JPH09306683A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the variation of a voltage level impressed on a discharge lamp by introducing such an arrangement that the two ends of the secondary coil of a lighting inverter and the terminations of two secondary coils of a preheating inverter are used as the output ends to the discharge lamp. SOLUTION: A preheating inverter 4 is previously driven, and when a switch S is pushed in the condition that the high frequency voltages V13 and V14 are given by coils 13 and 14, respectively, a high voltage with a high frequency is induced in a coil L3. If for example, the output voltage V3 of a lighting inverter 3 is made 300V and the output voltages V13 and V14 of the preheating inverter 4 are made 5V, the max. voltage impressed between the filaments 2a, 2b of a fluorescent lamp 2 becomes as follows; 305V when V3 is in the same phase as V13 and V14, 300V when difference is 90deg.; 305V when difference is 180deg.; and 300V when difference is 270deg. Therefore, the variation of the voltage remains within the range between 300-305 V, being one half of the conventional circuit configuration which involves a 10-V variation. This solves the problem of a lighting inverter 3, such as abnormal oscillation, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a high frequency high voltage discharge lamp.

[0002]

2. Description of the Related Art In a copying machine or the like, a hot cathode discharge lamp such as an FLR lamp or a fluorescent lamp driven by a high frequency and a high voltage is used as a light source for illuminating an original. Such a light source generally has the property of shortening the lamp life unless the filament is preheated. Therefore, in a high-frequency lighting device that is frequently used like a copying machine and has a large number of blinks, the filament is preheated before the high voltage for lighting is applied to the light source to extend the life.

FIG. 4 shows an example of such a high-frequency lighting device (hereinafter abbreviated as "lighting device"). The lighting device 21 is a self-excited inverter for lighting the fluorescent lamp 22. (Hereinafter referred to as "lighting inverter") 2
3, a self-excited inverter (hereinafter, referred to as “remaining heat inverter”) 24 for remaining heat for remaining heat of the filament of the fluorescent lamp 22, and an output circuit 25. Since the internal structure of the preheating inverter 24 is the same as that of the lighting inverter 23, the illustration of the internal structure is omitted.

The lighting operation will be described below. Switch S
Is turned on, the DC power supply E is supplied to the center tap of the primary coil L21 of the transformer T21 via the choke coil La, and the switching transistor Q1,
A base current is supplied to the base of Q2 via resistors R1 and R2.

When the primary coil L1 is energized, a voltage is induced in the feedback coil L22. And the feedback coil L2
The voltage V1 induced in 2 causes, for example, the transistor Q
When 1 operates in the ON state, a current I1 flows as indicated by an arrow in FIG. When the transistor Q2 operates in the on state, the current I2 flows in the path indicated by the arrow. Since the currents I1 and I2 flow in opposite directions when viewed from the center tap, an alternating output voltage V23 is induced across the secondary coil L23 by the alternating operation of the transistors Q1 and Q2.

On the other hand, the switching operation as described above is also performed in the preheating inverter 24, and the AC output voltage V33, is applied to the secondary side coils L33, L34 of the transformer T31.
V34 is induced.

The lighting inverter 23 has an oscillation frequency of 40.
It is set so as to obtain an output voltage V23 of about 300 V at ˜50 KHz, and the output voltage V23 is applied between the filaments of the fluorescent lamp 22. In addition, the preheat inverter 2
4 is set so as to obtain output voltages V33 and V34 having an oscillation frequency of 20 to 30 KHz and a voltage of about 5 V, and the output voltages V33 and V34 are applied to the filaments of both polarities of the fluorescent lamp 22, respectively.

Next, the output circuit 25 will be described.
As schematically shown in FIG. 5, the end of the secondary coil L34 of the preheating inverter 24 is connected to the start end of the secondary coil L23 of the lighting inverter 23 marked with a black dot, and the secondary coil of the lighting inverter 23 is connected. The start end of the secondary coil L33 of the preheating inverter 24 is connected to the end of L23.
Therefore, when the preheat inverter 24 is driven,
Each of the filaments of both polarities of the fluorescent lamp 22 is preheated with an output voltage of a frequency of 20 to 30 KHz and a voltage of 5V.

On the other hand, when the lighting inverter 23 and the preheating inverter 24 are simultaneously driven, in other words, at the time of lighting, the maximum voltage applied between the filaments of the fluorescent lamp 22 is as follows. That is, when the output voltage V23 of the lighting inverter 23 and the output voltages V33 and V34 of the preheating inverter 24 are in phase, 310 V, when there is a 90 degree difference, 300.4 V, when there is a 180 degree difference, 30 V.
When the difference is 0V and 270 degrees, it becomes 300.4V. That is, the maximum voltage level applied to the fluorescent lamp 22 is 300V.
It varies from ˜310V.

[0010]

Such a large voltage fluctuation causes a fluctuation in the lamp pin position, and the switching transistors Q1 and Q2 of the lighting inverter 23 are
As shown in FIG. 7, an abnormal oscillation operation is caused from the normal operation of FIG. 6 and, in some cases, flickering of brightness occurs. Further, due to the fluctuation of the voltage applied to the fluorescent lamp 22, the lamp current changes from the waveform shown in FIG. 8 to the AM modulation as shown in FIG. This fluctuation of the lamp current, that is, FIG.
Since the envelope part in the waveform of is at an audible frequency, it is one of the causes of noise.

As a means for solving such a problem, it is conceivable to apply a separately excited inverter instead of the self-excited inverter, but when the separately excited inverter is applied, the circuit configuration becomes complicated and the production cost is also increased. There is the problem of becoming expensive.

The present invention has been made in view of the above situation, and an object thereof is to provide a lighting device for a discharge lamp capable of reducing the fluctuation of the voltage level applied to the discharge lamp while using a self-excited inverter. And

[0013]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a self-excited first inverter having a secondary coil for generating an output for lighting a discharge lamp, and an output for preheating the discharge lamp. In a discharge lamp lighting device including a self-exciting second inverter having two secondary coils, a starting end of a secondary coil of the first inverter and a starting end of one secondary coil of the second inverter. And a terminal of the secondary coil of the first inverter and a terminal of the other secondary coil of the second inverter are connected, and both ends of the secondary coil of the first inverter and the second coil This is achieved by providing a discharge lamp lighting device characterized in that the respective ends of the two secondary coils of the inverter serve as output terminals to the discharge lamp.

Another object of the present invention is to provide a self-excited first inverter having a secondary coil for generating an output for lighting a discharge lamp, and two secondary sides for generating an output for preheating the discharge lamp. A self-excited second inverter having a coil and a lighting device for a discharge lamp, comprising:
The starting end of the secondary coil and the starting end of one secondary coil of the second inverter are connected, and the terminal end of the secondary coil of the first inverter and the starting end of the other secondary coil of the second inverter are connected. And both ends of the secondary side coil of the first inverter and the ends of the two secondary side coils of the second inverter are output ends to the discharge lamp, and the second end of the first inverter is connected. A changeover switch is provided at one end of the secondary side coil and at the end of the secondary side coil of the second inverter whose start end is connected to the one end, and the changeover switch selectively preheats and lights a plurality of discharge lamps. The present invention can also be achieved by providing a discharge lamp lighting device characterized by the above.

According to the above feature of the present invention, the lighting voltage applied to the discharge lamp is the voltage of the secondary coil of the first inverter and the secondary coil of either one of the second inverters at that voltage. Is suppressed to a variation with the added voltage, and therefore, the variation of the lighting voltage applied to the discharge lamp is halved, and various problems caused by the voltage variation can be solved. .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of a discharge lamp lighting device according to the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram of an example of a discharge lamp lighting device according to the present invention, FIG. 2 is a circuit diagram of FIG. 1, and FIG. 3 is a circuit diagram of another example of a discharge lamp lighting device according to the present invention. In the figure, the black dots indicate the same polarity, which means the start end (winding start) of the coil.

In FIG. 1, 1 is a lighting device, 2 is a discharge lamp (in this example, a fluorescent lamp), 3 is a lighting inverter,
4 is a preheating inverter, 5 is an output circuit, and E is a DC power supply. Note that the internal circuit configuration of the preheating inverter 4 may be qualitatively the same as the configuration of the lighting inverter 3, so the internal configuration is not shown and is shown in blocks.

The lighting inverter 3 is a self-excited type, and a transformer (hereinafter referred to as "transformer") T1 has a primary coil L.
1, the feedback coil L2 and the secondary coil L3 are wound, and the center tap of the primary coil L1 is connected to one pole of the DC power source E via the choke coil (inductor) La. Further, one end of the primary coil L1 is connected to the collector of a transistor Q1 which is a switching element, and the other end is a transistor Q2 which is a switching element.
Connected to the collector. Transistors Q1, Q2
Are both connected to the other pole of the DC power source E.

The bases of the transistors Q1 and Q2 are connected to one pole of the current source E through the resistors R1 and R2,
Further, it is connected to the feedback coil L2. Transformer T1
Both ends of the secondary coil L3 of the above are drawn to the output circuit 5.

On the other hand, the preheating inverter 4 is also a self-exciting type, and although not shown in the figure, it is constructed in the same manner as the lighting inverter 3.
The DC power supply E is connected to the primary coil L11 of the transformer T11, and switching transistors are connected to both ends. Both ends of each of the two secondary coils L13 and L14 of the transformer T11 are drawn to the output circuit 5.

In the output circuit 5, the starting end of the secondary coil L3 of the transformer T1 of the lighting inverter 3 and the preheating inverter 4 are connected.
The starting end of the secondary coil L14 of the transformer T11 is connected, and the secondary coil L of the transformer T1 of the lighting inverter 3 is connected.
3 is connected to the starting end of the secondary coil L13 of the transformer T11 of the preheating inverter 4, both ends of the secondary coil L3 of the transformer T1 of the lighting inverter 3 and the secondary coil L13 of the transformer T11 of the preheating inverter 4, The end of each L14 is an output end to the fluorescent lamp 2.

In the fluorescent lamp 2, the filaments 2a and 2b attached to both ends are connected to the output end of the output circuit 5. In this case, one filament 2a is the lighting inverter 3
Is connected between the end of the secondary coil L3 of the transformer T1 and the end of the secondary coil L13 of the transformer T11 of the preheating inverter 4, and the other filament 2b is connected to the secondary coil L3 of the transformer T1 of the lighting inverter 3. It is connected between the start end and the end of the secondary coil L14 of the transformer T11 of the preheating inverter 4.

That is, the filament 2a is heated by the output V13 of the secondary coil L13 of the transformer T11 of the preheating inverter 4, and the filament 2b is heated by the output V14 of the secondary coil L14 of the transformer T11 of the preheating inverter 4. , And the filaments 2a, 2
2 of transformer T1 of lighting inverter 3 applied between b
It is turned on by the output V3 of the secondary coil L3.

The operation for lighting the fluorescent lamp 2 of the discharge lamp lighting device thus configured will be described. However, the preheat inverter 4 is driven, and the transformer T11 2
It is assumed that the high-frequency voltage from the secondary coil L13 to V13 and the secondary coil L14 to V14 is output, and the filaments 2a and 2b of the fluorescent lamp 2 are preheated.

In this state, in order to turn on the fluorescent lamp 2,
When the switch S of the lighting inverter 3 is turned on, the base current is supplied to the transistors Q1 and Q2 through the resistors R1 and R2, and both the transistors Q1 and Q2 are turned on, and the DC power source E passes through the choke coil La. Current is supplied to the center tap of the primary coil L1 of the transformer T1 to induce a voltage V1 induced in the feedback coil L2.
Thereby, conduction of one of the transistors Q1 and Q2 is promoted, and the other is turned off.

Next, when the conduction of the transistor in the ON state is saturated, the voltage -V induced in the feedback coil L2.
By 1, the transistor in the on state is turned off, the transistor in the off state is turned on, and this operation is repeated thereafter, and the high frequency high voltage V3 is induced in the secondary coil L3 of the transformer T1.

In this case, the lighting inverter 3 is used as in the conventional case.
When the output voltage V3 of the fluorescent lamp 2 is 300V and the output voltages V13 and V14 of the preheating inverter 4 are 5V, the maximum voltage applied between the filaments 2a and 2b of the fluorescent lamp 2 is as follows. That is, when the output voltage V3 of the lighting inverter 3 and the output voltages V13 and V14 of the preheating inverter 4 are in the same phase, 305 V, when they are 90 degrees apart, 300 V and 180
305V when there is a difference and 300 when there is a 270 degree difference
V.

That is, the filament 2a of the fluorescent lamp 2,
The fluctuation of the voltage applied between 2b is 300V to 305V
Therefore, the problems such as the abnormal oscillation of the lighting inverter 3 and the generation of the audible frequency due to the fluctuation of the filament current as described in the conventional example are suppressed.

FIG. 3 shows an example in which a plurality of fluorescent lamps 2 can be switched and turned on in the discharge lamp lighting device of FIG. 1, and the characteristic part of this example is that the plurality of fluorescent lamps 2 are minimized. The point is that the limit switch is used for switching. Therefore, the output circuit 5 is provided with two changeover switches S1 and S2 in a path for applying an output voltage to one filament of the fluorescent lamp 2, that is, in a path marked with a and b. The changeover switch S1 is adapted to individually apply the output voltage between A and b to the two fluorescent lamps 2. The changeover switch S2 is adapted to individually apply the output voltage between A and A to the two fluorescent lamps 2.

That is, when the switches S1 and S2 are switched as shown by the solid line, the output voltage is applied to the fluorescent lamp 2 shown on the right side of FIG. 3 regardless of preheating and lighting.
On the other hand, when the changeover switches S1 and S2 are changed over as indicated by the dotted line, the fluorescent lamp 2 shown on the left side of FIG.
The output voltage is applied to.

As described above, even if a plurality of fluorescent lamps 2 are switched, the same operational effects as those of the discharge lamp lighting device of FIG. 1 can be enjoyed, and the plurality of fluorescent lamps 2 are on standby. One of the filaments of the fluorescent lamp 2 is placed in a preheated state, and the lighting of the fluorescent lamp 2 at the time of switching can be accelerated.

[0032]

As described above, according to the present invention, the lighting voltage applied to the discharge lamp is either the voltage of the secondary coil of the first inverter and the voltage of the second inverter. The fluctuation of the voltage of the secondary side coil is suppressed to the fluctuation with the added voltage, and therefore the fluctuation of the lighting voltage applied to the discharge lamp is halved. It is possible to solve various problems that occur as a result.

Further, even when a plurality of discharge lamps are provided side by side, by providing the changeover switch only in the output path applied to one filament of the discharge lamp, the circuit structure is simplified and its operation is also easy. Secure and easy. Further, one filament of the discharge lamp is in a preheated state, and the startup at the time of lighting becomes quick.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an example of a lighting device for a discharge lamp according to the present invention.

FIG. 2 is an operation explanatory diagram of the example of FIG.

FIG. 3 is a circuit diagram of another example of the discharge lamp lighting device according to the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional discharge lamp lighting device.

FIG. 5 is an operation explanatory diagram of FIG. 4;

FIG. 6 is a waveform diagram showing an operation mode of a switching transistor.

FIG. 7 is a waveform diagram showing an oscillation mode of a switching transistor.

FIG. 8 is a waveform diagram showing a mode of filament current.

FIG. 9 is a waveform diagram showing an abnormal filament current.

[Explanation of symbols]

 1 Discharge Lamp Lighting Device 2 Fluorescent Lamp (Discharge Lamp) 3 Lighting Inverter Circuit 4 Preheating Inverter Circuit 5 Output Circuit E DC Power Supply Q1, Q2 Switching Transistor S, S1, S2 Switch T1, T11 Transformer (Transformer) L3, L13, L14 Secondary coil

Claims (2)

[Claims] 1. A self-excited first inverter having a secondary coil for generating an output for lighting a discharge lamp, and a self-excited type inverter having two secondary coils for generating an output for preheating the discharge lamp. In the discharge lamp lighting device including the second inverter, the starting end of the secondary coil of the first inverter and the starting end of one secondary coil of the second inverter are connected to each other, and The end of the secondary coil is connected to the start of the other secondary coil of the second inverter,
A discharge lamp lighting device, characterized in that both ends of a secondary coil of the first inverter and respective ends of two secondary coils of the second inverter serve as output terminals to the discharge lamp. 2. A changeover switch is provided at one end of the secondary side coil of the first inverter and at the end of the secondary side coil of the second inverter whose start end is connected to the one end, and a plurality of discharge switches are provided by the changeover switch. The lighting device for a discharge lamp according to claim 1, wherein the electric lamp is selectively preheated and turned on.