Sensor device

Abstract

To provide a sensor device with good detection sensitivity and a simple configuration.SOLUTION: A sensor device comprises: a sensor electrode operable as a heating element; an electrostatic detection circuit that detects a capacitance of the sensor electrode; a high-side MOSFET provided between a power supply that supplies electric power for heating and the sensor electrode; a low-side MOSFET provided between the sensor electrode and a reference potential point; a node located 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 controls the high-side MOSFET and the low-side MOSFET to be in a conduction state when the electric power for heating is supplied from the power supply to the sensor electrode, and controls the high-side MOSFET and the low-side MOSFET to be in an open state, and applies a predetermined voltage to the node when the electrostatic detection circuit detects the capacitance.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a sensor device. [Background technology]

[0002] Conventionally, there has been a sensor device including an electrode assembly having a heating element as a sensor electrode, a detection device that detects the capacitance of the sensor electrode, a high-side switch provided between a heating power supply and the heating element, a low-side switch provided between the heating element and a reference potential point, a gate controller that opens the high-side switch and the low-side switch 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 conducts the decoupling MOSFET in the heating mode and opens 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. In addition, 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). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US Patent Application Publication No. 2023 / 0046256 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional sensor devices have a complex configuration, including a high-side switch, a low-side switch, a decoupling MOSFET, a first node, and a node to which a potential different from the third potential is supplied. On the other hand, the sensor device is required to have good detection sensitivity when detecting the capacitance of the sensor electrode, but the detection sensitivity is reduced by the parasitic capacitance of the MOSFETs used as the high-side switch and low-side switch, so it is preferable to minimize the reduction in detection sensitivity.

[0005] Therefore, an object of the present invention is to provide a sensor device that has good detection sensitivity and a simple configuration. [Means for solving the problem]

[0006] A sensor device according to an embodiment of the present disclosure includes a sensor electrode operable as a heating element, an electrostatic detection circuit that detects the capacitance between the sensor electrode and an object, a power source that supplies heating power to the sensor electrode, a high-side switch provided between the sensor electrode and the power source, 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 that controls the high-side switch and the low-side switch, wherein the control unit controls the high-side switch and the low-side switch to a conductive state when the heating power is supplied from the power source to the sensor electrode, and controls the high-side switch and the low-side switch to an open state when the electrostatic detection circuit detects the capacitance, and applies a predetermined voltage to the node. [Effects of the Invention]

[0007] A sensor device with good detection sensitivity and a simple configuration can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram schematically illustrating a steering wheel on which a sensor device according to an embodiment is mounted; [Figure 2] FIG. 2 is a diagram illustrating an example of a circuit configuration of a sensor device according to an embodiment. [Figure 3] 4 is a diagram illustrating an example of a parasitic capacitance Coss between the drain and source of a high-side MOSFET and a low-side MOSFET of the sensor device according to the embodiment. FIG. [Figure 4A] FIG. 10 is a diagram illustrating an example of electrical characteristics of a high-side MOSFET. [Figure 4B] FIG. 10 is a diagram illustrating an example of electrical characteristics of a low-side MOSFET. [Figure 5A] FIG. 10 is a diagram illustrating an example of a circuit configuration of a part of a sensor device according to a modified example of the embodiment. [Figure 5B] FIG. 10 is a diagram illustrating an example of a circuit configuration of a part of a sensor device according to a modified example of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment to which the sensor device of the present disclosure is applied will be described.

[0010] <Embodiment> 1 is a diagram schematically illustrating 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 driving circuit 120, an electrostatic detection circuit 130, and a control circuit 140. The control circuit 140 is an example of a control unit.

[0011] A steering wheel 10 is mounted on a vehicle, and a sensor electrode 110 of a sensor device 100 is mounted on the inside of the surface of the rim 11. The sensor electrode 110 is an example of a sensor electrode that can operate 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. The sensor device 100 also warms 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 heater. A hand is an example of an object. The rim 11 of the steering wheel 10 is an example of a fixed part to which the sensor electrode 110 is fixed. The surface 11A of the rim 11 is an example of a contact part that can be contacted by a detection object.

[0012] Hereinafter, the driver of the vehicle will be referred to as the operator of the sensor device 100. The operator's touching the rim 11 of the steering wheel 10 on which the sensor electrode 110 is provided will be referred to as the operator's operation.

[0013] The steering wheel 10 has a rim 11, a hub 12, and spokes 13. The rim 11, hub 12, and spokes 13 shown in FIG. 1 are core metal portions of the rim 11, hub 12, and spokes 13. In FIG. 1, the surface 11A of the rim 11 is shown separated from the rim 11 in order to show the sensor electrode 110. Also, in FIG. 1, covers that cover the hub 12 and spokes 13 are omitted.

[0014] The ground terminal of the steering wheel 10 is electrically connected to a core metal that is provided around the entire circumference of the rim 11 of the steering wheel 10. By connecting the core metal to the ground terminals of the heater drive circuit 120, the electrostatic detection circuit 130, and the control circuit 140 via connectors (not shown), the ground potentials of the heater drive circuit 120, the electrostatic detection circuit 130, and the control circuit 140 become equal to the ground potential of the steering wheel 10.

[0015] <Schematic configuration of sensor device 100> 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). Although Fig. 1 shows a simplified connection relationship between the sensor electrode 110, the heater driving circuit 120, the electrostatic detection circuit 130, and the control circuit 140, the control circuit 140 is also connected to the heater driving circuit 120 via a cable, a connector, etc. (not shown).

[0016] The sensor device 100 has two modes: a heating mode in which heating power is supplied from a vehicle power source to the sensor electrode 110, and a non-heating mode in which the supply of heating power to the sensor electrode 110 is stopped. When the sensor device 100 is in the non-heating mode, the electrostatic detection circuit 130 may detect capacitance. The control circuit 140 switches between the two modes in a time-division manner. That is, the control circuit 140 selectively switches between the heating mode and the non-heating mode as time passes.

[0017] <Sensor electrode 110> The sensor electrode 110 is provided around the rim 11 of the steering wheel 10 while being insulated from a core metal that is provided around the rim 11 of the steering wheel 10. The sensor electrode 110 is connected to the heater drive circuit 120, the electrostatic detection circuit 130, and the control circuit 140 via signal lines and the like. The sensor electrode 110 is a thin, sheet-like, strip-shaped electrode that is provided around the rim 11, and can be produced, for example, by applying a conductor such as silver paste to the surface of a resin film.

[0018] <Heater driving circuit 120> The heater driving circuit 120 is connected to the sensor electrode 110, and supplies heating power to the sensor electrode 110 from the vehicle power supply in the heating mode.

[0019] <Static electricity detection circuit 130> The electrostatic detection circuit 130 is connected to the sensor electrode 110 and detects the electrostatic capacitance between the sensor electrode 110 and the operator's hand.

[0020] <Control circuit 140> The control circuit 140 is realized by a computer including a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), an input / output interface, an internal bus, etc. 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 on (ON). In the non-heating mode, the control circuit 140 turns both the high-side MOSFET 121 and the low-side MOSFET 122 off (OFF).

[0021] <Circuit configuration of sensor device 100> Fig. 2 is a diagram showing an example of the circuit configuration of the sensor device 100. Fig. 2 also shows a power supply circuit 50 of the vehicle 1 on which the sensor device 100 is mounted. The power supply circuit 50 has a power supply 51 and a relay 52. ​​The power supply 51 is, for example, a battery of the vehicle 1. In Fig. 2, the power supply 51 is described as being a battery, but the power supply 51 may also include a generator, a regenerative device, or the like of the vehicle 1 in addition to the battery. The output voltage of the power supply 51 is V1.

[0022] The power supply circuit 50 has two power supply paths 50A and 50B. Both power supply paths 50A and 50B are connected to a power supply 51 and branch off along the way. A relay 52 is inserted in series into the power supply path 50B.

[0023] <Sensor electrode 110> The sensor electrode 110 is provided on the steering wheel 10 and connected to the heater drive circuit 120. More specifically, the sensor electrode 110 is a conductor having both ends as shown in FIG. 1 , and one end is connected to the drain of the high-side MOSFET 121 and a node 123. The other end of the sensor electrode 110 is connected to the drain of the low-side MOSFET 122.

[0024] The parasitic capacitance between the sensor electrode 110 and the ground potential point is Crgl, and the parasitic capacitance between the sensor electrode 110 and the hand H is Chg. The parasitic capacitance Chg changes significantly depending on whether the hand H is in contact with the sensor electrode 110 or not.

[0025] <Heater driving circuit 120> The heater driving circuit 120 includes a high-side MOSFET 121, a low-side MOSFET 122, a node 123, a resistor R1, and a resistor R2. The high-side MOSFET 121 is an example of a high-side switch, and the low-side MOSFET 122 is an example of a low-side switch. The resistor R1 is an example of a first voltage dividing resistor, and the resistor R2 is an example of a second voltage dividing resistor.

[0026] The high-side MOSFET 121 is, for example, a P-channel MOSFET, and has a source connected to the power supply 51 via the relay 52 via node V1, a drain connected to the sensor electrode 110 and a node 123, and a 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 its gate from the control circuit 140.

[0027] The low-side MOSFET 122 is, as an example, a P-channel type MOSFET. Its drain is connected to the sensor electrode 110 and the node 123, its source is connected to the node V2, and its gate is connected to the control circuit 140. The node V2 is a node with a voltage value of V2 (<V3 < V1) and is an example of a reference potential point held at the ground potential. The low-side MOSFET 122 is provided between the sensor electrode 110 and the node V2 and is driven by a gate drive signal supplied from the control circuit 140 to the gate.

[0028] The node 123 is connected between the resistors R1 and R2, and a DC power (voltage V1) supplied from the power supply 51 to the resistor R1 is divided by the resistors R1 and R2 to supply a voltage V3. The voltage V3 is an example of a predetermined voltage. The node 123 is connected between the resistors R1 and R2, the drain of the high-side MOSFET 121, the sensor electrode 110, and the capacitor 134 of the electrostatic detection circuit 130.

[0029] <Electrostatic detection circuit 130> The electrostatic detection circuit 130 includes a charge amplifier 131, an AC signal source 132, an amplitude adjustment unit 133, and a capacitor Cd. The electrostatic detection circuit 130 detects the capacitance of the sensor electrode 110 in the non-heating mode. The AC signal source 132 is an example of a sine wave signal source.

[0030] The charge amplifier 131 has a non-inverting input terminal (+) connected to the output terminal of the amplitude adjustment unit 133, an inverting input terminal (-) connected to the sensor electrode 110 via the capacitor Cd, and an output terminal connected to the control circuit 140. The output voltage of 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 of the non-inverting input terminal (+) and the input of the inverting input terminal (-) and outputs an output signal.

[0031] The AC signal source 132 is connected to the amplitude adjustment unit 133 and is also connected to the sensor electrode 110 via a capacitor Cd. The AC signal source 132 outputs an AC signal (sine wave signal) that drives the sensor electrode 110. The AC signal source 132 may output the AC signal that drives the sensor electrode 110 only in the non-heating mode.

[0032] The amplitude adjustment unit 133 adjusts the amplitude so that when there is no hand H, which is an object close to the sensor electrode 110 (when the parasitic capacitance Crg is zero), the difference between the inverting input terminal (-) and the non-inverting input terminal (+) is eliminated and the output of Vo becomes extremely small.

[0033] Capacitor Cd has an inverting input terminal (-) of charge amplifier 131, a terminal (the terminal on the left side in FIG. 2) connected to amplitude adjustment unit 133, and a terminal connected to sensor electrode 110. That is, 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 DC components between heater drive circuit 120 and electrostatic detection circuit 130.

[0034] <Control circuit 140> 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 outputs 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 in a non-conductive state (off). With the high-side MOSFET 121 and the low-side MOSFET 122 in a non-conductive state (off), the sensor electrode 110 is no longer affected by the power supply circuit 50.

[0035] 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.

[0036] In addition, 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 outputs an H-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 in a conductive state (ON).

[0037] 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. The high-side MOSFET 121 and the low-side MOSFET 122 are kept in a conductive state (ON) except for the time required to detect the capacitance of the sensor electrode 110, thereby heating the sensor electrode 110. On the other hand, when the temperature of the steering wheel 10 is above the target temperature, the control circuit 140 keeps the high-side MOSFET 121 and the low-side MOSFET 122 in an open state (OFF). When switching the heating power in multiple stages, the control circuit 140 may PWM-control the high-side MOSFET 121 and the low-side MOSFET 122. In this case, the control circuit 140 may determine the duty ratio of the PWM signal by feedback control based on the target temperature of the heater of the steering wheel 10, the current temperature of the heater of the steering wheel 10, and the like. The temperature of the heater of the steering wheel 10 may be measured by a temperature sensor provided in the steering wheel 10.

[0038] <Parasitic capacitance of the high-side MOSFET 121 and the low-side MOSFET 122> 3 is a diagram showing an example of the 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.

[0039] 3 shows the sensor electrode 110, the high-side MOSFET 121, the low-side MOSFET 122, the node 123, and the capacitor 134 of the electrostatic detection circuit 130, among the components shown in FIG. 2, and omits other components.

[0040] A parasitic capacitance Coss exists between the drain and source of the high-side MOSFET 121 and the low-side MOSFET 122. MOSFETs have electrical characteristics in which the parasitic capacitance Coss between the drain and source changes with the voltage between the drain and source, and generally, the parasitic capacitance Coss decreases as the voltage between the drain and source increases.

[0041] Therefore, in the P-channel high-side MOSFET 121, the parasitic capacitance Coss decreases as the voltage of the source relative to the drain increases, and in the N-channel low-side MOSFET 122, the parasitic capacitance Coss decreases as the voltage of the drain relative to the source increases.

[0042] The parasitic capacitance Coss affects the detection sensitivity when detecting the capacitance of the sensor electrode 110. That is, in the sensor device 100, in the non-heating mode in which the capacitance of the sensor electrode 110 is detected, in order to minimize the decrease in detection sensitivity and obtain good detection sensitivity, it is preferable to reduce the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 to some extent.

[0043] In the sensor device 100, a node 123 is connected between the drain of the P-channel high-side MOSFET 121 and the sensor electrode 110 in order to reduce the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122.

[0044] 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.

[0045] Therefore, by appropriately setting the voltage V3, it is possible to realize a source-drain voltage that can reduce the parasitic capacitance Coss of the high-side MOSFET 121, and a drain-source voltage that can reduce the parasitic capacitance Coss of the low-side MOSFET 122.

[0046] The voltage V3 can be adjusted by adjusting the ratio of the resistance values ​​of resistors R1 and R2. It is assumed that the high-side MOSFET 121 and the low-side MOSFET 122 have the same electrical characteristics, i.e., the change in parasitic capacitance Coss with respect to the drain-source voltage. This is because if the electrical characteristics of the high-side MOSFET 121 and the low-side MOSFET 122 are the same, it is easy to set the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122.

[0047] In this case, voltage V3 may be an intermediate voltage between voltage V1 and voltage V2 (GND), and is preferably voltage V2 plus 40% to 60% of the voltage difference between voltages V1 and V2, and most preferably voltage V3 plus 50% of the voltage difference between voltages V1 and V2. In other words, voltage V3 is most preferably voltage V2 plus half the voltage difference between voltages V1 and V2.

[0048] In other words, 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 approximately equal. The parasitic capacitance Coss of the high-side MOSFET 121 and the parasitic capacitance Coss of the low-side MOSFET 122 being approximately equal 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%.

[0049] <Example of Electrical Characteristics of the High-Side MOSFET 121 and the Low-Side MOSFET 122 in the Sensor Device 100> FIG. 4A is a graph showing an example of the electrical characteristics of the high-side MOSFET 121. FIG. 4B is a graph showing an example of the electrical characteristics of the low-side MOSFET 122. In FIG. 4A, the horizontal axis represents the source-to-drain voltage VSD (V) of the P-channel high-side MOSFET 121, and in FIG. 4B, the horizontal axis represents the drain-to-source voltage VDS (V) of the N-channel low-side MOSFET 122. In FIGS. 4A and 4B, the vertical axis represents the parasitic capacitance Coss (pF). In FIGS. 4A and 4B, the region where the voltage on the horizontal axis is approximately 1 V or higher is the region where the parasitic capacitance Coss drops sharply.

[0050] Before 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 will also be described.

[0051] The comparative sensor device has a configuration in which the node 123 is omitted from the sensor device 100 of the embodiment. In the comparative sensor device that does not include the node 123, the drain voltage of the high-side MOSFET 121 is lower and the drain voltage of the low-side MOSFET 122 is lower than in the sensor device 100 of the embodiment.

[0052] 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 than in the sensor device 100 of the embodiment.

[0053] Therefore, in the comparative sensor device, the parasitic capacitance Coss of the high-side MOSFET 121 is smaller and the parasitic capacitance Coss of the low-side MOSFET 122 is larger than in the sensor device 100 of the embodiment.

[0054] That is, the parasitic capacitance Coss of the high-side MOSFET 121 of the comparison sensor device becomes a small value (about 150 pF) as shown by a black circle (●) in FIG. 4A, for example, and the parasitic capacitance Coss of the low-side MOSFET 122 of the comparison sensor device becomes a large value (about 1000 pF) as shown by a black circle (●) in FIG. 4B, for example. The sum of the two parasitic capacitances Coss is about 1150 pF, and since this total parasitic capacitance becomes the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point, the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point becomes very large.

[0055] In the comparison sensor device, since the voltage VSD between the source and drain of the high-side MOSFET 121 is large and the voltage VDS between the drain and source of the low-side MOSFET 122 is small, the parasitic capacitance Coss of the low-side MOSFET 122 is large, so the parasitic capacitance Crgl becomes very large, and the detection sensitivity when detecting the capacitance of the sensor electrode 110 decreases significantly.

[0056] On the other hand, in the sensor device 100, due to the presence of the node 123 with the voltage V3 (V2 < V3 < V1), it is possible to achieve a state where the voltage VSD between the source and drain of the high-side MOSFET 121 is large and the voltage VDS between the drain and source of the low-side MOSFET 122 is large.

[0057] Therefore, the parasitic capacitance Coss of the high-side MOSFET 121 of the sensor device 100 of the embodiment is a small value (approximately 200 pF) as shown by the open circle (◯) in FIG. 4A, and the parasitic capacitance Coss of the low-side MOSFET 122 of the sensor device 100 is a small value (approximately 200 pF) as shown by the open circle (◯) in FIG. 4B. The parasitic capacitance Coss of the high-side MOSFET 121 (approximately 200 pF) is slightly larger than the parasitic capacitance Coss of the high-side MOSFET 121 of the comparative sensor device (approximately 150 pF), but is still sufficiently small. The parasitic capacitance Coss of the low-side MOSFET 122 (approximately 200 pF) is also a favorable value that is significantly smaller than the parasitic capacitance Coss of the low-side MOSFET 122 of the comparative sensor device (approximately 1000 pF). The parasitic capacitance Coss (approximately 200 pF) of the high-side MOSFET 121 and the parasitic capacitance Coss (approximately 200 pF) of the low-side MOSFET 122 are approximately equal in value.

[0058] The sum of the two parasitic capacitances Coss is approximately 400 pF, and this total parasitic capacitance becomes the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point, so the parasitic capacitance Crgl between the sensor electrode 110 and the ground potential point is very small.

[0059] Therefore, in the sensor device 100 of the embodiment, the parasitic capacitance Coss of both the high-side MOSFET 121 and the low-side MOSFET 122 can be reduced, and the parasitic capacitance Crgl is therefore very small, so that the decrease in detection sensitivity when detecting the capacitance of the sensor electrode 110 can be minimized and good detection sensitivity can be obtained.

[0060] 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 decrease in detection sensitivity when detecting the capacitance of the sensor electrode 110 and achieving good detection sensitivity.

[0061] Such low parasitic capacitance Crgl can be achieved by setting the voltage V3 at the node 123 to an appropriate value. Therefore, the voltage V3 can be set to an optimized value so that the parasitic capacitance Crgl is low, and the resistance values ​​of the resistors R1 and R2 can be set to appropriate values. For example, the appropriate resistance values ​​of the resistors R1 and R2 are equal to each other.

[0062] <Modification> 5A and 5B are diagrams showing an example of a circuit configuration of a part of the sensor device 100 according to a modified example of the embodiment. 5A and 5B show a part of the sensor device 100 corresponding to the part shown in FIG.

[0063] <Circuit configuration shown in Figure 5A> 5A, node 123 is connected between sensor electrode 110 and the drain of low-side MOSFET 122. The voltage V3 at node 123 may be the same as the voltage V3 at node 123 shown in FIG.

[0064] 5A, the node 123 is connected to the drain of the high-side MOSFET 121 via the sensor electrode 110, and the node 123 is directly connected to the drain of the low-side MOSFET 122. Therefore, the source-drain voltage VSD of the high-side MOSFET 121 and the drain-source voltage VDS of the low-side MOSFET 122 shown in Fig. 5A are substantially equivalent to the source-drain voltage VSD of the high-side MOSFET 121 and the drain-source voltage VDS of the low-side MOSFET 122 of the sensor device 100 shown in Fig. 3.

[0065] Therefore, even in a circuit configuration in which the node 123 is connected between the sensor electrode 110 and the drain of the low-side MOSFET 122 as shown in FIG. 5A, the parasitic capacitances Coss of both the high-side MOSFET 121 and the low-side MOSFET 122 can be reduced, thereby minimizing the decrease in detection sensitivity when detecting the capacitance of the sensor electrode 110 and achieving good detection sensitivity.

[0066] <Circuit configuration shown in Figure 5B> 5B, the high-side MOSFET 121 is replaced with an N-channel MOSFET, which is connected in such a manner that the positions of the source and drain of the P-channel high-side MOSFET 121 are interchanged.

[0067] When driving the N-channel high-side MOSFET 121, the control circuit 140 only needs to invert the H level and L level, as compared to when driving the high-side MOSFET 121 shown in FIG.

[0068] In this way, even if the high-side MOSFET 121 is an N-channel type, when detecting the capacitance of the sensor electrode 110, the decrease in detection sensitivity can be minimized and good detection sensitivity can be obtained, similar to the sensor device 100 shown in FIGS. 2 and 3.

[0069] <Effects> The sensor device 100 includes a sensor electrode 110 operable as a heating element, an electrostatic detection circuit 130 that detects the electrostatic capacitance between the sensor electrode 110 and an object, a high-side MOSFET 121 provided between the sensor electrode 110 and a power supply 51 that supplies heating power to the sensor electrode 110, a low-side MOSFET 122 provided between the sensor electrode 110 and a reference potential point, a node 123 located between the high-side MOSFET 121 or the low-side MOSFET 122 and the sensor electrode 110, and a control circuit 140 that controls the high-side MOSFET 121 and the low-side MOSFET 122. When supplying heating power from the power supply 51 to the sensor electrode 110, the control circuit 140 controls the high-side MOSFET 121 and the low-side MOSFET 122 to a conductive state, and when detecting the electrostatic capacitance with the electrostatic detection circuit 130, controls the high-side MOSFET 121 and the low-side MOSFET 122 to an 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, thereby achieving good detection sensitivity by minimizing the decrease in detection sensitivity when detecting the capacitance of the sensor electrode 110. In addition, the number of components is small, making the configuration simple.

[0070] Therefore, it is possible to provide a sensor device 100 with good detection sensitivity and a simple configuration.

[0071] Furthermore, voltage V3 may be an intermediate voltage between the supply voltage (V1) supplied from power supply 51 to high-side MOSFET 121 and the voltage of the reference potential point (GND). By using voltage V3, which is an intermediate voltage between voltage V1 and voltage GND, it is possible to increase the voltage of the terminal of low-side MOSFET 122 on the sensor electrode 110 side, and to realize a state in which the parasitic capacitance Coss of high-side MOSFET 121 and low-side MOSFET 122 is small. In this way, it is possible to provide a sensor device 100 with good detection sensitivity and a simple configuration.

[0072] Alternatively, voltage V3 may be a voltage obtained by adding half the voltage difference between the supply voltage (V1) and the voltage of the reference potential point (GND) to the voltage of the reference potential point (GND). By using voltage V3 as the median value between voltage V1 and voltage GND, the voltage of the terminal of low-side MOSFET 122 on the sensor electrode 110 side can be increased, and the parasitic capacitances Coss of high-side MOSFET 121 and low-side MOSFET 122 can be reduced and balanced. In this way, a sensor device 100 with good detection sensitivity and a simple configuration can be provided.

[0073] Furthermore, 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 approximately equal. By using the voltage V3 that makes the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 approximately equal, it is possible to achieve a state in which the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122 is small and well-balanced. In this way, it is possible to provide a sensor device 100 that has good detection sensitivity and a simple configuration.

[0074] The sensor device 100 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 a reference potential point, and the voltage V3 may be a voltage divided by the resistors R1 and R2. By dividing the voltage of the power supply 51 by the resistors R1 and R2, the voltage V3 can be easily obtained, and a stable voltage V3 can be obtained. Therefore, it is possible to provide a sensor device 100 that has good detection sensitivity, a simple configuration, and stable operation.

[0075] The sensor device 100 further includes a resistor R1 connected between the power supply 51 and the node 123 and a resistor R2 connected between the node 123 and a reference potential point. The voltage V3 is a voltage divided by the resistors R1 and R2, and the resistors R1 and R2 may have equal resistance values. Dividing the voltage of the power supply 51 by the resistors R1 and R2 facilitates the generation of the voltage V3, and the voltage V3 is stable. Furthermore, since the resistors R1 and R2 have equal resistance values, the voltage V3 is the midpoint between the voltage V1 and the voltage GND. Therefore, the parasitic capacitances Coss of the high-side MOSFET 121 and the low-side MOSFET 122 are small and well-balanced. In this way, a sensor device 100 with excellent detection sensitivity and a simple configuration can be provided.

[0076] Furthermore, the electrical characteristics of the high-side MOSFET 121 and the electrical characteristics of the low-side MOSFET 122 may be equal. Equal electrical characteristics of the high-side MOSFET 121 and the low-side MOSFET 122 make it easier to set the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122. In this way, it is possible to provide a sensor device 100 that has good detection sensitivity, a simple configuration, and allows easy setting of the parasitic capacitance Coss of the high-side MOSFET 121 and the low-side MOSFET 122.

[0077] Furthermore, the control circuit 140 may periodically drive the high-side MOSFET 121 and the low-side MOSFET 122 when supplying heating power from the power supply 51 to the sensor electrode 110. Heating can be performed efficiently according to a target value when using the sensor electrode 110 as a heater, the current heater temperature, and the like.

[0078] The sensor may further include an AC signal source 132 capable of supplying a sine wave signal to the sensor electrode 110, and the control circuit 140 may cause the AC signal source 132 to supply the sine wave signal to the sensor electrode 110 when the electrostatic detection circuit 130 detects the capacitance. With the sine wave signal being supplied to the sensor electrode 110, the presence or absence of an object can be determined with high accuracy.

[0079] The sensor may further include a capacitor Cd for DC isolation provided between the AC signal source 132 and the sensor electrode 110. By isolating the electrostatic detection circuit 130 from the DC signal, the electrostatic capacitance of the sensor electrode 110 can be accurately detected.

[0080] Furthermore, 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 a sensor device 100 that has good detection sensitivity and a simple configuration.

[0081] 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 a sensor device 100 that has good detection sensitivity and a simple configuration.

[0082] 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 a sensor device 100 that has good detection sensitivity and a simple configuration.

[0083] Furthermore, N-channel MOSFETs may be used as the high-side MOSFET 121 and the low-side MOSFET 122. With such a circuit configuration, it is possible to provide a sensor device 100 that has good detection sensitivity and a simple configuration.

[0084] The above describes a sensor device according to an exemplary embodiment of the present disclosure. However, the present disclosure is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims.

[0085] The following additional notes are provided regarding the above-described embodiments. (Appendix 1) a sensor electrode operable as a heating element; an electrostatic detection circuit that detects the electrostatic capacitance between the sensor electrode and the object; a power supply that supplies power for heating the sensor electrode and a high-side switch that is provided between the power supply 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; a control unit that controls the high-side switch and the low-side switch; Equipped with The control unit When the power supply supplies the heating power to the sensor electrode, the high-side switch and the low-side switch are controlled to be in a conductive state; When the electrostatic capacitance is detected by the electrostatic detection circuit, the high-side switch and the low-side switch are controlled to an open state, and a predetermined voltage is applied to the node. (Appendix 2) 2. The sensor device according to claim 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. (Appendix 3) 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 of the reference potential point to the voltage of the reference potential point. (Appendix 4) 4. The sensor device according to claim 1, wherein the predetermined voltage is a voltage that makes a first parasitic capacitance of the high-side switch and a second parasitic capacitance of the low-side switch approximately equal to each other. (Appendix 5) a first voltage divider resistor connected between the power supply and the node; a second voltage dividing resistor connected between the node and the reference potential point; further comprising 3. The sensor device according to claim 2, wherein the predetermined voltage is a voltage divided by the first voltage dividing resistor and the second voltage dividing resistor. (Appendix 6) a first voltage divider resistor connected between the power supply and the node; a second voltage dividing resistor connected between the node and the reference potential point; further comprising the predetermined voltage is a voltage divided by the first voltage dividing resistor and the second voltage dividing resistor, 4. The sensor device according to claim 3, wherein the first voltage dividing resistor and the second voltage dividing resistor have equal resistance values. (Appendix 7) 7. The sensor device according to claim 6, wherein the high-side switch and the low-side switch have the same electrical characteristics. (Appendix 8) The sensor device according to any one of claims 1 to 7, wherein the control unit periodically drives the high-side switch and the low-side switch when supplying the heating power from the power source to the sensor electrode. (Appendix 9) further comprising a sinusoidal signal source capable of supplying a sinusoidal signal to the sensor electrodes; The sensor device according to any one of appendixes 1 to 8, wherein the control unit causes the sine wave signal source to supply the sine wave signal to the sensor electrode when the electrostatic detection circuit detects the electrostatic capacitance. (Appendix 10) 10. The sensor device of claim 9, further comprising a capacitor for DC isolation provided between the sinusoidal signal source and the sensor electrode. (Appendix 11) 11. The sensor device according to claim 1, wherein the node is provided between the sensor electrode and the high-side switch. (Appendix 12) 11. The sensor device according to claim 1, wherein the node is provided between the sensor electrode and the low-side switch. (Appendix 13) the high-side switch is a P-channel MOSFET, 13. The sensor device according to claim 1, wherein the low-side switch is an N-channel MOSFET. (Appendix 14) 13. The sensor device according to claim 1, wherein the high-side switch and the low-side switch are N-channel MOSFETs. [Explanation of symbols]

[0086] 51 Power supply 100 Sensor device 110 Sensor electrode 120 Heater drive circuit 121 High-side MOSFET (an example of a high-side switch) 122 Low-side MOSFET (an example of a low-side switch) 123 nodes R1 Resistor (example of the first voltage divider resistor) R2 Resistor (an example of a second voltage dividing resistor) 130 Electrostatic detection circuit 132 AC signal source 140 Control circuit

Claims

1. a sensor electrode operable as a heating element; an electrostatic detection circuit that detects the electrostatic capacitance between the sensor electrode and the object; a power supply that supplies power for heating the sensor electrode and a high-side switch that is provided between the power supply 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; a control unit that controls the high-side switch and the low-side switch; Equipped with The control unit When the power supply supplies the heating power to the sensor electrode, the high-side switch and the low-side switch are controlled to be in a conductive state; When the electrostatic capacitance is detected by the electrostatic detection circuit, the high-side switch and the low-side switch are controlled to an open state, and a predetermined voltage is applied to the node.

2. 2. The sensor device according to claim 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.

3. 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 to the voltage at the reference potential.

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

5. a first voltage divider resistor connected between the power supply and the node; a second voltage dividing resistor connected between the node and the reference potential point; further comprising The sensor device according to claim 2 , wherein the predetermined voltage is a voltage divided by the first voltage dividing resistor and the second voltage dividing resistor.

6. a first voltage divider resistor connected between the power supply and the node; a second voltage dividing resistor connected between the node and the reference potential point; further comprising the predetermined 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 first voltage dividing resistor and the second voltage dividing resistor have the same resistance value.

7. The sensor device according to claim 6 , wherein the high-side switch and the low-side switch have the same electrical characteristics.

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 power supply supplies the heating power to the sensor electrode.

9. further comprising a sinusoidal signal source capable of supplying a sinusoidal signal to the sensor electrodes; The sensor device according to claim 1 , wherein the control unit controls the sinusoidal signal source to supply the sinusoidal signal to the sensor electrode when the electrostatic capacitance is detected by the electrostatic detection circuit.

10. 10. The sensor device of claim 9, further comprising a capacitor for DC isolation provided between the sinusoidal signal source and the sensor electrode.

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

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

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