JPH06151067A - Highly reliable lighting circuit - Google Patents

Abstract

PURPOSE:To immediately light a filament of waiting system at the filament disconnection of a bulb, and prevent the interruption of lighting. CONSTITUTION:A filament 8a is heated by the opening of a switch 13. A filament current 1A is detected by a current transformer 10, and a DC power source is supplied to a control part 11 from a switching regulator 12 to operate the control part 11. When the output of the current transformer 10 is suddenly changed by the disconnection of the filament 7a, the control part 11 detects this and outputs a DC Voltage to terminals D1, D2. Thus, a filament 8b is lighted. When the filament 8a is disconnected, a LED 14 is lighted. An operator knows that the filament is changed to waiting system by this.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting circuit for a lighting device, and more particularly to a lighting circuit used for a lighting device which requires high reliability.

[0002]

2. Description of the Related Art At present, lighting devices are used all over the world. As a light source of these lighting devices, a discharge lamp such as an incandescent lamp, a mercury lamp, or a fluorescent lamp is used, and particularly as a light source for high-power lighting, its color tone, economic efficiency, stability, easiness of control of light quantity, etc. From the point, incandescent lamps are often used.

Among various illuminating devices, there is one that requires particularly high reliability. As such a lighting device,
For example, it may be used for lighting in a television studio or used for surgery in a hospital. Traffic signals for traffic also fall into this category. Further, there is also a system in which a light source is placed at one location, which is guided by an optical fiber and branched to various locations for use.

[0004]

SUMMARY OF THE INVENTION In a lighting device that requires high reliability as described above, it is very inconvenient for the filament of a light bulb to suddenly break. That is, in the case of lighting in a television studio, the lighting device has conventionally been manually switched at such a time, but the image quality and brightness suddenly change on the image receiving side, so it is possible to avoid impairing serviceability. There wasn't.

In the case of an illuminating device used for surgery in a hospital, it may affect the success or failure of the surgery in the worst case. In the case of traffic signals, it will cause traffic confusion.
Furthermore, it may create an opportunity for a traffic accident.
Further, in a device or the like configured to be dispersed and used in one place from one light source using an optical fiber, disconnection of one light bulb stops all functions.

The present invention has been made in order to solve such a conventional problem, and even if the filament of an incandescent lamp, which is a light source, is suddenly broken, the illuminance is almost affected. The aim is to provide a lighting device that is not reliable.

[0007]

According to the present invention, the above-mentioned problems can be solved by the means described in the claims. That is, the invention of claim 1 is such that an electric light bulb having a plurality of filaments that can be independently lighted, a selection circuit that selects one of the plurality of filaments, and a current supplied to the selected filaments. When the current detection circuit to detect and the current of the current detection circuit becomes smaller than a predetermined value, controlling the selection circuit,
It is a highly reliable lighting circuit having a control circuit for switching to another filament and energizing a newly selected filament.

Further, the invention of claim 2 comprises a preheating circuit for energizing at least one filament other than the filament currently selected in the above invention for preheating the filament.

Further, the invention of claim 3 is the invention of claim 1 or claim 2, further comprising an indicator for indicating that the filament is switched when the filament is switched to another filament. It is configured by providing means for sending out.

[0010]

FIG. 1 is a diagram showing the principle configuration of the present invention.
(A) corresponds to claim 1, (b) corresponds to claim 2, and (c) corresponds to claim 3. In the figure, 1 is an incandescent lamp, 1a and 1b are filaments, 2 is a changeover switch, 3 is a current detection unit, 4 is a control unit, 5 is a power input terminal, 6 is a resistor, and 7 is a display signal terminal. ing. In FIG. 3A, the contact of the changeover switch 2 is normally connected to the side a. When the power supply voltage is input from the power supply input terminal 5, "power supply input terminal 5" → "current detection unit 3" → "c contact → a contact of changeover switch 2" → "filament 1a" →
A closed circuit is formed like the "power input terminal 5" and the filament 1a lights up. The amount of current in this circuit is detected by the current detector 3 and monitored by the controller 4. The control unit 4 compares the detected current with a reference value, and when it becomes smaller than a predetermined value, sends a signal A to the changeover switch 2.
Is sent to switch the contact of the changeover switch 2 to the b side. As a result, power is supplied to the filament 1b and the filament 1b lights up. By using a switch with a fast response speed as the changeover switch 2, the incandescent light bulb 1
The decrease in illuminance can be negligible at a practical level.

In the configuration shown in FIG. 1B, a small amount of current is constantly supplied to the filament 1b of the standby system through the resistor 6 to prepare for switching. By doing so, when the filament is switched to the filament 1b, the rising thereof can be accelerated. Further, since the temperature change width of the filament at the time of switching can be reduced, it is possible to suppress the rush current to a considerable extent, and the possibility that the filament 1b is broken at the moment of switching can be reduced. Therefore, a more reliable illumination system can be constructed.

In the configuration shown in FIG. 1C, when the filament is switched to the standby system, a signal indicating this is output from the display signal terminal 7. With this, for example, it is possible to inform the operator that the filament is switched to the standby system by lighting the light emitting diode or the like. The operator can know from this sign that the filament 1a is broken, and can take measures such as replacing the incandescent light bulb 1 by the time of next use. Therefore, it becomes possible to maintain higher reliability.

In the above description, for facilitating understanding, the case where the number of filaments is two is described, but the number of filaments is not limited to two, and it is needless to say that three or more filaments can be configured. is there. At this time, changeover switch 2
It is possible to adopt a system in which the number of contact points is set to a number corresponding to the number of filaments and sequentially switched.

[0014]

FIG. 2 is a diagram showing a first embodiment of the present invention and shows an example of a lighting circuit used in a television studio or the like. In the figure, 8 is an incandescent light bulb for illumination, 8a is an active filament, 8b is a standby filament, 9 is a changeover switch (SSR), 10 is a current transformer for current detection, 11 is a controller, 12 Is a switching regulator, 13 is a lighting switch, 14 is a light emitting diode, and 15 is a resistor. AC for lighting circuits used in TV studios, etc.
In many cases, a voltage-controlled dimming circuit using a triac for 0V is used. The present embodiment shows an example of applying the present invention to such an illumination circuit. The operation of the embodiment will be described in detail below with reference to the drawings.

When the lighting switch 13 is closed, the dimming power source between the terminals DE is terminal D → lighting switch 13 → filament 8
A closed circuit is formed as in a-> current transformer 10-> terminal E, and the filament 8a is incandescent. The current 1A flowing through the filament 8a is detected by the current transformer 10, and the result is input to the control unit 11. The control unit 11 uses the AC 10
Switching regulator 1 that operates with 0V as the power supply
It receives a DC power supply of + 15V and -15V from 2 and operates by using this. When the filament 8a of the light bulb 8 is broken, the current 1A of this circuit is cut off, and the output of the current transformer 10 suddenly decreases, the control unit 11 detects this and detects D1 and D2.
DC voltage is output to.

This voltage is applied to the changeover switch 9.
As a result, the changeover switch 9 contacts the contacts DB1 and DB2.
Close the circuit between. As a result, the dimming current is at terminal D →
Lighting switch 13 → filament 8b switching switch DB1 contact → DB2 contact → terminal E through filament 8
Turn on b. By the above operation, the filament 8a
When the wire breaks, the filament 8b is immediately turned on, so that the illumination is not interrupted. Filament 8a
When the line is disconnected, the DC voltage appears at the D1 and D2 terminals of the control unit 11 as described above, and thus the light emitting diode 14 is turned on. This allows the operator to know that the filament has switched to the standby system.

FIG. 3 is a diagram showing a second embodiment of the present invention. In this embodiment, a resistor 16 and a constant current circuit 17 are added to the circuit of the first embodiment described above. In this embodiment, when the filament 8a is currently used, a small current is constantly supplied to the filament 8b of the standby system through the resistor 16 and the constant current circuit 17 to preheat the filament 8b. The constant current circuit 17 is provided because the filament 8b is used in an unsaturated state, and therefore even a slight change in the dimming current may cause a large change in the inflow current. This is to prevent the spread of Other operations and the like are the same as those in the case of FIG.

FIG. 4 is a diagram showing an example of the circuit of the current detecting unit and the control unit of the embodiment, 20 is a lighting circuit of the current filament, 21 is a current detecting unit using a Hall element, 22
-25 are operational amplifiers (op amps), 26 is a switching control voltage generator, R is resistors, VR1 and VR2 are variable resistors, Z is a zener diode, d is a diode, and T is a diode.
R1 and TR2 represent transistors, and C represents a capacitor. In the figure, when an alternating current (for lighting an active filament) flows through the lighting circuit 20, the current detection unit 21 detects this and generates a voltage of about 0.5 mV at the terminal indicated by. At this time, the circuit composed of TR1 and VR1 determines the threshold value of the detection level of the input current.

This voltage is amplified by the operational amplifiers 22 to 24, and a constant voltage of -5 V is generated at the point indicated by. The operational amplifier 25 is used as a comparator, and its + side input terminal is V
The comparison voltage from R2 is input. Then, while the voltage at the point indicated by is -5V, the voltage at the point indicated by is negatively adjusted by VR2. When the current filament is broken and the current of the lighting circuit 20 is cut off, the voltage at the point indicated by becomes 0V, and the voltage at the point indicated by changes to the positive side. By this, TR2 is "on"
Then, the switching control voltage generator operates to generate a DC voltage of 15 V between the D1 and D2 terminals. This voltage of 15V is applied to the changeover switch 9 shown in FIG. 2 or 3. The changeover switch 9 thereby closes the circuit between DB1 and DB2, and immediately turns on the filament 8b.

FIG. 5 is a diagram showing an example of the configuration of the switching regulator shown in FIGS. 2 and 3, where 30 is a power transformer, 31 is a rectifier, 32 and 33 are switching regulator elements, and C is a capacitor. , CC represents an electrolytic capacitor. In the figure, the power transformer 30 is an AC
The commercial power supply of 100V is stepped down to 40V. And
The center tap of the secondary winding is grounded. This voltage is rectified by the rectifier and is approximately ± 2 with respect to ground.
It becomes a pulsating voltage of 0 V, is smoothed by CC1 and CC2, and is input to the switching elements 32 and 33. The switching elements 32 and 33 perform a switching operation so that the output voltage becomes constant, and the outputs are CC3 and
It is smoothed by CC4 and output as a stabilized DC voltage of ± 15V. It should be noted that C1 and C2 are inserted to bypass noise (high frequency component) associated with switching.

FIG. 6 is a diagram showing an example of a circuit obtained by adding a preheating section to the circuit shown in FIG. In this example, the preheating circuit is provided in two systems, a main circuit and a sub circuit. VR3
By adjusting the variable resistor of VR4 and VR4, a small amount of current is supplied to the spare filament b even while the main filament a is in use. When the filament a is disconnected and the TR2 operates as described above, the FET operates via the photocoupler 34 and the filament b is turned on.

[0022]

As described below, according to the present invention, even if the filament of the light bulb is broken during use, the filament of the standby system is immediately turned on, so that the illumination is not interrupted. Therefore, it can be used as an illumination source that requires high reliability. Further, since the operator can know that the filament has been broken, there is an advantage that the bulb can be replaced at the time of the next use so that high reliability can always be maintained.

[Brief description of drawings]

FIG. 1 is a diagram showing a principle configuration of the present invention.

FIG. 2 is a diagram showing a first embodiment of the present invention.

FIG. 3 is a diagram showing a second embodiment of the present invention.

FIG. 4 is a diagram illustrating an example of circuits of a current detection unit and a control unit.

FIG. 5 is a diagram showing an example of a configuration of a switching regulator.

FIG. 6 is a diagram showing an example of circuits of a preheating unit, a current detection unit, and a control unit.

[Explanation of symbols]

1,8 Incandescent light bulb 1a, 1b, 8a, 8b Filament 3,21 Current detection part 4,11 Control part 5 Power input terminal 6,15,16 Resistor 7 Display signal terminal 9 Changeover switch 10 Current transformer 12 Switching regulator 13 Lighting switch 14 Light emitting diode 17 Constant current circuit 20 Current filament lighting circuit 22, 23, 24, 25 Operational amplifier 26 Switching control voltage generator 30 Power transformer 32, 33 Switching regulator element

Claims (4)

[Claims] 1. A light bulb having a plurality of filaments that can be turned on independently, a selection circuit that selects one of the plurality of filaments, and a current detection that detects a supply current to the selected filament. And a control circuit for controlling the selection circuit to switch to another filament and energize the newly selected filament when the current of the current detection circuit becomes smaller than a predetermined value. A highly reliable lighting circuit characterized in that 2. The high reliability lighting circuit according to claim 1, further comprising a preheating circuit for energizing at least one filament other than the currently selected filament to preheat the filament. 3. The method according to claim 1, further comprising a display for indicating that the filament is switched when the filament is switched to another filament, or means for transmitting a signal therefor. High reliability lighting circuit. 4. The high reliability lighting circuit according to claim 1, 2 or 3, wherein a light bulb in which filaments are provided in independent spheres or tubes is used.