KR200378024Y1 - Lamp load-sharing circuit - Google Patents

Abstract

In lamp load-sharing, the winding coils on one side of the plurality of transformers are connected to the plurality of lamps, and the winding coils on the other side of the transformer are connected in series with each other to form a closed loop. The same current flows through the winding coils connected in series with each other to form a closed loop. Through the electromagnetic induction characteristic of the transformer, the same working current is generated in the lamp connected to the winding coil on the other side of the transformer.

Description

Lamp load sharing circuit {LAMP LOAD-SHARING CIRCUIT}

TECHNICAL FIELD The present invention relates to lamp load-sharing circuits, and more particularly, to lamp load-sharing circuits that adjust the balance of current between lamps using a connection relationship between a plurality of transformers and a plurality of lamps.

As technology advances and customer demands, LCD panels continue to grow in size such that a single lamp cannot illuminate the entire panel. Thus, two or more lamps are required. In order to ensure the uniformity of the brightness of the LCD panel, it is necessary to adjust the current of each lamp momentarily to equalize the current flowing through each lamp. Since the cold cathode fluorescent lamp (CCFL) is very unstable and has a negative impedance, it is difficult to match the impedance of each lamp. Thus, the impedance of each lamp changes, and the current of each lamp cannot be equalized. Fluctuations in the current of each lamp result in irregular brightness of each lamp. Furthermore, excessively large currents shorten the life of the lamps, resulting in different aging rates for each lamp.

Figure 1 shows a simple circuit for adjusting the current of two lamps using a conventional differential ballast. This circuit includes a transformer 12 having a first coil 121 and a second coil 122. One end of the first coil 121 is connected to the AC power supply 10, and the other end of the first coil 121 is connected to the first lamp 141. The other end of the first lamp 141 is connected to the reference potential G. One end of the second coil 122 is connected to the AC power supply 10, and the other end of the second coil 122 is connected to the second lamp 142. The other end of the second lamp 142 is connected to the reference potential G. The AC power supply 10 forms a differential ballast through the first coil 121 and the second coil 122 of the transformer 12 to supply the stable currents I ₁ and I ₂ to the first lamp 141 and the first lamp 121. By providing for the two lamps 142, the effect of balancing the current flowing through the first and second lamps 141 and 142 is achieved.

1 and 2, the magnetic core 120 includes two side columns A1 and A2 and two shoulder columns A3 and A4. When the currents I ₁ and I ₂ are the same, the current flowing through the first coil 121 and the second coil 122 is also the same. Moreover, the magnetomotive force generated in the first coil 121 by the current I ₁ is the same as the magnetomotive force generated in the second coil 122 by the current I ₂ . That is, the press force in the side column A1 and the side column A2 cancels each other. Thus, magnetic flux is not interconnected in the shoulder columns A3 and A4. The magnetic flux φ1 and φ2 in the side columns A1 and A2 can form closed loops through the outer voids, respectively. Because the magnetic resistance of the voids is very high, the inductance effect caused by such a loop can generally be ignored.

1 and 3, the current of the lamp (141) (I ₁₎ and the second is not identical, the current (I ₂₎ of the lamp 142, the first coil by the current (I ₁₎ ( The magnetomotive force generated in the second coil 122 by the magnetomotive force generated in 121 and the current I ₂ is not the same. In other words, the magnetomotive force in the side columns A1 and A2 is not the same. The difference between them is applied to the low resistance loop formed by the side column A1, the side column A2, the shoulder column A3 and the shoulder column A4 to generate a large magnetic flux φ. The magnetic flux φ generates a correction voltage ΔV across the ends of the first coil 121 and the second coil 122 by induction. The correction voltage (△ V) are then restored to the current (I ₁₎ and the parallel forcing a current (I ₂₎ of the second ramp 142 and the same state of the first lamp 141. The

4 shows a conventional circuit for adjusting the current of multiple lamps using a differential ballast. This circuit comprises a plurality of transformers 12 each having a first coil 121 and a second coil 122. One end of each of the first coils 121 is connected to the reference potential G, and the other end thereof is connected to the first lamp 141. Each other end of the first lamp 141 is connected to an AC power source 10. One end of each of the second coils 122 is connected to the reference potential G, and the other end thereof is connected to the second lamp 142. Each other end of the second lamp 142 is connected to an AC power source 10. The AC power supply 10 forms a differential ballast through the first coil 121 and the second coil 122 of the transformer 12 to supply the stable currents I ₁ and I ₂ to the first lamp 141 and the first lamp 121. By providing for the two lamps 142, the balancing effect of the currents I ₁ and I ₂ flowing through the first lamp 141 and the second lamp 142 connected to the same transformer 12 is achieved. However, the current balancing effect is not achieved for the first and second lamps connected to the other transformers 12.

5 shows another conventional circuit for adjusting the current of multiple lamps using a differential ballast. This embodiment is illustrated by two lamps. The two lamps 31 and 31 are shunt connected. The high voltage ends of the two lamps 31 and 31 are connected to the AC power supply 10 via a differential stabilizer 39. This differential stabilizing element 39 can generate a correction voltage in proportion to a mismatch between the currents I ₃₁ and I ₃₂ of the lamps 31 and 32. This correction voltage may be superimposed to the common drive voltage. The corrected driving voltage can be evenly distributed by adjusting the currents I ₃₁ and I ₃₂ of the lamps 31 and 32 as appropriate. While such a circuit can certainly make the current of the lamp the same, its structure generally includes a magnetic coil and a coil support of a particular shape. These magnetic coils and coil supports are not standardized products, which is inconvenient for material and cost control.

6 shows another conventional circuit for adjusting the current of a plurality of lamps using a differential ballast. The plurality of differential stabilizing elements T1, T2, T3, T4, T5, T6, and T7 are connected to the AC power supply 10 in a tree structure. The current is bypassed to a plurality of lamps L1, L2, L3, L4, L5, L6, L7, L8 based on the hierarchy and bypass principles, to achieve current balance. Since this principle is the same as that described in FIG. 5, it is not described herein any further.

The conventional circuit for the adjustment of lamp current has a general drawback that can be used only for the current balance between two lamps, but not for the current balance of odd lamps. Furthermore, as shown in FIG. 6, the inductance on the coil of each stage must be different, and this circuit can be used only for even lamps.

It is an object of the present invention to provide a lamp rod-sharing circuit in which a winding coil of one side of a plurality of transformers is connected to a plurality of lamps, and the winding coils of the other side of the transformer are connected in series with each other to form a closed loop. The same current flows through the winding coils connected in series with each other to form a closed loop. Through the electromagnetic induction characteristic of the transformer, the same operating current is generated in the lamp connected to the winding coil on the other side of the transformer.

In one embodiment of the invention, one end of each of the plurality of lamps is connected to a power source, each other end of the lamps is connected to a winding coil on one side of the plurality of transformers, and the winding coils on the other side of the transformer are connected in series with each other. To form a closed loop. Thus, the power supply can provide the same operating current for the lamp.

In another embodiment of the present invention, one end of each of the plurality of lamps is interconnected, and each other end of the lamps is connected to each one end of the winding coil on one side of the plurality of transformers, and the winding coils on this side of the transformer are connected. Each other end is connected to a power supply, and the winding coils on the other side of the transformer are connected in series with each other to form a closed loop. Thus, the power supply can provide the same operating current for the lamp.

In another embodiment of the present invention, one end of each of the plurality of lamps is connected to each one end of the winding coil on one side of the plurality of transformers in the first set of transformers, and at this side of the transformer in the first set of transformers. Each other end of the winding coil is connected to a first power source, and in the first set of transformers, the winding coils on the other side of the transformer are connected in series to each other to form a closed loop, and each other end of the lamp is connected to the second set of transformers. One end of each of the winding coils on one side of the plurality of transformers, each end of the winding coils on this side of the transformer in the second set of transformers is connected to a second power source, and the other side of the transformer in the second set of transformers. The winding coils are connected in series with each other to form a closed loop. Thus, the first power supply and the second power supply can provide the same operating current for the lamp.

The present invention takes advantage of the electromagnetic induction characteristics of the transformer. Through a closed loop formed by connecting the winding coils on one side of the transformer in series, the same current flows through the winding coils on this side, providing the same operating current for the lamps connected to the winding coils on the other side of the transformer. Moreover, the present invention can be used for the balance and uniformity of the current of odd or even lamps.

Various objects and advantages of the invention will be more readily understood from the following detailed description taken in conjunction with the accompanying drawings.

7 is a circuit diagram of two lamp load-sharing circuits of the present invention. This circuit comprises two lamps L1 and L2. One end of each of the two lamps L1 and L2 is connected to a power supply Vsec, and each other end of the lamps L1 and L2 is a winding coil L1 _P and L2 on one side of the two transformers T1 and T2. _P ) Is connected to. The winding coils L1 _S and L2 _S on the other side of the transformers T1 and T2 are connected in series with each other to form a closed loop. Through the closed loop formed by connecting the electromagnetic induction characteristics of the transformers T1 and T2 and the winding coils L1 _S and L2 _{S on} one side of the transformers T1 and T2 in series, the same current ix is generated by the transformer T1. And winding coils L1 _S and L2 _S on this side of T2. Thus, the power supply Vsec provides the same operating current i ₁ and i ₂ for the lamps L1 and L2. The rotation speeds of the winding coils on the two sides of the transformers T1 and T2 are the same, and the transformers T1 and T2 are equivalently balanced transformers. The lamps L1 and L2 may be cold cathode fluorescent lamps CCFL or external electrode fluorescent lamps EEFL.

Referring back to FIG. 7, transformers T1 and T2 are balanced transformers. The rotation speeds of the winding coils on the two sides of the transformer T1 are the same (N1 _P = N1 _S ). The rotation speeds of the winding coils on the two sides of the transformer T2 are the same (N2 _P = N2 _S ). Thus, the equivalent inductance on the winding coils on the two sides of the transformer is as follows:

L1 _P = L1 _S ; L2 _P = L2 _S (1)

Where L1 _P and L1 _S represent the equivalent inductance on the winding coil of the transformer T1, respectively, and L2 _P and L2 _S are Each represents the equivalent inductance on the winding coil of transformer T2. If the speeds of the transformers T1 and T2 are also the same, then:

L1 _P = L1 _S = L2 _P = L2 _S (2)

Since the equivalent inductance on the winding coils of transformers T1 and T2 are the same, the mutual inductances M1 and M2 generated between the winding coils of two sides of transformers T1 and T2 are approximately:

M1 = M2 (3)

Here, M1 is mutual inductance between the winding coils of two sides of transformer T1, and M2 is mutual inductance between the winding coils of two sides of transformer T2.

Referring back to FIG. 7, the voltage of the power supply Vsec includes the internal resistances Z1 and Z2 of the lamps L1 and L2, the operating currents i ₁ and i ₂ , and a winding of one side of the transformers T1 and T2. Mutual inductance M1 generated between the equivalent inductance L1 _P and L2 _P of the coil and the winding coils of two sides of the transformers T1 and T2 And M2) and current ix flowing through winding coils L1 _S and L2 _S on the other side of transformers T1 and T2:

Vsec = (Z1 + jωL1 _P ) · i ₁ -ix (jωM1) (4)

Vsec = (Z2 + jωL2 _P ) ・ i ₂ -ix (jωM2) (5)

Is the operating angular frequency of the power supply Vsec.

From equations (4) and (5), the following is obtained:

(Z1 + jωL1 _P ) · i ₁ -ix (jωM1) = (Z2 + jωL2 _P ) · i ₂ -ix (jωM2) (6)

After rearranging equation (6), the operating current i ₁ can be calculated by the following equation:

Referring to equation (7), the mutual inductance M1 generated between the winding coils of the two sides of the transformers T1 and T2. And M2) are the same (M1 = M2), the operating current i ₁ in equation (7) can be expressed as:

By rearranging equations (2) and (8), the following equations can be obtained:

Equation (9) from the operating current (i ₁₎ of the lamp when the same internal resistance (Z1 and Z2) of (L1 and L2), lamp (L1) is the same as the operating current (i ₂₎ of the lamp (L2) It can be seen (i ₁ = i ₂ ). If the internal resistances Z1 and Z2 of the lamps L1 and L2 are not equal, but much smaller than jωL1 _P , the operating currents i ₁ and i ₂ are nearly equal (i ₁ = i ₂ ).

As mentioned above, the present invention takes advantage of the electromagnetic inductive characteristics of the transformer. Through the closed loop formed by connecting the winding coils on one side of the transformers T1 and T2 in series, the same current ix flows through the winding coils on this side of the transformers T1 and T2, thereby transforming the transformers T1 and T2. The same operating current i ₁ is provided to the lamps L1 and L2 connected to the winding coils on the other side of the circuit, so that the balance and uniformity of the operating currents i ₁ and i ₂ of the lamps L1 and L2 are achieved. do. Moreover, the present invention can improve the problem that different inductances are generated on the coils at each stage of the conventional circuit, which are only applicable to even lamps. The invention can be used for odd or even lamps.

8 is a circuit diagram of three lamp load-sharing circuits of the present invention. This circuit comprises three lamps L1, L2, L3. One end of each of the three lamps L1, L2, L3 is connected to a power supply Vsec, and each other end of the lamps L1, L2, L3 is wound on one side of the three transformers T1, T2, T3. It is connected to the coils L1 _P , L2 _P , L3 _P. The winding coils L1 _S , L2 _S , L3 _{S on} the other side of the transformers T1, T2, T3 are connected in series to each other to form a closed loop. Through the closed loop formed by connecting the electromagnetic induction characteristics of the transformers T1, T2, T3 and the winding coils L1 _S , L2 _S , L3 _{S on} one side of the transformers T1, T2, T3 in series, the same current (ix) flows through winding coils L1 _S , L2 _S , L3 _{S on} this side of transformers T1, T2, T3. Thus, the power supply Vsec provides the same operating current i ₁ , i ₂ , i ₃ for the lamps L 1, L 2, L ₃ . The rotational speeds of the winding coils on the two sides of the transformers T1, T2 and T3 are the same, and the transformers T1, T2 and T3 are equivalently balanced transformers. The lamps L1, L2, and L3 may be cold cathode fluorescent lamps CCFL or external electrode fluorescent lamps EEFL.

Referring again to FIG. 8, the principles and inductions dealing with the equations of the three lamp load-sharing circuits of FIG. 8 are the same as for the two lamp load-sharing circuits of FIG. 7 and will not be described any further. The present invention can ameliorate the problem that different inductances are created on the coils at each stage of a conventional circuit, which are only applicable to even lamps. The present invention can be used for odd or even lamps to provide uniformity and balance of current.

9 is a circuit diagram of two other lamp load-sharing circuits of the present invention. This circuit comprises two lamps L1, L2. One end of each of the lamps L1, L2 is connected to the reference terminal G, and each other end of the lamps L1, L2 is a winding coil L1 _P , L2 _P of one side of the two transformers T1, T2. Is connected to a power supply (Vsec). The winding coils L1 _S and L2 _{S on} the other side of the transformers T1 and T2 are connected in series with each other to form a closed loop. Through the closed loop formed by connecting the electromagnetic induction characteristics of the transformers T1 and T2 and the winding coils L1 _S and L2 _{S on} one side of the transformers T1 and T2 in series, the same current ix is generated by the transformer T1. Flows through winding coils L1 _S and L2 _S on this side of T2. Thus, the power supply Vsec provides the same operating current i ₁ , i ₂ for the lamps L1, L2. The number of turns of the winding coils on the two sides of the transformers T1 and T2 is the same, and the transformers T1 and T2 are equivalently balanced transformers. The lamps L1 and L2 may be cold cathode fluorescent lamps CCFL or external electrode fluorescent lamps EEFL.

10 is a circuit diagram of three other lamp load-sharing circuits of the present invention. This circuit comprises three lamps L1, L2, L3. One end of each of the three lamps L1, L2, L3 is connected to the reference terminal G, and each other end of the lamps L1, L2, L3 is connected to one side of the three transformers T1, T2, T3. through the winding coils (L1 _{P, P} L2, L3 _P) it is connected to the power supply (Vsec). The winding coils L1 _S , L2 _S , L3 _{S on} the other side of the transformers T1, T2, T3 are connected in series to each other to form a closed loop. Through the closed loop formed by connecting the electromagnetic induction characteristics of the transformers T1, T2, T3 and the winding coils L1 _S , L2 _S , L3 _{S on} one side of the transformers T1, T2, T3 in series, the same current (ix) flows through winding coils L1 _S , L2 _S , L3 _{S on} this side of transformers T1, T2, T3. Thus, the power supply Vsec provides the same operating current i ₁ , i ₂ , i ₃ for the lamps L 1, L 2, L ₃ . The rotational speeds of the winding coils on the two sides of the transformers T1, T2 and T3 are the same, and the transformers T1, T2 and T3 are equivalently balanced transformers. The lamps L1, L2, and L3 may be cold cathode fluorescent lamps CCFL or external electrode fluorescent lamps EEFL.

Referring back to FIGS. 9 and 10, the principles and inductions dealing with the equations of the load-sharing circuits of FIGS. 9 and 10 are the same as for the two ramp load-sharing circuits of FIG. 7 and will not be described any further. The present invention can ameliorate the problem that different inductances are created on the coils at each stage of a conventional circuit, which are only applicable to even lamps. The present invention can be used for odd or even lamps to provide uniformity and balance of current.

11 is a circuit diagram of multiple lamp load-sharing circuits of the present invention. This circuit is based on the principle of a floating circuit that turns on the lamp by inputting an inverting voltage at the two ends of the lamp. This embodiment is illustrated by three lamps. Each of the three lamps L1, L2, L3 has two ends. One end of each of the three lamps L1, L2, L3 is connected to the first power supply Vsec1 through a winding coil of one side of the three transformers T1, T2, T3. The winding coils on the other side of the transformers T1, T2, and T3 are connected in series to each other to form a closed loop. Each other end of the lamps L1, L2, L3 is connected to the second power supply Vsec2 via a winding coil on one side of the three transformers T4, T5, T6. The winding coils on the other side of the transformers T4, T5, and T6 are connected in series to each other to form a closed loop. Transformers T1, T2 and T3 form a first set of transformers, and transformers T4, T5 and T6 form a second set of transformers.

Electromagnetic induction characteristics of transformers T1, T2, T3, T4, T5, T6, and winding coils L1 _S , L2 _S , L3 _S , L4 on one side of transformers T1, T2, T3, T4, T5, T6 Through a closed loop formed by connecting _S , L5 _S and L6 _S in series, the same currents ix1 and ix2 are connected to the winding coil L1 _S on this side of the transformers T1, T2, T3, T4, T5, T6. , L2 _S , L3 _S , L4 _S , L5 _S , L6 _S ). Thus, the first power supply Vsec1 and the second power supply Vsec2 provide the same operating current i ₁ , i ₂ , i ₃ for the lamps L 1, L 2, L ₃ . The number of turns of the winding coils on the two sides of the transformers T1, T2, T3, T4, T5, and T6 is the same, and the transformers T1, T2, T3, T4, T5, and T6 are equivalently balanced transformers. The lamps L1, L2, and L3 may be cold cathode fluorescent lamps CCFL or external electrode fluorescent lamps EEFL.

The above is illustrated by two and three lamps. If the present invention is applied to other numbers of lamps, the circuit connection scheme can be modified to increase or decrease the number of lamps. Moreover, the circuit principle is as described above.

Referring again to FIG. 11, the principles and derivations that address the equation of the load-sharing circuit of FIG. 11 are the same as for the load-sharing circuit of FIGS. 7 and 8, and will not be described any further. The present invention can ameliorate the problem that different inductances are created on the coils at each stage of a conventional circuit, which are only applicable to even lamps. The present invention can be used for odd or even lamps to provide uniformity and balance of current.

In summary, the present invention proposes a lamp load-sharing circuit, which uses the electromagnetic induction characteristics of the transformer and a closed loop formed by connecting the winding coils on one side of the transformer in series, so that the same current is generated by the transformer. It flows through the winding coil of the side. Thus, the same operating current is provided to the lamp connected to the winding coil on the other side of the transformer. The present invention can ameliorate the problem that different inductances are created on the coils at each stage of a conventional circuit, which are only applicable to even lamps. The present invention can be used in odd or even lamps to achieve uniformity and balance of current.

Although the invention has been described with reference to the preferred embodiments, it is understood that the invention is not limited to the details thereof. Various alternatives and modifications have been presented in the foregoing description, and others may occur to those skilled in the art. Thus, all such substitutions and modifications may be made within the scope of the invention as defined in the appended claims.

1 is a conventional simplified circuit diagram for adjusting the current of two lamps using a differential ballast.

2 is an equivalent magnetic circuit diagram of the transformer of FIG.

3 is a diagram illustrating how the equivalent magnetic circuit of FIG. 1 is connected to a lamp.

4 is another conventional simplified circuit diagram for adjusting the current of a plurality of lamps using a differential ballast.

5 is another conventional simplified circuit diagram for adjusting the current of two lamps using a differential ballast.

6 is another conventional simplified circuit diagram for adjusting the current of multiple lamps using a differential ballast.

7 is a circuit diagram of two lamp load-sharing circuits of the present invention.

8 is a circuit diagram of three lamp load-sharing circuits of the present invention.

9 is a circuit diagram of two other lamp load-sharing circuits of the present invention.

10 is a circuit diagram of three other lamp load-sharing circuits of the present invention.

11 is a circuit diagram of a plurality of lamp load-sharing circuits of the present invention.

Claims (12)

In the ramp load-sharing circuit, A plurality of lamps, one end of each lamp being connected to a power source, A plurality of transformers, wherein the winding coils on one side of the transformer are connected to each other end of the lamp, and the winding coils on the other side have the plurality of transformers connected in series to each other to form a closed loop, And the power supply provides the same operating current for the lamp. The method of claim 1, And the number of lamps is even or odd. The method of claim 1, And the lamp is a cold cathode fluorescent lamp or an external electrode fluorescent lamp. The method of claim 1, And the winding coil of the transformer has the same rotational speed. In the ramp load-sharing circuit, A plurality of lamps, one end of each lamp being connected to one end of the other lamps; And As a plurality of transformers, one end of each winding coil on one side is connected to each other end of the lamp, the other end of each winding coil on the side is connected to a power supply, and the winding coils on the other side are connected in series to each other to form a closed loop. By having the plurality of transformers to form, And the power supply provides the same operating current for the lamp. The method of claim 5, wherein And the number of lamps is even or odd. The method of claim 5, wherein And the lamp is a cold cathode fluorescent lamp or an external electrode fluorescent lamp. The method of claim 5, wherein And the winding coil of the transformer has the same rotational speed. In the ramp load-sharing circuit, A plurality of lamps each having two ends; A first set of transformers having a plurality of transformers, wherein one end of each winding coil on one side of the transformer is connected to each one end of the lamp, and the other end of the winding coil on the side of the transformer is a first power source. A first set of transformers connected to the winding coils on the other side of the transformer, connected in series with each other to form a closed loop; And A second set of transformers having a plurality of transformers, wherein one end of each winding coil on one side of the transformer is connected to each one end of the lamp, and each other end of the winding coil on the side of the transformer is a second power source. Wherein the winding coils of the other side of the transformer are connected to each other in series to form a closed loop, And the first and second power supplies provide the same operating current for the lamp. The method of claim 9, And the number of lamps is even or odd. The method of claim 9, And the lamp is a cold cathode fluorescent lamp or an external electrode fluorescent lamp. The method of claim 9, And the winding coil of the transformer has the same rotational speed.