JPS60119098A - 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] [Technical Field of the Invention] , / This invention provides a starting auxiliary circuit unit that generates a high voltage for starting assistance to facilitate the transition from glow discharge to arc discharge in a discharge lamp. A main circuit section that supplies power to maintain the arc discharge in the discharge lamp is provided, and the full-light lighting 1L
The present invention relates to a discharge lamp lighting device that can switch between IlIIIl and dimming lighting control.

[Technical Background of the Invention and Problems Therewith] Conventionally, in this type of discharge lamp lighting device, lamp power switching between full-light lighting control and dimming lighting control was performed only in the main circuit section. Figure 1 is a graph showing the relationship between the lamp current and lamp voltage, that is, the load characteristics, during full-light lighting and dimming lighting in a conventional circuit.The solid line graph in the figure shows the load characteristics during full-light lighting. The dotted line graph in the figure shows the load characteristics during dimmed lighting. As you will see, the full load characteristics are narrowed down during dimming.

However, unless the main circuit section has a sufficiently high secondary open circuit voltage with respect to the lamp voltage, there is a problem that the lamp voltage will rise during dimming, causing the lamp to turn off. This phenomenon was particularly noticeable in high-pressure discharge lamps. In order to prevent this turning off, in conventional circuits, the secondary open-circuit voltage is made sufficiently high, or the dimming ratio with respect to full-light lighting is made small so that the dimming does not occur too much. However, in order to make the secondary open-circuit voltage sufficiently high, circuit components with high withstand voltage must be used, and the circuit efficiency decreases due to the large difference between the open-circuit voltage and the lamp voltage when the lamp is lit. There were various problems such as decline. Furthermore, reducing the dimming ratio has the problem that the originally required dimming cannot be achieved sufficiently.

[Purpose of the Invention] This invention has been made to solve such problems, and even in high-pressure discharge lamps that can switch between full-light lighting control and dimming lighting control, there is a risk that the lamps will go out. An object of the present invention is to provide a discharge lamp lighting device which can perform stable dimming lighting control at a sufficient dimming rate without causing a drop in circuit efficiency.

[Summary of the Invention] This invention provides a starting auxiliary circuit unit that generates a high voltage for starting auxiliary power to facilitate the transition from glow discharge to arc discharge in a discharge lamp, and electric power for maintaining arc discharge in the discharge lamp. In a discharge lamp lighting device, which is equipped with a main circuit section that supplies the current, and is capable of switching between full-light lighting control and dimming lighting control, the current supplied from the starting auxiliary circuit section to the discharge lamp is adjusted compared to when full-light lighting is performed. The electric power supplied from the main circuit to the discharge lamp is increased when the light is turned on, and is decreased when the lamp is dimmed, compared to when the lamp is turned on at full brightness.

[Embodiments of the invention] An embodiment of the present invention will be described below with reference to the drawings.

As shown in Figure 2, one of the power transformers 2 is connected to the AC power supply 1.
The next winding 2p is connected. Both ends of the secondary winding 2S of the power transformer 2 are connected to each other via diodes 3.4, and a capacitor 5 is connected between the connection point and the intermediate tap t of the secondary winding 2S to generate a direct current. Configuring the power supply. A starting circuit 9 and a discharge lamp 10 are connected between both ends of the capacitor 5 via an NPN switching transistor 6, a choke coil 7, and a diode 8 in series to form a main circuit section A. Note that the main circuit section Δ
A diode 11 is connected in parallel to the capacitor 5 with the polarity shown through the transistor 6, and a capacitor 12 is further connected in parallel through the choke coil 7. The amount of current flowing through the main circuit section A is detected by a coil 13, and the transistor 6 is subjected to chopping control by a control circuit 14 that responds to the detection output from the coil 13. That is, the transistor 6, the coil 13, and the control circuit 14 constitute a chopper circuit. Further, a starting auxiliary circuit section B is connected between one end of the secondary winding 2S of the power transformer 2 and the intermediate tap t. The starting auxiliary circuit section B connects one end of the secondary winding 2S to a connection point between an anode of a diode 18 and a cathode of a diode 19 via an inductance coil 15, 16 in series and a capacitor 17. ing. Then, the cathode of the diode 18 is connected to one end of the output terminal of the main circuit section A to the discharge lamp 10,
The anode of the diode 19 is connected to the other end of the output terminal of the main circuit section A to the discharge lamp 10, and a capacitor 20 is connected between the cathode of the diode 18 and the anode of the diode 19. . Note that the diodes 18 and 19 and the capacitor 20 constitute a voltage doubler circuit. A changeover switch 21 for switching between full-light lighting and dimmed lighting is connected in parallel to the inductance coil 16 of the starting auxiliary circuit section B. The control circuit 14 performs chopping control on the transistor 6 so that the amount of current flowing through the main circuit section A during dim lighting is reduced compared to when full light is lit. Further, the changeover switch 21 is turned off when the entire light is on, and turned on when the light is dimmed.

In the device according to the embodiment of the present invention configured in this manner, the changeover switch 21 is turned off when all lights are turned on, so the inductance coil 16 is connected in series between the inductance coil 15 and the capacitor 17 in the starting auxiliary circuit section B. As a result, the current flowing through this circuit portion B is further limited and reduced. Therefore, the load characteristics caused by this starting auxiliary circuit section B are such that the lamp current is suppressed, as shown in the graph (a) in FIG. 3(a).

On the other hand, in the main circuit section A, the transistor 6 is subjected to chopping control by the control circuit 14, and a relatively large lamp current is supplied to the discharge lamp 10. The load characteristic at this time is the third
The result is as shown in the graph (b) in (a) of the figure. Therefore,
The overall load characteristics are as shown in FIG. 3(b), and the lamp current and lamp voltage when the lamp is turned on are approximately determined at the point x1.

In addition, since the changeover switch 21 is turned on during dimming lighting, the inductance coil 1 is turned on in the starting auxiliary circuit section B.
6 is short-circuited by the changeover switch 21, and the current flowing through this circuit section B increases. As a result, the load characteristic caused by this starting auxiliary circuit section B becomes a characteristic in which the lamp current increases compared to when the lamp is fully lit, as shown by the graph (c) in FIG. On the other hand, in the main circuit section, the transistor 6 is subjected to chopping control by the control circuit 14, and a lamp current reduced from that during full-light lighting is supplied to the discharge lamp 10. The load characteristics at this time are shown in graph (d) in FIG. 3(C).

Therefore, the overall load characteristic becomes as shown in FIG. 3(d), which is the stable point of 2 lamps when the lamp is turned on.

By controlling the lighting of the discharge lamp 10 during full-light lighting and dimming lighting in this way, the lamp voltage becomes extremely high during dimming lighting, and the lamp current becomes extremely small, causing the discharge lamp to go out. Never. Therefore, even if a high-voltage discharge lamp such as a high-pressure discharge lamp is used as a discharge lamp, stable dimming and lighting control can be performed. Moreover, the dimming ratio can be made sufficiently large. Furthermore, since there is no need to set the secondary open-circuit voltage high in the main circuit section A, there is no need to use circuit components with high breakdown voltages, and there is no risk of inconveniences such as a decrease in circuit efficiency.

Next, another embodiment of the invention will be described with reference to the drawings.

Note that the same parts as in the above embodiment are given the same reference numerals, and detailed explanations will be omitted.

As shown in FIG. 4, the inductance coil 15, 16 and changeover switch 21 are eliminated as the starting auxiliary circuit section B, and instead, the cathode of the diode 18 and one end of the output terminal of the main circuit section Δ to the discharge lamp 10 are connected. resistance 2 between
2.23 series circuits are inserted, and a changeover switch 24 for switching between full-light lighting and dimming lighting is connected in parallel to the resistor 23. In this case as well, the resistor 23 acts as a current-limiting impedance, so the lamp current supplied from the starting auxiliary circuit section B to the discharge lamp 10 increases or decreases by switching the changeover switch 24, and the same effect as in the previous embodiment can be obtained. It is something that can be done.

[Effects of the Invention] As described in detail above, according to the present invention, in a device that can switch between full-light lighting control and dimming lighting control, there is no risk of the lamp going out even if it is a high-pressure discharge lamp, and the lamp is sufficiently light. Therefore, it is possible to provide a discharge lamp lighting device that can perform stable dimming lighting control with a stable dimming rate and that does not cause a risk of deterioration in circuit efficiency.

[Brief explanation of the drawing]

Fig. 1 is a graph showing the load characteristics during conventional full-light lighting and dimmed lighting, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 3 is a graph showing the conventional load characteristics during full-light lighting. (a) is a graph showing the load characteristics of the starting auxiliary circuit section and the main circuit section when all lights are on, (b) is a graph showing the combined load characteristics, ( C) is a graph showing the load characteristics of the starting auxiliary circuit section and the main circuit section during dimmed lighting, (d) is a graph showing the combined load characteristics thereof, and FIG. 4 is a circuit diagram showing another embodiment of the present invention. It is. A... Main circuit section, B... Starting auxiliary circuit section, 6...
Switching transistor, 1Q...Discharge lamp, 14.
... Control circuit, 15.16 ... Inductance coil, 21 ... Changeover switch. Applicant's agent Patent attorney Takehiko Suzue Figure 3 ((,) (d) IL IL Figure 4

Claims (1)

[Claims] A starting auxiliary circuit unit that generates a high voltage for starting assistance to facilitate the transition from glow discharge to arc discharge in the discharge lamp, and a main circuit unit that supplies power to maintain arc discharge in the discharge lamp, In the discharge lamp lighting device capable of switching between full-light lighting control and dimming lighting control, the starting auxiliary circuit section increases the current supplied to the discharge lamp during dimming lighting compared to full-light lighting, and 1. A discharge lamp lighting device, wherein the circuit section reduces the power supplied to the discharge lamp during dim lighting compared to when full light is lit.