JPS5914299A - Device for firing discharge 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 The present invention relates to a discharge lamp lighting device using a high frequency conversion circuit.

High-frequency lighting uses low-frequency white lamps like commercial frequencies, and relamping has excellent luminous efficiency. Among them, high-frequency lighting with a constant amplitude is highly efficient, but three-phase power supplies are used as discharge lamp lighting devices. High frequency lighting using a high frequency conversion circuit is known. The principle diagram is shown in Fig. 1 and Fig. 2.
In order to obtain a high frequency with constant amplitude, the voltage between each phase of the three-phase power line 1 is converted to a high frequency by a high frequency conversion circuit 2.3.4,
By combining each high-frequency output in series, a high-frequency voltage V ou+ 'a whose amplitude is approximately constant as shown in Fig. 2 is generated:
(N-(There.

Further, FIG. 3 shows a conventional discharge lamp lighting device shown in a specific circuit configuration. The problem with this type of lighting device using a high-frequency conversion circuit that uses a three-phase electric whale as an input is how to synchronize the switching of the three high-frequency conversion circuits.
Generally speaking, two types of synchronization methods are known: a self-excited type and a separately excited type, and the discharge lamp lighting device shown in FIG. 3 uses the self-excited type. That is, the switching is synchronized by supplying the high frequency vibration waveform generated in the secondary winding of the feedback lance 5 as a drive signal to the transistors in each frequency conversion circuit.

By the way, the discharge lamp lighting device using the above-mentioned high-frequency conversion circuit basically lights multiple lamps, and the secondary side of the high-frequency conversion circuit, that is, the load side, has a current limiting element (current limiting impedance) and its Multiple lamp lighting is realized by connecting several circuits in parallel, with each discharge lamp being lit via a current limiting element as one circuit. However, in a multiple lamp lighting circuit, the load fluctuation rate when the number of lamps changes becomes a problem. In other words, even if the choke coil as a current limiting element is designed so that the load current IL becomes the rated current at a certain number of lamps, when the number of lamps changes due to the occurrence of end-of-life lamps or dimming due to energy saving, etc. This is because the load current iL, that is, the current flowing through the white discharge lamp, changes and is no longer the rated current. In this regard, in the conventional discharge lamp lighting device shown in Fig. 3, if the number of circuits is reduced to reduce the light, for example,
Assuming that the rated current flows through each discharge lamp in the 5 lamp circuits,
When changing to 6 lamps and 3 circuits, the frequency of the high frequency oscillating voltage generated in the feedback transformer decreases, which reduces the current reducing effect of the current limiter IR%+, which is 7 ctance, and the load As the current increases, the current flowing into the pair exceeds the rated value. This phenomenon has been confirmed through experiments and is a major problem with the above circuit.

The present invention has been proposed in view of the above considerations, and in order to prevent the fluctuation of current that occurs in a conventional high frequency conversion circuit that inputs a three-phase power supply, the current limiting element of each lighting circuit is Separately, a new current limiting element for load fluctuation countermeasures is installed, and a circuit is also installed to detect the number of lights that are lit, so that the current limiting element for load fluctuation countermeasures can be changed, regardless of the number of lights. An object of the present invention is to provide a discharge lamp lighting device that can supply a constant load current (rated current) and eliminates the drawbacks of the conventional discharge lamp lighting device.

Hereinafter, the speed of this light will be measured according to the drawings showing the embodiments.

The discharge lamp lighting device of the present invention is shown in FIG. 1-,,L, 3-phase power supply 1, a high-frequency conversion circuit 2.3.4 to which each phase-to-phase voltage of the 3-phase power supply 1 is input, and an output transformer of the high-frequency conversion circuit 2.3.4. A current is connected to the series-combined output via a transformer 5 which supplies a drive signal, and a current limiting element 8 for load fluctuation countermeasures. It consists of a plurality of lighting circuits including a limiting element 6 and a discharge lamp 7. FIG. 5 specifically shows the current limiting element 8 for load fluctuation countermeasures and the voltage detection means of the current limiting element 6. A relay R is connected to the secondary winding of the current limiting element 6 on each side. The contact S is connected in series with a current limiting element provided corresponding to each side of the lighting circuit inside the current limiting element 8 for load fluctuation countermeasures.

To explain the operation below, the high frequency conversion circuit 2.3゜4 constitutes a push-pull type inverter, and the three-phase power supply 1
The interphase voltage of each phase is input, and a high frequency oscillating voltage is obtained by alternately turning on and off the internal switching transistors.

Then, the oscillating voltage induced in the secondary winding of the output transformer of each high frequency conversion circuit 2.3.4 is superimposed in series.
Since the instantaneous value of three-phase AC power is constant, a high-frequency voltage waveform with a nearly constant amplitude is obtained. The switching transistors are driven and synchronized by the secondary winding of the feedback transformer 5 connected between both terminals of the secondary circuit (high-frequency vibration waveform generated by two lights).

On the other hand, voltage is generated in the secondary winding of the current limiting element 6 connected in series with the discharge lamp when the discharge lamp is lit, and voltage is generated in the secondary winding of the current limiting element 6 connected in series with the discharge lamp. does not occur. The relay R driven by this voltage has a driving voltage /J'! Since the structure is such that contact S is turned on when the light is turned on, the lighting circuit is
When in the load state (all lights on), all contacts in the current limiting element 8 for load fluctuation countermeasures are on, and the inductance of the current limiting element 8 for load fluctuation countermeasures is substantially a small value. It becomes. After that, the number of self-lights decreased and C1
For example, if 5 circuits are changed to 3 circuits, the voltage on the secondary side of the current limiting element of the 2 faulty circuits disappears, and the contact corresponding to %j in the current limiting element 8 for load fluctuation countermeasure is turned off. However, its inductance increases substantially. Therefore, the increase in the load current due to the reduction in the number of circuits can be offset by the current limiting action of the current limiting element 8 as a countermeasure against load fluctuations, and the supply of the rated current can be maintained.

As described above, in the discharge lamp lighting device of the present invention, each phase-to-phase voltage of a three-phase power source is inputted, each phase-to-phase voltage is full-wave rectified, and a pair of transistors connected to the rectified output are alternately connected. The output terminals of three sets of high-frequency conversion circuits that generate high-frequency voltages through switching operations are connected in series to obtain a nearly constant high-frequency output voltage, and the high-frequency output voltage is used to light a plurality of discharge lamps connected in parallel. In the light lighting device,
The voltage across the current limiting element connected in series with the discharge lamp is detected, and when a change in the voltage across the terminal is detected, the size of the current limiting element connected in series to the output ends of the three sets of high frequency conversion circuits is determined. Since a control circuit is provided to supply a constant rated current to the discharge lamps regardless of the number of discharge lamps, load fluctuations can be reduced and a stable discharge lamp lighting device can be provided. can.

[Brief explanation of the drawing]

FIGS. 1 to 3 are explanatory diagrams of a conventional discharge phantom white lamp device, and FIGS. 4 and 5 are diagrams showing an embodiment of the present invention. 1. 3-phase power supply 2.3.4. High frequency conversion circuit 5.
・Feedback transformer 6. Current limiting element 7. Discharge lamp 8. Current limiting element R for load fluctuation countermeasures. Rido-S. Patent applicant Matsushita Electric Co., Ltd.

Claims (1)

[Claims] Three sets of high-frequency conversion circuits each inputting each phase-to-phase voltage of a three-phase power supply, full-wave rectifying the phase-to-phase voltage, connecting to the rectified output, and generating a high-frequency voltage by alternating switching operations of two pairs of transistors. A discharge lamp multi-lamp lighting device in which a plurality of discharge lamps connected in parallel are connected in series to obtain a substantially constant high-frequency output voltage, and a plurality of discharge lamps connected in parallel are connected with the high-frequency output voltage in series. The voltage across the limiting element is detected, and when it is detected that the voltage across the limiting element changes to i, the size of the current limiting element connected in series to the output end of the three sets of high frequency conversion circuits is changed. What is claimed is: 1. A discharge lamp lighting device characterized in that a control circuit is provided to supply a constant rated current to discharge lamps regardless of the number of discharge lamps.