JPH03191876A - Method for detecting filament breakage of lamp - 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 (a) Field of Industrial Application This invention relates to a method for detecting breakage of a light bulb for lighting a light buoy, for example.

(σ) Conventional technology A detection resistor (2) is inserted in series in the circuit of a light bulb (1) as shown in Fig. 3 as a method for detecting the breakage of a lighting bulb in a conventional light buoy, etc. However, the voltage generated at both ends of this resistor is extracted as a current signal via a comparator (3), that is, the breakage is detected by the presence or absence of voltage generated at both ends of the detection resistor. .

(8) Problems to be solved by the invention In such conventional methods, in order to reduce the voltage drop loss in the detection resistor, it is necessary to lower the resistance value as much as possible, but if the resistance value is too low, When using a light bulb with a small current, the voltage generated at the detection resistor is low and detection is difficult.On the other hand, if the detection resistor is increased, even a small current can be detected, but when a light bulb with a large current is used. The disadvantage is that the voltage loss increases.

For example, if the detection resistance value is 0.1Ω and the bulb voltage used is 12V, the detection (loss) voltage when the bulb current is 0.25 A is 0.025V, but the detection (loss) voltage when the bulb current is 8A is It becomes 0.8■.

In other words, for a 0.25A light bulb, the drop in light bulb voltage is 2.1%.
However, as a detection voltage, it is a low value and difficult to detect. Conversely, an 8A light bulb generates a voltage of 0.8V, which is sufficient for detection, but the drop in light bulb voltage is also large, at 6.7%.

(d) Means for solving the problem This invention focuses on the fact that core breakage detection does not need to be performed continuously all the time, and uses a detection resistor with an appropriate resistance value.
FE equipped with an automatic control device (not shown) in the detection resistor circuit
By arranging T in parallel, this is an intermittent detection method in which the detection operation is not performed for a short period of time, for example, about 1 m5 ec, and then the detection operation is stopped for about 100 m5 ec.

(f) Function By doing this, the gate of the FET is brought to the L level for a very short period of time, for example, about 1 m5 ec, and the FET is turned off. As a result, all the bulb current flows to the detection resistor,
Generates a voltage across the detection resistor. During this time, a detection operation is performed. Next, if the gate of the FET is closed by 1 level for about 100 m5ec and the FET is turned on, most of the bulb current flows through the FET and the voltage loss at the detection resistor is minimized. During this time, the detection operation is stopped.

Therefore, a sufficient detection voltage can be obtained even with a small Il flow lamp, and
Loss voltage is low even at large currents.

(F) Embodiment To explain this invention according to the circuit diagram shown in FIG. , F E
T (5) is provided by connecting its source S and drain D.

Figure 2 is a waveform diagram showing the gate G of FET (5) from the top.
1 detection resistor (2) and the output waveform of the controller (3). In this example, the H level of the gate G of FET (5) is set to the 1 m5ecL level at 100m5ec intervals. At this time, all of the lamp current flows through the detection resistor (2), generating a voltage across the detection resistor, and the current detection output of the comparator (3) appears.During this time, the disconnection detection operation is performed.

In other words, the detection operation time is 1m every 100m5ec.
This is an intermittent detection that is performed at the time of "see".

As a result, the average loss voltage becomes close to that during non-detection. To explain this more specifically, for example, if the resistance value of the detection resistor (2) is 0.5Ω, and the ON value of FET (5) is
When the current resistance is 0.05Ω and the bulb voltage used is 12μ, the detection (loss) voltage is 0°25 when the bulb current is 0.25A.
v When the bulb current is 8A, the detection (loss) voltage is 4V,
In addition, when the detection is stopped, the detection (loss) voltage is 0°11 when the bulb current is 0.25A.
v When the bulb current is 8A, the detection (loss) voltage is 0.36V, and even with a 0.25A bulb, sufficient voltage for detection can be obtained.
8 Ai! Even with flt, the loss voltage can be kept as low as 3%.

Note that a method of intermittently supplying a signal to the gate G of the FET (5) and detecting a break in the light bulb from the output of the comparator (3) may be performed as follows, for example. FIG. 4 is a block diagram of the detection section, and FIG. 5 is a core breakage detection time chart.

The output of oscillation N (6) is counted by a binary counter (7), the output is input to the address of ROM (8), and the timing is determined by sequentially reading out the ROM (8) data written in advance from address O. Signal (Signal A
, No. 48B) is obtained.

Signal A is L for 1m5ec once every 100m5ec.
Insert data into the ROM (8) so that the level is met.

Further, signal B has data stored in the ROM so that an H level pulse is output once when signal A is at L level.

Signal A is input to the gate of the FET, and signal B is input to the input circuit (9), so that No. 18A h (becomes L level and the FET is turned off, so the bulb current flows to the current detection resistor. The comparator output when all flows are signal B.
At the rising edge of , the latch circuit holds the comparator output state at the core breakage detection timing.

When the bulb is normal, when the signal A is at L level, the detection resistor voltage becomes high, so the comparator output becomes H level, and this state (H level) is maintained by the latch circuit and signal B. Also, when the bulb is broken, the current is zero, so the signal A
Even if it becomes L level, the detection resistance voltage becomes zero, and since this is held by the latch circuit and (g-B), it can be taken out as a core break signal (L level).

(g) Effects As described above, the simple method can handle a wide range of current loads from small current bulbs to large current bulbs without any adjustment, and there is little reduction in the luminous power of the bulb. In addition, the power consumption of the detection resistor is small, and because it generates little heat, it can be made smaller.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of the present invention, FIG. 2 is a waveform diagram showing its operation, and FIG. 3 is a circuit diagram showing the conventional configuration. FIG. 4 is a block diagram of a detection section that supplies an intermittent signal to the gate of the FET and detects a break in the light bulb from the output from the comparator, and FIG. 5 is a time chart of the break detection. (1)... Light bulb, (2)... Detection resistor, (
3)... Comparator, (4)... Reference power supply for comparator, (5)... FET. F ζ−Z

Claims (1)

[Claims] In a light bulb breakage detection method, a detection resistor is inserted in series in the light bulb circuit, and a light bulb breakage is detected based on the presence or absence of voltage between both terminals of the detection resistor. 1. A method for detecting a broken core in a light bulb, characterized in that the voltage between both terminals of a detection resistor is detected intermittently by arranging a plurality of transistors (effect transistors) in parallel.