Sensor device

Abstract

The invention provides a sensor device which consumes less power. A sensor device is provided with: a sensor electrode capable of operating as a heating element; an electrostatic detection circuit that detects electrostatic capacitance between the sensor electrode and the object; a high-side switch connected to a power source that supplies power for heating to the sensor electrode; a decoupling switch; a low side switch; a voltage supply circuit that supplies a voltage to the node such that a voltage of the node between the decoupling switch and one end of the sensor electrode is higher than a voltage of a reference potential point; an electronic component comprising a resistor or a switch provided between a reference and a connection point between the high-side switch and the decoupling switch; and a control unit that controls the high-side switch, the decoupling switch, and the low-side switch, the source of the high-side switch and the source of the decoupling switch being connected to the connection point, and being connected to a reference potential point via an electronic element.

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 detection mode; and a decoupling circuit comprising a decoupling MOSFET connected between the high-side switch and the heating element. The gate controller turns on the decoupling MOSFET in heating mode and turns off the decoupling MOSFET in detection mode. In 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. The high-side switch is an N-channel MOSFET, the low-side switch is a P-channel MOSFET, and the decoupling circuit is an N-channel MOSFET (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

[0006] However, P-channel MOSFETs have larger on-resistance and consume more power than N-channel MOSFETs. Summary of the Invention

[0007] Therefore, an object of the present invention is to provide a sensor device that consumes less power.

[0008] -Methods for solving the problem-

[0009] The sensor device of the 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 connected to a power source for supplying heating power to the sensor electrode; a decoupling switch provided between the high-side switch and one end of the sensor electrode; a low-side switch provided between the other end of the sensor electrode and a reference potential point; a voltage supply circuit for supplying a voltage to a node between the decoupling switch and the one end of the sensor electrode so that the voltage of the node is higher than the voltage of the reference potential point; and an electronic component provided at a connection between the high-side switch and the decoupling switch. a resistor or switch between the point and the reference; and a control unit that controls the high-side switch, the decoupling switch, and the low-side switch, the voltage of the power supply being higher than the voltage of the reference potential point, the high-side switch, the decoupling switch, and the low-side switch being N-channel MOSFETs, the drain of the high-side switch being connected to the power supply, the drain of the decoupling switch being connected to the node, the drain of the low-side switch being connected to the other end of the sensor electrode, the source of the low-side switch being connected to the reference potential point, the source of the high-side switch and the source of the decoupling switch being connected to the connection point, and being connected to the reference potential point via the electronic component.

[0010] -Effects of the Invention-

[0011] A sensor device with low power consumption can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a diagram schematically showing a steering wheel on which the sensor device according to the embodiment is mounted.

[0013] Figure 2 This is a diagram showing an example of a circuit configuration of a sensor device according to an embodiment.

[0014] Figure 3A This is a diagram showing an example of parasitic capacitance Coss between the drain and source of the high-side MOSFET, the low-side MOSFET, and the decoupling MOSFET in the non-heating mode.

[0015] Figure 3B This is a diagram showing an example of parasitic capacitance Coss between the drain and source of the high-side MOSFET, the low-side MOSFET, and the decoupling MOSFET in the non-heating mode.

[0016] Figure 4 This is a diagram showing an example of electrical characteristics of an N-channel MOSFET.

[0017] Figure 5This is a diagram showing an example of a circuit configuration of a sensor device according to a modified example of the embodiment.

[0018] -Description of Reference Numerals-

[0019] 51 Power Supply

[0020] 100 sensor devices

[0021] 110 sensor electrodes

[0022] 120 Heater drive circuit

[0023] 121 High-side MOSFET (Example of a high-side switch)

[0024] 122 Low-side MOSFET (Example of a low-side switch)

[0025] 123 Decoupling MOSFET

[0026] 123A connection point

[0027] 123B line

[0028] 124 Switching MOSFET (An Example of Electronic Components)

[0029] 125 nodes

[0030] 126 Voltage Regulator (An Example of a Voltage Supply Circuit)

[0031] 130 static electricity detection circuit

[0032] 132 AC signal source

[0033] 134 capacitors

[0034] 140 Control Circuit

[0035] 150 Active shield electrode. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of a sensor device to which the present disclosure is applied will be described.

[0037] <Implementation Method>

[0038] 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.

[0039] 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 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. In addition, 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 fixed portion to which the sensor electrode 110 is fixed. The surface 11A of the rim 11 is an example of a contact area that can be touched by the detection object.

[0040] 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.

[0041] 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 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.

[0042] 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.

[0043] <Schematic Structure of Sensor Device 100 >

[0044] 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).

[0045] Sensor device 100 has two modes: a heating mode in which heating power is supplied from the vehicle's power supply to sensor electrode 110, and a non-heating mode in which heating power is not supplied. Control circuit 140 switches the modes of sensor device 100 on a time-sharing basis. That is, control circuit 140 has times when sensor device 100 is in heating mode and times when it is in non-heating mode.

[0046] <Sensor electrode 110>

[0047] 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.

[0048] <Heater drive circuit 120>

[0049] 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.

[0050] <Static Electricity Detection Circuit 130>

[0051] 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.

[0052] <Control Circuit 140>

[0053] The control circuit 140 is implemented as 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. In the heating mode, the control circuit 140 heats the sensor electrodes 110, thereby heating the rim 11 of the steering wheel 10. Furthermore, in the non-heating mode, the control circuit 140 determines whether a hand is in contact with the rim 11 of the steering wheel 10 based on the output of the static electricity detection circuit 130. Details of the control performed by the control circuit 140 in the non-heating and heating modes will be described later.

[0054] <Circuit Configuration of Sensor Device 100>

[0055] 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 2 In the description, the power source 51 is assumed to be a battery. However, 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.

[0056] The power supply circuit 50 includes a power supply 51 and a relay 52. ​​The relay 52 is inserted in series into the power supply path between the power supply 51 and the heater drive circuit 120. For example, the relay 52 is opened and closed by a vehicle body ECU (not shown).

[0057] <Sensor electrode 110>

[0058] 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 .

[0059] 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 .

[0060] <Heater drive circuit 120>

[0061] Heater drive circuit 120 includes a high-side MOSFET 121, a low-side MOSFET 122, a decoupling MOSFET 123, a switching MOSFET 124, a node 125, and a voltage regulator 126. High-side MOSFET 121 is an example of a high-side switch, low-side MOSFET 122 is an example of a low-side switch, and decoupling MOSFET 123 is an example of a decoupling switch. Switching MOSFET 124 is an example of an electronic component. Voltage regulator 126 is an example of a voltage supply circuit.

[0062] The high-side MOSFET 121 , the low-side MOSFET 122 , the decoupling MOSFET 123 , and the switching MOSFET 124 are formed of N-channel MOSFETs. N-channel MOSFETs have a lower on-resistance than P-channel MOSFETs, and thus have the advantage of easily reducing power consumption.

[0063] The high-side MOSFET 121 has its drain connected to the power supply 51 via the relay 52, its source connected to the source of the decoupling MOSFET 123, and its gate connected to the control circuit 140. The voltage V1 of the power supply 51 is supplied to the drain of the high-side MOSFET 121. Therefore, the drain of the high-side MOSFET 121 is denoted as V1. The high-side MOSFET 121 is driven by a PWM gate drive signal supplied to the gate from the control circuit 140.

[0064] The low-side MOSFET 122 has its drain connected to the sensor electrode 110, its source connected to the reference potential point (V2), and its gate connected to the control circuit 140. The reference potential point is ground potential, and its voltage is V2 (GND). The low-side MOSFET 122 is provided between the sensor electrode 110 and the reference potential point and is driven by a PWM gate drive signal supplied to the gate from the control circuit 140.

[0065] The decoupling MOSFET 123 is provided between the high-side MOSFET 121 and the sensor electrode 110. The decoupling MOSFET 123 has its drain connected to the node 125, its source connected to the source of the high-side MOSFET 121, and its gate connected to the control circuit 140. The point where the source of the decoupling MOSFET 123 is connected to the source of the high-side MOSFET 121 is a connection point 123A. Connection point 123A is the connection point between the high-side MOSFET 121 and the decoupling MOSFET 123. The decoupling MOSFET 123 is driven by a PWM gate drive signal supplied to the gate from the control circuit 140.

[0066] In heating mode, the control circuit 140 sets the gate voltages of the high-side MOSFET 121, decoupling MOSFET 123, and low-side MOSFET 122 to an H (High) level, turning them on. When switching to non-heating mode, the control circuit 140 first sets the gate voltages of the high-side MOSFET 121 and decoupling MOSFET 123 to an L (Low) level, turning them off. Next, the control circuit 140 sets the gate voltage of the low-side MOSFET 122 to a L (Low) level, turning them off. When switching to non-heating mode, the control circuit 140 sets the gate voltage of the high-side MOSFET 121 and decoupling MOSFET 123 to an open (Low) level, turning them off. When switching to non-heating mode, the control circuit 140 sets the potential of the sensor electrode 110 in the non-heating mode to the reference potential (GND) by setting the time during which the high-side MOSFET 121 and decoupling MOSFET 123 are open and the low-side MOSFET is on.

[0067] The gate drive signals driving high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 are not limited to PWM. When not heating sensor electrode 110, each gate drive signal can be maintained at an L level. Furthermore, the body ECU can adjust the temperature of sensor electrode 110 (heating element) by varying the voltage of V1. In this case, control circuit 140 can also maintain fixed gate drive signal H and L levels.

[0068] Switching MOSFET 124 is connected to line 123B, which connects connection point 123A to the reference potential point. The drain of switching MOSFET 124 is connected to connection point 123A, the source is connected to the reference potential point, and the gate is connected to control circuit 140. Switching MOSFET 124 is driven by a gate drive signal supplied to the gate from control circuit 140. Line 123B connects connection point 123A to the reference potential point and, on the reference potential point side, is connected to the source of low-side MOSFET 122. Switching MOSFET 124 is always in the on state (on) in heating mode and always in the open state (off) in non-heating mode.

[0069] Node 125 is a node between the drain of decoupling MOSFET 123 and sensor electrode 110. Node 125 is connected to voltage regulator 126 and supplied with voltage V3 output by voltage regulator 126. The voltage at node 125 is higher than the voltage at reference potential point V2. Node 125 is located between the drain of decoupling MOSFET 123, sensor electrode 110, and capacitor 134 of static electricity detection circuit 130.

[0070] The voltage regulator 126 is connected to the node 125 and outputs a voltage V3 to the node 125. The voltage regulator 126 converts the voltage V1 supplied from the power supply 51 into a voltage V3. The voltage V3 output by the voltage regulator 126 is lower than the voltage V1 of the power supply 51. Alternatively, a voltage-dividing resistor may be used instead of the voltage regulator 126 to convert the voltage V1 into the voltage V3. To prevent backflow to the voltage regulator 126, a diode 125A may be provided between the voltage regulator 126 and the node 125. Alternatively, if a switch is provided between the voltage regulator 126 and the node 125 and the switch is opened in the heating mode, the voltage V3 output by the voltage regulator 126 can be made higher than the voltage V1 of the power supply 51.

[0071] <Static Electricity Detection Circuit 130>

[0072] The static electricity detection circuit 130 includes a charge amplifier 131, an AC signal source 132, an amplitude adjustment unit 133, and a capacitor 134. The static electricity detection circuit 130 detects the static capacitance of the sensor electrode 110 using the self-capacitance method. The AC signal source 132 is an example of a sine wave signal source. By detecting the static capacitance using the self-capacitance method, the static electricity detection circuit 130 can improve the sensitivity of the static capacitance of the sensor electrode 110. The static electricity detection circuit 130 can also detect the static capacitance using the self-capacitance method of the sensor electrode 110 only in the non-heating mode.

[0073] Charge amplifier 131 has a positive-inverting input terminal (+) connected to the output terminal of amplitude adjustment unit 133, a negative-inverting input terminal (-) connected to sensor electrode 110 via capacitor 134, and an output terminal connected to control circuit 140. The output voltage at the output terminal of charge amplifier 131 is V0. Charge amplifier 131 is a differential amplifier that amplifies the difference between the input at its positive-inverting input terminal (+) and the input at its negative-inverting input terminal (-) and outputs an output signal.

[0074] The AC signal source 132 is connected to the amplitude adjustment unit 133 and to the sensor electrode 110 via the capacitor 134. The AC signal source 132 outputs an AC signal (sine wave signal) for driving the sensor electrode 110. The AC signal source 132 may stop outputting the AC signal in the heating mode.

[0075] When the hand H, an object approaching the sensor electrode 110 , is not present (parasitic capacitance Crg is zero), the amplitude adjustment unit 133 cancels the difference between the inverting input terminal (−) and the non-inverting input terminal (+), and adjusts the amplitude so that the output voltage V0 of the charge amplifier 131 becomes minimal.

[0076] The capacitor 134 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 the terminal connected to sensor electrode 110. Specifically, capacitor 134 is inserted in series between the inverting input terminal (-) of charge amplifier 131 and sensor electrode 110. Capacitor 134 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. The capacitance of capacitor 134 is Cd.

[0077] <Control Circuit 140>

[0078] The control circuit 140 performs control to switch between an on state and an open state by outputting gate drive signals to the gates of the high-side MOSFET 121 , the low-side MOSFET 122 , the decoupling MOSFET 123 , and the switching MOSFET 124 .

[0079] In the non-heating mode, the control circuit 140 outputs a low-level gate drive signal to the gates of the high-side MOSFET 121 , the low-side MOSFET 122 , and the decoupling MOSFET 123 , and outputs a high-level gate drive signal to the gate of the switching MOSFET 124 .

[0080] Thus, in the non-heating mode, the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 are in an open state (off). With the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 in an open state (off), the sensor electrode 110 is equivalent to a state without the power supply circuit 50.

[0081] 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. The control circuit 140 may also determine whether the hand H is touching the sensor electrode 110 only in the non-heating state.

[0082] Furthermore, in heating mode, the control circuit 140 outputs a PWM gate drive signal synchronized at the same frequency and at an H level to the gates of the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123, and outputs an L-level gate drive signal to the gate of the switching MOSFET 124. This turns the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 into an on state (turned on), while the switching MOSFET 124 turns into an open state (turned off). Consequently, power flows from the power supply 51 through the high-side MOSFET 121, the decoupling MOSFET 123, the sensor electrode 110, and the low-side MOSFET 122 toward the reference potential point. As a result, the sensor electrode 110 generates heat, functioning as a heater.

[0083] The duty cycle of the PWM gate drive signal (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 the like. Furthermore, the temperature of the steering wheel 10 heater can be measured by providing a temperature sensor on the steering wheel 10.

[0084] Alternatively, a high-resistance resistor may be provided in line 123B instead of switching MOSFET 124. If a high-resistance resistor is provided in line 123B instead of switching MOSFET 124, connection point 123A can be maintained at a reference potential in non-heating mode, and in heating mode, current hardly flows through the high-resistance resistor, thereby allowing current to flow from high-side MOSFET 121 through a path passing through decoupling MOSFET 123, sensor electrode 110, and low-side MOSFET 122, thereby heating sensor electrode 110. However, in order to reduce the power consumed by the resistor in heating mode, the resistance value is made greater than 1 kΩ. Furthermore, when switching to non-heating mode, in order to shorten the time it takes for the voltage at connection point 123A to reach V2, the resistance value is made less than 100 kΩ.

[0085] <Parasitic Capacitance of High-Side MOSFET 121 , Low-Side MOSFET 122 , and Decoupling MOSFET 123 >

[0086] Figure 3A This diagram shows an example of parasitic capacitance Coss between the drain and source of the high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 in the non-heating mode. As an example, the high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 are the same type of N-channel MOSFETs, and their parasitic capacitance Coss characteristics relative to the drain-source voltage VDS are equal.

[0087] exist Figure 3A Shown in Figure 2 The sensor electrode 110, the high-side MOSFET 121, the low-side MOSFET 122, the decoupling MOSFET 123, the node 125, and the capacitor 134 of the static detection circuit 130 are shown in FIG. Figure 3A In FIG. 1 , the switching MOSFET 124 that is turned on in the non-heating mode is shown as a switch in a closed state, and the power supply 51 is shown as a power supply V1 , and other components are omitted.

[0088] A parasitic capacitance Coss exists between the drain and source of the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123. MOSFETs have an electrical characteristic in which the parasitic capacitance Coss between the drain and source changes relative to the voltage between the drain and source. Generally, the greater the voltage between the drain and source, the smaller the parasitic capacitance Coss. Therefore, in an N-channel MOSFET, the greater the voltage between the drain and source, the smaller the parasitic capacitance Coss.

[0089] 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 the parasitic capacitance Coss of high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 to a certain extent.

[0090] Here, in non-heating mode, as Figure 3A As shown, the switching MOSFET 124 is turned on (ON), and the high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 are all turned off (OFF). The decoupling MOSFET 123 has its drain-source connected in the opposite direction to that of the high-side MOSFET 121 and low-side MOSFET 122, between the power supply V1 and the reference potential point.

[0091] Figure 3B It will Figure 3A The structure shown is further deformed as shown in FIG. Figure 3B In FIG. 1 , the high-side MOSFET 121 and the decoupling MOSFET 123 are folded downward relative to the sensor electrode 110, and the power supply V1 is represented by a DC power supply symbol. Figure 3B In, with Figure 3A Similarly, in the non-heating mode, the switching MOSFET 124 is in the conductive state (ON), so the switching MOSFET 124 provided in the line 123B is omitted and only the position of the switching MOSFET 124 is shown by a dotted rectangle.

[0092] In sensor device 100, high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 are all N-channel. To implement this structure, decoupling MOSFET 123 is connected between power supply V1 and a reference potential point, with its drain connected to the reference potential point and its source connected to power supply V1. To operate decoupling MOSFET 123 connected in this manner, voltage regulator 126 applies voltage V3 to the drain of decoupling MOSFET 123.

[0093] Furthermore, in the non-heating mode, the high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 are all set to an open state (disconnected). In this state, as viewed from connection point 123A, the high-side MOSFET 121 is connected in parallel with line 123B connected to the reference potential point. This is equivalent to a state in which the high-side MOSFET 121 is not present, and the parasitic capacitance Coss between the drain and source of the high-side MOSFET 121 does not affect the sensor electrode 110.

[0094] Therefore, in the non-heating mode, the parasitic capacitance Crgl of the sensor electrode 110 is the sum of the parasitic capacitance Coss between the drain and source of the low-side MOSFET 122 and the parasitic capacitance Coss between the drain and source of the decoupling MOSFET 123. Furthermore, the parasitic capacitance Crgl of the sensor electrode 110 is not affected by the parasitic capacitance Coss between the drain and source of the high-side MOSFET 121 and is therefore not affected by the parasitic capacitance Coss between the drain and source of the high-side MOSFET 121 caused by voltage fluctuations in the power supply V1.

[0095] Since the low-side MOSFET 122 and the decoupling MOSFET 123 are connected via the sensor electrode 110 , the drain-source voltages of the low-side MOSFET 122 and the decoupling MOSFET 123 in the non-heating mode are substantially equal to the voltage V3 .

[0096] <An example of MOSFET electrical characteristics>

[0097] Figure 4 This is a diagram showing an example of the electrical characteristics of an N-channel MOSFET. Figure 4 In the figure, the horizontal axis represents the voltage VDS (V) between the drain and source of an N-channel MOSFET. Figure 4 In the figure, the vertical axis represents the parasitic capacitance Coss (pF). Figure 4 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.

[0098] In the sensor 100 , the voltage VDS of the low-side MOSFET 122 and the decoupling MOSFET 123 in the non-heating mode is substantially equal to the voltage V3 . Therefore, if the voltage V3 is set to approximately 1 V or higher, the parasitic capacitance Coss of the low-side MOSFET 122 and the decoupling MOSFET 123 can be reduced.

[0099] As a result, it is possible to reduce the parasitic capacitance Crg1 of the sensor electrode 110. Furthermore, it is possible to prevent the parasitic capacitance Crg1 of the sensor electrode 110 from being affected by voltage fluctuations of the power supply V1.

[0100] For example, if power supply V3 is set to approximately 3V, the parasitic capacitance Coss of low-side MOSFET 122 and decoupling MOSFET 123 each becomes a very small value of approximately 200 pF. The total of the two parasitic capacitances Coss is approximately 400 pF, and this total parasitic capacitance becomes the parasitic capacitance Crgl between sensor electrode 110 and the ground potential point. Therefore, the parasitic capacitance Crgl between sensor electrode 110 and the ground potential point is very small.

[0101] In the sensor device 100 of the embodiment, the parasitic capacitance Crgl of the sensor electrode 110 in the non-heating mode is extremely small, minimizing the decrease in detection sensitivity when detecting the static capacitance of the sensor electrode 110, thereby achieving excellent detection sensitivity. Furthermore, the high-side MOSFET 121, low-side MOSFET 122, and decoupling MOSFET 123 of such a sensor device 100 are all N-channel MOSFETs. N-channel MOSFETs consume less power than P-channel MOSFETs.

[0102] Therefore, even if the high-side MOSFET 121 , the low-side MOSFET 122 , and the decoupling MOSFET 123 are all turned on in the heating mode, power consumption is small.

[0103] Effects

[0104] The sensor device 100 includes: a sensor electrode 110 capable of operating as a heating element; an electrostatic detection circuit 130 for detecting electrostatic capacitance between the sensor electrode 110 and an object; a high-side MOSFET 121 connected to a power source 51 for supplying heating power to the sensor electrode 110; a decoupling MOSFET 123 provided between the high-side MOSFET 121 and one end of the sensor electrode 110; a low-side MOSFET 122 provided between the other end of the sensor electrode 110 and a reference potential point; a voltage regulator 126 for supplying a voltage to a node 125 so that the voltage of the node 125 between the decoupling MOSFET 123 and one end of the sensor electrode 110 becomes higher than the voltage of the reference potential point; and a switching MOSFET 124 provided at a connection point 123A between the high-side MOSFET 121 and the decoupling MOSFET 123. and a resistor or switch between the reference; and a control circuit 140, which controls the high-side MOSFET 121, the decoupling MOSFET 123 and the low-side MOSFET 122. The voltage V1 of the power supply 51 is higher than the voltage V2 of the reference potential point. The high-side MOSFET 121, the decoupling MOSFET 123 and the low-side MOSFET 122 are N-channel MOSFETs. The drain of the high-side MOSFET 121 is connected to the power supply 51, the drain of the decoupling MOSFET 123 is connected to the node 125, the drain of the low-side MOSFET 122 is connected to the other end of the sensor electrode 110, the source of the low-side MOSFET 122 is connected to the reference potential point, the source of the high-side MOSFET 121 and the source of the decoupling MOSFET 123 are connected to the connection point 123A, and are connected to the reference potential point via the switching MOSFET 124. Since the high-side MOSFET 121 , the low-side MOSFET 122 , and the decoupling MOSFET 123 are all N-channel MOSFETs, power consumption is low even when they are all turned on in the heating mode.

[0105] Therefore, it is possible to provide a sensor device 100 that consumes less power. Furthermore, since the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 are all N-channel MOSFETs, manufacturing is facilitated, product variations can be suppressed, and electrical reliability can be improved. Furthermore, manufacturing costs can be reduced.

[0106] Furthermore, a capacitor 134 for DC isolation may be further provided between the sensor electrode 110 and the static detection circuit 130. The static detection circuit 130 can accurately detect the electrostatic capacitance of the sensor electrode 110 by isolating the DC signal from the static detection circuit 130.

[0107] Alternatively, voltage regulator 126 may be a constant-voltage regulator that outputs a voltage V3 higher than voltage V1 of power supply 51. By increasing voltage V3 independently of voltage V1 of power supply 51, the parasitic capacitance Coss between the drain and source of low-side MOSFET 122 and decoupling MOSFET 123 can be reduced, thereby reducing the parasitic capacitance Crgl of sensor electrode 110. This improves the sensitivity of electrostatic detection.

[0108] Alternatively, the source of the high-side MOSFET 121 and the source of the decoupling MOSFET 123 may be connected to a reference potential point via a switch (124), wherein the switch is an N-channel MOSFET having a drain connected to the source of the high-side MOSFET 121 and the source of the decoupling MOSFET 123 and a source connected to the reference potential point. By using the switch (124) as an N-channel MOSFET, manufacturing is easier, and product deviation can be further suppressed, thereby further improving electrical reliability. In addition, manufacturing costs can be reduced.

[0109] In addition, the source of the high-side MOSFET 121 and the source of the decoupling MOSFET 123 are connected to the reference potential point via a resistor (124), and the resistance value of the resistor is preferably a resistance value of 1 kΩ to 100 kΩ. In the heating mode, the current can be suppressed from flowing from the connection point 123A to the reference potential point, and in the non-heating mode, the connection point 123A can be reliably maintained at the reference potential. In addition, the structure is very simple, which can achieve improved electrical reliability and reduced manufacturing costs.

[0110] Alternatively, the static electricity detection circuit 130 may detect the static capacitance using a self-capacitance method, thereby increasing the sensitivity of the static capacitance in the sensor electrode 110 .

[0111] Furthermore, the control circuit 140 may control the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 to be in an on state when power for heating is supplied from the power supply 51 to the sensor electrode 110. When power for heating is stopped from the power supply 51 to the sensor electrode 110, the control circuit 140 may control the high-side MOSFET 121 and the decoupling MOSFET 123 to be in an open state and then set the low-side MOSFET 122 to an open state. By switching the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 between the on and open states, a circuit in a heating mode and a circuit in a non-heating mode can be easily implemented. Furthermore, when power for heating is stopped from the power supply 51 to the sensor electrode 110, safety can be improved by disconnecting the circuit from the side closest to the power supply 51.

[0112] In addition, the electronic component may also be a switch (124). The control circuit 140 may also control the switch (124) to be in an open state when the power supply 51 supplies heating power to the sensor electrode 110, and control the high-side MOSFET 121 and the decoupling MOSFET 123 to be in an open state when the power supply 51 stops supplying heating power to the sensor electrode 110, and after controlling the switch to be in an on state, control the low-side switch to be in an open state. By switching the on state and the open state of the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123, a circuit in a heating mode and a circuit in a non-heating mode can be easily realized. By switching the on state and the open state of the high-side MOSFET 121, the low-side MOSFET 122, and the decoupling MOSFET 123 and the switch (124), a circuit in a heating mode and a circuit in a non-heating mode can be easily realized. In addition, when the power supply 51 stops supplying heating power to the sensor electrode 110, safety can be improved by disconnecting from the side close to the power supply 51.

[0113] Furthermore, the electronic component may be a resistor (124). The electronic component can be realized with a simple structure.

[0114] <Modification of the embodiment>

[0115] Figure 5 This is a diagram showing an example of a circuit configuration of a sensor device 100M1 according to a modification of the embodiment. Figure 5 Also shown is the power supply circuit 50 of the vehicle 1 on which the sensor device 100M1 is mounted.

[0116] The sensor device 100M1 has a Figure 2 The sensor device 100 shown in the figure has an additional structure of an active shield electrode 150. In addition, in order to prevent the reverse current to the voltage regulator 126, a switch 125B may be provided between the voltage regulator 126 and the node 125. The switch 125B replaces Figure 2 The diode 125A is provided as shown. Figure 2 The sensor devices 100 shown are identical.

[0117] Active shield electrode 150 is disposed near sensor electrode 110 on the back side of sensor electrode 110. The back side of sensor electrode 110 refers to the side opposite to the side where hand H is close to sensor electrode 110. Furthermore, near sensor electrode 110 means that sensor electrode 110 and active shield electrode 150 are close enough to form capacitive coupling. The capacitance between sensor electrode 110 and active shield electrode 150 is denoted by Crs.

[0118] Active shield electrode 150 is connected to AC signal source 132 and is driven by a signal including an AC component having the same frequency and phase as the AC component included in the signal supplied to sensor electrode 110. Furthermore, the amplitude of the AC component of the signal supplied to active shield electrode 150 is greater than the amplitude of the AC component of the signal supplied to sensor electrode 110.

[0119] Active shield electrode 150 is provided to shield sensor electrode 110 from noise and to suppress the effects of parasitic capacitance. Active shield electrode 150 is arranged near sensor electrode 110 at predetermined intervals to shield sensor electrode 110 primarily from noise originating from a reference potential point such as ground, while also suppressing the effects of parasitic capacitance between the sensor electrode 110 and the reference potential point.

[0120] The amplitude adjustment unit 133 adjusts the current flowing from the active shield electrode 150 to the sensor electrode 110 through the electrostatic capacitance Crs and the current flowing from the sensor electrode 110 to the reference potential point through the parasitic capacitance Crg1 to cancel each other out. Specifically, when there is no hand H as an object approaching the sensor electrode 110 (when the electrostatic capacitance Crg is zero), the amplitude is adjusted so that the drive current flowing through the sensor electrode 110 is zero.

[0121] The sensor device 100M1 of the modified example of the embodiment further includes an active shielding electrode 150 arranged near the sensor electrode 110. Therefore, the active shielding electrode 150 can reduce the influence of noise and parasitic capacitance in the sensor electrode 110, and can also reduce the influence of noise and parasitic capacitance in the wiring, etc. included in the electrostatic detection circuit 130.

[0122] 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.

[0123] Regarding the above-mentioned embodiment, the following supplementary notes are further disclosed.

[0124] (Note 1)

[0125] 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 connected to a power source for supplying heating power to the sensor electrode; a decoupling switch provided between the high-side switch and one end of the sensor electrode; a low-side switch provided between the other end of the sensor electrode and a reference potential point; a voltage supply circuit for supplying a voltage to a node between the decoupling switch and the one end of the sensor electrode so that the voltage of the node is higher than the voltage of the reference potential point; and an electronic component provided at a connection point between the high-side switch and the decoupling switch and the reference potential point. a resistor or switch between the reference points; and a control unit that controls the high-side switch, the decoupling switch, and the low-side switch, the voltage of the power supply being higher than the voltage of the reference potential point, the high-side switch, the decoupling switch, and the low-side switch being N-channel MOSFETs, the drain of the high-side switch being connected to the power supply, the drain of the decoupling switch being connected to the node, the drain of the low-side switch being connected to the other end of the sensor electrode, the source of the low-side switch being connected to the reference potential point, the source of the high-side switch and the source of the decoupling switch being connected to the connection point, and being connected to the reference potential point via the electronic component.

[0126] (Note 2)

[0127] The sensor device according to Supplementary Note 1, further comprising a capacitor for direct current isolation provided between the sensor electrode and the static electricity detection circuit.

[0128] (Note 3)

[0129] The sensor device according to Supplementary Note 1 or 2, wherein the voltage supply circuit is a constant voltage regulator that outputs a voltage higher than a voltage of the power supply.

[0130] (Note 4)

[0131] A sensor device according to any one of Notes 1 to 3, wherein the source of the high-side switch and the source of the decoupling switch are connected to the reference potential point via the switch, and the switch is an N-channel MOSFET having a drain connected to the source of the high-side switch and the source of the decoupling switch, and a source connected to the reference potential point.

[0132] (Note 5)

[0133] The sensor device according to any one of Notes 1 to 3, wherein the source of the high-side switch and the source of the decoupling switch are connected to the reference potential point via the resistor, and the resistance value of the resistor is greater than 1 kΩ and less than 100 kΩ.

[0134] (Note 6)

[0135] The sensor device according to any one of Supplementary Notes 1 to 5, wherein the static electricity detection circuit detects the static capacitance using a self-capacitance method.

[0136] (Note 7)

[0137] The sensor device according to any one of Supplementary Notes 1 to 6, further comprising an active shielding electrode arranged near the sensor electrode.

[0138] (Note 8)

[0139] A sensor device according to any one of Notes 1 to 7, wherein the control unit performs the following processing: when the power for heating is supplied from the power supply to the sensor electrode, the high-side switch, the low-side switch and the decoupling switch are controlled to be in an on state; when the power for heating is stopped from being supplied from the power supply to the sensor electrode, after the high-side switch and the decoupling switch are controlled to be in an open state, the low-side switch is controlled to be in an open state.

[0140] (Note 9)

[0141] A sensor device according to any one of Notes 1 to 7, wherein the electronic component is the switch, and the control unit performs the following processing: when the power for heating is supplied from the power supply to the sensor electrode, the switch is controlled to be in an open state; when the power for heating is stopped from being supplied from the power supply to the sensor electrode, the high-side switch and the decoupling switch are controlled to be in an open state; and after the switch is controlled to be in an on state, the low-side switch is controlled to be in an open state.

[0142] (Note 10)

[0143] The sensor device according to any one of Supplementary Notes 1 to 8, wherein the electronic component is the resistor.

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 connected to a power source for supplying heating power to the sensor electrode; a decoupling switch, disposed between the high-side switch and one end of the sensor electrode; a low-side switch, disposed between the other end of the sensor electrode and a reference potential point; a voltage supply circuit for supplying a voltage to a node between the decoupling switch and the one end of the sensor electrode so that the voltage of the node is higher than a voltage of the reference potential point; an electronic component consisting of a resistor or a switch provided between a connection point between the high-side switch and the decoupling switch and the reference; and a control unit, controlling the high-side switch, the decoupling switch, and the low-side switch, The voltage of the power supply is higher than the voltage of the reference potential point, The high-side switch, the decoupling switch, and the low-side switch are N-channel MOSFETs. The drain of the high side switch is connected to the power supply, The drain of the decoupling switch is connected to the node, The drain of the low side switch is connected to the other end of the sensor electrode, The source of the low side switch is connected to the reference potential point, The source of the high-side switch and the source of the decoupling switch are connected to the connection point and are connected to the reference potential point via the electronic component.

2. The sensor device according to claim 1, wherein The sensor device further includes a capacitor for direct current isolation provided between the sensor electrode and the static electricity detection circuit.

3. The sensor device according to claim 1, wherein The voltage supply circuit is a constant voltage regulator that outputs a voltage higher than a voltage of the power supply.

4. The sensor device according to any one of claims 1 to 3, wherein: The source of the high-side switch and the source of the decoupling switch are connected to the reference potential point via the switch. The switch is an N-channel MOSFET having a drain connected to the source of the high-side switch and the source of the decoupling switch, and a source connected to the reference potential point.

5. The sensor device according to any one of claims 1 to 3, wherein The source of the high side switch and the source of the decoupling switch are connected to the reference potential point via the resistor. The resistance value of the resistor is greater than 1 kΩ and less than 100 kΩ. The sensor device according to claim 1 , wherein: The static electricity detection circuit detects the static capacitance in a self-capacitance manner.

7. The sensor device according to claim 1, wherein The sensor device further includes an active shield electrode disposed adjacent to the sensor electrode.

8. The sensor device according to claim 1, wherein 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, the low side switch, and the decoupling switch are controlled to be in an on state, When the supply of the heating power from the power source to the sensor electrode is stopped, the high side switch and the decoupling switch are controlled to be in the open state, and then the low side switch is controlled to be in the open state.

9. The sensor device according to claim 1, wherein The electronic component is the switch, The control unit performs the following processing: When the power for heating is supplied from the power supply to the sensor electrode, the switch is controlled to be in an open state. When the supply of the heating power from the power source to the sensor electrode is stopped, the highside switch and the decoupling switch are controlled to be open, and then the switch is controlled to be conductive, and then the lowside switch is controlled to be open.

10. The sensor device according to claim 1, wherein The electronic component is the resistor.

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