JPH0444000Y2 - - Google Patents

Description

[Detailed explanation of the idea] This invention relates to a high frequency discharge lamp lighting device.

In this type of lighting device, a configuration is known in which a high-frequency inverter is used and a discharge lamp is lit by the high-frequency output of the high-frequency inverter. In this case, it has been considered to preheat the filament of the discharge lamp using direct current. Incidentally, discharge lamps used in copying machines, facsimile machines, etc. are required to have a short starting time. For this purpose, it is sufficient to shorten the preheating time, so it is usually considered to increase the preheating current. However, if the preheating current is designed to increase in this way, for example, if the power supply voltage fluctuates and increases, the filament voltage will also increase, so if the preheating current is kept in a continuous state,
The discharge lamp will darken early and its life will be shortened. Therefore, it has not been possible to increase the preheating current unnecessarily.

The purpose of this invention is to reduce the direct current resistance of the preheating circuit to increase the preheating current at the initial stage of preheating, without impairing the life of the discharge lamp even in this case.

An embodiment of this invention will be described with reference to the drawings. 1 is a positive power supply terminal of a DC power supply, 2 is a switching element for starting, and 3 is a high frequency inverter, which is mainly composed of a pair of transistors 4 and an oscillation transformer 5, and a primary coil 6 of the oscillation transformer 5.
The center tap of the transistor 4 is connected to the power supply terminal 1, and the emitters of both transistors 4 are connected to the negative terminal (ground) of the DC power supply. Reference numerals 7 and 8 denote secondary coils of the oscillation transformer 5, which are wound with the same polarity and connected with opposite polarity when viewed from the terminal 9 of the preheating DC power supply.
10 is a discharge lamp, 11 and 12 are its filaments,
13 is a switching element for preheating.

When the switching element 13 is turned on, a DC circuit (preheating circuit) is completed. The direct current flowing thereby preheats each filament 11, 12. At this time, since the directions of the direct currents flowing through the secondary coils 7 and 8 are opposite, the oscillation transformer is not biased. Next, switching element 2
When turned on, the high frequency inverter 3 operates in oscillation. The discharge lamp 10 is started and lit by the high frequency output induced in the secondary coil 8 by this. Furthermore, if the capacitor 14 is connected, the secondary coil 7 is also connected to the discharge lamp 10 in a high frequency manner. Capacitor 14 may be connected to the opposite end of filament 11.

According to this idea, a parallel circuit 17 consisting of a capacitor with a large capacity (for example, 1F) (for example, an electrolytic capacitor 15 and a resistor 16 for suppressing the preheating current) is connected to the preheating circuit. When the preheating circuit is completed by turning it on, the current from the terminal 9 passes through the preheating circuit and initially flows rapidly to the capacitor 15 as a charging current.Therefore, a large DC current flows through the preheating circuit. As a result, the filaments 11, 12 can be rapidly heated to a predetermined temperature in a short period of time.

In this way, the filament 11,
If the temperature of the discharge lamp 12 is increased, the time required for preheating will be shortened, so that the life of the discharge lamp will not be impaired.

The current flowing through the capacitor 15 gradually decreases over time, but as mentioned above, when the filaments 11 and 12 reach a predetermined temperature,
Capacitor 15 reaches a certain voltage, after which no current flows through capacitor 15. and resistance 16
It will only flow. The resistor 16 is a normal preheating current limiting resistor, so that the subsequent preheating current flows at its normal value.

As detailed above, according to this invention, the preheating time is shortened by rapidly passing current at the initial stage of preheating, so the life of the discharge lamp is not impaired, and the structure for this purpose is as follows: Since a parallel circuit of a capacitor and a resistor is used, there is no need for a timer or other configuration, making the configuration inexpensive and easy. Even if the discharge lamp is kept in a continuous preheating state, early blackening of the discharge lamp can be sufficiently prevented.

[Brief explanation of drawings]

The figure is a circuit diagram showing an embodiment of this invention. 3... High frequency inverter, 5... Oscillation transformer, 7, 8... Secondary coil, 9... Terminal of DC power supply for preheating, 10... Discharge lamp, 11, 12... Filament, 15... Capacitor, 16...Resistance.

Claims (1)

[Scope of utility model registration request] The first secondary coil of the first and second secondary coils wound around the oscillation transformer of the high-frequency inverter is connected between one end of each filament of the discharge lamp. One terminal of a DC power supply is connected to the other end of one filament of the discharge lamp via a preheating switch, and the other end of the other filament of the discharge lamp is connected to the second secondary A high-frequency discharge lamp lighting device connected between the other terminals of the DC power source via a parallel circuit including a coil, a preheating current suppressing resistor, and a capacitor.