WO2011141785A1

WO2011141785A1 - Power converter and vehicle provided with the same

Info

Publication number: WO2011141785A1
Application number: PCT/IB2011/000907
Authority: WO
Inventors: Wanleng Ang
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2010-05-14
Filing date: 2011-04-27
Publication date: 2011-11-17
Also published as: JP2011244523A; JP5071519B2

Abstract

A power converter includes a transformer (200). The transformer (200) includes an input winding (N1) and output windings (N2, N3). The power converter includes an input circuit (201) for supplying the electric power from the external power supply (500) to the input winding (N1), an output circuit (202) that converts the electric power from the output winding (N2) and charges a power storage device (110), an output circuit (203) that converts the electric power from the output winding (N3) and charges an auxiliary battery (180). The power converter includes at least one switch, from among a first switch (SW1) provided in a path connecting the input winding (N1) to the input circuit (201), a second switch (SW2) provided in a path connecting the output circuit (202) to the output winding (N2), and a third switch (SW3) provided in a path connecting the output circuit (203) to the output winding (N3).

Description

POWER CONVERTER AND VEHICLE PROVIDED WITH THE SAME

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The invention relates to power converter and a vehicle provided with this power converter. More particularly, the invention relates to a multi-output power converter and a vehicle provided with this multi-output power converter. 2. Description of the Related Art

[0002] In recent years, vehicles that are provided with a power storage device (such as a secondary battery or a capacitor) and that run using driving force generated from electric power stored in this power storage device are receiving a lot of attention as environmentally friendly vehicles. Examples of such vehicles include electric vehicles, hybrid vehicles, and fuel cell vehicles. Hereinafter, such vehicles will simply be referred to as "electric vehicles". Also, technology has been proposed to charge the power storage device onboard these vehicles using a commercial power supply that generates power with high efficiency.

[0003] One known hybrid vehicle has an onboard power storage device that can be charged from a power supply outside the vehicle (hereinafter, such a power supply may also be referred to simply as an "external power supply" and such charging may also be referred to simply as "external charging"), similar to an electric vehicle. For example, a so-called plug-in hybrid vehicle is known in which a power storage device can be charged from a power supply of a typical home by connecting a charging inlet of the vehicle to an electrical outlet of a house, for example. This makes an increase in fuel consumption efficiency of hybrid vehicles promising.

[0004] Also, an electric vehicle of the type described above is typically provided with an auxiliary battery for supplying electric power to auxiliary equipment onboard the vehicle, in addition to a main power storage device that stores electric power for driving the vehicle. Also, the vehicle may be configured such that the auxiliary battery can also be charged in addition to the main power storage device, using electric power from the external power supply, during external charging.

[0005] Japanese Patent Application Publication No. 2006-211832 (JP-A-2006-211832) describes a structure that draws a plurality of stable direct current (DC) outputs via an output rectifier circuit from secondary windings, in a multi-output resonance DC/DC converter that is provided with a plurality of secondary windings of a transformer and in which a magnetic amplifier to is connected to only the second and subsequent secondary windings.

[0006] With the DC/DC converter according to JP-A-2006-211832, stable DC outputs from the second and subsequent secondary windings are able to be obtained by controlling a reset current of the magnetic amplifier of the second and subsequent secondary windings.

[0007] When the multi-output DC/DC converter described in JP-A-2006-211832 is used in a vehicle in which a main power storage device and an auxiliary battery can be charged with electric power from an external power supply, with a circuit that is connected to the plurality of secondary windings, excitation current constantly flows through the corresponding secondary windings even if the circuit is not being used. Loss due to this excitation current may reduce the power conversion efficiency of the DC/DC converter on the whole.

SUMMARY OF THE INVENTION

[0008] The invention thus provides a multi-output power converter with improved power conversion efficiency, and a vehicle provided with this multi-output power converter.

[0009] A first aspect of the invention relates to a power converter that has a plurality of outputs and has a transformer in which electric power supplied from an external power supply and the plurality of outputs are able to be magnetically insulated. The transformer includes an input winding, a first output winding, and a second output winding. The power converter also has an input circuit, a first output circuit, and a second output circuit. The input circuit supplies the electric power from the external power supply to the input winding. The first output circuit converts the electric power from the first output winding and supplies the converted electric power to a first electrical apparatus. The second output circuit converts the electric power from the second output winding and supplies the converted electric power to a second electrical apparatus. In addition, the power converter also has at least one switch, from among i) a first switch that is provided in a path connecting the input winding to the external power supply, and that selectively electrically cuts off the input winding from the external power supply, ii) a second switch that is provided in a path connecting the first electrical apparatus to the first output winding, and that selectively electrically cuts off the first electrical apparatus from the first output winding, and iii) a third switch that is provided in a path connecting the second electrical apparatus to the second output winding, and that selectively electrically cuts off the second electrical apparatus from the second output winding.

[0010] The power converter described above may also have a control apparatus for controlling the at least one switch, from among the first switch, the second switch, and the third switch. If the power converter is provided with the first switch, the control apparatus may electrically open the first switch when the input circuit is not being used. If the power converter is provided with the second switch, the control apparatus may electrically open the second switch when the first output circuit is not being used. If the power converter is provided with the third switch, the control apparatus may electrically open the third switch when the second output circuit is not being used.

[0011] In this power converter, the power converter may be provided with the first switch, and the first switch may be provided between the input circuit and the input winding.

[0012] In the power converter described above, the input circuit may include a rectifier circuit that is configured to convert alternating current electric power from the external power supply into direct current electric power, and an inverter that is configured to convert the direct current electric power converted by the rectifier circuit into high frequency alternating current electric power, and supply the high frequency alternating current electric power to the input winding.

[0013] In this power converter, the power converter may be provided with the first switch, and the first switch may be provided between the rectifier circuit and the inverter.

[0014] In the power converter described above, the power converter may be provided with the second switch, and the second switch may be provided between the first output winding and the first output circuit.

[0015] In the power converter described above, the power converter may be provided with the second switch, the first output circuit may include an AC/DC converter that is configured to convert alternating current electric power from the first output winding into direct current electric power, and a capacitor that is connected in parallel to a direct current side terminal of the AC/DC converter. The second switch may be provided between the AC/DC converter and the capacitor.

[0016] In the power converter described above, the power converter may be provided with the third switch, and the third switch may be provided between the second output winding and the second output circuit.

[0017] In the power converter described above, the power converter may be provided with the third switch, the second output circuit may include a rectifier circuit that is configured to convert alternating current electric power from the second output winding into direct current electric power, and a DC/DC converter for voltage-converting output voltage from the rectifier circuit. The third switch may be provided between the rectifier circuit and the DC/DC converter.

[0018] In the power converter described above, the first electrical apparatus may be a first power storage device, and the second electrical apparatus may be a second power storage device.

[0019] In this power converter, the control apparatus may have a first threshold value, a second threshold value, and a third threshold value for a state-of-charge of the second power storage device, in which the second threshold value is set larger than the first threshold value, and the third threshold value is set larger than the second threshold value. When the state-of-charge of the second power storage device falls below the first threshold value when charging the first power storage device, the control apparatus may interrupt charging of the first power storage device and charge the second power storage device until the state-of-charge of the second power storage device reaches the third threshold value. When the state-of-charge of the second power storage device falls below the second threshold value when charging the first power storage device, the control apparatus may charge the first power storage device and the second power storage device in parallel until the state-of-charge of the second power storage device reaches the third threshold value. When the state-of-charge of the second power storage device reaches the third threshold value when charging the first power storage device, the control apparatus may charge the first power storage device and stop charging the second power storage device.

[0020] In the power converter described above, the first output circuit may be configured to convert electric power from the first power storage device and supply the converted electric power to the transformer.

[0021] In the power converter described above, the transformer may also include a third output winding. The power converter may also include a third output circuit that is configured to convert electric power from the third output winding and supply the converted electric power to a third electrical apparatus.

[0022] This power converter may also include a fourth switch that is provided in a path connecting the third electrical apparatus to the third output winding, and that selectively electrically cuts off the third electrical apparatus from the third output winding.

[0023] A second aspect of the invention relates to a vehicle that is provided with a first power storage device and a second power storage device, both of which are able to be charged, a driving apparatus, and a power converter having a plurality of outputs, and that can be charged using electric power from an external power supply. The driving apparatus generates driving force for running the vehicle, using electric power from the first power storage device. The power converter includes a transformer in which the electric power supplied from the external power supply and the plurality of outputs are able to be magnetically insulated. The transformer includes an input winding, a first output winding, and a second output winding. The power converter also includes an input circuit, a first output circuit, and a second output circuit. The input circuit supplies the electric power from the external power supply to the input winding. The first output circuit converts the electric power from the first output winding and supplies the converted electric power to the first power storage device. The second output circuit converts the electric power from the second output winding and supplies the converted electric power to the second power storage device. The power converter also includes at least one switch, from among i) a first switch that is provided in a path connecting the input winding to the external power supply, and that selectively electrically cuts off the input winding from the external power supply, ii) a second switch that is provided in a path connecting the first power storage device to the first output winding, and that selectively electrically cuts off the first power storage device from the first output winding, and iii) a third switch that is provided in a path connecting the second power storage device to the second output winding, and that selectively electrically cuts off the second power storage device from the second output winding.

[0024] Accordingly, the invention makes it possible to improve the power conversion efficiency of a multi-output power converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The foregoing and/or further objects, features and advantages of the invention will become more apparent from the following description of example embodiments with reference to the accompanying drawings, in which like numerals are used to represent like elements and wherein:

FIG. 1 is an overall block diagram of a vehicle provided with a power converter according to a first example embodiment of the invention;

FIG. 2 is a diagram of an example of the internal structure of a PCU in FIG. 1;

FIG. 3 is a diagram of a first example of the internal structure of a PFC in FIG. 1;

FIG. 4 is a diagram of a second example of the internal structure of the PFC in FIG. 1;

FIG. 5 is a graph showing an overview of external charging control in the first example embodiment;

FIG. 6 is a flowchart illustrating the details of an external charging control routine executed by an ECU in the first example embodiment;

FIG. 7 is an overall block diagram of a vehicle provided with a power converter according to a modified example of the first example embodiment; and

FIG 8 is an overall block diagram of a vehicle provided with a power converter according to a second example embodiment of the invention. DETAILED DESCRIPTION OF EMBODIMENTS

[0026] Example embodiments of the invention will be described in greater detail below with reference to the accompanying drawings. Incidentally, like or corresponding parts will be denoted by like reference characters and descriptions of those parts will not be repeated.

[0027] (First example embodiment)

FIG. 1 is an overall block diagram of a vehicle 100 provided with a power converter according to a first example embodiment.

[0028] Referring to FIG. 1, the vehicle 100 includes a power storage device 110, a system main relay (SMR) 115, a PCU (Power Control Unit) 120, a motor-generator 130, a power transmitting gear 140, driving wheels 150, and a control apparatus (ECU) 300. Incidentally, the PCU 120, the motor- generator 130, the power transmitting gear 140, and the driving wheels 150 together form the driving apparatus of the invention.

[0029] The power storage device 110 is a power storing element that is capable of storing and discharging electric power. The power storage device 110 may include, for example, a secondary battery such as a lithium-ion battery, a nickel-metal hydride battery, or a lead battery, or a power storing element such as an electric double layer capacitor.

[0030] The power storage device 110 is connected to the PCU 120 for driving the motor-generator 130, via the SMR 115. The power storage device 110 supplies the PCU 120 with electric power for generating driving force for the vehicle 100, as well as stores electric power generated by the motor- generator 130. The output of the power storage device 110 is 200 V, for example.

[0031] One end of each of two relays in the SMR 115 is connected to a positive terminal and a negative terminal, respectively, of the power storage device 110, and the other end of each of the relays in the SMR 115 is connected to a power line PLl and an earth line NLl, respectively, that are connected to the PCU 120. Also, the SMR 115 switches between allowing and interrupting the supply of electric power between the power storage device 110 and the PCU 120 based on a control signal SE1 from the ECU 300. The SMR 115 is closed when the vehicle is running and when driving an air conditioner 160 or a DC/DC converter 170.

[0032] FIG. 2 is a diagram of an example of the internal structure of the PCU 120. Referring to FIG. 2, the PCU 120 includes a converter 121, an inverter 122, and capacitors CI and C2.

[0033] The converter 121 performs power conversion between the power line

PLl and the earth line NLl, and a power line HPL and the earth line NLl, based on a control signal PWC from the ECU 300.

[0034] The inverter 122 is connected to the power line HPL and the earth line NLl. This inverter 122 converts direct current (DC) electric power that is supplied from the converter 121 into alternating current (AC) electric power based on a control signal PWI from the ECU 300, and uses this AC current electric power to drive the motor-generator 130. Incidentally, in this example embodiment, there is only one set of a motor-generator and an inverter, but there may also be a plurality of sets of motor-generators and inverters.

[0035] The capacitor CI is provided between the power line PLl and the earth line NLl, and reduces voltage fluctuation between the power line PLl and the earth line NLl. Also, the capacitor C2 is provided between the power line HPL and the earth line NLl, and reduces voltage fluctuation between the power line HPL and the earth line NLl.

[0036] Referring back to FIG. 1 again, the motor-generator 130 is an alternating current rotating electrical machine, and may be a permanent-magnet synchronous motor having a rotor with permanent magnets embedded in it, for example.

[0037] The output torque from the motor-generator 130 is transmitted, via the power transmitting gear 140 that is formed by a reduction gear and a power split device, to the driving wheels 150 where it is used to propel the vehicle. The motor-generator 130 is able to generate electric power using the rotational force of the driving wheels 150 during regenerative braking of the vehicle 100. Also, the electric power that is generated is converted into charging power for the power storage device 110 by the PCU 120.

[0038] Also, with a hybrid vehicle that is provided with an engine, not shown, in addition to the motor-generator 130, the necessary vehicle driving force can be generated by operating the motor-generator 130 in coordination with the engine. In this case, the power storage device 110 can also be charged using the electric power generated by the rotation of the engine.

[0039] That is, the vehicle 100 in this example embodiment represents a vehicle that has an electric motor for generating vehicle driving force, and may be a hybrid vehicle that generates vehicle driving force using an engine and an electric motor, or an electric vehicle or a fuel cell vehicle that is not provided with an engine, for example.

[0040] The vehicle 100 also includes, as the structure of a low voltage system

(i.e., an auxiliary system), the air conditioner 160, the DC/DC converter 170, an auxiliary battery 180, and auxiliary loads 190.

[0041] The air conditioner 160 is connected to the power line PL1 and the earth line NL1, and controls the air temperature inside a cabin of the vehicle 100.

[0042] The DC/DC converter 170 is connected to the power line PL1 and the earth line NL1, and steps down the DC voltage supplied from the power storage device 110, based on a control signal PWD from the ECU 300. The DC/DC converter 170 also supplies electric power to the low voltage system of the entire vehicle, such as the auxiliary battery 180, the auxiliary loads 190, and the ECU 300, via a power line PL5.

[0043] The auxiliary battery 180 is representatively formed by a lead battery.

The output voltage of the auxiliary battery 180 is lower than the output voltage of the power storage device 110, e.g., approximately 12 V.

[0044] The auxiliary loads 190 include, for example, lamps, windshield wipers, a heater, audio equipment, and a navigation system, and the like.

[0045] The ECU 300 includes a CPU (Central Processing Unit), a storage

(memory) device, and an input / output buffer, none of which are shown in FIG. 1. The ECU 300 is activated in response to the ignition being turned on or a charge cable 400 being connected to the vehicle 100. The ECU 300 receives signals from various sensors and the like, outputs control signals to various equipment, and controls the vehicle 100 and various equipment. Incidentally, this control is not limited to being executed by software, but may also be executed by special hardware (an electronic circuit).

[0046] The ECU 300 receives detection values of a voltage VB 1 and a current IB1 from sensors, not shown, in the power storage device 110. The ECU 300 then calculates the state-of-charge SOC of the power storage device 110 based on the voltage VB1 and the current IB1. The ECU 300 also receives a detection value(s) of a voltage VB2 and/or a current IB 2 from sensors, also not shown, in the auxiliary battery 180. The ECU 300 then calculates the state-of-charge SOC of the auxiliary battery 180 based on the voltage VB2 and/or the current IB 2.

[0047] The vehicle 100 has, as the structure for charging the power storage device 110 with electric power from an external power supply 500, a transformer 200, an input circuit 201, output circuits 202 and 203, a voltage sensor 230, a charging relay CHR 250, a connecting portion 280, and switches SW1 to SW3. Incidentally, the transformer 200, the input circuit 201, the output circuits 202 and 203, and the switches SW1 to SW3 together form a circuit for the power converter of the invention.

[0048] The connecting portion 280 is provided in the body of the vehicle 100 in order to receive AC electric power from the external power supply 500. A charge connector 430 of the charge cable 400 is connected to the connecting portion 280. Also, AC electric power from the external power supply 500 is transmitted to the vehicle 100 via a power line portion 420 of the charge cable 400 by a plug 410 of the charge cable 400 being connected to an outlet 510 of the external power supply 500 (such as a commercial power supply, for example). A charging circuit interrupt device (CCID) 440 is interposed in the power line portion 420 of the charge cable 400 for switching between allowing and interrupting the supply of electric power from the external power supply 500 to the vehicle 100.

[0049] The transformer 200 includes an input winding Nl and output windings N2 and N3. The input winding Nl and the output windings N2 and N3 are wound around a common core. Also, the transformer 200 is configured such that the AC electric power supplied from the external power supply 500 and the output of the transformer 200 are magnetically insulated. The AC voltage input from the input winding Nl is converted into AC voltage according to the winding ratio, and then output from the output windings N2 and N3.

[0050] The input circuit 201 is a circuit for converting commercial electric power transmitted from the external power supply 500 into high frequency AC electric power and supplying it to the transformer 200. [0051] The input circuit 201 includes an inverter 210 and a power factor correction circuit (PFC) 220.

[0052] The PFC 220 is connected to the connecting portion 280 by power lines ACL1 and ACL2. The PFC 220 converts the AC electric power transmitted from the external power supply 500 into DC electric power, and outputs it to a power line PL3 and an earth line NL3.

[0053] FIGS. 3 and 4 are diagrams of examples of the internal structure of the PFC 220. A PFC220A shown in FIG. 3 includes a switching element Q41, a diode D45, and a diode bridge that includes reactors L41 to L43 and diodes D41 to D44.

[0054] The diodes D41 and D42 that are connected in series are connected in parallel to the diodes D43 and D44 that are connected in series.

[0055] On end of the reactor L43 is connected to cathodes of the diodes D41 and D43, and the other end of the reactor L43 is connected to the power line PL3. Anodes of the diodes D42 and D44 are connected to the earth line NL3.

[0056] The switching element Q41 is connected between the power line PL3 and the earth line NL3. Also, the diode D45 is connected in inverse-parallel to the switching element Q41, with the direction from the earth line NL3 toward the power line PL3 being the forward direction.

[0057] One end of the reactor L41 is connected to the power line ACL1, and the other end of the reactor L41 is connected to a connection node of the diode D41 and the diode D42. Also, one end of the reactor L42 is connected to the power line ACL2, and the other end of the reactor L42 is connected to a connection node of the diode D43 and the diode D44.

[0058] Also, the switching element Q41 is driven by a control signal PWH from the ECU 300, such that AC electric power transmitted from the external power supply 500 is converted into DC electric power.

[0059] A PFC 220B shown in FIG. 4 includes reactors L51 and L52, switching elements Q51 to Q54, diodes D51 to D54, and a capacitor C50. This PFC 220B forms a so-called full-bridge converter.

[0060] The switching elements Q51 and Q52 that are connected in series and the switching elements Q53 and Q54 that are connected in series are connected in parallel between the power line PL3 and the earth line NL3. The diodes D51 to D54 are connected in inverse-parallel to the switching elements Q51 to Q54, respectively.

The capacitor C50 is connected between the power line PL3 and the earth line NL3.

[0061] One end of the reactor L51 is connected to the power line ACL1, and the other end of the reactor L51 is connected to a connection node of the switching element Q51 and the switching element Q52. Also, one end of the reactor L52 is connected to the power line ACL2, and the other end of the reactor L52 is connected to a connection node of the switching element Q53 and the switching element Q54.

[0062] The switching elements Q51 to Q54 are driven by the control signal

PWH from the ECU 300, such that AC electric power transmitted from the external power supply 500 is converted into DC electric power.

[0063] Incidentally, the structure of the PFC 220 is not limited to the structures shown in FIGS. 3 and 4. Referring back to FIG. 1 again, the inverter 210 includes switching elements Qll to Q14 and diodes Dll to D14.

[0064] The switching elements Qll and Q12 that are connected in series and the switching elements Q13 and Q14 that are connected in series are connected in parallel between the power line PL3 and the earth line NL3. The diodes Dll to D14 are connected in inverse-parallel to the switching elements Qll to Q14, respectively.

[0065] One end of the input winding Nl is connected to a connection node of the switching element Qll and the switching element Q12, and the other end of the input winding Nl is connected to a connection node of the switching element Q13 and the switching element Q14.

[0066] Also, the switching elements Qll to Q14 are driven by a control signal PWF from the ECU 300, such that DC electric power from the PFC 220 is converted into high frequency AC electric power and supplied to the input winding Nl of the transformer 200.

[0067] Also, a switch SWl that is controlled by a control signal SE3 from the ECU 300 is provided in a path that connects the inverter 210 to the input winding Nl. This switch SWl enables the input circuit 201 to be electrically cut off from the input winding Nl.

[0068] The output circuit 202 is a circuit for converting the AC electric power supplied from the output winding N2 into charging power for the power storage device 110.

[0069] This output circuit 202 includes a capacitor C3 and an AC/DC converter 240 that includes switching elements Ql to Q4 and diodes Dl to D4.

[0070] The switching elements Ql and Q2 that are connected in series and the switching elements Q3 and Q4 that are connected in series are connected in parallel between a power line PL2 and an earth line NL2. The diodes Dl to D4 are connected in inverse-parallel to the switching elements Ql to Q4, respectively. [0071] One end of the output winding N2 is connected to a connection node of the switching element Ql and the switching element Q2, and the other end of the output winding N2 is connected to a connection node of the switching element Q3 and the switching element Q4.

[0072] Also, the switching elements Ql to Q4 are driven by a control signal

PWE from the ECU 300, such that AC electric power supplied from the output winding N2 is converted into DC electric power and supplied to the power line PL2 and the earth line NL2.

[0073] Also, the output circuit 202 is also able to convert the DC electric power from the power storage device 110 into AC electric power and supply it to the transformer 200 via the output winding N2.

[0074] The capacitor C3 is connected between the power line PL2 and the earth line NL2, and reduces voltage fluctuation between the power line PL2 and the earth line NL2.

[0075] One end of each of two relays in the charging relay CHR 250 is connected to the power line PL2 and the earth line NL2, respectively, and the other end of each of the relays in the charging relay CHR 250 is connected to a positive terminal and a negative terminal, respectively, of the power storage device 110.

[0076] The charging relay CHR 250 switches between allowing and interrupting the supply of electric power between the power storage device 110 and the output circuit 202, based on a control signal SE2 from the ECU 300. The charging relay CHR 250 is closed when charging the power storage device 110 using electric power from the output circuit 202.

[0077] Also, a switch SW2 that is controlled by a control signal SE4 from the ECU 300 is provided in a path that connects the AC/DC converter 240 to the output winding N2. This switch SW2 enables the output circuit 202 to be electrically cut off from the output winding N2.

[0078] The output circuit 203 is a circuit that converts AC electric power supplied from the output winding N3 into DC electric power, which it then supplies to a power line PL5 of the auxiliary system.

[0079] The output circuit 203 includes a DC/DC converter 270 and a diode bridge 260 that includes diodes D21 to D24.

[0080] The diodes D21 and D22 that are connected in series are connected in parallel to the diodes D23 and D24. The cathodes of the diodes D21 and D23, and the anodes of the diodes D22 and D24, are connected to the DC/DC converter 270. [0081] One end of the output winding N3 is connected to a connection node of the diode D21 and the diode D22, and the other end of the output winding N3 is connected to a connection node of the diode D23 and the diode D24.

[0082] Also, the diode bridge 260 rectifies the AC electric power supplied from the output winding N3 and supplies it to the DC/DC converter 270.

[0083] The DC/DC converter 270 includes a chopper circuit, for example, and is controlled by a control signal PWG from the ECU 300 to step the DC voltage rectified by the diode bridge 260 up or down to a predetermined voltage, and output the resultant voltage to a power line PL4. The power line PL4 is connected to the power line PL5 of the auxiliary system. Here, whether the DC/DC converter 270 is made to be a step-up circuit or a step-down circuit depends on the winding ratio of the input winding Nl and the output winding N3. Incidentally, the DC/DC converter that is used as the DC/DC converter 270 has a smaller capacity than the DC/DC converter 170 does. Also, the output circuit 203 may be a full-bridge AC/DC converter like the output circuit 202.

[0084] Also, a switch SW3 that is controlled by a control signal SE5 from the ECU 300 is provided in a path that connects the diode bridge 260 to the output winding N3. This switch SW3 enables the output circuit 203 to be electrically cut off from the output winding N3.

[0085] The voltage sensor 230 is connected between the power lines ACL1 and ACL2. This voltage sensor 230 detects an AC voltage VAC transmitted from the external power supply 500, and outputs a detection value of this detected AC voltage VAC to the ECU 300.

[0086] In the vehicle 100, electric power is supplied to the auxiliary system by the DC/DC converter 170 as described above when the vehicle 100 is running normally. A relatively large capacity DC/DC converter is often times provided as the DC/DC converter 170 because it needs to drive the auxiliary loads 190 when the vehicle 100 is running. However, the amount of electric power that is consumed by the auxiliary loads 190 during external charging is extremely small compared to what it is when the vehicle 100 is running, so if the large capacity DC/DC converter 170 is used when not much electric power is needed, operating efficiency may decrease.

[0087] Therefore, as shown in FIG. 1, electric power is supplied to the auxiliary system using electric power from the output circuit 203 that is connected to the output winding N3 of the transformer 200 that has a plurality of outputs, and that includes the small capacity DC/DC converter 270. As a result, during external charging, the ECU 300 can be driven and the auxiliary battery 180 can be charged without driving the large capacity DC/DC converter 170.

[0088] By employing a structure that enables the power storage device 110 and the auxiliary battery 180 to be charged during external charging using a multi-output power converter, both a reduction in cost due to the sharing of parts and a reduction in required space due to the equipment being made smaller can be expected compared to a case in which a separate charging apparatus is provided for both the power storage device 110 and the auxiliary battery 180.

[0089] However, the windings are magnetically joined in the transformer 200, so excitation current ends up running through the windings even in a circuit that is not being used. As a result, loss occurs in the circuits due to this excitation current, which may cause the charging efficiency during external charging to decrease.

[0090] Therefore, in this example embodiment, a switch is provided between the input circuit and the output circuits, and the corresponding windings, as described above, and control is performed to open this switch for the circuit that is not being used during external charging. Accordingly, a reduction in unnecessary excitation current can be expected.

[0091] FIG. 5 is a graph showing an overview of external charging control in this example embodiment. In FIG. 5, the horizontal axis represents time and the vertical axis represents the state-of-charge SOC1 of the power storage device 110, the state-of-charge SOC2 of the auxiliary battery 180, and the operating states of the switches SW1 to SW3. Incidentally, the voltage VB2 of the auxiliary battery 180 may be used instead of the state-of-charge SOC2 of the auxiliary battery 180.

[0092] Referring to FIG. 5, the states-of-charge of the power storage device 110 and the auxiliary battery 180 before external charging is performed is S10 (βΐ < S10 < β2) and S20 (a2 < S20 < a3), respectively, in FIG. 5. Here, βΐ and β2 are threshold values representing the lower and upper limit values, respectively, of the SOC1 of the power storage device 110. Also, al and oc3 are threshold values that represent the lower and upper limit values, respectively, of the SOC2 of the auxiliary battery 180, and oc2 is a threshold value for determining whether the auxiliary battery 180 needs to be charged.

[0093] At time tl, external charging starts but the SOC2 of the auxiliary battery 180 is larger than the threshold value a2, as described above, so at this time, the auxiliary battery 180 does not start to be charged, only the power storage device 110 starts to be charged. Therefore, the switches SW1 and SW2 are closed (i.e., turned on) and the switch SW3 is kept open. Hereinafter, this state will be referred to as a "main battery charging mode" (state (1) in FIG. 5).

[0094] Thus, the power storage device 110 starts to be charged. On the other hand, the SOC2 of the auxiliary battery 180 drops due to electric power being consumed by driving the ECU 300 and the other auxiliary loads 190.

[0095] Then when the SOC2 drops to the threshold value cc2 at time t2, the switch SW3 is also closed such that both the power storage device 110 and the auxiliary battery 180 are charged with the electric power from the external power supply 500. Hereinafter, this state will be referred to as a "simultaneous charging mode" (state (2) in FIG. 5). Incidentally, at this time, electric power is distributed to the output circuits 202 and 203 in such a way that priority is given to charging the power storage device 110.

[0096] When the SOC2 reaches the upper limit threshold value oc3 that indicates a full charge at time t3, the switch SW3 is opened such that the main battery charging mode in which only the power storage device 110 is charged is established again.

[0097] Between times t3 and t4, electric power stored in the auxiliary battery 180 is consumed. If the amount of electric power consumed by the auxiliary loads 190 increases due to a user using audio equipment or the like, for example, the rate of decrease per hour in the SOC2 will increase. Therefore, even if the SOC2 decreases to the threshold value oc2, and as a result, the simultaneous charging mode is established again at time t4, the electric power supplied from the output circuit 203 is consumed by the auxiliary loads 190, so the auxiliary battery 180 may not be able to be charged.

[0098] Also, when the SOC2 decreases further to the threshold value ocl that represents the lower limit at time t5, the switch SW2 is opened to interrupt the charging of the power storage device 110 in order to give priority to charging the auxiliary battery 180. Hereinafter, this state will be referred to as an "auxiliary battery charging mode" (state (3) in FIG. 5). Therefore, electric power that is close to the rated output can be supplied from the output circuit 203 to the auxiliary battery 180, so the auxiliary battery 180 can be charged in a short period of time.

[0099] When the SOC2 of the auxiliary battery 180 reaches the threshold value oc3 at time t6, the main battery charging mode is established again. Then at time t7 when the power storage device 110 is fully charged, charging ends and all of the switches SW1 to SW3 are opened.

[0100] FIG. 6 is a flowchart illustrating the details of an external charging control routine executed by the ECU 300 in the first example embodiment. The routine in the flowchart shown in FIG. 6 is realized by a program stored in advance in the ECU 300 being called up from a main routine and executed at predetermined cycles. Alternatively, some or all of the steps may be realized by special hardware (an electronic circuit).

[0101] Referring to FIGS. 1 and 6, when the charge cable 400 is connected to the connecting portion 280 and preparations for external charging using electric power from the external power supply 500 are complete, the ECU 300 determines whether there is a charging command from at least one of the power storage device 110 or the auxiliary battery 180 in step S100.

[0102] If there is no charging command from either the power storage device 110 or the auxiliary battery 180 (i.e., NO in step S100), the process proceeds on to step S210 where the ECU 300 determines that there is no need for a charging operation, and turns off (i.e., opens) all of the switches SW1 to SW3. Then the process returns to the main routine.

[0103] If, on the other hand, there is a charging command from at least one of the power storage device 110 or the auxiliary battery 180 (i.e., YES in step S100), the ECU 300 first closes the switch SW1 and electrically connects the input circuit 201 with the input winding Nl in step SI 10.

[0104] Then in step SI 20, the ECU 300 determines whether the SOC2 of the auxiliary battery 180 is greater than the threshold value o3 that indicates a full charge.

[0105] If the SOC2 is larger than the threshold value a3 (i.e., YES in step S120), the process proceeds on to step S140. Here, the ECU 300 closes the switch SW2 to charge only the power storage device 110 that is the main battery, because the auxiliary battery 180 does not need to be charged. Then in step SI 50, the ECU 300 charges the power storage device 110 by selecting the main battery charging mode and controlling the input circuit 201 and the output circuit 202.

[0106] If, on the other hand, the SOC2 is equal to or less than the threshold value a3 (i.e., NO in step S120), the ECU 300 determines whether the SOC2 is greater than the second threshold value cc2 in step S130.

[0107] If the SOC2 is greater than the threshold value cc2 (i.e., YES in step S130), the process proceeds on to step S140, and only the power storage device 110 is charged as described above.

[0108] If, on the other hand, the SOC2 is equal to or less than the threshold value oc2 (i.e., NO in step S130), then the process proceeds on to step S160. In this case, the ECU 300 determines that the auxiliary battery 180 needs to be charged, and then further determines in step SI 60 whether the SOC2 is greater than the threshold value al (a2 > al) that represents a lower limit.

[0109] If the SOC2 is greater than the threshold value al (i.e., YES in step S160), the process proceeds on to step S170, where the ECU 300 closes both of the switches SW2 and SW3. Then in step SI 80, the ECU 300 selects the simultaneous mode for the power storage device 110 and the auxiliary battery 180. The ECU 300 then charges the power storage device 110 and the auxiliary battery 180 by controlling the input circuit 201 and the output circuits 202 and 203. Incidentally, in this simultaneous charging mode, priority is given to charging the power storage device 110 over the auxiliary battery 180, so the duties of the output circuits 202 and 203 are controlled such that, of the electric power supplied from the input circuit 201, as much of that electric power as possible is drawn (i.e., taken) from the output circuit 202.

[0110] If, on the other hand, the SOC2 is equal to or less than the threshold value al (i.e., NO in step S160), the process proceeds on to step S190. In this case, the ECU 300 determines that there is an urgent need to charge the auxiliary battery 180. Therefore, the ECU 300 opens the switch SW2 and closes the switch SW3 in step SI 90 in order to preferentially charge the auxiliary battery 180. Then in step S200, the ECU 300 charges the auxiliary battery 180 by selecting the auxiliary battery charging mode and controlling the input circuit 201 and the output circuit 203. At this time, the ECU 300 controls the output circuit 203 to output electric power close to its rated output in order to charge the auxiliary battery 180 in as short a time as possible.

[0111] Incidentally, in FIG. 6, if the SOC2 is equal to or less than the threshold value al (i.e., NO in step S160), the switch SW2 is opened to stop the charging of the power storage device 110. However, when the electric power supplied from the input circuit 201 is greater than the rated output electric power of the output circuit 203, the ratio of electric power supplied to the auxiliary battery 180 may instead be increased while simultaneously charging the power storage device 110 and the auxiliary battery 180 by closing both of the switches SW2 and SW3 as in step S170. Accordingly, the power storage device 110 is able to be charged also while the auxiliary battery 180 is being charged, so the charging time of the power storage device 110 can be made even shorter.

[0112] Also, if the auxiliary battery 180 needs to be charged when the charge cable 400 is not connected to the vehicle 100, electric power from the power storage device 110 can also be supplied to the transformer 200 using the output circuit 202, and the auxiliary battery 180 can be charged by the output circuit 203. In this case, the switch SW1 is opened and the switches SW2 and SW3 are closed.

[0113] Performing the control according to this kind of routine makes it possible to switch the charging of the power storage device 110 and the auxiliary battery 180 according to the SOC of the auxiliary battery 180 during external charging using the multi-output power converter. Also, at the time of the switch, excitation current generated in the corresponding windings can be reduced by opening the switch of the circuit not being used, from among the input circuit and the output circuits. As a result, during external charging, the charging efficiency of external charging can be improved while the SOC of the auxiliary battery 180 and the power storage device 110 can be managed appropriately.

[0114] Incidentally, the effect of reducing the excitation current of the transformer can be obtained as long as at least one switch corresponding to the input winding and the output windings is provided. However, it is more preferable to provide a switch corresponding to each input winding and output winding, to as shown in FIG. 1.

[0115] (Modified example of the first example embodiment)

In FIG 1 described above, a structure in which the switches SW1 to SW3 are provided between the input circuit 201 and the output circuits 202 and 203, and the each corresponding winding of the transformer 200 is shown.

[0116] In a modified example of the first example embodiment, a structure in which the switches SW1 to SW3 are provided in other positions will be described.

[0117] FIG. 7 is an overall block diagram of a vehicle 100A provided with a power converter according to a modified example of the first example embodiment. In FIG. 7, the switches SW1 to SW3 are included in an input circuit 201A and output circuits 202A and 203A, respectively. Descriptions of elements in FIG. 7 that are the same as those in FIG. 1 will not be repeated.

[0118] The switch SW1 is interposed in the power line PL3 that connects the PFC 220 and the inverter 210 in the input circuit 201A, and the switch SW2 is provided between the AC/DC converter 240 and a connection node of the capacitor C3 of the power line PL2, in the output circuit 202A. Furthermore, the switch SW3 is provided between the diode bridge 260 and the DC/DC converter 270, in the output circuit 203 A.

[0119] With this kind of configuration, the inverter 210, the AC/DC converter 240, and the diode bridge 260 are electrically connected to corresponding windings, so the excitation current of each winding may be somewhat increased compared to the first example embodiment. On the other hand, however, the switches SW1 to SW3 can be incorporated into the circuit board of the input circuit or the like beforehand, which enables various effects to be achieved. For example, the size of the overall equipment can be reduced, the work in the manufacturing process can be simplified due to the elimination of the wire connection portions, and/or the occurrence of abnormalities can be suppressed.

[0120] (Second example embodiment)

In the first example embodiment and the modified example thereof, the transformer has two outputs. However, the number of outputs that the transformer has is not limited to two. That is, the transformer may have even more outputs.

[0121] FIG. 8 is an overall block diagram of a vehicle 100B provided with a power converter according to a second example embodiment of the invention. In FIG.

8, the transformer 200 in FIG. 1 is replaced by a three-output transformer 200A having output windings N2 to N4, and an output circuit 204 for converting the AC electric power from the output winding N4 into DC electric power is added. Also, a switch

SW4 is provided between the output winding N4 and the output circuit 204.

Descriptions of the elements in FIG. 8 that are the same as those in FIG. 1 will not be repeated.

[0122] The input circuit 201 is connected to the input winding Nl of the transformer 200A via the switch SW1. The output circuit 202 is connected to the output winding N2 of the transformer 200A via the switch SW2. The output circuit 203 is connected to the output winding N3 of the transformer 200 A via the switch SW3. The output circuit 204 is connected to the output winding N4 of the transformer 200A via the switch SW4.

[0123] The output circuit 204 includes a DC/DC converter 270A and a diode bridge 260A that includes diodes D31 to D34. The diode bridge 260A and the DC/DC converter 270A have basically the same structure as the diode bridge 260 and the DC/DC converter 270, respectively, so detailed descriptions of these will not be repeated.

[0124] The output of the output circuit 204 is connected to other electrical equipment that may be used during external charging, such as the air conditioner 160. Therefore, with so-called pre-air conditioning that controls the air temperature during external charging, the SMR 115 no longer needs to be closed. Therefore, leakage current due to the parasitic capacity of the PCU 120 and the like can be suppressed, so a decrease in charging efficiency can be avoided even when pre-air conditioning is performed.

[0125] Incidentally, the output winding N2 and the output winding N3 in this example embodiment are examples of the first output winding and the second output winding, respectively, of the invention. Also, the power storage device 110 and the auxiliary battery 180 in this example embodiment are examples of the first power storage device and the second power storage device, respectively, of the invention.

[0126] The invention has been described with reference to example embodiments for illustrative purposes only. It should be understood that the description is not intended to be exhaustive or to limit form of the invention and that the invention may be adapted for use in other systems and applications. The scope of the invention embraces various modifications and equivalent arrangements that may be conceived by one skilled in the art.

Claims

1. A power converter having a plurality of outputs, characterized by comprising: a transformer in which electric power supplied from an external power supply and the plurality of outputs are able to be magnetically insulated, and that includes an input winding, a first output winding, and a second output winding;

an input circuit for supplying the electric power from the external power supply to the input winding;

a first output circuit configured to convert the electric power from the first output winding and supply the converted electric power to a first electrical apparatus;

a second output circuit configured to convert the electric power from the second output winding and supply the converted electric power to a second electrical apparatus; and

at least one switch, from among i) a first switch that is provided in a path connecting the input winding to the external power supply, and that selectively electrically cuts off the input winding from the external power supply, ii) a second switch that is provided in a path connecting the first electrical apparatus to the first output winding, and that selectively electrically cuts off the first electrical apparatus from the first output winding, and iii) a third switch that is provided in a path connecting the second electrical apparatus to the second output winding, and that selectively electrically cuts off the second electrical apparatus from the second output winding.

2. The power converter according to claim 1, further comprising:

a control apparatus for controlling the at least one switch, from among the first switch, the second switch, and the third switch,

wherein if the power converter is provided with the first switch, the control apparatus electrically opens the first switch when the input circuit is not being used; wherein if the power converter is provided with the second switch, the control apparatus electrically opens the second switch when the first output circuit is not being used; and

wherein if the power converter is provided with the third switch, the control apparatus electrically opens the third switch when the second output circuit is not being used.

3. The power converter according to claim 2, wherein the power converter is provided with the first switch, and the first switch is provided between the input circuit and the input winding.

4. The power converter according to claim 2, wherein the input circuit includes a rectifier circuit that is configured to convert alternating current electric power from the external power supply into direct current electric power, and an inverter that is configured to convert the direct current electric power converted by the rectifier circuit into high frequency alternating current electric power, and supply the high frequency alternating current electric power to the input winding.

5. The power converter according to claim 4, wherein the power converter is provided with the first switch, and the first switch is provided between the rectifier circuit and the inverter.

6. The power converter according to claim 2, wherein the power converter is provided with the second switch, and the second switch is provided between the first output winding and the first output circuit.

7. The power converter according to claim 2, wherein the power converter is provided with the second switch, the first output circuit includes an AC/DC converter that is configured to convert alternating current electric power from the first output winding into direct current electric power, and a capacitor that is connected in parallel to a direct current side terminal of the AC/DC converter; and the second switch is provided between the AC/DC converter and the capacitor.

8. The power converter according to claim 2, wherein the power converter is provided with the third switch, and the third switch is provided between the second output winding and the second output circuit.

9. The power converter according to claim 2, wherein the power converter is provided with the third switch, the second output circuit includes a rectifier circuit that is configured to convert alternating current electric power from the second output winding into direct current electric power, and a DC/DC converter for voltage-converting output voltage from the rectifier circuit; and the third switch is provided between the rectifier circuit and the DC/DC converter.

10. The power converter according to claim 2, wherein the first electrical apparatus is a first power storage device, and the second electrical apparatus is a second power storage device.

11. The power converter according to claim 10, wherein the control apparatus has a first threshold value, a second threshold value, and a third threshold value for a state-of-charge of the second power storage device; the second threshold value is set larger than the first threshold value; the third threshold value is set larger than the second threshold value; when the state-of-charge of the second power storage device falls below the first threshold value when charging the first power storage device, the control apparatus interrupts charging of the first power storage device and charges the second power storage device until the state-of-charge of the second power storage device reaches the third threshold value; when the state-of-charge of the second power storage device falls below the second threshold value when charging the first power storage device, the control apparatus charges the first power storage device and the second power storage device in parallel until the state-of-charge of the second power storage device reaches the third threshold value; and when the state-of-charge of the second power storage device reaches the third threshold value when charging the first power storage device, the control apparatus charges the first power storage device and stops charging the second power storage device.

12. The power converter according to claim 10, wherein the first output circuit is configured to convert electric power from the first power storage device and supply the converted electric power to the transformer.

13. The power converter according to claim 1, wherein the transformer further includes a third output winding, the power converter further comprising a third output circuit that is configured to convert electric power from the third output winding and supply the converted electric power to a third electrical apparatus.

14. The power converter according to claim 13, further comprising a fourth switch that is provided in a path connecting the third electrical apparatus to the third output winding, and that selectively electrically cuts off the third electrical apparatus from the third output winding.

15. A vehicle provided with a power converter having a plurality of outputs, and that is configured to be charged using electric power from an external power supply, characterized by comprising:

a first power storage device and a second power storage device, both of which are able to be charged; and

a driving apparatus that is configured to generate driving force for running the vehicle, using electric power from the first power storage device,

wherein the power converter includes a transformer in which the electric power supplied from the external power supply and the plurality of outputs are able to be magnetically insulated, and that includes an input winding, a first output winding, and a second output winding; an input circuit for supplying the electric power from the external power supply to the input winding; a first output circuit configured to convert the electric power from the first output winding and supply the converted electric power to the first power storage device; a second output circuit configured to convert the electric power from the second output winding and supply the converted electric power to the second power storage device; and at least one switch, from among i) a first switch that is provided in a path connecting the input winding to the external power supply, and that selectively electrically cuts off the input winding from the external power supply, ii) a second switch that is provided in a path connecting the first power storage device to the first output winding, and that selectively electrically cuts off the first power storage device from the first output winding, and iii) a third switch that is provided in a path connecting the second power storage device to the second output winding, and that selectively electrically cuts off the second power storage device from the second output winding.