Linear LED power supply protection circuit

Abstract

The utility model discloses a linear LED power supply protection circuit. The problem that an existing linear constant-current power supply protection circuit cannot cut off a heating source in time in a non-constant-current failure mode is solved. According to the utility model, the sampling resistor loop, the triode sampling loop and the breakdown loop are adopted; wherein the sampling resistor loop comprises a sampling resistor and a constant-current power supply loop electrically connected with the sampling resistor and is used for acquiring a protection current value; the triode sampling loop comprises a triode and a sampling resistor which is electrically connected with a base electrode and an emitting electrode of the triode respectively, and also comprises a coordination diode which is connected between the sampling resistor and the base electrode and is used for modulating triode voltage; the breakdown loop comprises a triode sampling loop and a constant-current power supply loop connected with a triode collector, and elements in the constant-current power supply loop are broken down to be disconnected. And the overheating protection of the circuit is completed by adopting the minimum circuit change, so that the circuit overhead can be greatly saved, and the circuit complexity is reduced.

Description

Technical Field

[0001] The utility model relates to the field of protection circuits, in particular to a linear LED power supply protection circuit. Background Art

[0002] The development of LED and driving technology has made product cost requirements increasingly stringent. LED lamps need to take into account miniaturization, lightness and cost minimization. Therefore, plastic-shell downlights, bulbs, tubes and ceiling lamps are widely used; and their power supplies are developing towards the direction of non-inductance. However, the current-voltage conversion constant current power supply without inductance, or the linear power supply with constant current diode, all have the following common problems. That is, when static electricity or lightning surge causes the collector and emitter of the internal triode of the linear power supply, the drain and source of the MOS tube or the cathode and cathode of the constant current diode to break down, the power supply loses its constant current function, causing the load LED to bear very high ripple current and voltage, causing the LED load to continue to heat for a long time, thereby melting the protective shell of the lamp, and there is a great risk of causing fire; similarly, in the constant current failure mode of the IC power supply, the same risk will also occur. The existing LED protection circuit usually adopts the switching power supply circuit to solve the above problems, which will lead to a significant increase in circuit complexity and manufacturing costs.

[0003] For example, a "surge protection type high-voltage constant current switching power supply based on common emitter amplifier circuit" disclosed in Chinese patent documents, with announcement number CN105896994A, is mainly composed of a main control chip U, a current modulation circuit, a transformer T, a transistor VT2, a voltage stabilizing diode D3 whose N pole is connected to the IN pin of the control chip U and whose P pole is respectively connected to the current modulation circuit and the collector of the transistor VT2, and a diode D4 whose N pole is connected to the emitter of the transistor VT2 and whose P pole is connected to the RC pin of the control chip U. The UC3845 integrated chip is combined with the peripheral circuit to improve its efficiency in high-voltage conversion, output a stable current after high-voltage conversion, prevent nonlinear distortion, and improve circuit stability. However, the switch circuit structure is complex and the cost is too high, and there are still limitations in its use in fast-moving consumer goods such as downlights. Summary of the invention

[0004] The utility model mainly solves the problem that the existing linear constant current power supply protection circuit cannot cut off the heat source in time in the non-constant current failure mode; provides a linear LED power supply protection circuit, which simulates the failure phenomenon of the linear constant current power supply, captures the LED current in the failure mode, sets a resistor in series with the load LED to obtain the required voltage signal, applies it to the triode to start it instantly, thereby instantly loading the overload current to the LED load, breaking down the load circuit, thereby protecting the linear power supply while cutting off the heat source to avoid causing the lampshade to burn; in addition, the overheat protection of the circuit is completed with minimal circuit modification, which can greatly save circuit overhead, reduce circuit complexity, and cut manufacturing costs.

[0005] The above technical problems of the utility model are mainly solved by the following technical solutions:

[0006] The utility model includes a constant current power supply circuit, and also includes: a sampling resistor circuit, a triode sampling circuit and a breakdown circuit; wherein the sampling resistor circuit includes a sampling resistor and a constant current power supply circuit electrically connected thereto, and obtains a protection current value; the triode sampling circuit includes a triode and a sampling resistor electrically connected to its base and emitter respectively, and also includes a coordination diode connected between the sampling resistor and the base, and modulates the triode voltage; the breakdown circuit includes a triode sampling circuit and a constant current power supply circuit connected to the triode collector, and breaks down the components in the constant current power supply circuit to break the circuit. Among them, the sampling resistor has high precision and stability, can provide accurate current or voltage measurement results, and meet the high-precision measurement requirements of the circuit; the cost of the sampling resistor is relatively low, so that the entire circuit has high cost-effectiveness while maintaining high performance; by modulating the voltage of the triode through the coordination diode, the triode sampling circuit can realize flexible signal sampling and modulation, which can meet the requirements of targeted breakdown of the LED load string in the breakdown circuit under the predicted current, thereby effectively preventing it from heating.

[0007] Preferably, the coordination diode in the transistor sampling loop is set as a voltage-stabilizing diode; the transistor base is connected to the positive electrode of the voltage-stabilizing diode, the negative electrode of the voltage-stabilizing diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the emitter of the transistor. The voltage-stabilizing diode can stabilize the base voltage, ensuring that the amplification factor of the transistor is maintained at a high and stable level, thereby improving the overall performance of the circuit. At the same time, when the input signal is too large, the voltage-stabilizing diode can limit the signal amplitude, prevent the transistor from being damaged by excessive voltage, and provide effective protection for the circuit. In addition, the voltage-stabilizing diode can automatically cut off when the input voltage is too high, avoiding the transistor from burning due to overvoltage, further enhancing the reliability and safety of the circuit.

[0008] Preferably, the coordination diode in the transistor sampling loop is set as a Schottky diode; the transistor base is connected to the cathode of the Schottky diode, the anode of the Schottky diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the emitter of the transistor. The Schottky diode has the characteristics of low forward voltage drop, high switching speed and low reverse leakage current, which enables it to respond quickly to changes in the circuit and effectively modulate the voltage of the transistor. At the same time, the forward voltage drop of the Schottky diode is small, which can reduce energy loss and improve circuit efficiency. When used in conjunction with the transistor, the Schottky diode can stabilize the working state of the transistor and improve the performance of the entire sampling loop.

[0009] Preferably, the transistor sampling loop also includes a filter capacitor connected to both ends of the sampling resistor or the base and collector of the transistor; and also includes a sampling voltage point set at the connection between the sampling resistor and the corresponding end of the coordination diode. The addition of the filter capacitor effectively filters out the noise and interference signals at both ends of the sampling resistor or the base and collector of the transistor, improves the purity and stability of the sampling signal, and thus enhances the safety of the circuit. At the same time, the filter capacitor can also reduce the ripple in the circuit, reduce voltage fluctuations, and ensure the accuracy of the sampling voltage. The setting of the sampling voltage point facilitates the real-time monitoring and measurement of the sampling voltage, and improves the debugging and maintenance efficiency of the circuit. By accurately obtaining the sampling voltage, potential problems in the circuit can be discovered in time.

[0010] Preferably, in the breakdown circuit, the transistor collector is electrically connected to the LED load string in the constant current power supply circuit; the LED load string is provided with m LED loads, and the connection position of the transistor collector is set at the nth LED load, where n<=m. By connecting the transistor collector to a specific position of the LED load string, precise control of the LED load string is achieved; when an abnormality occurs in the circuit, the transistor can respond quickly and disconnect the LED load string through a breakdown operation, effectively protecting other LED loads from damage; according to actual needs, the number of LED loads m is reasonably set to ensure the brightness and stability of the entire lighting system. The selection of the transistor collector connection position n can achieve flexible segmented control of the LED load string and improve the reliability and safety of the system.

[0011] Preferably, the two ends of the sampling resistor are electrically connected to the LED load string and one end of the constant current power chipset in the constant current power supply circuit respectively; the other end of the LED load string is connected to a circuit composed of a rectifier bridge and a constant current linear compensation electrolytic capacitor in parallel, and the LED load string is also connected to the power supply through an anti-surge fuse resistor; one of the pins at the other end of the constant current power chip is connected to a circuit composed of several current sampling resistors, and is connected to the ground after being connected to another pin. The connection of the sampling resistor with the LED load string and the constant current power chipset realizes accurate sampling and monitoring of the LED load current, ensures constant LED brightness, and improves user experience. The parallel connection of the rectifier bridge and the constant current linear compensation electrolytic capacitor not only ensures the stable output of the power supply, but also reduces the current fluctuation through linear compensation, thereby extending the service life of the LED. The setting of the anti-surge fuse resistor effectively prevents the damage of the surge current to the LED load and enhances the safety of the circuit. The loop connection of the constant current power chip and the current sampling resistor realizes accurate control and regulation of the current.

[0012] Preferably, one end of the sampling resistor is connected to one end of several foot power supply resistors through a string of forward LED loads, the other end of the foot power supply resistor is connected to the pin of the constant current power supply chip in the constant current power supply loop, and the other end of the forward LED load string is connected to the power supply through a rectifier diode; the other end of the sampling resistor is directly connected to the other pin on one side of the constant current power supply chip, and is respectively connected to the remaining pins on one side through a string of reverse LED loads; the other pin on one side of the constant current power supply chip is connected to several current sampling resistors or connected to the power supply through a compensation capacitor and a rectifier bridge stack. All components are closely linked together to achieve efficient and stable circuit operation. The sampling resistor is connected to the constant current power supply chip through the LED load string to ensure the accuracy and stability of current sampling. The setting of the forward and reverse LED load strings not only improves the anti-interference ability of the circuit, but also enhances the stability of the overall circuit. The connection of the constant current power supply chip with the current sampling resistor, the compensation capacitor and the rectifier bridge stack achieves accurate control of the current and stable output of the power supply, and simplifies the circuit structure.

[0013] Preferably, one end of the sampling resistor is connected to the LED load string in the constant current power supply circuit, and the other end is grounded together with the transistor emitter; the other end of the LED load string is connected to the single-side pin of the constant current power supply chip through a number of current sampling resistors, and the other pins on the same side of the constant current power supply chip are grounded, and the opposite pin is connected to the power supply through the rectifier bridge stack and the anti-surge fuse resistor. The connection between the sampling resistor and the LED load string realizes the accurate sampling of the circuit current and ensures the normal operation of the LED. The transistor emitter and the other end of the sampling resistor are grounded together, which stabilizes the working voltage of the transistor and improves its working reliability. The use of the constant current power supply chip in conjunction with the current sampling resistor, the rectifier bridge stack and the anti-surge fuse resistor ensures the constant output of the power supply and effectively prevents the impact of surge current on the circuit.

[0014] Preferably, one end of the sampling resistor is connected to the LED load string in the constant current power supply circuit, and the other end is grounded together with the transistor emitter; the other end of the LED load string is connected to the loop composed of the constant current linear compensation electrolytic capacitor and the point release discharge resistor, and the other end of the loop is connected to the constant current linear chip, which is connected to the power supply through the rectifier bridge stack. The connection between the sampling resistor and the LED load string realizes the accurate sampling of the current and ensures the stable operation of the LED. The common grounding of the transistor emitter and the sampling resistor stabilizes the operating voltage and improves the circuit reliability. The loop composed of the constant current linear compensation electrolytic capacitor and the point release discharge resistor effectively compensates for the current fluctuation and improves the stability of the power supply. The rectifier bridge stack converts the alternating current into direct current, ensuring the stability and safety of the power supply.

[0015] The beneficial effects of the utility model are:

[0016] 1. The utility model is a linear LED power protection circuit. By optimizing the circuit design, a combination of a constant current power supply circuit, a sampling resistor circuit, a transistor sampling circuit and a breakdown circuit is adopted to ensure stable power supply and accurate sampling of the circuit. A coordination diode is set to further enhance the modulation capability and response speed of the circuit, achieve the effect of rapid breakdown, and effectively prevent the overheating risk caused by continuous heating of the components; it solves the protection of linear ICs or constant current diodes in non-constant current failure modes. When a failure occurs, the heat source is quickly cut off within the shortest time, i.e., ≤500ms, so that the circuit is in a closed, open, standby or other states, thereby ensuring the safety of the lamp.

[0017] 2. A linear LED power protection circuit of the utility model simplifies the circuit structure, reduces unnecessary components and connection points, and reduces the complexity and failure rate of the circuit through carefully designed component connections and loop layouts; the optimized circuit structure improves the current transmission efficiency, reduces energy loss, and improves the efficiency of the overall circuit; the constant current power supply chip is used in conjunction with current sampling resistors, compensation capacitors and other components to achieve precise control and regulation of the current, further improving the performance and efficiency of the circuit; and reducing circuit overhead and manufacturing costs.

[0018] 3. The linear LED power supply protection circuit of the utility model can also achieve other beneficial effects, namely, by accurately controlling the current and voltage of the LED load string, the constant and uniform brightness of the LED is achieved; the connection of the sampling resistor to the LED load string ensures accurate sampling and monitoring of the current, avoiding brightness changes caused by current fluctuations; the coordinated use of constant current linear compensation electrolytic capacitors and point-to-point electrolytic resistors effectively compensates for current fluctuations, further improving the stability and life of the LED; the setting of the anti-surge fuse resistor effectively prevents damage to the LED by surge current and extends the service life of the LED. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a circuit diagram combining a breakdown circuit and a triode sampling circuit of a linear LED power supply protection circuit of the utility model;

[0020] Figure 2 This is a LED current measurement diagram of a linear LED power supply protection circuit of the utility model;

[0021] Figure 3 This is a linear LED power supply protection circuit diagram of embodiment 3 of the utility model;

[0022] Figure 4 This is a linear LED power supply protection circuit diagram of embodiment 4 of the utility model;

[0023] Figure 5 This is a linear LED power supply protection circuit diagram of embodiment 5 of the utility model;

[0024] Figure 6 This is a linear LED power supply protection circuit diagram of embodiment 6 of the utility model;

[0025] Figure 7 This is a linear LED power supply protection circuit diagram of embodiment 7 of the utility model;

[0026] Figure 8 This is a linear LED power supply protection circuit diagram of Example 8 of the utility model. DETAILED DESCRIPTION

[0027] The technical solution of the utility model is further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0028] Embodiment 1:

[0029] A linear LED power supply protection circuit of this embodiment, such as Figure 1 As shown, it includes an LED load string with one end connected to the power supply V+ and the other end connected to the sampling resistor RS1, and the number of loads is m; one end of the sampling resistor RS1 is connected to one end of the coordination diode ZS1, and the other end of the sampling resistor is grounded to form a sampling loop. The other end of the coordination diode ZS1 is connected to a small loop formed by the transistor QS1 and the filter capacitor CS1, and the emitter E of the transistor QS1 is grounded, which can also be regarded as connected to the sampling resistor RS1. Therefore, the small loop and the sampling resistor RS1 together form a transistor sampling loop. The base B of the transistor QS1 is connected to the other end of the coordination diode ZS1, and the collector C of the transistor QS1 is connected to the nth LED load among the m LED loads to form a breakdown loop.

[0030] When the coordination diode ZS1 in the transistor sampling loop is set as a voltage-stabilizing diode, the transistor base is connected to QS1 and the positive electrode of the voltage-stabilizing diode, the negative electrode of the voltage-stabilizing diode is connected to one end of the sampling resistor RS1, and the other end of the sampling resistor is connected to the emitter E of the transistor QS1. When the coordination diode ZS1 in the transistor sampling loop is set as a Schottky diode; the base B of the transistor QS1 is connected to the negative electrode of the Schottky diode, the positive electrode of the Schottky diode is connected to one end of the sampling resistor, and the other end of the sampling resistor RS1 is connected to the emitter E of the transistor.

[0031] The sampling resistor loop, as a key link in the circuit, is mainly composed of a sampling resistor and a constant current power supply loop, which jointly shoulder the important task of obtaining and monitoring the protection current value. The sampling resistor is tightly electrically connected to the constant current power supply loop to ensure the accurate transmission and real-time feedback of the current value, providing a solid guarantee for the safe operation of the circuit. The transistor sampling loop is centered on the transistor, whose base and emitter are electrically connected to the sampling resistor respectively to form a tight sampling network. In this loop, the coordination diode plays a vital role. It is connected between the sampling resistor and the base of the transistor, and by modulating the voltage of the transistor, it ensures that the transistor can work stably and efficiently.

[0032] In the transistor sampling circuit, the setting of the coordination diode is also exquisite. When a voltage regulator diode is used, the base of the transistor is connected to the positive electrode of the voltage regulator diode, and the negative electrode of the voltage regulator diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the emitter of the transistor. This connection method can ensure that the transistor operates under a stable operating voltage and improve the stability and reliability of the circuit. When a Schottky diode is used as a coordination diode, the base of the transistor is connected to the negative electrode of the Schottky diode, the positive electrode of the Schottky diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is also connected to the emitter of the transistor. The Schottky diode provides more sensitive and accurate voltage modulation for the transistor with its low forward voltage drop and high switching speed.

[0033] As a safety barrier in the circuit, the breakdown circuit is composed of a transistor sampling circuit and a constant current power supply circuit connected to the transistor collector. When an abnormality occurs in the circuit, the breakdown circuit can respond quickly by breaking down the components in the constant current power supply circuit to break the circuit, thereby protecting the circuit from damage such as overload or short circuit.

[0034] In the breakdown circuit, the transistor collector is electrically connected to the LED load string in the constant current power supply circuit. This design enables the transistor to directly control the working state of the LED load string. Multiple LED loads are set in the LED load string, and the transistor collector is connected to the nth LED load. This segmented control method not only realizes the flexible management of the LED load string, but also improves the safety and reliability of the entire circuit.

[0035] In order to further improve the performance and stability of the circuit, filter capacitors are added to the transistor sampling loop. These filter capacitors are connected to the two ends of the sampling resistor or the base and collector of the transistor respectively, effectively filtering out the noise and interference signals in the circuit and ensuring the purity and stability of the sampling voltage. At the same time, the sampling voltage point set at the connection between the sampling resistor and the coordination diode provides convenience for real-time monitoring and measurement of the sampling voltage.

[0036] In the actual operation of the above circuit, the failure phenomenon of the linear constant current IC / constant current diode will be simulated, the LED current in the failure mode will be captured, and the required voltage signal will be obtained through the LED series sampling resistor RS1, which will be given to the transistor QS1; and the collector C of the transistor QS1 is connected to an LED in the middle of the LED light string, and the emitter is connected to the ground (either real or virtual ground). The voltage required to turn on the transistor is set by sampling, and the V(BR)CBO of the transistor is selected by placing the transistor C electrode at the position of the LED light string.

[0037] Approximate calculation description (ignore Ibe), the trigger transistor turn-on current is calculated by the following expression: Vbe = VRT – Vzs1 = R (Rs1) * Iled - Vzs1;

[0038] Right now,

[0039] By referring to the Vbe curve chart in the transistor specification, such as Figure 2 As shown, take the appropriate RS1 and ZS1 values ​​to get the current value you want to protect. When the IC is working normally, Vbe is much smaller than the transistor turn-on voltage, and the transistor does not work. When the IC pin is short-circuited or a lightning surge causes the IC to lose its constant current function (DS breakdown of the IC's internal MOS / CE breakdown of the transistor / cathode breakdown of the constant current diode), the AC input voltage is rectified by the rectifier bridge and Vo is approximately 1.414*Vinac, which will cause the Ied light string (total m strings) current Iled to suddenly change (ripple increases, circuit value increases), then Vbe increases to the transistor turn-on voltage, causing the transistor to turn on instantly, so that LEDI (the cathode of the nth LED in series) is connected to GND, and the original Vo is all loaded on the n strings of LEDs, and the instantaneous high voltage and high current cause the LED to instantly break down (through actual testing, the current breakdown failure time t≤500ms is the safest), and the actual debugging value is much smaller than this time (see the above "abnormal state LED current monitoring" measured data chart). The circuit operation described above causes the LED circuit to break down but the IC chip circuit to not break down, thereby protecting the internal components and preventing heat generation.

[0040] The advantages of the above circuit in actual operation are mainly reflected in the comprehensive protection of the LED lighting system. By simulating the failure phenomenon of the linear constant current IC / constant current diode, the circuit can accurately capture the LED current in the failure mode, and obtain the required voltage signal through the sampling resistor RS1, thereby controlling the switching state of the transistor QS1. This design not only improves the safety and reliability of the circuit, but also provides a strong guarantee for the stable operation of the LED lighting system.

[0041] Specifically, when the IC is working normally, Vbe is much smaller than the transistor turn-on voltage, and the transistor is in a non-working state, thereby ensuring the normal lighting of the LED light string. However, once the IC pin is short-circuited or suffers from abnormal conditions such as lightning surge, the IC loses its constant current function, and the current and voltage in the circuit will change suddenly. At this time, the sampling resistor RS1 can quickly sense this change and trigger the turn-on of the transistor by adjusting the voltage signal. Once the transistor is turned on, a certain LED in the LED light string is connected to the ground wire, so that the original high voltage and high current are concentrated on this part of the LED. Since the instantaneous high voltage and high current will cause the LED to break down instantly, this design can quickly cut off the abnormal current and prevent the LED light string from being further damaged.

[0042] This circuit also has the advantage of protecting internal components and eliminating heat. Under abnormal conditions, although the LED circuit will break down, the IC chip circuit will not be damaged. This is because the opening of the transistor directs the abnormal current to the LED light string, avoiding the impact of the current on the IC chip. At the same time, because the breakdown process occurs very quickly, the heat accumulation in the circuit is effectively suppressed, thus eliminating the potential risks caused by overheating.

[0043] Embodiment 2:

[0044] A linear LED power supply protection circuit of this embodiment is a further design of the circuit described in Embodiment 1. A 16-string 18V LED light string is taken as an example for detailed description. The number of LED light strings here is 16 (i.e. m=16), and the cathode of the 7th LED is selected as the connection point of the collector of the transistor QS1 (i.e. n=7). In practical applications, the number of LED light strings m can be selected as 14, 15, 16, etc. as needed, and the value range of n is 1 to 16, depending on the total number of LED light strings and the requirements of the protection strategy. In order to select a more economical transistor model, n is usually set to m / 2 or less.

[0045] We also need to make clear the number of LEDs and the voltage Vf of the LEDs. When the AC input voltage Vac is in the range of 110-120V, the total voltage Vled of the LED string should be maintained between 120V and 144V. When Vac is 220-240V, Vled should be in the range of 250V to 288V. The number of LED strings will be directly determined by Vled and the voltage Vf of each LED.

[0046] When using the circuit of the embodiment given above, these parameters will directly affect the working state and protection effect of the circuit. The resistance value of the sampling resistor RS1 will determine the size of Vbe, which in turn affects the switching state of the transistor QS1. By reasonably selecting the resistance value of RS1, it can be ensured that under normal working conditions, Vbe is much smaller than the turn-on voltage of the transistor, so that the transistor remains in the off state. When the IC fails and the current suddenly changes, Vbe will quickly increase to the turn-on voltage of the transistor, triggering the turn-on of the transistor, thereby realizing the protection of the LED light string. It is also necessary to pay attention to the voltage distribution of the LED light string. Since the cathode of the 7th LED is selected as the connection point of the transistor collector, when the transistor is turned on, the LEDs after this point will be subjected to a higher voltage.

[0047] Embodiment 3:

[0048] A linear LED power supply protection circuit of this embodiment, such as Figure 3 As shown, the circuit is further improved on the basis of Example 1 to obtain a single-segment linear circuit diagram of an IC of a power supply low-end current sampling block diagram, wherein the two ends of the sampling resistor RS1 are electrically connected to the LED load string in the constant current power supply loop and the pin 7 of the constant current power supply chip US1 respectively; the other end of the LED load string is connected to a loop composed of a rectifier bridge stack BD1 and a constant current linear compensation electrolytic capacitor CD1, and the LED load string is also connected to the power supply L / N through an anti-surge fuse resistor FR1; and pin 2 of the constant current power supply chip US1 is connected to a loop composed of several current sampling resistors, and is connected to pin 1 and then grounded.

[0049] In the above circuit, the power supply L / N is the power input power supply end, FR1 is the anti-surge fuse resistor, BD1 is the rectifier bridge stack, US1 is the high-end current sampling constant current linear IC, R1 / 2 is the current sampling resistor, CD1 is the constant current linear compensation electrolytic capacitor, R3 is the electrolytic discharge resistor, D1-D2-…-D16 is the LED. RS1 is the protection circuit transistor sampling resistor, ZS1 is the transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forward connected), CS1 is the transistor B pole filter capacitor, LEDI is the load output port connected to the transistor C pole when the functional circuit is in action. RT is the sampling voltage point of the transistor action.

[0050] Under normal working conditions, the constant current power chip US1 maintains the constant current operation of the LED load string through its internal linear circuit. The sampling resistor RS1 monitors the current of the LED load string in real time and transmits the corresponding voltage signal to the base of the transistor QS1. Since the current of the LED load string is in the normal range at this time, Vbe is much smaller than the turn-on voltage of the transistor QS1, so the transistor QS1 remains in the off state and will not affect the LED load string.

[0051] When the constant current power chip US1 fails, or the circuit is affected by abnormalities such as lightning surges, the current of the LED load string will change suddenly. At this time, the sampling resistor RS1 senses the change in current and adjusts the voltage signal at both ends of it. When this voltage signal reaches or exceeds the turn-on voltage of the transistor QS1, the transistor QS1 will turn on quickly. The turning on of the transistor connects a part of the LED load string (the LED connected to the collector of the transistor and the LED after it) to the ground wire, causing this part of the LED to withstand instantaneous high voltage and high current, resulting in breakdown.

[0052] The benefit of the above design is that by accurately monitoring the current of the LED load string and quickly cutting off the current under abnormal conditions, this circuit effectively protects the LED load string from overcurrent damage. The breakdown of the LED is instantaneous and occurs in a specific part of the circuit, thus avoiding damage to the entire LED load string; due to the fast response and precise action of the transistor, the constant current power supply chip US1 will not be impacted by overcurrent under abnormal conditions, thus being effectively protected. This extends the service life of the constant current power supply chip and improves the reliability of the entire circuit; the setting of components such as filter capacitors, surge protection fuse resistors, etc. in the circuit effectively filters out noise and interference in the circuit and improves the stability of the system.

[0053] At the same time, by rationally designing the connection mode of the LED load string and the selection of transistors, the circuit can quickly resume normal operation under abnormal conditions, improving the fault tolerance of the system; by optimizing the circuit design and selecting appropriate component models and parameters, this circuit can achieve protection functions while reducing costs. In particular, by rationally setting the connection position of the transistor (such as n≤m / 2), the selection of the transistor is more economical, greatly reducing the overall cost.

[0054] Embodiment 4:

[0055] A linear LED power supply protection circuit of this embodiment, such as Figure 4 As shown, the circuit is further improved on the basis of Example 1 to obtain a 2-segment linear driving circuit diagram of an IC of a power supply low-end current sampling block diagram, one end of the sampling resistor is connected to one end of a plurality of foot power supply resistors through a string of positive LED loads, the other end of the foot power supply resistor is connected to the pin of a constant current power supply chip in a constant current power supply loop, and the other end of the positive LED load string is connected to the power supply through a rectifier diode; the other end of the sampling resistor is directly connected to the other pin on one side of the constant current power supply chip, and is respectively connected to the remaining pins on one side through a string of reverse LED loads; the other pin on one side of the constant current power supply chip is connected to a plurality of current sampling resistors or is connected to the power supply through a compensation capacitor and a rectifier bridge stack.

[0056] In the above circuit, L / N is the power input supply terminal. FR1 is the surge protection fuse resistor. BD1 is the rectifier bridge. US1 is the low-end current sampling 2-stage constant current linear IC, R2 / 3 / 5 is the current sampling resistor, CD1 is the constant current linear compensation electrolytic capacitor. D1-D2-…-D16 is the LED. R1A / 1B is the ICHV pin power supply resistor, C1 is the Comp pin bypass capacitor. R4 / 6 is the pull-up and pull-down resistors for high and low voltage detection, and D2 is a diode for increasing surge capability. D1 is a rectifier diode. RS1 is the protection circuit transistor sampling resistor, ZS1 is the transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forwarded). CS1 is the transistor B-pole filter capacitor. LEDI is the load output port connected to the C-pole of the transistor when the functional circuit is in action, and RT is the sampling voltage point of the transistor action. This circuit is a 2-stage constant current linear drive circuit based on low-end current sampling, mainly used for the protection of LED power supply. Its core components include constant current power supply chip US1, LED load string, sampling resistor RS1, transistor QS1 and related auxiliary components.

[0057] Under normal working conditions, the constant current power chip US1 maintains the constant current operation of the LED load string through its internal linear circuit. At this time, the sampling resistor RS1 monitors the current of the LED load string in real time and transmits the corresponding voltage signal to the base of the transistor QS1. Since the current of the LED load string is in the normal range at this time, Vbe is much smaller than the turn-on voltage of the transistor QS1, so the transistor QS1 remains in the off state and will not affect the LED load string.

[0058] When the circuit is abnormal, such as the constant current power chip US1 fails or is impacted by lightning surge, the current of the LED load string will change suddenly. At this time, the sampling resistor RS1 senses the change in current and adjusts the voltage signal at both ends. When this voltage signal reaches or exceeds the turn-on voltage of the transistor QS1, the transistor QS1 will turn on quickly. The turning on of the transistor connects a part of the LED load string (the LED connected to the collector of the transistor and the LED after it) to the ground wire, causing this part of the LED to withstand instantaneous high voltage and high current, resulting in breakdown.

[0059] In addition, a series of auxiliary components are designed in this circuit to improve the stability and reliability of the system. For example, the anti-surge fuse resistor FR1 and the rectifier bridge stack BD1 can effectively filter out the noise and interference in the circuit; the constant current linear compensation electrolytic capacitor CD1 and the Comp foot bypass capacitor C1 can compensate for the voltage fluctuation in the circuit; the high and low voltage detection pull-up and pull-down resistors R4 / 6 can monitor the changes in the power supply voltage in real time; the diode D2 that increases the surge capacity can improve the circuit's resistance to surge impact.

[0060] Embodiment 5:

[0061] A linear LED power supply protection circuit of this embodiment, such as Figure 5 As shown, the circuit is further improved on the basis of Example 1, and the IC of the power supply high-end current sampling block diagram includes a single-segment linear circuit diagram, one end of the sampling resistor is connected to the LED load string in the constant current power supply loop, and the other end is grounded together with the transistor emitter; the other end of the LED load string is connected to the single-side pin of the constant current power supply chip through a plurality of current sampling resistors, and the other pins on the same side of the constant current power supply chip are grounded, and the opposite pins are connected to the power supply through a rectifier bridge stack and an anti-surge fuse resistor.

[0062] In the above circuit, L / N is the power input supply terminal, FR1 is the anti-surge fuse resistor, BD1 is the rectifier bridge stack, and US1 is the high-end current sampling constant current linear IC. R1 / 2 is the current sampling resistor, CD1 is the constant current linear compensation electrolytic capacitor, R3 is the electrolytic release resistor, and D1-D2-…-D16 is the LED. RS1 is the protection circuit transistor sampling resistor, and ZS1 is the transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forward connected). CS1 is the transistor B-pole filter capacitor, LEDI is the load output port connected to the C-pole of the transistor when the functional circuit is in action, and RT is the sampling voltage point of the transistor action. The core of the circuit is the US1 high-end current sampling constant current linear IC, which is responsible for monitoring and adjusting the current of the LED load string to ensure that it is stable and works within a safe current range.

[0063] Under normal working conditions, the LED load string is connected to the constant current power chip US1 through several current sampling resistors R1 / R2. These current sampling resistors not only monitor the current size of the LED load string, but also provide real-time working status information to US1 as part of the current feedback signal. The constant current power chip US1 adjusts its internal circuit according to these feedback signals to maintain the constant current operation of the LED load string. One end of the sampling resistor RS1 is connected to the LED load string, and the other end is grounded together with the emitter of the transistor QS1. Under normal working conditions, since the current of the LED load string is within the normal range, the voltage across RS1 is not enough to turn on the transistor QS1, so QS1 remains in the off state and will not have any effect on the circuit.

[0064] When an abnormality occurs in the circuit, such as a sudden increase in the current of the LED load string (possibly due to a short circuit of an LED or failure of the constant current power supply chip, etc.), the voltage across the sampling resistor RS1 will also increase. When this voltage reaches or exceeds the turn-on voltage of the transistor QS1, QS1 will quickly turn on. The conduction of the transistor will short-circuit a portion of the LED load string (usually the LED connected to the collector of the transistor and its subsequent LEDs) to the ground wire, causing this portion of the LED to withstand instantaneous high voltage and high current, resulting in breakdown. This breakdown is instantaneous and occurs in a specific part of the circuit, so it can avoid causing greater damage to the entire LED load string.

[0065] In addition, other components in the circuit also play an important auxiliary role. For example, the rectifier bridge stack BD1 and the surge protection fuse resistor FR1 can filter out noise and interference in the circuit and protect the circuit from surge impact. The constant current linear compensation electrolytic capacitor CD1 and the electrolytic release resistor R3 are used to compensate for the voltage fluctuations in the circuit to ensure the stable operation of the constant current power supply chip. This linear LED power supply protection circuit achieves effective protection for the LED load string through high-end current sampling and precise transistor control. Under normal working conditions, it ensures the constant current operation of the LED load string; under abnormal conditions, it can quickly respond and cut off the abnormal current to prevent the LED load string from continuing to heat up.

[0066] Embodiment 6:

[0067] A linear LED power supply protection circuit of this embodiment, such as Figure 6 As shown, the circuit is further improved on the basis of Example 1 to obtain a single-stage constant current diode circuit diagram at the high end of the power supply, one end of the sampling resistor is connected to the LED load string in the constant current power supply loop, and the other end is grounded together with the emitter of the transistor; the other end of the LED load string is connected to a loop composed of a constant current linear compensation electrolytic capacitor and a point-release electrolytic resistor, and the other end of the loop is connected to a constant current linear chip, which is connected to the power supply through a rectifier bridge stack.

[0068] In the above circuit, L / N is the power input supply terminal, FR1 is the surge protection fuse resistor, and BD1 is the rectifier bridge stack. US1 is a high-end current sampling constant current linear IC. CD1 is a constant current linear compensation electrolytic capacitor, R1 is an electrolytic discharge resistor, D1-D2-…-D16 is an LED, RS1 is a protection circuit transistor sampling resistor, ZS1 is a transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forward connected). CS1 is a transistor B-pole filter capacitor, LEDI is the load output port connected to the C-pole of the transistor when the functional circuit is in action, and RT is the sampling voltage point of the transistor action. The core of the circuit is to achieve stable power supply and abnormal protection of the circuit through high-end current sampling and constant current linear IC (US1) control.

[0069] Under normal working conditions, the LED load string is connected to the constant current power supply circuit through the sampling resistor RS1. The sampling resistor RS1 monitors the current of the LED load string in real time and transmits the corresponding voltage signal to the emitter of the transistor QS1. Since the current of the LED load string is in the normal range at this time, the voltage across the sampling resistor RS1 is not enough to turn on the transistor QS1, so the transistor QS1 remains in the off state and has no effect on the circuit. The other end of the LED load string is connected to the constant current linear IC (US1) through a loop composed of the constant current linear compensation electrolytic capacitor CD1 and the electrolytic discharge resistor R1. This loop is used to compensate for voltage fluctuations in the circuit to ensure that the constant current linear IC can work stably. The constant current linear IC maintains the constant current operation of the LED load string by adjusting its own internal circuit according to the current demand of the LED load string.

[0070] When an abnormality occurs in the circuit, such as a short circuit in an LED in the LED load string or failure of the constant current linear IC, the current of the LED load string increases abnormally, and the voltage across the sampling resistor RS1 also increases. When this voltage exceeds the turn-on voltage of transistor QS1, transistor QS1 will quickly turn on. The turned-on transistor will short-circuit a part of the LED load string (the LED connected to the collector of the transistor and the LEDs after it) to the ground wire, causing this part of the LED to withstand instantaneous high voltage and high current and breakdown. This breakdown is instantaneous and occurs in a specific part of the circuit, avoiding damage to the entire LED load string.

[0071] The constant current linear chip US1 is connected to the power supply L / N through the rectifier bridge stack BD1 to ensure its normal power supply. The anti-surge fuse resistor FR1 is used to protect the circuit from the impact of surges and improve the reliability of the circuit. The B-pole filter capacitor CS1 of the transistor QS1 is used to smooth the voltage fluctuation of the B-pole to ensure the stable operation of the transistor. The Vbe coordination diode ZS1 is used to coordinate the Vbe voltage of the transistor to ensure that it is turned on under appropriate conditions.

[0072] Embodiment 7:

[0073] A linear LED power supply protection circuit of this embodiment, such as Figure 7As shown, the circuit is further improved on the basis of Example 1, and a circuit block diagram of multiple low-end sampling ICs is obtained. In the figure, one end of the sampling resistor RS1 is connected to the LED load string, and the other end is connected to several low-end sampling constant current IC chips; the other end of the LED load string is connected to a single pin on one side of the low-end sampling constant current IC chip, and the other side of the low-end sampling constant current IC chip is connected to the current sampling resistor RC1 to form a loop and then grounded for protection. The other end of all low-end sampling constant current IC chips connected to the sampling resistor RS1 is connected to the power supply through the rectifier bridge BD1 and the surge protection fuse resistor FR1.

[0074] In the above circuit, L / N is the power input supply terminal, FR1 is the surge protection fuse resistor, and BD1 is the rectifier bridge stack. US1 to USn are low-end current sampling constant current linear ICs, and RC1 to RC2 are current sampling resistors. D1-D2-…-D16 is the LED, RS1 is the protection circuit transistor sampling resistor, and ZS1 is the transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forward connected). CS1 is the transistor B-pole filter capacitor, LEDI is the load output port connected to the C-pole of the transistor when the functional circuit is in action, and RT is the sampling voltage point of the transistor action. The core of the circuit is to achieve stable power supply and abnormal protection of the circuit through high-end current sampling and constant current linear IC (US1) control.

[0075] During the operation of the circuit, the power enters the circuit through the L / N power supply. The FR1 surge protection fuse resistor first protects the circuit to prevent damage to the circuit caused by excessive instantaneous current. The BD1 rectifier bridge converts the input AC power into DC power, and the circuit provides a stable DC power supply foundation. On this basis, the sampling resistor RS1 begins to play a role. One end of the sampling resistor is connected to the LED load string, and the other end is connected to multiple low-end sampling constant current IC chips. As the current flows, a certain voltage drop will be generated on the sampling resistor RS1. The size of this voltage drop directly reflects the current size of the overcurrent load LED.

[0076] The low-end sampling constant current IC chip adjusts its output current according to the voltage value on the sampling resistor RS1. They ensure that the current on the LED load string remains constant through a precise feedback mechanism. When the current of the LED load changes, these IC chips can respond quickly and adjust the output current accordingly to maintain the current constant. At the same time, a single pin on one side of each low-end sampling constant current IC chip is connected to the other end of the LED load string, and the other pin is grounded through a current sampling resistor to form a loop. These current sampling resistors further accurately monitor and adjust the output current of the IC chip to ensure stable operation of the circuit.

[0077] During the operation of the circuit, if an abnormal situation occurs, such as a short circuit or overload of the LED load, the voltage on the sampling resistor RS1 will change rapidly. The low-end sampling constant current IC chip can quickly detect this change and take corresponding protection measures. They may reduce the output current or completely shut down the output to prevent circuit damage or cause safety accidents. In addition, ZS1, as a transistor Vbe coordination diode (or other alternative components), plays a coordination role in the circuit. It ensures that different components can work together stably and efficiently to jointly maintain the normal operation of the circuit. CS1, as a transistor B-pole filter capacitor, filters out noise and interference signals in the circuit, improving the stability and reliability of the circuit.

[0078] Finally, when the circuit is in normal working state, LEDI acts as the load output port, allowing current to pass through and flow to the LED load. The LED load is supplied with a stable current, thus emitting bright light. Once an abnormal situation occurs in the circuit, the relevant components will respond quickly and cut off the current to protect the LED load from damage.

[0079] Embodiment 8:

[0080] A linear LED power supply protection circuit of this embodiment, such as Figure 8 As shown, the circuit is further improved on the basis of Example 7 to obtain a circuit schematic diagram of multiple constant current diodes or high-end sampling. In the figure, one end of the sampling resistor RS1 is connected to the LED load string, and the other end is connected to several high-end sampling constant current IC chips; the other end of the LED load string is connected to a single pin on one side of the high-end sampling constant current IC chip. The other end of all high-end sampling constant current IC chips connected to the sampling resistor RS1 is connected to the power supply through the rectifier bridge BD1 and the surge protection fuse resistor FR1.

[0081] In the above circuit, L / N is the power input supply terminal, FR1 is the surge protection fuse resistor, and BD1 is the rectifier bridge stack. US1 to USn are high-end current sampling constant current linear ICs or constant current diodes, and RC1 to RC2 are current sampling resistors. D1-D2-…-D16 is the LED, RS1 is the protection circuit transistor sampling resistor, and ZS1 is the transistor Vbe coordination diode (actually, the voltage regulator can be reversed and the Schottky diode can be forward connected). CS1 is the transistor B-pole filter capacitor, LEDI is the load output port connected to the C-pole of the transistor when the functional circuit is in action, and RT is the sampling voltage point of the transistor action. The core of the circuit is to achieve stable power supply and abnormal protection of the circuit through high-end current sampling and constant current linear IC (US1) control.

[0082] In this embodiment, the low-end sampling constant current IC in embodiment 7 is replaced with a high-end sampling constant current IC, which will cause the following differences in the circuit: the sampling point of the high-end sampling constant current IC is usually located on the positive side of the power supply, and the current or voltage of the input power supply is directly sampled; compared with the low-end sampling constant current IC, its working principle is similar, both belong to the negative feedback control mechanism, but the difference in sampling position may cause the overall current control response speed and accuracy to affect. Due to the change in the sampling point, the layout of the high-end sampling constant current IC in the circuit needs to be redesigned, and the routing needs to be adjusted. In addition, it requires a higher operating voltage, so there are slight differences in component selection.

[0083] In this embodiment, the low-end sampling constant current IC is replaced with a constant current diode, which will cause the following differences in the circuit: the working principle of the constant current diode is completely different from that of the constant current IC. It uses a special internal structure, such as an N-channel JFET, to keep the current constant within a specific valve, so it has a current limiting effect on the circuit, which is different from the negative feedback regulation mechanism. The constant current diode is mainly used to protect the circuit from the influence of National VI or short circuit, and only allows the current to rise to a certain level and then remain constant. Therefore, in the process of the breakdown loop modulating the overall store in the circuit, the use of a constant current diode can minimize the impact on the circuit where the diode is located, thereby protecting itself and other important circuits in the circuit.

[0084] It should be understood that the embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A linear LED power supply protection circuit, comprising a constant current power supply circuit, characterized in that: Also includes: A sampling resistor circuit, including a sampling resistor and a constant current power supply circuit electrically connected thereto, for obtaining a protection current value; The triode sampling circuit includes a triode and a sampling resistor electrically connected to the base and the emitter thereof respectively, and also includes a coordination diode connected between the sampling resistor and the base to modulate the triode voltage; The breakdown circuit includes a transistor sampling circuit and a constant current power supply circuit connected to the transistor collector, and breaks down the components in the constant current power supply circuit to disconnect it.

2. A linear LED power supply protection circuit according to claim 1, characterized in that: The coordination diode in the triode sampling loop is set as a voltage-stabilizing diode; The base of the transistor is connected to the positive electrode of the voltage-stabilizing diode, the negative electrode of the voltage-stabilizing diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the emitter of the transistor.

3. A linear LED power supply protection circuit according to claim 1, characterized in that: The coordination diode in the transistor sampling loop is set as a Schottky diode; The base of the transistor is connected to the cathode of the Schottky diode, the anode of the Schottky diode is connected to one end of the sampling resistor, and the other end of the sampling resistor is connected to the emitter of the transistor.

4. A linear LED power supply protection circuit according to claim 1, 2 or 3, characterized in that: The transistor sampling loop also includes a filter capacitor connected to both ends of the sampling resistor or the base and collector of the transistor respectively; It also includes a sampling voltage point set at the connection between the sampling resistor and the corresponding end of the coordination diode.

5. A linear LED power supply protection circuit according to claim 4, characterized in that: In the breakdown circuit, the transistor collector is electrically connected to the LED load string in the constant current power supply circuit; The LED load string is provided with m LED loads, and the position where the transistor collector is connected thereto is set at the nth LED load, wherein n<=m.

6. A linear LED power supply protection circuit according to claim 1 or 5, characterized in that: The two ends of the sampling resistor are electrically connected to the LED load string in the constant current power supply circuit and one end of the constant current power supply chipset respectively; The other end of the LED load string is connected to a loop consisting of a rectifier bridge stack and a constant current linear compensation electrolytic capacitor. The LED load string is also connected to the power supply through an anti-surge fuse resistor. One of the pins at the other end of the constant current power supply chip is connected to a loop formed by a plurality of current sampling resistors, and is connected to the other pin and then grounded.

7. A linear LED power supply protection circuit according to claim 1 or 5, characterized in that: One end of the sampling resistor is connected to one end of a plurality of foot power supply resistors through a string of forward LED loads, the other end of the foot power supply resistors is connected to the pin of the constant current power supply chip in the constant current power supply loop, and the other end of the forward LED load string is connected to the power supply through a rectifier diode; The other end of the sampling resistor is directly connected to the other pin on one side of the constant current power supply chip, and is connected to the remaining pins on one side through a string of reverse LED loads; The other single-side pin of the constant current power supply chip is connected to a plurality of current sampling resistors or is connected to the power supply through a compensation capacitor and a rectifier bridge stack.

8. A linear LED power supply protection circuit according to claim 1 or 5, characterized in that: One end of the sampling resistor is connected to the LED load string in the constant current power supply circuit, and the other end is grounded together with the transistor emitter; The other end of the LED load string is connected to a single-side pin of the constant current power supply chip through several current sampling resistors, the other pins on the same side of the constant current power supply chip are grounded, and the opposite pins are connected to the power supply through a rectifier bridge stack and an anti-surge fuse resistor.

9. A linear LED power supply protection circuit according to claim 1 or 5, characterized in that: One end of the sampling resistor is connected to the LED load string in the constant current power supply circuit, and the other end is grounded together with the transistor emitter; The other end of the LED load string is connected to a loop composed of a constant current linear compensation electrolytic capacitor and a point-release electrolytic resistor, and the other end of the loop is connected to a constant current linear chip, which is connected to a power supply through a rectifier bridge stack.

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