JPS644316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a lighting device for a low-pressure mercury vapor discharge lamp such as a fluorescent lamp.

(Prior art) When a low-pressure mercury vapor discharge lamp containing an inert gas with a large atomic weight such as argon or krypton, such as a fluorescent lamp or a germicidal lamp, is lit with alternating current at low temperatures, a striped pattern appears on the tube wall. It is known that a phenomenon (hereinafter referred to as striation) is likely to occur.

(Problems to be Solved by the Invention) Although the mechanism by which this striation occurs is not detailed, it sometimes continues throughout the lighting period and causes discomfort such as flickering of brightness.

In contrast, the present inventors first applied a DC bias to the lamp current of the discharge lamp to make the lamp current asymmetric between positive and negative, thereby substantially preventing the flickering of brightness associated with the above-mentioned striation. I discovered what I could do (Special Application No. 56-4366). The present invention further improves the above-described invention by the present inventors, and prevents the component parts of the DC bias means from being destroyed when the discharge lamp undergoes half-wave discharge at the end of its life. The purpose is to enable the use of inexpensive elements.

[Structure of the invention]

The present invention has a half-wave rectifier device and an impedance device, and is provided in conjunction with a discharge lamp to provide positive and
Biasing means for DC biasing the lamp current by passing a current through the impedance device in either negative half-wave, and changing the current flowing through the impedance device in response to half-wave discharge of the discharge lamp. Accordingly, the present invention is characterized by comprising bias control means for reducing or stopping the DC bias.

(Function) When the discharge lamp is normally lit, the bias means causes the lamp current of the discharge lamp to be asymmetric between positive and negative. As a result, striations may occur in discharge lamps, but the DC electric field causes the stripes to move faster, making them visually equivalent to no striations, and thus reducing the brightness. Flickering can be virtually prevented.

When the discharge lamp performs a half-wave discharge in the direction of passing current through the impedance device of the bias means, an excessive current tends to flow through the impedance device, but in the present invention, the impedance is controlled by the bias control means. Since the current flowing through the device is changed to be reduced or cut off, an excessive current due to half-wave discharge will not flow through the impedance device. Therefore, it is possible to prevent the impedance device from generating abnormal heat or being destroyed, and as a result, it is possible to use a relatively low withstand voltage, small capacitance, and inexpensive element. Note that an excessive current containing a DC component due to half-wave discharge flows through the ballast and the like. On the other hand, it is possible to arbitrarily choose whether the stabilizer or the like is designed to withstand the above-mentioned excessive current or whether a protection function is added.

When the discharge lamp performs half-wave discharge in a direction in which no current flows through the impedance device of the bias means, no excessive current flows through the impedance device.

The direction in which the discharge lamp produces a half-wave discharge is determined by the deviation of the discharge lamp electrodes, and the direction of the half-wave discharge will not be affected by a slight DC bias as in the present invention. Nakatsuta.

(Example) An example of the present invention will be described below with reference to FIG.

1 is an alternating current power source, such as a high frequency power source or a commercial power source. 2 is a low-pressure mercury vapor discharge lamp such as a fluorescent lamp or a germicidal lamp. Reference numeral 3 designates a current limiting device for the discharge lamp 2, which is a chiyoke coil in this embodiment. Biasing means 4 biases the lamp current of the discharge lamp 2 to direct current, and is composed of, for example, a parallel circuit of a half-wave rectifier 5 and an impedance device 6, and in this embodiment, it is provided in series with the discharge lamp 2. There is. Reference numeral 7 denotes a bias control means which prevents lamp current from flowing through the impedance device 6 of the bias means 4 when the discharge lamp 2 enters a half-wave discharge state. In this embodiment, it is composed of a bidirectional semiconductor switching element, which is turned on and off according to the voltage across the impedance device 6.

Next, we will discuss the effect. In a normal state in which the discharge lamp 2 does not undergo half-wave discharge, the lamp current of the discharge lamp 2 is subjected to a DC bias by the biasing means 4, and the polarity of the lamp current is asymmetrical. Of course, the impedance value of the impedance device 6 is selected so that the asymmetry is not excessive (for example, the average value of the positive and negative values of the lamp current is 1:1.05 to 1.1). Therefore, the discharge lamp 2 does not cause flickering or striped patterns on the tube wall that may cause discomfort to the user. Next, discharge lamp 2
When becomes a half-wave discharge state with the polarity shown by the broken line in the figure,
A half-wave lamp current flows. Therefore, the impedance value of the current limiting device 3 decreases, the current flowing through the impedance device 6 increases, and the voltage across the impedance device 6 also increases. Therefore, the bias control means 7 is turned on, and from then on the lamp current flows through the bias control means 7 without passing through the impedance device 6. Therefore, power loss due to the impedance device 6 is eliminated, and abnormal heat generation is also eliminated. In addition, in this example,
The impedance device 6 has a bias control means 7.
A small amount of lamp current flows until the lamp is turned on, but it is easy to suppress it to a level that does not cause abnormal heat generation.

The experimental results of this example are shown below.

AC power supply 1: 430V, 43KHz Discharge lamp 2: Toshiba 40W fluorescent lamp (FLR40S/
M/37) Two-lamp series impedance device 6: Resistor (22Ω) During steady lighting, the impedance device 6 had a current of 0.23A (effective value) and power consumption of 1.2W. On the other hand, during half-wave discharge, the conducting current is
0.38A (effective value), power consumption increased to 3.2W, but
By providing the bias control means 7, the above-mentioned conduction current and power consumption during half-wave discharge can be made extremely small.

FIGS. 2 and 3 show only the main parts of other embodiments. In FIG. 2, bias means 10 consists of a parallel circuit of a diode 11 and a capacitor 12. Moreover, the bias control means 13
It consists of an SCR 14 and a gate control circuit 15 for the SCR 14, and the gate control circuit 15 outputs a gate signal according to the voltage across the capacitor 12. In the one shown in FIG. 3, the bias control means 16 consists of a transistor 17, a constant voltage element 18 provided between the collector and base of the transistor 17, and a resistor 19 provided between the base and emitter of the transistor 17. Also, the capacitor 12 of the biasing means 10
The transistor 17 changes depending on the voltage across the
It is something that is turned on and off. The components shown in FIGS. 2 and 3 can be used in place of the bias means 4 and bias control means 7 shown in FIG. The voltage applied to the capacitor 12 as an impedance device is reduced, thereby solving the problem of withstand voltage. Since other effects are easily understood, their explanations will be omitted.

FIG. 4 shows yet another embodiment.
In this embodiment, the AC power supply 20 is mainly composed of a well-known transistor inverter, and outputs a high frequency voltage of, for example, several KHz to several hundred KHz. In this embodiment, the leakage inductance of the inverter transformer is used as a current limiting device. Further, in this embodiment, two discharge lamps 21 and 22 are provided in series (the filament circuit is omitted). Bias means 23
is the half-wave rectifier 24 and the impedance device 2
It consists of 5 series circuits and is connected in parallel to one discharge lamp 21. Therefore, in the discharge lamps 21 and 22, the lamp current becomes asymmetric between the polarity in which the impedance device 25 is inserted and the other polarity. The bias control means 26 is connected in series with the bias means 23, and is turned on during normal operation and turned off during half-wave discharge. Such bias control means 26
can be easily constructed using semiconductor switching elements.

In this embodiment, when the discharge lamp 21 enters a half-wave discharge state with the polarity indicated by the broken line in the figure, an excessive current attempts to flow through the impedance device 25, but at this time the bias control means 26 detects an overcurrent or the like.
It turns it off. Other functions are similar to those in FIG. 1, but in this embodiment, the AC power supply 20 includes electronic components such as transistors, so it is necessary to protect them from excessive thermal influence. However, since abnormal heat generation of the impedance device 25 can be prevented, even if the transistor inverter, bias means 23, and bias control means 26 are housed in the same case, they will not be adversely affected by the heat generated by the impedance device 25.

It should be noted that the present invention is not limited to the above embodiments, and for example, the AC power source for lighting the discharge lamp may be any one that outputs a sine wave voltage, a rectangular wave voltage, or the like. Further, the impedance device of the bias means may be a capacitor, a resistor, or a combination thereof. Furthermore, the bias control means can be modified in various ways, for example, it may be responsive to the lamp current, lamp voltage, or light output of the discharge lamp instead of responding to the voltage across the impedance device of the biasing means. It will be easily understood. In this case, well-known configurations can be used.
Furthermore, it will be readily understood that the current limiting device for the discharge lamp may be of any type.

〔Effect of the invention〕

As described above, the present invention includes a half-wave rectifier device and an impedance device, and includes bias means for direct-current biasing the lamp current by passing a current of either positive or negative polarity through the impedance device. , and bias control means for reducing or stopping the DC bias by changing the current flowing through the impedance device in response to half-wave discharge, it is possible to substantially prevent brightness flickering due to striation. of course,
It is possible to prevent the impedance device from generating abnormal heat or being destroyed during half-wave discharge.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
3 and 3 are circuit diagrams showing only essential parts of other embodiments, respectively, and FIG. 4 is a circuit diagram showing still another embodiment. DESCRIPTION OF SYMBOLS 1, 20... AC power supply, 2, 21, 22... Discharge lamp, 3... Current limiting device, 4, 10, 23... Bias means, 7, 13, 16, 26... Bias control means.

Claims (1)

[Claims] 1. A low-pressure mercury vapor discharge lamp operated with alternating current; comprising a half-wave rectifier and an impedance device, which are provided in relation to the discharge lamp;
biasing means for DC biasing the lamp current by passing current through the impedance device during either positive or negative half-waves; A discharge lamp lighting device comprising: bias control means for reducing or stopping DC bias by changing the current flowing through the impedance device. 2. The discharge lamp lighting device according to claim 1, wherein the bias means includes a parallel circuit of a diode and an impedance device, and is provided in series with the discharge lamp. 3. The two discharge lamps are connected in series; and the bias means is comprised of a series circuit of a diode and an impedance device, and is provided in parallel with one of the two discharge lamps. A discharge lamp lighting device according to claim 1. 4. The bias control means includes a switch device that turns on and short-circuits the impedance device in response to a rise in voltage across the impedance device during half-wave discharge of the discharge lamp; A discharge lamp lighting device according to claim 1 or 2. 5. The discharge lamp lighting device according to claim 3, wherein the bias control means forms a series circuit of the diode and an impedance device during half-wave discharge of the discharge lamp.