Apparatus and method for charging vehicle batteries

Abstract

This invention relates to an apparatus and method for charging a vehicle battery. The apparatus for charging a vehicle battery includes: a power factor correction (PFC) circuit, the PFC comprising: a rectifier for rectifying AC power to DC power; a link capacitor for smoothing the rectified DC power; a bidirectional DC-DC converter including: a first switch for converting DC power from the PFC circuit to AC power; a transformer for boosting or bucking the voltage of the AC power converted by the first switch; a second switch for rectifying AC power from the transformer to DC power; and a controller configured to: before entering a battery charging mode, when the voltage of the link capacitor is lower than a predetermined reference voltage, control the phase of a PWM signal applied to the second switch such that the link capacitor is charged by power from the battery.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2020-0073830, filed on June 17, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to an apparatus and method for charging a vehicle battery. Background Technology

[0004] Recently, due to global warming caused by environmental pollution and the depletion of fossil fuels, the automotive industry is rapidly developing electric vehicles. Major automakers around the world are currently researching and developing electric vehicles as their primary mode of transportation.

[0005] Electric vehicles (EVs) can be powered by accumulating electrical energy in a battery that serves as a rechargeable battery and then converting that accumulated energy into kinetic energy using a motor. Methods for accumulating electrical energy in the battery can be categorized into fast charging and slow charging schemes. In a fast charging scheme, high-voltage DC power (e.g., approximately 50 kW or higher) is applied directly to the battery. In a slow charging scheme, AC power with a commercial AC voltage (e.g., approximately 3-6 kW) is applied to the battery.

[0006] Regarding slow charging solutions, on-board chargers (OBCs) can be damaged by inrush current (IR), and a pre-charge relay is typically located at the input terminal to avoid this possibility. That is, by switching the pre-charge relay, the link capacitor is charged via an external power source before charging the battery through the driving DC-DC converter. This reduces the occurrence of inrush current (IR) when the OBC is connected to an external power source.

[0007] Meanwhile, the pre-charge relays used for the initial charging of the link capacitors have the disadvantage of being relatively large, requiring a design that ensures durability, especially in three-phase input scenarios where more than three pre-charge relays are needed. Furthermore, conventional pre-charge relays may experience a decrease in durability due to continuous on / off operations.

[0008] Therefore, a new solution is needed to charge the link capacitor while addressing the problem of the pre-charge relay.

[0009] The above information disclosed in this Background section is only for understanding of the background of the present application and, therefore, it can contain information that does not constitute prior art that is already known in this country to those who have skill in the art. SUMMARY

[0010] An exemplary apparatus for charging a battery of a vehicle includes: a PFC circuit portion including: a rectifier portion configured to rectify alternating current applied from a commercial alternating current power source into direct current in a battery charging mode in which the battery of the vehicle is charged; and a link capacitor connected in parallel to the rectifier portion to smooth the rectified direct current; a bidirectional DC-DC converter including: a first switch portion configured to convert the direct current applied from the PFC circuit portion into alternating current; a transformer configured to step up or step down a voltage of the alternating current converted in the first switch portion; and a second switch portion configured to rectify the alternating current applied from the transformer into direct current to charge the battery of the vehicle; and a controller configured to: before entering the battery charging mode, when a voltage of the link capacitor is lower than a predetermined reference voltage, control a phase of a PWM signal applied to the second switch portion so that the link capacitor is charged with power discharged from the battery of the vehicle.

[0011] The second switch portion can include a first MOSFET and a second MOSFET connected in series between a first electrode and a second electrode of the battery of the vehicle, and a third MOSFET and a fourth MOSFET connected in series between a first terminal of the first MOSFET and a second terminal of the second MOSFET. A first terminal of a primary coil of the transformer can be connected to a first node between the first MOSFET and the second MOSFET; and a second terminal of the primary coil can be connected to a second node between the third MOSFET and the fourth MOSFET.

[0012] The controller can be configured to: calculate a magnitude of a charging current to be applied to the link capacitor in order to charge the link capacitor to be higher than or equal to the reference voltage; and shift phases of a third PWM signal for controlling the third MOSFET switch and a fourth PWM signal for controlling the fourth MOSFET switch so that a voltage corresponding to the calculated charging current is applied to the transformer.

[0013] The controller can be configured to: calculate an increment of the charging current per unit time; and shift the phases of the third PWM signal and the fourth PWM signal so that a voltage corresponding to the calculated increment of the charging current is applied to the transformer.

[0014] The controller can control the first, second, third, and fourth PWM signals such that, when the first and third MOSFET are turned on, the second and fourth MOSFET are turned off, and when the first and third MOSFET are turned off, the second and fourth MOSFET are turned on, when the voltage of the link capacitor is charged to be higher than or equal to a predetermined reference voltage. The power applied from the commercial AC power source can be applied to the battery of the vehicle via a charging path including the PFC circuit portion, the first switching portion, the transformer, and the body diodes of the first to fourth MOSFETs.

[0015] An example method of charging a battery of a vehicle using a bidirectional DC-DC converter includes a first switching portion connected to an output terminal of a PFC circuit portion for rectifying AC power of a commercial AC power source to DC power and configured to convert the DC power to AC power, a transformer configured to step up or step down a voltage of the AC power converted in the first switching portion, and a second switching portion configured to rectify the AC power applied from the transformer to DC power to charge the battery of the vehicle. The example method includes sensing a voltage of a link capacitor connected in parallel to the output terminal of the PFC circuit portion in synchronization with a time point of entering a charging mode for charging the battery of the vehicle, determining whether the sensed voltage of the link capacitor is lower than a predetermined reference voltage, charging the link capacitor using power discharged from the battery of the vehicle by controlling a phase of a PWM signal applied to the second switching portion when the sensed voltage of the link capacitor is lower than the predetermined reference voltage, and charging the battery of the vehicle using power applied from the commercial AC power source when the voltage of the link capacitor is charged to be higher than or equal to the predetermined reference voltage.

[0016] The second switching portion can include first and second MOSFETs connected in series between a first electrode and a second electrode of the battery of the vehicle, and third and fourth MOSFETs connected in series between a first terminal of the first MOSFET and a second terminal of the second MOSFET. A first terminal of a primary coil of the transformer can be connected to a first node between the first and second MOSFETs, and a second terminal of the primary coil can be connected to a second node between the third and fourth MOSFETs.

[0017] The charging the link capacitor can include calculating a magnitude of a charging current to be applied to the link capacitor in order to charge the link capacitor to be higher than or equal to a reference voltage, and shifting phases of a third PWM signal for controlling the third MOSFET switch and a fourth PWM signal for controlling the fourth MOSFET switch so that a voltage corresponding to the calculated charging current is applied to the transformer to charge the link capacitor.

[0018] In calculating the magnitude of the charging current, an increment of the charging current per unit time can be calculated. In charging the link capacitor, the phases of the third PWM signal and the fourth PWM signal can be shifted so that a voltage corresponding to the calculated increment of the charging current is applied to the transformer to charge the link capacitor.

[0019] In charging the battery of the vehicle, when the voltage of the link capacitor is charged to be higher than or equal to the reference voltage, the first to fourth PWM signals can be controlled so that the second and fourth MOSFETs are turned off when the first and third MOSFETs are turned on, and the second and fourth MOSFETs are turned on when the first and third MOSFETs are turned off.

[0020] The power applied from the commercial alternating current power source can be applied to the battery of the vehicle via a charging path including a PFC circuit portion, a first switching portion, a transformer, and body diodes of the first to fourth MOSFETs.

[0021] According to an exemplary embodiment, an inrush current (IR) can be prevented by initially charging the link capacitor without using a conventional pre-charge relay for charging the link capacitor, thereby simplifying the circuit without an additional design for control of the pre-charge relay. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 A block diagram of an apparatus for charging a battery of a vehicle according to an exemplary embodiment is shown.

[0023] Figure 2 A circuit diagram of an apparatus for charging a battery of a vehicle in Figure 1

[0024] Figure 3 A flowchart of a method for charging a battery of a vehicle according to an exemplary embodiment is shown.

[0025] Figures 4 to 7A , Figure 7B , Figure 7C First to fourth PWM signals applied to a second switching portion of a power supply apparatus 100 and transformer voltages according to the PWM signals are shown, respectively. Figure 2 First to fourth PWM signals applied to a second switching portion of a power supply apparatus 100 and transformer voltages according to the PWM signals are shown, respectively.​

[0026] Figure 8 A voltage variation of a link capacitor which is initially charged by the released power of a battery of a vehicle according to an exemplary embodiment is shown compared to the prior art.

[0027] Figure 9A and Figure 9B Exemplary diagrams to show voltage and current variations of a link capacitor with and without initial charging of the link capacitor. DETAILED DESCRIPTION

[0028] A battery of a vehicle is a power source of an electric vehicle (EV), and can be implemented as a rechargeable battery (e.g., typically a lithium ion battery) capable of repeatedly charging and discharging electric energy. Here, the electric vehicle can include any kind of vehicle including a battery that can store electric energy for driving the vehicle, such as a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc. For example, the battery of the vehicle is configured by stacking battery cells in series therein, and can have an internal voltage in the range of about 240V to 413V according to a state of charge.

[0029] In order to charge the battery of the vehicle, a fast charging scheme for charging the battery by directly applying high voltage DC power can be efficient. However, at present, infrastructure for the fast charging scheme has not been sufficiently built, and thus, a scheme for charging the vehicle using a commercial AC voltage of a home is also used. For this purpose, the electric vehicle can include an on-board charger (OBC) that rectifies an AC voltage (or current) to a DC voltage (or current), and steps up or steps down the DC voltage (or current) to charge the battery of the vehicle.

[0030] Hereinafter, exemplary embodiments disclosed in the present specification will be described in detail with reference to the accompanying drawings. In the present specification, the same or similar components will be denoted by the same or similar reference numerals, and repetitive description thereof will be omitted. The terms "module" and / or "unit" of a component used in the following description are only for the convenience of describing the present specification. Therefore, these terms do not have a meaning or role that distinguishes them from each other. In describing the exemplary embodiments of the present specification, when it is determined that a detailed description of the well-known technology associated with the present invention can obscure the gist of the present invention, it will be omitted. The accompanying drawings are provided only to facilitate understanding of the exemplary embodiments disclosed in the present specification, and should not be interpreted as limiting the spirit disclosed in the present specification, and it should be understood that the present invention includes all modifications, equivalents, and substitutions without departing from the scope and spirit of the present invention.

[0031] Terms including ordinal numbers (e.g., first, second, etc.) will be used only to describe various components, and should not be construed to limit the components. The terms are used only to distinguish one component from another component.

[0032] It should be understood that when a component is referred to as being "connected" or "coupled" to another component, it can be directly connected or coupled to the other component, or can be connected or coupled to the other component through another component interposed therebetween. Also, it should be understood that when a component is referred to as being "directly connected" or "directly coupled" to another component, it can be directly connected or coupled to the other component without other components interposed therebetween.

[0033] It should be further understood that the terms "comprise" and "have", used in the present specification, designate the presence of the stated features, numbers, steps, operations, components, parts, or combinations thereof, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0034] Figure 1 A block diagram of an apparatus for charging a battery of a vehicle according to an exemplary embodiment is shown.

[0035] Reference Figure 1 The apparatus 1 for charging a battery of a vehicle includes a power factor correction (PFC) circuit portion 100, a bidirectional DC-DC converter 200, and a controller 300. The apparatus 1 for charging a battery of a vehicle can include a bidirectional on-board charger (OBC) that charges a battery BT of a vehicle by an input power source (e.g., a commercial alternating current power source AC) and supplies power discharged from the battery BT of the vehicle to an electrical load. Figure 1 A link capacitor C link is used as an element separate from the PFC circuit portion 100, but is not limited thereto. The link capacitor C link may be included in the PFC circuit portion 100.

[0036] A commercial alternating current power source AC is connected to an input terminal of the PFC circuit portion 100, and the bidirectional DC-DC converter 200 is connected to an output terminal of the PFC circuit portion 100. In a battery charging mode for slow charging of the battery BT of the vehicle, the PFC circuit portion 100 rectifies AC power applied from the commercial alternating current power source AC to DC power, and transmits the DC power to the bidirectional DC-DC converter 200.

[0037] The PFC circuit portion 100 is a power factor correction circuit, and can play a role in reducing power loss in the process of converting AC power to DC power.

[0038] According to an exemplary embodiment, the PFC circuit portion 100 can include a link capacitor C link When the link capacitor C link is charged to a predetermined reference voltage V ref before entering the battery charging mode, an inrush current (IR) immediately after entering the battery charging mode can be prevented. The inrush current (IR) can cause degradation, performance degradation, defects, etc. of other devices.

[0039] The commercial alternating current power source AC can be a single-phase alternating current power source that can be used for homes or businesses. In Korea, the commercial voltage is generally single-phase AC 220V, and the voltage used can vary between countries but is in the range of 85V to 265V. In addition, the frequency is generally 60Hz, but can also be 50Hz. Alternating current is generated by such a commercial alternating current power source AC, and power of about 3kW to 6kW can be supplied to the battery BT for a vehicle. For example, the commercial alternating current power source AC can be electric vehicle supply equipment (EVSE).

[0040] The battery BT for a vehicle is a power source of an electric vehicle (EV), and can be implemented as a rechargeable battery, for example, a lithium ion battery that can repeatedly charge and discharge electric power. The battery BT for a vehicle includes a plurality of batteries connected in series or in parallel, and can be a high-voltage battery in the range of about 240V to 413V according to a state of charge.

[0041] In a battery charging mode for charging the battery BT for a vehicle by the commercial alternating current power source AC, the bidirectional DC-DC converter 200 steps up or steps down the voltage of the DC power output from the PFC circuit portion 100 to charge the battery BT for a vehicle. The bidirectional DC-DC converter 200 can charge the battery BT for a vehicle at an appropriate charging voltage (for example, a voltage in the range of about 240V to 413V) of the battery BT for a vehicle.

[0042] In a battery discharging mode for supplying power discharged from the battery BT for a vehicle to a load, the bidirectional DC-DC converter 200 can step up or step down the power discharged from the battery BT for a vehicle, and supply the stepped-up or stepped-down voltage to the PFC circuit portion 100.

[0043] According to an exemplary embodiment, before entering the battery charging mode, when the voltage of the link capacitor C link parallel-connected between the output terminal of the PFC circuit portion 100 and the input terminal of the bidirectional DC-DC converter 200 is lower than a reference voltage V refAt that time, the bidirectional DC-DC converter 200, under the control of the controller 300, can utilize the power released from the vehicle's battery BT to power the link capacitor C. link Perform the initial charge.

[0044] Typically, devices for charging vehicle batteries utilize a pre-charge relay (not shown) located at the input terminal to charge the link capacitor C using power applied from a commercial AC power source. link Initial charging prevents inrush current (IR). However, space is required in the circuit for the pre-charge relay, and problems exist such as reduced durability due to continuous on / off operations. According to an exemplary embodiment, device 1 for charging a vehicle battery can charge the link capacitor C via a bidirectional DC-DC converter 200. link The initial charge does not include this pre-charge relay.

[0045] According to an exemplary embodiment, when the device 1 for charging the vehicle's battery is connected to a commercial AC power source (e.g., an Electric Vehicle Supply Equipment (EVSE)), the controller 300 determines the link capacitance C before charging the vehicle's battery BT. link Is the voltage lower than the reference voltage V? ref When the link capacitance C link The voltage is lower than the reference voltage V. ref At that time, the controller 300 first controls the bidirectional DC-DC converter 200, causing the link capacitor C to... link Charge to reference voltage V ref That's all. When the link capacitance C... link The voltage becomes the reference voltage V ref At this time, the controller 300 uses power applied from commercial AC power supply to charge the vehicle's battery BT.

[0046] Figure 2 for Figure 1 The circuit diagram of the device used to charge the vehicle's battery.

[0047] refer to Figure 2 The PFC circuit section 100 may include a rectifier section 110 and a link capacitor section 120. In battery charging mode, the rectifier section 110 rectifies the AC power applied from a commercial AC power source into DC power. The link capacitor section 120 includes a link capacitor C. link The link capacitance C link The rectified DC current rectified by the rectifier section 110 is smoothed. Link capacitor section 120 (more specifically, link capacitor C) link It is connected in parallel between the output terminal of the PFC circuit section 100 and the bidirectional DC-DC converter 200.

[0048] The bidirectional DC-DC converter 200 includes a first switching section 210, a transformer 220, and a second switching section 230.

[0049] In the battery charging mode, the first switching section 210 converts DC power applied from the PFC circuit section 100 into AC power. Under the control of the controller 300, the first switching section 210 controls the direction of power transmission between the battery BT of the vehicle and the link capacitor C link and the current magnitude of the output current of the battery BT of the vehicle.

[0050] The first switching section 210 includes a fifth MOSFET Q5, a sixth MOSFET Q6, a seventh MOSFET Q7, and an eighth MOSFET Q8. Each of the fifth to eighth MOSFETs Q5, Q6, Q7, and Q8 can include a body diode.

[0051] The fifth MOSFET Q5 and the sixth MOSFET Q6 are connected in series between the first terminal and the second terminal of the link capacitor C link . The seventh MOSFET Q7 and the eighth MOSFET Q8 are connected in series between the first terminal of the fifth MOSFET Q5 and the second terminal of the sixth MOSFET Q6. At this time, the first terminal of the secondary coil 222 of the transformer 220 is connected to a third node C between the fifth MOSFET Q5 and the sixth MOSFET Q6, and the second terminal of the secondary coil 222 is connected to a fourth node D between the seventh MOSFET Q7 and the eighth MOSFET Q8.

[0052] The transformer 220 steps up or steps down the voltage in the battery charging mode and / or the battery discharging mode. The transformer 220 includes a primary coil 221 and a secondary coil 222.

[0053] For example, when charging the link capacitor C link , the transformer 220 steps up or steps down the voltage of the AC power applied via the second switching section 230 and transmits the stepped-up or stepped-down voltage to the first switching section 210. In another example, when charging the battery BT of the vehicle, the transformer 220 steps up or steps down the voltage of the AC power applied via the first switching section 210 and transmits the stepped-up or stepped-down voltage to the second switching section 230.

[0054] In the battery charging mode, the second switching section 230 rectifies the AC power applied from the transformer 220 into DC power to charge the battery BT of the vehicle. Under the control of the controller 300, the second switching section 230 controls the direction of power transmission between the battery BT of the vehicle and the link capacitor C link and the application of the link capacitor Clink a charging current I link a current magnitude.

[0055] The second switching part 230 can include a first MOSFET Q1, a second MOSFET Q2, a third MOSFET Q3, and a fourth MOSFET Q4. Each of the first to fourth MOSFETs Q1, Q2, Q3, and Q4 can include a body diode.

[0056] In general, a unidirectional DC-DC converter includes unidirectional diodes at positions corresponding to the first to fourth MOSFETs Q1, Q2, Q3, and Q4, and can perform only a function of charging the battery BT of the vehicle. However, the second switching part 230 according to an exemplary embodiment includes the first to fourth MOSFETs Q1, Q2, Q3, and Q4 each including a body diode, and can function as a bidirectional DC-DC converter. That is, under the control of the second switching part 230, the battery BT of the vehicle can be charged, or power discharged from the battery BT of the vehicle can be supplied to the link capacitor C link or an electrical load.

[0057] The first MOSFET Q1 and the second MOSFET Q2 are connected in series between a first electrode (+) and a second electrode (-) of the battery of the vehicle. The third MOSFET Q3 and the fourth MOSFET Q4 are connected in series between a first terminal of the first MOSFET Q1 and a second terminal of the second MOSFET Q2. A first terminal of the primary coil 221 of the transformer 220 is connected to a first node A between the first MOSFET Q1 and the second MOSFET Q2, and a second terminal of the primary coil 221 is connected to a second node B between the third MOSFET Q3 and the fourth MOSFET Q4.

[0058] That is, the drain terminal of the first MOSFET Q1 is connected to the first electrode (+) of the battery BT of the vehicle, and the source terminal of the first MOSFET Q1 is connected in series with the drain terminal of the second MOSFET Q2. The first terminal of the primary coil 221 is connected to a first node A between the source terminal of the first MOSFET Q1 and the drain terminal of the second MOSFET Q2, and the source terminal of the second MOSFET Q2 is connected to the second electrode (-) of the battery of the vehicle. In addition, the drain terminal of the third MOSFET Q3 is connected to the first electrode (+) of the battery of the vehicle, and the source terminal of the third MOSFET Q3 is connected in series with the drain terminal of the fourth MOSFET Q4. The second terminal of the primary coil 221 is connected to a second node B between the source terminal of the third MOSFET Q3 and the drain terminal of the fourth MOSFET Q4, and the source terminal of the fourth MOSFET Q4 is connected to the second electrode (-) of the battery of the vehicle.

[0059] In the battery charging mode, in the first switch section 210, when the fifth MOSFET Q5 and the eighth MOSFET Q8 are turned on, the sixth MOSFET Q6 and the seventh MOSFET Q7 are turned off, and when the fifth MOSFET Q5 and the eighth MOSFET Q8 are turned off, the sixth MOSFET Q6 and the seventh MOSFET Q7 are turned on. Thereby, the DC power applied from the PFC circuit section 100 is converted to AC power. At this time, the first to fourth MOSFETs Q1, Q2, Q3, and Q4 included in the second switch section 230 are turned off. The AC power converted in the first switch section 210 is applied to the output terminal capacitor C obc charging. Thereafter, the power charged in the output terminal capacitor C obc is discharged to charge the battery BT of the vehicle.

[0060] In the battery discharging mode, in the second switch section 230, when the first MOSFET Q1 and the fourth MOSFET Q4 are turned on, the second MOSFET Q2 and the third MOSFET Q3 are turned off, and when the first MOSFET Q1 and the fourth MOSFET Q4 are turned off, the second MOSFET Q2 and the third MOSFET Q3 are turned on. Thereby, the DC power discharged from the battery BT of the vehicle is converted to AC power. At this time, the fifth to eighth MOSFETs Q5, Q6, Q7, and Q8 in the first switch section 210 are turned off. The AC power converted in the second switch section 230 is applied to the link capacitor C through a discharging path including the transformer 220 and the body diodes of the fifth to eighth MOSFETs Q5, Q6, Q7, and Q8.link Thereafter, the power charged can be discharged to be applied to the commercial alternating current power source AC via the PFC circuit portion 100. link The power charged can be discharged to be applied to the commercial alternating current power source AC via the PFC circuit portion 100.

[0061] According to an exemplary embodiment, before entering the battery charging mode, when the voltage V link of the link capacitor C link is lower than the reference voltage V ref , the device 1 for charging a battery of a vehicle can charge the voltage V link of the link capacitor C link to be higher than the reference voltage V ref by the power discharged from the battery BT of the vehicle. That is, after the voltage V link of the link capacitor C link is charged to be higher than the reference voltage V ref , the device 1 for charging a battery of a vehicle can charge the battery BT of the vehicle using the power applied from the commercial alternating current power source AC.

[0062] According to an exemplary embodiment, the first switch portion 210 and the second switch portion 230 can form a full-bridge converter and can be controlled in a phase-shift control scheme. For example, in the battery charging mode, the first switch portion 210 can control the phases of the seventh MOSFET Q7 and the eighth MOSFET Q8, so that the time periods in which the fifth MOSFET Q5 and the eighth MOSFET Q8 are simultaneously turned on to allow current to flow and the time periods in which the sixth MOSFET Q6 and the seventh MOSFET Q7 are simultaneously turned on to allow current to flow can be adjusted. At this time, as the time periods in which they are simultaneously turned on increase, the size of the charging current transmitted to the transformer 220 can increase. In another example, in the battery discharging mode or when charging the link capacitor C link , the second switch portion 230 can control the phases of the third MOSFET Q3 and the fourth MOSFET Q4, so that the time periods in which the first MOSFET Q1 and the fourth MOSFET Q4 are simultaneously turned on to allow current to flow and the time periods in which the second MOSFET Q2 and the third MOSFET Q3 are simultaneously turned on to allow current to flow can be adjusted. At this time, as the time periods in which they are simultaneously turned on increase, the size of the discharging current transmitted to the transformer 220 can increase.

[0063] Figure 3 A flowchart of a method for charging a battery of a vehicle according to an exemplary embodiment is shown. Figures 4 to 7A 、 Figure 7B 、 Figure 7C First to fourth PWM signals applied to the second switch portion of the transformer 220 and the transformer voltage according to the PWM signals are shown, respectively. Figure 2 First to fourth PWM signals applied to the second switch portion of the transformer 220 and the transformer voltage according to the PWM signals are shown, respectively.Figure 8 A voltage variation of a link capacitor which is initially charged with the discharged power of the battery of the vehicle according to the exemplary embodiment is shown in comparison with the prior art.

[0064] Hereinafter, a description will be given of a device for charging a battery of a vehicle and a method for charging a battery of a vehicle according to exemplary embodiments with reference to the accompanying drawings. Figures 2 to 8 A device for charging a battery of a vehicle and a method for charging a battery of a vehicle according to exemplary embodiments will be described in detail.

[0065] First, in step S10, the vehicle is connected to an electric vehicle supply equipment (EVSE). At this time, in step S20, in synchronization with the time point of entering a battery charging mode for charging the battery BT of the vehicle, the controller 300 senses the voltage V link of the link capacitor C link connected in parallel between the output terminal of the PFC circuit portion 100 and the input terminal of the bidirectional DC-DC converter 200.

[0066] That is, when a connection signal is received from a sensor (not shown) which senses connection to a commercial alternating current power source AC (for example, an electric vehicle supply equipment (EVSE)), the controller 300 can check the state of charge of the link capacitor C link .

[0067] Subsequently, in step S30, the controller 300 determines whether the voltage V link of the link capacitor C link is higher than or equal to a reference voltage V ref .

[0068] That is, when the electric vehicle supply equipment (EVSE) and the device for charging a battery of a vehicle 1 are physically connected to each other, before charging the battery BT of the vehicle, the controller 300 determines whether the voltage V link of the link capacitor C link is higher than or equal to a reference voltage V ref .

[0069] Subsequently, in step S40, when the voltage V link of the link capacitor C link is lower than the reference voltage V ref (S30-No), the controller 300 initially charges the link capacitor C link with the power discharged from the battery BT of the vehicle.

[0070] When the voltage V link of the link capacitor C link is lower than the reference voltage V refWhen the device 1 used to charge the vehicle's battery is electrically connected to a commercial AC power source to receive power, due to the link capacitance C... link voltage V link and charging current I link The rapid increase in [something] may cause damage to other components.

[0071] According to an exemplary embodiment, under the control of the controller 300, the DC power released from the vehicle's battery BT is converted into AC power by the second switching section 230 of the bidirectional DC-DC converter 200, and the converted AC power is applied to the link capacitor C via the transformer 220 and the body diode of the first switching section 210. link Subsequently, when the link capacitor C... link voltage V link Charge to reference voltage V ref After the above, when the device 1 used to charge the vehicle's battery is electrically connected to the electric vehicle power supply equipment (EVSE), surge current (IR) can be prevented, thereby reducing the possibility of damage to other components.

[0072] During step S40, first in step S41, the controller 300 calculates the amount to be applied to the link capacitance C. link Charging current I link The size and charging current I per unit time link The increment ΔI is used to reduce the link capacitance C. link voltage V link Charge to reference voltage V ref above.

[0073] For example, controller 300 can calculate the amount to be applied to the link capacitance C. link Charging current I link The value is 3A, so that the link capacitor C link Charge to the reference voltage V ref voltage V link Furthermore, the charging current I per unit time can be calculated. link The increment ΔI is 0.1A. That is, the controller 300 controls the charging current I. link The values ​​increase sequentially from 0A to 3A, that is, in the order of 0.1A, 0.2A, 0.3A, ..., 2.9A, 3A.

[0074] Subsequently, in step S42, the controller 300 controls the first PWM signal to the eighth PWM signal applied to the bidirectional DC-DC converter 200, thereby controlling the calculated charging current I. link For link capacitance C link Charge.

[0075] In battery discharge mode, in the second switching section 230, when the first MOSFET Q1 and the fourth MOSFET Q4 are turned on, the second MOSFET Q2 and the third MOSFET Q3 are turned off; when the first MOSFET Q1 and the fourth MOSFET Q4 are turned off, the second MOSFET Q2 and the third MOSFET Q3 are turned on. This converts the DC power released from the vehicle's battery BT into AC power. At this time, the fifth to eighth MOSFETs Q5, Q6, Q7, and Q8 in the first switching section 210 are turned off. The converted AC power from the second switching section 230 can be applied to the link capacitor C via a discharge path including the transformer 220 and the fifth to eighth body diodes. link The fifth through eighth body diodes can be connected in parallel with the fifth through eighth MOSFETs Q5, Q6, Q7, and Q8, respectively.

[0076] For example, suppose that in the link capacitance C link voltage V link Higher than or equal to the reference voltage V ref Under the premise of entering the battery charging mode, the controller 300 can first set the first PWM signal to the fourth PWM signal so that power is applied through the charging path.

[0077] refer to Figure 4 The controller 300 can set the first PWM signal to the fourth PWM signal such that the first PWM signal and the third PWM signal have the same 50% duty cycle and the same phase, and the second PWM signal and the fourth PWM signal have the same 50% duty cycle and a 180-degree phase difference compared to the first PWM signal and the third PWM signal, so that the power of the vehicle's battery BT is not applied to the transformer 220 via a discharge path that is the opposite direction to the charging path. That is, the voltage V of the AC power applied from the second switch section 230 to the transformer 220 TF It can be 0V.

[0078] More specifically, in the Figure 4 When the first to fourth PWM signals are applied to the first to fourth MOSFETs Q1, Q2, Q3, and Q4 respectively, the second MOSFET Q2 and the fourth MOSFET Q4 are turned off when the first MOSFET Q1 and the third MOSFET Q3 are turned on, and the second MOSFET Q2 and the fourth MOSFET Q4 are turned on when the first MOSFET Q1 and the third MOSFET Q3 are turned off. Therefore, power is not supplied via the discharge path including the first to fourth MOSFETs Q1, Q2, Q3, and Q4.

[0079] According to an exemplary implementation, when it is necessary to adjust the link capacitance C link During charging, the controller 300 can control the voltage V of the AC power applied from the second switch section 230 to the transformer 220 by controlling the phase shift of the third PWM signal and the fourth PWM signal. TF Size. Reference Figure 2 , Figure 5 and Figure 6 In response to the phase shift of the third PWM signal and the fourth PWM signal, the power of the vehicle's battery BT is applied to the transformer 220 through the second switch section 230.

[0080] More specifically, see reference Figure 5 During the first time period T1_1 (where the phase of the third PWM signal and the phase of the fourth PWM signal are offset by PS1), the first PWM signal and the fourth PWM signal at the on level are applied to the first MOSFET Q1 and the fourth MOSFET Q4, thereby turning on the first MOSFET Q1 and the fourth MOSFET Q4, and the second PWM signal and the third PWM signal at the off level are applied to the second MOSFET Q2 and the third MOSFET Q3, thereby turning off the second MOSFET Q2 and the third MOSFET Q3. Thus, the power V of the vehicle's battery BT... TF (+) is applied to transformer 220 via second switch section 230.

[0081] Additionally, during the third time period T1_3 (where the phases of the third and fourth PWM signals are shifted by PS1), the first and fourth PWM signals at the off level are applied to the first MOSFET Q1 and the fourth MOSFET Q4, thereby turning off the first MOSFET Q1 and the fourth MOSFET Q4, and the second and third PWM signals at the on level are applied to the second MOSFET Q2 and the third MOSFET Q3, thereby turning on the second MOSFET Q2 and the third MOSFET Q3. Thus, the vehicle's battery BT's power V... TF (-) is applied to transformer 220 via second switch section 230.

[0082] refer to Figure 6 When the phase shift of the third PWM signal and the fourth PWM signal increases (PS1 < PS2), during the time period corresponding to the increased phase shift, the power of the vehicle's battery BT is applied to the transformer 220 via the second switch section 230.

[0083] refer to Figure 7A , Figure 7B , Figure 7CThe controller 300 can control the phase shifts of the third and fourth PWM signals to achieve the same effect as controlling the duty cycle of the PWM signals, thereby controlling the level of power applied to the transformer 220. Therefore, as the phase shifts of the third and fourth PWM signals increase, the average value of the power applied to the transformer 220 increases, and correspondingly, the charging current I... link The size will increase. Figure 7A , Figure 7B , Figure 7C The schematic diagram in the diagram corresponds to the power V of transformer 220. TF level Figures 4 to 6 The image.

[0084] For example, in relation to the link capacitance C link During charging, the bidirectional DC-DC converter 200 can form a phase-shift full bridge (PSFB) converter. The first to fourth MOSFETs Q1, Q2, Q3 and Q4 of the second switching section 230 can form a primary-side full-bridge circuit, the fifth to eighth MOSFETs Q5, Q6, Q7 and Q8 of the first switching section 210 are all turned off, and the fifth to eighth body diodes can form a secondary-side full-wave rectifier circuit.

[0085] In conjunction with the PSFB converter, the controller 300 can control the phase of the third and fourth PWM signals, thereby controlling the time period during which the first and fourth PWM signals are simultaneously on, or the time period during which the third and fourth PWM signals are simultaneously on. As the time period during which the first and fourth PWM signals are simultaneously on increases, the applied capacitance C... link Charging current I link Its size may increase.

[0086] Subsequently, in step S43, the controller 300 determines the link capacitance C. link voltage V link Is it greater than or equal to the reference voltage V? ref .

[0087] Subsequently, when the link capacitance C link voltage V link Greater than or equal to the reference voltage V ref When (S30-Yes; or S43-Yes), in step S5, the controller 300 electrically connects the electric vehicle supply device (EVSE) to the device 1 for charging the vehicle's battery, and then in step S60, the battery charging mode for charging the vehicle's battery BT can be entered.

[0088] In battery charging mode, in the first switching section 210, when the fifth MOSFET Q5 and the eighth MOSFET Q8 are turned on, the sixth MOSFET Q6 and the seventh MOSFET Q7 are turned off, and when the fifth MOSFET Q5 and the eighth MOSFET Q8 are turned off, the sixth MOSFET Q6 and the seventh MOSFET Q7 are turned on. This converts the DC power applied from the PFC circuit section 100 to AC power. At this time, the first to fourth MOSFETs Q1, Q2, Q3, and Q4 in the second switching section 230 are turned off. The AC power converted by the first switching section 210 charges the output terminal capacitor C through a charging path including the transformer 220 and the first body diode to the fourth body diode. obc Charging. Then, at the output terminal capacitor C... obc The charged electricity can be released to charge the vehicle's battery BT.

[0089] refer to Figure 8 It was found that, according to an exemplary embodiment, the discharge power of the vehicle's battery is utilized via a bidirectional DC-DC converter 200 to link capacitor C. link The voltage change B obtained after the initial charging is approximately the same as that obtained using a conventional relay to control the link capacitor C. link The voltage change A obtained after charging.

[0090] Figure 9A This shows the voltage change of the link capacitor with and without initial charging. Figure 9B This shows the change in current of the link capacitor with and without initial charging of the link capacitor.

[0091] refer to Figure 9A and Figure 9B As shown by the dashed line, if the on-board charger (OBC) is connected to an external power source after the link capacitor has been initially charged, the voltage V of the link capacitor will be... link The current I increases slowly. link It also exhibits very minor variations. On the other hand, as shown by the solid line, if the on-board charger (OBC) is connected to an external power source without initial charging of the link capacitor, the voltage V of the link capacitor will... link_no and current I link_no The rapid increase in [something] may lead to damage to other components.

[0092] Although the invention has been described in conjunction with exemplary embodiments now regarded as practical, it should be understood that the invention is not limited to the disclosed embodiments. Rather, the invention is intended to cover various modifications and equivalents included within the spirit and scope of the appended claims.

Claims

1. An apparatus for charging a battery of a vehicle, comprising: a power factor correction circuit including: a rectifier configured to rectify alternating current applied from a commercial alternating current power source into direct current in a battery charging mode of charging the battery of the vehicle; and a link capacitor connected in parallel to the rectifier and configured to smooth the rectified direct current; a bidirectional DC-DC converter including: a first switch configured to convert the direct current applied from the power factor correction circuit into alternating current; a transformer configured to step up or step down a voltage of the alternating current converted at the first switch; and a second switch configured to rectify the alternating current applied from the transformer into direct current to charge the battery of the vehicle; and a controller configured to, before entering the battery charging mode, control a phase of a PWM signal applied to the second switch so that the link capacitor is charged with power discharged from the battery of the vehicle when a voltage of the link capacitor is lower than a predetermined reference voltage; wherein the first switch includes: a fifth MOSFET and a sixth MOSFET between two terminals of the link capacitor; and a seventh MOSFET and an eighth MOSFET connected in series between the two terminals of the link capacitor; wherein one end of a secondary coil of the transformer is connected to a third node between the fifth MOSFET and the sixth MOSFET, and the other end of the secondary coil is connected to a fourth node between the seventh MOSFET and the eighth MOSFET; wherein the second switch includes: a first MOSFET; a second MOSFET, wherein the first MOSFET and the second MOSFET are connected in series between a first electrode and a second electrode of the battery of the vehicle; a third MOSFET; and a fourth MOSFET, wherein the third MOSFET and the fourth MOSFET are connected in series between a first terminal of the first MOSFET and a second terminal of the second MOSFET; wherein a first terminal of a primary coil of the transformer is connected to a first node between the first MOSFET and the second MOSFET; a second terminal of the primary coil is connected to a second node between the third MOSFET and the fourth MOSFET; wherein, before entering the battery charging mode, if the voltage of the link capacitor is lower than the predetermined reference voltage: the second MOSFET and the third MOSFET are turned off when the first MOSFET and the fourth MOSFET are turned on, and the second MOSFET and the third MOSFET are turned on when the first MOSFET and the fourth MOSFET are turned off, thereby converting the direct current discharged from the battery into alternating current, the fifth MOSFET to the eighth MOSFET are turned off, and the converted alternating current is applied to the link capacitor through the transformer and body diodes of the fifth MOSFET to the eighth MOSFET.

2. The apparatus for charging a battery of a vehicle of claim 1, wherein, the controller is configured to: calculate a magnitude of a charging current to be applied to the link capacitor in order to charge the link capacitor to be higher than or equal to the predetermined reference voltage; The phases of a third PWM signal for controlling the third MOSFET switch and a fourth PWM signal for controlling the fourth MOSFET switch are shifted so that a voltage corresponding to the calculated charging current is applied to the transformer.

3. The device for charging a battery of a vehicle according to claim 2, wherein, The controller is configured to: calculate an increment of the charging current per unit time; shift the phases of the third PWM signal and the fourth PWM signal so that a voltage corresponding to the calculated increment of the charging current is applied to the transformer.

4. The apparatus for charging a battery of a vehicle according to claim 3, wherein: when the voltage of the link capacitor is charged to be higher than or equal to a predetermined reference voltage, the controller is configured to control the first PWM signal, the second PWM signal, the third PWM signal, and the fourth PWM signal so that: when the first MOSFET and the third MOSFET are turned on, the second MOSFET and the fourth MOSFET are turned off; when the first MOSFET and the third MOSFET are turned off, the second MOSFET and the fourth MOSFET are turned on; power applied from a commercial alternating current power source is applied to the battery of the vehicle via a charging path including a power factor correction circuit, the first switch, the transformer, and body diodes of the first MOSFET, the second MOSFET, the third MOSFET, and the fourth MOSFET.

5. A method of charging a battery of a vehicle by a bidirectional DC-DC converter, the method comprising: sensing a voltage of a link capacitor connected in parallel to output terminals of a power factor correction circuit in synchronization with a time point of entering a charging mode for charging the battery of the vehicle; determining whether the sensed voltage of the link capacitor is lower than a predetermined reference voltage; when the sensed voltage of the link capacitor is lower than the predetermined reference voltage, charging the link capacitor with power discharged from the battery of the vehicle by controlling a phase of a PWM signal applied to a second switch; when the voltage of the link capacitor is charged to be higher than or equal to the predetermined reference voltage, charging the battery of the vehicle with power applied from a commercial alternating current power source; wherein the bidirectional DC-DC converter includes: a first switch connected to output terminals of a power factor correction circuit configured to rectify alternating current of a commercial alternating current power source to direct current and convert the direct current to alternating current; a transformer configured to step up or step down a voltage of the alternating current converted by the first switch; and a second switch configured to rectify the alternating current applied from the transformer to direct current to charge the battery of the vehicle; wherein the first switch includes: a fifth MOSFET and a sixth MOSFET between both terminals of the link capacitor; and a seventh MOSFET and an eighth MOSFET connected in series between both terminals of the link capacitor; wherein one end of a secondary coil of the transformer is connected to a third node between the fifth MOSFET and the sixth MOSFET, and the other end of the secondary coil is connected to a fourth node between the seventh MOSFET and the eighth MOSFET; wherein the second switch includes: a first MOSFET; a second MOSFET, wherein the first MOSFET and the second MOSFET are connected in series between a first electrode and a second electrode of a battery of a vehicle; a third MOSFET; and a fourth MOSFET, wherein the third MOSFET and the fourth MOSFET are connected in series between a first terminal of the first MOSFET and a second terminal of the second MOSFET; wherein a first terminal of a primary coil of the transformer is connected to a first node between the first MOSFET and the second MOSFET, and a second terminal of the primary coil is connected to a second node between the third MOSFET and the fourth MOSFET; wherein, before entering the battery charging mode, if the voltage of the link capacitor is lower than a predetermined reference voltage, the method further includes: turning off the second MOSFET and the third MOSFET when the first MOSFET and the fourth MOSFET are turned on, and turning on the second MOSFET and the third MOSFET when the first MOSFET and the fourth MOSFET are turned off, thereby converting direct current for discharging the battery into alternating current; turning off the fifth MOSFET to the eighth MOSFET, and applying the converted alternating current to the link capacitor through the transformer and body diodes of the fifth MOSFET to the eighth MOSFET.

6. The method of claim 5, wherein, charging the link capacitor includes: calculating a magnitude of a charging current to be applied to the link capacitor in order to charge the link capacitor to be higher than or equal to a predetermined reference voltage; shifting phases of a third PWM signal for controlling a third MOSFET switch and a fourth PWM signal for controlling a fourth MOSFET switch so that a voltage corresponding to the calculated charging current is applied to the transformer to charge the link capacitor.

7. The method of claim 6, wherein, The method includes: calculating a magnitude of a charging current based on an increment of the charging current per unit time; shifting phases of a third PWM signal and a fourth PWM signal so that a voltage corresponding to the calculated increment of the charging current is applied to the transformer to charge the link capacitor.

8. The method of claim 7, wherein, The shifting of the phases of the third PWM signal and the fourth PWM signal includes: when the voltage of the link capacitor is charged to be higher than or equal to a predetermined reference voltage, controlling the first PWM signal, the second PWM signal, the third PWM signal, and the fourth PWM signal so that: when the first MOSFET and the third MOSFET are turned on, the second MOSFET and the fourth MOSFET are turned off; when the first MOSFET and the third MOSFET are turned off, the second MOSFET and the fourth MOSFET are turned on; applying power applied from a commercial alternating current power source to a battery of a vehicle through a charging path including a power factor correction circuit, a first switch, a transformer, and body diodes of first to fourth MOSFETs.

Images