JPH03119697A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To stabilize a filament voltage by supplying power to main discharge and a filament from the same power output for synchronizing them. CONSTITUTION:Power from DC power source is supplied to an inverter 1, and Tr1 and Tr2, and Tr3 and Tr4 among transistors are alternately turned on and off by means of oscillation of an inverter control unit 3 to produce AC output. A transformer Trf1 for main discharge and a transformer Trf2 for filament are respectively connected in parallel to the output side of the inverter 1 and a center tap is installed at the secondary winding of Trf1 and both the ends of winding are connected to a ballast transformer BT through diodes D1, D2. A transformer BT is connected to the anode A1 of an electric discharge lamp 4, and the center tap of the Trf1 is connected to the filament 5 of an electric discharge lamp 4, so that electric discharge is formed between the anode A1 and the filament 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge lamp lighting device for a discharge lamp that requires filament preheating.

(Prior Art) Conventionally, such a discharge lamp lighting device has had two power supply circuits: a main discharge power supply and a filament power supply.

In addition, a single power supply circuit constitutes a main discharge power supply and a filament power supply, detects the voltage applied to the filament, performs negative feedback control, and keeps the inverter output voltage constant against fluctuations in DC input. There was something I wanted to keep.

(Problems to be Solved by the Invention) However, the former method requires a filament power source and a main discharge power source, respectively, and thus has the problem of increasing the size of the device.

Furthermore, although the latter method allows for miniaturization of the device, there is a problem in that it is difficult to synchronize the main discharge and the filament.

The present invention has been made in view of the above problems, and its purpose is to supply power to the main discharge and the filament with the same power output, to make the filament voltage constant, and to synchronize both. An object of the present invention is to provide a discharge lamp lighting device that performs simultaneous lighting.

[Structure of the Invention] (Means for Solving the Problems) The discharge lamp lighting device of the present invention forms a main discharge circuit and a filament preheating circuit using a common inverter output, and lights a discharge lamp having a filament. Control.

The preheating circuit is provided with switching means such as a transistor.

The control system includes an inverter control section that controls oscillation of the inverter, and a pulse width control section that controls PWM (pulse width) switching means of the preheating circuit. A synchronization signal is obtained from the control section and a constant filament voltage is supplied in synchronization with the inverter.

(Function) According to the present invention, the main discharge and filament power can be supplied by a single inverter, so the device can be miniaturized.

Furthermore, since the filaments are synchronized and controlled on the output side of the inverter, synchronization can be easily achieved, and since this synchronization control is performed by PWM control, voltage can be made constant at the same time, which also simplifies the circuit.

Furthermore, although the discharge lamp load is an L-type load, since the filament is added as a load to the inverter, the power factor can be improved.

(Embodiment) An embodiment of the present invention will be described with reference to FIGS. 1 to 3. This embodiment is a lighting circuit for a fluorescent lamp which is one element of a large color vision system.

1 is an inverter, which is supplied with power from the DC power supply 1,
Due to the oscillation of the inverter control unit 3, for example, 100kHz, among the transistors Tri, Tr2 and Tr3. Tr4
For example, an AC output of 200V is produced by turning on and off alternately.

Main discharge transformer T is connected in parallel to the output side of inverter 1.
rfl and filament transformer Trf2 are connected, and Trfl is transformed to 100v, and Tri2 is transformed to 5v. The secondary winding of Trfl is provided with an intermediate tap, and both ends of the winding are connected to a diode Di.
, D2 to the ballast transformer BT, and supplies reverse-phase lighting AC power to the ballast transformer BT.

Then, DC power for lighting is generated by this ballast transformer BT. That is, the ballast transformer BT is connected to the anode A1 of the discharge lamp 4, the intermediate tap of Trfl is connected to the filament 5 of the discharge lamp 4, and a discharge is formed between the anode Al and the filament 5. The discharge is controlled by turning the base of the switching element Tr6, which is provided in parallel with the picture electrode of the discharge lamp 4, at 0FFL when a signal corresponding to, for example, a video signal is input, and by turning ON when no signal is input.

The circuit from Trfl to Tre6 is the main discharge circuit. Next is the filament circuit, inverter 1 and T
A diode bridge DB and a switch means 6 are interposed between ri2. Further, the output side of Tri2 is connected to filament 5.

Next is the PWM control section 11 that controls the switch means 6, which receives signals from the feedback circuit FB that monitors the voltage of the filament 5 and the inverter control section 3, and receives signals from the inverter control section 3 as shown in (n) in FIG. While synchronizing with the output waveform of inverter 1 ((I) in Figure 2), negative feedback control is performed by controlling the pulse width so that the output voltage of Tri2 becomes, for example, 5V (Figure 2). (■)).

According to this embodiment, since the main discharge power source and the filament power source are synchronized, when the voltage required to start discharge is non-zero, the filament voltage is also non-zero, so the filament position shown in FIG. In this case, discharge always occurs between either a or b and A1, and for example, discharge occurs between C and A1 at the end of the filament life, that is, when the emitter is gone. For example, if the distance between the filament 5 and the anode A1 is a short discharge lamp, the difference in discharge distance becomes noticeable between Al-a and AI-c, which affects the light emission caused by the discharge, and in the case of a conventional circuit. However, in this embodiment, if the discharge lamp has equal distances between both ends of the filament and the anode, the flickering problem can be solved.

In this embodiment, the signal input to Tr6 is configured not to be involved in the inverter control unit 3, but the signal input to Tr6 is PWM modulated and the signal input to the inverter control unit 3 is
If synchronization is established, a high voltage will always be generated between the filament 5 and the anode A1 when a discharge is formed, and a discharge will be formed immediately.

The lighting circuit of this embodiment is configured to light a plurality of discharge lamps arranged in a matrix on, for example, a display panel individually or collectively.

Therefore, it is possible to reduce the size of the entire device and to provide a display device with less flickering on the display screen.

[Effects of the Invention] The discharge lamp lighting circuit of the present invention is configured to supply the output of a common inverter to both the main discharge circuit of the discharge lamp and the filament circuit having a switch means, so that the circuit can be made smaller. can be achieved. In addition, the PW is synchronized by a signal from an inverter control circuit that feeds back the output voltage of the filament circuit and controls oscillation of the inverter.
Since the filament voltage is made constant by pulse width modulating the switching means of the filament circuit using the output of the M control section, it is easy to synchronize the main discharge voltage and the filament voltage, and it is also easy to adjust the filament voltage. Constant voltage can be achieved.

Further, although the discharge lamp load is an L-type load, since the filament is added as a load to the inverter, a resistance component is added, and the power factor can be improved without adding a separate resistance component.

[Brief explanation of drawings]

The figures show an embodiment of the present invention, in which Fig. 1 is a partially simplified circuit diagram, Fig. 2 is a timing chart showing voltage levels at predetermined points in the same circuit, and Fig. 3 is a It is an explanatory view showing the discharge path of the discharge lamp of the circuit same as the above. 1... Inverter, 3... Inverter control section. 4...Discharge lamp, X...Main discharge circuit. Y...Filament circuit, 5...Filament 11...PWM control section.

Claims (1)

[Claims] (1) An inverter that converts DC input into AC output; An inverter control unit that controls oscillation of the inverter; A discharge lamp having a filament; A main discharge circuit of the discharge lamp formed on the output side of the inverter; a filament circuit formed on the output side of the inverter and having a switch means; detecting the output voltage of the preheating circuit and controlling the switch means to make the output voltage of the filament circuit a constant voltage, and controlling the inverter; A discharge lamp lighting device comprising: a PWM control section that is synchronously controlled by a signal from the section;