CN100504527C - Circuit structure for LCD backlight - Google Patents

Abstract

A circuit structure for LCD backlight is disclosed in the present invention. The circuit structure includes an inverter topology, a current balance circuit, and a plurality of loads. The current balance circuit is coupled to the plurality of loads and capable of balancing current of N loads by using N/2-1 balance chokes. The circuit structure may further include a protection circuit which is coupled to the low voltage sides of the plurality of loads. The protection circuit is capable of sensing lamp voltages and providing a feedback signal to a controller. Furthermore, the protection circuit is composed of count-reduced and cost-competitive electronic elements.

Description

Circuit structure for LCD backlight

technical field

The present invention relates to a backlight circuit, and more particularly to a liquid crystal display (LCD) backlight circuit having a plurality of lamps.

Background technique

LCD panels are used in a variety of applications ranging from portable electronic devices to fixed positioning units such as video cameras, automatic positioning systems, laptop PCs, and industrial machines. The LCD panel itself cannot emit light but is illuminated from the back by a light source. The most commonly used backlights are cold cathode fluorescent lamps (CCFL). Typically, a high alternating current (AC) electrical signal is required to light and operate a CCFL. To generate such a high AC signal from a direct current (DC) source such as a rechargeable battery, a DC/AC inverter is designed.

However, in recent years there has been interest in large size LCD displays, as required in LCD televisions and computer monitors, which require multiple CCFLs to provide the necessary illumination. Typically, a DC/AC inverter drives multiple CCFLs connected in parallel, and CCFLs may also be configured in other ways. A parallel structure is the direct parallel connection method of CCFL. This configuration has the well-known problem of unbalanced CCFL current due to lamp voltage variations and the constant voltage load characteristics of CCFLs. The unbalance of the CCFL current leads to a reduced lifetime of the CCFL and non-uniformity of luminance.

Another parallel configuration is the parallel connection at the primary side of the transformer, as shown in FIG. 1 , which shows a schematic diagram of a prior art circuit 100 for driving multiple CCFLs 140A to 140N. The circuit 100 is composed of a DC power source 110 , an inverter circuit 120 , a plurality of transformers 130A to 130N, a protection circuit 150 and a controller 160 . The inverter circuit 120 is connected to the parallel connection method of the primary windings of the plurality of transformers 130A to 130N. The inverter circuit 120 and the plurality of transformers 130A to 130N form an inverter topology, which is well known in the art. The inverter topology converts the DC input voltage VIN from a DC power source 110 such as a battery to a desired AC output voltage VOUT. Those skilled in the art recognize that the inverter topology can be a Royer, a full bridge, half bridge, a push-pull, and a class D. The AC output voltage VOUT is finally delivered to the plurality of CCFLs 140A to 140N connected to the secondary windings of the plurality of transformers 130A to 130N, respectively.

In addition, by detecting the lamp currents IS1 to ISN, the protection circuit 150 can detect a short circuit and then generate a current feedback signal ISEN. By sensing the high-side voltages HV1 to HVN of the CCFLs, the protection circuit 150 can detect a disconnected or broken lamp condition, where the CCFLs are not connected to the inverter topology and cannot light or are damaged, and then generate a Voltage feedback signal VSEN. The current and voltage feedback signals ISEN and VSEN are then sent to the controller 160 which responds to these feedback signals and takes corresponding actions to prevent damage.

Although the parallel connection at the primary winding of the transformer shown in Figure 1 minimizes the effect of lamp voltage variations, which in turn improves current equalization, some drawbacks still affect the performance/cost of the structure shown in Figure 1 . One of the disadvantages is the increased cost of circuit 100 compared to the direct parallel configuration of CCFLs due to the very large number of transformers 130A to 130N. In addition, elements for sensing the lamp voltage in the protection circuit 150 are connected to the high voltage sides HV1 to HVN, which generally have a voltage higher than 1000 volts. Components capable of withstanding such high voltages are generally expensive and thus add to the overall cost. In addition, when connecting components to the high voltage sides HV1 to HVN, the operator needs to take extra care to prevent any breakdown or danger. Another disadvantage is that the protection circuit 150 shown in Figure 1 is complex, and the complexity of the protection circuit 150 becomes a problem as the number of lamps increases.

FIG. 2A shows a schematic diagram of another prior art drive circuit 200A, which is disclosed in US Patent No. US6781325B2 and has improved current balance compared to the circuit 100 shown in FIG. 1 . By introducing a plurality of common-mode choke coils 250A to 250(N-1), the driving circuit 200A can effectively achieve lamp current balance. Similarly, in order to prevent potential damage, a protection circuit 260 is included for sensing short circuit, broken tube or open lamp conditions. In FIG. 2A, common mode choke coils 250A to 250(N-1) are respectively connected to high voltage sides HV1 to HVN of CCFL, so these common mode choke coils have high cost and require additional Notice. In order to reduce cost and eliminate safety concerns, the structure of circuit 200B is shown in FIG. 2B, in which common mode chokes 250A to 250(N-1) are connected to the low voltage sides LV1 to LVN of CCFL, respectively.

While the circuits of Figures 2A and 2B can provide a solution to lamp current balancing, they do not overcome the disadvantages associated with circuit protection. In addition, those skilled in the art will recognize that with the structure of multiple transformers in FIG. 1 , the current flowing through the CCFL will be easily sensed to adjust the brightness of the CCFL. However, with a transformer structure, a current sensing circuit needs to be specially designed. In addition, if the number of transformers in Figures 2 and 3 can be further reduced, great cost savings can be achieved.

Contents of the invention

The disclosed circuit structure includes a transformer, a current balancing circuit and an electronic load. Transformers are designed to light and run electronic loads. The current balancing circuit can consist of choke coils and is connected to the low voltage side of the electronic load. The current balance circuit is designed to balance the current of N electronic loads by using N/2-1 choke coils. The circuit arrangement further includes a protection circuit connected to the low voltage side of the electronic load for protecting the circuit arrangement from an open or broken lamp condition or a short circuit condition.

Description of drawings

The advantages of the present invention will become apparent from the following detailed description of embodiments, the description of which will be considered together with the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a prior art circuit with multiple CCFLs.

FIG. 2A is a schematic diagram of another prior art circuit with multiple CCFLs.

2B is a schematic diagram of another prior art circuit with multiple CCFLs.

FIG. 3 is a schematic diagram of a circuit according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of a circuit according to another embodiment of the present invention.

FIG. 5A is an experimental waveform diagram depicting the lamp current in FIG. 3 .

5B and 5C depict experimental waveforms of the lamp current in FIG. 4 .

Fig. 6 is a schematic diagram of a circuit according to another embodiment of the present invention.

FIG. 7 is a table of lamp current in FIG. 6. FIG.

8A is a schematic diagram of a circuit according to another embodiment of the present invention.

FIG. 8B is a schematic diagram of a circuit according to another embodiment of the present invention.

Fig. 9 is a schematic diagram of a circuit according to another embodiment of the present invention.

Fig. 10 is a schematic diagram of a circuit according to another embodiment of the present invention.

Detailed ways

Reference will now be made in detail to embodiments of the present invention. While the invention is described in conjunction with embodiments, it should be understood that the invention is not limited to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims.

FIG. 3 shows a schematic diagram of a circuit 300 according to an embodiment of the present invention. Circuit 300 is used to drive CCFLs 342, 344, 346 and 348. In addition to the DC power supply 110, the inverter circuit 120, the transformer 130A and the controller 160, the circuit 300 further includes a current balancing circuit composed of a balancing choke 350, wherein the balancing choke is usually a common mode choke. High voltage sides HV1 and HV2 of CCFLs 342 and 344 are connected to high voltage side HVA of transformer 130A through ballast capacitors C1 and C2, respectively. High voltage sides HV3 and HV4 of CCFLs 346 and 348 are connected to high voltage side HVB of transformer 130A through ballast capacitors C3 and C4, respectively. The equalizing choke coil 350 is connected to the low voltage sides LV1 to LV4 of the CCFLs. The low voltage sides LV2 and LV3 of the CCFLs 344 and 346 are connected to terminals 1 and 2 of the first winding 352 of the balancing choke 350, respectively. The low voltage sides LV1 and LV4 of the CCFLs 342 and 348 are connected to terminals 3 and 4 of the second winding 354 of the balancing choke 350, respectively. Theoretically, the currents of series CCFLs 342 and 348 are equal, and the currents of series CCFLs 344 and 346 are the same. Thus, I1 is defined as the current of CCFL 342 or 348, and I2 is defined as the current of CCFL 344 or 346. When the first and second windings 352 and 354 have the same turns and reverse polarity, the current I1 will be equal to the current I2, thereby achieving current balance of the CCFLs 342 to 348.

Circuit 300 may be extended to circuit 400 as described in FIG. 4 with multiple CCFLs 420-1 through 420-N. Fully, the current balancing circuit in circuit 400 requires only N/2-1 balancing chokes connected to the low voltage sides LV1 to LVN of CCFLs 420-1 to 420-N, where N is an even number such as 4, 6, 8, 10... As depicted in Figure 4, the first winding 401 of the balanced choke 410-1 is connected between the CCFLs 420-1 and 420-2. The second winding 403 of the balancing choke 410-1 is connected to the first winding 405 of the next adjacent balancing choke 410-2. Second and first windings 403 and 405 are further connected between CCFLs 420-3 and 420-4. Similarly, the second winding 407 of the balancing choke 410-2 is connected in series with the first winding 409 of the next adjacent balancing choke 410-3. Second and first windings 407 and 409 are further connected between CCFLs 420-5 and 420-6. Sequentially, adjacent equalization chokes are all connected in this manner until the second winding 410a of the equalization choke 410-(N/2-) is connected between CCFLs 420-(N-1) and 420-N .

Compared with the conventional circuit, the number of equalizing choke coils in Fig. 4 has been greatly reduced. In addition, since the equalizing choke coil is connected to the low voltage side of the CCFL, an expensive transformer capable of withstanding high voltage is not necessary, so the overall cost is further reduced. In addition, when connecting the equalizing choke to the low voltage side, the operator does not need to pay extra attention to potential damage, such as breakdown, hazard, etc.

Those skilled in the art recognize that the ballast capacitors in Figures 3 and 4 can help light the CCFL, but these ballast capacitors are not necessary in these embodiments. In applications, the CCFLs may be directly connected to the high voltage sides HVA and HVB of the transformer 130A. Moreover, those skilled in the art know that a plurality of balanced choke coils 410-1 to 410-(N/2-1) can be made of molybdenum permalloy powder (MPP) material core, micro-metal powder iron core, ferrite EE Core (Ferrite EE-core), a transformer composed of a pot-shaped iron core and a ring core.

FIG. 5A shows experimental waveforms of lamp current flowing through the CCFL shown in FIG. 3 . Curves (A) to (D) represent lamp currents for CCFLs 342 to 348, respectively. In the experiment, the inductance of the balanced choke coil 350 was set to 300 millihenry (mH), and the iron core of the balanced choke coil 350 was made as EE10 core. It can be noted that the test lamp currents of CCFL 342 to 348 are equal to 5.40mA, 5.45mA, 5.49mA, 5.44mA respectively. The current deviation is kept at 0.1mA so that a good current balance can be obtained.

Assuming that the integer N in FIG. 4 is equal to 6, experimental waveforms of lamp currents flowing through CCFLs 420-1 to 420-6 are shown in FIGS. 5B and 5C. Curves (A) to (F) represent the lamp currents of CCFLs 420-1 to 420-6, respectively. In the experiment, the inductance of the balancing transformers 410-1 and 410-2 was set to 250 millihenry (mH), and the iron cores of the balancing transformers 410-1 and 410-2 were made of EE8.3 core. It can be seen that the test lamp currents of CCFL 420-1 to 420-6 are respectively equal to 4.79mA, 4.85mA, 4.95mA, 5.21mA, 4.95mA and 4.95mA. The current deviation is kept at 0.3mA to obtain a good current balance.

FIG. 6 shows a schematic diagram of a circuit structure 600 with multiple CCFLs 620-1 to 620-N according to another embodiment of the present invention. For clarity, identical elements appearing in FIG. 5 are omitted here, and only differences are emphasized. Referring to FIG. 6, the high voltage sides HV1, HV3, HV5 to HV(N-1) of odd numbers of CCFLs 620-1, 620-3, 620-5, to 620-(N-1) are connected to the transformer 130A shown in FIG. 5 The high voltage side HVB. High voltage sides HV2, HV4, HV6 to HVN of even numbers of CCFLs 620-2, 620-4, 620-6, through 620-N are connected to high voltage side HVA of transformer 130A shown in FIG. 5 . Low voltage sides of adjacent CCFLs, such as low voltage sides LV1, LV2, LV3 and LV4, to LV(N-1) and LVN, are connected to balancing choke coils in the current balancing circuit. In order to realize the current balance of CCFLs 620-1 to 620-N, the circuit 600 requires a total of N/2 balancing choke coils 610-1 to 610-N/2 in the current balancing circuit, where N is not less than 6.

Each equalizing choke has a first winding with terminals 1 and 2 and a second winding with terminals 3 and 4 . Terminals 2 and 3 of each equalizing choke are respectively connected to the low voltage side of the CCFL. For example, terminals 2 and 3 of equalizing choke 610-1 are connected to low voltage sides LV1 and LV2 of CCFL 620-1 and 620-2 respectively, and terminals 2 and 3 of equalizing choke 610-N/2 are connected to CCFL 620 respectively -LV(N-1) and LVN of the low voltage side of (N-1) and 620-N. Terminal 4 of each equalizing choke is connected to terminal 1 of the next adjacent equalizing choke. For example, terminal 4 of the balanced choke 610-1 is connected to terminal 1 of the balanced choke 610-2, and terminal 4 of the balanced choke 610-2 is further connected to terminal 1 of the balanced choke 610-3. Similarly, terminal 4 of transformer 610-(N/2-1) is ultimately connected to terminal 1 of equalizing choke 610-N/2, and terminal 4 of transformer 610-N/2 is connected backwards to terminal 4 of transformer 610-1. Terminal 1. In addition, a capacitor 630 may be connected between terminal 4 of the balancing choke coil 610-N/2 and terminal 1 of the transformer 610-1.

FIG. 7 shows a table of test lamp currents from experiments with the circuit of FIG. 6 . The experimental circuit is used to drive 12 CCFLs, CCFL1 to CCFL12, which provide backlight for a 30-inch LCD panel. The operating frequency of the test circuit is 55KHZ. It can be seen that when the root mean square (RMS) of the lamp current is set to the first value of 4mArms, the deviation range of the current flowing through CCFL1 to CCFL12 is within +/-0.25mA. When the RMS value is set to a second value of 6mArms, the deviation of the current flowing through CCFL1 to CCFL12 is within +/-0.25mA, and when the RMS value is set to a third value of 8mArms, the deviation of the current flowing through CCFL1 to CCFL12 is within within +/-0.17mA. Therefore, it can be concluded that multiple CCFLs can achieve good current balance when driven by the circuit in Figure 6, so that the LCD panel illuminated from the back by these CCFLs can obtain uniform brightness.

FIG. 8A shows a schematic diagram of a circuit 800 according to another embodiment of the present invention. Compared to the circuit in FIG. 3 , circuit 800 further includes a protection circuit 810A capable of sensing abnormal conditions such as disconnected or broken lamp conditions and short circuit conditions. The protection circuit 810A provides a voltage feedback signal VSEN to the controller 160 by detecting the abnormal condition of the low-side voltage of the CCFL. In response to the obtained voltage feedback signal VSEN, the controller 160 can identify abnormal conditions and then take corresponding actions to prevent damage.

Referring to FIG. 8A , protection circuit 810A is composed of voltage sensing circuits 862 , 864 , 866 and 868 and RC circuit 870 . Voltage sensing circuits 862 to 868 are connected to the low voltage sides LV1 to LV4 of the CCFLs, respectively. Meanwhile, all voltage sensing circuits 862 to 868 are further connected to RC circuit 870 at node 873 . RC circuit 870 includes a resistor 875 and a capacitor 877 connected in parallel between node 873 and ground. Each voltage sensing circuit further consists of a series resistor and a diode. For example, the current sensing circuit 862 includes a first resistor 861 , a second resistor 863 and a diode 865 . The first and second resistors 861 and 863 are connected in series between the low-end voltage LV1 and ground. The anode of the diode 865 is connected to the connection node of the first and second resistors 861 and 863 . The cathode of diode 865 is connected to RC circuit 870 at node 873 . The voltage sensing circuit 862 can sense the voltage of the low voltage side LV1 in time. In a similar manner, the voltage sensing circuits 864, 866 and 868 are configured to sense the voltages of the low voltage sides LV2 to LV4, respectively. Based on the sensed voltage, a voltage feedback signal VSEN is generated on node 873 and then fed to controller 160 .

If there is an abnormal condition, the controller 160 may recognize various abnormal conditions such as an open or disconnected lamp condition or a short circuit in response to the voltage sensing signal VSEN. These features will be readily understood by those skilled in the art through the following analysis. In normal operation, the low-side voltage of each lamp is almost equal to 0 volts, for example, V _LV1 is equal to 0V, where V _LV1 is defined as the voltage of the low-voltage side LV1. If there is an open or broken lamp condition, eg CCFL 342 is removed, broken or fails to light, the normal current 11 flowing through CCFLs 342 and 348 will be reduced to a current 11 ^! , and the low-side voltage V _LV1 will be greatly increased. The low-side voltage V _LV1 can be given by equation (1).

where V _HVA is defined as the voltage at the high side HVA, C is defined as the capacitance of the ballast capacitor C1 , L is defined as the inductance of the balancing choke 350 , and _RL4 is defined as the resistance of the CCFL 348 . Since current I1' is much lower than normal current I1, V _LV1 will increase significantly as a result. Thus, the protection circuit 810A can sense an increase in voltage at the low voltage side LV1 due to a disconnected or disconnected lamp condition, and the controller 160 can take immediate action to prevent damage. In a similar manner, protection circuit 810A may detect disconnected or broken lamp conditions occurring at other CCFLs.

If one of the high-side voltages HV1 to HV4 is shorted to ground, for example, the high-side voltage HV1 is shorted to ground, then the normal current I1 will be significantly reduced to the current I1', and the low-side voltage V _LV1 will accordingly occur Change. The low-side voltage V _LV1 is given by equation (2).

where V _HVB is defined as the voltage at the high side HVB. The protection circuit 810A sends the sensed voltage change to the controller 160, which in turn takes immediate action to prevent damage caused by the short circuit condition. If one of the high-side voltages HV1 to HV4 is short-circuited to the corresponding low-side voltage, for example, HV1 is short-circuited to LV1, the normal current I1 will increase significantly to the current I1"', and the low-side voltage V _LV1 will change accordingly The low-side voltage VLV1 is given by equation (3).

Again, the protection circuit 810A sends the sensed voltage change to the controller 160, which in turn takes immediate action to prevent damage caused by the short circuit condition. In a similar manner, protection circuit 810A can detect short circuit conditions occurring in other CCFLs.

Those skilled in the art will recognize that the protection circuit 810A can be extended to a circuit 810B as shown in FIG. 8B , which is used to protect the circuit arrangement 400 as shown in FIG. 4 from an open lamp or short circuit condition. The low voltage sides VL1 to LVN of the CCFL in FIG. 4 are respectively connected to voltage sensing circuits 810-1 to 810-N. Based on the low-side voltages sensed by the voltage sensing circuits 810 - 1 to 810 -N, a voltage feedback signal VSEN is generated on a node 873 and then fed to the controller 160 in FIG. 4 .

Those skilled in the art recognize that the protection circuit described therein is composed of cost-competitive components while the number of components is greatly reduced compared to conventional protection circuits. Thus, cost and size savings can be obtained. In addition, the protection circuit described therein is connected to the low voltage side of the CCFL, so that no extra care must be taken with regard to breakdown or other potential hazards. In addition, implementing the protection circuit is not limited to the circuits in FIGS. 4 and 6 . Indeed, those skilled in the art will recognize that the protection circuit described therein can be applied to various backlight circuit configurations in which at least one equalizing choke is connected to the low voltage side of the backlight.

FIG. 9 shows a schematic diagram of a circuit structure 900 with multiple CCFLs according to another embodiment of the present invention. Compared with the circuit in FIG. 8A , the circuit 900 further includes a current sensing circuit 910 composed of a current sensing resistor 901 . As shown in FIG. 9 , a current sense resistor 901 is connected between the CCFL 348 and the second winding 354 of the balancing choke 350 . The connection node of the current sensing resistor 901 and the second winding 354 is further connected to ground. At the connection node between the current sense resistor 901 and the CCFL 348, a current feedback signal ISEN is obtained and fed to the controller 160. In response to the current feedback signal ISEN, the controller 160 can adjust the lamp current and thus the brightness of the lamp. Thus, tight control over the brightness of the lamp can be obtained. In addition, it should be noted that the voltage sense circuit 868 in FIG. 8A is eliminated due to the effect of the current sense resistor 901, the low-side voltage LV4 is pulled down to a low voltage and no longer indicates conditions such as a disconnected or broken lamp. or short circuit abnormalities.

In effect, a current sense voltage indicative of the current flowing through CCFLs 342 and 348 is developed across current sense resistor 901 and input to controller 160 as current feedback signal ISEN. In response to the current feedback signal ISEN, the controller 160 adjusts the current flowing through the CCFL to adjust the brightness of the CCFL.

Those skilled in the art will recognize that it is not necessary for the current sense circuit 910 to be placed between the CCFL 348 and the second winding 354. There are other possible configurations, for example, the current sensing circuit 910 is placed between the CCFL 342 and the second winding 354. In addition, the current sensing circuit 910 can be applied to the circuit structure with multiple CCFLs in FIG. 4 in the same way.

FIG. 10 shows a schematic diagram of a circuit 1000 with multiple CCFLs according to another embodiment of the present invention. Compared to the circuit in FIG. 4, the current sensing circuit 1110 is connected between the second winding 403 of the balancing choke 410-1 and the first winding 405 of the balancing choke 410-2. The current sensing circuit 1110 is composed of a first diode D1, a second diode D2, a current sensing resistor Rs and a capacitor Cs. The anode of the first diode D1 is connected to terminal 3 of the second winding 403 and the cathode of the first diode D1 is connected to terminal 2 of the first winding 405 . The anode of the second diode D2 is connected to terminal 2 of the first winding 405 so that the second diode D2 is reverse biased with respect to the first diode D1. The cathode of the second diode D2 is connected to terminal 3 of the second winding 403 through a current sensing resistor Rs. The current sensing resistor Rs is further connected in parallel with the capacitor Cs. In addition, terminal 3 of the second winding 403 is connected to ground. At the connection node 1101 of the second diode D2 and the current sensing resistor Rs, a current feedback signal ISEN is generated and fed to the controller 160 .

In practice, a current sense voltage indicative of the current flowing through the CCFLs 420-3 and 420-4 is generated across the current sense resistor Rs and capacitor Cs, and is input to the controller 160 as a current feedback signal ISEN. In response to the current feedback signal ISEN, the controller 160 adjusts the current flowing through the CCFL to adjust the brightness of the CCFL.

Those skilled in the art will recognize that it is not necessary to connect the current sense circuit 1110 between the balancing chokes 410-1 and 410-2. On the contrary, the current sensing circuit 1110 can be located between any two adjacent balanced choke coils from 410-1 to 410-(N/2-1). Additionally, protection circuit 810B in FIG. 8B may be included to protect circuit 1000 from an open or broken lamp condition or a short circuit condition.

In operation, the circuit configuration may include an inverter topology, a plurality of loads, such as CCFLs, connected to the inverter topology for providing illumination of the LCD panel, at least one equalizer connected to the plurality of loads for balancing lamp current Choke current balance circuit. At least two of the plurality of loads are connected in series through at least one balancing choke. At least four of the plurality of loads are connected to one of the at least one load for current balancing of the at least four loads. At least one equalizing choke is connected continuously to each other for current balancing of a plurality of loads.

In addition, the circuit configuration may include a protection circuit connected to the low voltage side of the plurality of loads. The protection circuit is able to protect the circuit arrangement from a disconnected or disconnected lamp situation or a short circuit situation. Furthermore, the circuit configuration may include current sensing circuitry for tight control of current brightness.

Those skilled in the art know that the circuit structure disclosed therein can be applied to various inverter topologies including Royer, full-bridge, half-bridge, push-pull, and Class-D. In addition, the controller can adopt different dimming control methods, including analog control, pulse modulation (PWM) control and hybrid control. Those skilled in the art will recognize that all such modifications are within the scope of the claims.

The terms and expressions used therein are used as descriptions but not limitations. The use of such terms and expressions is not intended to exclude equivalent features (or parts thereof) shown and described, and various changes are recognized. within the scope of the claims. Other changes, variations, and substitutions are also possible, and the claims therefore attempt to cover all such equivalents.

Claims (19)

1. A circuit structure, characterized in that it comprises: a transformer; A plurality of loads, including first to Nth loads, N being an even number and N≥4, wherein the plurality of loads have a high voltage side and a low voltage side, wherein the transformer is connected to the high voltage side of the plurality of loads ;as well as a plurality of choke coils, including first to Mth choke coils, wherein the number of the plurality of choke coils is M=N/2-1, wherein the plurality of choke coils are connected to all The low-voltage side, wherein the first choke coil has a first input terminal, a second input terminal, a third input terminal, and a fourth input terminal, wherein the first load, the second load, and the third load And the fourth load is respectively connected to the first input end of the first choke coil, the second input end of the first choke coil, the third input end of the first choke coil, the first choke coil The fourth input end of the flow coil, wherein the Mth choke coil has a first input end, a second input end, a third input end and a fourth input end, wherein the (N-3)th load, the (Nth -2) load, the (N-1)th load and the Nth load are respectively connected to the first input end of the Mth choke coil, the second input end of the Mth choke coil, the The third input end of the M choke coil, the fourth input end of the Mth choke coil. 2. The circuit structure according to claim 1, wherein at least one load of said plurality of loads is a CCFL. 3. The circuit structure according to claim 1, further comprising: an inverter circuit connected to the transformer. 4. The circuit structure according to claim 1, further comprising: A protection circuit connected to the plurality of loads. 5. The circuit structure according to claim 4, wherein the protection circuit further comprises: a plurality of voltage sensing circuits including first to Nth voltage sensing circuits, wherein the plurality of voltage sensing circuits are connected to the low voltage side of the load; and A resistor capacitor circuit connected to the plurality of voltage sensing circuits. 6. The circuit structure according to claim 4, wherein the protection circuit is configured for short-circuit protection. 7. The circuit structure according to claim 4, characterized in that the protection circuit is configured for disconnected load protection. 8. The circuit arrangement of claim 1, wherein each of said plurality of choke coils is connected to at least four loads. 9. The circuit structure according to claim 1, further comprising: a plurality of capacitors, wherein each of the plurality of capacitors has a first terminal and a second terminal, wherein the first terminal is connected to the transformer, and the second terminal is connected to the plurality of loads one of the loads. 10. The circuit arrangement according to claim 1, wherein at least one of said plurality of choke coils is a common mode choke coil. 11. The circuit arrangement of claim 1, wherein at least one of said plurality of choke coils is a transformer. 12. The circuit structure according to claim 1, wherein at least one of said plurality of choke coils is composed of molybdenum permalloy powder core, micro metal powder iron core, ferrite EE core, pot iron core and ring core. 13. The circuit structure according to claim 1, characterized in that the (N-3)th load and the (N-2)th load among the multiple loads are connected in series, and the (N-1)th load and the N loads are connected in series. 14. A circuit structure, characterized by comprising: an inverter circuit; a transformer connected to said inverter circuit; A plurality of cold-cathode fluorescent lamps, including first to Nth cold-cathode fluorescent lamps, N is an even number and N≥4, wherein each cold-cathode fluorescent lamp has a high-voltage side and a low-voltage side; and A plurality of choke coils, including first to (N/2-1)th choke coils, wherein each choke coil has at least a first input terminal, a second input terminal, a third input terminal, and A fourth input terminal, wherein the first cold cathode fluorescent lamp is connected to the transformer through the high voltage side of the first cold cathode fluorescent lamp, wherein the Nth cold cathode fluorescent lamp is connected to the transformer through the high voltage side of the Nth cold cathode fluorescent lamp side connected to the transformer, wherein the first CCFL, the second CCFL, the third CCFL, and the fourth CCFL are connected to the first input of the first choke, the Two input terminals, a third input terminal, and a fourth input terminal, wherein the (N-3)th cold cathode fluorescent lamp, the (N-2)th cold cathode fluorescent lamp, the (N-1)th cold cathode fluorescent lamp, and the Nth cold cathode fluorescent lamp The fluorescent lamp is connected to the first input terminal, the second input terminal, the third input terminal and the fourth input terminal of the (N/2-1)th choke coil. 15. The circuit structure according to claim 14, characterized in that the (N-3)th cold-cathode fluorescent lamp and the (N-2)th cold-cathode fluorescent lamp among the plurality of cold-cathode fluorescent lamps are connected in series, and the (N-th) -1) The cold cathode fluorescent lamp and the Nth cold cathode fluorescent lamp are connected in series. 16. The circuit arrangement of claim 14, wherein at least one of said plurality of choke coils is a common mode choke coil. 17. The circuit structure of claim 14, wherein the plurality of choke coils are grounded. 18. The circuit structure according to claim 14, further comprising: A protective circuit that provides short-circuit protection and open-end circuit protection. 19. A circuit structure for driving multiple CCFLs, characterized by comprising: an inverter circuit; a transformer and a controller connected to said inverter circuit; A plurality of capacitors, including first to Nth capacitors, N is an even number and N≥4, wherein the plurality of capacitors are connected to the transformer; a plurality of cold-cathode fluorescent lamps including first to Nth cold-cathode fluorescent lamps, wherein a first cold-cathode fluorescent lamp of the plurality of cold-cathode fluorescent lamps is connected to the first capacitor of the plurality of capacitors, wherein the Nth cold-cathode fluorescent lamp a cathode fluorescent lamp connected to said Nth capacitor; A plurality of choke coils, including first to (N/2-1)th choke coils, wherein each choke coil has at least a first input terminal, a second input terminal, a third input terminal, and a The fourth input terminal, wherein the first CCFL, the second CCFL, the third CCFL, and the fourth CCFL are connected to the first input terminal of the first choke coil, and the second input terminal , the third input terminal, the fourth input terminal, wherein the (N-3) CCFL, the (N-2) CCFL, the (N-1) CCFL, and the N CCFL are connected to The first input terminal, the second input terminal, the third input terminal, and the fourth input terminal of the (N/2-1)th choke coil; and connected to the protection circuit of the controller.

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