JP4075223B2 - Sensor circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a sensor circuit configured to generate a detection signal for control given to a plurality of microcomputers for load control by a single sensor.
[0002]
[Problems to be solved by the invention]
In recent years, for example, in a load control device for automobiles, it is desired to reduce the cost and improve the design around the sensor by sharing the output from one sensor with multiple ECUs (Electronic Control Units). There is a request. Specifically, for example, a light sensor for detecting the amount of solar radiation for an air conditioner and an ambient light detection for a light control system (a system that automatically controls lighting devices to be turned on and off according to the ambient brightness). In this case, an optical sensor is disposed at an appropriate position (for example, on the dashboard), and an output from the optical sensor is converted into a detection signal to be used as an air conditioner control ECU. And a sensor circuit to be provided to the body ECU having the control function of the light control system. The power supply of the sensor circuit is supplied from the power supply terminals of both ECUs through a diode-or connected power supply line, that is, when at least one of the power supplies of the air conditioner control ECU and the body ECU is activated. Is configured to be switched to an active state.
[0003]
In general, a microcomputer in an ECU has a configuration in which an input protection diode is connected in a reverse polarity state (a cathode is on the power supply terminal side) between a power supply terminal and a signal input terminal. For this reason, when a detection signal is input to the signal input terminal when the ECU is not powered on, the detection signal flows to the power supply terminal side of the microcomputer through the input protection diode, and the power supply potential is increased. As a result, there is a possibility that the microcomputer malfunctions.
[0004]
Accordingly, when the output from one optical sensor is converted into a detection signal and supplied to the air conditioner control ECU and the body ECU as described above, the power is turned on when only one of the ECUs is turned on. A microcomputer on the ECU side that has not been operated may malfunction, which may cause the load to operate abnormally. However, in the automobile, the power supply of the air conditioner control ECU is cut off during the operation period of the starter motor for starting the engine, whereas the body ECU maintains the power-on state even during the operation period of the starter motor. It is the composition to do. For this reason, even during the period when the power supply of the air conditioner control ECU is cut off in accordance with the operation of the starter motor, the sensor circuit comes to be in an active state by the power supply of the body ECU. The detection signal from the sensor circuit is input to the signal input terminal of the microcomputer. As a result, the microcomputer may malfunction, and when such malfunction occurs, the air conditioner may malfunction.
[0005]
The present invention has been made in view of the above circumstances, and an object of the present invention is to supply a detection output from one sensor as a detection signal for control to a plurality of microcomputers. It is an object of the present invention to provide a sensor circuit that can surely prevent a situation given to a non-microcomputer and prevent a malfunction of the microcomputer.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the means described in claim 1 can be employed. According to this means, when any one of a plurality of microcomputers is powered on, the power is supplied to the sensor circuit, and in response to the detection output by the sensor from the signal generation circuit. The control detection signal is output. In this case, the power supply monitoring circuit individually monitors whether or not the power supplies of the plurality of microcomputers have risen, and among the plurality of signal output terminals for outputting the detection signal to each microcomputer, the microcomputer in which the power supply is not started up The output of the detection signal from the signal output terminal corresponding to is forcibly stopped. As a result, it is possible to reliably prevent the detection signal from being inadvertently given to a microcomputer that is not turned on, and to prevent malfunction of the microcomputer. Of course, for example, when all the microcomputers are powered on, the operation of forcibly stopping the output of the detection signal as described above is not performed, so only by providing one sensor, It is possible to supply detection signals for load control to a plurality of microcomputers, so that cost reduction and improvement in design around the sensor can be realized.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
A first embodiment in which the present invention is applied to an automobile will be described below with reference to FIG.
FIG. 1 shows a sensor circuit in which a photosensor for detecting the amount of solar radiation for an air conditioner and an optical sensor for detecting ambient light for a light control system are combined with one photodiode, and a circuit configuration of a part related thereto. Has been.
[0008]
In FIG. 1, a sensor circuit 1 includes, for example, a single photodiode 2 (corresponding to a sensor) arranged on a dashboard of an automobile, and the photodiode 2 is reverse-biased by a bias circuit (not shown). ing. As a result, a current of a level corresponding to the amount of received light (illuminance) is output from the photodiode 2, and the output current is amplified by the signal generation circuits 3 and 4 and then used as a control detection signal. The voltage signals Sv1 and Sv2 are converted. The voltage signals Sv1 and v2 output from the signal generation circuits 3 and 4 are applied to the signal output terminals 1a and 1b of the sensor circuit 1 through the output lines L1 and L2, respectively.
[0009]
The signal output terminals 1a and 1b are connected to the signal input terminals 5a and 6a of the body ECU 5 and the air conditioner control ECU 6, respectively. In this case, the body ECU 5 is for performing the operation control of the light control system and the operation control of other automobile loads. The body ECU 5 includes a voltage signal Sv1 applied to the signal input terminal 5a and other signal input terminal groups (not shown). A microcomputer (abbreviated as “microcomputer” in FIG. 1) 5b which receives a given signal (a signal necessary for controlling other automobile loads) is mainly configured. A pull-down resistor 5c is connected to the signal input terminal 5a. The above light control system automatically turns on the tail lamp system at twilight and automatically turns on the headlamp at night and in the tunnel. This is a system that performs control to automatically turn off the head lamp and tail lamp system in response to the above.
[0010]
The air conditioner control ECU 6 is for controlling the operation of the air conditioner. The voltage signal Sv2 given to the signal input terminal 6a and signals given to other signal input terminal groups (not shown) And a microcomputer 6b (abbreviated as “microcomputer” in FIG. 1) for receiving temperature information and signals indicating operation states of the operation switches. A pull-down resistor 6c is connected to the signal input terminal 6a.
[0011]
The body ECU 5 and the air conditioner control ECU 6 are supplied with power from the corresponding power terminals 5d and 6d. In this case, although not shown, the power supply terminal 5d of the body ECU 5 is supplied with power from the positive power supply terminal of the in-vehicle battery through the main relay (turned on when the ignition switch is in the ON position). The power supply terminal 6d of the air conditioner control ECU 6 is supplied with power from the positive power supply terminal of the on-vehicle battery through the ACC relay (turned on when the ignition switch is in the ACC position and the ON position). However, the power supply to the power supply terminal 6d of the air conditioner control ECU 6 is stopped during the period when the ignition switch is operated to the start position.
[0012]
The body ECU 5 and the air conditioner control ECU 6 are provided with power supply terminals 5e and 6e for supplying power to the power supply terminals 1c and 1d of the sensor circuit 1 when power is supplied to the power supply terminals 5d and 6d. The sensor circuit 1 is provided with a constant voltage circuit 8 that is supplied with power from the power supply terminals 1c and 1d through the diode OR circuit 7. The power supply for the signal generation circuits 3 and 4 and a bias circuit (not shown) is supplied to the constant voltage circuit. 8 has been given.
[0013]
A series circuit of a resistor 9a and a capacitor 9b constituting the low-pass filter 9 is connected between the power supply terminal 1c and the ground terminal of the sensor circuit 1, and the low-pass filter 10 is similarly connected between the power supply terminal 1d and the ground terminal. Is connected to a series circuit of a resistor 10a and a capacitor 10b. The resistors 9a and 10a also function as current limiting resistors.
[0014]
Between the output terminal of the constant voltage circuit 8 and the ground terminal, the emitter-collector of the pnp transistor 11 and the resistor 12 are connected in series, and the base of the transistor 11 is common to the resistor 9a and the capacitor 9b. It is connected to a connection point (output terminal of the low-pass filter 9). A resistor 13 is connected between the base of the transistor 11 and the ground terminal. Similarly, between the output terminal of the constant voltage circuit 8 and the ground terminal, the emitter-collector of the pnp transistor 14 and the resistor 15 are connected in series, and the base of the transistor 14 is the resistor 10a and the capacitor 10b. It is connected to a common connection point (output terminal of the low-pass filter 10). A resistor 16 is connected between the base of the transistor 14 and the ground terminal.
[0015]
Here, the low-pass filter 9, 10, the transistors 11 and 14, and the resistors 12, 13, 15 and 16 constitute a voltage detection circuit 17. The voltage detection circuit 17 operates as described below. That is, the voltage detection circuit 17 detects the potential level of the power terminals 5d and 6d of the body ECU 5 and the air conditioner control ECU 6 through the low-pass filters 9 and 10, and in each state where the power terminals 5d and 6d are raised. Turns off the transistors 11 and 14 to output a signal at the ground potential level from the point Q1 (collector of the transistor 11) and the point Q2 (collector of the transistor 14) in the figure. In contrast, when the power supply terminal 5d of the body ECU 5 is not raised, the transistor 11 is turned on and a detection signal of a predetermined potential level (a level close to the output voltage level of the constant voltage circuit 8) is output from the point Q1. When the power supply terminal 6d of the air conditioner control ECU 6 is not raised, the transistor 14 is turned on to output a detection signal at a predetermined potential level (a level close to the output voltage level of the constant voltage circuit 8) from the point Q2.
[0016]
The output line L1 corresponding to the signal generating circuit 3 is connected to the ground terminal via the collector-emitter of an npn transistor 18 (corresponding to switching means), and the base of the transistor 18 is connected to the point Q1. Has been. Accordingly, during the period in which the detection signal is output from the point Q1 (period in which the power supply terminal 5d of the body ECU 5 is not raised), the transistor 18 is turned on and the line L1 (that is, the signal output terminal 1a) is connected to the ground terminal. Will be.
[0017]
The output line L2 corresponding to the signal generating circuit 4 is connected to the ground terminal via the collector-emitter of an npn transistor 19 (corresponding to switching means), and the base of the transistor 19 is the Q2 point. It is connected to the. Therefore, during a period in which the detection signal is output from the point Q2 (a period in which the power supply terminal 6d of the air conditioner control ECU 6 is not raised), the transistor 19 is turned on and the line L2 (that is, the signal output terminal 1b) becomes the ground terminal. Will be connected.
The voltage detection circuit 17 and the transistors 18 and 19 constitute a power supply monitoring circuit 20 referred to in the present invention.
[0018]
According to the above-described configuration of the present embodiment, when the power source of the body ECU 5 and the air conditioner control ECU 6, that is, one of the power sources of the two microcomputers 5 b and 6 b is started up, it is determined via the diode OR circuit 7. Power is supplied to the voltage circuit 8. As a result, the power of the sensor circuit 1 is turned on, and the voltage signals Sv1 and Sv2 are output from the signal generating circuits 3 and 4 accordingly.
[0019]
In this case, the power supply monitoring circuit 20 individually monitors the presence or absence of rising of the power supply terminals 5d and 6d for the plurality of microcomputers 5b and 6b through the voltage detection circuit 17, and supplies the voltage signals Sv1 and Sv1 to the microcomputers 5b and 6b. Forcing the output of the voltage signal (Sv1 or Sv2) from the signal output terminal (1a or 1b) corresponding to the microcomputer (5b or 6b) of which the power is not turned on among the signal output terminals 1a and 1b for outputting Sv2 Will come to a halt.
[0020]
As a result, for example, the voltage signal Sv2 is inadvertently given to the microcomputer 6b that is not turned on during the period when the ignition switch is operated to the start position and the power supply to the power supply terminal 6d of the air conditioner control ECU 6 is stopped. Thus, the malfunction of the microcomputer 6b can be prevented in advance. Of course, when both the power supplies of the microcomputers 5b and 6b are activated, the operation of forcibly stopping the output of the voltage signals Sv1 and Sv2 is not performed, and therefore one photodiode 2 is provided. As a result, the voltage signals Sv1 and Sv2 for controlling the load can be supplied to the two microcomputers 5b and 6b, so that the cost can be reduced and the design around the photodiode 2 can be improved.
[0021]
Further, since the voltage detection circuit 17 is provided with low-pass filters 9 and 10 at its input stage, the transistor 18 or 19 is inadvertently turned off when there is an instantaneous voltage change caused by a surge or the like. Thus, the power monitoring function of the power monitoring circuit 20 can be normally operated at all times.
[0022]
(Second Embodiment)
FIG. 2 shows a second embodiment of the present invention that exhibits the same effect as the first embodiment, and only the parts different from the first embodiment will be described below.
The second embodiment is characterized in that a voltage detection circuit 21 using a comparator is provided in place of the voltage detection circuit 17 in the first embodiment. In this voltage detection circuit 21, the voltage dividing circuits 22 and 23 are provided between the output terminal and the ground terminal of the constant voltage circuit 8, respectively, of the voltage dividing circuit 22 and the resistors 23 a and 23 b formed by series circuits of resistors 22 a and 22 b. Each of the voltage dividing circuits 22 and 23 generates a reference voltage Vf1 and Vf2 at a certain level, respectively. The comparator 24 is connected so as to compare the reference voltage Vf1 and the power supply voltage Vb1 divided by the resistors 9a and 13 and when Vf1> Vb1 is satisfied (when the power supply terminal 5d is not raised). The transistor 18 is turned on. The comparator 25 is connected so as to compare the reference voltage Vf2 with the power supply voltage Vb2 divided by the resistors 10a and 16, and when the relationship Vf2> Vb2 is satisfied (the power supply terminal 6d is not raised). The transistor 18 is turned on.
[0023]
(Other embodiments)
The present invention is not limited to the above-described embodiment, and the following modifications or expansions are possible.
Although the bipolar transistors 18 and 19 are used as the switching means, other switching means such as an FET may be used. The constant voltage circuit 8 is not required when the voltage applied to the power supply terminals 1c and 1b is stable, and therefore may be provided as necessary. Although the photodiode 2 which is an optical sensor has been described as an example of the sensor, it is needless to say that the present invention can be applied to a sensor circuit using another sensor. Of course, the present invention can be applied to a case where a larger number of microcomputers are connected.
[0024]
As the control detection signal, a current signal, a frequency signal, a PWM signal, or the like can be applied in addition to the voltage signal as in the above embodiment. In particular, when the control detection signal is a current signal, the circuit of the above embodiment can be coped with by making the sink capability of the transistor larger than the current signal.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention. FIG. 2 is a circuit configuration diagram showing a second embodiment of the present invention.
1 is a sensor circuit, 2 is a photodiode (sensor), 3 is a signal generation circuit, 5 is a body ECU, 5a is a signal input terminal, 5b is a microcomputer, 5d is a power supply terminal, 6 is an air conditioner control ECU, 6a is Signal input terminal, 6b is a microcomputer, 6d is a power supply terminal, 7 is a diode OR circuit, 9 and 10 are low-pass filters, 17 is a voltage detection circuit, 18 and 19 are transistors (switching means), 20 is a power supply monitoring circuit, 21 Indicates a voltage detection circuit.

Claims (3)

A signal generation circuit that outputs the detection output of one sensor as a control detection signal for a plurality of microcomputers for load control is provided, and power is supplied in a state where any one of the plurality of microcomputers is started up. In the sensor circuit to be
Provided to individually monitor the presence or absence of power supply rise of the plurality of microcomputers, and corresponds to a microcomputer in which the power supply is not started among a plurality of signal output terminals for outputting the detection signal to each microcomputer A sensor circuit comprising a power supply monitoring circuit for forcibly stopping output of a detection signal from a signal output terminal. The power of the signal generation circuit is configured to be supplied through a diode OR circuit from a power supply terminal for the plurality of microcomputers.
The power supply monitoring circuit individually detects potential levels of the plurality of power supply terminals, and performs an operation of forcibly stopping the output of the detection signal when the detection level is a predetermined level or less. The sensor circuit according to claim 1. The power monitoring circuit includes a plurality of switching means connected between the plurality of signal output terminals and a ground terminal, and forcibly stops the output of the detection signal when the switching means is turned on. 3. The sensor circuit according to claim 1, wherein the sensor circuit is characterized in that:

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