TW201225726A - Current balance scheme for multiple LED strings driving - Google Patents

Abstract

This invention discloses a driver for driving multiple LED, methodand LCD thereof. The driver comprises voltage converting unit, receiving input voltage and generating output voltage in output terminal based on the input voltage, the output voltage applied on a teminal of each LED; current balance unit, coupled to another terminal of each LED, providing and regulating driving current for multiple LED to balance driving current of each LED; and feedback selecting unit, selecting the minimum value of feedback voltages which represent driving current respectively and providing for voltage converting unit via input terminal of feedback. The LED driver, method and LCD thereof disclosed by this invention may improve the efficiency, balance current and include function of short current protection.

Description

201225726 VI. Description of the Invention: [Technical Leadership of the Invention] [0001] Embodiments of the present invention relate to a driver and display of a light-emitting element. Further, it relates to a driver, a driving method, and a display device thereof, which are related to a plurality of Yilian light-emitting elements. [Prior Art] [0002] Today, light-emitting diode (LED) technology has been rapidly developed. The technology can be widely used in various fields such as liquid crystal display (LCD) backlighting, low power lighting, automotive lighting, decorative lighting, camera flashing, and the like. For large area lighting applications, multiple LEDs need to be used simultaneously to achieve higher illumination levels. If these LEDs are connected in series, that is, a series LED string is formed, the series LED string will withstand a voltage of several hundred volts, which means that the driving circuit for driving the series LED string must be able to handle several hundred The volt-sized high voltage and power devices in the circuit must also be capable of carrying high voltages of several hundred volts in size. This is difficult to implement in practical applications, and even if it can be realized, the cost is quite high. Therefore, in the circuit, a plurality of led strings are connected in parallel to obtain high-brightness illumination. In a parallel led string circuit, it is required that the parallel LED string has a high precision current equalization capability to obtain a high power output. Fig. 1 shows a conventional circuit 10 for driving a parallel LED string. As shown in Fig. 1, in the circuit 10, a plurality of LED strings SI, S2, ..., Sn are connected in parallel, where η is a natural number. Taking the LED string S1 as an example, it includes a plurality of anodes and cathodes interconnecting light-emitting diodes 1 : 1) 11, LEDs 12, ..., LEDlm, where m is a natural number, and a town Current resistance RBi. The first end of the ballast resistor RB1 is connected in series to the cathode of the LEDim. The LED string 82........ also has the same structure, in order to avoid redundancy, here is not 099144045 Form No. A0101 Page 4 / Total 27 Page 1003117448-0 201225726 Further details. LED 】, LED21 ........ The anodes of LEDnl are connected together to form a common anode terminal, which is connected to the output terminal of the DC/DC converter (DC-DC converter). The second ends of the ballast resistors RB1' RB2........RBn are connected together to form a common cathode terminal connected to the first end of the current detecting resistor RS1. The second end of the current sense resistor RS1 is coupled to ground. The current sense resistor {^1 is used to detect the sum of the currents of the individual LED strings, i.e., the total LED current, which may be integrated into the circuit' or may be a discrete device. In the circuit, by electricity

The feedback voltage obtained by sampling the flow detecting resistor RS1 is supplied to the conversion

The feedback pin FB of the device, the DC-DC converter provides a bus voltage according to the feedback voltage, which should be large enough to drive the individual LED strings. Since the forward voltages of each of the LED strings are different from each other, a ballast resistor is used in each of the LED strings to adjust the current of the LED string in which it is placed. In some applications, in order for the circuit to utilize pulse width modulation (PWM) techniques to achieve fast dimming capability, a transistor SD1 can be connected in series between the common cathode terminal and the current sense resistor RS1. The circuit 1 shown in Fig. 1 uses a ballast resistor to regulate the current of the LED string without the need to specifically design a current balancing control circuit, thereby simplifying the system circuit. However, in circuit 10, the power loss on the ballast resistor is large and the accuracy of current balancing is also poor. In particular, these disadvantages are more pronounced for situations where the LED forward voltage or LED string current is large. In addition, for a circuit employing transistor SD1 for dimming, if there is a shorted LED string in the circuit, the voltage stress experienced by SD1 is very high 'can be as many as several hundred volts' which may damage the transistor. Figure 2 shows another conventional circuit 20 for driving a parallel led string. Part of the circuit in the figure has the same structure as the part of the circuit in Fig. 1, 099144045 2nd is 1003117448-0 Form nickname A0101 Page 5 / Total 27 page 201225726 Avoiding the same description of the limbs 2 and 1BI The circuit portion will not be described in detail, and only the different circuit portions in FIG. 2 and FIG. 1 will be described. As shown in Fig. 2, L_S1, S2.....Sn each include a current source CS1, CS2 CSn, and the first ends of the current sources CS1, CS2, CSn are respectively connected to the LEDs of the LED1ni, the LED2ni, and the LED nm. And their second end is connected to the ground. All current sources - form a current source circuit 2〇1. Similarly, current source circuit 2〇1 can be integrated into the circuit' or it can be a discrete device. a current setting resistor

The first end of the SET is connected to the current source circuit 201, and the second end thereof is grounded. In a drop application, the dimming terminal dim of the DC-DC converter can be connected to the dimming terminal DIM of the current source circuit 201 to provide a pulse width modulated signal for dimming. The first end of the resistor R1 is connected to the input A^&OUT of the "DC converter", the first end of the resistor R2 is connected to the second end of the resistor ri, and the second end of the resistor R2 is grounded. The first end of the resistor and the first end of the resistor are both connected to the feedback end (9) of the DC-DC converter to provide a feedback voltage for the DC_DC conversion. In the circuit 2〇 shown in FIG. 2, the current source CS1 'CS2 ........CSn current equalizes the LED string in which it is located according to the value of the current setting resistor rset. The team-turn converter provides a busbar voltage large enough to illuminate each LED string. The converter adjusts the bus voltage according to the feedback voltage and no longer needs to adjust the current of the LED string. This method has good current balancing capability. However, due to the large bus voltage provided by the DC-DC converter, The forward voltage required by the LED, the remaining voltage will be consumed by the current source. The larger the busbar voltage, the more voltage is consumed by the current source, and the power loss is greater. In addition, the circuit shown in Figure 1 Similarly, for a circuit that uses PWM technology for dimming, if there is a shorted LED string in the circuit, current 099144045 1003117448-0 Form No. A0] 01 Page 6 / Total 27 Page 201225726 , '., and voltage stress very high, Up to several hundred volts, which may damage the current source. SUMMARY OF THE INVENTION [0003] 99 ❹ 099144045 = one or more problems in the prior art, an object of the present invention is to provide a driver for driving a plurality of light-emitting elements A driving method and a display device including the same. In an aspect of the invention, a driver for driving a plurality of light emitting elements is provided, comprising: a voltage conversion single 7G 'receiving wheel human voltage, based on the received input voltage at the output end Generating an output voltage 'where the output voltage is applied to one end of each of the light-emitting elements; an electric peach equalization unit 70,_ coupled to the other end of each of the light-emitting elements for providing and regulating the plurality of light-emitting 7L pieces Driving current so that the driving currents of the respective light emitting elements are matched; and a feedback selection unit 70' whose input end is connected between the current equalizing unit and the other end of the plurality of light emitting elements, and the output end thereof is pure Go to the feedback input of the voltage conversion unit for selecting a minimum feedback voltage from among the respective feedback voltages characterization of the respective drive currents, and via the a feedback input is provided to the voltage conversion unit. According to an embodiment of the invention, the voltage conversion unit adjusts the output voltage based on the minimum feedback voltage such that the output voltage has a minimum sufficient to drive each of the light-emitting elements According to another aspect of the present invention, a driving method of driving a plurality of light emitting elements is provided, comprising: receiving an input voltage, generating an output voltage at an output based on the received input voltage, wherein the output voltage is applied to each of the light emitting One end of the component, the form number Α0101, page 7 / total 27 pages, 201225726, provides and adjusts the driving for the plurality of U-pieces, so that the driving currents of the respective illuminating elements are matched; and from the respective "characteristics" that characterize each of her currents The minimum feedback voltage is applied and the selected minimum feedback voltage is provided. A display device, including the above. According to still another aspect of the present invention, it is proposed that the driving of driving a plurality of light-emitting elements provides a light-emitting element driver, a driving method, and a short-circuit protection function with high efficiency, uniformity, uniformity, and short-circuit protection. display screen. [Embodiment] [0004] The driver of the light-emitting element of the embodiment. In the following, the specific details, such as the i-body circuit structure in the embodiment and the specific parameters of these circuit elements, provide a better understanding of the embodiments of the present invention. Those skilled in the art will appreciate that embodiments of the present invention can be implemented even in the absence of a combination of details or other methods, components, materials, and the like. The following description is based on a plurality of LED strings connected in parallel. However, embodiments of the present invention are not limited thereto, and other types of light-emitting elements and other coupling forms may also be considered. The parallel light-emitting diode (LED) driving circuit in the prior art uses a ballast resistor or a current source to balance the current of each LED string, and the current adjustment precision is poor, and the power loss caused by the ballast resistor or the current source is also Larger, making the system less efficient and when the LED string is short-circuited, the 0991440445 is vulnerable to damage to the circuit. According to an embodiment of the present invention, a novel parallel LED string driving circuit and a method thereof are provided. The parallel LED string driving circuit has a form number A0101, a δ page, a total of 27 pages, 1003117448-0 201225726, a good current balancing capability, and a system efficiency. High and capable of providing short circuit protection. One embodiment of the present invention provides an LED driver including a DC-DC converter, a current balancing circuit, and a feedback selector as described below, which is capable of converting from a current balancing circuit to a DC-DC Providing a minimum feedback voltage among the respective feedback voltages that characterize the respective drive currents, such that the DC_DC converter adjusts the output voltage based on the minimum feedback voltage such that the output voltage has a minimum value sufficient to drive each of the light-emitting elements, thereby Providing high-precision current equalization and matching while improving the efficiency of LED driving and preventing power loss caused by excessive busbar voltage. Different embodiments of the present invention also provide protection functions for the LED driver, which can prevent the circuit from being Excessive current damages the circuit components when there is a shorted LED string. Different embodiments of the present invention also provide a self-regulating current source that is capable of adjusting the drive current of the LED string to follow a reference value for perfect current balancing and matching. Various embodiments of the present invention are directed to corresponding driving methods, and display devices including the above-described drivers and/or associated circuits, such as LED displays and the like. In the following detailed description, an LED driver of one embodiment of the present invention will be described by taking a DC-DC converter as a power supply circuit for an LED as an example, so that those skilled in the art can better understand the present invention. However, it should be understood by those skilled in the art that these descriptions are only exemplary and are not intended to limit the scope of the invention. Fig. 3 is a circuit diagram showing an LED driver according to an embodiment of the present invention, generally showing a circuit for driving a plurality of LED strings connected in parallel. 30 099144045 Form No. A0101 Page 9 of 27 1003117448-0 201225726

/ As shown in Fig. 3, the circuit 3 includes a DC_DC converter 3〇2, a current equalization circuit 301, a feedback selector 3〇3, and a plurality of parallel hunger ED strings S1, S2. .Sn, where η is an arbitrary natural number. Taking the LED string S1 as an example, it comprises a plurality of anodes and cathodes interconnecting light-emitting diodes LEI) 11 'LED12, LEDlm, wherein m is an arbitrary natural number, according to an embodiment of the invention, the circuit 3〇 also includes a current Setting

SET As shown in Fig. 3, one end of each of the led strings SI, S2, ..., Sn is connected to the DC-DC converter 302, and the other end is coupled to the current equalization circuit 3〇1. According to an embodiment of the present invention, the anodes of the LEDs 11, LEDs 21, ..., LEDn1 of all the LED strings are connected together, forming a common anode terminal which is connected to the output terminal out of the DC-DC converter 302, and each LED The last LED of the string, that is, LEDlm, LED2m........ The cathode of LEDnm is respectively coupled to the current equalization circuit. According to an embodiment of the present invention, the DC_DC converter 3〇2 receives an input voltage, generates an output voltage at the output based on the received input voltage, and applies an output voltage to each LEd string S1, s2 through the output terminal OUT. One end of .^. Here, the output voltage that is outputted to the common anode terminal through the output terminal 〇ϋτ is also referred to as a bus bar voltage. According to an embodiment of the present invention, the current equalization circuit, such as pure to the other end of each of the LED strings 099144045 . . . , provides and regulates the driving current for each of the LED strings SI, S2, ..., Sn, so that each of the driving The drive currents of the LED strings S1, S2, ..., Sn are matched. According to an embodiment of the invention, the =feed terminal FB' of the ship_sink converter 302 is provided to provide the respective feedbacks characterization of the respective turbulent currents to Dc - this converter 3 〇 2 . According to an embodiment of the present invention, the input form of the feedback selection form number A0101, page 10 / page 27, 1003117448-0 201225726 is coupled to the current equalization circuit 3〇2 and the plurality of 1::) strings S1, S2. Between the other ends of Sn, its output is coupled to the feedback terminal FB of the DC_DC converter 302, and the feedback selector 303 selects the minimum feedback voltage from among the respective feedback voltages that characterize the respective drive currents. And supplied to the DC-DC converter 302 via the feedback terminal FB. According to an embodiment of the present invention, the DC-DC converter 302 is responsive to the return voltage supplied from the feedback selector 303, that is, the busbar voltage outputted to the common anode terminal through the output terminal OUT, thereby providing sufficient driving of the respective LED strings SI, S2. The minimum busbar voltage, such as Ο, provides high-precision current balancing and matching while increasing the efficiency of LED driving and preventing excessive power loss due to busbar voltage. According to an embodiment of the invention, the current equalization circuit 3〇1 includes a plurality of current sources CS1, CS2, . . . , CSn 'each of the current sources CS1, CS2, ..., CSn is consumed by the LED The other end of the corresponding LED string in the strings SI, S2, ..., Sn provides and regulates the drive current for the LED string. For example, as shown in Figure 3, the first end of current source CS1 is connected in series to the cathode of LEDlm,

The second end is grounded. The LED strings S2.....Sn also have the same structure, and are not described in detail here in order to avoid redundancy. The current sources CS1, CS2, ..... CSn can be integrated in the circuit or can be discrete devices. The current source is described in more detail later. The current sources CS1, CS2, ..., CSn are current-balanced according to the value of the current setting resistor RSET, respectively, to provide a high-accuracy, self-regulating current balancing function. As shown in Fig. 3, one end of the current setting resistor RSET is coupled to the current equalization circuit 301, and the other end is connected to the ground. When the circuit 30 is in operation, each current source adjusts its corresponding LED string current according to the value of the current setting resistor RSET. 099144045 Form No. A0101 Page 11 of 27 1003117448-0 201225726 According to an embodiment of the invention, each of the current sources CS1, CS2........ CSn is also coupled to the dimming of the DC-DC converter 302 Terminal dim to apply pulse width modulation (PWM) dimming to the corresponding LED string. According to an embodiment of the present invention, the feedback selector 303 is implemented by a minimum voltage selection circuit MIN, and the input terminals of the minimum voltage selection circuit MIN are respectively connected to the first ends of the current sources CS1, CS2, ..., CSn. Its wheel end is connected to the feedback terminal FB of the DC-DC converter. Although the feedback selector 303 is shown in a separate arrangement from the current sources CS1, CS2, ..., CSn, they may be integrated together, for example integrated together in the current balancing circuit 3〇1, in accordance with the present invention. In an embodiment, the minimum voltage selection circuit MIN 3〇3 detects the voltage drop across the respective current sources as a feedback voltage characterizing the respective drive currents of the respective LED strings, selects a minimum voltage from the plurality of feedback voltages, and feeds the minimum voltage back to DC-DC converter 302. The DC-DC converter 302 can provide a minimum bus voltage sufficient to drive each LEI string based on the minimum return voltage. According to an embodiment of the invention, the current equalization circuit 3〇1 may be integrated in the circuit 3〇 or may be a discrete device. According to the embodiment of the present invention, since a current source is used to adjust the current in each of the LED strings, the circuit 3 has good current balance control capability, and the LED current is adjusted more accurately, so that the circuit efficiency is improved. . In addition, since the bus voltage is adjusted by feeding back the minimum value of the voltage drop across the respective current sources to the DC-DC converter, the circuit 3 is greatly reduced due to the excessive confluence compared with the conventional parallel LED string driving circuit. The power loss that is formed on the current source by discharging the voltage. 4 is a circuit diagram of an LED driver according to another embodiment of the present invention. 1003117448-0 099144045 Form No. A010I Page 12 of 27 201225726 忍 Shows a picture, generally not driving multiple LED strings in parallel Circuit Lee'. Compared with the circuit 30 shown in Fig. 3, the circuit 3A shown in Fig. 4 is different in that a protection circuit is added. The other circuit arrangement is the same as the circuit arrangement shown in Fig. 3, which will not be described in detail herein. Those skilled in the art will appreciate that the current equalization circuit 301 can withstand very high voltage stresses in the presence of shorted LED strings, which can be as high as several hundred volts, which can damage the current balancing circuit 3〇1. According to the embodiment of the present invention, a protection circuit 304 is coupled between the other end of the plurality of LED strings and the current equalization circuit 3〇1 for limiting the current flowing through the current equalization circuit 3〇1 to protect the current equalization circuit 3 1 Protected from high currents. According to an embodiment of the present invention, the protection circuit 3〇4 may be an N-type field effect transistor, and the breakdown voltage of the transistor may be set to be larger than the drain-source voltage on the transistor when the LED string is short-circuited. According to an embodiment of the invention, the current equalization circuit 3.1 includes a plurality of current sources CS1 'CS2........CSn. Can be set separately for each current source

protect the circuit. As shown in Fig. 4, an n-type field effect transistor NFET T1 is connected between the cathode of the LEDlm and the current source CS1, between the cathode of the LED 2m and the current source CS2, ..., between the cathode of the LED nm and the power source CSnm. •, Τη's 'Τη结构' Τη. The N-type field effect transistor τι gates each receive a predetermined gate voltage V. NFET T1,

G becomes the protection circuit 304. According to an embodiment of the present invention, the protection circuit 304 may be provided separately or integrated with other circuit devices. For example, the protection circuit 〇4 can be integrated with the feedback selector 303 and the current equalization circuit 3〇i. The following describes how the protection circuit protects in conjunction with Figure 5. Figure 5 shows the output characteristics of the NFET. As shown in Figure 5, during normal operation, 099144045 Form No. A0101 Page 13 / Total 27 Page 1003117448-0 201225726 That is, the gate-source voltage VGs of the NFET is greater than the threshold voltage, and when VGS>v, the NFET is turned on to conduct the LED. Tilt current. When the LED string is shorted, the NFET will carry a voltage of up to several hundred volts, ie the NFET's drain-to-source voltage will be as high as several hundred volts. However, as long as the drain-source voltage is less than the rated breakdown voltage VDS_BV, the current flowing through the LED will be limited to a lower value of 1 DS, ensuring that the current flowing through each current source is lower, will not Will suffer damage due to high current. Therefore, as long as the breakdown voltage of the transistor is set to be larger than the drain-source voltage on the transistor when the LED string is short-circuited, the current flowing through each current source can be limited to a lower value to prevent it from being damaged by a large current. Embodiments of the invention are not limited to the above described protection circuit 3〇4 4NFET, but any suitable current or voltage limiting measure can be applied. Fig. 6 is a flow chart showing a method of driving an LED according to an embodiment of the present invention. As shown in FIG. 6, the method is generally shown as 6〇. In step 6〇2, the DC-DC converter 302 receives the wheel-in voltage, generates an output voltage at the output based on the received input voltage, and applies the output voltage to One end of each LED string. At step 604, the current balancing circuit 〇1 provides and adjusts the drive current for each of the LED strings such that the drive currents of each of the LED strings match. At step 606, the feedback selection circuit 303 selects the minimum return power I from among the respective feedback powers that characterize the respective drive currents, and provides the selected minimum feedback voltage. At step 608, the DC-DC converter 3〇2 adjusts the output voltage based on the minimum feedback voltage such that the output voltage has a minimum value sufficient to drive each of the LEDs. The method 6Q may further include the following steps (not shown): a current limiting circuit 304 is provided at the other end of each LED string to prevent damage to the current balancing circuit 301 caused by a large current generated when the LED string is short-circuited. . 099144045 Form No. A0101 Page 14 of 27 1003117448-0 201225726 The current sources shown in Figures 3 and 4 will be described in detail below with reference to Figures 7 and 8. Ο Figure 7 shows an example of a specific circuit for each of the current sources shown in Figures 3 and 4. As shown in Fig. 7, the current source CS1 is taken as an example, and the other current sources have the same configuration. The current source CS1 includes a germanium crystal Q1, a current detecting resistor RS1, and an error amplifier ΕΑ. The transistor Q1 is used as an adjustment switch, and the collector is the first end of the current source CS1 described in FIG. 3 and FIG. 4, coupled to the cathode of the LEDlm, and the emitter of the transistor Q1 is connected to the first of the current detecting resistor RS1. The second end of the current detecting resistor RS1 is the second end of the current source described in FIG. 3 and FIG. 4, and is connected to the ground. The inverting input of the error amplifier EA is connected to the first end of the current detecting resistor R S1 for receiving the sampling voltage sampled by the current detecting resistor RS1, and the non-inverting input of the error amplifier EA is received by the third and fourth figures The current setting resistor RSET is shown to set the reference voltage VREF, and the output of the error amplifier EA is connected to the base of the transistor Q1. The error amplifier EA is also connected to the dimming terminal DIM of the DC-DC converter shown in Figures 3 and 4 to provide PWM dimming. When the current source CS1 is operating, if the drive current flowing through the LED string S1 is small, the current sense resistor RS1 samples the sampled voltage by detecting the drive current to be smaller than the reference voltage vREF. In this case, the output voltage of the error amplifier EA will increase, so that the gate drive current of the transistor Q1 is increased, so that more current flows through the LED string S1, increasing the drive current. On the other hand, if the drive current flowing through the LED string S1 is large, the current sense resistor RS1 samples the sampled voltage by detecting the drive current to be larger than the reference voltage. In this case, the output voltage of the error amplifier ^ is reduced by K γ so that the gate drive current of the transistor Q1 is decreased 'so that the reduced current flows through the LED string S1, reducing the drive current. Thus, Fig. 7 099144045 Form No. A0101 Page 15 of 27 1003117448-0 201225726 The example structure of the current source CS1 forms a closed loop that regulates the drive current of the LED string S1. The self-regulating current source shown in Figure 7 is capable of adjusting the drive current following reference value of the LED string for perfect current balancing and matching. Fig. 8 shows another specific circuit example of each of the current sources shown in Figs. 3 and 4. As shown in Fig. 8, the current source CS1 is still taken as an example. The other current sources have the same configuration. The example of Fig. 8 uses a PNP transistor Q1' as an adjustment switch that emits the first end of the current source CS1 as shown in Figs. 3 and 4, coupled to the cathode of the LEDlm, and the collector connection of the transistor Q1'. To the first end of the current detecting resistor RS1, the second end of the current detecting resistor RS1 is the second end of the current source described in FIGS. 3 and 4, and is connected to the ground. The non-inverting input of the error amplifier EA is connected to the first end of the current detecting resistor RS1 for receiving the sampling voltage sampled by the current detecting resistor RS1, and the inverting input terminal of the error amplifier EA is received by the third and fourth figures. The reference voltage VDF1? set by the current setting resistor Ret?T is shown, and the output of the error amplifier EA is connected to the base of the transistor Q1'. The error amplifier EA is also connected to the dimming terminal DIM of the DC-DC converter shown in Figures 3 and 4 to provide PWM dimming. When the current source CS1 is operating, if the driving current flowing through the LED string S1 is small, the sampling voltage sampled by the current detecting resistor R S1 by detecting the driving current is smaller than the reference voltage VD17l:. In this case, the output voltage of the error amplifier EA will decrease, causing the gate drive current of the transistor Q1' to decrease, thereby causing more current to flow through the LED string S1, increasing the drive current. Conversely, if the drive current flowing through the LED string S1 is large, the current sense resistor R S1 samples the sampled voltage by detecting the drive current to be greater than the reference voltage VDPP. In this case, the output voltage of the error amplifier EA will increase by 099144045 Form No. A0101 Page 16 / Total 27 Page 1003117448-0 201225726 'The gate drive current of the transistor Q 减小 is reduced, and the current flows through the LED string. S1, the drive current is reduced. The exemplary structure of the current source C S1 forms a closed loop such that the same 'Fig. 8' is reduced to adjust the drive current of the led string si. The self-regulating | source shown in Figure 8 can adjust the drive current of the LED string to follow the reference value to achieve a good current balance and matching.

The embodiments of the present invention are not limited to the specific examples described above, and those skilled in the art should understand that a 场-type field effect transistor, a p-type field effect transistor, or other devices having similar functions may also be used as the adjustment switch, and other Any suitable configuration is used to implement the current source. The above description and embodiments of the present invention are merely illustrative of the LED driver and the driving method of the embodiments of the present invention, and are not intended to limit the scope of the present invention. Variations and modifications of the disclosed embodiments are possible, and other possible alternative embodiments and equivalent variations to the elements of the embodiments will be apparent to those of ordinary skill in the art. Other variations and modifications of the disclosed embodiments of the invention do not depart from the spirit and scope of the invention. BRIEF DESCRIPTION OF THE DRAWINGS [0005] The following drawings illustrate embodiments of the invention. These drawings and embodiments provide some embodiments of the invention in a non-limiting, non-exhaustive manner. 1 is a schematic diagram of an LED driving circuit in the prior art; FIG. 2 is a schematic diagram of another LED driving circuit in the prior art; and FIG. 3 is a circuit diagram 099144045 of an LED driver according to an embodiment of the present invention; 4 is a schematic diagram of a circuit diagram of an LED driver according to another embodiment of the present invention. A No. A0101, page 17 of 27, 1003Π7448-0 201225726; FIG. 5 shows an output characteristic of an N-type field effect transistor; 6 illustrates an LED driving method according to an embodiment of the present invention; FIG. 7 shows a specific circuit example of a current source in the driver circuit shown in FIGS. 3 and 4; and FIG. 8 shows a third diagram. And another specific circuit example of the current source in the driver circuit shown in FIG. [Main component symbol description] [0006] 10, 20, 30, 30' circuit 201 current source circuit 301 current equalization circuit 302 DC-DC converter 303 feedback selector 304 protection circuit CS1, CS2, CSn current source DC-DC DC /DC DIM dimming terminal EA error amplifier FB feedback pin LED light-emitting diode MIN minimum voltage selection circuit OUT output

Ql, SD1 transistor

Rl, R2 Resistor RBI ' RB2 ' RBn Ballast Resistor 099144045 RS1 Current Sense Resistor Form No. A0101 Page 18 of 27 1003117448-0 201225726 D SET , Current Setting Resistor si, S2 ' Sn LED String T1 ' T2, Tn N Field Effect Transistor NFET VDS Drain Source Voltage V βν Breakdown Power, Whole VG Gate Voltage VGS Gate Source Voltage Vref Reference Voltage Vt Threshold Voltage 099144045 Form No. A0101 Page 19 of 27 1003117448-0

Claims (1)

201225726 VII. Patent application scope: 1. A driver for driving a plurality of light-emitting elements, comprising: a voltage conversion unit that receives an input voltage, generates an output voltage at an output terminal based on the received input voltage, wherein the output voltage is applied to each One end of the light emitting element; a current equalizing unit coupled to the other end of each of the light emitting elements for supplying and adjusting a driving current for the plurality of light emitting elements such that driving currents of the respective light emitting elements are matched; and a feedback selecting unit An input end is coupled between the current equalization unit and the other end of the plurality of light emitting elements, and an output end thereof is coupled to a feedback input end of the voltage conversion unit for respectively characterizing each driving current A minimum feedback voltage is selected among the feedback voltages and supplied to the voltage conversion unit via the feedback input. 2. The driver of claim 1, wherein the voltage conversion unit adjusts the output voltage based on the minimum feedback voltage such that the output voltage has a minimum value sufficient to drive each of the light-emitting elements . 3. The driver of claim 1, wherein the current equalization unit comprises: a plurality of current sources, each current source coupled to the other end of a corresponding one of the plurality of light emitting elements The driving current is supplied and regulated for the light emitting element, and the input end of the feedback selecting unit is coupled to the plurality of current sources to detect the voltage drop across the respective current sources as respective feedback voltages for characterizing the respective driving currents. 4. The driver of claim 3, wherein each current source provides and adjusts a drive current according to a value of a current setting resistor, wherein the electric 099144045 form number A0101 page 20/27 pages 1003117448-0 201225726 One end of the current setting resistor is coupled to the corresponding current source, and the damper of the voltage conversion unit is coupled to each current source to pass through The smattering of the singularity is applied to the plurality of illuminating elements by applying pulse width modulation dimming. μ The driver of claim 3, wherein the source to the internal source includes an adjustment switch, an error amplifier, and a current sensing resistor. One input end of the error amplifier is coupled to the reference voltage, and is connected to one end of the current sensing resistor, the output end is coupled to the regulating end, and the other end of the current sensing resistor is grounded; The control terminals are respectively lightly connected to the one end of the light-emitting element and the current sensing resistor, wherein the error amplifier receives the sampling voltage provided by the current sensing resistor through the sense current, and based on the sampling voltage and the reference, The voltage at the output is adjusted to control the drive current regulated by the adjustment switch. Comparison of the electrical voltage that flows through to the light-emitting element 7. The driver of claim 6, wherein the switch is an NPN transistor, a base of the transistor is coupled to the error terminal, and a collector is coupled to the other end of the light emitting element, the current sensing resistor The one end; the regulated open-amplifier's wheel-out emitter is connected to the error amplifier at its non-inverting input terminal to receive the reference voltage terminal to receive the sampling voltage, and its inverting input is 099144045, and the voltage at the output terminal is controlled, thereby controlling the electricity. The crystal is increased to the driving current of the light-emitting element, and when the sampling voltage is greater than the reference voltage, the (4)_ transistor is reduced to the driving current of the light-emitting element. The driver of the invention of claim 6 wherein the adjustment switch is a PNP transistor and the base of the transistor is coupled. To the output of the error amplifier, the emitter is coupled to the other end of the light emitting element, and the collector is coupled to the one end of the current sensing resistor; the error amplifier receives the reference voltage at its inverting input, at its non-inverting input Receiving the sampling voltage, the error amplifier reduces the voltage of the output terminal when the sampling voltage is less than the reference voltage, thereby controlling the driving current of the transistor to increase to the light emitting element, and increasing the voltage of the output terminal when the sampling voltage is greater than the reference voltage, thereby The control transistor is reduced to the drive current of the light emitting element. 9. The driver of claim 1, further comprising: a protection unit coupled between the other end of the light emitting element and the current balancing unit for limiting current flowing through the current balancing unit to protect The current balancing unit is protected from large currents. 10. The driver of claim 9, wherein the protection unit comprises an N-type field effect transistor, a gate of the transistor is coupled to a predetermined gate voltage, and a drain is coupled to the light emitting element. At the other end, the source is coupled to the current equalization unit, and the breakdown voltage of the transistor is set to be larger than the drain-source voltage on the transistor when the light-emitting element is short-circuited. The driver of claim 3, further comprising: a plurality of protection units respectively coupled between the other end of each of the light-emitting elements and a corresponding current source for limiting flow through the current source Current to protect the current source from large currents. 12. The driver of claim 11, wherein each of the protection units comprises an N-type field effect transistor, 099144045 Form No. A0101 Page 22 / Total 27 Page 1003117448-0 201225726 13 . 15. The gate of the transistor is coupled to a predetermined gate/iL key, the drain is coupled to the other end of the light emitting device, the source is switched to a current source of the desired phase, and the breakdown voltage of the transistor A driving method for driving a plurality of light-emitting elements on the transistor when the material member is short-circuited, receiving an input voltage, based on the received wheel-in. The fort is generating a wheel-out voltage at the output terminal, wherein the output voltage is applied Providing to each of the light-emitting elements a drive current matching for the plurality of light-emitting elements to provide and adjust the drive elements; and selecting a minimum feedback voltage from among the respective feedback U-feed voltages characterizing the respective drive currents, and providing the selected minimum back镔 voltage. For example, the application for the full-time thirteenth pin _ calling method further includes: adjusting based on the minimum back (four) press ride "pressure so that the output voltage has a minimum value sufficient to drive each of the light-emitting elements. The driving method of item 13 or 14, further comprising: terminating the current so that each of the light-emitting lamps 16 is provided with a current limiting current protection unit at the other end of each of the light-emitting elements to prevent damage caused by a large current generated when the light-emitting element is short-circuited. A display device comprising a driver 099144045 as described in claim 1 of the patent application Form No. A0101 Page 23 / Total 27 Page 1003117448-0