Electronic circuits, modules and systems

Abstract

This invention provides an electronic circuit with good convenience for switching using power obtained through weak radio waves. The electronic circuit includes: a switch connected between a power source that outputs DC power and a load driven by the DC power supplied from the power source, switching the connection state of the power source and the load from a non-conducting state to a conducting state; a power conversion circuit having a power input terminal for power received from radio waves received by an antenna capable of receiving radio waves, and a DC power output terminal for outputting DC power, converting the power input to the power input terminal into DC power and outputting it from the DC power output terminal; and a control circuit having an input terminal connected to the DC power output terminal of the power conversion circuit, and an output terminal connected to the switch and controlling the connection state of the switch, controlling the connection state of the switch to a conducting state when the power conversion circuit outputs DC power after receiving radio waves through the antenna.

Description

Technical Field

[0001] This invention relates to an electronic circuit, module, and system. Background Technology

[0002] Conventionally, in electronic keys used in vehicle key systems, the electronic key uses power obtained from radio waves from the vehicle to connect a battery built into the electronic key and a control circuit, thereby enabling communication with the vehicle. A known technique involves disconnecting the battery and circuit again when the electronic key leaves the vehicle (i.e., in standby mode), thereby suppressing battery consumption in standby mode (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent document 1: Japanese Patent Application Publication No. 2011-24332. Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] In the aforementioned conventional technology, power obtained from radio waves from the vehicle is used to activate the analog front-end circuit (AFE) inside the electronic key. In this case, power obtained from radio waves from a specific device in the vehicle or similar equipment is used to activate the AFE.

[0008] However, when using radio waves from the vehicle to start the AFE, the electronic key has a problem: it takes time to accumulate the power required to start the AFE. That is, during the time until the electronic key is started, it must be brought close to a position where it can receive radio waves from the vehicle, which is very inconvenient.

[0009] The present invention was created in view of this situation, and its object is to provide an electronic circuit with good convenience for switching using power obtained through weak radio waves.

[0010] Solution for solving the problem

[0011] An electronic circuit according to one aspect of the present invention comprises: a switch connected between a power source that outputs DC power and a load driven by DC power supplied from the power source, switching the connection state of the power source and the load from a non-conducting state that cuts off the power supply from the power source to the load to a conducting state that supplies power from the power source to the load; a power conversion circuit having a power input terminal for receiving power obtained from radio waves received by an antenna capable of receiving radio waves, a DC power output terminal for outputting DC power, converting the power input to the power input terminal into DC power and outputting it from the DC power output terminal; and a control circuit having an input terminal connected to the DC power output terminal of the power conversion circuit, an output terminal connected to the switch and controlling the connection state of the switch, controlling the connection state of the switch to a conducting state when the power conversion circuit outputs DC power after receiving the radio waves through the antenna.

[0012] Furthermore, in one embodiment of the electronic circuit of the present invention, the control circuit further includes a power terminal for receiving a power supply, wherein when the switch is switched to the on state, the control circuit uses the power supplied from the power source to the power terminal to keep the switch in the on state.

[0013] Furthermore, in one embodiment of the electronic circuit of the present invention, the control circuit includes a trigger circuit for switching control signals output from the output terminal.

[0014] Furthermore, in one embodiment of the electronic circuit of the present invention, the control circuit includes a power sensor having a reference input terminal, a detection input terminal, and a voltage detection output terminal that outputs a potential corresponding to the potential of the detection input terminal and the potential of the reference input terminal, wherein the detection input terminal is connected to the voltage detection output terminal.

[0015] Furthermore, one embodiment of the electronic circuit of the present invention also includes a resistor with a resistance value of 10 megohms or more, and the detection input terminal is connected to the voltage detection output terminal via the resistor.

[0016] Furthermore, one embodiment of the electronic circuit of the present invention further comprises: a first diode, the anode of which is connected to the DC power output terminal of the power conversion circuit and the cathode of which is connected to the power supply terminal of the control circuit; and a second diode, the anode of which is connected to the connection point of the load and the switch and the cathode of which is connected to the power supply terminal of the control circuit.

[0017] Furthermore, in one embodiment of the electronic circuit of the present invention, the power supply has a positive terminal and a negative terminal, and the power conversion circuit has a reverse current reduction unit for suppressing the current flowing from the positive terminal of the power supply through the control circuit and the power conversion circuit to the negative terminal of the power supply.

[0018] Furthermore, in one embodiment of the electronic circuit of the present invention, the reverse current reduction unit supplies the DC power converted from the power input terminal to the DC power output terminal, thereby suppressing the current flowing from the DC power output terminal to the power conversion circuit.

[0019] Furthermore, in one embodiment of the electronic circuit of the present invention, the reverse current reduction unit includes a third diode in which the DC power input to the power input terminal is converted and flows in the forward direction, thereby supplying the DC power output terminal.

[0020] Furthermore, in one embodiment of the electronic circuit of the present invention, the reverse current reduction unit includes a transistor that: when the control circuit controls the connection state of the switch to the on state, suppresses the current flowing from the DC power output terminal to the power conversion circuit; and when the control circuit controls the connection state of the switch to the off state, supplies the DC power converted from the power input terminal to the DC power output terminal.

[0021] Furthermore, in one embodiment of the electronic circuit of the present invention, the transistor is an n-channel MOSFET.

[0022] Furthermore, in one embodiment of the electronic circuit of the present invention, the power conversion circuit includes at least: a first capacitor having a first electrode and a second electrode connected to the power input terminal; a fourth diode having its anode connected to a ground point and its cathode connected to the second electrode of the first capacitor; a second capacitor having a first electrode connected to the DC power output terminal and a second electrode connected to the ground point; and a fifth diode having its anode connected to the input terminal via the capacitor and its cathode connected to the first electrode of the second capacitor, wherein the reverse current reduction unit suppresses current flowing from the DC power output terminal to the ground point via the fourth diode and the fifth diode.

[0023] Furthermore, in one embodiment of the electronic circuit of the present invention, the reverse current reduction unit includes the fifth diode.

[0024] Furthermore, in one embodiment of the electronic circuit of the present invention, the reverse current reduction unit includes the fourth diode.

[0025] Furthermore, one embodiment of the present invention includes the aforementioned electronic circuitry, a power supply that outputs DC power, and a load driven by DC power supplied from the power supply.

[0026] Furthermore, in one aspect of the invention, the module is housed within a waterproof housing.

[0027] Furthermore, one aspect of the system of the present invention includes the aforementioned module and a transmitter that sends a specified radio wave to the module.

[0028] Invention Effects

[0029] According to the present invention, an electronic circuit with good convenience can be provided that can switch using power obtained through weak radio waves. Attached Figure Description

[0030] Figure 1 This is a diagram illustrating an example of the structure of the latching system according to an embodiment.

[0031] Figure 2 This is a diagram illustrating an example of the structure of the latch module according to the first embodiment.

[0032] Figure 3 This is a diagram showing a first variation of the structure of the latch module according to the first embodiment.

[0033] Figure 4 This is a diagram illustrating an example of the structure of the control circuit in the first embodiment.

[0034] Figure 5 This is a diagram showing a second variation of the structure of the latch module of the first embodiment.

[0035] Figure 6 This is a diagram illustrating an example of a frame with a waterproof structure according to the first embodiment.

[0036] Figure 7 This is a diagram illustrating an example of a power conversion circuit according to the second embodiment.

[0037] Figure 8 This is a diagram showing a first variation of the power conversion circuit of the second embodiment.

[0038] Figure 9 This is a diagram illustrating a second variation of the power conversion circuit according to the second embodiment.

[0039] Figure 10 This is a diagram illustrating an example of the first antenna and the second antenna in the third embodiment.

[0040] Figure 11 This is a diagram illustrating an example of the first antenna and the second antenna in the third embodiment.

[0041] Figure 12 This is a diagram illustrating an example of the structure of the latch module according to the third embodiment.

[0042] Figure 13 This is a diagram showing a first variation of the structure of the latch module according to the third embodiment.

[0043] Figure 14 This is a diagram showing a second variation of the structure of the latch module according to the third embodiment.

[0044] Figure 15 This is a diagram showing a third variation of the structure of the latch module according to the third embodiment.

[0045] Figure 16 This is a diagram showing a fourth variation of the structure of the latch module according to the third embodiment.

[0046] Figure 17 This is a diagram showing a fifth variation of the structure of the latch module according to the third embodiment.

[0047] Figure 18 This is a diagram illustrating an example of a frame with a waterproof structure according to the third embodiment.

[0048] Figure 19 This is a diagram illustrating an example of the structure of the latching system according to the fourth embodiment.

[0049] Figure 20 This is a diagram showing the situation where the first antenna receives radio waves in an example of the structure of the latching system in the fourth embodiment.

[0050] Figure 21 This is a diagram showing an example of the structure of the latching system in the fourth embodiment, in which the second antenna receives radio waves.

[0051] Figure 22 This is a diagram illustrating an example of the structure of the power sensor according to the fourth embodiment.

[0052] Figure 23 This is a diagram illustrating an example of the structure of a power sensor with gain switching according to the fourth embodiment.

[0053] Figure 24 This is a diagram illustrating an example of the circuit structure of a power sensor with gain switching according to the fourth embodiment.

[0054] Figure 25 This is a diagram illustrating an example of a frame with a waterproof structure according to the fourth embodiment.

[0055] Figure 26 This is a diagram used to illustrate the problem solved in the fifth embodiment.

[0056] Figure 27 This is a diagram illustrating an example of the structure of the latch module according to the fifth embodiment.

[0057] Figure 28 This is a diagram showing a modified example of the power conversion circuit according to the fifth embodiment.

[0058] Figure 29 This is a diagram showing a second variation of the power conversion circuit according to the fifth embodiment.

[0059] Figure 30 This is a diagram showing a third variation of the power conversion circuit according to the fifth embodiment.

[0060] Figure 31 This is a diagram showing a fourth variation of the power conversion circuit according to the fifth embodiment.

[0061] Figure 32 This is a diagram showing a fifth variation of the power conversion circuit according to the fifth embodiment.

[0062] Figure 33 This is a diagram showing a sixth variation of the power conversion circuit according to the fifth embodiment. Detailed Implementation

[0063] [Structure of latching system 100]

[0064] The structure of the latching system 100 will now be described with reference to the accompanying drawings.

[0065] Figure 1 This is a diagram illustrating an example of the structure of the latching system 100 according to an embodiment. As shown in the figure, the latching system 100 includes a transmitter 70 and a latching module 1.

[0066] Transmitter 70 is a terminal capable of transmitting radio waves. Here, for example, the radio waves are those transmitted by the transmitting device when conducting wireless communication according to communication standards such as Bluetooth (registered trademark) or Wi-Fi (registered trademark). The radio waves are not limited to communication standards such as Bluetooth (registered trademark) or Wi-Fi (registered trademark), and can employ various communication methods, including communication using proprietary standards that do not conform to established communication standards.

[0067] For example, transmitter 70 can be a multi-functional mobile phone terminal (smartphone), mobile phone terminal, PDA (Personal Digital Assistant), laptop PC, tablet PC, or other portable information processing terminal capable of wireless communication. Transmitter 70 is not limited to portable information processing terminals; it can also be other information processing terminals.

[0068] In this example, transmitter 70 transmits radio wave 71.

[0069] The latch module 1 includes a power supply 50, a load 60, and a latch circuit 10. The latch module 1 receives radio waves 71 transmitted from the transmitter 70.

[0070] Power supply 50 is a power source that outputs DC power. For example, power supply 50 is a battery such as a lithium battery. In the case that latch module 1 is a small device, power supply 50 may also be a battery mounted on the substrate. Power supply 50 supplies power to load 60.

[0071] The payload 60 has functions such as communication. For example, the payload 60 may also have ROM (Read Only Memory) (not shown), RAM (Random Access Memory) (not shown), and CPU (Central Processing Unit) (not shown).

[0072] A latching circuit 10 is connected between a power source 50 and a load 60. The power source 50 supplies power to the load 60 via the latching circuit 10.

[0073] Latch circuit 10 receives radio wave 71 transmitted from transmitter 70. By receiving radio wave 71 transmitted from transmitter 70, latch circuit 10 controls the conduction state between power supply 50 and load 60. Hereinafter, latch circuit 10 will also be described as an electronic circuit.

[0074] [First Implementation Method]

[0075] The first embodiment of the present invention will now be described with reference to the accompanying drawings.

[0076] Figure 2 This is a diagram illustrating an example of the structure of the latch module 1 according to the first embodiment. In this diagram, the latch module 1 includes a latch circuit 10, a power supply 50, and a load 60.

[0077] The latching circuit 10 includes an antenna 140, a power conversion circuit 110, a control circuit 120, and a switch 130.

[0078] Antenna 140 is connected to power conversion circuit 110. Antenna 140 receives radio waves 71 transmitted from transmitter 70.

[0079] The power conversion circuit 110 has a power input terminal 111 as an input terminal and a DC power output terminal 112 as an output terminal. Radio waves received by the antenna 140 are input to the power input terminal 111. The power obtained from the radio waves received by the antenna 140 is converted into DC power and output. The DC power output terminal 112 outputs the DC power converted by the power conversion circuit 110. In other words, the power conversion circuit 110 has a power input terminal 111 for receiving power obtained from radio waves received by the antenna 140, and a DC power output terminal 112 for outputting DC power. Furthermore, the power conversion circuit 110 converts the power input to the power input terminal 111 into DC power and outputs it from the DC power output terminal 112.

[0080] In addition, the power conversion circuit 110 may include an RF-DC conversion circuit 113 and a boost circuit 114.

[0081] The RF-DC conversion circuit 113 converts the power obtained through the electromagnetic waves input to the power input terminal 111 into DC power. The RF-DC conversion circuit 113 outputs the converted DC power to the boost circuit 114.

[0082] The boost circuit 114 boosts the voltage of the DC power converted by the RF-DC conversion circuit 113. The boost circuit 114 outputs the boosted power through the DC power output terminal 112.

[0083] The control circuit 120 includes an input terminal 121 connected to the DC power output terminal 112 of the power conversion circuit 110 and an output terminal 122 connected to the switch 130 and controlling the connection state of the switch 130. Additionally, the control circuit 120 includes a power supply terminal 123 as a power supply terminal.

[0084] The DC power output from the power conversion circuit 110 is input to the input terminal 121. The output terminal 122 outputs an output signal corresponding to the state of the input terminal 121. Power is supplied from the power supply 50 to the power supply terminal 123.

[0085] Switch 130 is connected between power supply 50, which outputs DC power, and load 60, which is driven by DC power supplied from power supply 50. Switch 130 switches the connection state between power supply 50 and load 60 from a non-conducting state to a conducting state.

[0086] The non-conducting state is the state in which the power supply from power source 50 to load 60 is cut off, and the conducting state is the state in which power source 50 supplies power to load 60.

[0087] In this example, the control circuit 120 includes a flip-flop 127. The flip-flop 127 switches the control signal output from the output terminal 122.

[0088] Figure 2 The example shown is of a D flip-flop (DF / F), but it can also be made of flip-flops other than T types.

[0089] Control circuit 120 controls the conduction state of switch 130. Specifically, when power conversion circuit 110 receives radio wave 71 through antenna 140 and outputs DC power, control circuit 120 controls the connection state of switch 130 to the conduction state.

[0090] More specifically, the input terminal 121 of the control circuit 120 is connected to the CLK terminal 1271 and the D terminal 1272 of the flip-flop 127. Additionally, the output terminal 122 of the control circuit 120 is connected to the Q terminal 1273 of the flip-flop 127.

[0091] When antenna 140 does not receive radio wave 71 (i.e., transmitter 70 is disconnected from latching circuit 10 or is not transmitting radio wave 71), input terminal 121 is at a low level (the same potential as ground), therefore, Q terminal 1273 remains at a low level. In this state, switch 130 is controlled to be in a non-conducting state. That is, in this state, no power is supplied from power source 50 to load 60.

[0092] When antenna 140 receives radio wave 71 (i.e., radio wave 71 has been transmitted from transmitter 70 and transmitter 70 is close to latching circuit 10), RF-DC conversion circuit 113 outputs DC power to boost circuit 114. Boost circuit 114 boosts the voltage until it exceeds the threshold potential that causes a change in the Q terminal 1273 of trigger 127. At this time, power conversion circuit 110 inputs a sufficient potential to cause a change in the state of Q terminal 1273 to the CLK terminal 1271 and D terminal 1272 of trigger 127, thus Q terminal 1273 becomes high. In this state, switch 130 is controlled to be in the ON state.

[0093] If switch 130 is controlled to be in the ON state, power supply 50 supplies power to load 60 via switch 130.

[0094] The trigger 127 is powered by the power supply 50, so even when the state changes to the state where the antenna 140 does not receive the radio wave 71 (i.e., the state where the latch circuit 10 does not receive the radio wave due to the transmitter 70 moving away from the latch circuit 10, etc.), the Q terminal 1273 continues to output a high level.

[0095] In this embodiment, when the switch 130 is switched to the on state, the control circuit 120 keeps the switch 130 in the on state by supplying power from the power source 50 to the power terminal 123.

[0096] Furthermore, in this example, the trigger 127 is connected to the power supply 50 via the power supply terminal 123. Therefore, the trigger 127 with low power consumption can be selected to minimize the impact on battery life. For example, a trigger 127 with power consumption of less than 1 μA (microamp) can also be selected.

[0097] Figure 3 This is a diagram showing a first variation of the structure of the latch module 1 according to the first embodiment. The latch module 1b shown in this diagram is a first variation of the latch module 1. Furthermore, the same reference numerals are used for structures that are the same as those in the latch module 1 described above, and their descriptions are omitted. The latch module 1b differs from the latch module 1 described above in that it includes a control circuit 120b instead of a control circuit 120.

[0098] The control circuit 120b includes an input terminal 121b connected to the DC power output terminal 112 of the power conversion circuit 110 and an output terminal 122b connected to the switch 130 and controlling the connection state of the switch 130. Additionally, the control circuit 120b includes a power supply terminal 123b as a power supply terminal.

[0099] The DC power output from the power conversion circuit 110 is input to the input terminal 121b. The output terminal 122b outputs an output signal corresponding to the state of the input terminal 121b. Power is supplied from the power supply 50 to the power supply terminal 123b.

[0100] In this example, the control circuit 120b includes a power sensor 126. The power sensor 126 has a detection input terminal 1261, a reference input terminal 1262, and a voltage detection output terminal 1263 as input / output terminals. The reference input terminal 1262 is connected to ground point TG. The voltage detection output terminal 1263 outputs a potential corresponding to the potential of the detection input terminal 1261 and the potential of the reference input terminal 1262.

[0101] When antenna 140 does not receive radio wave 71 (i.e., transmitter 70 is disconnected from latching circuit 10 or not transmitting radio wave 71), input terminal 121b is at a low level, therefore, a low level is input to detection input terminal 1261. Reference input terminal 1262 is connected to ground point TG (fixed at low level), therefore, voltage detection output terminal 1263 outputs a low level. In this state, switch 130 is controlled to be in a non-conducting state.

[0102] When antenna 140 receives radio wave 71 (i.e., radio wave 71 has been transmitted from transmitter 70 and transmitter 70 is close to latching circuit 10), RF-DC conversion circuit 113 outputs DC power to boost circuit 114. Boost circuit 114 boosts the voltage to the operating potential (high level) of power sensor 126. Power conversion circuit 110 outputs a high level. The high level is input to the detection input terminal 1261 of power sensor 126, therefore, voltage detection output terminal 1263 outputs a high level. In this state, switch 130 is controlled to be in the on state.

[0103] In this example, the detection input terminal 1261 of the power sensor 126 is connected to the voltage detection output terminal 1263.

[0104] Furthermore, the control circuit 120b may also include a resistor 124b. In this case, the detection input terminal 1261 of the power sensor 126 is connected to the voltage detection output terminal 1263 via the resistor 124b. As an example, the resistance value of the resistor 124b may be 10 megohms or more. By including the resistor 124b in the control circuit 120b, power consumption can be further suppressed.

[0105] The power sensor 126 outputs a high level, thereby controlling the switch 130 to be in the on state. With the power supply 50 and the load 60 connected, the current flowing in the control circuit 120b is only the current flowing in the resistor 124b and the current consumed by the power sensor 126, both of which are very small.

[0106] Thus, the power consumption of the power sensor 126 is theoretically zero, and therefore, the switch 130 can make the power consumption of the power supply 50 in the non-conducting state approximately zero. Therefore, compared with the example with the trigger 127 described above, the example with the power sensor 126 can further reduce power consumption.

[0107] Figure 4 This is a diagram showing an example of the structure of the power sensor 126 according to the first embodiment.

[0108] Figure 4 (A) is an example of the structure of power sensor 126. In this figure, power sensor 126 includes transistor Q1, transistor Q2, transistor Q3, transistor Q4, inverter 1264, and resistor 1265.

[0109] Transistors Q1, Q2, and Q4 are enhancement-mode devices. Transistor Q3 is a depletion-mode device.

[0110] When the output terminal 122b outputs a low level, transistors Q2 and Q3 are in the ON state. When the output terminal 122b outputs a high level, transistors Q1 and Q4 are in the ON state.

[0111] In this example, there are two paths for current to flow from power terminal 123b to ground point TG. The first path is the path from power terminal 123b through transistors Q1 and Q3 to ground point TG, and the second path is the path from power terminal 123b through transistors Q2 and Q4 to ground point TG. For the power sensor 126, regardless of the state of output terminal 122b, the path for current to flow from power terminal 123b to ground point TG is always interrupted.

[0112] Therefore, the power consumption of the power sensor 126 is theoretically zero.

[0113] Figure 4 (B) is Figure 4 (A) shows a truth table of an example of the structure of the power sensor 126. The figure illustrates the correspondence between the potentials of the input terminal 121b and the output terminal 122b and the states of transistors Q1, Q2, Q3 and Q4.

[0114] IN represents the potential level of input terminal 121b, and OUT represents the potential level of output terminal 122b. Transistors Q1, Q2, Q3, and Q4 represent the states of each transistor.

[0115] Figure 5 This figure shows a second variation of the structure of the latch module 1 according to the first embodiment. The latch module 1c shown in this figure is a second variation of the latch module 1. Furthermore, structures identical to those in the latch module 1 described above are labeled with the same reference numerals, and their descriptions are omitted. Regarding the latch module 1c, the power supply to the power terminal 123c of the control circuit 120c differs from that of the latch modules 1a and 1b. The control circuit 120c is an example of the control circuit 120.

[0116] The control circuit 120c includes an input terminal 121c connected to the DC power output terminal 112 of the power conversion circuit 110 and an output terminal 122c connected to the switch 130 and controlling the connection state of the switch 130. Additionally, the control circuit 120c includes a power supply terminal 123c as a power supply terminal.

[0117] The DC power output from the power conversion circuit 110 is input to the input terminal 121c. The output terminal 122c outputs an output signal corresponding to the state of the input terminal 121c. Power is supplied to the power terminal 123c from at least one of the power conversion circuit 110 or the power supply 50.

[0118] In this example, the latching module 1c includes diodes D1 and D2. For diode D1, the anode is connected to the DC power output terminal 112 of the power conversion circuit 110, and the cathode is connected to the power supply terminal 123c of the control circuit 120c. For diode D2, the anode is connected to the connection point of the switch 130 and the load 60, and the cathode is connected to the power supply terminal 123c of the control circuit 120c. Hereinafter, diode D1 will be referred to as the first diode, and diode D2 as the second diode.

[0119] When the antenna 140 does not receive radio wave 71 (i.e., the transmitter 70 is disconnected from the latching circuit 10 or is not transmitting radio wave 71 from the transmitter 70), no power is supplied to the control circuit 120c. In this state, the switch 130 is controlled to be in a non-conducting state. Furthermore, the output terminal 122c can be fixed to a low level by means of a resistor (not shown) or the like.

[0120] When antenna 140 receives radio wave 71 (i.e., radio wave 71 has been transmitted from transmitter 70 and transmitter 70 is close to latching circuit 10), RF-DC conversion circuit 113 outputs DC power to boost circuit 114. Boost circuit 114 boosts the voltage to a level higher than the operating potential of power sensor 126 plus the voltage drop across diode D1. Power conversion circuit 110 supplies power from DC power output terminal 112 to power terminal 123c of control circuit 120c via diode D1.

[0121] In this case, the potential output from the DC power output terminal 112 of the power conversion circuit 110 is also input to the input terminal 121c of the control circuit 120c. Regarding the control circuit 120c, if a high level is input to the input terminal 121c, a high level is output to the output terminal 122c. Therefore, the switch 130 is controlled to be in the ON state.

[0122] If switch 130 is controlled to be in the on state, power supply 50 supplies power to power terminal 123c of control circuit 120c via switch 130 and diode D2.

[0123] Even when the antenna 140 does not receive radio waves 71 (i.e., the latching circuit 10 does not receive radio waves due to reasons such as the transmitter 70 moving away from the latching circuit 10), the control circuit 120c can still receive power from the power supply 50 via the switch 130 and the diode D2.

[0124] Therefore, in this embodiment, regarding switch 130, if antenna 140 receives radio wave 71 and switch 130 is controlled to be in the conducting state, then switch 130 is kept in the conducting state.

[0125] Figure 6 This figure shows an example of a frame with a waterproof structure according to the first embodiment. As shown in the figure, the latching waterproof module 2 includes a latching circuit 10, a power supply 50 that outputs DC power, a load 60 driven by the DC power supplied from the power supply 50, and a frame 80.

[0126] The housing 80 houses the latching circuit 10, the power supply 50, and the load 60. The housing 80 is waterproof.

[0127] [Summary of the effects of the first implementation method]

[0128] According to the above-described implementation method, the latching circuit 10 controls the connection state of the power supply 50 and the load 60 to be in the conducting state by receiving the radio waves through the antenna 140.

[0129] In the past, in small devices shipped with the battery mounted on the substrate, power was supplied the moment the battery was installed, and battery consumption began. From a battery life perspective, ideally, power should only be supplied after the device is delivered to the customer or when the customer wants power, but contact switches or (removable) insulating films have led to the increasing size of small devices.

[0130] By receiving radio waves through antenna 140, latching circuit 10 controls the connection state of power supply 50 and load 60 to be in the on state, thereby suppressing the enlargement of small devices.

[0131] Furthermore, according to the above-described embodiment, regarding the latching circuit 10, the power conversion circuit 110 converts the power received from the radio waves through the antenna 140 into DC power, and the control circuit 120 controls the conduction state of the switch 130. Since the latching circuit 10 includes the control circuit 120, the state of the switch 130 can be switched to the conduction state even with weak radio waves, thus the startup of the AFE as a load is time-efficient. Therefore, a latching module 1 can be provided that provides time-efficient startup of the load 60 from receiving radio waves.

[0132] Therefore, a convenient latching circuit 10 can be provided.

[0133] Furthermore, according to the above embodiment, the control circuit 120 of the latching circuit 10 receives power from the power supply 50. Therefore, even when the antenna 140 does not receive radio waves after receiving radio waves, the latching circuit 10 can maintain the connection state of the switch 130 in the on state.

[0134] Furthermore, according to the above embodiment, the control circuit 120 includes a trigger 127. Therefore, the control circuit 120 can switch and maintain the connection state of the switch 130 through a simple structure.

[0135] Additionally, according to the above-described embodiment, the control circuit 120 includes a power sensor 126 with feedback.

[0136] The output signal of the control circuit 120 is fed back to the input, thus enabling the control circuit 120 to maintain the connection state of the switch 130. Furthermore, the state of the switch 130 can be maintained with minimal power consumption.

[0137] Furthermore, according to the above embodiment, the power sensor 126 also includes a resistor 124b with a resistance of 10 megohms or more. Therefore, since the control circuit 120 includes the resistor 124b, the power consumed by the control circuit 120 can be further suppressed.

[0138] Furthermore, according to the above embodiment, the latch module 1 includes a diode D1, thereby providing power to the control circuit 120 via the power conversion circuit 110. Therefore, the latch module 1 can obtain power from the radio waves received by the antenna 140 for switching the switch 130 to the on state. That is, the latch module 1 can switch the switch 130 to the on state without consuming power from the power supply 50.

[0139] Furthermore, according to the above embodiment, the latching module 1 includes a diode D2, thereby enabling it to receive power from the power supply 50 after the switch 130 is controlled to be in the on state. Therefore, the switch 130 can remain in the on state.

[0140] Furthermore, according to the above embodiment, the latch module 1 is housed in a waterproof housing 80. For example, in a device used in a water-sealed state, when a non-contact system start-up is required, the latch module 1 of this embodiment enables non-contact system start-up.

[0141] Devices used in a sealed state underwater include, for example, water quality survey equipment and small camera equipment. Furthermore, the term "underwater" is not limited to water itself, but broadly includes liquids such as electrolytes or bodily fluids.

[0142] [Second Implementation]

[0143] The second embodiment of the present invention will now be described with reference to the accompanying drawings.

[0144] Figure 7 This is a diagram showing an example of the power conversion circuit 110d according to the second embodiment. The power conversion circuit 110d is an example of the power conversion circuit 110.

[0145] In this figure, the power conversion circuit 110d includes a first capacitor C11, a first diode D11, a second diode D12, and a second capacitor C12.

[0146] The first capacitor C11 has a first electrode C11a and a second terminal C11b. The first electrode C11a of the first capacitor C11 is connected to the power input terminal 111a, and the second electrode C11b is connected to the junction of the cathode of the first diode D11 and the anode of the second diode D12.

[0147] Regarding the first diode D11, the anode is connected to the ground point TG, and the cathode is connected to the second electrode C11b of the first capacitor C11.

[0148] The second capacitor C12 has a first electrode C12a and a second electrode C12b. The first electrode C12a of the second capacitor C12 is connected to the DC power output terminal 112d, and the second electrode C12b is connected to the ground point TG.

[0149] The anode of the second diode D12 is connected to the power input terminal 111d via a capacitor. In this example, the anode of the second diode D12 is connected to the power input terminal 111d via the first capacitor C11. Furthermore, the cathode of the second diode D12 is connected to the first electrode C12a of the second capacitor C12.

[0150] If a positive potential is applied to the power input terminal 111d, a current I11 flows from the power input terminal 111d through the first capacitor C11 and the second diode D12. Charge is stored in the second capacitor C12 due to the current I11.

[0151] If a negative potential is applied to the power input terminal 111d, a current I12 flows from the ground point TG through the first diode D11 and the first capacitor C11. Charge accumulates in the first capacitor C11 due to the current I12.

[0152] By applying a positive potential to the power input terminal 111d again, current I11 flows from the power input terminal 111d through the first capacitor C11 and the second diode D12. As a result, twice the potential of the power input terminal 111d is output to the DC power output terminal 112d. This is the operation of the half-wave voltage doubler rectifier circuit.

[0153] The power conversion circuit 110d is a voltage doubler rectifier circuit used to boost weak radio waves. The weak radio waves utilize a 2.4 GHz frequency band, such as the Bluetooth (Trademarked) Low Energy (BLE) standard used in smartphones. The first diode D11 and the second diode D12 (hereinafter, without distinction, the diodes included in the power conversion circuit 110 will be referred to as diode D) are preferably diodes with excellent high-frequency characteristics, low forward voltage, and small inter-terminal capacitance. In this example, diode D can be a Schottky barrier diode.

[0154] Regarding the first capacitor C11 and the second capacitor C12 (hereafter, without distinction, the capacitors included in the power conversion circuit 110 will be referred to as capacitor C), the response speed and the reached voltage value of the boost voltage vary depending on the capacitance. Furthermore, regarding capacitor C, if the capacitance value is insufficient, the output voltage ripple (voltage fluctuation) increases, and the DC characteristics deteriorate. On the other hand, regarding capacitor C, if the capacitance value is too large, charging time is prolonged, and responsiveness deteriorates.

[0155] Therefore, depending on the application of each selected diode D or latch-up circuit 10, the capacitance value of capacitor C is adjusted to obtain a balanced and good voltage multiplication characteristic. For example, in this embodiment, 33pF or 24pF is preferred at 2.4GHz.

[0156] The optimal capacitance value varies depending on factors such as the stray capacitance of the substrate, the substrate pattern, and the mounting layout. Figure 7 In the circuit shown, the optimal value varies between several and tens of pF (including tens of pF). The optimal capacitance value needs to be determined based on the stray capacitance of the substrate, the substrate pattern, the mounting layout, etc.

[0157] The power conversion circuit 110 adopts a multi-stage structure by assembling the aforementioned voltage doubler rectifier circuit, thereby obtaining a potential that enables the control circuit 120 to operate even under weaker electromagnetic waves.

[0158] Figure 8 This diagram shows a first variation of the power conversion circuit 110 according to the second embodiment, namely, power conversion circuit 110e. Power conversion circuit 110e is an example of the power conversion circuit 110 described above. Furthermore, structures identical to those in the power conversion circuit 110 described above are labeled with the same symbols, and their descriptions are omitted.

[0159] In this figure, the power conversion circuit 110e includes a first capacitor C21, a first diode D21, a second capacitor C22, a second diode D22, a third capacitor C23, a third diode D23, a fourth capacitor C24, and a fourth diode D24.

[0160] In this example, the first capacitor C21 is the same as the first capacitor C11, the first diode D21 is the same as the first diode D11, the second capacitor C22 is the same as the second capacitor C12, and the second diode D22 is the same as the second diode D12.

[0161] Compared with the power conversion circuit 110d, the power conversion circuit 110e also includes a third capacitor C23, a third diode D23, a fourth capacitor C24, and a fourth diode D24, thus forming a two-stage voltage multiplier rectifier circuit.

[0162] The third capacitor C23 has a first electrode C23a and a second electrode C23b. The first electrode C23a of the third capacitor C23 is connected to the cathode of the third diode D23, and the second electrode C23b is connected to the ground point TG.

[0163] Regarding the third diode D23, its anode is connected to the second electrode C21b of the first capacitor C21, and its cathode is connected to the first electrode C23a of the third capacitor C23.

[0164] The fourth capacitor C24 has a first electrode C24a and a second electrode C24b. The first electrode C24a of the fourth capacitor C24 is connected to the power input terminal 111e, and the second electrode C24b is connected to the cathode of the fourth diode D24.

[0165] Regarding the fourth diode D24, its anode is connected to the junction of the cathode of the third diode D23 and the first electrode C23a of the third capacitor C23, and its cathode is connected to the second electrode C24b of the fourth capacitor C24.

[0166] In this particular case, the anode of the second diode D22 is connected to the power input terminal 111e via the fourth capacitor C24.

[0167] exist Figure 8 In one example shown, a voltage four times the input voltage input to the power input terminal 111e can be output from the DC power output terminal 112e.

[0168] In this way, by constructing a multi-stage voltage multiplier rectifier circuit, the power conversion circuit 110 can obtain a potential that enables the control circuit 120 to operate.

[0169] However, constructing a multi-stage voltage multiplier rectifier circuit leads to a decrease in RF-DC conversion efficiency. Furthermore, the increased number of components in a multi-stage voltage multiplier rectifier circuit results in increased cost. Therefore, it is ideal to construct a suitable number of stages for each application.

[0170] Figure 9This is a diagram showing a second variation of the power conversion circuit 110 according to the second embodiment, namely power conversion circuit 110f. Power conversion circuit 110f is an example of the power conversion circuit 110 described above. Furthermore, structures that are the same as those in the power conversion circuit 110 described above are labeled with the same symbols, and their descriptions are omitted.

[0171] In this figure, the power conversion circuit 110f includes a first capacitor C31, a first diode D31, a second capacitor C32, a second diode D32, a third capacitor C33, a third diode D33, a fourth capacitor C34, a fourth diode D34, a fifth capacitor C35, a fifth diode D35, a sixth capacitor C36, and a sixth diode D36.

[0172] In this example, the first capacitor C31 is the same as the first capacitor C21, the first diode D31 is the same as the first diode D21, the second capacitor C32 is the same as the second capacitor C22, the second diode D32 is the same as the second diode D22, the third capacitor C33 is the same as the third capacitor C23, the third diode D33 is the same as the first diode D23, the fourth capacitor C34 is the same as the fourth capacitor C24, and the fourth diode D34 is the same as the fourth diode D24.

[0173] Compared to the power conversion circuit 110e, the power conversion circuit 110f also includes a fifth capacitor C35, a fifth diode D35, a sixth capacitor C36, and a sixth diode D36, thus forming a three-stage voltage multiplier rectifier circuit.

[0174] The fifth capacitor C35 has a first electrode C35a and a second electrode C35b. The first electrode C35a of the fifth capacitor C35 is connected to the cathode of the fifth diode D35, and the second electrode C35b is connected to the ground point TG.

[0175] Regarding the fifth diode D35, its anode is connected to the second electrode C34b of the fourth capacitor C34, and its cathode is connected to the first electrode C35a of the fifth capacitor C35.

[0176] The sixth capacitor C36 has a first electrode C36a and a second electrode C36b. The first electrode C36a of the sixth capacitor C36 is connected to the power input terminal 111f, and the second electrode C36b is connected to the cathode of the sixth diode D36.

[0177] Regarding the sixth diode D36, its anode is connected to the junction point of the cathode of the fifth diode D35 and the first electrode C35a of the fifth capacitor C35, and its cathode is connected to the second electrode C36b of the sixth capacitor C36.

[0178] In this particular case, the anode of the second diode D32 is connected to the power input terminal 111f via the sixth capacitor C36.

[0179] exist Figure 9 In one example shown, a voltage six times the input voltage input to the power input terminal 111f can be output from the DC power output terminal 112f.

[0180] Thus, by constructing a multi-stage voltage multiplier rectifier circuit, the power conversion circuit 110 can obtain a potential that enables the control circuit 120 to operate. Compared to the example shown in power conversion circuit 110e, in the example shown in power conversion circuit 110f, the control circuit 120 can be operated by a much weaker electromagnetic wave.

[0181] [Summary of the effects of the second implementation method]

[0182] According to the implementation method described above, Figure 1 The latching circuit 10 shown utilizes a voltage doubler rectifier circuit to form a power conversion circuit 110. The latching circuit 10, by utilizing a voltage doubler rectifier circuit to form the power conversion circuit 110, generates DC power boosted from a weak electromagnetic wave. The power conversion circuit 110 can supply the boosted DC power to the control circuit 120, thereby driving the control circuit 120.

[0183] Furthermore, according to the above embodiment, the voltage doubler rectifier circuit is composed of a capacitor C and a diode D. Therefore, the latch-up circuit 10 can be configured into a power conversion circuit 110 with a simple structure.

[0184] Furthermore, according to the above embodiment, the latching circuit 10 constitutes a power conversion circuit 110 via a two-stage voltage doubler rectifier circuit. Because the latching circuit 10 is configured as a power conversion circuit 110 via a two-stage voltage doubler rectifier circuit, the control circuit 120 can be driven even under very weak electromagnetic waves. By driving the control circuit 120 even under very weak electromagnetic waves, the latching circuit 10 can control the power supply 50 and the load 60 to be in a conducting state.

[0185] Furthermore, according to the above embodiment, the latching circuit 10 constitutes the power conversion circuit 110 through a three-stage voltage doubler rectifier circuit. Compared to a two-stage voltage doubler rectifier circuit, the latching circuit 10, by constituting the power conversion circuit 110 through a three-stage voltage doubler rectifier circuit, can drive the control circuit 120 even under weaker electromagnetic waves. By driving the control circuit 120 even under weaker electromagnetic waves, the latching circuit 10 can control the power supply 50 and the load 60 to be in a conducting state.

[0186] [Third Implementation Method]

[0187] The third embodiment of the present invention will now be described with reference to the accompanying drawings.

[0188] Figure 10 This is a diagram illustrating an example of the first antenna 240 and the second antenna 340 of the third embodiment. Figure 10 (A) is a diagram showing an example of the structure of the latch module 1 described above when it includes an antenna 140. In this case, the radio waves received by the antenna 140 are converted into DC power by the power conversion circuit 110 and input to the control circuit 120.

[0189] Control circuit 120 controls switch 130 from a non-conducting state to a conducting state. In this example, control circuit 120 cannot control switch 130 from a conducting state to a non-conducting state.

[0190] Figure 10 (B) is a diagram showing an example of the structure of the latch module 1 when it has two antennas (a first antenna 240 and a second antenna 340). In this case, the latch module 1 includes a first antenna 240, a first power conversion circuit 210, a second antenna 340, a second power conversion circuit 310, and a control circuit 220.

[0191] In this example, the first antenna 240 and the second antenna 340 can be provided at different angles.

[0192] The first antenna 240 is provided in such a way that it can receive a first radio wave from a first direction.

[0193] The first power conversion circuit 210 includes a first power input terminal 211 and a first DC power output terminal 212. The first power input terminal 211 is connected to the first antenna 240. The first DC power output terminal 212 is connected to the control circuit 220.

[0194] The power received by the first radio wave through the first antenna 240 is input to the first power input terminal 211. If power is input to the first power input terminal 211, the first power conversion circuit 210 converts the power input to the first power input terminal 211 into DC power. The first power conversion circuit 210 outputs DC power from the first DC power output terminal 212.

[0195] It is equipped with a second antenna 340 in a manner that enables it to receive second radio waves from a second direction different from the first direction.

[0196] The second power conversion circuit 310 includes a second power input terminal 311 and a second DC power output terminal 312. The second power input terminal 311 is connected to the second antenna 340. The second DC power output terminal 312 is connected to the control circuit 220.

[0197] The power received by the second radio wave through the second antenna 340 is input to the second power input terminal 311. If power is input to the second power input terminal 311, the second power conversion circuit 310 converts the power input to the second power input terminal 311 into DC power. The second power conversion circuit 310 outputs DC power from the second DC power output terminal 312.

[0198] The control circuit 220 has a first input terminal 221, a second input terminal 225, and an output terminal 222 as input and output terminals.

[0199] The first input terminal 221 is connected to the first DC power output terminal 212 of the first power conversion circuit 210. The second input terminal 225 is connected to the second DC power output terminal 312 of the second power conversion circuit 310. The output terminal 222 is connected to the switch 130 to control the connection state of the switch 130.

[0200] When the first antenna 240 receives the first radio wave and the first power conversion circuit 210 outputs DC power, the control circuit 220 controls the connection state of the switch 130 to the on state. When the second antenna 340 receives the second radio wave and the second power conversion circuit 310 outputs DC power, the control circuit 220 controls the connection state of the switch 130 to the off state.

[0201] Thus, in Figure 10 In the example shown in (B), the control circuit 220 can not only control the switch 130 from the non-conducting state to the conducting state, but also control the switch 130 from the conducting state to the non-conducting state.

[0202] Figure 11 This is a diagram illustrating an example of the first antenna 240 and the second antenna 340 of the third embodiment.

[0203] Figure 11 (A) is a diagram showing an example of an electric field type antenna 500 according to the third embodiment. This diagram shows an example of the type of antenna when the first antenna 240 or the second antenna 340 is an electric field type antenna 500.

[0204] When the first antenna 240 or the second antenna 340 is an electric field type antenna 500, it can be a dipole antenna 501, a monopole antenna 502, an inverted F antenna 503, a bent line antenna 504, or a sheet antenna 505.

[0205] Figure 11(B) is a diagram showing an example of a magnetic field type antenna 600 according to the third embodiment. This diagram shows an example of the type of antenna when the first antenna 240 or the second antenna 340 is a magnetic field type antenna 600.

[0206] If the first antenna 240 or the second antenna 340 is a magnetic field type antenna 600, it can be a loop antenna 601.

[0207] The types of antennas for the first antenna 240 and the second antenna 340 in this embodiment are not limited to... Figure 11 (A) and Figure 11 (B) shows the types of antennas that can be selected.

[0208] Figure 12 This figure shows an example of the structure of the latch module 1g according to the third embodiment. The latch module 1g shown in this figure is a variation of the latch module 1 of the first embodiment. Furthermore, structures identical to those of the latch module 1 described above are labeled with the same symbols, and their descriptions are omitted.

[0209] In this figure, the latch module 1g includes a latch circuit 10g, a power supply 50, and a load 60.

[0210] The latching circuit 10g includes an electric field antenna 500a, a magnetic field antenna 600a, a first power conversion circuit 210a, a second power conversion circuit 310a, a control circuit 220, and a switch 130. The electric field antenna 500a is an example of the first antenna 240, and the magnetic field antenna 600a is an example of the second antenna 340.

[0211] In addition, the first power conversion circuit 210a may include an RF-DC conversion circuit 213a and a boost circuit 214a, and the second power conversion circuit 310a may include an RF-DC conversion circuit 313a and a boost circuit 314a.

[0212] An electric field antenna 500a receives a first radio wave from a first direction. The power generated by the electric field antenna 500a in receiving the first radio wave is input to the first power input terminal 211a of the first power conversion circuit 210a. The first power conversion circuit 210a converts the input power into DC power and outputs the converted DC power to the first DC power output terminal 212a.

[0213] In this case, the magnetic field antenna 600a is configured to receive a second radio wave from a second direction different from the first direction, and therefore does not receive the first radio wave. Therefore, in the control circuit 220, DC power is only input to the first input terminal 221.

[0214] The magnetic field antenna 600a receives a second radio wave from a second direction. The power generated by the magnetic field antenna 600a in receiving the second radio wave is input to the second power input terminal 311a of the second power conversion circuit 310a. The second power conversion circuit 310a converts the input power into DC power and outputs the converted DC power to the second DC power output terminal 312a.

[0215] In this case, the electric field antenna 500a is configured to receive a first radio wave from a first direction different from the second direction, and therefore does not receive a second radio wave. Therefore, in the control circuit 220, DC power is only input to the second input terminal 225.

[0216] In this example, the control circuit 220 includes a trigger 227. The trigger 227 switches the control signal output from the output terminal 222 based on the potential of the first input terminal 221 and the potential of the second input terminal 225.

[0217] Furthermore, specifically, the trigger 227 is an SR trigger (SR-F / F). More specifically, the first input terminal 221 is connected to the S terminal of the trigger 227, the second input terminal 225 is connected to the R terminal of the trigger 227, and the output terminal 222 is connected to the Q terminal.

[0218] When the electric field antenna 500a receives the first radio wave, the first power conversion circuit 210a outputs DC power. A potential corresponding to the output DC power is input to the first input terminal 221, i.e., the S terminal, of the trigger 227. When the input potential exceeds the threshold voltage for a state change in the trigger 227, i.e., if a high level is input to the S terminal of the trigger 227, the Q terminal of the trigger 227 outputs a high level. In this state, the switch 130 is controlled to be in the ON state. If the switch 130 is controlled to be in the ON state, the power supply 50 supplies power to the load 60.

[0219] When the magnetic field antenna 600a receives the second radio wave, the second power conversion circuit 310a outputs DC power. A potential corresponding to the output DC power is input to the second input terminal 225, i.e., the R terminal, of the trigger 227. When the input potential exceeds the threshold voltage for a state change in the trigger 227, i.e., if a high level is input to the R terminal of the trigger 227, the Q terminal of the trigger 227 outputs a low level. In this state, the switch 130 is controlled to be in a non-conducting state.

[0220] Power is supplied from power source 50 to control circuit 220, which includes trigger 227. Therefore, when neither the electric field antenna 500a nor the magnetic field antenna 600a receives a radio wave, trigger 227 maintains the output state of its Q terminal. That is, the connection state of switch 130 differs depending on whether the last antenna to receive a radio wave is the electric field antenna 500a or the magnetic field antenna 600a, and is either controlled to be in a conducting or non-conducting state. If switch 130 is controlled to be in a non-conducting state, power source 50 stops supplying power to load 60.

[0221] Furthermore, in this example, the trigger 227 is connected to the power supply 50 via the power supply terminal 223. Therefore, the trigger 227 with low power consumption can be selected to minimize the impact on battery life. For example, a trigger with power consumption of less than 1 μA (microamp) can be selected.

[0222] Alternatively, the control circuit 220 can be constructed from a low-power latching circuit that has the same function as a trigger.

[0223] Figure 13 This is a figure showing a first variation of the structure of the latch module 1 according to the third embodiment. The latch module 1h shown in this figure is a variation of the latch module 1g described above. Furthermore, the same symbols are used to denote the same structures as the latch module 1g, and their descriptions are omitted. The latch module 1h differs from the latch module 1g in that the control circuit 220 includes a power sensor 226 but does not include a trigger 227.

[0224] The structure of the control circuit 220 included in the latch module 1h is similar to... Figure 3 The control circuit 120b shown is the same. That is, the power sensor 226 included in the control circuit 220 has the same structure as... Figure 4 The power sensor 126 shown has the same structure.

[0225] In one example shown in latch module 1h, the first DC power output terminal 212a of the first power conversion circuit 210a is connected to the first input terminal 221 of the control circuit 220. That is, when the electric field antenna 500a receives a first radio wave, a current proportional to the power generated by the received radio wave is input to the detection input terminal 2261 of the power sensor 226. In this case, if the potential proportional to the current input to the input terminal 2261 is higher than the reference input potential VDET in the power sensor 226, a high level is output to the voltage detection output terminal 2263, and the switch 130 is controlled to be in the on state.

[0226] Furthermore, the second DC power output terminal 312a of the second power conversion circuit 310a is connected to the second input terminal 225 of the control circuit 220. That is, when the magnetic field antenna 600a receives a second radio wave, a current proportional to the power obtained through the received radio wave is input to the reference input terminal 2262 of the power sensor 226. Within the power sensor 226, a current amplifier exists in the next stage after the input terminal 2262. The current input to the reference input terminal 2262 is amplified by the current amplifier to twice its original value. Using the next stage of current adder, the current input to the reference input terminal 2262 is subtracted from the current input to the detection input terminal 2261. When the potential proportional to the current after the current adder passes is lower than the reference input potential VDET within the power sensor 226, a low level is output to the voltage detection output terminal 2263, and the switch 130 is controlled to be in a non-conducting state.

[0227] In this way, the latch module 1h, which includes a control circuit 220 containing a power sensor 226, performs the same operation as the latch module 1g, which includes a control circuit 220a containing a trigger 227.

[0228] Compared to latch module 1g, latch module 1h achieves lower power consumption by including a power sensor 226 in the control circuit 220.

[0229] Figure 14 This is a figure showing a second variation of the structure of the latch module 1 according to the third embodiment. The latch module 1i shown in this figure is a variation of the latch module 1g described above. Furthermore, the same symbols are used for structures identical to those in latch module 1g, and their descriptions are omitted. The latch module 1i differs from the latch module 1g in that both the first antenna 240 and the second antenna 340 use electric field type antennas 500.

[0230] In one example shown in the figure, electric field type antenna 500b (first antenna 240) and electric field type antenna 500c (second antenna 340) are located at different positions. That is, in the latching module 1i, the mounting positions of each antenna are different. The mounting position is the location where the antennas are set in the latching module 1i.

[0231] The electric field antenna 500b is configured to receive a first radio wave from a first direction. The electric field antenna 500c is configured to receive a second radio wave from a second direction different from the first direction.

[0232] Figure 15This figure shows a third variation of the structure of the latch module 1 according to the third embodiment. The latch module 1j shown in this figure is a variation of the latch module 1i described above. Furthermore, the same symbols are used to denote the same structures as latch module 1i, and their descriptions are omitted. The latch module 1j differs from the latch module 1i in that the setting angles of the first antenna 240 and the second antenna 340 are different.

[0233] In one example shown in the figure, the latching module 1j includes an electric field antenna 500d and an electric field antenna 500e. The electric field antenna 500d is an example of the first antenna 240, and the electric field antenna 500e is an example of the second antenna 340.

[0234] In one example shown in the figure, an electric field antenna 500b (first antenna 240) and an electric field antenna 500c (second antenna 340) are provided at different angles. That is, the first radio wave and the second radio wave are provided at different angles, so the first radio wave and the second radio wave will not interfere with each other.

[0235] As an example, an electric field type antenna 500b (first antenna 240) and an electric field type antenna 500c (second antenna 340) can be provided perpendicularly to each other.

[0236] Figure 16 This is a diagram showing a fourth variation of the structure of the latch module 1 according to the third embodiment.

[0237] Figure 16 (A) is a diagram showing the configuration of antennas 701 and 702 in a two-dimensional orthogonal coordinate system with x and y axes. Antenna 701 shown in this diagram is an example of the first antenna 240 described above, and antenna 702 is an example of the second antenna 340 described above. Hereinafter, antennas 701 and 702 will be referred to as antenna 700 without distinction. Antenna 700 is an example of an electric field type antenna 500.

[0238] Antenna 701 is configured along the x-axis. Antenna 702 is configured along the y-axis. In this example, antennas 701 and 702 are configured at different angles.

[0239] Figure 16 (B) is a diagram showing the configuration of antennas 701 and 702 using a three-dimensional orthogonal coordinate system of the x, y, and z axes. In this diagram, [the following will be shown]. Figure 16 The configuration of antennas 701 and 702, shown in (A) by a two-dimensional orthogonal coordinate system of x-axis and y-axis, is shown in three-dimensional space.

[0240] Antennas 701 and 702 are housed within a housing 703. Furthermore, antennas 701 and 702 are arranged on the same plane. As shown in the figure, antennas 701 and 702 are arranged at different angles, thus ensuring that the first and second radio waves do not interfere with each other even when antennas 701 and 702 are arranged on the same plane.

[0241] Figure 17 This is a figure showing a fifth variation of the structure of the latch module 1 according to the third embodiment. The latch module 1k shown in this figure is a variation of the latch module 1j described above. Furthermore, structures identical to those in latch module 1j are labeled with the same symbols, and their descriptions are omitted. Latch module 1k differs from latch module 1j in that the first antenna 240 and the second antenna 340 have the same setting angle but different lengths of dipole antennas 501.

[0242] In one example shown in the figure, the latching module 1k includes an electric field antenna 500f and an electric field antenna 500g. The electric field antenna 500f is an example of the first antenna 240, and the electric field antenna 500g is an example of the second antenna 340.

[0243] In this example, the electric field antenna 500f and the electric field antenna 500g each have antennas of different lengths. To suppress interference between the first and second radio waves, the lengths of the electric field antenna 500f and the electric field antenna 500g are selected based on the frequency of the radio waves. For example, the lengths of the electric field antenna 500f and the electric field antenna 500g are preferably 1 / 2 or 1 / 4 of the wavelength λ of the radio waves received by each antenna. In this case, the electric field antenna 500f and the electric field antenna 500g can efficiently receive radio waves without generating reflected waves.

[0244] Specifically, with the first radio wave having a frequency of 2.4 GHz and the second radio wave having a frequency of 5 GHz, the wavelength of the first radio wave is approximately 12.5 cm, and the wavelength of the second radio wave is approximately 6 cm. Furthermore, when using a λ / 2 wavelength dipole antenna, the antenna length for receiving the first radio wave is 6.25 cm, and the antenna length for receiving the second radio wave is 3 cm.

[0245] As described above, by constructing a latching module 1k of a dipole antenna 501 with an antenna length of half the wavelength λ of the first and second radio waves having different wavelengths, interference between the first and second radio waves can be suppressed. In this case, it is also possible to use one radio wave to turn on the switch 130 and use the other radio wave to turn off the switch 130.

[0246] Furthermore, the example of using a dipole antenna 501 illustrates a case where the lengths of the first antenna 240 and the second antenna 340 are different, but this is not limited to the example of the dipole antenna 501; the same applies to the monopole antenna 502, the inverted-F antenna 503, the bent-line antenna 504, and the sheet antenna 505. These antennas can also be configured such that the lengths of the antennas in the first antenna 240 and the second antenna 340 are different.

[0247] Figure 18 This figure shows an example of a frame with a waterproof structure according to the third embodiment. As shown in the figure, the latching waterproof module 2b includes a latching circuit 101, a power supply 50 that outputs DC power, a load 60 driven by DC power supplied from the power supply 50, and a frame 80.

[0248] The housing 80 houses the latching circuit 101, the power supply 50, and the load 60. The housing 80 is waterproof.

[0249] [Summary of the effects of the third implementation method]

[0250] According to the embodiment described above, the latching module 1 detects the first radio wave received by the first antenna 240 and the second radio wave received by the second antenna 340, thereby switching the connection state of the switch 130. The latching module 1 is configured in this way to switch the switch 130 from a non-conducting state to a conducting state. Furthermore, the latching module 1 can switch the switch 130 from a conducting state to a non-conducting state.

[0251] Furthermore, according to the above embodiment, the first antenna 240 and the second antenna 340 are provided at different locations. Therefore, the latching module 1 can prevent interference between a first radio wave from a first direction and a second radio wave from a direction different from the first direction. That is, it can prevent malfunctions.

[0252] Furthermore, according to the above embodiment, the first antenna 240 and the second antenna 340 are provided at different angles. Therefore, the latching module 1 can prevent interference between a first radio wave from a first direction and a second radio wave from a direction different from the first direction. That is, it can prevent malfunctions.

[0253] Furthermore, according to the above embodiment, the first antenna 240 and the second antenna 340 are provided perpendicularly to each other. Therefore, according to the above embodiment, mutual interference between the first radio wave and the second radio wave can be prevented. That is, malfunction can be prevented.

[0254] Furthermore, according to the above-described embodiment, the first antenna 240 is an electric field type antenna 500, and the second antenna 340 is a magnetic field type antenna 600. Therefore, mutual interference between the first and second radio waves can be prevented. That is, malfunctions can be prevented.

[0255] [Fourth Implementation Method]

[0256] The fourth embodiment of the present invention will now be described with reference to the accompanying drawings.

[0257] Figure 19 This is a diagram illustrating an example of the structure of the latching system 100 according to the fourth embodiment. In this diagram, the latching module 1m includes a first antenna 740a, a second antenna 740b, a first power conversion circuit 710a, a second power conversion circuit 710b, a control circuit 720, a switch 130, a power supply 50, and a load 60.

[0258] Furthermore, the first power conversion circuit 710a may include an RF-DC conversion circuit 713a and a boost circuit 714a, and the second power conversion circuit 710b may include an RF-DC conversion circuit 713b and a boost circuit 714b.

[0259] A first antenna 740a is provided in a manner capable of receiving radio waves. A second antenna 740b is provided in a manner capable of receiving radio waves, and the second antenna 740b has approximately the same characteristics and gain as the first antenna 740a. The first antenna 740a and the second antenna 740b are configured to be spaced apart by a predetermined distance.

[0260] In this example, the transmitting point T1 represents a location far from both the location equipped with the first antenna 740a and the location equipped with the second antenna 740b. Specifically, it is located at a point where the radio waves transmitted from the transmitting point T1 are in the far field.

[0261] Radio waves are divided into far-field and near-field based on their distance from the transmitting point. For example, the boundary between the far-field and near-field is represented by the wavelength λ of the radio wave, expressed as λ / 2π. As an example, at 2.4 GHz, the boundary between the far-field and near-field is approximately 2 cm from the transmitting point.

[0262] In the far field, radio waves can be captured as plane waves. Therefore, theoretically, the electric or magnetic field strength will be the same as long as the distance from the transmitting point is the same. The strength is inversely proportional to the first power of the distance.

[0263] On the other hand, in the near field, the electric field strength in an electric field antenna is inversely proportional to the cube of the distance, and the magnetic field strength is inversely proportional to the square of the distance; similarly, in a magnetic field antenna, the electric field strength is inversely proportional to the square of the distance, and the magnetic field strength is inversely proportional to the cube of the distance. That is, in terms of the electric or magnetic field strength in the near field, the change in intensity due to distance is much larger compared to the far field.

[0264] When receiving radio waves from the far field, the radio waves observed from the first antenna 740a and the second antenna 740b are plane waves, and the magnitudes of the electric forces P1 and P2 received by each antenna are almost equal.

[0265] In this embodiment, the first antenna 740a and the second antenna 740b have approximately the same characteristics and gain. Therefore, when the first antenna 740a and the second antenna 740b receive radio waves from the transmitting point T1, the DC power output by the first power conversion circuit 710a and the DC power output by the second power conversion circuit 710b are almost equal.

[0266] In this example, the radio waves from the far field are captured as noise. The radio waves from the far field are those floating in the environment. For example, this could cause a malfunction such as switching the connection state of switch 130 by receiving radio waves from the far field through latch module 1m.

[0267] The first power conversion circuit 710a has a first power input terminal 711a for receiving power from radio waves received by the first antenna 740a and a first DC power output terminal 712a for outputting DC power. The power input to the first power input terminal 711a is converted into DC power and output from the first DC power output terminal 712a.

[0268] The second power conversion circuit 710b has a second power input terminal 711b for receiving power from radio waves received by the second antenna 740b and a second DC power output terminal 712b for outputting DC power. The power input to the second power input terminal 711b is converted into DC power and output from the second DC power output terminal 712b.

[0269] The control circuit 720 includes a first input terminal 721 connected to a first DC power output terminal 712a of the first power conversion circuit 710a, a second input terminal 725 connected to a second DC power output terminal 712b of the second power conversion circuit 710b, an output terminal 722 connected to the switch 130 and controlling the connection state of the switch 130, and a power supply terminal 723.

[0270] The power supply terminal 723 of the control circuit 720 is connected to the power supply 50. The load 60 is connected to the power supply 50 via the switch 130.

[0271] The control circuit 720 switches the connection state of the switch 130 based on the result of comparing the power input to the first input terminal 721 and the power input to the second input terminal 725.

[0272] Figure 20This diagram illustrates an example of the structure of the latching system 100 in the fourth embodiment, where the first antenna 740a receives a radio wave with a higher intensity than the second antenna 740b. Furthermore, structures identical to the latching module 1m described above are labeled with the same symbols, and their descriptions are omitted.

[0273] In this example, the transmitting point T2 is located in the near field of the first antenna 740a. In the near field, the electric or magnetic field strength varies greatly due to distance; therefore, the electrical power generated by the radio waves received by the first antenna 740a is significantly different from the electrical power generated by the radio waves received by the second antenna 740b.

[0274] For example, if radio waves are transmitted near the first antenna 740a, the electric field strength or magnetic field strength around the second antenna 740b will be significantly reduced relative to the electric field strength or magnetic field strength around the first antenna 740a.

[0275] When the transmitting point T2 is located in the near field of the first antenna 740a, the power generated by the radio wave received by the first antenna 740a is significantly different from the power generated by the radio wave received by the second antenna 740b. Therefore, the DC power output by the first power conversion circuit 710a is significantly different from the DC power output by the second power conversion circuit 710b. That is, the power input to the first input terminal 721 of the control circuit 720 is significantly different from the power input to the second input terminal 725.

[0276] The control circuit 720 switches the connection state of the switch 130 based on the result of comparing the power input to the first input terminal 721 and the second input terminal 725. Therefore, when the transmitting point T2 is located in the near field of the first antenna 740a, the connection state of the switch 130 is switched.

[0277] For example, when the power input to the first input terminal 721 is more than twice the power input to the second input terminal 725, the control circuit 720 controls the switch 130 to be in the on state.

[0278] Figure 21 This diagram illustrates an example of the structure of the latching system 100 in the fourth embodiment, where the second antenna 740b receives a radio wave with a higher intensity than the first antenna 740a. Furthermore, structures identical to the latching module 1m described above are labeled with the same symbols, and their descriptions are omitted.

[0279] In this example, the transmitting point T3 is located in the near field of the second antenna 740b. If radio waves are transmitted from the vicinity of the second antenna 740b, i.e., the transmitting point T3, the electric field strength or magnetic field strength around the first antenna 740a is significantly attenuated relative to the electric field strength or magnetic field strength around the second antenna 740b.

[0280] For example, if the power input to the second input terminal 725 is greater than the power input to the first input terminal 721 by a specified amount, the control circuit 720 controls the switch 130 to a non-conducting state.

[0281] like Figure 20 as well as Figure 21 As shown, by transmitting near-field radio waves near either the first antenna 740a or the second antenna 740b, the latching circuit 10 can sense the position of the transmitter and switch the connection state of the switch 130 without error.

[0282] Figure 22 This is a diagram showing an example of the structure of the control circuit 720 according to the fourth embodiment.

[0283] Figure 22 (A) is a diagram showing an example of the circuit structure of the control circuit 720. As shown in the diagram, the control circuit 720 consists of a power sensor 726 and a feedback resistor 724. The power sensor 726 has a first input terminal 7212, a second input terminal 7252, and an output terminal 7222 as input and output terminals. The output terminal 7222 of the power sensor 726 is connected to the first input terminal 7212 via the feedback resistor 724. The feedback resistor 724 feeds back the power from the output terminal 7222 of the power sensor 726 to the input terminal 7212. Therefore, if the output terminal 7222 is high, the power sensor 726 maintains the high level of the output terminal 7212 as long as a large amount of power, such as that required to de-energize the switch 130, is not input to the second input terminal 7252. The power sensor 726 includes a current amplifier 7261, a current adder 7262, and a current comparator 7263 as components. The power sensor 726 compares the power input to the first input terminal 7212 and the second input terminal 7252 by comparing the current input according to a value proportional to the power input to the first input terminal 7212 and the second input terminal 7252.

[0284] The current amplifier 7261 inputs the current I to the second input terminal 7252. INM Amplification. In this example, current amplifier 7261 amplifies the current input to the second input terminal 7252 by a factor of G.

[0285] The current adder 7262 uses the current amplifier 7261 to amplify the current input to the second input terminal 7252 to a factor of G (G×I). INM ) and the current I input to the first input terminal 7212 INP Add them together. The current adder 7262 outputs the summed current.

[0286] The current output by the current comparator 7263 after adding the result of the current adder 7262 is the current (I). INP -G×I INM ) and the detected current I DET The comparison is performed. The current comparator 7263 outputs a voltage corresponding to the comparison result to the output terminal 7222.

[0287] Specifically, the output current after the summation by the current adder 7262 is the detection current I. DET In the above scenario, the current comparator 7263 outputs a high level, and the current output after being added by the current adder 7262 is less than the detected current I. DET In this case, the current comparator 7263 outputs a low level. Therefore, the current comparator 7263 will also be referred to as a comparator from now on.

[0288] That is, the difference between the current flowing in the first input terminal 7212 and the current amplified by the current amplifier 7261 to a factor of G in the second input terminal 7252 is the detection current I. DET Under the above conditions, the current comparator 7263 outputs a high level. Additionally, the difference between the current flowing in the first input terminal 7212 and the current amplified by the current amplifier 7261 to a factor of G in the second input terminal 7252 is less than the detection current I. DET In this case, the current comparator 7263 outputs a low level.

[0289] For example, when the gain (amplification) of the current amplifier 7261 is set to 2, if the current flowing in the first input terminal 7212 is not twice the current flowing in the second input terminal 7252, the detection current I is added. DET If the obtained value is higher than or equal to the value obtained, the current comparator 7263 will not output a high level.

[0290] In the future, the state in which the current comparator 7263 outputs a low level to the output terminal 7222 will be recorded as the off state, and the state in which the current comparator 7263 outputs a high level to the output terminal 7222 will be recorded as the on state.

[0291] Figure 22 (B) is a table showing the correspondence between the current input to the power sensor 726 and the output potential.

[0292] The current value obtained by subtracting the current flowing in the second input terminal 7252 by amplification to G times from the current flowing in the first input terminal 7212 is the detection current I. DETIn the above case, output terminal 7222 outputs a high level. Output terminal 7222 is connected to switch 130, therefore, in this case, control circuit 720 controls switch 130 to be in the on state.

[0293] The current value obtained by subtracting the current that amplifies the current flowing in the second input terminal 7252 by a factor of G from the current flowing in the first input terminal 7212 is less than the detection current I. DET In this case, output terminal 7222 outputs a low level. Output terminal 7222 is connected to switch 130, therefore, in this case, control circuit 720 controls switch 130 to a non-conducting state.

[0294] Figure 23 This is a diagram illustrating an example of the structure of a power sensor 726a with gain (amplification) switching according to the fourth embodiment. Power sensor 726a is an example of power sensor 726. Structures identical to those in power sensor 726 are labeled with the same symbols, and descriptions are omitted.

[0295] Referring to the figure, an example of gain switching for the power sensor 726a will be explained. As an example, the following situation will be explained: when the power sensor 726a is in the off state, the gain is doubled to prevent malfunction; conversely, when the power sensor 726a is in the on state, the gain is halfdred to make it difficult to switch to the off state.

[0296] In this example, the power sensor 726a includes a gain switch 7264.

[0297] The current amplifier 7261 is connected to the second input terminal 7252 of the power sensor 726a, thereby enabling the current flowing in the second input terminal 7252 to obtain a gain of 2 times.

[0298] When the power sensor 726a is off and a radio wave transmitted from the far field is received, the currents input to the first input terminal 7212 and the second input terminal 7252 are almost the same. Therefore, the current at the second input terminal 7252, which has a gain of 2, increases, and the potential at the output terminal 7222 remains off. That is, the latch module 1m includes the power sensor 726a, thereby preventing malfunctions.

[0299] On the other hand, when the power sensor 726a is in the on state due to receiving near-field electromagnetic waves, the current I flowing in the first input terminal 7212 is used to... INP Set to be greater than the current I flowing in the second input terminal 7252 INM This allows the power sensor 726a to remain on.

[0300] For example, if the gain (amplification) connected to the second input terminal 7252 is changed from 2x to 1 / 2, even if the current input to the first input terminal 7212 and the current input to the second input terminal 7252 are almost the same, the current flowing in the first input terminal 7212 will increase. Therefore, the power sensor 726a will have difficulty switching to the off state. That is, the latch module 1m will easily remain in the on state.

[0301] Figure 24 This figure shows an example of the circuit structure of a power sensor 726a with gain switching according to the fourth embodiment. The same reference numerals are used for structures identical to those of the power sensor 126 described in the first embodiment, and descriptions are omitted. In this figure, the power sensor 726a also includes a current amplifier 7261, a current adder 7262, and a gain switch 7264.

[0302] The current amplifier 7261 includes transistors Q5 and Q6. Both transistors Q5 and Q6 are n-channel transistors. For transistor Q5, its source is connected to ground TG, its gate is connected to its own drain and the gate of transistor Q6, and its drain is connected to the second input terminal 7252. For transistor Q6, its source is connected to ground TG, its gate is connected to the gate of transistor Q5, and its drain is connected to the current adder 7262. Transistors Q5 and Q6 form a current mirror circuit. The current I input to the second input terminal 7252... INM As current I1 flows between the drain and source of transistor Q5. In this example, as current I2, 1 / 2 × I1 flows between the drain and source of transistor Q6.

[0303] The gain switch 7264 includes transistors Q7 and Q8. Transistor Q7 is an n-channel transistor, and transistor Q8 is a p-channel transistor.

[0304] For transistor Q7, the source is connected to ground TG, the gate is connected to the gate of transistor Q6, and the drain is connected to the drain of transistor Q8.

[0305] In the case of transistor Q8, its source is connected to the drain of transistor Q6 and the connection point of current adder 7262, its gate is connected to output terminal 7222, and its drain is connected to the drain of transistor Q7. In this example, current I3, 3 / 2 × I1 flows between the drain and source of transistor Q7.

[0306] Gain switcher 7264 controls current I3 according to the state of output terminal 7222, thereby switching the current value of the current flowing in current adder 7262.

[0307] When output terminal 7222 is low, current I3 flows between the source and drain of transistor Q8. In this case, I2 + I3 (i.e., 1 / 2 × I1 + 3 / 2 × I1 = 2 × I1) flows in current adder 7262, thus the gain becomes twice.

[0308] When output terminal 7222 is high, current does not flow between the source and drain of transistor Q8. In this case, I2 (i.e., 1 / 2 × I1) flows in current adder 7262, and therefore the gain becomes 1 / 2 times.

[0309] Here, the current flowing between the drain and source of the MOS transistor is proportional to the gate width W and inversely proportional to the gate length L.

[0310] The gain of the power sensor 726a can be arbitrarily adjusted based on the gate width W and gate length L of the MOS transistors that constitute transistors Q6 and Q7.

[0311] Figure 25 This figure shows an example of a frame 80 with a waterproof structure according to the fourth embodiment. As shown in the figure, the latching waterproof module 2c includes a latching circuit 10p, a power supply 50 that outputs DC power, a load 60 driven by DC power supplied from the power supply 50, and a frame 80.

[0312] The housing 80 houses the latching circuit 10p, the power supply 50, and the load 60. The housing 80 is waterproof.

[0313] [Summary of the effects of the fourth implementation method]

[0314] According to the embodiment described above, the latching module 1m includes a first antenna 740a and a second antenna 740b having substantially the same characteristics and gain as the first antenna 740a. The control circuit 720 compares the power generated by the radio waves received by the first antenna 740a with the power generated by the radio waves received by the second antenna 740b.

[0315] If the difference between the power generated by the radio wave received by the first antenna 740a and the power generated by the radio wave received by the second antenna 740b is less than a predetermined value, the transmitting point of the radio wave is considered to be in the far field, and therefore, the control circuit 720 does not switch the connection state of the switch 130. If the difference between the power generated by the radio wave received by the first antenna 740a and the power generated by the radio wave received by the second antenna 740b is greater than or equal to a predetermined value, the transmitting point of the radio wave is considered to be in the near field, and therefore, the control circuit 720 switches the connection state of the switch 130.

[0316] Therefore, with regard to the latch module 1m, regardless of the strength of the radio waves from the far field, it can sense that the transmitter is not nearby and prevent malfunctions caused by radio waves from the far field.

[0317] Moreover, these controls utilize the electric field characteristics of the transmitted radio waves, so no battery consumption occurs in the circuit regarding detection.

[0318] Furthermore, according to the above-described embodiment, when the power input from the first input terminal 721 is greater than the power input from the second input terminal 725, the control circuit 720 switches the connection state of the switch 130 to the on state, and when the power input from the first input terminal 721 is less than the power input from the second input terminal 725, the control circuit 720 switches the connection state of the switch 130 to the off state.

[0319] Therefore, the latch module 1m has a control circuit 720, which enables the power supply 50 and the load 60 to be switched to an on state and a non-on state.

[0320] Furthermore, according to the above embodiment, the control circuit 720 includes a power sensor 726. Therefore, the control circuit 720 with the power sensor 726 can maintain the state of the switch 130 with low power consumption.

[0321] Furthermore, according to the above embodiment, the power sensor 726 includes a current amplifier 7261, thereby switching the connection state of the switch 130 when there is a difference between the power input to the first input terminal 7212 and the power input to the second input terminal 7252.

[0322] The power sensor 726 switches the connection state of the switch 130 only when it detects a difference greater than a predetermined value set according to the gain of the current amplifier 7261, thus preventing malfunction.

[0323] Furthermore, according to the above embodiment, the power sensor 726a includes a gain switch 7264, thereby enabling gain switching. This allows switching between the gain when the power sensor 726a is on and when it is off.

[0324] When the power sensor 726a is in the off state, the power sensor 726a increases the weight of the gain, thereby making it easier for the power sensor 726a to remain in the off state and preventing malfunctions.

[0325] When the power sensor 726a is in the ON state, the power sensor 726a reduces the weight of the gain, thereby making it easy to maintain the ON state.

[0326] Furthermore, according to the above embodiment, the first antenna 740a and the second antenna 740b are configured to be at a predetermined distance apart. When the transmitter 70 approaches the first antenna 740a or the second antenna 740b, the connection state of the latch module 1m switch 130 is changed.

[0327] Therefore, since the position where the transmitter 70 is brought close to make the switch 130 in the conducting state is different from the position where the transmitter 70 is brought close to make the switch 130 in the non-conducting state, malfunction can be prevented.

[0328] [Fifth Implementation]

[0329] The fifth embodiment of the present invention will now be described with reference to the accompanying drawings.

[0330] First, the problem to be solved in the fifth embodiment will be explained. Figure 26 This is a diagram used to illustrate the problem to be solved in the fifth embodiment. In this diagram, reference is made to... Figure 3 The structure of the latch module 1b described herein explains the problem to be solved in the fifth embodiment.

[0331] The control circuit 120b has an input terminal 121b, an output terminal 122b, and a power supply terminal 123b as input and output terminals. Power is supplied from the power supply 50 to the power supply terminal 123b, and the control circuit 120b controls the output terminal 122b according to the state of the input terminal 121b. In this case, current I51 flows from the positive terminal of the power supply 50 to the control circuit 120b.

[0332] The control circuit 120b includes a power sensor 126, which has a detection input terminal 1261, a reference input terminal 1262, and a voltage detection output terminal 1263 as input / output terminals. The power sensor 126 is controlled by power supplied to the power supply terminal 123b. The power sensor 126 outputs a potential corresponding to the potential of the detection input terminal 1261 and the potential of the reference input terminal 1262 to the voltage detection output terminal 1263. In this case, current I52 flows from the voltage detection output terminal 1263. Current I52 is branched into current I53 flowing to the detection input terminal 1261 and current I54 flowing to the power conversion circuit 110. Here, the current I54 flowing to the power conversion circuit 110 is an unwanted current, so in this embodiment, the purpose is to reduce current I54. In addition, in the following description, current I54 is sometimes referred to as reverse current.

[0333] Figure 27 This is a diagram illustrating an example of the structure of the latch module 1p according to the fifth embodiment. The latch module 1p is... Figure 3The description describes a variation of latch module 1b. Latch module 1p differs from latch module 1b in that it includes a power conversion circuit 860 instead of a power conversion circuit 110. In the description of latch module 1p, sometimes the same symbols are used to mark structures identical to those in latch module 1b, and the description is omitted.

[0334] The power conversion circuit 860 has a power input terminal 861 as an input terminal and a DC power output terminal 862 as an output terminal. The radio waves received by the antenna 140 are input to the power input terminal 861. The power conversion circuit 860 converts the power obtained from the radio waves received by the antenna 140 into DC power and outputs it. The DC power output terminal 862 outputs the DC power converted by the power conversion circuit 860.

[0335] The power conversion circuit 860 includes a capacitor (first capacitor) C41, a diode (fourth diode) D41, a capacitor (second capacitor) C42, a diode (fifth diode) D42, and a reverse current reduction unit 863.

[0336] Capacitor C41 has a first electrode C41a and a second electrode C41b. The first electrode C41a of capacitor C41 is connected to the power input terminal 861, and the second electrode C41b is connected to the junction of the cathode of diode D41 and the anode of diode D42. Regarding diode D41, the anode is connected to ground TG, and the cathode is connected to the second electrode C41b of capacitor C41. Capacitor C42 has a first electrode C42a and a second electrode C42b. The first electrode C42a of capacitor C42 is connected to the first terminal 8631 of the reverse current reduction unit 863, and the second electrode C42b is connected to ground TG. The anode of diode D42 is connected to the power input terminal 861 via capacitor C41. Furthermore, the cathode of diode D42 is connected to the first electrode C42a of capacitor C42.

[0337] The reverse current reduction unit 863 includes an input terminal 8631 and an output terminal 8632. Current flows from the input terminal 8631 to the output terminal 8632, but not from the output terminal 8632 to the input terminal 8631. That is, the reverse current reduction unit 863 supplies DC power (converted from the power input terminal 861) to the DC power output terminal 862, suppressing the current flowing from the DC power output terminal 862 to the power conversion circuit 860. Therefore, the reverse current reduction unit 863 can suppress the current flowing from the positive terminal of the power supply 50 to the negative terminal of the power supply 50 via the control circuit 120b and the power conversion circuit 860.

[0338] As an example, the reverse current reduction unit 863 includes a diode (third diode) D43. The DC power input to the power input terminal 861 is converted and flows in the forward direction in the diode D43, thereby being supplied to the DC power output terminal 862. The diode D43 can be, for example, a high-frequency Schottky barrier diode with low reverse current.

[0339] Figure 28 This is a diagram showing a first variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 870 will be described with reference to this diagram. The power conversion circuit 870 is a variation of the power conversion circuit 860. In the description of the latch module 1q, sometimes the same symbols are used to denote the same structure as the latch module 1p, and the description is omitted. The latch module 1q differs from the latch module 1p in that it includes the power conversion circuit 870 instead of the power conversion circuit 860.

[0340] The power conversion circuit 870 has a capacitor C51 to replace the capacitor C41 in the power conversion circuit 860, a diode D51 to replace the diode D41, a capacitor C52 to replace the capacitor C42, and a diode D52 to replace the diode D42.

[0341] In this embodiment, diode D52 functions as a reverse current reduction unit 873. Diode D52 can be, for example, a high-frequency Schottky barrier diode with low reverse current.

[0342] Figure 29 This is a diagram showing a second variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 880 will be described with reference to this diagram. The power conversion circuit 880 is a variation of the power conversion circuit 860. In the description of the latch module 1r, sometimes the same symbols are used to denote structures identical to those in the latch module 1p, and the description is omitted. The latch module 1r differs from the latch module 1p in that it includes the power conversion circuit 880 instead of the power conversion circuit 860.

[0343] The power conversion circuit 880 has a capacitor C61 to replace the capacitor C41 in the power conversion circuit 870, a diode D61 to replace the diode D41, a capacitor C62 to replace the capacitor C42, and a diode D62 to replace the diode D42.

[0344] In this embodiment, diode D61 functions as a reverse current reduction unit 873. Diode D61 can be, for example, a high-frequency Schottky barrier diode with low reverse current.

[0345] Figure 30This is a diagram showing a third variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 890 will be described with reference to this diagram. The power conversion circuit 890 is a variation of the power conversion circuit 860. In the description of the latch module 1s, sometimes the same symbols are used to denote structures identical to those in the latch module 1p, and the description is omitted. The latch module 1s differs from the latch module 1p in that it includes the power conversion circuit 890 instead of the power conversion circuit 860.

[0346] The power conversion circuit 890 has a capacitor C71 to replace the capacitor C41 in the power conversion circuit 870, a diode D71 to replace the diode D41, a capacitor C72 to replace the capacitor C42, and a diode D72 to replace the diode D42.

[0347] In this embodiment, the reverse current reduction unit 893 includes a transistor Q11. The transistor Q11 can be, for example, an n-channel MOSFET (metal-oxide-semiconductor field-effect transistor). When the transistor Q11 is an n-channel MOSFET, it functions as a diode by short-circuiting its gate and source. The source of the transistor Q11 is connected to the input terminal 8931 of the reverse current reduction unit 893, and the drain of the transistor Q11 is connected to the output terminal 8932 of the reverse current reduction unit 893.

[0348] Figure 31 This is a diagram showing a fourth variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 890A will be described with reference to this diagram. The power conversion circuit 890A is a variation of the power conversion circuit 890. In the description of the latch module 1t, sometimes the same symbols are used to denote structures identical to those in the latch module 1s, and the description is omitted. The latch module 1t differs from the latch module 1s in that it incorporates the power conversion circuit 890A instead of the power conversion circuit 890.

[0349] The power conversion circuit 890A differs from the power conversion circuit 890 in that it has a reverse current reduction unit 893A instead of the reverse current reduction unit 893. In the description of the power conversion circuit 890A, sometimes the same symbols are used to mark the same structures as those in the power conversion circuit 890, and the description is omitted.

[0350] The reverse current reduction unit 893A includes a transistor Q12. Transistor Q12 can be, for example, a p-channel MOSFET. When transistor Q12 is a p-channel MOSFET, it functions as a diode by short-circuiting its gate and source. The source of transistor Q12 is connected to the output terminal 8932A of the reverse current reduction unit 893A, and the drain of transistor Q12 is connected to the input terminal 8931A of the reverse current reduction unit 893A.

[0351] Figure 32 This is a diagram showing a fifth variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 890B will be described with reference to this diagram. The power conversion circuit 890B is a variation of the power conversion circuit 890. In the description of the latch module 1u, sometimes the same symbols are used to denote structures identical to those in the latch module 1s, and the description is omitted. The latch module 1u differs from the latch module 1s in that it includes the power conversion circuit 890B instead of the backup power conversion circuit 890.

[0352] The power conversion circuit 890B differs from the power conversion circuit 890 in that it has a reverse current reduction unit 893B instead of a reverse current reduction unit 893. In the description of the power conversion circuit 890B, sometimes the same symbols are used to mark the same structures as those in the power conversion circuit 890, and the description is omitted.

[0353] The reverse current reduction unit 893B includes a transistor Q13 and an inverter INV. The transistor Q13 may be, for example, an n-channel MOSFET. In this embodiment, the gate of the transistor Q13 is controlled according to the state of the voltage detection output terminal 1263 provided by the power sensor 126, thereby controlling the conduction state of the transistor Q13. When the transistor Q13 is an n-channel MOSFET, the gate of the transistor Q13 is connected to the voltage detection output terminal 1263 via the inverter INV.

[0354] When control circuit 120b controls switch 130 to the ON state (when voltage detection output terminal 1263 outputs a high level), inverter INV outputs a low level, and transistor Q13 is controlled to the OFF state, with no current flowing through it. Since no current flows through transistor Q13, the reverse current flowing to ground TG via resistor 124b, diode D72, and diode D71 is suppressed. At this time, the voltage input to input terminal 1261 of control circuit 120b is maintained at a high level using resistor 124b; therefore, the ON state of switch 130 is maintained independently of the power supply from DC power output terminal 892A.

[0355] When control circuit 120b controls switch 130 to the non-conducting state (when voltage detection output terminal 1263 outputs a low level), inverter INV outputs a high level, and transistor Q13 is controlled to the conducting state, allowing current to flow. Since voltage detection output terminal 1263 is low, current does not flow through resistor 124b, diode D72, and diode D71 to ground point TG. At this time, because transistor Q13 is controlled to the conducting state, preparation for the subsequent turn-on state can be achieved without obstructing the current flow between power conversion circuit 890B and control circuit 120b.

[0356] That is, when the control circuit 120b controls the connection state of the switch 130 to the on state, the reverse current reduction unit 893B suppresses the current flowing from the DC power output terminal 892B to the power conversion circuit 890B. When the control circuit 120b controls the connection state of the switch 130 to the off state, the DC power converted from the power input terminal 891B is supplied to the DC power output terminal 892B.

[0357] Figure 33 This is a diagram showing a sixth variation of the power conversion circuit according to the fifth embodiment. The power conversion circuit 890C will be described with reference to this diagram. The power conversion circuit 890C is a variation of the power conversion circuit 890B. In the description of the latch module 1v, sometimes the same symbols are used to denote structures identical to those in the latch module 1u, and the description is omitted. The latch module 1v differs from the latch module 1u in that it incorporates the power conversion circuit 890C instead of the power conversion circuit 890B.

[0358] The power conversion circuit 890C differs from the power conversion circuit 890B in that it has a reverse current reduction unit 893C instead of a reverse current reduction unit 893B. In the description of the power conversion circuit 890C, sometimes the same symbols are used to mark the same structures as those in the power conversion circuit 890B, and the description is omitted.

[0359] The reverse current reduction unit 893C includes a transistor Q14. Transistor Q14 may be, for example, a p-channel MOSFET. In this embodiment, the gate of transistor Q14 is controlled according to the state of the voltage detection output terminal 1263 provided by the power sensor 126, thereby controlling the conduction state of transistor Q14. When transistor Q14 is a p-channel MOSFET, the gate of transistor Q14 is connected to the voltage detection output terminal 1263.

[0360] When control circuit 120b controls switch 130 to the ON state (when voltage detection output terminal 1263 outputs a high level), transistor Q14 is controlled to the OFF state and no current flows through it. Since no current flows through transistor Q14, the reverse current flowing to ground TG via resistor 124b, diode D72, and diode D71 is suppressed. At this time, the voltage input to input terminal 1261 of control circuit 120b is maintained at a high level using resistor 124b; therefore, the ON state of switch 130 is maintained independently of the power supply from DC power output terminal 892C.

[0361] When control circuit 120b controls switch 130 to the non-conducting state (when voltage detection output terminal 1263 outputs a low level), transistor Q14 is controlled to the conducting state, and current flows through it. Since voltage detection output terminal 1263 is low, current does not flow to ground point TG through resistor 124b, diode D72, and diode D71. At this time, because transistor Q14 is controlled to the conducting state, preparation for the subsequent turn-on state can be achieved without obstructing the current flow between power conversion circuit 890C and control circuit 120b.

[0362] That is, when the control circuit 120b controls the connection state of the switch 130 to the on state, the reverse current reduction unit 893C suppresses the current flowing from the DC power output terminal 892C to the power conversion circuit 890C. When the control circuit 120b controls the connection state of the switch 130 to the off state, the DC power converted from the power input terminal 891C is supplied to the DC power output terminal 892C.

[0363] By using the structure of power conversion circuit 890C, the inverter INV can be omitted compared to the structure of power conversion circuit 890B, thus enabling the circuit to be constructed with fewer components.

[0364] [Summary of the effects of the fifth implementation method]

[0365] According to the embodiment described above, in the latch module 1p, the power conversion circuit 860 includes a reverse current reduction unit 863. The reverse current reduction unit 863 suppresses the current flowing from the positive terminal of the power supply 50 to the negative terminal of the power supply 50 via the control circuit 120b and the power conversion circuit 860. Therefore, according to this embodiment, power consumption can be reduced. For example, without the reverse current reduction unit 863, the current flowing from the positive terminal of the power supply 50 to the negative terminal of the power supply 50 via the control circuit 120b and the power conversion circuit 860 is about 100 nA (nanoampere), while by including the reverse current reduction unit 863, it can be reduced to about 8 nA.

[0366] Furthermore, according to this embodiment, the power consumption of the power supply 50 can be suppressed, thereby extending the battery life of the power supply 50.

[0367] Furthermore, according to the above embodiment, the reverse current reduction unit 863 supplies DC power, converted from the power input to the power input terminal 861, to the DC power output terminal 862. In addition, the reverse current reduction unit 863 suppresses the current flowing from the DC power output terminal 862 to the power conversion circuit 860. Therefore, the reverse current reduction unit 863 can suppress reverse current without affecting the rectifier circuit.

[0368] Here, the diode used in the rectifier circuit is preferably a Schottky barrier diode with low voltage and fast recovery, so that even small amounts of power can be sensed. According to this embodiment, since it does not affect the rectifier circuit, sensing can be performed even when the power received by the antenna 140 is small.

[0369] Furthermore, according to the above embodiment, the reverse current reduction unit 863 can be a high-frequency Schottky barrier diode. The high-frequency Schottky barrier diode is preferably a high-frequency Schottky barrier diode with low reverse current. Therefore, by using a high-frequency Schottky barrier diode as the reverse current reduction unit 863, reverse current can be suppressed.

[0370] Furthermore, according to the above embodiment, in the latch module 1q, the power conversion circuit 870 includes a reverse current reduction unit 873. The reverse current reduction unit 873 suppresses the current flowing from the DC power output terminal 872 to the ground point via the diode (fourth diode) D51. Therefore, according to this embodiment, reverse current can be suppressed, and power consumption can be reduced.

[0371] Furthermore, according to the above embodiment, in the latch module 1q, the power conversion circuit 870 can suppress reverse current without adding a new component as the reverse current reduction unit 873. Therefore, according to this embodiment, the circuit can be made smaller, and costs can be reduced.

[0372] Furthermore, according to the above embodiment, in the latching module 1q, the reverse current reduction unit 873 includes a diode (fifth diode) D52. Therefore, according to this embodiment, reverse current can be suppressed without adding a new component as the reverse current reduction unit 873. Therefore, according to this embodiment, the circuit can be made smaller, and costs can be reduced.

[0373] Furthermore, according to the above embodiment, the reverse current reduction unit 883 in the latching module 1r includes a diode (fourth diode) D61. Therefore, according to this embodiment, reverse current can be suppressed without adding a new component as the reverse current reduction unit 883. Therefore, according to this embodiment, the circuit can be made smaller, and costs can be reduced.

[0374] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific structure is not limited to these embodiments and may include designs that do not depart from the spirit of the present invention. Furthermore, in the embodiments of the present invention, operation has been described in terms of the current corresponding to the power generated by the electromagnetic waves received by the antenna. However, operation may also be described in terms of the voltage corresponding to the power generated by the electromagnetic waves received by the antenna.

[0375] Symbol Explanation

[0376] 100 latching system

[0377] 1. Latch Module

[0378] 70 transmitters

[0379] 71 Radio Waves

[0380] 10. Latch circuit

[0381] 50 power supply

[0382] 60 load

[0383] 80 frame

[0384] 110 Power Conversion Circuit

[0385] 111 Power Input Terminal

[0386] 112 DC power output terminal

[0387] 113 RF-DC Conversion Circuit

[0388] 114 Boost Circuit

[0389] 120 control circuit

[0390] 121 Input Terminals

[0391] 122 Output Terminals

[0392] 123 Power terminals

[0393] 126 Power Sensor

[0394] 127 trigger

[0395] Transistors Q1, Q2, Q3, and Q4

[0396] diodes D1 and D2

[0397] 130 switch

[0398] 140 antenna

[0399] TG grounding point

[0400] 240 First Antenna

[0401] 340 Second Antenna

[0402] 210 First power conversion circuit

[0403] 310 Second power conversion circuit

[0404] 211 First power input terminal

[0405] 212 First DC power output terminal

[0406] 311 Second power input terminal

[0407] 312 Second DC power output terminal

[0408] 220 Control Circuit

[0409] 221 First Input Terminal

[0410] 222 Output Terminal

[0411] 225 Second Input Terminal

[0412] 224 resistor

[0413] 226 Power Sensor

[0414] 227 trigger

[0415] 500 electric field type antenna

[0416] 600 Magnetic Field Antenna

[0417] T1, T2, T3 are the sending points.

Claims

1. An electronic circuit comprising: a switch connected between a power source that outputs direct current and a load that is driven by direct current supplied from the power source, the switch switching a connection state of the power source and the load from a non-conductive state in which supply of power from the power source to the load is cut off to a conductive state in which the power source supplies power to the load; a power conversion circuit comprising a power input terminal to which power obtained by an antenna capable of receiving an electric wave receiving the electric wave is input, and a direct current output terminal that outputs direct current, the power conversion circuit converting power input to the power input terminal into direct current and outputting the direct current from the direct current output terminal; and a control circuit comprising an input terminal connected to the direct current output terminal of the power conversion circuit, and an output terminal connected to the switch and controlling a connection state of the switch, the control circuit controlling the connection state of the switch to the conductive state when the power conversion circuit outputs direct current by the antenna receiving the electric wave, the control circuit including a power sensor comprising a reference input terminal, a detection input terminal, and a voltage detection output terminal that outputs a potential corresponding to a potential of the detection input terminal and a potential of the reference input terminal, the control circuit further comprising a feedback resistor connecting the detection input terminal and the voltage detection output terminal, the control circuit maintaining the switch in the conductive state after reception of the electric wave is stopped by the feedback resistor feeding back power of the voltage detection output terminal of the power sensor to the detection input terminal when the switch is switched to the conductive state.

2. The electronic circuit according to claim 1, wherein the control circuit further comprises a power terminal to which the power source is supplied, the control circuit maintaining the switch in the conductive state by power supplied from the power source to the power terminal when the switch is switched to the conductive state.

3. The electronic circuit according to claim 1, wherein the control circuit includes a trigger circuit that switches a control signal output from the output terminal.

4. The electronic circuit according to claim 1, wherein the detection input terminal is connected to the voltage detection output terminal.

5. The electronic circuit according to claim 1, wherein a resistance value of the resistor is 10 megaohms or more. further comprising: a first diode having an anode connected to the direct current output terminal of the power conversion circuit and a cathode connected to the power terminal of the control circuit; and a second diode having an anode connected to a connection point of the load and the switch and a cathode connected to the power terminal of the control circuit.

7. The electronic circuit according to any one of claims 1 to 6, wherein the power source comprises a positive terminal and a negative terminal, the power conversion circuit has a reverse current reduction unit that suppresses current flowing from the positive terminal of the power source to the negative terminal of the power source via the control circuit and the power conversion circuit. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 6. The electronic circuit of claim 2, wherein, ​ ​ ​ ​ ​ ​ ​ 8. The electronic circuit according to claim 7, wherein the reverse current reduction unit supplies the direct current power converted from the power input to the direct current power output, and suppresses the current flowing from the direct current power output to the power conversion circuit.

9. The electronic circuit according to claim 8, wherein the reverse current reduction unit includes a third diode, the direct current power converted from the power input flows in the forward direction in the third diode, and thereby, is supplied to the direct current power output.

10. The electronic circuit according to claim 8, wherein the reverse current reduction unit includes a transistor that suppresses the current flowing from the direct current power output to the power conversion circuit when the control circuit controls the connection state of the switch to the on state, and supplies the direct current power converted from the power input to the direct current power output when the control circuit controls the connection state of the switch to the off state.

11. The electronic circuit according to claim 10, wherein the transistor is an n-channel MOSFET.

12. The electronic circuit according to claim 7, wherein the power conversion circuit includes at least: a first capacitor having a first electrode connected to the power input and a second electrode; a fourth diode having an anode connected to a ground and a cathode connected to the second electrode of the first capacitor; a second capacitor having a first electrode connected to the direct current power output and a second electrode connected to a ground; and a fifth diode having an anode connected to the power input via the capacitor and a cathode connected to the first electrode of the second capacitor, the reverse current reduction unit suppresses the current flowing from the direct current power output to the ground via the fourth diode and the fifth diode.

13. The electronic circuit according to claim 12, wherein the reverse current reduction unit includes the fifth diode.

14. The electronic circuit according to claim 12, wherein the reverse current reduction unit includes the fourth diode.

15. A module including: the electronic circuit according to any one of claims 1 to 14; a power supply that outputs direct current power; and a load that is driven by the direct current power supplied from the power supply.

16. The module according to claim 15, wherein the module is housed in a frame having waterproof properties.

17. A system including: the module according to claim 15 or claim 16; and a transmitter that transmits a prescribed electric wave to the module. ​ ​ ​ ​ ​ ​

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