JPH0935690A - Flat fluorescent lamp drive device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flat fluorescent lamp drive device capable of instantaneously lighting a flat fluorescent lamp and obtaining uniform surface luminescence. SOLUTION: A cathode 22 and an anode 21 are faced and arranged in an substantially flat luminescent space, and a conductive film 23 is stuck to a portion corresponding to the cathode 22 on the outer surface to constitute a drive device for lighting a flat fluorescent lamp. The drive device has an inverter transformer T, each end of the secondary winding of the inverter transformer T is connected to the anode 21 and the cathode 22 respectively, and a means for simultaneously applying positive and negative pulse voltage between both electrodes is arranged. The conductive film 23 is grounded, and a wire branched from between the secondary winding is also grounded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a flat fluorescent lamp used as a backlight of a liquid crystal display. In particular, the present invention relates to a driving device for a flat fluorescent lamp used as a backlight of a liquid crystal viewfinder of a camera-integrated VTR.

[0002]

2. Description of the Related Art In recent years, flat fluorescent lamps have rapidly become popular as a backlight for a liquid crystal viewfinder of a camera-integrated VTR. The flat fluorescent lamp (hereinafter, also simply referred to as “fluorescent lamp”) has a substantially flat shape as a whole, has a light emitting space in which a phosphor is applied, and is disposed in the space. Surface emission is obtained by the discharge between the electrodes. There are various sizes of the light emitting surface, but for the liquid crystal viewfinder, 0.7- and 0.5-inch home camera integrated VTRs and professional camera integrated VTs are used.
Since R type 1.3 type is used, the fluorescent lamp as the backlight is required to have substantially the same size. In response to the recent demand for smaller and lighter electric products, this LCD viewfinder is becoming smaller and lighter. For example, Japanese Patent Laid-Open No. 5-21040 discloses such a fluorescent lamp.

By the way, the camera-integrated VTR is generally used by being driven by a battery, and in consideration of battery replacement and charging, the fluorescent lamp also consumes as low power as possible and lights up with high brightness. In addition, uniform surface emission is required to obtain a highly accurate image. In addition, recently, the application has spread to other than the camera-integrated VTR, for example, a monitor of an electronic still camera, and even in such other applications, the fluorescent lamp can be turned on with high brightness and low power consumption. Naturally, uniform surface emission is required.

Here, the fluorescent lamp used for the above-mentioned purpose is usually turned on in a dark environment. Generally, when a fluorescent lamp is left for a long time, residual electrons inside the lamp are extremely reduced, and even if a predetermined voltage is applied to the fluorescent lamp in order to relight it in a dark environment, the fluorescent lamp can be turned on instantly. No
Lights up with some delay. This delay of relighting is known as a statistical delay time of discharge, but
For a product such as a TR, turning on the switch for shooting and reproducing and then turning on the light without delaying the light is a fatal problem in that the image is not displayed in the viewfinder in an instant. For such problems,
In addition to improving the fluorescent lamp itself, it is necessary to improve the driving device for lighting the fluorescent lamp. Improved fluorescent lamps include, for example, Kaikaihei 6-569.
No. 62, Jitsukaihei 6-68290 and the like.

By the way, heretofore, as a driving device for lighting such a flat fluorescent lamp, that is, as a lighting circuit, an MO has been used.
A switching type circuit using an SFET or the like is known. Specifically, the secondary output of the inverter transformer is applied as a pulse to the fluorescent lamp. More specifically, the circuit system shown in FIG. 3 and the circuit system shown in FIG. 4 are proposed. ing.

Referring to FIG. 3, the direct current supplied from the terminal B flows through the inductance L and the capacitor C into the primary winding of the transformer T. A switching element MOSFET (hereinafter, simply referred to as “FET”) is connected to the other end of the primary winding, and the transformer T is driven when a pulse signal is applied to the gate of the FET. The secondary side of the transformer T is grounded on the positive side and connected to the anode of the fluorescent lamp,
The negative electrode side is connected to the cathode of the fluorescent lamp. Further, a conductive film is attached on the outer surface of the fluorescent lamp at a position corresponding to the cathode, and a wire extending from the conductive film is directly grounded, or is connected to the primary side of the transformer T and grounded via a switching element. . Next, the operation of this circuit will be described. When the transformer T is driven, a voltage having a potential difference Hv is generated at both ends on the secondary side. On the other hand, since the positive electrode is grounded and connected to the anode of the lamp, 0v is applied to the anode, which causes a potential difference of Hv between both electrodes of the lamp. Furthermore, between the conductive film and the cathode, about H
It has a function of generating a potential difference of v to enhance lighting start. Here, since the transformer T adopts the flyback method,
Pulses in the same direction (DC) are always applied to the lamp.

Referring to FIG. 4, the primary side of the transformer T is the same as the circuit shown in FIG. 3, and on the secondary side of the transformer, the positive side is connected to the anode of the fluorescent lamp without being grounded, and the negative side is also connected. It is connected to the cathode without being grounded. Then, a conductive film is similarly provided. In the operation of this circuit, when the transformer T is driven, a voltage having a potential difference Hv is generated across the secondary side thereof. In this case, positive and negative pulse voltages are simultaneously applied to the anode and cathode of the lamp, and H
A voltage having a potential difference of v is applied. In addition, a predetermined potential difference is generated between the conductive film and the cathode, which has a function of enhancing lighting start. Similarly, since the transformer T adopts the flyback method, pulses in the same direction (direct current) are always applied to the lamp.

However, such a lighting circuit causes the following problems. (1) In the circuit shown in FIG. 3, since a strong electric field is localized in the vicinity of the cathode, it becomes difficult to cause uniform discharge between the electrodes when the lighting power is low, and as a result, uniform light emission becomes difficult. . In other words, a phenomenon that locally emits light occurs, which is a fatal problem when considering the use of a camera-integrated VTR. In particular, as mentioned above, under the current circumstances where liquid crystal is downsized and power consumption is reduced, this problem becomes more serious. Specifically, the fluorescent lamp has a rated voltage of 5V,
This phenomenon occurs when the rated power is 0.2 W or less. To solve this problem, there is a method of increasing the number of windings of the transformer T to increase the voltage generated on the secondary side. However, as described above, in the current situation where the device itself such as the camera-integrated VTR is downsized, The method is less than preferred. (2) In the circuit shown in FIG. 4, since positive and negative pulse voltages are applied to both electrodes of the fluorescent lamp at the same time, the fluorescent lamp can emit light uniformly even in the case of low power lighting as compared with the circuit of FIG. . However, the potential difference generated between the conductive film and the cathode is substantially halved as compared with the circuit of FIG. 3, which causes a problem in startability. In other words, while it enables uniform light emission for low power lighting,
The problem of delayed start-up cannot be solved.

Therefore, a circuit combining the functions of both the circuit shown in FIG. 3 and the circuit shown in FIG. 4 has been proposed. That is, the circuit is capable of simultaneously applying positive and negative pulse voltages to the anode and cathode of the fluorescent lamp and also applying the same voltage as the voltage generated on the secondary side of the transformer between the conductive film and the cathode. This circuit is shown in FIG. The primary side of the transformer T is the same as the circuit shown in FIG. 3, and the positive side of the transformer T is connected to the anode of the fluorescent lamp without being grounded, and the negative side is also connected to the cathode without being grounded. Further, the positive electrode on the secondary side is connected to the conductive film. In the operation of this circuit, when the transformer T is driven, a voltage having a potential difference Hv is generated on the secondary side thereof, and positive and negative pulse voltages are simultaneously applied between both electrodes of the fluorescent lamp, and this voltage is applied. Further, a voltage substantially the same as the potential generated on the secondary side is applied between the conductive film and the cathode. However, the voltage applied between the conductive film and the cathode affects the discharge between the anode and the cathode, making it impossible to maintain uniform light emission. This results in the same problems as the circuit shown in FIG.

[0010]

The problem to be solved by the present invention is to solve the following problems in a driving device for lighting a flat fluorescent lamp. (1) Instantly turn on the flat fluorescent lamp. In particular, even if left in a dark environment for a long time, it is possible to instantly turn on the light again. (2) A uniform surface emission is possible and a phenomenon such as local light emission is not caused. In particular, with the miniaturization of the liquid crystal size, uniform surface emission can be achieved even in a fluorescent lamp with a relatively low lighting power. (3) With the miniaturization of a device in which the flat fluorescent lamp is incorporated, for example, a camera-integrated VTR, the flat fluorescent lamp and its driving device are made as small as possible.

[0011]

In order to solve the above problems, a flat fluorescent lamp driving device according to the present invention has the following configuration. (1) A flat fluorescent light having a substantially flat shape as a whole, a cathode and an anode arranged to face each other in a light emitting space inside thereof, and a conductive film attached to a portion of the outer surface corresponding to the cathode. A driving device for lighting a lamp, comprising an inverter transformer, wherein the secondary winding of the inverter transformer has both ends connected to the anode and the cathode, respectively, and a positive and negative electrode between the electrodes. It is characterized in that it has means for simultaneously applying a pulse voltage, and that the conductive film is grounded, and the connection branched from between the secondary windings is also grounded. (2) Further, the connection between the secondary windings is characterized in that the connection is made from substantially the center of the secondary winding. (3) As a separate configuration, the driving device includes two inverter transformers, and has means for applying a positive pulse to the anode of the flat fluorescent lamp from one end of the first inverter transformer on the secondary side. The other end is grounded, and there is provided means for applying a negative pulse to the cathode of the flat fluorescent lamp from one end on the secondary side of the second inverter transformer. It comprises means for simultaneously applying positive and negative pulses to both electrodes of the flat fluorescent lamp, the voltage generated on the next side,
The other end is grounded, the other end of the first inverter transformer and the other end of the second inverter transformer are connected, and the connection branched therefrom is also grounded, and the connection from the conductive film is further formed. Is also grounded. (4) Further, the primary windings of the two inverter transformers are connected in series or in parallel.

[0012]

The present inventors have invented that such a problem can be solved by the above means. (1) The electric potential generated between the conductive film attached to the outer surface of the flat fluorescent lamp and the cathode arranged in the light emitting space of the lamp is defined by the relation between the electric potential generated between the cathode and the anode. Then, I found that the flat fluorescent lamp can be instantly turned on. Specifically, by grounding the connection from the conductive film and applying a negative pulse voltage to the cathode, a sufficient voltage for instantaneous lighting can be applied. Then, even if the fluorescent lamp is left in a dark environment for a long time, it can be instantly turned on again. (2) Next, since both ends of the secondary side of the inverter transformer are respectively connected to the anode and cathode of the fluorescent lamp, positive and negative pulse voltages can be simultaneously applied between both electrodes, and
By grounding the connection branched from between the secondary windings,
A higher voltage can be applied to the lamp than if such a connection is not grounded. The reason for this is not clear in theory, but it is confirmed experimentally. In this way, with a very simple configuration in which the connection branched from the middle of the secondary winding is grounded, even if a starting voltage is applied between the conductive film and the cathode, good lighting is achieved without being affected by it. Can be made. That is, it is possible to perform good uniform surface emission while keeping the transformer and other elements small. Particularly, as the size of the liquid crystal becomes smaller, a fluorescent lamp with a relatively low lighting power is required, and it is possible to sufficiently meet such a requirement. (3) Further, by branching the connection from approximately the center of the secondary winding, it is possible to apply positive and negative opposite voltage levels to the anode and cathode of the fluorescent lamp. (4) Also, by providing two inverter transformers,
Positive and negative pulses can be applied to the anode and cathode of the flat fluorescent lamp from the secondary side of each transformer. By doing so, the same effect as grounding the connection branched from the secondary winding can be obtained.

[0013]

1 shows a flat fluorescent lamp driving device according to the present invention. A DC power supply terminal B to which a battery or the like is connected supplies a DC voltage of, for example, + 6V. Then, it is connected to the other end of a capacitor C whose one end is grounded via an inductance L, and is further supplied to the primary side of an inverter transformer (hereinafter, also simply referred to as “transformer”) T. A FET, which is a switching element, is connected to the other end of the primary side of the transformer T. Secondary end T of transformer T
21 is connected to the anode 21 of the fluorescent lamp 2. Further, the end T22 on the secondary side is connected to the cathode 22 of the fluorescent lamp 2. A conductive film 23 is attached to a position corresponding to the cathode 22 on the outer surface of the fluorescent lamp 2. The fluorescent lamp 2 has a light emitting unit 3 on one surface, and the surface emitting is uniformly performed from the light emitting unit 3. The secondary side winding of the transformer T is grounded with a connection branched from approximately the middle T20. This ground may be grounded directly as shown in the figure, or may be grounded by being connected to the primary side of the transformer T.
Here, as the switching element, a transistor other than the FET can be used, and a half bridge type or a full bridge type can be connected as a switching method.
Further, the self-excited circuit is not limited to the separately excited circuit and a self-excited circuit can be adopted.

FIG. 2 shows a fluorescent lamp which is turned on by the driving device according to the present invention. FIG. 2a represents its overall appearance and FIG. 2b represents its disassembled state. The flat glass 24, which is the light emitting surface, and the box 25 are combined to form a substantially flat shape as a whole. The combination is hermetically sealed using a low melting point glass powder paste as a bonding agent. An anode 21 and a cathode 22 are arranged inside the box 25 so as to face both ends thereof, and light is emitted as a discharge space between them.
Here, the plate glass 24 is coated with a phosphor by printing to a portion having a predetermined thickness on one surface on the discharge space side and serving as a light emitting portion, and the inner surface of the box 25 is also coated with the phosphor. Box 24
Has a size of, for example, 16 mm in length, 19 mm in width, and 3 mm in height, and is made of ceramics for maintaining strength. Gas is enclosed in a part of the box 25 when the lamp is manufactured,
A gas introduction pipe for exhausting gas is attached, but the remaining portion 26 after removing the introduction pipe remains after the lamp is completed. A rare gas mixed gas containing mercury and at least xenon gas is sealed in the fluorescent lamp at a predetermined pressure. The conductive film 23 is, for example, a copper foil tape having a width of 12 mm. The conductive film 23 is formed between the cathode 22 and the plate glass 2
4 is used to generate a voltage across it, and a conductive material that can be easily attached to the plate glass 24 is applied.

Next, a simple operation of this circuit will be described.
By applying a predetermined pulse signal to the gate of the FET, conduction is established between the drain and the source. Due to this conduction, a current flows through the primary side of the transformer T and the current is stored in the winding. After that, when the pulse signal is stopped and there is no conduction between the drain and the source, the energy stored in the primary winding is released as a high voltage pulse through the secondary winding. Here, a positive pulse is applied to the anode from one end T21 of the secondary winding, and a negative pulse is applied to the cathode from the other end T22.
Since the positive and negative pulses can be applied to both electrodes at the same time, the discharge between the electrodes can be made uniform. Here, since the intermediate T21 of the secondary winding or the branched connection is grounded, it is possible to generate a higher voltage than a transformer without grounding. The reason for this is not clear theoretically, but it is presumed that the loss in the transformer is related. The present inventors have confirmed this point by experiments.

In the experiment, a ferrite core of the same material (Mn-Zn system in this case) was used, and the number of primary windings was 15
5 μH, the number of secondary windings is 600 turns, and a connection without a branched connection between the secondary windings is sample 1; the connection branched from almost the center of the secondary winding is grounded. Was designated as Sample 2. Then, the open circuit voltage generated at both ends of the secondary winding was measured when the electric power to the driving device was changed from 0.5 W to 1.7 W.
The results are shown in the table below. Comparing sample 1 and sample 2, the output voltage differs greatly even if the number of windings is the same, just by grounding the connection branched from between the secondary windings. I understand. In other words, it has been shown that grounding the secondary winding substantially at the center thereof is effective in improving startability. Regarding the polarity of the pulse applied to the fluorescent lamp, positive or negative can be arbitrarily selected by combining the wirings of the primary winding and the secondary winding.

FIG. 6 shows a time chart of the signal applied to the gate of the FET and the voltage generated on the secondary side of the transformer T. When a pulse signal (5V) is applied to the gate of the FET, a drain current (2A) flows. When the pulse signal is stopped, a negative high voltage pulse (-2400V) is generated at the end T22 of the secondary winding, and a positive high voltage pulse (+ 2400V) is generated at the end T21 at the same time. In this case, by applying the pulse signal at a cycle of 64 μsec, the fluorescent lamp is turned on at a high frequency of 15 KHz. Also, the transformer T
Adopts a flyback system to always supply current (DC current) in the same direction.

In this embodiment, according to the above operation principle,
Positive and negative high voltage pulses can be applied simultaneously to the cathode and anode of the fluorescent lamp, and stable uniform surface emission can be achieved even with low power consumption for lighting. Furthermore, since a voltage sufficient for instantaneous lighting can be applied between the conductive film and the cathode, the delay of light emission can be improved. Further, the circuit configuration can be realized very easily by grounding the connection obtained by branching the secondary winding of the transformer from the middle thereof.

Next, an experiment on the uniformity of light emission when the lighting power is small will be described. The results are shown in Figure 7,
The one in which the lamp is turned on by the driving method shown in FIG. 3 (shown by A), the one by which the lamp is turned on by the driving method according to the present invention shown in FIG. 1 (shown by B), and the driving shown in FIG. The lamp is lit by the method (shown by C), and represents the relationship between the input power to the lamp and the brightness when the input is lowered to the limit where uniform surface discharge can be obtained at an ambient temperature of 25 ° C. . From the figure, it can be seen that the driving method (A) shown in FIG.
Is the minimum power value that enables uniform discharge,
The driving method (B) shown in FIG. 4 and the driving method (C) shown in FIG. 4 show that uniform surface emission can be maintained even when the power is reduced to around 0.1 W of input. In other words, it has been proved that uniform positive light emission can be achieved by applying positive and negative high voltage pulses to both electrodes of the fluorescent lamp at the same time, and discharge is localized in the driving method in which either the cathode or the anode is grounded. It has been proved that it is not possible to achieve uniform lighting even with low power lighting. Here, the ambient temperature of 25 ° C. is used as a reference, because it can be said that an average environmental temperature is assumed and measurement at such a temperature is suitable for the environment in which the camera-integrated VTR is used. However, it goes without saying that almost the same results can be obtained even if the experiment is performed at other temperatures. In addition, all the experiments were performed using a 1.3-inch flat fluorescent lamp.

Next, an experiment on lighting startability was conducted. In the experiment, similar to the above, the lamp was turned on by the driving method shown in FIG. 3 (shown by A) and the lamp was turned on by the driving method according to the present invention shown in FIG. 1 (shown by B). , Fig. 4
The same 1.3-inch flat fluorescent lamp is installed in a dark environment at room temperature by driving the lamp by the driving method shown in FIG. The time from the start of the lamp to the start of the lamp (statistical delay time) was measured 100 times at 5-minute intervals.
The results are shown in FIG. 8, where the horizontal axis represents the time until the lamp starts (statistical delay time), and the vertical axis represents the number of times the lamp was started at each delay time of 100 times of lighting, that is, discharge. Represents the start probability. A start delay can be seen in any driving method, but for example, the start delay time is 637 μs.
Focusing on ec, in the drive system shown in A and B,
It shows that almost 100% of the discharge can be started.
On the other hand, in the drive system shown in C, 15 to 17
The discharge start probability is about%, indicating that the discharge cannot be started sufficiently in this time. In the drive system shown in C, the discharge start probability is about 70% even if the starting delay time is 6370 μsec.

The branch connection T of the secondary winding of the transformer T
By providing 20 at approximately the center of the secondary winding, it is possible to apply substantially the same voltage value to the anode 21 and the cathode 22 of the fluorescent lamp for positive and negative objects, but in order to solve the problem of the invention, It is not always necessary to apply the same voltage value, that is, the branch point T20 does not have to be located approximately in the center of the secondary winding. Further, the connection from the branch point T20 can be connected to the current supply source side and grounded instead of being directly grounded.

Next, an embodiment of the invention according to claim 3 will be described. FIG. 9 has two transformers T1 and T2 as inverter transformers, each of which is connected in parallel to the FET. The negative electrode T1-2 of the secondary winding of the transformer T1 is connected to the cathode 22 of the fluorescent lamp, and the positive electrode T1-1.
Is grounded. On the other hand, the positive electrode T of the secondary winding of the transformer T2
2-1 is connected to the anode 21 of the fluorescent lamp, and the negative electrode T1-2 is grounded. Then, the positive electrode T1- of the secondary winding of the transformer T1.
1 is connected to the negative electrode T2-2 of the secondary winding of the transformer T2, and the connection from this connection point T0 is grounded.

Next, the operation of this circuit will be described. FET
By applying a predetermined pulse signal to the gate of, the drain and the source are electrically connected. Due to this conduction, a current flows through the primary side of each of the transformers T1 and T2, and the current is stored in each winding. After that, when the pulse signal is stopped and conduction is lost between the drain and the source, the energy stored in each primary winding is released as a high voltage pulse through each secondary winding. Then, from the positive electrode T2-1 of the secondary winding of the transformer T2 to the positive electrode 21, the transformer T1
Positive and negative high voltage pulses are simultaneously applied from the negative electrode T1-2 of the secondary winding to the cathode 22. Here, providing two transformers means that there are two transformers technically, and does not necessarily mean that two transformers physically exist. That is, by devising the winding using one core, one transformer can be physically configured and two transformers can be functionally configured. That is, it is possible to reduce the size of the device. However, it goes without saying that two transformers may be physically provided.

Next, another circuit example using two transformers is shown in FIG. That is, two transformers T1 and T2
Represents a circuit example in which the primary side is connected in series instead of in parallel. In this case, there is a slight time difference in the voltage generated on the secondary side of each transformer when the FET is operated, but it has been confirmed that there is no problem in lighting the fluorescent lamp. Also in this circuit, positive and negative high-voltage pulses can be simultaneously applied to both electrodes of the lamp 2 from the transformer T1 and the transformer T2, and a voltage sufficient for starting lighting between the conductive film and the cathode can be applied. it can.

[0025]

The present invention has the following effects. (1) A flat fluorescent lamp can be instantly turned on. In particular, even if it is left in a dark environment for a long time, it can be instantly turned on again. (2) Uniform surface emission is possible. In particular, even in a fluorescent lamp with relatively low lighting power, uniform surface emission can be achieved. (3) With the miniaturization of a device incorporating a flat fluorescent lamp, for example, a camera-integrated VTR, the flat fluorescent lamp and its driving device can be made as small as possible.

[Brief description of drawings]

FIG. 1 shows a flat fluorescent lamp driving device according to claim 1 of the present invention.

FIG. 2 shows a flat fluorescent lamp according to the present invention.

FIG. 3 shows a conventional flat fluorescent lamp driving device.

FIG. 4 shows a conventional flat fluorescent lamp driving device.

FIG. 5 shows a conventional flat fluorescent lamp driving device.

FIG. 6 shows a time chart of the operation of the flat fluorescent lamp driving device of the present invention.

FIG. 7 shows an experimental result of the flat fluorescent lamp according to the present invention.

FIG. 8 shows an experimental result of the flat fluorescent lamp according to the present invention.

FIG. 9 shows a flat fluorescent lamp driving device according to claim 4 of the present invention.

FIG. 10 shows a flat fluorescent lamp driving device according to claim 4 of the present invention.

[Brief description of reference numerals]

 2 Flat fluorescent lamp 3 Light emitting part 21 Anode 22 Cathode 23 Conductive film T Inverter transformer

Claims (4)

[Claims] 1. A cathode and an anode are arranged so as to face each other in a light emitting space inside, and a conductive film is attached to a portion of the outer surface corresponding to the cathode. A driving device for lighting a flat fluorescent lamp comprising: an inverter transformer, wherein a secondary winding of the inverter transformer has both ends connected to the anode and the cathode, respectively. And a means for simultaneously applying positive and negative pulse voltages between the electrodes, the conductive film is grounded, and a connection branched from between the secondary windings is also grounded. A driving device for a flat fluorescent lamp, characterized by: 2. The drive for a flat fluorescent lamp according to claim 1, wherein the connection branched from between the secondary windings is branched from substantially the center of the secondary winding. apparatus. 3. The whole has a substantially flat shape, and a cathode and an anode are arranged to face each other in a light emitting space inside thereof, and a conductive film is attached to a portion of the outer surface thereof corresponding to the cathode. A driving device for lighting a flat fluorescent lamp, wherein the driving device includes two inverter transformers, and a positive pulse is applied to the anode of the flat fluorescent lamp from one end on the secondary side of the first inverter transformer. And a means for applying a negative pulse to the cathode of the flat fluorescent lamp from one end on the secondary side of the second inverter transformer, and these means generate on the secondary side of the inverter transformer. Means for simultaneously applying positive and negative pulses to both electrodes of the flat fluorescent lamp, the other end of the first inverter transformer and the second inverter transformer. A flat fluorescent lamp driving device, wherein the other end of the fluorescent lamp is connected to the other end, and a connection branched therefrom is grounded, and the conductive film is grounded. 4. The driving device for a flat fluorescent lamp according to claim 3, wherein primary windings of the two inverter transformers are connected in series or in parallel.