JPS61156698A - 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 discharge lamp lighting device that prevents striation (striped light emission) of a discharge lamp at low temperatures.

[Background of the Invention] As a conventional discharge lamp lighting device, one is known that converts electric power from a commercial power source, a battery, etc. into high frequency to light one or multiple discharge lamps.

By the way, in such devices, depending on the frequency of high-frequency power and environmental conditions, the discharge lamp (lamp) may
There is a problem in that striations (moving stripe phenomenon) occur, in which light is emitted in a striped manner. In addition, in order to prevent this striation, it is sufficient to make the lamp voltage at low temperatures asymmetric between positive and negative, but conventionally, as shown in Figure 8, a diode 21 and a resistor (or a positive characteristic A striation prevention circuit 2 is connected, which consists of a series circuit with a thermistor 22, and which equivalently superimposes a DC component on the lamp current IL (the shaded area in FIG. 9). However, in this case, as shown in FIG. 9, the current IL flows through the striation prevention circuit 2 over the entire cycle of the high-frequency power supplied to the lamp 1, so that the power consumption in this circuit 2, that is, the resistor 21 is reduced. For example, each 40 W fluorescent lamp has a relatively large power of 0.2 to 0.5 W, which poses problems in the power capacity and reliability of the resistor, and also reduces the efficiency of the lighting device.

[Object of the Invention] The present invention has been made in view of the problems in the conventional type described above, and an object of the present invention is to further reduce the power consumption of the striation prevention circuit in a discharge lamp lighting device.

[Explanation of Examples] Hereinafter, the present invention will be explained in detail using the drawings.

Note that parts that are common or correspond to those of the conventional example are denoted by the same reference numerals. -0 Figures 1 (a) to (d) show a discharge lamp lighting device according to an embodiment of the present invention and a modification thereof. It is a main part circuit diagram. The lighting device shown in FIG. 2A includes a DC power supply (not shown), and a transistor inverter 3 as a high frequency conversion device is connected between output terminals a and b of the DC power supply.

This inverter 3 uses a so-called series inverter, and has an output terminal a of the DC power supply.

A series circuit of transistors 31 and 32 is connected between 6,
A base drive circuit (not shown) is connected to the bases of these transistors 31 and 32 to alternately drive these transistors 31 and 32 on and off.
．． Diodes 33 and 34 are connected in antiparallel to 32, and a series circuit of DC cut capacitors 35 and 36 is connected between the output terminals a and b of the DC power supply, and
The high frequency output @C which is the connection point of the above transistors 31J3 and 32 and the connection point d of the above capacitors 35 and 36
A discharge lamp (lamp) 1, a palast inductor 41 between
, a load circuit consisting of a capacitor 42 for starting the lamp, etc. is connected thereto.

Furthermore, a striation prevention circuit 2 consisting of a series circuit of a diode 21 and a resistor 22 is connected between the connection point e between the lamp 1 and the palast inductor 41 and the negative output terminal of the DC power supply. Connect in a direction that does not allow direct current to flow from the power supply.

Next, the operation of this lighting device will be explained.

When the DC power supply 1 is turned on, transistors 31 and 32 are turned on alternately by a signal from the base drive circuit, thereby generating a high frequency rectangular wave output at the high frequency output terminal C. This square wave output is supplied to both filaments of lamp 1 via a series resonant circuit of inductor 41 and capacitor 42, heating them. Further, the series circuit of the inductor 41 and the capacitor 42 almost resonates with the frequency of the rectangular wave output, and a high voltage is applied between both filaments of the lamp 1 due to this resonance, and the lamp 62 is lit. After lighting, the lamp load connected in parallel with the capacitor 42 becomes a low impedance, and the Q of the LC resonance circuit consisting of the inductor 41 and the capacitor 42 decreases. act.

In this case, the voltage applied to the load circuit is
5.36, the DC component is cut and the DC voltage becomes 1/
2E (where E is the output voltage of the DC power supply) is a rectangular AC wave with a wave height of ±1/2E.

In addition, the voltage applied to the lamp 1 has a peak value of 1 as shown in FIG.
It is a substantially sinusoidal alternating current larger than /2E.

After the lamp 1 is turned on, the substantially sinusoidal voltage is applied to both ends of the striation prevention circuit 2 with a DC bias of 1/2E, as shown in FIG.

Therefore, in a section where the instantaneous value of the substantially sinusoidal voltage in the negative phase is larger than the DC bias 1/2E, the diode 21 of the striation prevention circuit 2 is forward biased and turned on. Therefore, part of the lamp current IL of the lamp 1 (the shaded area in FIG. 7) is bypassed to the circuit 2 in this section.

In Figure 1, (b) to (small) show modified examples of (a), (b) is an example in which the striation prevention circuit 2 is connected to the positive output terminal a of the DC power supply, and (C) is an example in which the lamp is connected to the positive side output terminal a of the DC power supply. An example in which two lamps are lit in series. The figure is shown in Figure 1 (
In contrast to C), an example is shown in which the connection position of the striation prevention circuit 2 is moved from the connection point between the inductor 41 and the lamp 1 to the connection point between the lamp 1 and the lamp 1'.
In contrast to FIG. 1C, an example is shown in which the striation prevention circuit 2 is connected to the positive output terminal a of the DC power supply, and in contrast to FIG. An example is shown in which the connection order (polarity) of the yoke series circuit of ′ is reversed.

In addition, in FIGS. 3 and 4, the capacitor 37 is a DC cut capacitor similar to the capacitors 35 and 36 in FIG. 1 and the like.

As mentioned above, in a series inverter, the DC power supply and the lamp current path are connected in a DC manner, so
A DC component can be superimposed on the lamp current IL by using the DC power supply voltage. That is, when a certain point of the voltage at the terminal connected to the striation prevention circuit 2 of the lamp 1 becomes higher or lower than the voltage of the DC power supply, the diode 21 clips it. As a result, the effective value of the current flowing through the resistor 22 can be reduced, and the resistor can be omitted in some cases, thereby reducing circuit loss. Furthermore, by clipping only when VF is high, it is possible to superimpose the DC component only during dimming. The loss in the above striation prevention circuit is, for example, in a 200V 40W two-lamp discharge lamp lighting device, where the loss of the resistor 22 per lamp was 0.36 W in the conventional case, but the present invention is applied. If the striation prevention effect is made the same, 0.1
It became 3 W.

FIG. 5 shows an example in which a single-stone transistor inverter is used as the high frequency conversion device. In the discharge lamp lighting device shown in the figure, one end of the output winding of the output transformer 38 of the inverter 3 is connected to the positive output terminal a of the DC power supply, and a high-frequency AC voltage to be output is biased by a DC power supply voltage E. is granted. In addition, 1 of such a single inverter
The AC component peak value of the surrounding lit electromotive force is the DC power supply voltage E
Therefore, in order to ensure that the peak value of the voltage applied to the lamp 1 exceeds the DC bias E, a high-frequency AC output with the other end of the output transformer 38 tapped up is supplied to the load circuit. I try to do that. The action of the striation prevention circuit 2 is similar to that of FIGS. 1-4.

Note that the output transformer 38 may be provided with a secondary winding to boost the AC voltage. In this case, one end of the secondary winding is connected to one of the output terminals of the inverter DC power supply or other DC power supply, and the striation prevention circuit 2
is connected to the other terminal.

The device shown in FIG. 6 uses a constant current push-pull inverter instead of the single type inverter shown in FIG. In the figure, the inverter 3 connects the center tap of the output winding of the output transformer 38 to the positive output terminal a of the DC power supply.
, the output high-frequency AC voltage has a DC bias equal to the DC power supply voltage E added to it. In addition,
In a push-pull inverter, the peak value of the AC component of the primary winding induced voltage is the same as the DC power supply voltage E, and considering the effect of the inductance 41, the peak value of the AC voltage applied to the lamp 1 is the same as the DC power supply voltage E. Since the voltage is higher than the voltage E, there is no need to tap up the output winding of the skewer transformer 38 as in the single type inverter shown in FIG. The action of the striation prevention circuit 2 is similar to that of FIGS. 1-4.

Note that the connection when the output transformer 38 is provided with a secondary winding is the same as that shown in FIG.

[Modified example of the embodiment] In the above embodiment, resistor 2 is used as the impedance element.
Although the case where impedance element 2 is used has been described, other impedance elements can also be used.

For example, if a positive temperature coefficient thermistor is used, the striation prevention circuit 2 is more effective at low temperatures where striation is likely to occur, and reduces loss at normal or high temperatures where striation is less likely to occur. Applying a DC bias with a voltage lower than the peak value of the AC voltage, and bypassing part of the current to the discharge lamp only in the section where the absolute value of one polarity of the AC voltage exceeds this DC bias voltage, the lamp current is changed to DC bias. Since the striation of the discharge lamp is prevented by superimposing the components, the loss of this bypass circuit, that is, the striation prevention circuit, is reduced, improving the efficiency of the device, and the striation prevention circuit is configured. By reducing losses in the resistor, its power capacity can be reduced or the resistor can be eliminated, improving device reliability and reducing cost.

[Brief explanation of the drawing]

1 to 6 are circuit diagrams of main parts of a discharge lamp lighting device according to an embodiment of the present invention, FIG. 7 is a voltage/current waveform diagram of the discharge lamp in the discharge lamp lighting device of FIG. 1, and FIG. 8 is a conventional diagram. FIG. 9 is a circuit diagram showing a striation prevention circuit portion of the discharge lamp lighting device of FIG. 8, and FIG. 9 is a voltage/current waveform diagram of the discharge lamp in the discharge lamp lighting device of FIG. DESCRIPTION OF SYMBOLS 1...Lamp, 2...Striation prevention circuit, 21...Diode''-ode, 22...Resistor, 3...
Inverter, 41...inductor.

Claims (1)

[Claims] 1. A device comprising one or more DC power supplies and a conversion device that generates AC power from one DC power supply, and supplies the AC power to a series circuit of an inductor and one or more discharge lamps. In a discharge lamp lighting device for lighting the discharge lamp, there is a predetermined DC potential difference between the connection point of one of the discharge lamps with the inductor or another discharge lamp and the DC power supply with respect to the discharge lamp. A discharge lamp lighting device characterized in that a series circuit of a diode and an impedance element is connected between a DC power supply having a DC power source and a DC power source having a diode and an impedance element in a direction in which the diode has a polarity opposite to the DC potential difference. 2. A patent in which the conversion device is a series inverter in which a pair of switching elements that are turned on and off alternately are connected in series to the one DC power source, and a high frequency rectangular wave voltage is output from a connection point of these switching elements. A discharge lamp lighting device according to claim 1. 3. The discharge lamp lighting device according to claim 1, wherein the conversion device is a single transistor inverter. 4. The discharge lamp lighting device according to claim 1, wherein the conversion device is a two-stone transistor inverter. 5. The discharge lamp lighting device according to claim 1, wherein the impedance element is a resistance circuit including a positive temperature coefficient thermistor.