CN1980509B - Multi-lamp drive system - Google Patents

Abstract

A multi-lamp driving system is used to drive multiple lamps, which includes a converter circuit, a control circuit, a feedback circuit, a transformer circuit, a current balance circuit and a lamp group. The transformer circuit includes N transformers, and each transformer includes a first secondary coil and a second secondary coil. Wherein, the first secondary coil includes a first output end and a second output end, and the second secondary coil includes a third output end and a fourth output end. The current balancing circuit includes 2N current balancing units, wherein the 2Nth current balancing unit is connected to the fourth output end of the Nth transformer, and the 2N-1th current balancing unit is connected to the first output end of the Nth transformer, and Each current balancing unit includes two output terminals. The lamp tube group includes 4N lamp tubes, and one end of the lamp tubes is connected to the output end of the current balance unit in one-to-one correspondence, and the other end is grounded. The multi-lamp driving system is small in size and low in cost.

Description

Multi-lamp drive system

【Technical field】

The present invention relates to a lamp tube driving system, in particular to a multi-lamp tube driving system for a liquid crystal display (Liquid Crystal Display, LCD) backlight module (Backlight module).

【Background technique】

The liquid crystal display (Liquid Crystal Display, LCD) panel uses a discharge lamp (Discharge Lamp), especially a cold cathode fluorescent lamp (Cold Cathode Fluorescent Lamp, CCFL) as the light source of the backlight (Backlight) system. Typically, CCFLs are driven by an inverter circuit (Inverter Circuit), which supplies an AC signal to the lamp. In larger LCD panels, two or more CCFLs are required to provide sufficient brightness.

FIG. 1 is a functional module diagram of an existing multi-lamp driving circuit. The system includes a DC power supply Vc, a commutation circuit 100, a control circuit 110, a plurality of feedback circuits 120, a plurality of transformers T11, T12, T13, T14, a plurality of capacitors C11, C12, C13, C14 and a plurality of Lamps Lp11, Lp12, Lp13, Lp14. The commutation circuit 100 is used for converting the DC signal received from the DC power supply Vc into an AC signal. The control circuit 110 is used to control the commutation circuit 100 to convert the received DC signal into an AC signal. The feedback circuit 120 is respectively used to feed back a current signal from the corresponding lamps Lp11 , Lp12 , Lp13 , Lp14 to the control circuit 110 . The transformers T11 , T12 , T13 , T14 are connected to the commutation circuit 100 , one end of the secondary coil is correspondingly connected to one end of the capacitors C11 , C12 , C13 , C14 , and the other end is grounded. The other ends of the capacitors C11, C12, C13, and C14 are respectively connected to the light tubes Lp11, Lp12, Lp13, and Lp14.

The above multi-lamp driving circuit can balance the current flowing through the lamps Lp11, Lp12, Lp13, Lp14 by selecting the transformers T11, T12, T13, T14 with the same characteristics. However, because one transformer is used to drive one lamp, when the number of lamps is large, the multi-lamp driving circuit needs more transformers, so the volume is larger and the cost is higher.

【Content of invention】

In view of this, it is necessary to provide a multi-lamp driving system, which is small in size and low in cost.

A multi-lamp driving system includes a commutation circuit, a control circuit, a feedback circuit, a transformer circuit, a current balance circuit and a lamp group. The commutation circuit is used to convert the DC signal received from the DC power supply into an AC signal. The control circuit is used to control the converter circuit to convert the received DC signal into an AC signal. The transformer circuit is connected with the converter circuit and is used for converting the voltage level of the AC signal, which includes N transformers, and each transformer includes a first secondary coil and a second secondary coil. Wherein, the first secondary coil includes a first output end and a second output end, and the second secondary coil includes a third output end and a fourth output end. The current balancing circuit includes 2N current balancing units, wherein the 2Nth current balancing unit is connected to the fourth output end of the Nth transformer, and the 2N-1th current balancing unit is connected to the first output end of the Nth transformer, and Each current balancing unit includes two output terminals. The lamp tube group includes 4N lamp tubes, and one end of the lamp tubes is connected to the output end of the current balance unit in one-to-one correspondence, and the other end is grounded. The feedback circuit is connected with the transformer circuit and is used to feed back a current signal to the control circuit.

A multi-lamp driving system includes a commutation circuit, a control circuit, a feedback circuit, a transformer circuit, a current balance circuit and a lamp group. The commutation circuit is used to convert the DC signal received from the DC power supply into an AC signal. The control circuit is used to control the converter circuit to convert the received DC signal into an AC signal. The transformer circuit is connected with the converter circuit and is used to convert the voltage level of the AC signal, which includes N transformers, wherein each transformer includes a first secondary coil, a second secondary coil and a third secondary coil. Wherein, the first secondary coil includes a first output end and a second output end, the second secondary coil includes a third output end and a fourth output end, and the third secondary coil includes a fifth output end and a sixth output end. output. The current balance circuit includes 3N current balance units, wherein the 3Nth current balance unit is connected to the fifth output terminal of the Nth transformer, the 3N-1th current balance unit is connected to the third output terminal of the Nth transformer, and the 3Nth current balance unit is connected to the third output terminal of the Nth transformer. 3N-2 current balance units are connected to the first output terminal of the Nth transformer, wherein each current balance unit includes two output terminals. The lamp group includes 6N lamp tubes, and one end of the lamp tubes is connected to the output end of the current balance unit in one-to-one correspondence, and the other end is grounded. The feedback circuit is connected with the transformer circuit and is used to feed back a current signal to the control circuit.

The above-mentioned multi-lamp driving system can balance the current flowing through multiple lamp tubes, and use N transformers to drive 4N or 6N lamp tubes, so the volume is small and the cost is low.

【Description of drawings】

FIG. 1 is a functional block diagram of an existing multi-lamp driving system.

FIG. 2 is a block diagram of a multi-lamp driving system in an embodiment of the present invention.

FIG. 3 is a specific circuit diagram of a multi-lamp driving system in an embodiment of the present invention.

FIG. 4 is a specific circuit diagram of a multi-lamp driving system in another embodiment of the present invention.

Fig. 5 is a specific circuit diagram of a multi-lamp driving system in another embodiment of the present invention.

FIG. 6 is a specific circuit diagram of a multi-lamp driving system in yet another embodiment of the present invention.

【Detailed ways】

Please refer to FIG. 2 , which is a functional block diagram of a multi-lamp driving system in an embodiment of the present invention. In this embodiment, the multi-lamp driving system includes: a DC power supply Vc, a commutation circuit 200, a control circuit 210, a feedback circuit 220, a transformer circuit 230, a current balance circuit 240 and a lamp group 250 , wherein the lamp tube group 250 includes a plurality of lamp tubes, and the multi-lamp tube driving system is used to drive a plurality of lamp tubes in the lamp tube group 250 . The commutation circuit 200 is used for converting the DC signal received from the DC power supply Vc into an AC signal. In an actual circuit, the commutation circuit 200 may be a Half-bridge commutation circuit, a Full-bridge commutation circuit or a Push-pull commutation circuit, etc. . The control circuit 210 is used to control the commutation circuit 200, that is, to control the commutation circuit 200 to convert the DC signal received from the DC power supply Vc into an AC signal. The transformer circuit 230 is coupled to the inverter circuit 200 for converting the voltage level of the AC signal to provide the power required by the lamp group 250 . The current balancing unit 240 is coupled between the transformer circuit 230 and the lamp set 250 for balancing the current flowing through each lamp in the lamp set 250 . The feedback circuit 220 is coupled to the transformer circuit 230 and the control circuit 210 for feeding back a current signal to the control circuit 210 .

FIG. 3 is a specific circuit diagram of an embodiment of the multi-lamp driving system in FIG. 2 . In this embodiment, the lamp set 250a includes four lamps Lp31, Lp32, Lp33, Lp34. The transformer circuit 230a includes a transformer T31, and the transformer T31 includes a primary coil, a first secondary coil and a second secondary coil. The primary winding of the transformer T31 is connected to the converter circuit 200 , the first secondary winding includes a first output end and a second output end, and the second secondary winding includes a third output end and a fourth output end. In this embodiment, the number of turns of the first secondary coil is the same as that of the second secondary coil.

The current balance circuit 240a includes two current balance units CT31 and CT32, wherein the current balance unit CT31 is connected to the first output terminal of the transformer T31, the current balance unit CT32 is connected to the fourth output terminal of the transformer T31, and the second output terminal of the transformer T31 and the third output terminal are connected together to the feedback circuit 220a. The current balancing unit CT31 and the current balancing unit CT32 respectively include two input terminals and two output terminals. The two input ends of the current balance unit CT31 are connected and connected to the first output end of the transformer T31. The two input terminals of the current balancing unit CT32 are connected and connected to the fourth output terminal of the transformer T31. The output terminals of the current balancing units CT31 and CT32 are respectively connected to a lamp tube of the lamp tube group 250a, that is, one end of the lamp tube Lp31 is connected to an output end of the current balancing unit CT31, and one end of the lamp tube Lp32 is connected to the other output of the current balancing unit CT31 One end of the lamp tube Lp33 is connected to an output end of the current balance unit CT32, one end of the lamp tube Lp34 is connected to the other output end of the current balance unit CT32, and the other ends of the lamp tubes Lp31, Lp32, Lp33, and Lp34 are all grounded .

The current balancing units CT31 and CT32 are the same, and both include two magnetic element coils, and the number of turns of the two magnetic element coils is the same. In this embodiment, the current balancing units CT31 and CT32 are common mode choke coils.

Because the number of turns of the first secondary coil of the transformer T31 is the same as that of the second secondary coil, the current flowing through the first secondary coil and the second secondary coil is the same, and because the number of turns of the coils of the current balance unit CT31 and CT32 They are all the same, so the currents flowing through the magnetic element coils of the current balancing units CT31 and CT32 are the same, thus the currents flowing through the lamps Lp31 , Lp32 , Lp33 and Lp34 of the lamp group 250 a are the same.

In this embodiment, the multi-lamp driving system utilizes a transformer T31 and two current balancing units to drive four lamps Lp31, Lp32, Lp33, and Lp34, with less volume and lower cost.

FIG. 4 is a specific circuit diagram of another embodiment of the multi-lamp driving system in FIG. 2 . In this embodiment, the multi-lamp driving system needs to drive more lamps, that is, the lamp group 250b includes a plurality of lamps Lp41, Lp42, . . . , Lp4 (4N). The transformer circuit 230b includes a plurality of identical transformers T41, T42, . . . , T4N, and the transformers T41, T42, . The transformers T41 , T42 , . . . , T4N are connected in parallel to the converter circuit 200 , that is, the primary coils of the transformers T41 , T42 , . . . , T4N are connected in parallel. In other embodiments of the present invention, the transformers T41 , T42 , . . . , T4N may also be connected to the converter circuit 200 in series. The first secondary coils of the transformers T41, T42, ..., T4N respectively include a first output terminal and a second output terminal, and the second secondary coils respectively include a third output terminal and a fourth output terminal . In this embodiment, the number of turns of the first secondary coil is the same as that of the second secondary coil.

The feedback circuit 220 b includes a plurality of feedback units 421 , 422 , . . . , 42N, and the feedback units 421 , 422 , .

The current balancing circuit 240b includes a plurality of current balancing units CT41, CT42, . terminal, the second output terminal and the third output terminal of the transformer T41 are connected and are commonly connected to the feedback unit 421 of the feedback circuit 220b; the current balance unit CT44 is connected to the fourth output terminal of the transformer T42, and the current balance unit CT43 is connected to the transformer T42. The first output terminal, the second output terminal and the third output terminal of the transformer T42 are connected and commonly connected to the feedback unit 422 of the feedback circuit 220b; and so on, the current balance unit CT4 (2N) is connected to the fourth output terminal of the transformer T4N , the current balance unit CT4 (2N-1) is connected to the first output terminal of the transformer T4N, and the second output terminal and the third output terminal of the transformer T4N are connected to the feedback unit 42N of the feedback circuit 220b.

The current balancing units CT41, CT42, . . . connected to the input. One end of the lamp tubes of the lamp tube group 250b is connected to the output terminals of the current balance unit CT41, CT42, . . . One end of the lamp tube Lp42 is connected to the other output end of the current balancing unit CT41, one end of the lamp tube Lp43 is connected to one output end of the current balancing unit CT42, one end of the lamp tube Lp44 is connected to the other output end of the current balancing unit CT42; and so on , one end of the lamp tube Lp4 (4N-3) is connected to an output end of the current balance unit CT4 (2N-1), and one end of the lamp tube Lp4 (4N-2) is connected to the other output of the current balance unit CT4 (2N-1) One end of the lamp tube Lp4 (4N-1) is connected to an output end of the current balance unit CT4 (2N), and one end of the lamp tube Lp4 (4N) is connected to the other output end of the current balance unit CT4 (2N), and the The other ends of the lamp tubes Lp41, Lp42, ..., Lp4 (4N) are all grounded.

The current balancing units CT41 , CT42 , . In this embodiment, the current balancing units CT41 , CT42 , . . . , CT4 (2N) are common mode choke coils.

Because the transformers T41, T42, ..., T4N are the same, and the number of turns of the first secondary coil is the same as that of the second secondary coil, the first secondary coil flowing through the transformers T41, T42, ..., T4N The current of the primary coil is the same as that of the second secondary coil, and because the coil turns of the current balance units CT41, CT42, ..., CT4 (2N) are all the same, so the current flows through the current balance units CT41, CT42, ... The currents of the magnetic coils of CT4 (2N) are the same, so the currents flowing through the lamps Lp41 , Lp42 , . . . , Lp4 (4N) of the lamp group 250 b are the same.

FIG. 5 is a specific circuit diagram of another embodiment of the multi-lamp driving system in FIG. 2 . In this embodiment, the lamp set 250c includes six lamps Lp51, Lp52, Lp53, Lp54, Lp55, Lp56. The transformer circuit 230c includes a transformer T51, and the transformer T31 includes a primary coil, a first secondary coil, a second secondary coil and a third secondary coil. The primary coil of the transformer T51 is connected to the commutation circuit 200, the first secondary coil includes a first output end and a second output end, the second secondary coil includes a third output end and a fourth output end, and the third The secondary coil includes a fifth output terminal and a sixth output terminal. In this embodiment, the number of turns of the first secondary coil, the second secondary coil and the third secondary coil are the same.

The feedback circuit 220c includes three feedback units 521 , 522 , 523 for feeding back current signals to the control circuit 210 respectively.

The current balance circuit 240c includes three current balance units CT51, CT52, and CT53, wherein the current balance unit CT51 is connected to the first output end of the transformer T51, the current balance unit CT52 is connected to the third output end of the transformer T51, and the current balance unit CT53 is connected to To the fifth output terminal of the transformer T51, the second output terminal, the fourth output terminal and the sixth output terminal of the transformer T51 are respectively connected to the feedback units 521, 522, 523 of the feedback circuit 220c. In other embodiments of the present invention, the current balancing units CT51 , CT52 and CT53 may also be connected to the second output terminal, the fourth output terminal and the sixth output terminal of the transformer T51 respectively. The current balancing units CT51, CT52, and CT53 respectively include two input terminals and two output terminals. The two input terminals of the current balancing unit CT51 are connected and connected to the first output terminal of the transformer T51. The two input terminals of the current balancing unit CT52 are connected and connected to the third output terminal of the transformer T51. The two input terminals of the current balancing unit CT53 are connected and connected to the fifth output terminal of the transformer T51. The output ends of the current balancing units CT51, CT52, and CT53 are respectively connected to a lamp tube of the lamp tube group 250c, that is, one end of the lamp tube Lp51 is connected to an output end of the current balancing unit CT51, and one end of the lamp tube Lp52 is connected to the other end of the current balancing unit CT51. One output end, one end of the lamp tube Lp53 is connected to an output end of the current balance unit CT52, one end of the lamp tube Lp54 is connected to the other output end of the current balance unit CT52, one end of the lamp tube Lp55 is connected to an output end of the current balance unit CT53, One end of the lamp Lp56 is connected to the other output end of the current balancing unit CT53, and the other ends of the lamps Lp51, Lp52, Lp53, Lp54, Lp55, and Lp56 are all grounded.

The current balancing units CT51 , CT52 , and CT53 are the same, and all include two magnetic element coils, and the number of turns of the two magnetic element coils is the same. In this embodiment, the current balancing units CT51 , CT52 and CT53 are common mode choke coils.

Because the number of turns of the first secondary coil, the second secondary coil, and the third secondary coil of the transformer T51 is the same, the currents flowing through the first secondary coil, the second secondary coil, and the third secondary coil are the same, And because the coil turns of the current balancing units CT51, CT52, and CT53 are all the same, the currents flowing through the coils of the magnetic elements of the current balancing units CT51, CT52, and CT53 are the same, thus, the currents flowing through the lamp tubes Lp51, The currents of Lp52, Lp53, Lp54, Lp55, and Lp56 were the same.

In this embodiment, the multi-lamp driving system utilizes a transformer T51 and three current balancing units CT51, CT52, and CT53 to drive six lamps Lp51, Lp52, Lp53, Lp54, Lp55, and Lp56, with less volume and lower cost.

FIG. 6 is a specific circuit diagram of another embodiment of the multi-lamp driving system in FIG. 2 . In this embodiment, the multi-lamp driving system needs to drive more lamps, that is, the lamp group 250d includes a plurality of lamps Lp61, Lp62, . . . , Lp6 (6N). The transformer circuit 230d includes a plurality of identical transformers T61, T62, . . . , T6N, and the transformers T61, T62, . a third secondary coil. The transformers T61 , T62 , . . . , T6N are connected in parallel to the converter circuit 200 , that is, the primary coils of the transformers T61 , T62 , . . . , T6N are connected in parallel. In other embodiments of the present invention, the transformers T61 , T62 , . . . , T6N may also be connected to the converter circuit 200 in series. The first secondary coils of the transformers T61, T62, ..., T6N respectively include a first output terminal and a second output terminal, and the second secondary coils respectively include a third output terminal and a fourth output terminal , the third secondary coil respectively includes a fifth output terminal and a sixth output terminal. In this embodiment, the number of turns of the first secondary coil, the second secondary coil and the third secondary coil are the same.

The feedback circuit 220 d includes a plurality of feedback units 621 , 622 , . . . , 62 (3N), and the feedback units 621 , 622 , .

The current balancing circuit 240d includes a plurality of current balancing units CT61, CT62, . terminal, the current balance unit CT63 is connected to the fifth output terminal of the transformer T61, and the second output terminal, the fourth output terminal and the sixth output terminal of the transformer T61 are respectively connected to the feedback units 621, 622, 623 of the feedback circuit 220d; the current balance The unit CT64 is connected to the first output terminal of the transformer T62, the current balancing unit CT65 is connected to the third output terminal of the transformer T62, the current balancing unit CT66 is connected to the fifth output terminal of the transformer T62, the second output terminal of the transformer T62, the fourth The output terminal and the sixth output terminal are respectively connected to the feedback units 624, 625, and 626 of the feedback circuit 220d; and so on, the current balance unit CT6 (3N-2) is connected to the first output terminal of the transformer T6N, and the current balance unit CT6 ( 3N-1) is connected to the third output terminal of the transformer T6N, the current balance unit CT6 (3N) is connected to the fifth output terminal of the transformer T6N, and the second output terminal, the fourth output terminal and the sixth output terminal of the transformer T6N are respectively connected to To the feedback units 62(3N-2), 62(3N-1), 62(3N) of the feedback circuit 220d.

The current balance units CT61, CT62, ..., CT6 (3N) respectively include two input terminals and two output terminals, and two connected to the input. One end of the lamp tubes of the lamp tube group 250d is connected to the output terminals of the current balance unit CT61, CT62, . . . One end of lamp tube Lp62 is connected to the other output end of current balance unit CT61, one end of lamp tube Lp63 is connected to one output end of current balance unit CT62, one end of lamp tube Lp64 is connected to the other output end of current balance unit CT62, lamp tube Lp65 One end is connected to an output end of the current balance unit CT63, and one end of the lamp tube Lp66 is connected to the other output end of the current balance unit CT63; and so on, one end of the lamp tube Lp6 (6N-5) is connected to the current balance unit CT6 (3N- 2), one end of the lamp Lp6 (6N-4) is connected to the other output end of the current balance unit CT6 (3N-2), and one end of the lamp Lp6 (6N-3) is connected to the current balance unit CT6 (3N -1), one end of the lamp tube Lp6 (6N-2) is connected to the other output end of the current balance unit CT6 (3N-1), and one end of the lamp tube Lp6 (6N-1) is connected to the current balance unit CT6 ( 3N), one end of the lamp tube Lp6 (6N) is connected to the other output end of the current balance unit CT6 (3N), and the other ends of the lamp tubes Lp61, Lp62, ..., Lp6 (6N) are all grounded.

The current balancing units CT61 , CT62 , . In this embodiment, the current balancing units CT61 , CT62 , . . . , CT6 (3N) are common mode choke coils.

Because the transformers T61, T62, ..., T6N are the same, and the number of turns of the first secondary coil, the second secondary coil, and the third secondary coil are the same, the transformers T61, T62, . The currents of the first secondary coil, the second secondary coil, and the third secondary coil of ..., T6N are the same, and because the coil turns of the current balance unit CT61, CT62, ..., CT6 (3N) are all the same, Therefore, the currents flowing through the coils of the magnetic elements of the current balancing units CT61, CT62, ..., CT6 (3N) are the same, and thus, the currents flowing through the lamp tubes Lp61, Lp62, ..., Lp6 (6N) of the lamp tube group 250d are the same. the same current.

The multi-lamp driving system of the present invention can balance the current flowing through each lamp, and the whole circuit structure is small in size and low in cost.

Claims (15)

1. A multi-lamp tube drive system, used to drive a plurality of lamp tubes, is characterized in that the multi-lamp tube drive system comprises: an inverter circuit for converting a DC signal received from a DC power supply into an AC signal; A control circuit, used to control the converter circuit to convert the received DC signal into an AC signal; A transformer circuit, connected to the converter circuit, for converting the voltage level of the AC signal, comprising N transformers, wherein each transformer comprises: a first secondary coil including a first output terminal and a second output terminal; and a second secondary coil including a third output terminal and a fourth output terminal; A current balance circuit, including 2N current balance units, wherein the 2Nth current balance unit is connected to the fourth output terminal of the Nth transformer, and the 2N-1th current balance unit is connected to the first output terminal of the Nth transformer , wherein each current balancing unit includes two output terminals; A lamp tube group, including 4N lamp tubes, and one end of the lamp tubes is connected to the output end of the current balance unit one by one, and the other end is grounded; and A feedback circuit, connected to the transformer circuit, is used to feed back a current signal to the control circuit. 2. The multi-lamp driving system according to claim 1, wherein the number of turns of the first secondary coil is the same as that of the second secondary coil. 3. The multi-lamp driving system according to claim 2, wherein the second output terminal and the third output terminal of each transformer are commonly connected to a feedback circuit. 4. The multi-lamp driving system as claimed in claim 3, wherein the feedback circuit comprises N feedback units, and each feedback unit is connected to the second output terminal of a transformer. 5. The multi-lamp driving system as claimed in claim 4, wherein each current balancing unit comprises two input terminals, and the two input terminals are connected. 6. The multi-lamp driving system as claimed in claim 5, wherein each current balancing unit comprises two magnetic element coils. 7. The multi-lamp driving system according to claim 6, wherein the number of turns of the coils of the two magnetic elements is the same. 8. The multi-lamp driving system as claimed in claim 1, wherein the current balancing unit is a common mode choke coil. 9. A multi-lamp driving system for driving a plurality of lamps, characterized in that the multi-lamp driving system comprises: an inverter circuit for converting a DC signal received from a DC power supply into an AC signal; A control circuit, used to control the converter circuit to convert the received DC signal into an AC signal; A transformer circuit, connected to the converter circuit, for converting the voltage level of the AC signal, comprising N transformers, wherein each transformer comprises: a first secondary coil including a first output end and a second output end; a second secondary coil including a third output terminal and a fourth output terminal; and a third secondary coil including a fifth output terminal and a sixth output terminal; A current balance circuit, including 3N current balance units, wherein the 3Nth current balance unit is connected to the fifth output terminal of the Nth transformer, and the 3N-1th current balance unit is connected to the third output terminal of the Nth transformer , the 3N-2th current balance unit is connected to the first output terminal of the Nth transformer, wherein each current balance unit includes two output terminals; A lamp tube group, including 6N lamp tubes, and one end of the lamp tubes is connected to the output end of the current balance unit one by one, and the other end is grounded; and A feedback circuit, connected to the transformer circuit, is used to feed back a current signal to the control circuit. 10. The multi-lamp driving system as claimed in claim 9, wherein the number of turns of the first secondary coil, the second secondary coil and the third secondary coil is the same. 11. The multi-lamp driving system according to claim 10, wherein the feedback circuit comprises 3N feedback units, and the feedback units are respectively connected to the second, fourth and sixth output terminals of the transformer . 12. The multi-lamp driving system as claimed in claim 9, wherein each current balancing unit comprises two input terminals, and the two input terminals are connected. 13. The multi-lamp driving system as claimed in claim 12, wherein each current balancing unit comprises two magnetic element coils. 14. The multi-lamp driving system according to claim 13, wherein the number of turns of the coils of the two magnetic elements is the same. 15. The multi-lamp driving system as claimed in claim 9, wherein the current balancing unit is a common mode choke coil.

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