CN101360379B

CN101360379B - Light source protection circuit and application thereof in backlight module unit and LCD

Info

Publication number: CN101360379B
Application number: CN 200710140812
Authority: CN
Inventors: 沈里和; 陈建智
Original assignee: Chi Mei Optoelectronics Corp
Current assignee: Chi Mei Optoelectronics Corp
Priority date: 2007-08-03
Filing date: 2007-08-03
Publication date: 2013-05-08
Anticipated expiration: 2027-08-03
Also published as: CN101360379A

Abstract

The invention discloses a light source protecting circuit and application in a backlighting module group and LCD. The light source protecting circuit includes a plurality of rectifiers, a plurality of lighting tubes, a plurality of detection units and at least a judging unit. The detection unit is electrically connected with a nonadjacent lighting tube, utilizing the circuit link device can also detect the abnormality of the lighting tube under the status of any lighting tube to be cut off, , and also match with the judging unit simultaneously; after filtering the clutter and through at least dual compared result, the detection unit can improve the judging accuracy so as to achieve the perfectly integrated protection mechanism. Providing the lighting tube of the backlighting module group with a perfectly protection mechanism, the detection unit can not only comprehensively detect the lighting tube of abnormality occurring, but also filter the clutter so as to identify paroxysmal voltage surge, and can not shut off the lighting tubes to be operated as usual.

Description

Light source protection circuit and application thereof in backlight module and liquid crystal display

Technical Field

The present invention relates to a light source protection circuit and a protection method thereof, and more particularly, to a light source protection circuit and applications thereof in a backlight module and a liquid crystal display.

Background

For a lamp tube circuit in a liquid crystal display, if the protection mechanism is not complete, the so-called flashover phenomenon is easily caused by the open circuit of the lamp tube, so that the printed circuit board electrically connected with the lamp tube is smoky and even burned, which poses a great threat to the life and property of personnel.

First, a conventional lamp protection circuit design in a liquid crystal display is introduced, please refer to the block diagram of the conventional lamp protection circuit at a high voltage end disclosed in fig. 1a, which includes a current converting circuit 10, six rectifiers 141-: the secondary side high voltage end of the rectifier 141 and the secondary side high voltage end of the rectifier 142 are electrically connected to the connector 161, the secondary side high voltage end of the rectifier 143 and the secondary side high voltage end of the rectifier 144 are electrically connected to the connector 162, the secondary side high voltage end of the rectifier 145 and the secondary side high voltage end of the rectifier 146 are electrically connected to the connection 163, and are electrically connected to two lamps respectively through the

connection

161 and 163, for example: the connector 161 is electrically connected to the lamp 181 and the lamp 182, the connector 162 is electrically connected to the lamp 183 and the lamp 184, the connector 163 is electrically connected to the lamp 185 and the lamp 186, and simultaneously, each of the

lamps

181 and 186 is connected in parallel to a

corresponding detection circuit

201 and 206, and the secondary side low voltage terminals of all the

rectifiers

141 and 146 form a loop by themselves, when the

detection circuit

201 and 206 detects an error, it will notify the electrically connected driving circuit 12, so that the driving circuit 12 can close the lamp with the error according to the received signal. However, this method usually has misjudgment due to sudden change of working voltage caused by environmental factor variation at the instant of turning on the lamp or during the operation of the lamp, and the main reason is that under the design of the protection circuit in which the detection circuit is electrically connected to the high voltage end, the voltage of the lamp flowing through each time the lamp is turned on or the working voltage of the lamp itself is affected by environmental temperature and humidity can be as high as over 1000 volts, so that the detection circuit connected in parallel with the lamp often has misjudgment due to high voltage entering, and the lamp capable of operating normally is forced to be turned off.

In addition, in this design, a lamp is matched with a detection circuit, which not only can not meet the design concept of size reduction, but also increases the cost of circuit hardware.

Referring to fig. 1b, it is a schematic diagram of a conventional lamp protection circuit block at a low voltage end, including a current conversion circuit 10, six rectifiers 141-: the secondary side high voltage end of the rectifier 141 and the secondary side high voltage end of the rectifier 142 are electrically connected to the connector 161, the secondary side high voltage end of the rectifier 143 and the secondary side high voltage end of the rectifier 144 are electrically connected to the connector 162, the secondary side high voltage end of the rectifier 145 and the secondary side high voltage end of the rectifier 146 are electrically connected to the connector 163, and are electrically connected to two lamps respectively through the connectors, for example: the connector 161 is electrically connected to the lamp 181 and the lamp 182, the connector 162 is electrically connected to the lamp 183 and the lamp 184, and the connector 163 is electrically connected to the lamp 185 and the lamp 186, and in the conventional lamp protection circuit design of low voltage end, the secondary side low voltage end of the

rectifier

141 and 146 is electrically connected to two lamps at the same time, that is, the first low voltage detection circuit 221 is electrically connected to the first lamp 181 and the third lamp 183, the second low voltage detection circuit 222 is electrically connected to the second lamp 182 and the fourth lamp 184, the third low voltage detection circuit 223 is electrically connected to the fifth lamp 185 and the sixth lamp 186, and the first low voltage detection circuit 221, the second low voltage detection circuit 222 and the third low voltage detection circuit 223 are also affected by the first connector 161, the second connector 162 and the third connector 163, respectively, so that when the power is turned on, in terms of the

lamp

181 and 186, the first low voltage detection circuit 221 receives signals from the first lamp 181 and the third lamp 183 simultaneously, and similarly, the second low voltage detection circuit 222 receives signals from the second lamp 182 and the fourth lamp 184 simultaneously, and the third low voltage detection circuit 223 receives signals from the fifth lamp 185 and the sixth lamp 186 simultaneously, each low voltage detection circuit utilizes the received signals from the two lamps for destructive comparison, if the difference between the two signals is zero, it is determined that no error occurs, conversely, if the difference between the two signals is not zero, it indicates that one of the two lamps has an error and an open circuit, and at this time, the low

voltage detection circuit

221 and 223 directly notifies the driving circuit 12 to turn off the wrong lamp to protect the circuit of the whole lamp.

However, although this circuit design effectively solves the requirement of reducing the size, the hardware cost of the circuit is also reduced. However, because each low voltage detection circuit is also affected by a corresponding connector, the received signal difference is not simple, because the meaning of the circuit also includes the situation that two lamps are open-circuited at the same time, in addition to the situation that two lamps are normal, please refer to the schematic circuit block diagram shown in fig. 1b again, taking the fifth lamp 185 and the sixth lamp 186 as an example, because the fifth lamp 185 and the sixth lamp 186 are electrically connected to the third connector 163 at the same time, and when the third connector 163 fails, the fifth lamp 185 and the sixth lamp 186 are open-circuited at the same time, and for the third low voltage detection circuit 223, the difference of the received two signals is also zero, therefore, no error can be found for the low voltage detection circuit 223, and therefore, the protection mechanism cannot be effectively started and the risk is greatly increased, also, a certain area on the lcd will appear a darker or even a whole block of dark blocks due to insufficient light source, and the function of the lcd cannot display a complete picture completely, which is a serious defect. In addition, although the detection circuit is not electrically connected to the high voltage end, the lamp protection circuit design is less likely to cause erroneous determination due to the generation of the surge, but it is difficult to prevent the erroneous determination if the surge occurs.

In addition, when the protection circuit is applied to the actual lamp circuit design, different detection circuit designs need to be matched according to different lamp polarities, and if the existing protection circuit design is adopted, the problem of quite complex circuit design is faced.

Disclosure of Invention

The present invention is based on the above factors and difficulties, and provides a light source protection circuit, a method thereof and an application thereof in a backlight module and a liquid crystal display, so as to solve the problems in the prior art.

The present invention provides a light source protection circuit and a protection method thereof, wherein a detection unit is electrically connected to two non-adjacent lamps for detecting the two non-adjacent lamps simultaneously, thereby effectively avoiding the error that the two lamps electrically connected to the same connector are opened simultaneously and are not detected.

Another objective of the present invention is to provide a light source protection circuit of a backlight module and a protection method thereof, wherein a judgment unit is used for performing at least two signal comparisons, so that the signal from the detection unit can be subjected to at least two determinations and comparisons, and then the driving unit is informed whether to turn off the lamp according to the judgment result, thereby effectively eliminating the surge generated due to the starting moment or the influence of environmental factors, and not turning off the lamp which can normally operate.

It is still another object of the present invention to provide a light source protection circuit and a protection method thereof, which can be applied to various lamp protection circuits with different driving polarities and without limiting the number of lamps, so as to protect two lamps electrically connected to the same connector, and at the same time, the judgment capability will not be affected by the generation of the burst wave.

In order to achieve the above object, the present invention provides a light source protection circuit, which comprises a plurality of rectifiers, a plurality of connectors, a plurality of lamps, a plurality of detecting units and at least one determining unit, wherein the primary side of each rectifier is electrically connected with a power supply end, the secondary side high-voltage end of each rectifier is electrically connected with the lamp tubes, the two adjacent lamp tubes are electrically connected with a connector, the two receiving terminals of the detecting unit are electrically connected to the secondary side low voltage terminals of the rectifier electrically connected to the two non-adjacent lamps, and outputs the detection signal to the judgment unit through an output end, so that the judgment unit can compare the received detection signal and generate a corresponding control signal, and the control signal is transmitted to the driving unit, and the lamp tube with the error is closed through the electric connection of the driving unit and the power supply end.

The invention also provides a protection method of the light source protection circuit of the backlight module, firstly, continuously receiving and detecting a plurality of signals from different lamp tubes, and then comparing two corresponding signals, namely, carrying out cancellation action on the two corresponding signals received at the same time to confirm whether an error is generated in the circuit: (a) when the signals corresponding to the two phases can be completely cancelled, a protection mechanism is not started, namely no error occurs; (b) when the M groups of corresponding signals can not be completely cancelled, and if the M +1 th group of corresponding signals can be completely cancelled, the protection mechanism is not started, and the situation indicates that a surge is generated in the circuit; (c) when the signals corresponding to the M groups cannot be completely cancelled, and if the signals corresponding to the M +1 th group cannot be completely cancelled, a protection mechanism is started, namely, a long-time abnormal signal is generated in the circuit, namely, an error is generated.

In addition, the invention also provides a backlight module with the light source protection circuit and a liquid crystal display. Wherein:

a backlight module with a light source protection circuit, which can be electrically connected with a liquid crystal panel module, is characterized in that the backlight module with the light source protection circuit comprises:

a plurality of rectifiers, each of the rectifiers having a primary side end and a secondary side end, the secondary side end having a high voltage end and a low voltage end;

each lamp tube is electrically connected with the high-voltage end, and two connected lamp tubes are electrically connected with the high-voltage end through a connector;

a plurality of detecting units, each of which has a first connecting end, a second connecting end and an output end, wherein the first connecting end and the second connecting end are respectively electrically connected with the low voltage ends of the rectifiers electrically connected with the two nonadjacent fluorescent tubes so as to detect a first signal and a second signal from the two nonadjacent fluorescent tubes and output a detecting signal from the output end; and

and the judging unit is electrically connected with the output end of the detecting unit, receives the detecting signal, compares the detecting signal and generates a corresponding control signal according to the detecting signal.

A liquid crystal display, comprising:

a liquid crystal display panel module; and

a backlight module for providing light to the liquid crystal display panel module, the backlight module comprising:

a plurality of detecting units, each of which has a first connecting end, a second connecting end and an output end, wherein the first connecting end and the second connecting end are respectively electrically connected with the low voltage ends of the rectifiers electrically connected with the two non-adjacent fluorescent tubes so as to detect a first signal and a second signal from the two non-adjacent fluorescent tubes and output a detection signal from the output end; and

The invention can provide an optimal protection mechanism for the lamp tubes in the backlight module, can comprehensively detect abnormal lamp tubes, can filter out foreign signals to distinguish sudden voltage surges, and cannot mistakenly close the lamp tubes capable of normally operating.

Drawings

The purpose, technical content, features and effects of the present invention will be more readily understood by the following detailed description of the embodiments taken in conjunction with the accompanying drawings.

Fig. 1a is a block diagram of a conventional lamp protection circuit at a high voltage end.

FIG. 1b is a block diagram of a conventional lamp protection circuit for low voltage terminals.

FIG. 2 is a block diagram of a lamp protection circuit according to the present invention.

FIG. 3a is a diagram of an internal circuit of the detecting unit of the present invention.

FIG. 3b is a diagram of an internal circuit of the determining unit according to the present invention.

Fig. 4a and 4b are flow charts of protection methods of the lamp protection circuit of the present invention.

FIG. 5 is a block diagram of a lamp protection circuit for driving one of six straight lamps according to the present invention.

FIG. 6 is a block diagram of a lamp protection circuit for driving one of ten lamps according to the present invention.

FIG. 7 is a block diagram of a lamp protection circuit for driving a lamp using fourteen straight lamps according to the present invention.

FIG. 8 is a block diagram of another lamp protection circuit for driving a lamp according to the present invention.

FIG. 9 is a block diagram of a lamp protection circuit for driving one of eight straight lamps according to the present invention.

FIG. 10 is a block diagram of another lamp protection circuit for driving eight straight lamps according to the present invention.

FIG. 11 is a block diagram of another lamp protection circuit for driving a lamp according to the present invention.

Fig. 12 is a schematic diagram of another lamp protection circuit block for driving a lamp according to the present invention.

Fig. 13 is a schematic diagram of another lamp protection circuit block for driving a lamp according to the present invention.

The main elements in the figures are indicated by the following symbols;

10 current conversion circuit

12 drive circuit

141-146 rectifier

161-163 connector

181-186 lamp tube

201-206 high voltage detection circuit

221-223 low voltage detection circuit

30 current conversion unit

32 drive unit

341-346 rectifier

361-363 connector

381 and 386 lamp tube

401 first detecting unit

402 second detection unit

403 third detection unit

42 judging unit

421 voltage dividing unit

601-604 resistor

701-702 rectifying diode

703 na accumulating diode

80 capacitor

82 delay unit

901 first comparing unit

902 second comparison unit

Detailed Description

As the technology of the lcd becomes more mature, the lcd is no longer only on the small-sized panels of the mobile phones, computer screens, machine operation interfaces, etc., but also on the large-sized screens of the home televisions or home video theaters, etc., which are the common application range of the lcd, and therefore, the safety of the lcd becomes a very important issue. Therefore, the present invention provides a light source protection circuit of a backlight module and a protection method thereof, and related descriptions and implementation methods will be described in detail below.

First, the present invention provides a light source protection circuit of a backlight module, which is shown in FIG. 2, and is a schematic diagram of a lamp protection circuit block of the present invention, in the present embodiment, the six lamps 381-386 are used to illustrate the positive/negative, and positive/negative driving polarity arrangement, which includes a current converting unit 30, six rectifiers 341-346, three connecting units 361-363, six lamps 381-386, three detecting units 401-403, a determining unit 42, and a driving unit 32, after the current converting unit 30 converts the received DC power into AC power, the current is outputted from the primary side of each rectifier 341 and 346, the two high voltage terminals on the secondary side of the rectifiers 341 and 346 are electrically connected to a connector, such as: the secondary side high voltage terminal of the rectifier 341 and the secondary side high voltage terminal of the rectifier 342 are electrically connected to the connector 361, the secondary side high voltage terminal of the rectifier 343 and the secondary side high voltage terminal of the rectifier 344 are electrically connected to the connector 362, the secondary side high voltage terminal of the rectifier 345 and the secondary side high voltage terminal of the rectifier 346 are electrically connected to the connector 363, and are electrically connected to the two adjacent lamps through the connectors 361 and 363, respectively, in detail, the first lamp 381 and the second lamp 382 are electrically connected to the first connector 361, the third lamp 383 and the fourth lamp 384 are electrically connected to the second connector 362, and the fifth lamp 385 and the sixth lamp 386 are electrically connected to the third connector 363, and the lamps have their polarities, wherein the driving polarities of the first lamp 381, the fourth lamp 384 and the fifth lamp 385 are all positive, in the design of the lamp protection circuit at the low voltage end of the present invention, because the low voltage end of the secondary side of the rectifier is electrically connected to two nonadjacent lamps at the same time and is influenced by two different connectors, that is, the first detection unit 401 is electrically connected to the second lamp 382 and the fourth lamp 384 with different polarities and is influenced by the first connector 361 and the second connector 362 at the same time, the second detection unit 402 is electrically connected to the third lamp 383 and the fifth lamp 385 with different polarities and is influenced by the second connector 362 and the third connector 363 at the same time, and the third detection unit 403 is electrically connected to the first lamp 381 and the sixth lamp 386 with different polarities and is influenced by the first connector 361 and the third connector 363 at the same time. Therefore, if no lamp is abnormal, the detection units 401 and 403 will not be activated, only when any lamp 381 and 386 or connector 361 and 363 is wrong, the detection units 401 and 403 will be activated and generate a detection signal to be transmitted to the determination unit 42 in real time, and after the two signal comparisons by the determination unit 42, if the abnormal signal is found to be maintained for a certain time, it is determined that there is a mistake and a control signal will be transmitted to the driving unit 32, so as to provide the information of the mistake occurrence for the control unit (not shown) to perform the operation of closing the lamp.

According to the above-mentioned lamp tube protection circuit structure, please refer to fig. 3a, which is an internal circuit diagram of the detection unit of the present invention, including the

resistors

601 and 602 and the

rectifier diodes

701 and 702, wherein the

resistors

601 and 602 can be used for voltage division, and the

rectifier diodes

701 and 702 can be used for rectification or suppressing abnormal signals. In addition, referring to fig. 3b, it is an internal circuit diagram of the determining unit of the present invention, which includes a voltage dividing unit 421, two comparing units 901, 902 and a delay unit 82, wherein the voltage dividing unit 421 includes resistors 603, 604, a capacitor 80 and a Zener Diode (Zener Diode)703, and can divide the voltage of the signal entering the determining unit, and then transmit the divided voltage to the first comparing unit 901, the delay unit 82 and the second comparing unit 902 of the comparing units, so as to be electrically connected to the first comparing unit of the comparing unitsPresetting a comparison signal (V)_ref1) And a second preset comparison signal (V) electrically connected to the second comparison unit_ref2) The comparison of the signals is performed separately.

The hardware architecture of the lamp protection circuit of the present invention is described above, and then, a protection method corresponding to the hardware architecture of the protection circuit will be described. Please refer to fig. 4a and fig. 4b, wherein fig. 4a and fig. 4b are a circuit protection determining process of any lamp of the present invention, and different products may have different determining standards, in this embodiment, it is assumed that the criterion for triggering the determining unit to start is that M comparison signals larger than the reference voltage are continuously received, that is, the driving unit receives a control signal after the determining unit continuously receives M comparison signals larger than the reference voltage and performs two comparison confirmations, so as to turn off the lamp having the abnormal condition.

First, in step S1, when the power is turned on, each detecting unit continuously receives the positive and negative polarity signals transmitted by the M lamps electrically connected to the detecting unit; following step S1, in step S2, the received positive and negative polarity signals are divided and whether they can be cancelled or not is confirmed: if the result is yes, it indicates that each corresponding positive and negative polarity signal can be cancelled, then step S21 is entered, i.e., no detection signal is generated by any of the detection units, and no protection mechanism is started, however, if the result is no, it indicates that not all corresponding positive and negative polarity signals can be cancelled, then step S22 is entered, i.e., the detection unit generates a corresponding detection signal according to the signal that cannot be cancelled, and transmits the corresponding detection signal to the determination unit; continuing to the step S22, in step S3, after each detection signal enters the determining unit, the voltage is divided again to generate a plurality of first comparison signals corresponding to the detection signal; next, in step S4, each first comparison signal immediately enters the first comparison unit, and is compared with a first preset comparison voltage preset in the first comparison unit: if the result is no, i.e. the first comparison signal is not greater than the first predetermined comparison voltage, the step S41 is executed, i.e. the lamp protection mechanism is not activated, and conversely, if the result is yes, i.e. the first comparison signal is greater than the first predetermined comparison voltage, the step S42 is executed, wherein the first comparison unit outputs the first comparison signal greater than the first predetermined comparison voltage to the delay unit; following the step S42, in step S5, the first comparison signal entering the delay unit determines the operation of the delay unit according to the number of signals accumulated: if the result is no, i.e. the number of the first comparison signals continuously entering the delay unit is less than M, the process proceeds to step S51, at which the delay unit will not be turned on because it cannot accumulate enough signals, and therefore, the number of the first comparison signals continuously entering the delay unit less than M will not generate a corresponding second comparison signal, so that the protection mechanism will not be activated, and there will not be a continuous operation, and conversely, if the result is yes, i.e. the number of the first comparison signals continuously entering the delay unit is M, the process proceeds to step S52, at which the delay unit will be turned on because it accumulates enough signals, and therefore, the number of the M first comparison signals continuously entering the delay unit will generate a corresponding second comparison signal, and output from the delay unit to the second comparison unit; following the step S52, in step S6, the second comparison signal entering the second comparing unit is compared with a second preset comparison voltage preset in the second comparing unit: if the result is no, that is, the input second comparison signal is not greater than the second preset comparison voltage, the step S61 is executed, that is, the lamp protection mechanism is not activated, otherwise, if the result is yes, the input second comparison signal is greater than the second preset comparison voltage, the step S62 is executed, and the second comparison unit outputs the second comparison signal, which is about to be greater than the second preset comparison voltage, to the driving unit as a control signal; finally, following the step S62, in step S7, the control signal entering the driving unit will activate the lamp protection mechanism to protect the abnormal lamp from the dangerous situation caused by the open circuit.

Therefore, according to the protection method, no matter the situation of sudden change of the working voltage caused by the variation of the environmental factors such as the instant of turning on the lamp tube and the period … … during which the lamp tube is working, the misjudgment caused by the sudden wave is generated, or, when there is open circuit of multiple lamps, even if two adjacent lamps have open circuit at the same time or the two adjacent lamps have open circuit at the same time due to failure of the connector electrically connected to the two lamps, the same judgment method can be used to protect the lamps, the main reason is that two adjacent lamps are electrically connected to different detecting units, i.e. different connectors are controlled by different detecting units, the abnormal lamp tube or connector can be accurately detected, and the situation that the lamp tube is abnormal and cannot be detected is avoided.

In addition, when the present invention is applied to the backlight module of the liquid crystal display, in order to adapt to the liquid crystal display with various sizes, the light guide unit in the backlight module is used for guiding the light from the lamp tubes and controlling the direction of the light to enhance the intensity of the light, and the design of different numbers of the lamp tubes can be used to match with different lamp tube driving polarities to achieve the best display quality. FIG. 5 is a block diagram of a lamp protection circuit providing six straight lamps and using positive/positive, negative/negative, positive/negative lamp driving polarities; in fig. 6, ten straight lamps are provided and the lamp driving polarities are sequentially positive/positive, negative/negative, positive/negative; in fig. 7, fourteen straight lamps are provided and the lamp driving polarities of positive/negative, negative/positive, positive/negative are provided, and in fig. 8, the fourteen straight lamps are provided, but the driving polarities of the lamps are positive/positive, negative/negative, positive/positive, negative/negative, negative/positive; in fig. 9, eight straight lamps are provided and the driving polarities of the lamps are positive/negative, negative/positive, and relative to fig. 9, in fig. 10, eight straight lamps are provided, but the driving polarities of the lamps are positive/positive, negative/negative, positive/positive, and negative/negative. However, no matter how many lamps are used and what lamp driving polarity is adopted, the detection circuits are electrically connected to the non-adjacent lamps to effectively detect, and meanwhile, whether each lamp is in a normal state or not can be further ensured through the multiple signal comparison result of the judgment unit.

As shown in fig. 11 to 13, the U-shaped lamps are used as the light source, the number of the lamps used is three, four, and seven, and the driving polarities of the lamps are electrically connected in a positive/negative, negative/positive, and positive/negative … … manner, and similarly, no matter how many U-shaped lamps are electrically connected, the detection circuits therein are electrically connected to non-adjacent lamps, and a judgment unit is used to protect the lamp circuits.

Therefore, by combining the above, it can be concluded that the light source protection circuit and the protection method thereof disclosed by the present invention can be suitably applied to the backlight module in the general liquid crystal display, and can provide an optimal protection mechanism for the lamp tubes in the backlight module, so that not only can abnormal lamp tubes be comprehensively detected, but also the noise can be filtered to distinguish the sudden voltage surge, and the lamp tubes which can normally operate can not be mistakenly closed.

The foregoing is a description of the features of the present invention by way of example only, and is not intended to limit the scope of the invention as claimed, which is defined by the appended claims.

Claims

1. A light source protection circuit, comprising:

a plurality of rectifiers, each of which has a primary side end and a secondary side end, and the secondary side end has a high voltage end and a low voltage end

Each lamp tube is electrically connected with the high-voltage end, and two adjacent lamp tubes are electrically connected with the high-voltage end through a connector;

a plurality of detecting units, each of which has a first connecting end, a second connecting end and an output end, wherein the first connecting end and the second connecting end are respectively electrically connected with the low voltage ends of the rectifiers electrically connected with the two nonadjacent fluorescent tubes so as to detect a first signal and a second signal from the two nonadjacent fluorescent tubes and output a detection signal from the output end; and

the judging unit is electrically connected with the output end of the detecting unit and receives the detecting signal so as to compare the detecting signal and generate a corresponding control signal; wherein,

the primary side end of the rectifier is electrically connected with a current conversion unit, the judgment unit is electrically connected with a driving unit, the driving unit is electrically connected with the current conversion unit, and when the driving unit receives the control signal, the current conversion unit is enabled to close each corresponding lamp tube according to the control signal.

2. The light source protection circuit according to claim 1, wherein the judgment unit further comprises:

at least one voltage dividing unit for dividing the received detection signal and generating a comparison signal

At least two comparing units electrically connected with the voltage dividing unit for receiving the comparison signals, each comparing unit presetting a reference signal to compare the received comparison signal with the reference signal and generating the corresponding control signal according to the comparison result

A delay unit electrically connected between the comparison units, wherein the delay unit can delay the comparison signal;

when the comparison signal meets the condition that the comparison signal is simultaneously greater than the reference signals, the judging unit generates the control signal to the driving unit.

3. A backlight module with a light source protection circuit, which can be electrically connected with a liquid crystal panel module, is characterized in that the backlight module with the light source protection circuit comprises:

the judging unit is electrically connected with the output end of the detecting unit, receives the detecting signal, compares the detecting signal and generates a corresponding control signal according to the detecting signal; wherein,

4. The backlight module with a light source protection circuit as claimed in claim 3, wherein the determining unit further comprises:

A delay unit electrically connected between the comparison units for delaying the comparison signal;

when the comparison signal satisfies the condition that the comparison signal is simultaneously greater than the reference signals, the judging unit generates the control signal to the driving unit.

5. A liquid crystal display, comprising:

a liquid crystal display panel module; and

a plurality of detecting units, each of which has a first connecting end, a second connecting end and an output end, wherein the first connecting end and the second connecting end are respectively electrically connected with the low voltage ends of the rectifiers electrically connected with the two nonadjacent lamp tubes so as to detect a first signal and a second signal from the two nonadjacent lamp tubes and output a detection signal from the output end; and

6. The liquid crystal display of claim 5, wherein the judging unit further comprises:

at least one voltage division unit, which divides the received detection signal and generates a comparison signal;

at least two comparing units electrically connected with the voltage dividing unit for receiving the comparison signal, each comparing unit presetting a reference signal to compare the received comparison signal with the reference signal and generating the corresponding control signal according to the comparison result