JPS6327440Y2 - - Google Patents

Description

[Detailed description of the invention] This invention prevents false detection due to voltage fluctuations at the detection point caused by line resistance in the power supply line of the lamp equipment or contact resistance of the lamp switch, etc., and provides stable alarms. This invention relates to a disconnection detection device that performs.

Conventionally, devices that detect disconnections in lamps and issue warnings have various detection methods depending on their purpose. For lamps that are turned on intermittently when the lamp is stopped, etc., the purpose can be achieved by issuing a disconnection alarm only when the lamp is not in use. A device with a time-only detection function is commonly used.

In this method, a lamp switch 2 and a lamp 3 to be detected are connected in series to a power supply 1, and a resistor 4, which has a much larger value than the internal resistance of the lamp 3, is connected in parallel with the switch 2. Then, P due to disconnection
A transistor 5 detects a voltage change at a point, and a warning light 7 connected to the output of an output transistor 6 is configured to notify the disconnection.

That is, when the lamp switch 2 is opened, a small current flows through the lamp 3 through the resistor 4, and under normal conditions, P
The voltage at point P does not reach a level that can make transistor 5 conductive, and due to the disconnection, a bias is applied to the base of transistor 5 from power supply 1 through resistor 4, and the voltage at point P under normal conditions is always Must be set below a threshold level of 5.

By the way, in terms of implementation, the installation location of the lamp device 3 to be detected and the installation location of the alarm circuit including the warning light 7 are usually relatively separate, and each ground line is connected to the power supply 1 by a conductor according to its current capacity. Since the supply line of the lamp unit 3, which has a particularly large current capacity, has a slight internal resistance that causes a slight voltage drop, this may cause a slight voltage difference with the alarm circuit, resulting in false detection. It is the cause of To explain more specifically, for example, when the lamp 3 is considered as a brake light for a vehicle, another lamp 8 such as a tail light is usually connected in parallel with this circuit in a separate circuit via a lamp switch 9. Each ground line may be connected to the negative pole of the power supply 1 in common. In this case, even if the lamp unit 3 is turned off and a disconnection can be detected, if the lamp unit 8 is turned on, the voltage at point P will be applied to the transistor 5 due to the voltage drop due to the minute line resistance 10 of the ground line. There is a problem in that the light rises to a level high enough to turn on, and the lamp 3 issues an alarm even though it is normal.

This invention takes into account the voltage fluctuations at the detection point due to the line resistance in the lamp's current supply line or the contact resistance of the lamp switch, etc., and compensates the operating range of the detection element by the above voltage fluctuation to ensure reliable lighting. It is an object of the present invention to provide a wire breakage detection device that can detect and notify a wire breakage in a device and also prevent malfunctions due to noise by optically coupling signal lines.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the accompanying drawings for a vehicle lamp.

In FIG. 2, a brake light switch 12 and a brake light 13 are connected in series to an on-vehicle power supply 11, and a resistor 14 having a larger value than the internal resistance of the brake light 13 is connected in parallel with the switch 12. A first photocoupler 1 in series with the resistor 14 and in parallel with the brake light 13
Five light emitting diodes 16 are connected. 1st
The cathode side of the light emitting diode 16 as a detection element is connected to a resistor 17 and a resistor 18 as a voltage dividing circuit that sets the operating point of the light emitting diode 16 to a higher potential than the detection voltage based on the voltage drop caused by the resistor 14. connected to the connection point, resistor 17 and resistor 18
The light emitting conditions of the light emitting diode 16 are set by determining the cathode potential based on the partial voltage between the light emitting diode 16 and the light emitting diode 16. The diode 19 is for backflow prevention and prevents overcurrent from flowing to the light emitting diode 16 and destroying it when the brake light switch 12 is closed.

The phototransistor 20 of the photocoupler 15 has its output connected to the gate of the thyristor 22 via a resistor 23, a diode 24, and a resistor 25 in order to activate the alarm circuit 21.
A warning light 26 connected to the anode side of No. 2 is turned on.

The capacitor 27 triggers the thyristor 22 with a slight delay when the phototransistor 20 is activated, and is also useful for preventing malfunctions due to noise.

Further, a light emitting diode 29 of a second photocoupler 28 is connected in parallel with the brake light 13, and a resistor 31 is connected to the cathode side of the light emitting diode 29, which determines the cathode potential by dividing the voltage with the resistor 30. Light emission conditions for the light emitting diode 29 are set. Phototransistor 3 of photocoupler 28
The output leads of thyristor 22 are connected to the connection point between resistor 23 and diode 24 and to the negative side of the power supply so that the gate of thyristor 22 is grounded when conductive.

In addition, the lighting circuits for the taillight switch 33 and the taillight 34 are connected in parallel to the lighting circuit for the brake light 13, with their ground lines in common, and their lighting mode is different from that of the brake light 13, so that they can be turned on continuously during night driving. It should be lit.

Note that the dotted line resistance 35 indicates the contact resistance at the brake switch 12 and the positive line resistance of the brake light 13, and the resistance 36 indicates the line resistance existing in the common ground line of the brake light 13 and tail light 34. There is a slight difference in length due to the wiring of the wire, and the value is as small as about 0.5Ω.

In the above configuration, when the brake light switch 12 and the tail light switch 33 are both open, the brake light 13
is normal, the light emitting diode 16 of the photocoupler 15 and the emission diode 2 of the photocoupler etc.
The voltage applied to 9 is determined by the voltage division between resistor 14 and brake light 13, and the value of resistor 4 is set much larger than the internal resistance of brake light 13.
The voltage at point P is extremely small and does not cause the light emitting diodes 16 and 29 to emit light. Therefore, the phototransistor 20 is not conductive and the thyristor 22 is not triggered, so the alarm circuit 21 is not activated.

Now, if the brake light 13 is disconnected, a power supply voltage is applied to the light emitting diode 16 via the resistor 14, and the light emitting diode 16 enters a light emitting state. Therefore, the phototransistor 20 receives light and becomes conductive, and the capacitor 27
This triggers the thyristor 22 with a slight delay and turns on the warning light 26.

At this time, the power supply voltage is also applied to the light emitting diode 29 of the photocoupler 28 via the resistor 14 and the diode 19, but the current is limited by the summation with the resistor 31, and the current that is sufficient to cause the light emitting diode 29 to emit light does not flow. Since the phototransistor 32 is also not conductive, the above-mentioned alarm operation is performed smoothly without grounding the input side of the alarm circuit 21, and the abnormality of the brake light 13 can be reliably notified to the driver.

The above detection operation is performed when both the brake light 13 and the tail light 34 are not lit, and the current flowing through the line resistors 35 and 36 is extremely small, and the effect of voltage fluctuations due to this can be completely ignored, so this is not considered a cause of malfunction. There is no need to consider it.

Now, if the brake light switch 12 is open and the tail lights 34 are turned on, a current much larger than the minute current flowing through the resistor 14, the diode 19, and the brake lights 13 flows through the earth line of the lighting circuit including the brake lights 13, and the voltage drop due to the line resistor 36 cannot be ignored. That is, the capacity of the tail lights 34 is relatively large, and the lighting current reaches several hundred mA to several A. When multiple lights are turned on simultaneously, a voltage drop of nearly 1V occurs even in a minute resistor such as the line resistor 36, and the voltage at the detection point P also rises to the same level, causing the brake lights 1 to turn on.
Even if line resistor 3 is normal, the photocoupler 15, which is the detection element, may be activated, causing a false alarm. In the case of this invention, the cathode potential of the light emitting diode 16 of the photocoupler 15 is set by resistors 17 and 18, and the light emission level of the light emitting diode 16 is compensated for by the voltage drop due to the line resistor 36. Therefore, the disconnection detection range is set within a range where there is no false detection, and a reliable alarm can be given.

Next, the lighting operation when the brake light switch 12 is closed will be described assuming that the line resistance 35 including the contact resistance of the switch 12 does not exist.

In this case, when the brake light 13 is turned on, the voltage at point P rises to the power supply voltage, so the power supply voltage is applied to the light emitting diode 16 of the photocoupler 15 via the resistor 14, and the light is emitted. Transistor 20 is turned on. At the same time, a voltage is also applied to the light emitting diode 29 of the photocoupler 28 through the brake light switch 12, causing it to emit light, making the phototransistor 32 conductive and grounding the input side of the thyristor 22. At this time, thyristor 2
The output of the phototransistor 20 is applied to the gate of the phototransistor 2 with a delay caused by the capacitor 27, but since the input side of the thyristor 22 is already grounded by the phototransistor 32, the thyristor 22 is turned on. The warning light 26 will not be turned on.

Furthermore, even if the brake light 13 is disconnected when the brake light 13 is in use, that is, when the brake light switch 12 is closed, the voltage at point P will not change, so the state of the photo couplers 15 and 28 will be the same as when the brake light 13 is normal. Similarly, the warning light 26 does not turn on while the brake light switch 12 is closed. however,
For lamps such as the brake light 13, which are off during normal driving and are turned on intermittently when stopped, etc., it is possible to detect an abnormality when the lights are off and maintain a warning display. Therefore, the alarm function can be fully satisfied. In the case of this embodiment, the thyristor 22 has the above-mentioned holding function, so if a disconnection is detected when the brake light switch 12 is opened and the thyristor 22 is turned on with the output of the photocoupler 15, the brake light switch 12 can be closed. By doing so, the photocoupler 28 is activated,
Even if the gate current is cut off by grounding on the input side of the alarm circuit 21, the thyristor 22 remains on and continues to light the warning light 26 until the anode voltage is cut off. Therefore, once a disconnection is detected, the alarm state is maintained regardless of whether the brake light switch 12 is opened or closed, and an abnormality in the brake light 13 can be reliably notified.

By the way, the above-mentioned operation describes the normal operation when the line resistance 35 is ignored.In terms of implementation, the brake light switch 1 is included in the lighting circuit of the brake light 13.
There are minute resistances including contact resistance 35 of 2, and setting a detection point ignoring the line resistance 35 may cause malfunction due to fluctuations in the detection point. In other words, the presence of the line resistor 36 does not affect the detection operation at all when the brake light switch 12 is opened, but when the brake light switch 12 is closed, the voltage drops due to the lighting current of the brake light 13, which has a large capacity. This appears as a voltage fluctuation at point P. This fluctuation sometimes reaches several volts, and although it does not affect the operation of the photocoupler 15 at all when the brake light switch 12 is closed due to its configuration, it does affect the detection operation of the photocoupler 28.
There is a risk of false alarm. More specifically, the photocoupler 28 must operate when the brake light switch 12 is closed to ground the input side of the alarm circuit 21, but the light emitting current of the light emitting diode 16 of the photocoupler 15 always flows through the resistor 14. The photocoupler 2
Since the light emitting current of the light emitting diode 29 of No. 8 is supplied through the same path as the lighting current of the brake light 13 including the brake light switch 12, a voltage fluctuation at point P immediately appears in the anode voltage of the light emitting diode 29. Therefore, when controlling the amount of conduction of the phototransistor 32 and setting the amount of light emitted from the light emitting diode 29, if the anode potential when the brake light switch 12 is closed, that is, the voltage at point P, is numerically set as the power supply voltage, P due to voltage drop at line resistor 35
Due to the voltage fluctuation at the point, the initial setting amount cannot be satisfied, and a phenomenon occurs in which the photocoupler 28 does not operate even when the brake light 12 is closed, causing the warning light 26 to turn on even though the brake light 13 is normal. If held, it may cause malfunction. In the case of the present invention, the cathode of the light emitting diode 29 as the second detection element for suppressing the activation of the alarm by the light emitting diode 16 as the first detection element for detecting the alarm point is connected to the activation of the light emitting diode 29. The point is connected to the connection point between resistors 30 and 31 as a voltage dividing circuit that sets the voltage at a lower potential than the detection voltage based on the power supply voltage. Since the light emitting level of the light emitting diode 29 is set with a margin greater than the voltage fluctuation at point P due to the line resistance 35, extremely stable operation can be obtained even with variations in the line resistance 35, and the photocoupler In combination with 15, a reliable disconnection alarm can be given.

Photocoupler 15,2 obtained from the above operation
To explain the operating conditions of No. 8 using FIG. 3, the voltage V P at the detection point _P with respect to the power supply voltage V _E on the horizontal axis changes depending on the opening/closing state of the brake light switch 12 and the disconnection of the brake light 13. The operating range of the photocouplers 15 and 28, ie, the operating range of the alarm circuit 21, can be represented by a hatched area A. The upper limit of the region A can be freely set by the ratio of the voltage dividing resistors 17, 18 and the resistors 30, 31 that determine the light emission level of the light emitting diodes 16, 29, so the line resistors 35, 3
Fluctuation voltage points a, b at point P due to voltage drop at 6
It is possible to limit the area A to a range with a certain degree of margin, and it is possible to obtain stable alarms without malfunctions. Furthermore, resistors 17, 18 and resistor 3
Since the voltage dividing point of 0 and 31 follows in proportion to the change in the power supply voltage V _E , the operation level of the photo couplers 15 and 28 changes accordingly, and also malfunctions occur due to fluctuations in the detection point P due to fluctuations in the power supply voltage. This makes it extremely effective especially when used in power sources that fluctuate rapidly for vehicles.

In addition, since the signal line from the detection section to the alarm section is optically coupled by the photocouplers 15 and 28, the influence of noise in the detection section does not propagate to the alarm section and cause false alarms. By connecting the light emitting diodes 16 and 29 in parallel with the detection light device, it is possible to replace not only the brake light 13 but also a light device with a different capacity such as a direction indicator light, thereby providing a versatile disconnection detection device. . Furthermore, since the simple configuration is such that the light emitting diodes 16, 29 of the photo couplers 15, 28 emit light due to a voltage change due to a break in the brake light 13, setting of the operating point is extremely easy, and the resistors 17, 18, 30, The alarm area A can be easily limited by the partial pressure ratio of 31, and excellent effects can be expected, such as being able to set the upper and lower limits of the operating point in accordance with changes in the capacity of the detector lamp.

Note that this embodiment uses a photocoupler 1 as a detection element.
5 and 28 are used to optically supply the detection section and the alarm section. However, the emitter potential of the transistor 5 as the detection element shown in FIG. Similar reliability can be obtained by setting the voltage divider circuit at a level that can compensate for the voltage fluctuation at point P due to line resistances 35 and 36. It does not impose any restrictions.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional disconnection detection device, Fig. 2 is a circuit diagram showing one embodiment of the device of the present invention, and Fig. 3 is a voltage characteristic diagram showing the alarm range of the present invention. Power supply 11, brake light switch 12, brake light 13, detection resistor 14, photocoupler 15, 28, voltage dividing resistor 17, 1
8, 30, 31, alarm circuit...21, thyristor...22, warning light...26.

Claims (1)

[Scope of utility model registration request] In parallel with the above switch of the series circuit connected between the positive and negative of the power source consisting of the lamp switch and the lamp,
A resistor having a value larger than the internal resistance of the lamp is connected, and the input of a detection element is connected to the connection point to detect the voltage change due to disconnection of the lamp when the lamp switch is opened. The device is configured to set the operating point of the detection element to a voltage change at the detection point due to a voltage drop due to a voltage drop in the conductor resistance inherent in the conductor of the negative side lighting path of the power supply of the lamp. A second detection element is provided with a voltage dividing circuit to set the electric potential, and is connected in parallel with the lamp, operates when the lamp switch is closed, and suppresses alarm operation by grounding the input side of the alarm circuit. and further set the operating point of the second detection element to
When the lamp switch is closed, a voltage divider circuit is installed to set the potential to a low level by the voltage fluctuation at the detection point due to voltage drop due to the switch contact resistance of the positive lighting path of the lamp or the conductor resistance inherent in the conductor. Characteristic disconnection detection device.