JPS5816320B2 - Howden - Google Patents

Description

[Detailed description of the invention] The present invention relates to a discharge lamp dimming device.

Figure 1 shows an example of the circuit of a conventional discharge lamp dimming device.
It consists of an AC power source 1 and a series circuit of a choke coil 3 for current limiting and a discharge lamp 4 connected via a triac 2 for dimming control to both ends of the AC power source 1.

In such a device, when a power supply voltage V1 as shown in FIG. 2A is applied, each half cycle of the power supply voltage V1 has a constant phase t,
A pulse voltage P is generated and applied to the control end of the triac 2, and the triac 2 begins to conduct from phase t1 as shown in c.

When the triac 2 becomes conductive, a voltage like E appears in the series circuit of the choke coil 3 and the discharge lamp 4.

is added, the discharge lamp 4 is ignited again, and the tube current 4 flows through the choke coil 3 to the discharge lamp 4 as shown in FIG.

The current 4 in the delayed phase extends to the next half cycle, and when its instantaneous value becomes less than the holding current of the triac 2, which is close to zero, in the phase t2, the triac 2 returns to the blocking state and the supply of the tube current I4 is also stopped.

Then, by changing the generation phase t1 of the pulse voltage vP, the phase t
Tube current ■4 by controlling the triac conduction section from 1 to t2
The discharge lamp 4 is dimmed by adjusting the size of the discharge lamp 4.

As mentioned above, the conventional discharge lamp dimming device connects a phase control element such as a triac or a cyrisk in series with the discharge lamp to perform phase control and dim the light, but the voltage at the phase t1.

The magnitude of the voltage applied to the discharge lamp 4 on the verge of re-ignition, which is instantaneous, changes according to the change in phase difference t1; in the region where the conduction section of the triac is short and the tube current ■4 is small, the magnitude of the voltage increases. In the dark areas of the discharge lamp 4 where the dimming is deep, it is difficult to re-ignite the discharge lamp 4 reliably, resulting in flickering or extinguishing.

In particular, in the case of a type in which the discharge lamp 4 is a fluorescent lamp and a starter such as a glow lamp is inserted between both filament non-power terminals to perform preheating conduction, the preheating current decreases as the applied voltage decreases. Therefore, in reality, the limit was control to a dimming ratio of about 50%.

The present invention has been made in view of the above points, and it connects a discharge lamp to both ends of an AC power supply through a current limiting element that supplies a tube current with a delayed phase, and also connects a discharge lamp in parallel with the discharge lamp for phase control. Provided is a discharge lamp dimmer characterized in that a cyrisk is connected to the discharge lamp dimmer.

FIG. 3 is a circuit diagram of an embodiment according to the present invention, in which the triac 2 in FIG. 1 is removed and connected in parallel with the discharge lamp 4.

In such a device, when the power supply voltage V1 is applied as shown in FIG.
When the current 1 is applied to the control end of the triac 2, the triac 2 becomes conductive as shown at 1, and a current 2 indicated by diagonal lines at 2 flows through the choke coil 3 and the triac 2.

This current I2 has a phase 90 degrees behind the power supply voltage V1, and becomes zero at phase t2. At this phase t2, the triac 2 also returns to the blocked state, the short-circuited state at both ends of the discharge lamp 4 is released, and the discharge lamp 4 is re-ignited. A voltage ■S close to the peak value of the power supply voltage ■1 is applied to the previous discharge lamp 4, and the discharge lamp 4 is stably re-ignited, and the tube current ■4 flows as if from phase t2.

When the triac 2 becomes conductive at phase t1, both ends of the discharge lamp 4 are short-circuited again, the supply of the tube current 4 is stopped, and the current 2 starts flowing.

In this way, the triac 2 is opened and closed once in each half cycle of the power supply voltage (1), and by adjusting the conductive phase t1 of the triac 2, the period from t2 to t1 through which the tube current (4) flows is controlled and released. The light 4 is dimmed.

Incidentally, the input current (1) of the device, which is the sum of the currents 11 and I2, has a continuous waveform with no rest period.

The discharge lamp dimmer according to the present invention is constructed and operated as described above, and a cyrisk such as a triac is inserted in parallel with the discharge lamp to supply tube current to the open section of the triac. However, the final phase of the current flowing through the thyrisk such as a triac is controlled by the delay current-limiting element, and is almost constant regardless of the phase in which the thyrisk conducts, and is located near the center phase of each half cycle of the power supply voltage. Therefore, the current flowing through the Cyrisk becomes less than the holding current of the Cyrisk, and the Cyrisk becomes non-conducting, and the voltage applied to the discharge lamp becomes close to the peak value of the power supply voltage, and the discharge lamp continues to operate even in the deep dimming state. Sufficient restriking voltage is applied to obtain stable lighting, no flickering,
This has the effect of eliminating inconveniences such as fading.

FIG. 5 shows a different embodiment of the present invention.
is used as a fluorescent lamp, and a triac 2 is inserted in parallel with the fluorescent lamp 4 via a filament, as shown in FIG.

The current I2 flowing through the triac 2 can be used to heat the filament, and the deeper the dimming state is and the shorter the section in which the tube current 4 flows, the larger the heating current is passed to ensure stable lighting in dark conditions.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example of a discharge lamp dimmer, Fig. 2 is a waveform diagram of each part to explain its operation, and Fig. 3 is a circuit diagram of an embodiment of a discharge lamp dimmer according to the present invention. FIG. 4 is a waveform diagram of each part thereof, and FIG. 5 is a circuit diagram of a different embodiment according to the present invention.

Claims (1)

[Claims] 1. A discharge lamp dimming device characterized in that a discharge lamp is connected to both ends of an AC power source via a current-limiting element that supplies a tube current with a delayed phase, and a cyrisk for phase control is connected in parallel with the discharge lamp. Device.