JPH0372200B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a discharge lamp lighting device that lights a discharge lamp at high frequency using an inverter output and also dims the discharge lamp in steps.

[Background technology]

Figure 1 shows an example of a conventional circuit, and Figure 2 is a circuit diagram of its main parts. In the figure, 1 is a commercial power supply, 2 is a rectifier bridge, and 3 is a smoothing capacitor. ing. B is a constant current type push-pull type inverter, which is composed of a choke coil 4, an output transformer 5 for oscillation, a capacitor 6, switching transistors 7 and 8, and base resistors 9 and 10. is an auxiliary power source consisting of a diode 11 and a capacitor 12, and its output drives the bases of the switching transistors 7 and 8, as well as a timer circuit 13 that controls a starting switch 26, which will be described later. 14 to 18 are preheating transformers each consisting of a current transformer, and these preheating transformers 14 to 18
The outputs a to e are the terminals a of the filaments of discharge lamps (hereinafter referred to as lamps) 22 to 25, which are fluorescent lamps.
- connected to e. Further, 19 is a light control coil provided as a dimming inductance, 20 is a noise prevention capacitor, 21 is a light control coil provided as a balancer, and 27 is a light control switch.

Thus, in the conventional example circuit shown in FIG. 1, when the commercial power supply 1 is turned on, the rectifier bridge 2 and the capacitor 3 form a DC power supply A, and the DC power supply A is formed by the rectifier bridge 2 and the capacitor 3, and the DC power supply A is formed by the rectifier bridge 2 and the capacitor 3. 6. Drives a constant current type push-pull type inverter consisting of switching transistors 7 and 8 and base resistors 9 and 10. Here, an auxiliary power source C consisting of a diode 11 and a capacitor 12 drives the bases of the switching transistors 7 and 8. The harmonic output of this inverter appears in the secondary winding of the output transformer 5, but for example, for one second after power is turned on, the timer circuit 13
When the starting switch 26 is turned on, the inverter output is supplied to the starting switch 26 and the circuit of the preheating transformers 14 to 18, and the lamp 2 connected to the secondary side of the preheating transformers 14 to 18 is supplied.
Preheat each filament from 2 to 25. here,
Since the preheating transformers 14 to 18 have relatively low impedance, when the starting switch 26 is turned on, no lighting voltage is applied to the lamps 22 to 25, and only preheating is performed. After about one second has elapsed, the starting switch 26 is turned off, and the high frequency output of the inverter is applied to the lamps 22 to 25, turning them on. In this case, when the dimming switch 27 is on the NC contact side, all lights are on,
When it is on the NO contact side, the light is dimmed. Note that during dimming lighting, current flows through the aforementioned preheating transformers 14 to 18, so the lamp filament is always preheated. Note that the capacitor 20 is a capacitor for reducing radiation noise during dimming lighting. By the way, as shown in Fig. 1, since a magnetic leakage type transformer is adopted as the output transformer 5 of the inverter, the leakage impedance inside the output transformer 5 becomes a current limiting element. It functions as a constant current type that keeps the output current approximately constant.
In order to achieve this purpose, the leakage impedance is set to be larger than the impedance of the chiyoke coil 19 and the preheating transformers 14 to 18, which are dimming inductances. Since the inverter is a constant current type, the current flowing to the starting switch 26 when the dimmer switch 27 is on the NC contact side and is fully lit is independent of the size of the dimmer inductance. It becomes almost constant.

FIG. 2 shows a circuit diagram of only the preheating circuit of the conventional circuit shown in FIG.
When turned on, the current flowing through the starting switch 26 is I ₀ , the current flowing through the primary side of the preheating transformers 14 to 18 is I ₁ , and the current flowing through the dimmer switch 27 is I ₂ , then the second The illustrated circuit operates as follows. That is, when the dimmer switch 27 is now on the NO contact side, I ₂ = 0, and with I ₀ = I ₁ , all the current flowing through the starting switch 26 flows into the preheating transformers 14 to 18 and preheats the filament, but the control When the light switch 27 is on the NC contact side, I ₁ = I ₀ - _{I 2} and the dimmer switch 27 is in NO mode.
The current flowing into the preheating transformers 14 to 18 is reduced compared to when it is on the contact side, and therefore the preheating current is also reduced. This means that the preheating current during dimming lighting is large and the preheating current during full lighting is small, which can be said to be preferable in consideration of dimming starting. however,
If the difference in preheating current becomes large, for example, if the preheating current during full lighting is designed to the optimum value, the preheating current during dimming will become too large, which will have a negative effect on lamp life, or conversely, when dimming will occur. If the preheating current is designed to be the optimum value at full lighting, the preheating current at full lighting is reduced, causing problems such as poor starting performance and the possibility of adversely affecting lamp life.

[Purpose of the invention]

The present invention provides a discharge lamp lighting device having means for lighting a discharge lamp at a high frequency using an inverter output and for stepwise dimming of the discharge lamp. It is an object of the present invention to provide a discharge lamp lighting device that compensates for current differences in a simple manner, improves lamp life, and further reduces radiation noise during dimming.

[Disclosure of the invention]

FIG. 3 shows an overall circuit diagram of an embodiment of the present invention, and FIG. 4 shows a circuit diagram of the same essential parts. In contrast to the circuit of the conventional example shown in FIG. The difference is that a capacitor 28 for current compensation and radiation noise reduction is connected. In the circuits shown in FIGS. 3 and 4, when the starting switch 26 is turned on, the current flowing through the starting switch 26 is I' ₀ and the current flowing through the primary side of the preheating transformers 14 to 18 is I' 0 . ' ₁ ,
Furthermore, if the current flowing through the dimmer switch 27 is I' ₂ , when the dimmer switch 27 is on the NO contact side, I' ₂ = 0, I' ₀ = I' ₁ , and the starting switch 26 All the current flowing through the preheating transformer 1
4 to 18 to preheat the filament,
When the dimming switch 27 is on the NC contact side, I' ₁
=I' ₀ -I' ₂ , and the current flowing into the preheating transformers 14 to 18 is reduced compared to when the dimmer switch 27 is on the NO contact side, and therefore the preheating current is also reduced. Comparing this with the conventional examples shown in Figs. 1 and 2, since the inverter is a constant current type, I ₀ ≒ I ₀ ' can be set, so when the dimming switch 27 is on the NC contact side, The current I′ ₁ becomes I′ ₁ 〓I ₁ (or I′ ₂ 〓I ₂ ). Therefore, various problems in the conventional example caused by the large preheating current during dim lighting and small preheating current during full lighting can be improved. In other words, if the capacitance value of the capacitor 28 is appropriately selected, the impedance of the parallel circuit of the chiyoke coil 19 and the capacitor 28 can be made larger than the impedance of the chiyoke coil 19 which is the dimming inductance, so naturally the current I' ₂ is Moreover, since the degree of this reduction is approximately determined by the capacity of the capacitor 28, it is possible to reduce the difference in the starting preheating current during dimming and during full lighting. On the other hand, after dimmed lighting, the starting switch 26 is off, the dimming switch 27 is on the NO contact side, and a capacitor 20 is connected between the secondary winding of the output transformer 5 via the NO contact of the dimming switch 27. is connected, which has the effect of reducing radiation noise due to harmonic components included in the output voltage of the output transformer 5, but as shown in Figs.
In the configuration of the present invention shown in the figure, a synergistic effect between the capacitor 20 and the capacitor 28 appears, making it possible to further reduce radiation noise. That is, in the dimming state, the output end of the output transformer 5 is connected to the lamps 22 to 25 and the balancer 2.
A chiyoke coil 19, which is a dimming inductance, and preheating transformers 14 to 18 are inserted in series with 1. In particular, the choke coil 19 has a relatively large impedance, and the current drop due to harmonic components contained in the lamp current becomes large, which becomes a source of radiation noise. Therefore, the capacitor 20 connected via the switch 27 reduces the harmonic components included in the output of the output transformer 5, and the capacitor 28 reduces the harmonic components included in the voltage drop across the choke coil 19. The effect can be obtained and radiation noise can be further reduced.

Since the present invention is configured as described above, in the conventional circuit, the starting preheating current in the dimming state is too large compared to the starting preheating current in the full lighting state, or the starting preheating current in the full lighting state is too large. We have investigated the negative effects on lamp life and startability that occur when the starting preheating current is too low compared to the starting preheating current in dimming mode.
In addition to having the effect of being able to be removed by simply adding one capacitor, it is also possible to further reduce radiation noise to a large extent during dimmed lighting.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 is a main circuit diagram of the same as above, Fig. 3 is a circuit diagram of an embodiment of the present invention, and Fig. 4 is a circuit diagram of a conventional example.
The figure is the main circuit diagram of the same as above, 1 is an AC power supply, 5
is an output transformer, 7 and 8 are switching transistors, 14 to 18 are preheating transformers, 19
is the chiyoke coil which is the inductance for dimming, 2
0 is a capacitor, 22 to 25 are lamps (discharge lamps), 26 is a starting switch, 27 is a dimming switch, and 28 is a capacitor.

Claims (1)

[Claims] 1 It has an inverter that obtains a substantially constant high-frequency output current from a DC power supply, and a discharge lamp, a dimming inductance, and a preheating transformer are connected between the output terminals of the inverter.
In a discharge lamp lighting device in which the secondary windings are connected in series in order and the secondary winding of the preheating transformer is connected to the filament of the discharge lamp, a starting switch is connected between both ends of the series circuit of the discharge lamp and the dimming inductance. and a first contact that shorts both ends of the series circuit between the primary winding of the preheating transformer and the dimming inductance in a fully lit state and opens in a dimmed lighting state, and a first contact that operates in conjunction with the first contact to dim. In the lighting state, a dimmer switch has a second contact that connects a first capacitor for reducing radiation noise between the output terminals of the inverter, and a second capacitor connected in parallel to the dimmer inductance. A discharge lamp lighting device comprising: