JP2015144538A - Power transmission method and power transmission system - Google Patents

Abstract

An object of the present invention is to prevent overcharging of a power storage unit. A power transmission system includes a power transmission unit including a primary side coil, and a power reception unit including a secondary side coil and a power storage unit. Power is transmitted from the power transmission unit to the power reception unit in a non-contact manner via the primary side coil and the secondary side coil, and power is stored from the secondary side coil to the power storage unit. In the power transmission unit, the current consumption of the power transmission system to the power reception unit is detected as a detection current, and when this detection current becomes smaller than the first threshold current, the power transmission unit stops power transmission. [Selection] Figure 1

Description

  The present invention relates to a power transmission method, and more particularly, to a power transmission method and a power transmission system that perform power transmission in a non-contact manner from a power transmission unit including a primary coil to a power reception unit including a secondary coil and a power storage unit.

  When a thin-pointed pen (stylus) is used with respect to the capacitive touch panel employed in a tablet terminal or the like, the contact area between the touch panel and the pen tip becomes small, and it is difficult to detect the contact position.

  On the other hand, Patent Document 1 discloses a stylus input device that enables input using a stylus with a small contact area. In the technique disclosed in Patent Document 1, a power source such as a battery is mounted on a stylus input device.

  Patent Document 2 uses electromagnetic induction when charging a battery mounted on a coordinate indicating pen (input device; power receiving unit) for instructing coordinates to a digitizer body (detecting device; power transmitting unit). A method of non-contact charging (digitizer) is disclosed. In the prior art disclosed in Patent Document 2, a primary coil and an iron core are mounted on the digitizer body (detection device; power transmission unit) side, and a spiral-shaped 2 in the coordinate pointing pen (input device; power reception unit). A secondary coil is provided. At the time of charging, the primary iron core is disposed in the hollow portion of the secondary coil. The secondary coil output is rectified and smoothed by a charging circuit (rectifying and smoothing circuit), and supplied to the rechargeable battery for charging.

  In Patent Document 2, when the coordinate pointing pen (input device; power receiving unit) is not used, the secondary coil thereof is electromagnetically coupled to the digitizer body (detecting device; power transmission unit) to form a charging transformer. . Thus, when the coordinate instruction pen (input device; power receiving unit) is not used, the rechargeable battery built in the coordinate instruction pen (input device; power reception unit) is always in a charging operation state.

  Furthermore, Patent Document 3 detects coordinates input from a vibration pen (input device; power receiving unit) by a plurality of sensors (detection devices) provided on the vibration transmission plate, and coordinates the vibration pen on the vibration transmission plate. Discloses a coordinate input device. In Patent Document 3, a vibration pen (input device; power receiving unit) includes a rechargeable battery, an input coil, and a rectifier circuit. The input coil is excited by an alternating current flowing through the charging coil when the vibration pen (input device) is standing on a pen stand (power transmission unit). The alternating current excited in the input coil is converted into direct current by the rectifier circuit and supplied to the battery as a charging current. The input coil is provided in the shape of a spiral wound around its axis in the housing of the vibration pen (input device; power receiving unit).

  On the other hand, Patent Document 4 discloses a position input device including a position indicator (input device) and a tablet (detection device) that detects a position indicated by the position indicator (input device). In Patent Document 4, a position indicator (input device) is charged with driving power through a power transmission unit that receives power supplied from the outside, a controller that is supplied with a predetermined driving voltage, and a power transmission unit. And a charging capacitor. The power transmission means receives an AC signal supplied from the outside. The position indicator includes a rectifier circuit (diode) that rectifies the AC signal received from the power transmission means. Electric power is supplied to the position indicator in a non-contact manner by an AC signal and the charging capacitor is charged. In Patent Document 4, as an embodiment, the power transmission means includes a resonance circuit in which a capacitor and a coil are connected in parallel. The charging capacitor is an electric double layer capacitor.

  Patent Document 4 also discloses a charger for charging a position indicator. The charger includes an insertion slot into which the position indicator is inserted, a support portion that supports the position indicator, and a power supply coil that is wound around the support portion. An AC voltage having the same frequency as the resonance frequency of the resonance circuit is applied to the power supply coil. When a position indicator is inserted into the insertion opening, an induced voltage is generated in the resonance circuit of the position indicator, and this induced voltage is rectified by a diode to charge the electric double layer capacitor. In Patent Document 4, power supply to the charger is started, and power supply to the charger is terminated after a predetermined time has elapsed.

  Furthermore, Patent Document 4 discloses a tablet computer in which an indicator storage part for storing a position indicator is formed in a case as a fifth embodiment. The indicator storage portion is a cylindrical hole that communicates with the insertion opening that opens on the side of the case, and the depth and the inner diameter of the indicator storage portion are sized to accommodate the case of the position indicator. A power supply coil (AC magnetic field generating means) is wound around the outside in a region where the tip of the position indicator is accommodated in the indicator storage portion. When the position indicator is not used, if it is stored in the indicator storage unit, the position indicator is charged.

  Patent Document 5 discloses a non-contact power transmission system that can supply only necessary power to the power receiving side with a simple configuration. The non-contact power transmission system disclosed in Patent Document 5 includes a power feeding device and a power receiving device. The power supply apparatus includes an AC constant voltage power supply unit, a power supply side resonance capacitor, and a power supply antenna coil. The power receiving device includes a power receiving antenna coil and a load, and can move relative to the power feeding device. A power supply side resonance capacitor and a power supply antenna coil are connected in parallel to the AC constant voltage supply unit to constitute a parallel resonance circuit.

  In Patent Document 5, in a state where the parallel resonant circuit has a high impedance (standby state), a certain electromagnetic field energy is stored in the vicinity of the feeding antenna coil. When the power feeding antenna coil of the power feeding device and the power receiving antenna coil of the power receiving device are close to each other and face each other, the load impedance of the power receiving device becomes low (power transmission state), and the energy of the electromagnetic field stored near the power feeding antenna coil is received. The power is transmitted to the antenna coil, and power is transmitted from the feeding antenna coil to the power receiving antenna coil. When the load of the power receiving device is a secondary battery via a rectifier circuit, and the secondary battery is in a fully charged state, the impedance of the load becomes high. Even when the power feeding antenna coil and the power receiving antenna coil are close to each other and facing each other, the impedance of the load is high, so that the impedance of the power receiving antenna coil is also increased, and the impedance of the parallel resonance circuit in the power feeding device is not reduced. Almost no power transfer to

  Patent Document 6 discloses a transmission system that transmits electric power and data using a magnetic field. The transmission system disclosed in Patent Document 6 includes a power feeding device (primary device) including a power transmission operation unit and an electronic device (secondary device) including a power reception operation unit. The power transmission operation unit performs power transmission (conductive operation) to the electronic device using a magnetic field using the shared coil. The power reception operation unit performs a power reception operation of receiving power transmitted by power transmission using a magnetic field using a shared coil. The power receiving operation unit includes an impedance matching circuit, a charging unit, and a battery. The impedance matching circuit performs impedance matching when performing power transmission. The charging unit charges the battery based on the electric power received in the shared coil. The battery stores electric power according to charging by the charging unit.

JP 2007-183809 A JP-A-3-139713 JP-A-3-4312 Japanese Patent No. 4751191 (FIGS. 3, 6, and 16) JP2013-121230A JP 2013-102594 A

  As described above, the input device disclosed in Patent Document 1 includes a power source such as a battery. However, Patent Document 1 does not disclose or suggest any method (method) of charging the battery.

  On the other hand, in the input device disclosed in Patent Document 2, in order to charge the battery, a spiral secondary coil is provided in the input device (coordinate indicating pen). As described above, in the digitizer disclosed in Patent Document 2, when the coordinate instruction pen (input device; power reception unit) is not used, the rechargeable battery built into the coordinate instruction pen (input device; power reception unit) is always used. Charging operation is in progress.

  In order to save energy, it is desirable for the digitizer body (detection device; power transmission unit) to stop power transmission when the battery on the input device (power reception unit) side is fully charged. However, Patent Document 2 does not disclose or describe such power transmission control.

  In the input device disclosed in Patent Document 3, a spiral input coil is provided in the input device (vibrating pen) in order to charge the battery. Even in the coordinate input device disclosed in Patent Document 3, when the vibration pen (input device: power receiving unit) is standing on the pen stand (power transmission unit), the battery of the vibration pen (input device: power reception unit) is It is supposed to be charged.

  Similar to Patent Document 2, Patent Document 3 does not disclose or describe any control of power transmission.

  In the input device disclosed in Patent Document 4, in order to charge an electric double layer capacitor, a resonance circuit in which a capacitor and a coil are connected in parallel is provided in the input device. In Patent Document 4, power supply to the charger is started, and power supply to the charger is terminated after a predetermined time has elapsed. However, in such control, it is not known whether the charging capacitor is actually fully charged.

  In the non-contact power transmission system disclosed in Patent Document 5, power transmission is controlled according to the level of impedance. However, in Patent Document 5, even if the secondary battery is in a fully charged state, power transmission is not completely stopped, and thus power transmission to the power receiving device is performed even a little.

  Patent Document 6 simply uses a magnetic field to transmit power (conductive operation) from a power transmission operation unit of a power supply device (primary device) to a power reception operation unit of an electronic device (secondary device) using a shared coil. ) Is merely disclosed. No description or consideration is given to what operation is performed when the battery of the power receiving operation unit is fully charged.

  Therefore, the technical problem of the present invention is to provide a power transmission method and a power transmission system that can prevent overcharging of the power storage unit of the power receiving unit.

  According to the first aspect of the present invention, there is provided a power transmission method in a power transmission system including a power transmission unit including a primary side coil and a power reception unit including a secondary side coil and a power storage unit. In a power transmission method in which power is transmitted to a power receiving unit through a primary coil and a secondary coil in a non-contact manner and power is stored from the secondary coil to a power storage unit, the power transmission unit transmits power to the power receiving unit. A power transmission method is obtained in which the current consumption of the system is detected as a detection current, and the power transmission unit stops power transmission when the detected current becomes smaller than the first threshold current.

  According to the second aspect of the present invention, there is provided a power transmission system having a power transmission unit including a primary coil and a power reception unit including a secondary coil and a power storage unit, from the power transmission unit to the power reception unit. In a power transmission system in which power is transmitted in a non-contact manner via a primary side coil and a secondary side coil and power is stored from the secondary side coil to the power storage unit, the power transmission unit is a current consumption of the power transmission system to the power reception unit A detection element that detects the detection current as a detection current, a comparator that compares the detection current with the first threshold current, and a stop unit that stops power transmission when the detection current becomes smaller than the first threshold current. Thus, a power transmission system comprising:

  In the power transmission method according to the present invention, since the power transmission is stopped when the detected current becomes smaller than the first threshold current, it is possible to prevent overcharging of the power storage unit.

It is a block diagram which shows the structure of the electric power transmission system which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the electric power transmission system which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the power transmission part of the electric power transmission system which concerns on 1st Example of this invention. It is a time chart for demonstrating operation | movement of the power transmission part shown in FIG. It is a block diagram which shows the structure of the power transmission part of the electric power transmission system which concerns on 2nd Example of this invention. It is a time chart for demonstrating operation | movement of the power transmission part shown in FIG. It is a block diagram which shows the structure of the power transmission part of the electric power transmission system which concerns on the 3rd Example of this invention. It is a time chart for demonstrating operation | movement of the power transmission part shown in FIG. It is a block diagram which shows the structure of the power transmission part of the electric power transmission system which concerns on the modification of this invention.

  Next, modes for carrying out the present invention will be described with specific examples.

(First embodiment)
FIG. 1 is a block diagram showing a configuration of a power transmission system 1 according to the first embodiment of the present invention. The illustrated power transmission system 1 shows an example applied to a coordinate input system.

  The coordinate input system 1 includes an input device 20 and a detection device 10 that detects a position designated by the input device 20.

  The detection device 10 includes, for example, a capacitive touch panel of a tablet terminal or a smartphone. The input device 20 includes, for example, a stylus (touch pen or digital pen) used for designating a position by bringing the tip of the capacitive touch panel into contact with the capacitive touch panel.

  The detection device 10 operates as a power transmission unit including the primary coil 11. The input device 20 operates as a power reception unit including a secondary coil 21 and a power storage unit (battery) 22. The primary side coil 11 is also called a power transmission antenna, and the secondary side coil 21 is also called a power receiving antenna.

  That is, the power transmission system 1 includes a power transmission unit 10 and a power reception unit 20. The power transmission system 1 performs power transmission in a non-contact manner from the power transmission unit 10 to the power reception unit 20 via the primary side coil 11 and the secondary side coil 21, and stores power from the secondary side coil 21 to the power storage unit 22. System.

  Although not shown, the detection device 10 includes an input device storage unit that can store the input device 20. When the input device 20 is stored in the input device storage portion of the detection device 10, the primary coil (power transmission antenna) 11 of the detection device 10 and the secondary coil (power reception antenna) 21 of the input device 20 are close to each other and face each other. Is configured to do. Thereby, it is possible to perform power transmission from the detection device 10 to the input device 20 in a non-contact manner via the primary side coil 11 and the secondary side coil 21.

  The illustrated detection device (power transmission unit) 10 includes a power supply 12 that generates a DC power supply voltage, an auxiliary power supply element 13, an oscillation circuit 14, and a matching circuit 15. The matching circuit 15 is a circuit for matching the impedance of the primary side coil (power transmission antenna) 11.

  The illustrated detection device (power transmission unit) 10 further includes a control circuit 30 and a high-frequency blocking choke coil 17.

  Although not shown in FIG. 1, in order to suppress the power consumption of the power source 12 in the detection device (power transmission unit) 10, the detection device (power transmission unit) 10 causes the detection device (power transmission unit) 10 to be intermittent. An intermittent oscillation circuit is provided for driving.

  The auxiliary power supply element 13 is connected to the power supply 12 and includes a capacitive element (for example, an electric double layer capacitor, a Li-ion capacitor, etc.). The auxiliary power supply element 13 eliminates a burden on the power supply 12 against a transient current rise when the battery 22 of the input device (power receiving unit) 20 is rapidly contactlessly charged. This is to suppress the descent.

  The control circuit 30 is connected to the power supply 12 through the auxiliary power supply element 13 and is connected to the oscillation circuit 14 through the choke coil 17. As described later, the control circuit 30 is configured to stop power transmission when detecting that the battery 22 of the input device (power receiving unit) 20 is fully charged.

  The oscillation circuit 14 includes a switch 141 connected between the choke coil 17 and the ground, and a drive circuit 142 for driving the switch 141. The illustrated switch 141 is composed of an N-channel MOSFET. That is, in the N-channel MOSFET 141, the drain is connected to one end of the choke coil 17, and the source is grounded. A pulse signal (drive signal) having a predetermined frequency is supplied from the drive circuit 142 to the gate of the N-channel MOSFET 141. The predetermined frequency is, for example, a frequency of 13.56 MHz. The drain of the N-channel MOSFET 141 is connected to one end of the primary side coil (power transmission antenna) 11 via the matching circuit 15. The other end of the primary side coil (power transmission antenna) 11 is grounded.

Although not shown in FIG. 1, as will be described in detail later, the control circuit 30 includes a detection element that detects a current consumption of the power transmission system to the input device (power receiving unit) 20 as a detection current I, and this detection. a comparator for comparing the current I and the first threshold current I _1, when the detected current I is smaller than the first threshold current I _1, and a stop means for stopping the power transmission.

  Here, the consumption current I is equivalent to the consumption current including the transmitted power to the secondary coil (power receiving antenna) 21 and other losses. When the battery 22 of the input device (power receiving unit) 20 is fully charged, the impedance viewed from the primary side increases and the current consumption I also decreases. The “impedance viewed from the primary side” will be described in detail later.

Therefore, the control circuit 30, by determining the detected current I is smaller than the first threshold current I _1, detects that the battery 22 is fully charged, and stops power transmission. Thereby, the overcharge to the electrical storage part (battery) 22 can be prevented. As a result, useless power consumption of the detection device (power transmission unit) 10 can be suppressed without increasing the size of the input device (power reception unit) 20.

Further, although not shown in FIG. 1, the control circuit 30, when the detected current I exceeds the first threshold current I _1, and a power transmission means for performing power transmission.

On the other hand, the comparator of the control circuit 30 may be configured to compare the detection current I with a second threshold current I ₂ that is smaller than the first threshold current I ₁ . In other words, the comparator may be composed of a hysteresis comparator.

In this case, the transmission means of the control circuit 30, when the detected current I is larger than the second threshold current I _2, performs power transmission. The reason for this configuration is that the detection current I flowing through the detection device (power transmission unit) 10 is reduced by intermittent driving, so the threshold for starting power transmission (in this example, the second threshold current I ₂ ) is set. This is because the power transmission can be started even with a small detection current I.

  The input device (power receiving unit) 20 further includes a matching circuit 23 connected to the secondary coil (power receiving antenna) 21, a rectifier circuit 24, and a constant voltage circuit 25.

  The matching circuit 23 is a circuit for matching the impedance between the secondary coil (power receiving antenna) 21 and the battery 22. The rectifier circuit 24 is composed of, for example, a diode or a diode bridge circuit.

  The battery 22 may be, for example, an electric double layer capacitor, a Li-ion capacitor, a Ni-MH battery, or a Li-ion battery.

  In the matching circuit 15 and the matching circuit 23, the primary coil (power transmission antenna) 11 of the detection device (power transmission unit) 10 and the secondary coil (21) of the input device (power reception unit) 20 are close to each other and face each other. In the state where the power storage unit (battery) 22 is empty, the impedance viewed from the primary side is reduced. As a result, the power storage unit (battery) 22 can be charged.

  On the other hand, even when the primary side coil (power transmission antenna) 11 of the detection device (power transmission unit) 10 and the secondary side coil (21) of the input device (power reception unit) 20 are close to each other and face each other, the power storage unit As the (battery) 22 is charged, the matching circuit 15 and the matching circuit 23 are configured such that the impedance viewed from the primary side increases. As a result, the detection current I flowing through the detection device (power transmission unit) 10 gradually decreases. By monitoring this detection current I, it can be determined whether or not the power storage unit (battery) 22 is fully charged. It becomes possible.

  Next, “impedance viewed from the primary side” will be described in detail. Here, “impedance viewed from the primary side” refers to the impedance Z viewed from the arrow C in FIG. That is, it means the impedance Z when the matching circuit 15, the primary side coil 11, the secondary side coil 21, and the matching circuit 23 side are viewed from the oscillation circuit 14 of the detection device (power transmission unit) 10. Hereinafter, “impedance viewed from the primary side” is simply referred to as impedance Z, and the description will be continued.

  In a state where the input device (power receiving unit) 20 is not stored in the input device storage unit of the detection device (power transmission unit) 10, the impedance Z is relatively large.

  On the other hand, the input device (power receiving unit) 20 is stored in the input device storage unit of the detection device (power transmitting unit) 10 (that is, the primary side coil (power transmitting antenna) 11 and the secondary side coil (power receiving antenna)). The impedance Z is lower than the case where it is not housed.

  In this state (the state where the input device 20 is stored in the input storage unit), the range of the impedance Z when the remaining amount of the power storage unit (battery) 22 of the input device 20 is empty is expressed by the following equation.

0.5Ω <| Z | <50Ω
Re (Z) / | Z |> 0.6
Here, | Z | represents the absolute value of impedance Z, and Re (Z) represents the real part of impedance Z.

More preferably, it is preferably in the following range.
Re (Z) / | Z |> 0.8

  On the other hand, in this state (state where input device 20 is stored in the input storage unit), the range of impedance Z when power storage unit (battery) 22 of input device 20 is fully charged is expressed by the following equation.

50Ω <| Z | <500Ω
Re (Z) / | Z |> 0.6

More preferably, it is preferably in the following range.
Re (Z) / | Z |> 0.8

In addition, the impedance Z is in the following range regardless of the remaining amount of the power storage unit (battery) 22 of the input device 20.
Re (Z) / | Z |> 0.6
More preferably, it exists in the following range.
Re (Z) / | Z |> 0.8

(Second Embodiment)
FIG. 2 is a block diagram showing a configuration of a power transmission system 1A according to the second embodiment of the present invention. The illustrated power transmission system 1A also shows an example applied to a coordinate input system.

  The power transmission system (coordinate input system) 1A is the same as the power transmission system (coordinate input system) 1 shown in FIG. 1 except that the configuration of the input device (power receiving unit) is changed as described later. It has a configuration and operates. Therefore, the reference numeral 20A is attached to the input device (power receiving unit). Components having the same functions as those shown in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity. Hereinafter, only differences from FIG. 1 will be described.

  The input device (power receiving unit) 20A has the same configuration as that of the input device (power receiving unit) 20 shown in FIG. 1 except that an impedance element 26 is further provided between the rectifier circuit 24 and the constant voltage circuit 25. To operate.

  The impedance element 26 is configured such that the primary side coil (power transmission antenna) 11 of the detection device (power transmission unit) 10 and the secondary side coil (power reception antenna) 21 of the input device (power reception unit) 20A face each other close to each other. In addition, due to the impedance reduction in the process of accumulating the charge of the impedance element 26 in the input device (power receiving unit) 20A, the input device (power receiving unit) serves as charge storage means for temporarily reducing the impedance of the secondary coil 21.

  In the illustrated example, the impedance element 26 is constituted by a parallel circuit of a smoothing capacitor 261 and a resistor 262.

By adopting such a configuration, it is possible to increase the detection current I of the first threshold current I ₁ also temporarily more. As a result, the power transmission means of the control circuit 30 performs power transmission. Incidentally, when the detected current I is smaller than the first threshold current I _1, the stop means of the control circuit 30 will stop the power transmission.

  Next, the superior effect of the power transmission system 1A according to the second embodiment shown in FIG. 2 with respect to the power transmission system 1 according to the first embodiment shown in FIG. 1 will be described by comparing the two. To do.

In the power transmission system 1 according to the first embodiment illustrated in FIG. 1, the primary side coil (power transmission antenna) 11 of the detection device (power transmission unit) 10 and the secondary side coil (power reception) of the input device (power reception unit) 20. In the case where the antenna) 21 is opposed and the detection current I is smaller than the first threshold current I ₁ (I <I ₁ ), the power storage unit 22 may be charged by about 50%. . In this case, the power storage unit 22 may not be charged when the detection current I does not exceed the first threshold current I ₁ (I <I ₁ ).

Even in such a case, in the power transmission system 1A according to the second embodiment shown in FIG. 2, the impedance element (charge storage unit) 26 temporarily converts the detection current I to the first threshold current I. It can be raised above ₁ (I> I ₁ ). In other words, by providing the smoothing capacitor 261 of the impedance element 26, the impedance Z seen from the primary side at the start of charging can be made low even when the storage unit (battery) 22 is in a state of progressing charging. it can. As a result, the power storage unit 22 can be charged.

Note that the comparator of the control circuit 30 may be configured to compare the detection current I with a third threshold current I ₃ that is greater than the first threshold current I ₁ . In other words, the comparator may be composed of a hysteresis comparator.

In this case, the transmission means of the control circuit 30, when the detected current I is larger than the third threshold current I _3, performs power transmission. The reason for this configuration is that the primary side coil (power transmission antenna) 11 of the detection device (power transmission unit) 10 and the secondary side coil (power reception antenna) 21 of the input device (power reception unit) 20 do not face each other. may detect current I exceeds the first threshold current I _1, in which case, because the power of the power supply 12 of the detection device (power transmission unit) 10 is consumed. That is, in such a case, by setting the threshold value to start charging the first threshold current I ₁ is greater than the third threshold current I _3, the detected current I does not exceed the third threshold current I ₃ In this way, useless power consumption can be suppressed.

  Note that the power transmission system 1A also has the same effects as the power transmission system 1 described above, and thus description thereof is omitted.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram showing a configuration of a detection device (power transmission unit) 10 used in the power transmission system 1A (FIG. 2) according to the first embodiment of the present invention. FIG. 4 is a time chart for explaining the operation of the detection device (power transmission unit) 10.

  As described above, the detection device (power transmission unit) 10 includes the primary side coil (power transmission antenna) 11, the power source 12, the auxiliary power source element 13, the oscillation circuit 14, the matching circuit 15, the choke coil 17, And a control circuit 30.

The illustrated detection device (power transmission unit) 10 further includes an intermittent oscillation circuit 18. As described above, the intermittent oscillation circuit 18 is a circuit for driving the power supply 12 intermittently. Intermittent oscillation circuit 18, as shown in FIG. 4 (A), for example, at a repetition frequency of 1 Hz, oscillates a pulse signal having a pulse width T _W of about 1m sec.

  The illustrated control circuit 30 includes a resistor 31, a comparator 32, an OR circuit 33, and a switch (SW) 34.

  As shown in FIG. 4B, the resistor 31 functions as a detection element that detects the current consumption of the power transmission system to the input device (power transmission unit) 20A as a detection current I.

To the comparator 32 shown, the first threshold current I ₁ is set. That is, the comparator 32 compares the threshold current I ₁ of the detected current I and the first. As shown in FIG. 4 (C), when the detected current I is smaller than a first threshold current I _1, the comparator 32 outputs a low level signal L. When the detected current I is first greater than the threshold current I _1, the comparator 32 outputs a signal of high level H.

  The OR circuit 33 calculates the logical sum of the output signal of the intermittent oscillation circuit 18 and the output signal of the comparator 32 and outputs an OR result signal.

  The switch (SW) 34 is provided between the power supply 12 (auxiliary power supply element 13) and the oscillation circuit 14. As shown in FIG. 4D, the switch (SW) 34 is turned on when the OR result signal is at the high level H, and turned off when the OR result signal is at the low level L. The switch (SW) 34 is composed of, for example, an N-channel MOSFET.

  While the switch (SW) 34 is on, the DC voltage of the power supply 12 is supplied to the drive circuit 142 of the oscillation circuit 14 via the auxiliary power supply element 13. The drive circuit 142 supplies a pulse signal (drive signal) having a predetermined frequency (for example, 13.56 MHz) to the switch (N-channel MOSFET) 141 while the DC voltage is supplied. Therefore, the switch 141 is repeatedly turned on and off in accordance with the pulse signal (drive signal) from the drive circuit 142. As a result, while the switch (SW) 34 is on, power (magnetic field) is sent from the primary coil (power transmission antenna) 11 as shown in FIG.

  Next, the operation of the detection apparatus (power transmission unit) 10 shown in FIG. 3 will be described with reference to FIG.

At time t ₁ , when the power storage unit (battery) 22 of the input device (power reception unit) 20 A (FIG. 2) is empty, the input device (power reception unit) 20 A (FIG. 2) is connected to the detection device (power transmission unit) 10. It is assumed that it is stored in the input device storage unit. Thereby, the primary side coil (power transmission antenna) 11 of the detection device 10 and the secondary side coil (power reception antenna) 21 of the input device (power reception unit) 20A are close to each other and face each other. As a result, power can be transmitted from the detection device 10 to the input device 20 in a non-contact manner via the primary side coil 11 and the secondary side coil 21. In other words, the impedance Z seen from the primary side is in a low state by the matching circuit 15 of the detection device 10 and the matching circuit 23 of the input device 20A (FIG. 2).

In this state, when the intermittent oscillation circuit 18 outputs a pulse, a high level H signal is output from the OR circuit 33, so that the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 operates, so that the current I from the power source 12 and the auxiliary power source element 13 to the primary side coil (power transmission antenna) 11 via the resistor (detection element) 31, the choke coil 17, and the matching circuit 15. Flows. As described above, since the low impedance Z as viewed from the primary side, at time t _2, the detected current I exceeds the first threshold current I _1.

  As a result, as shown in FIG. 4B, the comparator 32 outputs a high level H signal. Since the OR circuit 33 outputs a high level H signal, the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 is in an operating state. Therefore, as shown in FIG. 4E, power (magnetic field) from the primary side coil (power transmission antenna) 11 is supplied to the secondary of the input device (power reception unit) 20A. It is transmitted to the input device (power receiving unit) 20 </ b> A via the side coil 21.

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30 cooperates with the oscillation circuit 14, when the detected current I exceeds the first threshold current I _1, the power transmission It works as power transmission means (33, 34) for Further, the intermittent oscillation circuit 18 functions as an intermittent drive means for intermittently driving the power transmission means (33, 34).

  Since power is transmitted in this manner, in the input device (power receiving unit) 20A (FIG. 2), the secondary coil 21 is passed through the matching circuit 23, the rectifier circuit 24, the impedance element 26, and the constant voltage circuit 25. Thus, electric power is stored in the power storage unit (battery) 22.

  If electric power continues to be stored in the power storage unit (battery) 22, the impedance Z as viewed from the primary side gradually increases, so that the value of the detection current I gradually decreases as shown in FIG. 4B. .

When the power storage unit at time t ₃ (battery) 22 is fully charged, the detected current I is smaller than the first threshold current I _1. As a result, as shown in FIG. 4C, the output of the comparator 32 becomes a low level L, and the output signal of the OR circuit 33 also becomes a low level L. As a result, the switch (SW) 34 is turned off, and the voltage supply to the oscillation circuit 14 is stopped. As a result, the oscillation circuit 14 stops oscillating, and as shown in FIG. 4E, the primary side coil (power transmission antenna) 11 stops power transmission (no magnetic field is generated).

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30 cooperates with the oscillation circuit 14, when the detected current I is smaller than the first threshold current I _1, the power Acts as a stopping means to stop transmission.

As described above, in the first embodiment, when the detected current I is smaller than the first threshold current I _1, the detection device (power transmission unit) 10 stops power transmission, the input device (power reception Part) 20 </ b> A can be prevented from being overcharged to the power storage part (battery) 22. As a result, useless power consumption in the detection device (power transmission unit) 10 can be suppressed.

  A second embodiment of the present invention will be described with reference to FIGS. FIG. 5 is a block diagram showing a configuration of a detection device (power transmission unit) 10A used in the power transmission system 1 (FIG. 1) according to the second embodiment of the present invention. FIG. 6 is a time chart for explaining the operation of the detection apparatus (power transmission unit) 10A.

  The illustrated detection apparatus (power transmission unit) 10A has the same configuration as that of the detection apparatus (power transmission unit) 10 illustrated in FIG. 3 and operates except that the control circuit is changed as described later. Therefore, the reference numeral 30A is attached to the control circuit. Components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and only differences will be described below for the sake of simplicity.

  The control circuit 30A has the same configuration as the control circuit 30 shown in FIG. 3 except that the operation of the comparator is different as will be described later. Therefore, the reference numeral 32A is attached to the comparator.

The comparator 32A shown not only the first threshold current I _1, it is also set a second threshold current I _2. The second threshold current _{I 2} is smaller than the first threshold current _{I 1.} Therefore, the comparator 32A is composed of a hysteresis comparator. That is, the comparator 32A, the detection current I and not only compares the first and the threshold current I _1, and compares the threshold current I ₂ of the detected current I and the second.

As shown in FIG. 6 (C), when the detected current I is smaller than a first threshold current I _1, the comparator 32A outputs a signal of low level L. On the other hand, when the detected current I is greater than the second threshold current I _2, the comparator 32A outputs a signal of high level H.

  Next, the operation of the detection apparatus (power transmission unit) 10A shown in FIG. 5 will be described with reference to FIG.

At time _{t 4,} the power storage unit of the input device (power receiving unit) 20 (FIG. 1) (the battery) 22 in an empty state, the input device (power receiving unit) 20 (FIG. 1), the detection device (power transmission unit) 10A of the It is assumed that it is stored in the input device storage unit. Thereby, the primary side coil (power transmission antenna) 11 of the detection device 10A and the secondary side coil (power reception antenna) 21 of the input device (power reception unit) 20 are close to each other and face each other. As a result, power can be transmitted from the detection device 10A to the input device 20 in a non-contact manner via the primary side coil 11 and the secondary side coil 21. In other words, the impedance Z seen from the primary side is in a low state by the matching circuit 23 (FIG. 1) of the input device 20.

In this state, when the intermittent oscillation circuit 18 outputs a pulse, a high level H signal is output from the OR circuit 33, so that the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 operates, so that the current I from the power source 12 and the auxiliary power source element 13 to the primary side coil (power transmission antenna) 11 via the resistor (detection element) 31, the choke coil 17, and the matching circuit 15 Flows. As described above, since the impedance Z seen from the primary side is low, the detection current I becomes larger than the second threshold current I ₂ at time t ₅ .

  As a result, as shown in FIG. 6B, the comparator 32A outputs a high level H signal. As a result, the OR circuit 33 outputs a high level H signal, so that the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 is in an operating state. Therefore, as shown in FIG. 6E, power (magnetic field) is supplied from the primary coil (power transmission antenna) 11 to the secondary of the input device (power reception unit) 20. The signal is transmitted to the input device (power receiving unit) 20 via the side coil 21.

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30A, in cooperation with the oscillating circuit 14, when the detected current I is larger than the second threshold current _{I 2,} the power Acts as power transmission means (33, 34) for transmission. Further, the intermittent oscillation circuit 18 functions as an intermittent drive means for intermittently driving the power transmission means (33, 34).

  Since power transmission is performed in this way, in the input device (power receiving unit) 20 (FIG. 1), the power storage unit is connected from the secondary coil 21 via the matching circuit 23, the rectifier circuit 24, and the constant voltage circuit 25. Electric power is stored in (battery) 22.

  If electric power continues to be stored in the power storage unit (battery) 22, the impedance Z as viewed from the primary side gradually increases, so that the value of the detection current I gradually decreases as shown in FIG. 6B. .

When the power storage unit at time t ₆ (battery) 22 is fully charged, the detected current I is smaller than the first threshold current I _1. 6C, the output of the comparator 32A becomes a low level L, and the output signal of the OR circuit 33 also becomes a low level L. As a result, the switch (SW) 34 is turned off, and the voltage supply to the oscillation circuit 14 is stopped. As a result, the oscillation circuit 14 stops oscillating, and as shown in FIG. 6E, the primary side coil (power transmission antenna) 11 stops power transmission (no magnetic field is generated).

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30A, in cooperation with the oscillating circuit 14, when the detected current I is smaller than the first threshold current _{I 1,} the power It serves as a stopping means (33, 34) for stopping transmission.

As described above, in this second embodiment, when the detected current I is smaller than the first threshold current I _1, the detection device (power transmission unit) 10A stops power transmission, the input device (power reception Part) 20 can be prevented from being overcharged to the power storage part (battery) 22. As a result, useless power consumption in the detection apparatus (power transmission unit) 10A can be suppressed.

Further, when the detection current I becomes larger than the second threshold current I _{2 that} is smaller than the _first threshold current I ₁ , the detection device (power transmission unit) 10A starts power transmission, so that the detection current I is intermittently driven. (Specifically, for example, if the pulse width T _W of the intermittent oscillator 18 is narrow) when it is small even can be performed reliably power transmission.

  A third embodiment of the present invention will be described with reference to FIGS. FIG. 7 is a block diagram showing a configuration of a detection device (power transmission unit) 10B used in the power transmission system 1A (FIG. 2) according to the third embodiment of the present invention. FIG. 8 is a time chart for explaining the operation of the detection device (power transmission unit) 10B.

  The illustrated detection device (power transmission unit) 10B has the same configuration as the detection device (power transmission unit) 10 illustrated in FIG. 3 and operates except that the control circuit is changed as described later. Therefore, the reference numeral 30B is attached to the control circuit. Components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and only differences will be described below for the sake of simplicity.

  The control circuit 30B has the same configuration as the control circuit 30 shown in FIG. 3 except that the operation of the comparator is different as will be described later. Therefore, the reference numeral 32B is attached to the comparator.

In the illustrated comparator 32B, not only the first threshold current I ₁ but also the third threshold current I ₃ is set. The third threshold current _{I 3} of greater than the first threshold current _{I 1.} Therefore, the comparator 32B is composed of a hysteresis comparator. That is, the comparator 32B is detected current I and not only compares the first and the threshold current I _1, and compares the threshold current I ₃ of the detected current I and the third.

As shown in FIG. 8 (C), when the detected current I is smaller than a first threshold current I _1, the comparator 32B outputs a signal of low level L. On the other hand, when the detected current I is larger than the third threshold current I _3, comparator 32B outputs a signal of high level H.

  Next, the operation of the detection apparatus (power transmission unit) 10B shown in FIG. 7 will be described with reference to FIG.

At time _{t 7,} the power storage unit (battery) 22 of the input device (power receiving unit) 20A (FIG. 2) is in the empty state, the input device (power receiving unit) 20A (FIG. 2) is, the detection device (power transmission unit) 10B of It is assumed that it is stored in the input device storage unit. Thereby, the primary side coil (power transmission antenna) 11 of the detection device 10B and the secondary side coil (power reception antenna) 21 of the input device (power reception unit) 20A are close to each other and face each other. Thereby, it will be in the state in which electric power transmission can be performed non-contactedly via the primary side coil 11 and the secondary side coil 21 from the detection apparatus 10B to the input device 20A. In other words, the impedance Z seen from the primary side is in a low state by the matching circuit 23 (FIG. 2) of the input device 20A.

In this state, when the intermittent oscillation circuit 18 outputs a pulse, a high level H signal is output from the OR circuit 33, so that the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 operates, so that the current I from the power source 12 and the auxiliary power source element 13 to the primary side coil (power transmission antenna) 11 via the resistor (detection element) 31, the choke coil 17, and the matching circuit 15. Flows. As described above, since the low impedance Z as viewed from the primary side, at time t _8, the detected current I is larger than the third threshold current I _3.

  As a result, as shown in FIG. 8B, the comparator 32B outputs a high level H signal. Since the OR circuit 33 outputs a high level H signal, the switch (SW) 34 is turned on. As a result, the oscillation circuit 14 is in an operating state, and as shown in FIG. 8E, power (magnetic field) from the primary side coil (power transmission antenna) 11 is supplied to the secondary of the input device (power reception unit) 20A. It is transmitted to the input device (power receiving unit) 20 </ b> A via the side coil 21.

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30B cooperates with the oscillation circuit 14, when the detected current I is larger than the third threshold current _{I 3,} power Acts as power transmission means (33, 34) for transmission. Further, the intermittent oscillation circuit 18 functions as an intermittent drive means for intermittently driving the power transmission means (33, 34).

  Since power transmission is performed in this way, in the input device (power receiving unit) 20A (FIG. 2), the secondary side coil 21 passes through the matching circuit 23, the rectifier circuit 24, the impedance element 26, and the constant voltage circuit 25. Thus, electric power is stored in the power storage unit (battery) 22.

  As electric power continues to be stored in the power storage unit (battery) 22, the impedance Z viewed from the primary side viewed from the primary side (detection device 10B) gradually increases, so as shown in FIG. 8B. The value of the detection current I gradually decreases.

When the power storage unit at time t ₉ (battery) 22 is fully charged, the detected current I is smaller than the first threshold current I _1. Accordingly, as shown in FIG. 8C, the output of the comparator 32B becomes the low level L, and the output signal of the OR circuit 33 also becomes the low level L. As a result, the switch (SW) 34 is turned off, and the voltage supply to the oscillation circuit 14 is stopped. As a result, the oscillation circuit 14 stops oscillating, and as shown in FIG. 8E, the primary side coil (power transmission antenna) 11 stops power transmission (no magnetic field is generated).

Thus, the combination of an OR circuit 33 and a switch (SW) 34 of the control circuit 30B cooperates with the oscillation circuit 14, when the detected current I is smaller than the first threshold current _{I 1,} the power It serves as a stopping means (33, 34) for stopping transmission.

As described above, in this third embodiment, when the detected current I is smaller than the first threshold current I _1, the detection device (power transmission unit) 10B stops power transmission, the input device (power reception Part) 20 </ b> A can be prevented from being overcharged to the power storage part (battery) 22. As a result, useless power consumption in the detection device (power transmission unit) 10B can be suppressed.

Further, when the detected current I is larger than a first threshold current I ₁ is greater than the third threshold current I _3, the detection device (power transmission unit) 10B has to start power transmission, the primary coil when 11 and the secondary coil 21 does not face the detected current I can be not exceed the third threshold current I _3. This makes it possible to charge the power storage unit (battery) 22 of the input device (power reception unit) 20A without malfunction.

[Modification]
A modification of the present invention will be described with reference to FIG.

  FIG. 9 is a block diagram showing a configuration of a detection device (power transmission unit) 10C used in the power transmission system according to the modification of the present invention.

  The illustrated detection device (power transmission unit) 10C has the same configuration as the detection device (power transmission unit) 10 illustrated in FIG. 3 except that the arrangement position of the switch (SW) is changed as described later. It works. Therefore, the reference numeral 30C is attached to the control circuit. Components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and only differences will be described below for the sake of simplicity.

  In the detection device (power transmission unit) 10 illustrated in FIG. 3, the switch (SW) 34 of the control circuit 30 is provided between the power supply 12 (auxiliary power supply element 13) and the oscillation circuit 14.

  In contrast, in the detection apparatus (power transmission unit) 10C illustrated in FIG. 9, the switch (SW) of the control circuit 30C is provided at the position A or B in FIG. That is, at the position A, the switch (SW) 34 </ b> A is inserted between the resistor (detecting element) 31 and the choke coil 17. On the other hand, at the position B, the switch (SW) 34B is inserted between the power supply 12 (auxiliary power supply element 13) and the resistor (detection element) 31.

  Thus, even when the switch (SW) 34A or 34B is arranged, the detection device (power transmission unit) 10C operates in the same manner as the detection device (power transmission unit) 10 illustrated in FIG. Therefore, the detailed operation description is omitted.

  Further, the detection device (power transmission unit) 10C has the same effect as the detection device (power transmission unit) 10 illustrated in FIG.

  The present invention has been described above with reference to the embodiments (and examples), but the present invention is not limited to the above embodiments (and examples). Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention.

  The present invention can be used for a tablet terminal, a portable terminal, and other devices equipped with a secondary battery. The present invention can also be used for digital pens other than the electrostatic coupling method (for example, an ultrasonic wave + infrared method).

1, 1A Power transmission system (coordinate input system)
10, 10A, 10B Power transmission unit (detection device)
11 Primary coil (power transmission antenna)
12 Power supply 13 Auxiliary power supply element 14 Oscillation circuit 141 Switch (N-channel MOSFET)
142 Drive Circuit 15 Matching Circuit 17 Choke Coil 18 Intermittent Oscillation Circuit 20, 20A Power Receiving Unit (Input Device)
21 Secondary coil (power receiving antenna)
22 Power storage unit (battery)
23 Matching Circuit 24 Rectifier Circuit 25 Constant Voltage Circuit 26 Impedance Element 261 Smoothing Capacitor 262 Resistor 30, 30A, 30B, 30C Control Circuit 31 Resistor (Current Detection Element)
32 Comparator 32A Comparator (Hysteresis Comparator)
32B comparator (hysteresis comparator)
33 OR circuit 34, 34A, 34B Switch (SW)

Claims (14)

A power transmission method in a power transmission system including a power transmission unit including a primary coil and a power reception unit including a secondary coil and a power storage unit, wherein the primary coil is transferred from the power transmission unit to the power reception unit. And in the power transmission method of performing power contactlessly through the secondary side coil and storing power from the secondary side coil to the power storage unit,
In the power transmission unit, the current consumption of the power transmission system to the power receiving unit is detected as a detection current,
When the detected current becomes smaller than a first threshold current, the power transmission unit stops the power transmission;
A power transmission method characterized by the above.   The power transmission method according to claim 1, wherein the power transmission unit performs the power transmission when the detected current exceeds the first threshold current.   The power transmission method according to claim 1, wherein the power transmission unit performs the power transmission when the detected current exceeds a second threshold current smaller than the first threshold current.   When the primary side coil and the secondary side coil face each other, the impedance of the secondary side coil is temporarily reduced, and when the detected current becomes larger than the first threshold current, the power transmission unit The power transmission method according to claim 1, wherein power transmission is performed.   When the primary side coil and the secondary side coil face each other, the impedance of the secondary side coil is temporarily reduced, so that the detected current is larger than the third threshold current larger than the first threshold current. The power transmission method according to claim 1, wherein the power transmission unit performs power transmission when it becomes larger.   The power transmission method according to claim 2, wherein when the power transmission unit performs the power transmission, the power is supplemented for a transient current increase.   The power transmission method according to claim 2, wherein the power transmission unit intermittently performs the power transmission. A power transmission system including a power transmission unit including a primary coil and a power reception unit including a secondary coil and a power storage unit, wherein the primary coil and the secondary are transmitted from the power transmission unit to the power reception unit. In a power transmission system that performs non-contact power transmission through a side coil and stores power from the secondary coil to the power storage unit, the power transmission unit includes:
A detection element for detecting a current consumption of a power transmission system to the power receiving unit as a detection current;
A comparator for comparing the detected current with a first threshold current;
Stop means for stopping the power transmission when the detected current becomes smaller than a first threshold current;
A power transmission system comprising:   The power transmission system according to claim 8, wherein the power transmission unit includes a power transmission unit configured to perform the power transmission when the detected current exceeds the first threshold current. The comparator compares the detected current with a second threshold current smaller than the first threshold current;
The power transmission system according to claim 8, wherein the power transmission unit includes a power transmission unit configured to perform the power transmission when the detected current becomes larger than the second threshold current. The power receiving unit includes a charge storage unit that temporarily reduces the impedance of the secondary coil when the primary coil and the secondary coil face each other.
The power transmission system according to claim 8, wherein the power transmission unit includes a power transmission unit configured to perform the power transmission when the detected current becomes larger than the first threshold current. The comparator compares the detected current with a third threshold current greater than the first threshold current;
The power receiving unit includes a charge storage unit that temporarily reduces the impedance of the secondary coil when the primary coil and the secondary coil face each other.
The power transmission system according to claim 8, wherein the power transmission unit includes a power transmission unit configured to perform the power transmission when the detected current becomes larger than the third threshold current.   The said power transmission part is further equipped with the auxiliary power supply element which supplements electric power with respect to a transient electric current rise, when the said power transmission means performs the said electric power transmission, It is any one of Claims 9-12 Power transmission system.   The power transmission system according to any one of claims 9 to 13, wherein the power transmission unit further includes an intermittent drive unit that intermittently drives the power transmission unit.

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