JPH0463519B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION FIELD OF INDUSTRIAL APPLICATION The present invention relates to a device for starting and lighting a discharge lamp.

Prior Art A circuit diagram of a conventional discharge lamp lighting device is shown in FIG.

In FIG. 3, 1 is an AC power supply, and 7 is a DC power supply, which is composed of diodes 2, 3, 4, and 5 and a capacitor 6, and receives the output of the AC power supply 1, rectifies it, and outputs DC. 8 is a high-pressure sodium lamp that is a discharge lamp; 14 is a step-down chopper power circuit, which is an inductance element including a transformer 9, a diode 10, a capacitor 11, and a resistor 1;
2 and a transistor 13, which is a switching element with a control terminal, one end of which is connected to a transformer 9. When the transistor 13 is on, current flows through the high-pressure sodium lamp 8 through the transformer 9, and when the transistor 13 is off, current flows through the transformer 9. The stored electromagnetic energy is passed through the diode 10 to the high-pressure sodium lamp 8, and the lamp is lit with direct current. Capacitor 11 smoothes the lamp voltage, and resistor 12 limits the base current from secondary winding 9a of transformer 9 to transistor 13. Reference numeral 20 denotes a resistor serving as a current detection means, which generates a voltage proportional to the lamp current across its ends. Reference numeral 24 denotes a voltage detection means, which is composed of a resistor 25 and a transistor 26 whose terminal is connected to the resistor 25.
A ramp voltage is applied between the opposite side of the transistor 5 and the base of the transistor 26. Therefore, resistance 25
A voltage approximately equal to the lamp voltage is applied to the transistor 26 , and a current approximately proportional to the lamp voltage limited by the resistor 25 is output from the collector of the transistor 26 to the calculation means 21 . The calculating means 21 includes resistors 15, 16, 17 and a resistor 2 which is a current detecting means.
0, an operational amplifier 18, and a voltage reference device 19. A current proportional to the lamp voltage output from the voltage detection means 24 flows through resistors 15, 16, 1.
7 and 20, and a voltage proportional to the lamp voltage is generated across the resistor 15. This resistance 15
The sum of the voltages generated across the resistors 20 of the current detecting means and the voltages generated across the respective resistors 20 of the current detecting means corresponds to the voltage obtained by multiplying each of the lamp voltage and lamp current by a predetermined coefficient and then adding them together. This voltage is divided by resistors 16 and 17,
The output of the voltage reference device 19 is input to the non-inverting terminal of the operational amplifier 18, and is compared with the non-inverting terminal input.If the non-inverting terminal input exceeds a certain value, , operational amplifier 18
Output the signal from the output terminal. Reference numeral 22 denotes a control transistor, which is turned on and off by inputting the output signal of the calculation means 21. Reference numeral 23 denotes a control circuit consisting of an arithmetic means 21 and a transistor 22 for control means, and uses the collector of the transistor 22 as an output terminal to short-circuit the base and emitter of the transistor 13 to turn the transistor 13 on and off.

With the above structure, the lamp voltage and lamp current are detected by the voltage detecting means 24 and the current detecting means 20, and compared with a constant voltage by the calculating means 21, the lamp voltage and the lamp current are determined by a predetermined coefficient. When the addition result after multiplying exceeds a certain value, transistor 22 is turned on and transistor 13 is turned off. In this way, by controlling the transistor 13 on and off so that the addition result becomes a constant value, the high-pressure sodium lamp 8 can be lit with direct current while reducing variations in individual color temperatures.

Problems to be Solved by the Invention In such a conventional lighting device, first, when starting the discharge lamp, when a starting voltage is applied to the discharge lamp, the discharge lamp breaks down and almost simultaneously shifts to arc discharge. . At this time, immediately after the transition to arc discharge, the vapor pressure in the arc tube of the high-pressure sodium lamp is low and the lamp voltage drops rapidly. Thereafter, the lamp voltage remains low for a while until the vapor pressure within the arc tube rises. In the discharge lamp lighting device shown in Fig. 3, the transistor
3 on/off control. Therefore, at this starting time when the lamp voltage is lower than the lighting characteristics during predetermined steady lighting, the transistor 13 is controlled to cause a very large lamp current to flow so as to bring the characteristics to the predetermined characteristics. As a result, an excessive load is applied to the electrodes and arc tube of the high-pressure sodium lamp 8, shortening its life and deteriorating the movement characteristics.
The circuit elements of discharge lamp lighting equipment have large ratings and are expensive, and the lamp may suddenly change or
There was a problem that circuit elements could be destroyed due to abnormalities. Furthermore, in the case of a self-excited step-down chopper, there is a characteristic that as the load voltage, that is, the lamp voltage of the high-pressure sodium lamp 8 decreases, the on-time ratio of the transistor 13 decreases. Therefore, if the lamp current is controlled to increase in response to a decrease in the lamp voltage, the on-time of the transistor 13 will be gradually increased, and the oscillation frequency of the circuit will decrease significantly, causing a drop in the audible frequency band. There was also the problem of noise generation. The shaded area in FIG. 2 shows the area where the relationship between lamp voltage and lamp current corresponding to audible audio frequencies was experimentally determined.
To improve the above problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 55-25980, constant lamp current control is performed using a step-down chopper so that the lamp current remains below the rated lamp current even during startup, and the current detection resistor is There is an example of applying negative thermal feedback as a thermal saaster.
This method has problems in that it takes a long time to start up and is not suitable for accurate circuits.

Means for Solving the Problems In order to solve the problems described above, the present invention provides a power supply whose output voltage has a constant polarity, a discharge lamp that is a high-pressure sodium lamp, a metal halide lamp, or a high-pressure mercury lamp, and an output of the power supply. a power circuit connected between an end of the discharge lamp and the discharge lamp, the power circuit having at least an inductance element and a switching element with a control terminal, and supplying power to the discharge lamp by turning on and off the switching element; a voltage detection means for outputting a voltage signal proportional to the voltage; a current detection means for outputting a current signal proportional to the lamp current of the discharge lamp; and a control signal for inputting the voltage signal and the current signal to the power circuit. control means for controlling the lamp current in accordance with the lamp voltage by outputting the voltage signal and controlling switching, the control means inputting the voltage signal and the current signal, The first
a second control signal which inputs the voltage signal and the current signal, and outputs a second control signal such that the lamp current is decreased as the lamp voltage is higher than the predetermined lamp voltage; and a calculation means C that outputs a control signal obtained by adding the first control signal and the second control signal to the power circuit. This is a discharge lamp lighting device that controls the lamp current so that it is proportional to the lamp voltage at lamp voltages that are lower than the lamp voltage, and that the lamp current decreases as the lamp voltage increases at lamp voltages that are higher than the predetermined lamp voltage.

Effects According to the present invention, the lamp can be lit with a lamp current proportional to the lamp voltage when the lamp voltage is lower than a predetermined voltage lower than that during steady lighting.

Embodiment FIG. 1 is a circuit diagram showing an embodiment of the lighting device of the present invention, and FIG. 2 shows a lamp current-voltage characteristic diagram of the lighting device of the present invention. In FIG. 1, 1 to 14 are the same as the conventional example shown in FIG. 3, and a step-down chopper type DC power source 7 is used which rectifies and smoothes the voltage of the AC power source 1 and whose output voltage has a constant polarity. DC voltage is supplied to the power circuit 14, and the transistor 13 is turned on and off so that the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient by the control circuit 46 becomes a constant value.
By performing off control, as shown in Fig. 2, the high-pressure sodium discharge lamp 8 has a predetermined characteristic that the higher the lamp voltage is, the lower the lamp current is, at least when the discharge lamp is rated, and the color of each discharge lamp is changed. This allows direct current lighting with reduced temperature variations.

The difference from the conventional discharge lamp lighting device is the voltage detection means 30 and the control circuit 46. In the voltage detection means 30, 31 is a resistor, 32 is a resistor 31
It is a transistor with 33 connected to the emitter.
is a resistor connected between the collector of the transistor 32 and the emitter of the transistor 13 of the voltage detection means 30. Further, 34 is a resistor, 35 is a transistor whose emitter is connected to the resistor 34,
36 is a resistor connected to the collector of the other transistor 35 of the voltage detection means 30 and the negative terminal of the DC power supply 7. A ramp voltage is applied between the anti-emitter side of the resistor 31 and the base of the transistor 32. Therefore, a voltage approximately equal to the lamp voltage is applied to the resistor 31, and a current approximately proportional to the lamp voltage limited by the resistor 31 is output from the collector of the transistor 32. A voltage proportional to the lamp voltage is generated. Similarly, a ramp voltage is applied between the anti-emitter side of the resistor 34 and the base of the transistor 35. Therefore,
A voltage approximately equal to the lamp voltage is applied to the resistor 34, a current approximately proportional to the lamp voltage limited by the resistor 34 is output from the collector of the transistor 35, and a voltage proportional to the lamp voltage is applied across the resistor 36. Occur. A resistor 37 serves as a current detection means, and generates a voltage proportional to the lamp current across the resistor. Reference numeral 38 denotes an operational amplifier which is the calculating means A, and the output signal of the current detecting means 37, which is a voltage proportional to the lamp current generated across the resistor 37, is input to the non-inverting input terminal, and the output signal of the current detecting means 37, which is a voltage proportional to the lamp current generated across the resistor 37, is input to the inverting input terminal. The output signal of the voltage detection means 30, which is a voltage proportional to the lamp voltage generated at both ends, is inputted, compared with the input of the non-inverting input terminal, and controlled so that the two match, so that the lamp voltage and lamp current are proportional. A signal is output from the output terminal of the operational amplifier 38 so that the signal is output from the output terminal of the operational amplifier 38. 43 is an arithmetic means B, which is composed of resistors 39 and 40, an operational amplifier 41, and a voltage reference 42. Voltage detection means 3
A voltage proportional to the lamp voltage is generated across the zero resistance 33. The sum of the voltages generated across this resistor 33 and the resistor 37 of the current detection means corresponds to the voltage obtained by multiplying each of the lamp voltage and lamp current by a predetermined coefficient and then adding them. This voltage is divided by resistors 39 and 40, and an operational amplifier 41
Furthermore, input the output of the voltage reference device 42 to the inverting terminal of the operational amplifier, compare it with the non-inverting terminal input, and if the non-inverting terminal input exceeds a certain value, the calculation is performed. A signal is output from the output terminal of the amplifier 41. 44 is calculation means C
It is an OR circuit, and arithmetic means A38 and arithmetic means B43
When the output of the calculating means A38 or the calculating means B43 is inputted, an output signal is outputted accordingly. 45 is a transistor, which is turned on by inputting the output signal of the calculation means C44.
Turn off. 46 is a calculation means A38 and a calculation means B
43, arithmetic means C44, and a transistor 45, the collector of the transistor 45 is used as an output terminal, and the base and emitter of the transistor 13 are short-circuited to turn the transistor 13 on and off. With this configuration, when the lamp voltage is low, such as when starting the lamp, the resistor 3
A low voltage proportional to the lamp voltage is generated across the terminals 3 and 36. Therefore, the calculation means B43 does not output an output signal unless the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient exceeds a certain value, so when the lamp voltage is low, a very large lamp current will not flow. and no output signal is output. However, an output signal is outputted from the output end of the calculation means A38 before that of the calculation means B43 with a small lamp current proportional to the low lamp voltage. Therefore, a lamp current proportional to the lamp voltage flows through the high-pressure sodium lamp 8 to maintain lighting. After that, when the lamp voltage increases and reaches a predetermined voltage Vt which is lower than the lamp voltage in the steady lighting state shown in Fig. 2 and higher than the lamp voltage at startup, an output signal is output from the output terminal of the calculation means A38. At the same time, since the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient exceeds a certain value, calculation means B
An output signal is output from the output terminal of 43. After that, if the lamp voltage becomes larger than Vt,
A high voltage proportional to the lamp voltage is generated across the resistors 33 and 36. Therefore, an output signal will not be output unless a very large lamp current such that the lamp voltage and lamp current are proportional flows from the output end of the calculation means A38. Therefore, when the lamp voltage is higher than Vt, the calculation means A38 Before outputting an output signal from the output terminal, an output signal is output from the output terminal of the calculation means B43 because the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient exceeds a certain value, and as in the conventional example. The transistor 13 is controlled on/off so that the addition result after multiplying the lamp voltage and the lamp current by a predetermined coefficient becomes a constant value, and the variation in color temperature of the high-pressure sodium lamp 8 is reduced and DC lighting is performed.

With the above configuration, as shown in FIG. 2, it is possible to flow a lamp current proportional to the lamp voltage when starting the lamp, and the current can be minimized immediately after starting. At this time, the temperature of the arc tube electrodes and arc tube has not risen sufficiently, and by not passing an excessive current, the thermal gradient is prevented from becoming too steep, causing the electrode material to scatter and the arc tube to become distorted. can be reduced. Further, by subsequently increasing the lamp current in proportion to the rise in lamp voltage, the temperature of the arc tube can be gradually raised, thereby reducing strain on the arc tube and extending its life. Further, after that, the lamp current can be temporarily increased compared to the lamp current during steady lighting, and the starting time can be shortened without shortening the life. Furthermore, control at the time of starting can be made more accurate, and variations in lamp life can be reduced. One can then move on to the precise control characteristics required for the discharge lamp. Therefore, the lamp can be started quickly and accurately and stably without shortening the life of the lamp. In addition, even if the lamp voltage at startup is low, the lamp current can be reduced accordingly, so the lamp current-voltage characteristics can be accurately set to prevent the oscillation frequency of the circuit from dropping to the audible frequency range shown in Figure 2. You can eliminate the noise that was occurring. Furthermore, since it is easy to use an integrated circuit for the control circuit 46, the influence of temperature characteristics and power supply voltage characteristics can be easily eliminated, and accurate and stable control of lamp characteristics is possible. Further, it is possible to prevent the life of the high-pressure sodium lamp 8 from being shortened and the movement characteristics from deteriorating. Moreover, the rating of the circuit elements of the discharge lamp lighting device can be prevented from increasing, resulting in lower cost. Furthermore, it is safe even if a sudden change or abnormality occurs in the lamp.
Further, during steady lighting, the characteristics of the high-pressure sodium lamp 8 can be set to predetermined characteristics as in the conventional example, and DC lighting can be achieved with reduced variation in color temperature of each lamp.

In the above embodiments, the high-pressure sodium lamp 8 may be any other discharge lamp, such as a metal halide lamp or a high-pressure mercury lamp. Further, although the DC power source 7 rectifies and smooths the alternating current, it may be a battery or other switching power source. Moreover, the power circuit 14 may be another type such as an inverter, or one having an inductance element and a switching element with a control terminal such as a transistor or a thyristor, and supplying power to the discharge lamp by turning on and off the switching element. Good. Further, the drive and control circuit for the transistor 13 may have other configurations. In the case of separate excitation, the oscillation frequency can be set arbitrarily, so there is no problem of the oscillation frequency decreasing as in the case of self-excitation, but controlling the lamp current as described above can shorten the lamp life. Needless to say, the discharge lamp can be started and lit accurately, stably, and quickly without any problems. In addition, during steady lighting, the lamp control characteristics by the control circuit 46 are such that the transistor 13 is turned on and off so that the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient becomes a constant value, as shown in FIG. However, other characteristics may be used as long as the control is such that the higher the lamp voltage of the discharge lamp, the lower the lamp current. Moreover, since the lamp voltage is DC, the voltage detection means 30 is directly inputted, but if the lamp voltage is AC, it may be inputted after rectification. Further, the transistors 32 and 35 do not have to be bipolar type transistors, and may be other types such as FETs.

Effects of the Invention The present invention can provide a discharge lamp lighting device that can accurately, stably, and promptly start and light a discharge lamp without shortening the life of the lamp with the simple configuration described above.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 2 is a lamp current-voltage characteristic diagram of the same lighting device, and FIG. 3 is a circuit diagram of a conventional discharge lamp lighting device. . DESCRIPTION OF SYMBOLS 1... AC power supply, 7... DC power supply, 8... High pressure sodium lamp, 14... Power circuit of step-down type chopper, 23, 46... Control circuit, 24, 30... Voltage detection means.

Claims (1)

[Claims] 1. A power source whose output voltage has a constant polarity, a discharge lamp that is a high-pressure sodium lamp, a metal halide lamp, or a voltage mercury lamp, and is connected between the output end of the power source and the discharge lamp, and includes at least an inductance element and a control terminal. a power circuit that supplies power to the discharge lamp by turning on and off the switching element; a voltage detection means that outputs a voltage signal proportional to the lamp voltage of the discharge lamp; A current detecting means outputs a current signal proportional to the lamp current, the voltage signal and the current signal are input, and a control signal is output to the power circuit to control switching, thereby adjusting the lamp current in accordance with the lamp voltage. and a control means for controlling the
The control means is a calculation means A that receives the voltage signal and the current signal and outputs a first control signal so that the lamp voltage and lamp current are proportional below a predetermined lamp voltage lower than that during steady lighting.
and a calculation means B that inputs the voltage signal and the current signal and outputs a second control signal such that the lamp current decreases as the lamp voltage increases at a lamp voltage higher than the predetermined lamp voltage; calculation means C for outputting a control signal obtained by adding the first control signal and the second control signal to the power circuit; A discharge lamp lighting device in which the current is proportional to the lamp voltage, and when the lamp voltage is higher than the predetermined lamp voltage, the lamp current is controlled to decrease as the lamp voltage increases.