Power transmission device and non-contact power supply system

Abstract

According to the present invention, a series element made up of an inductor (2) and a first capacitor (3) is connected to the AC side of an inverter (1), a series element made up of a second capacitor (4) and a power transmission coil (5) is connected in parallel with the first capacitor (3), a controller (7) that controls the inverter (1) is configured to control switching between two modes that include an electric power transmission mode in which electric power is transmitted to the power transmission coil (5) and a coil detection mode in which a low-output interval of operation at a lower output than in the power transmission mode and a zero-output interval in which the output of the inverter (1) is set to zero repeat in an alternating manner, and mode switching is executed based on a post-mode transition state in which information changes at the time when a predetermined condition is satisfied after the mode has been switched and the value of an operation parameter related to at least the input electric power to the inverter.

Description

[Technical field]

[0001] The present application relates to a power transmitting device and a contactless power supply system. [Background technology]

[0002] One contactless power supply technology is a technology that transmits power by magnetic field coupling between two coils separated by a space. Research is being conducted on the application of this contactless power supply to a moving body such as a moving automobile. In contactless power supply to a moving body, a receiving coil passes directly above a transmitting coil in a short time, and the coupling state between the coils, that is, the electrical state seen from the power transmitting side, is constantly fluctuating, resulting in a system. Various technologies are being studied, such as a receiving coil passing directly above a transmitting coil and a technology for controlling the transmission power when the coupling state between the coils fluctuates (for example, Non-Patent Document 1). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Katsuhiro Hata, et. al, "Driving Test Evaluation of Sensorless Vehicle Detection Method for In-motion Wireless Power Transfer", Proc. The 2018 International Power Electronics Conference, pp 663-668. Summary of the Invention [Problem to be solved by the invention]

[0004] In the technology described in Non-Patent Document 1, due to the existence of a sequence in which the power transmitting and receiving sides work together in sequence, it is not possible to switch between modes in less than the time required for switching between them, and there is a problem that the entrance and exit detection of the receiving coil cannot be performed quickly.In addition, the tolerance to failure in the exit detection is low, and if the detection of the exit of the receiving coil fails once, the current flows for a considerable time, causing an increase in noise and an increase in power loss.

[0005] The present application has been made to solve the above-mentioned problems, and aims to provide a power transmission device in which the entrance and exit of the receiving coil can be determined quickly by the power transmission side alone, thereby suppressing an increase in power loss and suppressing noise. [Means for solving the problem]

[0006] The power transmission device disclosed in the present application is a power transmission device including a power transmission coil that transmits power to an external power receiving coil by magnetically coupling with the external power receiving coil, an inverter that supplies AC power to the power transmission coil, and a controller that controls the inverter, wherein a series arrangement of an inductor and a first capacitor is connected to the AC side of the inverter, and a series arrangement of a second capacitor and the power transmission coil is connected in parallel to the first capacitor, and the controller is configured to control the inverter by switching between two modes: a power transmission mode in which the inverter is operated to transmit power to the power transmission coil, and a coil detection mode in which a low output period in which the inverter is operated at an output power lower than the rated power and a zero output period in which the output of the inverter is set to zero are alternately repeated, and the mode switching is performed based on a post-mode transition state in which information changes when a predetermined condition is satisfied after the mode switching, and the value of an operating parameter related to at least the input power to the inverter. Effect of the Invention

[0007] According to the power transmitting device disclosed in the present application, the entrance and exit of the power receiving coil can be determined quickly only on the power transmitting side, and an increase in power loss and noise can be suppressed. [Brief description of the drawings]

[0008] [Figure 1] 1 is a circuit diagram illustrating a configuration of a contactless power supply system including a power transmitting device according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram illustrating a state of a contactless power supply system including a power transmitting device according to the first embodiment. [Diagram 3] 4 is a flowchart showing an outline of an operation in a power transmission mode of the power transmitting device according to the first embodiment. FIG. [Figure 4] 4 is a flowchart showing an outline of an operation in a coil detection mode of the power transmitting device according to the first embodiment. FIG. [Diagram 5] 4 is a diagram illustrating a relationship between a state after mode transition and a coil detection mode and a power transmission mode in the power transmitting device according to the first embodiment. FIG. [Figure 6] 6A and 6B are diagrams showing post-mode transition states and incorrect mode relationships. [Figure 7] 10 is a diagram showing operational waveforms in a small output mode during a coil detection mode of the power transmitting device according to the first embodiment. FIG. [Figure 8] 10 is a flow diagram showing an operation of sequence A in a coil detection mode of the power transmitting device according to the first embodiment. FIG. [Figure 9] 10 is a flowchart showing an operation of a sequence X in a coil detection mode of the power transmitting device according to the first embodiment. FIG. [Figure 10] 10 is a flow diagram showing an operation of sequence B in a power transfer mode of the power transmitting device according to the first embodiment. FIG. [Figure 11] 4 is a flow diagram showing an operation of a sequence Y in a power transmission mode of the power transmitting device according to the first embodiment. FIG. [Figure 12] FIG. 2 is a first diagram illustrating an operation of the power transmitting device according to the first embodiment. [Figure 13] FIG. 4 is a second diagram illustrating the operation of the power transmitting device according to the first embodiment. [Figure 14] 1 is a circuit diagram showing an example of a configuration of a contactless power supply system. [Figure 15]FIG. 11 is a circuit diagram showing another example of the configuration of a contactless power supply system. [Figure 16] FIG. 11 is a circuit diagram illustrating a configuration of a contactless power supply system including a power transmitting device according to a second embodiment. [Figure 17] FIG. 11 is a diagram illustrating the operation of the power transmitting device according to the second embodiment. [Figure 18] 2 is a block diagram showing an example of a specific configuration of a controller of a power transmitting device disclosed in the present application. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Embodiment 1 1 is a circuit diagram showing a schematic configuration of a contactless power supply system including a power transmitting device according to embodiment 1. Power transmitting device 100 includes an inverter 1 that converts DC power into AC power and outputs the AC power, an inductor 2, a first capacitor 3, a second capacitor 4, a power transmitting coil 5, a current sensor 6 that detects an input current to the inverter 1, and a controller 7 that receives information from the current sensor 6 as an input and controls the operation of the inverter.

[0010] The elements are connected as follows: An inductor 2 and a first capacitor 3 are connected in series to the output terminal of an inverter 1. A second capacitor 4 and a power transmitting coil 5 are connected in series, and are connected in parallel to the first capacitor 3.

[0011] The inverter 1 is composed of semiconductor switches. In FIG. 1, a full-bridge configuration using four semiconductor switches is used, but a half-bridge configuration or other configuration is also acceptable. There are no particular limitations on the bridge configuration. The semiconductor switches may be IGBTs, FETs, or other types of switches, and there are no particular limitations on the type of switch.

[0012] The power receiving side device 200 is composed of a power receiving coil 11, a first power receiving side capacitor 12, a second power receiving side capacitor 13, a power receiving side inductor 14, a rectifier 15 that rectifies the AC current, and a smoothing capacitor 16 that smoothes the waveform after rectification. A load such as a battery 17 is connected to the downstream of the smoothing capacitor 16.

[0013] The power receiving coil 11 and the first power receiving side capacitor 12 are connected in series, and the second power receiving side capacitor 13 is connected in parallel to this series connection. The power receiving side inductor 14 is connected in the subsequent stage of the second power receiving side capacitor 13, and the rectifier 15 and the smoothing capacitor 16 are connected in that order in the subsequent stage. The rectifier 15 is composed of diodes, and may be either half-wave rectifier or full-wave rectifier as long as it can rectify AC. The above describes a configuration on the power receiving side that has a greater effect. The inductor and capacitor on the power receiving side are not limited to this configuration, and inductors and capacitors may be added or removed.

[0014] Next, the operation of the contactless power supply system will be described. For example, the power transmitting device 100 is installed on a road, and the power receiving device 200 is mounted on a moving object such as an automobile. It is assumed that the road is, for example, a highway, on which automobiles travel in one direction at high speed. This state is shown in Fig. 2. The moving object 300 equipped with the power receiving device 200 moves from a state of approaching the power transmitting device 100 installed on the road to a state of being close to the power transmitting device 100, and then to a state of being away from the power transmitting device 100.

[0015] The power transmitting device 100 has two operation modes. One of the operation modes is called a coil detection mode (hereinafter, may be simply referred to as a detection mode), and the other is called a power transmission mode (hereinafter, may be simply referred to as a transmission mode). The power transmitting device 100 operates while switching between the coil detection mode and the power transmission mode. FIG. 3 shows a flow chart of an overview of the operation in the power transmission mode, and FIG. 4 shows a flow chart of an overview of the operation in the coil detection mode.

[0016] An outline of the operation of the power transmitting device 100 will be described with reference to FIG. 3 and FIG. 4. When operating in the power transmission mode, if a power receiving coil is present directly above the power transmitting coil (step ST11 yes) and the coupling state between the coils is appropriate, the power transmission mode continues (step ST12). If it is detected that the power receiving coil is not present above the power transmitting coil (step ST11 no), the mode is switched to the coil detection mode (step ST13). If the presence of the power receiving coil is detected in the coil detection mode (ST21 yes), the mode is switched to the power transmission mode (ST22). If the power receiving coil is not present (step ST21 no), the coil detection mode continues (step ST23). The presence or absence of the power receiving coil is determined using values ​​of operation parameters related to input power, such as the input current or input power to the inverter, and information on the state after the mode transition. The amount of phase shift may be used for the determination. Details of the state after the mode transition will be described later.

[0017] Figure 5 shows the relationship between the state after mode transition and each mode. The state after mode transition is information that changes when a predetermined condition is met, such as the elapsed time after switching between coil detection mode and power transfer mode, and is a minimum of 1 bit of information with states 0 and 1. It changes from 1 to 0 when a predetermined condition is met after switching from coil detection mode to power transfer mode. It also changes from 0 to 1 when a predetermined condition is met after switching from power transfer mode to coil detection mode. Details of the predetermined conditions will be described later.

[0018] For supplementary information, the relationship between the illegal post-mode transition state and the mode is shown in Figures 6A and 6B. When the post-mode transition state is 0, the mode is not switched from the coil detection mode to the power transmission mode as shown in Figure 6A. Also, when the post-mode transition state is 1, the mode is not switched from the power transmission mode to the coil detection mode as shown in Figure 6B. Note that the relationship between 0 and 1 of the post-mode transition state may be reversed, and the information on the post-mode transition state (usually a simple signal such as 0 and 1) may be any information as long as it is possible to determine whether or not a predetermined condition is satisfied after the mode has changed.

[0019] First, the details of the coil detection mode will be described. In the coil detection mode, the operation of setting the output of the inverter 1 to 0 (stopping the operation of the inverter) and the operation of outputting from the inverter 1 are alternately repeated. FIG. 7 shows the waveform of the output voltage of the inverter 1 in the operation of outputting from the inverter 1. The coil detection mode is performed in most cases when the power receiving device 200, that is, the power receiving coil is absent. Therefore, when outputting from the inverter 1, the output is performed in a state where the output is lowered. Although this output is not particularly specified, an output smaller than the rated power of the inverter 1, for example, a small output of 1 / 10 or less of the rated power is used. The period of the operation state of output 0 during the coil detection mode is defined as the zero output period, and the period of the operation state of outputting is defined as the small output period.

[0020] Sequence A is executed during the operation of the coil detection mode. The flow of sequence A is shown in FIG. 8. In sequence A, the input current to the inverter 1 is measured by the current sensor 6 (step ST201), and a sequence for determining whether the current value I is equal to or greater than the value Ith1 set as the entry threshold is executed (step ST202). When the current value I is less than the entry threshold (I < Ith1) (step ST202 no), it is determined that the power receiving coil is absent, and the process returns to step ST201 to continue the detection mode. When the input current is equal to or greater than the entry threshold (I ≥ Ith1) (step ST202 yes), the determination of the state after mode transition is performed (step ST203). In the determination of the state after mode transition, if the state after mode transition is 0 (step ST203 yes), it is determined that the power receiving coil is absent, and the coil detection mode is continued (step ST23). In the determination of the state after mode transition, if the state after mode transition is 1 (step ST203 no), it is determined that the power receiving coil is present, and the power transmission mode is switched (step ST22).

[0021] In parallel with the above, sequence X is executed. FIG. 9 shows the flow of sequence X. After switching from the power transmission mode to the coil detection mode, counting of the elapsed time T (step ST211) is started. If the elapsed time T is equal to or less than the reference time Tx (step ST212 no), the process returns to step ST211 to continue counting T, and when T becomes greater than Tx (step ST212 yes), the state after the mode transition is set to 1 (step ST213). Here, the reference time Tx is set to the time ta of one repetition period of the zero output period and the small output period of the inverter in the coil detection mode. In other words, the predetermined condition after the mode is switched, which changes the state after the mode transition, is that one repetition period of the zero output period and the small output period has elapsed after switching to the coil detection mode. Here, the reference time Tx is set to the time ta of one repetition cycle of the zero output period and the small output period of the inverter in the coil detection mode, but it is not necessarily limited to one cycle, and the reference time Tx for judgment may be any time longer than the time ta of one repetition cycle. In other words, the predetermined condition after the above-mentioned mode switching is that at least one repetition cycle of the zero output period and the small output period of the inverter in the coil detection mode has elapsed. Note that Tx can be increased to more than the time of one repetition cycle, but the effect becomes smaller as it is increased. Therefore, it is desirable that Tx is ideally set to two repetition cycles or less.

[0022] Next, the power transmission mode will be described. In the power transmission mode, the power of the power transmission device 100 is controlled by phase shift control of the inverter or the like so as to be the rated power or the desired power. Here, the phase shift control will be described as an example of a power control method. However, the power control may be a method other than the phase shift control. For example, the voltage input to the front stage of the inverter may be controlled. In this case, the same effect can be obtained by replacing the phase shift amount with the control amount in the control and performing the control. The control amount in the control is the input voltage of the inverter, or the PWM duty of the converter that directly controls the input voltage of the inverter. Another example of control may be normal PWM control of the inverter, not phase shift control.

[0023] In controlling power, any control may be used as long as it is control that follows a target value. Here, an explanation will be given using PID control as an example. When switching to power transmission mode and performing PID control, the deviation between the input current detected by the current sensor 6 and the target value during power transmission is input to the PID calculation, and the phase shift amount is adjusted according to the output of the PID calculation, so that the input current is controlled to the target value. PID control itself is a common method. It may be P control, PD control, or PI control.

[0024] In parallel with the above power control, sequence B is executed. The flow of sequence B is shown in FIG. 10. In sequence B, the input current value is measured by the current sensor 6 (step ST101). If the input current value is equal to or greater than the exit threshold Ith2 (step ST102 no), it is determined that a power receiving coil is present, and the power transmission mode is continued (step ST12). If the input current value is less than the exit threshold Ith2 (step ST102 yes), the phase shift amount at that time is determined (step ST103). If the phase shift amount θ is equal to or greater than the preset exit threshold θth (step ST103 no), it is determined that a power receiving coil is present, and the power transmission mode is continued (step ST12). If the phase shift amount is less than θth (step ST103 yes) and the state after mode transition is 1 (step ST104 no), it is determined that a power receiving coil is present, and the power transmission mode is continued (step ST12). If the phase shift amount is less than θth (yes in step ST103) and the state after mode transition is 0 (yes in step ST104), it is determined that the receiving coil is absent or that the coupling has deteriorated to an extent that it is unsuitable for power transmission, and the mode is switched from the power transmission mode to the coil detection mode (step ST11).

[0025] In addition, in parallel with the above power control, sequence Y is executed. FIG. 11 shows the flow of sequence Y. After switching from the coil detection mode to the power transmission mode, counting of the elapsed time T (step ST111) is started. When the elapsed time T becomes greater than Tx (step ST112 yes), the state after the mode transition is set to 0 (step ST113). Tx is set to one repetition period ta of the zero output period and the small output period in the coil detection mode or a time longer than ta. That is, when the elapsed time T is at least one repetition period ta of the zero output period and the small output period in the coil detection mode, the state after the mode transition is set to 0. Even if T is equal to or shorter than Tx (step ST112 no), in the power control, when the measured value I (which may be power) of the current input current to the inverter reaches the target value Iref (target power value in the case of power) (step ST114 yes), the state after the mode transition is set to 0 (step ST113). If T is equal to or less than Tx (no in step ST112) and if the measured current I is equal to or less than the target value (no in step ST114), the process returns to step ST111 to continue counting the elapsed time. In other words, the point in time when the predetermined condition after the mode switching described above, which changes the state after the mode transition, is satisfied is the point in time when at least one repetition period of the small output period and the zero output period in the coil detection mode has elapsed since switching to the power transmission mode, or the point in time when the input current or input power to the inverter exceeds a predetermined threshold, whichever comes first.

[0026] Here, for example, when Tx is a small value and it is not expected that the measured value I of the current input current to the inverter will reach the target value Iref at a time earlier than Tx after switching from the coil detection mode to the power transmission mode, step ST114 may be omitted, and if the answer is no in step ST112, the process may return to step ST111 without passing through ST114. In this case, the predetermined condition after the above-mentioned mode switching is that at least one repetitive cycle of the small output period and the zero output period in the coil detection mode has elapsed since switching to the power transmission mode.

[0027] FIG. 12 shows the relationship between each mode, current waveform, and state after mode transition when transitioning from coil detection mode to power transmission mode. The middle part of FIG. 12 shows the current waveform. In coil detection mode, the current repeats output and zero at regular intervals. One cycle of this is called ta. When the power receiving coil 11 approaches the power transmitting coil 5, do not When the current exceeds the entry threshold Ith1 and the post-mode-transition state is 1, the mode transition occurs to the power transfer mode.

[0028] FIG. 13 shows the relationship between each mode, current waveform, state after mode transition, and phase shift amount when transitioning from power transmission mode to coil detection mode. The second row of FIG. 13 shows the current waveform, and the fourth row shows the phase shift amount. In power transmission mode, if the power receiving coil 11 moves away from the power transmitting coil 5, the phase shift amount decreases. In other words, the inverter output voltage required to output current increases. If it moves further away, the current decreases even if the inverter phase shift amount is minimized (maximum inverter output voltage). When the current value reaches the exit threshold Ith2 and the state after mode transition is 0, the mode transitions to coil detection mode.

[0029] The circuit operation and effects of the power transmitting device 100 of the first embodiment will be described below. When the power transmitting coil and the power receiving coil are magnetically coupled, power can be transmitted from the power transmitting device 100 to the power receiving device 200 with high efficiency. In power supply to a moving object as envisioned in the present application, this coupling state changes from moment to moment. As the moving object moves, the coupling state between the power transmitting coil and the power receiving coil changes from a low state to a high state and from a high state to a low state. This corresponds to a state in which a car enters the power transmitting coil on the road, passes directly above the power transmitting coil, and then exits the power transmitting coil.

[0030] In this case, when the moving object is leaving, that is, when the coupling between the power transmitting coil and the power receiving coil is decreasing, the change in impedance seen from the inverter of the power transmitting device varies greatly depending on the resonance configuration of the contactless power transfer system including the power receiving device. Figure 14 shows a contactless power transfer system with a series resonance configuration. In a series resonance configuration in which the power transmitting side is a series connection of the power transmitting coil 5 and the second capacitor 4, and the power receiving side is a series connection of the power receiving coil 11 and the first power receiving side capacitor 12, which is often used in contactless power transfer, the impedance decreases when the coupling between the coils decreases. Conversely, when the coupling between the coils increases, the impedance increases. In other words, when the power receiving coil is absent, the current increases, and when the coil is present, the current decreases. Based on this characteristic, when trying to detect the presence of the power receiving coil, a method is used in which the power transmitting coil current is measured, and when the power transmitting coil current is equal to or greater than a certain value, it is determined that the power receiving coil is absent, and when the power transmitting coil current is equal to or less than a certain value, it is determined that the power receiving coil is present. However, because current flows through the transmitting coil even during normal power transmission, it is difficult to clearly determine the difference between the current value during power transmission and the current when the coil is not present. For example, if the current during normal power transmission is 10A, it is necessary to determine whether the threshold current at the time of coil detection is greater than 10A. This can cause unnecessary electromagnetic field radiation and power loss.

[0031] Also, there is a method of detecting the receiving coil by utilizing the characteristic that impedance increases by mounting a converter on the receiving side and keeping the receiving side in a short-circuit state. An example of such a configuration is shown in FIG. 15. By using this method, the current threshold value when determining the coupling between the coils can be set to a small value, and unnecessary electromagnetic field radiation and power loss can be reduced. In other words, the current for detecting the entrance of the receiving coil can be set independently of the current value of the power transmission. For example, the low side of the converter 21 on the receiving side is turned on to create a short-circuit state and detect the receiving side. After detecting the receiving side, the operation of the converter 21 on the receiving side is returned from the short-circuit state to the normal power transmission mode. After that, it is necessary to operate the power transmitting device with an output for normal power transmission, and it takes time from detection to rated power transmission. Also, if the detection of the exit of the receiving coil fails in the configuration of FIG. 15, there is a problem that power continues to be output even though the coil is absent.

[0032] Since the threshold is determined by the increase in current, if the increase in current value after the receiving coil leaves is missed for some reason (for example, instantaneous noise or processing of another event), it is difficult to determine whether power is being transmitted or whether it is an unnecessary transmission when the receiving coil is absent. This is because it has a mode suitable for entrance detection but does not have a mode suitable for exit detection. Ideally, by matching the resonance configuration of the non-contact power transfer device to the resonance frequency of the inverter, the current becomes maximum when the receiving coil is absent, so that the exit detection can be prevented from failing. However, in actual operation, it is usually necessary that the resonance frequency when the receiving coil is present and the resonance frequency when it is absent are different, and that the inverter operating frequency is shifted to a certain extent. Due to this condition, the current does not become maximum when the receiving coil is completely absent, making it difficult to determine the exit. As the coupling between the coils decreases, areas where the current increases and areas where it decreases are generated.

[0033] When a resonant configuration in which a parallel capacitor and a series inductor are added to the series resonant configuration of the first embodiment is used, - Impedance increases as the coupling between coils decreases. · As the coupling between the coils increases, the impedance decreases. This characteristic allows the determination method to be such that when the current exceeds a certain value, it is determined that the receiving coil is present, and when the current falls below the certain value, it is determined that the receiving coil is absent. This means that the current can be reduced when the receiving coil is absent, making it possible to suppress unnecessary electromagnetic field radiation and power loss. However, while a simple resonant system configuration and a current threshold value alone work well for detecting the coil of a stationary target, they do not work well for contactless power supply to a moving object. This is because the following cases, in particular, cannot be distinguished when detecting the state:

[0034] When the power receiving coil starts to enter, in the power transmission mode, the current value is low and the phase shift amount is small when the current value is increased to the target value. On the other hand, when the power receiving coil is about to leave, in the power transmission mode, even when the operation amount is maximum (the phase shift amount is minimum), the current value is below the target value. These two states cannot be distinguished by the current threshold alone, nor can they be distinguished by using the phase shift amount. This causes problems such as switching to coil detection mode as the power receiving coil is absent even when the power receiving coil has started to enter, or operating in power transmission mode for a while even when the power receiving coil has left. Or, there is a problem that the transition between power transmission mode and coil detection mode occurs frequently, making it impossible to transmit power appropriately or to stop it.

[0035] The above problem can be solved to some extent by increasing the threshold current in the coil detection mode and setting the threshold current when determining whether the power receiving coil is to be removed in the power transmission mode to a very small value. However, the time available for power transmission is shortened accordingly, and unnecessary power transmission, electromagnetic field radiation, and power loss increase after the power receiving coil is removed. Ideally, the power transmission mode is quickly switched to when a coil coupling state in which proper power transmission is possible is reached, that is, the smallest possible current value is used as the threshold value for the power transmission mode from the coil detection mode, and when a coil coupling state in which proper power transmission is not possible is reached, the power transmission mode is quickly switched to the coil detection mode, that is, the largest possible current value is used as the threshold value, thereby maximizing the transmission power and minimizing unnecessary electromagnetic field radiation.

[0036] In the first embodiment, by adding information on the state after the mode transition in addition to the current threshold, it is possible to reduce the threshold when detecting the power receiving coil in the coil detection mode and to increase the current value when determining whether the power receiving coil is leaving in the power transmission mode, as described above. Since it is possible to determine whether the mode is in an entry transition or an exit transition based on the state after the mode transition, it is possible to clearly distinguish the state after the mode transition, making it possible to use more time for power transmission and further reducing unnecessary power loss.

[0037] In addition, since the status information after the mode transition requires a minimum of 1 bit, the burden on the control device is small, the judgment is not complicated, and there is no need to store in memory a large number of judgment parameters for the presence or absence of the receiving coil for each expected situation.

[0038] The present application is characterized in that the upper and lower limits of the current threshold can be set to more ideal values. The specific current threshold setting is determined depending on the system to which it is applied. The present application does not limit the current threshold, but is characterized in that it uses information on the state after the mode transition to solve problems related to threshold setting constraints, such as unnecessary radiation and a decrease in the time available for power transmission. Note that, although the input current of the inverter has been described as an example of a parameter for determining mode switching, the input power of the inverter may also be used as a parameter for determination. In that case, in the above description, the input current may be read as input power and the current as power. In addition, other operating parameters related to the input power of the inverter may be used as a parameter for determination.

[0039] Embodiment 2 16 is a diagram showing a schematic configuration of a contactless power supply system including a power transmitting device according to a second embodiment. The basic configuration of the power transmitting device in this embodiment will be described. In addition to the configuration shown in the first embodiment, the power transmitting device has a mobile object proximity information sensor 8 that detects when a mobile object approaches closer than a preset distance. The mobile object proximity information sensor 8 is connected to a controller 7.

[0040] The moving body proximity information sensor 8 transmits moving body proximity information to the controller 7 when a moving body approaches. It is to be noted that there is no restriction on the method for sensing this moving body proximity information. In addition, the moving body proximity information from another mounted device may be used to transmit the moving body proximity information to the controller 7. When the moving body proximity information is sent to the controller 7, the operation shown in FIG. 17 is performed. When there is no moving body proximity information, one repetition cycle of the low output period and the zero output period in the detection mode is set to ta1, and when there is moving body proximity information, the cycle ta2 is set to be shorter than ta1. In this case, the reference time Tx for judgment in FIG. 9 and FIG. 11 may be based on, for example, the short cycle ta2. In other words, the reference time Tx for judgment may be set to a time longer than ta2. Also, Mobile Proximity information is only necessary in coil detection mode, so after switching to power transfer mode, Mobile Proximity information is turned off.

[0041] This configuration and operation can minimize unnecessary power radiation and power loss when no mobile object is present. Also, when a mobile object is approaching, the mode can be switched from coil detection mode to power transmission mode in a short time, which has the effect of enabling more power transmission.

[0042] Specifically, as shown in FIG. 18, the controller 7 in each of the above embodiments includes an arithmetic processing device 101 such as a central processing unit (CPU), a storage device 102 that exchanges data with the arithmetic processing device 101, and an input / output interface 103 that inputs and outputs signals between the arithmetic processing device 101 and the outside. The arithmetic processing device 101 may include an application specific integrated circuit (ASIC), an integrated circuit (IC), a digital signal processor (DSP), a field programmable gate array (FPGA), and various signal processing circuits. The storage device 102 includes a random access memory (RAM) that is configured to be able to read and write data from the arithmetic processing device 101, a read only memory (ROM) that is configured to be able to read data from the arithmetic processing device 101, and the like. The input / output interface 103 includes, for example, an A / D converter that inputs a signal output from the current sensor 6 to the arithmetic processing device 101, and a circuit for outputting a signal from the arithmetic processing device 101 to the inverter 1.

[0043] Although various exemplary embodiments and examples are described in this application, various features, aspects, and functions described in one or more embodiments are not limited to the application of a specific embodiment, but can be applied to the embodiments alone or in various combinations. Therefore, countless modifications not illustrated are expected within the scope of the technology disclosed in this specification. For example, the modification, addition, or omission of at least one component, and the extraction and combination of at least one component with components of other embodiments are included. [Explanation of symbols]

[0044] REFERENCE SIGNS LIST 1 inverter, 2 inductor, 3 first capacitor, 4 second capacitor, 5 power transmission coil, 6 current sensor, 7 controller, 8 mobile object proximity information sensor, 11 power receiving coil, 12 first power receiving side capacitor, 13 second power receiving side capacitor, 14 power receiving side inductor, 15 rectifier, 100 power transmission device, 200 power receiving side device, 300 mobile object

Claims

1. A power transmission device including a power transmission coil that transmits power to an external power receiving coil by being magnetically coupled to the power receiving coil, an inverter that converts direct current into alternating current and supplies AC power to the power transmission coil, and a controller that controls the inverter, a series circuit of an inductor and a first capacitor is connected to an AC side of the inverter, and a series circuit of a second capacitor and the power transmission coil is connected in parallel to the first capacitor; The controller is configured to control the inverter by switching between two modes: a power transmission mode in which the inverter is operated to transmit power to the transmission coil, and a coil detection mode in which a small output period in which the inverter is operated at an output power lower than a rated power and a zero output period in which the output of the inverter is zero are alternately repeated, and the power transmission device performs the mode switching based on a post-mode transition state in which information changes when a predetermined condition is satisfied after the mode is switched, and on the value of an operating parameter related to at least the input power to the inverter.

2. 2. The power transmitting device according to claim 1, wherein the predetermined condition when the power transmission mode is switched to the coil detection mode is that at least one repeating cycle of the low output period and the zero output period has elapsed since the power transmission mode is switched to the coil detection mode.

3. 3. The power transmission device according to claim 1, wherein the predetermined condition when switching from the coil detection mode to the power transmission mode is that at least one repeating cycle of the low output period and the zero output period has elapsed since switching from the coil detection mode to the power transmission mode.

4. The time when the predetermined condition is satisfied when the mode is switched from the coil detection mode to the power transmission mode is:

3. The power transmission device according to claim 1, wherein the time when at least one cycle of the small output period and the zero output period in the coil detection mode has elapsed since switching from the coil detection mode to the power transmission mode, or the time when the input current or input power to the inverter exceeds a predetermined threshold value, whichever is earlier.

5. 5. The power transmission device according to claim 1, wherein the controller executes switching from the coil detection mode to the power transmission mode when the information on the post-mode transition state is information after the mode transition state has changed after switching from the power transmission mode to the coil detection mode, and when an input current or input power to the inverter exceeds a predetermined entry threshold.

6. The inverter is a phase-shift controlled inverter that controls an output by changing a phase shift amount, The power transmission device according to any one of claims 1 to 5, wherein the controller executes switching from the power transmission mode to the coil detection mode when the post-mode transition state information is information after it has changed after switching from the coil detection mode to the power transmission mode, and when the input current or input power to the inverter is less than a predetermined exit threshold and the phase shift amount is less than a predetermined exit threshold.

7. The controller is configured to receive moving object proximity information notifying that a moving object has approached closer than a preset distance; The power transmitting device according to claim 1 , wherein, when the moving object proximity information is received, a repetition period of the small output period and the zero output period is set to be shorter than the repetition period until the moving object proximity information is received.

8. The power transmitting device according to claim 1 , a power receiving side device mounted on a moving object, the power receiving side device including a series circuit of a power receiving side inductor and a second power receiving side capacitor connected to an AC side of a rectifier, a first power receiving side capacitor and the power receiving coil connected in parallel to the second power receiving side capacitor; A non-contact power supply system consisting of:

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