JPH0143651B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a lighting control circuit that outputs an intermittent signal when the first switch is turned on, and a continuous signal when the second switch is turned on.
This invention relates to a disconnection detection circuit for a vehicle lamp that is powered on and turned on via a switching element that turns on and off.

Turn on one vehicle lamp continuously in a dark manner (hereinafter referred to as
Conventionally, a two-filament bulb with two filaments in one bulb has been used to selectively light in two ways, such as dim lighting (dim lighting) or bright continuous lighting (hereinafter referred to as bright lighting). However, recently, a method has been proposed in which this can be done using an ordinary one-filament sphere.

FIG. 1 shows an example of a vehicle lamp lighting circuit, in which when a first switch, for example a tail lamp switch 1, is turned on, a lighting control circuit, in this case a dimmer circuit 3, is turned on at a frequency of, for example, 100Hz.
An intermittent signal to turn OFF is output, and the PNP transistor 4, which is a switching element, is repeatedly turned ON-
When turned off, the vehicle lamp consisting of one filament bulb, in this case the tail lamp, is dimly lit, and when the second switch, for example stop lamp switch 2, is turned on, a continuous signal of low potential is output from the dimmer circuit 3. output and transistor 4
When turned on, the tail and stop lamps 5 will be lit brightly.

Incidentally, vehicle lamps are extremely important for preventing accidents when the vehicle is running, and therefore great care must be taken to prevent their disconnection. Therefore, a disconnection detection circuit as shown in FIG. 2 has been devised to detect such a disconnection of a vehicle lamp so that the lamp can be quickly replaced. In FIG. 2, 4 and 5 are the same as in FIG. 6 is a charging resistor whose one end is connected to the + power supply via a main switch 7 such as an ignition key, and the other end is grounded via a capacitor 8; 9 is a connection point between the charging resistor 6 and the capacitor 8; The anode is connected to a, and the connection point b between the transistor 4, the tail, and the stop lamp 5
This is a backflow blocking diode whose cathode is connected to the . 10 has a base connected to the connection point a through a resistor 11, and a collector connected to the connection point between the charging resistor 6 and the main switch 7 through an intermittent indicator, here a disconnection indicator lamp 12. , and is an NPN type display driving transistor with its emitter grounded.

In such a disconnection detection circuit, when the switches (switches 1 and 2) that turn on and off the tail and stop lamps 5 are in the OFF state (hereinafter referred to as
When the main switch 7 is turned ON when the transistor 4 is OFF (referred to as the lamp extinguishing operation),
If the tail and stop lamps 5 are not disconnected, the connection point a is grounded through the diode 9 and the tail and stop lamps 5 and has a low potential, the transistor 10 is not turned on, and the disconnection indicator lamp 12 is not lit. If the tail and stop lamps 12 are disconnected, the connection point a will not be grounded via the diode 9 and the tail and stop lamps 5.
Capacitor 5 is charged via resistor 6 and has a high potential. Therefore, the transistor 10 is turned on and the disconnection indicator lamp 12 lights up to indicate that the tail and stop lamps 5 are disconnected. That is, according to such a disconnection detection circuit, disconnection can be detected when the lamp is turned off, in other words, even before the vehicle is running, which is highly effective in preventing accidents.

However, in the above-mentioned disconnection detection circuit, the lamp 5
Since it detects only the state where the lamp 5 is actually disconnected, it
Even if the lamp 5 is in a malfunctioning state, such as when the filament of the lamp 5 is once broken, but the broken parts come into contact with each other due to vibration, etc., the lamp 5 (socket) is not connected during actual detection. ) If there is no disconnection between both ends, the disconnection indicator lamp 12 will not light up, and the lamp 5 will be displayed as being normal. Also, when transistor 4 is turned on with a continuous signal to light lamp 5 brightly (when switch 2 is turned on), transistor 4 is turned on with an intermittent signal to light lamp 5 dimly (or blinking). (switch 1)
(when transistor 4 is turned on), even though it is a lamp lighting operation, the
Unlike the case where there is an OFF time, the capacitor 8 is only charged once the main switch 7 is turned on. Therefore, connection point a is connected to transistor 1
0 reaches a sufficient potential to turn ON, and even if the lamp 5 is not broken, the breakage indicator lamp 12 lights up, resulting in an erroneous display.

The present invention has been made to eliminate the above-mentioned drawbacks, and once a wire is broken, it can be detected as a wire break even when there is no wire breakage, and the switching element that energizes the lamp can be controlled by a continuous signal. An object of the present invention is to provide a disconnection detection circuit for a vehicle lamp that can prevent erroneous display when the lamp is turned on and brightly lit.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 5.

FIG. 3 is a diagram showing an embodiment of the disconnection detection circuit for a vehicle lamp according to the present invention, and in the figure, numerals 1 to 10 and 12 are the same as those in FIGS. 1 and 2. 11 is also a resistor inserted between the connection point a and the base of the display driving transistor 10, as in FIG. A series circuit is formed with the blocking diode 13 and inserted between the connection point a and the base of the transistor 10. 14 is
This is an NPN type display drive/holding transistor, whose base is connected to the collector of the transistor 10 through a resistor 15, and whose collector is connected to the non-power supply side terminal of the main switch 7 through a resistor 16. It is connected to the base of the transistor 10 through the transistor 10, and its emitter is grounded. Reference numeral 18 denotes an NPN type display drive temporary stop transistor, whose base is connected to the non-power supply side terminal of the stop lamp switch 2 via a resistor 19, whose collector is directly connected to the anode of the diode 13, and whose emitter is grounded. ing.

Next, the operation of the above-mentioned circuit of the present invention will be explained.
First, when the lamp 5 is turned off, that is, when the transistor 4 is off and the main switch 7 is turned on, if the lamp 5 is not disconnected, the connection point a connects the diode 9 and the lamp 5 (micro filament resistance when the lamp is turned off). Since it is grounded through the wire, its potential is low, the transistor 10 is not turned on, and the disconnection indicator lamp 12 is not lit. (At this time, the transistor 14 is connected to the disconnection indicating lamp 12 and the resistor 15.
It is ON because the base current is flowing through it. ) If the lamp 5 is disconnected, the connection point a will not be grounded through the diode 9 and the lamp 5 as described above, but will charge the capacitor 8 through the resistor 6 and will have a high potential. Therefore, the transistor 10 is turned on, lighting up the disconnection indicating lamp 12, and indicating that the lamp 5 is disconnected. On the other hand, when the transistor 10 turns on, its collector potential decreases, so the transistor 14 turns off, so the collector potential of the transistor 14 increases,
A current flows through the base of the transistor 10 via resistors 16 and 17. Therefore, transistor 10
Once turned on, the contact status with the lamp 5 socket (not shown) etc. will return to normal.
Even after the filament of the lamp 5 is once disconnected, the transistor 10 remains on even if the potential at the connection point a drops due to contact between the disconnected parts, etc., and the lamp 5 is disconnected due to the lighting of the disconnection indicator lamp 12. Display continues.

Next, when the main switch 7 is in the ON state and the tail lamp switch 1 is turned on, that is, when an intermittent signal as shown in FIG. 4a is applied to the base of the transistor 4, the transistor 4 is turned on and off accordingly. do. Therefore, if lamp 5 is not disconnected, connection point b is also connected to transistor 4.
The high potential and low potential are repeated according to ON and OFF (see FIG. 4c), and the lamp 2 is lit (darkly lit) at a brightness that corresponds to the timing of these repetitions.
Note that the connection point a has a high potential when the connection point b has a high potential and charges the capacitor 8, but the charged charge is transferred to the transistor 4 which repeats ON and OFF.
Since it is discharged through the diode 9 and the lamp 5 when it is OFF, its potential becomes as shown in FIG. (Therefore,
Transistor 14 remains on. )on the other hand,
If lamp 5 is disconnected, connection point b is ON-
Even when the transistor 4 is repeatedly turned off, it remains at a high potential as shown in FIG. As shown in FIG. 4f, the potential becomes high, the transistor 10 is turned on, and the disconnection indicating lamp 12 is turned on to indicate that the lamp 5 is disconnected. Furthermore, at this time,
The transistor 14, which had been on until then, turns off, and the resistor 16,1 is connected to the base of the transistor 10.
Even when the current flows through the terminal 7 and the potential at the connection point a drops, the ON state of the transistor 10 is maintained and the disconnection indication of the lamp 5 continues, as in the case when the lamp 5 is turned off. The same is true.

Further, when the main switch 7 is in the ON state and the stop lamp switch 2 is turned on, that is, when a continuous low potential signal as shown in FIG. 4b is applied to the base of the transistor 4, the transistor 4 is turned on.
Turns on and lamp 5 lights up brightly. At this time, since the connection point b is continuously at a high potential, the connection point a is also at a high potential, and an attempt is made to turn on the transistor 10 and turn on the disconnection indicator lamp 12 to give an erroneous indication, but the stop lamp switch When 2 is turned on, a base current flows through the display drive temporary stop transistor 18, and by turning it on, the connection point between the low resistor 11 and the diode 13 is grounded, so that the connection point a is brought to a low potential. Therefore, even if the connection point b becomes a high potential continuously, the connection point a becomes a low potential, and the transistor 1
0 is never turned on, and the disconnection indicator lamp 12
will not light up, that is, there will be no erroneous display.

In the above-mentioned embodiment, a case has been described in which disconnection of one lamp 5 is detected using one display driving transistor 10 and a disconnection indicating lamp 12, but the same or corresponding parts as in FIG. As illustrated in FIG. 5, a forward diode 20 is connected between each connection point a and the resistor 11 to form an OR circuit, and when one of the lamps 5 is disconnected, the transistor is activated. 10 is turned ON, it is also possible to detect disconnection of a plurality of (two in FIG. 5) lamps 5 using one display driving transistor 10 and one disconnection indicating lamp 12. be.

Further, in the above embodiment, the lamp 12 is used to indicate the disconnection of the lamp 5, but the present invention is not limited to this, and for example, a light emitting diode or the like may be used. The first switch, second switch, vehicle lamp, and lighting control circuit are not limited to the tail lamp switch, stop lamp switch, tail, stop lamp, and dimmer circuit, respectively.

As described above, the present invention enables the display device driving transistor to continue to be turned on even if the potential at the connection point a between the charging resistor and the capacitor drops below a predetermined value after the display device driving transistor is turned on. The transistor is equipped with a transistor to drive and hold the display, which applies a base potential to the transistor and continues to indicate a disconnection.For example, if the vehicle lamp has a poor contact, or if the filament of the vehicle lamp is once disconnected, then vibrations may occur. A disconnection can also be detected when the vehicle lamp is in a malfunctioning state, such as when the disconnected parts come into contact with each other due to such a problem. In addition, when the lighting control circuit outputs a continuous signal and the switching element is turned on continuously, that is, when the second switch is turned on to brightly light the vehicle lamp, the base of the display driving transistor and the charging resistor and A display drive temporary stop transistor is provided that grounds the connection point side electrode of the reverse current blocking diode provided between the connection point of the capacitor, so the vehicle lamp will not be disconnected when the vehicle lamp is turned on brightly. Even if it is not, the display device driving transistor is turned on, that is, the display device is not driven, and there are effects such as being able to prevent erroneous display.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of a vehicle lamp lighting circuit that selectively lights a vehicle lamp in two ways using one filament bulb, and Figure 2 is a diagram showing an example of a vehicle lamp lighting circuit that selectively lights a vehicle lamp using one filament bulb. FIG. 3 is a diagram showing an embodiment of the disconnection detection circuit for a vehicle lamp according to the present invention, and FIGS. 4a to 4f are diagrams showing a disconnection detection circuit.
FIG. 5 is a diagram showing signal waveforms of various parts for explaining the operation of the above circuit, and FIG. 5 is a diagram showing another embodiment of the circuit of the present invention. 1... Tail lamp switch, 2... Stop lamp switch, 3... Dimming circuit, 4... Transistor, 5... Tail, stop lamp, 6...
Charging resistor, 7... Main switch, 8... Capacitor, 9, 13... Backflow blocking diode, 10...
...Display drive transistor, 11...Resistor, 1
2... Lamp for indicating disconnection, 14... Transistor for display drive holding, 18... Transistor for temporarily stopping display drive.

Claims (1)

[Claims] 1 Turns on and off according to the output signal of the lighting control circuit, which outputs an intermittent signal when the first switch is turned on, and a continuous signal when the second switch is turned on.
In a vehicle lamp that is turned on by being energized through a switching element that is turned on, a capacitor that can be charged via a charging resistor by turning on a main switch, a connection point between the charging resistor and the capacitor, the switching element and the vehicle a first reverse current blocking diode connected between the connecting point of the charging lamp and a base connected to the connecting point of the charging resistor and the capacitor through a series circuit of a resistor and a second reverse current blocking diode; , a display driving transistor that turns on when the potential at this connection point is equal to or higher than a predetermined value and drives the disconnection indicator, and after this display drive transistor turns on, the potential at the connection point between the charging resistor and the capacitor becomes a predetermined value. a display device drive holding transistor that applies a base potential to the display device drive transistor so that the display device drive transistor continues to be turned on even if the voltage becomes lower than the current value; 1. A disconnection detection circuit for a vehicle lamp, comprising: a display drive temporary stop transistor that grounds the charging resistor of the backflow blocking diode and the connection point side electrode of the capacitor.