Vehicle charger and control method thereof

Abstract

The present invention relates to a vehicle charger and a control method thereof. A vehicle charger is provided, including: a power factor correction converter configured to correct a power factor of alternating current (AC) power, the power factor correction converter being integrated with input terminals of a DC-DC converter configured to generate a direct current (DC) voltage having a magnitude required for an energy storage device in a vehicle, thereby reducing a size of the vehicle charger, reducing a number of required elements, and allowing the vehicle charger to have a high efficiency; and a control method thereof.

Description

Technical Field

[0001] This disclosure relates to a vehicle charger and a control method thereof, and more specifically, to a vehicle charger wherein a power factor correction converter configured to correct the power factor of alternating current (AC) power is integrated with the input terminal of a DC-DC converter configured to generate a direct current (DC) voltage having the amplitude required for energy storage devices in the vehicle, thereby reducing the size of the vehicle charger, reducing the number of required components, and allowing the vehicle charger to have high efficiency; and a control method thereof. Background Technology

[0002] With global warming and environmental pollution becoming serious problems, the automotive industry has been actively researching and developing environmentally friendly vehicles that can minimize environmental pollution, and the market for these vehicles is growing.

[0003] Examples of environmentally friendly vehicles already introduced worldwide include hybrid vehicles, plug-in hybrid vehicles, and electric vehicles. Each type of vehicle has an electric motor configured to generate driving power using electrical energy, rather than an engine configured to generate driving power by burning conventional fossil fuels. Electric and plug-in hybrid vehicles, among other environmentally friendly vehicles that use electricity, charge their batteries by receiving power from external charging facilities connected to the grid, and generate the kinetic energy needed for vehicle operation using the electrical energy from the charging batteries. Therefore, every environmentally friendly vehicle has an on-board charger (OBC) configured to receive grid power from external charging facilities and convert it into power for charging the battery. That is, the vehicle charger, or on-board charger (OBC), converts alternating current (AC) grid power into DC power with the desired voltage and supplies this DC power to the high-voltage battery, which serves as an on-board energy storage device, to charge the high-voltage battery.

[0004] The vehicle charger (OBC) can affect a vehicle's fuel efficiency, thus requiring highly efficient power conversion. Structurally, the OBC is located in the vehicle's engine compartment, therefore, for efficient space utilization, its size needs to be reduced and its density increased.

[0005] The information disclosed in the Background section is only intended to enhance the understanding of the background of this disclosure and should not be construed as forming prior art known to those skilled in the art. Summary of the Invention

[0006] The technical problem to be solved by the disclosure is to provide a vehicle charger and a control method thereof, in which the vehicle charger reduces the number of switching elements and driving circuits to achieve miniaturization and power densification thereof, and has high output and a wide input / output range.

[0007] To solve the technical problem, the disclosure provides a vehicle charger including an inductor connected to one end of an AC power source, a first leg including first and second switching elements connected in series to each other. The connection terminals of the first and second switching elements are connected to the other end of the inductor. The vehicle charger further includes a capacitor connected in parallel to the first leg, a second leg including third and fourth switching elements connected in series to each other between both ends of the capacitor. The connection terminals of the third and fourth switching elements are connected to the other end of the AC power source. The vehicle charger further includes a transformer having a primary coil connected to the connection terminals of the third and fourth switching elements and a secondary coil electromagnetically coupled to the primary coil, and a third leg including fifth and sixth switching elements connected in series to each other between both ends of the capacitor. The connection terminals of the fifth and sixth switching elements are connected to the other end of the primary coil. The vehicle charger further includes a controller configured to control the first and second switching elements to regulate the voltage of the capacitor, and configured to control the third and fourth switching elements to convert the voltage of the capacitor substantially.

[0008] In one embodiment of the disclosure, to regulate the voltage of the capacitor, the controller can determine the duty ratio of the switching elements included in the first leg to control the turn-on / off of the switching elements included in the first leg, can control the turn-on / off of the switching elements included in the second leg by using a switching frequency synchronized with the switching frequency of the switching elements included in the first leg, and can control the turn-on / off of the switching elements included in the third leg so that the switching elements included in the third leg have a phase difference therebetween compared to the switching elements included in the second leg.

[0009] In one embodiment of the disclosure, the controller can generate a detection voltage of the capacitor and a first reference voltage for making the detection voltage of the capacitor subject to an external input voltage command of the capacitor, and the first reference voltage can have the form of an alternating current synchronized with an alternating current of the AC power source.

[0010] In one embodiment of the disclosure, the controller can compare the first reference voltage with a carrier signal of a triangular waveform voltage having a predetermined period to determine the duty ratio of the first and second switching elements, and the first and second switching elements can operate complementarily to each other.

[0011] In one embodiment of the present disclosure, the controller can compare the carrier signal with a second reference voltage having an amplitude corresponding to half of a peak value of the carrier signal to determine duty ratios of the third and fourth switching elements, and the third and fourth switching elements can operate complementarily to each other.

[0012] In one embodiment of the present disclosure, the controller can determine a phase difference for making an output voltage of the vehicle charger comply with a predetermined output voltage command, and can control the fifth and sixth switching elements to be delayed by the phase difference compared to the third and fourth switching elements.

[0013] In one embodiment of the present disclosure, the controller can include a first subtractor configured to determine a first error between a detected voltage of the capacitor and an external input voltage command of the capacitor, a first voltage controller configured to generate a direct current (DC) voltage control value for reducing the first error, a current command generator configured to generate a current command by multiplying the DC voltage control value determined by the first voltage controller by a phase component for synchronization with an AC power source, a second subtractor configured to determine a second error between the current command and a detected current of the inductor, a current controller configured to determine a first reference voltage for determining duty ratios of first and second switching elements of the first leg so as to reduce the second error, and the first reference voltage having an alternating current form synchronized with an alternating current of the AC power source, a triangle wave generator configured to generate a carrier signal that is a triangular waveform voltage having a predetermined period, a DC voltage source configured to generate a second reference voltage that is a predetermined DC voltage having an amplitude corresponding to half of a peak value of the carrier signal, a first comparator configured to compare an amplitude of the first reference voltage with an amplitude of the carrier signal, determine duty ratios of the first and second switching elements, and output the determined duty ratios as control signals for the first and second switching elements, a second comparator configured to compare an amplitude of the second reference voltage with an amplitude of the carrier signal, determine duty ratios of third and fourth switching elements, and output the determined duty ratios as control signals for the third and fourth switching elements, a third subtractor configured to determine a third error between an output voltage of the vehicle charger and a predetermined output voltage command, a second voltage controller configured to generate a current peak command for reducing the third error, a third comparator configured to output a comparison result between a peak value of a primary side current of the transformer and the current peak command, and a D flip-flop configured to delay an output of the second comparator based on an output of the third comparator and output the output of the second comparator as control signals for the fifth and sixth switching elements.

[0014] In one embodiment of the present disclosure, the vehicle charger can further include a rectifier connected to the secondary coil of the transformer and configured to rectify power induced by the secondary coil and output the rectified power to the device to be charged.

[0015] To achieve the above technical objects, the present disclosure provides a method for controlling a vehicle charger, the method including generating a detection voltage of a capacitor and a first reference voltage for subjecting the detection voltage of the capacitor to an external input voltage command of the capacitor, generating a second reference voltage that is a DC voltage having a predetermined amplitude, comparing the first reference voltage with a carrier signal having a triangular waveform voltage with a predetermined period and determining a duty ratio of first and second switching elements that are turned off / shorted complementarily to each other, comparing the second reference voltage with the carrier signal and determining on / off states of third and fourth switching elements that are turned off / shorted complementarily to each other, and determining a phase difference for subjecting an output voltage of the vehicle charger to a predetermined output voltage command, delaying the on / off states of the third and fourth switching elements by the phase difference, and determining on / off states of fifth and sixth switching elements.

[0016] In one embodiment of the present disclosure, the first reference voltage can have an alternating current form synchronized with an alternating current of the AC power source.

[0017] In one embodiment of the present disclosure, the second reference voltage can be a DC voltage having an amplitude corresponding to half of a peak value of the carrier signal.

[0018] In one embodiment of the present disclosure, generating the first reference voltage can include an operation of determining a first error between the detection voltage of the capacitor and the external input voltage command of the capacitor, a voltage control operation for generating a DC voltage control value for reducing the first error, a current command generation operation for generating an alternating current command by multiplying the DC voltage control value determined in the voltage control operation by a phase component for synchronization with the AC power source, an operation of determining a second error between the current command and a detection current of the inductor, and a current control operation for determining the first reference voltage having an alternating current form synchronized with an alternating current of the AC power source so as to reduce the second error.

[0019] In one embodiment of the present disclosure, in determining the on / off states of the fifth and sixth switching elements, regarding a third error between the output voltage of the vehicle charger and the predetermined output voltage command, based on a comparison result between the current peak command for reducing the third error and the current peak of the primary side of the transformer, the output of the second comparator can be delayed, and can be output as a control signal of the fifth and sixth switching elements.

[0020] According to the vehicle charger and the control method thereof, the number of switches and driving circuits can be reduced by integrating a power factor correction circuit and a phase-shift full-bridge DC-DC converter required for the vehicle charger, the vehicle charger can have high price competitiveness, and high power density can be achieved through a simple structure thereof.

[0021] In particular, according to the vehicle charger and the control method thereof, six switches can be simultaneously controlled to operate a continuous conduction mode boost power factor correction circuit and a phase-shift full-bridge converter, thereby improving the output of the vehicle charger and expanding the input / output voltage range. BRIEF DESCRIPTION OF DRAWINGS

[0022] The above and other aspects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0023] Figure 1 is a circuit diagram of a vehicle charger according to one exemplary embodiment of the present disclosure;

[0024] Figure 2 is a block configuration diagram more specifically illustrating a controller of a vehicle charger according to one embodiment of the present disclosure;

[0025] Figure 3 shows an example in which the controller of the vehicle charger according to one embodiment of the present disclosure compares a reference voltage with a carrier signal and determines a duty ratio of a switching element based on the comparison; and

[0026] Figure 4 and Figure 5 shows the resonant current of the switching element, the inductor current, and the off / short-circuit state in each of region A and region B corresponding to one period of the carrier signal shown in Figure 3 DETAILED DESCRIPTION

[0027] Hereinafter, the vehicle charger and the control method thereof according to various embodiments of the present disclosure will be described in greater detail with reference to the accompanying drawings.

[0028] Figure 1 is a circuit diagram of a vehicle charger according to one exemplary embodiment of the present disclosure;​

[0029] Reference Figure 1 A vehicle charger according to one embodiment of the present disclosure can include: an inductor 13 connected to one end of an AC power source 11; a first leg P1 including a first switching element Q1 and a second switching element Q2 commonly connected to the other end of the inductor 13; a capacitor 15 connected in parallel to the first leg P1; a second leg P2 connected in parallel to the capacitor 15 and including a third switching element Q3 and a fourth switching element Q4 commonly connected to the other end of the AC power source 11; a third leg P3 including a fifth switching element Q5 and a sixth switching element Q6 connected in series with each other between both ends of the capacitor 15; a transformer 17 including a primary coil 171 having one end connected to a connection terminal of the third and fourth switching elements Q3 and Q4 and the other end connected to a connection terminal of the fifth and sixth switching elements Q5 and Q6; a rectifier 19 implemented as a plurality of diodes D 01 to D 04 so as to rectify an output of a secondary coil 172 of the transformer 17 and provide the rectified output to an energy storage device 20 to be charged; and a controller 100 configured to control opening / closing of the switching elements Q1 to Q6 included in the first to third legs P1 to P3.

[0030] As described above, the vehicle charger according to one embodiment of the present disclosure has a charger structure in which a phase-shifted full-bridge (PSHB) DC-DC converter is integrated with a continuous conduction mode (CCM) boost power factor correction circuit without a bridge circuit.

[0031] In the vehicle charger according to one embodiment of the present disclosure, the switching elements Q1 and Q2 included in the first leg P1 can be used to control a continuous conduction mode (CCM) boost power factor correction circuit without a bridge circuit to generate a DC voltage (V PFC ) for the capacitor 15. That is, the controller 100 can control opening / closing of the switching elements Q1 and Q2 included in the first leg P1 to determine the voltage (V PFC ) of the capacitor 15 to be a desired value.

[0032] Further, the switching elements Q3 and Q4 included in the second leg P2 and the switching elements Q5 and Q6 included in the third leg P3 can be used to control a phase-shifted full-bridge DC-DC converter to convert the DC voltage (V PFC ) generated in the capacitor 15 to a desired magnitude. In one embodiment of the present disclosure, the controller 100 can control opening / closing of the switching elements Q1 to Q6 included in the first to third legs P1 to P3 so that a desired power can be provided to the energy storage device 20 to be charged.

[0033] The operation of the vehicle charger according to one embodiment of the disclosure and the method for controlling the vehicle charger according to one embodiment of the disclosure can be performed by the controller 100. Accordingly, hereinafter, a more detailed configuration of the controller 100 and a control flow performed by the controller 100 will be described in more detail.

[0034] Figure 2 is a block diagram more specifically illustrating the controller of the vehicle charger according to one embodiment of the disclosure. The vehicle charging method according to one embodiment of the disclosure can be performed in the controller 100 shown in Figure 2 in blocks.

[0035] The controller 100 can include a processor performing various functions of the following modules 120, 130, 140, and 150. The modules 101, 103, 105, 107, 109, 111, 113, 115, 117, 123, 125, 129, 131, 133, and 135 described below can be implemented with software instructions executed on a processor. The controller 100 can include a subtracter 101 configured to determine an error between a capacitor detection voltage (V PFC ) obtained by measuring a voltage of the capacitor 15 and a capacitor voltage command (V PFC,Ref ) input from an external host controller or the like; and a voltage controller 103 configured to generate a DC voltage control value for minimizing the error between the capacitor detection voltage (V PFC ) and the capacitor voltage command (V PFC,Ref ), that is, such that the capacitor detection voltage (V PFC ) is subject to the capacitor voltage command (V PFC,Ref ).

[0036] The voltage controller 103 can generate the voltage control value for minimizing the error between the capacitor detection voltage (V PFC ) and the capacitor voltage command (V PFC,Ref ) by selectively using a control technique well known in the corresponding technical field: proportional control in which the error between the capacitor detection voltage (V PFC ) and the capacitor voltage command (V PFC,Ref ) is multiplied by a proportional constant; integral control in which the error between the capacitor detection voltage (V PFC ) and the capacitor voltage command (V PFC,Ref ) is integrated; and differential control in which the error between the capacitor detection voltage (V PFC ) and the capacitor voltage command (V PFC,Ref ) can be differentiated. In Figure 2An example in which a proportional-integral (PI) controller is implemented is shown.

[0037] Further, the controller 100 can further include a current command generator 105 configured to generate an AC current command (i PFC,Ref ) by multiplying a DC voltage control value generated by the voltage controller 103 by a phase component (Theta) for synchronization with a power current provided by the AC power source 11. LB PFC,Ref Further, the controller 100 can further include a current command generator 105 configured to generate an AC current command (i PFC,Ref ) by multiplying a DC voltage control value generated by the voltage controller 103 by a phase component (Theta) for synchronization with a power current provided by the AC power source 11. ref_P1 LB Further, the controller 100 can further include a current command generator 105 configured to generate an AC current command (i PFC,Ref ) by multiplying a DC voltage control value generated by the voltage controller 103 by a phase component (Theta) for synchronization with a power current provided by the AC power source 11. PFC,Ref

[0038] The current command generator 105 can be implemented as a subtractor configured to receive a phase component (Theta) for synchronization with a power current provided by the AC power source 11 and multiply a DC voltage control value determined by the voltage controller 103 by the phase component (Theta). The phase component (Theta) can be determined by adjusting an amplitude of the AC power to a value 1, or can be derived by a normal phase calculation technique or a phase detection technique known in the corresponding technical field, for example, a technique of detecting a phase component by an external phase locked loop (PLL).

[0039] The current controller 109 can further determine a reference voltage (V ref_P1 ) for determining a duty ratio of the switching elements Q1 and Q2 to minimize an error between the inductor detection current (i LB ) and the current command (i PFC,Ref ) by selectively using proportional control, integral control, and differential control well known in the corresponding technical field. Figure 2 An example in which the current controller 109 is implemented as a proportional-integral (PI) controller is shown.

[0040] The reference voltage (V ref_P1 ) generated by the current controller 109 is generated by comparing the current command (i PFC,Ref ) synchronized with a power current from the AC power source 11 with a current (i LB ) flowing in the inductor 13. Accordingly, the reference voltage (V ref_P1) can also be provided in the form of a voltage synchronized with the power current from the AC power source 11.

[0041] Further, the controller 100 can further include a first comparator 111 configured to compare a reference voltage (V ref_P1 ) (hereinafter referred to as "first reference voltage") generated by the current controller 109 with a carrier signal (V carr ) which is a triangular waveform voltage signal having a predetermined frequency and amplitude, and a second comparator 113 configured to compare the carrier signal (V carr ) with a reference voltage (V ref_P2 ) (hereinafter referred to as "second reference voltage") having a predetermined amplitude.

[0042] The controller 100 can further include a triangular wave generator 115 configured to generate the carrier signal (V carr ), and a DC voltage source 117 configured to generate the second reference voltage (V ref_P2 ) having a predetermined amplitude.

[0043] The output from the first comparator 111 can be provided to the first switching element Q1, and the output from the first comparator 111 which has been inverted by the inverting buffer 119 can be provided to the second switching element Q2. Likewise, the output from the second comparator 113 can be provided to the third switching element Q3, and the output from the second comparator 113 which has been inverted by the inverting buffer 121 can be provided to the fourth switching element Q4.

[0044] The first comparator 111 and the second comparator 113 can output HIGH signals when the values of the first reference voltage (V ref_P1 ) and the second reference voltage (V ref_P2 ) are greater than the value of the carrier signal, and can output LOW signals when the values of the first reference voltage (V ref_P1 ) and the second reference voltage (V ref_P2 ) are less than the value of the carrier signal, and vice versa.

[0045] As described above, the first switching element Q1 and the second switching element Q2 for the first leg P1 are used to determine the voltage of the capacitor 15 and the current of the inductor 13, and the third switching element Q3 and the fourth switching element Q4 for the second leg P2 operate with a duty ratio of 0.5 and are operated in synchronization with the switching frequency of the first switching element Q1 and the second switching element Q2. Further, the third switching element Q3 and the fourth switching element Q4 have a duty ratio of 0.5 at a fixed frequency, and thus can be used as a lead for a phase-shift full-bridge converter which receives the voltage (V PPC) and converts the amplitude thereof. The fifth and sixth switching elements Q5 and Q6 of the third leg P3 serve as a lag leg of the phase-shift full-bridge converter, and can control the on / off according to the result of controlling the phase-shift amplitude of the phase-shift full-bridge converter based on the predetermined output voltage command (V O,Ref ) of the transformer 17 and the amplitude of the primary-side current (i Llkg ).

[0046] To this end, the controller 100 can include a subtracter 123 configured to generate an error between the output voltage (V O ) of the vehicle charger and a predetermined voltage command (V O,Ref ) of the energy storage device 20 to be charged, a voltage controller 125 configured to generate a current peak command (I peak,Ref ) of the current of the primary coil 171 of the transformer 17 so as to minimize the error between the output voltage (V O ) and the voltage command (V O,Ref ), a comparator 129 configured to compare the current (i Llkg ) flowing through the primary side of the transformer 17 with the current peak command (I peak,Ref ) output by the voltage controller 125, an inverter buffer 131 configured to invert the output of the comparator 129, a D flip-flop 133 configured to receive the output from the inverter buffer 131 through a clock input and output the output value of the comparator 113 at the point in time when the signal provided through the clock input becomes a rising edge, and an inverter buffer 135 configured to invert the output of the inverting output terminal of the D flip-flop 133 and set it as the control signal of the fifth switching element Q5. The output of the inverting output terminal of the D flip-flop 133 can be set as the control signal of the sixth switching element Q6.

[0047] The voltage controller 125 can selectively apply control known in the corresponding technical field, for example, proportional control, integral control, differential control, and mixed control. In addition, the application of the inverter buffers 131 and 135, the selection of the input terminal of the comparator 129, and the selection of the input / output terminal of the D flip-flop 133 can be appropriately changed as needed, and thus some of the constituent elements can be omitted. The comparator 129 compares the current peak command (I peak,Ref ) with the current (i Llkg ) flowing through the primary side of the transformer 17. The comparator 129 generates a pulse waveform according to the comparison result. The D flip-flop 133 receives the pulse waveform output by the comparator 129 through a clock input and outputs the output of the second comparator 113 as it is at the rising edge or the falling edge of the pulse waveform, or inverts and then outputs the output.Figure 2 In the example, the D flip-flop 133 can be controlled through the inverting output terminal. Invert and output the output of the second comparator 113.

[0048] Figure 3 An example of one embodiment according to the present disclosure is shown, wherein the controller of the vehicle charger compares a reference voltage with a carrier signal and determines the duty cycle of a switching element based on the comparison.

[0049] refer to Figure 2 and Figure 3 When the reference voltage (V) of the corresponding switching element used to control pins P1 and P2 ref_P1 and V ref_P2 The voltage of the carrier signal is greater than the voltage of the carrier signal (V). carr1 When the reference voltage (V) is short-circuited, the upper switching elements Q1 and Q3 of the supports P1 and P2 are short-circuited by the HIGH signals output by the comparators 111 and 113 of the controller 100, respectively, and the lower switching elements Q2 and Q4 are disconnected by the LOW signals output by the inverting buffers 119 and 121, respectively. On the other hand, the reference voltage (V) ref_P1 and V ref_P2 When the voltage is less than that of the carrier signal, the upper switching elements Q1 and Q3 of the pins P1 and P2 are disconnected by the LOW signals output by the comparators 111 and 113 of the controller 100, respectively, and the lower switching elements Q2 and Q4 are short-circuited by the HIGH signals output by the inverting buffers 119 and 121, respectively.

[0050] Similarly, the third reference voltage (V) used to control the switching element of pin P3 can be... ref_P3 It is considered to be related to the second reference voltage (V) ref_P2 The same applies, and compared to the switching element of pin P2, its switching can be considered to be phase-shifted. Therefore, the reference voltage (V) ref_P3 ) and by using the carrier signal (V carr1 Phase shift The obtained carrier signal (V) carr2 The switching elements Q5 and Q6 are compared to determine whether they are on or off.

[0051] Considering that the phase-shifted full-bridge circuit operates with a duty cycle of 0.5, the second reference voltage (V) ref_P2 ) and the third reference voltage (V ref_P3 ) can be converted into the voltage (V) of the carrier signal. carr1 V carr2 Half of the peak value.

[0052] Due to the reference voltage (V) ref_P1The current is generated by using a command generated by the current command generator 105 and synchronized with the phase (θ) of the AC power input from the AC power source, so the controller 100 will have a current in the first pin P1 that is synchronized with the AC voltage (V). g Synchronous AC current form of reference voltage (V) ref_P1 ) and the voltage (V) of the carrier signal carr The comparison is performed, and the switch is driven with the AC switch duty cycle to control the boost inductor (L) in continuous conduction mode. B Current.

[0053] Furthermore, in the second pin P2, the controller 100 will have a DC-type reference voltage (V) of a predetermined amplitude. ref_P2 ) and the voltage (V) of the carrier signal carr The controller 100 compares the switching elements Q3 and Q4 with a duty cycle of 0.5, and drives them with a duty cycle of 0.5. In the third pin P3, the controller 100 is offset relative to the switching element in the third pin P3. The phase drive switching elements Q5 and Q6 are used. Therefore, the controller 100 controls the switching elements to operate as a phase-shift full-bridge converter.

[0054] In the second pin P2, the two switching elements Q3 and Q4 operate with a duty cycle of 0.5. Therefore, the average voltage at the node where the two switching elements Q3 and Q4 are connected corresponds to the voltage of capacitor 15 (V). PFC Half of the voltage at the node where the two switching elements Q1 and Q2 on the first pin P1 operate with an AC duty cycle, relative to the voltage of capacitor 15 (V). PFC Half of the AC input voltage (V) is similar to that of the AC input voltage. g )change.

[0055] As a result, the vehicle charger according to one embodiment of this disclosure has the voltage of capacitor 15, namely the power factor correction circuit voltage (V). PFC As shown in Equation 1. Regarding the final output voltage (V) O According to the operation of the phase-shift full-bridge converter, the output voltage can be related to V. PFC The voltage and turns ratio are generated proportionally, as shown in Equation 2.

[0056] [Equation 1]

[0057] V PFC >2*v g_max

[0058] [Equation 2]

[0059]

[0060] In equations 1 and 2, V PFCrepresents the voltage of the capacitor 15, v g_max represents the voltage peak of the AC power source, V O represents the output voltage of the vehicle charger, N p represents the number of turns of the primary coil 171 of the transformer 17, N s represents the number of turns of the secondary coil 172 of the transformer 17.

[0061] Figure 4 and Figure 5 shows the resonant current of the switching elements, the inductor current, and the open / short state in each region A and region B for one period of the carrier signal shown. Figure 3

[0062] As shown in Figure 4 and Figure 5 , as the first reference voltage (V ref_P1 ) changes, the duty ratio of the switching elements Q1 and Q2 of the first leg P1 changes, and the switching elements Q3 and Q4 of the second leg P2 and the switching elements Q5 and Q6 of the third leg P3 operate with a duty ratio of 0.5, with a phase difference therebetween. According to the short / open state of the switching elements Q1 to Q4, the supply voltage (v g ) of the AC power source and the voltage corresponding to the difference (V PFC -v g ) between the capacitor voltage (V PFC ) and the voltage (v g ) of the AC power source are alternately applied to the boost inductor 13, thereby generating a current ripple, and generating an inductor current (i LB ) in a continuous conduction mode (CCM). At the same time, the phase-shifted full-bridge converter is driven by the short / open of the switching elements Q3, Q4, Q5, and Q6 operating with a duty ratio of 0.5, and the primary-side current (i Llkg ) and the magnetizing current (i Lm ) are generated by the phase difference between the voltages (V carr1 and V carr2 ) of the two carrier signals. The primary-side current (i Llkg ) and the magnetizing current (i Lm ) transfer power to the secondary side of the transformer 17, thereby generating an output voltage (V O ) as shown in Equation 2.

[0063] In one embodiment of the present disclosure, with respect to the currents of the switching elements Q1 and Q2 of the first leg P1, the current (i LB ) of the boost inductor 13 flows according to the switching operation in Equation 3 below. In addition, the current (i LB ) of the boost inductor 13 and the primary-side current (i Llkg ​) flowing through the second leg P2 of the switching elements Q3 and Q4, the sum of which is shown in Equation 4 below. The primary-side current (i Llkg ) flowing through the third leg P3 of the switching elements Q5 and Q6, as shown in Equation 5 below.

[0064] [Equation 3]

[0065] i Q1 = i LB (when the switching element Q1 is turned on)

[0066] i Q2 = i LB (when the switching element Q2 is turned on)

[0067] [Equation 4]

[0068] i Q3 = i LB + i Llkg (when the switching element Q3 is turned on)

[0069] i Q4 = i LB + i Llkg (when the switching element Q4 is turned on)

[0070] [Equation 5]

[0071] i Q5 = i Llkg (when the switching element Q5 is turned on)

[0072] i Q6 = i Llkg (when the switching element Q6 is turned on)

[0073] In Equations 3 to 5, i Q1 to i Q6 denote currents flowing through the switching elements Q1 to Q6, respectively.

[0074] As described above, in various embodiments of the disclosure, by integrating a power factor correction circuit and a phase-shift full-bridge DC-DC converter required for a vehicle charger to reduce switches and driving circuits, the vehicle charger can have high price competitiveness and can achieve high power density through its simple structure. In particular, in various embodiments of the disclosure, since six switches are simultaneously controlled to operate a continuous conduction mode boost power factor correction circuit and a phase-shift full-bridge converter, the vehicle charger can improve output and can expand an input / output voltage range.

[0075] The present disclosure has been made only by referring to specific embodiments. However, it will be apparent to those skilled in the art that various modifications and changes can be made within the technical idea of the present disclosure provided by the appended claims.

Claims

1. A vehicle charger comprising: an inductor having a first end connected to a first end of an alternating current power supply; a first leg including a first switching element and a second switching element connected in series to each other, wherein connection terminals of the first switching element and the second switching element are connected to a second end of the inductor; a capacitor connected in parallel to the first leg; a second leg including a third switching element and a fourth switching element connected in series to each other between both ends of the capacitor, wherein connection terminals of the third switching element and the fourth switching element are connected to a second end of the alternating current power supply; a transformer having a primary coil and a secondary coil, a first end of the primary coil being connected to the connection terminals of the third switching element and the fourth switching element, and the secondary coil being electromagnetically coupled to the primary coil; a third leg including a fifth switching element and a sixth switching element connected in series to each other between both ends of the capacitor, wherein connection terminals of the fifth switching element and the sixth switching element are connected to a second end of the primary coil; and a controller configured to control the first switching element and the second switching element so as to regulate a voltage of the capacitor, and the controller is configured to control the third switching element and the fourth switching element so as to convert a voltage amplitude of the capacitor; wherein the controller generates a detected voltage of the capacitor and a first reference voltage for subjecting the detected voltage of the capacitor to an external input voltage command of the capacitor, and the first reference voltage has a form of an alternating current synchronized with an alternating current of the alternating current power supply.

2. The vehicle charger of claim 1, wherein, To regulate the voltage of the capacitor, the controller is further configured to: determine a duty ratio of the first switching element and the second switching element included in the first leg to control turn-on / off of the first switching element and the second switching element, control turn-on / off of the third switching element and the fourth switching element included in the second leg by using a switching frequency synchronized with a switching frequency of the first switching element and the second switching element included in the first leg, and control turn-on / off of the fifth switching element and the sixth switching element included in the third leg so that there is a phase difference between the fifth switching element and the sixth switching element compared to the third switching element and the fourth switching element included in the second leg.

3. The vehicle charger of claim 1, wherein, the controller compares the first reference voltage with a carrier signal of a triangular waveform voltage having a predetermined period to determine a duty ratio of the first switching element and the second switching element, and the first switching element and the second switching element operate complementarily to each other.

4. The vehicle charger of claim 3, wherein, the controller compares the carrier signal with a second reference voltage to determine a duty ratio of the third switching element and the fourth switching element, an amplitude of the second reference voltage corresponding to half of a peak value of the carrier signal, and the third switching element and the fourth switching element operate complementarily to each other. the controller compares the first reference voltage with a carrier signal of a triangular waveform voltage having a predetermined period to determine a duty ratio of the first switching element and the second switching element, and the first switching element and the second switching element operate complementarily to each other. the controller compares the carrier signal with a second reference voltage to determine a duty ratio of the third switching element and the fourth switching element, an amplitude of the second reference voltage corresponding to half of a peak value of the carrier signal, and the third switching element and the fourth switching element operate complementarily to each other.

5. The vehicle charger of claim 4, wherein, The controller determines a phase difference for making an output voltage of the vehicle charger comply with a predetermined output voltage command, and controls the fifth and sixth switching elements to be delayed from the third and fourth switching elements by the phase difference, respectively.

6. The vehicle charger of claim 1, wherein, The controller includes: a first subtractor configured to determine a first error between a detected voltage of the capacitor and an external input voltage command of the capacitor; a first voltage controller configured to generate a direct-current voltage control value for reducing the first error; a current command generator configured to generate a current command by multiplying the direct-current voltage control value determined by the first voltage controller by a phase component for synchronization with the alternating-current power source; a second subtractor configured to determine a second error between the current command and a detected current of the inductor; a current controller configured to determine a first reference voltage for determining duty ratios of the first and second switching elements of the first leg so as to reduce the second error, and the first reference voltage has a form of an alternating-current current synchronized with an alternating-current current of the alternating-current power source; a triangular wave generator configured to generate a carrier signal that is a triangular waveform voltage having a predetermined period; a direct-current voltage source configured to generate a second reference voltage that is a predetermined direct-current voltage having an amplitude corresponding to half of a peak value of the carrier signal; a first comparator configured to compare the amplitude of the first reference voltage with the amplitude of the carrier signal, determine duty ratios of the first and second switching elements, and output the determined duty ratios as control signals for the first and second switching elements; a second comparator configured to compare the amplitude of the second reference voltage with the amplitude of the carrier signal, determine duty ratios of the third and fourth switching elements, and output the determined duty ratios as control signals for the third and fourth switching elements; a third subtractor configured to determine a third error between an output voltage of the vehicle charger and a predetermined output voltage command; a second voltage controller configured to generate a current peak value command for reducing the third error; a third comparator configured to output a comparison result between a peak value of a primary side current of the transformer and the current peak value command; and a D flip-flop configured to delay an output of the second comparator based on an output of the third comparator, and output the output of the second comparator as control signals for the fifth and sixth switching elements. 7.The vehicle charger of claim 1, further comprising a rectifier connected to a secondary coil of the transformer, and configured to rectify power induced by the secondary coil, and output the rectified power to a device to be charged. 8.A method for controlling the vehicle charger of claim 1, the method comprising the steps of: generating a detection voltage of a capacitor and a first reference voltage for subjecting the detection voltage of the capacitor to an external input voltage command of the capacitor; generating a second reference voltage that is a direct-current voltage having a predetermined amplitude; comparing the first reference voltage with a carrier signal of a triangular waveform voltage having a predetermined period, and determining duty ratios of the first switching element and the second switching element that are turned off / short-circuited complementarily to each other; comparing the second reference voltage with the carrier signal, and determining on / off states of the third switching element and the fourth switching element that are turned off / short-circuited complementarily to each other; and determining a phase difference for subjecting an output voltage of the vehicle charger to a predetermined output voltage command, delaying the on / off states of the third switching element and the fourth switching element by the phase difference, and determining on / off states of the fifth switching element and the sixth switching element.

9. The method of claim 8, wherein, The first reference voltage has a form of an alternating-current current synchronized with an alternating-current current of the alternating-current power supply.

10. The method of claim 8, wherein, The second reference voltage is a direct-current voltage having an amplitude corresponding to half of a peak value of the carrier signal.

11. The method of claim 8, wherein, The generating of the first reference voltage includes the following steps: an operation of determining a first error between the detection voltage of the capacitor and the external input voltage command of the capacitor; a voltage control operation of generating a direct-current voltage control value for reducing the first error; a current command generation operation of generating an alternating-current current command by multiplying the direct-current voltage control value determined in the voltage control operation by a phase component for synchronization with the alternating-current power supply; an operation of determining a second error between the alternating-current current command and a detection current of the inductor; and a current control operation of determining the first reference voltage having a form of an alternating-current current synchronized with an alternating-current current of the alternating-current power supply so as to reduce the second error.

12. The method of claim 8, wherein, In determining the on / off states of the fifth switching element and the sixth switching element with respect to a third error between the output voltage of the vehicle charger and the predetermined output voltage command, an output of a second comparator is delayed based on a comparison result between a current peak value command for reducing the third error and a current peak value of a primary side of the transformer, and the output of the second comparator is output as a control signal for the fifth switching element and the sixth switching element.

Images