Power conversion device

Abstract

A power conversion device according to an embodiment of the present application includes a first input / output unit connected to a high voltage side, a first switching unit connected to the first input / output unit, a transformer unit including a first transformer and a second transformer each having a primary side connected to the first switching unit, a second switching unit connected to a secondary side of the transformer unit, and a second input / output unit connected to a low voltage side and the secondary side of the transformer unit, wherein the first switching unit includes a first switch and a second switch configured to be complementarily energized, and the second switching unit includes a third switch connected to the secondary side of the first transformer and a fourth switch connected to the secondary side of the second transformer.

Description

Technical Field

[0001] This invention relates to power conversion devices, and more specifically, to power conversion devices having high power conversion efficiency. Background Technology

[0002] Recently, with the increase in battery capacity used to store electrical energy in vehicles such as electric or hybrid vehicles, the voltage of each battery has increased from 400 V to 800 V. In order to use the electrical energy charged in high-voltage batteries to operate internal components such as the vehicle's electronic equipment, it is necessary to convert the voltage to a low level.

[0003] A converter with high power conversion efficiency is needed to stably supply power by converting the voltage of a high-voltage battery to a low voltage. Summary of the Invention

[0004] Technical issues

[0005] The technical problem to be solved by the present invention is to provide a power conversion device with high efficiency in power conversion.

[0006] Technical solution

[0007] To address the above-mentioned technical problems, a power conversion device according to an embodiment of the present invention includes: a first input / output unit connected to a high-voltage side; a first switching unit connected to the first input / output unit; a transformer unit including a first transformer and a second transformer, each of the first transformer and the second transformer having a primary side connected to the first switching unit; a second switching unit connected to the secondary side of the transformer unit; and a second input / output unit connected to the secondary side and the low-voltage side of the transformer unit, wherein the first switching unit includes a first switch and a second switch that are complementaryly electrically connected, and the second switching unit includes: a third switch connected to the secondary side of the first transformer; and a fourth switch connected to the secondary side of the second transformer.

[0008] In addition, the first switch can be connected in series to the transformer unit, and the second switch can be connected in parallel to the transformer unit.

[0009] In addition, the second switch can be turned off, and the first switch can be turned on after a first time, wherein the first time can vary depending on the applied voltage.

[0010] In addition, the first switch can be turned off, and after a second time, the second switch can be turned on, wherein the second time can be a preset time to be applied.

[0011] Additionally, the power conversion device may include: a first inductor connected in series with the transformer unit between the first input / output unit and the transformer unit; a second inductor connected in parallel with the primary side of the first transformer; a third inductor connected in parallel with the primary side of the second transformer; and a first capacitor connected to a first node between the first input / output unit and the first inductor and connected in series with a second switch, wherein the first switch may be connected to a second node between the first switch and the transformer unit.

[0012] Furthermore, when the first switch is on and the second switch is off, the current can flow in the direction of connection between the first inductor, the second inductor, the third inductor and the first switch, and when the first switch is off and the second switch is on, the current can flow in the direction of connection between the first capacitor, the second switch, the third inductor, the second inductor and the first inductor.

[0013] In addition, the first switching unit can change the direction of the current applied to the transformer unit according to the operation of the first switch and the second switch.

[0014] In addition, the third switch can be operated in response to the operation of the second switch, or in response to the operation after a preset time.

[0015] In addition, the fourth switch can be turned on after a third time following the turn-off of the second switch, and can be turned off after a fourth time following the turn-off of the first switch. The third and fourth times can vary depending on the output current.

[0016] Additionally, each of the third and fourth switches may include a FET.

[0017] Additionally, each of the third and fourth switches may include a MOSFET, which includes a body diode.

[0018] In addition, when the voltage is input from the high voltage side to the first input / output unit, the voltage can be output from the second input / output unit to the low voltage side, and when the voltage is input from the low voltage side to the second input / output unit, the voltage can be bidirectionally operated, so that the voltage can be output from the first input / output unit to the high voltage side.

[0019] Beneficial effects

[0020] According to embodiments of the present invention, bidirectional operation is possible during voltage conversion, and efficiency can be improved. Furthermore, zero-voltage switching can be performed, and the input voltages of series-connected inputs can be balanced to achieve equilibrium. Additionally, bidirectional drive and initial charging are possible. Attached Figure Description

[0021] Figure 1 This is a block diagram of a power conversion device according to an embodiment of the present invention.

[0022] Figure 2 This is a block diagram of a power conversion device according to an embodiment of the present invention.

[0023] Figure 3 and Figure 4 This is an example circuit diagram of a power conversion device according to an embodiment of the present invention.

[0024] Figures 5 to 7 This is a diagram illustrating the switching operation of a power conversion device according to an embodiment of the present invention.

[0025] Figures 8a to 8c This is a diagram illustrating the simulation results of the operation of a power conversion device according to an embodiment of the present invention.

[0026] Figure 9 This is a diagram illustrating the connection relationship of a power conversion device according to an embodiment of the present invention, in which the input is connected in series and the output is connected in parallel.

[0027] Figures 10 to 13 This diagram illustrates the process of balancing the input voltage using a power conversion device according to an embodiment of the present invention.

[0028] Figure 14a and Figure 14b This is a graph showing the simulation results of the input voltage balancing operation of the power conversion device according to an embodiment of the present invention.

[0029] Figure 15 This is a block diagram of an input series-connected power conversion device according to an embodiment of the present invention.

[0030] Figures 16 to 19 This is a diagram illustrating the process of driving a power conversion device in two directions according to an embodiment of the present invention.

[0031] Figures 20a to 20c and Figures 21a to 21c This is a diagram showing the simulation results of a bidirectional drive power conversion device according to an embodiment of the present invention.

[0032] Figure 22 This is a diagram illustrating the process in which a power conversion device performs initial charging according to an embodiment of the present invention.

[0033] Figure 23a and Figure 23b This is a diagram showing the simulation results of the initial charging of the power conversion device according to an embodiment of the present invention. Detailed Implementation

[0034] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0035] However, the technical concept of the present invention is not limited to some of the embodiments described herein, but can be implemented in various different forms, and can even selectively combine or replace one or more components in the embodiments for use within the scope of the technical concept of the present invention.

[0036] Furthermore, unless explicitly and specifically defined and described, the terms (including technical and scientific terms) used in the embodiments of the present invention may be interpreted as having a meaning that is generally understood by one of ordinary skill in the art to which the present invention pertains, and commonly used terms, such as those defined in dictionaries, may be interpreted in consideration of the contextual meaning of the relevant art.

[0037] Furthermore, the terminology used in the embodiments of the present invention is for the purpose of describing the embodiments and is not intended to limit the present invention.

[0038] In this specification, unless otherwise specifically stated in the phrase, the singular may also include the plural, and when it is described as “at least one of A and / or B, C”, it may include one or more of all combinations that can be combined with A, B, C.

[0039] Furthermore, when describing components of embodiments of the present invention, terms such as first, second, A, B, (a), (b) may be used. These terms are intended only to distinguish one component from another and are not intended to limit the nature, order, or sequence of the components.

[0040] In addition, when a component is described as being “connected,” “coupled,” or “linked” to another component, it can include not only cases where the component is directly “connected,” “coupled,” or “linked” to another component, but also cases where the component is “connected,” “coupled,” or “linked” through another component between that component and the other component.

[0041] Furthermore, when described as being formed or arranged "above" or "below" each component, "above" or "below" includes not only the case where two components are in direct contact with each other, but also the case where one or more other components are formed or arranged between the two components. Additionally, when expressed as "above" or "below," it can include not only an upward meaning based on a component, but also a downward meaning based on a component.

[0042] Figure 1 This is a block diagram of a power conversion device according to an embodiment of the present invention.

[0043] The power conversion device according to an embodiment of the present invention may consist of a first input / output unit 110, a first switching unit 120, a transformer unit 130, a second switching unit 140, and a second input / output unit 150, and may include a controller 170, a first inductor L1, a second inductor L2, a third inductor L3, and a first capacitor C1. The power conversion device according to an embodiment of the present invention may be an active clamp forward-flyback converter. Alternatively, the power conversion device may be a converter with the input side connected in series and the output side connected in parallel.

[0044] The first input / output unit 110 is connected to the high voltage side.

[0045] The first input / output unit 110 can be connected to a high-voltage side to input a high voltage, or output a converted voltage to a high-voltage side. In buck mode, the first input / output unit 110 can be used as an input unit, and in boost mode, the first input / output unit 110 can be used as an output unit. The first input / output unit 110 may include a high-voltage side capacitor. Here, "high voltage" means that, when compared with each other, the voltage of the battery or power supply connected to the first input / output unit 110 is relatively higher than the voltage of the battery or load side connected to the second input / output unit 150, and does not mean a voltage with a specific value.

[0046] A high-voltage battery can be connected to the first input / output unit 110. Alternatively, an external power source can be connected. For example, the voltage of the external power source or battery connected to the first input / output unit 110 can be in the range of 400 V to 800 V. Two 400 V batteries can be connected in series to operate as an 800 V battery. This will be described in detail below.

[0047] The first switching unit 120 is connected to the first input / output unit 110.

[0048] The first switching unit 120 can be connected to the first input / output unit 110 to transmit the voltage input to the first input / output unit 110 to the transformer unit 130 or to transmit the voltage output from the transformer unit 130 to the first input / output unit 110.

[0049] The first switching unit 120 may include a first switch 122 and a second switch 121 that are electrically connected in a complementary manner. The connection relationship and operation of the first switch 122 and the second switch 121 will be described in detail later.

[0050] Transformer unit 130 includes a first transformer 131 and a second transformer 132, the primary side of each of the first transformer 131 and the second transformer 132 being connected to a first switching unit 120. The transformers may be insulated transformers. Transformer unit 130 may include a bidirectional transformer that converts the voltage input to the primary side to output the converted voltage to the secondary side, or converts the voltage input to the secondary side to output the converted voltage to the primary side. The direction of the first input / output unit 110 is described as the primary side of transformer unit 130, and the direction of the second input / output unit 150 is described as the secondary side of transformer unit 130. That is, the primary side of the transformer can be at a high voltage, and the secondary side can be at a low voltage, and therefore the turns ratio of the primary side to the secondary side can be n:1.

[0051] The second switching unit 140 is connected to the secondary side of the transformer unit 130.

[0052] The second switching unit 140 can be connected to the secondary side of the transformer unit 130 so that the voltage output from the transformer unit 130 is output to the second input / output unit 150. The second switching unit 140 can operate as a rectifier to rectify the output voltage of the transformer unit 130. The second switching unit 140 may include a third switch 141 connected to the secondary side of the first transformer 131 and a fourth switch 142 connected to the secondary side of the second transformer 132.

[0053] Each of the third switch 141 and the fourth switch 142 may include a FET and may be a MOSFET including a body diode. Alternatively, each of the third switch 141 and the fourth switch 142 may be a synchronous rectifier (SR) MOSFET. Each of the first switch 122 and the second switch 121 may be the same as each of the third switch 141 and the fourth switch 142, and may be a FET, a MOSFET including a body diode, or an SR MOSFET.

[0054] The second input / output unit 150 is connected to the secondary side and the low-voltage side of the transformer unit 130.

[0055] The second input / output unit 150 is connected to the secondary side of the transformer unit 130 and can output the voltage converted by the transformer unit 130 to the low-voltage side, or receive voltage from the low-voltage side to transmit the received voltage to the transformer unit 130. In buck mode, the second input / output unit 150 can be used as an output unit, and in boost mode, the second input / output unit 150 can be used as an input unit. The second input / output unit 150 may include a low-voltage side capacitor. Here, "low voltage" means that, when compared with each other, the voltage of the battery or load connected to the second input / output unit 150 is relatively lower than the voltage of the battery or power supply connected to the first input / output unit 110, and does not mean a voltage of a specific magnitude.

[0056] A low-voltage battery can be connected to the second input / output unit 150. Alternatively, a load can be connected. For example, the voltage of the battery connected to the second input / output unit 150 can be 12 V.

[0057] A first switch 122 can be connected in series to transformer unit 130, and a second switch 121 can be connected in parallel to transformer unit 130. The first switch 122 may include a first inductor L1 connected in series between the first input / output unit 110 and transformer unit 130, and may also include a second inductor L2 connected in parallel to the primary side of the first transformer 131 and a third inductor L3 connected in parallel to the primary side of the second transformer 132. Additionally, a first capacitor C1 may be provided connected to a first node between the first input / output unit 110 and the first inductor L1 and connected in series to the second switch 121. The first switch 122 may be configured to connect to a second node between the first switch 122 and transformer unit 130.

[0058] The first input / output unit 110, the first switching unit 120, the voltage transformer unit 130, the second switching unit 140, and the second input / output unit 150 can be configured as follows: Figure 3 The implementation is shown. Each component can correspond to... Figure 4 Components.

[0059] exist Figure 3 In this circuit, the first switch 122 can be referred to as the main switch Q_M, the second switch 121 can be referred to as the auxiliary switch Q_A, the first inductor can be referred to as L1, the second inductor can be referred to as L2, the third inductor can be referred to as L3, and the first capacitor can be referred to as C1. Furthermore, the third switch 141 can be referred to as Q_SR_Flyback, and the fourth switch can be referred to as Q_SR_Forward, and so on. Figure 3The connection is shown. The first input / output unit 110 may include a high-voltage side capacitor, and the second input / output unit 150 may include a low-voltage side capacitor. The first inductor L1, the second inductor L2, the third inductor L3, and the first capacitor C1 can form an LC filter, thereby forming a noise filter unit to remove noise from the input voltage.

[0060] The direction of the current applied to the transformer unit 130 can be changed according to the operation of the first switch 122 and the second switch 121. The first switch 122 and the second switch 121 are electrically turned on in a complementary manner so that current can flow through the first transformer 131 and the second transformer 132 and the direction of current flow can be changed.

[0061] The battery is connected to the high-voltage side, and the voltage is input to the first input / output unit 110. Here, when the first switch 122 is on and the second switch 121 is off, current flows in the first direction, and the first inductor L1, the second inductor L2, the third inductor L3, and the first switch 122 are connected along the first direction. Current flows through the first transformer 131 and the second transformer 132, and voltage is applied to the first transformer 131 and the second transformer 132. The first transformer 131 and the second transformer 132 convert the input voltage to output the voltage to the secondary side. Here, when the fourth switch 142 is on, a current path is formed through the fourth switch 142 and the secondary side of the second transformer 132, so that voltage is output to the low-voltage side.

[0062] When the first switch 122 is off and the second switch 121 is on, no current flows through the first switch 122, and the current flows in the second direction. The first capacitor C1, the second switch 121, the third inductor L3, the second inductor L2, and the first inductor L1 are connected in the second direction. That is, the current flows in the opposite direction, and thus the noise generated by applying voltage to the first transformer 131 and the second transformer 132 can be eliminated. In addition, when the third switch 141 is on, a current path to the second input / output unit 150 is provided through the third switch 141 and the secondary side of the first transformer 131, so that the voltage is output to the low-voltage side.

[0063] Since noise is removed by the operation of the first switch 122 and the second switch 121, a noise-removing inductor may not be required on the secondary side of the transformer unit 130, i.e., the second input / output unit 150. To handle high currents, the inductor's size may increase, leading to increased cost. However, the inductor may be omitted from the second input / output unit 150 to reduce size and cost.

[0064] The controller 170 controls the first to the fourth switches such that when a voltage is input from the high voltage side to the first input / output unit, a voltage is output from the second input / output unit to the low voltage side, and when a voltage is input from the low voltage side to the second input / output unit, a voltage is output from the first input / output unit to the high voltage side.

[0065] The controller 170 can electrically turn on the first switch 122 and the second switch 121 in a complementary manner, and can control the switches by applying a dead time or delay time for zero-voltage switching (ZVS).

[0066] At the point when the second switch 121 is turned off and the first switch 122 is turned on, the second switch 121 can be controlled to turn off, and then, after a first time, the first switch 122 can be controlled to turn on. Here, the first time can vary depending on the applied voltage. After the second switch 121 turns off, causing the first switch 122 to turn on at zero voltage, a dead time is applied to turn off both the first switch 122 and the second switch 121 until the first time. Here, the higher the input voltage, the longer the first time can become. For example, as... Figure 6 As shown, when the input voltage V_IN is less than 240 V, a dead time of 90 ns is applied, which is the minimum dead time for zero-voltage switching. Within the range of 240 V to 260 V, the dead time can increase linearly from 90 ns to 130 ns. When the dead time exceeds 130 ns, it may be difficult to ensure the duty cycle time for voltage switching, and therefore, the first time can be limited to 130 ns or less. Simulation results of the first time varying according to the input voltage are shown below. Figures 8a to 8c As shown, as the input voltage increases, it can be increased immediately to achieve zero-voltage switching.

[0067] At the point when the first switch 122 is turned off and the second switch 121 is turned on, the first switch 122 can be controlled to turn off, and then, after the first time, the second switch 121 can be controlled to turn on. Here, the second time can be a preset time to be applied. When the second switch 121 is turned on, since the effect of the zero-voltage switch is not significant, the second time can be fixed to the preset time to apply the dead time. Here, the second time can be set to the minimum dead time for the zero-voltage switch. For example, as... Figure 6 As shown, the second time can be set to 90 ns. Alternatively, the second time can be controlled to vary in response to the first time.

[0068] The controller 170 can also apply a delay time to control the third switch 141 and the fourth switch 142.

[0069] The third switch 141 can be controlled to operate in response to the operation of the second switch 121, or it can be controlled to operate after a preset time. Since the operation of the third switch 141 is not significantly affected by the zero-voltage switch and its peak voltage is not high, similar to the second switch 121, a preset time can be applied to the third switch 141. Here, a fixed time of 80 ns or 70 ns can be applied.

[0070] The fourth switch 142 can be controlled to be off, and then turned on after the second switch 121 has been off for a third time, and the first switch 122 can be controlled to be turned off after the first switch 122 has been off for a fourth time. Here, the third and fourth times can vary according to the output current. After the second switch 121 turns off, causing the fourth switch 142 to turn on at zero voltage, the second switch 121 may not turn on immediately, but may be subject to a third time delay. Here, the third time can be longer as the output current increases. Additionally, after the first switch 122 turns off, the first switch 122 may not turn off immediately, but may remain on for a fourth time, and then turn off by applying a delay time. For example, as... Figure 6 As shown, when the output current i_out is less than 30 A, a delay time of 60 ns can be applied to reduce the peak voltage of the fourth switch under light load on the SR MOSFET. Alternatively, within the range of 30 A to 50 A, the delay time can be linearly increased from 60 ns to 100 ns to perform zero-voltage switching of the SR MOSFET under intermediate load. When the delay time is 100 ns, it may be difficult to ensure the duty cycle time of the voltage transition, and therefore, the third and fourth times can be limited to 100 ns or less.

[0071] The power conversion device according to an embodiment of the present invention may consist of a first-1 input / output unit 111, a first-2 input / output unit 112, a first power conversion unit 161, a second power conversion unit 162, and a second input / output unit 150, and may include a controller 170. Multiple batteries, instead of a single battery, may be connected to the first input / output unit 110. Here, the multiple batteries may be connected in series. For example, two 400 V batteries may be connected in series to operate at 800 V.

[0072] like Figures 9 to 11As shown, the two high-voltage sides can be connected in series to the first input / output terminal, and the voltage can be converted through two power conversion units 161 and 162, i.e., two channels. The outputs of the channels can be connected in parallel, so that the voltage is output to the second input / output terminal. Here, the power conversion device can be a two-channel DC-DC converter with a series input and parallel output structure, and can be a bidirectional driven active clamp forward-flyback converter.

[0073] The first -1 input / output unit 111 and the first -2 input / output unit 112 can be connected to a first high-voltage side and a second high-voltage side connected in series, respectively. A first power conversion unit 161 can be connected to the first -1 input / output unit 111, and a second power conversion unit 162 can be connected to the first -2 input / output unit 112. The first power conversion unit 161 and the second power conversion unit 162 can be connected in parallel to the second input / output unit 150.

[0074] Here, with the voltages on the two high-voltage sides differing from each other, the current I_M flows between the two channels of the first power conversion unit 161 and the second power conversion unit 162, potentially disrupting the balance between the two channels. That is, if one of the batteries connected to the high-voltage side discharges first, and the voltage difference increases, efficient charging and discharging of the battery may become difficult, and the battery life may be shortened.

[0075] To maintain balance, the operation of either the first or second power conversion unit can be controlled by using the difference between the first input voltage of the first power conversion unit and the second input voltage of the second power conversion unit. Therefore, input voltage balance can be achieved.

[0076] The controller 170 can operate the first power conversion unit 161 and the second power conversion unit 162 in peak current mode, and can compensate for the current rise slope in peak current mode based on the difference between the first input voltage and the second input voltage.

[0077] Peak current mode is a control mode in which the switch remains on when the control switch is activated until the current increases according to the current rise slope and meets the reference voltage at the specified time point.

[0078] like Figure 12 As shown, the controller 170 generates a PWM signal to be applied to each switch according to the peak current mode, and can compensate for the current rise slope in the peak current mode according to the difference between the first input voltage and the second input voltage.

[0079] When the first input voltage is less than the second input voltage, the current rise slope in the peak current mode of the first power conversion unit 161 becomes smaller. Here, the current rise compensation slope in the peak current mode of the first power conversion unit 161 can be increased, and therefore, the average current of the first power conversion unit can become less than the average current of the second power conversion unit. Consequently, the current of the first power conversion unit 161 decreases, causing a slower discharge, thereby maintaining balance with the second power conversion unit 162.

[0080] The power conversion device may further include a compensation unit configured to compensate for the difference between a first input voltage of the first power conversion unit and a second input voltage of the second power conversion unit, and to generate a PWM signal applied to either the first or second power conversion unit based on the operation of the compensation unit. A first battery may be connected to a first high-voltage side, and a second battery may be connected to a second high-voltage side. A controller 170 may control the operation of the first power conversion unit 161 and the second power conversion unit 162, thereby balancing the first and second batteries.

[0081] Figure 13 (A) shows the basic current rise slope, and Figure 13 (B) illustrates the case where balancing is not performed. In this case, the low input voltage causes a smaller current rise slope, and since the current rise compensation slope is applied equally to both the first power conversion unit 161 and the second power conversion unit 162, the input current of the first power conversion unit 161 becomes larger than the input current of the second power conversion unit 162. Therefore, the battery connected to the first high-voltage side discharges faster than the battery connected to the second high-voltage side, and the current I_M at the midpoint between the first and second high-voltage sides gradually increases.

[0082] To prevent this, although the current rise slope is compensated, the current rise compensation slope can be calculated using the following formula.

[0083] [Formula 1]

[0084] (slope-1) = k1 + k2 (V_H, CH2 - V_H, CH1)

[0085] (slope-2) = k1 + k2 (V_H, CH1 - V_H, CH2)

[0086] Here, slope-1 is the current rise compensation slope of the first power conversion unit, k1 and k2 are constants, V_H,CH1 is the first input voltage, and V_H,CH2 is the second input voltage.

[0087] When balance control is applied, such as Figure 13 As shown in (C), the current rise compensation slope of the first power conversion unit 161 increases. Therefore, the average current of the first power conversion unit 161 decreases, and the battery connected to the first high-voltage side discharges more slowly than the battery connected to the second high-voltage side. The current I_M at the midpoint between the first and second high-voltage sides gradually decreases until it reaches equilibrium, and then becomes zero under normal conditions.

[0088] For example, when V_H, CH1 is less than V_H, CH2, slope-1 can increase and slope-2 can decrease. As slope-1 increases, the switch of the first channel on the first power conversion unit side is turned off first. Therefore, the battery connected to the first high-voltage side discharges more slowly, and V_H, CH1 and V_H, CH2 gradually become equal to each other to maintain balance.

[0089] like Figure 14a As shown, when HV1 is 300 V and HV2 is 310 V, without balancing, the rising slope of the pulse current I_H,CH1 in channel 1 is less than that of the pulse current I_H,CH2 in channel 2, but the current rise compensation slopes are the same. Therefore, the average current of the pulse current I_H,CH1 in channel 1 becomes greater than the average current of I_H,CH2 in channel 2. Since the input battery current I_HV1 is the average current of the pulse current I_H,CH1 in channel 1, the HV1 current becomes greater than the HV2 current. Conversely, where balancing is performed... Figure 14b In this case, the rising slope of the pulse current I_H,CH1 in channel 1 is less than the slope of the pulse current I_H,CH2 in channel 2. Therefore, the average current of the pulse current I_H,CH1 in channel 1 becomes less than the average current of I_H,CH2 in channel 2. Since the input battery current I_HV1 is the average current of the pulse current I_H,CH1 in channel 1, the current on the first high-voltage side HV1 becomes less than the current on the second high-voltage side HV2. Therefore, the midpoint current becomes positive, indicating that battery HV1 discharges more slowly than battery HV2. Consequently, the midpoint current decreases and becomes zero under normal conditions.

[0090] As mentioned above, the power conversion device according to one embodiment of the present invention operates in two directions. That is, when the first input / output unit and the second input / output unit, which are respectively connected in series to the first high-voltage side and the second high-voltage side, can convert the voltage of the first high-voltage side and the voltage of the second high-voltage side to output to the low-voltage side, or convert the voltage of the low-voltage side to output to the first high-voltage side or the second high-voltage side, and can operate in both directions.

[0091] The controller 170 can control the first to fourth switches, enabling the switches to operate in buck and boost modes. Here, the controller 170 can control the power conversion unit 160 in peak current mode in buck mode, where the voltage is input from a first high-voltage side or a second high-voltage side and is stepped down; and it can control the power conversion unit 160 in average current mode in boost mode, where the voltage is input from a low-voltage side and is boosted.

[0092] The controller 170 may be configured with a constant current control signal generation unit 171, a soft start control signal generation unit 173, a signal selection unit 174 and a PWM generation unit 176 to perform control in buck mode or boost mode, and may also include a constant voltage control signal generation unit 172 and a slope compensation unit 175.

[0093] The configurations for buck mode and boost mode can be provided as separate modules or as a single module. Here, only the configurations required for each mode are used to operate in both directions.

[0094] In buck mode, control can be achieved through a constant current control signal generation unit 171, a soft-start control signal generation unit 173, a signal selection unit 174, a PWM generation unit 176, a constant voltage control signal generation unit 172, and a slope compensation unit 175. The constant current control signal generation unit 171 rectifies the low-voltage side voltage to generate a constant current control signal. The constant voltage control signal generation unit 172 rectifies the low-voltage side current and power to generate a constant voltage control signal. The soft-start control signal generation unit 173 generates a soft-start control signal to suppress inrush current or peak voltage. The signal selection unit 174 selects the signal with the smallest value from the constant current control signal, constant voltage control signal, and soft-start control signal. Additionally, the controller 170 can control the first and second power conversion units in peak current mode, and the slope compensation unit 175 can compensate for the current rise slope in peak current mode based on the difference between the first and second input voltages. The controller 170 can control the first to fourth switches in buck mode and can adjust the current based on a reference... Figure 5 The controller 170 operates in buck mode as described above. Figure 17 This is achieved as shown.

[0095] In boost mode, control can be achieved through a constant current control signal generation unit 171, a soft-start control signal generation unit 173, a signal selection unit 174, and a PWM generation unit 176. The constant current control signal generation unit 171 rectifies the low-voltage side voltage to generate a constant current control signal. The soft-start control signal generation unit 173 generates a soft-start control signal to suppress inrush current or peak voltage. The signal selection unit 174 selects the signal with the smallest value from the constant current control signal, constant voltage control signal, and soft-start control signal. Additionally, the controller 170 can control the first and second power conversion units in average current mode. In boost mode, the controller 170 operates as follows: Figure 18 This is achieved as shown.

[0096] Unlike the buck mode, in the boost mode, the controller 170 can control the first to the fourth switches 142. The controller 170 may include a PWM generation unit 176, which controls the dead time or delay time of each of the first to the fourth switches 144.

[0097] The controller 170 performs control to turn off the second switch 121, and then turns on the first switch 122 after a first time. It also performs control to turn off the first switch 121, and then turns on the second switch 121 after a second time. Here, the first time can vary depending on the applied voltage, and the second time can be a preset time to be applied.

[0098] Additionally, the controller 170 can control the third switch 141 to operate in response to the operation of the second switch 121 or in response to a preset time, and can also control the fourth switch to turn on after a third time has elapsed after the second switch 121 has turned off, and to turn off after a fourth time has elapsed after the first switch 122 has turned off. Here, the third and fourth times can vary according to the output current.

[0099] The controller 170 can control the third switch 141 to turn on after a fifth time interval following the first switch 122 being turned off, and to turn off after a sixth time interval following the fourth switch 142 being turned on.

[0100] like Figure 19 As shown, during one cycle of boost mode, the second switch can be turned off at time t0, the fourth switch can be turned on at time t1, the third switch can be turned off at time t2, the first switch can be turned on at time t3, the first switch can be turned off at time t4, the third switch can be turned on at time t5, the fourth switch can be turned off at time t6, and the second switch can be turned on at time t7. The "duty cycle" refers to the time the first switch remains in the "on" state.

[0101] As described above, the operation of the first through fourth switches can be controlled differently to operate in either buck or boost mode. Simulation results of bidirectional operation in buck and boost modes are shown in Figures 20A through 20C and Figures 21A through 21C.

[0102] According to an embodiment of the present invention, the power conversion device can use the low-voltage side voltage to initially charge the capacitor on the high-voltage side. In accordance with... Figures 1 to 4 In the power conversion device of the embodiment, initial charging can be performed without a separate initial charging circuit by controlling the operation of the first to fourth switches.

[0103] Controller 170 can turn on the fourth switch 142 and then turn it off after a seventh time interval, and can turn on the second switch 121 and the third switch 141 to initially charge the first capacitor C1. The second switch 121 and the third switch 141 can be turned off after the seventh time interval to charge the high-voltage side capacitor. For all switches—second switch 121, third switch 141, and fourth switch 142—the time to maintain the on state for initial charging can be the seventh time interval. The seventh time interval can be a preset time or the minimum time that initial charging must be maintained. During the initial charging period, controller 170 can keep the first switch 122 in the off state.

[0104] like Figure 22 As shown, the first switch 122 can remain in the off state, the fourth switch 142 can be turned on for a predetermined time, and after the seventh time, the fourth switch 142 can be turned off, and the second switch 121 and the third switch 141 can be turned on and then turned off after the seventh time, thereby performing the initial charging.

[0105] During initial charging, such as Figure 23a As shown, with an input voltage of 13.8 V on the low-voltage side, an initial charging target voltage of 400 V, a high-voltage side capacitor with a capacitance of 5 μF, a switching frequency of 10 kHz, and a maximum seventh time of 3 μs, it can be confirmed that the high-voltage side capacitor takes 17 ms to charge from 0 V to 400 V.

[0106] As described above, the power conversion device according to an embodiment of the present invention includes a first input / output unit 110, a first switching unit 120, a transformer unit 130, a second switching unit 140, a second input / output unit 150, a controller 170, a first inductor L1, a second inductor L2, a third inductor L3, and a first capacitor C1. Therefore, the first switch 122 and the second switch 121 of the first switching unit 120, as well as the third switch 141 and the fourth switch 142, which are SR MOSFETs of the first switching unit 120, can be controlled to operate bidirectionally in both buck and boost modes, and input voltage balancing and initial charging are possible. Therefore, a stable voltage can be provided, and efficient power conversion is possible.

[0107] Those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed methods should be considered descriptive only and not for limiting purposes. Consequently, the scope of the invention is not defined by the detailed description thereof, but by the appended claims, and all differences within that scope shall be construed as included in the invention.

Claims

1. A power conversion device, comprising: The first input / output unit connected to the high-voltage side; A first switching unit connected to the first input / output unit; A transformer unit, comprising a first transformer and a second transformer, each of the first transformer and the second transformer having a primary side connected to the first switching unit; A second switching unit is connected to the secondary side of the transformer unit; as well as The second input / output unit is connected to the low-voltage side and the secondary side of the transformer unit. The first switching unit includes a first switch and a second switch that are complementaryly electrically connected, and The second switching unit includes: A third switch, the third switch being connected to the secondary side of the first transformer; and A fourth switch is connected to the secondary side of the second transformer.

2. The power conversion device according to claim 1, wherein, The first switch is connected in series to the transformer unit, and The second switch is connected in parallel to the transformer unit.

3. The power conversion device according to claim 2, wherein, After a first period of time elapsed since the second switch was turned off, the first switch is turned on, and The first time varies depending on the applied voltage.

4. The power conversion device according to claim 2, wherein, After a second time elapses since the first switch was turned off, the second switch is turned on, and The second time is the preset time to be applied.

5. The power conversion device according to claim 2, comprising: A first inductor is connected in series with the transformer unit between the first input / output unit and the transformer unit; The second inductor is connected in parallel to the primary side of the first transformer; A third inductor is connected in parallel to the primary side of the second transformer; as well as A first capacitor is connected to a first node between the first input / output unit and the first inductor, and is connected in series with the second switch. The first switch is connected to a second node between the first switch and the transformer unit.

6. The power conversion device according to claim 5, wherein, When the first switch is on and the second switch is off, current flows in the direction connecting the first inductor, the second inductor, the third inductor, and the first switch. When the first switch is off and the second switch is on, the current flows in the direction of connection between the first capacitor, the second switch, the third inductor, the second inductor, and the first inductor.

7. The power conversion device according to claim 1, wherein, The first switching unit changes the direction of the current applied to the transformer unit according to the operation of the first switch and the second switch.

8. The power conversion device according to claim 1, wherein, The third switch operates in response to the operation of the second switch, or in response to the operation after a preset time.

9. The power conversion device according to claim 1, wherein, The fourth switch is turned on after a third time elapsed since the second switch was turned off, and turned off after a fourth time elapsed since the first switch was turned off. The third time and the fourth time vary according to the output current.

10. The power conversion device according to claim 1, wherein, Each of the first switch and the fourth switch includes a field-effect transistor (FET).

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