JPS6031079B2 - discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, and its purpose is to reduce the cost required for switching elements of the control circuit by reducing the repetition frequency of the voltage applied to the discharge lamp to a relatively low frequency. It is an object of the present invention to provide an inexpensive discharge lamp lighting device that is inexpensive, eliminates the generation of transient high voltage in a circuit, and can use low-voltage components.

When a discharge lamp is turned on via a stabilizing element and its voltage-current characteristics are determined under various conditions, so-called negative resistance characteristics (static characteristics) are obtained.

Because of this negative resistance characteristic, a stabilizing element (current limiting element) is essential for stable lighting of a discharge lamp. If a discharge lamp is turned on without this stabilizing element, the current will escape and destroy the lamp, but the rate at which this current increases is by no means infinite. The characteristics exhibited by the discharge lamp in such cases are so-called dynamic characteristics.
The present invention relates to a lighting circuit that utilizes the dynamic characteristics and does not have a current limiting element. That is, this dynamic characteristic is expressed as follows: the rate of increase in lamp conductance g due to ions in the tube over time is proportional to the product of lamp current i and lamp voltage V, and the rate of decrease is proportional to the product of lamp conductance g due to ions in the tube. g
is proportional to. This can be expressed by the formula shown by Frais et al. as dg. ．．
．． ．． 、． ．． ■ City=QVI-3g where g=i/v
......■Q, 8: Constant specific to discharge lamps For example, when the lamp electric power is suddenly increased by 10% in a fluorescent lamp for 4 skin types, the time required for the lamp current to increase to twice the original value is as shown above. Calculation based on equations (1) and (2) shows that the time is approximately 1.6 mSec, and the current continues to increase even after this, and is finally lost.

Similarly, if the lamp voltage is lowered by 10%, approximately 1.8 hSe
c, the lamp current decreases to 1/2, and thereafter the current continues to decrease until it finally reaches zero. Now, when the voltage of the constant voltage source is e(t) and it is connected to the discharge lamp without a current limiting element, the lamp current i(t) is calculated as follows from the above equations (1) and (2). i(t)=egoeXp{Anomo. (
e2-VDC2)dt} However, the arc is the equivalent conductance A of the discharge lamp at t=to, and Voc is a constant specific to the discharge lamp.As is known from now on, if the period of e(t) is T, then E=〆main no 5e2dt When E>VM, the current escapes, and when E<VDc, the current disappears, where E is the effective value of e(t), as is clear from the above definition.

Therefore, it is clear that in order to maintain lighting by directly connecting a discharge lamp to a constant voltage source, it is sufficient to make the effective value of this constant voltage source equal to Voc and to set the current in some way.

Focusing on the above-mentioned points, a conventional example of a system that eliminates ocular flow factors that are the main cause of power loss in a discharge lamp lighting device will be described below. FIG. 1 is a block diagram showing a subsidiary example, FIG. 2a shows the voltage applied to both ends of the discharge lamp 2, and FIG. 2b shows the waveform of the current flowing through the discharge lamp 2. As can be seen from this, in this method, instead of applying a voltage higher than the above-mentioned Voc, the time is divided into 7, to prevent the current from escaping. Further, the setting of the current is realized by controlling the switch opening/closing element 4 by the negative feedback circuit 3 and changing the ratio of 1, 72. However, in such conventional methods, the high voltage required to compensate for the disappearance of residual ions due to diffusion and recombination, which progresses significantly during the current stop period, is directly applied to the power supply voltage for the discharge lamp. Therefore, if the current increase rate increases and the voltage application time becomes longer, a large current region may occur, which may put the discharge lamp 2 in a dangerous state. For this reason, it is necessary to avoid the above dangerous situation by shortening the voltage application time and selecting a high switch opening/closing frequency of 500 Hz to 4 Hz. This had the disadvantage of increasing losses. The present invention has been provided in view of the above-mentioned drawbacks.As expressed by the above-mentioned equations (1) and (2), it takes a certain amount of time to increase the current or decrease the flow depending on the conditions, and it is possible to utilize this time lag. In a lighting circuit that can maintain stability substantially without the use of current limiting elements, the negative feedback means detects the momentary state of the discharge lamp and controls the time, thereby controlling the voltage applied to the discharge lamp. This allows stable lighting to be maintained.

In other words, following the high voltage necessary to compensate for the disappearance of ions due to diffusion and recombination that significantly progresses during the current rest period, a lower voltage close to the discharge lamp rated voltage Voc is applied to the discharge lamp. The lamp current is kept almost constant according to the lamp conductance.
An embodiment of the present invention will be described in detail below with reference to the drawings. Figure 3a,
b shows a waveform diagram of an embodiment of the present invention, in which the voltage rest period t,
Next, during period t3, a voltage relatively higher than the discharge lamp rated voltage Voc is applied, and with this high voltage, the discharge lamp 2 is heated to increase the ion concentration in the tube, and then, during period t3, the discharge lamp rated voltage is A voltage close to voltage VDc is applied. Here, the voltage applied during the period is
If the value is close to the discharge lamp rated voltage Voc, the discharge lamp rated voltage V as shown in FIG. 3a. Even if the value is higher than c, the discharge lamp rated voltage V as shown in b in the same figure. It is acceptable to have a value lower than c, and in the case of a voltage higher than VDc as shown in Figure 3a, t
In period 3, the current tends to rise slowly;
It is also clear from equations (1) and (2) above that in the case of a voltage lower than Voc as shown in FIG. Figure 4 is Shougonchi Figure 3a
, b is a block diagram of a specific circuit example for obtaining current and voltage waveforms as shown in FIG. By switching, the power supply voltage waveforms shown in FIGS. 3a and 3b are obtained, and the negative feedback circuit 3
The load condition of the discharge lamp 2 is detected and fed back to the constant voltage source 1, and the lamp current is set to a specified value by controlling switching of the switch lc. Here, la is a battery constituting the main power source, and its output voltage is approximately close to the rated voltage of the discharge lamp 2. Also, lb is a battery that constitutes an auxiliary power source, and its output voltage is applied to the battery la that is the main power source.
When added to the voltage of the discharge lamp 2, a high voltage higher than the rated voltage of the discharge lamp 2 can be generated. A constant voltage source 1 is constituted by batteries la, lb and switch lc. Furthermore, FIG. 5 is a circuit block diagram of another embodiment of the present invention, which focuses on the fact that the power supply frequency may be low frequency, so that it is possible to directly utilize the commercial AC power supply. . However, in the embodiment of FIG. 5, the main power source and the auxiliary power source are
These AC power sources la, lb and switch lc constitute a constant voltage source 1, and a warehouse feedback circuit 3
detects the state of the discharge lamp 2, for example, the lamp current, and controls the on-phase and off-phase of the switch opening/closing element 4 so that the lamp current reaches a specified value, thereby supplying power to the discharge lamp 2. The voltage waveform applied to the discharge lamp 2 from the constant voltage source 1 is as shown by the solid line in FIG. As described above, the present invention includes a constant voltage source that sequentially repeats a voltage rest period, a period of fin pressure relatively higher than the rated voltage of the discharge lamp, and a period of voltage close to the rated voltage of the discharge lamp. The current changes during the period of voltage close to the rated voltage of the lamp, so there is no need to shorten the voltage application time as in the conventional case, and the repetition frequency of the constant voltage source can be reduced. Therefore, even when using switching elements, low-cost elements can be used regardless of performance such as switching loss, and the control circuit thereof can be simplified.

Furthermore, since there is no need to abruptly forcibly cut off a large current, transient high voltages are less likely to occur in the circuit, and parts with low withstand voltages can be used as circuit elements, resulting in an inexpensive circuit configuration. Furthermore, the ratio of the voltage application time to the voltage rest time can be increased, which makes it possible to effectively supply power to the discharge lamp, resulting in high efficiency, eliminating any negative effects on the lifespan of the discharge lamp, and preventing flickering. It has little effect. Furthermore, since the discharge lamp is connected to the constant voltage source virtually without a current-limiting element, there is no need to separately install a large-capacity current-limiting element (ballast). This has the effect of not causing problems such as increase in weight, increase in weight, heat generation, and power loss.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the conventional example, Fig. 2 a and b are the same voltage and waveform diagrams as above, Fig. 3 a and b are voltage waveform diagrams of the embodiment of the present invention, and Fig. 4 is the implementation of the same as above. FIG. 5 is a block diagram of another embodiment of the present invention, and FIG. 6 is a voltage waveform diagram of the same as above, where 1 is a constant voltage source, 2 is a discharge lamp, and V. c is the rated voltage of the discharge lamp, t is the voltage rest period, t2 is a period of voltage relatively higher than the rated voltage of the discharge lamp, and W is a period of voltage close to the rated voltage of the discharge lamp. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A main power supply whose output voltage is approximately close to the rated voltage of the discharge lamp, an auxiliary power supply connected in series to the main power supply, a first switching means for applying the output voltage of the main power supply to the discharge lamp, and a main power supply. A second switch means for applying to the discharge lamp a voltage higher than the rated voltage of the discharge lamp produced by the series circuit with the auxiliary power supply, and a third switch means for disconnecting the main power supply and the auxiliary power supply from the discharge lamp. , a no-voltage period during which the third switch means is open, and a high-voltage period during which the second switch means is closed;
A discharge lamp lighting device characterized by comprising a control means for controlling opening and closing of each switch means so that the low voltage period during which the first switch means is closed is sequentially repeated cyclically at a period of several tens of cycles or more per second. .