JPH09218233A - Load disconnection detection device in vehicle - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To eliminate the need for correction of the detection voltage applied to the resistance for measuring disconnection, to save labor and to improve detection accuracy. A switching element SW ₀ between the load R ₀ to the switching element SW _C and the branch passage 1 voltage and constant measuring power E _C the measurement resistor R _C 'are connected in this order and the power for the power supply E ₀ Set up. The switching element SW ₀ is turned off to disconnect the power supply E ₀ and the load R ₀ , and the switching element SW _C is turned on at the same timing to turn on the measurement power supply E.
_C causes a current I _C to flow through the measuring resistor R _C 'and the load R ₀ . 'Voltage drop V _C at' the current I _C for measurement by the resistance _{R C (= I C · R} C ') a previously memory M voltage drop value in the non-disconnection is set to _e V _com comparator C To determine if there is a disconnection or non-disconnection. This operation is performed many times to prevent erroneous determination.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for detecting load disconnection of a stop lamp, a traveling direction indicating lamp, a heater and the like in a vehicle.

[0002]

2. Description of the Related Art A vehicle is provided with a load disconnection detection circuit such as a stop lamp, a traveling direction indicator lamp, and a defero star heater. When a load disconnection is detected, the driver is notified of that fact. There is. As an example of the disconnection circuit, FIG. 4 shows that the load R ₀ has a stop lamp, and this circuit has a detection resistor R _C for detecting disconnection between the power supply E ₀ and the loads R ₀ and R _0. A measuring circuit A is connected in parallel to the detection resistor R _C , and the measuring circuit A is composed of a corrector 11, a comparator C and an adjusting resistor 12.

The circuit A detects disconnection by detecting the current I ₀ flowing through the load R ₀ by the power source E ₀ for detection by the detection resistor R _C.
Is measured based on the voltage drop V _C (= I ₀ · R _C ) at the predetermined voltage drop V _com
If it is smaller than the value of, it is judged as a disconnection. This disconnection / non-interruption determination operation is performed by a comparator C such as an operational amplifier, and the comparator C issues a disconnection / non-interruption signal based on the result. For example, when one of the stop lamps R ₀ is disconnected, the resistance value of the load increases, so that the voltage drop V _C at the detection resistor R _C is the voltage drop V when there is no disconnection.
The value becomes smaller than the value of _com , and by detecting the disconnection of one of the stop lamps R ₀ , it is indicated. This time,
The corrector 11 corrects the voltage sent to the comparator C according to the voltage fluctuation of the power source E ₀ for power. In addition, the adjustment resistor 12 is a load R ₀
The value is appropriately set depending on the type (resistance value) of.

[0004]

In the above disconnection detecting device, an on-vehicle battery is usually used as the power source E ₀ for the power source, and the battery has a circuit other than the load R ₀ such as a lamp. Various loads are connected. Therefore, the voltage applied to the disconnection detection resistor R _C changes or noise is generated depending on whether or not these other loads are driven. The voltage change and the generation of noise cause a detection error. The error will be compensated by the corrector 11, but there is a limit and the detection accuracy is not reliable.

Further, since the standard and quantity of the load R ₀ are different depending on the type of vehicle and the destination (export destination), in this case, adjustment of the adjusting resistor 12 alone cannot cope.
The detection resistor R _C itself also needs to be adjusted and replaced, and this adjustment and replacement work is very troublesome and requires new adjustment parts and takes time.

Therefore, according to the present invention, such a load R ₀
In view of the conventional problem in detecting disconnection of the power source E ₀
It is an object of the present invention to provide a disconnection detection device that is not affected by the voltage fluctuation of

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention relates to a disconnection of a load such as a stop lamp, a traveling direction indicator lamp and a heater in a vehicle, a current flowing through the load or a voltage across the load. A device for detecting by fluctuation, having a measurement power supply separated from the power supply for the load, and detecting a disconnection, switching the connection of the power supply to the load from the power supply for the measurement to the measurement power supply, and measuring the same. A current is passed from the power supply for use to the load, and the disconnection of the load is detected by the current flowing through the load or the voltage across the load (claim 1). By doing so, the detection power supply is secured by the measurement power supply separated from the power supply when the disconnection is detected, so that the voltage change of the power supply does not occur in the detection circuit and There is no influence of noise or the like due to driving of the connected load. Further, since it is not necessary for the resistance and the like provided in the detection circuit to correspond to the power supply for motive power, for example, if a battery with a small voltage is used for the measurement power supply of the detection circuit, the resistance corresponding to this is also inexpensive. A small resistor can be used.

In the present invention, the load to be detected for disconnection may be a plurality of loads connected in parallel (Claim 2), and the measuring power source is a constant current source,
If the disconnection of the load is detected by the fluctuation of the voltage across the load (claim 3), the power consumption at the time of detection can be reduced (for details, refer to the section of the embodiment of FIG. 3).

Further, the current flowing through the load or the voltage across the load is measured, and the measured value is compared with a predetermined reference value, so that the fluctuation range of the current or voltage becomes a certain value or more. It is possible to judge that the load is broken when it occurs (Claim 4). In this way, if the comparison is made with a predetermined reference value, the detection accuracy is improved because the reference is constant.

Further, the connection of the power source to the load is switched, and the current flowing through the load or the voltage across the load is measured by the microcomputer, and the internal power source of the microcomputer is used as the power source for measurement (claim 5). ), The disconnection detection function becomes smooth, and the microcomputer can also be used for other functions.

In addition, when the microcomputer is used, a plurality of the predetermined reference values to be compared with the measured values may be input to the internal memory of the microcomputer, and each reference value may be set to the vehicle type or destination standard. In this case (claim 6), it is not necessary to change the setting of the reference value each time the type of vehicle is changed.

[0012]

[Embodiment]

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. In this circuit, a branch path 1 for disconnection detection is provided in parallel with a load R ₀ , and a switching element S is provided in this branch path 1.
W _C , the power source E _C for measurement, and the resistance R _C 'for measurement are connected in series in this order. Switching elements SW ₀ and SW _C are provided between the branch path 1 and the power supply E ₀ for power supply, and the load R ₀ is supplied to the power supply E ₀ for measurement or the power supply E _C for measurement by the switching elements SW ₀ and SW _C. Connected selectively. As the switching elements SW ₀ and SW _C , those that switch from a solid line to a broken line like the switching element SW of FIG. 3 may be used.

As the measuring power source E _C , a stabilized power source such as a constant voltage regulator is adopted in addition to the battery.

Further, a comparator C for comparing the measured value with a reference value and a memory M in which the reference value is recorded are provided in the branch path 1.
_e is connected.

Under such a circuit configuration, the disconnection is detected as follows. First, the switching element SW ₀
Is turned off to cut off the power supply E ₀ and the load R ₀ , and at the same timing, the switching element SW _C is turned on to bring the branch path 1 into conduction, and the measurement power supply E _{C is used} to connect the measurement resistance R _C 'and the load. A current I _{C is} passed through R ₀ . This current I
Measuring resistor R _C by _C 'voltage drop in V _C' (= I _C
· R _C ') is compared with the voltage drop value V _com of the time of non-disconnection which is previously recorded in the memory M _e. When the compared value is out of the range specified as non-disconnection, that is, when disconnection occurs, the comparator C issues a disconnection warning signal.

When the determination of the presence / absence of disconnection is completed, each of the switching elements SW ₀ and SW _C is returned to the initial state,
The load R ₀ is connected to the power supply E ₀ for power supply and is disconnected from the branch path 1. This series of operations is performed many times to prevent erroneous determination.

(Second Embodiment) In the embodiment shown in FIG. 2, the switching elements SW ₀ and S shown in FIG.
The case where the switching operation of W _C and the detection / comparison operation of the voltage drop value are performed by the microcomputer will be described. In this embodiment, the power supply E _M in the microcomputer MC is used as the power supply E _C for measurement. Between the power source E _M and the measuring resistor R _C ', the A / D converter 2, the comparison circuit C _c ,
To connect the internal memory M _e. Further, the switching elements SW ₀ and SW _C are connected to the microcomputer MC by the wirings d ₀ and d _C , respectively, and are operated by the microcomputer MC.

The basic operation of such a circuit is shown in FIG.
First, when the switching element SW ₀ is turned off and the switching element SW _C is turned on at the same timing according to a command from the microcomputer MC, the load R ₀ is disconnected from the power source E ₀ for driving. Is connected to the branch path 1, and a current I _C flows through the load R ₀ and the measurement resistor R _C ′ by the measurement power supply E _M.

Then, the voltage drop V _C '(= I _C · R _C ') in the measuring resistor R _C 'is measured by the microcomputer M.
Imported to the A / D converter 2 built into C,
The analog value is digitized. Comparing the digital value of the voltage drop values V _com non disconnection time which is previously recorded in the internal memory M _e of the digital values microcomputer MC of 'voltage drop V _C at' the measuring resistor R _C.

The compared value, that is, the voltage fluctuation ΔV _C (=
If V _C '-V _com ) is outside the range specified as non-disconnection, for example, ΔV _C = 0.5 in consideration of noise of the comparator C _C
If V is larger than the value of 0.5, the microcomputer MC issues a disconnection warning signal.

[0021] In this case, if the microcomputer MC of the internal memory M _e to various load voltage drop value in the non-disconnection corresponding to the standard of R ₀ V _com (reference value) more inputs, vehicle type and destination Even if the standard of the load R ₀ is different depending on the ground, it is not necessary to change the setting of the reference value each time, and the operation efficiency is good. If each reference value corresponds to the disconnection of each load R ₀ , the number of disconnected loads R ₀ and the disconnected load R ₀ itself can be specified.

When the microcomputer MC is used in this way, the microcomputer MC can also be used for various functions, and the disconnection detection function can be made smooth.

(Third Embodiment) Next, FIG. 3 shows a third embodiment of the present invention. In this circuit, a resistor R _C ″ having a sufficiently large resistance value is connected to a load R _0. A constant current source B is formed in the branch path 1 to detect disconnection, and the other configuration is the same as the circuit configuration shown in FIG.
By doing so, a constant minute current I _{C is} applied to the resistor R _C ″.
Flows, the load across the voltage drop of the R ₀ can be measured, "allows the measurement to reduce the power consumption in. In this case, the resistance R _C" resistance R _C, as shown below in the position of chain line Good.

Under the configuration of this circuit, the voltage drop V _{0 at the} load R ₀ is expressed by the following equation.

V ₀ = I _C · R _0/2 = {E _C / (R _C ″ + R _0/2 )} · R _0/2 Here, since R _C ″ >> R ₀ , V ₀ = { E _C · R ₀ } / 2R _C ″ The voltage drop V ₀ ′ when one of the loads R ₀ is disconnected is V ₀ ′ = {E _C · R ₀ } / R _C ″. The difference ΔV ₀ in the voltage drop across the load R ₀ is ΔV ₀ = V ₀ ′ −V ₀ = {E _C · R ₀ } / R _C ″ − {E _C · R ₀ } / 2R _C ″ = {E _C · R ₀ } / 2R _C ″ E _C , R ₀ , ΔV ₀ , by substituting specific numerical values, the measurement power supply E _C = 5V (the internal power supply E of the microcomputer E
_M ) and the load R ₀ is a stop lamp, for example,
R ₀ = 7Ω and ΔV considering noise of the comparator C _{C
If 0} = 0.5 [V], then R _C ″ = {E _C · R ₀ } / 2ΔV ₀ = (5 × 7) / (2
× 0.5) = 35 [Ω] Further, I _C = E _C / (R _C ″ + R _0/2 ) = 5 / (35
+7/2) = 0.14 [A] Therefore, the power consumption P _C ′ at the resistor R _C ″ is P _C ′ = I _C ² · R _C ″ = (0.14) ² × 35 = 0.69 [W ] in contrast, in the conventional example of FIG. 4, the load rather than the ends of R _0, as measured voltage variations across the sense resistor _{R C, V C = R C} · I 0 = R C · {E 0 / (R _C + R ₀ /
2)} Here, since R ₀ >> R _C , V _C = 2E ₀ · R _C / R ₀ Also, the voltage drop V _C ′ when one load R ₀ is disconnected.
Is V _C '= E ₀ · R _C / R ₀ Therefore, the difference ΔV _C in the voltage drop across the load R ₀ with and without disconnection is ΔV _C = V _C −V _C ' = 2E ₀ · R Substituting specific numerical values for _C / R ₀ −E ₀ · R _C / R ₀ = E ₀ · R _C / R ₀ E ₀ , R ₀ , ΔV _C , for example, the power source for power E ₀ = 12V, R ₀ and ΔV _C are respectively R ₀ = 7 [Ω] and ΔV _C = 0.5 similarly to the above.
If [V], then R _C = ΔV _C · R ₀ / E ₀ = 0.5 × 7/12 = 0.3 [Ω] Further, the flowing current I ₀ is I ₀ = E ₀ / (R ₀ / 2) = 12 / (7/2) = 3.5 [A] Therefore, the power consumption P _C at the detection resistor R _C is ^{_{P C = I 0 2 · R}} C = (3.5) 2 × 0. 3 = 3.6 [W] As described above, it can be understood that the power consumption can be suppressed small in the disconnection detection method by the constant current source B.

[0026]

As described above, according to the present invention, the power source for measurement supplies a current to the load to detect the disconnection of the load. Therefore, the power source for power use which causes voltage fluctuation and noise is used. Since it is not necessary to correct the power supply voltage as in the case where the voltage drop in the measuring resistor is detected by using the measurement resistance, accurate determination can be performed easily.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a circuit diagram showing a second embodiment.

FIG. 3 is a circuit diagram showing a third embodiment.

FIG. 4 is a circuit diagram showing a conventional example.

[Explanation of symbols]

1 Branch 2 A / D converter E ₀ Power supply for power E _C , E _M Measurement power supply SW ₀ , SW _C , SW Switching element R ₀ Load R _C 'Measurement resistance R _C "Resistance _RC Detection resistance MC Micro Computer _Me memory (internal memory)

Claims (6)

[Claims] 1. A device for detecting a disconnection of a load such as a stop lamp, a traveling direction indicator lamp, a heater, etc. in a vehicle by a current flowing through the load or a voltage fluctuation across the load, the power source for powering the load. It has a separate power supply for measurement,
When a disconnection is detected, the connection of the power supply to the load is switched from the power supply for the power supply to the measurement power supply, a current is passed from the measurement power supply to the load, and the disconnection of the load is caused by the current flowing through the load or the voltage across the load. A load disconnection detection device for a vehicle, which detects the load. 2. The load disconnection detecting device for a vehicle according to claim 1, wherein the load is a plurality of loads connected in parallel. 3. The load disconnection detection device for a vehicle according to claim 2, wherein the measurement power supply is a constant current source, and disconnection of the load is detected by fluctuation of the voltage across the load. 4. The current flowing through the load or the voltage across the load is measured, and the measured value is compared with a predetermined reference value, so that the fluctuation range of the current or voltage becomes a certain value or more. The load disconnection detecting device for a vehicle according to claim 2 or 3, wherein it is determined that the load disconnection occurs. 5. The microcomputer switches the connection of the power supply to the load and measures the current flowing through the load or the voltage across the load, and the internal power supply of the microcomputer is used as the measurement power supply. A load disconnection detection device for a vehicle according to claim 1. 6. The microcomputer switches the connection of the power source to the load and measures the current flowing through the load or the voltage across the load, and uses the internal power source of the microcomputer as the power source for measurement and the predetermined reference value. 5. The load disconnection detection device for a vehicle according to claim 4, wherein a plurality of types of the above are input to an internal memory of the microcomputer.