CN117596743A

CN117596743A - LED driver for optimal supply voltage, light emitting system and display device

Info

Publication number: CN117596743A
Application number: CN202310838899.3A
Authority: CN
Inventors: 黄钟泰; 赵成勋
Original assignee: Welland Ltd
Current assignee: Welland Ltd
Priority date: 2022-08-18
Filing date: 2023-07-10
Publication date: 2024-02-23
Also published as: KR102533747B1

Abstract

The invention discloses an LED driver, a light emitting system and a display device for optimal supply voltage. The LED driver may include: a first synchronization pin, a feedback input pin, and a feedback output pin; a first LED current source configured to draw a first LED drive current through a first synchronization pin by at least one first LED (ligh emitting diode); a first controller configured to generate a first control voltage based on a first headroom (headroom) voltage of a first LED current source; and a first feedback current source configured to generate a first feedback current flowing from a feedback input pin to a feedback output pin based on a first control voltage, and the first headroom voltage may correspond to the first synchronization pin.

Description

LED driver for optimal supply voltage, light emitting system and display device

Technical Field

The technical idea of the present disclosure relates to LED (light emitting diode) driving, and in particular, to an LED driver, a light emitting system, and a display device for optimal supply voltage.

Background

LED (light emitting diode) has the advantageous characteristics of low power consumption, small size, etc., and is therefore used in various applications. For example, LEDs may be used as a backlight of a display, and in an example in which LEDs are used as a backlight, mini (mini) LEDs may be a manner in which LEDs of a small size (for example, hundreds of μm) are compactly arranged and the brightness of the LEDs is adjusted according to the content of the display. In order to drive a plurality of LEDs, a plurality of LED drivers may be used, however, due to the deviation between the plurality of LED drivers, a margin may be included in the supply voltage, and a high margin may cause a decrease in the efficiency of the LED drivers.

Disclosure of Invention

Technical problem

The technical idea of the present disclosure is to provide an LED driver, a light emitting system, and a display device for providing an optimal supply voltage.

Technical proposal

An LED driver according to an aspect of the disclosed technical idea may include a first synchronization pin, a feedback input pin, and a feedback output pin; a first LED current source configured to draw a first LED drive current through a first synchronization pin by at least one first LED (light emitting diode); a first controller configured to generate a first control voltage based on a first headroom (headroom) voltage of a first LED current source; and a first feedback current source configured to generate a first feedback current flowing from a feedback input pin to a feedback output pin based on a first control voltage, wherein the headroom voltage corresponds to a voltage of the first synchronization pin.

According to an exemplary embodiment of the present disclosure, the first controller may include: a comparator configured to compare the first headroom voltage with a reference voltage; and a voltage generator configured to generate a first control voltage that increases or decreases according to an output signal of the comparator.

According to an exemplary embodiment of the present disclosure, the voltage generator may include: a counter configured to generate a digital signal that increases or decreases according to the output signal; and a digital-to-analog converter configured to convert the digital signal into a first control voltage.

According to an exemplary embodiment of the present disclosure, the voltage generator may include: a capacitor configured to provide a first control voltage; and a switching circuit configured to charge or discharge the capacitor according to the output signal.

According to an exemplary embodiment of the present disclosure, the first feedback current source may include: a transistor connected to the feedback input pin and the feedback output pin; and an amplifier configured to amplify a difference between the first control voltage and the voltage of the feedback output pin and to provide the amplified voltage to the control electrode of the transistor.

According to an exemplary embodiment of the present disclosure, the LED driver may further include: a second sync pin; a second LED current source configured to draw a second LED drive current from at least one second LED through a second synchronization pin; a second controller configured to generate a second control voltage based on a second headroom voltage of a second LED current source; and a second feedback current source configured to generate a second feedback current flowing from the feedback input pin to the feedback output pin based on the first control voltage.

According to an exemplary embodiment of the present disclosure, the LED driver may further include a control input pin, and the first LED current source is configured to adjust a magnitude of the LED driving current based on a control signal received through the control input pin.

The light emitting system according to another aspect of the technical ideas of the present disclosure may include: a plurality LED (light emitting diode); a voltage supply circuit configured to supply a supply voltage to the plurality of LEDs; a first LED driver configured to draw a first LED driving current by at least one first LED of the plurality of LEDs and draw a first feedback current by the voltage supply circuit based on a first headroom (headroom) voltage; a second LED driver configured to draw a second LED drive current from at least one second LED of the plurality of LEDs and generate a second feedback current from the voltage supply circuit based on the second headroom voltage; and a resistor configured to receive the first feedback current by the first LED driver and the second feedback current by the second LED driver.

According to an exemplary embodiment of the present disclosure, the first LED driver and the second LED driver may be commonly connected to a feedback pin of the voltage supply circuit, and the first feedback current and the second feedback current may be respectively drawn by the feedback pin.

According to an example embodiment of the present disclosure, the voltage supply circuit may generate a feedback voltage in the feedback pin by dividing the supply voltage, and adjust the supply voltage based on the feedback voltage.

According to an exemplary embodiment of the present disclosure, the first LED driver and the second LED driver may be commonly connected to a resistor.

According to an exemplary embodiment of the present disclosure, the first LED driver may compare the first headroom voltage with the reference voltage and increase or decrease the first feedback current according to the comparison result, and the second LED driver may compare the second headroom voltage with the reference voltage and increase or decrease the second feedback current according to the comparison result.

According to an exemplary embodiment of the present disclosure, the first and second LED drivers may be included in the first and second semiconductor packages, respectively, and may further include a substrate on which the first and second semiconductor packages are mounted.

Drawings

Fig. 1 is a block diagram of a system according to an exemplary embodiment of the present disclosure.

Fig. 2 is a block diagram of a system according to an exemplary embodiment of the present disclosure.

Fig. 3 is a block diagram of a semiconductor package according to an exemplary embodiment of the present disclosure.

Fig. 4 is a block diagram of an LED driver according to an exemplary embodiment of the present disclosure.

Fig. 5A and 5B are example block diagrams of controllers according to example embodiments of the present disclosure.

Fig. 6 is a block diagram of a system according to an exemplary embodiment of the present disclosure.

Fig. 7 is a diagram of a display device according to an exemplary embodiment of the present disclosure.

Fig. 8 is a flowchart of a method for generating an optimal supply voltage according to an exemplary embodiment of the present disclosure.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments of the present invention are provided to more fully illustrate the invention to those of ordinary skill in the art. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown in the drawings and will be described below in detail. However, it should be understood that the invention is not limited to the specific embodiments disclosed, but includes all modifications, equivalents, and alternatives falling within the technical spirit and scope of the invention. In describing the various drawings, like elements are referred to by like reference numerals. In the drawings, the size of the structures will be exaggerated or reduced compared to the actual size in order to make the present invention clear.

The terminology used in the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise. In this application, it should be understood that terms such as "comprises" or "comprising," are intended to specify the presence of stated features, integers, steps, acts, components, elements, or groups thereof disclosed in the specification, but are not intended to preclude the presence or addition of one or more other features, integers, steps, acts, components, elements, or groups thereof.

Unless otherwise defined, all terms (including technical or scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms as defined in commonly used dictionaries should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

Fig. 1 is a block diagram of a system 10 according to an exemplary embodiment of the present disclosure. As shown in fig. 1, the system 10 may include first to nleds L1 to Ln, a voltage supply circuit 12, first to nleds drivers 14_1 to 14—n, and a resistor R (n is an integer greater than 1). In some embodiments, voltage supply circuit 12 may be located external to system 10.

In some embodiments, the first to nleds L1 to Ln may include at least two LEDs connected in series and/or parallel with each other, respectively. In the drawings of the present specification, one LED may include at least two LEDs connected in series and/or parallel to each other. In some embodiments, the voltage supply circuit 12 and/or the first to nlde drivers 14_1 to 14—n may be manufactured by a semiconductor process, and may be included in at least one semiconductor package. In some embodiments, the system 10 may include a printed circuit substrate (printed circuit board; PCB) on which at least one semiconductor package may be mounted.

The system 10 may be any system that uses light emitted through the first to nleds L1 to Ln. In some embodiments, the system 5 may be an indoor lighting, an outdoor lighting, a portable lighting, a vehicular lighting, a separately sold light tube, or the like. In some embodiments, as described in the following description with reference to fig. 7, the system 10 may be a display device, and the first through nleds L1 through Ln may provide backlights for the display device.

The voltage supply circuit 12 may generate a supply voltage VSUP from the input voltage VIN. In some embodiments, the input voltage VIN and the supply voltage VSUP may be DC (direct current) voltages. For example, voltage supply circuit 12 may include a DC-DC converter, which may include a boost (boost) converter, a buck (buck) converter, or a buck-boost converter, depending on the magnitude of input voltage VIN and supply voltage VSUP. In addition, the voltage supply circuit 12 may also include a linear regulator, such as a low dropout LDO (low dropout) regulator.

The first to nlde drivers 14_1 to 14—n may draw first to nlde driving currents ILED1 to ILEDn from the first to nlde L1 to Ln, respectively. For example, the second LED driver 14_2 may draw a second LED drive current ILED2 from the second LED l 2. In some embodiments, as described in the later description with reference to fig. 2, the first to nth LED drivers 14_1 to 14—n may receive control signals through control input pins, respectively, and adjust the magnitudes of LED driving currents based on the control signals.

The first to nlde drivers 14_1 to 14—n may have a variation (variation). For example, as described in the later description with reference to fig. 2, the first to n-th led drivers 14_1 to 14—n may have first to n-th headroom (headroom) voltages, respectively, which may be different from each other. For example, the second LED driver 14_2 may have a second headroom voltage, and when the second headroom voltage is lower than the reference voltage, the magnitude of the second LED driving current ILED2 may be smaller than the designed magnitude. The voltage supply circuit 12 may generate a supply voltage VSUP large enough to apply voltages greater than or equal to the reference voltage to the first to nLED drivers 14_1 to 14—n, respectively. In order for the first to nlde drivers 14_1 to 14—n to receive voltages greater than or equal to the reference voltage, respectively, when a higher margin is included in the supply voltage VSUP, excessive voltages may be applied in the first to nlde drivers 14_1 to 14—n, respectively, which may result in a decrease in efficiency of the first to nlde drivers 14_1 to 14—n. Thus, in order to make the minimum headroom voltage among the first to nth headroom voltages greater than or equal to the predefined reference voltage, it is necessary to generate the supply voltage VSUP of the minimum magnitude.

The first to nth led drivers 14_1 to 14—n may respectively draw first to nth feedback currents IFB1 to IFBn from the voltage supply circuit 12. For example, the second LED driver 14_2 may draw the second feedback current IFB2 from the voltage supply circuit 12 based on its own second headroom voltage. Further, as shown in fig. 1, the first to nth led drivers 14_1 to 14—n may provide the first to nth feedback currents IFB1 to IFBn to the resistor R. For example, the second LED driver 14_2 may provide the second feedback current IFB2 to the resistor R.

As the first to n-th feedback currents IFB1 to IFBn increase, the voltage VR applied to the resistor R increases. As described in the later description with reference to fig. 6, as the voltage VR increases, only the LED driver having the minimum headroom voltage among the first to n-th LED drivers 14_1 to 14—n may generate the feedback current, and thus the feedback current drawn from the voltage supply circuit 12 may be based on the minimum headroom voltage, ultimately generating the supply voltage VSUP based on the minimum headroom voltage.

In order to detect the minimum headroom voltage, a comparison circuit may be additionally provided, which functions to compare the detected first to nth headroom voltages and detect the minimum headroom voltage when the first to nth headroom voltages are detected in the first to nth led drivers 14_1 to 14—n, respectively, unlike as shown in fig. 1. The first to nlde drivers 14_1 to 14—n may be connected to the comparison circuit independently of each other, so that when the number of the first to nlde drivers 14_1 to 14—n increases, the wiring complexity between the first to nlde drivers 14_1 to 14—n and the comparison circuit may be significantly increased. However, as shown in fig. 1, the first to nlde drivers 14_1 to 14—n may be commonly connected to the voltage supply circuit 12, and may be commonly connected to the resistor R. Thus, not only can the wiring of the first through nlde drivers 14_1 through 14—n be simplified, but the addition of LEDs and LED drivers can be facilitated, and the system 10 can have high scalability.

Fig. 2 is a block diagram of a system 20 according to an exemplary embodiment of the present disclosure. Specifically, one LED driver 24 is illustrated in the block diagram of fig. 2, along with the LEDL, voltage supply circuit 22, and resistor R. In some embodiments, the LED driver 24 of fig. 2 may be an example of each of the first to nlde drivers 14_1 to 14—n of fig. 1.

Referring to fig. 2, the LED driver 24 may include first to third pins P21 to P23, an LED current source CS1, a controller CTR, and a feedback current source CS2. The first pin P21 may be connected to the LED L, and may pass the LED driving current ILED. The second pin P22 may be connected to the voltage supply circuit 22, and may allow the feedback current IFB to pass. The third pin P23 may be connected to the resistor R, and may allow the feedback current IFB to pass. In this specification, the first to third pins P21 to P23 may be referred to as a synchronization pin, a feedback input pin, and a feedback output pin, respectively.

The LED current source CS1 may generate an LED driving current ILED, which may be LED out from the LEDL through the first pin P21. Thus, the LED driving current ILED may flow from the voltage supply circuit 22 to the ground potential through LEDL, the first pin P21, and the LED current source CS1 in order. The LED current source CS1 may have any structure that generates the LED driving current ILED, and an example of the LED current source CS1 will be described later with reference to fig. 4. In some embodiments, as shown in fig. 1, the LED current source CS1 may receive the dimming signal DIM and may adjust the magnitude of the LED driving current ILED based on the dimming signal DIM. The dimming signal DIM may be directly input from the outside of the LED driver 24, and may also be generated by a control signal received through a control input pin of the LED driver 24 (e.g., by performing decoding).

The controller CTR may be connected to the LED current source CS1 and may generate a control voltage VCTR based on the headroom voltage VHDR. For example, the controller CTR may compare the headroom voltage VHDR with a reference voltage and generate a control voltage VCTR that decreases when the headroom voltage VHDR is below the reference voltage and increases when the headroom voltage VHDR is above the reference voltage. An example of the controller CTR is described later with reference to fig. 4. In this specification, the controller CTR may be referred to as a control circuit.

The feedback current source CS2 may receive the control voltage VCTR from the controller CTR and may generate the feedback current IFB based on the control voltage VCTR. For example, the feedback current source CS2 may generate the feedback current IFB based on the control voltage VCTR and the resistance value of the resistor R. As shown in fig. 2, the feedback current IFB may flow from the voltage supply circuit 22 to the ground potential through the second pin P22, the feedback current source CS2, the third pin P23, and the resistor R. In some embodiments, when the voltage of the third pin P23 (i.e., VR of fig. 1) is higher than the control voltage VCTR, the feedback current source CS2 may not generate the feedback current IFB, and the magnitude of the feedback current IFB may be close to zero. An example of the feedback current source CS2 is described later with reference to fig. 4.

In some embodiments, the LED driver 24 may be implemented as one semiconductor package. For example, the first to third pins P21 to P23 of fig. 2 may be pins exposed outside the semiconductor package, and may be connected to a pattern of the printed circuit substrate when the semiconductor package is mounted on the printed circuit substrate. As described above, when the first to nlde drivers 14_1 to 14—n of fig. 1 are implemented as the first to nth semiconductor packages, respectively, the first to nlde drivers 14_1 to 14—n may be commonly connected to the voltage supply circuit 12 through the pattern of the printed circuit substrate, and may be commonly connected to the resistor R.

Fig. 3 is a block diagram of a semiconductor package 30 according to an exemplary embodiment of the present disclosure. In the following, the description of fig. 3 will be omitted in duplicate with the description of fig. 2.

In some embodiments, at least two LED drivers of the first to nlde drivers 14_1 to 14—n of fig. 1 may be included in one semiconductor package. For example, as shown in fig. 3, the semiconductor package 30 may include first to fourth pins P31 to P34, a first LED driver 31, and a second LED driver 32. In some embodiments, the semiconductor package may further include at least three LED drivers.

Referring to fig. 3, the first LED driver 31 may include a first LED current source CS11, a first controller CTR1, and a first feedback current source CS12. A first LED (e.g., L1 of fig. 1) may be connected to the first pin P31, and the first LED current source CS11 may draw the first LED driving current ILED1 through the first pin P31. The first controller CTR1 may generate a first control voltage VCTR1 based on the first headroom voltage VHDR 1. The first feedback current source CS12 may generate a first feedback current IFB1 flowing from the second pin P32 to the fourth pin P34. Similarly, the second LED driver 32 may include a second LED current source CS21, a second controller CTR2, and a second feedback current source CS22. A second LED (e.g., L2 of fig. 1) may be connected to the third pin P33, and the second LED current source CS21 may draw the second LED driving current ILED2 through the third pin P33. The second controller CTR2 may generate a second control voltage VCTR2 based on the second headroom voltage VHDR 2. The second feedback current source CS22 may generate a second feedback current IFB2 flowing from the second pin P32 to the fourth pin P34.

The second pin P32 may be connected to the voltage supply circuit 12 of fig. 1, and the fourth pin P34 may be connected to the resistor R of fig. 1. The first feedback current source CS12 of the first LED driver 31 and the second feedback current source CS22 of the second LED driver 32 may be connected to each other through a pattern inside the semiconductor package 30, and may be commonly connected to each of the second pin P32 and the fourth pin P34. For example, when the first LED driver 31 and the second LED driver 32 are included in one chip, the first feedback current source CS12 and the second feedback current source CS22 may be connected to each other through a pattern formed in a conductive layer included in the chip. When the first and second LED drivers 31 and 32 are respectively included in different chips, that is, the semiconductor package 30 is a multi-chip package (MCP), the first and second feedback current sources CS12 and CS22 may be connected to each other through a pattern of a printed circuit substrate, wires, and/or TSVs (through-silicon vias) within the semiconductor package 30. Comparing the LED driver 24 of fig. 2 with the semiconductor package 30 of fig. 3, only pins for drawing LED driving current may be added when the LED driver is added in the semiconductor package.

Fig. 4 is a block diagram of an LED driver 40 according to an exemplary embodiment of the present disclosure. As shown in fig. 4, the LED driver 40 may include first to third pins P41 to P43, an LED current source CS1, a controller CTR, and a feedback current source CS2. Hereinafter, the repetition of the description of fig. 4 with reference to the drawings will be omitted.

Referring to fig. 4, the led current source CS1 may include a first amplifier a41, a first transistor T41, and a resistor R4. The first amplifier a41 may have a non-inverting input for receiving the dimming voltage VDIM and an inverting input connected to the first transistor T41 and the resistor R4, and may amplify a difference between the dimming voltage VDIM and a voltage applied to the resistor R4. The amplified voltage may be provided to a control terminal (e.g., gate) of the first transistor T41, whereby the LED current ILED may depend on the dimming voltage VDIM and the resistance value of the resistor R4 (e.g., iled=vdim/R4). In some embodiments, the dimming voltage VIDM may be variable, e.g., adjustable based on the dimming signal DIM of fig. 2. In some embodiments, the first transistor T41 is a different transistor than the NFET (n-channel field effect transistor) shown in fig. 4, e.g., may be replaced by a bipolar junction transistor (bipolar junction transistor) (e.g., NPN junction transistor).

The controller CTR may include a comparator 41 and a voltage generator 42. The comparator 41 may have a non-inverting input for receiving the reference voltage VREF and an inverting input for receiving the headroom voltage VHDR from the LED current source CS1, and may generate a comparison signal SIG for representing a comparison result. Thus, the comparison signal SIG may be activated when the headroom voltage VHDR is lower than the reference voltage VREF, and may be deactivated when the headroom voltage VHDR is higher than the reference voltage VREF. In some embodiments, unlike as shown in fig. 4, comparator 41 may also have an inverting input for receiving reference voltage VREF and a non-inverting input for receiving headroom voltage VHDR from LED current source CS 1.

The reference voltage VREF may be predefined based on the structure of the LED current source CS 1. For example, the reference voltage VREF may be predefined based on the dimming voltage VDIM, the resistance value of the resistor R4, the characteristics of the first amplifier a41 and the first transistor T41, etc., and may correspond to, for example, the design (or preferred) magnitude of the headroom voltage VHDR (or a magnitude after reacting a certain margin on the basis thereof). In some embodiments, the reference voltage VREF may be generated internally within the LED driver 40. In some embodiments, the reference voltage VREF may be provided externally of the LED driver 40, and a plurality of LED drivers (e.g., 14_1 to 14—n of fig. 1) may commonly receive the reference voltage VREF.

The voltage generator 42 may receive the comparison signal SIG from the comparator 41 and generate the control voltage VCTR increased or decreased based on the comparison signal SIG. For example, the voltage generator 42 may generate the control voltage VCTR that increases in response to the activated comparison signal SIG, and may additionally generate the control voltage VCTR that decreases in response to the deactivated comparison signal SIG. Thus, the control voltage VCTR may increase when the headroom voltage VHDR is lower than the reference voltage VREF, and may decrease when the headroom voltage VHDR is higher than the reference voltage VREF. An example of the voltage generator 42 is described later with reference to fig. 5A and 5B.

The feedback current source CS2 may include a second amplifier a42 and a second transistor T42, and may generate a feedback current IFB flowing from the second pin P42 to the third pin P43. The second amplifier a42 may have a non-inverting input for receiving the control voltage VCTR and an inverting input connected to the third pin P43, and may amplify a difference between the control voltage VCTR and the voltage of the third pin P43. The amplified voltage may be provided to a control terminal (e.g., gate) of the second transistor T42, so that the feedback current IFB may depend on a resistance value (ifb=vctr/R) of a resistor connected to the control voltage VCTR and the third pin P43, i.e., the resistor R of fig. 1. In some embodiments, the second transistor T42 may be replaced by a transistor other than the NFET illustrated in fig. 4, such as a junction transistor (e.g., NPN junction transistor). As described in the description with reference to fig. 1, when the voltage of the third pin P43 is made higher than the control voltage VCTR by another LED driver different from the LED driver 40 of fig. 4, the second transistor T42 may be turned off, and the magnitude of the LED driver 40 feedback current IFB may be approximately zero.

Fig. 5A and 5B are block diagrams of examples of controllers according to exemplary embodiments of the present disclosure. As described in the description with reference to fig. 4, the controllers 50a, 50B of fig. 5A and 5B may generate the control voltage VCTR that increases in response to the activated comparison signal SIG and may generate the control voltage VCTR that decreases in response to the deactivated comparison signal SIG.

Referring to fig. 5A, the controller 50a may include a counter 51 and a digital-to-analog converter (DAC) 52. The counter 51 may have an up-down input for receiving the comparison signal SIG and a clock input for receiving the clock signal CLK. The counter 51 may operate as an up counter in response to the activated comparison signal SIG, and may generate a digital signal DIG having a value that increases with the edge of the clock signal CLK. In addition, the counter 51 may operate as a down counter in response to the deactivated comparison signal SIG, and may generate a digital signal DIG having a value decreasing with the edge of the clock signal CLK. The clock signal CLK may be generated inside the controller 50a or may be generated outside the controller 50a (or LED driver). The digital-to-analog converter 52 may generate a control voltage VCTR having a magnitude corresponding to the value of the digital signal DIG.

Referring to fig. 5B, the controller 50B may include a switching circuit 53 and a capacitor C. The switching circuit 53 may charge the capacitor C in response to the activated comparison signal SIG, and may discharge the capacitor C in response to the deactivated comparison signal SIG. For example, as shown in fig. 5B, the switching circuit 53 may include a first switch SW1 and a second switch SW2. The first switch SW1 may be turned on in response to the activated comparison signal SIG and may be turned off in response to the deactivated comparison signal SIG. Further, the second switch SW2 may be turned off in response to the activated comparison signal SIG and may be turned on in response to the deactivated comparison signal SIG. Thus, when the comparison signal SIG is activated, the capacitor C can be charged by a current flowing from the positive voltage VDD through the first switch SW1, and, in addition, when the comparison signal SIG is deactivated, the capacitor C can be discharged by a current flowing from the capacitor C through the second switch SW2. In some embodiments, the second switch SW2 may be omitted, and the capacitor C may be discharged by the leakage current by turning off the first switch SW 1.

In some embodiments, the first switch SW1 and the second switch SW2 may each include at least one transistor. Further, in some embodiments, the switching circuit 53 may further include a circuit (e.g., an inverter) that generates a signal provided to a control electrode of the transistor from the comparison signal SIG. In some embodiments, the controller 50b may further include a clamping (clamping) circuit connected to the capacitor C in order to limit the range of the control voltage VCTR, and the clamping circuit may include at least one diode.

Fig. 6 is a block diagram of a system 60 according to an exemplary embodiment of the present disclosure. Specifically, the voltage supply circuit 62 and the resistor R are illustrated in the block diagram of fig. 6, while also illustrating the first to nth feedback current sources 64_1 to 64—n included in each of the first to nth led drivers 14_1 to 14—n of fig. 1. Next, fig. 6 will be described with reference to fig. 1.

Referring to fig. 6, the voltage supply circuit 62 may include a voltage regulator 62_1, a first resistor R61, and a second resistor R62. The regulator 62_1 may generate the supply voltage VSUP from the input voltage VIN based on the feedback voltage VFB. For example, the supply voltage VSUP may increase when the feedback voltage VFB decreases, and the supply voltage VSUP may decrease when the feedback voltage VFB increases. In some embodiments, the voltage regulator 62_1 may be a switching regulator. In some embodiments, the voltage regulator 62_1 may be a linear voltage regulator.

The first resistor R61 and the second resistor R62 may provide the feedback voltage VFB to the regulator 62_1 by dividing the supply voltage VSUP. As shown in fig. 6, the first to nth feedback currents IFB1 to IFBn may be drawn from a node to which the first and second resistors R61 and R62 are connected, i.e., a node generating the feedback voltage VFB, so that the feedback voltage VFB may depend not only on the first and second resistors R61 and R62 but also on the first to nth feedback currents IFB1 to IFBn. For example, when the sum of the first to n-th feedback currents IFB1 to IFBn increases, the feedback voltage VFB may decrease and the supply voltage VSUP may increase. In addition, when the sum of the first to n-th feedback currents IFB1 to IFBn is reduced, the feedback voltage VFB may be increased and the supply voltage VSUP may be reduced.

The first feedback current source 64_1 may include a first amplifier a61 and a first transistor T61. The first amplifier a61 may receive the first control voltage VCTR1, may amplify a difference between the first control voltage VCTR1 and the voltage VR, and may provide the first control voltage VCTR1 and the voltage VR to the first transistor T61. The second feedback current source 64_2 may include a second amplifier a62 and a second transistor T62. The second amplifier a62 may receive the second control voltage VCTR2, may amplify a difference between the second control voltage VCTR2 and the voltage VR, and may provide the second control voltage VCTR2 to the second transistor T62. The nth feedback current source 64—n may include an nth amplifier A6n and an nth transistor T6n. The nth amplifier A6n may receive the nth control voltage VCTRn, may amplify a difference between the nth control voltage VCTRn and the voltage VR, and may provide the difference to the nth transistor T6n.

In some embodiments, among the first to n-th feedback currents IFB1 to IFBn, only the feedback current corresponding to the maximum control voltage has a magnitude substantially greater than zero. For example, when the LED current source included in the LED driver including the second feedback current source 64_2 has the minimum headroom voltage, the headroom voltage of the remaining LED drivers except for the second LED driver 14_2 may reach the reference voltage VREF in the process that the voltage supply circuit 62 starts to operate and the supply voltage VSUP increases, and only the headroom voltage of the second LED driver 14_2 may not reach the reference voltage VREF. Thus, the second control voltage VTRC2 may be greater than other control voltages (vctr2=max (VCTR 1, VCTR2, …, VCTRn)) including the first control voltage VTRC1 and the n-th control voltage VCTRn, and other transistors including the first transistor T61 and the n-th transistor T6n other than the second transistor T62 may be turned off.

The voltage VR applied to the resistor R may be substantially the same as the second control voltage VCTR2, and other feedback currents of the first to n-th feedback currents IFB1 to IFBn except for the second feedback current IFB2 may be substantially zero. Thus, the magnitude of the feedback current drawn from the voltage supply circuit 62 may be substantially the same as the magnitude of the second feedback current IFB2 (ifb2=vctr2/R). Finally, a second feedback current IFB2 based on the minimum headroom voltage may be provided to the voltage supply circuit 62, and the voltage supply circuit 62 may generate a supply voltage VSUP based on the feedback voltage VFB that decreases with the second feedback current IFB2.

Fig. 7 is a diagram of a display device 70 according to an exemplary embodiment of the present disclosure. In particular, fig. 7 separately illustrates a backlight module 71 (BLU) and a color panel 72 included in a display panel of the display device 60 for convenience of illustration.

The display device 70 may refer to any device that outputs content, i.e., images or videos, through a display panel. For example, the display device 70 may be a stand-alone device for display purposes, such as a TV, a display, etc., and may also be included as a component in the system to meet display function requirements, such as a display screen of a smart phone, a dashboard of a vehicle, etc. The display device 70 can output content in any manner using the backlight module 71. For example, the backlight module 71 and the color panel 72 may be included in the LCD (liquid crystal display) panel, and the color panel 72 may include a polarizing plate, a TFT (thin film transistor ), a liquid crystal, a color filter, and the like.

The backlight module 71 may include a plurality of LEDs as a light source. For example, as shown in fig. 7, the backlight module 71 may include a plurality of LEDs arranged in an array form. The light output from the LEDs of the backlight module 71 may be combined by the color panel 72 to correspond to the color of the content and output. Mini LEDs may refer to the following ways: LEDs of small size (for example, hundreds of μm) are compactly arranged in the backlight module 71, and the brightness of the local dimming area (local dimming zone) composed of at least one LED, that is, the intensity of light output by the local dimming area is adjusted according to the content. The mini LED can solve the problem of low contrast ratio of LCD display, thus realizing high quality and low cost of display device. The foregoing system described with reference to the drawings can be used as the backlight unit 71, whereby the deviation between the plurality of LED drivers can be easily detected with a simple structure, so that the optimum supply voltage can be supplied to the LEDs. Thereby, the efficiency of the LED driver can be increased, and eventually the efficiency of the backlight unit 71 and the display device 70 can be increased.

Fig. 8 is a flowchart of a method for generating an optimal supply voltage according to an exemplary embodiment of the present disclosure. As shown in fig. 8, the method for generating the optimal supply voltage may include a plurality of steps (S20, S40, S60, and S80). In some embodiments, the method of fig. 8 may be performed by the system 10 of fig. 1. Next, fig. 8 will be described with reference to fig. 1.

Referring to fig. 8, an LED driving current may be generated in step S20. In some embodiments, the first to nlde drivers 14_1 to 14—n may generate the first to nlde driving currents ILED1 to ILEDn, respectively, and the first to nlde driving currents ILED1 to ILEDn may be drawn from the first to nlde L1 to Ln, respectively.

In step S40, a control voltage may be generated based on the headroom voltage. In some embodiments, the first to nth led drivers 14_1 to 14—n may generate first to nth control voltages, respectively, based on the first to nth headroom voltages. For example, the second LED driver 14_2 may generate a second control voltage that increases when the second headroom voltage is lower than the reference voltage and decreases when the second headroom voltage is higher than the reference voltage.

In step S60, a feedback current may be generated based on the control voltage. In some embodiments, the first to nth led drivers 14_1 to 14—n may generate the first to nth feedback currents IFB1 to IFBn, respectively, based on the first to nth control voltages. For example, as described in the description with reference to fig. 6, only the feedback current corresponding to the minimum headroom voltage among the first to n-th feedback currents IFB1 to IFBn may have a magnitude greater than zero.

In step S80, a supply voltage may be generated based on the feedback current. In some embodiments, the sum of the first through n-th feedback currents IFB1 through IFBn may be drawn from the voltage supply circuit 12, and the voltage supply circuit 12 may generate the supply voltage VSUP based on the sum of the first through n-th feedback currents IFB1 through IFBn. As previously described, other feedback currents than the feedback current corresponding to the minimum headroom voltage may be substantially zero, whereby the voltage supply circuit 12 may generate the supply voltage VSUP based on the feedback current corresponding to the minimum headroom voltage.

According to the LED driver, the light emitting module, and the display device of the exemplary embodiments of the present disclosure, a supply voltage having a minimum margin may be generated, and thus the efficiency of the LED driver, the light emitting module, and/or the display device may be increased.

Further, according to the LED driver, the light emitting module, and the display device of the exemplary embodiments of the present disclosure, a deviation between a plurality of LED drivers can be detected by a simple structure, and thus high expandability can be provided.

The effects obtainable in the exemplary embodiments of the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned herein can be clearly deduced and understood by those having ordinary skill in the art to which the exemplary embodiments of the present disclosure belong based on the following description. That is, for unexpected effects in practicing the exemplary embodiments of the present disclosure, those having ordinary skill in the art to which the exemplary embodiments of the present disclosure pertain can also derive.

Exemplary embodiments are disclosed in the figures and description above. The present specification describes embodiments using specific terms, and the use of such terms is intended to describe the objects of the present disclosure, not to limit the scope of the present disclosure as set forth in the claims. Accordingly, it will be understood by those of ordinary skill in the art that various modifications may be made and equivalents may be implemented without departing from the scope of the present disclosure. Therefore, the true technical scope of the present disclosure should be determined by the technical ideas of the appended claims.

Claims

1. An LED driver, comprising:

a first synchronization pin, a feedback input pin, and a feedback output pin;

a first LED current source configured to draw a first LED drive current from at least one first LED through the first synchronization pin;

a first controller configured to generate a first control voltage based on a first headroom voltage of the first LED current source; and

a first feedback current source configured to generate a first feedback current flowing from the feedback input pin to the feedback output pin based on the first control voltage, wherein the headroom voltage corresponds to a voltage of the first synchronization pin.

2. The LED driver of claim 1, wherein,

the first controller includes:

a comparator configured to compare the first headroom voltage with a reference voltage; and

a voltage generator configured to generate the first control voltage that increases or decreases according to an output signal of the comparator.

3. The LED driver of claim 2, wherein,

the voltage generator includes:

a counter configured to generate a digital signal that increases or decreases according to the output signal; and

a digital-to-analog converter configured to convert the digital signal to the first control voltage.

4. The LED driver of claim 2, wherein,

the voltage generator includes:

a capacitor configured to provide the first control voltage; and

and a switching circuit configured to charge or discharge the capacitor according to the output signal.

5. The LED driver of claim 1, wherein,

the first feedback current source includes:

a transistor connected to the feedback input pin and the feedback output pin; and

an amplifier configured to amplify a difference between the first control voltage and the voltage of the feedback output pin and to provide the amplified voltage to a control electrode of the transistor.

6. The LED driver of claim 1, further comprising:

a second sync pin;

a second LED current source configured to draw a second LED drive current from at least one second LED through the second synchronization pin;

a second controller configured to generate a second control voltage based on a second headroom voltage of the second LED current source;

a second feedback current source configured to generate a second feedback current from the feedback input pin to the feedback output pin based on the second control voltage.

7. The LED driver of claim 1, wherein,

further comprising a control input pin for providing a control signal,

the first LED current source is configured to adjust a magnitude of the LED drive current based on a control signal received through the control input pin.

8. A lighting system, comprising:

a plurality of LEDs;

a voltage supply circuit configured to supply a supply voltage to the plurality of LEDs;

a first LED driver configured to draw a first LED drive current from at least one first LED of the plurality of LEDs and to draw a first feedback current from the voltage supply circuit based on a first headroom voltage;

a second LED driver configured to draw a second LED drive current from at least one second LED of the plurality of LEDs and generate a second feedback current from the voltage supply circuit based on a second headroom voltage; and

a resistor configured to receive the first feedback current from the first LED driver and the second feedback current from the second LED driver.

9. The lighting system of claim 8, wherein the light emitting device comprises a light emitting device,

the first LED driver and the second LED driver are configured to be commonly connected to a feedback pin of the voltage supply circuit and to draw the first feedback current and the second feedback current, respectively, from the feedback pin.

10. The lighting system of claim 9, wherein the light emitting device comprises a light emitting device,

the voltage supply circuit is configured to generate a feedback voltage in the feedback pin by dividing the supply voltage and to regulate the supply voltage based on the feedback voltage.

11. The lighting system of claim 8, wherein the light emitting device comprises a light emitting device,

the first LED driver and the second LED driver are commonly connected to the resistor.

12. The lighting system of claim 8, wherein the light emitting device comprises a light emitting device,

the first LED driver is configured to compare the first headroom voltage with a reference voltage, and to increase or decrease the first feedback current based on the comparison,

the second LED driver is configured to compare the second headroom voltage with the reference voltage and increase or decrease the second feedback current according to the comparison result.

13. The lighting system of claim 8, wherein the light emitting device comprises a light emitting device,

the first and second LED drivers are contained in first and second semiconductor packages, respectively, and the light emitting system further includes a substrate on which the first and second semiconductor packages are mounted.