JPS6035498A - Device for firing discharge lamp - Google Patents

Abstract

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

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a discharge lamp lighting device in which a dimmable discharge lamp circuit is connected to a lighting power supply, and particularly to a discharge lamp lighting device in which a dimming type discharge lamp circuit is connected to a lighting power supply, and in particular, a discharge lamp lighting device in which the configuration of the discharge lamp circuit is simplified. Regarding equipment.

[Technical background of the invention and its problems]

2. Description of the Related Art As a conventional discharge lamp lighting device, one shown in FIGS. 1 and 2, for example, is known.

The discharge lamp lighting device shown in FIG. 1 has a plurality of dimmable discharge lamp circuits 2 connected to a lighting power source 1. It is composed of a series circuit with a switch circuit 5 that controls the lighting period. Here, the switch circuit 5 is composed of a bidirectional thyristor 6 and a base circuit 7, and by giving a gate signal having a predetermined pulse width from the pace circuit 7 to the thyristor 6, the discharge lamp 4 is dimmed at a predetermined brightness. Light. In this type of discharge lamp lighting device, in order to downsize the ballast circuit 3,
If a high frequency power source is used as the lighting power source 1, the size 1
It is also necessary to use a high-speed one star 6. but,
This high-speed thyristor 6 is very expensive and has the drawback of increasing the cost of the lighting device.

On the other hand, in the discharge lamp lighting device shown in FIG. 2, the switch circuit 5 includes a rectifier bridge circuit 16 connected in series to the discharge lamp 4, and a transistor 17 that turns on and off the direct current supplied from the rectifier bridge circuit 16. and the transistor 1
7 base circuit 7 and a driving circuit for the transistor 17;
By configuring the AC switch with the power source 18, there is an advantage that it can be provided at a low cost as an AC switch capable of high-speed operation. However, in this type of lighting device, when multiple discharge lamp circuits 2 are connected in parallel to the lighting power supply 1, the drive power supply 18 of the transistor 17
Since it is not possible to share the power source, a potential-independent drive power source is required for each switch circuit 5. That is, when each drive power source 7 is connected as shown by the broken line in FIG. Because of this, it is not possible to share the drive power supply [8]. Therefore, an independent driving power source is required for each switch circuit 5, which results in a complicated circuit configuration, which has the disadvantage that the lighting device is expensive and expensive.

[Purpose of the invention]

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide a dimming type discharge lamp lighting device that has a simple circuit configuration and is inexpensive.

[Summary of the invention]

In order to achieve the above object, the present invention is characterized in that the ballast circuit has at least a capacitor, and the switch circuit is a dimming switch circuit that is a combination of a diode and a unidirectional switching device. Here, the expression "having at least a capacitor" includes a capacitor alone or a capacitor and an inductor connected in series, but does not include a capacitor and an inductor connected in parallel. However, this includes cases where a discharge resistor (with a considerably large discharge time constant), etc. is connected in parallel with the capacitor.

[Embodiments of the invention]

An embodiment of the present invention will be described with reference to the attached drawings below. In the drawings below, the same elements as those in FIGS. 1 and 2 are given the same reference numerals.

FIG. 3 is a schematic diagram of a discharge lamp lighting device according to this embodiment. Similar to FIGS. 1 and 2, this lighting device includes a lighting power source 1 that supplies alternating current, and one or more discharge lamp circuits 102 connected to the lighting power source 1. The lighting power source 1 is a low frequency power source such as a commercial frequency,
Alternatively, it is constituted by a high-frequency power source that rectifies this low-frequency electric power and converts it into a high-frequency wave of several tens of KH2 using an inverter or the like. When a large number of discharge lamp circuits 102 are connected in parallel to the lighting power source 1 to create a display device for characters, figures, etc., the lighting power source 1 is It is preferable to use a high frequency power source. The discharge lamp circuit 102 connected to this lighting power supply 1 is
It is composed of a series circuit including a ballast circuit 103 consisting of a capacitor C, a discharge lamp 4, and a switch circuit 105 that controls the lighting period.

The switch circuit 105 is an antiparallel circuit of a unidirectional switching device 117 consisting of a diode 116 and a transistor connected in series to the discharge lamp 4, and the switching device 1.
17, and a DC drive power source 118 that drives a switching device 117.

FIG. 4 shows an example of the configuration of the base circuit 107, in which the one-shot multivibrator 1 is activated by the falling edge of the clock pulse a output from the clock pulse generator 120.
21 outputs a square wave signal (dimmer signal) b with a predetermined pulse width, and sends this square wave signal b to a switching device 1170.
The switching device 117 is turned on and off by applying it to the base. The pulse width is controlled based on, for example, a video signal.

The operation of the discharge lamp lighting device configured as described above is explained in the fifth section.
This will be explained with reference to the figures. When a clock pulse a is generated from the clock pulse generator 120 shown in FIG. , controlled off.

Then, the switching device 117 switches the dimming signal l) to
When the switching device 117 and the diode 116 are electrically conductive, the anti-parallel circuit of the switching device 117 and the diode 116 acts with the AC switch, and the output from the lighting power source 1, for example, several tens of KI
-I.

In the forward direction, the high frequency current flows between the collector and emitter of the ballast circuit 103 → discharge lamp 4 → switching device 117,
When in the reverse direction, diode 116 → discharge lamp 4 → ballast 10
3, and the discharge lamp 4 is lit at high frequency.

Next, when the switching device 117 becomes non-conductive due to the dimming signal 10'', the diode 11 is initially turned off.
Only the forward bias of 6 becomes conductive, and at this time, the ballast circuit 1
Capacitor C of 03 is charged only in that direction. Next, when the charging voltage of the capacitor C reaches approximately the power supply voltage of the lighting power supply 1, no charging current flows through the capacitor C, the lamp current becomes zero, and the discharge lamp 4 turns on when the switching device 1170 turns on. The light goes out after a predetermined period of time.

In the next half cycle of the lighting power supply 1, the diode 116
becomes reverse biased, no lamp current flows, and capacitor C remains charged. Furthermore, power supply for lighting 1
In the next half cycle, the diode 116 becomes forward biased, but since the capacitor C is already charged to the power supply voltage, the lamp current does not flow and the lamp remains off, and the switching device 117 outputs the dimming signal bσ door. This state continues unless conduction occurs at 1". Therefore, by changing the pulse width of the dimming signal, the discharge lamp 4 can be dimmed and lit easily and accurately. As shown in FIG. 3, since the transistor as the switching device 117 can be used with its emitter grounded, when a plurality of discharge lamp circuits 20 are connected in parallel to the lighting power supply 1, the drive power supply 118 of the switch circuit 105 can be shared. Therefore, the number of wires for supplying the drive power source 118 is small.
The simpler the circuit configuration, the lower the cost. Note that when the discharge lamp 4 remains off for a long time, that is, when the unidirectional switching device 117 is not turned on for a long time, the charging voltage of the capacitor C decreases due to self-discharge 1 etc. of the capacitor C, and the charging voltage of the capacitor C decreases through the diode 116. It is conceivable that a high frequency current flows through the discharge lamp 4. However, such a problem can be solved by selecting the capacitor C, and there is no problem if the conduction period of the unidirectional switching device 117 is short. Further, even if a high frequency current flows as described above, there may be cases in which there is no substantial problem except for discharge and the lamp 4 emitting light. Furthermore, if the light is to be turned off for a long time, the power may be cut off. In any case, it is possible to solve the above problem.

Further, in the above embodiment, the ballast circuit 103 is connected to the capacitor 1.
03 may be constructed, for example, by a series circuit of a capacitor 103' and an inductor 104 shown in FIG. By inserting the inductor in this way, the impedance in the high frequency region can be increased, and when the lighting power source 1 is particularly configured with a high frequency power source, the current limiting function of the ballast circuit 103 can be effectively exhibited.

Furthermore, the unidirectional switching device 1]7 in the switch circuit 105 includes a FET, a G
TO etc. can be used. It is also possible to use an 8CR; in this case, only a half-wave current flows through the SCR, so a thyristor with much slower switching characteristics than the bidirectional thyristor shown in Figure 1 should be used. is clear.

〔Effect of the invention〕

As explained above, according to the present invention, the ballast circuit has at least a capacitor, and the switch circuit has an anti-parallel circuit of a diode and a unidirectional switching device, so that the charging/discharging action of the capacitor and the unidirectional switching device are combined. Due to the switching action of the directional switching device, a dimming type AC switch can be constructed easily and inexpensively.

[Brief explanation of the drawing]

1 and 2 are schematic configuration diagrams of a conventional discharge lamp lighting device, FIG. 3 is a schematic configuration diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 4 is a gate in FIG. 3. A block diagram showing an example of a circuit configuration, FIG. 5 is an operation explanatory diagram of FIG. 3, and FIG.
The figure is a block diagram of a ballast circuit according to another embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Power supply for lighting, 4... Discharge lamp, 102... Discharge lamp circuit, 103... Ballast circuit, 105... Switch circuit, 107... Base circuit, 116... Diode , 117...unidirectional switching device,]
18... Drive power supply. Applicant's agent Kiyoshi Inomata Figure 4

Claims (1)

[Scope of Claims] (]) In a discharge lamp lighting device in which a discharge lamp circuit comprising a series circuit of a ballast circuit, a discharge lamp, and a switch circuit for controlling a lighting period is connected to a lighting power source, the ballast circuit A discharge lamp lighting device characterized in that the switch circuit has at least a capacitor, and the switch circuit has an anti-parallel circuit of at least a diode and a unidirectional switching device. (2. The device according to claim 1, wherein the discharge lamp circuit is a discharge lamp lighting device in which a plurality of discharge lamp circuits are connected in parallel to the lighting power source. (3) The device according to claim 1. In the discharge lamp lighting device, the lighting power source is a high-frequency power source. (4) In the device according to claim 2, each switch circuit of the discharge lamp circuit is driven by a single power source. Discharge lamp lighting device.