照明用发光二极管电流自动辨识方法 LED current automatic identification method for illumination
技术领域 本发明属于发光二极管驱动领域， 具体的讲， 涉及一种发光二极管的电流辨识方法。 背景技术 发光二管从发明至现今的广泛应用已有 40多年历史，由于以往发光二极管主要用于显 示用途， 电源利用效率相对次要、 甚至有时被视为不考虑的因素， 基于以上原因， 发光二 极管驱动电流控制一般十分简单， 如一般产品只使用固定电压源供电辅以串接电阻限流， 而有的低端应用例甚至不加入任何限流措施， 只利用电源或控制器件内阻达到限流目的， 这类形的电路设计在日常低功率、 低成本应用无疑是足够的， 但从电源效率、 可靠性及稳 定性角度看， 还是差强人意。 受益于新材料及制造工艺的高速发展， 发光二极管在亮度表现较过去已有大幅改进， 由于发光二极管属于固态器件， 机械强度高， 体积小巧， 有利于高效光学设计， 损坏机理 速度缓慢， 能提供过十万小时以上使用寿命， 不含有害重金属汞， 最近成为一个十分具吸 引力照明用光源。 照明用发光二极管与一般发光二极管比较， 在应用上有很多需要注意的地方： 首先， 其驱动电流较大， 功耗较高， 其次， 发光二极管原本不利并联连接， 近期发光二极管生产 技术已有效掌握比较统一电气参数， 容许多个发光二极管并联连接。 再次， 电流需要控制 于合理范围内， 以避免在一定散热条件下温升过高， 影响发光效率及寿命。 现时所有成熟电力光源都几乎清一色使用电压源供电， 例如普通灯泡、 霓虹灯等， 光 源负载数量变化在固定供电电压下只影响负载电流， 电源电压无需根据光源负载数量作出 调节。 发光二极管供电源需求为直流电流源， 与一般直流电源并不直接兼容， 原因是发光 二极管的等效电路为一个二极管压降加一个串接动态电阻， 发光二极管在固定电压供电条 件下因为参数的变化， 如出厂参数偏差、 温度、 导线电阻等， 而不能达致稳定负载电流。
在实际应用中， 当发光二极管负载数量改变， 供电电流需要作出适当调节， 在供电电 流改变后系统电压会随着改变， 并不是一个恒定数值。 现有技术中的并联连接发光二极管供电系统一般包括以下几类： 固定输出电压电源， 通过发光二极管内阻及系统接线电阻限流， 因参数变化甚多， 这 种方案很难对负载电流作准确调控， 一般只用于低要求产品。 固定输出电压电源， 在每个发光二极管单元加上限流电路达到稳流目的， 能有效准确 控制电流， 但系统元件数量较多， 不利降低成本及提高可靠性。 可调电流源供电， 需要根据系统内已知发光二极管数量在安装时对电源输出电流作适 当调整配合， 对不熟识发光二极管光源电气特性安装人员容易造成错误设置， 影响系统寿 命， 甚至造成安全问题。 发明内容 本发明的一个目的在于提供一种照明用发光二极管电流自动辨识方法， 当发光二极管 并联网络中的某些发光二极管参数发生变化， 或发光二极管并联网络中加入新的支路时， 自动辨识负载的电流要求， 并适当的对输出电流作出调节。 为实现上述目的， 本发明所提供的照明用发光二极管网络电流自动辨识方法， 用 以辨识一个发光二极管网络所需的供电电流， 该发光二极管网络包括并至少两条并联的支 路， 且每条支路上串联至少一个发光二极管， 该方法包括以下步骤： a) 在每条支路内提供一个与所在支路电流需求成反比的辨识电阻，使得每条支路 中的辨识电阻与支路电流需求的乘积均相等； b) 在这些辨识电阻两端施加一小于所在支路的发光二极管导通电压的检测电压，从而
优选的， 所述参考电流通过一个电流电压转换电流转换为参考电压供给驱动该发光二 极管网络的控制电源。 优选的是， 所述等效电阻与支路电流需求的乘积为具有第一值的常数。 优选的是， 所述驱动电流与参考电流的比值为具有第二值的常数。 优选的是， 所述设置于支路内的辨识电阻的一端连接一个辨识端子， 另一端连接控制 电源的负极输出。 优选的是， 所述设置于支路内的辨识电阻的一端连接一个辨识端子， 另一端连接控制 电源的负极输出。 优选的是， 所述设置于支路内的辨识电阻的两端分别连接发光二极管网络的正极输入 和负极输入。 优选的是， 如果所述支路内的辨识电阻的两端分别连接发光二极管网络的正极输入和 负极输入， 则还可以为每个电阻串接一个开关， 以至于在辨识过程中， 该开关闭合， 在便 是过程完毕后， 该开关打开。 优选的， 上述所有辨识电阻由电流源代替。 本发明的这些或其他特征和优点的一个或部分将通过下面的说明书对本技术领域内的 技术人员变得显而易见， 在说明书中， 通过描述实施发明的最适当的方式， 给出并阐述了 本发明的一种具体实施方式。 正如其将被认识到的， 本发明可有不同的实施方式， 且在不 背离本发明的情况下， 其一些细节也可有多种变体。 据此， 附图及说明书仅应被看作是描 述性的而非限制性的。 附图说明 图 1 一种发光二极管网络的结构图。
图 2 是根据本发明的一种辨识方法所基于的电路的电路图。 图 3 是一种改进的辨识方法所基于的电路的电路图。 图 4 为增加了辨识端子的辨识方法所基于的电路的电路图。 图 5 为增加了辨识端子以及辨识回路端子的辨识方法所基于的电路的电路图。 图 6 为将辨识电流转换为辨识电压的电路的电路图。、 图 7 为用电流源替换辨识电阻后的结构图。 具体实施方式 以下结合附图详细说明本发明的各种具体实施方式。 图 1示出了应用本发明的电流量自动判别方法的发光二极管网络的结构。 其为由第一 支路 Bl、 第二支路 B2、 第三支路 B3、 第四支路 B4和第五支路 B5并联组成； 其中， 第一 支路 Bl、 第二支路 B2、 第三支路 B3、 第四支路 B4和第五支路 B5分别包括多个串联的发 光二极管。该模块可以由有控制电源供电，其正负极分别连接正供电端 +Ve和负供电端 Rtn。 作为本发明的第一种具体实施方式，如需判别对图 1中的发光二极管网络的供电电流， 则需要进行以下步骤的操作： 首先在第一支路 Bl、 第二支路 B2、 第三支路 B3、 第四支路 B4和第五支路 B5分别 并联辨识电阻 Rl、 R2、 R3、 R4和 R5， 如图 2所示， 即辨识电阻 R1并联于第一支路， 辨 识电阻 R2并联于第二支路， 辨识电阻 R3并联于第三支路， 辨识电阻 R4并联于第四支路， 辨识电阻 R5并联于第五支路。 照明发光二极管一般具有 3.5至 4.5V的正向导通电压， 当施加于正供电端 +Ve和负供 电端 Rtn之间的电压低于一条支路的发光二极管总串联电压时， 发光二极管不导通， 此时 电路呈现高阻状态，正供电端 +Ve和负供电端 Rtn间的等效电阻为 R1与 R2至 R5并联的总
电阻值 Rtot。 TECHNICAL FIELD The present invention relates to the field of LED driving, and in particular to a current identification method for a LED. BACKGROUND OF THE INVENTION Light-emitting diodes have been widely used in inventions for more than 40 years. Since LEDs have been mainly used for display purposes, power utilization efficiency is relatively minor, and sometimes even considered as an unconsidered factor. Diode drive current control is generally very simple, such as the general product only uses a fixed voltage source for power supply and serial resistor current limit, and some low-end applications do not even add any current limiting measures, only use the power supply or control device internal resistance to reach the limit The purpose of this type of circuit design is undoubtedly sufficient in daily low-power, low-cost applications, but it is still unsatisfactory in terms of power efficiency, reliability and stability. Benefiting from the rapid development of new materials and manufacturing processes, LEDs have been greatly improved in brightness performance. Because LEDs are solid-state devices, they have high mechanical strength and small size, which is conducive to efficient optical design. The damage mechanism is slow and can provide Over 100,000 hours of service life, free of harmful heavy metal mercury, has recently become a very attractive source of lighting. Compared with general light-emitting diodes, there are many places to pay attention to in the application of light-emitting diodes. First, the drive current is large and the power consumption is high. Secondly, the light-emitting diodes are not suitable for parallel connection. Recently, the light-emitting diode production technology has been effectively mastered. Compare uniform electrical parameters to allow multiple LEDs to be connected in parallel. Again, the current needs to be controlled within a reasonable range to avoid excessive temperature rise under certain heat dissipation conditions, affecting luminous efficiency and lifetime. At present, all mature electric light sources are almost always powered by a voltage source, such as ordinary light bulbs, neon lights, etc. The change in the amount of light source load only affects the load current at a fixed supply voltage, and the power supply voltage does not need to be adjusted according to the amount of light source load. The power supply requirement of the LED is a DC current source, which is not directly compatible with the general DC power supply. The reason is that the equivalent circuit of the LED is a diode voltage drop plus a series connected dynamic resistor. The LED is in a fixed voltage supply condition because of the parameter. Changes, such as factory parameter deviations, temperature, wire resistance, etc., do not achieve a stable load current. In practical applications, when the amount of LED load changes, the supply current needs to be properly adjusted. The system voltage will change with the supply current change, not a constant value. The parallel connection LED power supply system in the prior art generally includes the following categories: a fixed output voltage power supply, through the internal resistance of the light emitting diode and the system wiring resistance current limit, due to a large number of parameters, this scheme is difficult to accurately calculate the load current. Regulation, generally only for low-demand products. Fixed output voltage power supply, in each LED unit plus upper limit flow circuit to achieve steady flow, can effectively and accurately control the current, but the system components are large, which is unfavorable to reduce costs and improve reliability. The adjustable current source is powered. It is necessary to adjust the output current of the power supply according to the number of known LEDs in the system. It is easy for the installer who is unfamiliar with the electrical characteristics of the LED light source to cause incorrect settings, affect the system life, and even cause safety problems. . SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic current identification method for an LED for illumination, which automatically recognizes when certain LED parameters in a parallel network of LEDs change, or when a new branch is added to a parallel network of LEDs. The current requirement of the load, and the output current is adjusted appropriately. To achieve the above object, the present invention provides an automatic current identification method for a light-emitting diode network for illumination, which is used for identifying a supply current required for a light-emitting diode network, the light-emitting diode network including at least two parallel branches, and each strip At least one light-emitting diode is connected in series on the branch circuit, and the method comprises the following steps: a) providing an identification resistor in each branch that is inversely proportional to the current demand of the branch, so that the identification resistance and the branch current demand in each branch The products are equal; b) applying a detection voltage across the identification resistors that is less than the conduction voltage of the LEDs in the branch, thereby Preferably, the reference current is converted into a reference voltage by a current-voltage conversion current to supply a control power source for driving the LED network. Preferably, the product of the equivalent resistance and the branch current demand is a constant having a first value. Preferably, the ratio of the drive current to the reference current is a constant having a second value. Preferably, one end of the identification resistor disposed in the branch is connected to one identification terminal, and the other end is connected to the negative output of the control power source. Preferably, one end of the identification resistor disposed in the branch is connected to one identification terminal, and the other end is connected to the negative output of the control power source. Preferably, both ends of the identification resistor disposed in the branch are respectively connected to the positive input and the negative input of the LED network. Preferably, if both ends of the identification resistor in the branch are respectively connected to the positive input and the negative input of the LED network, a switch may be connected in series for each resistor, so that the switch is closed during the identification process. , after the process is completed, the switch is turned on. Preferably, all of the above identification resistors are replaced by current sources. These and other features and advantages of the invention will be apparent to those skilled in the art in the <RTIgt; A specific embodiment of the invention. As will be realized, the invention may be embodied in various embodiments and various modifications may be Accordingly, the drawings and description are to be regarded as BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a structural diagram of a light emitting diode network. 2 is a circuit diagram of a circuit upon which an identification method is based in accordance with the present invention. Figure 3 is a circuit diagram of a circuit on which an improved identification method is based. Fig. 4 is a circuit diagram of a circuit on which the identification method of the identification terminal is added. FIG. 5 is a circuit diagram of a circuit on which an identification method of the identification terminal and the identification circuit terminal is added. Figure 6 is a circuit diagram of a circuit that converts the identification current into an identification voltage. Figure 7 shows the structure after replacing the identification resistor with a current source. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Various embodiments of the present invention will be described in detail below with reference to the drawings. Fig. 1 shows the structure of an LED network to which the current amount automatic discrimination method of the present invention is applied. It is composed of a first branch B1, a second branch B2, a third branch B3, a fourth branch B4 and a fifth branch B5; wherein, the first branch Bl and the second branch B2 The three-way B3, the fourth branch B4, and the fifth branch B5 respectively include a plurality of light-emitting diodes connected in series. The module can be powered by a control power supply, and its positive and negative terminals are respectively connected to the positive power supply terminal +Ve and the negative power supply terminal Rtn. As a first embodiment of the present invention, if it is necessary to determine the supply current to the LED network in FIG. 1, the following steps are required: First, in the first branch B1, the second branch B2, and the third The branch circuit B3, the fourth branch road B4 and the fifth branch road B5 respectively identify the resistors R1, R2, R3, R4 and R5 in parallel, as shown in Fig. 2, that is, the identification resistor R1 is connected in parallel to the first branch, and the identification resistor R2 is connected in parallel. In the second branch, the identification resistor R3 is connected in parallel to the third branch, the identification resistor R4 is connected in parallel to the fourth branch, and the identification resistor R5 is connected in parallel to the fifth branch. The illuminating diode generally has a forward voltage of 3.5 to 4.5 V. When the voltage applied between the positive supply terminal +Ve and the negative supply terminal Rtn is lower than the total series voltage of the LED of one branch, the LED does not conduct. At this time, the circuit exhibits a high resistance state, and the equivalent resistance between the positive power supply terminal +Ve and the negative power supply terminal Rtn is the total of R1 and R2 to R5 in parallel. Resistance value Rtot.
Rtot的检测通过以下步骤实现： a) 由发光二极管驱动电源输出一个低于发光二极管导通电平的检测电压 Vdet。 b) 通过相应测量电路或测量用微型计算机， 测量等效电阻值， 测量方法如下： 首先， 设定每条支路的电流需求， 例如 1.4 A。 其次， 选定一个流经并联的辨识电阻 Rl、 R2、 R3、 R4以及 R5的参考电流 Iref来表 示流经第一支路、 第二支路、 第三支路、 第四支路以及第五支路的总的电流值， 即电源的 输出电流 lout, 其中， 参考电流 Iref与电源输出电流 Itot为等比例输出的。 参考电流的选定 需要满足以下原则， 首先， 电流不能过小， 如果电流过小则会使电路容易受到环境电气噪 音干扰； 其次， 电流不能过大， 如果电流过大会造成不必要的功耗并会导致成本及体积增 加。 例如， 可以选择用 Iref为 lOuA表示 Itot为 1A， 在这种情况下， 参考电流至输出电流 的变换常数， 即输出电流与草烤电流之比 K1为 1/1000000， 还可以选择用 Iref为 10mA表 示 Itot为 1A， 在这种情况下， 参考电流至输出电流的变换常数 K1为 1/100。 上述两种选择 均是可行的。 在正供电端 +Ve与负供电端 Rtn之间接入检测电压 Vdet， 该检测电压的选择原则是， 一定要小于各条支路上所需的最大导通电压， 但也不能过小， 过小的检测电压会使电路容 易受参数变动及电气噪音的影响； 且不能过大， 过大的检测电压会招致不必要的损耗、 以 及产品成本和体积增大等问题。 在这样的约束下， 设计者会选用 Vdet等于如 IV、 2.5V、 5V或 10V。 例如， 在选定 Vdet等于 IV时， 同时选定参考电流至输出电流的变换常数 K1 为 1/100， 则代表 1A的 LED电流使用的电阻为 1K欧姆， 2A的 LED电流的电阻是 500欧 姆。 确定了上述辨识电阻的总电阻值后， 可以按平均分配的方法分配至各条支路中， 也可 以采用优先的方法分配， 即参数变化可能性较大的支路放入较大的电阻值， 这样参数的变 化容易通过电阻的变化体现出来。
事实上， 大部分的电路实施例都使用电压代表输出电源电流量， 图 6示出了这样的一 种电路， 可将检出的参考电流 Iref转换为参考电压 Vref。 图中， R6远小于 R1至 R5并联的 等效电阻 Rtot,这样可以减小检测误差，运算放大器 U1B使 R5上的压降等于 R6上的压降， 三极管 Q1集电极电流与 Iref成反比，电阻 R8上压降 V_Iref与 Iref成正比，电源通过 V_Iref 建立发光二极管驱动电流。 电阻 R1-R5若由电流源代替可直接测量辨识电流量然後转换成电源输出电流量， 如图 7所示。 c) 发光二极管驱动电源把输出电压提升至正常工作电压， 进入稳流工作模态， 电流量 由测量到的 Rtot决定。 上述实施方式中的辨识电阻虽然可以达到自动辨识电流需求的功能， 但是将辨识电阻 一直连接于发光二极管网络中势必导致不必要的功耗。 因此， 作为以上具体实施方式的改 进， 在本发明的第二种具体实施方式中， 参照图 3， 在辨识电阻所在的回路上分别增加了控 制开关， 即将控制开关 S1串联入辨识电阻 R1的回路， 将控制开关 S2串联入辨识电阻 R2 的回路， 将控制开关 S3串联入辨识电阻 R3的回路， 将控制开关 S4串联入辨识电阻 R4的 回路， 将控制开关 S5串联入辨识电阻 R5的回路。 这样， 通过在低电源电压时使控制开关 S1至 S5闭合， 并对 Rtot按上述步骤进行测量， 以及通过在正常电压工作时， 将控制开关 S1至 S5断开， 可以有效的减小功耗。 在本发明的第三种实施方式中，可以通过增加辨识端实现电流的辨识。具体说明如下： 增加辨识端 ID， 在辨识端 ID与负供电端 Rtn之间分别为第一支路、 第二支路、 第三支路、 第四支路以及第五支路并联辨识电阻 Rl、 R2、 R3、 R4和 R5。 增加后的结构如图 4所示， 电阻 R1连接于第一支路的一端与辨识端 ID之间， 电阻 R2连接于第二支路的一端与辨识 端 ID之间， 电阻 R3连接于第三支路的一端与辨识端 ID之间， 电阻 R4连接于第四支路的 一端与辨识端 ID之间， 电阻 R5连接于第五支路的一端与辨识端 ID之间。其中， 辨识电阻 R1可随第一支路的参数的变化而等比例变化， 辨识电阻 R2可随第二支路的参数的变化而 等比例变化， 辨识电阻 R3可随第三支路的参数的变化而等比例变化， 辨识电阻 R4可随第 四支路的参数的变化而等比例变化， 辨识电阻 R5 可随第五支路的参数的变化而等比例变
化。 当二极管网络中的发光二极管数量较多时， 负供电端 Rtn回线上的电压将会增加到一 个足以影响辨识端 ID的电压的值， 如果发生了这种情况， 则可以增加辨识回路端 IDrtn, 并把辨识电阻 Rl、 R2、 R3、 R4、 R5分别从第一支路、 第二支路、 第三支路、 第四支路和 第五支路断开， 并将其与辨识回路端 IDrtn相连接， 如图 5所示。 这样， 辨识电阻就由辨识 端 ID和辨识回路端 IDrtn并联起来， 同时， 正供电端 +Ve和负供电端 Rtn将第一支路、 第 二支路至第五支路并联起来。 在这种情况下， 仍采用与上述方法相同的方法确定辨识电阻总的电阻值， 并将其分配 给辨识电阻 R1至 R5， 再在辨识端 ID和辨识回路端 IDrtn施加偏压， 即辨识电压 Vdet， 从 而得到参考电流 Iref, 再通过图 3中的电路将其转化为控制电压信号， 通过该控制电压信号 可以控制电源的输出。 本领域内的技术人员应该知道， 以上在说明书及附图描述的本发明的具体实施方式仅 是示例性的而非限制性的。 前述对本发明具体实施方式的说明仅以示例和描述为目的。 其并非意于穷尽各实施方 式或将发明局限于已揭示的实施方式或某一定式。 据此， 上述描述应被看作是示例性的而 非局限性的。 显而易见是， 很多修改及变体对本领域内的技术人员来说的可见的。 选定并 描述了各具体实施方式是为了最清楚的解释本发明的原理以及最佳的实际应用方式， 以令 本领域内的技术人员了解本发明的适合于预期的特殊用途或实现的各种实施例及各种变 体。 意欲由后续的权利要求及其等效变化限定本发明的范围， 在权利要求中， 除非另行指 出， 所有术语都应解释为其最广的含义。 应该意识到， 本领域内的一般技术人员可以在不 脱离由下面的权利要求定义的本发明的范围的情况下， 在具体实施方式中作出变化。 此外， 无论下述的权利要求是否明确描述了某些要素及组件， 均不意在将现有公开中的这些要素 及组件献于公知领域。
The detection of Rtot is achieved by the following steps: a) The LED driving power supply outputs a detection voltage Vdet lower than the LED conduction level. b) Measure the equivalent resistance value by means of the corresponding measuring circuit or measuring microcomputer. The measuring method is as follows: First, set the current demand of each branch, for example 1.4 A. Secondly, a reference current Iref flowing through the parallel identification resistors R1, R2, R3, R4 and R5 is selected to indicate flow through the first branch, the second branch, the third branch, the fourth branch and the fifth The total current value of the branch, that is, the output current lout of the power supply, wherein the reference current Iref is output in equal proportion to the power supply output current Itot. The selection of the reference current needs to meet the following principles. First, the current should not be too small. If the current is too small, the circuit will be easily disturbed by environmental electrical noise. Secondly, the current should not be too large. If the current is too large, unnecessary power consumption is caused. Will lead to increased costs and volume. For example, you can choose Iref as lOuA to indicate that Itot is 1A. In this case, the reference current to the output current conversion constant, that is, the ratio of the output current to the grass-baked current K1 is 1/1000000, and Iref can be selected as 10mA. It is indicated that Itot is 1A, and in this case, the conversion constant K1 of the reference current to the output current is 1/100. Both of the above options are feasible. The detection voltage Vdet is connected between the positive power supply terminal +Ve and the negative power supply terminal Rtn. The selection principle of the detection voltage is that it must be smaller than the maximum conduction voltage required on each branch, but it cannot be too small or too small. Detecting the voltage makes the circuit susceptible to parameter variations and electrical noise; it should not be too large, too large a detection voltage will cause unnecessary losses, and product cost and volume increase. Under such constraints, the designer would choose Vdet equal to IV, 2.5V, 5V or 10V. For example, when Vdet is equal to IV, the conversion constant K1 of the reference current to the output current is selected to be 1/100, the resistance of the LED current representing 1A is 1K ohm, and the resistance of the LED current of 2A is 500 ohm. After determining the total resistance value of the above identification resistor, it can be distributed to each branch according to the method of average distribution, or can be allocated by a priority method, that is, the branch with a large possibility of parameter change is put into a larger resistance value. , such changes in parameters are easily reflected by changes in resistance. In fact, most circuit embodiments use voltage to represent the amount of output supply current. Figure 6 shows a circuit that converts the detected reference current Iref to a reference voltage Vref. In the figure, R6 is much smaller than the equivalent resistance Rtot of R1 to R5 in parallel, which can reduce the detection error. The operational amplifier U1B makes the voltage drop across R5 equal to the voltage drop across R6. The collector current of the transistor Q1 is inversely proportional to Iref. The voltage drop V_Iref on R8 is proportional to Iref, and the power supply establishes the LED driving current through V_Iref. If the resistors R1-R5 are replaced by current sources, the amount of identification current can be directly measured and then converted into the output current of the power supply, as shown in FIG. c) The LED driving power supply raises the output voltage to the normal working voltage and enters the steady current working mode. The current is determined by the measured Rtot. Although the identification resistor in the above embodiment can achieve the function of automatically recognizing the current demand, connecting the identification resistor to the LED network inevitably leads to unnecessary power consumption. Therefore, as a modification of the above specific embodiment, in the second embodiment of the present invention, referring to FIG. 3, a control switch is added to the loop where the identification resistor is located, that is, the control switch S1 is connected in series to the circuit of the identification resistor R1. , the control switch S2 is connected in series to the circuit of the identification resistor R2, the control switch S3 is connected in series to the circuit of the identification resistor R3, the control switch S4 is connected in series to the circuit of the identification resistor R4, and the control switch S5 is connected in series to the circuit of the identification resistor R5. Thus, by closing the control switches S1 to S5 at a low power supply voltage, and measuring the Rtot as described above, and by turning off the control switches S1 to S5 while operating at a normal voltage, power consumption can be effectively reduced. In the third embodiment of the present invention, the identification of the current can be realized by adding the identification end. The specific description is as follows: Add the identification end ID, and between the identification end ID and the negative power supply end Rtn, the first branch, the second branch, the third branch, the fourth branch and the fifth branch are respectively parallel identification resistors Rl , R2, R3, R4 and R5. The structure after the addition is as shown in FIG. 4, the resistor R1 is connected between one end of the first branch and the identification end ID, the resistor R2 is connected between one end of the second branch and the identification end ID, and the resistor R3 is connected to the third. Between one end of the branch and the identification end ID, a resistor R4 is connected between one end of the fourth branch and the identification end ID, and the resistor R5 is connected between one end of the fifth branch and the identification end ID. Wherein, the identification resistor R1 can be changed proportionally with the change of the parameters of the first branch, and the identification resistor R2 can be changed proportionally with the change of the parameter of the second branch, and the identification resistor R3 can follow the parameters of the third branch. The change and the proportional change, the identification resistance R4 can be changed proportionally with the change of the parameters of the fourth branch, and the identification resistance R5 can be proportionally changed with the change of the parameters of the fifth branch. Chemical. When the number of LEDs in the diode network is large, the voltage on the Rtn return line of the negative supply terminal will increase to a value sufficient to affect the voltage of the identification terminal ID. If this happens, the identification circuit end IDrtn can be increased. And disconnecting the identification resistors R1, R2, R3, R4, and R5 from the first branch, the second branch, the third branch, the fourth branch, and the fifth branch, respectively, and identifying the loop end IDrtn Connected as shown in Figure 5. Thus, the identification resistor is connected in parallel by the identification terminal ID and the identification loop terminal IDrtn. Meanwhile, the positive power supply terminal +Ve and the negative power supply terminal Rtn connect the first branch and the second branch to the fifth branch in parallel. In this case, the total resistance of the identification resistor is determined by the same method as described above, and is assigned to the identification resistors R1 to R5, and then the bias is applied to the identification terminal ID and the identification loop terminal IDrtn, that is, the identification voltage. Vdet, thereby obtaining the reference current Iref, is converted into a control voltage signal by the circuit in Fig. 3, by which the output of the power supply can be controlled. The specific embodiments of the present invention described in the specification and drawings are to be understood The foregoing description of the specific embodiments of the invention has It is not intended to be exhaustive or to limit the invention to the disclosed embodiments. Accordingly, the above description should be considered as illustrative and not limiting. It will be apparent that many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to explain the embodiments of the invention and the invention Examples and various variants. The scope of the invention is intended to be defined by the appended claims, and the claims It will be appreciated that a person skilled in the art can make variations in the specific embodiments without departing from the scope of the invention as defined by the following claims. In addition, some of the elements and components of the prior disclosure are not intended to be used in the known art.