KR100875705B1 - Digital control inverter and control method thereof for external electrode fluorescent lamp - Google Patents

Abstract

A digital control inverter for an external electrode fluorescent lamp and a control method thereof are provided to control a duty of a pulse width modulation signal for controlling an AC driving power according to the measured voltage and current by measuring the voltage and current of the AC driving power provided to the external electrode fluorescent lamp. Backlight drivers(10,110) receive a first pulse width modulation signal and a second pulse width modulation signal and generate a first AC driving power and a second AC driving power according to the first and second pulse width modulation signals to output the generated result to the backlight. A microprocessor unit(40) converts the voltage and current value of the alternating current drive power into the DC power and measures the DC power. The microprocessor unit determines the measured voltage and current value within the reference voltage and current range and controls the duty of the first and second pulse width modulation signal if the measured voltage and current value is less than the reference voltage and current value or more.

Description

DIGITAL CONTROL INVERTER AND CONTROL METHOD THEREOF FOR EXTERNAL ELECTRODE FLUORESCENT LAMP}

1 is a view showing the configuration of a digital control inverter for an external electrode fluorescent lamp according to the present invention

2 is a flowchart illustrating a control operation of a digital control inverter for an external electrode fluorescent lamp according to the present invention.

<Description of the symbols for the main parts of the drawings>

10: first backlight driver 11, 111: transformer

12, 112: full bridge 13, 113: gate driver

40: MPU 41: CPU

42: ROM 43: RAM

44: MUX 45: A / D converter

46: input and output port 47: the first PWM generator

48: second PWM generator 100: master

110: second backlight driver 150: EEFL lamp unit

200: slave

The present invention relates to a backlight inverter, and more particularly, to a digital control inverter for an external electrode fluorescent lamp that can digitally control an external electrode fluorescent lamp (EEFL) and a control method thereof. .

Current display devices are being replaced by liquid crystal displays (LCDs) in cathode ray tubes (CRTs). The LCD has a backlight device that provides a light source on the back of the panel. The light sources include the Cold Cathode Fluorescent Lamp (CCFL), which is currently used the most, and the External Electrode Fluorescent Lamp (EEFL), which is recently attracting attention as the next generation light source.

Conventional backlights using cold cathode fluorescent lamps have limitations in achieving sufficient brightness and efficiency.In the case of external electrode fluorescent lamps, the electrodes can avoid direct interaction with the plasma, which is advantageous for their lifetime, and the electrodes are installed outside. It is emerging as a light source for LCD because it can be driven by connecting lamps in parallel.

The EEFL backlight device is composed of a plurality of EEFL and the inverter for lighting the EEFL. Inverters typically consist of drive elements for EEFL driving, such as analog controllers, gate drivers, half bridges or full bridges, transformers, and a plurality of protection circuits to protect the EEFL and the drive elements. The protection circuit measures the voltage or current output from the transformer to the EEFL, compares the measured voltage or current value with each of the upper and lower reference values, determines whether it is out of a predetermined range, cuts off the power, or measures it with the analog controller. There is an output voltage protection circuit and an output current protection circuit for outputting a signal indicating that the value is out of range. In addition, other protection circuits may include an overvoltage and overcurrent protection circuit that cuts power when overvoltage or overcurrent is detected by comparing the measured voltage and current with the respective overvoltage and overcurrent reference values while measuring voltage and current in the same manner.

As described above, the inverter of the general EEFL backlight device has a problem in that the size of the inverter increases and the production cost increases because the number of devices due to the driving elements and the plurality of protection circuits increases.

In addition, the inverter of the conventional EEFL backlight device has a problem that the power consumption increases because it has many elements due to the analog protection circuits.

In addition, since the drive elements and the protection circuits of the inverter of the general EEFL backlight device are composed of analog elements, there is a problem of low efficiency.

Accordingly, an object of the present invention is to provide a digital control inverter for an external electrode fluorescent lamp and a control method thereof, which can digitally control an external electrode fluorescent lamp (EEFL).

Another object of the present invention is to digitally measure the voltage and current of the AC drive power provided by the external electrode fluorescent lamp, and to adjust the duty of the pulse width modulation signal for adjusting the AC drive power according to the measured voltage and current values. Disclosed is a digital control inverter for controlling an external electrode fluorescent lamp and a control method thereof.

It is still another object of the present invention to measure an input voltage input from an LCD panel and to stop the generation of a pulse width modulation signal or to reduce the duty when the measured value is outside a preset reference range. And to provide a control method thereof.

Still another object of the present invention is to measure the phases of the first PWM and the second PWM for adjusting the AC driving power provided by the external electrode fluorescent lamp, and to measure the phase of the first PWM and the second PWM so that the measured phase is within a preset phase reference range. Disclosed is a digital control inverter for an external electrode fluorescent lamp for adjusting duty and a control method thereof.

It is still another object of the present invention to provide a digital control inverter for an external electrode fluorescent lamp and a method of controlling the same, which monitor whether an overvoltage or overcurrent is applied to the external electrode fluorescent lamp and stop the generation of PWM when the overvoltage and overcurrent flow. have.

Another object of the present invention is to provide a digital control inverter for an external electrode fluorescent lamp for controlling dimming by turning on / off a PWM signal at regular intervals according to a dimming control signal input from an LCD panel, and a control method thereof.

The apparatus of the present invention for achieving the above object; An inverter for supplying a first and a second AC drive power to the at least one external electrode fluorescent lamp is connected in parallel with the backlight is configured to emit light of the external electrode fluorescent lamp of the backlight, the first and second pulse width modulation A backlight driver configured to receive a signal and generate the first and second AC driving powers according to the first and second pulse width modulation signals, and output the first and second AC driving powers to the backlight; Converts and measures, and determines whether the measured voltage and current values are within a pre-stored voltage and current reference range, and if the measured voltage or current value is out of the voltage or current reference range, A microprocessor unit for adjusting the duty of the first and second pulse width modulated signals according to whether It is characterized by including.

The method of the present invention for achieving the above object; When the power is applied, the pulse width modulation signal generation and the initialization process for driving the analog / digital converter, the dimming control value measured after the initialization, the input voltage value, the voltage value and current value of the AC drive power, and the pulse width modulation signal An input / output signal measuring process for measuring and storing a phase value, a dimming adjusting process for turning on / off the pulse width modulation signal at a predetermined period according to the dimming control value, the measured input voltage, voltage and current of an AC driving power source, Compares the input voltage reference range, the voltage and current reference range of the AC drive power supply, and the phase reference range previously stored in phase values, and the pulse width modulation signal according to whether each measured value is out of or within the reference range. It characterized in that it comprises a pulse width modulation signal duty adjustment process for adjusting the duty of.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that in the following description, only parts necessary for understanding the operation according to the present invention will be described, and descriptions of other parts will be omitted so as not to deviate from the gist of the present invention.

1 is a view showing the configuration of a digital control inverter for an external electrode fluorescent lamp according to the present invention.

Referring to FIG. 1, the digital control inverter for an external electrode fluorescent lamp according to the present invention includes a backlight 150 having a plurality of EEFLs configured in parallel, and an input voltage and a dimming control signal from an LCD panel. The master 100 for applying AC drive power to one end of the slave and the slave 200 for applying AC drive power to the other end of the backlight 150 by receiving a pulse width modulation (PWM) signal from the master 100. It is composed of

The master 100 includes a first backlight driving unit 10 and a microprocessor unit (MPU) 40 for performing digital control.

The first backlight driver 10 receives the first and second PWM signals from the MPU 40 to provide AC driving power to one end of the backlight 150. In the present invention, the external electrode fluorescent lamp driver 10 includes a gate driver 13, a full bridge 12, and a transformer 11. The gate driver 13 receives the first and second PWM signals and outputs a high or low signal for turning on / off a field effect transistor (FET) of the full bridge 12. The full bridge 12 includes four FETs, and generates and outputs a primary AC driving power under the control of the gate driver 13. The transformer 11 receives the primary AC driving power and boosts and outputs the secondary AC driving power as the first AC driving power.

The microprocessor unit 40 includes a central processing unit (CPU) 41, a ROM 42, a RAM 43, a multiplexer (MUX) 44, and an analog / digital converter. (A / D converter) 45, input / output port (I / O) 46, first PWM generator 47, and second PWM generator 48 are included.

The CPU 41 controls the overall operation of the microprocessor unit 40 of the digital inverter according to the present invention.

ROM 42 is a control program for controlling the operation of the digital inverter according to the invention and the reference range of the input voltage, the voltage and current reference range for the secondary AC drive power output from the transformer 11 and the first PWM Stores the phase reference range values of the signal and the second PWM signal. The ROM 42 may use an EEPROM or a flash ROM.

The RAM 43 temporarily stores data generated during the execution of the control program.

The A / D converter 45 receives an analog type dimming control signal, an input voltage, a first PWM signal, a second PWM signal, and a voltage obtained by converting the voltage and current of the secondary AC drive power of the transformer 10 into DC. The signals are converted into the signals and output to the CPU 41.

The MUX 44 receives the digital input voltage, the output voltage, the output current, the first and second PWM signals and the dimming control signal output from the A / D converter 45, and multiplexes the signals to provide the CPU 41. Will output

The first PWM generator (PWM0) 47 is turned on / off at regular intervals under the control of the CPU 41, and generates and outputs the first PWM signal when turned on.

The second PWM generator (PWM1) 48 is turned on / off at regular intervals under the control of the CPU 41, and generates and outputs the first PWM signal when turned on.

The duty of the PWM of the first PWM generator 47 and the duty of the PWM of the second PWM generator 48 are the same, and the phases are 180 degrees out of phase.

 The input / output port (I / O) 46 is connected to an external host computer through an input / output terminal such as RS-232C or Universal Serial Bus (USB) to communicate data between the CPU 41 and the host computer. Perform. The CPU 41 receives and updates update software from an external host computer through the input / output port 46.

The slave 200 includes a second backlight driver 110 including a gate driver 113, a full bridge 112, and a transformer 111 for outputting a second AC driving power. This is because the distance between the two electrodes of the EEFL is large when the backlight 150 is large, and may be configured without dividing into a master and a slave when the backlight is small.

2 is a flowchart illustrating a control operation of a digital control inverter for an external electrode fluorescent lamp according to the present invention. Hereinafter, a description will be given with reference to FIGS. 1 and 2.

When power is applied, the CPU 41 drives the dark drive, the first PWM generator 47 and the second PWM generator 48 to generate and output the first and second PWM signals, and to drive the A / D converter 45. Perform an initialization operation. The dark driving is to emit an LED (not shown) for the initial light emission in the low temperature and dark state according to the characteristics of the EEFL.

 After the initialization, the CPU 41 outputs the dimming control signal and the input voltage input from the LCD panel from the A / D converter 45 and the first and second PWM generators 48 and 48. ROM (in case of 42-flash ROM) or RAM (43-PWM signal) and the second PWM signal and the digital value of the voltage and current of the secondary AC power supply of the transformer 11 of the first backlight driver 10 are input. ).

After the step 213, the CPU 41 proceeds to step 215 to control the first PWM generator 47 and the second PWM generator 48 to turn the first and second PWM signals on / off at regular intervals according to the stored dimming control value. To start.

After the step 215, the CPU 41 determines whether the input voltage is within the input voltage reference range previously stored in the ROM 42 in steps 217, 219, 221, and 223, respectively. It is determined whether it is within the range, the voltage of the AC drive power source that is the secondary output voltage of the transformer 11 is within a preset voltage reference range, or whether the current of the AC drive power source that is the secondary side output current is within the preset current reference range.

As a result of determination, if the input voltage is outside the preset voltage reference range in step 217, the CPU 41 proceeds to step 225 to control the first PWM generator 47 and the second PWM generator 48 to provide the first and second PWM signals. OFF or decrease the PWM duty and return to step 213 to repeat the above process.

In addition, when it is determined in step 219 that the output phase is out of a preset phase reference range, the CPU 41 proceeds to step 227 and when the output phase is less than the set phase reference range, the first PWM generator 47 and the second PWM generator ( 48) to increase the duty of the first and second PWM signals and to reduce the duty of the first and second PWM signals if the phase reference range is exceeded.

If the voltage value of the AC driving power supply is not within the voltage reference range in step 221, the CPU 41 proceeds to step 229 and determines whether the voltage value is greater than the pre-stored overvoltage reference value in excess of the voltage reference range. .

As a result of determination, when the measured voltage value does not exceed the overvoltage reference value, the CPU 41 proceeds to step 227 and adjusts the duty of the first and second PWM signals according to whether the voltage reference range is exceeded or less. On the other hand, if the measured voltage value exceeds the overvoltage reference value, the CPU 41 proceeds to step 231 and counts the timer. In step 233, the CPU 41 determines whether the time counted by the timer exceeds a predetermined reference time. As a result of determination, when the counted time exceeds a predetermined time, the CPU 41 proceeds to step 235 to turn off the first PWM generator 47 and the second PWM generator 48 to stop generating the first and second PWM signals.

In addition, if the output current value measured in step 223 is outside the preset current reference range, the CPU 41 proceeds to step 237 and determines whether the current value is greater than the pre-stored overcurrent reference value. As a result of determination, if the current value is smaller than the overcurrent reference value, the CPU 41 proceeds to step 227 described above. If the current value is larger, the CPU 41 performs a process after step 231 described above to stop generation of the first and second PWM signals.

Meanwhile, in the detailed description of the present invention, specific embodiments have been described, but various modifications are possible without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the scope of the following claims, but also by the equivalents of the claims.

According to the present invention as described above, by controlling the backlight consisting of an external electrode fluorescent lamp using a microprocessor unit, which is a digital system, it is possible to process the protection circuit in software, which reduces the number of parts, thereby reducing the production cost. And the size can be reduced.

In addition, the present invention can reduce the power consumption due to the reduction of the number of parts, has the advantage of increasing the efficiency.

In addition, the present invention has an advantage of improving the reliability of the inverter because the control can be performed more accurately than the analog control by performing digital control.

Claims (12)

An inverter for supplying first and second alternating current driving power so that at least one external electrode fluorescent lamp is connected to a backlight configured in parallel, the external electrode fluorescent lamps of the backlight emit light. A backlight driver configured to receive first and second pulse width modulation signals and generate the first and second AC driving powers according to the first and second pulse width modulation signals, and output the first and second pulse width modulation signals to the backlight; The voltage and current values of the AC drive power supply are measured by converting them into direct current power sources, and determining whether the measured voltage and current values are within a pre-stored voltage and current reference range value, respectively, and measuring the measured voltage or current values. And a microprocessor unit for adjusting the duty of the first and second pulse width modulation signals when the voltage or current reference range value is above or below the voltage or current reference range value. The method of claim 1, The backlight drive unit, The microprocessor unit is configured as a master, and receives the first and second pulse width modulation signals and supplies the first AC driving power to external electrode fluorescent lamps of a backlight according to the first and second pulse width modulation signals. A first backlight driving unit provided at one end; Slaves are configured at the other end of the external electrode fluorescent lamps to receive the first and second pulse width modulation signals and to supply a second alternating current driving power to the external electrode fluorescent lamps according to the first and second pulse width modulation signals. A digital control inverter for an external electrode fluorescent lamp, characterized in that it comprises a second backlight driving unit provided to the other end. The method according to claim 1 or 2, The microprocessor unit, A ROM for storing a control program, a voltage reference range value and a current reference range value of an AC driving power supply; RAM for temporarily storing data generated during the execution of the control program; An analog / digital converter for converting and outputting analog signals of voltage and current of the AC driving power source into digital signals; A multiplexer (MUX) for multiplexing and outputting a voltage and a current of an AC driving power source converted into the digital signal; A first pulse width modulated signal generator for generating and outputting the first pulse width modulated signal; A second pulse width modulated signal generator for generating and outputting the second pulse width modulated signal; A central processing unit that increases or decreases the duty of the first and second pulse width modulation signals when the voltage and current values of the AC driving power output through the multiplexer are above or below the voltage reference range value and the current reference range value; Digital control inverter for external electrode fluorescent lamp, characterized in that consisting of. The method of claim 3, Further store an overvoltage reference value in the ROM; The central processing unit, When the measured voltage value of the AC driving power is out of a preset voltage reference range value, it is determined whether the voltage value exceeds the overvoltage reference value, and when the voltage value exceeds the overvoltage reference value, the first and second pulses. A digitally controlled inverter for an external electrode fluorescent lamp, characterized in that it stops generating a width modulated signal. The method of claim 4, wherein Further store an overcurrent reference value in the ROM; The central processing unit, When the measured current value of the AC drive power is out of a preset current reference range value, it is determined whether the current value exceeds the overcurrent reference value, and when the current value exceeds the overcurrent reference value, the first and second pulse widths are determined. Digital control inverter for external electrode fluorescent lamp, characterized in that the generation of the modulated signal. The method of claim 5, The central processing unit, Digital control inverter for external electrode fluorescent lamp, characterized in that the dimming control signal applied from the display panel side is input through the multiplexer, and the dimming control is controlled by turning on / off the pulse width modulation signal at a period corresponding to the dimming control signal. . The method of claim 6, Further stores an input voltage reference range value in the ROM; The central processing unit, The analog / digital converter and the multiplexer further receive the input voltage value, and when the input voltage value is out of the input voltage reference range value, the first and second pulse width modulation signals are turned off or the duty is reduced. Digital control inverter for external electrode fluorescent lamps. The method of claim 3, Further storing a phase reference range value in the ROM; The CPU further receives phases of the first and second pulse width modulation signals output from the pulse width modulation generators through the analog / digital converter and the multiplexer, and the input phase values are stored in advance. And controlling the duty of the first and second pulse width modulation signals when the phase reference range value is above or below a reference value. . The method of claim 3, And an input / output port for connecting to an external host computer; And the microprocessor unit performs data communication with the external host computer through the input / output port to update the control program. Initializing process of generating pulse width modulated signal and driving analog / digital converter when power is applied, An input / output signal measuring process of measuring and storing a dimming adjustment value, an input voltage value, a voltage value and a current value of an AC driving power source, and a phase value of the pulse width modulation signal measured after initialization; A dimming control process of turning on / off the pulse width modulation signal at a predetermined cycle according to the dimming control value; The measured input voltage, voltage and current and phase values of the AC driving power supply are compared with respective input voltage reference range values, voltage and current reference range values and phase reference range values of the AC driving power supply, respectively, and measured. Control of the digital converter for an external electrode fluorescent lamp comprising a pulse width modulation signal duty adjustment process for determining whether the values are out of the reference range value, and if the value exceeds or less than the reference range value, the duty of the pulse width modulated signal is adjusted. Way. The method of claim 10, When the voltage value of the AC driving power exceeds the preset reference range value after the duty adjustment process, if the voltage value of the AC driving power is larger than the previously stored reference overvoltage value, the generation of the pulse width modulation signal is performed. A control method of a digital converter for an external electrode fluorescent lamp, characterized in that it further comprises a step of preventing overvoltage. The method of claim 11, After the duty adjustment process or the overvoltage prevention process, when the current value of the AC drive power exceeds a preset reference range value, the pulse width is greater when the current value of the AC drive power is larger than the previously stored reference overcurrent value. A control method of a digital converter for an external electrode fluorescent lamp, characterized in that it further comprises an overcurrent prevention process for turning off the generation of the modulated signal.

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