CN201138887Y - Multi-lamp tube driving device - Google Patents

Abstract

The utility model discloses a multi-tube driving device, which is used for driving at least two cold cathode fluorescent lamps CCFL and comprises a control module and a power driving and converting module, wherein the control module outputs a driving signal to drive the CCFL through the power driving and converting module; a sampling resistor is connected between the low-voltage end of each CCFL and the ground, the low-voltage end of one path of CCFLs is at least connected with a first divider resistor, the low-voltage ends of other paths of CCFLs are at least connected with an open-circuit protection diode, the first divider resistor and the open-circuit protection diode are connected with the control module through a rectifier diode together, a second divider resistor and a second filter capacitor are connected between the connecting end of the rectifier diode and the control module and the ground, and the resistance values of the first divider resistor and the second divider resistor are far greater than the resistance value of the sampling resistor; when the CCFL normally works, the open-circuit protection diode is reversely cut off, and when any one path of the CCFL is open, the open-circuit protection diode is forwardly conducted.

Description

A multi-lamp driving device

technical field

The utility model relates to a driving device for multiple lamp tubes.

Background technique

Liquid crystal display technologies such as liquid crystal displays and LCD TVs are increasingly widely used. As the backlight of an important part of the liquid crystal display, most of them use multi-CCFL (cold cathode fluorescent lamp, Cold Cathode Fluorescent Lamp) technology. CCFL usually needs a higher start-up voltage to light it, and needs to reduce the voltage to the normal working voltage after start-up to ensure its normal operation. Usually, the process of voltage conversion is realized through a multi-lamp driving device.

Figure 1 is a schematic circuit diagram of a multi-CCFL multi-lamp driving device. As shown in the figure, the multi-lamp driving device usually includes a control module, a power drive and conversion module connected between the control module and the high-voltage end of the CCFL, A voltage feedback module connected between the control module and the power drive and conversion module, a current feedback module and an open circuit protection module connected between the control module and the CCFL low voltage end. When the CCFL is started, it needs a higher lighting voltage to ensure that the CCFL can be lit normally. Because too low lighting voltage cannot light CCFL, and too high lighting voltage is harmful to CCFL, so the control module controls the output of the power drive and conversion module according to the input of the voltage feedback module to ensure that the lighting voltage is within a reasonable range. In addition, when the CCFL is started, the CCFL generally works at a constant current. At this time, the control module controls the output of the power drive and conversion module according to the input of the current feedback module, so that the lamp works in a constant current state. Since the working voltage of CCFL is relatively high, once the CCFL is opened, the power drive and conversion module will output a very high voltage, which is very dangerous and harmful, so it usually needs to be protected by an open circuit protection module.

In the multi-lamp driving device in the prior art, there are usually multiple CCFLs. Figure 2 and Figure 3 are the circuit schematic diagrams of two kinds of multi-CCFL lamp multi-lamp drive devices. Figure 2 shows the circuit schematic diagram of the current feedback and open circuit protection module based on the operational amplifier. Each operational amplifier corresponds to a lamp. Open circuit protection. When the lamp is open, the operational amplifier outputs a low voltage, the transistor Q1 is cut off, and Q1 outputs a high voltage, so that the field effect transistor Q2 is turned on, so that the feedback voltage of the current feedback of the control module is very low, and the open circuit protection is realized. However, the circuit structure of the current feedback and open circuit protection module of this multi-lamp driving device is complex and the cost is relatively high. Figure 3 shows the schematic diagram of the current feedback and open-circuit protection module based on FETs. Each FET adopts a series connection mode. When a lamp is open, the corresponding FETs in Q1~Qn are cut off and output high voltage, so that The field effect transistor Q is turned on, so that the feedback voltage of the current feedback terminal of the control module is very low, and the open circuit protection is realized. However, the circuit structure of the current feedback and open circuit protection module of this multi-lamp drive device is relatively complicated, the cost is high, and the open circuit The number of protected lights should not be too many.

Utility model content

The utility model provides a multi-lamp tube driving device, which can reduce the complexity of current feedback and open circuit protection module circuits and save costs.

The utility model discloses a multi-lamp driving device, which is used to drive at least two cold cathode fluorescent lamps (CCFL). The signal drives the CCFL through the power drive and conversion module, and the current feedback and open circuit protection module feeds back the electrical signal of the CCFL to the control module; each of the CCFL low-voltage terminals is connected to a sampling The low-voltage end of one of the CCFLs is at least connected to a first voltage dividing resistor, and the low-voltage end of the other CCFL is at least connected to an open-circuit protection diode, and the first voltage-dividing resistor and the open-circuit protection diode pass through The rectifier diode is connected to the control module, and a second voltage divider resistor and a second filter capacitor are connected between the connection end of the rectifier diode and the control module and the ground, and the resistance values of the first and second voltage divider resistors are Far greater than the resistance value of the sampling resistor; when the CCFL is working normally, the open circuit protection diode is reversely cut off, and when any path of the CCFL is open circuit, the open circuit protection diode is forward conducting.

Wherein, the low-voltage end of one of the CCFLs is further connected with an open-circuit protection diode connected in parallel with the first voltage dividing resistor.

Further, the low-voltage end of the other CCFL path may also be connected with a first voltage dividing resistor connected in parallel with the open-circuit protection diode.

In addition, the number of rectifying diodes may be greater than one, and each rectifying diode is connected in series in sequence.

Wherein, the power drive and conversion module includes at least two output terminals, and each output terminal is respectively connected to the high voltage terminal of each CCFL lamp.

The utility model also provides a multi-lamp drive device, which includes at least two cold cathode fluorescent lamps CCFL, a control module, a power drive and conversion module, and a voltage feedback module. The power drive and conversion module includes an even number of secondary outputs transformer, each of the even-numbered secondary outputs of the transformer corresponds to one of the CCFLs, and a pair of different-named ends of each of the two secondary outputs are respectively connected to both ends of the corresponding CCFL , the other pair of opposite ends of each of the two secondary outputs are respectively connected to the two ends of the corresponding CCFL through a pair of voltage sampling units in the voltage feedback module; the output drive signal of the control module is passed through the The power drive and conversion module drives the CCFL, and the voltage feedback module and current feedback and open circuit protection module feed back the electrical signal of the CCFL to the control module;

A sampling resistor is connected between at least one of the pair of voltage sampling units and the ground, and at least a first voltage dividing resistor is connected to the common connection end of the pair of voltage sampling units and the sampling resistor, and the other pair The common connection end of the voltage sampling unit and the sampling resistor is at least connected to an open-circuit protection diode, and the first voltage dividing resistor and the open-circuit protection diode are connected to the control module through a rectifier diode, and the rectifier diode and the A second voltage dividing resistor and a second filter capacitor are connected between the connection terminal of the control module and the ground, and the resistance values of the first and second voltage dividing resistors are far greater than the resistance value of the sampling resistor; when the CCFL is normal When working, the open-circuit protection diode is reverse-blocked, and when any channel of the CCFL is open-circuit, the open-circuit protection diode is forward-conducting.

A rectifier diode connected in parallel with the first voltage dividing resistor is also connected to the low-voltage end of the pair of voltage sampling units.

Further, the low-voltage terminals of other pairs of voltage sampling units that are different from the pair of voltage sampling units are also connected with a first voltage dividing resistor connected in parallel with the open circuit protection diode.

In addition, the number of the rectifying diodes may be greater than one, and each rectifying diode is serially connected in sequence.

The utility model simplifies the circuit structure of the current feedback and open circuit protection module of the multi-lamp drive device, the circuit of the current feedback and open circuit protection module is simple and stable, and because of the simplification of the circuit, the cost is saved, and the PCB board is effectively reduced. space. In addition, the circuit adjustment is more convenient, and the required output current can be obtained very conveniently only by properly adjusting the second voltage dividing resistor, and it is suitable for current feedback and open-circuit protection of any number of CCFL lamps.

Description of drawings

Fig. 1 is a functional block diagram of a multi-lamp driving device in the prior art;

Fig. 2 is a circuit diagram of a multi-lamp driving device in the prior art;

Fig. 3 is a circuit diagram of another multi-lamp driving device in the prior art;

Fig. 4 is a schematic circuit diagram of the multi-lamp driving device of the first embodiment;

Fig. 5 is a schematic circuit diagram of the multi-lamp driving device of the second embodiment;

Fig. 6 is a schematic circuit diagram of the multi-lamp driving device of the third embodiment;

Fig. 7 is a schematic circuit diagram of the multi-lamp driving device of the fourth embodiment;

Fig. 8 is a schematic circuit diagram of the multi-lamp driving device of the fifth embodiment.

Detailed ways

The first embodiment: FIG. 4 is a schematic circuit diagram of a multi-lamp driving device in an embodiment of the present invention. As shown in the figure, the LCD screen contains several CCFL lamps, which are respectively marked by CCFL1, CCFL2, ... CCFLn in the figure, and the power drive and conversion module includes multiple output terminals, which are respectively connected to the high voltage terminal of each CCFL lamp A current feedback and open-circuit protection module is connected between the low-voltage end of the CCFL lamp and the control module. The current feedback and open-circuit protection module may include several sampling resistors RA1, RA2...RAn; open-circuit protection diodes D1, D2... Dn; first voltage dividing resistors RB1 , RB2 . The control module outputs a drive signal to drive the CCFL through the power drive and conversion module, and the current feedback and open circuit protection module feeds back the electrical signal of the CCFL to the control module.

The sampling resistors RA1~RAn are respectively connected between the low-voltage terminals of the corresponding CCFL1-CCFLn lamps and the ground, for example, RA1 is connected between the low-voltage terminals of CCFL1 and the ground; the open circuit protection diodes D1-Dn are respectively connected to the CCFL1-CCFLn lamps Between the low-voltage terminal and the anode of the rectifier diode connected to the control module, the cathode of each open-circuit protection diode is connected to the low-voltage terminal of each CCFL lamp, and the contact of the anode of the open-circuit protection diode of each branch is connected to the anode of the rectifier diode of the control module In this embodiment, the corresponding first divider resistors RB1-RBn are connected in parallel at both ends of the open-circuit protection diodes D1-Dn; the anode of the rectifier diode D is connected to the anode contact of each open-circuit protection diode, and the cathode is connected to the control The modules are connected; the two contacts of the parallel connection of the second filtering capacitor Cis and the second voltage dividing resistor Ris are respectively connected to the ground and the cathode of the rectifying diode D; the resistance values of the first and second voltage dividing resistors are much larger than the sampling resistor.

When the CCFL lamp is working normally, the open circuit protection diodes D1~Dn are cut off, the current flowing through CCFL1~CCFLn is sampled by the sampling resistors RA1~RAn, and divided by the first voltage dividing resistors RB1~RBn and the second voltage dividing resistor Ris, After being rectified by the rectifier diode D and filtered by the second filter capacitor Cis, a current feedback signal is provided to the control module, and the control module sends a control signal to the power drive and conversion module according to the current feedback signal, thereby controlling the current of the CCFL lamp. When one of the lights (for example, the kth road) is open circuited, the open circuit protection diode Dk of this branch is turned on, usually because the first voltage dividing resistors RB1~RBn and the second voltage dividing resistor Ris are much larger than the sampling resistors RA1~RAn Therefore, at this time, the divided voltage obtained by the open-circuit protection diode Dk and the sampling resistor RAk corresponding to RB1~RBn and the open-circuit lamp CCFLk is very small, so that the voltage of Ris is very small, so the current feedback input voltage of the control module is very low , so as to realize the protection function.

The second embodiment: as shown in Figure 5, this embodiment shows an example of the circuit schematic diagram of the power drive and conversion module, as shown in the figure, the power drive and conversion module includes several power drive and conversion sub-modules, the power drive and conversion module In the conversion sub-module, the power driving and conversion functions are completed through the transformers T1-Tn. The contacts of the input end of the power drive and conversion sub-module are connected to the control module, and one end of the secondary coil of the transformers T1-Tn is connected to the high-voltage end of the CCFL1-CCFLn lamps. For the circuit structure and working principle of the current feedback and opening protection module, reference may be made to the relevant content of the first embodiment, and details are not repeated here.

The third embodiment: as shown in Figure 6, this embodiment shows a schematic circuit diagram of another multi-lamp driving device. This embodiment is based on the disclosure of the first embodiment and the second embodiment for current feedback and open circuit The protection module has been further simplified. As shown in the figure, different from the previous two embodiments, the first voltage dividing resistor in this embodiment only includes RB1 connected in parallel to both sides of the open circuit protection diode D1, and the circuit structure of the current feedback and open circuit protection modules can be referred to in Section 1. 1. Relevant content of the second embodiment will not be repeated here.

When the CCFL lamp is working normally, the open-circuit protection diodes D1~Dn are cut off, the current flowing through CCFL1~CCFLn is sampled by the sampling resistors RA1~RAn, and the voltage is divided by the first voltage dividing resistor RB1 and the second voltage dividing resistor Ris, and the rectifying diode After D rectification and filtering by the second filter capacitor Cis, a current feedback signal is provided to the control module, and the control module sends a control signal to the power drive and conversion module according to the current feedback signal, thereby controlling the current of the CCFL lamp. When CCFL1 is open-circuited, the open-circuit protection diodes D1~Dn are still in the cut-off state, so no feedback current is generated, so as to realize the protection function; The protection diode Dk is turned on, usually because the first voltage dividing resistor RB1 and the second voltage dividing resistor Ris are much larger than the sampling resistor RAk, therefore, at this time, the divided voltage obtained by passing through the open circuit protection diode Dk corresponding to the open circuit lamp CCFLk and the sampling resistor RAk The voltage is very small, so that the voltage of Ris is very small, so the current feedback input voltage of the control module is very low, so as to realize the protection function.

The fourth embodiment: this embodiment further simplifies the current feedback and open circuit protection module on the basis of the disclosure of the third embodiment. In this embodiment, the low voltage end of CCFL1 is connected with the first voltage dividing resistor RB1, and the open circuit is omitted. For the circuit structure and working principle of the protection diode D1, the current feedback and the open protection module, reference may be made to the relevant content of the third embodiment, which will not be repeated here.

It can be seen from the above-mentioned first to fourth embodiments that the first voltage dividing resistor on the low-voltage end of one of the CCFL lamps in the utility model can have an open-circuit protection diode connected in parallel at both ends of the first voltage-dividing resistor, or there can be no parallel open-circuit protection Diode; at least an open-circuit protection diode is connected between the low-voltage end of the CCFL lamp in the other circuit and the control module, and the two ends of the open-circuit protection diode may be connected in parallel with a first voltage dividing resistor, or there may be no first voltage dividing resistor. In addition, the rectifier diode D may be a series connection of one or more diodes to increase the anti-interference capability of the circuit. The above embodiment only takes one rectifier diode D as an example.

The fifth embodiment: as shown in Figure 7, different from the above-mentioned embodiments, the transformer of the power drive and conversion module in this embodiment includes a transformer with an even number of secondary outputs, such as T1 ~ Tn in the figure, the transformer In an even number of secondary outputs, every two secondary outputs correspond to one CCFL; a pair of different-name terminals of every two secondary outputs are respectively connected to the two ends of the corresponding CCFL, and the other pair of different-name terminals of every two secondary outputs The terminals are respectively connected to the two ends of the corresponding CCFL through a pair of voltage sampling units in the voltage feedback module; the output drive signal of the control module drives the CCFL through the power drive and conversion module, and the voltage feedback module and the current feedback and open circuit protection module connect the CCFL The electrical signal is fed back to the control module. Sampling resistors RA1~RAn are connected between one power sampling unit of each pair of voltage sampling units and the ground. Considering the interference of the transformer, the sampling resistors RA1~RAn are respectively connected in parallel with the first filter capacitors CA1~CAn, that is, each group of sampling One end of the resistor and the first filter capacitor is connected to the first low potential end of the secondary output of each transformer, and the other end is connected to the second low potential end of the secondary output of each transformer and ground simultaneously, and the first potential end can be It is a positive phase terminal, and it can also be a negative phase terminal, but it is necessary to connect the sampling resistors and filter capacitors corresponding to all CCFL lamps in the same way. In addition, this embodiment shows a circuit structure diagram of a voltage feedback module, the voltage feedback module includes several voltage sampling units, which are respectively connected to both ends of each secondary output of the transformer, and the low The potential end is connected to the current sampling end, for example, the two contacts of the sampling resistor RA1 and the filter capacitor CA1 are respectively connected to one end of the two voltage sampling units for voltage sampling of the CCFL1 lamp. In addition, the rectifier diode D can be connected in series with one or more diodes to increase the anti-interference capability of the circuit. One rectifier diode D is taken as an example in FIG. 7 . The circuit structure of the current feedback and open circuit protection module can refer to the relevant content of the foregoing embodiments. The first voltage dividing resistor in the current feedback and open circuit protection module is connected to the common connection end of one pair of voltage sampling units and the sampling resistor, and the current The open-circuit protection diode in the feedback and open-circuit protection module is connected to the common connection end of other voltage sampling units and the sampling resistor, and the first voltage dividing resistor and the open-circuit protection diode are connected to the control module through a rectifier diode.

When the CCFL lamp is working normally, the open circuit protection diodes D1~Dn are cut off, the current flowing through CCFL1~CCFLn is sampled by the sampling resistors RA1~RAn, and divided by the first voltage dividing resistors RB1~RBn and the second voltage dividing resistor Ris, After being rectified by the rectifier diode D and filtered by the second filter capacitor Cis, a current feedback signal is provided to the control module, and the control module sends a control signal to the power drive and conversion module according to the current feedback signal, thereby controlling the current of the CCFL lamp. When one of the lamps (for example, the kth road) is open circuited, the open circuit protection diode Dk of the street lamp is turned on, usually because the first voltage dividing resistor RBk and the second voltage dividing resistor Ris are much larger than the sampling resistor RAk, therefore, at this time The divided voltage obtained by RBk and the open circuit protection diode Dk corresponding to the open circuit lamp CCFLk and the sampling resistor RAk is very small, so that the voltage on Ris is very small, so the current feedback input voltage of the control module is very low, thereby realizing the protection function.

Embodiment 6: As shown in FIG. 8 , this embodiment further simplifies the current feedback and open circuit protection modules on the basis of the technical solution disclosed in the fifth embodiment. The first voltage dividing resistor in this embodiment only includes RB1 connected in parallel to both sides of the open circuit protection diode D1, and the circuit structure of the current feedback and open circuit protection module can refer to the relevant content of the fifth embodiment, and will not be repeated here.

When the CCFL lamp is working normally, the open-circuit protection diodes D1~Dn are cut off, the current flowing through CCFL1~CCFLn is sampled by the sampling resistors RA1~RAn, and the voltage is divided by the first voltage dividing resistor RB1 and the second voltage dividing resistor Ris, and the rectifying diode After D rectification and filtering by the first filter capacitors CA1~CAn and the second filter capacitor Cis, a current feedback signal is provided to the control module, and the control module sends a control signal to the power drive and conversion module according to the current feedback signal, thereby controlling the current of the CCFL lamp. When CCFL1 is open circuited, the sampling voltage of sampling resistor RA1 is zero, so the divided voltage between RB1 and the second voltage dividing resistor Ris is zero, and the feedback voltage of the current feedback input terminal is zero, thereby realizing the protection function; when other street lights ( For example, when an open circuit occurs in the k-th branch, the open circuit protection diode Dk of this branch is in a conduction state. Usually, the first voltage dividing resistor RB1 and the second voltage dividing resistor Ris are much larger than the sampling resistor RAk. The divided voltage obtained by the open-circuit protection diode Dk and the sampling resistor RAk corresponding to the street lamp CCFLk is very small, so that the voltage on Ris is very small, so the current feedback input voltage of the control module is very low, thereby realizing the protection function.

It can be seen from Embodiment 5 and Embodiment 6 that at least the first voltage dividing resistor is connected to the common connection end of the pair of voltage sampling units and the sampling resistor in the utility model, and an open circuit protection diode can be connected in parallel at both ends of the first voltage dividing resistor , and there may be no open circuit protection diode in parallel; other common connection ends of the voltage sampling unit and the sampling resistor are at least connected with an open circuit protection diode, and the two ends of the open circuit protection diode may be connected in parallel with the first voltage divider resistor, or there may be no first voltage divider resistance.

The embodiments of the utility model described above do not constitute a limitation to the protection scope of the utility model. Any modifications, equivalent replacements and improvements made within the spirit and principle of the utility model shall be included in the protection scope of the claims of the utility model.

Claims (9)

1. A multi-lamp driving device for driving at least two cold cathode fluorescent lamps CCFL, the multi-lamp driving device includes: a control module and a power drive and conversion module, wherein the control module outputs a driving signal through the The power drive and conversion module drives the CCFL; It is characterized by: A sampling resistor is connected between the low voltage end of each CCFL and the ground, the low voltage end of one of the CCFLs is at least connected to the first voltage dividing resistor, and the low voltage end of the other CCFLs is at least connected to an open circuit protection diode, so The first divider resistor and the open circuit protection diode are connected to the control module through a rectifier diode, and a second divider resistor and a second filter capacitor are connected between the connection end of the rectifier diode and the control module and the ground , the resistance values of the first and second voltage dividing resistors are far greater than the resistance value of the sampling resistor; when the CCFL is working normally, the open circuit protection diode is reversely cut off; when any one of the CCFL is open circuit , the open circuit protection diode is forward conducting. 2. The multi-lamp driving device according to claim 1, wherein the low-voltage end of one of the CCFLs is further connected with an open-circuit protection diode connected in parallel with the first voltage dividing resistor. 3. The multi-lamp driving device according to claim 1 or 2, characterized in that, the low-voltage end of the other CCFL circuit is also connected with a first voltage dividing resistor connected in parallel with the open-circuit protection diode. 4. The multi-lamp driving device according to claim 3, wherein the number of said rectifying diodes is greater than one, and each rectifying diode is connected in series in sequence. 5. The multi-lamp driving device according to claim 4, wherein the power driving and conversion module includes at least two output terminals, and each output terminal is respectively connected to the high voltage terminal of each CCFL lamp. 6. A multi-lamp driving device, used to drive at least two cold cathode fluorescent lamps CCFL, the multi-lamp driving device includes: a control module, a power driving and conversion module, and a voltage feedback module, and the power driving and conversion module It includes a transformer with an even number of secondary outputs, every two secondary outputs of the even number of secondary outputs of the transformer correspond to one CCFL, and a pair of opposite ends of each two secondary outputs are respectively connected to the The two ends of the corresponding CCFL are connected, and the other pair of opposite ends of each two secondary outputs are respectively connected to the two ends of the corresponding CCFL through a pair of voltage sampling units in the voltage feedback module; The control module outputs a drive signal to drive the CCFL through the power drive and conversion module, and the voltage feedback module feeds back the electrical signal of the CCFL to the control module; It is characterized by: A sampling resistor is connected between at least one of the pair of voltage sampling units and the ground, and at least a first voltage dividing resistor is connected to the common connection end of the pair of voltage sampling units and the sampling resistor, and the other pair The common connection end of the voltage sampling unit and the sampling resistor is at least connected to an open-circuit protection diode, and the first voltage dividing resistor and the open-circuit protection diode are connected to the control module through a rectifier diode, and the rectifier diode and the A second voltage dividing resistor and a second filter capacitor are connected between the connection terminal of the control module and the ground, and the resistance values of the first and second voltage dividing resistors are far greater than the resistance value of the sampling resistor; when the CCFL is normal When working, the open-circuit protection diode is reverse-blocked, and when any channel of the CCFL is open-circuit, the open-circuit protection diode is forward-conducting. 7. The multi-lamp driving device according to claim 5, wherein a rectifier diode connected in parallel with the first voltage dividing resistor is connected to the low-voltage end of the pair of voltage sampling units. 8. The multi-lamp driving device according to claim 6 or 7, characterized in that the low-voltage terminals of other pairs of voltage sampling units different from the pair of voltage sampling units are also connected with the open circuit protection diode in parallel The first divider resistor. 9. The multi-lamp driving device according to claim 8, wherein the number of said rectifying diodes is greater than one, and each rectifying diode is connected in series in sequence.

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