and lower-arm switching elements (S'a, S'b, S'c) that are each connected in series with each other, and a total of three pairs of upper and lower-arm switching elements are connected in parallel with each other (Sa&S'a, Sb&S'b, Sc&S'c). A diode is connected in antiparallel to each switching element (Sa, S'a, Sb, S'b, Sc, S'c).

[0114] The switching elements within the inverter (420) perform on / off operations of each switching element based on the inverter switching control signal (Sic) from the inverter control unit (430). As a result, a three-phase AC voltage having a predetermined frequency is output to the three-phase synchronous motor (250).

[0115] The inverter control unit (430) can control the switching operation of the inverter (420) based on a sensorless method.

[0116] To this end, the inverter control unit (430) can receive the output current (io) detected by the output current detection unit (E).

[0117] The inverter control unit (430) can output an inverter switching control signal (Sic) to each gate terminal of the inverter (420) in order to control the switching operation of the inverter (420). Accordingly, the inverter switching control signal (Sic) may also be referred to as a gate driving signal.

[0118] Meanwhile, the inverter switching control signal (Sic) is a switching control signal of pulse width modulation (PWM) method, and is generated and output based on the output current (io) detected by the output current detection unit (E).

[0119] The output current detection unit (E) detects the output current (io) flowing between the inverter (420) and the three-phase motor (250). That is, the current flowing to the motor (250) can be detected.

[0120] The output current detection unit (E) can detect all output currents (ia, ib, ic) of each phase, or can detect the output currents of two phases using three-phase balance.

[0121] The output current detection unit (E) may be located between the inverter (420) and the motor (250), and a CT (current transformer), shunt resistor, etc. may be used to detect the current.

[0122] The detected output current (io) can be applied to the inverter control unit (430) as a discrete signal in the form of a pulse, and a switching control signal (Sic) is generated based on the detected output current (io).

[0123] The position detection sensor (105) can sense the rotor position information (θ) of the motor (250). The sensed position information (θ) can be input to the inverter control unit (430).

[0124] Meanwhile, a three-phase motor (250) has a stator and a rotor, and an AC voltage of a predetermined frequency is applied to the coils of the stator of each phase (a, b, c phase) to cause the rotor to rotate.

[0125] Such motors (250) may include, for example, a surface-mounted permanent-magnet synchronous motor (SMPMSM), an interior permanent magnet synchronous motor (IPMSM), and a synchronous reluctance motor (Synrm). Among these, SMPMSM and IPMSM are synchronous motors that apply permanent magnets (Permanent Magnet Synchronous Motors (PMSM), and Synrm is characterized by not having a permanent magnet.

[0126] Meanwhile, the motor (250) according to the embodiment of the present disclosure is mainly described as an interior permanent magnet synchronous motor (IPMSM).

[0127] Fig. 5 is an example of an internal block diagram of the inverter control unit of Fig. 4.

[0128] Referring to the drawing, the inverter control unit (430) of FIG. 5 can receive the detected output current (io) from the output current detection unit (320) and receive the rotor position information (θ) of the motor (250) from the position detection sensor (105).

[0129] The position detection sensor (105) can detect the magnetic pole position (θ) of the rotor of the motor (250). That is, the position detection sensor (105) can detect the position of the rotor of the motor (250).

[0130] For this purpose, the position detection sensor (105) may include an encoder or a resolver.

[0131] The coordinate system and coordinate axes used are defined here in the following description.

[0132] The αβ coordinate system is a two-dimensional fixed coordinate system with the α and β axes as fixed axes. The α and β axes are orthogonal to each other, and the β axis advances the α axis by an electrical angle of 90˚.

[0133] The dq coordinate system is a two-dimensional rotational coordinate system with the d axis and the q axis as the rotational axis. In a rotational coordinate system that rotates at the same speed as the rotational speed of the magnetic flux created by the permanent magnet of the motor (250), the axis in the direction of the magnetic flux created by the permanent magnet is the d axis, and the axis that is 90 degrees ahead of the d axis in phase is the q axis.

[0134] Referring to FIG. 5, the inverter control unit (430) may include a speed calculation unit (320), an axis conversion unit (310), a torque calculation unit (325), a current command generation unit (330), a voltage command generation unit (340), an axis conversion unit (350), and a switching control signal output unit (360).

[0135] The axis conversion unit (310) within the inverter control unit (430) receives the three-phase output current (ia, ib, ic) detected by the output current detection unit (E) and converts it into a two-phase current (iα, iβ) of the stationary coordinate system.

[0136] Meanwhile, the axis conversion unit (310) can convert the two-phase current (iα, iβ) of the stationary coordinate system into the two-phase current (id, iq) of the rotating coordinate system.

[0137] The speed calculation unit (320) within the inverter control unit (430) estimates the rotor position of the motor (250) based on the two-phase current (iα, iβ) of the stationary coordinate system converted by the axis conversion unit (310). In addition, the calculated speed can be output based on the estimated rotor position.

[0138] The torque calculation unit (325) in the inverter control unit (430) can calculate the current torque (T) based on the calculated speed.

[0139] The current command generation unit (330) in the inverter control unit (430) generates the calculated current torque (T) and the torque command value (T * ), the current command value (i * d,i * q) is generated.

[0140] For example, the current command generation unit (330) generates the calculated current torque (T) and the torque command value (T * ), PI control is performed in the PI controller (335), and the current command value (i * d,i * q) can be generated. Meanwhile, the d-axis current command value (i * The value of d) may be set to 0.

[0141] Meanwhile, the current command generation unit (330) generates a current command value (i * d,i * q) may further include a limiter (not shown) to limit the level so that it does not exceed the allowable range.

[0142] Next, the voltage command generation unit (340) converts the d-axis and q-axis currents (id, iq) converted to a two-phase rotating coordinate system in the axis conversion unit, and the current command value (i) in the current command generation unit (330). * d,i * Based on q), d-axis and q-axis voltage reference values ​​(V * d,V * q) is generated.

[0143] For example, the voltage command generation unit (340) generates a q-axis current (iq) and a q-axis current command value (i * Based on the difference in q), PI control is performed in the PI controller (344), and the q-axis voltage command value (V * q) can be generated. In addition, the voltage command generation unit (340) generates the d-axis current (id) and the d-axis current command value (i * Based on the difference of d), PI control is performed in the PI controller (348), and the d-axis voltage command value (V * d) can be generated. Meanwhile, the d-axis voltage command value (V * The value of d) is the d-axis current command value (i * The value of d) may be set to 0, corresponding to the case where it is set to 0.

[0144] Meanwhile, the voltage command generation unit (340) generates the d-axis and q-axis voltage command values ​​(V * d,V * q) may further include a limiter (not shown) to limit the level so that it does not exceed the allowable range.

[0145] Meanwhile, the generated d-axis and q-axis voltage command values ​​(V * d,V * q) is input to the axis conversion unit (350).

[0146] The axis conversion unit (350) calculates the position calculated in the speed calculation unit (320) and the d-axis and q-axis voltage command values ​​(V * d,V * q) is input and axis transformation is performed.

[0147] First, the axis transformation unit (350) performs a transformation from a two-phase rotational coordinate system to a two-phase stationary coordinate system. At this time, the position calculated by the speed calculation unit (320) can be used.

[0148] And, the axis conversion unit (350) performs a conversion from a two-phase stationary coordinate system to a three-phase stationary coordinate system. Through this conversion, the axis conversion unit (350) obtains a three-phase output voltage command value (V * a,V * b,V * c) will be printed.

[0149] The switching control signal output section (360) outputs a three-phase output voltage command value (V * a,V * b,V * c) A switching control signal (Sic) according to a pulse width modulation (PWM) method can be generated and output.

[0150] The output inverter switching control signal (Sic) is converted into a gate driving signal in a gate driving unit (not shown) and can be input to the gate of each switching element within the inverter (420). As a result, each switching element (Sa, S'a, Sb, S'b, Sc, S'c) within the inverter (420) performs a switching operation.

[0151] FIG. 6 is a diagram illustrating the operation of a battery and an inverter related to the present disclosure.

[0152] Referring to the drawing, when the battery (205h) stores a high voltage of approximately 800 V, when the switching element (SWm) between the battery (205h) and the inverter (420) is turned off as in (a) of FIG. 6 and then turned on as in (b) of FIG. 6, an inrush current (Irs) flows momentarily from the battery (205h) to the capacitor (C) at the on point of the switching element (SWm).

[0153] For example, when a high voltage of approximately 800 V from a battery (205h) is applied while the voltage of the capacitor (C) is discharged and at 0 V, a significantly large inrush current (Irs) occurs, increasing the possibility of damage to the capacitor (C) or inverter (420).

[0154] Accordingly, the present disclosure proposes a method for preventing damage to a capacitor (C) or an inverter (420). In particular, a method is proposed for stably pre-charging the capacitor to lower the level of inrush current. This is described with reference to FIG. 7 and below.

[0155] FIG. 7 is a block diagram illustrating a power conversion device according to an embodiment of the present disclosure.

[0156] Referring to the drawing, a power conversion device (600) according to an embodiment of the present disclosure includes a dc / dc converter (700) that is connected between a first battery (205b) and a second battery (205h) to convert the level of a direct current voltage, and a capacitor (C) that is a dc capacitor.

[0157] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure further includes an inverter (420) connected to a capacitor (C), which is a DC capacitor.

[0158] Meanwhile, the inverter (420) can operate to drive the motor (250) by converting the direct current voltage into an alternating current voltage based on the voltage of the capacitor (C), which is a dc capacitor.

[0159] Meanwhile, the capacitor (C) and the inverter (420) can correspond to the capacitor (C) and the inverter (420) in the motor driving device (200) of FIG. 3.

[0160] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a converter (650) that converts an input AC voltage into a DC voltage. That is, the converter (650) may be an AC / DC converter.

[0161] Meanwhile, the converter (650) can be installed in the vehicle as an on board charger.

[0162] Meanwhile, the second battery (205h) may be placed between the converter (650) and the inverter (420). Specifically, the second battery (205h) may be placed between the converter (650) and the capacitor (C), which is a DC capacitor.

[0163] Meanwhile, the dc / dc converter (700) in the power conversion device (600) according to the embodiment of the present disclosure may be a bidirectional converter.

[0164] For example, the second battery (205h) is a high-voltage battery that can store a high voltage of approximately 800 V, and the first battery (205b) is a low-voltage battery that can store a low voltage of approximately 15 V.

[0165] The power conversion device (600) according to the embodiment of the present disclosure can convert the input AC voltage into a DC voltage by the converter (650) according to the charging mode and store the converted DC voltage in the second battery (205h).

[0166] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure can store the DC voltage stored in the second battery (205h) in the first battery (205b) in the charging mode.

[0167] At this time, in the charging mode, current can flow from the second battery (205h) toward the first battery (205b), and this current can be called forward current.

[0168] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure can operate the motor (250) by having the inverter (420) perform a switching operation based on the voltage stored in the second battery (205h) according to the motor driving mode.

[0169] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure can store regenerative power from the motor (250) in the second battery (205h) through the inverter (420) according to the motor regeneration mode.

[0170] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure performs a pre-charge mode when the ignition is turned on.

[0171] That is, the power conversion device (600) according to the embodiment of the present disclosure supplies the voltage stored in the first battery (205b) to the capacitor (C), which is a DC capacitor, during the pre-charge mode period.

[0172] In particular, the power conversion device (600) according to the embodiment of the present disclosure, during the pre-charge mode period, does not supply the DC voltage from the second battery (205h) to the capacitor (C), which is a DC capacitor, but supplies the voltage stored in the first battery (205b) to the capacitor (C), which is a DC capacitor. Accordingly, in the pre-charge mode, the capacitor (C) can be stably pre-charged.

[0173] In addition, by pre-charging the capacitor (C) using the voltage stored in the first battery (205b) rather than the DC voltage from the second battery (205h), it is possible to prevent the possibility of damage to the capacitor (C) due to the inrush current.

[0174] Meanwhile, the detailed operation of the dc / dc converter (700) in the power conversion device (600) according to the embodiment of the present disclosure is described with reference to FIG. 9 and below.

[0175] Fig. 8 is a drawing illustrating an example of the operation of the power conversion device of Fig. 7.

[0176] Referring to the drawing, the power conversion device (600) of FIG. 7 can supply current from the first battery (205b) toward the second battery (205h) or the capacitor (C) depending on the pre-charge mode. This current (IPC) can be referred to as reverse current.

[0177] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a battery switching element (SW) connected between the capacitor (C) and the second battery (205h), as shown in the drawing.

[0178] In the pre-charge mode, the battery switching element (SW) can be turned off, thereby not supplying the DC voltage from the second battery (205h) to the capacitor (C), which is a DC capacitor.

[0179] Meanwhile, in motor drive mode or motor regeneration mode, the battery switching element (SW) can be turned on.

[0180] Meanwhile, in charging mode, it is desirable that the battery switching element (SW) be turned off.

[0181] Fig. 9 is a diagram illustrating the dc / dc converter of Fig. 7.

[0182] Referring to the drawings, a dc / dc converter (700) in a power conversion device (600) according to an embodiment of the present disclosure includes a first capacitor (Cp) connected to a first battery (205b), a second capacitor (C) connected to a second battery (205h), a transformer (TF), a first full bridge switching unit (710) between the input side of the first capacitor (Cp) and the transformer (TF), and a second full bridge switching unit (720) between the output side of the second capacitor (C) and the transformer (TF).

[0183] Meanwhile, in the pre-charge mode, during the operation of the first full bridge switching unit (710) and the second full bridge switching unit (720), the turn-off timing of some switching elements of the second full bridge switching unit (720) is delayed. Accordingly, the capacitor (C) can be stably charged in advance. In particular, damage to the capacitor (C) can be prevented.

[0184] Meanwhile, the first full bridge switching unit (710) may include a first switching element (QL1) and a second switching element (QL2) corresponding to the first leg and connected in series with each other, and a third switching element (QL3) and a fourth switching element (QL4) corresponding to the second leg connected in parallel with the first leg and connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0185] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include an inductor (LB) connected between the first capacitor (Cp) and the first full bridge switching unit (710), and a first current detection unit (DIa) that detects the current flowing in the inductor (LB).

[0186] Referring to the drawing, a first capacitor (Cp) is placed between the na1 node and the na2 node, which are the opposite ends of the first battery (205b).

[0187] Meanwhile, one end of the primary side of the transformer (TF) can be connected to the na4 node, which is a node between the first switching element (QL1) and the second switching element (QL2), and the other end of the primary side of the transformer (TF) can be connected to the na5 node, which is a node between the third switching element (QL3) and the fourth switching element (QL4).

[0188] Meanwhile, an inductor (LB) and a first current detection unit (DIa) that detects a current (iLB) flowing in the inductor (LB) may be placed between the na3 node and the na1 node, which are terminals of the first switching element (QL1).

[0189] The current (iLB) detected by the first current detection unit (DIa) can be input to the control unit (770).

[0190] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a first voltage detection unit (A) that detects the voltage across both ends of the first capacitor (Cp).

[0191] That is, a first voltage detection unit (A) that detects the voltage (Vcp) at both ends of the first capacitor (Cp) can be placed between the na1 node and the na2 node, which are both ends of the first battery (205b).

[0192] The voltage (Vcp) detected by the first voltage detection unit (A) can be input to the control unit (770).

[0193] Meanwhile, the second full bridge switching unit (720) may include a fifth switching element (QH1) and a sixth switching element (QH2) that correspond to the third leg and are connected in series with each other, and a seventh switching element (QH3) and an eighth switching element (QH4) that correspond to the fourth leg that is connected in parallel with the third leg and are connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0194] Meanwhile, the second full bridge switching unit (720) may further include a first diode element (D1) and a second diode element (D2) that are connected in parallel to the third and fourth legs and connected in series with each other. Accordingly, power conversion can be performed efficiently.

[0195] Meanwhile, one end of the secondary side of the transformer (TF) can be connected to the nb4 node, which is a node between the fifth switching element (QHL1) and the sixth switching element (QH2).

[0196] Meanwhile, a leakage inductor (LIkg) may be placed between the nb5 node, which is a node between the first diode element (D1) and the second diode element (D2), and the other end of the primary side of the transformer (TF).

[0197] Meanwhile, a zero voltage inductor (Lzv) can be placed between the na6 node and the nb5 node, which are nodes between the seventh switching element (QH3) and the eighth switching element (QH4).

[0198] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a battery switching element (SW) connected between the second capacitor (C) and the second battery (205h).

[0199] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a second current detection unit (DIb) disposed between the second full bridge switching unit (720) and the second capacitor (C), and a third current detection unit (DIc) disposed between the second capacitor (C) and the second battery (205h).

[0200] That is, a second current detection unit (DIb) can be placed between the nb5 node and the nb1 node, which is one end of the second capacitor (C).

[0201] Accordingly, the second current detection unit (DIb) can detect the current (iCT) flowing in the second full bridge switching unit (720). The current (iCT) detected by the second current detection unit (DIb) can be input to the control unit (770).

[0202] Meanwhile, a third current detection unit (DIc) may be placed between the nb1 node, which is one end of the second capacitor (C), and the second battery (205h).

[0203] Accordingly, the third current detection unit (DIc) can detect the current (iprechg) flowing between the second capacitor (C) and the second battery (205h). The current (iprechg) detected by the third current detection unit (DIc) can be input to the control unit (770).

[0204] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a second voltage detection unit (B) that detects the voltage (Vdc) across both ends of the second capacitor (C).

[0205] Both ends of the second capacitor (C) are dc terminals, and the dc terminal voltage (Vdc) detected by the second voltage detection unit (B) can be input to the control unit (770).

[0206] Meanwhile, the power conversion device (600) according to the embodiment of the present disclosure may further include a control unit (770) that controls the first full bridge switching unit (710) and the second full bridge switching unit (720).

[0207] The control unit (770) according to the embodiment of the present disclosure can control the turn-off timing of some switching elements of the second full bridge switching unit (720) to be delayed during the operation of the first full bridge switching unit (710) and the second full bridge switching unit (720) in the pre-charge mode.

[0208] In particular, the control unit (770) can control the turn-off timing of some switching elements of the second full bridge switching unit (720) to be delayed during the operation of the first full bridge switching unit (710) and the second full bridge switching unit (720) in the pre-charge mode. Accordingly, the capacitor (C) can be stably charged in advance. In particular, damage to the capacitor (C) can be prevented.

[0209] Meanwhile, the control unit (770) can control the delay to decrease as the difference between the voltage of the first battery (205b) and the voltage of the second battery (205h) increases in the pre-charge mode.

[0210] For example, if the voltage of the first battery (205b) is approximately 15 V and the voltage of the second battery (205h) is approximately 400 V, and the difference in voltage is approximately 385 V, the delay period can be controlled to be approximately Tda.

[0211] As another example, if the voltage of the first battery (205b) is approximately 15 V and the voltage of the second battery (205h) is approximately 800 V, and the voltage difference is approximately 785 V, the delay period can be controlled to be approximately Tda / 2, which is smaller than Tda. Accordingly, the capacitor (C) can be efficiently precharged.

[0212] Meanwhile, the control unit (770) can control the delay to become smaller when the voltage of the second capacitor (C) increases in the pre-charge mode.

[0213] For example, in the pre-charge mode, if the voltage of the second capacitor (C) is 0 V at the first point in time and increases to 5 V at the second point in time, the control unit (770) can control the delay set at the second point in time to be Tdbb, which is smaller than the delay Tdb set at the first point in time. Accordingly, the capacitor (C) can be efficiently pre-charged.

[0214] Meanwhile, the control unit (770) can control the delay to be reduced when the current (iLB) flowing in the inductor (LB) decreases in the pre-charge mode.

[0215] For example, in the pre-charge mode, if the current (iLB) flowing in the inductor (LB) is approximately 10A at the first point in time and decreases to approximately 5A at the second point in time, the control unit (770) can control the delay set at the second point in time to be Tdcb, which is smaller than the delay Tdc set at the first point in time. Accordingly, the capacitor (C) can be efficiently pre-charged.

[0216] Meanwhile, the control unit (770) can control reverse current to flow from the first capacitor (Cp) toward the second capacitor (C) in the pre-charge mode.

[0217] Meanwhile, the control unit (770) can control forward current to flow from the second capacitor (C) toward the first capacitor (Cp) after the pre-charge mode ends. Accordingly, the first battery (205b) can be stably charged after the pre-charge mode.

[0218] Meanwhile, the control unit (770) can control the voltage from the second battery (205h) to be stored in the second capacitor (C) after the pre-charge mode, and control the inverter (420) to operate based on the voltage stored in the second capacitor (C). Accordingly, the motor operation mode can be stably performed.

[0219] Meanwhile, the control unit (770) can control the battery switching element (SW) to be turned off in the pre-charge mode. Accordingly, the capacitor (C) can be efficiently pre-charged.

[0220] Meanwhile, the control unit (770) can control the battery switching element (SW) to be turned on after the pre-charge mode. Accordingly, the first battery (205b) can be stably charged after the pre-charge mode.

[0221] Figures 10a to 11f are drawings referenced in the operation description of Figure 9.

[0222] FIG. 10a illustrates an example of the operation of a dc / dc converter related to the present disclosure.

[0223] Referring to the drawings, (a) of FIG. 10a is an example of an operation waveform of a plurality of switching elements (QL1 to QL4) within a first full bridge switching unit (710) and a plurality of switching elements (QL1 to QL4) within a second full bridge switching unit (720) related to the present disclosure in a pre-charge mode.

[0224] First, during the first section among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned off, and the sixth switching element (QH2) and the seventh switching element (QH3) in the second full bridge switching unit (720) may be turned on.

[0225] Next, during a second period following the first period among the turn-on periods of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) may be turned on, and the seventh switching element (QH3) may be turned off.

[0226] Next, during the third period following the second period among the turn-on periods of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, and the sixth switching element (QH2) and the eighth switching element (QH4) in the second full bridge switching unit (720) may be turned on.

[0227] Next, the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) are turned off after the turn-on period.

[0228] Meanwhile, during a first section among the turn-off sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) may be turned off, and the eighth switching element (QH4) may be turned on.

[0229] Next, during the second period following the first period among the turn-off periods following the turn-on periods of the first switching element (QL1) and the fourth switching element (QL4) within the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) within the first full bridge switching unit (710) may be turned on, and the fifth switching element (QH1) and the eighth switching element (QH4) within the second full bridge switching unit (720) may be turned on.

[0230] Next, after the turn-off period of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), it is turned on again.

[0231] Meanwhile, during the fourth section among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the fifth switching element (QH1) in the second full bridge switching unit (720) may be turned on, and the eighth switching element (QH4) may be turned off.

[0232] Next, during the fifth section following the fourth section among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) are turned on, the fifth switching element (QH1) in the second full bridge switching unit (720) is turned on, and the seventh switching element (QH3) can be turned on.

[0233] That is, according to (a) of Fig. 10a, based on the first switching element (QL1) and the fourth switching element (QL4), the turn-on section can be divided into a first section, a second section, and a third section, the turn-off section can be divided into a first section, a second section, and a fourth section and a fifth section, the turn-on section.

[0234] Meanwhile, based on the first switching element (QL1) and the fourth switching element (QL4), a boost operation is performed during the second and third sections of the turn-on section.

[0235] Meanwhile, (b) to (c) of FIG. 10a illustrate, based on the driving waveform of (a) of FIG. 10a, the current (iLIkg) flowing in the leakage inductor (LIkg), the current (iLM) flowing in the secondary side of the transformer (TF), the current (iLB) flowing in the inductor (LB), the voltages (VdsL2, VdsL3) between the drain sources of the second switching element (QL2) and the third switching element (QL3), and the voltages (VdsL1, VdsL4) between the drain sources of the first switching element (QL1) and the fourth switching element (QL4), respectively.

[0236] According to (c) of Fig. 10a, in the pre-charge mode, when the first full bridge switching unit (710) and the second full bridge switching unit (720) are operated by the waveform of (a) of Fig. 10a, there is a disadvantage that a ringing voltage is generated in each switching element of the first full bridge switching unit (710).

[0237] This ringing voltage can occur in pre-charge mode if the build-up time is insufficient. However, a wider input / output range has the disadvantage of increasing transient current.

[0238] In this disclosure, a method for reducing ringing voltage, such as that shown in (c) of Fig. 10a, is proposed by controlling the build-up time. This is described with reference to Fig. 10b.

[0239] FIG. 10b illustrates an example of the operation of a dc / dc converter according to an embodiment of the present disclosure.

[0240] Referring to the drawings, (a) of FIG. 10a is an example of an operation waveform of a plurality of switching elements (QL1 to QL4) within a first full bridge switching unit (710) and a plurality of switching elements (QL1 to QL4) within a second full bridge switching unit (720) according to an embodiment of the present disclosure in a pre-charge mode.

[0241] First, during the first section (TP0 to TP1) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned off, and the sixth switching element (QH2) and the seventh switching element (QH3) in the second full bridge switching unit (720) may be turned on.

[0242] Next, during the second section (PP1) after the first section (TP0 to TP1) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) are turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) is turned on, and the seventh switching element (QH3) can be turned on.

[0243] That is, in the pre-charge mode, during the turn-off delay period (PP1) in which the turn-off point of the seventh switching element (QH3), which is a part of the second full bridge switching unit (720), is delayed, the sixth switching element (QH2), which is another part of the switching element of the second full bridge switching unit (720), is turned on, and the switching elements (QL1 to QL4) in the first full bridge switching unit (710) can be turned on.

[0244] Compared to (a) of Fig. 10a, the turn-off point of the seventh switching element (QH3), which is a part of the second full bridge switching unit (720), is delayed to TP2, not TP1.

[0245] That is, the turn-off point of the seventh switching element (QH3), which is a part of the second full bridge switching unit (720), can be delayed by the PP1 period.

[0246] Meanwhile, the PP1 period may vary depending on the difference between the voltage of the first battery (205b) and the voltage of the second battery (205h), as described above, or depending on an increase in the voltage of the second capacitor (C).

[0247] Meanwhile, in the pre-charge mode, the turn-off time of the seventh switching element (QH3), which is a part of the switching element of the second full bridge switching unit (720), is delayed, so that the interval (DTb) between the turn-off time (TP2) of the seventh switching element (QH3) of the second full bridge switching unit (720) and the turn-off time (TP4) of the sixth switching element (QH2), which is another part of the switching element, may be smaller than the interval (DTa) between the turn-off time (TP2) of the seventh switching element (QH3), which is a part of the switching element of the second full bridge switching unit (720), and the turn-on time (TP0) of the sixth switching element (QH2), which is another part of the switching element. Accordingly, the capacitor (C) can be stably pre-charged.

[0248] Next, during the third section (PP2) following the second section (PP1) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) may be turned on, and the seventh switching element (QH3) may be turned off.

[0249] That is, after the turn-off delay period (PP1), the seventh switching element (QH3), which is a part of the second full bridge switching unit (720), is turned off.

[0250] Meanwhile, during the turn-off section (PP2) in which the seventh switching element (QH3), which is a part of the switching element of the second full bridge switching unit (720), is turned off, the sixth switching element (QH2), which is another part of the switching element of the second full bridge switching unit (720), is turned on, and the switching elements (QL1 to QL4) in the first full bridge switching unit (710) can be turned on.

[0251] Next, during the fourth section (PP3) after the third section (PP2) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) are turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) is turned on, and the eighth switching element (QH4) can be turned on.

[0252] That is, after the turn-off section (PP2) of the seventh switching element (QH3), during the turn-on section (PP3) in which the eighth switching element (QH4), which is another switching element of the second full bridge switching unit (720), is turned on, the sixth switching element (QH2), which is another switching element of the second full bridge switching unit (720), is turned on, and the switching elements (QL1 to QL4) in the first full bridge switching unit (710) can be turned on.

[0253] Next, the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) are turned off at time TP4.

[0254] Next, during the first section (PP4) among the turn-off sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the sixth switching element (QH2) in the second full bridge switching unit (720) may be turned off, and the eighth switching element (QH4) may be turned on.

[0255] That is, after the turn-on section (PP3) of the eighth switching element (QH4), the eighth switching element (QH4), which is another switching element of the second full bridge switching unit (720), remains turned on, the sixth switching element (QH2), which is another switching element of the second full bridge switching unit (720), is turned off, some switching elements (QL1, QL4) in the first full bridge switching unit (710) are turned off, and other switching elements (QL2, QL3) in the first full bridge switching unit (710) can be turned on.

[0256] Next, during the second section (TP5 to TP6) after the first section (PP4) among the turn-off sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, and the fifth switching element (QH1) and the eighth switching element (QH4) in the second full bridge switching unit (720) may be turned on.

[0257] Next, at TP6, the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) are turned on again.

[0258] Meanwhile, during the fifth section (TP6 to TP7) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the fifth switching element (QH1) in the second full bridge switching unit (720) may be turned on, and the eighth switching element (QH4) may be turned off.

[0259] Next, during the sixth section (TP7 to TP8) following the fifth section (TP6 to TP7) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) may be turned on, the fifth switching element (QH1) in the second full bridge switching unit (720) may be turned on, and the eighth switching element (QH4) may be turned off.

[0260] Next, during the seventh section after the sixth section (TP7 to TP8) among the turn-on sections of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710), the second switching element (QL2) and the third switching element (QL3) in the first full bridge switching unit (710) are turned on, the fifth switching element (QH1) in the second full bridge switching unit (720) is turned on, and the seventh switching element (QH3) can be turned on.

[0261] That is, according to (a) of Fig. 11a, based on the first switching element (QL1) and the fourth switching element (QL4), the turn-on section can be divided into the first section (TP0~TP1), the second section (PP1), the third section (PP2), the fourth section (PP3), the turn-off section, the first section (PP4), the second section, the fifth section, the sixth section, and the seventh section of the turn-on section.

[0262] Compared to (a) of Fig. 10, according to (a) of Fig. 11a, the turn-off timing of the seventh switching element (QH3) of the second section (PP1) and the eighth switching element (QH4) of the fifth section can be delayed.

[0263] Meanwhile, based on the first switching element (QL1) and the fourth switching element (QL4), a boost operation is performed during the second section (PP1), third section (PP2), and fourth section (PP3) of the turn-on period.

[0264] Meanwhile, (b) to (c) of FIG. 11a illustrate, based on the driving waveform of (a) of FIG. 11a, the current (iLIkg) flowing in the leakage inductor (LIkg), the current (iLM) flowing in the secondary side of the transformer (TF), the current (iLB) flowing in the inductor (LB), the voltages (VdsL2, VdsL3) between the drain sources of the second switching element (QL2) and the third switching element (QL3), and the voltages (VdsL1, VdsL4) between the drain sources of the first switching element (QL1) and the fourth switching element (QL4), respectively.

[0265] Referring to (c) of Fig. 11a, when the first full bridge switching unit (710) and the second full bridge switching unit (720) are operated by the waveform of (a) of Fig. 11a, a ringing voltage is not generated in each switching element of the first full bridge switching unit (710).

[0266] Meanwhile, a power conversion device (600) according to another embodiment of the present disclosure includes a first capacitor (Cp) connected to a first battery (205b), a second capacitor (C) connected to a second battery (205h), a first full bridge switching unit (710) between the first capacitor (Cp) and the input side of a transformer (TF), and a second full bridge switching unit (720) between the second capacitor (C) and the output side of the transformer (TF), and in the pre-charge mode, the turn-off time of the seventh switching element (QH3) of the second full bridge switching unit (720) is delayed, so that the interval (DTb) between the turn-off time (TP2) of the seventh switching element (QH3) of the second full bridge switching unit (720) and the turn-off time (TP4) of the sixth switching element (QH2) of the other switching element is The gap (DTa) between the turn-off point (TP2) of the seventh switching element (QH3) and the turn-on point (TP0) of the sixth switching element (QH2), which is another switching element, is smaller. Accordingly, the capacitor (C) can be stably precharged. In particular, damage to the capacitor (C) can be prevented.

[0267] Meanwhile, the control unit (770) according to the embodiment of the present disclosure can calculate the voltage (vCT) of the output terminal of the second full bridge switching unit (720) based on the current (iCT) flowing in the second full bridge switching unit (720) detected by the second current detection unit (DIb).

[0268] Meanwhile, the control unit (770) according to the embodiment of the present disclosure can calculate the build-up time or delay time based on the current (iprechg) flowing between the second capacitor (C) from the third current detection unit (DIc) and the second battery (205h), the current (iLB) flowing in the inductor (LB) from the first current detection unit (DIa), and the voltage (vCT) of the output terminal of the second full bridge switching unit (720).

[0269] Meanwhile, the control unit (770) according to the embodiment of the present disclosure can calculate the phase of the build-up time or the phase of the delay time based on the dc voltage (Vdc) from the second voltage detection unit (B) and the current (iprechg) flowing between the second capacitor (C) and the second battery (205h) from the third current detection unit (DIc).

[0270] Meanwhile, the control unit (770) according to the embodiment of the present disclosure can output a first switching control signal (Sma) for switching control of the first full bridge switching unit (710) and a second switching control signal (Smb) for switching control of the second full bridge switching unit (720) based on the calculated build-up time or delay time and the phase of the build-up time or the phase of the delay time.

[0271] That is, the control unit (770) according to the embodiment of the present disclosure can calculate the optimal build-up time through feedback control and stably precharge the capacitor (C) without generating a ringing voltage. In particular, it can prevent damage to the capacitor (C).

[0272] Fig. 11a is a drawing illustrating an example of an operating waveform corresponding to the driving method of Fig. 10a.

[0273] Referring to the drawings, (a) of FIG. 11a shows an example of the driving waveforms of the fifth switching element (QH1) and the sixth switching element (QH2) in the second full bridge switching unit (720) according to the driving method of FIG. 10a. The fifth switching element (QH1) and the sixth switching element (QH2) can operate complementarily.

[0274] Figure 11a (b) shows an example of the driving waveforms of the seventh switching element (QH3) and the eighth switching element (QH4) in the second full bridge switching unit (720) according to the driving method of Figure 10a. The seventh switching element (QH3) and the eighth switching element (QH4) can operate complementarily.

[0275] (c) of Fig. 11a shows an example of the driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) according to the driving method of Fig. 10a, and the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0276] The driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) may be complementary to the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0277] Figure 11a (d) shows an example of the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF) based on the driving waveforms of Figure 11a (a) to (c).

[0278] Fig. 11a (e) shows an example of the output current (iLo) of the dc / dc converter based on the driving waveforms of Fig. 11a (a) to (c).

[0279] (f) of Fig. 11a illustrates the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively, based on the driving waveforms of (a) to (c) of Fig. 11a.

[0280] As in the area (Ara) of (f) of Fig. 11a, there is a disadvantage in that a ringing voltage is generated in each switching element of the first full bridge switching unit (710).

[0281] Fig. 11b is a drawing illustrating an example of an operating waveform corresponding to the driving method of Fig. 10b.

[0282] Referring to the drawings, (a) of FIG. 11b shows an example of the driving waveforms of the fifth switching element (QH1) and the sixth switching element (QH2) in the second full bridge switching unit (720) according to the driving method of FIG. 10b. The fifth switching element (QH1) and the sixth switching element (QH2) can operate complementarily.

[0283] (b) of Fig. 11b shows an example of the driving waveforms of the seventh switching element (QH3) and the eighth switching element (QH4) in the second full bridge switching unit (720) according to the driving method of Fig. 10b. The seventh switching element (QH3) and the eighth switching element (QH4) can operate complementarily.

[0284] (c) of Fig. 11b shows an example of the driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) according to the driving method of Fig. 10b, and the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0285] The driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) may be complementary to the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0286] Figure 11b (d) shows an example of the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF) based on the driving waveforms of Figure 11b (a) to (c).

[0287] Referring to the drawing, in pre-charge mode, it operates based on the optimal build-up time, so there is no tolerance due to leakage inductance, such as in the area (Arma).

[0288] Fig. 11b (e) shows an example of the output current (iLo) of the dc / dc converter based on the driving waveforms of Fig. 11b (a) to (c).

[0289] (f) of Fig. 11b illustrates the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively, based on the driving waveforms of (a) to (c) of Fig. 11b.

[0290] As in the area (Armb) of (f) of Fig. 11b, ringing voltage does not occur in each switching element of the first full bridge switching unit (710).

[0291] Fig. 11c is a drawing illustrating another example of an operating waveform corresponding to the driving method of Fig. 10a.

[0292] Referring to the drawings, FIG. 11c illustrates a high voltage based operating waveform compared to FIG. 11a.

[0293] That is, (a) of Fig. 11c shows another example of the driving waveforms of the fifth switching element (QH1) and the sixth switching element (QH2) in the second full bridge switching unit (720) according to the driving method of Fig. 10a.

[0294] (b) of Fig. 11c shows another example of the driving waveforms of the seventh switching element (QH3) and the eighth switching element (QH4) in the second full bridge switching unit (720) according to the driving method of Fig. 10a.

[0295] (c) of Fig. 11c shows another example of the driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) according to the driving method of Fig. 10a, and the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0296] Figure 11c (d) shows another example of the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF), based on the driving waveforms of Figure 11c (a) to (c).

[0297] Referring to the drawing, the current (iLIkg) flowing through the leakage inductor (LIkg) may appear unstable.

[0298] Fig. 11c (e) shows another example of the output current (iLo) of the dc / dc converter based on the driving waveforms of Fig. 11c (a) to (c).

[0299] (f) of Fig. 11c illustrates the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively, based on the driving waveforms of (a) to (c) of Fig. 11c.

[0300] Referring to the drawing, there is a disadvantage in that noise occurs in the voltage (VdsL1, VdsL2) between the drain source of the first switching element (QL1) and the second switching element (QL2).

[0301] Fig. 11d is a drawing illustrating an example of an operating waveform corresponding to the driving method of Fig. 10b.

[0302] Referring to the drawings, FIG. 11d illustrates a high voltage based operating waveform compared to FIG. 11b.

[0303] (a) of Fig. 11d shows another example of the driving waveforms of the fifth switching element (QH1) and the sixth switching element (QH2) in the second full bridge switching unit (720) according to the driving method of Fig. 10b.

[0304] (b) of Fig. 11d shows another example of the driving waveforms of the seventh switching element (QH3) and the eighth switching element (QH4) in the second full bridge switching unit (720) according to the driving method of Fig. 10b.

[0305] (c) of Fig. 11d shows another example of the driving waveforms of the first switching element (QL1) and the fourth switching element (QL4) in the first full bridge switching unit (710) according to the driving method of Fig. 10b, and the driving waveforms of the second switching element (QL2) and the third switching element (QL4).

[0306] Figure 11d (d) shows another example of the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF), based on the driving waveforms of Figure 11d (a) to (c).

[0307] Referring to the drawing, in pre-charge mode, it operates based on the optimal build-up time, so there is no tolerance due to leakage inductance, such as area (Armc).

[0308] Fig. 11d (e) shows another example of the output current (iLo) of the dc / dc converter based on the driving waveforms of Fig. 11d (a) to (c).

[0309] (f) of Fig. 11d illustrates the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively, based on the driving waveforms of (a) to (c) of Fig. 11d.

[0310] Referring to the drawing, compared to (f) of FIG. 11c, noise can be reduced in the voltage (VdsL1, VdsL2) between the drain source of the first switching element (QL1) and the second switching element (QL2).

[0311] Fig. 11e illustrates an example of a waveform during charging in a manner corresponding to Fig. 10a.

[0312] Referring to the drawings, (a) of FIG. 11e shows the voltage waveform (VHV) of the second battery (205h), and (b) of FIG. 11e shows the current (iprechg) flowing between the second capacitor (C) and the second battery (205h).

[0313] (c) of Fig. 11e shows the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF), and (d) of Fig. 11e shows the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively.

[0314] Figure 11f illustrates an example of a waveform during charging in a manner corresponding to Figure 10b.

[0315] Referring to the drawings, (a) of FIG. 11f shows the voltage waveform (VHV) of the second battery (205h), and (b) of FIG. 11f shows the current (iprechg) flowing between the second capacitor (C) and the second battery (205h).

[0316] (c) of Fig. 11f shows the current (iLIkg) flowing in the leakage inductor (LIkg) and the current (iLM) flowing in the secondary side of the transformer (TF), and (d) of Fig. 11f shows the voltages (VdsL1, VdsL2) between the drain sources of the first switching element (QL1) and the second switching element (QL2), respectively.

[0317] Comparing (d) of Fig. 11f with (d) of Fig. 11e, in the case of (d) of Fig. 11f, the voltage (VdsL1, VdsL2) between the drain source of the first switching element (QL1) and the second switching element (QL2) can be stable.

[0318] FIG. 11g illustrates another example of a waveform during charging in a manner corresponding to FIG. 10a.

[0319] Referring to the drawing, FIG. 11g illustrates the voltage (Vgs) between the gate sources of each switching element (QL1 to QL4), the voltage (Vds) between the drain sources, and the current waveform (ipri) flowing through each switching element (QL1 to QL4).

[0320] According to Fig. 11g, there is a disadvantage that a ringing voltage occurs in the area (Arm).

[0321] Figure 11h illustrates another example of a waveform during charging in a manner corresponding to Figure 10b.

[0322] Referring to the drawing, FIG. 11h illustrates the current waveform (ipri) flowing in each switching element (QL1 to QL4), the voltage (Vds) between the drain and source of each switching element (QL1 to QL4), and the voltage waveform (VHV) of the second battery (205h), respectively.

[0323] Each waveform is stable, and in particular, the voltage waveform (VHV) of the second battery (205h) increases sequentially as it is charged.

[0324] Although the preferred embodiments of the present disclosure have been illustrated and described above, the present disclosure is not limited to the specific embodiments described above, and various modifications may be made by a person skilled in the art to which the present invention pertains without departing from the gist of the present disclosure as claimed in the claims, and such modifications should not be understood individually from the technical idea or prospect of the present disclosure.

Claims

1. A first capacitor connected to the first battery; A second capacitor connected to a second battery; Transformers; A first full bridge switching unit having a plurality of switching elements and between the first capacitor and the input side of the transformer; A second full bridge switching unit having a plurality of switching elements and between the second capacitor and the output side of the transformer; A power conversion device in which, in the pre-charge mode, the turn-off timing of some switching elements of the second full bridge switching unit is delayed during the operation of the first full bridge switching unit and the second full bridge switching unit.

2. In paragraph 1, A power conversion device in which, in the pre-charge mode, the turn-off timing of some of the switching elements of the second full bridge switching unit is delayed, so that the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-off timing of other switching elements is smaller than the interval between the turn-off timing of some of the switching elements of the second full bridge switching unit and the turn-on timing of other switching elements.

3. In paragraph 1, A power conversion device in which, in the pre-charge mode, during a turn-off delay period in which the turn-off timing of some of the switching elements of the second full bridge switching unit is delayed, some of the other switching elements of the second full bridge switching unit are turned on, and the switching elements in the first full bridge switching unit are turned on.

4. In paragraph 3, After the above turn-off delay period, some of the switching elements of the second full bridge switching unit are turned off, A power conversion device wherein, during a turn-off period in which some of the switching elements of the second full bridge switching unit are turned off, some of the other switching elements of the second full bridge switching unit are turned on, and the switching elements in the first full bridge switching unit are turned on.

5. In paragraph 4, A power conversion device wherein, after the turn-off section, during a turn-on section in which another part of the switching elements of the second full bridge switching unit is turned on, the other part of the switching elements of the second full bridge switching unit is turned on, and the switching elements in the first full bridge switching unit are turned on.

6. In paragraph 5, A power conversion device wherein, after the turn-on section, another part of the switching elements of the second full bridge switching unit remains turned on, another part of the switching elements of the second full bridge switching unit is turned off, another part of the switching elements in the first full bridge switching unit is turned off, and another part of the switching elements in the first full bridge switching unit is turned on.

7. In paragraph 1, A power conversion device further comprising a control unit that controls the first full bridge switching unit and the second full bridge switching unit.

8. In paragraph 7, The above control unit, A power conversion device that controls the turn-off timing of some switching elements of the second full bridge switching unit to be delayed during the operation of the first full bridge switching unit and the second full bridge switching unit in the above pre-charge mode.

9. In paragraph 7, The above control unit, A power conversion device that controls the delay to decrease as the difference between the first battery voltage and the second battery voltage increases in the above pre-charge mode.

10. In paragraph 7, The above control unit, A power conversion device that controls the delay to become smaller when the voltage of the second capacitor increases in the above pre-charge mode.

11. In paragraph 7, An inductor connected between the first capacitor and the first full bridge switching unit; Further comprising a first current detection unit for detecting the current flowing in the inductor; The above control unit, A power conversion device that controls the delay to decrease when the current flowing in the inductor decreases in the above pre-charge mode.

12. In paragraph 7, A second current detection unit disposed between the second full bridge switching unit and the second capacitor; A power conversion device further comprising a third current detection unit disposed between the second capacitor and the second battery.

13. In paragraph 7, The above control unit, In the above pre-charge mode, current is controlled to flow in the direction of the second capacitor from the first capacitor, A power conversion device that controls current to flow in the direction of the first capacitor from the second capacitor after the pre-charge mode ends.

14. In paragraph 7, Further comprising a battery switching element connected between the second capacitor and the second battery; The above control unit, A power conversion device that controls the battery switching element to be turned off in the above pre-charge mode.

15. In paragraph 14, The above control unit, A power conversion device that controls the battery switching element to be turned on after the above pre-charge mode.

16. In paragraph 7, Further comprising an inverter connected to both ends of the second capacitor; The above control unit, A power conversion device that controls the voltage from the second battery to be stored in the second capacitor after the pre-charge mode, and controls the inverter to operate based on the voltage stored in the second capacitor.

17. In paragraph 7, Further comprising a converter for converting input AC voltage into DC voltage; A power conversion device in which the second battery is placed between the converter and the inverter.

18. In paragraph 1, The above first full bridge switching unit is, A first switching element and a second switching element corresponding to the first leg and connected in series with each other; A third switching element and a fourth switching element are connected in series with each other, corresponding to a second leg connected in parallel to the first leg; The above second full bridge switching unit is, A fifth switching element and a sixth switching element corresponding to the third leg and connected in series with each other; A power conversion device comprising a seventh switching element and an eighth switching element that correspond to a fourth leg connected in parallel to the third leg and are connected in series with each other.

19. In paragraph 1, The above second full bridge switching unit is, A power conversion device further comprising a first diode element and a second diode element connected in parallel to the third leg and the fourth leg and connected in series with each other.

20. A first capacitor connected to the first battery; A second capacitor connected to a second battery; Transformers; A first full bridge switching unit having a plurality of switching elements and between the first capacitor and the input side of the transformer; A second full bridge switching unit having a plurality of switching elements and between the second capacitor and the output side of the transformer; A power conversion device in which, in the pre-charge mode, the interval between the turn-off time of some of the switching elements of the second full bridge switching unit and the turn-off time of some of the other switching elements is smaller than the interval between the turn-off time of some of the switching elements of the second full bridge switching unit and the turn-on time of some of the other switching elements.

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