JPH04154095A - Discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To perform high accurate control of an output level of dimming light by providing AC and DC lighting circuits in a discharge lamp, and variably generating a DC current, flowing in the discharge lamp, to control a beam of light generated by the discharge lamp. CONSTITUTION:An AC power supply AC is connected to a discharge lamp 1 through a ballast, formed of an inductance element L1, to form an AC lighting circuit. A variable DC power supply 4 is connected to the discharge lamp 1 through a series circuit of an AC current impeding inductance L2 and diode D1 to form a DC lighting circuit. In main lighting, a lamp current, limited by the inductance element L1, is allowed to flow in the discharge lamp 1 from the AC power supply AC to perform AC lighting. On the other hand, in dimming light of the discharge lamp 1, a DC current is variably generated to flow in the discharge lamp 1 from the variable DC power supply 4. In this way, change width of the lamp current is decreased in the case of changing DC voltage only for a unit time, and consequently, also a change amount of light output is decreased to make the light output high accurately controllable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device that performs dimming control of a discharge lamp.

[Prior Art] As shown in FIG. 7, a discharge lamp lighting device that controls dimming of a discharge lamp uses a triac to input power from an AC power supply AC to a ballast 2 that constitutes an AC lighting circuit that lights the discharge lamp 1. Q
0 and a trigger circuit TR, and as shown in FIG. , or insert the ninth
As shown in the figure, variable impedance elements CH2 consisting of saturable reactors are inserted in parallel, and the impedance of these variable impedance elements CH, CH2 is changed by the dimming controller 3', thereby controlling the power to the discharge lamp 1. Is there a device to control it?

The transformer Tr shown in FIGS. 8 and 9 is a transformer for preheating the discharge lamp 1. Further, CH1 in FIG. 9 is an inductance element that prevents a current exceeding a certain level from flowing.

In addition to the above devices, there is a device for varying the frequency of the alternating current power supply AC to the discharge lamp 1, as shown in Japanese Patent Laid-Open No. 61-69377. That is, as shown in FIG. 10, the inductance of the ballast inductance element CH0 inserted between the alternating current power supply AC and the discharge lamp 1. Finally, if the frequency of the AC power supply AC is f, the impedance Z at the inductance element CH is Z = j 2πfL, and when the frequency of the AC power supply AC is increased, the impedance Z increases and the impedance Z to the discharge lamp 1, which is the load, becomes larger. power decreases. At this time, power is given as preheating power to the filament of the discharge lamp 1 either at a constant level or in accordance with the degree of dimming.

Other devices include a method of varying the amplitude of the voltage applied to the discharge lamp 1, and a method of controlling power by periodically cutting power.

[Problem M to be solved by the invention] By the way, in a discharge lamp lighting device using any of the above-mentioned dimming control methods, a deep dimming level (dimming control in which the luminance of the discharge lamp P is low and dark) is not possible. There was a problem in that it was difficult to control the dimming with high precision. Even if highly accurate dimming settings could be made, a very complicated circuit would be required to correct and control the light output. Furthermore, the human eye is sensitive to differences in luminous flux at deep dimming levels. For example, assuming that the luminous flux of the discharge lamp 1 when lit is 100, it is possible to recognize the difference in brightness between a luminous flux ratio of 5% and a luminous flux ratio of 6%. This is because, for example, at a shallow dimming level with a luminous flux ratio of 80% (discharge lamp l has high brightness and bright dimming mode vA), even if the luminous flux ratio varies by 1%, the variation is relatively small. This is because it is difficult for the human eye to perceive brightness9, but at deep dimming levels, even if the variation is the same, the variation is relatively large, making it possible to clearly perceive differences in brightness. According to experiments conducted by the inventors of the present invention, it has been found that differences in brightness can be recognized when the luminous flux ratio is 20% or less.

In other words, with each of the above-mentioned conventional spotlight control methods, it is difficult to control the dimming output level (light output level) with high precision at a deep dimming level.

The present invention has been made in view of the above points, and an object thereof is to provide a discharge lamp lighting device that can control the dimming output level with high precision at a deep dimming level. .

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention includes an AC lighting circuit for lighting a discharge lamp with an AC current, and a DC lighting circuit for lighting the discharge lamp with a DC current. The discharge lamp is equipped with a direct current control means for controlling the luminous flux emitted by the discharge lamp by varying the direct current flowing through the discharge lamp.

[Function] According to the discharge lamp lighting device of the present invention, the luminous flux of the discharge lamp can be slightly changed by simply varying the DC current flowing through the discharge lamp by the DC lighting circuit using the DC current control means, and therefore deep dimming is possible. The dimming output level can be controlled with high precision.

[Example] The present invention will be explained below with reference to Examples.

Figure 1 shows the circuit configuration of Example 1, in which a discharge lamp 1 is connected to an AC power source AC via a ballast consisting of an inductance element, and an AC lighting circuit is formed. A variable DC power supply 4 is connected to the discharge lamp 1 through a series circuit of an inductance element L2 and a diode D1 for blocking AC current to form a DC lighting circuit, and these AC/DC lighting circuits are used to light the discharge lamp! Configure. Note that the starting circuit for the discharge lamp 1 is omitted to simplify the explanation, but it goes without saying that an appropriate starting circuit is provided.

Therefore, the main lighting in this embodiment is powered by an AC power source A such as a commercial power source.
AC lighting is performed by passing the lamp current limited by the inductance element C to the discharge lamp 1. The dimming of the discharge lamp 1 is performed by varying the DC current flowing from the variable DC power supply 4 to the discharge lamp 1. .

Here, the dimming ability by varying the DC current of the variable DC power supply 4 will be explained. First, the relationship between the light output and the lamp current is almost proportional, and when the voltage of the variable DC power supply 4 is changed by IV, the lamp current changes by about 4 mA assuming that the impedance of the discharge lamp 1 is about 250Ω. If the lamp current for AC lighting is about 400 mA, the light output can be changed by 1%. Since it is quite easy to control the voltage of the variable DC power supply 4 in units of 1 V, highly accurate optical output control is possible. In particular, when dimming is performed by reducing the lamp current caused by the alternating current flowing through the discharge lamp 1, the discharge lamp impedance increases significantly, so the range of change in lamp current when changing the variable DC voltage by a unit time becomes extremely small. Therefore, the amount of change in optical output is reduced, making it possible to control optical output with extremely high precision.

K Nose ■λ The first embodiment described above uses the variable DC power supply 4 so that the output can be controlled by the power supply itself, but in this embodiment, the DC power supply 4' is used as shown in FIG. A variable DC power supply 4 is constructed by inserting a variable impedance VR in series, and in this case, the DC current flowing to the discharge lamp 1 can be varied by varying the variable impedance VR.

In the above embodiments 1 and 2, an AC power source AC as a commercial power source and an inductance element are used in the AC lighting circuit, but in this embodiment, an inverter circuit 5 is used as shown in FIG. ing.

This embodiment circuit obtains a DC power source by rectifying and smoothing AC power (aAC), which is a commercial power source, using a full-wave rectifier DB and a smoothing capacitor C1, and uses the output of an inverter circuit 5 that operates using this DC power source as a power source to power a discharge lamp 1 at a frequency of 20 KHz. More than high frequency lighting. in! The circuit 5 uses a so-called series inverter in which MOS transistors Q, , Q are connected to both ends of a smoothing capacitor CI, and the MOS transistors Q, , Q2 are alternately switched by a control section 5a, which will be described later. It converts DC voltage into high frequency voltage and outputs it. Here, the discharge lamp 1 is a DC cut capacitor C2.
and an inductance element L1' to both ends of the MOS transistor Q2, and a capacitor C1 forming a series resonant circuit together with the inductance element is connected in parallel to both ends of the discharge lamp 1.

That is, a high voltage generated across the capacitor C3 of the series resonant circuit that resonates with the output of the inverter circuit 5 is applied to the discharge lamp 1 to start and light the discharge lamp 1.

Note that the capacitor C0 also serves to preheat the discharge lamp 1.

The control unit 5a that controls the inverter circuit 5 is a switching regulator IC [μPC494
C manufactured by NEC Corporation] 6 and a high voltage bridge drive IC (manufactured by IR211OIR) 7, terminals a to C are connected to terminals a to c of the circuit in Figure 3. . IC6 oscillates at a frequency determined by resistor R1 and capacitor C6 and a duty ratio determined by the voltage division ratio of resistors R2 and R3, and IC7 outputs a signal with the same waveform as the input signal with an isolation voltage of 500V between the signals. It is something. In other words, this control section 5a is a MOS transistor Q.
. Note that the circuit consisting of diode D2, capacitor C2, and resistor R6 of IC7 is a bootstrap circuit, and terminal a on the high potential side MOS) transistor Q side.
It creates the output of

In this way, in this embodiment, the main lamp current of the discharge lamp 1 is obtained from the inverter circuit 5, which is a high frequency power source.

In addition, the DC lighting circuit has a DC component cutting capacitor C in the high frequency rectangular wave part where the output of the inverter circuit 5 is a rectangular wave.
A transformer T r 1 whose primary side is connected via 4,
A full-wave rectifier DB2 connected to the secondary side of the transformer T r via a saturable reactor L3, and a full-wave rectifier DB2.
Using a variable DC power supply 4 composed of a capacitor C3 that smoothes the rectified flow of the variable DC power supply 4, the DC flow of the variable DC power supply 4 is connected to a discharge lamp via an inductance element L2 for blocking high frequency current and a diode D1. 1.

By controlling the saturable reactor L3, the voltage generated by the variable DC power supply 4 can be varied. For example, by increasing the inductance value of the saturable reactor L3, the DC current flowing through the discharge lamp 1 can be reduced, and vice versa. By reducing the inductance value, the direct current flowing through the discharge lamp 1 can be increased, and the discharge lamp 1 can be controlled to dim.

Limitation 1 - As shown in FIG. 5, the DC lighting circuit of this embodiment includes a step-down transformer Tr2 that steps down the AC power supply AC, which is a commercial power source, a full-wave rectifier DB, a smoothing capacitor C8, and a step-down transformer T. Three taps t provided on the secondary side of r2. ~
Tap 1 in t2. , 12 to change the secondary output voltage input to the full-wave rectifier D Bi.The variable DC power source 4 is configured with a changeover switch S1 that changes the secondary output voltage input to the full-wave rectifier DBi by switching the changeover switch S1. It is possible to switch in stages. The DC output of the variable DC power supply 4 is applied to the discharge lamp 1 via an inductance element L2 for blocking high frequency current and a diode D1.

In this embodiment, tap the selector switch S.
When switched to the upper tap side, the discharge lamp 1 is dimmed, and when switched to the upper tap 2 side, the discharge lamp 1 is dimmed brightly.

Note that the control section 5a of the inverter circuit 5 of this embodiment pA4 is the sixth
As shown in the figure, basically the same circuit as the control section 5a of the third embodiment is used. However, a variable resistor R1° is used as a resistor to determine the oscillation frequency of IC6, and by changing this resistance value, the oscillation frequency of the inverter circuit 5 is changed, and when the resistance value is increased, the frequency is lowered. For slow phase lighting, the optical output can be increased, and by decreasing the resistance value, the frequency can be increased and the optical output can be decreased.

As described above, the AC lighting circuit of the discharge lamp lighting device of the present invention may be a lighting circuit using a commercial power source or a lighting circuit using a high frequency power source, and even if the AC lighting circuit itself cannot perform dimming, it may be a lighting circuit using a commercial power source or a lighting circuit using a high frequency power source. It does not matter at all if it is capable of dimming or continuous dimming, and the method of making the DC power supply is not limited to the embodiments. In other words, the present invention includes anything that includes an AC lighting circuit and a DC lighting circuit, and can change the luminous flux by changing the DC flowing from the DC power source of the DC lighting circuit to the discharge lamp 1.

[Effects of the Invention] The present invention includes an AC lighting circuit that lights a discharge lamp with an AC current, and a DC lighting circuit that lights the discharge lamp with a DC current, and
Since the DC current control means is provided for controlling the luminous flux emitted by the discharge lamp by varying the DC current flowing through the discharge lamp, the DC current control means is configured to vary the DC current flowing through the discharge lamp by the DC lighting circuit, The luminous flux of the discharge lamp can be slightly changed, and therefore the dimming output level can be controlled with high precision at a deep dimming level.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of Embodiment 1 of the present invention, Fig. 2 is a circuit diagram of Embodiment 2 of the present invention, Fig. 3 is a circuit diagram of Embodiment 3 of the present invention, and Fig. 4 is the inverter circuit of the same as above. 5 is a circuit diagram of the fourth embodiment of the present invention, FIG. 6 is a circuit diagram of the control section of the same inverter circuit, and FIGS. 7 to 10 are circuit diagrams of conventional examples, respectively. It is. 1 is a discharge lamp, 4 is a variable DC power supply, 5 is an inverter circuit,
L is an inductance element, and AC is an alternating current power source. Agent Patent Attorney Ishi 1) Chief 71 is a discharge lamp 1 is a discharge lamp 4 is a variable DC power supply Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] (1) An AC lighting circuit that lights a discharge lamp with an AC current, and a DC lighting circuit that lights the discharge lamp with a DC current, and a DC current that controls the luminous flux emitted by the discharge lamp by varying the DC current flowing through the discharge lamp. A discharge lamp lighting device characterized by comprising a control means.