JPH05242984A - Discharge lamp lighting circuit - Google Patents

Abstract

PURPOSE:To provide a discharge lamp lighting circuit preheating filaments without using a glow discharge tube regarding the preheating circuit of the discharge lamp lighting circuit while the preheating circuit and the lighting circuit are independently constituted. CONSTITUTION:When a power source is turned on, power is fed to preheating filaments 23 on both ends of a discharge lamp via an inverter 14 dedicated to preheating, and power is fed to a main circuit by a delay circuit 12 when the preset period elapses after the power source is turned on.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting circuit, and more particularly to a preheating circuit for the discharge lamp lighting circuit.

[0002]

2. Description of the Related Art In the case of lighting a discharge lamp, for example, a fluorescent lamp, preheating the electrodes at both ends thereof facilitates lighting. Therefore, conventionally, when the power is turned on, a current is temporarily applied to the filaments that form both electrodes through the glow discharge bulb, and the extinction of the glow discharge bulb is used to apply a high voltage between both filaments (electrodes) to turn it on. There is a way to do it. In addition, as shown in FIG.
There is also a configuration in which the filament 23 at both ends of the discharge lamp is supplied with a current at the same time when the power is turned on by supplying the electric current to the filament No. 3 to facilitate lighting.

[0003]

According to the conventional method using the glow discharge bulb, there is a drawback that it takes a long time for lighting and the life of the glow discharge bulb is short and replacement is troublesome.

Further, in the structure in which the step-up transformer is shunted to supply electric power to the filament 23, a large current flows through the filament 23 at the time of lighting, which shortens the life of the discharge tube 30. Further, in the above configuration, only the preheating circuit cannot be turned on prior to lighting, which causes non-lighting in cold regions. Further, there is a drawback that the both ends of the discharge tube become black after long-term use, that is, a so-called blackening phenomenon occurs and the appearance is impaired.

The present invention has been proposed in view of the above-mentioned conventional circumstances, and does not use a glow discharge bulb, and has a preheating circuit and a lighting circuit independent of each other. The purpose is to provide a circuit.

[0006]

The present invention employs the following means in order to achieve the above object. When the power is turned on, power is supplied to the preheating filaments at both ends of the discharge lamp through the inverter dedicated to preheating, and the delay circuit is configured to supply power to the main circuit after a predetermined time has passed after the power was turned on. The preheating inverter may be configured to supply a small amount of power to the precharging filament when the power is off, or the preheating inverter may be configured to change the power supplied to the precharging filament when the power is on and off.

[0007]

In FIG. 1, when the power supply is turned on while SW2 is turned on, the inverter 15 for exclusive use of preheating is operated and electric power is supplied to the filaments 23 at both ends of the discharge tube 30. When the delay circuit operates in this state, the main circuit, that is, the inverter 40 that applies a high-voltage and high-frequency wave between both electrodes (filament 23) at both ends of the discharge tube 30 is activated after a predetermined time has elapsed since the power was turned on. Further, when the SW2 is turned on, the inverter 15 dedicated to preheating always operates, and the electric power is supplied to the filaments 23 at both ends of the discharge tube 30. When the power source is turned on (SW1 is turned on) in this state, the inverter 40 for applying a high-voltage and high-frequency wave between both electrodes of both ends of the discharge tube 30 is operated similarly to when SW2 is turned on. The power is controlled by the chopper circuit 13 of the preheating-dedicated inverter 15 based on the establishment of the power source of the main circuit, which allows an optimum current to flow through the filament 23 during lighting.

[0008]

1 is a block diagram showing an embodiment of the present invention. Electric power is directly applied to the primary winding T ₁ of the transformer T ₀ without passing through the rectifying bridge 21 to the main circuit of the power supply unit,
Electric power is supplied to the preheating dedicated inverter 15 via the secondary winding T ₂ and the rectifying unit 11. Preheater dedicated inverter 1
5 is, for example, a bistable multivibrator (PP switching circuit) and a chopper circuit which are activated by turning on the power supply, and alternately turns on the two outputs A and B of the multivibrator 12 at, for example, 60 KHz. This 2
Receiving the two outputs, the output side transistors Tr _14a , T
r _14b is alternately turned on, and the transistor Tr _14a ,
A current is passed through the primary winding of the output transformer T ₁₀ connected in parallel with the Tr _14b , and a current is passed through the filaments 23 at both ends of the discharge lamp 30 by the secondary winding thereof.

On the other hand, a delay circuit 12 is connected to the rectifier circuit 11, starts operating at the same time when power is turned on, and turns on the transistor Tr ₁₂ on the output side after a lapse of a predetermined time, and is inserted into the power line. Photo Triac T
by applying a current to the series circuit formed by the light emitting diode D ₁₅ of the r _15, the light emitting diode D ₁₅ to ON (to emit light), it is turned ON triac Tr _15a in a pair with the light emitting diode D _15.

The triac Tr _15a has a function of turning on and off the current line to the rectifying bridge 21 of the main circuit. When the diode D ₁₅ is turned on, the rectifying bridge 21 is turned on and power is supplied to the main circuit. Is supplied. As described above, when power is supplied to the main circuit while the filament 23 is preheated, the discharge lamp is immediately turned on.

As described above, when the lighting time is sent by the delay circuit 12 (the preheating time is lengthened), the discharge lamp is turned on as soon as power is supplied to the main circuit as described above. However, the degree of occurrence of the blackening phenomenon of the discharge tube is reduced. For example, conventionally, a blackening phenomenon occurs when 40 seconds on and 40 seconds off are repeated 9,000 times or more, but in the present invention, the blackening phenomenon does not occur even when the same test is repeated 70,000 times or more.

Further, by leaving SW2 on the side, the preheating dedicated inverter 14 is always energized, and power is supplied to the filament 23. As a result, the discharge lamp 30 enters the hot standby state (the discharge lamp is warmed). The preheat-dedicated inverter 15 can change the gain when the power is on and when it is off. That is, when the power is turned off, the chopper circuit 13 is operated with a small gain so that a minute current is made to flow through the preheating filament 23, and at the same time when the power is turned on, the voltage detection means 10 detects that the power is turned on. Then, the reference voltage of the chopper circuit 13 is changed (decreased) to operate with a large gain. As a result, the inverter 15 can supply a larger current to the preheating filament than when the power is off, and the lighting can be performed smoothly.

[0013]

As described above, according to the present invention, since the power for preheating is supplied from the part different from the step-up transformer, the power control process can be performed by the low voltage circuit, the design is easy, and the lighting is on. Since an appropriate electric current is passed through the filament, the filament consumption can be reduced and the life of the discharge tube can be extended. Further, since the preheating time is lengthened and an excessive current does not flow at the time of lighting, it is possible to prevent the blackening of the both electrodes due to long-term use. In addition, turning on the preheating circuit at all times has the effect of facilitating lighting at low temperatures.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional example.

[Explanation of symbols]

 12 Delay circuit 13 Switching circuit 14 Preheating dedicated inverter 23 Filament

Claims (3)

[Claims] 1. When power is turned on, power is supplied to preheat filaments at both ends of the discharge lamp through an inverter dedicated to preheating, and a delay circuit is used to supply power to the main circuit after a predetermined time has elapsed since the power was turned on. Discharge lighting circuit characterized by. 2. The discharge lighting circuit according to claim 1, wherein the preheating inverter supplies a small amount of electric power to the precharging filament even when the power is off. 3. The preheating inverter is turned on when the power is on.
A discharge lighting circuit configured to change the power supplied to the precharge filament at the time of F.