JPS6332239B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a discharge lamp dimming device.

FIG. 1 is a circuit diagram of a discharge lamp dimmer device which is the basis of this invention. In the figure, B is the dimming ballast, T is the leaky transformer which is the main component of the dimming ballast B, P is its shunt winding, S is its series winding, and TH is the shunt winding. A thyristor for phase control is inserted and connected in series to P, f ₁ and f ₂ are preheating windings wound on the same iron core as the shunt winding P, E is an AC power supply,
SW is a power switch, L is a discharge lamp load consisting of a fluorescent lamp connected to the output end of a dimming ballast B, and both filament ends are connected to preheating windings f ₁ and f ₂ , respectively.

In such a device, when the power switch SW is turned on and a phase control signal is applied to the thyristor TH, the conduction phase of the thyristor TH is controlled, the phase of the current flowing through the shunt winding P is controlled, and the series winding The induced voltage of S is controlled, the output voltage of the leakage transformer T is controlled, the lamp current of the discharge lamp load L is controlled, the brightness of the discharge lamp load L changes, and the thyristor TH is fully conductive to obtain rated lighting. , thyristor
The lowest brightness can be obtained in the shortest conduction section of TH, and dimming control can be performed.

The device shown in Fig. 1 operates in this manner and is capable of controlling the dimming of the discharge lamp load L, since the phase control by the thyristor TH is performed by the shunt winding P of the leaky transformer T. , the control current is smaller compared to the conventional system in which a phase control element is placed on the input side of the device to control the phase of the input current, and therefore the current capacity of the thyristor TH may be small, and the Also, shunt winding P
Although no voltage is induced in the series winding S, a small amount of current is supplied through the series winding S, which has the effect of reducing the period during which the lamp current stops. However, since the preheating windings f ₁ and f ₂ of the discharge lamp load L are wound on the same iron core as the shunt winding P, the conduction section of the thyristor TH is short, and when the lamp current is small, the preheating windings The voltages of the wires f ₁ and f ₂ are also low and the discharge lamp load L is not sufficiently preheated. For example, in a control state where the lamp current is 20% of the rated value, the preheating windings f ₁ and f ₂ Under such deep dimming conditions, the lighting condition of the discharge lamp load L becomes unstable due to insufficient preheating, and combined with the decrease in lamp current, the discharge lamp As a result of maintaining the lighting in a state where the electrode of the load L is lower than a predetermined value, there is a drawback that the service life is shortened.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a discharge lamp dimming device that can sufficiently preheat a discharge lamp load even in a deep dimming state.

FIG. 2 shows an embodiment of the present invention. In FIG. 1, a preheating transformer FT is used instead of the preheating windings f ₁ and f ₂ wound on the same iron core as the shunt winding P.
and its primary winding is connected in parallel with the series circuit of the thyristor TH and part _n1 of the shunt winding P, and its two secondary windings are connected to both filaments of the discharge lamp load L. ing.

As a result of this configuration, it is possible to perform dimming control of the discharge lamp load L by controlling the conduction phase of the thyristor TH, as in the case of FIG. 1, but in this device, the preheating transformer is Since the power for FT is taken from both ends of the series circuit of thyristor TH and part _n1 of shunt winding P, the thyristor
If the conducting section of TH is t ₁ and the non-conducting section is t ₂ , and the remainder of part n ₁ of shunt winding P is n ₂ , then the preheating transformer
The voltage applied to FT is t ₂ V / (t ₁ + t ₂ ) + t ₁ n ₁ V / (t ₁ + t ₂ ) (n ₁ + n ₂ ), and when the thyristor TH is fully conductive and the discharge lamp load is lit, n The filament preheating voltage shows the rated value at ₁ V/(n ₁ + n ₂ ), and when the thyristor TH is completely non-conducting, a voltage approximately equal to the power supply voltage V is applied to the preheating transformer FT, and the filament preheating voltage reaches the rated value (n ₁ +n ₂ )/n ₁ times, and the filament preheating voltage can be minimized at rated lighting and increased as the dimming becomes deeper. As a result, when dimming is deep and the lamp current is small, the preheating current is increased to eliminate instability in lighting due to insufficient preheating, offset the decrease in electrode temperature of the discharge lamp load L due to the decrease in lamp current, and load the discharge lamp. It is possible to prevent the life of L from decreasing. Of course, the voltage division ratio of the shunt winding P is
By arbitrarily selecting n ₁ and n ₂ , the characteristics of the preheating voltage can be obtained freely.

FIG. 3 shows another embodiment of this invention,
Directly connect the primary winding of the preheating transformer FT to the thyristor
The preheating windings f ₁ , f are connected to both ends of the TH and their two secondary windings are respectively wound on the same iron core as the shunt winding P of the leaky transformer T, as shown in FIG. ₂
It is connected in series with the filament of the discharge lamp load L.

In such a device, a voltage is generated in the preheating windings f ₁ and f ₂ that decreases as the conduction section of the thyristor TH becomes shorter and the dimming of the discharge lamp load L becomes deeper. Since a voltage is generated in the secondary winding that increases as the conduction section of the thyristor TH becomes shorter, the preheating voltage expressed by the sum of these voltages is determined by the winding ratio of the preheating windings f ₁ and f ₂ and the preheating transformer FT. By appropriately selecting , it is possible to increase the desired characteristics as the lamp current decreases, and it is possible to prevent unstable lighting during dimming and shortening of life.

As described above, the discharge lamp dimmer device of the present invention has the following features:
A thyristor for phase control is connected in series to the shunt winding of a single-turn leaky transformer, and the series winding of the leaky transformer is connected in series to the shunt winding and the series circuit of the thyristor. In a discharge lamp dimmer device in which an AC power source is connected between both ends of a series circuit of a wire and a thyristor, and a discharge lamp load is connected between both ends of the series circuit of the series winding, shunt winding, and thyristor, a leakage transformer is provided. A voltage equal to a portion of the voltage in the shunt winding of the thyristor plus at least a portion of the voltage across the thyristor was applied to the filament of the discharge lamp load (second
In the embodiment shown, the voltage is the sum of a portion of the voltage in the shunt winding of the leaky transformer and the entire voltage across the thyristor; in the embodiment shown in FIG. and at least a portion of the voltage across the thyristor). By setting the ratio appropriately, the preheating current can be increased as the dimming becomes deeper, and when the lamp current decreases due to deeper dimming and the filament temperature tends to decrease, the preheating current can be increased. The dimming limit can be increased to compensate for the decrease in filament temperature, thus lowering the dimming limit at which the discharge lamp load goes out, increasing the dimming range, and extending the life of the discharge lamp load.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a discharge lamp dimmer device which is the basis of this invention, FIG. 2 is a circuit diagram of one embodiment of this invention, and FIG. 3 is a circuit diagram of another embodiment. B...Dimmer ballast, T...Leakage transformer, P...Shunt winding, S...Series winding, _f1 , _f2 ...Preheating winding, TH...
Thyristor, L...discharge lamp load, FT...preheating transformer, _n1 , _n2 ...part of the primary winding.

Claims (1)

[Claims] 1. A thyristor for phase control is connected in series to the shunt winding of a single-turn leaky transformer, and the series winding of the leaky transformer is connected in series to the series circuit of the shunt winding and the thyristor. an alternating current power source is connected across the series circuit of the shunt winding and the thyristor, and a discharge lamp load is connected between the series circuit of the series winding, the shunt winding, and the thyristor. The dimmer is characterized in that a voltage equal to the sum of part of the voltage of the shunt winding of the leaky transformer and at least part of the voltage across the thyristor is applied to the filament of the discharge lamp load. Electric light dimmer.