WO2005008320A1

WO2005008320A1 - Inverter for eefl and backligth

Info

Publication number: WO2005008320A1
Application number: PCT/KR2004/000480
Authority: WO
Inventors: Seongju Lee
Original assignee: Seongju Lee
Priority date: 2003-06-04
Filing date: 2004-03-08
Publication date: 2005-01-27

Abstract

This patent is about backlight inverter which supplies AC power to EEFL or similar structural lamps. EEFL is made that electrode into exposing outer and it replaces the defect of CCFL which is adhered to the past TFT-LCD panel or for large panel. EEFL has structural problems that cannot receive feedback. It can replace the various problems. This patent has origin in making the method of receiving feedback and in this case, it can secure variegated protective functions and stable operation. And among EEFL that use numbers to connect with parallel circuit, it senses presence disorder and generates abnormal signal. So, it solves the problems that can occur when we use the manufactured goods for a long time. This inverter settles EEFL”s technical problems completely. It can make possible to supply electric power simply and stably. This patent solve the problems and make more EEFL markets.

Description

<Invention Title> {INVERTER FOR EEFL AND BACKLIGHT}

This patent is about backlight inverter which supplies AC power for TFT-LCD panel.

The past TFT-LCD backlight inverter get divided into Buck-Royer circuit and exclusive

used-chip system in accordance with its method to use. Now generally use inverter for

CCFL(Cold Cathode Fluorescent Lamp). We choose and use a necessary system according to unit

cost or situations.

background Art>

Here we are going to explain backlight inverter for EEFL and similar structural Lamps.

EITL is made that electrode into exposiⁿg outer ii it replaces the ^•'/<?--■' r -nt of CCFL like

efficiency, life time and inverter cost. And EEFL is suitable large size panel.

Therefore, frequency in use and demand of EEFL is on an increasing trend to the panel

becoming larger.

But, when we use EEFL, there is a structural defect that can't receive feedback. So we could

not realize stable operating and protective function with the past inverter for CCFL.

This patent is about development of inverter which is stable and possible to protect by

complement this defect.

In addition, CCFL have two electrode, one is high voltage, the other is low voltage. Inverter senses voltage passing the lamp again and uses this with feedback signal.

But, EEFL inverter can't receive feedback because both electrodes are connected to high

voltage side of transformer.

It is impossible to add the protective function and it is difficult to stable operating of

backlight inverter. That's why EEFL cannot be common in spite of its efficiency, life time

and cost better than other lamps.

we usually use backlight inverter's input supply DC power to rectify with 12V-24V, but this

power is on an high voltage trend. The circuit becomes complex the more the higher voltage.

There are more difficult to produce goods by common components.

This inverter solves these technical problems. It can applicate easily independent of DC

power's size. So it's possible to prepare of higher voltage here after.

The purpose of this patent is to make stable EEFL product and to lead EEFL m rket.

description of Drawings>

Figurel is block diagram of EEFL inverter,

Figure2 is the block diagram of existing CCFL inverter,

Figure3,4,5 are the explanations to sense feedback in EEFL inverter,

Figureβ is the explanation to sense each lamp's operations,

Figure7 is the circuit to operate high voltage FET using low voltage PM signal <Disclosure>

To make stable EEFL backlight inverter we must make the structure to sense stable feedback signal .

This is the point of this patent.

This patent is about stable inverter using EEFL and similar structural lamps. Now explain with the figures.

In figurel, the inverter is consist of Input part(l), Control ρart(2), Operating part(3), Power part(4) and Output part(5). And external lamp(6) is connected.

Input part(l) is consist of input ^'connector and this is the path ef DC. ower and external control signals.

•Control part(2) is consist of Buck-Royer circuit or exclusive used-chip. This part make PWM signals and transfer to Operating part(3). Also, this part accept feedback signal and control other functions.

Operating part(3) is consist of power FET. This part accept DC power, PWM signal and transfer power to transformer.

Power part (4) is consist of high voltage transformers. This part make high voltage AC power and supply the power to lamps. Output part(5) is consist of output connectors. This is the path of high voltage AC power and

feedback signal .

In figure2, existing method, the EEFL(7) is connected to high voltage AC power from

transformerO) through the high voltage wire(lθ).

This method is not possible to receive stable feedback signal.

EEFL is possible parallel operating like in figure2.

The number of EEFL is changeable and figure2 is approximate.

This patent solve this problem with return wire etc. Below more explains.

The needs of EEFL are on an increasing trend to the panel size becoming larger.

To use EEFL, we must develop the stable and capable- inverter .

If inverter have- defect or problems, we don't use EEFL.

This problems is caused by feedback signal and lack of design flexibility. EEFL is difficult

to sense stable feedback signal. This patent solve the problems and make more EEFL markets. <Mode for Invent ion>

In figure3, we use the return wire(ll) to sense feedback signal. Secondary part of

transformerO) is connected EEFL directly. And return wire(ll) is connected high voltage

wire(lθ). Inverter board(8) is accept the signal through return wire and divide this signal

using devide resistor(12) and rectify using capacitor to get feedback signal level. This

feedback signal transfer to control par (2).

From this stable feedback signal, inverter can have protective functions and stable

operation.

Second method, in figure4, we devide and rectify secondary high voltage of transformer and

use feedback signal .

This method do not have return wires so do not detect lamp out situation, but it is possible

to operate stably.

Third method, in figureδ, we use return wire and use these signal like feedback. It is

similar to first method, this method is using antenna effect.

Return wire(ll) will be fixed to high voltage wire(lθ) using tape, glue or holding pin.

Turn ratio is changeable according to the EEFL's shape, size and voltage.

We use this signal to feedback, so we can make protective function in inverter.

From now on, We explain inverter that can sense each lamp's difference and malfunction.

This patent use light sensor, CDS, photo Transistor etc(15), to sense malfunction signals.

From this signals inverter knows each lamp's conditions and control. In figureβ, the lamp holder(lβ) grasp the EEFL. Lamp holder is fixed to backlight panel (13).

Light sensor(15) is located to near EEFL to isolate from other lamp's lights.

The signal from light sensor is transfered to inverter board through the signal line(17).

Inverter calculate this signal with comparator or gate. And inverter can sense that lamp is

operating or not, and malfunction. So we can sense and prepare malfunction lamp and other

problems in long time operating.

Now we usually use DC voltage to 12V-24V range. This DC input voltage tend to high.

Here we explain inverter using the high voltage input power. Higher the input DC power, more

complicate and difficult to add another functions to the inverter circuits. Now we explain

the inverter that solved problems.

Figure7 shows the main driving circuit.

The- 5V level PWM(Pulse Width Modulation) -signal cannot operate high voiiage FET. This method

can operate high voltage FET by 5V level signal components. This method have design

flexibility like frequency adjusting, less component and timing control etc.

And easy apply to higher DC input voltage.

In figure7, high voltage DC power(~310V) is used the input power of inverter. To use common

IC, FET, and common parts it is necessary outer 10-20 volt level DC power or zener diode or

linear transformer.

Figure7 shows the circuit to operate high voltage FETs using 5V level PWM signals. High

voltage DC input power contributes the inverter's efficiency and functions.

Claims

1. As an inverter that supplies an high voltage alternating current to the lamps, especially

for EEFL and similar structural lamps with EEFL. As an inverter or backlight unit, use return

wire connected one or both side of transformer and use divide resistor or capacitor in order

to receive stable feedback signal.

2. As an inverter that supplies an high voltage alternating current to the lamps, especially

for EEFL and similar structural lamps with EEFL. As an inverter or backlight unit, use divide

resistor and rectify parts, connected with secondary of transformers in order to receive

stable feedback signal.

3. As an inverter that supplies an high voltage alternating current to the lamps, especially

for EEFL and similar structural lamps with EEFL. As an inverter or backlight unit, use

winding return wire connected with high voltage wire using antenna effect, and use this

signal by mean of feedback signal.

4. In backlight unit to have structure like directly under^' structure, As an inverter or

backlight unit, use sensor to sense light like photo Transistor, CDS etc, in order to sense

feedback signal from lamps like EEFL and similar structural lamps.

5. As an inverter that supplies an high voltage alternating current to the lamps, use low

level common IC and driving circuit in order to operate high voltage FET and to secure design

flexibilities.