GB2434044A

GB2434044A - Backlight module control circuit of multi-lamp display device

Info

Publication number: GB2434044A
Application number: GB0600119A
Authority: GB
Inventors: Chih-Liang Lee; Chung-Ming Leng; Hsien-Min Yeh Liang; Sy-Shang Chen
Original assignee: Chuntex Electronic Co Ltd
Current assignee: Chuntex Electronic Co Ltd
Priority date: 2006-01-05
Filing date: 2006-01-05
Publication date: 2007-07-11
Also published as: GB0600119D0

Abstract

A backlight module control circuit comprises a control circuit 10, lamp driving circuits 20 and a fault detection unit 40. When fault detection unit 40 detects that one of lamps 30 is out of order it outputs a control signal that causes the driving circuit 20 of the failure lamp to be shut down, and continue to maintain an operation of the other, normal, lamps. After shutting down the failure lamp, control unit 10 may enhance the operation current flowing through the normal lamps. Lamps 30 may be connected to ground through a resistor 32 and control unit 10 may be a microprocessor. Each of the lamp driving circuits 20 may comprise a PWM controller. Outputs of fault detection unit 40 may be connected to lamp driving circuits (20a, figure 2) to shut down a failure lamp where the controller is a PWM controller (50, figure 2). The lamps may be used to back light a flat panel display device such as a liquid crystal display (LCD).

Description

1 2434044 BACI(LIGHT MODULE CONTROL CIRCUIT OF MULTI-LAMP

DISPLAY DEVICE

1. Fie]d of the Invention The invention relates in general to a backlight module contro] circuit, and moi-e particularly to a backlight modu]c control circuit for a multi-lamp display device.

2. Description of the Related Art

A flat display panel such as a plasma display panel or a liquid crystal display (LCD) becomes more and more popular nowadays. Although with the advances of processing technique, the size of the flat display panel is enlarged to satisfy the consumers. In terms of operation principle, a basic operation principle of the plasma display panel makes use of voltage to control gas molecules, so as to activate fluorescent material to produce chemical reaction to present various colors. Moreover, the light source of the LCD is provided by a backlight module configured inside the display. The backlight module includes a light emitting device, which is commonly made up by lamps. The number of the lamps varies in accordance with the size of the display device.

For wide screen display device, the number of the lamps can be up to eight, twelve or more lamps. A conventional method uses a control circuit to control onloff operations and brightness of the lamps. However, a main drawback of the conventional control circuit is that when any one of the lamp is out of order, all of the other lamps are closed, so as to stop the display device.

In view of the drawback of the conventional control circuit, the present invention provides a hacklight module control circuit of a multi-lamp display device including a control unit, a plurality of lamp driving circuits and a fault detection unit. The control unit includes a plurality of signal output terminals.

The control unit can be made up by a microprocessor or a control circuit having a plurality of active or passive electronic components. An input terminal of each of the lamp driving circuits is coup]ed to a signal output terminal of the control unit and an output terminal of each of the lamp driving circuits is coupled to a terminal of a lamp. A fault detection unit includes a plurality of signal detection input terminals. The signal detection input terminals are respectively coupled to the lamp driving circuits and a plurality of lamps. The fault detection unit further includes a control signal output terminal coupled to the control unit.

The fault detection unit can detect whether any one of the lamps is out of order and then output a signal to the control unit, so as to make the control unit shut down the driving circuit of the failure lamp and continue to maintain an operation of other normal lamps. In this way, high voltage of the driving circuits can avoid damaging the display device by shutting down the high voltage of the driving circuit of the failure lamp. Moreover, the whole brightness of the display device still can keep normal without decreasing the display quality of the images by the control unit to enhance the driving electric circuit of the other normal lamps.

In the drawings: FIG. 1 is a block diagram of a first embodiment of a backlight module control circuit of a rnu]ti-lamp display device of the present invention.

FIG. 2 is a block diagram of a second embodiment of a backlight module control circuit of a multi-lamp display device of the present invention.

FIG 3 is a block diagram of a third embodiment of a backlight module control circuit of a multi-lamp display device of the present invention.

FIG. 4 shows a detailed circuit diagram of the backlight module control circuit of a multi-lamp display device of the present invention.

With reference to FiG. 1, a first embodiment of a backlight module control circuit of a mu]ti-]amp display device of the present invention includes a control unit 10, multiple lamp driving circuits 20 and a fault detection unit 40. The control unit 10 includes multiple signal output terminals. The control unit 1 0 can be made up by a microprocessor or a control circuit having active or passive electronic components.

Further, an input terminal of each lamp driving circuits 20 is coupled to a signal output terminal of the control unit 10. An output terminal of each lamp driving circuits 20 is coupled to a terminal of a lamp 30. The other terminal of the lamp 30 is coupled to the ground through a resistor 31. Each lamp driving circuits includes an individual PWM controller to control on/off cycles of the corresponding lamps 30.

The fault detection unit 40 has multiple signal detection input terminals. The signal detection input terminals are respectively coupled to the lamp driving circuits 20 and the corresponding resistors 31. The fault detection unit 40 further includes an alarm signal output terminal and a control signal output terminal which is feedback-connected to the control unit 10.

When any one of the lamps 30 is out of order, an electric current can not go through the failure lamp 30 due to a broken circuit. At this moment, the fault detection unit 40 can detect the failure lamp 30 and then output an alarm signal to the control unit 10, so as to make the control unit 10 shut down the driving circuit of the failure lamp 30.

On the other hand, for a multi-lamp display device, other normal lamps 30 still continue to operate even though one of the lamps 30 is out of order.

Moreover, the contro] unit 1 0 also can enhance a driving cuiTent to output to the other normal lamps, so as to increase brightness of every operating lamp 30.

Hence in terms of a user's perspective, the display device still keeps in a good operation status.

Furthermore, the fault detection unit 40 also outputs a signal through the alarm signal output terminal to inform the user of the failure lamp 30, so as to remind the user to repair the failure lamp 30.

With reference to FIG. 2, a second embodiment of a backlight module control circuit of a multi-lamp display device of the present invention includes a PWIvI controller 50, multiple lamp driving circuits 20a and a fault detection unit 40. The PWM controller 50 includes a signal output terminal. An input terminal of each lamp driving circuits 20a is coupled to the signal output terminal of the PWM controller 50. An output terminal of each lamp driving circuits 20a is coupled to a terminal of a lamp 30. The other terminal of the lamp 30 is coupled to the ground through a resistor 31.

The fault detection unit 40 includes multiple signal detection input teminals.

The signal detection input terminals are respectively feedback-connected to the corresponding resistors 31 to detect whether any abnormal lamp 30 exists. The fault detection unit 40 further includes an alarm signal output terminal and a plurality of control signal output terminals. The control signal output terminals are feedback-connected to the PWM controller 50 and the lamp driving circuits 20a.

When any one of the lamps 30 is out of order, an electric current can not go through the failure lamp 30 due to a broken circuit. At this moment, the fault detection unit 40 can detect the failure lamp 30 and then output a signa] via the control signal output terminal, so as to shut down the driving circuit 20 of the failure lamp 30. At the same time, the fault detection unit 40 outputs a feedback signal to the PWM controller 50, so as to make the PWM controller 50 acquire the normal/abnormal status of the lamps 30. The PWM controller 50 accordingly enhances a working period of the output signal within a permitted range after shutting down the driving circuit 20 of the failure lamp 30, so as to enhance an operation current that flows through other normal lamps 30 to reinforce a loss of the brightness of the failure lamp 30.

The PWM controller 50 samples a part of the electric current from each lamp 30 to determine whether all the lamps 30 are normal. For example, the PWM controller 50 collects IrnA form each of the lamps. Assume that there are sixteen lamps; the PWN'1 controllers 50 can collect 1 6mA electric current in total.

By using a current to voltage converter circuit, suppose I.6V voltage can be gained. However, when any of the lamps 30 is abnormal, the total feedback electric current will be less than I 6mA and the converted voltage will be less than 1.6V. The vo]tage value can be a reference for the PWM controller 50 to determine whether the working period should be adjusted. If the voltage value is less than I.6V the PWM controller 50 enhances the working period, so as to enhance an operation current that flows through other normal lamps 30.

With reference to FIG. 3, a third embodiment of a bac]dight module control circuit of a multi-lamp display device of the present invention is shown. The third embodiment is similar to the second preferred embodiment. A main difference is that the driving circuit 20 can be coupled to a plurality of lamps 30. The circuit operation principle of this preferred embodiment is the same as the aforesaid example of the second preferred embodiment.

FIG. 4 is a detai]ed circuit diagram of Fig. 3. . Assume that six lamps are driven for example. The input terminals ADO to ADS of the fault detection unit detect whether there is any failure lamp in accordance with the signal OP I to 0P6. The output terminal of the PWM controller 50 is coupled to three transformers T702, T702 and T703. An output side of each of the transformers T702, T702 and T703 can drive two lamps (not shown). The lamps are coupled to connectors CN7OI, CN702, CN703 and CN704. When any lamp is out of order, the feedback electric current of an INN pin of the PWM controller 50 changes, so as to make the PWM controller 50 adjust the working period. Then the fault detection unit 40 controls its output pins AS, DS, and PS to shut down a corresponding transformer. For example, when OP1 and 0P2 signal display lamps are out of order, the PS pin is of low electric potential and a transistor Q720 is closed, so as to disconnect the working voltage of the first transformer T70 1.

On the other hand, at an initial instance of starting the power, the output pins AS, DS and PS all keep at high electric potential for a period of time. During this period of time, all transformers ensure to continue outputting the electric current to drive the lamps, so as to determine whether the lamps can operate normally.

To conclude, the aforesaid examples of the preferred embodiment of the present invention of the backlight module control circuit provide the following features in comparison with the conventiona] control circuit: First of all, the backlight module control circuit of the present invention can shut down the failure lamp independently: with the fault detection unit to detect the failure lamp, the control unit can shut down the driving circuit of the failure lamp independently and also continue to keep the operation of the other normal lamps.

Secondly, the backlight module control circuit of the present invention can maintain display quality of images: the control unit can enhance the driving electric circuit of the other normal lamps despite one of the lamp is out of order.

Hence the whole brightness of the display device still can keep normal without decreasing the display quality of the images.

Thirdly, the backlight module control circuit of the present invention can avoid high-voltage damage: since the driving circuits use high voltage to light up the lamps, the high voltage of the driving circuits can avoid damaging the display device by shutting down the high voltage of the driving circuit of the failure lamp.

Therefore, the backlight module control circuit of the present invention includes novelty and obviously improves the conventional control circuit.

Claims

Claims: I. A backlight module control circuit of a multi-lamp disp]ay

device comprising: a control unit (10) having multiple signal output terminals; rnu]tiple lamp driving circuits (20) connected between the signal output terminals of the control unit (10) and multiple lamps (30); and a fault detection unit (40) having multiple signal detection input terminals respectively coupled to the lamp driving circuits (20) and the lamps (30), and having a control signal output terrriinal coupled to the control unit (10); wherein the fault detection unit (40) detects whether any one of the lamps (30) is out of orderand then outputs a signal to the control unit (10), so as to make the control unit (10) shut down the driving circuit of the failure lamp (30) and continue to maintain an operation of other normal lamps (30).

2. The backlight module control circuit as claimed in claim 1, wherein the fault detection unit (40) comprises an alarm signal output terminal.

3. The backlight module control circuit as claimed in claim 1, wherein the control unit (10) enhances an operation current that flows through normal lamps (30) after shutting down the driving circuit of the failure lamp (30).

4. The backlight module control circuit as claimed in claim 2, wherein the control unit (10) enhances an operation current that flows through normal lamps (30) after shutting down the driving circuit of the failure lamp (30).

5. The backlight module control circuit as claimed in claim 1, wherein each lamp (30) is coupled to ground through a resistor (31).

6. The hacklight module control circuit as claimed in claim 1, wherein the control unit (10) is a microprocessor.

7. The backlight module control circuit as claimed in claim I, wherein each of the lamp driving circuits (20) comprises a PWM controller.

8. The backlight module control circuit as claimed in claim 1, wherein the control unit (10) is a control circuit made up by a plurality of electronic components.

9. A backlighi module control circuit of a multi-lamp display device comprising: a PWM controller 50 having a signal output terminal; multiple lamp driving circuits (20a) connected between the signal output terminal of the PWM controller 50 and at least one lamp (30); and a fault detection unit (40) comprising signal detection input terminals and signal output terminals, wherein the signal detection input terminals are respectively coupled to the lamps (30), wherein the signal output terminals are respective coupled to the lamp driving circuits (20a) and the PWM controller 50; wherein the fault detection unit (40) detects whether any one of the lamps (30) is out of order and shut down the driving circuit of the failure lamp (30), and also output a signal to the PWM controller 50 to continue to maintain an operation of other normal lamps (30).

10. The backlight module control circuit as claimed in claim 9, wherein the fault detection unit (40) comprises an alarm signal output terminal.

11. The backlight module control circuit as claimed in claim 9, wherein the PWM contro]Ier 50 enhances a working period of an output signal after shutting down the driving circuit of the failure lamp (30), so as to enhance an operation current that flows through normal lamps (30).

12. The backlight module control circuit as claimed in claim 10, wherein the PWM controller 50 enhances a working period of an output signal after shutting down the driving circuit of the failure lamp (30), so as to enhance an operation current that flows through normal lamps (30).

13. The backlight module control circuit as claimed in claim 11, wherein the other terminal of each of the lamps (30) is coupled to the ground via a resistor (31).

14. The backlight module control circuit as claimed in claim 12, wherein each of the lamps (30) is coupled to ground through a resistor (31).