JPH04255696A - Method and device for line determination of discharge lamp - Google Patents

Abstract

PURPOSE:To solve such problems as disabling assured result to be obtained due to an effect of a difference in characteristics of individual discharge lamps or environmental condition in a method of judging the life of a hot cathode discharge lamp. CONSTITUTION:Secure detection of the life of a discharge lamp becomes possible with a simple construction so as to achieve an object by providing such a life judging method of the discharge lamp as grounding the electrode 1b on one side of a hot cathode type discharge lamp 1, to a circuit ground G, detecting the positive/negative symmetry of a,c, lighting voltage of the other side electrode 1a to the abovementioned ground G by mean a positive/negative asymmetry detecting circuit 6 and judging the end of the lift of the abovementioned hot cathode type discharge lamp 1 when the above-mentioned lighting voltage comes to include assymmetry.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for determining the lifespan of a hot cathode discharge lamp such as a fluorescent lamp, and an apparatus therefor.

0002

[Prior Art] Conventional methods for determining lifespan of this type include:
For example, as disclosed in Japanese Patent Application Laid-Open No. 117162/1983, there is a known method of detecting the asymmetry between the positive and negative voltages in the voltage across the electrode filament, and determining that the life has come to an end when the voltage becomes symmetrical.

0003

[Problems to be Solved by the Invention] However, in the conventional method described above, it is certainly possible to detect the consumption of the electrode material applied to the electrode filament on the side where the measurement is being carried out, but the electrode filament is a hot cathode. Since they are provided at both ends of a type discharge lamp, there is a problem that it is not possible to detect when the electrode material of the other electrode filament is consumed first. In this case, a pair of determination devices are required to correspond to both electrode filaments, resulting in a problem that the configuration becomes complicated.

0004

[Means for Solving the Problems] The present invention is a specific means for solving the above-mentioned conventional problems, in which one electrode of a hot cathode discharge lamp is grounded to the circuit ground, and the other electrode is connected to an AC By providing a lifespan determination method of a discharge lamp, which verifies the positive/negative symmetry of the lighting voltage with respect to the circuit ground, and determines that the lifespan of the hot cathode discharge lamp has come to an end when the lighting voltage has asymmetry. , which solves the conventional problems described above.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be explained in detail based on an embodiment shown in the drawings. FIG. 1 is a circuit diagram showing a method for determining the lifespan of a hot cathode discharge lamp (hereinafter referred to as a discharge lamp) 1 according to the present invention.
A filament power supply 2 is connected to a and 1b, and the discharge lamp 1
The structure is such that a current is applied and preheated prior to lighting, and on the other hand, for example, the electrode filament 1b side is grounded to the ground G.

[0006] Furthermore, the lighting power supply 3 has a frequency of several tens of KHz, for example.
The discharge lamp 1 is lit by applying the output from the lighting power source 3 between the electrode filaments 1a and 1b, and the lighting power source 3 3 is connected to a power source 4 that converts a commercial power source into direct current, for example. Incidentally, a dimming circuit 5 of a pulse width control (PWM) type, for example, may be connected between the lighting power source 3 and the power source 4 to adjust the brightness of the discharge lamp 1.

In the present invention, a positive/negative asymmetry detection circuit (hereinafter abbreviated as a detection circuit) 6 is provided between the electrode filament 1a and the electrode filament 1b having the above-described structure, thereby shortening the life of the discharge lamp 1. The determination method is explained in more detail below.

FIG. 2 shows the voltage waveform generated between the electrode filament 1a and the electrode filament 1b, and the waveform indicated by the symbol N in the figure is, for example, the normal waveform of the discharge lamp 1 immediately after it starts to be used. Similarly, the waveform indicated by symbol E is the final waveform when the life at the same measurement position reaches its final stage. Here, an electrode material called an emitter is applied to the electrode filament 1a and the electrode filament 1b, and due to the action of this electrode material, the discharge voltage between the electrode filaments 1a and 1b is a relatively low voltage, and the lighting The discharge is performed with almost the same interelectrode voltage for both the positive half cycle and the negative half cycle from the power supply 3, that is, as shown in the normal waveform N, the positive and negative voltages are symmetrical. Become.

However, the electrode filament 1a
In 1b and 1b, the above-mentioned electrode material wears out over time, and as a result, the discharge voltage also tends to rise for a while. At this time, as a result of observation by the inventor for accomplishing the present invention, both electrode filaments 1a
, 1b are extremely rare, and one half cycle of the discharge voltage increases particularly markedly, and as a result, the terminal waveform E becomes asymmetrical in positive and negative with respect to the ground G. This was confirmed. The present invention has been achieved based on the above observation results, and the life of the discharge lamp 1 is determined to be reached at the point in time when the positive and negative waveforms of the discharge voltage between the electrode filament 1a and the electrode filament 1b become asymmetrical. .

Next, the specific configuration of the detection circuit 6 will be explained with reference to FIG. 3. In this detection circuit 6, the input terminal P1 is connected to the electrode filament 1a on the side not connected to the ground G (see FIG. 1). An integrating circuit consisting of a resistor R6 and a capacitor C2 is connected to the input terminal P1, so that the potential difference between the positive half cycle and the negative half cycle of the discharge voltage generated at the electrode filament 1a with respect to the ground G, That is, the asymmetric amount is the capacitor C.
It is held by one terminal 2 of 2. In addition, a resistor R whose one end is connected to the power supply V is connected to the terminal P2.
5 is connected to the resistor R5, which constitutes the above-mentioned integrating circuit.
A first voltage dividing circuit B1 is configured, and a bias of an appropriate positive potential, for example, +6 volts, is applied to the terminal P2.

The detection circuit 6 is provided with a comparison circuit CM using, for example, a commercially available comparator IC, and a resistor R1 and a resistor R2 are connected to the non-inverting input terminal of the comparison circuit CM.
As a result, the same positive potential as that of the first voltage dividing circuit B1 is applied to the terminal P3.
A second voltage dividing circuit B2 set at
．． 7 volts) is connected to a third voltage dividing circuit B3 with a positive potential set to the terminal P4, and in addition, a first diode D3 whose cathode is on the terminal P2 side is connected between the terminals P2 and P3. is connected between the terminals P2 and P4, and a second diode D4 whose cathode is on the terminal P4 side is connected between the terminals P2 and P4.
is connected.

Here, if the discharge lamp 1 is normal (that is, within the life span) and the positive half cycle and negative half cycle of the discharge voltage are symmetrical, the terminal P2 is connected to the first voltage dividing circuit. B
Only the bias voltage due to 1 is generated, and as a result, (potential of terminal P2=potential of terminal P3)>(potential of terminal P4)
Therefore, "H" is generated at the output terminal 5 of the comparator circuit CM.

If lighting is continued in this state and the discharge lamp 1 reaches the end of its life, if an asymmetry such as positive half cycle < negative half cycle occurs, (potential of terminal P2) < (
Since the first diode D3 conducts in the forward direction so that (potential of terminal P2) = (potential of terminal P3), (potential of terminal P3) < (potential of terminal 4). At the point in time, the output terminal 5 of the comparator circuit CM
is reversed and generates "L" to notify the end of life.

On the other hand, if an asymmetry occurs such that positive half cycle > negative half cycle, (the potential of terminal P2)
> (potential of terminal P3), and at this time, the first diode D3 goes in the opposite direction and does not conduct (potential of terminal P3).
is held by the second voltage dividing circuit B2, and the (potential of terminal 4) is increased by the second diode D4 conducting in the forward direction, and at the time when (potential of terminal P3) < (potential of terminal 4). Then, the output terminal 5 of the comparator circuit CM is inverted and outputs "L" to similarly notify the end of life.

That is, according to the detection circuit 6 of the present invention, even when asymmetry occurs due to an increase in the number of positive and negative half cycles, it is possible to notify the end of the life. This makes it possible to notify the end of life even if the electrode material wears out on either side. Further, the difference in potential set between the terminals P3 and the terminals 4 may be due to an asymmetry in the initial characteristics of the discharge lamp 1 that exists due to manufacturing variations, for example, or a difference in characteristics due to a difference in the rated values of the discharge lamp 1. It is set appropriately to absorb fluctuations in characteristics due to changes in ambient temperature, and according to the inventor's experiments, by setting the voltage to 1.3 to 1.5 volts, fluorescent lamps currently on the market can be It has been confirmed that it is applicable to all varieties.

[0016]

As explained above, according to the present invention, one electrode of a hot cathode discharge lamp is grounded to the circuit ground, and the positive/negative symmetry of the AC lighting voltage of the other electrode with respect to the circuit ground is tested. However, by providing a method and apparatus for determining the life of the hot cathode discharge lamp, the life of the hot cathode discharge lamp is determined to have reached the end of its life when the lighting voltage becomes asymmetrical, so that wear is not caused on either side of the electrode. This has the extremely excellent effect of making detection possible even at the end of its life, improving detection accuracy, and simplifying the configuration.

Furthermore, the present invention provides a lifespan determination method that detects asymmetry in AC lighting voltage, making it less susceptible to the effects of differences in rated values such as wattage of discharge lamps, fluctuations in lighting voltage due to ambient temperature, etc. As a result, it is possible to further improve detection accuracy, and it also has an excellent effect in improving reliability.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of a discharge lamp life determination method according to the present invention.

FIG. 2 is a graph showing the operating principle of the discharge lamp life determination method according to the present invention using the lighting voltage of the discharge lamp.

FIG. 3 is a circuit diagram showing a discharge lamp life determination device according to the present invention.

[Explanation of symbols]

1... Discharge lamps 1a, 1b... Electrode filament 6... Positive/negative asymmetry detection circuit B1... First voltage dividing circuit, B2... Second voltage dividing circuit, B3...
...Third voltage divider circuit D3...First diode, D4...Second diode CM
...comparison circuit

Claims (2)

[Claims] 1. One electrode of a hot cathode discharge lamp is grounded to a circuit ground, and the positive/negative symmetry of the AC lighting voltage of the other electrode with respect to the circuit ground is verified, and the lighting voltage is found to be asymmetric. A method for determining the lifespan of a discharge lamp, in which the lifespan of the hot cathode discharge lamp is determined to have come to an end when . 2. An integrating circuit connected to an electrode on the non-grounded side of the hot cathode discharge lamp to hold a positive and negative potential difference of an AC lighting voltage; and an integrating circuit connected to the integrating circuit to apply a positive potential bias to the potential difference. a second voltage divider circuit connected to the non-inverting input of the comparator circuit and set to the same positive potential as the first voltage divider circuit; and a second voltage divider circuit connected to the inverting input of the comparator circuit and said first voltage divider circuit. a second voltage divider circuit set to a positive potential lower than that of the circuit; a first diode connected between the first voltage divider circuit and the second voltage divider circuit with a cathode facing the first voltage divider circuit; and a second diode connected between the first voltage dividing circuit and the third voltage dividing circuit with its cathode facing the third voltage dividing circuit.