Sensor device

Abstract

The invention provides a sensor device which is good in detection sensitivity and simple in structure. A sensor device is provided with: a sensor electrode capable of operating as a heating element; an electrostatic detection circuit that detects an electrostatic capacitance of the sensor electrode; a high-side MOSFET provided between a power source for supplying power for heating and the sensor electrode; a low-side MOSFET disposed between the sensor electrode and the reference potential point; a node between the high side MOSFET or the low side MOSFET and the sensor electrode; and a control unit that controls the high-side MOSFET and the low-side MOSFET, the control unit controlling the high-side MOSFET and the low-side MOSFET to be in an ON state when power for heating is supplied from the power source to the sensor electrode, and the control unit controlling the high-side MOSFET and the low-side MOSFET to be in an OFF state when electrostatic capacitance is detected by the electrostatic detection circuit, and applying a predetermined voltage to the node.

Description

Technical Field

[0001] The present disclosure relates to sensor devices. Background Art

[0002] Conventionally, a sensor device includes: an electrode body having a heating element serving as a sensor electrode; a detection device for detecting the electrostatic capacitance of the sensor electrode; a high-side switch disposed between a heating power supply and the heating element; a low-side switch disposed between the heating element and a reference potential point; a gate controller for turning on both the high-side and low-side switches in a detection mode; and a decoupling circuit having a decoupling MOSFET connected between the high-side switch and the heating element. The gate controller turns on the decoupling MOSFET in the heating mode and turns off the decoupling MOSFET in the detection mode. In the detection mode, the decoupling circuit supplies a third potential to a first node connected between the high-side switch and the decoupling MOSFET. Furthermore, a potential different from the third potential is supplied to a node between the low-side switch and the heating element (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: U.S. Patent Application Publication No. 2023 / 0046256 Summary of the Invention

[0006] -Problems to be solved by the invention-

[0007] However, conventional sensor devices include a high-side switch, a low-side switch, a decoupling MOSFET, a first node, and a node supplied with a potential different from a third potential, resulting in a complex structure. Meanwhile, sensor devices require good detection sensitivity when detecting the electrostatic capacitance of sensor electrodes. However, the presence of parasitic capacitance in the MOSFETs serving as the high-side and low-side switches reduces detection sensitivity, and therefore, it is desirable to minimize this reduction in detection sensitivity.

[0008] Therefore, an object of the present invention is to provide a sensor device having excellent detection sensitivity and a simple structure.

[0009] -Methods for solving the problem-

[0010] A sensor device according to an embodiment of the present disclosure includes: a sensor electrode capable of operating as a heating element; an electrostatic detection circuit for detecting electrostatic capacitance between the sensor electrode and an object; a high-side switch provided between a power supply for supplying heating power to the sensor electrode and the sensor electrode; a low-side switch provided between the sensor electrode and a reference potential point; a node located between the high-side switch or the low-side switch and the sensor electrode; and a control unit for controlling the high-side switch and the low-side switch, wherein the control unit controls the high-side switch and the low-side switch to be in an on state when the heating power is supplied from the power supply to the sensor electrode, and controls the high-side switch and the low-side switch to be in an open state when the electrostatic detection circuit detects the electrostatic capacitance, and applies a given voltage to the node.

[0011] -Effects of the Invention-

[0012] A sensor device having good detection sensitivity and a simple structure can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram schematically showing a steering wheel on which the sensor device according to the embodiment is mounted.

[0014] Figure 2 This is a diagram showing an example of a circuit configuration of a sensor device according to an embodiment.

[0015] Figure 3 This is a diagram showing an example of parasitic capacitance Coss between the drain and source of the high-side MOSFET and the low-side MOSFET of the sensor device according to the embodiment.

[0016] Figure 4A This is a diagram showing an example of electrical characteristics of a high-side MOSFET.

[0017] Figure 4B This is a diagram showing an example of electrical characteristics of a low-side MOSFET.

[0018] Figure 5A This is a diagram showing an example of a circuit configuration of a portion of a sensor device according to a modified example of the embodiment.

[0019] Figure 5B This is a diagram showing an example of a circuit configuration of a portion of a sensor device according to a modified example of the embodiment.

[0020] -Description of Reference Numerals-

[0021] 51 Power Supply

[0022] 100 sensor devices

[0023] 110 sensor electrodes

[0024] 120 Heater drive circuit

[0025] 121 High-side MOSFET (Example of a high-side switch)

[0026] 122 Low-side MOSFET (Example of a low-side switch)

[0027] 123 nodes

[0028] R1 resistor (an example of the first voltage-dividing resistor)

[0029] R2 resistor (an example of a second voltage-dividing resistor)

[0030] 130 static electricity detection circuit

[0031] 132 AC signal source

[0032] 140 control circuit. DETAILED DESCRIPTION

[0033] Hereinafter, embodiments of a sensor device to which the present disclosure is applied will be described.

[0034] <Implementation Method>

[0035] Figure 1 1 is a diagram schematically showing a steering wheel 10 equipped with a sensor device 100 according to an embodiment. The sensor device 100 includes a sensor electrode 110, a heater drive circuit 120, a static electricity detection circuit 130, and a control circuit 140. The control circuit 140 is an example of a control unit.

[0036] The steering wheel 10 is mounted on a vehicle, and the sensor electrode 110 of the sensor device 100 is mounted on the inner side of the surface of the rim 11. The sensor electrode 110 is an example of a sensor electrode that can function as a heating element. The sensor device 100 determines whether the driver's hand is in contact with the rim 11 of the steering wheel 10. Furthermore, the sensor device 100 heats the steering wheel 10 by supplying heating power to the sensor electrode 110. In other words, the sensor device 100 has both the functions of HOD (Hands On Detect) and a steering wheel heater. A hand is an example of an object. The rim 11 of the steering wheel 10 is an example of a fixing portion that fixes the sensor electrode 110. The surface 11A of the rim 11 is an example of a contact area that can be touched by the detection object.

[0037] Hereinafter, the driver of the vehicle is referred to as the operator of the sensor device 100. The operator touching the rim 11 of the steering wheel 10 provided with the sensor electrode 110 is referred to as the operator's operation.

[0038] The steering wheel 10 has a rim 11 , a hub 12 , and spokes 13 . Figure 1 The rim 11, the hub 12 and the spokes 13 are shown as the core metal of the rim 11, the hub 12 and the spokes 13. Figure 1 In FIG. 1 , in order to show the sensor electrode 110 , the skin 11A of the rim 11 is separated from the rim 11 and shown. Figure 1 In the figure, the cover covering the hub 12 and the spokes 13 is omitted.

[0039] The ground terminal of the steering wheel 10 is electrically connected to a core bar provided around the rim 11 of the steering wheel 10. By connecting the core bar to the ground terminals of the heater drive circuit 120, the static electricity detection circuit 130, and the control circuit 140 via a connector (not shown), the ground potential of the heater drive circuit 120, the static electricity detection circuit 130, and the control circuit 140 is equal to the ground potential of the steering wheel 10.

[0040] <Schematic Structure of Sensor Device 100 >

[0041] The sensor device 100 includes a sensor electrode 110, a heater driving circuit 120, an electrostatic detection circuit 130, and a control circuit 140. The control circuit 140 may be an ECU (Electronic Control Unit). Figure 1 , the connection relationship among the sensor electrode 110 , the heater driving circuit 120 , the static electricity detection circuit 130 , and the control circuit 140 is briefly shown, but the control circuit 140 is also connected to the heater driving circuit 120 via a cable and a connector (not shown).

[0042] Sensor device 100 has two modes: a heating mode in which heating power is supplied to sensor electrode 110 from the vehicle's power supply, and a non-heating mode in which the heating power supply to sensor electrode 110 is stopped. Sensor device 100 can also detect static capacitance using static detection circuit 130 in the non-heating mode. Control circuit 140 switches between the two modes in a time-sharing manner. Specifically, control circuit 140 selectively switches between the heating mode and the non-heating mode over time.

[0043] <Sensor electrode 110>

[0044] The sensor electrodes 110 are provided around the rim 11 of the steering wheel 10, insulated from a core metal provided around the rim 11 of the steering wheel 10. The sensor electrodes 110 are connected to the heater drive circuit 120, the static electricity detection circuit 130, and the control circuit 140 via signal lines, etc. The sensor electrodes 110 are thin sheet-like or strip-like electrodes provided around the rim 11, and can be manufactured, for example, by applying a conductive material such as silver paste to the surface of a resin film.

[0045] <Heater drive circuit 120>

[0046] The heater drive circuit 120 is connected to the sensor electrode 110 , and supplies heating power to the sensor electrode 110 from a power source of the vehicle in a heating mode.

[0047] <Static Electricity Detection Circuit 130>

[0048] The static electricity detection circuit 130 is connected to the sensor electrode 110 and detects the static capacitance between the sensor electrode 110 and the operator's hand.

[0049] <Control Circuit 140>

[0050] The control circuit 140 is implemented by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), input / output interfaces, and an internal bus. The control circuit 140 switches the mode of the sensor device 100 between a heating mode and a non-heating mode. The control circuit 140 controls the high-side MOSFET 121 and the low-side MOSFET 122. In the heating mode, the control circuit 140 turns both the high-side MOSFET 121 and the low-side MOSFET 122 into a conductive state (on). In the non-heating mode, the control circuit 140 turns both the high-side MOSFET 121 and the low-side MOSFET 122 into a non-conductive state (off).

[0051] <Circuit Configuration of Sensor Device 100>

[0052] Figure 2 2 is a diagram showing an example of a circuit configuration of the sensor device 100 . Figure 2 The power supply circuit 50 of the vehicle 1 equipped with the sensor device 100 is also shown. The power supply circuit 50 includes a power supply 51 and a relay 52. ​​As an example, the power supply 51 is a battery of the vehicle 1. Figure 2In the description, the power source 51 is described as a battery, but the power source 51 may include a generator, a regeneration device, etc. of the vehicle 1 in addition to the battery. The output voltage of the power source 51 is V1.

[0053] The power supply circuit 50 includes two power supply paths, 50A and 50B. Both the power supply paths 50A and 50B are connected to a power source 51 and branched midway. A relay 52 is inserted in series in the power supply path 50B.

[0054] <Sensor electrode 110>

[0055] The sensor electrode 110 is provided on the steering wheel 10 and is connected to the heater driving circuit 120. More specifically, Figure 1 As shown, the sensor electrode 110 is a conductor having two ends, one end of which is connected to the node 125 . The other end of the sensor electrode 110 is connected to the drain of the low-side MOSFET 122 .

[0056] The parasitic capacitance between the sensor electrode 110 and the ground potential point is Crgl, and the capacitance between the sensor electrode 110 and the hand H is Chg. The capacitance Chg varies greatly depending on whether the hand H touches the sensor electrode 110 .

[0057] <Heater drive circuit 120>

[0058] Heater drive circuit 120 includes a high-side MOSFET 121, a low-side MOSFET 122, a node 123, a resistor R1, and a resistor R2. High-side MOSFET 121 is an example of a high-side switch, and low-side MOSFET 122 is an example of a low-side switch. Resistor R1 is an example of a first voltage-dividing resistor, and resistor R2 is an example of a second voltage-dividing resistor.

[0059] The high-side MOSFET 121 is, for example, a P-channel MOSFET, with its source connected to the power supply 51 via the node V1 and the relay 52, its drain connected to the sensor electrode 110 and the node 123, and its gate connected to the control circuit 140. Node V1 is a node with a voltage value of V1 and is located between the source of the high-side MOSFET 121 and the relay 52. ​​The high-side MOSFET 121 is provided between the power supply 51 and the sensor electrode 110 and is driven by a PWM gate drive signal supplied to the gate from the control circuit 140.

[0060] Low-side MOSFET 122 is, for example, a P-channel MOSFET. Its drain is connected to sensor electrode 110 and node 123, its source is connected to node V2, and its gate is connected to control circuit 140. Node V2 has a voltage value of V2 (< V3 < V1) and is an example of a reference potential point maintained at ground potential. Low-side MOSFET 122 is provided between sensor electrode 110 and node V2 and is driven by a gate drive signal supplied to the gate from control circuit 140.

[0061] Node 123 is connected between resistors R1 and R2 and is supplied with a voltage V3 obtained by dividing the DC power (voltage V1) supplied from power supply 51 to resistor R1 by resistors R1 and R2. Voltage V3 is an example of a given voltage. Node 123 is connected between resistors R1 and R2, the drain of high-side MOSFET 121, sensor electrode 110, and capacitor 134 of static electricity detection circuit 130.

[0062] <Static Electricity Detection Circuit 130>

[0063] The static electricity detection circuit 130 includes a charge amplifier 131, an AC signal source 132, an amplitude adjustment unit 133, and a capacitor Cd. In the non-heating mode, the static electricity detection circuit 130 detects the static capacitance of the sensor electrode 110. The AC signal source 132 is an example of a sine wave signal source.

[0064] The charge amplifier 131 has a positive-inverting input terminal (+) connected to the output terminal of the amplitude adjustment unit 133, a negative-inverting input terminal (-) connected to the sensor electrode 110 via a capacitor Cd, and an output terminal connected to the control circuit 140. The output voltage at the output terminal of the charge amplifier 131 is V0. The charge amplifier 131 is a differential amplifier that amplifies the difference between the input at the positive-inverting input terminal (+) and the input at the negative-inverting input terminal (-) and outputs an output signal.

[0065] AC signal source 132 is connected to amplitude adjustment unit 133 and to sensor electrode 110 via capacitor Cd. AC signal source 132 outputs an AC signal (sine wave signal) that drives sensor electrode 110. Alternatively, AC signal source 132 may output an AC signal that drives sensor electrode 110 only in the non-heating mode.

[0066] When there is no object, i.e., a hand H, approaching the sensor electrode 110 (parasitic capacitance Crg is zero), the amplitude adjustment unit 133 adjusts the amplitude so as to eliminate the difference between the inverting input terminal (−) and the non-inverting input terminal (+) and minimize the output Vo.

[0067] The capacitor Cd has a terminal (−) connected to the inverting input terminal (−) of the charge amplifier 131 and the amplitude adjustment unit 133. Figure 2 (left terminal in FIG); and a terminal connected to sensor electrode 110. Specifically, capacitor Cd is inserted in series between the inverting input terminal (-) of charge amplifier 131 and sensor electrode 110. Capacitor Cd is an example of a DC isolation capacitor provided to block the DC component between heater drive circuit 120 and static electricity detection circuit 130.

[0068] <Control Circuit 140>

[0069] In the non-heating mode, the control circuit 140 outputs an H (high) level gate drive signal to the gate of the high-side MOSFET 121 and an L (low) level gate drive signal to the gate of the low-side MOSFET 122. This causes the high-side MOSFET 121 and the low-side MOSFET 122 to be non-conductive (off). By making the high-side MOSFET 121 and the low-side MOSFET 122 non-conductive (off), the sensor electrode 110 is not affected by the power supply circuit 50.

[0070] In the non-heating mode, the control circuit 140 digitally converts the signal output from the charge amplifier 131 and demodulates it using a demodulation signal having the same frequency as the AC signal. Based on the demodulated output, the control circuit 140 determines whether the hand H is touching the sensor electrode 110 .

[0071] Furthermore, in the heating mode, the control circuit 140 outputs an L-level gate drive signal to the gate of the high-side MOSFET 121 and an H-level gate drive signal to the gate of the low-side MOSFET 122. As a result, the high-side MOSFET 121 and the low-side MOSFET 122 are turned on.

[0072] When the temperature of the steering wheel 10 is below the target temperature, the control circuit 140 periodically switches the gate drive signals output to the gates of the high-side MOSFET 121 and the low-side MOSFET 122. Except for the time required to detect the electrostatic capacitance of the sensor electrode 110, the high-side MOSFET 121 and the low-side MOSFET 122 are kept in the conductive state (ON) to heat the sensor electrode 110. On the other hand, when the temperature of the steering wheel 10 exceeds the target temperature, the control circuit 140 keeps the high-side MOSFET 121 and the low-side MOSFET 122 in the open state (OFF). Alternatively, when switching the heating power in multiple stages, the control circuit 140 can perform PWM control of the high-side MOSFET 121 and the low-side MOSFET 122. In this case, the duty cycle of the PWM signal can be determined by the control circuit 140 through feedback control based on the target temperature of the steering wheel 10 heater, the current temperature of the steering wheel 10 heater, and other factors. Alternatively, the temperature of the steering wheel 10 heater can be measured by a temperature sensor provided on the steering wheel 10.

[0073] <Parasitic Capacitance of High-Side MOSFET 121 and Low-Side MOSFET 122>

[0074] Figure 3 1 is a diagram showing an example of parasitic capacitance Coss between the drain and source of the high-side MOSFET 121 and the low-side MOSFET 122. The parasitic capacitance Coss of the high-side MOSFET 121 is an example of a first parasitic capacitance, and the parasitic capacitance Coss of the low-side MOSFET 122 is an example of a second parasitic capacitance.

[0075] exist Figure 3 Shown in Figure 2 Among the components shown, the sensor electrode 110 , the high-side MOSFET 121 , the low-side MOSFET 122 , the node 123 , and the capacitor 134 of the static electricity detection circuit 130 are shown, and other components are omitted.

[0076] A parasitic capacitance Coss exists between the drain and source of high-side MOSFET 121 and low-side MOSFET 122. MOSFETs have an electrical characteristic in which the parasitic capacitance Coss between the drain and source changes with the voltage between the drain and source. Generally, the greater the voltage between the drain and source, the smaller the parasitic capacitance Coss.

[0077] Therefore, in the P-channel high-side MOSFET 121 , the greater the voltage between the source and the drain, the smaller the parasitic capacitance Coss. In the N-channel low-side MOSFET 122 , the greater the voltage between the drain and the source, the smaller the parasitic capacitance Coss.

[0078] Parasitic capacitance Coss affects the detection sensitivity when detecting the electrostatic capacitance of sensor electrode 110. Specifically, in sensor device 100, in the non-heating mode for detecting the electrostatic capacitance of sensor electrode 110, in order to minimize the decrease in detection sensitivity and obtain good detection sensitivity, it is preferable to reduce parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122 to a certain extent.

[0079] In the sensor device 100 , in order to reduce the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 , a node 123 is connected between the drain of the P-channel high-side MOSFET 121 and the sensor electrode 110 .

[0080] The voltage V3 supplied to the node 123 is lower than the voltage V1 supplied to the source of the high-side MOSFET 121 , and higher than the voltage V2 (GND) supplied to the source of the low-side MOSFET 122 .

[0081] Therefore, by appropriately setting the voltage V3 , it is possible to reduce the voltage between the source and drain of the parasitic capacitance Coss of the high-side MOSFET 121 and reduce the voltage between the drain and source of the parasitic capacitance Coss of the low-side MOSFET 122 .

[0082] Adjustment of voltage V3 can be achieved by adjusting the ratio of the resistance values ​​of resistors R1 and R2. As a prerequisite, the electrical characteristics of the parasitic capacitance Coss that change with respect to the voltage between the drain and source of high-side MOSFET 121 and low-side MOSFET 122 are equal. This is because if the electrical characteristics of high-side MOSFET 121 and low-side MOSFET 122 are equal, it is easy to set the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122.

[0083] In this case, voltage V3 can be any voltage intermediate between voltage V1 and voltage V2 (GND). Preferably, voltage V3 is a voltage obtained by adding 40% to 60% of the voltage difference between voltages V1 and V2 to voltage V2, and most preferably, a voltage obtained by adding 50% of the voltage difference between voltages V1 and V2. In other words, voltage V3 is most preferably a voltage obtained by adding half the voltage difference between voltages V1 and V2 to voltage V2.

[0084] Alternatively, the voltage V3 may be a voltage that makes the parasitic capacitance Coss of the high-side MOSFET 121 and the parasitic capacitance Coss of the low-side MOSFET 122 substantially the same. The parasitic capacitance Coss of the high-side MOSFET 121 and the parasitic capacitance Coss of the low-side MOSFET 122 being substantially the same means, for example, that the difference between the parasitic capacitance Coss of the high-side MOSFET 121 and the parasitic capacitance Coss of the low-side MOSFET 122 is within ±10%.

[0085] <Example of Electrical Characteristics of the High-Side MOSFET 121 and the Low-Side MOSFET 122 in the Sensor Device 100>

[0086] Figure 4A 1 is a diagram showing an example of the electrical characteristics of the high-side MOSFET 121 . Figure 4B 1 is a diagram showing an example of the electrical characteristics of the low-side MOSFET 122. Figure 4A In the graph, the horizontal axis represents the voltage VSD (V) of the source to the drain of the P-channel high-side MOSFET 121. Figure 4B In FIG, the horizontal axis represents the voltage VDS (V) of the drain of the N-channel low-side MOSFET 122 relative to the source. Figure 4A as well as Figure 4B In the figure, the vertical axis represents the parasitic capacitance Coss (pF). Figure 4A as well as Figure 4B In FIG. 1 , the region where the voltage on the horizontal axis is approximately 1 V or higher is a region where the parasitic capacitance Coss decreases sharply.

[0087] Here, when describing the electrical characteristics of the high-side MOSFET 121 and the low-side MOSFET 122 in the sensor device 100 , the electrical characteristics of the high-side MOSFET 121 and the low-side MOSFET 122 in a comparative sensor device are also described.

[0088] The comparative sensor device has a configuration in which node 123 is omitted from sensor device 100 of the embodiment. In the comparative sensor device not including node 123, the drain voltage of high-side MOSFET 121 is lower than that of sensor device 100 of the embodiment, and the drain voltage of low-side MOSFET 122 is lower.

[0089] That is, in the comparative sensor device, the source-drain voltage VSD of the high-side MOSFET 121 is larger, and the drain-source voltage VDS of the low-side MOSFET 122 is smaller, compared to the sensor device 100 according to the embodiment.

[0090] Therefore, in the comparative sensor device, the parasitic capacitance Coss of the high-side MOSFET 121 is smaller than that of the sensor device 100 according to the embodiment, and the parasitic capacitance Coss of the low-side MOSFET 122 is larger.

[0091] That is, the parasitic capacitance Coss of the high-side MOSFET 121 of the comparative sensor device becomes, for example, Figure 4A The parasitic capacitance Coss of the low-side MOSFET 122 of the comparative sensor device is as small as the value (about 150 pF) indicated by the black circle (●). Figure 4B The large value (about 1000 pF) shown by the black circle (●) in the middle. The total of the two parasitic capacitances Coss is about 1150 pF. This total parasitic capacitance becomes the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point. Therefore, the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point is very large.

[0092] In the comparative sensor device, the voltage VSD between the source and the drain of the high-side MOSFET 121 is large, and the voltage VDS between the drain and the source of the low-side MOSFET 122 is small, so that the parasitic capacitance Coss of the low-side MOSFET 122 is large, and therefore the parasitic capacitance Crgl is very large, and the detection sensitivity when detecting the electrostatic capacitance of the sensor electrode 110 is greatly reduced.

[0093] In contrast, in the sensor device 100 , the node 123 having the voltage V3 ( V2 < V3 < V1 ) allows the source-drain voltage VSD of the high-side MOSFET 121 and the drain-source voltage VDS of the low-side MOSFET 122 to be high.

[0094] Therefore, the parasitic capacitance Coss of the high-side MOSFET 121 of the sensor device 100 of the embodiment becomes, for example, Figure 4A For example, the parasitic capacitance Coss of the low-side MOSFET 122 of the sensor device 100 is as small as the value (about 200 pF) shown by the white circle (○). Figure 4BThe small value (approximately 200 pF) shown in the middle white circle (○) is shown. The parasitic capacitance Coss of high-side MOSFET 121 (approximately 200 pF) is slightly larger than the parasitic capacitance Coss of high-side MOSFET 121 in the comparative sensor device (approximately 150 pF), but sufficiently smaller. Furthermore, the parasitic capacitance Coss of low-side MOSFET 122 (approximately 200 pF) is significantly smaller than the parasitic capacitance Coss of low-side MOSFET 122 in the comparative sensor device (approximately 1000 pF), achieving a favorable value. Furthermore, the parasitic capacitance Coss of high-side MOSFET 121 (approximately 200 pF) and the parasitic capacitance Coss of low-side MOSFET 122 (approximately 200 pF) are approximately equal.

[0095] The total of the two parasitic capacitances Coss is approximately 400 pF. This total parasitic capacitance becomes the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point. Therefore, the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point is very small.

[0096] Therefore, in the sensor device 100 of the embodiment, the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 can be reduced at the same time, so that the parasitic capacitance Crgl is very small, thereby minimizing the reduction in detection sensitivity when detecting the electrostatic capacitance of the sensor electrode 110 and obtaining good detection sensitivity.

[0097] More specifically, the sensor device 100 of the embodiment can reduce the parasitic capacitance Crgl by approximately 65% ​​compared to the comparative sensor device, thereby minimizing the reduction in detection sensitivity when detecting the electrostatic capacitance of the sensor electrode 110 and achieving good detection sensitivity.

[0098] Such a low parasitic capacitance Crg1 is achieved by setting the voltage V3 of the node 123 to an appropriate value. Therefore, it is sufficient to set the voltage V3 to an optimized value that reduces the parasitic capacitance Crg1, and it is sufficient to set the resistance values ​​of the resistors R1 and R2 to appropriate values. As an example, the appropriate resistance values ​​of the resistors R1 and R2 are equal to each other.

[0099] Modifications

[0100] Figure 5A as well as Figure 5B FIG. 1 is a diagram showing an example of a circuit configuration of a portion of a sensor device 100 according to a modified example of the embodiment. Figure 5A as well as Figure 5B FIG. 1 shows the sensor device 100 corresponding to Figure 3 Part of the section shown.

[0101] <Circuit Structure Shown in Figure 5A>

[0102] exist Figure 5A In FIG. 1 , node 123 is connected between sensor electrode 110 and the drain of low-side MOSFET 122. The voltage V3 at node 123 can be Figure 3 The voltage V3 of the node 123 is shown to be the same.

[0103] exist Figure 5A In the circuit structure shown, the drain of the high-side MOSFET 121 is connected to the node 123 via the sensor electrode 110, and the drain of the low-side MOSFET 122 is directly connected to the node 123. Figure 5A The voltage VSD between the source and drain of the high-side MOSFET 121 and the voltage VDS between the drain and source of the low-side MOSFET 122 are shown in FIG. Figure 3 In the illustrated sensor device 100 , a source-drain voltage VSD of the high-side MOSFET 121 and a drain-source voltage VDS of the low-side MOSFET 122 are substantially equal.

[0104] Therefore, if Figure 5A As shown, in the circuit structure in which the node 123 is connected between the sensor electrode 110 and the drain of the low-side MOSFET 122, the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 can also be reduced at the same time, thereby minimizing the reduction in detection sensitivity when detecting the static capacitance of the sensor electrode 110 and obtaining good detection sensitivity.

[0105] < Figure 5B Circuit structure shown>

[0106] exist Figure 5B In FIG, the high-side MOSFET 121 is replaced with an N-channel type. The N-channel type high-side MOSFET 121 has a connection relationship in which the positions of the source and the drain of the P-channel type high-side MOSFET 121 are reversed.

[0107] When driving the N-channel high-side MOSFET 121, Figure 3 Compared with the case of the high-side MOSFET 121 shown in FIG. 1 , the control circuit 140 may simply invert the H level and the L level.

[0108] Thus, even if the high-side MOSFET 121 is an N-channel type, Figure 2 as well as Figure 3 Similarly, the sensor device 100 shown can minimize the decrease in detection sensitivity when detecting the electrostatic capacitance of the sensor electrode 110 , thereby achieving good detection sensitivity.

[0109] Effects

[0110] The sensor device 100 includes: a sensor electrode 110, which can operate as a heating element; an electrostatic detection circuit 130, which detects the electrostatic capacitance between the sensor electrode 110 and an object; a high-side MOSFET 121, which is arranged between the power supply 51 that supplies heating power to the sensor electrode 110 and the sensor electrode 110; a low-side MOSFET 122, which is arranged between the sensor electrode 110 and a reference potential point; a node 123, which is located between the high-side MOSFET 121 or the low-side MOSFET 122 and the sensor electrode 110; and a control circuit 140, which controls the high-side MOSFET 121 and the low-side MOSFET 122. When the power supply 51 supplies heating power to the sensor electrode 110, the control circuit 140 controls the high-side MOSFET 121 and the low-side MOSFET 122 to be in the on state, and when the electrostatic detection circuit 130 detects the electrostatic capacitance, the control circuit 140 controls the high-side MOSFET 121 and the low-side MOSFET 122 to be in the open state, and applies a voltage V3 to the node 123. Therefore, the voltage between the drain and source of the high-side MOSFET 121 and the low-side MOSFET 122 can be increased to a certain extent, so that the reduction in detection sensitivity when detecting the electrostatic capacitance of the sensor electrode 110 can be suppressed to a minimum and good detection sensitivity can be obtained. In addition, since the number of structural elements is small, the structure is simple.

[0111] Therefore, it is possible to provide the sensor device 100 having excellent detection sensitivity and a simple structure.

[0112] Alternatively, voltage V3 may be a voltage intermediate between the supply voltage (V1) supplied from power supply 51 to high-side MOSFET 121 and the voltage at the reference potential point (GND). Using voltage V3, which is an intermediate voltage between voltages V1 and GND, increases the voltage at the terminal of low-side MOSFET 122 on the sensor electrode 110 side, minimizing the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122. This provides a sensor device 100 with excellent detection sensitivity and a simple structure.

[0113] Alternatively, voltage V3 may be a voltage obtained by adding half the voltage difference between the supply voltage (V1) and the voltage at the reference potential point (GND) to the voltage at the reference potential point (GND). Using voltage V3, which is the midpoint between voltages V1 and GND, increases the voltage at the terminal of low-side MOSFET 122 on the sensor electrode 110 side. This reduces the parasitic capacitance Coss between high-side MOSFET 121 and low-side MOSFET 122, achieving a balanced parasitic capacitance Coss between high-side MOSFET 121 and low-side MOSFET 122. This provides a sensor device 100 with excellent detection sensitivity and a simple structure.

[0114] Alternatively, voltage V3 may be a voltage that makes the parasitic capacitance Coss of high-side MOSFET 121 and the parasitic capacitance Coss of low-side MOSFET 122 approximately equal. By using voltage V3 that makes the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122 approximately equal, it is possible to achieve a state in which the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122 is small and balanced. This allows for a sensor device 100 with excellent detection sensitivity and a simple structure.

[0115] Furthermore, a resistor R1 connected between power supply 51 and node 123 and a resistor R2 connected between node 123 and a reference potential point may also be included. Voltage V3 is the voltage divided by resistors R1 and R2. By dividing the voltage of power supply 51 using resistors R1 and R2, voltage V3 can be easily obtained and can be stable. Consequently, a sensor device 100 with excellent detection sensitivity, a simple structure, and stable operation can be provided.

[0116] In addition, the sensor may further include: a resistor R1 connected between the power supply 51 and the node 123; and a resistor R2 connected between the node 123 and the reference potential point. The voltage V3 is the voltage divided by the resistors R1 and R2, and the resistance values ​​of the resistors R1 and R2 are equal. By dividing the voltage of the power supply 51 using the resistors R1 and R2, the voltage V3 can be easily obtained, and a stable voltage V3 can be obtained. In addition, by making the resistance values ​​of the resistors R1 and R2 equal, the voltage V3 becomes the midpoint between the voltage V1 and the voltage GND. Therefore, the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 can be small, and the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 can be balanced. In this way, a sensor device 100 with good detection sensitivity and a simple structure can be provided.

[0117] Furthermore, the electrical characteristics of high-side MOSFET 121 and low-side MOSFET 122 can be made equal. By making the electrical characteristics of high-side MOSFET 121 and low-side MOSFET 122 equal, it is easier to set the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122. This provides a sensor device 100 that has excellent detection sensitivity, a simple structure, and easy setting of the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122.

[0118] Furthermore, the control circuit 140 may periodically drive the high-side MOSFET 121 and the low-side MOSFET 122 when power for heating is supplied from the power supply 51 to the sensor electrode 110. This allows efficient heating based on the target value when the sensor electrode 110 is used as a heater, the current heater temperature, and the like.

[0119] Furthermore, an AC signal source 132 capable of supplying a sinusoidal wave signal to the sensor electrode 110 may be further included. When the static capacitance is detected by the static detection circuit 130, the control circuit 140 causes the AC signal source 132 to supply the sinusoidal wave signal to the sensor electrode 110. When the sinusoidal wave signal is supplied to the sensor electrode 110, the presence or absence of an object can be determined with high accuracy.

[0120] Furthermore, a capacitor Cd for DC isolation may be further provided between the AC signal source 132 and the sensor electrode 110 . By isolating the static electricity detection circuit 130 from the DC signal, the static capacitance of the sensor electrode 110 can be accurately detected.

[0121] Alternatively, the node 123 may be provided between the sensor electrode 110 and the high-side MOSFET 121. With such a circuit configuration, it is possible to provide the sensor device 100 having excellent detection sensitivity and a simple structure.

[0122] The node 123 may be provided between the sensor electrode 110 and the low-side MOSFET 122. With such a circuit configuration, it is possible to provide the sensor device 100 having excellent detection sensitivity and a simple structure.

[0123] Alternatively, the high-side MOSFET 121 may be a P-channel MOSFET, and the low-side MOSFET 122 may be an N-channel MOSFET. With such a circuit configuration, it is possible to provide the sensor device 100 having excellent detection sensitivity and a simple structure.

[0124] Furthermore, the high-side MOSFET 121 and the low-side MOSFET 122 may be N-channel MOSFETs. With such a circuit configuration, it is possible to provide the sensor device 100 having excellent detection sensitivity and a simple structure.

[0125] As mentioned above, the sensor device according to the exemplary embodiment of the present disclosure has been described. However, the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and changes can be made without departing from the scope of the claims.

[0126] Regarding the above-mentioned embodiment, the following supplementary notes are further disclosed.

[0127] (Note 1)

[0128] A sensor device comprises: a sensor electrode capable of operating as a heating element; an electrostatic detection circuit for detecting electrostatic capacitance between the sensor electrode and an object; a high-side switch provided between a power supply for supplying heating power to the sensor electrode and the sensor electrode; a low-side switch provided between the sensor electrode and a reference potential point; a node located between the high-side switch or the low-side switch and the sensor electrode; and a control unit for controlling the high-side switch and the low-side switch, wherein the control unit controls the high-side switch and the low-side switch to be in an on state when the heating power is supplied from the power supply to the sensor electrode, and controls the high-side switch and the low-side switch to be in an open state when the electrostatic detection circuit detects the electrostatic capacitance, and applies a given voltage to the node.

[0129] (Note 2)

[0130] The sensor device according to Supplementary Note 1, wherein the predetermined voltage is an intermediate voltage between a supply voltage supplied from the power supply to the high-side switch and a voltage at the reference potential point.

[0131] (Note 3)

[0132] The sensor device according to Supplementary Note 2, wherein the predetermined voltage is a voltage obtained by adding a voltage of half a voltage difference between the supply voltage and the voltage at the reference potential point to the voltage at the reference potential point.

[0133] (Note 4)

[0134] The sensor device according to any one of Supplementary Notes 1 to 3, wherein the predetermined voltage is a voltage that makes the first parasitic capacitance of the high-side switch and the second parasitic capacitance of the low-side switch approximately the same.

[0135] (Note 5)

[0136] The sensor device according to Note 2 further includes: a first voltage-dividing resistor connected between the power supply and the node; and a second voltage-dividing resistor connected between the node and the reference potential point, and the given voltage is a voltage divided by the first voltage-dividing resistor and the second voltage-dividing resistor.

[0137] (Note 6)

[0138] The sensor device according to Note 3 further includes: a first voltage-dividing resistor connected between the power supply and the node; and a second voltage-dividing resistor connected between the node and the reference potential point, the given voltage is a voltage divided by the first voltage-dividing resistor and the second voltage-dividing resistor, and the resistance values ​​of the first voltage-dividing resistor and the second voltage-dividing resistor are equal to each other.

[0139] (Note 7)

[0140] The sensor device according to Supplementary Note 6, wherein the electrical characteristics of the high side switch are equal to the electrical characteristics of the low side switch.

[0141] (Note 8)

[0142] The sensor device according to any one of Supplementary Notes 1 to 7, wherein the control unit periodically drives the high side switch and the low side switch when the power supply for heating is supplied to the sensor electrode.

[0143] (Note 9)

[0144] The sensor device according to any one of Notes 1 to 8, further comprising: a sinusoidal wave signal source capable of supplying a sinusoidal wave signal to the sensor electrode, wherein the control unit supplies the sinusoidal wave signal from the sinusoidal wave signal source to the sensor electrode when the electrostatic capacitance is detected by the electrostatic detection circuit.

[0145] (Note 10)

[0146] The sensor device according to Supplementary Note 9, further comprising: a capacitor for DC isolation, provided between the sinusoidal wave signal source and the sensor electrode.

[0147] (Note 11)

[0148] The sensor device according to any one of Supplementary Notes 1 to 10, wherein the node is provided between the sensor electrode and the high side switch.

[0149] (Note 12)

[0150] The sensor device according to any one of Supplementary Notes 1 to 10, wherein the node is provided between the sensor electrode and the low-side switch.

[0151] (Note 13)

[0152] The sensor device according to any one of Supplementary Notes 1 to 12, wherein the high-side switch is a P-channel MOSFET, and the low-side switch is an N-channel MOSFET.

[0153] (Note 14)

[0154] The sensor device according to any one of Supplementary Notes 1 to 12, wherein the high-side switch and the low-side switch are N-channel MOSFETs.

Claims

1. A sensor device, characterized in that: have: A sensor electrode capable of operating as a heating element; an electrostatic detection circuit for detecting an electrostatic capacitance between the sensor electrode and an object; a high-side switch provided between a power source for supplying heating power to the sensor electrode and the sensor electrode; a low-side switch, disposed between the sensor electrode and a reference potential point; a node located between the highside switch or the lowside switch and the sensor electrode; and a control unit, controlling the high-side switch and the low-side switch, The control unit performs the following processing: When the heating power is supplied from the power supply to the sensor electrode, the high side switch and the low side switch are controlled to be in an on state. When the static capacitance is detected by the static electricity detection circuit, the high-side switch and the low-side switch are controlled to be in an open state, and a predetermined voltage is applied to the node.

2. The sensor device according to claim 1, wherein The predetermined voltage is a voltage intermediate between a supply voltage supplied from the power supply to the high-side switch and a voltage at the reference potential point.

3. The sensor device according to claim 2, wherein: The predetermined voltage is a voltage obtained by adding half the voltage difference between the supply voltage and the voltage at the reference potential point to the voltage at the reference potential point.

4. The sensor device according to claim 1, wherein The predetermined voltage is a voltage that makes the first parasitic capacitance of the high-side switch and the second parasitic capacitance of the low-side switch approximately the same.

5. The sensor device according to claim 2, wherein The sensor device further comprises: a first voltage-dividing resistor connected between the power supply and the node; and a second voltage dividing resistor connected between the node and the reference potential point; The given voltage is a voltage divided by the first voltage-dividing resistor and the second voltage-dividing resistor. The sensor device according to claim 3 , wherein: The sensor device further comprises: a first voltage-dividing resistor connected between the power supply and the node; and a second voltage dividing resistor connected between the node and the reference potential point; The given voltage is the voltage divided by the first voltage-dividing resistor and the second voltage-dividing resistor, The resistance values ​​of the first voltage-dividing resistor and the second voltage-dividing resistor are equal to each other.

7. The sensor device according to claim 6, wherein: The electrical characteristics of the high-side switch are equal to the electrical characteristics of the low-side switch.

8. The sensor device according to claim 1, wherein The control unit periodically drives the high side switch and the low side switch when the heating power is supplied from the power supply to the sensor electrode.

9. The sensor device according to claim 1, wherein The sensor device further includes: a sinusoidal wave signal source capable of supplying a sinusoidal wave signal to the sensor electrode; The control unit causes the sinusoidal wave signal source to supply the sinusoidal wave signal to the sensor electrode when the static capacitance is detected by the static detection circuit.

10. The sensor device according to claim 9, wherein The sensor device further includes a capacitor for direct current separation, which is arranged between the sinusoidal wave signal source and the sensor electrode.

11. The sensor device according to claim 1, wherein The node is disposed between the sensor electrode and the high-side switch.

12. The sensor device according to claim 1, wherein The node is disposed between the sensor electrode and the low-side switch.

13. The sensor device according to claim 1, wherein The high-side switch is a P-channel MOSFET. The low-side switch is an N-channel MOSFET.

14. The sensor device according to claim 1, wherein The high-side switch and the low-side switch are N-channel MOSFETs.

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