Short circuit protection method and circuit for LED constant voltage control device

Abstract

The invention relates to a short circuit protection method and circuit of an LED constant voltage control device. The short-circuit protection method comprises the following steps: S10, controlling a direct-current voltage output by an LED constant-voltage control device to be a preset first voltage; s20, collecting a direct-current voltage output by the LED constant-voltage control device to obtain a sampling voltage; collecting the current of the output end of the LED constant voltage control device to obtain a sampling current; judging whether a short circuit occurs or not according to the sampling current and the sampling voltage; s31, if it is judged that the short circuit does not occur, the direct-current voltage output by the LED constant-voltage control device is controlled to be the normal power supply voltage; and S41, if it is judged that the short circuit occurs, the direct-current voltage output by the LED constant-voltage control device is controlled to be a preset second voltage. According to the invention, the short circuit condition of the output load end circuit of the LED constant voltage control device or the LED lamp body can be detected in time before the LED lamp body is lightened and in the working process of the LED lamp, and the short circuit protection measure is triggered in time, so that the practical application safety is ensured.

Description

Technical Field

[0001] The invention relates to the field of LED lamp driving, and in particular to a short-circuit protection method and circuit for an LED constant voltage control device. Background Art

[0002] Existing LED lamps are powered by direct current voltage (e.g., 12V, 24V, or 36V DC power supply), which has high requirements for the stability of the power supply voltage. Therefore, LED lamps are generally equipped with LED constant voltage control devices. The LED constant voltage control device is used to generate a stable direct current voltage to power the LED lamp.

[0003] In actual work, the output load end circuit of the LED constant voltage control device or the LED lamp body connected to the output load end of the LED constant voltage control device may be short-circuited, causing the wire to heat up and easily cause a fire. Therefore, the LED constant voltage control device needs to be equipped with a short-circuit protection circuit that automatically detects whether its output load end circuit or LED lamp body has a short circuit. Once a short circuit is detected, the short-circuit protection measure is triggered to avoid safety hazards caused by the short circuit.

[0004] The short-circuit protection circuit of the existing LED constant voltage control device simply determines whether a short circuit occurs based on whether the current in the circuit is greater than a preset threshold value, and cuts off the circuit if it is detected that the current is greater than the preset threshold value. In order to prevent the short-circuit protection measures from being mistakenly triggered when the LED lamp body is working normally, the preset threshold value is greater than the rated current of the LED lamp body when it is working normally. The short-circuit protection circuit of this existing LED constant voltage control device has the following defects: due to the internal resistance of the wire, the internal resistance of the wire becomes the output end load when a short circuit occurs, so even if a short circuit has occurred, the short-circuit current will still not be greater than the preset threshold value. In this case, the short-circuit protection circuit of the existing LED constant voltage control device cannot detect the occurrence of a short circuit, and cannot cut off the circuit in time. At this time, the output power of the LED constant voltage control device is consumed by the heat generated by the wire, and the temperature of the wire rises, causing a fire hazard. Summary of the invention

[0005] Based on this, the purpose of the present invention is to provide a short-circuit protection method and circuit for an LED constant voltage control device, which can promptly detect the existence of a short circuit in the output load end circuit of the LED constant voltage control device or the LED lamp body before lighting the LED lamp body and during the operation of the LED lamp, and promptly trigger the short-circuit protection measures to ensure the safety of actual application.

[0006] The present invention provides a short-circuit protection method for an LED constant-voltage control device, comprising the following steps: S10, controlling a DC voltage output by the LED constant-voltage control device to be a preset first voltage; S20, collecting the DC voltage output by the LED constant-voltage control device to obtain a sampled voltage; collecting a current at an output end of the LED constant-voltage control device to obtain a sampled current; judging whether a short circuit occurs according to the sampled current and the sampled voltage; S31, if it is judged that a short circuit does not occur, controlling the DC voltage output by the LED constant-voltage control device to be a normal power supply voltage; S41, if it is judged that a short circuit occurs, controlling the DC voltage output by the LED constant-voltage control device to be a preset second voltage.

[0007] The present invention completes short-circuit detection when the DC voltage output by the LED constant-voltage control device is a smaller first voltage, and adjusts the DC voltage output by the LED constant-voltage control device to a normal power supply voltage only after ensuring that there is no short circuit at the output load end. Therefore, it is possible to detect the existence of a short circuit in the output load end circuit or the LED lamp body before lighting the LED lamp body, and trigger the short-circuit protection action in time, effectively avoiding the harm caused by the short circuit.

[0008] Furthermore, the short-circuit protection method also includes a step S32 after step S31: obtaining a sampled voltage and a sampled current at every set first time interval, and judging whether a short circuit is likely to occur based on the sampled voltage and the sampled current; if it is judged that a short circuit is likely to occur, returning to step S10.

[0009] Furthermore, the short-circuit protection method also includes a step S42 after step S41: returning to step S10 at every set second time interval to re-determine whether a short circuit occurs; if a short circuit is determined to occur N times in succession, then after completing step S41, no longer returning to step S10; N is a set cycle number threshold.

[0010] Further, in step S20, judging whether a short circuit occurs based on the sampled current and the sampled voltage specifically includes: if the sampled voltage is equal to a preset first voltage, judging whether the sampled current is greater than a preset short circuit threshold; if the sampled current is greater than the preset short circuit threshold, judging that a short circuit occurs; if the sampled current is not greater than the preset short circuit threshold, judging that a short circuit does not occur.

[0011] Further, step S10 is specifically: controlling the DC voltage output by the LED constant voltage control device to be a preset first voltage, and controlling the connection between the output end of the LED constant voltage control device and the LED lamp body to be turned on; step S41 is specifically: if it is determined that a short circuit occurs, controlling the DC voltage output by the LED constant voltage control device to be a preset second voltage, and controlling the connection between the output end of the LED constant voltage control device and the LED lamp body to be turned off.

[0012] Based on the same inventive concept, the present invention also provides a short-circuit protection circuit of an LED constant voltage control device, comprising: a current sampling unit, used to collect the current at the output end of the LED constant voltage control device to obtain a sampled current; a voltage sampling unit, used to collect the DC voltage output by the LED constant voltage control device to obtain a sampled voltage; a controller, used to determine whether a short circuit occurs based on the sampled current and the sampled voltage, and output a voltage control signal to an output voltage control unit; an output voltage control unit, used to control the magnitude of the DC voltage output by the LED constant voltage control device based on the voltage control signal; wherein the controller executes the above-mentioned short-circuit protection method.

[0013] Further, the output voltage control unit includes: a third MOS tube, an eighteenth resistor, a fourth MOS tube, a nineteenth resistor, a diode string, a twentieth resistor, a twenty-first resistor, a third triode, a twenty-second resistor and a twenty-third resistor; the third MOS tube is an NMOS tube, whose source is connected to the second output end of the LED constant voltage control device, whose drain is connected to the LED lamp body, and whose gate is connected to the drain of the fourth MOS tube through the eighteenth resistor; the source of the third MOS tube is connected to its own gate through the nineteenth resistor; the diode string includes a plurality of diodes whose cathodes and anodes are connected in series; the equivalent cathode of the diode string is connected to the source of the third MOS tube through the twentieth resistor, and the equivalent anode is connected to the drain of the third MOS tube; the fourth MOS tube is an NMOS tube, whose drain is connected to the voltage source through the twenty-first resistor, whose gate is connected to the collector of the third triode, and whose source is grounded; the collector of the third triode is connected to the voltage source through the twenty-second resistor, whose emitter is grounded, and whose base is connected to the output voltage control signal of the controller through the twenty-third resistor.

[0014] Furthermore, it also includes an output switch unit for controlling the on / off connection between the output end of the LED constant voltage control device and the LED lamp body according to the switch control signal output by the controller; the controller executes the short-circuit protection method described in claim 5.

[0015] Further, the output switch unit includes: a first MOS tube, a sixth resistor, a second MOS tube, a seventh resistor, an eighth resistor, a second triode, a ninth resistor, and a tenth resistor; the first MOS tube is an NMOS tube, whose source is connected to the second output end of the LED constant voltage control device, whose drain is connected to the LED body, and whose gate is connected to the drain of the second MOS tube through the sixth resistor; the seventh resistor is connected between the source and the gate of the first MOS tube; the second MOS tube is an NMOS tube, whose drain is connected to the voltage source through the eighth resistor, whose gate is connected to the collector of the second triode, and whose source is grounded; the collector of the second triode Q2 is connected to the voltage source through the ninth resistor, whose emitter is grounded, and whose base is connected to the switch control signal output by the controller through the tenth resistor.

[0016] Further, the output voltage control unit includes: a first optical coupler, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a second voltage regulator, a fifteenth resistor, a second optical coupler, a three-pin voltage regulator, a sixteenth resistor, a seventeenth resistor and a sixth capacitor; the anode of the light-emitting diode of the first optical coupler is connected to the voltage control signal output by the controller through the eleventh resistor, and the cathode is grounded; the collector of the phototransistor of the first optical coupler is connected to the first output end of the LED constant voltage control device through the twelfth resistor, and the emitter is grounded through the thirteenth resistor; the fourteenth resistor is connected across the collector and emitter of the phototransistor of the first optical coupler; The cathode of the second voltage-stabilizing tube is connected to the first output end of the LED constant-voltage control device, and the anode is connected to the anode of the light-emitting diode of the second optocoupler through the fifteenth resistor; the cathode of the three-pin voltage-stabilizing tube is connected to the anode of the light-emitting diode of the second optocoupler through the sixteenth resistor, the anode is grounded, and the reference electrode is connected to the emitter of the phototransistor of the first optocoupler; the collector of the phototransistor of the second optocoupler is connected to the primary network in the LED constant-voltage control device that can control the DC voltage output by its first output end; one end of the seventeenth resistor is connected to the emitter of the phototransistor of the first optocoupler, and the other end is connected to the cathode of the three-pin voltage-stabilizing tube through the sixth capacitor.

[0017] For better understanding and implementation, the present invention is described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of a module of an LED lamp according to Embodiment 1 of the present invention;

[0019] Figure 2 This is a module schematic diagram of a short-circuit protection circuit of an LED constant voltage control device according to Embodiment 1 of the present invention;

[0020] Figure 3 A schematic flow chart of a short-circuit protection method executed by a controller of a short-circuit protection circuit according to Embodiment 1 of the present invention;

[0021] Figure 4 A schematic diagram of the circuit structure of a short-circuit protection circuit according to Embodiment 1 of the present invention;

[0022] Figure 5 This is a module schematic diagram of a short-circuit protection circuit of an LED constant voltage control device according to Embodiment 2 of the present invention;

[0023] Figure 6 A schematic diagram of a partial circuit structure of a short-circuit protection circuit according to Embodiment 2 of the present invention;

[0024] Figure 7 It is a flowchart of a short-circuit protection method executed by a controller of a short-circuit protection circuit according to Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0025] The following embodiments of the technical solution of the present application will be described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" and "several" is more than two, unless otherwise clearly and specifically defined.

[0028] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0030] As described in the background technology, the short-circuit protection circuit of the existing LED constant voltage control device cannot detect the occurrence of a short circuit at the output end in time, and there is still a risk of burning the circuit or even causing a fire. In view of the defects of the prior art, the present invention redesigns a short-circuit protection circuit that can detect the occurrence of a short circuit in time. It lights up the LED lamp only after confirming that there is no short circuit at the output load end, effectively avoiding the harm caused by the short circuit. The short-circuit protection circuit of the present invention can also detect the short circuit in real time during the operation process. Once it is found that a short circuit may occur, the output voltage of the LED constant voltage control device is lowered or the power supply circuit is cut off, thereby ensuring the safety of the circuit to the greatest extent.

[0031] Example 1

[0032] See also Figure 1 , Figure 1 Schematic diagram of a module of an LED lamp according to Embodiment 1 of the present invention. The LED lamp of the present invention comprises an LED lamp body 1 and an LED constant voltage control device 2. The first output terminal OUT1 and the second output terminal OUT2 of the LED constant voltage control device 2 are respectively connected to the anode LED+ and the cathode LED- of the LED lamp body 1, so as to generate a stable DC voltage to supply power to the LED lamp body 1.

[0033] In this embodiment, the LED lamp includes, in addition to the LED lamp body 1 and the LED constant voltage control device 2, a short circuit protection circuit E electrically connected to the LED constant voltage control device 2. In another embodiment, the LED constant voltage control device 2 is provided with a short circuit protection circuit E. In other words, the short circuit protection circuit E of the LED constant voltage control device of the present invention can be provided inside the LED constant voltage control device 2 as a part of the LED constant voltage control device 2; or it can be independent of the LED constant voltage control device 2 as an external accessory electrically connected to the LED constant voltage control device 2. The present invention does not limit the relationship between the short circuit protection circuit E and the LED constant voltage control device 2.

[0034] See also Figure 2 , Figure 2 The module diagram of the short circuit protection circuit of the LED constant voltage control device of the present invention is shown in FIG. The short circuit protection circuit E comprises: a current sampling unit E1, a voltage sampling unit E2, a controller MCU, an output switch unit E3 and an output voltage control unit E4.

[0035] The current sampling unit E1 is used to collect the current at the output end of the LED constant voltage control device to obtain a sampled current.

[0036] The voltage sampling unit E2 is used to collect the DC voltage output by the LED constant voltage control device to obtain a sampled voltage.

[0037] The controller MCU is used to determine whether a short circuit occurs according to the sampled current and the sampled voltage, and output a switch control signal to the output switch unit, and output a voltage control signal to the output voltage control unit.

[0038] The output switch unit E3 is used to control the on / off connection between the output end of the LED constant voltage control device and the LED lamp body according to the switch control signal.

[0039] The output voltage control unit E4 is used to control the magnitude of the DC voltage output by the LED constant voltage control device according to the voltage control signal.

[0040] See also Figure 3 , Figure 3 The flowchart of the short-circuit protection method executed by the controller of the short-circuit protection circuit of Embodiment 1 of the present invention is shown in FIG. The controller MCU executes the following short-circuit protection method:

[0041] S10, in the initial stage, the output voltage control unit controls the DC voltage output by the LED constant voltage control device to be a preset first voltage, and the output switch unit controls the connection between the output end of the LED constant voltage control device and the LED lamp body.

[0042] The first voltage V1 is smaller than the power supply voltage required for the normal operation of the LED lamp body, and can be specifically set to a voltage value that just maintains the LED lamp body in a non-conducting state. When the DC voltage output by the LED constant voltage control device is a smaller first voltage, the LED lamp body is not yet lit. Even if a short circuit occurs, the short circuit current is relatively small, and the risk of electric shock and fire is relatively small.

[0043] S20, obtaining a sampling voltage through the voltage sampling unit, and judging whether the DC voltage output by the LED constant voltage control device is equal to a preset first voltage based on the sampling voltage; if the DC voltage output by the LED constant voltage control device is equal to the preset first voltage, obtaining a sampling current through the current sampling unit, and judging whether the sampling current is greater than a preset short-circuit threshold.

[0044] S31, if step S20 determines that the sampling current is not greater than the preset short-circuit threshold, it is determined that short circuit does not occur, and then the output voltage control unit controls the DC voltage output by the LED constant voltage control device to be a normal power supply voltage.

[0045] At this time, the power supply voltage value output by the LED constant voltage control device is equal to the voltage value required for the normal operation of the LED lamp body, and the LED lamp body operates normally.

[0046] S32, at every set first time interval, the voltage sampling unit and the current sampling unit obtain the sampling voltage and the sampling current, and judge whether a short circuit is likely to occur based on the sampling voltage and the sampling current; if it is judged that a short circuit is likely to occur, return to step S10. Further, judging whether a short circuit is likely to occur based on the sampling voltage and the sampling current, specifically: if the sampling voltage is unstable, the sampling voltage drops, or the sampling current suddenly increases, it is judged that a short circuit is likely to occur. The controller can judge whether the sampling voltage is unstable, the sampling voltage drops, or the sampling current suddenly increases by calculating the derivative of the sampling voltage and / or the sampling current with respect to time, or by judging whether the fluctuation of the sampling voltage and / or the sampling current is greater than a preset threshold.

[0047] S41, if the sampling current is greater than the preset short-circuit threshold value in step S20, it is determined that a short circuit occurs, and then the output switch unit is used to control the output end of the LED constant voltage control device to be disconnected from the LED lamp body, and the output voltage control unit is used to control the DC voltage output by the LED constant voltage control device to be a preset second voltage. The second voltage is less than the normal power supply voltage, and can be any voltage value within a closed interval from 0 to a voltage value that just maintains the LED lamp body in a non-conducting state.

[0048] S42, at every set second time interval, return to step S10 and re-determine whether a short circuit occurs; if step S20 determines that a short circuit occurs for N consecutive times (N is a set cycle number threshold), then step S41 controls the output end of the LED constant voltage control device to disconnect from the LED lamp body through the output switch unit, and controls the output DC voltage of the LED constant voltage control device to be a preset second voltage through the output voltage control unit, and then does not return to step S10, and does not re-enter step S10 until the LED constant voltage control device is restarted.

[0049] The short-circuit protection method of the present invention completes short-circuit detection when the DC voltage output by the LED constant-voltage control device is a smaller first voltage, and adjusts the DC voltage output by the LED constant-voltage control device to a normal power supply voltage only after ensuring that no short circuit occurs. Therefore, the present invention can detect a short circuit before lighting the LED lamp body, trigger the short-circuit protection action in time, and effectively avoid the harm caused by the short circuit.

[0050] See also Figure 4 , Figure 4 A schematic diagram of the circuit structure of a short-circuit protection circuit according to Embodiment 1 of the present invention.

[0051] In this embodiment, the LED constant voltage control device 2 is connected to the LED lamp body 1 through a transformer L1. The transformer L1 includes a first coil and a second coil. The first output terminal OUT1 of the LED constant voltage control device 2 is connected to the first end of the first coil; the anode LED+ of the LED lamp body 1 is connected to the second end of the first coil. The second output terminal OUT2 of the LED constant voltage control device 2 is connected to the first end of the second coil; the cathode LED- of the LED lamp body 1 is connected to the second end of the second coil. The voltage of the first output terminal OUT1 of the LED constant voltage control device 2 is the DC voltage output by the LED constant voltage control device 2. The voltage of the second output terminal OUT2 of the LED constant voltage control device is 0V (grounded).

[0052] In another embodiment, the LED constant voltage control device 2 may be directly connected to the LED lamp body 1 instead of being connected to the LED lamp body 1 through the transformer L1 , by replacing the first coil and the second coil of the transformer L1 of this embodiment with wires.

[0053] In this embodiment, since the active devices involved in the short circuit protection circuit E need +5V DC voltage for power supply, the short circuit protection circuit E also includes: a voltage stabilizing unit E5 for providing a +5V chip power supply voltage. In other embodiments, the value of the chip power supply voltage can be set as needed.

[0054] Specifically, the voltage stabilizing unit E5 includes: a first transistor Q1, a voltage stabilizing chip V0, a ​​first voltage stabilizing tube ZD1, a first resistor R1, a first capacitor C1 and a second capacitor C2. The collector of the first transistor Q1 is connected to the first output terminal OUT1 of the LED constant voltage control device 2, the emitter is connected to the input terminal of the voltage stabilizing chip V0, and the base is connected to the cathode of the first voltage stabilizing tube ZD1. The anode of the first voltage stabilizing tube ZD1 is grounded. The first resistor R1 is connected across the collector and the base of the first transistor Q1. The input terminal of the voltage stabilizing chip V0 is connected to the voltage source VccA, the ground terminal is grounded, and the output terminal outputs the chip supply voltage +5V. One end of the first capacitor C1 is connected to the input terminal of the voltage stabilizing chip V0, and the other end is grounded. One end of the second capacitor C2 is connected to the output terminal of the voltage stabilizing chip V0, and the other end is grounded. In this embodiment, the voltage source VccA is a +10V regulated power supply generated by other modules of the LED constant voltage control device 2. In other embodiments, the value of the voltage source VccA can be set as needed.

[0055] Specifically, the controller MCU is a single-chip microcomputer, and its pin P1.4 is connected to the sampled voltage Vs output by the voltage sampling unit; pin P1.1 is connected to the sampled current Is output by the current sampling unit; pin P1.2 outputs a switch control signal to the switch control unit; and pin P1.5 outputs a voltage control signal to the output voltage control unit. Furthermore, pin P1.3 of the single-chip microcomputer MCU is connected to a thermistor RT / NTC for over-temperature protection; pin VDD is connected to the chip power supply voltage +5V; and pin GND is grounded.

[0056] Specifically, the current sampling unit E1 includes a current sampling resistor Rs1, a current sampling amplifier U1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a third capacitor C3 and a fourth capacitor C4. The current sampling resistor Rs1 is connected in series between the second output terminal OUT2 of the LED constant voltage control device 2 and the first end of the second coil of the transformer L1, and its end away from the second output terminal OUT2 of the LED constant voltage control device 2 is the current sampling node ISEN. The inverting input terminal of the current sampling amplifier U1 is connected to the current sampling node ISEN through the second resistor R2, the non-inverting input terminal is grounded through the third resistor R3, the output terminal is connected to its own inverting input terminal through the fourth resistor R4, and the output terminal is connected to the pin P1.1 of the single-chip microcomputer MCU, which is the sampling current output terminal Is. One end of the fifth resistor R5 is connected to the output terminal of the current sampling amplifier U1, and the other end is grounded. The third capacitor C3 is connected across the output terminal and the inverting input terminal of the current sampling amplifier U1. One end of the fourth capacitor C4 is connected to the inverting input terminal of the current sampling amplifier U1 , and the other end is grounded.

[0057] The current output from the second output terminal OUT2 of the LED constant voltage control device 2 is converted into the voltage of the current sampling node ISEN after passing through the current sampling resistor Rs1. The current sampling amplifier U1, the second resistor R2, the third resistor R3, and the fourth resistor R4 form a proportional amplifier circuit, so that the voltage at the output terminal of the current sampling amplifier U1 is proportional to the voltage of the current sampling node ISEN. Therefore, the sampling current signal Is obtained by the pin P1.1 of the single-chip microcomputer MCU is proportional to the current output by the LED constant voltage control device 2, and the single-chip microcomputer MCU can obtain the current output by the LED constant voltage control device 2 through the sampling current Is.

[0058] Specifically, the voltage sampling unit E2 includes a first voltage sampling resistor Rv1, a second voltage sampling resistor Rv2 and a fifth capacitor C5. The first end of the first voltage sampling resistor Rv1 is connected to the first output terminal OUT1 of the LED constant voltage control device 2, and the second end is connected to the pin P1.4 of the single-chip microcomputer MCU. The first end of the second voltage sampling resistor Rv2 is connected to the pin P1.4 of the single-chip microcomputer MCU, and the second end is grounded. The first end of the fifth capacitor C5 is connected to the pin P1.4 of the single-chip microcomputer MCU, and the second end is grounded. Obviously, the connection point between the first voltage sampling resistor Rv1 and the second voltage sampling resistor Rv2 is the sampling voltage output terminal Vs. The sampling voltage Vs is proportional to the DC voltage OUT1 output by the LED constant voltage control device 2, and the single-chip microcomputer MCU can obtain the DC voltage OUT1 output by the LED constant voltage control device through the sampling voltage Vs.

[0059] Specifically, the output switch unit E3 includes a first MOS transistor MOS1, a sixth resistor R6, a second MOS transistor MOS2, a seventh resistor R7, an eighth resistor R8, a second triode Q2, a ninth resistor R9, and a tenth resistor R10. The first MOS transistor MOS1 is an NMOS transistor, whose source is connected to the current sampling node ISEN, whose drain is connected to the first end of the second coil of the transformer L1, and whose gate is connected to the drain of the second MOS transistor MOS2 through the sixth resistor R6. The seventh resistor R7 is connected between the source and the gate of the first MOS transistor MOS1. The second MOS transistor MOS2 is an NMOS transistor, whose drain is connected to the voltage source VccA through the eighth resistor R8, whose gate is connected to the collector of the second triode Q2, and whose source is grounded. The collector of the second triode Q2 is connected to the voltage source VccA through the ninth resistor R9, whose emitter is grounded, and whose base is connected to the pin P1.2 of the single-chip microcomputer MCU through the tenth resistor R10, that is, connected to the switch control signal output by the single-chip microcomputer MCU.

[0060] When the switch control signal output by the pin P1.2 of the single-chip computer MCU is at a low level, the base of the second transistor Q2 is at a low level, and the collector of the second transistor Q2 is connected to the voltage source VccA through the ninth resistor R9, which is at a high level; therefore, the gate of the second MOS transistor MOS2 is at a high level, the ds channel of the second MOS transistor MOS2 is turned on, and the gate of the first MOS transistor MOS1 is grounded through the sixth resistor R6 and the ds channel of the second MOS transistor MOS2, which is at a low level; therefore, the ds channel of the first MOS transistor MOS1 is cut off, and the second output terminal OUT2 of the LED constant voltage control device 2 is disconnected from the first end of the second coil, that is, the connection with the cathode LED- of the LED lamp body 1 is disconnected.

[0061] On the contrary, when the switch control signal output by the pin P1.2 of the single-chip computer MCU is at a high level, the base of the second transistor Q2 is at a high level, and the collector of the second transistor Q2 is grounded due to being connected to the emitter, which is at a low level; therefore, the gate of the second MOS transistor MOS2 is at a low level, the ds channel of the second MOS transistor MOS2 is cut off, and the gate of the first MOS transistor MOS1 is connected to the voltage source VccA through the sixth resistor R6 and the eighth resistor R8, which is at a high level; therefore, the ds channel of the first MOS transistor MOS1 is turned on, and the connection between the second output terminal OUT2 of the LED constant voltage control device 2 and the first end of the second coil is turned on, that is, the connection with the cathode LED- of the LED lamp body 1 is turned on.

[0062] Based on the structure and working principle of the output switch unit E3, the single chip computer MCU can control the connection between the output end of the LED constant voltage control device and the LED lamp body by controlling the switch control signal output by its pin P1.2.

[0063] Specifically, the output voltage control unit E4 includes: a first optical coupler OPT1, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a second voltage regulator ZD1, a fifteenth resistor R15, a second optical coupler OPT2, a three-pin voltage regulator Y1, a sixteenth resistor R16, a seventeenth resistor R17 and a sixth capacitor C6. The anode of the light-emitting diode of the first optical coupler OPT1 is connected to the pin 1.5 of the single-chip microcomputer MCU through the eleventh resistor R11 to connect the voltage control signal, and the cathode is grounded. The collector of the phototransistor of the first optical coupler OPT1 is connected to the first output terminal OUT1 of the LED constant voltage control device 2 through the twelfth resistor R12, and the emitter is grounded through the thirteenth resistor R13. The fourteenth resistor R14 is connected between the collector and the emitter of the phototransistor of the first optical coupler OPT1. The cathode of the second voltage regulator ZD2 is connected to the first output terminal OUT1 of the LED constant voltage control device 2, and the anode is connected to the anode of the light-emitting diode of the second optocoupler OPT2 through the fifteenth resistor R15. The cathode of the three-pin voltage regulator Y1 is connected to the anode of the light-emitting diode of the second optocoupler OPT2 through the sixteenth resistor R16, the anode is grounded, and the reference electrode is connected to the emitter of the phototransistor of the first optocoupler OPT1. The collector of the phototransistor of the second optocoupler OPT2 is connected to the primary network of the LED constant voltage control device that can control the DC voltage output by its first output terminal OUT1. One end of the seventeenth resistor R17 is connected to the emitter of the phototransistor of the first optocoupler OPT1, and the other end is connected to the cathode of the three-pin voltage regulator Y1 through the sixth capacitor C6.

[0064] When the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a high level, the light-emitting diode of the first optical coupler OPT1 emits light, so that the collector and emitter of the phototransistor of the first optical coupler OPT1 are turned on, so that the fourteenth resistor R14 is short-circuited, and the equivalent resistance in the circuit is 0. On the contrary, when the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a low level, the fourteenth resistor R14 is not short-circuited, and the equivalent resistance in the circuit is its own resistance value. The voltage control signal SW outputted from the pin P1.5 of the single-chip microcomputer MCU is a PWM signal. The single-chip microcomputer MCU can control the equivalent resistance value of the fourteenth resistor R14 in the circuit by controlling the duty cycle of the voltage control signal SW, and further control the voltage of the reference electrode of the three-pin voltage regulator Y1. The cathode voltage of the three-pin voltage regulator tube Y1 is related to the voltage of its reference electrode, so the voltage control signal SW can control the cathode voltage of the three-pin voltage regulator tube Y1, and then control the voltage drop between the anode and cathode of the light-emitting diode of the second optical coupler OPT2, and control the equivalent voltage of the collector of the phototransistor of the second optical coupler OPT2. Since the collector of the phototransistor of the second optical coupler OPT2 is connected to the primary network of the LED constant voltage control device that can control the DC voltage output by its first output terminal OUT1, the single-chip microcomputer MCU can control the value of the DC voltage output by the first output terminal OUT1 of the LED constant voltage control device by controlling the duty cycle of the voltage control signal SW.

[0065] Based on the structure and working principle of the output voltage control unit E4, the single chip microcomputer MCU can control the magnitude of the DC voltage output by the LED constant voltage control device 2 by controlling the voltage control signal SW output by the pin 1.5.

[0066] Furthermore, the model of the voltage regulator chip V0 is HT7550, the model of the single-chip microcomputer MCU is MC51F003, the model of the current detection amplifier U1 is TS321, and the model of the three-pin voltage regulator tube Y1 is TL431.

[0067] Example 2

[0068] See also Figure 5 , Figure 5 Schematic diagram of a module of a short-circuit protection circuit of Embodiment 2 of the present invention. The difference between the short-circuit protection circuit E of Embodiment 2 of the present invention and Embodiment 1 is that: the output switch unit E3 is not included; the current sampling unit E1 includes a first current sampling unit E11 and a second current sampling unit E12; the sampling current includes a first sampling current and a second sampling current; the specific circuit structures of the output voltage control unit E4 and the current sampling unit E1 are different.

[0069] See also Figure 6 , Figure 6 A schematic diagram of a partial circuit structure of a short-circuit protection circuit E according to Embodiment 2 of the present invention.

[0070] In this embodiment, the output voltage control unit E4 includes: a third MOS transistor MOS3, an eighteenth resistor R18, a fourth MOS transistor MOS4, a nineteenth resistor R19, a diode string D1-Dn, a twentieth resistor R20, a twenty-first resistor R21, a third triode Q3, a twenty-second resistor R22 and a twenty-third resistor R23.

[0071] The third MOS transistor MOS3 is an NMOS transistor, whose source is connected to the second output terminal OUT2 of the LED constant voltage control device, whose drain is connected to the first end of the second coil of the transformer L1 (that is, connected to the cathode LED- of the LED lamp body through the second coil), and whose gate is connected to the drain of the fourth MOS transistor MOS4 through the eighteenth resistor R18. The source of the third MOS transistor MOS3 is connected to its own gate through the nineteenth resistor R19. The ds channel of the third MOS transistor MOS3 is in series with the ds channel of the first MOS transistor MOS1 of the first embodiment.

[0072] The diode string includes a plurality of diodes D1-Dn whose cathodes and anodes are connected in series, where n is the number of diodes. In this embodiment, n=9, and the diode string includes 9 diodes D1-D9 whose cathodes and anodes are connected in series, which are equivalent to a diode with a large voltage drop in the circuit. The equivalent cathode of the diode string is connected to the source of the third MOS tube MOS3 through the twentieth resistor R20, and the equivalent anode is connected to the drain of the third MOS tube MOS3.

[0073] The fourth MOS transistor MOS4 is an NMOS transistor, whose drain is connected to the voltage source VccA through the twenty-first resistor R21, the gate is connected to the collector of the third triode Q3, and the source is grounded. The collector of the third triode Q3 is connected to the voltage source VccA through the twenty-second resistor R22, the emitter is grounded, and the base is connected to the pin P1.5 of the single-chip microcomputer MCU through the twenty-third resistor R23, that is, connected to the output voltage control signal SW of the single-chip microcomputer MCU.

[0074] When the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a low level, the base of the third triode Q3 is at a low level, and the collector of the third triode Q3 is connected to the voltage source VccA through the twenty-second resistor R22, which is at a high level; therefore, the gate of the fourth MOS tube MOS4 is at a high level, the ds channel of the fourth MOS tube MOS4 is turned on, and the gate of the third MOS tube MOS3 is grounded through the eighteenth resistor R18 and the ds channel of the fourth MOS tube MOS4, which is at a low level; therefore, the ds channel of the third MOS tube MOS3 is cut off. Since the ds channel of the third MOS tube MOS3 is cut off, the second output terminal OUT2 of the LED constant voltage control device 2 can only be connected to the first end of the second coil through the diode string D1-Dn, that is, connected to the cathode LED- of the LED lamp body 1. The diode string D1-Dn has a stable voltage dividing effect. Those skilled in the art can adjust the number of diodes included in the diode string D1-Dn so that when the voltage control signal SW output by pin 1.5 of the single-chip microcomputer MCU is at a low level, the DC voltage output by the first output terminal OUT1 of the LED constant voltage control device 2 is stabilized at a preset first voltage by the diode string D1-Dn.

[0075] On the contrary, when the voltage control signal SW outputted from the pin 1.5 of the single-chip computer MCU is at a high level, the base of the third triode Q3 is at a high level, and the collector of the third triode Q3 is grounded through its emitter; therefore, the gate of the fourth MOS tube MOS4 is at a low level, the ds channel of the fourth MOS tube MOS4 is cut off, and the gate of the third MOS tube MOS3 is connected to the voltage source VccA through the twenty-first resistor R21, which is at a high level; therefore, the ds channel of the third MOS tube MOS3 is turned on, and the second output terminal OUT2 of the LED constant voltage control device 2 is connected to the first end of the second coil through the ds channel of the third MOS tube MOS3, that is, connected to the cathode LED- of the LED lamp body 1. The conduction of the ds channel of the third MOS tube MOS3 causes the branch where the diode string D1-Dn is located to be short-circuited, and the diode string D1-Dn no longer participates in voltage division. Therefore, when the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a high level, the DC voltage outputted from the first output terminal OUT1 of the LED constant voltage control device 2 is a normal power supply voltage.

[0076] Based on the structure and working principle of the output voltage control unit E4, the single chip microcomputer MCU can control the DC voltage output by the LED constant voltage control device 2 to switch between a smaller first voltage and a normal supply voltage by controlling the voltage control signal SW output by the control pin 1.5.

[0077] Specifically, the structure of the first current sampling unit E11 is the same as that of the current sampling unit E1 of Embodiment 1. One end of the current sampling resistor Rs1 is connected to the second output end OUT2 of the LED constant voltage control device 2, and the other end is connected to the first end of the second coil of the transformer L1 through the ds channel of the third MOS tube MOS3. The end away from the second output end OUT2 of the LED constant voltage control device 2 is the first current sampling node ISEN1. The first sampling current signal Is1 output by the first current sampling unit E11 is connected to the first sampling current input end ( Figure 5 The connection relationship of the remaining components of the first current sampling unit E11 is the same as that of the current sampling unit E1 in Embodiment 1, and will not be repeated here.

[0078] Specifically, the second current sampling unit E12 includes: a twenty-first resistor R21, a twenty-second resistor R22, and a twenty-third resistor R23. One end of the twenty-first resistor R21 is connected to the equivalent cathode of the diode string D1-Dn, and the other end is the second current sampling node ISEN2. One end of the twenty-second resistor R22 is connected to the second current sampling node ISEN2, and the other end is connected to the second sampling current input terminal ( Figure 5 middle pin P1.2).

[0079] When the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a high level, the current outputted from the output terminal of the LED constant voltage control device 2 is converted into the voltage of the first current sampling node ISEN1 after passing through the current sampling resistor Rs1, and the voltage of the first current sampling node ISEN1 is converted into the first sampling current signal Is1 after being amplified by the first current sampling unit E11. The single-chip microcomputer MCU receives the first sampling current signal Is1 through its first sampling current input terminal ( Figure 5 The middle pin P1.1) obtains the first sampling current signal Is1.

[0080] When the voltage control signal SW outputted from the pin 1.5 of the single-chip microcomputer MCU is at a low level, the current outputted from the output terminal of the LED constant voltage control device 2 is converted into the voltage of the second current sampling node ISEN2 through the twenty-first resistor R21. Figure 5 The middle pin P1.2) obtains the second sampling current signal Is2 through the twenty-second resistor R22.

[0081] It can be seen that the second sampling current Is2 reflects the current at the output end of the LED constant voltage control device LED constant voltage control device when the output DC voltage is a smaller first voltage; the first sampling current Is1 reflects the current at the output end of the LED constant voltage control device LED constant voltage control device when the output DC voltage is a normal power supply voltage.

[0082] The structures and working principles of other modules of the short-circuit protection circuit of Example 2 of the present invention are basically the same as those of Example 1 and will not be described in detail here.

[0083] See also Figure 7 , Figure 7 A flow chart of the short-circuit protection method executed by the controller of the second embodiment of the present invention. Since the short-circuit protection circuit E of the second embodiment of the present invention does not include the output switch unit E3, and the sampling current includes the first sampling current and the second sampling current, the short-circuit protection method executed by the controller MCU of the second embodiment of the present invention is changed to:

[0084] S10, in an initial stage, the output voltage control unit controls the direct current voltage output by the LED constant voltage control device to be a preset first voltage.

[0085] S20, obtaining a sampling voltage through the voltage sampling unit, and judging whether the DC voltage output by the LED constant voltage control device is equal to a preset first voltage according to the sampling voltage; if the DC voltage output by the LED constant voltage control device is equal to the preset first voltage, obtaining a second sampling current Is2 through the second current sampling unit, and judging whether the second sampling current is greater than a preset second short-circuit threshold.

[0086] S31, if step S20 determines that the second sampling current is not greater than the preset second short-circuit threshold, it is determined that short circuit does not occur, and then the output voltage control unit controls the DC voltage output by the LED constant voltage control device to be a normal power supply voltage.

[0087] S32, at every set first time interval, obtaining a sampled voltage and a first sampled current through the voltage sampling unit and the first current sampling unit, and judging whether a short circuit is likely to occur according to the sampled voltage and the first sampled current; if it is judged that a short circuit is likely to occur, returning to step S10.

[0088] S41, if step S20 determines that the second sampling current is greater than the preset second short-circuit threshold, it is determined that a short circuit occurs, and then the output voltage control unit controls the DC voltage output by the LED constant voltage control device to be a preset first voltage. Since the output voltage control unit E4 of embodiment 2 can only control the DC voltage output by the LED constant voltage control device to switch between the first voltage and the power supply voltage, the second voltage described in embodiment 1 is equal to the first voltage in embodiment 2.

[0089] S42, at every set second time interval, return to step S10 and re-determine whether a short circuit occurs; if step S20 determines that a short circuit occurs N times in a row (N is the set cycle number threshold), after completing step S41, no longer return to step S10, and re-enter step S10 after the LED constant voltage control device is restarted.

[0090] The present invention has the following technical effects: the present invention completes short circuit detection when the DC voltage output by the LED constant voltage control device is a smaller first voltage, and adjusts the DC voltage output by the LED constant voltage control device to a normal power supply voltage only after ensuring that a short circuit does not occur. Therefore, the short circuit can be detected before the LED lamp body is lit, and the short circuit protection measures are triggered in time, effectively avoiding the harm caused by the short circuit. Furthermore, the present invention can also detect the short circuit in real time during the working process. Once it is found that a short circuit may occur, the output voltage of the LED constant voltage control device is lowered or the power supply circuit is cut off, thereby ensuring the safety of the circuit to the greatest extent.

[0091] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, and the present invention is also intended to include these modifications and modifications.

Claims

1. A short-circuit protection method for an LED constant voltage control device, characterized in that: Includes steps: S10, controlling the DC voltage output by the LED constant voltage control device to be a preset first voltage; S20, collecting the DC voltage output by the LED constant voltage control device to obtain a sampled voltage; collecting the current at the output end of the LED constant voltage control device to obtain a sampled current; judging whether a short circuit occurs according to the sampled current and the sampled voltage; S31, if it is determined that the short circuit does not occur, then the DC voltage output by the LED constant voltage control device is controlled to be a normal power supply voltage; S41, if it is determined that a short circuit occurs, the DC voltage output by the LED constant voltage control device is controlled to be a preset second voltage.

2. The short-circuit protection method of the LED constant voltage control device according to claim 1, characterized in that: The method further includes a step S32 after the step S31: obtaining a sampled voltage and a sampled current at every set first time interval, and judging whether a short circuit is likely to occur according to the sampled voltage and the sampled current; if it is judged that a short circuit is likely to occur, returning to the step S10.

3. The short-circuit protection method of the LED constant voltage control device according to claim 2, characterized in that: The step S42 is also included after the step S41: At every set second time interval, returning to step S10, re-determining whether a short circuit occurs; If a short circuit is determined to occur N times in succession, after completing step S41 , the process does not return to step S10 ; N is a set cycle number threshold.

4. The short-circuit protection method of the LED constant voltage control device according to claim 3, characterized in that: In step S20, judging whether a short circuit occurs according to the sampled current and the sampled voltage specifically includes: If the sampled voltage is equal to a preset first voltage, determining whether the sampled current is greater than a preset short-circuit threshold; If the sampled current is greater than a preset short-circuit threshold, it is determined that a short circuit occurs; If the sampled current is not greater than the preset short-circuit threshold, it is determined that a short circuit does not occur.

5. The short-circuit protection method for a LED constant voltage control device according to any one of claims 1 to 4, characterized in that: Step S10 specifically includes: controlling the DC voltage output by the LED constant voltage control device to be a preset first voltage, and controlling the connection between the output end of the LED constant voltage control device and the LED lamp body to be turned on; Step S41 specifically includes: if it is determined that a short circuit occurs, controlling the DC voltage output by the LED constant voltage control device to be a preset second voltage, and controlling the output end of the LED constant voltage control device to be disconnected from the LED lamp body.

6. A short-circuit protection circuit of an LED constant voltage control device, characterized in that: include: A current sampling unit, used to collect the current at the output end of the LED constant voltage control device to obtain a sampling current; The voltage sampling unit is used to collect the DC voltage output by the LED constant voltage control device to obtain a sampling voltage; A controller, configured to determine whether a short circuit occurs according to the sampled current and the sampled voltage, and output a voltage control signal to an output voltage control unit; An output voltage control unit, used to control the magnitude of the DC voltage output by the LED constant voltage control device according to the voltage control signal; Wherein, the controller executes the short-circuit protection method described in any one of claims 1-4.

7. The short-circuit protection circuit of the LED constant voltage control device according to claim 6, characterized in that: The output voltage control unit comprises: a third MOS tube, an eighteenth resistor, a fourth MOS tube, a nineteenth resistor, a diode string, a twentieth resistor, a twenty-first resistor, a third triode, a twenty-second resistor and a twenty-third resistor; the third MOS tube is an NMOS tube, a source of which is connected to the second output end of the LED constant voltage control device, a drain of which is connected to the LED lamp body, and a gate of which is connected to the drain of the fourth MOS tube through the eighteenth resistor; the source of the third MOS tube is connected to its own gate through the nineteenth resistor; the diode string comprises a plurality of diodes whose cathodes and anodes are connected in series; the equivalent cathode of the diode string is connected to the source of the third MOS tube through the twentieth resistor, and the equivalent anode is connected to the drain of the third MOS tube; the fourth MOS tube is an NMOS tube, a drain of which is connected to a voltage source through the twenty-first resistor, a gate of which is connected to the collector of the third triode, and a source of which is grounded; the collector of the third triode is connected to the voltage source through the twenty-second resistor, an emitter of which is grounded, and a base of which is connected to the output voltage control signal of the controller through the twenty-third resistor.

8. The short-circuit protection circuit of the LED constant voltage control device according to claim 6, characterized in that: It also includes an output switch unit for controlling the on / off connection between the output end of the LED constant voltage control device and the LED lamp body according to the switch control signal output by the controller; the controller executes the short-circuit protection method described in claim 5.

9. The short-circuit protection circuit of the LED constant voltage control device according to claim 8, characterized in that: The output switch unit includes: a first MOS tube, a sixth resistor, a second MOS tube, a seventh resistor, an eighth resistor, a second triode, a ninth resistor, and a tenth resistor; the first MOS tube is an NMOS tube, a source of which is connected to the second output end of the LED constant voltage control device, a drain of which is connected to the LED body, and a gate of which is connected to the drain of the second MOS tube through the sixth resistor; the seventh resistor is connected across the source and the gate of the first MOS tube; the second MOS tube is an NMOS tube, a drain of which is connected to the voltage source through the eighth resistor, a gate of which is connected to the collector of the second triode, and a source of which is grounded; the collector of the second triode Q2 is connected to the voltage source through the ninth resistor, the emitter is grounded, and the base is connected to the switch control signal output by the controller through the tenth resistor.

10. The short-circuit protection circuit of the LED constant voltage control device according to claim 9, characterized in that: The output voltage control unit includes: a first optical coupler, an eleventh resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a second voltage regulator, a fifteenth resistor, a second optical coupler, a three-pin voltage regulator, a sixteenth resistor, a seventeenth resistor and a sixth capacitor; the anode of the light-emitting diode of the first optical coupler is connected to the voltage control signal output by the controller through the eleventh resistor, and the cathode is grounded; the collector of the phototransistor of the first optical coupler is connected to the first output end of the LED constant voltage control device through the twelfth resistor, and the emitter is grounded through the thirteenth resistor; the fourteenth resistor is connected across the collector and emitter of the phototransistor of the first optical coupler; the The cathode of the second voltage-stabilizing tube is connected to the first output end of the LED constant-voltage control device, and the anode is connected to the anode of the light-emitting diode of the second optocoupler through the fifteenth resistor; the cathode of the three-pin voltage-stabilizing tube is connected to the anode of the light-emitting diode of the second optocoupler through the sixteenth resistor, the anode is grounded, and the reference electrode is connected to the emitter of the phototransistor of the first optocoupler; the collector of the phototransistor of the second optocoupler is connected to the primary network in the LED constant-voltage control device that can control the DC voltage output by its first output end; one end of the seventeenth resistor is connected to the emitter of the phototransistor of the first optocoupler, and the other end is connected to the cathode of the three-pin voltage-stabilizing tube through the sixth capacitor.

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