JPS5910036B2 - discharge lamp lighting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp lighting device, and an object of the present invention is to enable miniaturization without requiring a current limiting element, to have a simple circuit configuration, and to provide a power source. To provide a discharge lamp lighting device with less loss.

Discharge lamps generally have negative resistance characteristics, so it is said that a current limiting element is necessary to maintain stable lighting. A method for directly lighting a discharge lamp without using a current limiting element has been reported.

The present invention relates to a lighting circuit that does not have a current-limiting element as described above, and generally has a dynamic characteristic of a discharge lamp in which there is a considerable time delay in the rise of current when voltage is applied to the discharge lamp. This is what was used. That is, this dynamic characteristic is expressed as follows, where the rate of increase in lamp conductance g over time due to ions in the tube 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. It is proportional to g. Expressing this in the formula: -=αvi-βg ・・・・・・・・・1 where g ■
i/ri...2α, β: Constants specific to discharge lamps For example, when the lamp voltage is suddenly increased by 10% in a 40W fluorescent lamp, the lamp current increases to twice the original value. Calculating the time required for this to occur based on Equation 12 above, it is approximately 1.6 mSeC, and the current continues to increase even after this, eventually leading to an escape.

Similarly, if the lamp voltage is lowered by 10%, it will be approximately 1.8 mSe.
Once the lamp current reaches C, the lamp current decreases to H, and thereafter the current continues to decrease and finally reaches zero. Now, when the voltage of the constant voltage source is set to et and it is connected to the discharge lamp without using a current limiting element, the lamp current it becomes as follows from the above equation 12. However, G.

are the equivalent conductances A, V of the discharge lamp at t=TO
DC is a constant unique to discharge lamps.As is known from now on, if the period of Et is T, then E
-VA-11e2dt, when E>VDC, the current escapes in TO, and when E<VDC, the current disappears, where E is the effective value of Et 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 necessary to make the effective value of this constant voltage source equal to DC and to set the current by some method. Become.

Focusing on the above-mentioned points, a conventional example of a system that eliminates current-limiting elements that are the main cause of power loss in a discharge lamp lighting device will be described below. FIG. 5 shows a conventional example in the form of a block diagram. FIG. 6a shows the voltage applied to both ends of the discharge lamp 3, and FIG. 6b shows the waveform of the current flowing through the discharge lamp 3. As you will see, this method is described above. Instead of applying a voltage higher than c, the time is divided into t1 to prevent the current from escaping. Further, the setting of the current is realized by controlling the switching element 4 by the negative feedback circuit 5 and changing the ratio between t1 and T2. However, in such a conventional system, the voltage of the power supply 1 is high and the switching frequency of the switching element 4 is high, 500 Hz to 40 KHz, so the switching element forming the switching element 4 has a disadvantage that the withstand voltage and loss are large. . These shortcomings are mostly due to the fact that the voltage rest period is used for current setting.
The presence of the pause section causes the ionization of the vapor in the discharge lamp to rapidly disappear, and therefore a high voltage must be applied to generate ionization again.On the other hand, if such a high voltage is used as it is to maintain the discharge, the current of the tube current will decrease. The rate of increase also became faster, and it became necessary to shorten the switching cycle.
Furthermore, as previously described in Japanese Patent Publication No. 49-3181, a DC power source and a discharge lamp are connected through a switch element and an inductance element, and during a period when the switch element is on, an inductance element is used as a current limiting element. A chipper-type discharge lamp that supplies lighting current to the discharge lamp through the switch element, and supplies the discharge lamp with the energy stored in the inductance element during the period when the switch element is on during the period when the switch element is off. Electric light lighting devices have been developed, but in such conventional examples, since the lighting device always includes an inductance element, a winding and an iron core are necessary, and it is necessary to make the lighting device smaller and lighter. However, the problem was that it naturally had its own limitations.

In view of this point, the present invention provides that the power supply voltage is the discharge lamp rated voltage V.
.

By raising and lowering c, it is possible to connect to a discharge lamp without using a current limiting element.In order to obtain such voltage, two types of power sources are provided and these are alternately switched by a switching element. One embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows a block diagram of an example of the present invention, in which power sources 1 and 2 are low impedance power sources that may be either alternating current or direct current, and the waveform is not limited to a sine wave. . The switching elements 4 and 4a alternately switch the power supplies 1 and 2 described above at a frequency of several tens of cycles per second or more, so that the effective value of the voltage applied to the discharge lamp 3 becomes the discharge lamp rated voltage DC. In the configuration of the circuit shown in FIG. 1, a control element C detects the current or electric power of the discharge lamp 3 and maintains stable lighting by controlling the power supply 2. However, the configuration of the circuit shown in FIG. 1 makes it easier to control the power source 2 by setting the power supplied by the power source 2 to the discharge lamp 3 to be smaller than that of the power source 1, and also to reduce its energy. It is something that can be demonstrated.
FIG. 2 shows another embodiment of the present invention, and the embodiment in FIG. 2 differs from the embodiment in FIG. 1 in that the control element C controls the switching element 4. The major feature of this circuit is that the control loss is extremely small. In this way, the control element C can control either the two power supplies 1, 2 or the two switching elements 4, 4a, or can also combine them to achieve the control objective. FIG. 3 shows a specific embodiment of the present invention having the configuration shown in the embodiment of FIG. is a transistor Tr and a diode. 1
'D, and the switching elements 4, 4a are driven by the control element C. The control element C is a Schmitt trigger circuit that detects the current flowing through the discharge lamp 3 as a voltage drop across a small resistor 6. Thus, each time the current value 1 min Jmax set in advance is passed, the control element C turns the transistor Tr ON or OFF, thereby achieving the purpose of current control. The DC power supply 7 is connected to this control element C.
It is intended to supply electricity to the FIGS. 4A and 4B show the relationship between the voltage applied to the discharge lamp 3 and the current flowing through the discharge lamp 3 in the above embodiment. Here, the switching elements 4 and 4a are configured to turn ON and OFF in synchronization with each other, and depending on the method of synchronization, both can be opened at the same time to provide a voltage rest period to the discharge lamp 3. This is also possible when the power supplies 1 and 2 are much larger than the discharge lamp rated voltage VDC. It is also possible to configure the power supply with a large number of power supplies.
Note that although the above description does not mention the starting of the discharge lamp, any of the power sources may also have this function, or a starting device may be provided separately. The present invention is configured as described above, and a discharge lamp is provided with a plurality of power supplies having low internal impedance that are alternately connected to the discharge lamp in a switching manner substantially without using a current-limiting element, The one with the highest voltage is set slightly higher than the rated voltage of the discharge lamp, and the one with the lowest voltage is set slightly lower than the rated voltage of the discharge lamp. A switching element is inserted between the power supply and the discharge lamp, detects the current and power flowing through the discharge lamp, and converts the effective voltage applied to the discharge lamp via the switching element to the discharge lamp rated voltage. Since a control element is provided to control the switching element so as to match, there is no need to provide a current limiting element such as an inductance element, and all switching elements and control elements can be integrated into ICs. Therefore, compared to a lighting device having a conventional inductance element, it has the advantage that it is significantly easier to reduce the size and weight.

Furthermore, since there is no inductance element, there is an advantage that noise due to leakage magnetic flux and noise due to high voltage pulses generated when the current flowing through the inductance element is interrupted is not generated. Furthermore, in the present invention, since a power source with low internal impedance is used as the power source connected to the discharge lamp, it is easy to increase the average amount of electric power supplied to the discharge lamp. This method also has the advantage that it is not necessary to use a large-capacity inductance element, unlike the conventional example, even when lighting a high-capacity discharge lamp.

[Brief explanation of drawings]

Fig. 1 is a block diagram of one embodiment of the present invention, Fig. 2 is a block diagram of another embodiment of the same, Fig. 3 is a diagram of a specific circuit example of the same, and Fig. 4 is an explanation of the operation of the circuit shown in Fig. 3 of the same. 5 is a block diagram of the conventional example, and FIG. 6 is an explanatory diagram of the same operation.
, 2 are power supplies, 3 is a discharge lamp, and 4 and 4a are switching elements.

Claims (1)

[Claims] 1. A discharge lamp is provided with multiple power supplies with low internal impedance that are connected alternately and selectively without substantially using current limiting elements, and the highest voltage of each power supply voltage is lower than the rated voltage of the discharge lamp. The lowest voltage is set slightly higher than the rated voltage of the discharge lamp, and a switching element that alternately switches the plurality of power supplies at a frequency of several tens of cycles per second or more is connected between the power supply and the discharge lamp. A control is inserted between the switching elements and detects the current, power, etc. flowing through the discharge lamp and controls the switching element so that the effective voltage applied to the discharge lamp via the switching element substantially matches the rated voltage of the discharge lamp. 1. A discharge lamp lighting device comprising: an element.