JPS61224297A - Discharge lamp lighting apparatus - 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 [Field of the Invention] The present invention relates to a device for lighting a discharge lamp at a high frequency, and particularly to a series lighting type discharge lamp lighting device for lighting a plurality of discharge lamps connected in series.

[Background of the Invention] Conventionally, as this type of device, one having the configuration shown in FIG. 4 is known. The device in the figure has an input terminal a.

The DC power supplied between 6 and 6 is converted into high frequency power by a high frequency converter 4, and the discharge lamps (lamps) Fl and F2 connected in series are lit by this high frequency power.

This high frequency converter 4 uses a so-called series inverter, and has a transistor Q1 between input terminals a and b.
A and 011) are connected in series, and the bases of these transistors Q1a and Qlb are connected to a base drive circuit 11 that alternately turns on and off these transistors Q1a and Q1b. Diodes 1) 1a and Dlb are for bypassing the current of the ballast inductor (choke coil) CH to the power supply side when the transistors Qlb and Qla are off, respectively.
This prevents a high voltage back electromotive force from being generated across the choke coil CH and protects the transistors Q 1a and Q 1b. Capacitors C3a and C3b are DC cut capacitors.

A series circuit of two lamps F1 and F2 is connected as a load between the high-frequency output terminal of the inverter 4, that is, the connection point C between the transistors Q1a and Qlb, and the connection point d between the DC cut capacitors C3a and C3b. It is connected via coil CH.

Capacitors C21 and C22 are connected to lamp F1. This is the starting capacitor for F2.

In this lighting device, when DC power is supplied between input terminals a and b, transistors Q1a and 01b are turned on alternately by a signal from a base drive circuit 11 in an inverter 4, and this causes a high frequency output terminal C to output a high frequency signal. generates a square wave output. This rectangular wave output is transmitted to the lamp F through a series circuit of choke coil CH and capacitors C21 and C22.
l, is supplied to the F2 filaments and heats these filaments. Also, coil CH and capacitor C2
1 and C22 substantially resonates with the frequency of the rectangular wave output, and each lamp F1 and F2 is lit by applying a high voltage due to resonance between both filaments. After lighting, the lamps F1 and F2 connected in parallel with the capacitors C21 and C22 become low impedance, and the Q of the LC resonance circuit consisting of the coil CH and the capacitors C21 and C22 decreases. , acts as a ballast for F2 and lamp F
1, F2 lights up stably.

By the way, in this device, if the inductance of the choke coil CH is L1 and the capacitance of capacitor C21°C22 is C, then the resonant frequency f1 before the two lamps F1°F2 start together is approximately 1/2πET]r = 1 be. Generally, this resonant frequency f1 is matched to the output frequency fO of the inverter 4. However, the resonant frequency f2 after starting one lamp is approximately 1/2π1, which is f2\f1.

For this reason, in a lighting device that uses a separately excited inverter or an inverter whose output frequency is relatively stable against changes in load even if it is a self-excited type, after starting one lamp, the resonance frequency f2 of the LC resonant circuit will decrease. The output frequency fO of the inverter 4 is different from that of the inverter 4, and there is a problem that the second lamp may not turn on due to insufficient applied voltage.

[Object of the Invention] The present invention has been made in view of the above-mentioned problems with the conventional type, and is aimed at improving the starting characteristics of a series-type discharge lamp lighting device in which a plurality of discharge lamps are connected in series and lit. The purpose is to improve.

[Configuration of the invention] In order to achieve the above object, the present invention provides a series lighting type discharge lamp lighting device in which a resonant capacitor for applying a high voltage to the discharge lamp at startup is connected to a series circuit of a plurality of discharge lamps. Connected to both ends.

Therefore, according to the present invention, at the time of starting, the resonance frequency can be kept almost constant regardless of the number of unstarted discharge lamps, so that a sufficiently high voltage can be applied to any of the discharge lamps connected in series. This makes it possible to prevent some discharge lamps from causing lighting errors. In other words, if the high-frequency generator is a separately excited type, or even if it is a self-excited type, the switching frequency does not completely follow the change in the resonant frequency of the LC resonant circuit for starting the discharge lamp, the starting characteristics of the discharge lamp may be affected. will improve.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 shows the configuration of a discharge lamp lighting device according to an embodiment of the present invention. Further, FIG. 2 shows a more specific circuit example of the device shown in FIG. 1. The device shown in Figure 2 consists of a noise prevention/power factor improvement circuit 1 and a surge absorption circuit 2 from an AC 200V power supply.
The rectifier circuit 3 converts the AC input through the rectifier circuit 3 into a DC smoothed output, which is then converted to a 5EPP switching transistor Q1a.

Qlb is converted into a high frequency current by an automatic series inverter circuit 4 consisting of auxiliary transistors Q2a and Q2b, which lights up fluorescent lamps F1 and F2 connected to an output terminal C via a choke coil CH. It is something.

The apparatus of FIGS. 1 and 2 differs from the apparatus of FIG. 4 by eliminating the resonant capacitors C21, C22 for the load circuit including the lamps Fl, F2, and instead replacing the filaments P11. F12 (+3 and F21
．． A resonance capacitor C1 is connected between the filaments P11 and F22 which are not directly connected to each other among F22.
and connect both filaments P11. of one lamp F1.
A sequence capacitor C2 with a capacity sufficiently smaller than the capacitance of the resonance capacitor C1 is connected between F12, and further,
Common side filament p12 of the above lamp. The preheating power of p21 is changed to be supplied from the secondary winding provided in the choke coil CH. Sequence capacitor C2
is for applying a higher voltage to one of the lamps F2, thereby making it possible to start the lamp F2 more reliably. In the device shown in FIG. 2, capacitors C1a and 01b are connected in series and used as the resonance capacitor C1.

Next, the operation of the lighting device shown in FIG. 2 will be explained.

First, when the AC 200V power is turned on and a smoothed DC output is generated at the DC output terminal of the rectifier circuit 3, the resistors R4, R5,
Charge is accumulated in capacitor C5 via R6. As a result, the potential at the connection point J rises, and when it exceeds the breakdown voltage of the bidirectional thyristor SS, SS becomes conductive and supplies base current to the switching transistor Qlb on one side, and the collector of the transistor Q1b Since current is supplied from the connection point J via the diode D1, the transistor Q
1b becomes conductive, the inverter is activated, and oscillation begins. Then, capacitor C4b is connected to 2 of transformer T1.
The voltage induced in the next winding W2b charges the resistor R3b, and as soon as the voltage between its terminals exceeds the Zener voltage of the Zener diode 7D1b and the base-emitter ON voltage of the auxiliary transistor Q2b, the transistor Q2b turns on and the transistor Q1b turns off. As a result, the current in the load circuit is reversed, and switching transistor Q1a is now turned on. Thereafter, in the same manner] transistors Q1a and Qlb are alternately turned on and off, and oscillation continues.

Immediately after startup, the fluorescent lamps F1 and F2 have not yet reached the dischargeable state, so the choke coil CH is connected to the output terminal C.
Which series resonant circuit is connected to the starting capacitors C1 and C2 between the heaters of the lamps Fl and F2, and because the Q of this resonant system is high, the current in the load circuit is higher than normal. , the oscillation frequency tries to increase. However, in this inverter 4, the Zener diode ZD2b in the feedback loop becomes conductive before the feedback voltage carried across the secondary winding W2b of the feedback transformer T1 reaches its peak, limiting the charging current to the capacitor C4b. This suppresses the increase in oscillation frequency.

Also, at this time, a high frequency voltage (hereinafter referred to as secondary voltage) generated across the capacitor C1 due to the resonance of the above-mentioned resonance system is applied to the series circuit of the lamps F1 and F2. Since the high frequency current is bypassed by C2, the applied voltage is low, and a correspondingly higher voltage is applied to the lamp F2.

In this state, filaments P11 and F22 of the fluorescent lamp
A filament current flows through the capacitor C1 to the filaments P12 and F21 through the secondary winding of the choke coil CH, and each of these filaments P11.
F12. F21. When F22 is sufficiently preheated, lamp F2 to which a higher voltage is applied starts discharging first. This lowers the impedance of the lamp F2, and a higher voltage is now applied to the lamp F1.

In the device shown in Fig. 4, when only this lamp F2 starts, the resonant frequency f2 becomes the resonant frequency f before starting the two lamps.
1/E7, which deviates from the output frequency FO of the inverter 4, and the above secondary voltage is 440 Hz before starting the two lamps.
There were cases where the lamp F1 did not start because sufficient starting voltage was not applied to the lamp F1 because the voltage dropped by 45% from V to 240V.

However, in the device shown in Figure 1, the resonant frequency f1 before the two lamps F1°F2 start together is approximately 1/2
]-, and the resonant frequency f2 after starting one lamp F2
is approximately 1/2π 1+G. Therefore, the capacitance of the sequence capacitor C2 is set to, for example, C2=0. ICI
Then, fl /f2 = 1 / m = 0.95, and the decrease in secondary voltage is several percent. In other words, the capacitance of capacitor C2 is set to C2≦0. If ICI is selected, the drop in secondary voltage will be less than a few percent, which will cause no practical problems.

FIG. 3 shows another embodiment of the invention. Same figure.

The apparatus shown in FIG. 1 includes a common filament P12 . Preheating power for the filament P12. Preheating power for F21 is supplied from the secondary winding of this transformer CT. Since the choke coil CH has a large capacity 1t (VA), if we insulate it and install a secondary winding on it, the choke coil CH will become larger or the loss will increase, but as shown in Figure 3. By separately providing a transformer for filament power supply, the overall shape can be made smaller or loss can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to one embodiment of the present invention, FIG. 2 is a circuit diagram of a discharge lamp lighting device according to another embodiment of the present invention, and FIG. 3 is a circuit diagram of a discharge lamp lighting device according to another embodiment of the present invention. FIG. 4 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 4 is a circuit diagram of a conventional discharge lamp lighting device. Lamp, CH...Choke coil, C1...Resonance capacitor, C2...Sequence capacitor, CT...Current transformer.

Claims (1)

[Claims] 1. The discharge lamps are connected in series and a high frequency voltage is applied between two non-common electrodes located at both ends of the series circuit through a ballast inductor. A series lighting type discharge lamp lighting device, characterized in that a resonant capacitor is connected between the non-common electrodes for applying high voltage to the discharge lamp in cooperation with the inductor when starting the discharge lamp. Discharge lamp lighting device. 2. The discharge lamp according to claim 1, wherein the high frequency voltage is connected between each one terminal of a preheating filament that also serves as the non-common electrode, and the capacitor is connected between each other terminal of the filament. lighting device. 3. The discharge lamp lighting device according to claim 1 or 2, wherein the number of discharge lamps is two. 4. The discharge lamp lighting device according to claim 3, wherein a sequence capacitor having a capacity of 1/10 or less of the capacity of the resonance capacitor is connected between both electrodes of one of the two discharge lamps. . 5. A secondary winding is provided in the ballast inductor, and the ballast inductor is provided with a secondary winding.
5. The discharge lamp lighting device according to claim 3, wherein electric power for preheating the filament of the common side electrode of the discharge lamp is supplied from the secondary winding. 6. A current transformer is connected in series with the resonance capacitor, and power for preheating the filament of the common side electrode of the two discharge lamps is supplied from the secondary side of the current transformer. The discharge lamp lighting device described.