WO2001095519A1

WO2001095519A1 - Communication system

Info

Publication number: WO2001095519A1
Application number: PCT/JP2000/003784
Authority: WO
Inventors: Masahiro Nakamoto; Yasumasa Hanazaki
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2000-06-09
Filing date: 2000-06-09
Publication date: 2001-12-13

Abstract

A microcomputer for inverting the logic of a communication signal outputted from an SCI transmission terminal and outputting the inverted signal to control the current flowing through a power feed line.

Description

Description Communication system Technical field

TECHNICAL FIELD The present invention relates to a communication system that performs overnight communication between electronic control units mounted on a vehicle. Background art

In an airbag system installed in a vehicle, data communication is performed between a satellite sensor that detects acceleration applied to the vehicle and a main ECU that deploys an airbag to protect the occupants of the vehicle. The configuration of such an airbag system is described in, for example, Japanese Patent Application Publication No. Hei 11-365677. FIG. 1 is a configuration diagram showing a typical communication circuit of the system. In the figure, 1 is a main ECU that is an airbag deployment control device, 2 is a satellite sensor that performs current communication with the main ECU 1, and 3 is a sensor that detects acceleration applied to the vehicle and outputs a signal corresponding to it. Sensors 4 and 5 are a power supply line and a ground line that electrically connect main ECU 1 and satellite sensor 2, and 6 is supplied with power from power supply line 4 and generates a regulated voltage of 5 V. , A power supply circuit for supplying power to each component of the satellite sensor 2, a microcomputer 7 for converting an acceleration signal output from the G sensor 3 into a digital acceleration signal, and outputting the converted signal to a switching element 8, and a microcomputer 8 for Switching element controlled by icon 7, 9 is current limiting resistor

Reference numeral 10 denotes a stabilized power supply that generates a stabilized voltage of 12 V and supplies power to the satellite sensor 2 and the like, and 11 detects a current flowing through the power supply line 4. 12 is a differential amplifier that amplifies the voltage generated across both ends of the current detection resistor 11, 13 is a voltage generator that generates the reference voltage V ref, 14 is a differential amplifier 1 A comparator that compares the output voltage of 2 with the reference voltage V ref, 15 is a microcomputer that reads the output voltage of 14, 16 is an ignition circuit for deploying the airbag 17, and 17 is An airbag that protects occupants.

Next, the operation will be described.

When power is supplied from the constant voltage power supply 10 of the main ECU 1 via the power supply line 4 to the power supply circuit 6 of the satellite sensor 2, the power supply circuit 6 of the satellite sensor 2 generates a stabilized voltage of 5 V, and the power supply circuit 6 of the satellite sensor 2 Provides power to each component.

The microcomputer 7 of the satellite sensor 2 starts operating when receiving power supply from the power supply circuit 6, converts an acceleration signal output from the G sensor 3 into a digital acceleration signal, and outputs the signal to the switching element 8. . The switching element 8 is opened when the output signal of the microcomputer 7 is at the L level, and only the current normally consumed by the satellite sensor 2 flows through the power supply line 4. On the other hand, when the output signal of the microcomputer 7 is at the H level, the circuit is closed, and the current flowing through the current limiting resistor 9 causes the current flowing through the power supply line 4 to be larger than the current normally consumed by the satellite sensor 2.

The differential amplifier 12 of the main ECU 1 amplifies the voltage generated across the current detection resistor 11, and the comparator 14 generates the output voltage of the differential amplifier 12 and the reference generated by the voltage generator 13. The voltage V ref is compared, and when the output signal of the microcomputer 7 is at the L level, a comparison result indicating that the output voltage of the differential amplifier 12 is smaller than the reference voltage V ref is output, and the output signal of the microcomputer 7 is at the H level. In the case of a level, a comparison result indicating that the output voltage of the differential amplifier 12 is larger than the reference voltage V ref is output.

The microcomputer 15 of the main ECU 1 is the digital output of the comparator 13 Receives the acceleration signal and determines the magnitude of acceleration applied to the vehicle. Further, the microcomputer 15 determines whether or not it is necessary to deploy the airbag 17 based on the magnitude of the acceleration, and outputs a signal for deploying the airbag 17 when occupant protection is required. Output to the ignition circuit 16 to deploy the airbag 17.

In the above conventional example, communication can be easily performed using a serial communication interface (hereinafter, SCI) of a microcomputer to simplify communication control.

FIG. 2 is a configuration diagram showing a communication circuit for performing communication using SCI. In the figure, the same reference numerals as those in FIG. 1 denote the same or corresponding parts, and a description thereof will not be repeated. Reference numeral 18 denotes an inversion buffer for inverting the logic of the communication signal output from the SCI transmission terminal of the microcomputer 7. Since the SCI transmission pin is at the H level in the standby state (during non-communication), the switching element 8 is closed and the current flows to the current limiting resistor 9 if there is no inverting buffer. The current consumption of sensor 2 increases.

Next, the operation will be described.

When the satellite sensor 2 transmits a communication signal to the main ECU 1, the microcomputer 7 of the satellite sensor 2 outputs a communication signal from the SCI transmission terminal.

The inversion buffer 18 in the satellite sensor 2 inverts the logic of the communication signal output from the SCI transmission terminal of the microcomputer 7, and outputs the inverted signal to the gate of the switching element 8.

Since the switching element 8 is open when the SCI transmission terminal is at the H level (the output of the inverting buffer 18 is at the L level), as shown in FIG. 3, the switching element 8 normally consumes the power supply line 4. Only current 10 flows. On the other hand, when the SCI transmission terminal is at L level (the output of the inverted buffer 18 is at H level), it is closed. As shown in FIG. 3, the current I 1 flowing through the power supply line 4 increases more than the normal current consumption I 0.

Therefore, when the SCI transmission pin is at H level (the output of the inverting buffer 18 is at L level), the output voltage V 0 of the differential amplifier 12 is equal to the reference voltage V 0. A comparison result indicating that the output voltage is smaller than ref is output. When the SCI transmission terminal is at L level (the output of the inverting buffer 18 is at H level), the output voltage V 1 of the differential amplifier 12 is higher than the reference voltage V ref. The comparison result indicating that the value is larger is output.

The result of this comparison is input to the SCI reception terminal of the microcomputer 15 and reception processing is performed.

In addition to the above conventional example, a communication system that outputs a communication signal from an I0 port of a microcomputer and controls a switching element is disclosed in Japanese Patent Application Laid-Open No. H11-68662. Since the SCI transmission function of the microcomputer is not used, the load on the microcomputer for communication increases.

Since the conventional communication circuit is configured as described above, when performing communication using SCI, the inversion buffer 18 must be mounted, and there have been problems such as an increase in the size of the device. .

The present invention has been made to solve the above problems, and has as its object to obtain a circuit capable of performing communication using SCI without mounting an inversion buffer. Disclosure of the invention

The communication circuit according to the present invention includes a microcomputer that inverts the logic of the communication signal and outputs the inverted signal to the gate terminal of the switching element. Use SCI This has the effect of enabling communication. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram showing a conventional communication circuit.

FIG. 2 is a configuration diagram showing a communication circuit that performs SCI communication.

FIG. 3 is a waveform diagram showing logic of a communication signal and the like.

FIG. 4 is a configuration diagram showing a communication circuit according to Embodiment 1 of the present invention.

FIG. 5 is a waveform diagram showing logic of a communication signal and the like. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, in order to explain this invention in greater detail, the preferred embodiments of the present invention will be described with reference to the accompanying drawings.

Embodiment 1

FIG. 4 is a configuration diagram showing a communication circuit according to the first embodiment of the present invention. In the figure, 21 is a main ECU (sensing device) which is an airbag deployment control device, and 22 is a main ECU 21 Satellite sensor that performs current communication with the vehicle, 23 detects the acceleration applied to the vehicle, and outputs a signal in accordance with that acceleration.G sensors 24 and 25 electrically connect the main ECU 21 and the satellite sensor 22. Power supply line and ground line connected to the power supply, and 26 receive power from the power supply line 24, generate a regulated voltage of 5 V, and supply power to each component of the satellite sensor 22 A power supply circuit 27 converts the acceleration signal output from the G sensor 23 into a digitized acceleration signal, a microcomputer that inverts the logic of the signal and outputs the inverted signal to the switching element 28, and 28 a microcomputer 2 Switching element controlled by 7, 29 current limit Anti, 3 0 is a protective resistor. 31 is a stabilized power supply for generating a stabilized voltage of, for example, 12 V and supplying power to the satellite sensor 23 and the like, and 32 is a current detecting resistor for detecting a current flowing through the power supply line 24 , 33 is a differential amplifier for amplifying the voltage generated across the current detection resistor 32, 34 is a voltage generator for generating the reference voltage V ref, and 35 is the output voltage of the differential amplifier 33. A comparator for comparing the reference voltage V ref, 36 is a microcomputer for reading the output voltage of the comparator 35, 37 is an ignition circuit for deploying the air bag 38, and 38 is for protecting the occupant at the time of collision It is a hair bag.

Next, the operation will be described.

When the satellite sensor 22 transmits an acceleration signal to the main ECU 21, the microcomputer 27 of the satellite sensor 22 outputs an acceleration signal from the SCI transmission terminal.

The acceleration signal output from the SCI transmission terminal is input to the external interrupt terminal via the protection resistor 30. When the state of the external interrupt terminal changes (H level L level, L level-H level), the microcomputer 27 As shown in Fig. 5, the output level of the inverting terminal is changed.

Since the switching element 28 enters the state when the SCI transmitting terminal is at the H level (the inverting terminal is at the L level), the power supply line 24 has only the normal current consumption I 0 as shown in FIG. Flows. On the other hand, when the SCI transmitting terminal is at the L level (the inverting terminal is at the H level), it closes and the current flows through the current limiting resistor 29, and as shown in FIG. I1 is larger than the normal current consumption I0.

Therefore, the comparator 35 in the main ECU 21 indicates that the output voltage V 0 of the differential amplifier 33 is smaller than the reference voltage V ref when the SCI transmission terminal is at the H level (the inversion terminal is at the L level). Outputs the comparison result. When the SCI transmission terminal is at L level (the inversion terminal is at H level), the differential amplifier 33 Outputs the comparison result indicating that the output voltage V1 of 3 is higher than the reference voltage Vref.

Therefore, the main ECU 21 can recognize the acceleration signal of the satellite sensor 22.

As is clear from the above, according to this embodiment, the microcomputer 27 that inverts the logic of the communication signal output from the SCI transmission terminal and outputs the inverted signal to the gate terminal of the switching element 28 is used. Since it is configured to be provided, the communication signal of the satellite sensor 22 can be transmitted to the main ECU 21 without mounting the inversion buffer 18 as in the conventional example described above. Industrial applicability

As described above, the communication circuit according to the present invention is suitable for an airbag system that transmits acceleration applied to a vehicle detected by a G sensor in a satellite sensor to a sensor device.

Claims

The scope of the claims

1. A satellite sensor connected to the transmitter and receiver via a power supply line and a ground line superimposes data on the power supply line and outputs the data from the SCI transmission terminal in the communication system that communicates with the transmitter and receiver. A communication system, comprising: a micro-computer for inverting the logic of a communication signal, and outputting the inverted signal to control a current flowing through the power supply line, in the satellite sensor.