JPS58115797A - Lamp disconnection detecting circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a lamp disconnection detection circuit which is particularly suitable for detecting disconnection of a vehicle rung whose lighting is controlled by a switching element.

A conventional circuit of this type is shown in FIG. In the figure, B1 is a battery that is a DC power supply whose negative pole is grounded, LL is a rung connected between the positive and negative poles of this battery B1 through the collector emitter of a thin circular NPN transistor TR1, and SWI is transistor T
RI t-ON is a switch that turns OFF, and one end is directly connected to the positive electrode of batch IJBI, and the other end is connected to the pace of transistor TRI through resistor R1 and is grounded through resistor R2. TR2 is a PNP transistor whose pace is connected to the emitter of the transistor TRI through a resistor R3', the emitter is directly connected to the positive electrode of the battery B1, and its collector is grounded through a resistor R4. It is an NPN type transistor connected to the collector of the transistor TR2 via R5'), whose collector is connected to the positive electrode of the battery B1 via the display lamp PLI, and whose emitter is grounded.

In other words, in the conventional circuit, the lamp LLI is normal (no disconnection).
When , the voltage drop between collector and emitter of transistor TRI is V. E is amplified by transistors TR2°TR3, the display lamp PLI lights up, and the lamp °LLI
When is disconnected, the collector current I of the transistor TRi does not flow and its voltage drop V.E becomes O, turning off the transistors TR2 and TR3, and the display run fP
The L1 light went out.

However, in the conventional circuit described above, the transistor TRI has a ■. XvoECW] loss occurs, so the voE'
It is desirable to keep it as small as possible. For example, 8 [W] or V for a Z3 (W) vehicle rear combination lamp. EZo is 1 (V), but preferably less than that. However, the voltage drop V across transistor TRI. If E is small, this means that the range of change in the detected voltage between when the lamp LLI is normal and when it is disconnected is small.1. It is prone to malfunction due to fluctuations in battery voltage, etc., and requires two or more stages of amplification circuits as shown in the figure. Therefore, the amplifier circuit is reduced by one stage (transistor TR3), and in order to switch the display lamp PLI with transistor TR2, the transistor TR
For example, if vCE of I is approximately 1.0 (V), a large loss of -58% will occur when the battery voltage is 12[V].Furthermore, in the conventional circuit described above, the transistor TRI is
Turn on the lamp LLI brightly (lighting up (bright point -) by turning it on continuously.
It is only possible to detect a disconnection when the lamp is turned on, such as turning the lamp on (turning on) or switching it on (ON, 0FF) with a pulse with a variable repetition frequency to dim the lamp LLI (or turn it on brighter (dimmer lighting)). First, disconnection cannot be detected when the transistor TRI is turned off continuously to 0FFj.Furthermore, when the rung LL1i is dimmed and turned on,
There was a drawback that the detection output voltage, in other words, the brightness of the display lamp PLI also changed depending on the switching frequency of the transistor TRI.

The present invention has been made in order to eliminate the above-mentioned drawbacks.
It is a simple circuit, and it can be made large regardless of whether the loss is large or small in the switching element for lamp control.Therefore, malfunctions can be prevented, and disconnection can be detected even when the lamp is turned off. 21. The detected output voltage changes depending on the switching frequency of the element. The purpose of the present invention is to provide a lamp disconnection detection circuit that is free from the above problems.

The present invention will be described in detail below with reference to Figures 2 to 7. Figure 2 is a block diagram showing an embodiment of the lamp burnout detection circuit according to the present invention, and B1 in the figure is the same as Figure 1. A similar battery, LLI, is Lang. This lamp LLI is connected between the positive and negative electrodes of the battery B1 via a lamp control switching element of the lamp controller l which is switched by turning ON and OFF the switch SWI, here a transistor TRI similar to the transistor TRI in FIG. It is connected.

2 is a DC-DC converter which is commonly grounded with the battery B1 and is driven by the battery B1 to output a voltage (Voo2) higher than the voltage (V, ol) of the battery B1, an example of which is shown in FIG. In addition, in FIG. 3, TR4~
TR6 is a transistor, R6 to R8 are resistors, C1, C2
is a capacitor, Ll is a coil, DI is a diode, ZD
I is a Zener diode.

R9 is the output terminal 2a of the C-DC converter 2.
and a high-resistance resistor connected between the transistor TRI and the connection point a of the run fLL1 in the rung controller 1; 3 is a switching circuit preferably having a high input impedance that switches by the voltage drop across the resistor R9; 4 is an output terminal. A display, here a display run f PLI, is connected to this output terminal 4 directly or, if necessary, via an amplifier circuit (not shown).

Next, the operation of the circuit of the present invention will be explained based on FIG. First, when the switch 5W1t is turned ON, the conductance of the lamp controller 1 is controlled and the lamp LLI is energized, and the lamp LLI is turned on.
Table 1 below shows in advance how the voltage Va at the connection point a changes depending on whether I is ON or OFF. In this Table 1, vool is the voltage of battery B1, vco2 is the output voltage of DC-DC converter 2,
As already mentioned, these are in the relationship v 1 <voo2.

Table 1: In other words, when LLI is normal and switch SWI is
'When iON, as in the case of Figure 1, voo
l-voE becomes the voltage Va at the connection point a. vCE (switching element for rung control of lamp controller 1, here transistor T similar to transistor TRI in FIG. 1)
RI collector-emitter voltage) is 0.1 to 0.5
(V), so Va is approximately V. It becomes OL. At this time, a current I flows through the DC-DC converter output terminal & the resistor R9 → the connection point a → the lamp LLI, but the resistor R9 has a higher resistance than the resistor r of the lamp LLI, so the current is connected! is extremely small, and for the current passing between the collector and emitter of transistor TR1, ' -C
I, > Engineering 28, there. Pia=rl (I, or I,
), rl x, : VCCI. When the switch SWI is turned on when the lamp LLI is disconnected, the power to the transistor TRI of the rung controller 1 is cut off, and since the input impedance of the next stage switching circuit 3 is high, the connection point a is lifted from the ground. At this time, v. Since ol〈■oo2, Va : V((
It becomes 2. Note that in this case, the voltage (vCo2-vool
) is applied to the emitter of the transistor TRI, but this is set within the reverse breakdown voltage range of the transistor TRI, so no problem occurs. Further, even if the reverse breakdown voltage is exceeded, since the resistor R9 has a high resistance, the reverse current value is extremely small and does not damage the transistor TRI.

Next, the lamp 'LL1 is normal and the switch SWI is OFF.
When the transistor TRI is off, and the resistance value of the resistor R) is the resistance value of the ramp 'LL1,
& becomes approximately O[V] (earth potential). Lamp Ltl
When the wire is disconnected and the switch SWI is ON, the transistor TRI is OFF and OFF. Also, since the connection point a is floating from the ground, V
a z V((, becomes 2.

As can be seen from the above explanation, the voltage v at the connection point a, F
i, Switch SWI 17) Regardless of ON or 0FFK, turn ON only when the 5th fLLI is disconnected. o2, which is a different value from other cases. For example, Vcc 1
= 12 (V).

VCC2: 18 L'V:l 7! : Then, v,
H, Lamp LLI (7) Always 18-12:61V, regardless of whether the transistor TRIQ is large or small, whether it is normal or disconnected.
or more voltage difference (18- if switch swi is OFF)
A voltage difference of 0=18 degrees will occur. this is,
This is extremely large compared to the voltage difference (0.1 to 0.5 M) between the lamp LLI when it is normal and when it is disconnected in the conventional circuit shown in Figure 1, and facilitates the next stage of signal processing. . In addition, the above Va is the loss in the transistor TRI (ICX
Since this occurs regardless of whether VCE (W) is large or small, it is possible to efficiently control run f LLI by selecting a transistor TRI with as little loss as possible.

4 to 6 are diagrams each showing a specific example of the circuit of the present invention, and hereinafter, each side will be described with the same or corresponding parts as in FIGS. 1 and 2 being given the same reference numerals. First, FIG. 4 illustrates a case where a comparator C0M1'e is used as the switching circuit 3 in FIG. 2. In this case, the reference voltage (Vs) input terminal of the comparator COMI is connected to a voltage dividing point of a voltage divider consisting of resistors RIO and R11 inserted between the DC-DC converter output terminal 2a and the ground, and is also compared. The input end of the voltage to be applied is connected to the connection point a, and the resistance values of the resistors RIO and R11 are set such that RIO<R11. That is, in the example of FIG. 4, the resistors RIO, R11iR10 ((R
11, the comparator C0M1's quasi-voltage is VCC2, in other words, it is slightly lower than ■8 when the lamps I and Ll are disconnected (
The voltage input terminal to be set and compared is connected to the connection point a
Since the voltage at the output terminal (output terminal 4) of the comparator COM 1 is Vs when the lamp LLI is normal,
>; Vcci becomes O[V], and Rump 'LL1
When is disconnected, Vs < Va and Vc
c2(V:l).That is, according to the circuit of the present invention illustrated in FIG.
, Regardless of OFF, if rung 'LL1 is normal, it will be 0 concave, if it is broken, V ((Z(V) will occur and rung LIL
When the disconnection of lamp LLI is detected, for example, an indicator run f PLI between output terminal 4 and ground is turned on when lamp LLI is disconnected.

FIG. 5 is the simplest circuit example using a PNP transistor TR7 as the switching circuit 3 in FIG. , the emitter is D
It is connected to the C-DC controller output end 2a, and its collector is grounded via the indicator lamp PL1'ji. In the example shown in FIG. 5, as in the case shown in Table 1 above, when the lamp LLI is normal, V((2)
Va, and when lamp LLI is disconnected, vc
c2~Va, and when the former is normal, the transistor TR7 is ON and the indicator lamp PLI is turned on, and when the latter is broken, the transistor TR7 is □FF and the indicator lamp PLI is turned off. In addition, in the example of FIG. 5,
A transistor is provided which performs an inverting operation with respect to the transistor TR7, and another transistor is provided in the collector circuit of this transistor.
If two indicator lamps are provided, and this indicator lamp is red and the indicator lamp PLI is green, it becomes possible to indicate a disconnection by lighting the red lamp and to indicate normality by lighting the green lamp.

FIG. 6 shows the lamp controller 1 in FIG. 2, in detail, a thyristor TH1f is used as a switching element for lamp control in the lamp controller 1, and its conduction duty ratio is determined by the Nors from the controller GC1. This is an example of a circuit in which the brightness of the lamp 'LL1 can be continuously controlled (dimmed) by changing the thyristor THI't-switching. This sixth
In the example shown in the figure, the ON and OFF of the thyristor THI are the ON and OFF of the transistor TRI in FIGS. 4 and 5.
It corresponds to an FF, and the detection operation is similar to the circuit illustrated in FIG.

Here, when the lamp LLI is dimmed and lit using the conventional circuit shown in FIG. 1, the detected output voltage, in other words, the display run 2' PL
It has already been mentioned that the brightness of LLI also changes, but in contrast to such a conventional circuit, in the circuit of the present invention, for example, the circuit illustrated in FIG. 6, the lamp LLI is normal regardless of the duty ratio. If so, the transistor TR7 will turn on and the display lamp 'PL1 will light up, and if the lamp LLI is disconnected, the transistor TR7 will turn off and the display lamp PLI will turn off. There is no change in brightness.

Note that in the circuits shown in FIGS. 4 to 6, there is only one switching circuit 3 (comparator COMI).

Although the case where disconnection of one lamp LLI is detected using the transistor TR7) has been described, the present invention is not limited to these circuit examples. For example, as illustrated in FIG. 7, in which the same or corresponding parts as in FIG. 4 are given the same reference numerals,
A forward diode D2? is connected between each connection point a and the comparator COMI. They are connected to form an OR circuit (wired OR), and when one of the lamps LLI is disconnected, the voltage at the output terminal 4 is changed, here ~Vcc 2 W
It is also possible to detect disconnection of a plurality of (three in FIG. 7) lamps LLI with one comparator COMI C switching circuit 3) by raising the voltage to

As described above, the present invention provides a lamp that is connected via a lamp control switching element between both poles of a DC power source, one electrode of which is grounded, and which is commonly grounded with the DC power source and driven by the DC power source. The switching circuit is switched by a voltage drop across a resistor connected between the output terminal of a DC-DC converter that outputs a voltage higher than the power source voltage and a connection point between the lamp control switching element and the lamp. Since the burnout of the lamp is detected, the range of change in the detected voltage between when the lamp is normal and when the lamp is burnout can be determined using a simple circuit as shown in the example, and also by reducing the loss in the lamp control switching element. Regardless of the size, it can be made thicker (larger or smaller), so malfunctions due to changes in the power supply voltage can be prevented, and even when the lamp control switching element switches at a high frequency, such as when dimming the lamp. , the detection output voltage does not change depending on the switching frequency.Furthermore, even when the lamp is turned off, the voltage at the connection point between the lamp switching element and the lamp changes greatly depending on whether the lamp is disconnected or not. Therefore, it is possible to detect wire breakage when the rung is turned off.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional circuit, FIG. 2 is a block diagram showing an embodiment of the lamp burnout detection circuit according to the present invention, and FIG. 3 is a circuit diagram showing an example of the DC-DC converter in FIG.
4 to 6 are diagrams each showing a specific example of the circuit of the present invention, and FIG. 7 is a diagram showing another embodiment of the circuit of the present invention. B1...Battery, LLI...Lamp, TRI...
・Lamp control transistor, R9...resistance, PLI
...Indication lamp, THI...Lamp control thyristor, GCI...Thyristor gate controller, 1...Lamp controller, 2.DC-DC converter, 2a-DC
-I) C controller output terminal, 3... switching circuit, 4... output terminal, VCCI... battery voltage, V
CC2...DC-DC converter output voltage. Patent Applicant: Ichikoh Industries Co., Ltd. Representative Patent Attorney Tadashi Akimoto Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] A rung connected between both electrodes of a DC power source, one electrode of which is grounded, via a switching element for lamp control, is commonly grounded with the shoulder of the DC power source, and is driven by this DC power source and has a voltage higher than the power supply voltage. DC that outputs voltage
- a DC converter; a resistor g connected between the output end of the DC-DC converter and a connection point between the lamp control switching element and the rung; and a switching circuit that performs switching based on a voltage drop across the resistor. A lamp disconnection detection circuit featuring: