JPH06101391B2 - Discharge lamp lighting device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a (inverter) circuit for lighting a fluorescent lamp with a DC power source. More specifically, it relates to an improvement of a circuit for preheating a filament of a fluorescent lamp.

[Prior art]

1 (a) and 1 (b) are basic circuits for lighting a fluorescent lamp using an inverter. (A) is a push-pull circuit,
(B) shows the case where a single flyback circuit is used. Conventionally, a filament of a fluorescent lamp is provided with an auxiliary winding on a transformer, and a current is passed through an impedance for current limiting to preheat at the time of starting. However, in this method, the number of windings of the oscillation transformer is increased, and the preheating current flows through the filament even during arc discharge, resulting in an increase in power loss. Further, if the ON-OFF is repeated in a short cycle, the filament preheating becomes insufficient, and the discharge has the drawback that the blackening of the fluorescent tube is promoted by the impact of the scion.

In addition, a circuit for preheating the filament by providing an inverter separately for sufficient preheating (Japanese Patent Laid-Open No. 58-161299) and a circuit for constantly flowing a direct current to the filament (Japanese Patent Laid-Open No. 55-1223)
97) was devised, but unnecessary preheating was added,
There is a problem that power consumption increases, and it is difficult to use for a DC power source, especially for a compact device using a battery. Also, there is a method of switching the preheat circuit by providing a time circuit (Japanese Patent Laid-Open No. 56-103895). However, the time switch may not be sufficiently preheated due to environmental conditions or changes in fluorescent lamp characteristics, or unnecessary preheat may occur. There was a problem that the emitter was damaged.

[Object of the Invention]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a lighting circuit which is a small and simple inverter circuit, which reduces unnecessary preheating current, improves startability, and does not cause a blackening phenomenon due to insufficient preheating.

[Summary of Invention]

The present invention detects the high frequency voltage of the inverter circuit (oscillation transistor voltage or oscillation transformer voltage), and switches the preheating circuit that preheats the filament by the detected voltage (OFF during normal arc discharge, ON during normal discharge and glow discharge). Is to do.

〔Example〕

Embodiment 1 FIG. 2 shows an embodiment in which one switching transistor and a transformer for flyback operation are used. In this case, the filament is preheated by the direct current from the direct current power source. The part surrounded by the broken line is the preheating circuit.
In the case of the single flyback operation, the current flowing through the fluorescent tube is a DC pulsating current as indicated by IL shown in FIG.
The diode is for backflow prevention. Therefore, the electrode for performing the cathode operation can be limited to one side, and as shown in FIG. 2, the arc discharge can be performed only by preheating the cathode side filament.

The operation of the control circuit will be briefly described. Since the tube impedance of a fluorescent lamp is several tens of KΩ or more during no discharge or glow discharge, the peak value of the collector voltage VCE applied to the switching transistor via the transformer rises. This is shown in FIG. The broken line indicates glow discharge, and the solid line indicates arc discharge. It suffices to detect this VCE and turn the preheating circuit on and off. This circuit consists of a Zener diode and a transistor. VCE is peak-held by the diode and the capacitor, and when this voltage Vh exceeds the threshold of the Zener diode, the transistor is turned on. In this way, a current flows from the DC power supply to the filament and is preheated. When the fluorescent tube shifts to arc discharge by sufficient preheating, the tube impedance decreases and VCE of the switching transistor is reduced.
Also decreases. The decrease of VCE decreases the above-mentioned Vh, and Vh cannot exceed the threshold of the Zener diode.
Turn off. Thus, the DC preheating is stopped, but the arc discharge can be continued because the cathode bright spots are formed. The capacitor is intended to adjust the peak voltage of VCE, protect the switching transistor, and assist filament preheating, but of course it is not necessary.

The detection voltage need not be limited to VCE. A voltage that reflects the change in tube impedance can be used. Fig. 4 shows the case where the voltage of the feedback winding is used, Fig. 5 shows the case where the voltage of the secondary winding is divided into the voltage for detection, and Fig. 6 shows that the resistance is inserted in the emitter current path. This is the case when the voltage is used.

Second Embodiment A second embodiment is an example in which a push-pull circuit is adopted as an inverter ballast circuit. FIG. 7 shows a circuit example. The switching transistor performs a complementary operation, and the generated AC voltage is boosted to a dischargeable voltage by a boosting transformer and applied to the fluorescent lamp. The VCE of the transistor is peak-held by the zener diode and the capacitor, and the preheating circuit is switched depending on the magnitude of the hold voltage Vh. The simplest preheating method is to pass a direct current from the direct current power source to the filament as in Example 1, but in the case of the push-pull circuit, the fluorescent lamp is discharged by alternating current, so preheating of both filaments is desirable. In order to realize this, a high voltage is applied between both filaments, so two series of preheating circuits with sufficient insulation are required. In FIG. 7, a preheating inverter is provided to insulate the preheating circuit for both filaments. The preheating inverter is not limited to that shown in FIG. Further, a method of applying a direct current from a direct current power source to only one side filament is also practically used if a slight blackening is allowed. It is because the energy of the plasma in the fluorescent lamp rises due to the significant electron emission from the cathode bright spot generated on the preheating side, and the ion bombardment heating of the non-preheating side cathode occurs instantaneously during the reverse cycle, and the cathode bright spot This is because the formation is easier than without preheating.

The method for obtaining the detection voltage from the inverter circuit is described in Example ↑
Similarly to, a feedback winding, a secondary winding, a detection resistor, etc. can be used.

Third Embodiment A third embodiment shows a case where a timer circuit for limiting the preheating current time is added. FIG. 8 is a block diagram thereof.
As the timer circuit, it is preferable to use the one shown in FIG. 9 which uses a comparator, a capacitor and a resistor, or a timer IC. In the case of FIG. 9, the voltage of the preheating circuit (power supply voltage) is detected, the output of the comparator is inverted, and the switching transistor of the inverter ballast is cut off. The reason for adding the timer circuit in this way is to prevent the phenomenon that the preheating circuit of Examples 1 and 2 operates and the preheating current continues to flow due to abnormal discharge due to deterioration of the fluorescent lamp, poor contact of electrodes, etc. is there. By adding this timer circuit, the reliability of the fluorescent lamp and the lighting circuit is significantly improved.

Example 4 Example 4 shows an example in which a device for displaying preheat is attached. By attaching a display device such as an LED (light emitting diode) that displays preheat as shown in FIG. 10 to the circuits shown in Examples 1 and 2, it is possible to prevent the preheat from being continuously applied during abnormal discharge. is there. It can also monitor fluorescent discharge abnormalities.

Although the present invention has been described in detail with reference to the embodiments, the present invention can be applied to other circuit types in accordance with the gist of the present invention.

〔The invention's effect〕

According to the present invention, in a discharge lamp lighting device including an inverter circuit that operates using a DC power supply as a power source, a discharge lamp that controls lighting by the inverter circuit, and a detection circuit that detects a signal according to a discharge state of the discharge lamp. , A preheating circuit for generating or stopping information for preheating the filament of the discharge lamp according to a signal from the detection circuit, a timer circuit for detecting that the information for preheating the filament from the preheating circuit has continued for a certain time, and By having a circuit for stopping the lighting of the discharge lamp by a signal from the timer circuit, at the time of starting, the preheating information is stopped by detecting that the discharge state of the discharge lamp shifts from glow discharge to arc discharge, and Discharge lamp Even if the discharge lamp goes into an abnormal lighting state after the normal arc discharge, it is detected and the preheating information is sent. Timer circuit is activated when raw,
When it detects that the preheating information has continued for a certain period of time, the circuit that stops the lighting of the discharge lamp is activated by the signal from the timer circuit, so it is possible to prevent the blackening phenomenon due to insufficient preheating, and compared to the conventional discharge lamp lighting device. , Power consumption has been reduced as much as possible. Therefore, it has the effects of extending the life of the discharge lamp and improving the reliability and safety of lighting.

Also, an inverter circuit that operates using a DC power source as a power source,
In a discharge lamp lighting device having a discharge lamp whose lighting is controlled by the inverter circuit, and a detection circuit which detects a signal according to a discharge state of the discharge lamp, a filament of the discharge lamp is preheated by a signal from the detection circuit. Preheating circuit for generating or stopping the information, and generation of information for preheating the filament from the preheating circuit, or by having a display device whose lighting state changes according to the stopped state, is in the preheating state or normal It is possible to quickly check whether the lamp is in a proper lighting state, and it is also possible to check whether or not abnormal oscillation is occurring because the preheating circuit generates information even during abnormal lighting.

As described above, the present invention is particularly effective for a light source of a copying machine or a display device, which is frequently turned on and off.

[Brief description of drawings]

FIG. 1 is a basic circuit of an inverter ballast.
(A) is a push-pull system, (b) is a single flyback system. FIG. 2 shows an example in which a DC preheating circuit is provided in a single flyback type inverter ballast. FIG. 3 shows changes in the VCE waveform. FIG. 4 shows the case where the voltage of the feedback winding is detected. FIG. 5 shows the case of detecting the secondary voltage of the fluorescent tube. FIG. 6 shows an example in which a detection resistor is inserted. FIG. 7 shows an example in which a push-pull inverter ballast is combined with a preheating inverter. FIG. 8 shows a block diagram when a timer circuit is included. FIG. 9 shows an example in which a timer circuit using a comparator is inserted. Fig. 10 shows an example of excessive preheat display by LED.

Front page continued (72) Inventor Junji Amioka 3-5 Yamato, Suwa City, Nagano Prefecture Suwa Seikosha Co., Ltd. (56) Reference JP-A-57-17597 (JP, A) JP-A-55- 60297 (JP, A) Actual development Sho 53-119774 (JP, U) Actual public Sho 48-15980 (JP, Y1)

Claims (2)

[Claims] 1. An inverter circuit which operates using a DC power supply as a power source, a discharge lamp whose lighting is controlled by the inverter circuit,
And in a discharge lamp lighting device having a detection circuit for detecting a signal according to the discharge state of the discharge lamp, information for preheating the filament of the discharge lamp by the signal from the detection circuit, or a preheating circuit for stopping, Discharge lamp lighting, comprising a timer circuit that detects that the information for preheating the filament from the preheating circuit has continued for a certain time, and a circuit that stops lighting of the discharge lamp in response to a signal from the timer circuit. apparatus. 2. An inverter circuit which operates using a DC power supply as a power source, a discharge lamp whose lighting is controlled by the inverter circuit,
And in a discharge lamp lighting device having a detection circuit for detecting a signal according to the discharge state of the discharge lamp, information for preheating the filament of the discharge lamp by the signal from the detection circuit, or a preheating circuit for stopping, A discharge lamp lighting device, comprising: a display device whose lighting state changes according to a state of generation or stop of information for preheating the filament from the preheating circuit.