JPH0539497Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a device for detecting faults such as disconnections and short circuits in loads such as motor vehicle lamps.

BACKGROUND ART Automobiles use many types of lamps, which are incandescent light bulbs. Many of those lamps are
The purpose is to ensure driving safety, and it is dangerous to drive without lights with the lamps disconnected.
Accordingly, various devices have been proposed to warn drivers of lamp burnout. The present invention realizes a configuration that detects failures such as wire breaks and short circuits when the balance between the two left and right lamp systems is lost.

A typical prior art is shown in FIG. Detection resistors R are connected to lamps L1 and L2, such as headlights of an automobile, respectively, and the potentials at connection points 1 and 2 are input to a potential difference comparator 3, respectively. The output of the potential difference comparator 3 is applied to a drive circuit 4 and then to a display element 5 such as an alarm lamp. Such an arrangement is powered by a power supply 6. Lamps L1 and L2 are of the same standard,
Currents i1 and i2 flowing through these lamps L1 and L2 are approximately equal (i1≈i2). This causes a voltage drop i1・R≒i in the detection resistor R.
2.R occurs.

If both lamps L1 and L2 are normal, the voltage applied to the terminals of lamps L1 and L2
V1 and V2 satisfy V1≈V2, and the potential difference between connection points 1 and 2 is approximately zero.

If one of the lamps L1 and L2 is disconnected, for example, lamp L2 is disconnected, the voltage of the power supply 6 is
If V _B , then V1=V _B -i1・R...(1) V2=V _B ...(2) Therefore, V1<V2...(3).

Further, when the lamp L1 is disconnected, the fourth equation holds true.

V1>V2...(4) The potential difference comparator 3 drives the display element 5 by the drive circuit 4 when the above-mentioned third and fourth equations are satisfied.
to drive. In this way, the state of disconnection of the lamps L1 and L2 can be detected.

Problems to be solved by the invention In this prior art, two lamps L1,
When both lamps L2 are disconnected at the same time, V1=V2 (5), which is the same as in a normal state, that is, when both lamps L1 and L2 are not disconnected, and no disconnection is detected.

Generally, under operating conditions with a lot of noise and surges, such as in automobiles, huge pulses are generated by lamps L1 and L.
2, it is quite possible that these lamps L1 and L2 will be burnt out at the same time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a load failure detection device that can reliably detect failures such as wire breakage even if a plurality of loads simultaneously experience failures such as wire breakage.

Means to Solve the Problem This invention divides multiple loads into two groups, connects the loads in each group in parallel, connects a resistor Ra in parallel to the load in one group, and connects the loads in each group in parallel. Detection resistors R1 and R2 are connected in series with the resistors R1 and R2, and the resistance value of the detection resistors R1 and R2 is such that when the load is normal, the voltages V11 and V12 at the connection point between the detection resistors R1 and R2 and the load are equal. A failure detection device for a load, characterized in that the voltages V11 and V12 are selected to have different values at the time of a failure of the load, and a means is provided for level-discriminating the difference between the voltages V1 and V2. It is.

Effect According to the present invention, multiple loads are divided into two groups, and one group's loads are connected to a resistor in parallel.
Detection resistors R1 and R2 are connected in series to the loads of each group. The resistance values of these detection resistors R1 and R2 are:
The voltages V11 and V12 are selected so that when the load is normal, the voltages V11 and V12 at the connection point between the detection resistors R1 and R2 and the load are equal, and when the load is in failure, the voltages V11 and V12 are different from each other. It can be done.

Therefore, under normal conditions, that is, when all loads are not faulty, there will be a difference between voltages V1 and V2, and when at least one load is faulty, the voltage will be different.
A difference occurs between V1 and V2, and this difference is level-discriminated,
A load failure is detected.

When all the loads are disconnected, since the resistor Ra is connected in parallel to the loads in one group, the difference between voltages V1 and V2 is detected by the level discrimination means, and a load failure is reliably detected. Ru.

By interposing the resistors R11 and R12 between the detection resistors R1 and R2 and the loads of each group, it is also possible to detect a short circuit in the loads.

Embodiment FIG. 1 is an electrical circuit diagram of an embodiment of the present invention. Lamp L11, L such as an incandescent bulb that is a load
12 belongs to the first group G1, and lamps L21,
L22 belongs to the second group G2, thus four lamps L11, L12, L21, L22
is divided into two groups G1 and G2. The lamps L11 and L12 of the first group G1 are connected in parallel, and similarly the lamps L of the second group G2
21 and L22 are connected in parallel. A resistor Ra is connected in parallel to the lamps L11 and L12 of the first group G1. Detection resistors R1 and R2 are connected to lamps L11, L12, L21 and L22 of each group G1 and G2 at connection points 8 and 9, respectively. These detection resistors R1 and R2 are connected to a power source 10. Connection points 8 and 9 are connected to two input terminals of differential amplifier 11, respectively.
The voltage applied to each input terminal of the differential amplifier 11 is
When V11 and V12 are used, the differential amplifier 11 derives an output having a voltage V0 shown by the sixth equation and supplies it to the level discrimination circuit 12. Level discrimination circuit 12
The output of the differential amplifier 11 is level-discriminated by the reference voltage source 18 at a predetermined discrimination level E1.

V0=|V11−V12| ...(6) When the output of the differential amplifier 11 is equal to or higher than the discrimination level E1, the level discrimination circuit 12 selects the output terminal 13.
is set to a low level, thereby driving the display element 14. The display element 14 may be a warning lamp, or may be a warning sound generating means such as a buzzer, or may have a structure that provides other visual or acoustic display.

The resistance values of lamps L11, L12, L21, and L22 are all R _L , and each of these lamps L
Assuming that the same current IL flows through all of 11, L12, L21, and L22, each voltage V11,
V12 is as shown in the seventh and eighth equations. The voltage of power supply 10 is indicated by reference V _B .

V11=V _B −R1 (2+R _L /Ra) I _L ...(7) V12=V _B −R2・2I _L ...(8) In this normal state, the detection resistor R1, Adjust R2. As a result, the detection resistor R2 becomes as shown in Equation 9.

R2=R1(2+R1/Ra)/2...(9) Therefore, lamps L11, L12, L21, L2
The operations a to d at the time of wire breakage in step 2 will be explained.

When only one a lamp L11 is disconnected, the 10th
Equations and Equation 11 are established, and therefore Equation 12 is established. As a result, the level discrimination circuit 12 sets the line 13 to a low level, and the display element 14 is driven.

V11=V _B −R1 (1+R _L /Ra) I _L …(10) V12=V _B −2R2・I _L = V _B −R1 (2+R _L /Ra) I _L …(11) V11＞V12 … …(12) When only one b lamp L21 is disconnected, the 13th
Equations and Equation 14 are established, and Equation 15 is thereby established, and the level discrimination circuit 12 sets the line 13 to a low level and drives the display element 14.

V11=V _B −R1(2+R _L ／Ra)I _L ……(13) V12=V _B −{R1(2+R _L ／Ra)I _L }／2 ……(14) V11＜V12 ……(15) c Lamps L11 and L2 of each group G1 and G2
1 is disconnected one by one at the same time, the 16th and 17th
Equation 18 is established, and the display element 14 is driven.

V11=V _B −R1 (1+R _L /Ra) I _L ……(16) V12=V _B −{R1 (2+R _L /Ra) I _L }/2 = V _B −R1 (1+1/2・R _L / Ra）I _L ...(17) V11<V12...(18) dAll lamps L1 of each group G1, G2
1, L12, L21, L22 2 lights at the same time,
When all the wires are disconnected, Equations 19 and 20 are established, and therefore Equation 21 is established, and the display element 14 is driven.

V11=V _B −R1×R _L /RaI _L ... V12=V _B ......(20) V11<V12 ...(21) In this way, the lamps L11, L12, L21, and L22 of each group G1 and G2 Even if one or all of them are disconnected at the same time, this can be reliably detected.

FIG. 2 is an electrical circuit diagram of another embodiment of the present invention. This embodiment is similar to the previous embodiment and corresponding parts are provided with the same reference numerals. It should be noted that in this example, the connection point 8 and the lamp L1
1, connection point 16 in parallel with L12 and resistor Ra
A resistor R11 is interposed between the two. Similarly, the parallel connection point 17 of lamps L21 and L22,
A resistor R12 is interposed between the connection point 9 and the connection point 9. In a normal state where lamps L11, L12, L21, and L22 are not disconnected or short-circuited, connection point 8,
9 so that the voltages V11 and V12 are equal, and R1
The resistance values of the detection resistors R1 and R2 and the resistors R11 and R12 are determined so that ≠R2.

Detection resistor R1, resistor R11, Ra and lamp L
The impedance Z of the circuit consisting of 11 and L12
is shown in Equation 22.

Z=R1+R11+1/2Ra・R _L /Ra+1/2R _L ...(22) Current I flowing from the power supply 10 through the resistors R1 and R11
is given by Equation 23, and therefore the voltage at connection point 8
V11 is expressed by the 24th equation, and similarly, the voltage V12 at the connection point 9 is expressed by the 25th equation.

I=V _B /(R1+R11+1/2Ra・R _L /Ra+1/2R _L )
...(23) V11=V _B −{V _B /R1+R11+1/2R _a・R _L /Ra+
1/2R _L )}・R1...(24) V12=V _B −{V _B /(R2+R12+R _L /2)}・R2)...(25) One or all of the lamps L11, L12, L21, and L22 The operation when the wire is disconnected is detected in the same manner as in the previous embodiment.

When a short circuit occurs in one or all of the lamps L11, L12, L21, L22, a difference between the voltages V1, V2 at the connection points 8, 9 also occurs, which is equal to or higher than the discrimination level E1, but Display element 14
is driven. In the embodiment shown in FIG. 2, the lamps L11, L12, L21, L
It becomes possible to detect not only a disconnection in 22 but also a short circuit.

The present invention is capable of detecting disconnections and short circuits not only in lamps but also in other loads.

Effects As described above, according to the present invention, it becomes possible to reliably detect a disconnection or short circuit in one or all of a plurality of loads.

[Brief explanation of the drawing]

Fig. 1 is an electrical circuit diagram of one embodiment of the present invention;
The figure is an electric circuit diagram of another embodiment of the present invention, and FIG. 3 is an electric circuit diagram of a prior art. 11...Differential amplifier, 12...Level discrimination circuit, 14...Display element, 18...Reference voltage source, R
1, R2...Detection resistor, Ra, R11, R12
...Resistance, L11, L12, L21, L22...
Lamp, G1, G2...Group.

Claims (1)

[Claim for Utility Model Registration] Multiple loads are divided into two groups, the loads of each group are connected in parallel, a resistor Ra is connected in parallel to the load of one group, and each group is connected in series, The detection resistors R1 and R2 are connected, and the resistance values of the detection resistors R1 and R2 are set so that the voltages V11 and V12 at the connection point between the detection resistors R1 and R2 and the load are equal when the load is normal. A load failure detection device characterized in that the voltages V11 and V12 are selected to have different values when the load fails, and means is provided for level-discriminating the difference between the voltages V1 and V2.