JPS6257001A - Electromagnetic wave disturbance reducing device for electronic equipment - Google Patents

Abstract

PURPOSE:To prevent the infuence of malfunction due to electromagnetic wave disturbance from extending by paying attention to the temporarity of the electromagnetic wave disturbance and stopping or reducing the function of electric equipment for the period of the disturbance. CONSTITUTION:An antiskid control circuit 11 uses a CPU, so a program runa way is considered. For the purpose, a runaway detecting circuit is provided and a relay driving circuit 12B is driven with an inhibition output INH' generat ed by the runaway detection of the detecting circuit. In this case, a normally-on relay 12A takes a measure to counter the electromagnetic wave disturbance only by inputting the inhibition output INH of an electromagnetic wave distur bance detecting circuit 13 to the circuit 12B. Namely, when the relay 12A is turned off, a solenoid 21 can not be powered on, so brake hydraulic pressure can not be reduced by a control circuit 11 forcibly. Namely, the effect of the brake enters a normal state wherein an antiskid controller 1 is not added, so braking effect corresponding to the operation of a driver is expected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electromagnetic interference (EMI) reduction device for electronic equipment.

[Conventional technology]

Electronic devices for automobiles are becoming increasingly diverse, and electronic devices related to driving control, such as anti-skid devices that forcibly release the brakes when tires are locked, and engine control devices that electronically control the amount of fuel injection, can malfunction. It is necessary to control the temperature accurately and without any problems.

Electromagnetic interference (EMI) is one of the causes of malfunctions in electronic equipment.
There is. This occurs when a car passes through a strong electromagnetic environment, such as near a broadcast station.

Conventional EMI countermeasures include, for example, installing LC or R to ground high-frequency components at the connector between electronic equipment and external wiring.
It is common to have a circuit configuration that is not affected by external electromagnetic waves, such as by adding a C-configuration protection circuit.

[Problem that the invention seeks to solve]

However, the EMI countermeasure described above has the disadvantage that the device configuration is complicated and expensive, such as by providing a protection circuit for each wiring. The present invention focuses on the fact that this type of electromagnetic interference is temporary, and attempts to prevent the malfunction from spreading by stopping or reducing the functionality of electronic equipment for only that period.

[Configuration and action]

FIG. 1 is a block diagram of the principle of the present invention, in which numeral 1 represents an electronic device for an automobile, and numeral 2 represents an actuator to be controlled by the electronic device.

The electronic device 1 has a circuit 11 that controls the actuator 2 in response to an external signal IN.
A fail-safe circuit 12 and an EMI detection circuit 13 are provided in order to prevent the actuator 2 from malfunctioning due to the output OUT when the actuator malfunctions due to the influence of external electromagnetic waves EM. The EMI detection circuit 13 detects electromagnetic waves EM through the antenna 14, and when the level exceeds a certain value, an inhibit output NH is generated to energize the failsafe circuit 12, and the output OUT of the control circuit 11 is output.
is not supplied to the actuator 2.

In this way, although it is not possible to prevent the control circuit 11 from malfunctioning due to the influence of electromagnetic waves EM, it is possible to prevent the influence from spreading to the actuator 2. Moreover, since the malfunction itself of the control circuit 11 is not directly detected, it is disadvantageous if the control circuit 11 is operating normally even in an electromagnetic environment. However, protective measures to prevent the control circuit 11 from malfunctioning even in an electromagnetic environment and methods for directly detecting abnormal operation require a complicated configuration, and are not necessarily a good idea when the EMI is temporary. This will be explained in detail below with reference to illustrated embodiments.

〔Example〕

FIG. 2 is a block diagram showing an embodiment of the present invention, and 11 is an anti-skid control circuit using a CPU. This control circuit 11 has a program that monitors the wheel speed sensor signal IN and detects tire lock (slip) from a sudden change in the signal. This program further activates the solenoid drive circuit 15 to generate an output OUT which energizes the brake hydraulic control solenoid 21 when tire lock is detected.

The solenoid 21 is a controlled object corresponding to the actuator 2 in FIG. 1, and when energized, it forcibly reduces the brake hydraulic pressure. Therefore, although there is an effect of preventing slippage when the tires are truly locked, there is a possibility that the control circuit 11 malfunctions due to the influence of EMr.

Therefore, in this example, a normally-on type relay 12A is interposed in the energization path of the solenoid 21, and its drive circuit 12B is provided on the electronic device 1 side, and this relay 12A and relay drive circuit 12B form the fail-safe circuit shown in FIG. 12.

The EMI detection circuit 13 consists of a high frequency detection circuit consisting of a diode D1, a capacitor C1, a resistor R, and a comparator CMP that compares the detection level with a constant value E. The inhibit output INH of the comparator CMP energizes the relay drive circuit 12B. The antenna 14 is formed, for example, by a conductive pattern on a printed circuit board, and extends along the periphery of the device housing. The form of this antenna 14 is not particularly limited, such as a Gooey ball type or a loop type, but it is designed to have as high a gain as possible.

Since the control circuit 11 uses a CPU, it is possible that the program may run out of control. For this reason, the device is generally configured to include a runaway detection circuit with a hardware configuration, and to energize the relay drive circuit 12B with the inhibit output INH' when the runaway is detected.

In such a case, relay 12A is already installed, so E
EMI countermeasures can be taken simply by inputting the output INH of the MI detection circuit 13 to the drive circuit 12B.

Incidentally, when the inhibitor 1 output INH is inputted to the control circuit 11, it can also be used for an EMI alarm or the like.

In the above configuration, when the relay 12A is turned off, the solenoid 21 cannot be energized, so the brake oil pressure cannot be forcibly reduced by the control circuit 11. In other words, the effectiveness of the brake is in the normal state without the addition of the anti-skid control device 1, so a braking effect corresponding to the driver's operation can be expected.

Although non-operation has been exemplified above as a type of fail-safe, there is also a method of switching to a hardware-based control circuit (backup circuit) if the software-based control circuit 11 malfunctions or breaks down. The present invention can also be applied to control system switching in this case. An example of this is engine control. Since this electronically controls the fuel injection amount, it is not desirable to interrupt the control even if it is temporary. In this case, it is better to switch to hardware control, which can maintain the minimum driving condition even if the accuracy is lower than software control.

Note that if the antenna 14 is provided outside the device 1, the sensitivity to EMI will increase. Furthermore, even if the detection output is amplified by the EMI detection circuit 13, the sensitivity will increase, but there is no point in detecting weak electromagnetic waves that do not affect the control circuit 11. You can consider inserting .

Furthermore, even without providing a special EMI detection circuit, the EMI resistance of the fail-safe circuit can be kept lower than other circuits, and the EMI
It is also possible to integrate the circuits by configuring the circuit to perform a fail-safe operation when inputting I. In addition, the electromagnetic waves to be detected are, for example, IMHz to IGHz.
The wireless band is approximately

〔Effect of the invention〕

As described above, according to the present invention, there is no need to cause a controlled object to malfunction due to electromagnetic interference, and the circuit configuration is simple, resulting in low cost and simplification of design.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the principle of the present invention, and FIG. 2 is a configuration diagram showing an embodiment of the present invention. In the figure, 1 is an automotive electronic device, 2 is a controlled object, 11 is a control circuit, I2 is a fail-safe circuit, 13 is an electromagnetic interference detection circuit, and 14 is an antenna.

Claims (1)

[Claims] Electronic devices equipped with control circuits that control the movement of objects,
Electromagnetic wave interference in electronic equipment, characterized in that it is provided with a circuit that detects electromagnetic waves from the outside, and a fail-safe circuit that disables the output of the control circuit when the detection circuit detects electromagnetic waves above a certain level. Reduction device.