JP2021114855A - Non-contact power supply system - Google Patents

Abstract

To make it possible to detect the presence or absence of a metal foreign matter between a power transmission unit and a power reception unit with a simple structure in a non-contact power supply system of a magnetic resonance type whose resonance frequency is set to be a low frequency.SOLUTION: A magnetic resonance type non-contact power supply system includes a power transmission unit including a primary side resonance circuit connected to a power source and a power reception unit including a secondary side resonance circuit connected to a load. By making a primary side resonance coil in the primary side resonance circuit and a secondary side resonance coil in the secondary side resonance circuit resonant together, the power is transmitted from the power transmission unit to the power reception unit. The non-contact power supply system includes a switch that opens and closes a secondary side main circuit connecting between the secondary side resonance circuit and the load. While the switch opens the secondary side main circuit, the phase of the current or the voltage input to or output from a primary side resonance capacitor in the primary side resonance circuit is detected.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic resonance type non-contact power feeding system capable of supplying electric power to a load in a non-contact manner.

Conventionally, as a non-contact power supply system that transmits electric power in a non-contact manner to a device such as a portable electronic device or a robot vacuum cleaner, a system using magnetic resonance is known. In this magnetic resonance type non-contact power feeding system, for example, as shown in Patent Document 1, a power transmission unit having a primary resonance coil connected to a power source and a secondary resonance coil connected to a battery (also referred to as a load) are provided. By resonating the primary side resonance coil and the secondary side resonance coil at the resonance frequency, power is transmitted from the power transmission unit to the power reception unit, thereby the battery built in the device. It can be charged.

By the way, in such a magnetic resonance type non-contact power feeding system, in order to increase the power transmission efficiency, the resonance frequency (also referred to as the operating frequency) of the primary side resonance coil and the secondary side resonance coil is set to a high frequency of, for example, 10 kHz or more. The one set in may be used. In this case, for example, if a metal foreign substance or the like exists between the power transmission unit and the power reception unit during charging, it is rapidly heated by a high-frequency magnetic field, which may cause burns or fire. In addition, a high-frequency magnetic field may adversely affect the health of the user.

Therefore, in recent years, a non-contact power feeding system in which the operating frequency is set to a low frequency (for example, 3 kHz or less) has been developed. It is believed that this can reduce the effects of heat generation and adverse health effects caused by the above-mentioned metallic foreign substances.

Japanese Unexamined Patent Publication No. 2014-90617

However, even if the above-mentioned operating frequency is set to a low frequency, if metal foreign matter exists between the power transmission unit and the power receiving unit during charging, the entire metal foreign matter is heated by the overcurrent, which has an effect. Cannot be ignored. Therefore, even if the operating frequency is low, it is required to be able to detect foreign matter existing between the power transmission unit and the power receiving unit, but there is no means to realize this by a conventional simple configuration. rice field.

Therefore, the main object of the present invention is to detect the presence or absence of metallic foreign matter between the power transmission unit and the power reception unit with a simple configuration in a magnetic resonance non-contact power supply system in which the resonance frequency is set to a low frequency. be.

When the secondary side resonant circuit and the load are separated from each other and power is supplied from the primary side resonant circuit to the secondary resonant circuit with no load on the secondary side, the present inventors combine the power transmission unit and the power receiving unit. When there is no metallic foreign matter between them, the ineffective power only increases, whereas when there is a metallic foreign matter between the power transmission unit and the power receiving unit, an eddy current is generated in the metal foreign matter. We focused on the consumption of electricity and the change in power factor. Further, the present inventors have focused on the fact that the phase of the voltage and current across the primary resonance capacitor shifts due to the change in power factor due to the presence of a metallic foreign substance, as shown in FIG. We have found that the presence or absence of metallic foreign matter can be detected by detecting the phases of the voltage and current at both ends, and came up with the present invention.

That is, the non-contact power supply system according to the present invention includes a power transmission unit having a primary resonance circuit connected to a power source and a power receiving unit having a secondary resonance circuit connected to a load, and the primary resonance circuit is provided. A magnetic resonance type non-contact power supply system that transmits power from the power transmission unit to the power receiving unit by resonating the primary side resonance coil and the secondary side resonance coil of the secondary side resonance circuit. The primary side resonance circuit has a switch for opening and closing the secondary side main circuit connecting the secondary side resonance circuit and the load, and the primary side resonance circuit has the primary side resonance circuit in a state where the switch opens the secondary side main circuit. It is characterized in that it is configured to detect the phase of the voltage or current input / output to / from the side resonance capacitor.

In this way, the phase of the voltage or current input to / from the primary side resonance capacitor is detected with the secondary side main circuit connecting the secondary side resonance circuit and the load open. Therefore, by observing the phase difference between the phase of the voltage or current input to the primary resonance capacitor and the phase of the voltage or current output from the primary resonance capacitor, the metal between the power transmission unit and the power reception unit. The presence or absence of foreign matter can be detected. As for the circuit configuration, it is only necessary to provide a switch for opening and closing the secondary side main circuit as compared with the conventional one, so that the presence or absence of metallic foreign matter can be detected by a simple configuration.

As a specific embodiment of the non-contact power feeding system, the phase difference of the current or voltage input / output to the primary resonance capacitor is calculated, and when the phase difference is within a predetermined numerical range, the power transmission unit and the said Examples thereof include those for determining that there is no metallic foreign matter between the power receiving unit and the power receiving unit. In this case, when the non-contact power feeding system determines that there is no metallic foreign matter, it is preferable to close the switch and start supplying electric power to the load.

As a specific embodiment of the non-contact power feeding system, when the calculated value of the phase difference exceeds a predetermined numerical range, it can be determined that the metallic foreign matter is present. In this case, when the non-contact power supply system determines that the metallic foreign matter is present, it is preferable to stop the transmission of electric power from the power transmission unit to the power receiving unit or reduce the amount of electric power to be transmitted.
By doing so, it is possible to prevent the metallic foreign matter from being rapidly heated in the presence of the metallic foreign matter, and it is possible to suppress the occurrence of burns and fire.

The non-contact power feeding system continuously measures the power feeding efficiency of the electric power transmitted from the power transmitting unit to the power receiving unit in a state where the switch closes the secondary main circuit, and determines the power feeding efficiency. It is preferable that the structure is such that the presence or absence of the metallic foreign matter is determined based on the time change.
In this way, it is possible to detect the entry of metallic foreign matter between the power transmission unit and the power reception unit while the load is being supplied.

As a specific embodiment of the non-contact power feeding system, the resonance frequency of the primary side resonance coil and the secondary side resonance coil is 3 kHz or less.

According to the present invention configured in this way, in a magnetic resonance non-contact power feeding system in which the resonance frequency is set to a low frequency, the presence or absence of metallic foreign matter between the power transmission unit and the power receiving unit can be detected by a simple configuration. can.

The figure which shows schematic the circuit structure of the non-contact power supply system of this embodiment. The figure which roughly explains the difference in the voltage (or current) waveform input / output to the primary side resonance capacitor depending on the presence or absence of metallic foreign matter. The flowchart explaining the foreign matter detection operation of the non-contact power supply system of the same embodiment. The flowchart explaining the foreign matter detection operation of the non-contact power supply system of the same embodiment.

The non-contact power feeding system 100 according to the embodiment of the present invention will be described below with reference to the drawings.

<Overall configuration>
The non-contact power supply system 100 of the present embodiment is for non-contact charging of a battery (load) 4 built in an electronic device such as a robot vacuum cleaner by a charger. Specifically, as shown in FIG. 1, the non-contact power supply system 100 includes a power transmission unit 2 built in a charger connected to a power source 1 and a power receiving unit built in a robot vacuum cleaner and connected to a load 4. It has 3 and. In this non-contact power feeding system 100, the primary side resonance coil 231 included in the power transmission unit 2 and the secondary side resonance coil 311 included in the power receiving unit 3 are opposed to each other, and the primary side resonance coil 231 and the secondary side resonance coil 311 are combined with each other. Is a so-called magnetic resonance system in which power is transmitted from the power transmission unit 2 to the power reception unit 3 by resonating with a low-frequency resonance frequency of 3 kHz or less (preferably a commercial power supply frequency). Hereinafter, a detailed description will be given.

<Power transmission unit>
The power transmission unit 2 transmits the electric power from the power source 1 to the power receiving unit 3. Specifically, the power transmission unit 2 is connected in parallel to a rectifying and smoothing circuit 21 that rectifies and smoothes an AC voltage supplied from a power source 1 to a DC voltage, and a rectifying and smoothing circuit 21, and transfers a DC voltage to an arbitrary frequency. It includes an inverter circuit 22 that converts to an AC voltage and outputs it, a primary side resonance circuit 23 that is connected in parallel to the inverter circuit 22, and a primary side control unit 24.

As the rectifying and smoothing circuit 21, a circuit having a known configuration may be applied, and the rectifying and smoothing circuit 21 includes, for example, a diode bridge and a smoothing capacitor. Further, as the inverter circuit 22, a circuit having a known configuration may be applied, and examples thereof include a full bridge system composed of four switching elements.

The primary side resonance circuit 23 is for generating an oscillating magnetic field by applying an AC voltage from the inverter circuit 22. Specifically, the primary resonance circuit 23 is an LC series resonant circuit composed of a primary resonant coil 231 and a primary resonant capacitor 232 connected in series with each other. The primary resonance coil 231 of the present embodiment is a solenoid type in which a conducting wire is wound around a plate-shaped magnetic core.

The primary side control unit 24 is physically provided with a CPU, a memory, an input means, and the like, and is output by at least the rectifying and smoothing circuit 21 by operating according to a predetermined program stored in the memory. It functions to control the frequency of the DC voltage and the frequency of the AC voltage output by the inverter circuit 22.

Here, the primary side control unit 24 also functions as a detection unit that detects the current and voltage input to the primary side resonance capacitor 232 and the current and voltage output from the primary side resonance capacitor 232. Further, the primary side control unit 24 detects the phase of the current and voltage input to the primary side resonance capacitor 232 and the phase of the current and voltage output from the primary side resonance capacitor 232, respectively, based on the detected current and voltage. It works to do.

The primary side control unit 24 also functions as a communication unit for transmitting and receiving various data to and from the secondary side control unit 35 included in the power receiving unit 3 described later. The transmission and reception of this data is performed by using, for example, infrared rays (IRDA or the like), short-range wireless communication technology (BLE or the like), or the like.

<Power receiving unit>
The power receiving unit 3 receives the electric power transmitted from the power transmitting unit 2 and outputs the electric power to the load 4. Specifically, the power receiving unit 3 includes a secondary side resonance circuit 31 that magnetically resonates with the primary side resonance circuit 23 to generate an AC voltage, and a rectifier circuit 32 that rectifies the AC voltage output from the secondary side resonance circuit 31. A smoothing circuit 33 that smoothes the DC voltage output from the rectifier circuit 32, a voltage conversion circuit 34 that adjusts the voltage value of the smoothed DC voltage and applies a voltage to the load 4, and secondary side control. A unit 35 is provided. These circuits included in the power receiving unit 3 are connected in parallel with each other and are connected in parallel with the load 4.

The secondary resonance circuit 31 is an LC series resonant circuit composed of a secondary resonant coil 311 and a secondary resonant capacitor 312 connected in series with each other. The secondary resonance coil 311 is a solenoid type in which a conducting wire is wound around a plate-shaped magnetic core, similarly to the primary resonance coil 231.

As the rectifier circuit 32, a known configuration may be applied, for example, a diode bridge composed of four diodes. The rectifier circuit 32 is connected in parallel to the secondary resonance coil 311 and the secondary resonance capacitor 312, and rectifies (that is, converts the AC voltage generated in the secondary resonance coil 311 and the secondary resonance capacitor 312) the AC voltage generated in the secondary resonance coil 311 and the secondary resonance capacitor 312. )do.

The smoothing circuit 33 includes a smoothing capacitor 331 connected in parallel to the rectifier circuit 32, and generates a DC voltage by smoothing the pulsating current voltage output from the rectifier circuit 32. One end of the smoothing capacitor 331 is connected to the output end of the rectifier circuit 32, and the other end is connected to the input end of the rectifier circuit 32.

The voltage conversion circuit 34 converts the DC voltage smoothed by the smoothing circuit 33 into a desired voltage, and a known configuration may be applied. Examples of the voltage conversion circuit 34 include a step-down circuit and a step-up circuit including semiconductor switches and coils such as MOSFETs and IGBTs.

The power receiving unit 3 also includes a switch SW that opens and closes the secondary side main circuit 30 that connects the secondary side resonance circuit 31 and the load 4. This switch SW is, for example, a semiconductor switching element such as a MOSFET, and is connected in series with the secondary side resonance coil 311 and the secondary side resonance capacitor 312 and the load 4. The open switch SW switches the On / Off state based on the control signal received from the secondary side control unit 35 (open / close command unit).

The secondary side control unit 35 physically includes a CPU, a memory, an input means, and the like, and controls the opening and closing of the release switch SW by operating according to a predetermined program stored in the memory. Functions as an open / close command unit. Further, the secondary side control unit 35 exerts a function as a communication unit for transmitting and receiving various data to and from the primary side control unit 24 included in the power transmission unit 2.

The non-contact power supply system 100 of the present embodiment is primary so as to be able to detect the presence or absence of metal foreign matter intervening between the power transmission unit 2 and the power reception unit 3 before the start of charging and during charging of the load 4. The side control unit 24 detects the phase of the voltage or current input to / from the primary resonance capacitor 232 of the primary resonance circuit 23 in a state where the switch SW is open to the secondary main circuit 30. Based on the detected voltage or current phase, it is configured to detect the presence or absence of metallic foreign matter intervening between the power transmission unit 2 and the power reception unit 3.

Specifically, the primary side control unit 24 has the phase of the current or voltage input from the inverter circuit 22 to the primary side resonance capacitor 232 and the primary side in a state where the switch SW opens the secondary side main circuit 30. It is configured to calculate the phase difference of the phase of the current or voltage output from the resonance capacitor 232. Then, the phase difference of the current or voltage input / output to the primary resonance capacitor 232 is compared with a predetermined numerical range (for example, −5 ° or more and + 5 ° or less) stored in the memory in advance. The primary side control unit 24 determines that there is no metallic foreign matter when the calculated phase difference is within a predetermined range, and when the calculated phase difference exceeds a predetermined range, a metallic foreign matter is present. Determine that it exists.

When it is determined that there is no metallic foreign matter, the primary side control unit 24 transmits a predetermined signal indicating that the power supply to the load 4 may be started to the secondary side control unit 35. When the secondary side control unit 35 receives the signal, it transmits a control signal to the switch SW and closes the switch SW.

When it is determined that there is a metallic foreign substance, the primary side control unit 24 transmits a predetermined control signal to the rectifying smoothing circuit 21 and the inverter circuit 22, and stops the transmission of electric power from the power transmission unit 2 to the power receiving unit 3. Alternatively, the amount of power to be transmitted is reduced. Further, in this case, the primary side control unit 24 notifies that a metallic foreign substance exists between the power transmission unit 2 and the power reception unit 3. For example, a predetermined signal for notifying the presence of a metallic foreign substance is transmitted to a notification means such as a speaker, a lamp, or a display provided in the power transmission unit 2.

Further, the primary side control unit 24 continuously measures the power supply efficiency of the electric power transmitted from the power transmission unit 2 to the power receiving unit 3 while charging the load 4, and the power transmission unit is based on the time change of the power supply efficiency. It is configured to detect the presence or absence of metal foreign matter intervening between the power receiving unit 3 and the power receiving unit 3. This power supply efficiency is the ratio (%) of the output power output from the power receiving unit 3 to the input power input to the power transmission unit 2. Specifically, in the primary side control unit 24, when the power supply efficiency drops by a predetermined ratio (for example, 2% or more) while the load 4 is being charged (while the switch SW is closed), metallic foreign matter is present. Judge that there is. In this case, the primary side control unit 24 weakens the AC voltage applied from the inverter circuit 22 to the primary side resonance circuit 23, or stops the application of the AC voltage. Further, in this case, the primary side control unit 24 notifies that a metallic foreign substance exists between the power transmission unit 2 and the power reception unit 3.

Next, the foreign matter detection operation of the non-contact power supply system 100 of the present embodiment will be described. The foreign matter detection operation of the non-contact power supply system 100 of the present embodiment includes a pre-charging detection mode that detects the presence or absence of metallic foreign matter before the start of charging of the load 4, and charging that detects the presence or absence of metallic foreign matter during charging of the load 4. It has a detection mode.

(Pre-charging detection mode)
In this mode, first, with the switch SW of the power receiving unit 3 closed, a low voltage (about 50V) is applied from the inverter circuit 22 to the primary resonance circuit 23, so that the secondary resonance coil 311 is in a position where power can be received. It is determined whether or not there is (step S11). When the secondary resonance coil 311 is present, the presence or absence of metallic foreign matter between the power transmission unit 2 and the power reception unit 3 is detected (step S12). Specifically, an AC voltage is applied from the inverter circuit 22 to the primary resonance circuit 23 in a state where the switch SW of the power receiving unit 3 is opened and the power receiving unit 3 is unloaded, and the primary resonance capacitor 232 is applied from the inverter circuit 22. It is determined whether or not the phase difference between the phase of the voltage or current input to the inverter and the phase of the voltage or current output from the primary resonance capacitor 232 is within a predetermined numerical range (within ± 5 °). If the phase difference between the voltage or current across the primary resonance capacitor 232 is within a predetermined numerical range, it is determined that there is no metal foreign matter, the switch SW is closed, and power supply to the load 4 is started (step S13). .. On the other hand, when the phase difference between the voltage or current across the primary resonance capacitor 232 exceeds a predetermined numerical range, a speaker or the like notifies that there is a metallic foreign substance (step S14).

(Charging detection mode)
In this mode, the power feeding efficiency from the power transmitting unit 2 to the power receiving unit 3 is continuously measured, and it is determined whether or not the power feeding efficiency drops by a predetermined ratio (%) or more while the load 4 is being fed (step S21). .. If the power supply efficiency does not decrease by a predetermined ratio or more, it is determined that there is no metal foreign matter between the power transmission unit 2 and the power reception unit 3, and power supply to the load 4 is continued as it is. On the other hand, if the power supply efficiency drops by a predetermined ratio (%) or more while power is being supplied to the load 4, it is determined that there is a metallic foreign substance between the power transmission unit 2 and the power reception unit 3, and the power transmission unit 2 sends the power reception unit. Stop or weaken the transmission of power to 3 (step S22). Further, the presence of metallic foreign matter is notified by a speaker or the like (step S23).

<Effect of this embodiment>
According to the non-contact power supply system 100 of the present embodiment configured in this way, the current input from the inverter circuit 22 to the primary side resonance capacitor 232 or the current input from the inverter circuit 22 to the primary side resonance capacitor 232 in a state where the switch SW opens the secondary side main circuit 30. Since it is configured to calculate the phase difference between the phase of the voltage and the phase of the current or voltage output from the primary resonance capacitor 232, the power transmission unit 2 and the power receiving unit are before starting power supply to the load 4. It is possible to detect the presence or absence of a metallic foreign substance between the three. Further, with the switch SW closed, the power supply efficiency of the power transmitted from the power transmission unit 2 to the power reception unit 3 is continuously measured, and the power transmission unit 2 and the power reception unit 3 are connected to each other based on the time change of the power supply efficiency. Since it is configured to determine the presence or absence of metal foreign matter intervening between them, it is possible to detect the entry of metal foreign matter even after the power supply to the load 4 is started.

<Other modified embodiments>
The present invention is not limited to the above embodiment.

In the above embodiment, the switching element 342 is a semiconductor switch such as a MOSFET or an IGBT, but the switching element 342 is not limited to this and may be a diode.

The non-contact power supply system 100 in the above embodiment is not limited to charging a robot vacuum cleaner, but may be used for charging other electronic devices such as mobile phones and smartphones.

In addition, various embodiments may be modified or combined as long as they do not contradict the gist of the present invention.

100 ・ ・ ・ Non-contact power supply system 1 ・ ・ ・ Power supply 231 ・ ・ ・ Primary side resonance coil 232 ・ ・ ・ Primary side resonance capacitor 3 ・ ・ ・ Power receiving unit 311 ・ ・ ・ Secondary side resonance coil 4 ・ ・ ・ Load SW ···switch

Claims (7)

A power transmission unit having a primary resonance circuit connected to a power source and a power receiving unit having a secondary resonance circuit connected to a load are provided, and a primary resonance coil included in the primary resonance circuit and a secondary resonance coil are provided. It is a magnetic resonance type non-contact power feeding system that transmits power from the power transmitting unit to the power receiving unit by resonating with the secondary resonance coil of the resonance circuit.
A switch for opening and closing the secondary side main circuit connecting the secondary side resonance circuit and the load is provided.
A non-contact power supply system configured to detect the phase of voltage or current input to / from the primary resonance capacitor of the primary resonance circuit while the switch has the secondary main circuit open. .. The phase difference of the current or voltage input / output to the primary resonance capacitor is calculated, and when the phase difference is within a predetermined numerical range, it is determined that there is no metallic foreign matter between the power transmission unit and the power receiving unit. The non-contact power supply system according to claim 1. The non-contact power supply system according to claim 2, wherein when it is determined that there is no metallic foreign matter, the switch is closed and power is started to be supplied to the load. The non-contact power feeding system according to claim 2 or 3, wherein when the calculated value of the phase difference exceeds the predetermined numerical range, it is determined that the metallic foreign matter is present. The non-contact power supply system according to claim 4, wherein when it is determined that the metal foreign matter is present, the transmission of electric power from the power transmission unit to the power receiving unit is stopped or the amount of electric power to be transmitted is reduced. With the switch closing the secondary side main circuit, the power supply efficiency of the electric power transmitted from the power transmission unit to the power receiving unit is continuously measured, and the metal is based on the time change of the power supply efficiency. The non-contact power supply system according to any one of claims 1 to 5, which determines the presence or absence of foreign matter. The non-contact power feeding system according to any one of claims 1 to 6, wherein the resonance frequency of the primary side resonance coil and the secondary side resonance coil is 3 kHz or less.

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