KR20050051912A - Driving unit of electric discharge lamp - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a discharge tube lamp having a same brightness in any environment by adjusting the brightness between lamps by using a brightness detector that converts the brightness of the lamp into an electrical signal, wherein the voltage source and the voltage supplied from the voltage source are boosted. AC conversion circuit for generating an AC signal, at least one discharge tube lamp for receiving the AC signal of the AC conversion circuit to emit light, a current detector for detecting a voltage supplied to each of the discharge tube lamps, And a control unit for controlling the AC conversion circuit by a luminance detector for detecting luminance and a detection signal supplied from the current detector and a luminance detection signal supplied from the luminance detector.

Description

Driving unit of electric discharge lamp

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight and, more particularly, to a drive device for a discharge tube lamp suitable for maintaining uniform brightness between lamps.

In general, liquid crystal display devices (hereinafter, referred to as "LCDs") have tended to be gradually widened due to their light weight, thinness, and low power consumption.

According to this trend, LCDs are used for office automation equipment, audio / video equipment, and the like.

On the other hand, the LCD is controlled to display the desired image on the screen by adjusting the transmission amount of the light beam according to the image signal applied to the plurality of control switches arranged in a matrix form.

Since the LCD is not a self-luminous display device, a light source such as a back light is required. As a light source used for the backlight, a cold cathode tube (hereinafter referred to as 'CCFL') is used.

The CCFL is a light source tube using a cold emission (electron emission generated by applying a strong electric field to the cathode surface), and is easy to generate low heat, high brightness, long life, and full color.

These CCFLs include a light guide type, a direct type type, a reflecting plate type, and the like, and a light source tube suitable for the type of LCD is adopted.

The CCFL uses an inverter circuit for obtaining a high voltage power from a low voltage DC power supply.

Currently, many CCFLs (Cold Cathode Fluorescent Lamps) are used for the backlights used in the development of large TV LCD modules, and a multi-output inverter is used to drive the CCFLs.

In order to create a uniform brightness of the backlight, the brightness of each lamp should be the same. Conventionally, the same luminance is produced by making the tube current of the lamp the same.

Hereinafter, a driving device of a conventional discharge tube lamp will be described with reference to the accompanying drawings.

1 is a block diagram showing a driving device of a conventional discharge tube lamp.

As shown in FIG. 1, a conventional CCFL driving apparatus is provided between a voltage source Vin, a plurality of CCFLs 10 emitted by an AC signal, and between the voltage source Vin and each CCFL 10. An inverter circuit 20 for supplying an AC signal to the CCFL 10 and a common circuit connected to each of the CCFLs 10 and installed between the inverter circuits 20 to detect a voltage commonly supplied to the CCFL 10. A voltage detector 30 is provided.

FIG. 2 is a circuit diagram illustrating the inverter circuit of FIG. 1 in detail.

As shown in FIG. 2, the first wire transformer T1 connected to one end of the CCFL 10 and the high frequency oscillation circuit 25 connected to the primary winding L1 of the first wire transformer T1. A first transistor Q1 connected between the high frequency oscillation circuit 25 and the voltage source Vin to switch the voltage from the voltage source Vin into the high frequency oscillation circuit 25, and the first transistor Q1. A pulse width modulation (PWM) control unit 24 for supplying a control signal to the power supply; and a power switch 26 connected between the PWM control unit 24 and the voltage source Vin; The control signal is supplied to the PWM controller 24 in accordance with the detected voltage supplied from the voltage detector 30.

The first wire transformer T1 is composed of a primary winding L1, a secondary winding L2, and an auxiliary winding L3. Each of the primary winding L1 and the auxiliary winding L3 of the first wire transformer T1 is connected to the high frequency oscillation circuit 25.

In addition, one end of the secondary winding L2 in the first wire transformer T1 is connected to one end of the CCFL 10 through the first capacitor C1, and the other end thereof is connected to the ground voltage source GND.

The high frequency oscillation circuit 25 includes a pair of second and third transistors Q2 and Q3 connected to the primary winding L1 of the first wire transformer T1 with the ground voltage source GND therebetween, and the primary A second capacitor C2 disposed in parallel with the winding L1 is provided.

Here, the collector terminals of the second and third transistors Q2 and Q3 are connected to both ends of the primary winding L1 of the first wire transformer T1 and the emitter terminal is common to the ground voltage source GND. Connected.

In addition, the base terminals of the second and third transistors Q2 and Q3 are connected to the midpoint of the primary winding L1 through the first and second resistors R1 and R2 and at the same time, the first wire transformer T1. It is connected to both ends of each auxiliary winding L3.

When the power switch 26 is turned on, the PWM controller 24 receives a control signal from the voltage detector 30 and supplies a PWM control signal to the base terminal of the first transistor Q1. In this case, the PWM control signal controls the switching period of the first transistor Q1 according to the control signal of the voltage detector 30.

The first transistor Q1 is turned on by the PWM control signal supplied from the PWM control unit 24 to be supplied from the voltage source Vin to switch the voltage of which the pulse width is modulated to the high frequency oscillation circuit 25. .

In this case, a coil is connected between the collector terminal of the first transistor Q1 and the high frequency oscillation circuit 25, and a coil is connected between the collector terminal of the first transistor Q1 and the ground voltage source GND. Diode D1 is connected.

Here, the coil serves to remove noise of the voltage supplied through the first transistor Q1, and the first diode D1 blocks the voltage flowing to the ground voltage source GND. .

In addition, a synchronization signal controller 28 is further disposed between the first node N1 and the PWM controller 24 between the coil and the first transistor Q1. The synchronization signal controller 28 receives a voltage signal from which noise is removed by a coil and generates a synchronization signal for determining an output time point of the PWM control signal output from the PWM controller 24 to generate a PWM controller 24. To feed.

3 is a circuit diagram illustrating the voltage detector of FIG. 1 in detail.

As shown in FIG. 3, the third and variable resistors R3 and RB connected in series between the second node N2 and the ground voltage source GND to which the CCFL 10 is commonly connected, and the second A rectifier diode D3 is disposed between the node N2 and the voltage detector 30 and a second diode D2 is disposed between the second node N2 and the ground voltage source GND.

Here, the third and variable resistors R3 and RB cause the voltage signal FB detected by the divided resistance value to the equivalent resistance value of the CCFL 10 to appear on the second node N2.

Subsequently, the detected voltage signal FB on the second node N2 is supplied to the PWM controller 24 through the rectifying diode D3. Here, the second diode D2 serves to block the detected voltage signal FB from flowing in the reverse direction.

In the conventional CCFL driving apparatus, when the power switch 26 is turned on, the first transistor Q1 is turned on by the PWM control signal from the PWM control unit 24 so that the driving power is supplied to the high frequency oscillation circuit 25. Supplied.

In this case, the second and third transistors Q2 and Q3 may be turned on / off and turned off / turn on according to the magnitude of the voltage charged in the second capacitor C2 to perform the operation of the first wire transformer T1. In the secondary winding L2, an alternating current high voltage is induced.

In this way, the alternating current high voltage induced in the secondary winding L2 of the first wire transformer T1 induces the alternating current high voltage in the auxiliary winding L3, thereby causing the second and third transistors Q2 and Q3 to repeat. Since switching is performed, the AC high voltage is continuously induced in the secondary winding L2 of the first wire transformer T1.

Therefore, the AC high voltage generated in the first wire transformer T1 is supplied to the CCFL 10 so that the CCFL 10 is turned on.

When the CCFL 10 is turned on in this way, the integrated voltage signal FB supplied to the CCFL 10 is detected by the voltage detector 30 commonly connected to the CCFL 10.

The detected voltage signal FB is applied to the PWM controller 24, and the PWM controller 24 generates a brightness control signal for controlling the brightness of the CCFL 10 using the detected voltage signal. According to the generated brightness control signal, the PWM controller 24 controls the current supplied to the CCFL 10 in common.

As such, the conventional CCFL driving apparatus has difficulty in adjusting the brightness of each of the CCFLs 10.

That is, the brightness of the lamp may vary according to the characteristic deviation of the CCFL 10, the leakage current, and the temperature characteristic of each location.

Therefore, in the case of a large area backlight, it is difficult to maintain luminance uniformity in the environment as described above.

The present invention has been made to solve the above problems to provide a driving device of the discharge tube lamp to have the same brightness in any environment by adjusting the brightness between the lamps using a brightness detector that converts the brightness of the lamp into an electrical signal. There is a purpose.

The driving device of the discharge tube lamp according to the present invention for achieving the above object is a voltage source, an AC conversion circuit for generating an AC signal by boosting the voltage supplied from the voltage source, and receives an AC signal of the AC conversion circuit At least one discharge tube lamp for emitting light, a current detector for detecting a voltage supplied to each of the discharge tube lamps, a luminance detector for detecting the luminance of each of the discharge tube lamps, a detection signal supplied from the current detector and the luminance detector And a controller for controlling the AC conversion circuit by the supplied luminance detection signal.

Here, the AC conversion circuit includes a primary winding and an auxiliary winding connected to the voltage source, and a secondary winding connected to the discharge tube and the current detector.

In addition, the discharge tube lamp is CCFL.

Hereinafter, with reference to the accompanying drawings will be described in more detail the driving device of the discharge tube lamp according to the present invention.

Fig. 4 is a block diagram showing the driving device of the discharge tube lamp according to the present invention, and Fig. 5 is a circuit diagram showing the driving device of the discharge tube lamp according to the present invention in detail.

As shown in FIG. 4 and FIG. 5, a voltage source Vin, a plurality of inverter circuits 40 for generating an AC signal, and a plurality of wire transformers for boosting and outputting an AC signal from the inverter circuit 40 70, a plurality of CCFLs 50 emitting light by receiving an AC signal boosted from the wire transformer 70, and a plurality of voltage detectors 60 for detecting voltages supplied to the CCFLs 50, respectively. ) And a plurality of luminance detectors 80 for detecting respective luminances in the CCFL 50.

Here, one end of each of the CCFLs 50 is connected to the inverter circuit 40, respectively, and the other end is commonly connected to the ground voltage source GND. Each of the CCFLs 50 receives an AC signal boosted from each wire transformer 70 and emits light.

In addition, since each of the inverter circuits 40 has the same circuit configuration, one inverter circuit 40 will be described as an example.

As shown in FIG. 5, the inverter circuit 40 includes a high frequency oscillation circuit 85 connected to the primary winding L1 of each wire transformer 70, and between the high frequency oscillation circuit 85 and the voltage source Vin. A first transistor Q1 connected to the switch to switch the voltage from the voltage source Vin to the high frequency oscillation circuit 85 and a pulse width modulation supplying a control signal to the first transistor Q1; And a voltage supplied to each of the power switch 86 connected between the PWM controller 84 and the voltage source Vin and the CCFL 50 to detect the voltage. The voltage detector 60 outputs to the control part 84, and the brightness detector 80 which detects each brightness | luminance in the said CCFL 50, and outputs it to the said PWM control part 84 are provided.

Here, the high frequency oscillation circuit 85 may include a pair of second and third transistors Q2 and Q3 connected to the primary winding L1 of the first wire transformer T1 with the ground voltage source GND therebetween; A second capacitor C2 disposed in parallel with the primary winding L1 is provided.

In the high frequency oscillation circuit 85, the collector terminals of the second and third transistors Q2 and Q3 are connected to both ends of the primary winding L1 of the wire transformer 70 and the emitter terminal is connected to the ground voltage source GND. Is commonly connected to.

In addition, a collector terminal of the first transistor Q1 is connected to the base terminal of each of the second and third transistors Q2 and Q3 through the first and second resistors R1 and R2. The collector terminal of the first transistor Q1 is connected to both ends of the auxiliary winding L3 of the wire transformer 70 and to the midpoint of the primary winding L1 of the wire transformer 70.

As shown in FIG. 5, the wire transformer 70 includes a primary winding L1, a secondary winding L2, and an auxiliary winding L3. Each of the primary winding L1 and the auxiliary winding L3 is connected to the inverter circuit 40, respectively.

In addition, one end of the secondary winding L2 is connected to the CCFL 50 through the first capacitor C1, and the other end thereof is connected to the voltage detector 60, respectively. Here, the first capacitor C1 stabilizes the voltage supplied to each CCFL 50 from the secondary winding L2 of the wire transformer 70 and removes the DC component.

In addition, the brightness detector 80 is connected to one end of each of the CCFL 50 to detect the brightness, PWM control unit for configuring the inverter circuit 40 to the brightness detection signal detected by the brightness detector 80 And a plurality of CCFLs 50 having the same brightness under any circumstances.

The PWM controller 84 receives the detection signal from the luminance detector 80 when the power switch 86 is on, and supplies the PWM control signal to the base terminal of the first transistor Q1. The PWM control signal PS controls the voltage supplied to the wire transformer 70 by controlling the switching period of the first transistor Q1 according to the luminance detection signal.

The first transistor Q1 is turned on by the PWM control signal PS supplied from the PWM control unit 84 to convert the voltage supplied from the voltage source Vin to the high frequency oscillation circuit 85. Will be switched.

In this case, a coil is connected between the collector terminal of the first transistor Q1 and the high frequency oscillation circuit 85, and a coil is connected between the collector terminal of the first transistor Q1 and the ground voltage source GND. Diode D1 is connected.

Here, the coil prevents switching loss of the first transistor Q1 and determines an oscillation frequency for magnetic oscillation with the high frequency oscillation circuit 85. The first diode D1 maintains the lowest potential of the collector terminal of the first transistor Q1 at zero potential.

That is, the first diode D1 generates a negative potential impulse when the first transistor Q1 is turned off. This impedes the impulse of the negative potential.

In addition, a synchronization signal controller 88 is further disposed between the first node N1 and the PWM controller 84 between the first transistor Q1 and the coil. The synchronization signal controller 88 receives a voltage signal from which noise is removed by a coil and generates a synchronization signal for determining an output time point of the PWM control signal PS output from the PWM controller 84. It supplies to 84.

6 is a circuit diagram illustrating the voltage detector of FIG. 4 in detail.

As shown in FIG. 6, the variable resistor VR and the third resistor R3 connected in parallel between the second node N2 connected to the secondary winding L2 of the wire transformer 70 and the ground voltage source GND. ), Between the rectifier diode D3 connected between the variable resistor VR and the output terminal, and between the third node point N3 and the ground voltage source GND between the rectifier diode D3 and the variable resistor VR. A second diode D2 is connected.

The voltage detector 60 configured as described above detects the voltage by the resistance ratio of the variable resistors R3 and VR connected in parallel with the secondary winding L2 of the wire transformer 70.

Subsequently, the detected voltage signal FB is rectified by the rectifying diode D3 and supplied to the PWM controller 64. Here, the second diode D2 blocks the detected voltage signal FB from flowing to the ground voltage source GND.

In the driving apparatus of the CCFL according to the present invention as described above, when the power switch 86 is turned on, the first transistor Q1 is turned on by the PWM control signal PS from the PWM control unit 84 so that the driving power is turned on. The high frequency oscillation circuit 85 is supplied.

In this case, the second and third transistors Q2 and Q3 are turned on / off and turned off / on according to the magnitude of the voltage charged in the second capacitor C2 to perform the secondary winding of the wire transformer 70. At L2, an alternating current high voltage is induced.

The AC high voltage induced in the secondary winding L2 of the wire transformer 70 induces the AC high voltage to the auxiliary winding L3, and thus the second and third transistors Q2 and Q3 are repeatedly switched, thereby making the wire transformer In the secondary winding L2 of 70, an alternating current high voltage is continuously induced. The AC high voltage generated by the wire transformer 70 is supplied to the CCFL 50 through the first capacitor C1 so that the CCFL 50 is turned on.

Subsequently, when the CCFL 50 is turned on, the voltage signal FB is detected by the voltage detector 60 connected to the secondary winding L2 of the wire transformer 70. The voltage supplied to the primary winding L1 of the wire transformer 70 is controlled by controlling the switching of the first transistor Q1 by the PWM controller 84 according to the detected voltage signal FB.

Accordingly, the current supplied to the CCFL 50 through the secondary winding L2 of the wire transformer 70 is adjusted.

In addition, when the CCFL 50 is driven by the current supplied to the CCFL 50, the luminance of the CCFL 50 is detected by the luminance detector 80 and output to the PWM control unit 84 to output the CCFL ( The luminance of 50) is the same.

Therefore, the driving device of the CCFL lamp according to the present invention by detecting the voltage through the voltage detector 60 connected to the secondary winding (L2) of the wire transformer 70, respectively, to control the current supplied to each of the CCFL (50) The luminance deviation of the two cold cathode tube lamps can be made uniform.

In addition, the voltage detector 60 is used to control the current supplied to the CCFL 50, and the luminance detector 80 is used to detect the luminance of each of the CCFLs 50 to make the luminance the same in any natural environment. I can keep it.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention. It will be apparent to those of ordinary skill in Esau.

As described above, the driving device of the discharge tube lamp according to the present invention has the following effects.

That is, by detecting and controlling the brightness of the lamp according to the characteristic variation of the lamp, the leakage current, and the temperature characteristic of each position, the brightness uniformity can be maintained in any environment.

1 is a block diagram showing a driving device of a conventional discharge tube lamp

FIG. 2 is a circuit diagram illustrating the inverter circuit of FIG. 1 in detail.

3 is a circuit diagram illustrating in detail the voltage detector of FIG.

4 is a block diagram showing a driving device of a discharge tube lamp according to the present invention.

5 is a circuit diagram showing in detail the driving device of the discharge tube lamp according to the present invention;

6 is a circuit diagram illustrating in detail the voltage detector of FIG.

Explanation of symbols for the main parts of the drawings

40: inverter circuit 50: CCFL

60: current detector 70: wire transformer

80: luminance detector

Claims (3)

Voltage source, An AC conversion circuit for boosting the voltage supplied from the voltage source to generate an AC signal; At least one discharge tube lamp for emitting light by receiving an AC signal of the AC conversion circuit; A current detector for detecting a voltage supplied to each of the discharge tube lamps; A brightness detector for detecting the brightness of each discharge tube lamp; And a control unit for controlling the AC conversion circuit by the detection signal supplied from the current detector and the brightness detection signal supplied from the brightness detector.  The apparatus of claim 1, wherein the AC conversion circuit comprises a primary winding and an auxiliary winding connected to the voltage source, and a secondary winding connected to the discharge tube and the current detector.  2. The driving device of a discharge tube lamp according to claim 1, wherein the discharge tube lamp is CCFL.