Battery-less sensor circuit.

Abstract

To provide a battery-less sensor circuit in which when generated power is output from a power generation element, the power can be stored in a power storage capacitance while operating a sensor circuit and a voltage detection circuit, and as a result, deterioration in sensing accuracy is reduced.SOLUTION: A battery-less sensor circuit 100 is provided, comprising a power generation element 101, a first switch element 108, a voltage control circuit 105, a first power storage capacitance 109, a sensor circuit 103, and a load 117, wherein the power generation element 101 is connected to the first power storage capacitance 109 via the first switch element 108, a power supply terminal of the sensor circuit 103 is connected to an input terminal of the first switch element 108, the voltage control circuit 105 receives as input, voltage of an input terminal of the first switch element 108 and controls current flowing through the first switch element 108, the load 117 is connected to the first power storage capacitance 109 and the sensor circuit 103.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a battery-less sensor circuit.

Background Art

[0002] Conventional sensor circuits that operate without a battery have a power generation element and operate with the electric power generated by the power generation element because there is no battery as a power source. Since this power generation element is miniaturized due to the need for miniaturization, the generated power is small and it cannot directly drive a load that outputs the result of sensor measurement. Therefore, a conventional battery-less sensor stores the electric power generated by the power generation element in a storage capacitor once, and when the electric power sufficient to operate the load for a predetermined time is stored in the storage capacitor, it operates the load with the stored electric power in the storage capacitor for a predetermined time (for example, see Japanese Unexamined Patent Application Publication No. 2018-085888, FIG. 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional battery-less sensor circuit, since the electric power generated by a small number of power generation elements is stored in a storage capacitor, the load cannot be operated until the electric power sufficient to operate the load voltage for a predetermined time is stored in the storage capacitor. For this reason, in sensing when the change in the sensing value of the sensor is large or occurs frequently, there is a problem that the sensing accuracy deteriorates because the period during which sensing cannot be performed is long. An object of the present invention is to provide a battery-less sensor circuit that can store a storage capacitor while operating a sensor circuit and a voltage detection circuit when electric power is output from a power generation element, and reduces the deterioration of sensing accuracy.

Means for Solving the Problems

[0005] The battery - less sensor circuit of the present invention includes a power - generating element, a first switch element, a voltage - control circuit, a first capacitor, a sensor circuit, and a load. The power - generating element is connected to the first capacitor via the first switch element. The power - supply terminal of the sensor circuit is connected to the input terminal of the first switch element. The voltage - control circuit receives the voltage at the input terminal of the first switch element and controls the current passing through the first switch element. The load is connected to the first capacitor and the sensor circuit.

Advantages of the Invention

[0006] The sensor accuracy of the battery - less sensor circuit can be improved.

Brief Description of the Drawings

[0007]

Figure 1

Embodiments for Carrying out the Invention

[0008] [First Embodiment] Hereinafter, with reference to the drawings, the first embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing an example of the battery - less sensor circuit 100 according to the present embodiment.

[0009] The configuration of the battery-less sensor circuit 100 according to this embodiment will be described. The battery-less sensor circuit 100 of the present invention includes a power generation element 101, a first boost circuit 102, a sensor circuit 103, a voltage control circuit 105, a resistance element 106, a second storage capacitor 104, a first N-channel MOS transistor (hereinafter referred to as an NMOS transistor) 107, a first P-channel MOS transistor (hereinafter referred to as a PMOS transistor) 108, a first storage capacitor 109, a voltage detection circuit 110, a diode 111, a second PMOS transistor 112, a second boost circuit 113, a second NMOS transistor 114, a delay circuit 115, and a wireless transmission circuit 116. The second boost circuit 113, the second NMOS transistor 114, and the wireless transmission circuit 116 constitute a load 117.

[0010] The power generation element 101 has a power output terminal 151. The first boost circuit 102 has a first input terminal 152 and a first output terminal 153. The sensor circuit 103 has a first power supply terminal 154 and a sensor current output terminal 155. The voltage control circuit 105 has a voltage monitor terminal 156 and a control terminal 157. The voltage detection circuit 110 has a voltage detection terminal 158, a second power supply terminal 159, and a detection signal output terminal 160. The second boost circuit 113 has a second input terminal 161, a second output terminal 162, and a third power supply terminal 163. The delay circuit 115 has a detection signal input terminal 164 and a delay signal output terminal 165. The wireless transmission circuit 116 has a fourth power supply terminal 166 and a fifth power supply terminal 167.

[0011] The connection of the battery-less sensor circuit 100 according to this embodiment will be described. The power output terminal 151 of the power generation element 101 is connected to the first input terminal 152 of the first boost circuit 102. The first output terminal 153 of the first boost circuit 102 is connected to the first node 201. The first power supply terminal 154 of the sensor circuit 103 is connected to the first node 201. The sensor current output terminal 155 of the sensor circuit 103 is connected to the first terminal of the second capacitor 104, the drain terminal of the first NMOS transistor 107, and the voltage detection terminal 158 of the voltage detection circuit 110. The voltage monitor terminal 156 of the voltage control circuit 105 is connected to the first node 201. The control terminal 157 of the voltage control circuit 105 is connected to the gate terminal of the first PMOS transistor 108 and the cathode terminal of the diode 111. The first terminal of the resistance element 106 is connected to the first node 201. The second terminal of the resistance element 106 is connected to the anode terminal of the diode 111 and the gate terminal of the second PMOS transistor 112.

[0012] The source terminal of the first PMOS transistor 108 is connected to the first node. The drain terminal of the first PMOS transistor 108 is connected to the first terminal of the first capacitor 109, the source terminal of the second PMOS transistor 112, and the second input terminal 161 of the second boost circuit 113 via the second node 202. The second output terminal 162 of the second boost circuit 113 is connected to the fourth power supply terminal 166 of the wireless transmission circuit 116. The third power supply terminal 163 of the second boost circuit 113 is connected to the source terminal of the second NMOS transistor 114 and the fifth power supply terminal 167 of the wireless transmission circuit 116. The second power supply terminal 159 of the voltage detection circuit 110 is connected to the first node 201. The detection signal output terminal 160 of the voltage detection circuit 110 is connected to the gate terminal of the second NMOS transistor 114 and the detection signal input terminal 164 of the delay circuit 115. The delay signal output terminal 165 of the delay circuit 115 is connected to the gate terminal of the first NMOS transistor 107. The description of the connection to the GND terminal is omitted.

[0013] The operation of the battery-less sensor circuit 100 according to this embodiment will be described. The generated power output from the power output terminal 151 of the power generation element 101 is input to the first input terminal 152 of the first boost circuit 102. The first boost circuit 102 converts the generated power input to the first input terminal 152 into a first boosted power with a higher voltage, and outputs the first boosted power from the first output terminal 153 to the first node 201. The first boosted power supplied to the first node 201 is charged to the first storage capacitor 109 via the first PMOS transistor 108.

[0014] The voltage control circuit 105 operates with the first boosted power input from the first node 201 to the voltage monitor terminal 156. At the same time, the voltage control circuit 105 monitors the voltage of the first node 201 at the voltage monitor terminal 156, and outputs a control signal for controlling the gate of the first PMOS transistor 108 from the control terminal 157. In this way, the voltage control circuit 105 controls the voltage of the first node 201 to a first predetermined voltage equal to or higher than the voltage at which the sensor circuit 103 and the voltage detection circuit 110 can operate.

[0015] The first storage capacitor 109 is charged with the first boosted power via the first PMOS transistor 108. Until the stored voltage of the first storage capacitor 109 reaches the voltage of the first node 201, the first node 201 is controlled to a first predetermined voltage by the first PMOS transistor 108. The second PMOS transistor 112 is turned off because the gate voltage is higher than the gate voltage of the first PMOS transistor 108 due to the diode 111 and the resistance element 106.

[0016] When the stored voltage of the first storage capacitor 109 reaches the voltage of the first node 201, the first PMOS transistor 108 is fully turned on. Since the first node 201 and the second node 202 are connected by the first PMOS transistor 108, the first node 201 and the second node 202 are controlled to a first predetermined voltage by the second PMOS transistor 112. Here, the first PMOS transistor 108 operates as a switch connecting the first node and the second node.

[0017] The sensor circuit 103 operates with the first boosted power input to the first power supply terminal 154. The sensor circuit 103 outputs a sensor current corresponding to the environment measured by the sensor from the sensor current output terminal 155. The sensor current output from the sensor current output terminal 155 of the sensor circuit 103 is stored in the second storage capacitor 104. The stored voltage of the second storage capacitor 104 is input to the voltage detection terminal 158 of the voltage detection circuit 110, and it is detected whether the stored voltage of the second storage capacitor 104 is equal to or higher than a second predetermined voltage. When the voltage detection circuit 110 detects that the stored voltage of the second storage capacitor 104 input to the voltage detection terminal 158 has become equal to or higher than the second predetermined voltage, the voltage detection circuit 110 outputs a detection signal from the detection signal output terminal 160. When a detection signal is output from the voltage detection circuit 110, the second NMOS transistor 114 is turned on.

[0018] When the second NMOS transistor 114 is turned on, the third power supply terminal of the second boosting circuit 113 and the fifth power supply terminal of the wireless transmission circuit 116 are connected to the GND terminal, and the second boosting circuit 113 and the wireless transmission circuit 116 enter an operable state. When the second boosting circuit 113 enters an operable state, the second boosting circuit 113 converts the stored power of the first storage capacitor 109 input from the second input terminal 161 into a higher voltage second boosted power and outputs it as the second boosted power from the second output terminal 162. When the wireless transmission circuit 116 enters an operable state, the wireless transmission circuit 116 operates with the second boosted power input to the fourth power supply terminal 166. The wireless transmission circuit 116 notifies the outside that the second storage capacitor 104 has been charged to the second predetermined voltage by the sensor current output from the sensor circuit 103.

[0019] When the wireless transmission circuit 116 operates, the stored power of the first storage capacitor 109 is consumed for the operation of the wireless transmission circuit 116, so the stored voltage of the first storage capacitor 109 drops to near 0V. However, when a power generation power equal to or more than a predetermined amount is output from the power generation element 101, the first node 201 is controlled to a first predetermined voltage by the voltage control circuit 105.

[0020] The delay circuit 115 delays the detection signal input to the detection signal input terminal 164 by the time until the operation of the wireless transmission circuit 116 is completed, and outputs it from the delay signal output terminal 165. When the detection signal is output from the delay circuit 115, the first NMOS transistor 107 is turned on, so the stored voltage of the second capacitor 104 decreases to near 0V.

[0021] When the voltage detection circuit 110 detects that the stored voltage of the second capacitor 104 input to the voltage detection terminal 158 has become less than the second predetermined voltage, it outputs a detection release signal from the detection signal output terminal 160. When the detection release signal is output from the voltage detection circuit 110, the second NMOS transistor 114 is turned off, so the second boost circuit 113 and the wireless transmission circuit 116 are disconnected from the GND terminal and enter an operation stop state.

[0022] When the second boost circuit 113 and the wireless transmission circuit 116 enter the operation stop state, the charging of the first capacitor 109 is resumed. The delay circuit 115 delays the detection release signal input to the detection signal input terminal 164 by the time until the stored voltage of the second capacitor 104 decreases to near 0V, and outputs it from the delay signal output terminal 165. When the detection release signal is output from the delay circuit 115, the first NMOS transistor 107 is turned off, so the charging of the second capacitor 104 is resumed.

[0023] The setting of the capacitance value of the first storage capacitor 109 and the capacitance value of the second storage capacitor 104 will be described. The first storage capacitor 109 is charged by the generated power of the power generation element 101. The capacitance value of the first storage capacitor 109 is set to be equal to or greater than the capacitance value that can operate the wireless transmission circuit 116 for a predetermined time by the stored power of the first storage capacitor 109 when the charging of the first storage capacitor 109 progresses and the stored voltage of the first storage capacitor 109 reaches the first predetermined voltage. The second storage capacitor is charged by the sensor current output from the sensor circuit 103. The capacitance value of the second storage capacitor 104 is set to be equal to or greater than the capacitance value such that the second time is always longer by comparing the first time until the first storage capacitor 109, in which the power storage has resumed, can store the stored power capable of operating the wireless transmission circuit 116 for a predetermined time, and the second time until the stored voltage of the second storage capacitor reaches the second predetermined voltage detected by the voltage detection circuit 110. By setting the capacitance value in this way, the wireless transmission circuit 116 can operate for a predetermined time with the stored power of the first storage capacitor when the stored voltage of the second storage capacitor reaches the second predetermined voltage.

[0024] In the configuration of the battery-less sensor of the present invention, when realizing, for example, a battery-less UV (ultraviolet) exposure amount sensor, the power generation element 101 is preferably a 1-cell solar cell. The first boost circuit 102 is preferably a boost circuit of a charge pump method. The sensor circuit 103 preferably has a configuration that outputs a sensor current according to the amount of received ultraviolet light, and a configuration that uses power generation by ultraviolet light is preferable because it results in low power consumption. The second boost circuit 113 is preferably a boost circuit using a coil. The wireless transmission circuit 116 preferably has a configuration having a function of outputting a wireless signal. When the voltage of the generated power output from the power generation element 101 is sufficiently high, the generated power may be input to the first node 201 without passing through the first boost circuit 102. When the stored power of the first storage capacitor 109 is sufficiently large, the stored power of the first storage capacitor 109 may be input to the fourth power supply terminal 166 of the wireless transmission circuit 116 without passing through the second boost circuit 113. The first PMOS transistor 108, the second PMOS transistor 112, the first NMOS transistor 107, and the second NMOS transistor 114 operate as switch elements whose on-resistance can be controlled by a control signal.

[0025] According to the battery-less sensor of the present invention, when power is output from the power generation element, while operating the sensor circuit and the voltage detection circuit, the first storage capacitor can store electricity, thus reducing the deterioration of sensing accuracy, which was a conventional problem. This can be achieved.

[0026] Furthermore, since the time it takes for the second storage capacitor charged by the sensor current output from the sensor circuit to reach the second predetermined voltage is output as the sensing result, compared with the conventional sensing method of detecting and storing the sensor current at predetermined time intervals, not only is the detection accuracy improved, but also the power consumption for sensing can be reduced. Therefore, even for a power generation element that has been miniaturized and has a reduced power generation power, sensing can be performed with the power generation power of the power generation element.

[0027] Furthermore, since the voltage of the detection signal that enables the second booster circuit and the load to operate does not decrease as the voltage of the first storage capacitor decreases, even when the voltage of the first storage capacitor decreases, the operation enable state of the second booster circuit and the load can be maintained by the detection signal.

Description of Reference Numerals

[0028] 100, Battery-less Sensor Circuit 101, Power Generation Element 103, Sensor Circuit 104, 109, Storage Capacitor 105, Voltage Control Circuit 110, Voltage Detection Circuit 116, Wireless Transmission Circuit 117, Load

Claims

1. A power generation element, a first switching element, a voltage control circuit, a first capacitor, a sensor circuit, and a load, wherein the power generation element is connected to the first capacitor via the first switching element, a power supply terminal of the sensor circuit is connected to an input terminal of the first switching element, the voltage control circuit receives the voltage of the input terminal of the first switching element and controls the current passing through the first switching element, and the load is a battery-less sensor circuit connected to the first capacitor and the sensor circuit.

2. further comprising a second capacitor and a voltage detection circuit, wherein the second capacitor is connected to the sensor circuit, and the voltage detection circuit receives the stored voltage of the second capacitor and controls the load, the battery-less sensor circuit according to Claim 1.

3. The battery-less sensor circuit according to Claim 2, wherein the capacitance value of the second capacitor is set to a value such that the time for the second capacitor to be charged to a second predetermined voltage by the output of the sensor circuit is longer than the time for the first capacitor to be charged to a first predetermined voltage by the output of the power generation element.

4. The battery-less sensor circuit according to Claim 2, wherein the voltage detection circuit is driven by the input power of the first switching element.

5. further comprising a delay circuit that delays the output signal of the voltage detection circuit by a predetermined time and outputs it, and a second switching element controlled by the signal output from the delay circuit, and the second switching element discharges the second capacitor, the battery-less sensor circuit according to Claim 2.

6. The battery-less sensor circuit according to Claim 1, further comprising a first boost circuit between the power generation element and the first switching element.

7. The battery-less sensor circuit according to Claim 1, wherein the load further comprises a second boost circuit connected to the first capacitor.

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