JP2004268688A - Operation diagnostic device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an operation diagnostic device having high diagnostic accuracy with almost no time lag of sampling. <P>SOLUTION: This operation diagnostic device 1 is provided with: an A/D converter 2 for reference inputted with a reference signal VO; an A/D converter 3 for evaluation separated from the A/D converter 2 for reference and inputted with an evaluation signal V1; and a diagnostic circuit 4 electrically connected to the A/D converter 2 for reference and the A/D converter 3 for evaluation, sampling the reference signal VO and the evaluation signal V1 at almost the same time, and performing an operation diagnosis by comparing the reference signal VO and the evaluation signal V1. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an operation diagnosis device, and more particularly, to an operation diagnosis device such as an electronic device or an element used in a system to which a signal is input using an A / D converter.
[0002]
[Prior art]
FIG. 5 is a schematic diagram showing the vicinity of the booster circuit of the airbag system. As shown in the figure, the booster circuit 100 is interposed between a battery 101 and a microcomputer (hereinafter abbreviated as “microcomputer”) 102. The booster circuit 100 is electrically connected to the battery 101 and an ignition circuit (not shown). The booster circuit 100 has a role of boosting the battery voltage to the squib ignition voltage. A bag (not shown) of the airbag system is deployed in the vehicle compartment by the combustion and inflation pressure of the medicine ignited by the squib. The deployed bag protects the occupant.
[0003]
By the way, in the event of an accident, the battery 101 and the booster circuit 100 may be disconnected. Alternatively, the battery 101 itself may be damaged. Even in such a case, it is necessary to deploy the bag body in the passenger compartment to protect the occupant. That is, even if the battery 101 and the booster circuit 100 are disconnected, it is necessary to secure the squib ignition voltage.
[0004]
Therefore, a backup capacitor 103 is provided in the airbag system (for example, see Patent Document 1). Backup capacitor 103 is electrically connected to battery 101 and booster circuit 100. The backup capacitor 103 is charged by the battery 101. Further, the backup capacitor 103 is also electrically connected to the ignition circuit. When the battery 101 and the booster circuit 100 are disconnected, the charged backup capacitor 103 is discharged to maintain the squib ignition voltage. That is, the backup capacitor 103 has a role of a standby power supply. Therefore, diagnosis of whether or not the backup capacitor 103 operates normally, that is, operation diagnosis, is extremely important in an airbag system.
[0005]
This operation diagnosis is performed by the microcomputer 102. The microcomputer 102 samples the circuit voltage V0 of the booster circuit 100 and the capacitor voltage V1 of the backup capacitor 103 via the A / D converter 104. Then, the circuit voltage V0 and the capacitor voltage V1 are compared. This comparison is repeated several times, and if the fluctuation of the capacitor voltage V1 with respect to the circuit voltage V0 is abnormal as compared with the previously input predetermined fluctuation, the microcomputer 102 determines that the backup capacitor 103 has failed.
[0006]
[Patent Document 1]
JP-A-10-129407
[Problems to be solved by the invention]
However, only one A / D converter 104 is provided. Therefore, the sampling of the circuit voltage V0 and the sampling of the capacitor voltage V1 cannot be performed simultaneously. Specifically, first, the switch 105 is closed with the switch 106 opened, and the circuit voltage V0 is input to the A / D converter 104. Next, the switch 105 is opened and the switch 106 is closed, and the capacitor voltage V1 is input to the A / D converter 104.
[0008]
Therefore, a time lag occurs between the sampling of the circuit voltage V0 and the sampling of the capacitor voltage V1. Here, the capacitor voltage V1 may fluctuate between the sampling of the circuit voltage V0 and the sampling of the capacitor voltage V1. For example, when the backup capacitor 103 is being charged, as shown in FIG. 6, the capacitor voltage V1 may increase by the variation width ΔV between the sampling of the circuit voltage V0 and the sampling of the capacitor voltage V1. In this case, the operation diagnosis accuracy of the backup capacitor 103 in the microcomputer 102 is reduced by the fluctuation width ΔV.
[0009]
The operation diagnosis device of the present invention has been completed in view of the above problems. Accordingly, it is an object of the present invention to provide an operation diagnostic apparatus with little diagnostic time lag and high diagnostic accuracy.
[0010]
[Means for Solving the Problems]
(1) In order to solve the above problem, an operation diagnostic apparatus according to the present invention includes a reference A / D converter to which a reference signal is input, and an evaluation signal that is separate from the reference A / D converter and has an evaluation signal. The input evaluation A / D converter is electrically connected to the reference A / D converter and the evaluation A / D converter, and samples the reference signal and the evaluation signal substantially simultaneously. And a diagnostic circuit for performing an operation diagnosis by comparing the reference signal with the evaluation signal.
[0011]
That is, the operation diagnostic device of the present invention includes a plurality of A / D converters. Conventionally, only one A / D converter is provided (see FIG. 5 described above). In addition, even when a plurality of external terminals are arranged in appearance, the plurality of external terminals are internally connected to the same converter circuit. That is, even when a plurality of external terminals are apparently arranged, the number of A / D converters is substantially one. The reason is that the area occupied by the A / D converter becomes large, and the installation space for other devices is reduced. Also, there is no diagnostic mechanism that requires simultaneous input of a plurality of signals. That is, there is no need to arrange a plurality of A / D converters.
[0012]
On the other hand, the operation diagnostic device of the present invention independently includes a plurality of A / D converters called a reference A / D converter and an evaluation A / D converter. Therefore, the reference signal and the evaluation signal can be sampled almost simultaneously. That is, the sampling time lag can be made substantially zero. Therefore, according to the operation diagnosis device of the present invention, high operation diagnosis accuracy can be ensured.
[0013]
(2) Preferably, the reference signal is a circuit voltage of a booster circuit that is electrically connected to a squib for deploying a bag of a battery and an airbag system, and boosts a battery voltage to a squib ignition voltage. It is preferable that the booster circuit be configured to back up the booster circuit when the battery and the booster circuit are disconnected, and to use a capacitor voltage of a backup capacitor for securing the squib ignition voltage.
[0014]
In other words, the present configuration realizes the operation diagnostic device of the present invention as a backup capacitor for an airbag system. As described above, the backup capacitor has a role of securing the squib ignition voltage when the battery and the booster circuit are disconnected. For this reason, the backup capacitor is required to have high operation reliability. That is, high accuracy is required for the operation diagnosis of the backup capacitor.
[0015]
According to this configuration, the circuit voltage and the capacitor voltage can be sampled simultaneously. Therefore, the time lag in sampling becomes almost zero. For this reason, when the voltage of the backup capacitor fluctuates sequentially, high operation diagnosis accuracy can be ensured even when the power is turned on. Thus, the operation diagnostic device of the present invention is particularly suitable for being embodied as a backup capacitor for an airbag system.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the operation diagnostic device of the present invention will be described.
[0017]
(1) First Embodiment The operation diagnostic device of the present embodiment is an embodiment in which the operation diagnostic device of the present invention is embodied as a backup capacitor for an airbag system. First, the configuration of the operation diagnostic device of the present embodiment will be described. FIG. 1 shows a schematic diagram of the vicinity of a booster circuit of an airbag system. The microcomputer 4 has the diagnostic circuit of the present invention. The microcomputer 4 has a role of receiving a signal from each collision sensor in the airbag system and issuing an ignition instruction to a squib (not shown). The microcomputer 4 includes the reference A / D converter 2 and the evaluation A / D converter 3. The microcomputer 4 is also electrically connected to a squib via an IC (not shown). The reference A / D converter 2 is connected to the booster circuit 5 via the changeover switch 10. The booster circuit 5 is also connected to the battery 6. Further, the booster circuit 5 is also connected to a backup capacitor 8 via a charging resistor 7. The evaluation A / D converter 3 is connected between the charging resistor 7 and the backup capacitor 8 via the switch 11.
[0018]
Next, the operation of the operation diagnostic device of the present embodiment will be described. When the ACC switch 92 is turned on, a current starts flowing from the battery 6 to the booster circuit 5. Then, charging of the backup capacitor 8 is started. Also, the microcomputer 4 starts. FIG. 2 shows a schematic diagram of the sampling. As shown in the figure, the sampling is performed during the charging of the backup capacitor 8. The sampling of the circuit voltage V0 and the sampling of the capacitor voltage V1 are performed almost simultaneously. The circuit voltage V0 is input to the microcomputer 4 via the reference A / D converter 2. The capacitor voltage V1 is input to the microcomputer 4 via the evaluation A / D converter 3. The microcomputer 4 compares the input circuit voltage V0 with the capacitor voltage V1. This comparison is repeated several times, and if the fluctuation of the capacitor voltage V1 with respect to the circuit voltage V0 is abnormal as compared with the previously input predetermined fluctuation, the microcomputer 4 determines that the backup capacitor 8 has failed. Then, the microcomputer 4 turns on an airbag warning light (not shown) incorporated in the meter panel of the driver's seat.
[0019]
Next, effects of the operation diagnosis device of the present embodiment will be described. The operation diagnostic device 1 of the present embodiment independently includes two A / D converters, that is, a reference A / D converter 2 and an evaluation A / D converter 3. Therefore, the circuit voltage V0 and the evaluation voltage V1 can be sampled almost simultaneously. That is, the sampling time lag can be made substantially zero. Therefore, according to the operation diagnosis device 1 of the present embodiment, high operation diagnosis accuracy can be ensured.
[0020]
(2) Second Embodiment In this embodiment, the operation diagnostic apparatus of the present invention is embodied for checking the operation of a transistor whose ON / OFF is controlled. First, the configuration of the operation diagnostic device of the present embodiment will be described. FIG. 3 shows a schematic diagram of the operation diagnostic device of the present embodiment. Parts corresponding to those in FIG. 1 are denoted by the same reference numerals. The microcomputer 4 includes the reference A / D converter 2 and the evaluation A / D converter 3. The evaluation A / D converter 3 is connected to the resistor 91. The resistor 91 is connected to the transistor 90. The reference A / D converter 2 is connected between the transistor 90 and the resistor 91.
[0021]
Next, effects of the operation diagnosis device of the present embodiment will be described. FIG. 4 shows a schematic diagram of the sampling. The reference voltage V0 and the evaluation voltage V1 fluctuate under the influence of external noise. If the A / D converter is single and the sampling of the reference voltage V0 and the evaluation voltage V1 has a time lag as in the related art, the accuracy of the operation diagnosis is reduced by the noise fluctuation width ΔV.
[0022]
On the other hand, the operation diagnostic apparatus according to the present embodiment includes two A / D converters, that is, the reference A / D converter 2 and the evaluation A / D converter 3. For this reason, it is less susceptible to external noise. That is, the reference voltage V0 and the evaluation voltage V1 are affected by external noise and fluctuate in substantially the same manner. Therefore, if the sampling timings are almost the same, the influence of noise can be canceled. As described above, the operation diagnostic device of the present invention is suitable for use in electronic devices, elements, and the like that are easily affected by external noise.
[0023]
(3) Others The embodiments of the present invention have been described above. However, embodiments are not particularly limited to the above embodiments. Various modifications and improvements that can be made by those skilled in the art are also possible.
[0024]
For example, in the above embodiment, two A / D converters are arranged, but a larger number of A / D converters may be arranged. The signal used for the operation diagnosis may be a current value instead of a voltage value. The A / D converter may be used for other signals except during sampling.
[0025]
【The invention's effect】
According to the present invention, it is an object of the present invention to provide an operation diagnostic device with little diagnostic time lag and high diagnostic accuracy.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing the vicinity of a booster circuit of an airbag system in which an operation diagnostic device according to a first embodiment is used.
FIG. 2 is a schematic diagram of sampling of the operation diagnostic device of the first embodiment.
FIG. 3 is a schematic diagram of an operation diagnostic device according to a second embodiment.
FIG. 4 is a schematic diagram of sampling of the operation diagnostic device of the second embodiment.
FIG. 5 is a schematic diagram showing the vicinity of a booster circuit of a conventional airbag system.
FIG. 6 is a schematic diagram of sampling of an operation diagnostic device used in a conventional airbag system.
[Explanation of symbols]
1: operation diagnostic device, 2: reference A / D converter, 3: evaluation A / D converter, 4: microcomputer, 5: booster circuit, 6: battery, 7: charging resistor, 8: backup capacitor, 90 : Transistor, 91: resistor, 92: ACC switch.

Claims (2)

A reference A / D converter to which a reference signal is input;
An evaluation A / D converter that is separate from the reference A / D converter and receives an evaluation signal;
By electrically sampling the reference A / D converter and the evaluation A / D converter, sampling the reference signal and the evaluation signal almost simultaneously, and comparing the reference signal with the evaluation signal A diagnostic circuit for performing operation diagnosis,
An operation diagnostic device comprising: The reference signal is a circuit voltage of a booster circuit that is electrically connected to a battery and a squib for deploying a bag of the airbag system, and boosts a battery voltage to a squib ignition voltage.
The operation diagnostic device according to claim 1, wherein the evaluation signal is a capacitor voltage of a backup capacitor that backs up the booster circuit and secures the squib ignition voltage when the battery and the booster circuit are disconnected.

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