JPH06203982A - Fluorescent lamp lighting system - Google Patents

Abstract

PURPOSE:To prevent the generation of a cold cathode discharge at discharge start, and extend the life of a fluorescent lamp by connecting both electrodes of the fluorescent lamp to the secondary winding of a current transformer with a capacitor between, and carrying a specified high frequency current to the primary winding in two stages. CONSTITUTION:A high frequency constant current of a first frequency is carried to a feed line 2 connected to an inverter 1 as the primary winding of a current transformer 3 and extended through the transformer 3 only for a short time at lighting, so that the terminal voltage of a capacitor C is lower than the discharge start voltage of a fluorescent lamp 5. A heater current is carried through the capacitor C to preheat electrodes 6, 7. Thereafter, a high frequency constant current of a second frequency lower than the first frequency is made to flow, so that the terminal voltage of the capacitor C is higher than the discharge start electrode voltage. Since the preheated electrodes 6, 7 immediately release thermions to start hot cathode discharge, scattering of a thermion emitting material is prevented, and the life of the fluorescent lamp 5 can be remarkably extended.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent lamp lighting system in a high frequency constant current power supply for supplying electric power to a fluorescent lamp by using a current transformer.

[0002]

2. Description of the Related Art The present applicant has developed a connectionless discharge tube lighting device in which a high frequency constant current power source is used to supply power to a fluorescent lamp using a current transformer, and has already been registered as a utility model ( See Japanese Utility Model Publication No. 64-5360). The outline thereof will be described with reference to FIG. 2. A single power supply line 12 connected to a high frequency constant current power supply 11 is allowed to pass a current transformer 13 and its secondary winding 14 is directly connected to both terminals of a fluorescent lamp 15. Since the current does not flow in the secondary winding 14 before the fluorescent lamp 15 starts discharging, the iron core of the current transformer 13 is saturated, and thus the discharge starting voltage of the fluorescent lamp 15 in the secondary winding 14 is increased. A higher voltage appears, and after the fluorescent lamp 15 starts to discharge due to this voltage, a constant current according to the number of turns of the secondary winding 14 flows.

However, when the fluorescent lamp 15 starts discharging, cold cathode discharge is first performed 2-3 times by a voltage higher than the discharge starting voltage appearing in the secondary winding 14, and then the hot cathode discharge is started. It has been found. The electrode part of the fluorescent lamp 15 has a structure in which the surface of the heater is coated with thermionic emission material, but the thermionic emission material on the surface easily scatters due to ion bombardment during the first cold cathode discharge, so that thermionic emission is generated. There is a drawback that the life of the fluorescent lamp 15 is significantly shortened due to the consumption of the substance.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a high frequency constant current power supply system in which a cold cathode discharge is prevented from occurring at the start of discharge of the fluorescent lamp and a hot cathode discharge is performed from the beginning. Is to provide.

[0005]

In order to solve the above-mentioned problems, a fluorescent lamp lighting system according to the present invention is designed so that a high frequency constant current is passed through the primary winding of a current transformer and both terminals of the secondary winding are connected to the fluorescent lamp. And a capacitor is connected between the other terminals of both electrodes, and a high-frequency constant current of the first frequency is applied to the primary winding for a short time during lighting so that the terminals of the capacitor are connected. The voltage is set lower than the discharge start voltage of the fluorescent lamp, and then a high frequency constant current of a second frequency lower than the first frequency is flowed to make the terminal voltage of the capacitor higher than the discharge start voltage.

[0006]

[Operation] When the high frequency constant current of the first frequency is applied to the primary winding of the current transformer for a short time during lighting to make the terminal voltage of the capacitor lower than the discharge start voltage of the fluorescent lamp, the heater current flows through the capacitor to preheat the heater. After that, when a high frequency constant current of a second frequency lower than the first frequency is passed to make the terminal voltage of the capacitor higher than the discharge starting voltage, hot electrons are ejected from the heater to start hot cathode discharge.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to FIG. A power supply line 2 that is connected to the output terminal of the inverter 1 and has a high-frequency constant current flowing through it penetrates the annular current transformer 3 (that is, is wound as a primary winding of one turn). The secondary winding 4 is wound around the current transformer 3 for 18 turns, and both terminals thereof are connected to one terminal of each of the two electrodes 6 and 7 of the fluorescent lamp 5. The electrode has a structure in which the surface of the heater is coated with thermionic emission material. Further, a capacitor C is connected between the other terminals of the electrodes 6 and 7, respectively.

The inverter 1 controls the frequency and current value of the high frequency constant current flowing through the power supply line 2 for lighting and dimming the fluorescent lamp 5. The control when the fluorescent lamp 5 is turned on will be described. First, the frequency is set to 100 kHz, the frequency is flowed for 0.5 sec, and then the frequency is lowered to 65 kHz.
During this time, the current value is not changed. Now, assuming that the current value of the primary winding is 6.3 A, the current flowing through the secondary winding 4 is 6.3 A ÷
18 = 0.35A. The value of condenser C is 0.00
If it is 39 μF, the frequency is 100 kHz and 6
The impedance of capacitor C for 5 kHz is 408Ω and 628Ω, respectively.

Secondary winding 4 when the frequency is set to 100 kHz
All the current flowing to the capacitor C flows, and the voltage across the capacitor C (that is, the voltage applied between the electrodes 6 and 7) is 143.
It becomes V. The cold cathode discharge starting voltage of this fluorescent lamp 5 is 150.
Since it is V, the fluorescent lamp 5 does not start discharging, and this current flows to the heaters of the electrodes 6 and 7 for 0.5 sec to preheat it, and electrons are easily emitted from the thermionic substance on the surface. It becomes a state. When the frequency is set to 65 kHz in this state, the voltage across the capacitor C becomes 219V,
Since it becomes higher than the hot cathode discharge starting voltage (a little lower than the cold cathode discharge starting voltage), the hot cathode discharge is started immediately.

In the above embodiment, the frequency at the time of lighting is changed from 100 kHz to 65 kHz, but the frequency is not limited to this. The point is that the terminal voltage of the first capacitor is ( Cold cathode) lower than the discharge start voltage,
Next, it is only necessary to make the terminal voltage after preheating for a short time higher than the discharge start voltage.The current value flowing in the power supply line, the winding ratio of the current transformer, the value of the capacitor, the rating of the fluorescent lamp, the preheating time (these are The value of can also be changed as appropriate) and the like.

[0011]

As described above, according to the fluorescent lamp lighting method of the present invention, in the high frequency constant current power supply method, generation of cold cathode discharge is prevented at the start of discharge of the fluorescent lamp, and hot cathode discharge is performed from the beginning. Therefore, it is possible to prevent scattering of thermionic emission materials due to ion bombardment at the time of starting the zero cathode discharge, and it is possible to significantly extend the life of the fluorescent lamp.

[Brief description of drawings]

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

FIG. 2 is a schematic view of a conventional device.

[Explanation of symbols]

1 Inverter 2 Feed line 3 Current transformer 4 Secondary winding 5 Fluorescent lamp 6, 7
Electrode C condenser

Claims (1)

[Claims] 1. A high-frequency constant current is passed through the primary winding of a current transformer, and both terminals of the secondary winding are connected to one terminal of each electrode of a fluorescent lamp and between the other terminals of both electrodes. A capacitor is connected, and a high frequency constant current of a first frequency is passed through the primary winding for a short time during lighting to lower the terminal voltage of the capacitor below the discharge start voltage of the fluorescent lamp, and then a second voltage lower than the first frequency. Fluorescent lamp lighting method, characterized in that a high-frequency constant current of the frequency is applied to make the terminal voltage of the capacitor higher than the discharge starting voltage.