JPH0332199B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a discharge lamp lighting circuit that sequentially lights one discharge lamp having a plurality of discharge paths or a plurality of discharge lamps at high speed.

[Background Art] We have specially developed a fluorescent lamp which has three inner tubes emitting light of different colors, and which is made into a variable color lamp by switching the inner tubes one after another at high speed to make the mutual light emission period ratio variable. The application has already been filed as Application No. 131593/1983. As shown in Figure 8, this is the outer tube 1.
In the discharge space airtightly formed by the stem 2 and the stem 2, there are three inner tubes 3R, 3 which are curved into a substantially U-shape and have their inner surfaces coated with phosphors that emit red, green, and blue light.
G, 3B are arranged. The inner tube 3R, 3
One end of each of G and 3B is hermetically fixed around the anode 4 by glass welding, and the other end is open near the common cathode 5 coated with an electron emissive material.

Figure 9 shows an example of a basic lighting circuit for such a lamp (discharge lamp FL), in which a discharge path selection switch SW is connected to the anode end of the DC power supply DC.
Three terminals x, y, and z of the switch SW are connected to three anodes 4x, 4y, and 4z of the discharge lamp FL, respectively. Further, the cathode end of the DC power source DC is connected to the cathode 5 of the discharge lamp FL via a current limiting resistor R. FIG. 10 shows a lighting time chart in such a lighting circuit, in which three discharge paths are sequentially switched by a discharge path selection switch SW. The figure shows an example in which t ₀ to _{t 2} are white and t ₂ to _{t 4} are yellow. In other words, the period T is divided into three discharges, and the inner tubes 3R, 3G, and 3B are time-divisionally lit.
By changing the division ratio, the mutual luminous flux ratio is changed and the color is changed.

In such an example, the cathode 5 is shared by the three discharges, so even if the hue (luminous flux ratio) is changed, the current flowing through the cathode 5 is kept almost constant, so there is no change in color change response, lifespan, etc. This is particularly advantageous because the current limiting element for the three discharge paths can also be shared, so the lighting circuit can be made smaller and lower in cost.

By the way, in the lighting circuit shown in Figure 9, the DC power supply DC
The discharge lamp FL is lit from the source, and for practical purposes, it is desirable to light it from a commercial AC power source. However, in that case, unless a sufficiently smoothed DC power source is used, the discharge current will fluctuate between each period (t ₀ -t ₁ , t ₁ -t ₂ , . . . ), causing flickering in the light emission. Therefore,
In order to obtain direct current with a low ripple rate, an extremely large capacity smoothing capacitor is required, resulting in a large and expensive lighting circuit.

[Object of the Invention] The present invention has been provided in view of the above-mentioned points, and provides variable color light emission through multiple discharge paths using an AC power source without flickering, and eliminates the need for a large-capacity smoothing capacitor. The purpose of this invention is to provide a discharge lamp lighting circuit that is smaller in size and lower in cost.

[Disclosure of the Invention] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a basic block diagram of the present invention, in which the discharge lamp FL is connected to an alternating current power source AC via a current limiting element (current limiting impedance). Further, a discharge path selection switch SW serving as a switching means is inserted between the current limiting impedance and the discharge lamp FL, and each terminal x, y, z of the switch SW is connected to the discharge lamp FL.
are connected to the anodes 4x, 4y, and 4z, respectively. Further, a cycle setting circuit 6 is connected to the AC power supply AC, and this cycle setting circuit 6 sets a cycle based on the AC power supply AC.
That is, it synchronizes with the alternating current power source AC and outputs a synchronizing signal to the time division circuit 7 at the next stage. The time division circuit 7 uses a synchronization signal from the period setting circuit 6 to time division control the discharge path selection switch SW at a desired division ratio, with one cycle being a half wave of the AC power supply. The discharge lamp FL has three inner tubes 3R, 3G, and 3B, which are discharge paths, as in the conventional example.

2 shows a specific circuit diagram of the lighting circuit, FIG. 3 shows a specific circuit diagram of the control circuit 8 consisting of the period setting circuit 6 and the time division circuit 7 shown in FIG. 2, and FIG. indicates the current or voltage waveform of each part of the circuit. In FIG. 2, an alternating current power source AC is full-wave rectified by a diode bridge DB ₁ and smoothed by a smoothing capacitor C ₁ . The positive side of the smoothing capacitor C ₁ or diode bridge DB ₁ connects each anode 4 of the discharge lamp FL, which has three discharge paths.
The negative side _{of the} smoothing capacitor _C1 or diode bridge _DB1 is connected to the common cathode of the discharge lamp FL via the current limiting resistor _R. 5. Further, the voltage is stepped down from the alternating current power supply AC via a transformer T, and then full-wave rectified by a diode bridge DB ₂ and smoothed by a smoothing capacitor C ₂ to supply power to the control circuit 8 . And the control circuit 8
A control signal is output from the transistors Tr ₁ to _{Tr 3} . The control circuit 8 shown in FIG. 3 is composed of the cycle setting circuit 6 and the time division circuit 7 as described above, and the cycle setting circuit 6 is composed of diodes d ₁ and d ₂ , a transistor Tr ₄ , a flip-flop 9, etc. , the time division circuit 7 includes flip-flops 10 to 1.
2. It is composed of transistors Tr ₅ to Tr ₇ , etc. Note that a to d in FIG. 3 correspond to a to d in FIG. 2.

Next, the operation will be explained. Here, Figure 4a shows the waveform of the AC power supply AC, and Figure 4b shows the smoothing capacitor.
Indicates the voltage V _D across C ₁ . Further, I to I in FIGS. 4C to 4I show the voltage waveforms at points I to I in FIG. 3, and FIG. 4J shows the discharge current _I1 of the discharge lamp FL. First, a pulse-like voltage B synchronized with the power cycle is formed by a transistor Tr ₄ from a voltage A obtained by fully rectifying the alternating current on the secondary side of the transformer T. This pulsed voltage is a one-shot flip-flop (4528).
9 input terminal A, capacitor C ₃ and resistor r ₄
A pulse output C having a width determined by a time constant according to the output terminal Q is outputted from the output terminal Q, and at the same time, its inverted output terminal C is outputted from the inverted output terminal. The pulse output C is input to the input terminal A of the flip-flop 10 of the time division circuit 7, and is also connected to the capacitor _C4 and the variable resistor.
A pulse output with a width determined by Vr ₁ can be obtained. Here, the pulse width is made variable by variable resistor _Vr1 . The inverted signal of the pulse output H output from the inverted output terminal of the flip-flop 10 is input to the input terminal A of the flip-flop 11, and from the time the pulse output H changes from the H level to the L level, the output of the flip-flop 11 is connected to the capacitor C. ₅ and a pulse output determined by variable resistor Vr ₂ . Similarly, a pulse output is obtained from the flip-flop 12. The inverted signal D of the pulse output C is input to the terminal C of the flip-flops 11 and 12, and is reset every cycle. The respective pulse outputs H, H, and G are inverted and amplified by transistors Tr ₅ to Tr ₇ , respectively, to obtain base signals for transistors Tr ₁ to _{Tr 3} of the main circuit (lighting circuit). In other words,
During the half-wave of the AC power source AC, pulse outputs H, H, and G are sequentially output as shown in Fig. 4 g to i, and the transistors Tr ₅ to _{Tr 7} and Tr ₁ to _{Tr 3} are time-divisionally controlled. The discharge current is switched and made to flow through the discharge path of the discharge lamp FL.

The current I ₁ flowing through one discharge path of the discharge lamp FL is
The current flows only during the conduction period of the transistor _Tr1 , that is, the period when the pulse output H is at the H level, and the current becomes irregular depending on the voltage _VD across the capacitor _C1 , as shown in FIG. 4J. Here, in order to make the voltage V _D completely direct current with no alternating current component, it is necessary to make the capacitor C ₁ extremely large, resulting in a large and expensive circuit. On the other hand, capacitor C ₁
Since the ripple rate increases when the capacitance of
The waveform becomes as shown in the figure, and the waveform of the current _I1 becomes irregular as shown in Fig. 5f. Therefore, the amount of light emitted from the discharge lamp FL changes every cycle, causing flickering. Therefore, in order to keep the circuit compact and low-cost and eliminate flickering in the discharge lamp FL, it is extremely effective to synchronize the cycle of the AC power source AC and the cycle of switching the discharge path, as in the present invention. It is something that brings.

FIG. 6 shows another embodiment, and
FIG. 7 is an example of a time chart of voltage and current waveforms showing the operation of this embodiment. This uses an inductance L as a current limiting impedance, and this inductance L is inserted and connected between the alternating current power supply AC and the diode bridge _DB1 . The rest of the configuration is almost the same as that shown in Fig. 2, but the voltage after rectification by the diode bridge _DB1 is not smoothed, or if a capacitor is inserted, one with extremely small capacitance is used. The control circuit 8 is exactly the same as in FIG.

When transistors Tr ₁ to Tr ₃ are turned on and off in the pulse output patterns shown in Figure 7 d, e, and f, the diode bridge
The output voltage V _D of DB ₁ produces a high voltage pulse at the moment of switching the discharge path, as shown in FIG. 7b. This is because the current I _D tends to become zero at the moment the discharge path is switched, as shown in FIG. 7c, and a high voltage pulse is generated from the inductance L. The currents I ₁ to I ₃ flowing in each discharge path are shown in Fig. 7g,
h and i, and the unevenness of each waveform is larger than in the case of FIG. 4, but since the waveform is periodic, flickering of the discharge lamp FL does not occur. In this way, in this embodiment, by eliminating the smoothing capacitor and setting the current limiting impedance to the inductance L, the resistance R
The loss is smaller than when using . In addition, since a high-voltage pulse is generated at the moment of switching the discharge path, lighting can be maintained (switching the discharge path) even at low power supply voltages. Therefore, the difference between the lamp voltage and the power supply voltage can be reduced, further reducing circuit loss. It can be made small. In both embodiments, the discharge path inside one discharge lamp as shown in FIG. 8 is switched, but the present invention can also be applied to the case where a plurality of discharge lamps are switched. By adopting such a lighting method, there is an effect that the current limiting resistor R or inductance L as a current limiting element can be made common (one).

[Effects of the Invention] As described above, the present invention includes an AC power source, a period setting circuit that synchronizes with the AC power source and outputs a synchronization signal, and a predetermined discharge current that is caused to flow through a plurality of discharge paths via a current limiting element. a switch means that causes a plurality of discharge paths to emit light in variable colors by switching within a cycle; and a time division circuit that is driven by a synchronizing signal from a cycle setting circuit and controls the switch means in a time division manner using a half wave of an AC power source as one cycle. Since it is equipped with a period setting circuit, it is synchronized with the AC power supply, and this synchronization signal is input to the time division circuit, and the synchronization signal drives the switch means for switching multiple discharge paths to perform time division control. By doing so, the discharge current flowing through the same discharge path has the same waveform, so it is possible to emit variable color light without flickering through multiple discharge paths using an AC power source as a power source, without using a large-capacity smoothing capacitor. In addition, since a large-capacity smoothing capacitor is not required, the circuit can be made smaller and lower in cost. Furthermore, this lighting method is not limited to the method of switching the discharge path inside one discharge lamp as shown in Fig. 8, but can also be applied to the case of switching multiple discharge lamps. This has the effect that current-limiting elements such as current-limiting resistors or inductances can be shared (used as one).

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a specific circuit diagram of the same lighting circuit, FIG. 3 is a specific circuit diagram of the same control circuit, and FIG.
The figure is a time chart of the same as above, Fig. 5 is a time chart of the same without synchronization, Fig. 6 is a specific circuit diagram of the lighting circuit of another embodiment of the same, and Fig. 7 is a time chart of the same as above, FIG. 8 is a perspective view of the discharge lamp, FIG. 9 is a circuit diagram of a conventional example, and FIG. 10 is a time chart of the same. 6 is a cycle setting circuit, 7 is a time division circuit, AC is an alternating current power supply, and L is an inductance.

Claims (1)

[Claims] 1. An AC power source, a period setting circuit that synchronizes with the AC power source and outputs a synchronization signal, and a plurality of discharge currents that switch discharge currents flowing through a plurality of discharge paths via current limiting elements within a predetermined period. A discharge path comprising a switch means for emitting variable color light through a discharge path, and a time division circuit that is driven by a synchronizing signal from a cycle setting circuit and controls the switch means in a time division manner using a half wave of an AC power source as one cycle. Light lighting circuit. 2. The discharge lamp lighting circuit according to claim 1, wherein the current limiting element is an inductance.