Contactless power supply system and power transmission device

Abstract

To provide a contactless power supply system that can determine whether a target power can be transmitted before initiation of power transmission and can minimize the time it takes for the transmitted power to reach the target power after the initiation of power transmission.SOLUTION: A contactless power supply system C1 transmits the power contactlessly from a power transmission device A to a power reception device B. The power transmission device A comprises: a high-frequency power source device 1; a power transmission unit 2 to which a high-frequency power is input; and a control device 5 that controls the high-frequency power source device 1. The power reception device B comprises: a power reception unit 3; and a rectification and smoothing circuit 4 that outputs a DC power by rectifying the high-frequency power, which is received from the power transmission unit 2 by the power reception unit 3. The power reception device B supplies a power storage device D with the DC power output by the rectification and smoothing circuit 4. Before initiation of power transmission of a charging power to the power storage device D, the control device 5 causes the high-frequency power source device 1 to output a test power, which is lower than the charging power, thereby determining an optimal frequency fx of the high-frequency power output by the high-frequency power source device 1 in order to allow the power reception device B to output a target power.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a contactless power supply system that transmits electric power in a contactless manner, and a power transmitting device. [Background technology]

[0002] A technology has been developed that transmits the power output by a power supply to a load in a non-contact manner, without directly connecting the load and the power supply. This technology is generally called non-contact power supply or wireless power supply. This technology is applied to power supply to mobile phones, home appliances, electric vehicles, automated guided vehicles (AGVs), etc.

[0003] In contactless power transfer, power is transferred contactlessly from a power transfer device equipped with a high-frequency power supply device to a power receiving device connected to a load. The power transfer device is equipped with a power transfer coil, and the power receiving device is equipped with a power receiving coil. The power transfer coil and the power receiving coil are magnetically coupled to transfer power contactlessly. Patent Document 1 discloses a contactless power transfer system. In this contactless power transfer system, the power transfer device is equipped with a full-bridge inverter circuit, and controls the high-frequency power output from the inverter circuit by phase shift control. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-89126 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, when the output is suppressed, the phase difference becomes large, which causes a problem of increased heat loss in one of the switching elements.

[0006] The present invention has been devised in light of the above circumstances, and has an object to provide a contactless power supply system and a power transmission device that can suppress heat loss in a switching element when output is suppressed. [Means for solving the problem]

[0007] A contactless power supply system provided by a first aspect of the present invention is a contactless power supply system that contactlessly transmits power from a power transmission device to a power receiving device, the power transmission device including a DC power supply device that outputs DC power, an inverter circuit in which a leading arm having two switching elements connected in series and a following arm having another two switching elements connected in series are connected in parallel, and a control device that controls the power transmission device, and the control device generates a first control signal to be input to one switching element of the leading arm and a second control signal to be input to a corresponding switching element of the following arm, with the first control signal and the second control signal shifted in phase by a fixed phase difference.

[0008] In a preferred embodiment of the present invention, the specified ratio, which is the ratio of the period during which the high level of the pulse of the first control signal overlaps with the high level of the pulse of the second control signal to the high level period of the pulse of the first control signal, is fixed and is greater than or equal to 50% and less than 100%.

[0009] In a preferred embodiment of the present invention, the predetermined ratio is equal to or greater than 2 / 3 and equal to or less than 80%.

[0010] In a preferred embodiment of the present invention, the control device adjusts the DC voltage that the DC power supply device outputs to the inverter circuit.

[0011] A power transmission device provided by a second aspect of the present invention is a power transmission device that supplies power to a power receiving device in a non-contact manner, and includes a DC power supply device that outputs DC power, an inverter circuit in which a leading arm having two switching elements connected in series and a following arm having another two switching elements connected in series are connected in parallel, and a control device that controls the inverter circuit, and the control device generates a first control signal that is input to one switching element of the leading arm and a second control signal that is input to the corresponding switching element of the following arm, with the phases shifted by a fixed phase difference. Effect of the Invention

[0012] According to the present invention, the control device generates the first control signal and the second control signal with a fixed phase difference. In the contactless power supply system C1, the phase difference does not become large even during output suppression, so that heat loss in the switching element can be suppressed. [Brief description of the drawings]

[0013] [Figure 1] 1 is a block diagram showing an overall configuration of a contactless power supply system according to a first embodiment. [Diagram 2] 1 is a block diagram showing an internal configuration of a high-frequency power supply device; [Diagram 3] FIG. 4 is a waveform diagram showing a high-frequency control signal generated by the control device. [Figure 4] 1 is a diagram for explaining a two-terminal pair circuit including a power transmitting unit, a power receiving unit, and a rectifying smoothing circuit. [Diagram 5] 4 is an example of a flowchart for explaining an appropriate frequency search process performed by a control device. [Figure 6] 13 is an example of a flowchart for explaining an appropriate frequency search process performed by a control device of a contactless power supply system according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0015] 1 and 2 are diagrams for explaining a contactless power supply system C1 according to a first embodiment. FIG. 1 is a block diagram showing the overall configuration of the contactless power supply system C1. FIG. 2 is a block diagram showing the internal configuration of a high-frequency power supply device 1. The contactless power supply system C1 includes a power receiving device B provided on a vehicle body such as an electric vehicle, and a power transmitting device A embedded in the floor of a parking lot or the like. The power transmitting device A includes a power transmitting coil arranged on the floor, and the power receiving device B includes a power receiving coil arranged on the bottom of the vehicle body. The power transmitting coil and the power receiving coil are magnetically coupled, so that the power receiving device B receives high-frequency power transmitted from the power transmitting device A. That is, a high-frequency current flows through the power transmitting coil, changing the magnetic flux, and a high-frequency current flows through the power receiving coil that is linked to this magnetic flux. This allows power to be transmitted contactlessly from the power transmitting device A to the power receiving device B. The power receiving device B rectifies the high-frequency current in a rectifying and smoothing circuit and supplies it to the power storage device D.

[0016] The power transmitting coil and the power receiving coil are planar coils wound in a spiral shape, and are arranged so that the coil surfaces are approximately parallel to the floor surface. When power is to be supplied, it is desirable to place the vehicle body so that the power receiving device B is directly above the power transmitting device A, and the power receiving coil overlaps the power transmitting coil when viewed from above. The contactless power supply system C1 can supply power even if there is a slight misalignment between the power receiving coil and the power transmitting coil, but cannot supply power if there is a large misalignment. In this case, the contactless power supply system C1 makes an announcement to the effect that power supply is not possible before starting power supply.

[0017] The power transmitting device A includes a high frequency power supply device 1, a power transmitting unit 2, a control device 5, and a communication device 6.

[0018] The high frequency power supply device 1 outputs high frequency power in response to a command from the control device 5. As shown in Fig. 2, the high frequency power supply device 1 includes a DC power supply device 11 and an inverter circuit 12. The high frequency power supply device 1 converts DC power generated by the DC power supply device 11 into high frequency power by the inverter circuit 12 and outputs the high frequency power.

[0019] The DC power supply device 11 generates and outputs DC power. The DC power supply device 11 includes a rectifying and smoothing circuit 111 and a DC / DC converter circuit 112.

[0020] The rectifying and smoothing circuit 111 rectifies and smoothes the AC voltage (for example, a commercial voltage of 200 [V]) input from a commercial power source, thereby converting it into a DC voltage. The rectifying and smoothing circuit 111 includes a full-wave rectifying circuit in which six diodes are bridge-connected. The rectifying and smoothing circuit 111 also includes a smoothing circuit for smoothing the output after rectification. The configuration of the rectifying and smoothing circuit 111 is not limited as long as it converts the AC voltage into a DC voltage.

[0021] The DC / DC converter circuit 112 converts the DC voltage input from the rectifying and smoothing circuit 111 in response to a command from the control device 5. The configuration of the DC / DC converter circuit 112 is not limited as long as it can convert the voltage in response to a command from the control device 5.

[0022] The inverter circuit 12 converts the DC voltage input from the DC power supply device 11 into a high-frequency voltage and outputs it. The inverter circuit 12 is a full-bridge type inverter circuit, and includes four switching elements Q1 to Q4. Each of the switching elements Q1 to Q4 switches between an on state and an off state in response to a high-frequency control signal input from the control device 5. In this embodiment, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) are used as the switching elements Q1 to Q4. Note that the switching elements Q1 to Q4 are not limited to MOSFETs, and may be bipolar transistors, IGBTs (Insulated Gate Bipolar Transistors), or the like.

[0023] The switching element Q1 and the switching element Q2 are connected in series with the source terminal of the switching element Q1 and the drain terminal of the switching element Q2 connected. The drain terminal of the switching element Q1 is connected to the high-potential output terminal of the DC power supply 11, and the source terminal of the switching element Q2 is connected to the low-potential output terminal of the DC power supply 11. As a result, the switching element Q1 and the switching element Q2 form a bridge structure. Similarly, the switching element Q3 and the switching element Q4 are connected in series to form a bridge structure. In the following, the bridge structure formed by the switching element Q1 and the switching element Q2 is referred to as a leading arm, and the bridge structure formed by the switching element Q3 and the switching element Q4 is referred to as a following arm. A high-frequency voltage is output to the power transmission unit 2 from the connection point between the switching element Q1 and the switching element Q2 of the leading arm and the connection point between the switching element Q3 and the switching element Q4 of the following arm.

[0024] A free wheel diode is connected in anti-parallel between the drain terminal and the source terminal of each of the switching elements Q1 to Q4. That is, the anode terminal of each free wheel diode is connected to the source terminal of the switching element Q1 to Q4, and the cathode terminal of each free wheel diode is connected to the drain terminal of the switching element Q1 to Q4. Each free wheel diode is provided to divert a reverse current from flowing into each of the switching elements Q1 to Q4.

[0025] The high frequency control signals CS1 to CS4 output from the control device 5 are input to the gate terminals of the switching elements Q1 to Q4, respectively. The high frequency control signals CS1 to CS4 are pulse signals that alternate between high and low levels at an appropriate frequency fx, which will be described later. The switching element Q1 (Q2, Q2, Q4) is in an off state when the high frequency control signal CS1 (CS2, CS3, CS4) is at a low level, and is in an on state when the high frequency control signal CS1 (CS2, CS3, CS4) is at a high level. The inverter circuit 12 switches between the on and off states of the switching elements Q1 to Q4 in response to the high frequency control signals CS1 to CS4 input from the control device 5, thereby converting the DC power input from the DC power supply device 11 into high frequency power and outputting it to the power transmission unit 2. The high frequency control signals CS1 to CS4 will be described later in detail.

[0026] The power transmitting unit 2 includes a power transmitting coil Lt and a resonant capacitor Ct. The power transmitting coil Lt transmits high-frequency power supplied from the high-frequency power supply device 1 to the power receiving device B. The resonant capacitor Ct is connected in series to the power transmitting coil Lt to form a series resonant circuit.

[0027] The power transmitting coil Lt and the resonant capacitor Ct are designed so that the resonant frequency coincides with the reference frequency f0. That is, the self-inductance L t and the capacitance C of the resonant capacitor Ct tand are designed to satisfy the relationship of the following formula (1). The reference frequency f0 is a reference frequency for the frequency of the high frequency power output by the high frequency power supply device 1, and is, for example, 85 kHz. Note that the reference frequency f0 is not limited.

number

[0028] The communication device 6 performs wireless communication with the power receiving device B (communication device 8 described later). The communication device 6 transmits a signal input from the control device 5 to the communication device 8. The communication device 6 also outputs a signal received from the communication device 8 to the control device 5. Note that the communication method of the communication device 6 and the type of electromagnetic waves used are not limited.

[0029] The control device 5 controls the power transmitting device A and is configured with a microcomputer including a central processing unit (CPU), a read only memory (ROM) and a random access memory (RAM), a field programmable gate array (FPGA), or the like.

[0030] The control device 5 generates high-frequency control signals CS1-CS4 for controlling the inverter circuit 12 so as to output a high-frequency voltage of an appropriate frequency fx from the high-frequency power supply device 1, and outputs the signals to the inverter circuit 12. The appropriate frequency fx is a frequency at which high-frequency power can be efficiently transmitted from the power transmitting device A to the power receiving device B, and is a frequency at which the power receiving device B can output a target power. A method for setting the appropriate frequency fx will be described later. The control device 5 generates a pulse signal with a predetermined duty ratio (for example, 50%) at the appropriate frequency fx based on a reference clock, and generates high-frequency control signals CS1-CS4 for controlling the switching elements Q1-Q4 from the pulse signal. The high-frequency control signals CS1-CS4 are amplified to a level at which the switching elements Q1-Q4 can be driven by a drive circuit (not shown), and are output to the switching elements Q1-Q4.

[0031] In this embodiment, the control device 5 delays the phase of the high frequency control signal CS4 (CS3) output to the switching element Q4 (Q3) of the follower arm from the phase of the high frequency control signal CS1 (CS2) output to the switching element Q1 (Q2) of the leading arm. The phase difference at this time is fixed, and the control of the output high frequency power is not performed by adjusting the phase difference as in so-called phase shift control. In this embodiment, the period during which the high level of the pulse of the high frequency control signal CS1 (CS2) and the high level of the pulse of the high frequency control signal CS4 (CS3) overlap is set to be a predetermined ratio of the high level period of the pulses of the high frequency control signals CS1 to CS4. The predetermined ratio is a fixed value and does not change. Note that the predetermined ratio is not limited, but is desirably 50% or more and less than 100% in order to suppress heat generation in each of the switching elements Q1 to Q4, to suppress an increase in the ratio of other harmonic components to the fundamental wave component of the output high frequency, and to prevent unnecessary suppression of the output. It is also known that in phase shift control, the distribution of harmonics contained in the output high frequency changes depending on the amount of phase shift. When the specified ratio is 2 / 3 (66.6666...%), the output high frequency contains almost no third harmonics, and the more it deviates from 2 / 3, the more third harmonics are included. Also, when the specified ratio is 50% or more, when it is 80%, the output high frequency contains almost no fifth harmonics, and the more it deviates from 80%, the more fifth harmonics are included. Of the harmonic components contained in the high frequency, the third and fifth harmonics account for a large proportion. By setting the specified ratio to be 2 / 3 or more and 80% or less, both the third and fifth harmonics, which account for a large proportion of the harmonic components contained in the high frequency, can be suppressed. Therefore, it is more preferable that the specified ratio is 2 / 3 or more and 80% or less.

[0032] FIG. 3 is a waveform diagram showing high frequency control signals CS1 to CS4 generated by the control device 5. FIG. 3(a) shows the high frequency control signal CS1 output to the switching element Q1, and FIG. 3(b) shows the high frequency control signal CS2 output to the switching element Q2. FIG. 3(c) shows the high frequency control signal CS3 output to the switching element Q3, and FIG. 3(d) shows the high frequency control signal CS4 output to the switching element Q4. FIG. 3(e) shows the waveform of the voltage output from the inverter circuit 12. For the sake of simplicity, dead time is omitted in FIG. 3. In reality, dead time is provided to prevent short circuit.

[0033] When one of the radio frequency control signals CS1 and CS2 is at a high level, the other is at a low level. The radio frequency control signal CS4 lags in phase with the radio frequency control signal CS1, and the radio frequency control signal CS3 lags in phase with the radio frequency control signal CS2. A predetermined ratio R (=T1 / T2) which is the ratio of the period T1 during which the high level of the pulse of the radio frequency control signal CS1 and the high level of the pulse of the radio frequency control signal CS4 overlap with respect to the high level period T2 of the pulse of the radio frequency control signal CS1 is fixed. The frequency of the radio frequency control signals CS1 to CS4 is an appropriate frequency fx. As shown in FIG. 3(e), the voltage output from the inverter circuit 12 is a radio frequency voltage of the appropriate frequency fx.

[0034] Moreover, the control device 5 controls the DC voltage output from the contactless power supply system C1 (power receiving device B) to a target voltage by PAM (Pulse Amplitude Modulation) control. Specifically, the control device 5 generates a control pulse signal for making the deviation between the output voltage of the contactless power supply system C1 and the set target voltage zero. Then, the control pulse signal is amplified to a level at which the DC / DC converter circuit 112 can be driven by a drive circuit (not shown), and is output to the DC / DC converter circuit 112 as a voltage control signal CS5. The DC / DC converter circuit 112 converts the output DC voltage by controlling the conversion operation by the voltage control signal CS5 input from the control device 5. This allows the control device 5 to control the DC voltage output from the contactless power supply system C1 to the target voltage. The control device 5 may control the DC voltage output from the contactless power supply system C1 by controlling the output voltage of the DC / DC converter circuit 112 to the target voltage.

[0035] The power receiving device B includes a power receiving unit 3, a rectifying and smoothing circuit 4, a control device 7, and a communication device 8.

[0036] The power receiving unit 3 includes a power receiving coil Lr and a resonant capacitor Cr. The power receiving coil Lr is magnetically coupled to the power transmitting coil Lt to receive power in a non-contact manner. The resonant capacitor Cr is connected in series to the power receiving coil Lr to form a series resonant circuit.

[0037] The receiving coil Lr and the resonant capacitor Cr are designed so that their resonant frequencies match the reference frequency f0, similar to the transmitting coil Lt and the resonant capacitor Ct.

[0038] Both the power transmitting unit 2 and the power receiving unit 3 are resonant circuits, and power is transmitted contactlessly from the power transmitting unit 2 to the power receiving unit 3 by magnetic field resonance. The power received by the power receiving unit 3 is output to a rectifying and smoothing circuit 4.

[0039] The rectifying and smoothing circuit 4 rectifies the high frequency voltage output from the power receiving unit 3 and converts it into a DC voltage. The rectifying and smoothing circuit 4 includes a full-wave rectifying circuit in which four diodes are bridge-connected. The rectifying and smoothing circuit 4 also includes a smoothing circuit for smoothing the output after rectification. The configuration of the rectifying and smoothing circuit 4 is not limited as long as it converts the high frequency voltage into a DC voltage. The DC voltage output from the rectifying and smoothing circuit 4 is supplied to the power storage device D.

[0040] The power storage device D includes a secondary battery such as a lithium ion battery. The power storage device D charges the secondary battery with DC power output from the rectifying and smoothing circuit 4, and supplies power to a motor (not shown) and the like. The type of the secondary battery is not limited, and may be a lead storage battery or the like. The power storage device D may include an electric double layer capacitor or a lithium ion capacitor instead of the secondary battery.

[0041] A switch 91 and a switch 92 are disposed between the power receiving device B (contactless power supply system C1) and the power storage device D. The switch 91 is a switch for switching between conduction and non-conduction between the power receiving device B and the power storage device D, and is switched in response to a command from the control device 7. When the switch 91 is off, the power receiving device B and the power storage device D are non-conductive. On the other hand, when the switch 91 is on, the power receiving device B and the power storage device D are conductive, and charging power can be supplied from the power receiving device B to the power storage device D. The switch 92 is a switch for short-circuiting the output of the power receiving device B (contactless power supply system C1), and is switched in response to a command from the control device 7. Normally, the switch 92 is off, and the output is not short-circuited. When the switch 92 is on, the output of the power receiving device B is in a short-circuited state. When the switch 91 is off and the switch 92 is off, the output of the power receiving device B is in an open state.

[0042] The communication device 8 performs wireless communication with the communication device 6 of the power transmission device A. The communication device 8 transmits a signal input from the control device 7 to the communication device 6. The communication device 8 also outputs a signal received from the communication device 6 to the control device 7. Note that the communication method of the communication device 8 and the type of electromagnetic waves used are not limited.

[0043] The control device 7 controls the power receiving device B, and is configured with a microcomputer having a CPU, ROM, and RAM, an FPGA, or the like. The control device 7 transmits the detection values ​​of the output voltage and the output current of the power receiving device B detected by each sensor to the power transmitting device A via the communication device 8. The control device 7 also switches the switches 91 and 92 based on a switching signal received by the communication device 8. The control device 7 also determines whether charging of the power storage device D is completed, and transmits a charging completion signal to the power transmitting device A via the communication device 8 when charging is completed. The power transmitting device A (control device 5) that receives the charging completion signal stops the output of the high frequency power supply device 1.

[0044] Next, a method for setting the appropriate frequency fx will be described.

[0045] The power transmission coil Lt and the resonant capacitor Ct of the power transmission unit 2 and the power receiving coil Lr and the resonant capacitor Cr of the power receiving unit 3 are designed so that their resonant frequencies coincide with the reference frequency f0. Therefore, in the non-contact power supply system C1, when there is no misalignment between the power transmission coil Lt and the power receiving coil Lr, the high-frequency power supply device 1 can efficiently transmit power when it outputs a high-frequency voltage of the reference frequency f0. However, when there is a misalignment between the power transmission coil Lt and the power receiving coil Lr, it is not possible to efficiently transmit power. The control device 5 does not fix the frequency of the high-frequency voltage output by the high-frequency power supply device 1 to the reference frequency f0, but searches for a frequency at which power can be efficiently transmitted before starting transmission of charging power to the power storage device D, and determines the frequency as the appropriate frequency fx. Then, the control device 5 controls the high-frequency power supply device 1 to output a high-frequency voltage of the appropriate frequency fx.

[0046] In this embodiment, the control device 5 searches for an appropriate frequency fx within a predetermined frequency range (for example, 79 to 90 kHz). The predetermined frequency range is not limited. When the control device 5 searches for the appropriate frequency fx and does not find the appropriate frequency fx within the predetermined frequency range, it determines that power cannot be transmitted from the power transmitting device A to the power receiving device B, and notifies the user of this through a notifying means (not shown). Instead of notifying the user that power cannot be transmitted, or in addition to this, the control device 5 may notify the user to change the stopping position to an appropriate position. The method of notifying the user is not limited, and may be displayed on a display screen (not shown), or may be notified by voice through a speaker (not shown).

[0047] The control device 5 performs an "appropriate frequency search process" for searching for an appropriate frequency fx before starting transmission of charging power to the power storage device D. The control device 5 sets a test frequency to the high frequency power supply device 1 and causes it to transmit the test power when the output of the power receiving device B is in an open state and when it is in a short-circuit state. The test frequency is any frequency within a predetermined frequency range. The test power is a frequency that is sufficiently small (for example, about several percent or less) compared with the charging power. The magnitude of the test power is not limited. The control device 5 outputs high frequency control signals CS1 to CS4 of the test frequency to the inverter circuit 12, and outputs a control signal to the DC / DC converter circuit 112 to control the magnitude of the output power of the inverter circuit 12 to the magnitude of the test power, thereby causing the high frequency power supply device 1 to output the test power. In addition, the control device 5 switches the switches 91 and 92 by outputting a switching signal to the control device 7 via the communication devices 6 and 8. Before starting transmission of power to the power storage device D, the switch 91 is off. The control device 5 turns off the switch 92 to put the output of the power receiving device B into an open state, and turns on the switch 92 to put the output of the power receiving device B into a short-circuit state.

[0048] The control device 5 detects the output voltage and output current of the high frequency power supply device 1 and the output voltage and output current of the power receiving device B when the high frequency power supply device 1 is caused to output test power in an open state. The control device 5 also detects the output voltage and output current of the high frequency power supply device 1 and the output voltage and output current of the power receiving device B when the high frequency power supply device 1 is caused to output test power in a short-circuit state. As shown in FIG. 4, the power transmitting unit 2 in which the power transmitting coil Lt and the power receiving coil Lr are magnetically coupled, the power receiving unit 3, and the rectifying and smoothing circuit 4 (the part surrounded by the thick dashed line shown in FIG. 4(a)) can be regarded as a two-terminal pair circuit as shown in FIG. 4(b). The input voltage Vin of the two-terminal pair circuit is equal to the output voltage of the high frequency power supply device 1, and the input current Iin is equal to the output current of the high frequency power supply device 1. The output voltage Vout of the two-terminal pair circuit is the output voltage of the power receiving device B, and the output current Iout is the output current of the power receiving device B. The control device 5 calculates the parameters F of the F matrix of the transmission line of the two-terminal pair circuit from the input voltage Vin, the input current Iin, the output voltage Vout, and the output current Iout in the open state. 11 , F 21 In addition, the control device 5 calculates a parameter F of the F matrix of the transmission line of the two-terminal pair circuit from the input voltage Vin, the input current Iin, the output voltage Vout, and the output current Iout in the short-circuit state. 12 , F 22 In this way, the control device 5 calculates the F matrix for the test frequency.

[0049] Based on the calculated F matrix, the control device 5 calculates the output voltage and output current (input current Iin and output voltage Vout) of the high frequency power supply device 1 when the output voltage and output current (output voltage Vout and output current Iout) of the power receiving device B are set to target values, respectively, as a judgment voltage and judgment current. The control device 5 judges whether or not the judgment voltage is equal to or less than the rated voltage of the inverter circuit 12 and the judgment current is equal to or less than the rated current of the inverter circuit 12, that is, an appropriate state. As described above, the process in which the control device 5 sets a test frequency to the high frequency power supply device 1, causes it to transmit test power, and judges whether or not the appropriate state is established is hereinafter referred to as a "frequency judgment process."

[0050] When the control device 5 determines that the state is appropriate (both the determination voltage and the determination current are equal to or lower than the rated voltage and the rated current are equal to or lower than the rated voltage and the state is not appropriate) in the frequency determination process, the control device 5 changes the test frequency and performs the frequency determination process. When the control device 5 determines that the state is not appropriate at any frequency within the predetermined frequency range, the control device 5 determines that power cannot be transmitted from the power transmitting device A to the power receiving device B. The method of searching for the test frequency is not limited. For example, the first test frequency may be set to a reference frequency f0 (e.g., 85 kHz), and the frequency may be searched for by moving away from the reference frequency f0 by a predetermined frequency change width (e.g., 0.1 kHz). In this case, if there is no positional deviation between the power transmitting coil Lt and the power receiving coil Lr, the frequency (reference frequency f0) at which power can be transmitted most efficiently can be determined as the test frequency. Even if there is a positional deviation, the test frequency can be determined relatively quickly. In addition, the first test frequency may be set to the minimum value of the predetermined frequency range, and the test frequency may be gradually increased by searching for a new frequency. Alternatively, the first test frequency may be set to the maximum value of the predetermined frequency range, and the test frequency may be gradually decreased by searching for a new frequency.

[0051] 5 is an example of a flowchart for explaining the appropriate frequency search process performed by the control device 5. The appropriate frequency search process is executed before the transmission of charging power to the power storage device D starts.

[0052] First, an initial value (reference frequency f0) is set as the test frequency f (S1). Next, it is switched to an open state (S2), and test power is output (S3). Specifically, the control device 5 switches off the switch 92, and causes the high frequency power supply device 1 to output the test power. Next, each detection value is acquired (S4). Specifically, the control device 5 acquires the detection values ​​from a sensor that detects the output voltage and output current of the high frequency power supply device 1. In addition, the control device 5 acquires the detection values ​​acquired by the control device 7 from the sensor that detects the output voltage and output current of the power receiving device B by receiving them via the communication device 8 and the communication device 6.

[0053] Next, the state is switched to a short-circuit state (S5), and test power is output (S6). Specifically, the control device 5 switches the switch 92 on, and causes the high frequency power supply device 1 to output test power. Next, each detection value is acquired (S7). Next, an F matrix is ​​calculated based on each detection value (S8). Specifically, the control device 5 calculates the F matrix based on each detection value in the open state and each detection value in the short-circuit state.

[0054] Next, each judgment value is calculated (S9). Specifically, the control device 5 calculates the output voltage and output current of the high frequency power supply device 1 when the output voltage and output current of the power receiving device B are set to the target values, respectively, based on the calculated F matrix, as the judgment voltage and judgment current. Next, it is determined whether or not the state is appropriate (S10). Specifically, the control device 5 determines whether or not the judgment voltage is equal to or lower than the rated voltage of the inverter circuit 12 and the judgment current is equal to or lower than the rated current of the inverter circuit 12.

[0055] If the state is not appropriate (S10: NO), it is determined whether the test frequency f can be changed (S11). Specifically, the control device 5 determines whether the test frequency f can be changed within a predetermined frequency range. If it is determined that the test frequency f can be changed (S11: YES), the test frequency f is changed (S12), and the process returns to step S2, and the processes of steps S2 to S12 are repeated. If it is determined that the test frequency f cannot be changed in step S11 (S11: YES), it is determined that power transmission is impossible, a notice to that effect is given (S13), and the appropriate frequency search process is terminated. On the other hand, if the state is appropriate in step S10 (S10: YES), the test frequency f at this time is determined to be the appropriate frequency fx (S14), and the appropriate frequency search process is terminated. Note that the process shown in the flowchart of FIG. 5 is an example, and the appropriate frequency search process performed by the control device 5 is not limited to the one described above.

[0056] Next, the operation and effects of the power transmitting device A and the contactless power supply system C1 according to the present embodiment will be described.

[0057] According to this embodiment, the control device 5 delays the phase of the high frequency control signal CS4 (CS3) output to the switching element Q4 (Q3) of the follower arm from the phase of the high frequency control signal CS1 (CS2) output to the switching element Q1 (Q2) of the leading arm. At this time, since the predetermined ratio R is fixed, the phase difference does not change. As a result, the contactless power supply system C1 (power transmission device A) can suppress the heat loss in the switching elements Q1 to Q4 because the phase difference does not become large even during output suppression. In addition, by setting the predetermined ratio R to a value equal to or greater than 50% and less than 100%, the heat loss in the switching elements Q1 to Q4 is further suppressed. Furthermore, by setting the predetermined ratio R to a value equal to or greater than 2 / 3 and less than 80%, both the third harmonic and the fifth harmonic, which have a large proportion among the harmonic components contained in the high frequency, are suppressed. As a result, the contactless power supply system C1 (power transmission device A) can suppress the generation of harmonic noise.

[0058] Furthermore, according to this embodiment, the control device 5 performs an "appropriate frequency search process" to search for an appropriate frequency fx before starting transmission of charging power to the power storage device D. In the appropriate frequency search process, the appropriate frequency fx of the high frequency power is determined by causing the high frequency power supply device 1 to output test power. This allows the contactless power supply system C1 (power transmission device A) to determine whether or not it can transmit the target power before starting transmission of the charging power. Furthermore, since the appropriate frequency fx is determined at the start of power transmission, the time from the start of power transmission until the transmitted power reaches the target power can be shortened as much as possible.

[0059] According to the present embodiment, in the appropriate frequency search process, the control device 5 sets a frequency within a predetermined frequency range as the test frequency, performs the frequency determination process, and determines the test frequency as the appropriate frequency fx when it is determined that the state is appropriate. Therefore, when the appropriate frequency fx is within the predetermined frequency range, the control device 5 can determine the appropriate frequency fx as quickly as possible. Furthermore, the control device 5 can determine that power transmission from the power transmitting device A to the power receiving device B is not possible when there is no appropriate frequency fx within the predetermined frequency range.

[0060] According to the present embodiment, in the frequency determination process, the control device 5 sets a test frequency to the high frequency power supply device 1 and transmits the test power when the output of the power receiving device B is in an open state and a short state, respectively, and detects the output voltage and output current of the high frequency power supply device 1 and the output voltage and output current of the power receiving device B. From these detected values, the control device 5 calculates the F matrix of the transmission line of the two-terminal pair circuit consisting of the power transmission unit 2, the power receiving unit 3, and the rectifying smoothing circuit 4. Then, based on the F matrix, the control device 5 calculates the output voltage and output current of the high frequency power supply device 1 when the output voltage and output current of the power receiving device B are set to the target values, respectively, as the judgment voltage and judgment current, and determines whether or not the judgment voltage and judgment current are both below the rated value and are in an appropriate state. Therefore, the control device 5 can determine whether or not the set test frequency is an appropriate frequency fx.

[0061] In the present embodiment, the control device 5 calculates the F matrix of the transmission line of the two-terminal pair circuit in the frequency determination process, but this is not limited to the above. The control device 5 may calculate a Z matrix instead of the F matrix.

[0062] In addition, in the present embodiment, the case where both the power transmission unit 2 and the power receiving unit 3 are series resonant circuits has been described, but the present invention is not limited thereto. At least one of the power transmission unit 2 and the power receiving unit 3 may be a parallel resonant circuit. In addition, in the present embodiment, the case where power is transmitted from the power transmission unit 2 to the power receiving unit 3 by a magnetic field resonance method has been described, but the present invention is not limited thereto. Power may be transmitted from the power transmission unit 2 to the power receiving unit 3 by an electromagnetic induction method. That is, the resonant capacitor Ct may be connected in series to the power transmission coil Lt, may be connected in parallel, or may not be provided. The resonant capacitor Cr may be connected in series to the power transmission coil Lt, may be connected in parallel, or may not be provided. In addition, the power transmission device A may include a filter circuit for impedance conversion between the high-frequency power supply device 1 and the power transmission unit 2.

[0063] In addition, in the present embodiment, the case where the control device 5 determines the appropriate frequency fx (performs appropriate frequency search processing) before starting transmission of the charging power has been described, but this is not limited to the case. The control device 5 may set a fixed frequency (e.g., a reference frequency f0) instead of the appropriate frequency fx and transmit the charging power without performing the appropriate frequency search processing. In this case, it is possible to speed up the start of charging compared to the case where the appropriate frequency search processing is performed.

[0064] In the present embodiment, the non-contact power supply system C1 is used to charge an electric vehicle or the like, but the present invention is not limited to this. The non-contact power supply system C1 can also be used to charge an automatic guided vehicle used for transportation within a factory, and can also be used to charge electrical appliances such as power tools and notebook computers.

[0065] 6 is a diagram for explaining a contactless power supply system C2 according to the second embodiment, and is an example of a flowchart for explaining an appropriate frequency search process performed by the control device 5. The configuration of the contactless power supply system C2 according to the second embodiment is the same as that of the contactless power supply system C1 according to the first embodiment, and therefore description and explanation will be omitted. The contactless power supply system C2 according to the second embodiment differs from the contactless power supply system C1 according to the first embodiment in the appropriate frequency search process performed by the control device 5.

[0066] In the suitable frequency search process according to the first embodiment, when the frequency determination process determines that the state is suitable, the test frequency f at that time is determined as the suitable frequency fx. In the suitable frequency search process according to the second embodiment, even when the frequency determination process determines that the state is suitable, the most suitable test frequency f is searched for and determined as the suitable frequency fx.

[0067] When the control device 5 according to the second embodiment determines that the frequency is in an appropriate state in the frequency determination process, it calculates a judgment power Px (=Vx·Ix) which is the product of the judgment voltage Vx and the judgment current Ix at that time. Then, the control device 5 changes the test frequency f to search for a test frequency f at which the judgment power Px is minimized, and determines this test frequency f as the appropriate frequency fx. Although the method of searching for a test frequency f at which the judgment power Px is minimized is not limited, in this embodiment, the search is performed using a so-called hill climbing method. That is, the control device 5 determines the direction of change of the test frequency f (whether to increase or decrease) based on the increase or decrease of the judgment power Px when the test frequency f is changed. If the judgment power Px becomes smaller when the test frequency f is increased, the control device 5 continues to increase the test frequency f, and if the judgment power Px becomes larger, the control device 5 decreases the test frequency f as it exceeds the minimum value. If the judgment power Px becomes smaller when the test frequency f is decreased, the control device 5 continues to decrease the test frequency f, and if the judgment power Px becomes larger, the control device 5 increases the test frequency f as it exceeds the minimum value.

[0068] As shown in Fig. 6, the appropriate frequency search process according to the second embodiment differs from the appropriate frequency search process according to the first embodiment shown in Fig. 5 in the process when YES is determined in step S10, that is, when the device is in an appropriate state. Note that in Fig. 6, the processes in steps S2 to S9 shown in Fig. 5 are collectively described as a frequency determination process (S21).

[0069] In step S10, if the state is appropriate (S10: YES), the determination power Px is calculated (S22). Specifically, the control device 5 calculates the determination power Px by multiplying the determination voltage Vx and the determination current Ix. Next, it is determined whether the determination power Px is minimum or not (S23). The method of determining whether the determination power Px is minimum or not is not limited. For example, the control device 5 may determine that the determination power Px is minimum when the determination power Px changes from a decrease to an increase or when the search direction has been reversed a predetermined number of times.

[0070] If the judgment power Px is not the minimum (S23: NO), it is determined whether the judgment power Px has increased from the previous judgment power Px (S24). If the judgment power Px has increased (S24: YES), the search direction of the test frequency f is reversed (S25). Specifically, the direction of change (increase or decrease) when the control device 5 changes the test frequency f is reversed from the previous time. Note that the initial search direction is not limited. On the other hand, if the judgment power Px has not increased in step S24 (S24: NO), the search direction of the test frequency f is not reversed.

[0071] Next, the test frequency f is changed (S26), and the process returns to step S21 to perform the frequency determination process (S21). When changing the test frequency f, the control device 5 increases or decreases the test frequency f according to the current search direction. Note that the frequency change width at this time may be fixed, or may be decreased each time the search direction is reversed.

[0072] In step S23, if the judgment power Px is the smallest (S23: YES), the test frequency f at this time is determined to be the appropriate frequency fx (S14), and the appropriate frequency search process is terminated. Note that the process shown in the flowchart of FIG. 6 is an example, and the appropriate frequency search process performed by the control device 5 is not limited to the above.

[0073] In this embodiment as well, the phase difference between the high frequency control signal CS4 (CS3) and the high frequency control signal CS1 (CS2) is fixed. Therefore, in the contactless power supply system C2 (power transmission device A), the phase difference does not become large even during output suppression, so that heat loss in the switching elements Q1 to Q4 can be suppressed. Furthermore, the control device 5 performs an "appropriate frequency search process" for searching for an appropriate frequency fx before starting transmission of charging power to the power storage device D. Therefore, the contactless power supply system C1 (power transmission device A) can determine whether the target power can be transmitted before starting transmission of charging power, and can shorten the time from the start of power transmission until the transmitted power reaches the target power as much as possible. Furthermore, the contactless power supply system C2 (power transmission device A) according to this embodiment has a common configuration with the contactless power supply system C1 (power transmission device A) according to the first embodiment, and thus has the same effects as the contactless power supply system C1 (power transmission device A).

[0074] Furthermore, according to this embodiment, in the appropriate frequency search process, the control device 5 does not end the search for the test frequency f even if the frequency determination process determines that the state is appropriate, and searches for the most appropriate test frequency f. Therefore, the control device 5 can determine the most appropriate test frequency f as the appropriate frequency fx. This allows the contactless power supply system C2 (power transmission device A) to improve the transmission efficiency. Also, according to this embodiment, when the control device 5 determines that the state is appropriate in the frequency determination process, it calculates a judgment power Px that is the product of the judgment voltage Vx and the judgment current Ix at this time. Then, the control device 5 changes the test frequency f to search for a test frequency f at which the judgment power Px is minimum, and determines this test frequency f as the appropriate frequency fx. This allows the control device 5 to search for the most appropriate test frequency f. Also, according to this embodiment, the control device 5 searches for the test frequency f using a so-called hill climbing method. Therefore, the optimal test frequency f can be searched for relatively quickly using a simple algorithm.

[0075] In the present embodiment, the control device 5 searches for the test frequency f at which the judgment power Px is minimized in the appropriate frequency search process, but this is not limited to the above. For example, the control device 5 may n Ix nA test frequency f may be searched for at which n (n is a natural number) is minimized. In this case, the larger n is, the easier it is to determine the minimum value.

[0076] As described above, when the control device 5 judges that the state is appropriate in the frequency judgment process, the contactless power supply system C1 according to the first embodiment determines the test frequency at this time to be the appropriate frequency fx. After starting the transmission of charging power at the determined appropriate frequency fx, the contactless power supply system C1 may search for an optimal appropriate frequency fx in a manner similar to the appropriate frequency search process according to the second embodiment during the transmission of charging power, and change the appropriate frequency fx. During the transmission of charging power, it is not possible to detect each current and voltage in the open state and the short-circuit state. However, during the transmission of charging power, the control device 5 detects the output voltage and output current (input current Iin and output voltage Vout) of the high-frequency power supply device 1 and the output voltage and output current (output voltage Vout and output current Iout) of the power receiving device B, and uses these detected values ​​to calculate the F matrix.

[0077] The non-contact power transmitting device and the non-contact power supply system according to the present invention are not limited to the above-described embodiment. The specific configurations of the components of the non-contact power transmitting device and the non-contact power supply system according to the present invention can be freely designed in various ways. [Explanation of symbols]

[0078] A: power transmission device, 11: DC power supply device, 12: inverter circuit, 5: control device, B: power receiving device, C1, C2: non-contact power supply system

Claims

1. A wireless power supply system that transmits power from a power transmitting device to a power receiving device in a wireless manner, The power transmitting device is A DC power supply device that outputs DC power; an inverter circuit in which a leading arm in which two switching elements are connected in series and a following arm in which another two switching elements are connected in series are connected in parallel; A control device that controls the power transmitting device; Equipped with The control device includes: a first control signal to be input to one of the switching elements of the leading arm and a second control signal to be input to the corresponding switching element of the following arm are generated in a state where the phases are shifted by a fixed phase difference; Contactless power supply system.

2. a predetermined ratio, which is a ratio of a period during which the high level of the pulse of the first control signal and the high level of the pulse of the second control signal overlap with respect to a high level period of the pulse of the first control signal, is fixed and is equal to or greater than 50% and less than 100%; The contactless power supply system according to claim 1 .

3. The predetermined ratio is 2 / 3 or more and 80% or less. The contactless power supply system according to claim 2 .

4. The control device adjusts the DC voltage output from the DC power supply device to the inverter circuit. The contactless power supply system according to claim 1 .

5. A power transmitting device that wirelessly supplies power to a power receiving device, A DC power supply device that outputs DC power; an inverter circuit in which a leading arm in which two switching elements are connected in series and a following arm in which another two switching elements are connected in series are connected in parallel; A control device for controlling the inverter circuit; Equipped with The control device includes: a first control signal to be input to one of the switching elements of the leading arm and a second control signal to be input to the corresponding switching element of the following arm are generated in a state where the phases are shifted by a fixed phase difference; Power transmission equipment.

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