KR101018171B1 - Driving device for light emitting diode with current limiting function - Google Patents

Abstract

The present invention relates to a driving device for a light emitting diode having a current limiting function for suppressing the LED peak current generated during dimming while satisfying the minimum dimming requirements according to the consumer's request, the power supply unit for supplying a driving power for the light emitting diode; A constant current controller for controlling a driving current supplied from the power supply unit to a light emitting diode as a first reference current having a preset current level, a dimming unit for adjusting the brightness of the light emitting diode according to a dimming signal, and the light emitting diode and And a current limiting unit connected between the constant current controllers and blocking the transmission path of the currents when the current flowing from the light emitting diode to the constant current controller is higher than a second reference current having a higher current level than the first reference current. Foot with current limiting feature It provides diode drive device.

Light Emitting Diode (LED), Dimming, Peak Current

Description

DRIVER HAVING CURRENT LIMITING FUNCTION FOR LIGHT EMITTING DIODE}

The present invention relates to a driving device for a light emitting diode, and more particularly to a driving device for a light emitting diode having a current limiting function for suppressing the LED peak current generated during dimming while satisfying the minimum dimming requirements according to the needs of consumers will be.

Recently, the display industry is dominated by the new technology Flat Panel Display (FPD) market, which reflects the demands of the multimedia era, such as high resolution and large screens.In the large display market, liquid crystal display (LCD) TVs are showing rapid growth. It is expected to play a leading role in terms of price and marketability in the future.

In the case of LCD TVs, Cold Cathode Fluorescent Lamps (CCFLs) are mainly used as backlight sources, but recently, LED lamps are gradually being replaced by light emitting diodes (LEDs) due to various advantages such as power consumption, lifespan, and environmental friendliness. Therefore, there is an urgent need for the construction of a low cost power electronic system of a backlight unit power module using LEDs and appropriate control elements.

In order to satisfy this requirement, conventionally, each LED channel is controlled in a constant current and a switch operating in a linear region for each LED channel configured in parallel after acquiring an arbitrary DC voltage in order to secure a minimum dimming range. It is controlled by constant current by inserting and has secured minimum dimming range. In this method, since the constant current control is a method of limiting a current above a certain level, the heat generation of the switch is increased so that the volume of the LED driving circuit such as an increase in the size of the heat sink is increased, and there is a problem of deterioration in efficiency and reliability.

To overcome this problem, DC / DC converters such as boost converters can be applied to precisely control the current of each LED channel to ensure constant current and minimum dimming range. Cost increases due to the configuration of the DC / DC converter and the control stage, there is a problem that the power conversion efficiency is reduced by the DC / DC converter and the volume of the LED driving circuit increases. In addition, there is a problem that the reliability of the product is lowered by active devices and ICs applied to the DC / DC converter.

In addition, a method may be employed in which a DC blocking capacitor is connected to each channel of the LED to control the current value transmitted by the capacitor's charge balance principle. However, the rising period of the current flowing to the LED by the capacitor is also adopted. And due to the delay time of the falling section there is a problem that the user does not meet the minimum dimming request that requires a minimum dimming range of 0.1%.

Lastly, a linear switch can be used to control the current flowing through the LED to ensure constant current dimming range, but the high output voltage of the output capacitor causes the LED to generate a large peak current. There is a problem that can be broken.

Therefore, there is a need for a new driving device that is low in manufacturing cost, high in reliability, and capable of suppressing LED peak current while meeting minimum dimming requirements.

In order to solve the above problems, it is an object of the present invention to provide a driving device for a light emitting diode having a current limiting function for suppressing the LED peak current generated during dimming while satisfying the minimum dimming requirements according to the needs of consumers.

In order to achieve the above object, one technical aspect of the present invention is a power supply unit for supplying a driving power for a light emitting diode, and a first reference having a preset current level supplied from the power supply to the light emitting diode flowing through the light emitting diode. A constant current control unit controlling the current, a dimming unit adjusting the brightness of the light emitting diode according to a dimming signal, and connected between the light emitting diode and the constant current control unit, a current flowing from the light emitting diode to the constant current controller When the current level is higher than the second reference current is set higher than the reference current to provide a driving device for a light emitting diode having a current limiting function, characterized in that it comprises a current limiting unit for blocking the transmission path of the current.

According to one technical aspect of the present invention, the current limiting unit is at least one switch electrically connected between the light emitting diode and the constant current control unit to conduct and block the transmission path of the current flowing from the light emitting diode, and the switch It may include at least one comparator for controlling the conduction and blocking of the switch by comparing the current delivered through the current level of the second reference current.

According to one technical aspect of the present invention, the plurality of light emitting diodes are provided, the current limiting portion is provided with a plurality of switches and a plurality of comparators, the plurality of switches are each one-to-one correspond to the plurality of light emitting diodes electrically The plurality of comparators may be connected one-to-one to each of the plurality of switches to control the conduction and disconnection of each switch.

According to one technical aspect of the present invention, a plurality of light emitting diodes are provided, a plurality of light emitting diodes are commonly connected to the current limiting unit, and the at least one switch is electrically connected to a common connection end of the plurality of light emitting diodes. The at least one comparator may control the conduction and disconnection of the at least one switch.

According to one technical aspect of the present invention, the constant current controller is a constant current comparator for comparing the current from the current limiting unit and the current level of the first reference current, and transfers the comparison result from the constant current comparator to the power supply unit It may include a photo coupler.

According to one technical aspect of the present invention, the power supply unit rectifies and smoothes the commercial AC power, a power factor correction unit for power factor correcting the rectified power from the rectifier, and a power factor corrected power source from the power factor correction unit And an inverter unit for switching and inverting the transformer, a transformer unit for transforming the inverted power from the inverter unit, and a controller for controlling the switching operation of the inverter unit under the control of the constant current controller.

According to one technical aspect of the present invention, the inverter unit may employ at least one inverter method of the LLC resonant type, full-bridge type or half-bridge type.

According to one technical aspect of the present invention, the dimming unit may adjust the brightness of the light emitting diode by controlling the conduction and blocking of the switch according to the dimming signal.

According to the present invention, the DC / DC converter and the control stage, which have been applied for the constant current control of the LED channel, are eliminated. Implement LED driving circuit, and satisfy the minimum dimming requirements according to the needs of the consumer, it is effective to suppress the LED peak current.

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

1 is a schematic configuration diagram of a first embodiment of the present invention.

Referring to FIG. 1, a first embodiment 100 of a driving device for a light emitting diode according to the present invention may include a power supply unit 110, a constant current controller 120, a dimming unit 130, and a current limiting unit 140. have.

The power supply unit 110 includes a rectifier 111 capable of rectifying and smoothing commercial AC power, a power factor correction unit 112 for correcting a power factor by adjusting a phase difference between a voltage and a current of the power rectified from the rectifier 111, and Inverter 113 for switching the power factor corrected power from the power factor corrector 112 to invert power, and a transformer 114 for transforming and outputting the voltage level of the inverted power from the inverter 113. And a control unit 115 for controlling the operation of the inverter unit 113 according to the control signal of the constant current control unit 120.

The driving power from the transformer unit 114 is rectified and transmitted to the light emitting diode. The light emitting diode may be a light emitting diode string in which a plurality of light emitting diodes are connected in series.

The current flowing through the LED may be fed back to regulate the supply of driving power.

The constant current controller 120 may compare the current flowing in the light emitting diode with a first reference current having a preset current level and a current level, and transmit a control signal according to the comparison result to the controller 115.

To this end, the constant current controller 120 may include a constant current comparator 121 and a photo coupler 122.

The constant current comparator 121 compares the current flowing in the light emitting diode with the first reference current having a preset current level and the current level, and transmits the comparison result to the photo coupler 122, and the photo coupler 122 does not work. The comparison result in which the car is insulated and transmitted is transmitted to the controller 115. The controller 115 controls the inverting operation of the inverter unit 113 according to the comparison result from the photo coupler 122 to control the supply of power delivered to the light emitting diode through the transformer unit 114.

The dimming unit 130 promotes the brightness of the light emitting diode according to a dimming signal from the outside. The dimming signal may be a pulse width modulation (PWM) dimming signal as shown in FIG. 2. Accordingly, the dimming unit 130 controls the current to flow in the light emitting diode in the high signal of the dimming signal, and prevents the current from flowing in the light emitting diode in the low signal of the dimming signal.

The current limiter 140 is at least one switch Ma1 electrically connected between the light emitting diode and the constant current comparator 121 of the constant current controller 120 to conduct and block a transmission path of the current flowing from the light emitting diode. At least one comparator Ca1 may be configured to control the conduction and disconnection of the switch Ma1 by comparing the current transmitted through the switch Ma1 with a preset current level of the second reference current. Preferably, the set current level of the second reference current is higher than the current level of the first reference current.

Accordingly, the constant current control unit 120 may control the current flowing through the light emitting diode to the first reference current, and the current limiting unit 140 is initially generated when power is supplied to the light emitting diode so that the current flows. The stress applied to the device can be reduced by limiting the peak current to the current level of the second reference current.

3A is a graph showing a signal waveform of a conventional driving device, FIG. 3B is a graph showing a signal waveform of a driving device of the present invention, and FIG. 3C is a graph showing a minimum dimming operation of the driving device of the present invention.

Referring to FIG. 3A, as shown in the drawing, it can be seen that the conventional driving device has a high peak current flowing through the light emitting diode as shown by the identification code A. FIG.

On the contrary, referring to FIG. 3B together with FIG. 1, it can be seen that the peak current is reduced by the current limiting unit 140 by the second reference current so that the peak current with limited current flows through the light emitting diode as shown by the identification code B. FIG. Can be.

In addition, referring to Figure 3c, while performing the peak current limiting function as described above, it can be seen that satisfies the 0.1% minimum dimming range required by the consumer.

On the other hand, the drive device of the present invention can be configured in various ways.

4-7 is a schematic block diagram of the 2nd-5th embodiment of this invention, respectively.

4 to 6, in the second to fourth embodiments 200, 300, and 400, the inverter units 213, 313, 413 of the power supply units 210, 310, and 410 may be configured in various ways. The other components of the rectifiers 211, 311, 411, the power factor correction units 212, 312, 412, the controllers 215, 315, 415, and the constant current comparators 221, 321, 421 and the photo couplers 222, 322, 422 and the photo couplers 222, 322, 422 of the power supply units 210, 310, 410 are the same as in FIG. 1. The description is omitted.

The inverter units 213, 313, 413 described above are LLC resonant type 213 having two series-connected switches M1, M2, a full bridge type 313 having four switches M1-M4, and two switches ( The half bridge type 413 having M1 and M2 can be configured.

The transformers 214, 314, and 514 correspond to the plurality of primary windings N _P1 to N _PN and the plurality of primary windings N _P1 to N _PN , respectively, to maintain a current balance of power delivered to the light emitting diodes, respectively. The windings N _S1 to N _SN may be included.

On the other hand, a plurality of light emitting diodes of the present invention may be provided, the current limiting unit (240, 340, 440) is a plurality of comparators (Ca1 ~ Ca2n) corresponding one-to-one to each of the plurality of switches (Ma1 ~ Ma2n) and a plurality of switches (Ma1 ~ Ma2n), respectively ) May be included. The plurality of switches Ma1 to Ma2n of the current limiting units 240, 340, and 440 correspond one-to-one to the plurality of light emitting diodes LED1 to LED2n, respectively, to respectively transfer paths of current flowing from the plurality of light emitting diodes LED1 to LED2n. Can conduct and interrupt. Accordingly, the plurality of comparators Ca1 to Ca2n control the conduction and blocking of the plurality of switches Ma1 to Ma2n, so that the peak current of each of the plurality of light emitting diodes LED1 to LED2n is set as a second preset reference current. You can limit it. In addition, the plurality of dimming units 230, 330, and 430 correspond one-to-one to each of the plurality of switches Ma1 to Ma2n to control the conduction and blocking of the switches Ma1 to Ma2n according to the dimming signal, thereby controlling the luminance of the plurality of light emitting diodes LED1 to LED2n. Can be adjusted.

7 is a schematic configuration diagram of a fifth embodiment of the present invention.

Referring to FIG. 7, the constant current comparator 521 of the rectifier 511, the power factor correction unit 512, the inverter unit 513, the transformer unit 514, the controller 515, and the constant current controller 520 of the power supply unit 510. ) And the photo coupler 522 are the same as those of FIG. 4, and thus detailed description thereof will be omitted.

Meanwhile, a plurality of light emitting diodes of the present invention may be provided, and cathodes of the plurality of light emitting diodes LED1 to LED2n may be connected in common. Accordingly, the current limiting unit 540 may include one switch Ma1 and one comparator Ca1, and the switch Ma1 is electrically connected to a common connection terminal of the plurality of light emitting diodes LED1 to LED2n. Connected to each other to conduct and block a transmission path of current flowing from the plurality of light emitting diodes LED1 to LED2n, and the comparator Ca1 controls the conduction and blocking of the switch Ma1 to a plurality of preset reference second currents. The peak current of the light emitting diodes LED1 to LED2n may be limited in common.

In addition, the dimming unit 530 may control the conduction and blocking of the switch Ma1 to adjust the luminance of the plurality of light emitting diodes LED1 to LED2n in common.

As described above, the DC / DC converter and the control stage, which have been applied for the constant current control of the LED channel, are eliminated, thereby reducing the manufacturing cost, improving the power conversion efficiency and power density of the LED driving circuit, and improving reliability. The LED driving circuit can be implemented and the LED peak current generated during dimming can be suppressed while satisfying the minimum dimming requirement according to the consumer's demand.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, but is defined by the claims below, and the configuration of the present invention may be modified in various ways without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art that the present invention may be changed and modified.

1 is a schematic configuration diagram of a first embodiment of the present invention.

2 is a graph showing the signal waveform of the dimming unit of the present invention.

3A is a graph showing a signal waveform of a conventional driving device, FIG. 3B is a graph showing a signal waveform of a driving device of the present invention, and FIG. 3C is a graph showing a minimum dimming operation of the driving device of the present invention.

4 is a schematic configuration diagram of a second embodiment of the present invention.

5 is a schematic configuration diagram of a third embodiment of the present invention.

6 is a schematic configuration diagram of a fourth embodiment of the present invention.

7 is a schematic configuration diagram of a fifth embodiment of the present invention.

<Detailed Description of Major Symbols in Drawing>

100,200,300,400,500 ... Drive

110,210,310,410,510 ... Power Supply

111,211,311,411,511 ... rectifier

112,212,312,412,512 ... power factor correction unit

113,213,313,413,513 ... Inverter part

114,214,314,414,514 ... Transformers

115,215,315,415,515 ... control unit

120,220,320,420,520 ... constant current control

121,221,321,421,521 ... Constant Current Comparators

122,222,322,422,522 ... Photo Coupler

130,230,330,430,530 ... Dimming part

140,240,340,440,540 ... current limiting

Ma1 to Ma2n ... switch

Ca1 ~ Ca2n ... Comparators

Claims (8)

A power supply unit supplying driving power for a light emitting diode; A constant current controller configured to control a driving current supplied from the power supply unit to the light emitting diode to a first reference current having a preset current level; A dimming unit configured to adjust luminance of the light emitting diode according to a dimming signal; And A current limit connected between the light emitting diode and the constant current controller to block a transmission path of the current when the current flowing from the light emitting diode to the constant current controller is higher than a second reference current having a higher current level than the first reference current. part Driving device for a light emitting diode having a current limiting function comprising a. The method of claim 1, wherein the current limiting unit At least one switch electrically connected between the light emitting diode and the constant current controller to conduct and block a transmission path of current flowing from the light emitting diode; And At least one comparator that controls the conduction and disconnection of the switch by comparing the current delivered through the switch with the current level of the second reference current Driving device for a light emitting diode having a current limiting function comprising a. The method of claim 2, The light emitting diode is provided in plurality, The current limiter includes a plurality of switches and a plurality of comparators, The plurality of switches are electrically connected to the plurality of light emitting diodes in a one-to-one correspondence, respectively. The plurality of comparators are one-to-one correspond to each of the plurality of switches to control the conduction and blocking of each switch, characterized in that the drive device for a light emitting diode having a current limiting function. The method of claim 2, A plurality of light emitting diodes are provided, a plurality of light emitting diodes are commonly connected to the current limiting unit, The at least one switch is electrically connected to a common connection end of the plurality of light emitting diodes, And said at least one comparator controls the conduction and interruption of said at least one switch. The method of claim 1, wherein the constant current control unit A constant current comparator for comparing a current level from the current limiting unit with a current level of the first reference current; And Photo coupler for transferring the comparison result from the constant current comparator to the power supply Driving device for a light emitting diode having a current limiting function comprising a. The method of claim 1, wherein the power supply unit Rectifier for rectifying and smoothing commercial AC power; A power factor correction unit for correcting the power factor rectified from the rectifier unit; An inverter unit for switching and inverting the power factor corrected power from the power factor correction unit; A transformer for transforming the inverted power from the inverter unit; And Control unit for controlling the switching operation of the inverter unit under the control of the constant current controller Driving device for a light emitting diode having a current limiting function comprising a. The method of claim 6, The inverter unit drive device for a light emitting diode having a current limiting function, characterized in that for adopting at least one inverter method of the LLC resonant type, full-bridge type or half-bridge type. The method of claim 2, And the dimming unit controls the conduction and blocking of the switch according to the dimming signal to adjust the brightness of the light emitting diode.

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