KR20080055085A - Initial frequency control circuit for inverter - Google Patents

Initial frequency control circuit for inverter Download PDF

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Publication number
KR20080055085A
KR20080055085A KR1020060127962A KR20060127962A KR20080055085A KR 20080055085 A KR20080055085 A KR 20080055085A KR 1020060127962 A KR1020060127962 A KR 1020060127962A KR 20060127962 A KR20060127962 A KR 20060127962A KR 20080055085 A KR20080055085 A KR 20080055085A
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South Korea
Prior art keywords
inverter
resistor
capacitor
fet
controller
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KR1020060127962A
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Korean (ko)
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염주홍
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엘지이노텍 주식회사
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Publication of KR20080055085A publication Critical patent/KR20080055085A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133604—Direct backlight with lamps
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/02—Details
    • H05B41/04—Starting switches
    • H05B41/042—Starting switches using semiconductor devices
    • H05B41/044—Starting switches using semiconductor devices for lamp provided with pre-heating electrodes
    • H05B41/046—Starting switches using semiconductor devices for lamp provided with pre-heating electrodes using controlled semiconductor devices
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/295—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps with preheating electrodes, e.g. for fluorescent lamps
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling

Abstract

An initial frequency control circuit for an inverter is provided to prevent dimming of an LCD(Liquid Crystal Display) screen by increasing output voltage and reducing an operating frequency in an initial driving of the inverter. An initial frequency control circuit for an inverter includes a controller(200), a first resistor(R1), a second resistor(R2), a capacitor(C1), an FET(Field Effect Transistor)(Q2), and a transistor(Q1). The controller controls output voltage of the inverter. The first resistor is connected to an RT terminal for controlling a time constant of a driving frequency outputted from the controller. The second resistor is connected to the first resistor in parallel. The capacitor charges and discharges constant voltage(Vcc) inputted in an initial driving of the inverter. The FET has a gate connected to the capacitor to be turned on during a discharge time of the capacitor. The transistor switches connection of the second resistor to the RT terminal of the controller.

Description

인버터의 초기주파수 가변회로 {Initial frequency control circuit for inverter}Initial frequency control circuit for inverter

도 1은 종래의 LCD의 인버터 회로도.1 is an inverter circuit diagram of a conventional LCD.

도 2는 본 발명의 일 실시예에 따른 인버터의 초기주파수 가변회로도.2 is an initial frequency variable circuit diagram of an inverter according to an embodiment of the present invention.

＜도면의 주요부분에 사용된 부호의 설명＞<Description of the code used in the main part of the drawing>

200: 컨트롤러 Vcc: 정전압200: controller Vcc: constant voltage

C1: 커패시터 Q2: FETC1: Capacitor Q2: FET

Q1: 트랜지스터 R1, R2: 저항Q1: transistors R1, R2: resistors

본 발명은 LCD에 사용되는 인버터의 초기 동작에 관련한 인버터의 초기주파수 가변회로에 관한 것이다.The present invention relates to an initial frequency variable circuit of an inverter related to the initial operation of an inverter used in an LCD.

일반적으로, LCD(Liquid Crystal Display divice: 액정표시소자)는 CRT(Cathod Ray Tube: 음극선관)과는 달리 자기발광성이 없어서 백라이트(Back-light)라 불리는 후광이 필요하지만, 동작전압이 낮아 소비전력이 적고, 휴대용으로 쓰일 수 있는 등의 장점이 커 널리 쓰이는 평판 디스플레이 중의 하나이다.In general, liquid crystal display devices (LCDs), unlike CRTs (Cathod Ray Tubes), have no self-luminous property and require a backlight, which is called a backlight, but consumes low power. It is one of the widely used flat panel displays because of its advantages such as being small and portable.

LCD의 백라이트장치에 전원을 공급하기 위해서는 LCD의 전원공급장치(Power Supply)에서 공급되는 DC 전원을 AC 전원으로 변환하여 트랜스포머에 의해 고전압으로 승압하는 일련의 구성이 필요하다.In order to supply power to the LCD backlight device, a series of configurations are required in which the DC power supplied from the LCD's power supply is converted to AC power and boosted by a transformer to a high voltage.

이때, 백라이트장치의 램프는 고유한 정전용량값을 가지고 있으며, 다수의 램프를 사용하는 백라이트장치의 경우 각각의 램프가 갖는 고유한 정전용량값의 편차로 인하여 화면의 밝기가 불안정해지는 원인이 발생한다.At this time, the lamp of the backlight device has a unique capacitance value, and in the case of a backlight device using a plurality of lamps, the brightness of the screen is unstable due to the deviation of the unique capacitance value of each lamp. .

종래에는 이러한 화면의 불안정한 현상을 방지하기 위하여 램프의 전단에 높은 정전용량을 갖는 커패시터 혹은 코일을 설치하여 각각의 램프에 공급되는 전류의 밸런스를 유지하도록 하였다.Conventionally, in order to prevent such an unstable phenomenon of the screen, a capacitor or a coil having a high capacitance is installed at the front of the lamp to maintain the balance of the current supplied to each lamp.

즉, 도 1은 종래의 LCD의 인버터 회로도로서, 도 1에 도시된 바와 같이, 4 in 1 인버터(4개의 출력단과 하나의 입력단 형태의 구성을 갖는 인버터)의 트랜스포머(T) 2차측과 다수의 램프(100) 사이에 다수의 램프(100) 각각의 정전용량값을 무시할 수 있는 정도의 높은 정전용량값을 갖는 커패시터(C1~C4) 혹은, 도시되지는 않았지만 코일을 설치함으로써, 각각의 램프(100)에 공급되는 전류를 충분한 크기로 유지시켜 화면의 불안정한 현상을 방지하도록 하였다.1 is an inverter circuit diagram of a conventional LCD, and as shown in FIG. 1, a transformer T secondary side and a plurality of 4 in 1 inverters (inverters having four output stages and one input stage configuration) are illustrated. Capacitors C1 to C4 having a high capacitance value that can neglect the capacitance value of each of the plurality of lamps 100 between the lamps 100 or coils (not shown) are provided, thereby providing the respective lamps ( The current supplied to 100) is kept at a sufficient size to prevent the unstable phenomenon of the screen.

그러나, 종래의 인버터회로는 램프에 공급되는 전류의 밸런스를 위해 고용량의 커패시터 혹은 코일을 설치하도록 구성되어, 각각의 커패시터 혹은 코일이 갖는 고유한 특성값으로 인해 램프에 공급되는 전류의 밸런스가 정확하게 유지되지 못하는 경우가 발생한다. 따라서, 초기 구동시에 화면이 부분적으로 어두워지는 문제점이 있다.However, the conventional inverter circuit is configured to install a high-capacitance capacitor or coil to balance the current supplied to the lamp, so that the balance of the current supplied to the lamp is accurately maintained due to the unique characteristic value of each capacitor or coil. It can't happen. Therefore, there is a problem that the screen is partially darkened at the time of initial driving.

본 발명은 인버터의 초기 구동시에도 LCD화면이 어두워지는 현상을 방지할 수 있는 인버터의 초기주파수 가변회로를 제공함에 있다.The present invention provides an initial frequency variable circuit of an inverter capable of preventing the LCD screen from darkening even when the inverter is initially driven.

본 발명은 인버터의 출력전압을 제어하는 컨트롤러와; 상기 컨트롤러에서 출력되는 구동주파수의 시정수를 제어하는 RT단자에 연결된 제1 저항과; 상기 제1 저항에 병렬 연결된 제2 저항과; 초기 구동시에 입력되는 정전압을 충/방전하는 커패시터와; 상기 커패시터에 게이트가 연결되어 상기 커패시터의 방전시간동안 턴-온되는 FET; 및 상기 FET에 의해 스위칭상태가 제어되어, 상기 제2 저항이 상기 컨트롤러의 RT단자에 연결되는 것을 스위칭하는 트랜지스터를 포함한다.The present invention includes a controller for controlling the output voltage of the inverter; A first resistor connected to an RT terminal for controlling a time constant of a driving frequency output from the controller; A second resistor connected in parallel with the first resistor; A capacitor for charging / discharging a constant voltage input during initial driving; A FET having a gate connected to the capacitor and turned on during a discharge time of the capacitor; And a transistor controlled by the FET to switch the second resistor connected to the RT terminal of the controller.

여기서, 상기 FET는 상기 커패시터에 게이트가 연결되고; 정전압원과 상기 트랜지스터의 베이스에 소스가 공통 연결되며; 드레인은 접지된 것이 바람직하다.Wherein the FET is gated to the capacitor; A source is commonly connected to a constant voltage source and a base of the transistor; The drain is preferably grounded.

또한, 상기 트랜지스터는 베이스가 정전압원과 상기 FET의 소스에 공통 연결 되고; 컬렉터가 상기 제2 저항에 연결되며; 이미터가 접지된 것이 바람직하다.The transistor also has a base connected in common to a constant voltage source and a source of the FET; A collector is connected to the second resistor; It is preferable that the emitter is grounded.

이하, 본 발명의 바람직한 실시예에 대하여 첨부도면을 참조하여 상세히 설명한다. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

도 2는 본 발명의 일 실시예에 따른 인버터의 초기주파수 가변회로도이다.2 is an initial frequency variable circuit diagram of an inverter according to an embodiment of the present invention.

도 2를 참조하면, 인버터의 동작주파수를 결정하는 컨트롤러(200)의 RT단자와 CT단자 중 저항과 관련된 RT단자에 초기주파수를 가변하기 위한 회로를 추가한 구성을 갖는다.Referring to FIG. 2, a circuit for varying an initial frequency is added to an RT terminal related to a resistance of an RT terminal and a CT terminal of the controller 200 for determining an operating frequency of the inverter.

즉, 컨트롤러(200)의 RT단자에는 저항(R1)이 연결되어 있고, 상기 저항(R1)과 병렬 연결된 다른 하나의 저항(R2)으로 구성된다. 또한, 상기한 각각의 저항(R1, R2) 사이는 접지되어 있다. That is, the resistor R1 is connected to the RT terminal of the controller 200, and the other resistor R2 is connected in parallel with the resistor R1. The resistors R1 and R2 described above are grounded.

또한, 저항(R2)에는 트랜지스터(Q1)의 컬렉터가 연결되어 있고, 트랜지스터(Q1)의 이미터는 접지된다. 그리고, 트랜지스터(Q1)의 베이스는 정전압(Vcc)이 공급되도록 연결된다.In addition, the collector of transistor Q1 is connected to resistor R2, and the emitter of transistor Q1 is grounded. The base of the transistor Q1 is connected to supply a constant voltage Vcc.

한편, 상기한 트랜지스터(Q1)의 베이스와 정전압(Vcc) 사이에는 FET(Q2)의 소스가 연결되고, FET(Q2)의 드레인은 접지된다. 그리고, FET(Q2)의 게이트는 정전압(Vcc)이 공급되도록 연결되며, 상기 정전압(Vcc)과 FET(Q2)의 게이트 사이에는 커패시터(C1)가 연결된다.On the other hand, the source of the FET Q2 is connected between the base of the transistor Q1 and the constant voltage Vcc, and the drain of the FET Q2 is grounded. The gate of the FET Q2 is connected to supply the constant voltage Vcc, and the capacitor C1 is connected between the constant voltage Vcc and the gate of the FET Q2.

이와 같이 구성된 본 발명은, 초기에 인버터 구동신호가 인가되어 정전압 (Vcc)이 공급되면, 이 정전압(Vcc)은 상기한 커패시터(C1)에 공급되어 커패시터(C1)를 충전시킨다. 커패시터(C1)가 만충전되면 이때부터 방전을 시작하는데, 방전된 전압은 FET(Q2)의 게이트에 공급되어 FET(Q2)를 턴-온시킨다.In the present invention configured as described above, when the inverter drive signal is initially applied and the constant voltage Vcc is supplied, the constant voltage Vcc is supplied to the above-described capacitor C1 to charge the capacitor C1. When the capacitor C1 is fully charged, the discharge starts from this time. The discharged voltage is supplied to the gate of the FET Q2 to turn on the FET Q2.

FET(Q2)가 턴-온되면 트랜지스터(Q1)의 베이스 전압이 그라운드로 패스되므로, 트랜지스터(Q1)는 오프상태로 유지된다. 따라서, 컨트롤러(200)의 RT단자에는 저항(R1)만이 연결된 상태가 되므로 인버터의 초기 출력주파수가 떨어지게 되며, 이로 인해 높은 전압이 트랜스포머(도시되지 않았음)의 2차측으로 유기된다.When the FET Q2 is turned on, the base voltage of the transistor Q1 is passed to ground, so the transistor Q1 is kept in the off state. Therefore, since only the resistor R1 is connected to the RT terminal of the controller 200, the initial output frequency of the inverter is decreased, thereby causing a high voltage to be induced to the secondary side of the transformer (not shown).

이후, 커패시터(C1)가 모두 방전되면, FET(Q2)의 게이트는 로우상태가 되어 FET(Q2)가 턴-오프된다. 이에 따라 트랜지스터(Q1)의 베이스에는 정전압(Vcc)이 공급되므로 컨트롤러(200)의 RT단자에는 저항(R1)과 저항(R2)이 병렬 연결된 상태가 된다. 따라서, 인버터의 출력주파수가 정상상태(즉, 초기 출력주파수보다 높은 주파수의 상태)로 복원되어 정상 전압이 트랜스포머의 2차측으로 유기된다.Thereafter, when the capacitor C1 is completely discharged, the gate of the FET Q2 is turned low so that the FET Q2 is turned off. Accordingly, since the constant voltage Vcc is supplied to the base of the transistor Q1, the resistor R1 and the resistor R2 are connected in parallel to the RT terminal of the controller 200. Thus, the output frequency of the inverter is restored to its normal state (i.e., the state of the frequency higher than the initial output frequency) and the normal voltage is induced to the secondary side of the transformer.

따라서, 초기 동작시에만 컨트롤러(200)의 RT단자에 저항(R2)이 연결되지 않도록 플로팅(floating)시켜 동작주파수를 다운시키고 출력전압을 상승시키도록 함으로써, 초기 동작시에 화면의 어두운 현상을 방지하도록 한 것이다.Therefore, by floating so that the resistor R2 is not connected to the RT terminal of the controller 200 during the initial operation, the operating frequency is lowered and the output voltage is increased, thereby preventing the dark phenomenon of the screen during the initial operation. I did it.

이와 같이, 본 발명의 상세한 설명에서는 구체적인 실시 예(들)에 관해 설명하였으나, 본 발명의 범주에서 벗어나지 않는 한도 내에서 여러 가지 변형이 가능함은 물론이다. 그러므로 본 발명의 범위는 설명된 실시 예(들)에 국한되어 정해져서는 안 되며, 후술하는 특허청구범위 뿐만 아니라 이 특허청구범위와 균등한 것들 에 의해 정해져야 한다.As described above, in the detailed description of the present invention, specific embodiment (s) 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 embodiment (s), but should be defined by the claims below and equivalents thereof.

본 발명은 인버터의 초기 동작시에 출력전압이 상승하여 화면의 어두운 현상이 방지되는 효과가 있다.The present invention has the effect that the output voltage is increased during the initial operation of the inverter to prevent the dark phenomenon of the screen.

Claims (3)

인버터의 출력전압을 제어하는 컨트롤러;A controller for controlling the output voltage of the inverter; 상기 컨트롤러에서 출력되는 구동주파수의 시정수를 제어하는 RT단자에 연결된 제1 저항;A first resistor connected to an RT terminal for controlling a time constant of a driving frequency output from the controller; 상기 제1 저항에 병렬 연결된 제2 저항;A second resistor connected in parallel with the first resistor; 초기 구동시에 입력되는 정전압을 충/방전하는 커패시터;A capacitor for charging / discharging a constant voltage input during initial driving; 상기 커패시터에 게이트가 연결되어 상기 커패시터의 방전시간동안 턴-온되는 FET; 및A FET having a gate connected to the capacitor and turned on during a discharge time of the capacitor; And 상기 FET에 의해 스위칭상태가 제어되어, 상기 제2 저항이 상기 컨트롤러의 RT단자에 연결되는 것을 스위칭하는 트랜지스터를 포함하는 인버터의 초기주파수 가변회로.Switching state is controlled by the FET, the initial frequency variable circuit of the inverter including a transistor for switching the second resistor is connected to the RT terminal of the controller. 제 1 항에 있어서, 상기 FET는 상기 커패시터에 게이트가 연결되고;The method of claim 1, wherein the FET is gated to the capacitor; 정전압원과 상기 트랜지스터의 베이스에 소스가 공통 연결되며;A source is commonly connected to a constant voltage source and a base of the transistor; 드레인은 접지된 것을 특징으로 하는 인버터의 초기주파수 가변회로.The initial frequency variable circuit of the inverter, characterized in that the drain is grounded. 제 1 항에 있어서, 상기 트랜지스터는 베이스가 정전압원과 상기 FET의 소스 에 공통 연결되고;2. The transistor of claim 1, wherein the transistor has a base commonly coupled to a constant voltage source and a source of the FET; 컬렉터가 상기 제2 저항에 연결되며;A collector is connected to the second resistor; 이미터가 접지된 것을 특징으로 하는 인버터의 초기주파수 가변회로.Initial frequency variable circuit of the inverter, characterized in that the emitter is grounded.
KR1020060127962A 2006-12-14 2006-12-14 Initial frequency control circuit for inverter KR20080055085A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100877831B1 (en) * 2007-12-14 2009-01-08 엘지이노텍 주식회사 Frequency variable circuit in inverter
KR20130041685A (en) * 2011-10-17 2013-04-25 엘지이노텍 주식회사 Led driving circuit

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100877831B1 (en) * 2007-12-14 2009-01-08 엘지이노텍 주식회사 Frequency variable circuit in inverter
KR20130041685A (en) * 2011-10-17 2013-04-25 엘지이노텍 주식회사 Led driving circuit

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