JP2008026010A - Electronic circuit and in-vehicle equipment equipped with the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electronic circuits each of which has separately a power source, and is separately grounded, wherein between the grounding lines are connected, when the first circuit becomes non-grounded, detection of non-grounded and erroneous operation of the circuit due to over voltage can be prevented. <P>SOLUTION: A microcomputer A1 of the electronic circuit 10 grounded by a ground GND1 supplied with power voltage from a VDD1 and a microcomputer B3 of the electronic circuit 20 grounded by the ground GND2 and supplied with the power voltage from a VDD2 are connected by signal lines 30 and 31. In the case the ground GND1 and the ground GND2 are connected with wiring 34, an abnormal voltage detection circuit A2 for monitoring the voltage of the VDD1 referring to the GND2 is provided to the electronic circuit 10. When the electronic circuit 10 becomes non-grounded state, large current flows through the wiring 34 the potential of the VDD1 rises higher than the prescribed voltage value, an abnormal voltage detection circuit A outputs the abnormal voltage detection signal to the microcomputer A1, the microcomputer A1 makes the electronic circuit 10 stop state. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electronic circuit capable of detecting non-grounding of a circuit and an in-vehicle device provided with the electronic circuit.

  Conventionally, in an electronic circuit included in an electronic device or the like, it may be necessary to ground the electronic circuit for operation.

  When transmitting and receiving signals by connecting electronic circuits each having a power source and grounded to each other, the ground lines may be connected to be a reference for the signal level to be transmitted and received.

  FIG. 1 shows an example in which the above-described ground lines of a plurality of electronic circuits are connected. In FIG. 1, an electronic circuit 100 and an electronic circuit 200 are connected.

  The electronic circuit 100 includes a microcomputer A101, a power supply VDD10, a ground GND10, and resistors R11, R12, R13, R14, and R15.

  The microcomputer A101 is supplied with a power supply voltage from the power supply VDD10 and is grounded to the ground GND10. In addition, signals are transmitted to and received from the electronic circuit 200 through the resistors R11, R12, R13, and R14.

  The signal line to which the resistors R13 and R14 are connected is connected to the power supply VDD10 through the resistor R15.

  The electronic circuit 200 includes a microcomputer B201, a power supply VDD20, a ground GND20, and resistors R16, R17, R18, R19, and R20.

  The microcomputer B201 is supplied with a power supply voltage from the power supply VDD20 and is grounded to the ground GND20. In addition, signals are transmitted to and received from the electronic circuit 100 through the resistors R16, R17, R18, and R19.

  The signal line to which the resistors R16 and R17 are connected is connected to the power supply VDD20 through the resistor R20.

  Further, the ground GND 10 of the electronic circuit 100 and the ground GND 20 of the electronic circuit 200 are connected to each other by a wiring 300.

  In the configuration described above, when the electronic circuit 100 is ungrounded, the electronic circuit 100 operates with reference to the ground GND 20 of the connected electronic circuit 200. At this time, if there is a circuit or element that consumes a large current such as an amplifier (not shown) in the electronic circuit 100, a large current is applied to the wiring 300 that connects the ground line of the electronic circuit 100 and the ground line of the electronic circuit 200. Flowing. As a result, a potential difference occurs in the wiring 300 and the potential of the power supply VDD10 of the electronic circuit 100 increases, so that the signal level between the electronic circuit 100 and the electronic circuit 200 fluctuates and an abnormal voltage is applied to the microcomputer B201, causing the circuit to malfunction. There was a problem to do.

  Conventionally, with respect to such a problem, a fuse is connected to the wiring 300 that connects the ground GND 10 and the ground GND 20, and when an overcurrent flows through the wiring 300, the fuse is disconnected, so that an abnormal voltage or circuit Malfunctions were prevented.

  However, in the method using the above-described fuse, when an overcurrent flows, it takes time and labor to replace the fuse, and the efficiency is poor.

  Therefore, the present invention is based on non-ground detection and overvoltage when the first circuit is ungrounded, for example, when the ground lines are connected between circuits that are individually grounded and individually grounded. It is an object of the present invention to provide an electronic circuit that can prevent malfunction of the circuit.

  In order to solve the above problem, the invention according to claim 1 is characterized in that a power supply voltage is supplied from a first power supply and grounded by a first ground line, and a power supply voltage is supplied from a second power supply. And a second circuit grounded by a second ground line, and the first circuit and the second circuit are connected to each other by a signal line and the first ground line and the second circuit An electronic circuit in which a ground line is also connected to each other includes an abnormal voltage detection unit that determines whether or not the voltage value of the first power supply is abnormal with reference to the second ground line.

  Hereinafter, an electronic circuit according to an embodiment of the present invention will be described. An electronic circuit according to an embodiment of the present invention detects whether or not the voltage value of the first power supply is abnormal based on the second ground line in the abnormal voltage detection means. By doing so, the first circuit becomes non-grounded and operates with reference to the grounding of the second circuit, so that an overcurrent flows through the grounding wire, and the first circuit and the second circuit It is possible to detect that an overvoltage is applied to the signal line between the circuits.

  The abnormal voltage detection means may determine that an abnormality has been detected when the voltage value exceeds a predetermined voltage value. In this way, an abnormal voltage corresponding to the circuit to be connected can be set in advance, so that the non-ground state or the like causes the second circuit to operate on the basis of the ground, and an overcurrent flows through the ground line. It is possible to detect that an overvoltage is applied to the signal line between the circuits.

  In addition, a control unit may be provided that stops the operation of the first circuit when the abnormal voltage detection unit detects an abnormality. By doing so, it is possible to stop the operation of the circuit when the abnormal voltage detecting means detects the abnormal voltage, so that the circuit can be prevented from operating abnormally due to overvoltage.

  The first power source, the first ground line, and the first circuit are provided in one housing, and the second power source, the second ground line, and the second circuit are provided in another housing. May be. This prevents the first circuit provided in one housing from operating on the ground line of the second circuit provided in the other housing, even between devices in which the circuit is divided into separate housings. As a result, malfunction of the device can be prevented.

  Moreover, you may equip a vehicle-mounted apparatus with the electronic circuit in any one of Claims 1 thru | or 3. By doing so, it is possible to prevent the malfunction of the circuit and the device due to the detection of the non-ground state and the non-ground state in the in-vehicle device.

  An electronic circuit 10 and an electronic circuit 20 as electronic circuits according to a first embodiment of the present invention will be described with reference to FIG. The electronic circuit 10 as a first circuit includes a microcomputer A1 as a control means, an abnormal voltage detection circuit A2 as an abnormal voltage detection means, a power supply VDD1 as a first power supply, and a ground GND1 as a first ground. And resistors R1, R2, R3, R4, and R5.

  The microcomputer A1 is supplied with a power supply voltage from the power supply VDD1, and is grounded to the ground GND1. The microcomputer A1 includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a control circuit for the electronic circuit 10, and a signal line 30 having resistors R1 and R2, and R3 and R4. Signals are transmitted / received to / from the electronic circuit 20 through the provided signal line 31.

  The abnormal voltage detection circuit A2 is connected to the power supply VDD1 and the ground GND2 of the electronic circuit 20 via the wiring 32. The abnormal voltage detection circuit A2 monitors the potential of the wiring connected to the power supply VDD1 with reference to the ground GND2 of the electronic circuit 20, and outputs an abnormality detection signal to the microcomputer A1 when the voltage exceeds a predetermined voltage value.

  The signal line 31 to which the resistors R3 and R4 are connected is connected to the power supply VDD1 through the resistor R5.

  The electronic circuit 20 as the second circuit includes a microcomputer B3 as the control means, an abnormal voltage detection circuit B4 as the abnormal voltage detection means, a power supply VDD2 as the second power supply, and a ground GND2 as the second ground. And resistors R6, R7, R8, R9, and R10.

  The microcomputer B3 is supplied with a power supply voltage from the power supply VDD2, and is grounded to the ground GND2. The microcomputer B3 includes a CPU, RAM, and ROM, controls the electronic circuit 20, and transmits and receives signals to and from the electronic circuit 10 through the signal line 30 having resistors R6 and R7 and the signal line 31 having R8 and R9. .

  The abnormal voltage detection circuit B4 is connected to the power supply VDD2 and the ground GND1 of the electronic circuit 10 via the wiring 33. The abnormal voltage detection unit B4 monitors the potential of the wiring connected to the power supply VDD2 with reference to the ground GND1 of the electronic circuit 10, and outputs an abnormality detection signal to the microcomputer B3 when the voltage exceeds a predetermined voltage value.

  The signal line 30 to which the resistors R6 and R7 are connected is connected to the power supply VDD1 through the resistor R5.

  The ground GND 1 of the electronic circuit 10 and the ground GND 2 of the electronic circuit 20 are connected to each other by a wiring 34.

  In the electronic circuit 10 and the electronic circuit 20 having such a configuration, when one of the electronic circuits is ungrounded, that is, in the case of the electronic circuit 10, the connection with the ground GND1 is disconnected, In this case, the abnormality detection operation when the connection with the ground GND2 is disconnected will be described.

  First, the case where the electronic circuit 10 is in a non-grounded state will be described. When the electronic circuit 10 is ungrounded, for example, when the ground GND1 is disconnected, the electronic circuit 10 operates with reference to the ground GND2 connected via the wiring 34. Here, if an element or a circuit that requires a large current during operation of an amplifier (not shown) connected to the power supply VDD1 and the ground GND1 is mounted on the electronic circuit 10, a large current flows through the wiring 34.

  When a large current of a predetermined value or more flows through the wiring 34, a potential difference Vn is generated between A and B in FIG. That is, since the potential at the point A (minus side of the power supply VDD1) rises, the potential of the wiring that supplies the power supply voltage from the power supply VDD1 (for example, the point C) becomes the voltage value + Vn of the power supply VDD1 with respect to the ground GND2.

  The microcomputer A1 in FIG. 2 is connected to the microcomputer A1 and the microcomputer B3 although the voltage at the grounded point A as a reference is also increased even if the potential at the point C is increased, the voltage is VDD1. Since the microcomputer B3 through the connected signal line 31 operates with reference to the ground GND2, a voltage value + Vn of the power supply VDD1 is applied to the terminal to which the signal line 31 of the microcomputer B3 is connected, and Vn is large. Depending on the situation, unexpected abnormal operation may occur.

  Therefore, the abnormal voltage detection circuit A2 monitors the point (for example, point C) where the power supply VDD1 is supplied with reference to the ground GND2, and if a voltage greater than a predetermined voltage value is detected, the microcomputer A1 Send an abnormal voltage detection signal. Receiving the abnormal voltage detection signal, the microcomputer A1 stops all operations of the electronic circuit 10 and shifts to a state where no abnormal voltage is detected, such as a halt state or a forced termination state.

  Next, a case where the electronic circuit 20 is in a non-grounded state will be described. Even when the ground GND2 becomes a non-grounded state, similarly to the ground GND1, the abnormal voltage detection circuit B4 monitors the power supply VDD2 with reference to the ground GND1, and if a voltage equal to or higher than a predetermined voltage value is detected, An abnormal voltage detection signal is transmitted to the microcomputer B3. Receiving the abnormal voltage detection signal, the microcomputer B3 stops all the operations of the electronic circuit 20 and shifts to a state where no abnormal voltage is detected, such as a pause state or a forced termination state.

  According to this embodiment, in the electronic circuit 10 and the electronic circuit 20 in which power is individually supplied and grounded, and the signal line and the ground line are connected to each other, for example, the electronic circuit 10 is connected to the electronic circuit 10. An abnormal voltage detection circuit A2 for monitoring the voltage value of the power supply VDD1 with respect to the ground GND2 of the electronic circuit 20 is provided, and when the voltage value of the power supply VDD1 with respect to the ground GND2 becomes equal to or higher than a predetermined voltage value. The abnormal voltage detection circuit A2 outputs an abnormality detection signal to the microcomputer A1. The microcomputer A1 stops the operation of the electronic circuit 10 when the abnormality detection signal is input. By doing this, the ground GND1 of the electronic circuit 10 is disconnected and becomes non-grounded, and when the electronic circuit 10 operates with the ground GND2 of the electronic circuit 20 as a reference, the wiring 34 that connects the ground lines of the electronic circuits 10 and 20 Since the abnormal voltage detection circuit A2 can detect an abnormality if the value of the potential difference Vn is equal to or greater than a predetermined value, malfunction of the microcomputer B3 can be prevented by stopping the electronic circuit 10.

  Next, the electronic circuit 10 and the electronic circuit 20 'according to the second embodiment will be described with reference to FIG. The same parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

  In the first embodiment described above, the abnormal voltage detection circuit is provided in both the electronic circuit 10 and the electronic circuit 20. However, in this embodiment, the electronic device 20 ′ may include an element that requires a large current. Since no circuit or the like is connected, the abnormal voltage detection circuit is omitted.

  Therefore, in FIG. 3, in the electronic circuit 20 ′, the abnormal voltage detection circuit is deleted, and the microcomputer B3 is changed to an integrated circuit IC3 ′ having no particular control function.

  Here, when the electronic circuit 10 is ungrounded, it is the same as in the first embodiment. That is, when the potential rise of VDD1 due to a current from an amplifier (not shown) is detected and becomes equal to or higher than a predetermined voltage value, the abnormal voltage detection circuit A2 determines that an abnormality has been detected, and the microcomputer A1 detects the abnormality. Output a signal. The microcomputer A1 stops the electronic circuit 10 when receiving the abnormality detection signal.

  When the electronic circuit 20 is ungrounded, the electronic circuit 20 operates with reference to the ground GND 1. However, since the electronic circuit 20 does not have a circuit that uses a large current, the current flowing through the wiring 34 is also low. The potential difference Vn generated between A and B is extremely small because it is extremely small. Therefore, since the potential of VDD2 is only slightly increased, an abnormal voltage that causes a malfunction of the microcomputer A1 is not applied.

  According to the present embodiment, there is no circuit or element that uses a large current in the electronic circuit 10 and the electronic circuit 20 in which power is individually supplied and grounded, and the signal line and the ground line are connected to each other. An abnormal voltage detection circuit is omitted from the electronic circuit 20. In this way, if it is clear that no overcurrent will flow through the wiring connected to each other's grounding wires, the abnormal voltage detection circuit is omitted, and unnecessary circuits are omitted. It can be suppressed only by adding the electronic circuit.

  Note that, in the above-described embodiment, an electronic device provided with the electronic circuit 10 and an electronic device provided with the electronic circuit 20 may be divided into one housing and another housing, and both devices may be connected by a connection cable or the like. good. By doing in this way, detection of a non-grounding state and malfunction can be prevented between electronic devices.

  In particular, in car-mounted equipment such as car audio, electronic circuits such as receivers, amplifiers, and power supplies are installed in a predetermined space such as an instrument panel in order to install electronic circuits of main functions as equipment such as optical disk devices and display devices. The circuit may be divided into separate enclosures and placed under the seat, and grounding is ensured by connecting the power supply and grounding from the vehicle body with dedicated wiring instead of connecting to the outlet as in household equipment. Since this may not be done, it is effective to apply the present invention.

  Further, the electronic circuit 10 and the electronic circuit 20 may be divided into different substrates in the same housing, and each has a power source and a signal line and a ground line are connected between the electronic circuits individually grounded. The present invention can be applied to electronic circuits such as those described above.

  According to the embodiment described above, the following electronic circuit 10 and electronic circuit 20 are obtained.

(Supplementary Note 1) An electronic circuit 10 that is supplied with a power supply voltage from a power supply VDD1 and grounded by a ground GND1, and an electronic circuit 20 that is supplied with a power supply voltage from a power supply VDD2 and is grounded by a ground GND2, In the electronic circuit 10 and the electronic circuit 20 in which the circuit 20 is connected to each other by the signal lines 30 and 31 and the ground GND1 and the ground GND2 are also connected,
An electronic circuit 10 and an electronic circuit 20 including an abnormal voltage detection circuit A2 that determines whether or not the voltage value of VDD1 is abnormal with reference to the ground GND2.

  According to the electronic circuit 10 and the electronic circuit 20, the electronic circuit 10 is not grounded and operates with reference to the grounding of the electronic circuit 20, so that an overcurrent flows through the wiring 34, and the electronic circuit 10 and the electronic circuit 20 It can be detected that an overvoltage is applied to the signal line 31 between the circuits 20.

  In addition, the Example mentioned above only showed the typical form of this invention, and this invention is not limited to an Example. That is, various modifications can be made without departing from the scope of the present invention.

It is a circuit diagram of the electronic circuit in a prior art. 1 is a circuit diagram of an electronic circuit according to a first embodiment of the present invention. It is a circuit diagram of the electronic circuit concerning the 2nd Example of this invention.

Explanation of symbols

1 Microcomputer A (control means)
2 Abnormal voltage detection circuit A (abnormal voltage detection means)
3 Microcomputer B (control means)
4 Abnormal voltage detection circuit B (abnormal voltage detection means)
10 Electronic circuit (first circuit)
20 Electronic circuit (second circuit)
30 signal line 31 signal line 34 wiring VDD1 power supply (first power supply)
GND1 grounding (first grounding)
VDD2 power supply (second power supply)
GND2 grounding (second grounding)

Claims (5)

A first circuit supplied with a power supply voltage from a first power supply and grounded by a first ground line; a second circuit supplied with a power supply voltage from a second power supply and grounded by a second ground line; In the electronic circuit in which the first circuit and the second circuit are connected to each other by a signal line, and the first ground line and the second ground line are also connected to each other,
An electronic circuit comprising: an abnormal voltage detecting means for determining whether or not the voltage value of the first power supply is abnormal with reference to the second ground line.   2. The electronic circuit according to claim 1, wherein the abnormal voltage detection unit determines that an abnormality has been detected when the voltage exceeds a predetermined voltage value.   3. The electronic circuit according to claim 1, further comprising a control unit that stops the operation of the first circuit when the abnormal voltage detection unit detects an abnormality.   The first power source, the first ground line, and the first circuit are provided in one housing, and the second power source, the second ground line, and the second circuit The electronic circuit according to claim 1, wherein the electronic circuit is provided in a housing.   An in-vehicle device provided with the electronic circuit according to claim 1.

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