KR20080081435A - Multi-channel inductor and led backlight multi driver using multi-channel inductor - Google Patents

Abstract

A multi-channel inductor and an LED(Light Emitting Diode) backlight multi-driver using the same are provided to maintain uniform brightness by constructing a single-colored LED with a plurality of arrays and correcting a lifetime difference due to a characteristic difference and deterioration of each of the LEDs. A multi-channel inductor includes a main coil(300) and at least one sub coil(301-303). The main coil is charged with energy and discharges the energy by being turned on and off at predetermined intervals by receiving power. At least one sub coil is sequentially charged with energy through electromotive force induced from the main coil by sequentially winding at least one winding around the same core as the main coil. The multi-channel inductor further includes a sensing coil for sensing an energy change of the main coil.

Description

Multi-channel inductor and LED backlight multi driver circuit using the same {Multi-Channel Inductor and LED backlight multi driver using Multi-Channel Inductor}

1 is a diagram illustrating a general LED backlight driving circuit using a boost converter.

2 is a block diagram of an LED backlight multi driving circuit according to an exemplary embodiment of the present invention.

3 is a diagram illustrating a structure of a multichannel inductor according to an exemplary embodiment of the present invention.

4A is an internal perspective view of a multichannel inductor having a ferrite bobbin as a core according to an embodiment of the present invention.

4B is an internal perspective view of a multichannel inductor using a bar core in accordance with an embodiment of the present invention.

5 is a diagram illustrating a structure of a sensing multichannel inductor according to an exemplary embodiment of the present invention.

6 is a diagram illustrating an LED backlight multi driver circuit employing the multi-channel inductor according to an exemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating an LED backlight multi driver circuit employing the sensing multichannel inductor according to an exemplary embodiment of the present invention.

* Description of the symbols for the main parts of the drawings *

202: switching controller 204: multichannel inductor

206: feedback resistor 208: FET

214a: LED first array 216: first constant current adjusting unit

218: constant current controller 300: main coil

301: first dependent coil 302: second dependent coil

303: Nth dependent coil 305: Sensing coil

The present invention relates to a multi-channel inductor having a plurality of coils and an LED backlight multi driving circuit using the same.

In general, the capacitor input type rectifier circuit, which is widely used as a DC power supply for various electronic devices, has low cost and simple configuration, which does not require complicated control, and has excellent characteristics such as output ripple due to the increase of capacitor capacity. Since many problems such as low power factor and distortion of the input current are greatly distorted, the improvement of the characteristics has been desired. Therefore, a step-up converter that connects a chopper circuit to a rectifier circuit to control the input current in the form of a sine wave to improve waveforms and to increase the input power factor is used.

On the other hand, the boost converter is used in the LED backlight driving circuit to light up the LED backlight of the liquid crystal panel such as the TFT-LCD panel and to stabilize the lighting of the backlight. An example of a boost converter serving as a hard switching chopper circuit in the LED backlight driving circuit is illustrated in FIG. 1. Referring to FIG. 1, when power is supplied to the LED backlight 114, the FET 106 is opened (off) to supply voltage to the LED backlight 114, and conversely, power is not supplied to the LED backlight 114. If not, the FET 106 is shorted (on) so that no voltage is supplied to the LED backlight 114 as a result.

That is, the DC power supply 100 introduced from the outside flows current from the inductor 104 to the FET 106 while the switching controller 102 turns on the FET 106 to allow energy to be charged in the inductor. In addition, the switching controller 102 senses the voltage of the feedback resistor 108 and turns off the FET 106 when the set voltage is reached and the energy of the inductor 104 passes through the capacitor 110 to the capacitor. At the same time as charging 112, and supplies power to the LED backlight 114, the switching controller 102 senses the output voltage and the drive to turn on the FET 106 again when it is lower than the set voltage Repeat the cycle.

A boost converter for driving the LED backlight is used as described above, and the LED backlight having a combination of a plurality of LED arrays in which the LEDs are connected in series or in parallel according to the application method of the LED is turned on by applying power through the boost converter. Done.

Therefore, in the related art, a plurality of boost type converters that boost the voltage according to the connection quantity and the input voltage of the LED are required. In particular, when the LED backlight is configured with a plurality of LED arrays, each of the boost type converters as shown in FIG. 1 requires as much as the number of LED arrays, which causes a problem that the LED backlight driving circuit becomes complicated. As a result, the number of parts to be designed increases, so there is a limit to miniaturization, which requires a lot of product development period and causes a cost increase.

The present invention can effectively drive an LED backlight consisting of a plurality of LED arrays. In addition, a structure of a multichannel inductor for supplying power to each LED array in the LED backlight is proposed.

In the multi-channel inductor of the present invention, the main coil to be energized / discharged by power is turned on / off at a constant cycle, and at least one winding is wound around the core of the main coil and the same core in turn, It includes at least one dependent coil in which energy is charged in turn due to the induced electromotive force. The multi-channel inductor may further include a sensing coil configured to detect an energy change state of the main coil.

In addition, the slave coil is wound around the winding in the same direction as the winding direction of the main coil. The sensing coil may have a winding wound in a direction opposite to the winding direction of the main coil, and the number of turns of the sensing coil is set in proportion to the number of turns of the main coil.

In addition, the LED backlight multi-drive circuit of the present invention, among the at least one LED array, the FET for switching the power supplied to the first LED array, a feedback resistor for sensing the output voltage of the FET, and the sensed in the feedback resistor A switching controller for outputting a PWM signal for switching the FET according to the output voltage value and the voltage value applied to the first LED array, and the charged energy power as a constant duty ratio according to the PWM signal of the switching controller. A multi-channel inductor with a plurality of coils respectively supplying the plurality of LED arrays, a capacitor for filtering the output voltage to the LED array, a diode for blocking the reverse flow of output current to the LED array, and each LED And a constant current controller for maintaining a constant output current flowing through the array. The switching controller turns off the FET when the voltage value measured by the feedback resistor reaches a specific value, and turns on the FET when the voltage value applied to the first LED array is lower than the specific value. ON).

The multi-channel inductor may include a main coil positioned between an external power supply and an input terminal of the FET to charge / discharge at a constant duty ratio according to switching of the FET, thereby supplying pulse power to the first LED array; A plurality of windings are wound in turn on the core of the main coil and the same core, and includes a plurality of subordinate coils, each of which supplies energy to the remaining LED arrays after the energy is sequentially charged by the electromotive force induced from the main coil. do. The multi-channel inductor further includes a sensing coil which senses a current state of the main coil and outputs it to the switching controller. When the output value of the sensing coil is 0 [V], the FET is turned on. To perform the control.

The constant current controller may include: a switching device configured to switch on / off current flowing through the LED array; a sensing resistor sensing a current flowing through the LED array; and a current detected by the sensing resistor and a predetermined reference voltage. A comparator for turning on / off the switching element, wherein the switching element is implemented by any one of a bipolar transistor (BJT) and a field effect transistor (FET).

In addition, the feedback resistor is characterized in that located at the output terminal of the FET, the constant current control unit is characterized in that each of which is provided at the end of the LED array, the switching element is provided at the end of the LED array It is characterized by.

Hereinafter, the detailed description of the preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description of the reference numerals to the components of the drawings it should be noted that the same reference numerals as possible even if displayed on different drawings.

2 is a block diagram of an LED backlight multi driving circuit according to an exemplary embodiment of the present invention.

The LED backlight multi-drive circuit of the present invention provides a backlight driving power consisting of a plurality of LED array (214a, 214b, 214c, 214n; LED first array, LED second array, LED third array, LED N array). As a circuit, each LED array 214a, 214b, 214c, 214n is allocated and connected to each coil in the multi-channel inductor 204 to receive driving power.

The LED backlight multi driving circuit includes a FET 208 for switching the power supplied to the first LED array 214a, and a switching controller 202 for outputting a PWM signal to perform the switching of the FET 208. ), A feedback resistor 206 for sensing the output voltage output to the first LED array 214a, a multi-channel inductor 204 where energy charging occurs when the turn-off period and the turn-on period are repeated, and each LED array Constant current controllers 218 are provided for controlling the constant current adjusting units 216a, 216b, 216c, and 216n provided at 214a, 214b, 214c, and 214n. In addition, each of the LED arrays 214a, 214b, 214c, and 214n includes diodes 210a, 210b, 210c, and 210n for preventing reverse current flow, and capacitors 212a, 212b, and 212c for filtering to keep the output voltage constant. 212n and constant current adjusting units 216a, 216b, 216c, and 216n for maintaining a constant output current flowing through each of the LED arrays 214a, 214b, 214c, and 214n.

The LED backlight multi-driving circuit having the above-described configuration includes a main coil in the multi-channel inductor 204 while turning on the FET 208 using the switching controller 202 with the power 200 flowing from the outside. Current flows from the FET 208 to charge the multichannel inductor.

The switching controller 202 turns off the FET when the voltage value measured at the feedback resistor reaches a specific value, and turns off the FET when the voltage value applied to the first LED array 214a is lower than the specific value. To turn on control. That is, when the voltage of the feedback resistor is sensed and the set voltage is reached, the FET 208 is turned off, and the energy of the multi-channel inductor is transferred through the diodes 210a, 210b, 210c, and 210n. While charging 212b, 212c and 212n, the LED backlights 214a, 214b, 214c and 214n are powered by the LED backlight, and then the switching controller 202 is applied to the first LED array 214a. When the voltage is sensed and lower than the set voltage, the driving cycle for turning on the FET 208 again is repeated.

The multichannel inductor 204 is implemented as a multichannel inductor having a plurality of coils wound in the same direction to supply power to each LED array. The structure of the multi-channel inductor will be described later in detail with reference to FIG. 3. However, when the multi-channel inductor consisting of the main coil and the dependent coil is used because of the physical characteristics of the FET for switching the main coil, heat is generated when the input / output parasitic capacitor and the inductor of the FET resonate. Therefore, when the multi-channel inductor 204 is used, heat generation measures are essential, and since a higher heat resistance component must be used, a lot of attention is required in the design, so that the development period can be long.

In order to compensate for the above, the present invention may be implemented as a multi-channel inductor (hereinafter, referred to as a “sense multi-channel inductor”) in which a sensing coil is added to the multi-channel inductor. When the sensing multi-channel inductor is used, heat generated may be reduced than when the multi-channel inductor is used. The structure of the sensing multichannel inductor will be described later in detail with reference to FIG. 5.

The structure of the multi-channel inductor is shown in FIG. 3, wherein the multi-channel inductor is the same as the main coil 300 and the core of the main coil 300, in which energy charging / discharging is performed by turning on / off a predetermined period by an external power supply. A plurality of windings are wound in turn on the core, and thus the plurality of slave coils 301, 302, and 303 are sequentially charged with energy due to the electromotive force induced from the main coil 300. That is, when current flows through the main coil 300 to form an electromotive force, the electromotive force affects the first dependent coil 301 to flow a current through the first dependent coil 301, thereby again causing the second dependent coil. A current flows to 302, and finally a current flows to the Nth slave coil 303 which is the last coil in this manner. Therefore, the electromotive force generated in the main coil 300 is transferred to the last Nth dependent coil 303 through the first dependent coil 301 and the second dependent coil 302.

The main coil 300 and the slave coils 301, 302, and 303 in the multi-channel inductor have a feature in which several coils are insulated from each other in the same direction on one core and wound in the same direction. At this time, the number of turns and the cross-sectional area of the coil may vary according to the capacity, and the number of coils to be wound may be increased to several induction energy amounts. In the circuit using the same, the main coil 300 is repeatedly turned ON and OFF at a predetermined cycle to intercept a current to charge and discharge energy, thereby generating an electromotive force. Energy is transferred to the coils 301, 302, 303. The polarity indicator shown in FIG. 3 means that each coil winding is wound in the same direction. 4 is a perspective view of an actual external appearance of the multi-channel inductor. In FIG. 4A, a plurality of coils of the main coil 300 and the slave coils 301, 302, and 303 are insulated from each other and wound in the same direction in the ferrite bobbin 310. 4B is a perspective view illustrating a state in which a plurality of coils of the main coil 300 and the slave coils 301, 302 and 303 are insulated from each other and wound in the same direction in the rod-shaped core 312.

Meanwhile, the structure of the sensing multichannel inductor is illustrated in FIG. 5, wherein the sensing multichannel inductor is a structure in which an inductor used in a critical conduction mode (CRM) is applied, and a sensing coil 304 has a main structure. It detects an energy change state of the coil 300 and informs the outside. The sensing multichannel inductor has a structure in which a sensing coil wound in a direction opposite to a winding direction of a main coil and a slave coil is added in the structures of the multichannel inductors of FIGS. 4A and 4B. That is, the sensing type multi-channel inductor senses additionally wound in the opposite direction in a state in which a plurality of coils of the main coil and the slave coil are insulated from each other and wound in the same direction as in the multi-channel inductor of FIG. 4A. It has a structure in which a coil is added. Similarly, when the sensing multichannel inductor is implemented as a bar coil as illustrated in FIG. 4B, a sensing coil wound in an opposite direction to the multichannel inductor structure of FIG. 4B is added.

The sensing coil 304 is set according to the turn ratio of the coil switching in the circuit and reverses the winding direction. In addition, the sensing coil 304 is a turn ratio is determined in proportion to the number of turns of the main coil (300). That is, when the turn ratio of the sensing coil 304 is Np as the number of turns of the main coil 300 to switch, and the number of turns of the sensing coil 304 is Ns, the equation is expressed as Ns / Np. The turn ratio of 304 is set to the required specific value. When the sensing multi-channel inductor is employed and used, a PWM controller in the form of PFC (Power Factor Correction) is used.

The constant current controllers 216a, 216b, 216c, and 216n perform a function of maintaining a constant output current flowing through each of the LED arrays 214a, 214b, 214c, and 214n, which maintains a uniform brightness of the LEDs. In order to provide a constant current control unit at the end of the LED array. That is, each coil in the multi-channel inductor may have a difference in the amount of energy, and because each LED may have a characteristic deviation, in order to compensate for this, the termination of each LED array 214a, 214b, 214c, and 214n. In order to maintain a uniform brightness of the LED by configuring a circuit such as a current sink (current sink), a current mirror (current mirror).

On the other hand, the power 200 flowing from the outside may be input in the form of alternating current (AC) or direct current (DC). When the input of the alternating current is performed, the secondary voltage of the transformer may be rectified using a bridge diode and a capacitor. .

6 is a diagram illustrating an LED backlight multi driver circuit employing the multi-channel inductor according to an exemplary embodiment of the present invention.

While the switching controller 202 turns on the FET 208, current flows from the main coil 300 in the multichannel inductor 204 to the FET 208 so that energy is applied to the main coil 300 in the multichannel inductor 204. The charging controller 202 senses the voltage measured at the feedback resistor 206 and turns off the FET 208 when the sensed voltage reaches the set voltage. At this time, the main coil 300 is changed in the current polarity and the energy of the main coil 300 charges the capacitor 212a through the diode and supplies power to the LED first array 214a and to the LED first array 214a. When the applied voltage is sensed and lower than the set voltage, the cycle of turning on the FET 208 again is repeated.

The LED backlight multi-drive circuit employing the multi-channel inductor of the present invention uses only the main coil 300 in the multi-channel inductor to the FET 208 by using the magnetic flux induced in the process of charging and discharging the remaining coils. The first slave coil 301, the second slave coil 302, and the third slave coil 303 induce energy.

That is, while the main coil 300 is charging the energy, the remaining inductors, the first slave coil 301, the second slave coil 302, and the Nth slave coil 303, are simultaneously charged with energy and vice versa. By emitting at the same time, the converter, which is configured separately in the related art, is synchronized and driven. Therefore, the main coil 300 in the multi-channel inductor is the LED first array 214a, the first slave coil 301 is the LED second array 214b, the second slave coil 302 is the LED third array ( At 214c, the last dependent coil, the Nth dependent coil 303, supplies the charged energy to the LED Nth array 214n as power, respectively.

Constant current regulators 216a, 216b, 216c, and 216n at the end of each LED array 214a, 214b, 214c, and 214n to compensate for the difference in energy amount of each coil in the multi-channel inductor and the characteristic deviation of the LED. Keep the brightness of LED uniformly. The electrostatic current adjusting units 216a, 216b, 216c, and 216n are provided at ends of the LED array to switch on / off the current flowing through the LED array, and the switching elements 230a, 230b, 230c, and 230n, The switching element is turned on by comparing the sensing resistors 234a, 234b, 234c, and 234n sensing current flowing through the LED array with a predetermined reference voltage output from the constant current controller 218 and the current sensed by the sensing resistor. Comparators 232a, 232b, 232c, and 232n to be turned off are provided.

The constant current adjusting units 230a, 230b, 230c, and 230n having the above-described configuration input the level set by the constant current controller 218 as a reference voltage to the comparator, and compare the switch with the amount of output current sensed through the sensing resistor. It keeps LED operation uniformly by turning it ON or OFF or operating the voltage as a load. The switching elements 230a, 230b, 230c, and 230n may use both a bipolar transistor (BJT) and a field effect transistor (FET). The constant current controller 218 may individually and variously control the operation of each LED in conjunction with the system of the main body module.

FIG. 7 is a diagram illustrating an LED backlight multi driver circuit employing the sensing multichannel inductor according to an exemplary embodiment of the present invention.

Compared with the LED backlight multi driving circuit employing the multi-channel inductor of FIG. 6, FIG. 7 includes a sensing coil 305 for sensing a change in the amount of current of the main coil 300, and thus, in the sensing coil 305. The sensed change in the amount of current of the main coil 300 is input from the switching controller 202 and used to switch the FET 208.

In detail, while the switching controller 202 turns on the FET 208, current flows from the main coil 300 in the sensed multi-channel inductor 204 to the FET 208 to energize the main coil 300. Is charged, and the switching controller 202 senses the voltage of the feedback resistor 206 and turns off the FET 208 when the set voltage is reached. At this time, the main coil 300 is changed in current polarity and the energy of the main coil 300 charges the capacitor 212a through the diode 210a and supplies power to the LED first array 214a. When current flows through the main coil 300, the current induced through the sensing coil 304 flows into the switching controller 202 and turns on the FET 208 again when it reaches zero voltage (V). Repeat the cycle). Also, when the voltage applied to the LED first array 214a is sensed and higher than the set voltage, the FET is turned off to maintain the set voltage.

The LED backlight multi-drive circuit employing the sensing multichannel inductor of the present invention charges and discharges only one main coil 300 in the sensing multichannel inductor by turning on and off the FET 208. Energy is induced to the remaining coils of the first dependent coil 301, the second dependent coil 302, and the Nth dependent coil 303 by using the magnetic flux induced in the.

While the main coil 300 charges the energy, the remaining inductors, the first slave coil 301, the second slave coil 302, and the Nth slave coil 303, are also simultaneously charged and vice versa. In addition, the conventionally configured separately driven converter is synchronized. Accordingly, the main coil 300 in the sensing multichannel inductor is connected to the LED first array 214a, the first dependent coil 301 is the LED second array 214b, and the second dependent coil 302 is the LED third. In the array 214c, the last slave coil 303 supplies the charged energy to the LED Nth array 214n as power, respectively.

In addition, in order to compensate for the difference in the amount of energy of each inductor or considering the characteristic variation of the LED, constant current adjusting units 216a, 216b, 216c, and 216n are provided at the ends of each LED array to maintain uniform brightness of the LED. . The constant current controllers 216a, 216b, 216c, and 216n input the level set by the constant current controller 218 to the comparators 232a, 232b, 232c, and 232n as reference voltages to sense resistors 234a, 234b, 234c, and 234n. Compared to the amount of output current sensed through), the switch elements 230a, 230b, 230c, 230n are turned on or off or voltage is operated as a load to maintain the LED operation uniformly. The switch elements 230a, 230b, 230c, and 230n may use both a bipolar transistor (BJT) and a field effect transistor (FET). The constant current controller 218 may implement various LED operations individually in association with the system of the main body module.

In the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention is not to be determined by the embodiments described above, but will be apparent in the claims as well as equivalent scope.

As described above, the present invention can drive a LED backlight composed of a plurality of LED arrays as a single multi-channel inductor, so that the circuit can be simplified and miniaturized. In addition, the product development period can be shortened and manufacturing costs can be reduced.

In addition, LEDs with a single color, ie, white, red, green, blue, yellow, etc., can be configured in a plurality of arrays, and the characteristic deviation and deterioration of each LED Can be used to correct the difference in lifespan. In addition, in the case of a device that implements color by mixing red, green, and blue, the voltage and current applied to the red, green, and blue can be controlled differently. Not only can the brightness be kept uniform, but also various colors can be realized.

Claims (18)

Main coil which is charged / discharged by supplying power and turning on / off at a predetermined cycle, At least one slave coil in which at least one winding is wound around the core of the main coil in the same core so that energy is sequentially charged due to the electromotive force induced from the main coil. Multi-channel inductor comprising a. The multichannel inductor of claim 1, wherein the multichannel inductor further comprises a sensing coil configured to sense an energy change state of the main coil. The multi-channel inductor of claim 1, wherein the slave coil has a winding wound in the same direction as the winding direction of the main coil. The multi-channel inductor of claim 2, wherein the sensing coil has a winding wound in a direction opposite to the winding direction of the main coil. The multi-channel inductor of claim 2, wherein the number of turns of the sensing coil is set in proportion to the number of turns of the main coil. A FET for switching power supplied to the first LED array among the at least one LED array; A feedback resistor for sensing the output voltage of the FET; A switching controller for outputting a PWM signal for switching the FET according to an output voltage value sensed by the feedback resistor and a voltage value applied to the first LED array; A multi-channel inductor having a plurality of coils respectively supplying charged energy power to the plurality of LED arrays as a constant duty ratio according to the PWM signal of the switching controller; A capacitor for filtering the output voltage to the LED array; A diode that blocks a reverse flow of output current to the LED array; Constant current regulator keeps output current flowing through each LED array constant LED backlight multi-drive circuit comprising a. The switching controller of claim 6, wherein the switching controller turns off the FET when the voltage value measured by the feedback resistor reaches a specific value, and a voltage value applied to the first LED array is lower than the specific value. LED backlight multi-drive circuit for performing the control to turn (ON) the FET. The method of claim 6, wherein the multi-channel inductor, A main coil positioned between an external power source and an input terminal of the FET to charge / discharge at a constant duty ratio according to the switching of the FET, thereby supplying pulse power to the first LED array; A plurality of windings are sequentially wound around the core of the main coil and a plurality of windings, and after the energy is sequentially charged due to the electromotive force induced from the main coil, a plurality of subordinate coils respectively supply the charged energy to the remaining LED arrays. LED backlight multi-drive circuit comprising a. The method of claim 8, wherein the multi-channel inductor, And a sensing coil configured to sense a current state of the main coil and output the sensing coil to the switching controller. 10. The LED backlight multi driver circuit of claim 9, wherein the control unit turns on the FET when an output value of the sensing coil becomes 0 [V]. The LED backlight multi-driving circuit of claim 9, wherein the sensing coil has a winding wound in a direction opposite to the winding direction of the main coil. The LED backlight multi-driving circuit of claim 9, wherein the number of turns of the sensing coil is set in proportion to the number of turns of the main coil. The LED backlight multi-driving circuit of claim 8 or 9, wherein the slave coil has a winding wound in the same direction as the winding direction of the main coil. The method of claim 6, wherein the constant current adjusting unit, A switching element for switching on / off current flowing through the LED array; A sensing resistor for sensing current flowing through the LED array; A comparator to turn on / off the switching element by comparing the current sensed by the sensing resistor with a predetermined reference voltage LED backlight multi-drive circuit comprising a. The LED backlight multi driver circuit of claim 14, wherein the switching device is implemented by any one of a bipolar transistor (BJT) and a field effect transistor (FET). The LED backlight multi driving circuit of claim 6, wherein the feedback resistor is located at an output terminal of the FET. The LED backlight multi-driving circuit of claim 6, wherein the constant current controller is provided at each end of the LED array. 15. The LED backlight driving circuit according to claim 14, wherein the switching element is provided at an end of the LED array.

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