KR20080099493A - Driving apparatus for cold cathode flat fluorescent lamp - Google Patents

Abstract

A drive unit for the cold cathode flat fluorescent lamp is provided to perform variable frequency control selectively by using the PFC IC and control dimming of the lamp. In a cold cathode flat fluorescent lamp, a filter unit removes surge from the AC input power and filters the noise. A rectifier rectifies the AC power supply inputted through the filter unit to the DC power. A power factor circuit(14) improves the power factor of the rectifying power outputted from the rectifier and boosts voltage the input voltage. An inverter unit(16) converts the DC voltage outputted from the power factor circuit into the high frequency AC with square wave. A frequency control unit controls the oscillation frequency of the switching element equipped in the inverter unit. A high voltage generation unit(22) boosts voltage with AC square wave outputted from the inverter unit to the sinusoidal AC voltage and generates the driving voltage of the cold cathode flat fluorescent lamp.

Description

Driving apparatus for cold cathode flat fluorescent lamps {Driving apparatus for Cold Cathode Flat Fluorescent Lamp}

1 is a block diagram schematically showing a drive device according to the present invention;

Figure 2 is a circuit diagram showing the configuration of the rectifier in the present invention

3 is a circuit diagram showing the configuration of the power factor circuit unit and the auxiliary power supply unit in the present invention;

Figure 4 is a circuit diagram showing the configuration of the inverter unit and the frequency control unit in the present invention

5 is a circuit diagram showing a configuration of a high voltage generator in the present invention;

6 is a circuit diagram showing a configuration of a protection circuit in the present invention;

7 is a waveform diagram of each part of the inverter unit and the high voltage generator according to the present invention.

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

10 filter unit 12 rectifying unit

14 power factor circuit section 16 inverter section

18: frequency control unit 20: CCFFL

22: high voltage generator 24: brightness control means

26: protection circuit 28: auxiliary power supply

The present invention relates to a drive device for a cold cathode planar fluorescent lamp, and more particularly, to a drive device for a cold cathode planar fluorescent lamp having a resonant inverter of a high voltage direct current input method for driving a planar cold cathode fluorescent lamp. will be.

In general, a conventional lighting device includes a filament electrode at both ends of the glass tube, a phosphor containing argon (Ar), neon (Ne), and a small amount of mercury (Hg) inside the glass tube, and emitting visible light on the inner wall of the glass tube. Hot Cathode Fluorescent Lamps (HCFLs) coated with the main components were mainly used. These hot cathode fluorescent lamps induce hot electron emission by applying a high tube current to the filament electrode, and the hot electrons emitted from the filament react with the encapsulating gas inside the glass tube to generate ultraviolet light, which acts to excite the phosphor to emit visible light. do.

However, in order to emit hot electrons from the filament electrode, a high tube current must be applied, which causes degradation of the phosphor or damage of the emission powder applied to the filament surface, which causes the lamp to be terminated early. Therefore, the development of a fluorescent lamp to replace this is required, the cold cathode fluorescent lamp (CCFL; Cold Cathode Fluorescent Lamp (CCFL) is a way to achieve a low tube current lighting, as a fluorescent lamp to compensate for the disadvantages of the hot cathode fluorescent lamp.

Meanwhile, as liquid crystal display (LCD) has become widespread in recent years, a backlight unit (BLU) has been developed to illuminate the LCD mounted on the back of the LCD to secure visibility of the LCD which cannot emit light by itself. ought. The backlight unit of the conventional LCD is configured to include a light guide plate to diffuse the linear light of the CCFL and CCFL as described above. However, due to the problem that the light efficiency is low and it is difficult to cope with the enlargement of the LCD, various types of planar fluorescent lamps have recently been developed at various angles.

For example, taking advantage of CCFL over HCFL, research and development of CCFFL (Cold Cathode Flat Flourescent Lamp), which planarizes CCFL, is underway. The CCFFL has a structure in which cathodes are arranged on a plane, and require a high-voltage direct current drive power supply (approximately 400 V DC) compared to the CCFL. That is, in order to accelerate the development of the planar lighting device to solve the advantages of the HCFL, a cold cathode planar fluorescent lamp suitable for driving CCFFL, that is, a high-efficiency, high power factor, long-life characteristics and generates a high-voltage direct-current driving power supply Development of the driving device for the lamp is urgently required.

The present invention provides a drive device for a cold cathode planar fluorescent lamp which can stably light a CCFFL replacing the conventional HCFL as described above, while supplying a square wave signal supplied to the switching element of the inverter unit from the frequency control IC It is an object of the present invention to provide a drive device for a cold cathode planar fluorescent lamp capable of selectively performing fixed frequency control and variable frequency control.

According to an aspect of the present invention, there is provided a cold cathode planar fluorescent lamp driving apparatus including: a filter unit for removing a surge from an AC input power source and filtering noise; A rectifier for rectifying the AC power input through the filter unit into a DC power source; A power factor circuit unit for improving a power factor of the rectified power output from the rectifier and boosting an input voltage; An inverter unit for oscillating the DC voltage output from the power factor circuit unit into a high frequency AC voltage having a square wave shape; A frequency control unit controlling an oscillation frequency of the switching element provided in the inverter unit; And a high voltage generator for boosting a square wave AC voltage output from the inverter unit to a sine wave AC voltage to generate a driving voltage of a cold cathode planar fluorescent lamp, wherein the inverter unit is alternately switched by a square wave signal generated by a frequency controller. And a pair of switching elements, wherein the frequency control unit outputs a square wave signal having a phase difference of 180 degrees to each of the switching element gate terminals, between an output terminal of the power factor circuit unit and an input terminal of the frequency control IC. It is characterized in that it comprises a resistor and a capacitor connected to generate a RC time constant for setting the oscillation frequency of the frequency control IC.

Preferably, the input of the frequency control IC is connected to the variable resistor in series for setting the oscillation frequency fixed by the selection of the switch, or the brightness control means is connected via an optical coupler, the frequency control IC is fixed frequency The inverter unit can be controlled by combining the method and the variable frequency method.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

First, the drive device for a cold cathode planar fluorescent lamp of the present invention (hereinafter referred to as 'CCFFL') is a drive device specialized for driving CCFFL. Unlike the conventional HCFL driving device or CCFL driving device, the driving device of the present invention to be described below receives AC power and boosts the CCFFL by boosting the voltage to a high-voltage DC power supply (approximately DC 400V). In the following description, a detailed description of parts similar to those of a conventional fluorescent lamp driving apparatus will be omitted, and the circuit configuration specialized in the present invention will be mainly described.

1 is a block diagram schematically showing a driving apparatus according to the present invention. Referring to this, the driving device for CCFFL of the present invention receives a commercial AC power supply (AC 220V, 60Hz), the filter unit 10 for filtering surge and noise, and the rectifying unit 12 for rectifying AC power to DC power and A power factor circuit unit 14 including a boost converter for improving the power factor of the rectified power source and boosting an input voltage, and an inverter unit for oscillating the DC voltage output from the power factor circuit unit 14 into a square wave type high frequency AC voltage ), The frequency control unit 18 for controlling the oscillation frequency of the switching element provided in the inverter unit 16, and the square wave AC voltage output from the inverter unit 16 to boost the sine wave AC voltage to drive the CCFFL 20. It consists of the high voltage generation part 22 which generates a voltage.

Preferably, the frequency control unit 18 controls the oscillation frequency of the inverter unit 16 according to the signal input from the external brightness control means 24 to enable the dimming control of the CCFFL 20, generating a high voltage In the secondary auxiliary winding L5-1 of the resonance inductor L5 provided in the unit 22, a protection circuit unit 26 for blocking driving power applied to the power factor circuit unit 14 and the frequency control unit 18 when the abnormal voltage is induced. ) Is connected. In addition, an auxiliary power source 28 for generating driving power of an integrated circuit provided in the power factor circuit unit 14 and the frequency controller 18 may be further provided at an input terminal of the power factor circuit unit 14.

The filter unit 10 filters surges and noises inputted through commercial AC power supplies 220V and 60Hz, and is generally configured as a known EMI filter. Meanwhile, in the present embodiment, a commercial AC power is illustrated as the input power of the driving device for the CCFFL. However, the present invention may be driven by various other input power methods, and the configuration of the filter unit 10 is changed according to the change of the input power method. It may also vary.

Figure 2 is a circuit diagram showing the configuration of the rectifier in the present invention. As shown, the rectifier 12 includes a rectifier circuit part 12a for rectifying the input AC power to a DC power source and a filter circuit part 12b for removing harmonic components from the DC voltage rectified in the rectifier circuit part 12a. do. The rectifier circuit part 12a is based on full-wave rectification by the bridge diode D1 consisting of four diodes. The bridge diode D1 is provided in an integrated form on a single chip to configure the circuit size as compactly as possible. . The power rectified by the bridge diode D1 includes harmonic noise that the filter unit 10 cannot remove. In order to remove such harmonic components, the filter circuit unit 12b has two capacitors C1 and C2 connected in parallel to the output terminal of the bridge diode D1 and a series of one end of each of the capacitors C1 and C2. It consists of an inductor L1 to be connected. The filter circuit part 12b forms an LC resonant circuit to remove harmonics and smooth the output of the rectifying circuit part 12a.

3 is a circuit diagram showing the configuration of the power factor circuit unit and the auxiliary power supply unit in the present invention. In the present invention, the power factor circuit unit 14 improves the power factor by suppressing reactive power, and at the same time, boosts the DC voltage output from the rectifying unit 12 to generate a high voltage DC voltage for lighting the CCFFL 20. . Referring to FIG. 3, the power factor circuit unit 14 includes power factor correction (PFC) IC U1, a switching element Q1 driven by an output signal of the PFC IC U1, and output terminals of the rectifier 12. It is configured to include an inductor (L2) is connected to the output of the rectifier 12 is selectively applied by the drive of the switching element (Q1). Preferably, the switching element Q1 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). As shown in the figure, the power factor circuit section 14 has an input power applied to both ends of the inductor L2 by switching of the MOSFET Q1, and thus boosts the output voltage by the charging / discharging action of the current. Boost Converter.

More specifically, the PFC IC U1 supplies starting power from a plurality of resistors R1, R2, and R3 connected in parallel to the output terminal of the rectifier 12 and a zener diode D3 connected in series to the resistors. Receive. It is driven by the constant voltage supplied from the auxiliary power supply 28 to be described later. The PFC IC U1 collects input voltage information, current information flowing through the inductor L2, output voltage information, and current information flowing through the MOSFET Q1. Each piece of information is provided to the input terminal side of the PFC IC U1 through the following circuit configuration. As shown, a voltage divider circuit formed by connecting a plurality of resistors R4, R5, R6, and R7 to both ends of the output terminal of the rectifier 12 is connected to pin 3 of the PFC IC U1. Input voltage information is collected from this voltage divider circuit. Pin 7 of the PFC IC U1 is connected to a first auxiliary winding L2-1 of the inductor L2 and a resistor R9 connected in series with the first auxiliary winding L2-1, and a PFC IC ( U1 collects current information flowing through the inductor L2 from the first auxiliary winding L2-1 of the inductor L2. Pin 1 of the PFC IC U1 is connected to a voltage divider circuit formed by connecting a plurality of resistors R11, R12, R13, and R14 across the output terminal of the power factor circuit section 14, and the PFC IC U1 is connected from the voltage divider circuit. Collect output voltage information. On pin 4 of the PFC IC U1, a plurality of resistors R15, R16, R17, R18, R19 are connected in parallel between the source terminal of the MOSFET Q1 and the ground side, and a resistor R8 connected in series with the connection point is provided. It is connected in series and collects the current information flowing through the MOSFET (Q1) from the resistor R8. The PFC IC U1 generates the gate driving signal of the MOSFET Q1 by calculating the collected information through the above circuit configuration. In other words, the PFC IC U1 controls the drive voltage of the MOSFET Q1 to improve the power factor of the input power, and to boost the input voltage by intermittent the power supplied to the inductor L2.

The auxiliary power supply 28 smoothes the voltage induced in the second auxiliary winding L2-2 of the inductor L2, thereby controlling the PFC IC U1 of the power factor circuit unit and the frequency control IC of the frequency control unit 18 described later. This circuit generates the driving power source (U2). The auxiliary power supply 28 includes a smoothing circuit part including an inductor L3 connected in series to the second auxiliary winding L2-2 of the inductor L2 and a capacitor C9 connected in parallel. The inductor L3 and the capacitor C9 smooth the auxiliary power applied to the second auxiliary winding L2-2 of the inductor L2. In addition, a linear voltage regulator combining a zener diode D5 and a transistor Q2 for generating a constant voltage is connected to a rear end of the capacitor C9 to supply stable power to each of the ICs U1 and U2. Do it.

4 is a circuit diagram showing the configuration of the inverter unit and the frequency control unit in the present invention. Referring to this, the inverter unit 16 has a half bridge structure, and the pair of switching elements Q11 and Q12 switched at 180 degrees out of phase by the switching frequency generated by the frequency control unit 18. It is configured to include. Preferably, the pair of switching elements Q11 and Q12 are MOSFETs. Capacitors C14 and C15 are connected in parallel to each of the MOSFETs Q11 and Q12 for DC voltage divider. In addition, inside of each of the MOSFETs Q11 and Q12, a reverse diode is installed for zero voltage switching. The reverse diode (Body Diode) is turned on by the current flowing through the resonant inductor (L5) of the high voltage generator 22 to be described later serves to eliminate the switching loss that can occur when each MOSFET (Q11, Q12) is turned on. . The MOSFET has a property that is very vulnerable to high current, and when an abnormality occurs in any one of the MOSFETs Q11 and Q12 of the inverter unit 16, the drive device of the present invention may cause a fatal failure. Therefore, in the present invention, in order to protect the respective MOSFETs Q11 and Q12 from an abnormal current, protection resistors R27 and R28 are provided between the gate terminal and the source terminal of each of the MOSFETs Q11 and Q12 as shown. .

The frequency control unit 18 includes a frequency control IC U2 for generating a switching frequency for alternately switching the MOSFETs Q11 and Q12 of the inverter unit 16. A resistor R21, R22 and a capacitor C13 are connected to an input terminal of the frequency control IC U2 between the output terminal of the power factor circuit section 14, and the frequency control IC U2 has these resistors R12, R22. The oscillation frequency is generated by the constant time constant of the capacitor C13. The frequency control IC U2 generates two square wave signals having a phase difference of 180 degrees from the oscillation frequency and having a pulse ratio of 50%. These two square wave signals are fed to MOSFET Q1 and MOSFET Q2, respectively.

The frequency control unit 18 of the present invention enables the fixed frequency control and the variable frequency control to be selectively implemented using the frequency control IC U2, unlike the conventional oscillation inductor. First, a fixed oscillation frequency may be set by adjusting the variable resistor R21 connected to the input terminal of the frequency control IC U2. In addition, the brightness control means 24 may be further connected to the input terminal of the frequency control IC U2 via a photocoupler PC. As an example, the brightness adjusting means 24 may be an external manually operable volume switch. As another example, the brightness adjusting means 24 may be a photosensor for detecting the ambient illumination. An input terminal of the frequency control IC U2 is provided with a switch SW1 for selectively switching the connection of the optical coupler PC. Therefore, by operating the switch SW1, the frequency control unit 18 selects the fixed frequency control by the RC time constant and the variable frequency control by the brightness adjusting means 24, so that the MOSFETs Q11 and Q12 of the inverter unit 16 are selected. ) Can control the switching frequency. On the other hand, as the external brightness control means 24 is connected to the frequency control IC (U2) via the optical coupler (PC) electrically isolated from the external signal, it is possible to remove noise that may be generated from the external signal. .

5 is a circuit diagram illustrating a configuration of a high voltage generator in the present invention. Referring to this, the high voltage generator 22 supplies the high frequency AC voltage generated by the inverter unit 16 to the CCFFL 20. The high voltage generator 22 of the present invention uses a single high voltage transformer in a conventional CCFL driving apparatus, and converts a square wave voltage into a sinusoidal voltage using a leakage inductance inside the transformer. The transformer loss is reduced by using TR1, and a maximum power transfer point for driving the CCFFL 20 is set by employing a resonance inductor.

As shown in FIG. 5, the high voltage generator 22 includes a resonant inductor L5 and a booster circuit part 22a that boosts the sinusoidal voltage converted by the resonant inductor L5 to a high voltage. The booster circuit unit 22a includes one high voltage transformer TR1 and two capacitors C21 and C22. The primary winding of the high voltage transformer TR1 is connected in series with the resonant inductor L5 and the high voltage transformer TR1. The secondary winding of) forms a parallel resonant circuit with two capacitors C21 and C22 and is connected to CCFFL 20.

The resonant inductor L5 of the high voltage generator 22 includes a first auxiliary winding L5-1 for detecting an abnormal state signal of the driving apparatus of the present invention, and a first auxiliary winding L5 of the resonance inductor L5. -1) may further be connected to the protection circuit (26).

6 is a circuit diagram showing the configuration of the protection circuit in the present invention. Referring to this, the protection circuit unit 26 detects a current flowing from the resonant inductor auxiliary winding L5-1 of the high voltage generator 22 to the resonant duct L5, and when the detected current rises above the set value, the power factor circuit unit (14) and the frequency control unit 18 serves to block the operation. Therefore, when an abnormal current occurs due to the opening or burning of the CCFFL 20, secondary accidents such as a failure and a fire of the driving apparatus of the present invention are prevented.

Referring to FIG. 6, the protection circuit unit 26 determines an abnormality by comparing the abnormal signal detection unit 26a for detecting an abnormal signal induced by the resonance inductor auxiliary winding L5-1 with the detected abnormal signal with a set value. The comparator 26b and the processor 26c which cut off the power supplied to the power factor circuit 14 and the frequency controller 18 when it is determined that the comparator 26b is an abnormal signal.

The comparison unit 26b includes a zener diode D31 reversely biased to one side of the resonant inductor auxiliary winding L5-1. The abnormal signal detection unit 26a is installed in front of the zener diode D31, and converts a signal of an AC component induced in the resonant inductor auxiliary winding L5-1 into a signal of a DC component and a capacitor ( C34) and a voltage divider circuit of resistors R33 and R34 for making an operation reference potential of the zener diode D31. The processor 26c bypasses the driving power supplied to the PFC IC U1 of the power factor circuit unit 14 and the frequency control IC U2 of the frequency controller 18 when the zener diode D31 is surrendered to the ground side. To switch. Preferably, the processing section 26c is composed of two-stage transistors Q31 and Q32 and a combination of resistors R31 and R32 and capacitors C31 and C32. The processing unit 26c greatly reduces the holding current loss compared to the SCR mainly used in the conventional protection circuit.

7 is an operation waveform diagram of each part of the inverter unit and the high voltage generation unit according to the present invention. Each waveform shown in FIG. 7 is sequentially formed by the gate driving waveforms Vgs1 and Vgs2 applied between the gate terminals and the source terminals of the respective MOSFETs Q11 and Q12 of the inverter unit 16, and the MOSFETs Q11 and Q12 of the inverter unit 16. The voltages Vds1 and Vds2 between the drain and source terminals of the MOSFETs Q11 and Q12 according to the gate driving signal are output voltage waveforms Vuv of the inverter unit 16, and the waveforms shown by dotted lines on the output voltage waveforms of the inverter unit 16 are high voltages. It is a current waveform iL flowing through the resonant inductor L5 of the generator 22.

For convenience of explanation, the time points of each operation waveform are divided into t0 to t6, and the operation mode between each time point is divided into modes 1 to mode 6 and described.

In the operating waveform diagram of FIG. 9, MOSFET Q11 is turned on at time t0 of mode1, and resonant inductor L5 current iL flows through MOSFET Q12 in the negative direction during mode1 interval. When the MOSFET Q12 is turned off at the time t1 of the mode2, the capacitor of the MOSFET Q12 is charged by the resonant inductor L5 current iL, and the voltage Vds2 between the drain terminal and the source terminal of the MOSFET Q12 increases by Vs / 2 during the Tc period. In addition, the reverse diode (Body Diode) installed inside the MOSFET Q11 that is already turned off is turned on by the resonant inductor (L5) current iL, and the voltage Vds1 between the drain terminal and the source terminal of the MOSFET Q11 is the reference voltage at Vs / 2. (0V) decreases during the Tc period.

As described above, since the voltage Vds1 between the drain terminal and the source terminal of the MOSFET Q11 can be made 0V by the resonant inductor L5 current iL, that is, the resonant inductor L5 is provided inside the MOSFET Q11 by the current iL. Switching losses that occur when the MOSFET is turned on by applying a gate drive signal between the gate terminal and the source terminal of the MOSFET Q11 during the period from mode2 to mode3 where the body diode is turned on to turn on the MOSFET Q11. Suppresses zero voltage switching. MOSFET Q12 proceeds in the same manner as above during mode4 to mode6.

In addition, in order to prevent the respective MOSFETs Q11 and Q12 from being turned on at the same time, a constant delay time Td is ensured. However, more delay than necessary will be a loss in the inverter circuit, allowing the internal capacitors of the MOSFETs Q11 and Q12 to be set to a minimum time, taking into account the time Tc required for charging.

The driving device for the cold cathode planar fluorescent lamp of the present invention as described above is a driving device specialized for stable lighting of the CCFFL 20, and each component of the present invention has the following characteristics.

The power factor circuit unit 14 of the present invention has a boost converter structure for improving a power factor of an input power source and generating a high voltage DC voltage for turning on the CCFFL 20. The power factor circuit unit 14 switches and drives the switching element Q1 using the PFC IC U1 which is an active integrated circuit, and interrupts the power applied to the inductor L2 by the switching element Q1, thereby improving the power factor. At the same time, the output of the rectifier 12 is boosted to a high-voltage DC voltage. Therefore, it is possible to provide a driving device for CCFFL having a high power factor.

The inverter section 16 of the present invention has a half-bridge structure and achieves zero voltage switching by using MOSFETs Q11 and Q12 incorporating a reverse diode. Thus, switching losses that can be generated by switching high voltage input power are minimized. In addition, damage to the MOSFETs Q11 and Q12 may occur when switching the high-voltage input power, so that the protection between the gate terminal and the source terminal of each of the MOSFETs Q11 and Q12 is performed to protect the MOSFETs Q11 and Q12. Install a resistor.

The frequency control unit 18 of the present invention supplies a square wave signal having a phase difference of 180 degrees to the gate terminals of the MOSFETs Q11 and Q12 of the inverter unit 16. Unlike providing a switching signal, by using the frequency control IC (U2) to control the switching frequency of the MOSFET (Q11, Q12), to control the fixed frequency system by RC time constant and to the external brightness control means 24 It is possible to selectively perform the control of the variable frequency method. At this time, the external brightness control means 24 is connected to the input terminal of the frequency control IC (U2) via the optical coupler (PC), thereby controlling the dimming control of the CCFFL 20 in the state of suppressing the noise by the external signal It can be realized.

The high voltage generator 22 of the present invention converts a square wave voltage into a sine wave voltage using a resonant inductor L5, and uses a single high voltage transformer TR1 to turn on the CCFFL 20. Therefore, the transformer loss is greatly reduced, and the inverter efficiency is greatly improved as compared with the conventional method using two high voltage transformers.

The protection circuit unit 26 of the present invention detects the abnormal current flowing through the resonant inductor L5 by the auxiliary winding L5-1 of the resonant inductor L5 rather than the method of detecting the output of the CCFFL 20. I use it. Accordingly, the initial lamp lighting failure and the load side abnormal current are detected without interfering with the driving of the CCFFL 20, and the MOSFETs of the power factor circuit section 14 as well as the MOSFETs Q11 and Q12 of the inverter section 16 are detected. It works to protect the entire circuit component, including Q1). Preferably, the protection circuit unit 26 bypasses the drive power supplied to the PFC IC U1 of the power factor circuit unit 14 and the frequency control IC U2 of the frequency control unit 18 to the ground side when detecting the abnormal current. It is configured to more securely protect the entire drive system.

Furthermore, the drive device for the CCFFL of the present invention enables a compact and lightweight design of a product by using a plurality of active integrated circuits, which has the advantage of allowing the drive device to be integrally designed in the CCFFL.

The present invention described above is a CCFFL dedicated driving device for driving the CCFFL, it will be apparent that the CCFFL driven by the present invention can be used in various lighting device fields such as a backlight unit or an independent lighting device of the LCD. In addition, the driving apparatus for the CCFFL of the present invention is not limited to the above-described embodiment and the accompanying drawings, and various substitutions, modifications, and changes are possible depending on the use of the CCFFL without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art to which the present invention pertains.

As described above, the cold cathode planar fluorescent lamp driving apparatus according to the present invention allows the frequency controller to selectively perform fixed frequency control and variable frequency control by using a PFC IC, and adjusts the external brightness through an optical coupler. By connecting the means, it is possible to effect dimming control of the lamp in an electrically insulated state from an external signal.

In addition, according to the present invention, by using a plurality of active integrated circuit, it is possible to design a compact, lightweight design of the product, and has the effect of being able to design the drive unit integrally to the CCFFL.

Claims (4)

A filter unit for removing surges from the AC input power and filtering noise; A rectifier for rectifying the AC power input through the filter unit into a DC power source; A power factor circuit unit for improving a power factor of the rectified power output from the rectifier and boosting an input voltage; An inverter unit for oscillating the DC voltage output from the power factor circuit unit into a high frequency AC voltage having a square wave shape; A frequency control unit controlling an oscillation frequency of the switching element provided in the inverter unit; And And a high voltage generator for generating a driving voltage of a cold cathode planar fluorescent lamp by boosting a square wave AC voltage output from the inverter unit to a sine wave AC voltage. The inverter unit includes a pair of switching elements that are alternately switched by square wave signals generated by a frequency control unit, and the frequency control unit outputs a square wave signal having a phase difference of 180 degrees to each of the switching element gate terminals. And a resistor and a capacitor connected between an IC and an output terminal of the power factor circuit unit and an input terminal of the frequency control IC to generate an RC time constant for setting the oscillation frequency of the frequency control IC. Drive for lamps. The method of claim 1, And a variable resistor is connected in series to the input terminal of the frequency control IC for setting a fixed oscillation frequency. The method of claim 1, Driving device for a cold cathode planar fluorescent lamp, characterized in that the brightness control means is further connected to the input terminal of the frequency control IC via an optical coupler. The method of claim 3, wherein A drive device for a cold cathode planar fluorescent lamp, characterized in that a switch for selectively switching the connection of the optical coupler is connected to the input terminal of the frequency control IC.

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