JPS62246297A - Discharge lamp lighting apparatus - 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 Field of the Invention The present invention relates to a device for starting and lighting a discharge lamp.

Conventional technology 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, 5, and a capacitor 6, and inputs the output of the AC power supply 1, rectifies it, and outputs DC.

8 is a high-pressure sodium lamp which is a discharge lamp, and 14 is a power circuit for a step-down chopper, which is an inductance element including a transformer 9, a diode 10, a capacitor 11, a resistor 12, and a switching element with a control terminal connected to the transformer 9 at one end. When the transistor 13 is on, a current flows through the high-pressure sodium lamp 8 through the transformer 9, and when the transistor 13 is off, the electromagnetic energy stored in the transformer 9 is passed through the diode 10 and flows into the high-pressure sodium lamp 8. and light the lamp 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. 24 is a voltage detection means, and a resistor 25
and a transistor 26 with this resistor 25 connected to its emitter.
A ramp voltage is applied between the anti-emitter side of the resistor 25 and the base of the transistor 26. Therefore, a voltage approximately equal to the lamp voltage is applied to the resistor 25, 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 rfJ calculating means 21. is the resistance 15,1
6.17, a resistor 20 serving as current detection means, an operational amplifier 18, and a voltage reference 19. A current proportional to the lamp voltage outputted from the voltage detection means 24 flows through the resistors 15.16° and 17.20, and a voltage proportional to the lamp voltage is generated across the resistor 15. The sum of the voltages generated across this resistor 15 and the resistor 20 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 16 and 17 and input to the non-inverting terminal of the operational amplifier 18, and the output of the voltage reference 19 is input to the inverting terminal of the operational amplifier, compared with the non-inverting terminal input, and When the input to the inverting terminal exceeds a certain value, a signal is output from the output terminal of the operational amplifier 18. A transistor 22 is a control means, and is turned on and off by inputting the output signal of the calculation means 21. 23 is a control circuit consisting of arithmetic means 21 and a transistor 22 for control means;
The collector of the transistor 22 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 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 a discharge lamp, when a starting voltage is applied to the discharge lamp, the discharge lamp breaks down and almost immediately shifts to arc discharge. do. At this time, immediately after transitioning to arc discharge, the vapor pressure inside the arc tube of the high-pressure sodium lamp is low (lamp voltage drops rapidly).Afterwards, for a while (1. lamp voltage decreases) until the vapor pressure inside the arc tube rises. In the discharge lamp lighting device shown in Fig. 3, the transistor 13 is controlled on/off so that the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient becomes a constant value. During startup, when the lamp voltage is lower than the lighting characteristics during steady lighting, the transistor 13 is controlled by flowing a very large lamp current to achieve the desired characteristics. This will put an excessive load on the tube, shortening its life and deteriorating its operating characteristics.Also, the circuit elements of the discharge lamp lighting device will have to be rated high and expensive, and the lamp will suddenly change.・There was a problem that circuit elements could be destroyed due to abnormalities.Also,
When a large lamp current flows, in the case of a self-excited chopper,
There was also the problem that the oscillation frequency of the circuit decreased significantly and fell into the audible frequency range, causing noise. To improve the above problems, for example, Japanese Patent Application Laid-open No. 55-2598
As stated in Publication No. 0, there is an example in which a step-down chopper is used to control the lamp current to keep it below the rated lamp current even during startup, and a negative thermistor is used as the current detection resistor to provide thermal negative feedback. However, this method has problems in that it takes a long time to start up and is not suitable for accurate control.

Means for Solving the Problems In order to solve the above problems, the present invention provides a power source whose output voltage has a constant polarity, a discharge lamp, and at least a power source connected between the output end of the power source and the discharge lamp. a power circuit that includes an inductance element and a switching element with a control terminal and supplies power to a discharge lamp by turning on and off the switching element; and a power circuit that detects a lamp voltage of the discharge lamp and outputs a signal proportional to the lamp voltage. a voltage detection means; a current detection means for detecting a lamp current and outputting a signal proportional to the lamp current; The output signals of the calculation means A and B are inputted, and the calculation means A outputs a signal such that the lamp current is proportional to the lamp current. arithmetic means C for outputting a signal so as to control on/off the switching element with priority given to the smaller signal;
and a control circuit configured to give priority to the output signal of the calculation means B at least during steady lighting.

According to the above-described structure, the present invention allows the lamp to be lit with a lamp current proportional to the lamp voltage when the lamp voltage is below a predetermined voltage which is 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 is used by a DC power supply 7, which is a power supply whose output voltage has a constant polarity, rectifying and smoothing the voltage of the AC power supply 1. By supplying DC voltage to the power circuit 14 of the m' control circuit 46 and controlling the transistor 13 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. 2, the high-pressure sodium lamp 8, which is a discharge lamp, has a predetermined characteristic that the higher the lamp voltage is, the lower the lamp current is, at least during rated operation, and the variation in color temperature of each discharge lamp is reduced. It can be used to turn on direct current.

The difference from the conventional discharge lamp lighting device is the voltage detection means 30 and the control circuit 46. In the voltage detecting means 30, 31 is a resistor, 32 is a transistor whose emitter is connected to the resistor 31, and 33 is a collector of the transistor 32, which is the output terminal of the voltage detecting means 30, and a transistor 13.
is a resistor connected between the emitter of Also, 34
is a resistor, 35 is a transistor whose emitter is connected to the resistor 34, and 36 is a resistor connected to the collector of the transistor 35, which is the other output terminal 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, and flows across the resistor 33, that is, the voltage of the transistor 32. A voltage proportional to the lamp voltage is generated at the collector. 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, and from the collector of the transistor 35 to the resistor 34.
A current approximately proportional to the lamp voltage limited by is output, and a voltage proportional to the lamp voltage is generated across the resistor 36. 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 a calculation means B, which is composed of a resistor 39.degree. 40, an operational amplifier 41, and a voltage reference device 42. A voltage proportional to the lamp voltage is generated across the resistor 33 of the voltage detection means 30.

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 the operational amplifier 4
1, the output of the voltage reference device 42 is input to the inverting terminal of the operational amplifier, and compared with the non-inverting terminal input, and if the non-inverting terminal input exceeds a certain value,
A signal is output from the output terminal of the operational amplifier 41. Reference numeral 44 denotes an OR circuit which is the arithmetic means C, which inputs the outputs of the arithmetic means A38 and the arithmetic means B43, and outputs an output signal in response to the output signal of the arithmetic means A38 or the arithmetic means B43. Reference numeral 45 denotes a transistor, which is turned on and off by inputting the output signal of the calculation means C44. 4
6 is arithmetic means Ap8, arithmetic means B43 and arithmetic means C4
4 and a transistor 45, with the collector of the transistor 45 as the output terminal and the transistor 1 as the output terminal.
The base and emitter of transistor 3 are short-circuited to turn transistor 13 on and off. With this configuration, when the lamp voltage is low, such as when starting the lamp, the resistor 33.3
6, a low voltage proportional to the lamp voltage is generated. Therefore, the calculation means B43 does not output an output signal unless the addition result after multiplying the lamp voltage and the lamp current by a predetermined coefficient is a constant value, so when the lamp voltage is low, a very large lamp current is generated. If there is no flow, no output signal will be output. However, from the output terminal of the calculation means A38, the calculation means A38 outputs a small lamp current proportional to the low lamp voltage.
The output signal is output before 38. Therefore, a lamp current proportional to the lamp voltage flows through the high-pressure sodium lamp 8 to maintain lighting. Then the lamp voltage increases,
When the predetermined voltage Vt is lower than the lamp voltage in the steady lighting state shown in FIG. Since the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient exceeds a certain value, calculation means B43
An output signal is output from the output terminal of. After that, when the lamp voltage becomes larger than Vt, a high voltage proportional to the lamp voltage is generated across the resistor 33, 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 to each other flows from the output end of the calculation means A38, so that the lamp voltage is Vt.
If it is higher than , the lamp voltage and lamp current are multiplied by a predetermined coefficient and the addition result exceeds a certain value from the output terminal of the calculation means B43 before the output signal is output from the output terminal of the calculation means A38. An output signal is output, and as in the conventional example, the transistor 13 is controlled on/off so that the addition result after multiplying the lamp voltage and lamp current by a predetermined coefficient becomes a constant value, and the color temperature of the high-pressure sodium lamp 8 is controlled. DC lighting is performed by reducing the variation in the current.

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. In addition, by increasing the lamp current in proportion to the rise in lamp voltage, the temperature of the arc tube can be gradually increased, reducing strain on the arc tube and extending its life. .Furthermore, the lamp current can be temporarily increased more than the lamp current during steady lighting, and the starting time can be shortened without shortening the life.
Control at the time of starting can be made 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, it is possible to start quickly, accurately and stably without shortening the life of the lamp.Also, even if the lamp voltage at startup is low, the lamp current can be reduced by 100%, so the oscillation frequency of the circuit can be reduced. Since the lamp current and voltage characteristics can be accurately set so as not to drop to the audible frequency range as shown in FIG. , the effects of temperature characteristics and power supply voltage characteristics can be easily eliminated,
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. In addition, the rating of the circuit elements of the discharge lamp lighting device can be prevented from becoming too large, resulting in lower cost.Also, 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 addition, in the above embodiment, the high pressure sodium lamp 8 is
Other discharge lamps such as fluorescent lamps may be used, and it is particularly effective for HID lamps such as metal halide lamps that have a large operating current. Further, the input signal of the calculation means B43 may be related to the input voltage and input current, or may be related to the input voltage and lamp current, or may be related to the lamp voltage and input current. Although the iii current power source 7 rectifies and smooths alternating current, it may be a battery or other switching power source. Further, 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 (not self-excitation or external excitation).Furthermore, during steady lighting, the lamp control characteristics by the control circuit 46 are as shown in FIG. The transistor 13 is controlled on and off so that the addition result after multiplying the voltage and lamp current by a predetermined coefficient becomes a constant value. Any other characteristic may be used as long as it is controlled so that the characteristic is achieved.Furthermore, since the lamp voltage is direct current, the voltage detection means 30 is directly inputted, but if the lamp voltage is alternating current, then other characteristics may be used. There is no problem as long as the transistors 32 and 35 are performed after rectification.Furthermore, the transistors 32 and 35 do not have to be bipolar type, but 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 quickly 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] A power supply whose output voltage has a constant polarity, a discharge lamp, and a switching element connected between the output end of the power supply and the discharge lamp and having at least an inductance element and a control terminal, the switching element being turned on and off. a power circuit that supplies power to the discharge lamp; a voltage detection means that detects the lamp voltage of the discharge lamp and outputs a signal proportional to the lamp voltage; and a voltage detection means that detects the lamp current and outputs a signal proportional to the lamp current. a current detecting means that inputs at least the output signal of the voltage detecting means and the output signal of the current detecting means, and an arithmetic means A that outputs a signal such that the lamp voltage and the lamp current are proportional; A calculation means B outputs a signal according to a predetermined characteristic where the lamp current is large, and the output signals of the calculation means A and B are inputted, and the signal with which the lamp current becomes smaller is given priority and the switching element is controlled on/off. A discharge lamp lighting device comprising: a calculation means C for outputting a signal; and a control circuit that gives priority to the output signal of the calculation means B at least during steady lighting.