PCT
`
`H02M
`
`PCT/JP20 13/00 1540
`Mar 8, 2013
`Japanese
`Japanese
`
`(19) World Intellectual Property Organization
`International Office
`(12) International Application based on Patent Cooperation Treaty
`(11) International Application No.
`(51) International Patent Classification
`A1
`H02M
`3/28
`(2006.01)
`WO2013/136755 A1
`7/48
`(2007.01)
`(43) International Publication Date: Sept. 19, 2013
`H02J
`17/00
`(2006.01)
`(81) Designated States (Unless otherwise indicated, all types of
`(21) International Application No.
`domestic protections are available): AE, AG, AL, AM, AO, AT,
`(22) International Application Date
`AU, AZ, BA, BB, BG, BH, BR, BW, BY, BZ, CA, CH, CL, CN,
`(25) International Application Language:
`CO, CR, CU, CZ, DE, DK, DM, DO, DZ, EC, EE, EG, ES, FI, GB,
`(26) International Publication Language:
`GD, GE, GH, GM, GT, HN, HR, HU, ID, IL, IN, IS, KE, KG, KM,
`KN, KP, KR, KZ, LA, LC, LK, LR, LS, LT, LU, LY, MA, MD,
`ME, MG, MK, MN, MW, MX, MY, ML, NA, NG, NI, NO, NZ,
`OM, PE, PG, PH, PL, PT, QA, RO, RS, RU, RW, SC, SD, SE, SG,
`SK, SL, SM, ST, SV, SY, TH, TJ, TM, TN, TR, TT, TZ, UA, UG,
`US, UZ, VC, VN, ZA, ZM, ZW.
`
`(30) Priority Rights Data
`Application No. 2012-059786
`
`Mar. 16, 2012 (16.03.2012) JP
`
`(71) Applicant
`PANASONIC CORPORATION
`1006 Oaza Kadoma, Kadoma-shi Osaka-fu, Japan 571-8501
`(72) Inventor; SADAKATA, Hideki; FUJITA, Atsushi; KASHIMOTO,
`Takashi; BESSYO, Daisuke
`MAEDA & PARTNERS 5F Osaka
`(74) Agent or Attorney:
`Marubeni Building, 2-5-7 Hon-cho, Chuo-ku, Osaka-shi, Osaka-fu 541-
`0053, Japan
`
`(84) Designated Countries (Unless otherwise indicated, all types of
`domestic protections are available): ARIPO (BW, GH, GM, KE,
`LR, LS, MW, MZ, NA, RW, SD, SL, SZ, TZ, UG, ZM, ZW),
`Eurasia (AM, AZ, BY, KG, KZ, RU, TJ, TM), Europe (AL, AT,
`BE, BG, CH, CY, CZ, DE, DK, EE, ES, FI, FR, GB, GR, HR, HU,
`IE, IS, ΓΓΓ, LT, LU, LV, MC, MK, MT, NL, NO, PL, PT, RO, RS,
`SE, SI, SK, SM, TR), OAPI (BF, BJ, CF, CG, CI, CM, GA, GN,
`GQ, GW, ML, MR, NE, SN, TD, TG).
`
`(54) Title: POWER FEED DEVICE OF INDUCTIVE CHARGING DEVICE
`
`Attached Publication
`
`International Search Report
`(Article 21(3) of the Treaty)
`
`(57) Abstract: A power feed device (2) of an inductive charging device (1) is provided with: a power factor
`correction circuit (10) that converts an AC power source into DC, and that corrects the power factor; a
`smoothing capacitor (lb that is connected to the output terminal of the power factor correction circuit; an
`inverter circuit (20) that has a plurality of switching elements (21, 23, 26, 28), and that generates an AC signal
`using the voltage of the smoothing capacitor as the power source; a power feed unit (9) that feeds power based
`on the AC signal to a power-receiving device (50); and a control circuit (6) that synchronizes the duty factor of
`the switching elements in the inverter circuit with the AC power source and modulates the duty factor. The
`control circuit controls the plurality of switching elements so that width fluctuations related to the modulation of
`the duty factor are asymmetrical.
`
`(57) ABSTRACT
`
`A power supply device (2) of a non-contact charging device (1) that converts AC power source (3) to DC and
`includes a power factor improvement circuit (10), a smoothing capacitor (16) connected to the output end of the
`power factor improvement circuit, a plurality of switching elements (21, 23, 26, 28), an inverter circuit (20) that
`generates an AC signal with the voltage of the smoothing capacitor as a power source, a power supply unit (9)
`that supplies the AC signal to the power receiving device (50) based on the AC signal, and a control circuit that
`modulates the duty factor of each of the switching elements of the inverter circuit in synchronization with the
`AC power source and the control circuit controls the plurality of switching elements such that the
`increase/decrease range related to the modulation of the duty factor is asymmetrical.
`
`Page 1 of 60
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`GOOGLE AND SAMSUNG EXHIBIT 1007
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`WO 2013/136755
`
`
`
`PCT/JP2013/001540
`
`1
`SPECIFICATION
`
`TITLE OF INVENTION: POWER SUPPLY DEVICE FOR NON-CONTACT CHARGING DEVICE
`
`TECHNICAL FIELD
`[0001]
`The present disclosure relates to a non-contact charging device for non-contact charging of, for example,
`secondary batteries installed in electric propulsion vehicles (electric vehicles and hybrid vehicles).
`
`CONVENTIONAL TECHNOLOGY
`[0002]
`Technologies that use magnetic, electric, radio waves, and the like have been developed for non-contact power
`transmission. This non-contact power transmission technology eliminates the need for wiring to connect the
`power supply device to the power receiving device, which saves time and effort for the user for making
`connection, and eliminates worries about electrical leakage and electric shock in rainy weather.
`
`[0003]
`However, with non-contact power transmission, for example, the positional relationship between the power
`supply device and the power receiving device is important for high efficiency. In order to address this problem,
`a technology has been proposed to reduce the constraint of the positional relationship between the power supply
`device and the power receiving device by equipping each of the power supply device and the power receiving
`device with a resonance part that generates resonance of an AC signal (see, for example, Patent Document 1).
`
`[0004]
`However, in the case of the technology described in Patent Document 1, harmonic components of the same
`frequency as that of the commercial power supply are superimposed on the power supply power output from the
`power supply device. As a result, current ripple or voltage ripple of harmonic components is generated in the
`output of the power supply device, and ripple is also generated in the output of the power receiving device, in
`other words, the output current to the battery.
`
`[0005]
`In addition, there is a conventional method of wired connection between the power source and the electric
`propulsion vehicle in order to charge such electric propulsion vehicles and the like. In the wired system, fast
`feedback control can be performed when a ripple in the output current to the battery is detected. However, in a
`non-contact charging method, when a ripple in the output current is detected, notification is provided to the
`power supply side via wireless communication, causing the problem of fast feedback control being difficult to
`perform.
`
`
`
`Page 2 of 60
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`PCT/JP2013/001540
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`WO 2013/136755
`[0006]
`Therefore, three circuits (converters) each made up of four series-connected circuits are connected in parallel to
`enable sharing a plurality of smoothing capacitors where each circuit is driven so that the phase of each circuit
`is offset by 2/3 (rad) has also been proposed (for example, see Patent Document 2). With this technology, the
`charge and discharge current to the plurality of smoothing capacitors converges between the circuits enabling
`reducing voltage ripple.
`
`PRIOR ART DOCUMENTS
`Patent Documents
`[0007]
`Patent Document 1: Japanese Unexamined Patent Application 2009-296857
`Patent Document 2: Japanese Unexamined Patent Application 2008-263715
`
`SUMMARY OF THE INVENTION
`PROBLEM TO BE SOLVED BY THE INVENTION
`[0008]
`In the case of the configuration described in Patent Document 2, although the voltage ripple of the smoothing
`capacitor can be reduced, the number of parts in the power supply device is large due to the need for a plurality
`of circuits (converters) and this leads to increase in size and cost and also has the problem of increased power
`supply losses.
`
`[0009]
`In light of these points, the present disclosure addresses the problem of providing a non-contact charging device
`power supply device with reduced ripple on the output, enables size reduction and cost reduction, and
`suppresses power supply losses to the extent possible.
`
`MEANS FOR SOLVING THE PROBLEM
`[0010]
`In order to resolve the problems described above, the following solutions have been achieved by the present
`disclosure. A power supply device for a non-contact charging device that supplies power to a power receiving
`device in a non-contact manner, comprising:
` a power factor improvement circuit that converts an AC power source to DC to improve the power factor;
` a smoothing capacitor connected to an output end of the power factor improvement circuit;
` an inverter circuit that has a plurality of switching elements and generates an AC signal by switching each of
`the switching elements using the voltage of the smoothing capacitor as a power source;
` a power supply unit that has a resonant capacitor and a first inductor connected to an output end of the inverter
`circuit, and supplies power generated between the first inductor and a second inductor provided in the power
`receiving device to the power receiving device based on the AC signal; and
` a control circuit that modulates the duty factor of each switching element of the inverter circuit in
`synchronization with the AC power source, when power is supplied from the power supply unit to the power
`receiving device; wherein
` the control circuit controls the plurality of switching elements such that the increase/decrease range related to
`the modulation of the duty factor is asymmetrical.
`
`
`
`2
`
`
`
`Page 3 of 60
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`PCT/JP2013/001540
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`WO 2013/136755
`EFFECT OF THE INVENTION
`[0011]
`With the present disclosure, ripples generated in the output can be reduced, size and cost reduction are feasible,
`and power supply losses can be suppressed for the power supply device of the non-contact charging device.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`[0012]
`FIG. 1 is a circuit diagram illustrating the non-contact charging device according to embodiment 1.
`FIG. 2 is a circuit diagram illustrating a configuration example of the input detecting part illustrated in FIG. 1.
`FIG. 3 is a circuit diagram illustrating a configuration example of a synchronous signal generating part
`illustrated in FIG. 1.
`FIG. 4 illustrates a waveform diagram of each part of a conventional power transfer system for comparison with
`the non-contact charging device in FIG. 1.
`FIG. 5 illustrates a waveform diagram of each part in the non-contact charging device illustrated in FIG. 1,
`when the duty factor of the inverter circuit illustrated in FIG. 1 is changed.
`FIG. 6 is a zoomed-in view of the operating waveform diagram of the inverter circuit at high input power.
`FIG. 7 is a zoomed-in view of the operating waveform diagram of the inverter circuit at low input power.
`FIG. 8 illustrates the relationship between the input current and the ∆ duty factor of the power supply device
`illustrated in FIG. 1.
`FIG. 9 illustrates the relationship between the input power and the duty factor of the power supply device
`illustrated in FIG. 1.
`
`
`
`3
`
`
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`PCT/JP2013/001540
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`4
`WO 2013/136755
`DESCRIPTION OF THE PREFERRED EMBODIMENTS
`[0013]
`The present disclosure is a power supply device for a non-contact charging device that supplies power to a
`power receiving device in a non-contact manner, comprising:
` a power factor improvement circuit that converts AC power source to DC to improve the power factor;
` a smoothing capacitor connected to an output end of the power factor improvement circuit;
` an inverter circuit that has a plurality of switching elements and generates an AC signal by switching each of
`the switching elements using the voltage of the smoothing capacitor as a power source;
` a power supply unit that has a resonant capacitor and a first inductor connected to an output end of the inverter
`circuit, and supplies power generated between the first inductor and a second inductor provided in the power
`receiving device to the power receiving device based on the AC signal; and
` a control circuit that modulates the duty factor of each switching element of the inverter circuit in
`synchronization with the AC power source, when power is supplied from the power supply unit to the power
`receiving device; wherein
` the control circuit controls the plurality of switching elements such that the increase/decrease range related to
`the modulation of the duty factor is asymmetrical.
`
`[0014]
`In addition, the control circuit increases the modulation amount of the duty factor for the plurality of switching
`elements in conjunction with increase in input power from the AC power source to this power supply device.
`
`[0015]
`Furthermore, the control circuit ensures that the pattern for modulating the duty factor is an approximate sine
`wave with two times the frequency of the AC power source.
`
`[0016]
`With this configuration, output ripple of the power supply device can be reduced not only during feedback
`control where high detection accuracy is required but also with feedforward control. As a result, the ripple in the
`output of the power receiving device can be reduced, and components for detecting output of the first inductor
`and for detecting voltage of the smoothing capacitor are not needed in the power supply device. Thus the
`number of components in the power supply device is reduced enabling size reduction and cost reduction of the
`power supply device.
`
`[0017]
`Embodiments of the present disclosure will be described in detail below with reference to the drawings.
`However, the present disclosure is not limited by this embodiment.
`
`[0018]
`Embodiment 1FIG. 1 is a circuit diagram of the non-contact charging device according to embodiment 1.
`
`[0019]
`As illustrated in FIG. 1, a non-contact charging device 1 includes a power supply device 2 installed in, for
`example, a parking space, and a power receiving device 50 equipped on an electric propulsion vehicle. The
`power supply device 2 includes a commercial power supply 3, a first rectifier circuit 4, a synchronous signal
`generating part 5, a control circuit 6 on the power supply device 2 side (simply “control circuit 6” below), a
`power supply unit 9, a power factor improvement circuit 10, and an inverter circuit 20.
`
`
`
`
`
`Page 5 of 60
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`PCT/JP2013/001540
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`WO 2013/136755
`[0020]
`The power receiving device 50 includes a second inductor 51, a second resonant capacitor 52, a second rectifier
`circuit 53, a load (for example, a battery) 18, a received power detecting part 54, and a control circuit 55 on the
`power receiving device 50 side (simply "control circuit 55" below).
`
`[0021]
`The configuration of these circuit blocks is described below.
`
`[0022]
`First, configuration of the power factor improvement circuit 10 will be described. The power factor
`improvement circuit 10 is a circuit that improves the power factor of the commercial power supply 3.
`Specifically, the power factor improvement circuit 10 includes a bypass capacitor 11, an input detecting part 12,
`a choke coil 13, a first switching element 14 (in the present embodiment, a MOSFET: metal-oxide-
`semiconductor field-effect transistor), one diode 15 and a smoothing capacitor (electrolytic capacitor) 16.
`
`[0023]
`The commercial power supply 3 is, for example, a 200V commercial power supply, which is a low-frequency
`AC power source, and is connected to the input end of the first rectifier circuit 4, which includes a bridge diode
`and an input filter.
`
`[0024]
`The high potential side (positive electrode side) output terminal of the first rectifier circuit 4 is connected to the
`high potential side terminal of the bypass capacitor 11 and the input detecting part 12. The output terminal of
`the input detecting part 12 is connected to the input side terminal of the choke coil 13.
`
`[0025]
`The high potential side terminal (drain) of the first switching element 14 is connected to the connection line
`between the output side terminal of the choke coil 13 and the anode of the first diode 15. The low potential side
`(negative electrode side) output terminal of the first rectifier circuit 4 is connected to the low potential side
`terminal of the bypass capacitor 11, the low potential side terminal (source) of the first switching element 14,
`and the low potential side terminal of the smoothing capacitor 16.
`
`In addition, the high potential side terminal of the smoothing capacitor 16 is connected to the cathode of the first
`diode 15.
`
`
`
`5
`
`
`
`Page 6 of 60
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`6
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`PCT/JP2013/001540
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`WO 2013/136755
`[0026]
`The output voltage of the first rectifier circuit 4 is input as a DC power source to the power factor improvement
`circuit 10, which is configured as described above. Specifically, the output voltage of the first rectifier circuit 4
`is first attenuated by the bypass capacitor 11 to reduce voltage fluctuation. Furthermore, the first switching
`element 14 ON/OFF operation and the choke coil 13 boosts the output voltage of the first rectifier circuit 4 to an
`arbitrary voltage, which is a DC voltage with a value greater than the peak value thereof. This boosted voltage
`is supplied to both ends of the smoothing capacitor 16 for smoothing.
`
`[0027]
`In the present embodiment, a MOSFET with a high switching speed is used as the first switching element 14 to
`increase the power factor improvement effect by operating the power factor improvement circuit 10 at high
`frequency. In this case, a diode may be attached to the MOSFET in the reverse direction, but the diode is not
`shown in the figure because the absence of this diode does not affect the basic operation of the present
`embodiment in any way. The output voltage of the smoothing capacitor 6 is supplied between the input
`terminals of the inverter circuit 20.
`
`[0028]
`The input terminals of the inverter circuit 20 are connected to the output terminals of the power factor
`improvement circuit 10, in other words, to both ends of the smoothing capacitor 16. Series-connected second
`and third switching elements 21, 23, and series-connected fourth and fifth switching elements 26, 28 are
`connected in parallel to both ends of the smoothing capacitor 16.
`
`[0029]
`The second and third diodes 22 and 24 are connected in reverse parallel to the second and third switching
`elements 21 and 23, respectively. Specifically, the high potential side terminal (collector) of the switching
`element is connected to the cathode of the diode.
`
` A
`
` snubber capacitor 25 is connected in parallel to the third switching element 23. Note, the snubber capacitor 25
`may be connected in parallel with the second switching element 21.
`
`[0030]
`Similarly, the fourth and fifth diodes 27 and 29 are connected in reverse parallel to the fourth and fifth
`switching elements 26 and 28, respectively. Specifically, the high potential side terminal (collector) of the
`switching element is connected to the cathode of the diode. A snubber capacitor 30 is connected in parallel to
`the fifth switching element 28. The snubber capacitor 30 may be connected in parallel with the fourth switching
`element 26.
`
`
`
`
`
`Page 7 of 60
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`PCT/JP2013/001540
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`WO 2013/136755
`[0031]
`In addition, the power supply unit 9 is connected to a connection line between the second switching element 21
`and the third switching element 23, and to a connection line between the fourth switching element 26 and the
`fifth switching element 28.
`
`[0032]
`The inverter circuit 20 generates an AC signal by switching the second through fifth switching elements 21, 23,
`26, and 28, and outputs this to the power supply unit 9.
`
`[0033]
`The power supply unit 9 can be composed of a first resonant capacitor 7 and a first inductor 8 connected in
`series.
`
`[0034]
`The second inductor 51 is arranged opposite the first inductor 8, for example, as the electric propulsion vehicle
`moves. As a result, the power supply unit 9 can supply the power generated between the first and second
`inductors 8, 51 to the power receiving device 50 based on the AC signal output from the inverter circuit 20.
`
`[0035]
`The second resonant capacitor 52 is connected to the high potential side of the second inductor 51. The second
`rectifier circuit 53, which contains a smoothing filter, is connected between the low potential side of the second
`inductor 51 and the second resonant capacitor 52.
`
`The received power detecting part 54 is connected to the high potential side of the second rectifier circuit 53,
`and a load, for example a battery 18, is connected between the received power detecting part 54 and the low
`potential side of the second rectifier circuit 53.
`
`[0036]
`Next, a specific example of the input detecting part 12 will be explained using FIG. 2. FIG. 2 is a circuit
`diagram illustrating a configuration example of the input detecting part illustrated in FIG. 1.
`
`[0037]
`As illustrated in FIG. 2, the input detecting part 12 includes a current detecting part 31, a voltage detecting part
`32, and a power calculating part 33. The power calculating part 33 is connected to a control circuit 6. Note that
`if power can be estimated by either current or voltage alone, having one of either the current detecting part 31 or
`the voltage detecting part 32 is sufficient.
`
`
`
`7
`
`
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`PCT/JP2013/001540
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`WO 2013/136755
`[0038]
`FIG. 3 is a circuit diagram illustrating a configuration example of synchronous signal generating part illustrated
`in FIG. 1. As illustrated in FIG. 3, the synchronous signal generating part 5 includes a plurality of resistive
`elements 34, 35, 36, and 37, and a transistor 38. The synchronous signal generating part 5 generates a signal
`with a frequency synchronized to the frequency of the commercial power supply 3, and outputs this frequency
`to the control circuit 6. The Vdd in FIG. 3 is the control voltage of the control circuit 6.
`
`[0039]
`Specifically, the synchronous signal generating part 5 outputs a synchronization signal to the control circuit 6,
`namely, the transistor 38 turns ON, abbreviated OV (= LOW), during the positive half wave period of
`commercial power supply 3 output, and the transistor 38 turns OFF, Vdd (= HIGH), during the negative half
`wave period of the commercial power supply 3 output.
`
`[0040]
`The control circuit 6 synchronizes with this synchronization signal, and performs modulation control for the
`inverter circuit 20. This will be described below; however, this synchronization signal includes the delay time
`due to the transistor 38 turning ON and OFF, and the delay time is relative to the commercial power supply 3.
`
`[0041]
`Also note that while no detailed explanations of the received power detecting part 54 provided, the received
`power detecting part 54 can have the same configuration as the input detecting part 12.
`
`[0042]
`Next, the configuration of the control circuit 6 will be described. The control circuit 6 receives, via wireless
`communication, a power command value from the control circuit 55 indicating the power value to be supplied
`to the power receiving device 50. The control circuit 6 compares the power based on the input current detected
`by the input detecting part 12 and the power command value received, and drive controls the second and third
`switching elements 2 and 3, and the fourth and fifth switching elements 26 and 28 of the inverter circuit 20, in
`addition to the first switching element 14 of the power factor improvement circuit 10, such that power
`corresponding to the power command value can be output. Note that the control circuit 6 does not control the
`first switching element 14, but a dedicated control IC may be used to control the first switching element 14.
`
`[0043]
`The control circuit 55 determines a power command value based on the remaining voltage of the battery 18
`detected by the received power detecting part 54, and transmits said power command value via wireless
`communication to the control circuit 6. In addition, when the power supply device 2 is in operation, the control
`circuit 55 changes the power command value sent to the control circuit 6 based on the received power detected
`by the received power detecting part 54 to prevent over-current or over-voltage from being applied to the
`battery 18.
`
`
`
`8
`
`
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`PCT/JP2013/001540
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`WO 2013/136755
`[0044]
`The battery 18 for the present embodiment is a battery for electric propulsion vehicles. When charging the
`battery, a voltage greater than the remaining battery voltage is supplied to perform charging; however, when the
`supply voltage exceeds the remaining battery voltage, charge current flows rapidly. This means that the
`impedance of the load as seen by the power supply device varies greatly depending on the remaining voltage of
`the battery and the supply voltage.
`
`[0045]
`The operation of the non-contact charging device 1 configured as described above shall be explained below.
`First, the voltage waveform, current waveform, and the like of each part in the power transfer system described
`in Patent Document 1 will be explained with reference to FIG. 4. However, the non-contact charging device 1
`according to the present embodiment and the power transfer system as described in Patent Document 1 naturally
`have different configurations. In FIG. 4, the terms "output voltage of the first rectifier circuit 4" and "output
`voltage of the power factor improvement circuit 10" are used to compare the non-contact charging device 1
`according to the present embodiment and the power transfer system as described in Patent Document 1 and to
`indicate the output voltage and the like of the corresponding parts of the power transfer system as described in
`Patent Document 1.
`
`[0046]
`FIG. 4(a) is a schematic diagram illustrating the AC voltage waveform of the commercial power supply 3. FIG.
`4(b) is an output voltage waveform of the DC power source, or in other words, a schematic diagram illustrating
`the output voltage waveform of the first rectifier circuit 4. This voltage is input to the power factor
`improvement circuit 10, boosted, and then output to the smoothing capacitor 16.
`
`[0047]
`FIG. 4(c) is a waveform of the voltage applied to the smoothing capacitor 16, or in other words, an output
`voltage waveform of the power factor improvement circuit 10, as well as a schematic diagram illustrating the
`input voltage waveform of the inverter circuit 20.
`
`[0048]
`FIG. 4(d) is a schematic diagram illustrating the waveform of a high frequency current generated in the first
`inductor 8. FIG. 4(e) is a schematic diagram illustrating a waveform of the voltage supplied from the power
`supply device 2 to the power receiving device 50.
`
`[0049]
`FIG. 4(f) is an output current waveform of the second rectifier circuit 53, or in other words, a schematic
`diagram illustrating the input current waveform of the load 18.
`
`[0050]
`In addition, FIG. 4(g) and FIG. 4(h) are schematic diagrams each illustrating the duty factor (duty ratio) and
`operating frequency of the inverter circuit 20.
`
`
`
`9
`
`
`
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`PCT/JP2013/001540
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`WO 2013/136755
`[0051]
`On the other hand, FIG. 5 illustrates the voltage waveforms, current waveforms, and the like of each part of the
`non-contact charging device according to the present embodiment. FIG. 5(a) to FIG. 5(h) each correspond to
`FIG. 4(a) to FIG. 4(h). Note that using conventional technology, the duty factor (duty ratio) and operating
`frequency of the inverter circuit 20 are constant, as illustrated in FIG. 4(g) and FIG. 4(h).
`
`[0052]
`First, an operation of the power factor improvement circuit 10 will be described.
`
`[0053]
`Output of the commercial power supply 3 shown in FIG. 5(A) is full-wave rectified by the first rectifier circuit 4
`to form a DC power source as shown in the voltage waveform in FIG. 5(b). The DC power source is supplied
`between input terminals of the power factor improvement circuit 10. In the power factor improvement circuit
`10, when the magnitude of the instantaneous value of the voltage of the DC power source is smaller than the
`voltage of the smoothing capacitor 16, the first diode 5 and a bridge diode of the first rectifier circuit 4 included
`in the power factor improvement circuit 10 cannot be turned ON, resulting in distortion of the input current
`waveform and a significantly lower power factor. At this time, the power factor in the power factor
`improvement circuit 10 is improved by the control circuit 6 turning ON/OFF the first switching element 14.
`
`[0054]
`When the first switching element 14 is turned ON, energy is stored in the choke coil 13 from the commercial
`power supply 3. Thereafter, when the first switching element 14 turns OFF, the energy stored in the choke coil
`13 is supplied to the smoothing capacitor 16 via the first diode 15. This allows the input current to flow from the
`commercial power supply 3 through the choke coil 13, and prevents the distorted input current from the
`commercial power supply 3 side.
`
`[0055]
`Furthermore, in present embodiment, the power factor improvement circuit 10 has not only a power factor
`improvement function but also a voltage boost function at the same time. Therefore, as shown in FIG. 5(c), the
`voltage of the smoothing capacitor 16 becomes higher than the peak value of the input voltage of the power
`factor improvement circuit 10, whose peak value is the peak value of the commercial power supply 3, in other
`words, the peak value of the DC power source, and is supplied to the inverter circuit 20 through the smoothing
`capacitor 16. As shown in FIG. 5(c), the voltage of the smoothing capacitor 16 has a voltage ripple of twice the
`frequency of the commercial power supply 3 that occurs at the target output voltage Vpfc of the power factor
`improvement circuit 10.
`
`
`
`10
`
`
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`PCT/JP2013/001540
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`WO 2013/136755
`[0056]
`Note that as is obvious by comparing FIGS. 4(a) to (c) and FIGS. 5(a) to (c), there is no significant difference in
`the AC voltage waveform of the commercial power supply 3, the output voltage waveform of the first rectifier
`circuit 4, and the output voltage waveform of the power factor improvement circuit 10 between the non-contact
`charging device 1 according to the present embodiment and the power transfer system described in Patent
`Document 1.
`
`[0057]
`Next, the operation of the inverter circuit 20 will be described.
`
`[0058]
`The smoothed and output DC voltage at two ends of the smoothing capacitor 16 connected between output ends
`of the power factor improvement circuit 10 is supplied to the inverter circuit 20 (see FIG. 5(c)).
`
`[0059]
`In the inverter circuit 20, by turning ON/OFF the second and third switching elements 21, 3, as well as the
`fourth and fifth switching elements 26, 28, a high-frequency current of a predetermined frequency is generated
`in the first resonant capacitor 7 and the first inductor 8, as shown in FIG. 5(d).
`
`[0060]
`The ON/OFF control of the second and third switching elements 21, 23, and the ON/OFF control of the fourth
`and fifth switching elements 26, 28 are performed by the control circuit 6 applying an ON signal or an OFF
`signal to the gate of the second to fifth switching elements 21, 23, 26, 28.
`
`[0061]
`FIG. 6 is an enlarged view of an operating waveform diagram of an inverter circuit at high input power, and
`FIG. 7 is an enlarged view of an operating waveform diagram of the inverter circuit at low input power.
`
`[0062]
`In FIG. 6 and FIG. 7, (a) indicates a current flowing through the second and fifth switching elements 21, 28 and
`the second and fifth diodes 22, 29, (b) indicates a current flowing through the third and fourth switching
`elements 23, 26 and the third and fourth diodes 23, 27, (c) indicates a voltage of the second and fifth switching
`elements 21, 28, (d) indicates a gate voltage of the second and fifth switching elements 21, 28, and (e) indicates
`a gate voltage of the third and fourth switching elements 23, 26.
`
`
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`Page 12 of 60
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`12
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`PCT/JP2013/001540
`
`WO 2013/136755
`[0063]
`Furthermore, (f) in FIG. 6 and FIG. 7 indicates a current IL1 flowing through the first inductor 8. In (f) of FIG.
`6 and FIG. 7, electric current flows through the second and fifth switching elements 21, 28 and the second and
`fifth diodes 22, 29 during the Ton period of the switching cycles. On the other hand, during the remaining
`period of the switching cycles (T_Td_Ton in the drawings), the current flows through the third and fourth
`switching elements 23, 26, and the third and fourth diodes 24, 27. During a dead time Td period described later,
`the resonant current of the first inductor 8, the first resonant capacitor 7, and the snubber capacitors 25 and 30
`flows.
`
`[0064]
`As shown in FIG. 6 and FIG. 7, the series-connected second and third switching elements 21, 23 are exclusively
`energized. Fu