Electronic devices

Abstract

To provide an electronic device which comprises a contact resistance recovery function of a connector terminal to miniaturize a control board.SOLUTION: In a connector terminal Rc, a first end T1 is connected with a battery VB via a power switch SW1, and a second end T2 on the opposite side of the first end T1 is connected with a high potential side of a high impedance input circuit 40. A contact resistance recovery circuit 50 is constituted of a semiconductor switch, and comprises: a recovery switch SW2 which can open and close a recovery current energization path for connecting the second terminal T2 of the connector terminal Rc with a ground; a current restriction resistor Rr serially connected with the recovery switch SW2; and an energization time setting circuit 55 or 60 which sets an energization time for bringing the recovery switch SW2 into an on state after the power switch SW1 is turned on. The contact resistance recovery circuit 50 causes current larger than current flowing in the high impedance input circuit 40 to flow in the connector terminal Rc so that contact resistance of the connector terminal Rc is reduced when the recovery switch SW2 is turned on during the energization time.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to electronic devices. [Background technology]

[0002] Conventionally, when an oxide film is formed due to fretting corrosion in terminals used in connectors of control boards and the like, and the contact resistance increases, a technique is known that uses the coherer effect to recover the contact resistance. The coherer effect is a phenomenon in which, when a voltage of a certain value or more is applied to an oxide film, a current flows suddenly, destroying the oxide film and increasing the contact resistance. After the oxide film is destroyed, the contact resistance becomes stable. If the contact resistance can be kept low, costs can be reduced by changing the gold plating of the terminals to tin plating.

[0003] For example, the device disclosed in Patent Document 1 receives an input voltage from a battery and generates an internal power supply (reference voltage source) in a regulator. When the switch is turned from off to on and power supply starts, an inrush current flows temporarily from the internal power supply to charge the capacitor. This inrush current destroys and removes the oxide film formed on the connector terminal. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-119814 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the conventional technology of Patent Document 1, in order to pass a contact resistance recovery current to remove the oxide film on the connector terminal, a power supply circuit that generates an internal power supply separate from the battery power supply and a power supply terminal for the internal power supply are required, which increases the number of mounted components on the control board. The power supply circuit for the internal power supply is required to have an output current specification that is sufficient to remove the oxide film. In addition, the conventional technology of Patent Document 1 requires a large-capacity capacitor, which increases the mounting area, making it difficult to miniaturize the control board.

[0006] The present invention has been made in view of the above-mentioned points, and its object is to provide an electronic device having a contact resistance recovery function for a connector terminal, in which a control board is made smaller. [Means for solving the problem]

[0007] The present invention is an electronic device mounted on a control board (70), and includes a processing circuit (30) that executes predetermined processing, a high impedance input circuit (40, 40U), a connector terminal (Rc), and a contact resistance recovery circuit (50).

[0008] The high impedance input circuit is composed of a plurality of voltage dividing resistors (R1, R2) connected in series to divide a power supply voltage (VBin) supplied from an external power supply (VB) to generate an input signal voltage (Vin) and output it to a processing circuit. Alternatively, the high impedance input circuit is composed of a pull-down resistor (R3) connected to a connection point where the power supply voltage is input as an input signal voltage of the processing circuit.

[0009] The connector terminal has a first end (T1) connected to an external power supply via a power switch (SW1), and a second end (T2) opposite to the first end connected to the high potential side of a high impedance input circuit.

[0010] The contact resistance recovery circuit is composed of a semiconductor switch, and includes a recovery switch (SW2) capable of opening and closing a recovery current path connecting the second end of the connector terminal and ground, a current limiting resistor (Rr) connected in series to the recovery switch, and a current flow time setting circuit that sets the current flow time for which the recovery switch is in the ON state from the time the power switch is turned ON. The road The contact resistance recovery circuit causes a current larger than the current flowing through the high impedance input circuit to flow through the connector terminal so as to reduce the contact resistance of the connector terminal by turning on the recovery switch during the energized time.

[0011] In a first aspect of the present invention, The current flow time setting circuit is Between the second end of the connector terminal and the base terminal or the gate terminal of the transistor constituting the recovery switch A CR circuit in which a capacitor (Cr) and a resistor (Rs) are connected in series (55) It is composed of: After the power switch is turned ON, the time until the voltage input to the base or gate of the recovery switch falls below the ON threshold of the recovery switch is determined based on the time constant of the CR circuit. In a second aspect of the present invention, The current-on time setting circuit is IC (204、206) A timer circuit provided inside (60) It is composed of: The input signal voltage obtained by dividing the voltage in a high impedance input circuit composed of multiple voltage dividing resistors (R1, R2) is used as the operating power supply for the timer circuit.

[0012] In the present invention, a contact resistance recovery circuit is provided in the middle of the path from the external power supply to the high impedance input circuit via the connector terminal. When the recovery switch of the contact resistance recovery circuit is turned on for a predetermined current flow time from the start of power supply from the external power supply, a large current flows through the connector terminal and destroys the oxide film. There is no need for a separate power supply circuit for flowing the contact resistance recovery current, as provided in the prior art of Patent Document 1.

[0013] In addition, since the contact resistance recovery circuit of the present invention uses a recovery switch composed of a semiconductor switch, the mounting area can be reduced and the control board can be made smaller than the conventional technology of Patent Document 1 which uses a large-capacity capacitor. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing a basic configuration of an electronic device according to each embodiment of the present invention. [Diagram 2]FIG. 1 is a block diagram of an electronic device according to a first embodiment. [Diagram 3] 4 is an operation chart of the electronic device according to the first embodiment. [Figure 4] FIG. 11 is a block diagram of an electronic device according to a second embodiment. [Diagram 5] FIG. 11 is a block diagram of an electronic device according to a third embodiment. [Figure 6] FIG. 10 is a block diagram of an electronic device according to a fourth embodiment. [Figure 7] FIG. 13 is a block diagram of an electronic device according to a fifth embodiment. [Figure 8] FIG. 8 is a circuit diagram embodying the block diagram of FIG. 7. [Figure 9] FIG. 13 is a block diagram of an electronic device according to a sixth embodiment. [Figure 10] FIG. 10 is a circuit diagram embodying the block diagram of FIG. 9. [Figure 11] FIG. 13 is a block diagram showing another example of the configuration of the high impedance input circuit; [Figure 12] FIG. 2 is a block diagram of an electronic device according to a first comparative example. [Figure 13] FIG. 11 is a block diagram of an electronic device according to a second comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, multiple embodiments of the electronic device according to the present invention will be described with reference to the drawings. The electronic device of each embodiment is a device including a processing circuit that determines the input state of the battery voltage in a control device that drives and controls an on-board actuator using DC power from an on-board battery. In multiple embodiments, substantially the same components are given the same reference numerals and descriptions thereof will be omitted.

[0016] (Basic configuration) First, the basic configuration of an electronic device 10 according to each embodiment of the present invention will be described with reference to Fig. 1. The electronic device 10 includes a processing circuit 30, a high impedance input circuit 40, and a contact resistance recovery circuit 50, and is mounted on a control board 70. A connector 75 is provided on one end of the control board 70, and the electronic device 10 further includes a connector terminal Rc.

[0017] The connector terminal Rc is illustrated as a kind of resistive element. A first end T1 of the connector terminal Rc is connected to a battery VB as an "external power supply" via a power switch SW1. A second end T2 of the connector terminal Rc, which is opposite to the first end T1, is connected to the high potential side of the high impedance input circuit 40.

[0018] Regarding symbols in the drawings and the specification, "VB" is a symbol that indicates a battery as an object and also means the battery voltage, which is a physical property value of the battery. "Rc" is a symbol for a connector terminal and also means the terminal contact resistance, which is a physical property value of the connector terminal. Other resistance symbols such as R1, R2, and Rr are also symbols for resistive elements and also mean the resistance (value), which is a physical property value of the resistive elements.

[0019] The processing circuit 30 executes a predetermined process. In this embodiment, the process executes a process to determine the supply state of the battery voltage VB when starting up the in-vehicle actuator. The processing circuit 30 determines whether the input signal voltage Vin is in a high impedance state or a low impedance state, and outputs the determination result. Based on the determination result, if power is being supplied normally, for example, a start-up circuit starts up the actuator.

[0020] The high impedance input circuit 40 is composed of a plurality of voltage dividing resistors R1 and R2 connected in series. A high impedance input circuit 40U having another configuration example without voltage dividing resistors R1 and R2 will be described later with reference to FIG. 11. A battery supply voltage VBin supplied from a battery VB via a connector terminal Rc is applied to the high potential side of the high impedance input circuit 40. The high impedance input circuit 40 outputs an input signal voltage Vin generated by dividing the battery supply voltage VBin to the processing circuit 30. The input signal voltage Vin is expressed by the following formula. Vin = VBin × R2 / (R1 + R2)

[0021] The contact resistance recovery circuit 50 has a recovery current path connected in parallel to the high impedance input circuit 40 between the second end T2 of the connector terminal Rc and ground. A current limiting resistor Rr and a recovery switch SW2 are connected in series to the recovery current path. The recovery switch SW2 is composed of a semiconductor switch such as a bipolar transistor or a FET (field effect transistor), and is capable of opening and closing the recovery current path.

[0022] When the recovery switch SW2 is ON (connected), the recovery current Ire flows through the recovery current path. The resistance value of the current limiting resistor Rr is set so that the recovery current Ire is larger than the current that flows through the high impedance input circuit 40 when the recovery switch SW2 is OFF (disconnected). While the recovery switch SW2 is ON, the recovery current Ire flows through the connector terminal Rc, destroying and removing the oxide film, thereby reducing the contact resistance Rc and restoring it to a normal level.

[0023] The energization time setting circuits 55 and 60 set the energization time for keeping the recovery switch SW2 in the ON state from when the power switch SW1 is turned ON. The reference numeral "55" of the energization time setting circuit corresponds to the CR circuit in the first and second embodiments, and the reference numeral "60" corresponds to the timer circuit in the third to sixth embodiments.

[0024] In FIG. 1, the operation will be explained using the following numerical example. VB=12V R1 = 60kΩ R2 = 20kΩ Rc=100Ω (oxidized state) Rr=200Ω

[0025] When the recovery switch SW2 of the contact resistance recovery circuit 50 is OFF, the voltage applied to the connector terminal Rc is (12×0.1 / (0.1+60+20)≒) 15 mV, which is very small. Most of the battery voltage VB (12 V) is applied to the voltage dividing resistors R1 and R2 of the high impedance input circuit 40. Therefore, although there may be some differences depending on the specifications of the connector terminal Rc, it is estimated that the oxide film cannot be destroyed.

[0026] When the recovery switch SW2 is turned ON, the voltage applied to the connector terminal Rc becomes (12 × 0.1 / (0.1 + 0.2) =) 4V, which is a voltage high enough to destroy the oxide film, and as a result, the oxide film is destroyed and the recovery current Ire (40 mA or more) flows.

[0027] However, constantly passing the recovery current Ire increases unnecessary power consumption and affects the original input signal voltage Vin. Therefore, when the contact resistance is expected to recover, the recovery switch SW2 is turned OFF to cut off the recovery current path.

[0028] In this way, by turning on the recovery switch SW2 of the contact resistance recovery circuit 50 for a specific current-carrying time from when the power switch SW1 is turned on, a voltage equal to or greater than a certain value can be applied to the connector terminal Rc. This removes the oxide film on the connector terminal Rc, and the contact resistance can be restored to a normal, stable resistance value before oxidation.

[0029] (Comparative Example) Here, comparative electronic devices 108 and 109 will be described with reference to Figures 12 and 13. Comparative electronic device 108 shown in Figure 12 corresponds to the configuration of Figure 3, etc., of Patent Document 1 (JP Patent Publication No. 2020-119814). VBAT and SWB correspond to the battery voltage and battery switch of Patent Document 1. Power supply circuit 81 provided in control board 70 corresponds to the regulator unit of Patent Document 1, and receives battery voltage VBAT to generate an internal power supply voltage VS for passing a recovery current.

[0030] The power supply circuit 81 is connected to the recovery current supply connector terminal Rcb via the recovery switch SWS and the power supply circuit protection resistor Rpv. When the SW control unit 82 turns on the recovery switch SWS during contact resistance recovery, the internal power supply voltage VS for recovery current supply is applied to the first end T1 of the connector terminal Rc via the recovery current supply connector terminal Rcb.

[0031] The contact resistance recovery circuit 508 of the comparative example 1 is composed of an RC circuit in which a current limiting resistor Rr and a capacitor Cr are connected in series. When the recovery switch SWS is turned on and the internal power supply voltage VS is applied, an inrush current flows temporarily to charge the capacitor Cr. This inrush current destroys and removes the oxide film formed on the connector terminal Rc.

[0032] The electronic device 108 of Comparative Example 1 requires a power supply circuit 81 for generating an internal power supply voltage VS for passing the recovery current and a connector terminal Rcb for passing the recovery current, which increases the number of mounted components on the control board 70. In addition, although it varies depending on conditions such as the material, surface treatment, and size of the connector terminal Rc, when assuming an in-vehicle control board 70, it is estimated that the capacitance of the capacitor Cr needs to be 1000 μF or more, which increases the mounting area.

[0033] An electronic device 109 of Comparative Example 2 shown in Fig. 13 is obtained by replacing the configuration of the contact resistance recovery circuit 508 of Fig. 12 with the contact resistance recovery circuit 50 of this embodiment. In this configuration, the recovery current flows by the battery supply voltage VBin input from the connector terminal Rc, so the power supply circuit 81 is not required. However, even in Comparative Example 2, the capacitance of the capacitor Cr needs to be 1000 μF or more, so the control board 70 cannot be made smaller.

[0034] (Point of view of the present invention) In contrast to the above Comparative Examples 1 and 2, the present invention aims to miniaturize the control board 70. As a means to achieve this, the voltage source for passing the recovery current Ire in the contact resistance recovery circuit 50 is the battery supply voltage VBin input to the connector terminal Rc, eliminating the need for a separate power supply circuit. Also, the contact resistance recovery circuit 50 is configured using a semiconductor switch without using a large-capacity capacitor.

[0035] In the third to sixth embodiments, all or part of the circuits on the control board 70 are incorporated into the IC. Further miniaturization is achieved by incorporating a current amplifier circuit and a timer circuit inside the IC. For example, the IC is configured as an "input IC" including the processing circuit 30. The operating power supply for the timer circuit 60 also uses the voltage of the high impedance input circuit 40, eliminating the need for a separate power supply circuit. In the sixth embodiment, the timer circuit is configured with a FET circuit that uses the input signal voltage Vin obtained by voltage division in the high impedance input circuit 40 as its operating power supply, making it possible to reduce the number of terminals of the IC.

[0036] Next, electronic devices according to first to sixth embodiments will be described in order with reference to Figures 2 to 10. In the following, the reference numerals of the electronic devices according to the first to sixth embodiments are designated by adding the embodiment number as the third digit following "10".

[0037] (First embodiment) In the electronic device 101 of the first embodiment shown in Fig. 2, the recovery switch SW2 of the contact resistance recovery circuit 50 is configured with an NPN bipolar transistor ("BT" in the figure). The collector of the recovery switch SW2 is connected to the high-potential side current limiting resistor Rr, and the emitter is connected to ground. Note that by logically inverting the configuration in Fig. 2, the recovery switch SW2 can also be configured with a PNP bipolar transistor.

[0038] A capacitor Cr, a resistor Rs, and a resistor Rt are connected in series in this order from the high potential side in parallel with the current limiting resistor Rr and the recovery switch SW2 that constitute the recovery current flow path. The connection point between the resistors Rs and Rt is connected to the base of the recovery switch SW2. The current flow time setting circuit is composed of a CR circuit 55 in which a capacitor Cr and a resistor Rs are connected in series. The voltage at the connection point between the resistors Rs and Rt, i.e., the voltage input to the base of the recovery switch SW2, is referred to as a base voltage Va.

[0039] The operation of the electronic device 101 will be described with reference to the operation chart of Fig. 3. The vertical axis of the operation chart indicates, from top to bottom, ON / OFF of the power switch SW1, base voltage Va, ON / OFF of the recovery switch SW2, and changes in the recovery current Ire. When the power switch SW1 is turned ON at time t1, the base voltage Va rises to a voltage close to the battery supply voltage VBin, more specifically, to a voltage minus the voltage drop due to resistor Rs. At this time, the base voltage Va exceeds the ON threshold Vth, turning on the recovery switch SW2 and starting the flow of the recovery current Ire.

[0040] After that, as the capacitor Cr is charged, the base voltage Va gradually decreases. When the base voltage Va falls below the ON threshold Vth at time t2, the recovery switch SW2 turns OFF and the flow of the recovery current Ire ends. Strictly speaking, the OFF operation of the recovery switch SW2 and the accompanying decrease in the recovery current Ire change with a slope from time t2 to time t3. However, the time ΔT from time t2 to time t3 is extremely short compared to the time Ton from time t1 to time t2, so it can be ignored. Therefore, the time until the base voltage Va falls below the ON threshold Vth after the power switch SW1 is turned ON is regarded as the flow time of the recovery current Ire.

[0041] Here, the time for the base voltage Va to fall is determined by the time constant of the CR circuit, i.e., the product of the capacitance of the capacitor Cr and the resistance of the resistor Rs. Therefore, the conduction time Ton of the recovery current Ire is determined based on the time constant of the CR circuit and the ON threshold Vth of the recovery switch SW2.

[0042] In this way, in the first embodiment, the current flow time setting circuit is configured by the CR circuit 55 connected in parallel to the recovery current flow path of the contact resistance recovery circuit 50. The voltage charged to the capacitor Cr of the CR circuit is the battery supply voltage VBin input from the connector terminal Rc, and a separate power supply circuit or power supply terminal as in the conventional technology of Patent Document 1 is not required. Therefore, the control board 70 can be made smaller.

[0043] Second embodiment In the electronic device 102 of the second embodiment shown in FIG. 4, the recovery switch SW2 of the contact resistance recovery circuit 50 is configured with an Nch FET (e.g., MOSFET). The drain of the recovery switch SW2 is connected to a high-potential side current limiting resistor Rr, and the source is connected to ground, forming a parasitic diode that allows a current from the source side to the drain side. In order to block the reverse current passing through the parasitic diode, a diode D1 that allows only a forward current is connected between the contact resistor Rr and the recovery switch SW2. Note that it is also possible to configure the recovery switch SW2 with a Pch FET by logically inverting the configuration of FIG. 4.

[0044] As in the first embodiment, the current flow time setting circuit is composed of a CR circuit 55 in which a capacitor Cr and a resistor Rs are connected in series. After the power switch is turned on, the time until the voltage Va input to the gate falls below the ON threshold Vth of the recovery switch SW2 is the current flow time Ton of the recovery current Ire. The current flow time Ton is determined based on the time constant of the CR circuit.

[0045] Third embodiment In the third to sixth embodiments, the energization time setting circuit is composed of a timer circuit 60 provided inside the input IC. The timer circuit 60 outputs an ON signal SWo to the recovery switch SW2 during the energization time. In the electronic device 103 of the third embodiment shown in FIG. 5, the high impedance input circuit 40 and the contact resistance recovery circuit 50 are all provided inside the input IC 203. A battery supply voltage VBin is used as the operating power source for the timer circuit 60. The input IC 203 has two terminals, the battery supply voltage VBin and the ground GND.

[0046] In this configuration, each circuit can be configured inside the input IC 203, thereby making it possible to reduce the size of the circuit. For example, by incorporating an amplifier circuit or the like in the timer circuit 60, a more complicated circuit can be configured, making it possible to reduce the size of the control board 70. For a specific circuit configuration of the timer circuit 60, see FIG. 8 in the fifth embodiment. Also, the number of terminals of the input IC 203 can be reduced.

[0047] (Fourth embodiment) 6, the high impedance input circuit 40 and the contact resistance recovery circuit 50 are all provided inside the input IC 204. The difference from the third embodiment is that the input signal voltage Vin obtained by voltage division in the high impedance input circuit 40 is used as the operating power supply for the timer circuit 60. In other words, the input signal voltage Vin output from the high impedance input circuit 40 to the processing circuit 30 is branched off and used as the operating power supply for the timer circuit 60.

[0048] In this configuration, it is possible to reduce the size of the control board 70, similarly to the third embodiment. For a specific circuit configuration of the timer circuit 60, see Fig. 10 of the sixth embodiment.

[0049] Fifth embodiment In the electronic device 105 of the fifth embodiment shown in Fig. 7, a timer circuit 60 is provided inside the input IC 205, and a battery supply voltage VBin is used as an operating power source for the timer circuit 60. In contrast to the third embodiment shown in Fig. 5, the high impedance input circuit 40 and the parts of the contact resistance recovery circuit 50 other than the timer circuit 60 are not included in the input IC 205. In this configuration, the timer circuit 60 can be configured inside the input IC 205, thereby making it possible to reduce the size. In addition, it is easy to respond to cases where the design of the voltage dividing resistors R1 and R2 and the current limiting resistor Rr is changed.

[0050] FIG. 8 shows a circuit diagram that is more specific than FIG. 7. In the example of FIG. 8, the recovery switch SW2 of the contact resistance recovery circuit 50 is composed of a bipolar transistor, as in the first embodiment shown in FIG. 2. The timer circuit 605 includes a capacitor Cr, resistors Rs and Rt, and a current amplifier circuit 65, and after the power switch SW1 is turned on, the battery supply voltage VBin is charged to the capacitor Cr. The ON time of the recovery switch SW2 is determined based on the time constant of the CR circuit. Depending on the energization time to be set, the capacitor Cr may be placed outside the input IC 205.

[0051] Sixth embodiment In the electronic device 106 of the sixth embodiment shown in Fig. 9, a timer circuit 60 is provided inside the input IC 206, and the divided input signal voltage Vin is used as the operating power supply for the timer circuit 60. In contrast to the fourth embodiment shown in Fig. 6, the high impedance input circuit 40 and the parts of the contact resistance recovery circuit 50 other than the timer circuit 60 are not included in the input IC 206.

[0052] In this configuration, the timer circuit 60 can be made smaller by configuring it inside the input IC 206. In addition, it is easy to respond when changing the design of the voltage dividing resistors R1 and R2 and the current limiting resistor Rr. Furthermore, the number of terminals of the input IC 206 can be reduced compared to the fifth embodiment.

[0053] Fig. 10 shows a circuit diagram that is more specific than Fig. 9. In the example of Fig. 10, the recovery switch SW2 of the contact resistance recovery circuit 50 is composed of a FET, similar to the second embodiment shown in Fig. 4. The timer circuit 606 is composed of a FET circuit in which a capacitor Ct1, a plurality of resistors Rt1 to Rt4, and a plurality of semiconductor switches (FETs) Trt1 and Trt2 are connected in multiple stages.

[0054] After the power switch SW1 is turned on, the input signal voltage Vin obtained by voltage division in the high impedance input circuit 40 is charged into the capacitor Ct1. A signal that has been multi-stage amplified by multiple semiconductor switches Trt1 and Trt2 is output to the gate of the recovery switch SW2. By configuring a multi-stage amplifier circuit etc. inside the input IC 206, it can be realized at a smaller size and lower cost than configuring a circuit outside the IC. The capacitance of the capacitor Ct1 can also be reduced, making it possible to further reduce the size. Depending on the current flow time to be set, the capacitor Ct1 may be placed outside the input IC 206.

[0055] (Effects of the present invention) (1) In the energization method using an RC circuit according to Comparative Examples 1 and 2, a large-capacity capacitor Cr estimated to be 1000 μF or more is required. In contrast, in each embodiment of the present invention, the capacitance of the capacitor Cr can be reduced to 50 μF to 0.01 μF or less by using a recovery switch SW2 formed of a semiconductor switch. Although the number of parts increases, this allows the overall mounting area of ​​the control board 70 to be reduced, making it possible to miniaturize the control board.

[0056] (2) In each embodiment of the present invention, the voltage source for passing the recovery current Ire is the battery supply voltage VBin input to the connector terminal Rc. There is no need for a power supply circuit for passing the recovery current as in Comparative Example 1. Since there is no need for a mounting area for the power supply circuit and its power supply terminal, the control board 70 can be made smaller. In addition, there is no need to increase the capacity of the power supply circuit for passing the recovery current.

[0057] (Other embodiments) Fig. 11 shows the basic configuration of another embodiment in which the configuration of the high impedance input circuit is different from that of Fig. 1. In the electronic device 10U shown in Fig. 11, the high impedance input circuit 40U is composed of a high resistance pull-down resistor R3 connected to a connection point where the power supply voltage VBin is input as the input signal voltage Vin of the processing circuit 30. Even with a configuration that does not use voltage dividing resistors in this way, the same effects as those of the above embodiment can be obtained.

[0058] The external power supply VB is not limited to a battery, and may be a capacitor, a fuel cell, etc. Furthermore, instead of power from a DC power supply, power obtained by rectifying the output of an AC power supply may be input to the electronic device.

[0059] The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the present invention. [Explanation of symbols]

[0060] 10(101-106), 10U...Electronic equipment, 20 ··· Input IC (IC), 30: processing circuit; 40, 40U: high impedance input circuit; 50...contact resistance recovery circuit, 55 CR circuit (power supply time setting circuit), 60 Timer circuit (power supply time setting circuit) 70 Control board, R1, R2: Voltage dividing resistors, Rc: Connector terminal, terminal contact resistance, Rr: Current limiting resistance, SW1: Power switch, SW2: Recovery switch, T1: First end (of connector terminal), T2: Second end (of connector terminal), VB: Battery (external power supply), battery voltage, VBin: Battery supply voltage (power supply voltage), Vin: Input signal voltage.

Claims

1. An electronic device mounted on a control board (70), A processing circuit (30) for executing a predetermined process; a high impedance input circuit (40, 40U) which is composed of a plurality of voltage dividing resistors (R1, R2) connected in series so as to output an input signal voltage (Vin) generated by dividing a power supply voltage (VBin) supplied from an external power supply (VB) to the processing circuit, or which is composed of a pull-down resistor (R3) connected to a connection point where the power supply voltage is input as an input signal voltage to the processing circuit; a connector terminal (Rc) having a first end (T1) connected to the external power supply via a power switch (SW1) and a second end (T2) opposite to the first end connected to a high potential side of the high impedance input circuit; a contact resistance recovery circuit (50) including a recovery switch (SW2) configured with a semiconductor switch and capable of opening and closing a recovery current path connecting the second end of the connector terminal and ground, a current limiting resistor (Rr) connected in series to the recovery switch, and a current flow time setting circuit that sets a current flow time for keeping the recovery switch in an ON state from when the power switch is turned ON; Equipped with the energization time setting circuit is configured with a CR circuit (55) in which a capacitor (Cr) and a resistor (Rs) are connected in series between the second end of the connector terminal and a base terminal or a gate terminal of a transistor constituting the recovery switch, a time until a voltage input to a base or a gate of the recovery switch falls below an ON threshold of the recovery switch after the power switch is turned ON is determined based on a time constant of the CR circuit; The contact resistance recovery circuit is an electronic device that, when the recovery switch is turned ON during the current-flow time, causes a current greater than the current flowing through the high-impedance input circuit to flow through the connector terminal so as to reduce the contact resistance of the connector terminal.

2. An electronic device mounted on a control board (70), A processing circuit (30) for executing a predetermined process; a high impedance input circuit (40) including a plurality of voltage dividing resistors (R1, R2) connected in series so as to divide a power supply voltage (VBin) supplied from an external power supply (VB) to generate an input signal voltage (Vin) and output the input signal voltage (Vin) to the processing circuit; a connector terminal (Rc) having a first end (T1) connected to the external power supply via a power switch (SW1) and a second end (T2) opposite to the first end connected to a high potential side of the high impedance input circuit; a contact resistance recovery circuit (50) including a recovery switch (SW2) configured with a semiconductor switch and capable of opening and closing a recovery current path connecting the second end of the connector terminal and ground, a current limiting resistor (Rr) connected in series to the recovery switch, and a current flow time setting circuit that sets a current flow time for keeping the recovery switch in an ON state from when the power switch is turned ON; Equipped with the energization time setting circuit is composed of a timer circuit (60) provided inside an IC (204, 206), and the input signal voltage obtained by voltage division in the high impedance input circuit is used as an operating power source for the timer circuit; The contact resistance recovery circuit is an electronic device that, when the recovery switch is turned ON during the current-flow time, causes a current greater than the current flowing through the high-impedance input circuit to flow through the connector terminal so as to reduce the contact resistance of the connector terminal.

3. 3. The electronic device of claim 2, wherein the high impedance input circuit and the contact resistance recovery circuit are all provided within the IC (204).

Images