JP2002352973A - Fluorescent lamp lighting circuit, image display application apparatus, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress effectively a falling amount of luminescence of a whole fluorescent light, deterioration of a luminosity distribution of the fluorescent light, reduction of the life of the fluorescent light, or the like. SOLUTION: It is a fluorescent lamp lighting circuit, equipped with a high frequency voltage generating circuit 11 which generates voltage for producing the fluorescent light 10 to be turned on, a current waveform detection circuit 12 which detects the current waveform of the voltage waveform from the current which flows to the turned-on fluorescent light 10, and a voltage control circuit 13 which controls generating of voltage, based on the result of the detection.

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 circuit used for, for example, a lighting device and a display device using a fluorescent lamp, a back light source of a display device, a document reading device, an image display application device, and a program.

[0002]

2. Description of the Related Art First, the configuration and operation of a conventional fluorescent lamp lighting circuit will be described with reference to FIG. 3, which is a block diagram of a conventional fluorescent lamp lighting circuit.

In the conventional fluorescent lamp lighting circuit, a fluorescent lamp 30 is lit at a high frequency by a high frequency voltage generating circuit 31 composed of a self-excited inverter circuit. In addition,
As an inverter circuit, a blocking oscillation circuit in which a push-pull transistor is connected to a differential winding high frequency transformer is widely used.

[0004]

However, the conventional fluorescent lamp lighting circuit has problems such as a decrease in the light emission amount of the entire fluorescent lamp, a deterioration in the luminance distribution of the fluorescent lamp, and a decrease in the life of the fluorescent lamp. .

More specifically, a fluorescent lamp operates as a capacitive load in an ideal state, but in an actual configuration, a metal optical reflector or a structural member is installed near the fluorescent lamp. In addition, a leak current is generated in these metal members, and the load on the inverter circuit is increased or becomes unstable.

Due to such a phenomenon, the high-frequency current actually flowing through the fluorescent lamp in the fluorescent lamp lighting circuit having the conventional configuration suffers from waveform distortion. Ideally, a positive / negative symmetrical AC current must flow through the fluorescent lamp, but the polarity of the current waveform flowing through the fluorescent lamp is broken, and a DC component is superimposed on the fluorescent lamp.

When such a DC component is applied to a fluorescent lamp, substances (such as mercury) uniformly contributing to light emission and dispersed inside the fluorescent lamp may be biased toward one electrode side. In the region where the dispersion amount of the substance is reduced, normal light emission cannot be performed. Then, not only the light emission amount of the entire fluorescent lamp is reduced, but also the luminance distribution of the fluorescent lamp is deteriorated and the life of the fluorescent lamp is shortened.

The present invention has been made in consideration of the above-described conventional problems, and is capable of suppressing a decrease in the light emission amount of the entire fluorescent lamp, a deterioration in the luminance distribution of the fluorescent lamp, and a reduction in the life of the fluorescent lamp. It is an object to provide a lamp lighting circuit, an image display application device, and a program.

[0009]

Means for Solving the Problems The first invention (claim 1)
Corresponds to) voltage generating means for generating a voltage for lighting the fluorescent lamp, detecting means for detecting a current waveform or a voltage waveform from a current flowing through the turned on fluorescent lamp, and a detection result based on the result of the detection. And a control means for controlling the generation of the voltage.

According to a second aspect of the present invention (corresponding to claim 2), the detection is a detection of a current waveform of a feedback current from the lit fluorescent lamp, and the control is a step of detecting a current waveform of the feedback current. A fluorescent lamp lighting circuit according to a first aspect of the present invention, which is a control performed so as to correct the polarity symmetry to the predetermined range when the polarity symmetry of the waveform deviates from a predetermined range.

According to a third aspect of the present invention (corresponding to claim 3), the polarity symmetry is defined as a symmetry obtained based on a comparison between respective effective voltage values regarding the positive polarity and the negative polarity of the detected current waveform. And a fluorescent lamp lighting circuit according to the second aspect of the present invention.

According to a fourth aspect of the present invention (corresponding to claim 4), the polarity symmetry is a symmetry obtained based on a comparison between respective average voltage values regarding the positive polarity and the negative polarity of the detected current waveform. And a fluorescent lamp lighting circuit according to the second aspect of the present invention.

According to a fifth aspect of the present invention (corresponding to claim 5), the polarity symmetry is defined as a symmetry obtained based on a comparison of each of the spire voltage values regarding the positive polarity and the negative polarity of the detected current waveform. And a fluorescent lamp lighting circuit according to the second aspect of the present invention.

A sixth invention (corresponding to claim 6) is the fluorescent lamp lighting circuit according to any one of the first to fifth inventions, wherein the fluorescent lamp is a cold cathode fluorescent tube.

A seventh aspect of the present invention (corresponding to claim 7) is a high frequency voltage generating circuit for lighting a fluorescent lamp at a high frequency, a voltage control circuit for controlling a voltage generated by the high frequency voltage generating circuit,
A current waveform detecting circuit for detecting a current waveform of a feedback current from the low voltage side of the fluorescent lamp to the high frequency voltage generating circuit, wherein a polarity symmetry of the detected current waveform of the feedback current is shifted from a predetermined value. In this case, by controlling the generated voltage,
A fluorescent lamp lighting circuit wherein the polarity symmetry of a current waveform flowing through the fluorescent lamp is corrected to a predetermined value by changing a voltage waveform or a voltage value of the high-frequency voltage generating circuit.

The eighth invention (corresponding to claim 8) is an image display application device using the fluorescent lamp lighting circuit according to any one of the first to seventh inventions.

According to a ninth aspect of the present invention (corresponding to claim 9), in the fluorescent lamp lighting circuit according to the first aspect of the present invention, a voltage generating means for generating a voltage for lighting the fluorescent lamp; This is a program for causing a computer to function as all or a part of detection means for detecting a current waveform or a voltage waveform from a current flowing through a fluorescent lamp, and control means for controlling generation of the voltage based on a result of the detection. .

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) First, the configuration of a fluorescent lamp lighting circuit of the present embodiment will be described with reference to FIG. 1 which is a block diagram of the fluorescent lamp lighting circuit of the present embodiment.

In the fluorescent lamp lighting circuit according to the present embodiment, the fluorescent lamp 10 is connected to the output of the high frequency voltage generating circuit 11, and the current waveform detecting circuit 12 is connected to the low voltage side terminal of the fluorescent lamp 10. The setting of the voltage control circuit 13 is varied according to the detection result of the detection circuit 12, and the high-frequency voltage generation circuit 1
1 is controlled.

Next, the operation of the fluorescent lamp lighting circuit according to the present embodiment will be described. In addition, while explaining the operation of the fluorescent lamp lighting circuit of the present embodiment, an embodiment of the fluorescent lamp lighting control method of the present invention will be described.

The high-frequency voltage generating circuit 11 generates a high-frequency high-voltage by supplying power (in this embodiment, the high-frequency voltage is about 20 kHz to 100 kHz.
A sine wave voltage of about 00 to 1500 V is generated, and the fluorescent lamp 10 is turned on with this high voltage / high frequency voltage.

A current waveform detection circuit 12 connected to the low voltage side terminal of the fluorescent lamp 10 detects an asymmetric component of the polarity of the current waveform from the current waveform flowing through the fluorescent lamp 10, and uses this asymmetric component as an error signal to perform voltage control. Input to the circuit 13.

The voltage control circuit 13 outputs a predetermined correction control signal to the high-frequency voltage generation circuit 11 and operates to correct the high-frequency voltage waveform.

The fluorescent lamp lighting circuit according to the present embodiment can correct the polarity symmetry of the current waveform flowing through the fluorescent lamp 10 in this manner, and can control the current waveform to be minimized.

Although the fluorescent lamp 10 is a cold cathode fluorescent lamp having no heater at each terminal, a similar configuration can be realized even with a hot cathode fluorescent lamp.

(Embodiment 2) Next, the configuration of the fluorescent lamp lighting circuit of the present embodiment will be described with reference to FIG. 2, which is a block diagram of the fluorescent lamp lighting circuit of the present embodiment.

The configuration of the fluorescent lamp lighting circuit of the present embodiment is substantially the same as the configuration of the fluorescent lamp lighting circuit of the present embodiment described above, but FIG. 2 shows a specific example of the current waveform detection circuit 12 '. The configuration is shown in detail.

That is, 20 is a detection resistor for detecting a current waveform, 21 is a buffer amplifier for a voltage generated in the detection resistor 20, 22 and 23 are positive and negative effective voltage conversion circuits, respectively, and 24 and 25 are effective voltage conversion circuits. An error amplifier that compares the effective voltage values converted by the voltage conversion circuits 22 and 23.

Next, the operation of the fluorescent lamp lighting circuit according to the present embodiment will be described.

The operation of the fluorescent lamp lighting circuit of the present embodiment is almost the same as the operation of the fluorescent lamp lighting circuit of the above-described embodiment, and therefore, the operation of the current waveform detection circuit 12 'will be mainly described below. .

The high-frequency voltage generating circuit 11 applies a high-frequency voltage to the fluorescent lamp 10 by receiving a power supply.

The tube current flowing from the low voltage side terminal of the fluorescent lamp 10 flows to the GND side through the detection resistor 20, and the detection voltage is input to the buffer amplifier 21.

The output voltage of the buffer amplifier 21 is input to a positive electrode effective voltage conversion circuit 22 and a negative electrode effective voltage conversion circuit 23, and is converted into an effective voltage value (equivalent DC voltage value) for each polarity. Note that these circuits can be easily realized by using an integrating circuit.

The outputs of the positive electrode effective voltage conversion circuit 22 and the negative electrode effective voltage conversion circuit 23 are output from an error amplifier 24,
25.

The error amplifier 24 compares the positive and negative effective voltages, outputs the polarity symmetry (polar symmetry) as an error voltage, and outputs the error voltage to the voltage control circuit 13. The error amplifier 25 compares the effective voltage of the negative polarity with the reference voltage 26, compares whether the current value of the fluorescent lamp 10 has reached a predetermined set current, and performs voltage control as a (set current) error voltage. Output to the circuit 13.

The voltage control circuit 13 includes error amplifiers 24, 2
5, a predetermined correction control signal is output to the high-frequency voltage generation circuit 11 based on the polarity symmetry error voltage and the set current error voltage respectively input from.

The high-frequency voltage generation circuit 11 controls the symmetry of the output current value and the output waveform to correct the asymmetry.

When dimming control by pulse width modulation is performed, the output current of the voltage control circuit 13 can be controlled by using, for example, a pulse duty variable circuit by voltage control.

For the control of the symmetry, a configuration in which a DC offset is applied by varying the base bias current of the push-pull transistor of the high-frequency voltage generating circuit 11 can be used. According to the effective current detection method, the asymmetry of the current waveform due to the waveform distortion of the fluorescent lamp can be accurately corrected.

Further, by using the positive electrode effective voltage conversion circuit 22 and the negative electrode effective voltage conversion circuit 23 as average voltage conversion circuits, the polarity symmetry of the tube current of the fluorescent lamp 10 can be detected as the difference between the average currents. Becomes possible. As such an average voltage conversion circuit, a circuit that converts a peak value after converting a voltage waveform into a sine wave by a low-pass filter that passes a lighting frequency of a fluorescent lamp into a DC voltage can be used. This average current detection method is a particularly effective detection method when the decrease in the light emission amount of the entire fluorescent lamp as described above is caused not by the waveform distortion component of the fluorescent lamp but rather by a DC offset. Become.

Further, by using the positive electrode effective voltage conversion circuit 22 and the negative electrode effective voltage conversion circuit 23 as spike voltage conversion circuits, respectively, the polarity symmetry of the tube current of the fluorescent lamp 10 can be detected as the difference between the spike currents. Becomes possible. As such a spire voltage conversion circuit, a circuit that directly converts a detected voltage by a peak hold circuit into a DC voltage as it is can be used. This spire current detection method is a particularly effective detection method when the decrease in the light emission amount of the entire fluorescent lamp as described above is mainly caused by a waveform distortion component of the fluorescent lamp. Can correct the symmetry of the waveform of the high-frequency current that actually flows to the correct value, making it difficult for the DC component current to flow through the fluorescent lamp, and preventing the bias of substances that contribute to light emission inside the fluorescent lamp as described above. Is done. For this reason, it is possible to suppress a decrease in the amount of light emission and a deterioration in uniformity of light emission due to abnormal light emission of the fluorescent lamp, and a reduction in the life of the fluorescent lamp.

In the above, Embodiments 1 and 2 have been described in detail.

The above-described embodiment is merely an example. For example, the configuration of the high-frequency voltage generating circuit is not limited to the blocking oscillation system, but may be other oscillation systems such as a piezoelectric inverter configuration using a piezoelectric transformer. It goes without saying that this may be the case.

The effective voltage conversion circuit, the average voltage conversion circuit, and the spire voltage conversion circuit may be any circuits that can detect the effective voltage, the average voltage, and the spire voltage, and output the control voltage to the voltage control circuit.

Further, in the above-described embodiment, an example of the configuration in the analog signal processing system has been described. However, the configuration is such that the current detection unit converts the signal into a digital signal, and the voltage control circuit 13 performs digital signal processing. Needless to say, it is good. Needless to say, in this case, the configuration from digital signal conversion to voltage output may be performed by software using a one-chip microcomputer with a program.

As described above, the fluorescent lamp lighting circuit of the present invention
For example, a high-frequency voltage generating circuit that turns on a fluorescent lamp at high frequency, a voltage control circuit that controls the generated voltage of the high-frequency voltage generating circuit, and a current waveform of a feedback current from the low-voltage side of the fluorescent lamp to the high-frequency voltage generating circuit are detected. The current waveform detection circuit detects polarity symmetry of the feedback current waveform, and when the waveform symmetry deviates from a predetermined value, the voltage control A fluorescent lamp lighting circuit characterized in that the polarity symmetry of a current waveform flowing through a fluorescent lamp can be corrected to a predetermined value by changing a voltage waveform or a voltage value of a generating circuit.

In the fluorescent lamp lighting circuit of the present invention, for example, the current waveform detecting circuit detects the symmetry by comparing the effective voltage values of the positive and negative polarities of the detected current waveform. The above-described fluorescent lamp lighting circuit is characterized in that:

In the fluorescent lamp lighting circuit of the present invention, for example, the current waveform detection circuit detects the symmetry by comparing the average voltage values of the positive and negative polarities of the detected current waveform. The above-described fluorescent lamp lighting circuit is characterized in that:

In the fluorescent lamp lighting circuit of the present invention, for example, the current waveform detection circuit is configured to detect the symmetry by comparing each of the positive and negative voltage values of the detected current waveform. The above-described fluorescent lamp lighting circuit is characterized in that:

The fluorescent lamp lighting circuit according to the present invention is, for example, the fluorescent lamp lighting circuit described above, wherein the fluorescent lamp is a cold cathode fluorescent tube. That is, a cold cathode fluorescent tube is used for the fluorescent lamp, and the effect of the present invention can be particularly effectively exhibited.

The fluorescent lamp lighting circuit according to the present invention is the fluorescent lamp lighting circuit described above, which is used for lighting a fluorescent lamp of a backlight used in a liquid crystal display device, for example. That is, the fluorescent lamp lighting circuit is used for lighting a fluorescent lamp of a backlight of a liquid crystal display device (applied image display device). In particular, the fluorescent lamp lighting circuit is applied to the above-described backlight using a thin tube cold cathode fluorescent lamp. The effects of the invention can be maximized.

In short, the present invention provides a fluorescent lamp lighting circuit for the purpose of achieving stable light emission of a fluorescent lamp and prolonging its life, and detects a current waveform flowing through the fluorescent lamp to generate a high-frequency voltage. By controlling the circuit, the polarity symmetry of the high-frequency voltage is corrected, and the fluorescent lamp is turned on with a current waveform having good polar symmetry.

The present invention uses a method of comparing the effective values of the positive and negative waveforms, a method of comparing the average values of the positive and negative waveforms, and a method of comparing the spire values of the positive and negative waveforms.

The voltage generating means of the present invention is a high-frequency voltage generating circuit in the above-described embodiment, but is not limited to this. In short, the voltage generating means generates a voltage for lighting a fluorescent lamp. Should be fine.

The detecting means of the present invention is a current waveform detecting circuit in the above-described embodiment, but is not limited to this. In short, the detecting means is based on the current flowing through the illuminated fluorescent lamp or the current waveform or the current waveform. Any means for detecting the voltage waveform may be used.

The control means of the present invention is a voltage control circuit in the present embodiment described above, but is not limited to this. In short, it is means for controlling the generation of a voltage based on the result of detection. I just need.

In the present embodiment, the detection of the present invention is the detection of the current waveform of the feedback current from the illuminated fluorescent lamp. However, the present invention is not limited to this. It is only necessary to detect a current waveform or a voltage waveform from the current flowing through the fluorescent lamp.

Further, in the above-described embodiment, the control of the present invention is performed such that when the polarity symmetry of the current waveform of the feedback current deviates from a predetermined range, the polarity symmetry is corrected to a predetermined range. Although the control is performed, the present invention is not limited to this. In short, any control may be used as long as it is a control for generating a voltage based on the result of detection.

According to the present invention, the functions of all or a part of the fluorescent lamp lighting circuit of the present invention and the image display application device (or an apparatus, an element, a circuit, a part, etc.) are executed by a computer. For operating in cooperation with a computer. Of course, the computer of the present invention is not limited to pure hardware such as a CPU,
S, and may further include peripheral devices.

The present invention also provides a program for causing a computer to execute all or some of the steps (or steps, operations, actions, etc.) of the above-described fluorescent lamp lighting control method of the present invention, A program that operates in cooperation with a computer.

Some of the means (or devices, elements, circuits, units, etc.) of the present invention, and some of the steps (or steps, operations, actions, etc.) of the present invention, It may mean some means or steps within a step, or some functions or some operations within one means or step.

Some devices (or elements, circuits, units, etc.) of the present invention mean some of the plurality of devices, or some of the means in one device. (Or an element, a circuit, a part, or the like) or a part of the function of one means.

The present invention also includes a computer-readable recording medium that records the program of the present invention. Further, one usage form of the program of the present invention may be a form in which the program is recorded on a computer-readable recording medium and operates in cooperation with the computer. One usage of the program of the present invention may be a mode in which the program is transmitted through a transmission medium, read by a computer, and operates in cooperation with the computer. The recording medium includes a ROM and the like, and the transmission medium includes a transmission medium such as the Internet, light, radio waves, and sound waves.

The configuration of the present invention may be realized by software or hardware.

As described above, the present invention detects the tube current waveform of a fluorescent lamp, detects the asymmetric component of the polarity of the current waveform, corrects the output waveform of the high-frequency generation circuit, and By controlling to maintain the symmetry of the tube current waveform, it is possible to prevent a decrease in the amount of light emission, deterioration of the uniformity of the light emission, and a decrease in the life due to the asymmetry of the polarity of the tube current, and stable lighting is possible. This has the effect that a simple fluorescent lamp lighting circuit can be realized. In addition, since the current waveform symmetry and the current value can be set by including the peripheral member such as a reflector in the fluorescent lamp, the correction can be improved including the individual difference of the fluorescent lamp and the configuration variation with the peripheral member. Even if there are individual variations of these members, it is possible to exhibit the effect that more stable lighting, uniform light emission, and longer life can be achieved.

The effect of the fluorescent lamp lighting circuit of this configuration can be further enhanced by using it for lighting a cold cathode fluorescent tube. Further, the fluorescent lamp lighting circuit of the backlight for a liquid crystal display device can be used. The practical effect is further increased by applying the method to applications.

[0068]

As is apparent from the above description, the present invention can suppress a decrease in the light emission amount of the entire fluorescent lamp, a deterioration in the luminance distribution of the fluorescent lamp, and a decrease in the life of the fluorescent lamp. It has the advantage of.

[Brief description of the drawings]

FIG. 1 is a block diagram of a fluorescent lamp lighting circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram of a fluorescent lamp lighting circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram of a conventional fluorescent lamp lighting circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fluorescent lamp 11 High frequency voltage generation circuit 12, 12 'Current waveform detection circuit, 13 Voltage control circuit, 20 detection resistor, 21 buffer amplifier, 22 Positive effective voltage conversion circuit, 23 Negative effective voltage conversion circuit, 24, 25 Error amplifier , 26 Reference voltage

Claims (9)

[Claims] 1. A voltage generating means for generating a voltage for lighting a fluorescent lamp; a detecting means for detecting a current waveform or a voltage waveform from a current flowing through the turned on fluorescent lamp; And a control means for controlling the generation of the voltage. 2. The detection is to detect a current waveform of a feedback current from the lit fluorescent lamp, and the control is performed when a polarity symmetry of the current waveform of the feedback current deviates from a predetermined range. 2. The fluorescent lamp lighting circuit according to claim 1, wherein the control is performed to correct the polarity symmetry to the predetermined range. 3. The fluorescent lamp lighting circuit according to claim 2, wherein the polarity symmetry is a symmetry obtained based on a comparison between respective effective voltage values regarding a positive polarity and a negative polarity of the detected current waveform. 4. The fluorescent lamp lighting circuit according to claim 2, wherein the polarity symmetry is a symmetry obtained based on a comparison between respective average voltage values regarding the positive polarity and the negative polarity of the detected current waveform. 5. The fluorescent lamp lighting circuit according to claim 2, wherein the polarity symmetry is a symmetry obtained based on a comparison between respective spike voltage values regarding the positive polarity and the negative polarity of the detected current waveform. 6. The fluorescent lamp lighting circuit according to claim 1, wherein the fluorescent lamp is a cold cathode fluorescent tube. 7. A high-frequency voltage generating circuit for lighting a fluorescent lamp at a high frequency, a voltage control circuit for controlling a generated voltage of the high-frequency voltage generating circuit, and a feedback current from a low voltage side of the fluorescent lamp to the high-frequency voltage generating circuit. A current waveform detection circuit for detecting a current waveform, wherein when the polarity symmetry of the current waveform of the detected feedback current deviates from a predetermined value, the voltage waveform of the high-frequency voltage generation circuit is controlled by controlling the generated voltage. Alternatively, a fluorescent lamp lighting circuit in which the polarity symmetry of a current waveform flowing through the fluorescent lamp is corrected to a predetermined value by changing a voltage value. 8. An image display application device using the fluorescent lamp lighting circuit according to claim 1. 9. A fluorescent lamp lighting circuit according to claim 1, wherein a voltage generator for generating a voltage for lighting the fluorescent lamp, and a current waveform or a voltage waveform is detected from a current flowing through the turned on fluorescent lamp. A program for causing a computer to function as all or a part of a detection unit that performs the detection and a control unit that controls generation of the voltage based on a result of the detection.