JPS6345806Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a device for detecting disconnection of a load such as a lamp such as a brake light or a taillight of an automobile.

It is difficult for the driver himself to confirm the breakage of brake lights and taillights installed in automobiles, and for this reason, various breakage detection devices have been devised (for example, Utility Model Publication No. 51-28947).

However, conventional devices of this type cannot detect a disconnection of a load lamp unless the open/close switch is closed to turn on the load lamp, which is the object of the disconnection detection, and therefore the driver notices the disconnection. There was a problem that the connection was slow and the vehicle could be driven with the wire disconnected.

In order to improve these points, a load circuit disconnection detection device has been proposed that is capable of detecting a load disconnection even when a lamp load is turned off by adding a load disconnection detection circuit (Utility Model No. 51). −152629
(see publication). However, this device is complicated and consists of a reference voltage generation circuit, a comparator, a load disconnection detection circuit, etc., and has the problem of high cost.

The present invention improves these points and provides a load disconnection detection device such as a lamp that has an extremely simple configuration and can detect load disconnection even when the load on/off switch is open. This is what I am trying to do.

Embodiments of the present invention will be described below with reference to the accompanying drawings.

The attached drawing shows an example in which the present invention is applied to a disconnection detection device for an automobile lamp, in which the negative electrode 1 is grounded, and the positive electrode is connected to a power switch 2 such as an ignition switch and an open/close switch 3 such as a brake switch. a battery power supply connected to one end of the
4 is a load lamp, such as a brake light, whose one end is grounded and the other end is connected to the other end of the on-off switch 3 via the current coil 5; 6 is a reed switch excited by the magnetomotive force of the current coil 5; One end is grounded, and the other end is connected to the base of the transistor 7. This transistor 7 has a base connected not only to the other end of the reed switch 6 but also to the other end of the power switch 2 via a resistor 8, and is connected to the load lamp 4 and the current coil via a backflow prevention diode 9. 5, and its collector is connected to the other end of the power switch 2 via an indicator 10 such as a miniature lamp, and its emitter is grounded via a voltage regulating diode 11.

Further, the base of the transistor 7 is grounded via a slow acting capacitor 12.

Next, the operation of the above-described device will be explained.

In the illustrated state, when the power switch 2 is closed, the load lamp 4 remains off, but unless it is disconnected, the transistor 7
The base of is grounded via the backflow prevention diode 9 and the load lamp 4 (the DC resistance value of the load lamp 4 is small when the light is off), and the base is connected to the positive terminal of the power supply 1 via the resistor 8 and the power switch 2. Although it is connected, its potential (base potential) is low. At this time, the emitter potential of the transistor 7 is also lowered to near the base potential due to the voltage drop of the voltage adjusting diode 11. Therefore, the voltage between the base and emitter of the transistor 7 is extremely small and is not conductive, so that the display 10 does not operate (lights up here). on the other hand,
When the load lamp 4 is disconnected, the base of the transistor 7 is not grounded, but is connected to the positive terminal of the power source 1 via the resistor 8 and the power switch 2. Therefore, the voltage between the base and emitter of the transistor 7 increases and becomes conductive, activating the display 10 to inform the driver that the load lamp 4 is disconnected.

Further, when the open/close switch 3 is further closed after the power switch 2 is closed, the load lamp 4 is supplied with power and lights up if it is not disconnected, and
Since the load current also flows through the current coil 5, a magnetomotive force is generated, which excites and closes the reed switch 6. Therefore, the transistor 7 has its base grounded and becomes non-conductive, and the display 10 does not operate. In this case, since the delay capacitor 12 is connected between the base of the transistor 7 and the ground, when the open/close switch 3 is closed, the reed switch 6
Until the circuit is completely closed, the base potential of the transistor 7 is kept low by the current flowing into the delay capacitor 12, thereby making it possible to prevent erroneous display.

If the load lamp 4 is disconnected, the load lamp 4 will not light up and no current will flow through the current coil 5, so no magnetomotive force will be generated and the reed switch 6 will not close. Therefore, the base of the transistor 7 is not grounded, but is connected to the positive terminal of the power source 1 via the resistor 8 and the power switch 2, and is conductive.
0 is activated to notify the driver that the load lamp 4 is disconnected. As described above, the disconnection can be detected without closing the switch 3 to turn on the load lamp 4, or in other words, regardless of whether the load lamp 4 is turned on or off.

Here, when the on-off switch 3 is closed, an excessive current flows through the current coil 5 (and the base of the transistor 7) to the reed switch 6.
This is provided to prevent damage to the equipment.

The voltage regulating diode 11 also prevents the emitter of the transistor 7 from becoming conductive since the base potential of the transistor 7 does not drop below the voltage drop of the reverse current prevention diode 9 when the transistor 7 is grounded. The voltage adjustment diode 11 is connected between the ground and the potential is increased by the amount of the voltage drop, which is provided so that the transistor 7 can switch accurately.

In the illustrated embodiment, a lamp such as a small lamp is used as the display device 10, but a light emitting diode, a buzzer, etc. may also be used.Furthermore, it is possible to use a light emitting diode, a buzzer, etc., and to configure the display device 10 with a relay, and to turn on the lamp etc. via the relay. Various modifications are possible, such as allowing the

As described above, although this invention has an extremely simple configuration, it is possible to detect a disconnection of the load without closing the on/off switch to operate the load, so it is possible to When used for a load lamp, it is possible to provide a low-cost disconnection detection device that can detect a disconnection of the load lamp before the vehicle is running, and allows the load lamp to be replaced, allowing the vehicle to run safely. .

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of a disconnection detection device for a load such as a lamp according to this invention. 1...Battery source, 2...Power switch, 3
...Open/close switch, 4...Load lamp, 5...Current coil, 6...Reed switch, 7...Transistor, 9...Reverse current prevention diode, 10...
Display device, 11...Voltage adjustment diode, 12...
...Slow acting capacitor.

Claims (1)

[Scope of utility model registration request] A current coil connected between a load such as a lamp, an on/off switch that opens and closes the energized path of this load, and a reed switch whose one end is grounded and is excited by the magnetomotive force of this current coil, and a base. is connected to the power switch via the other end of this reed switch and a resistor, and is also connected to the connection point between the current coil and the load via a backflow prevention diode, and the collector is connected to the power supply via the display and power switch. and a transistor whose emitter is grounded via a voltage regulating diode;
A disconnection detection device for a load such as a lamp, comprising a slow acting capacitor connected between the base of the transistor and ground.