JPH01292796A - Electric discharge lamp lighting device - Google Patents

Abstract

PURPOSE:To make it possible to hold the brightness of an apparatus to almost a constant level even when the temperature of a lamp is altered by making output characteristics of a high frequency inverter cycle those of constant power. CONSTITUTION:A power AC is converted to dc voltage at a rectificational smoothing circuit 11 and is applied to a high-frequency inverter circuit, and then switching transistors 3, 5 being set on-off alternately by means of a switching pulse that is supplied by a drive control circuit 21, a high-frequency voltage is generated at each of a second coil of an inverter transformer 11, and finally an electric discharge lamp 17 is burnt. At this time a high-frequency inverter circuit whose output characteristics are made to be of constant power is used. Thereby, for example, when the lamp voltage is lowered due to the increasing temperature of a floodlight 17, the current running in the lamp 17 is increased and the power supply thereto is sure to be decreased, thus the desired brightness is guaranteed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device that can ensure substantially constant brightness regardless of changes in lamp temperature.

[Prior Art] Conventionally, in a discharge lamp lighting device that lights a discharge lamp such as a fluorescent lamp using a high-frequency inverter circuit, the current flowing through the lamp load and the voltage of the lamp load are detected separately. By separately feeding back these load currents and load voltages, the current and voltage flowing through the lamp load are controlled so that they do not rise above predetermined values. For this reason, in conventional discharge lamp lighting devices, as shown in Figure 4, for example, the load curve becomes constant voltage when the current is below a predetermined value, and becomes constant current when the load voltage is below the predetermined value. It had become.

[Problems to be Solved by the Invention] However, in such a conventional discharge lamp lighting device, when the temperature of the lamp changes depending on the type of lighting equipment to be connected or the usage conditions of the lighting equipment, the problem occurs due to the temperature change. There was an inconvenience that the brightness changed accordingly. That is, for example, if the operating point is A when a lighting fixture with an open bottom is used as shown in Fig. 4, the temperature of the lamp will rise and the lamp voltage will drop if a fixture with louvers is used. Therefore, the operating point is, for example, point B.

Therefore, in the case of a louvered fixture, the electric power applied to the lamp is small, resulting in a reduction in illuminance. Also,
The lamp temperature changes not only depending on the type of lighting equipment, but also, for example, the installation environment of the equipment or the time of use of the equipment. Therefore, with conventional discharge lamp lighting devices, it is difficult to ensure a constant brightness. was difficult.

In view of the problems in conventional devices, an object of the present invention is to provide a discharge lamp lighting device that can ensure a predetermined illuminance regardless of changes in lamp temperature caused by the type or structure of the lighting fixture or other factors. Our goal is to provide the following.

[Means for Solving the Problems] In order to achieve the above-mentioned object, a high frequency inverter circuit with constant power output characteristics is used in a discharge lamp lighting device according to a first aspect of the present invention.

Further, a discharge lamp lighting device according to a second aspect of the present invention includes a high-frequency inverter circuit, voltage detection means for detecting a load voltage output from the high-frequency inverter circuit, and a load current output from the high-frequency inverter circuit. , an adder circuit that adds the outputs of the voltage detecting means and the output of the current detecting means, and a control circuit that feedback-controls the output of the high-frequency inverter circuit based on the output of the adder circuit. are doing.

Further, in the discharge lamp lighting device according to the third aspect of the present invention, there is provided a high frequency inverter circuit including a switching element, an inverter transformer, and a resonant capacitor, and a first primary circuit through which a load current of the high frequency inverter circuit flows. A current transformer having a winding and a second primary winding through which a resonant current of the resonant capacitor flows, and a control circuit for feedback controlling the output of the high frequency inverter circuit based on the output of the current transformer are used. Ru.

[Function] In the above-described first aspect of the discharge lamp lighting device according to the present invention, the output characteristics of the high-frequency inverter circuit are substantially constant power characteristics, so that, for example, when the lamp voltage decreases due to an increase in the temperature of the illumination lamp. In this case, the current flowing through the lamp increases, thus ensuring a reduction in the power supplied to the lamp and ensuring the desired brightness.

Further, in the second aspect described above, the signal corresponding to the load current detected by the current detection means and the signal corresponding to the load voltage detected by the voltage detection means are added to generate the control signal for feedback control. Since the load current is generated, the load current is controlled to increase when the load voltage decreases, and conversely, the load current is controlled to decrease when the load voltage increases. Therefore, the power supplied to the lamp is made uniform regardless of changes in lamp temperature, and the output illuminance is maintained substantially constant.

Furthermore, in the third aspect, a current transformer having two primary windings is used, the load current of the high frequency inverter circuit flows through the first primary winding of the current transformer, and the load current of the high frequency inverter circuit flows through the first primary winding of the current transformer. The primary winding is configured so that the resonant current of the resonant capacitor flows. Since the resonant current of the resonant capacitor is proportional to the load voltage, the current transformer ultimately provides a signal that is the sum of the signal values corresponding to the load current and load voltage of the illumination lamp.

Therefore, by feedback-controlling the output of the two front high-frequency inverter circuits using the output signal of this current transformer, a discharge lamp lighting device having substantially low power output characteristics can be realized.

[Example] Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a load curve representing the output characteristics of a discharge lamp lighting device according to an embodiment of the present invention. As is clear from the figure, in the present invention, at least a portion of the load curve is configured to have constant power, and the operating point of the device is located in this constant power portion. With this configuration, for example, even if the lamp voltage decreases due to a rise in lamp temperature and the operating point moves from point A to point B,
Since the lamp current increases as the lamp voltage decreases, a decrease in the power supplied to the lamp is prevented and a constant brightness can be ensured. In other words, for example, when a lamp is mounted in a lighting fixture with a louver, the temperature of the lamp is 5 to 10 degrees Celsius higher than that of an open-bottom fixture, resulting in a decrease in the luminous efficiency of the lamp. This reduction in luminous efficiency can be compensated for by a corresponding increase in lamp current.

FIG. 2 schematically shows a discharge lamp lighting device according to an embodiment of the present invention. The device shown in the figure includes a rectifying and smoothing circuit 1 powered by an AC power source, a high-frequency inverter circuit composed of a switching transistor 3.5, a capacitor 7.9, an inverter transformer 11, etc., and a resonance capacitor 13.
, a current transformer 15, a discharge lamp 17, for example a fluorescent lamp.
, an adder 19, and a drive control circuit 21.

Switching transistors 3, 5 and capacitor 7.
9 are connected in series between the DC output terminals of the rectifying and smoothing circuit 1, and the connection points of the switching transistors 3 and 5 and the connection points of the capacitors 7 and 9 are connected to the primary coil of the inverter transformer 11, forming a so-called half-bridge type. It constitutes an inverter. Inverter transformer 1
A resonance capacitor 13 is connected to both ends of the secondary coil N2 of 1, and power for lighting the discharge lamp 17 is taken out from both ends. Further, a current transformer (CT) 15 is inserted in a circuit extending from one end T1 of the secondary coil N2 to one electrode of the discharge lamp 17, and the output of this current transformer 15 is input to an adder 19. Further, the other input of the adder 19 is connected to the other two inputs of the inverter transformer 11.
The next coil N4 is connected. Winding N5 is used to control the no-load secondary voltage constant. The output of the adder 19 is supplied as a control signal to the drive control circuit 21, and the output of the secondary coil N6 of the inverter transformer 11 is used to obtain power for operating the drive control circuit 21.

In the device shown in FIG. 2, an alternating current power source AC, such as a commercial power source, is converted into a direct current voltage in a rectifying and smoothing circuit 11 and applied to a high frequency inverter circuit.

Then, the switching transistors 3.5 are alternately turned on and off by the switching pulses supplied from the drive control circuit 21, and a high frequency voltage is generated in each secondary coil of the inverter transformer 11.

As a result, the discharge lamp 17 is turned on as is well known.

In such an operation, two of the inverter transformers 11
A load current flowing from one end T1 of the secondary coil N2 to the discharge lamp 17 is detected by the current transformer 15, and a signal corresponding to the load current is applied to one input of the adder 19.

Further, a signal corresponding to the load voltage of the high frequency inverter circuit is taken out from the secondary coil N4 and applied to the other input of the adder 19. That is, the output of the adder 19 is a signal obtained by adding signals corresponding to the load current and load voltage of the high frequency inverter circuit, and this signal causes the drive control circuit 2
1 controls the switching frequencies of the switching transistors 3 and 5 to corresponding values, for example. Thus, for example, when the output voltage of the high frequency inverter circuit decreases, the output current is controlled to increase, and conversely, when the output voltage increases, the output current is controlled to decrease.

That is, according to the circuit shown in FIG. 2, a device having pseudo-low current characteristics is realized.

FIG. 3 schematically shows a discharge lamp lighting device according to another embodiment of the present invention. In the device shown in the figure, two primary coils Pi are used instead of the current transformer 15 in the device shown in FIG.
A current transformer 23 with P2 is used and the adder 19 in the device of FIG. 2 is omitted. One end of the primary coil P1 of the current transformer 23 is connected to one end of the resonance capacitor 13, and the other end of the primary coil P1 is connected to one end of the secondary coil N2 of the inverter transformer 25 together with one end of the other primary coil P2. It is connected to the output terminal T1. Further, the other end of the primary coil P2 is connected to one electrode of the discharge lamp 17.

Furthermore, in the device shown in FIG. 3, no adder is used, and the output of the secondary coil S1 of the current transformer 23 is directly input to the drive control circuit 21 as a control signal. Other parts are the same as the device of FIG. 2 and are designated by the same reference numerals and symbols.

In the device shown in FIG. 3, similarly to the device shown in FIG. 2, the switching transistors 3 and 5 are turned on and off alternately by a switching signal from the drive control circuit 21 to generate high-frequency power and light the discharge lamp 17. . In this case, a resonant current flowing through the resonance capacitor 13 flows through the primary coil P1 of the current transformer 23, and a load current supplied to the discharge lamp 17 flows through the other primary coil P2.

The magnitude of the resonant current of the resonant capacitor 13 is the same as that of the discharge lamp 17.
Since the voltage is approximately proportional to the load voltage supplied to the secondary coil S1 of the current transformer 23, each of these primary coils Pi, P
A signal corresponding to the sum of the two currents is output. Therefore, by using the signal output from the secondary coil S1 as a control signal to perform feedback control of the high frequency inverter circuit, it is possible to make the output characteristics of the inverter circuit roughly constant power characteristics as described above. can.

That is, according to the circuit shown in FIG. 3, constant power characteristics can be obtained with an extremely simple configuration without using an adder or the like.

[Effects of the Invention] As described above, according to the present invention, by making the output characteristics of the high frequency inverter circuit constant power characteristics, even if the lamp temperature changes depending on the type of lighting equipment, the usage environment of the lighting equipment, etc. It also becomes possible to maintain the brightness of the fixture at a substantially constant value. Particularly in high-output lighting devices, where the temperature of the lamp increases significantly, the use of the device according to the present invention can provide extremely significant effects. Furthermore, even if the equivalent impedance of the discharge lamp increases at the end of its lamp life, the lighting device will not be overpowered, thus improving the reliability of the device.

[Brief explanation of the drawing]

FIG. 1 shows one of the output characteristics of the discharge lamp lighting device according to the present invention.
Graphs showing examples; FIGS. 2 and 3 are block circuit diagrams schematically showing a discharge lamp lighting device according to an embodiment of the present invention, and FIG. 4 shows output characteristics of a conventional discharge lamp lighting device. This is a graph showing. 1: Rectifier and smoothing circuit, 3.5; Switching transistor, 7.9; Capacitor, 11.25; Inverter transformer, 13; Resonant capacitor, 15.23; Current transformer, 17; Discharge lamp, 19; Adder, 21 ; Drive side circuit, AC, AC power supply, Nl, N6. PI, P2. Primary coil, N2. N3. N
4. N5. SL, secondary coil, T1 one terminal.

Claims (1)

[Scope of Claims] 1. A discharge lamp lighting device comprising a high frequency inverter circuit for generating high frequency power for lighting a discharge lamp, the high frequency inverter circuit having substantially constant power output characteristics. 2. A high-frequency inverter circuit for generating high-frequency power for lighting a discharge lamp, voltage detection means for detecting the voltage supplied from the high-frequency inverter circuit to a load circuit, and voltage detection means for detecting the voltage supplied from the high-frequency inverter circuit to the load circuit. Current detection means for detecting current, an addition circuit for adding the output of the current detection means and the output of the voltage detection means, and control for feedback-controlling the output of the high frequency inverter circuit based on the output of the addition circuit. A discharge lamp lighting device characterized by comprising a circuit. 3. A high-frequency inverter circuit including a switching element, an inverter transformer, and a resonant capacitor, a first primary winding through which the load current of the high-frequency inverter circuit flows, and a second primary winding through which the resonant current of the resonant capacitor flows. 1. A discharge lamp lighting device comprising: a current transformer having a wire; and a control circuit for feedback controlling the output of the high frequency inverter circuit based on the output of the current transformer.