KR100956386B1 - Current balance circuit for lamp operated by interver - Google Patents

Abstract

PURPOSE: A current balance circuit for a lamp driven by an inverter is provided to secure uniform brightness of a display panel by maintaining the balance of the current flowing in first and second lamps. CONSTITUTION: A second lamp(230) has higher impedance higher than a first lamp(220). First and second lamps are connected in parallel to the inverter. A current equalizing unit includes first and second current equalizers(250,260). The first current equalizer is connected in series to the first lamp. The second current equalizer is connected in series to the second lamp and a first resistor, a first switch, and a fourth switch. The first resistor is connected in series to the second lamp. The first switch is connected in series to the first lamp. The fourth switch is connected in parallel to the first resistor.

Description

Current balance circuit for lamp operated by interver

The present invention relates to a current balancing circuit for a lamp driven by an inverter. More specifically, when a positive voltage is applied to two lamps having different impedances, including a current equalizing unit, the resistance value of the first resistor inside the current equalizing unit is increased. The current flowing through the two lamps is controlled to be equal to each other, and when a negative voltage is applied to the two lamps, the first switch inside the current equalizer is turned on so that the current flows from the lamp with the small impedance to the lamp with the large impedance. It is a current balancing circuit for lamps driven by an inverter that controls the flowing currents to be equal to each other to ensure cost reduction, system stabilization and uniform brightness of the display panel.

Today, with the development of display technology, liquid crystal display (LCD) monitors are increasingly used in computer or other display devices. Compared with Cathode-Ray Tube (CRT) monitors, LCD monitors have the advantage of slimmer profile and less flicker. LCD monitors have fluorescent lamps that are driven at high voltages for backlight systems requiring a backlight module.

In addition, an inverter with a driving circuit is used to drive a fluorescent lamp, which has a high-voltage transformer, which generates a high AC output voltage with a low AC input voltage to the lamp constituting the LCD panel. It serves to supply voltage.

On the other hand, as the LCD TV or monitor market enters maturity, the price of backlight unit-related components is falling as sales prices fall. Therefore, due to the price pressure of the components related to the backlight unit, efforts to reduce the number of parts and the unit price have been continued.

As an effort for this, conventionally, one transformer is driven to supply power to one lamp, but recently, a small number of transformers are driven to connect lamps in parallel to supply power to several lamps.

As described above, it is a recent trend to light several lamps in parallel, but when connecting lamps in parallel, a problem arises in that the luminance of each lamp becomes uneven because the magnitude of current flowing through each lamp is different.

Therefore, there is a continuous study on a method of controlling the current deviation of each lamp to make the brightness of each lamp uniform.

Hereinafter, a lamp current balancing circuit according to a conventional method will be described in more detail with reference to the accompanying drawings.

1 is a current balancing circuit 100 for a lamp in a conventional manner. The lamp current balancing circuit 100 includes an inverter 110, a transformer 120, a first lamp 130, a second lamp 140, a third lamp 150, a fourth lamp 160, and a first current. A balanced transformer 170, and a second current balanced transformer 180.

The lamp current balancing circuit 100 according to the conventional scheme includes a first current balancing transformer 170 for balancing the current flowing in the first lamp 130 and the second lamp 140, and the third lamp ( 150 and a second current balance transformer 180 to balance the current flowing through the fourth lamp 160.

That is, according to the conventional method, as the number of lamps to be driven increases, the number of current balancing transformers for balancing current flowing through the lamps increases. Since transformers are expensive and bulky compared to other devices in the circuit, the increase in the number of transformers has the disadvantage of causing an increase in the cost and volume of the current balancing circuit for the lamp.

Accordingly, the present invention has been made to solve the conventional problems as described above. When a positive voltage is applied to two lamps having different impedances including the current equalizer, the resistance of the first resistor inside the current equalizer is increased. When the current flowing through the lamp is controlled to be equal to each other, and when a negative voltage is applied to the two lamps, the current flowing through the two lamps is conducted by conducting a first switch inside the current equalizing unit so that current flows from the lamp with the small impedance to the lamp with the large impedance. It is an object of the present invention to provide a current balancing circuit for a lamp driven by an inverter, which is controlled to be equal to each other, thereby reducing cost, stabilizing a system, and ensuring uniform brightness of a display panel.

As a technical configuration for achieving the above object, a current balancing circuit for a lamp driven by an inverter according to the present invention comprises: a first lamp; A second lamp having a smaller impedance than the first lamp; And a current equalizer including a first current equalizer and a second current equalizer, wherein the first lamp and the second lamp are connected in parallel to the inverter, and the first current equalizer is connected to the first lamp. Connected in series, the second current equalizer is connected in series with the second lamp, the second current equalizer includes a first resistor and a first switch and a positive voltage is applied to the first lamp and the second lamp. When applied, increasing the resistance of the first resistor to reduce the current flowing through the second lamp; When a negative voltage is applied to the first lamp and the second lamp, the first switch is turned on so that a part of the current flowing from the second current equalizer to the second lamp flows to the first current equalizer. It is characterized by reducing the current flowing in the second lamp.

The current equalizer may include: a voltage divider configured to distribute a voltage of an input voltage terminal including a second resistor and a third resistor respectively connected to a first node; And a fourth resistor and a fifth resistor positioned between the first current equalizer and the second current equalizer, wherein the first node is positioned between the fourth resistor and the fifth resistor. can do.

The first current equalizer may include: a sixth resistor having one end connected to a second node to which the first lamp is connected and the other end connected to a third node; A seventh resistor having one end connected to the third node and the other end connected to ground; A first diode having an anode connected to said second node; A second switch connected to an anode of the first diode, the third node, and the fourth resistor; A third switch, one end of which is connected to the third node, the other end of which is connected between the second lamp and the second current equalizing unit; and an eighth end of which is connected to the third switch, and the other end of which is connected to ground Resistance; may be characterized in that it comprises a.

The second current equalizer may include: the first resistor having one end connected to a fourth node to which the second lamp is connected and the other end connected to a fifth node; A ninth resistor having one end connected to the fifth node and the other end grounded; A second diode having an anode connected to the fourth node; A fourth switch connected to the cathode of the second diode, the fifth node, and the fifth resistor; And a first switch connected to the second node and the fifth node; and a tenth resistor having one end connected to the fourth switch and the other end connected to ground.

Preferably, the first switch, the second switch, the third switch, and the fourth switch are any one of a bipolar junction transistor (BJT), a field effect transistor (FET), and a control integrated circuit (IC). It may be characterized by.

More preferably, the second switch and the fourth switch may be an npn transistor, and the first switch and the third switch may be a pnp transistor.

Here, the current balancing circuit for the lamp driven by the inverter includes: a third lamp and a fourth lamp connected in parallel with the inverter; Another current equalizer including a third current equalizer and a fourth current equalizer; And a transformer including a first primary winding, a first secondary winding, and a second secondary winding, wherein the first primary winding is connected to an inverter, and the first secondary winding is connected to the second lamp and the A second secondary winding is connected to the first lamp and the third lamp, the third current equalizer is connected in series with the third lamp, and the fourth current equalizer is connected to the fourth lamp. When the fourth current equalizer includes an eleventh resistor and a fifth switch and is connected in series with the fourth lamp and a positive voltage is applied to the third lamp and the fourth lamp, The resistance of the eleventh resistor is increased to decrease the current flowing in the fourth lamp, and when a negative voltage is applied to the third lamp and the fourth lamp, the fourth switch is turned on to conduct the fourth current. Equalization The flow from the part of the current flowing into the fourth ramp portion and the third current equalization to reduce the current flowing through the fourth ramp can be characterized.

The current balancing circuit for a lamp driven by the inverter according to the present invention includes a current equalizing unit and when a positive voltage is applied to two lamps having different impedances, the current flowing through the two lamps is increased by increasing the resistance value of the first resistor inside the current equalizing unit. Are controlled to be equal to each other, and when a negative voltage is applied to the two lamps, the current flowing through the two lamps is equal to each other by conducting a first switch inside the current equalizer so that current flows from the lamp with the small impedance to the lamp with the large impedance. Controls provide a current balancing circuit for lamps driven by an inverter that ensures cost reduction, system stabilization and uniform brightness of the display panel.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Preferably, the first switch 265, the second switch 254, the third switch 255, and the fourth switch 264 of FIG. 4 may include a bipolar junction transistor (BJT), a field effect transistor (FET), And an integrated circuit (IC), and more preferably, the second switch 254 and the fourth switch 264 may be npn transistors, and the first switch 265 and the third switch. 255 may be a pnp transistor.

In particular, in the following exemplary embodiment, the case where the second switch 254 and the fourth switch 264 are npn transistors, and the first switch 265 and the third switch 255 are pnp transistors will be described.

2 is a circuit diagram of a lamp current balancing circuit 200 according to an embodiment of the present invention. The lamp current balancing circuit 200 includes a current equalizer including an inverter 210, a first lamp 220, a second lamp 230, a first current equalizer 250, and a second current equalizer 260. The unit 240 is included. It should be noted that the first lamp 220 and the second lamp 230 may be electrically modeled as a resistor. The first lamp 220 and the second lamp 230 are connected to the inverter 210 in parallel.

Ideally, the impedances of the first lamp 220 and the second lamp 230 are equal to each other, but there are actually differences in impedance. Here, it is assumed that the impedance of the first lamp 220 is greater than the impedance of the second lamp 230.

The current equalizer 240 includes a first current equalizer 250 connected in series with the first lamp 220 and a second current equalizer 260 connected in series with the second lamp 230. The second current equalizer 260 includes a first resistor (not shown) and a first switch (not shown).

Since the second lamp 230 has a smaller impedance than the first lamp 220, more current flows in the second lamp 230 than the current flowing in the first lamp 220. In this case, the principle of equalizing the current flowing through the first lamp 220 and the second lamp 230 by the current equalizer 240 is as follows.

The inverter 210 supplies a voltage in the form of alternating current (AC) to the first lamp 220 and the second lamp 230. When the positive voltage is applied to the first lamp 220 and the second lamp 230, the second current equalizer 260 increases the resistance value of the first resistor to reduce the current flowing in the second lamp 230. Let's do it. When a negative voltage is applied to the first lamp 220 and the second lamp 230, a portion of the current flowing from the second current equalizer 260 to the second lamp 230 is conducted by conducting the first switch. The current flowing through the second lamp 230 is reduced by flowing through the first current equalizer 250 to the first lamp 220.

FIG. 3 is a circuit diagram of a lamp current balancing circuit 300 driven by an inverter in which a voltage divider 270 is added to the circuit of FIG. 2.

The current equalizer 240 may further include a voltage divider 270, a fourth resistor 274, and a fifth resistor 275.

The voltage divider 270 includes a voltage input terminal 271, a second resistor 272, and a third resistor 273, and the second resistor 272 and the third resistor 273 are in series with each other. Is connected. The second resistor 272 and the third resistor 273 are connected to the first node 276.

The voltage divider 270 provides a reference voltage to the first current equalizer 250 and the second current equalizer 260 through the fourth resistor 274 and the fifth resistor 275 connected to the first node 276. Serves to supply In this case, the fourth resistor 274 and the fifth resistor 275 electrically separate the first current equalizer 250 and the second current equalizer 260.

4 is a circuit diagram of a lamp current balancing circuit 400 driven by an inverter showing the internal structure of the first current equalizer 250 and the second current equalizer 260 in the circuit of FIG. 3.

The first current equalizer 250 of the lamp current balancing circuit 400 driven by the inverter of FIG. 4 includes a sixth resistor 257, a seventh resistor 258, an eighth resistor 253, and a second switch ( 254, a third switch 255, and a first diode 256.

Meanwhile, the second current equalizer 260 may include a first resistor 261, a ninth resistor 262, a tenth resistor 263, a first switch 265, a fourth switch 264, and a second diode. (266).

Connection relations and operating principles between the respective components of the lamp current balancing circuit 400 driven by the inverter of FIG. 4 will be described below.

FIG. 5 shows a lamp current driven by an inverter in which the second switch 254 and the fourth switch 264 are npn transistors, and the first switch 265 and the third switch 255 are pnp transistors in the circuit of FIG. 4. A circuit diagram of the balanced circuit 500 is shown.

An internal structure of the first current equalizer 250 of FIG. 5 is as follows.

The sixth resistor 257 has one end connected to a second node (not shown) to which the first lamp 220 is connected, and the other end is connected to a third node (not shown). The second node is a node to which the first lamp 220, the first diode 256, and the sixth resistor 257 are connected, and the third node is the sixth resistor 257, the seventh resistor 258, and the third node. It is a node to which the second switch 254 and the third switch 255 are connected. One end of the seventh resistor 258 is connected to the third node, and the other end thereof is connected to the ground.

In addition, the first diode 256 has an anode connected to the second node and a cathode connected to the second switch 254. The second switch 254 is connected to the cathode, the third node, and the fourth resistor 274 of the first diode 256. The third switch 255 is connected between the third node and the second lamp 230 and the second current equalizer 260. One end of the eighth resistor 253 is connected to the third switch 255, and the other end thereof is connected to the ground.

Next, the internal structure of the second current equalizer 260 of FIG. 5 is as follows.

One end of the first resistor 261 is connected to a fourth node (not shown) to which the second lamp 230 is connected, and the other end thereof is connected to a fifth node (not shown). Here, the fourth node is a node to which the second lamp 230, the anode of the second diode 266, and the first resistor 261 are connected, and the fifth node is the first switch 265 and the fourth switch 264. , The first resistor 261 and the ninth resistor 262 are connected to each other. One end of the ninth resistor 262 is connected to the fifth node, and the other end thereof is connected to the ground.

In addition, the second diode 266 has an anode connected to the fourth node and a cathode connected to the fourth switch 264. The fourth switch 264 is connected to the cathode and the fifth node of the second diode 266 and the fifth resistor 275. The first switch 265 is connected to the fifth node and the second node of the first current equalizer 250. One end of the tenth resistor 263 is connected to the first switch 265, and the other end thereof is connected to the ground.

The operation principle of the current balancing circuit 500 for the lamp driven by the inverter is as follows.

When a positive voltage is applied to the first lamp 220 and the second lamp 230, more current flows in the second lamp 230 as described above. This means that more current flows in the ninth resistor 262 than the seventh resistor 258, so that the voltage level of the fifth node is greater than the voltage level of the third node.

The base of the fourth switch 264, which is an npn transistor, is connected to the first node 276 through a fifth resistor 275 to receive a reference voltage from the voltage divider 270. As described above, when the voltage level of the fifth node 268 rises, the voltage difference between the base and the emitter of the fourth switch 264, which is the npn transistor, becomes small, and the fourth switch 264, which is the npn transistor, is cut off.

When the fourth switch 264 is blocked, the current flowing through the second lamp 230 no longer flows through the fourth switch 264 which is an npn transistor, but instead flows through the first resistor 261.

That is, since the same effect as the second lamp 230 and the first resistor 261 is connected in series occurs, the magnitude of the current flowing through the second lamp 230 is reduced, so that the first lamp 220 It is in equilibrium with the current flowing through it.

When a negative voltage is applied to the first lamp 220 and the second lamp 230, more current flows in the second lamp 230 in the same principle as when the positive voltage is applied, and the direction of the current is The reverse is the case with a positive voltage applied. In this case, the second diode 266 prevents the reference voltage applied to the first node 276 from being applied to the collector of the fourth switch 264, which is an npn transistor, so that the second lamp 266 is connected from the first node 276. It prevents the current to flow through 230). In addition, more current flows through the ninth resistor 262 than the seventh resistor 258 by the same principle as when the positive voltage is applied to the first lamp 220 and the second lamp 230. The voltage level at the node will decrease.

As a result, the voltage difference between the emitter and the base of the first switch 265, which is a pnp transistor, becomes large, so that the first switch 265, which is a pnp transistor, becomes conductive. Accordingly, some of the current flowing from the ninth resistor 262 to the second lamp 230 through the first resistor 261 is the first current equalizer 250 through the first switch 265 which is a conductive pnp transistor. Will flow into. The current flowing into the first current equalizer 250 does not flow to the first switch 254 because of the first diode 256, but flows to the first lamp 220 so that the second lamp 230 and the first lamp 220 flow. The current flowing through) is in equilibrium.

That is, in the lamp current balancing circuit 500 driven by the inverter of FIG. 5, when a positive voltage is applied to the first lamp 220 and the second lamp 230, the fourth switch 264 and the first resistor, which are npn transistors, are applied. The current flowing through the first lamp 220 and the second lamp 230 through the 261 is controlled to be the same, and when a negative voltage is applied to the first lamp 220 and the second lamp 230, a pnp transistor is used. The first switch 265 is turned on so that a part of the current flowing to the second lamp 230 flows through the first current equalizer 250 to the first lamp 220 so that the currents flowing to each other are the same.

FIG. 6 is a circuit diagram of a lamp current balancing circuit 600 driven by an inverter in which a third lamp 620 and a fourth lamp 630 are added to the lamp current balancing circuit 200 driven by the inverter according to FIG. 2. It is shown.

The lamp current balancing circuit 600 driven by the inverter of FIG. 6 is a circuit for equalizing the current of four lamps with one inverter 210 to the lamp current balancing circuit 200 driven by the inverter of FIG. 2. The transformer 610, the third lamp 620, the fourth lamp 630, and another current equalizer 640 may be further included.

The transformer 610 includes a first primary winding 611, a first secondary winding 612, and a second secondary winding 613. In this case, the first primary winding 611 is connected to the inverter 210, and the first secondary winding 612 is connected to the second lamp 230 and the fourth lamp 630. In addition, the second secondary winding 613 is connected to the first lamp 220 and the third lamp 620.

Another current equalizer 640 includes a third current equalizer 650 and a fourth current equalizer 660.

The third current equalizer 650 is connected in series with the third lamp 620, and the fourth current equalizer 660 includes an eleventh resistor (not shown) and a fifth switch (not shown). When a positive voltage is applied to the third lamp 620 and the fourth lamp 630 by being connected in series with the lamp 630, the current flowing through the fourth lamp 630 is reduced by increasing the resistance of the eleventh resistor. When a negative voltage is applied to the third lamp 620 and the fourth lamp 630, a part of the current flowing from the fourth current equalizer 660 to the fourth lamp 630 by turning on the fifth switch is conducted. The current flowing through the fourth lamp 630 is reduced by flowing through the third current equalizer 650 to the third lamp 620.

That is, the third current equalizer 650 and the fourth current equalizer 660 have the same structure and function as the first current equalizer 250 and the second current equalizer 260.

Accordingly, another current equalizer 640 may further include a voltage divider 270, a fourth resistor 274, and a fifth resistor 275.

In addition, the third current equalizer 650 and the fourth current equalizer 660 of the other current equalizer 640 are respectively the first current equalizer 250 and the second current equalizer of FIGS. 4 and 5. It may be implemented the same as 260.

In addition, although only a circuit for equalizing the currents flowing through the four lamps is illustrated in FIG. 6, it will be apparent to those skilled in the art that a current balancing circuit of a larger number of lamps can be configured in the same manner.

In the above description, only the case where the second switch 254 and the fourth switch 264 are npn transistors, and the first switch 265 and the third switch 255 are pnp transistors, the first switch 265, It will be apparent to those skilled in the art that the second switch 254, the third switch 255, and the fourth switch 264 may be a device such as a field effect transistor (FET) or a control IC.

FIG. 7 is a graph showing a current (mA) flowing through the first lamp 220, the second lamp 230, the third lamp 620, and the fourth lamp 630 of FIG. 6 over time (ms). . Currents flowing through the first lamp 220, the second lamp 230, the third lamp 620, and the fourth lamp 630 are represented by I5, I6, I17, and I18, respectively. In addition, the horizontal axis shows time (ms), and the vertical axis shows the intensity (A) of a current.

 Comparing the value of the current flowing through each lamp at t1 = 30.3912 ms, the current flowing through the first lamp 220 and the second lamp 230 is in equilibrium with I5 = -7.26546mA and I6 = -7.3312mA. Able to know. In addition, it can be seen that the current flowing through the third lamp 620 and the fourth lamp 630 at I17 = 7.26526mA and I18 = 7.3312mA is also in equilibrium.

That is, it can be seen that the value of the current flowing through each lamp is balanced by the current balancing circuit 600 of the four lamps of FIG. 6.

By configuring the circuit as shown in FIGS. 2 to 6, the currents flowing through lamps having different impedances can be made the same without using a transformer. The cost is reduced and PCB size can be reduced by not using transformers, which are relatively expensive and bulky devices. In addition, it is possible to ensure the stabilization of the system and uniform brightness of the display panel.

It is intended that the invention not be limited by the foregoing embodiments and the accompanying drawings, but rather by the claims appended hereto. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

1 is a circuit diagram of a current balancing circuit for a lamp according to the prior art.

2 is a circuit diagram of a current balancing circuit for a lamp driven by an inverter according to an embodiment of the present invention.

FIG. 3 is a circuit diagram of a current balancing circuit for a lamp driven by an inverter in which a voltage divider is added to the circuit of FIG. 2.

FIG. 4 is a circuit diagram of a current balancing circuit for lamps driven by an inverter showing the internal structures of the first and second current equalizers in the circuit of FIG. 3.

5 is a circuit diagram of a current balancing circuit for a lamp driven by an inverter in which the second switch and the fourth switch are npn transistors, and the first switch and the third switch are pnp transistors in the circuit of FIG.

FIG. 6 is a circuit diagram of a lamp current balancing circuit driven by an inverter in which a third lamp and a fourth lamp are added to the lamp current balancing circuit driven by the inverter according to FIG. 2.

FIG. 7 is a graph showing the current flowing through the first lamp, the second lamp, the third lamp, and the fourth lamp of FIG. 6 with time;

[Description of Major Symbols in Drawing]

210: inverter 220: first lamp

230: second lamp 240: current equalizing unit

250: first current equalizer 253: eighth resistor

254: second switch 255: third switch

256: first diode 257: sixth resistor

258: seventh resistor 260: second current equalizer

261: first resistance 262: ninth resistance

263: tenth resistor 264: fourth switch

265: first switch 266: second diode

270: voltage divider 271: voltage input terminal

272: second resistance 273: third resistance

274: fourth resistor 275: fifth resistor

400: Current balancing circuit for lamp driven by inverter

Claims (7)

In the current balancing circuit for lamps driven by an inverter, A first lamp; A second lamp having a smaller impedance than the first lamp; And a current equalizer including a first current equalizer and a second current equalizer. The first lamp and the second lamp are connected in parallel to the inverter, The first current equalizer is connected in series with the first lamp, the second current equalizer is connected in series with the second lamp, The second current equalizer includes a first resistor connected in series to the second lamp, a first switch connected in series to the first lamp, and a fourth switch connected in parallel to the first resistor, wherein the first lamp And when the positive voltage is applied to the second lamp, blocking the fourth switch so that the current flowing in the second lamp flows to the first resistor to reduce the current flowing in the second lamp; When a negative voltage is applied to the first lamp and the second lamp, the first switch is turned on so that a part of the current generated by the negative voltage is conducted through the path generated by the first switch. A current balancing circuit for a lamp driven by an inverter which flows into one lamp to reduce a current flowing in the second lamp. The method of claim 1, The current equalizer is: A voltage divider configured to distribute the voltage of the input voltage terminal, each of the second resistor and a third resistor connected to the first node; Further comprising a fourth resistor and a fifth resistor located between the first current equalizer and the second current equalizer, And a current balancing circuit for a lamp driven by an inverter in which the first node is located between the fourth resistor and the fifth resistor. The method of claim 2, The first current equalizer is: A sixth resistor having one end connected to a second node to which the first lamp is connected and the other end connected to a third node; A seventh resistor having one end connected to the third node and the other end connected to ground; A first diode having an anode connected to said second node; A second switch connected to an anode of the first diode, the third node, and the fourth resistor; A third switch having one end connected to the third node and the other end connected between the second lamp and the second current equalizer; and An eighth resistor having one end connected to the third switch and the other end connected to ground; A current balancing circuit for a lamp driven by an inverter comprising a. The method of claim 3, wherein The second current equalizer is: The first resistor having one end connected to a fourth node to which the second lamp is connected and the other end connected to a fifth node; A ninth resistor having one end connected to the fifth node and the other end grounded; A second diode having an anode connected to the fourth node; A fourth switch connected to the cathode of the second diode, the fifth node, and the fifth resistor; The first switch connected to the second node and the fifth node; and A tenth resistor having one end connected to the first switch and the other end connected to ground; A current balancing circuit for a lamp driven by an inverter comprising a. The method of claim 4, wherein The first switch, the second switch, the third switch, and the fourth switch are driven by an inverter which is one of a Bipolar Junction Transistor (BJT), a Field Effect Transistor (FET), and a Control IC (Integrated Circuit). Current balancing circuit for lamps. The method of claim 5, And the second switch and the fourth switch are npn transistors, and the first switch and the third switch are pnp transistors. 7. The method according to any one of claims 1 to 6, The current balancing circuit for the lamp driven by the inverter is: Third and fourth lamps connected in parallel with the inverter; Another current equalizer including a third current equalizer and a fourth current equalizer; A transformer comprising a first primary winding, a first secondary winding, and a second secondary winding; More, The first primary winding is connected to the inverter, The first secondary winding is connected to the second lamp and the fourth lamp, The second secondary winding is connected to the first lamp and the third lamp, The third current equalizer is connected in series with the third lamp, the fourth current equalizer is connected in series with the fourth lamp, The fourth current equalizer includes an eleventh resistor connected in series to the fourth lamp, a fifth switch connected in series to the third lamp, and a sixth switch connected in parallel to the eleventh resistor, wherein the third lamp and When the positive voltage is applied to the fourth lamp, the sixth switch is cut off so that the current flowing in the fourth lamp flows to the eleventh resistor to reduce the current flowing in the fourth lamp, and the third lamp and When a negative voltage is applied to the fourth lamp, the fifth switch is turned on so that a part of the current generated by the negative voltage flows to the third lamp through a path generated by the fifth switch. And a lamp current balancing circuit driven by an inverter for reducing a current flowing in the fourth lamp.

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