LED lighting frequency life test circuit

Abstract

The utility model relates to LED test technical field, concretely is a kind of LED lighting frequency life test circuit. Including 555 timer, its power supply end is connected with external DC power supply, for accessing working voltage;Its reset end is connected to the power supply end through first adjustable resistance. The utility model constructs with 555 timer as the core special test circuit, systematically solves the problem of test parameter in the prior art not adjustable, poor adaptability. Specifically, 555 timer is matched with the oscillation circuit of third adjustable resistance, fourth adjustable resistance and first discharge capacitor, the frequency and duty cycle of output pulse can be accurately set by adjusting resistance resistance value and capacitor capacity value, so that test circuit can output rectangular pulse signal covering wide range frequency, to realize accurate regulation and control to LED flicker frequency, meet the test demand of different dimming scene such as high frequency, low frequency.

Description

Technical Field

[0001] This utility model relates to the field of LED testing technology, specifically to an LED lighting frequency life test circuit. Background Technology

[0002] In the field of reliability assessment of LED devices and driver circuits, the lighting frequency lifetime test is a crucial step in verifying the frequency stability and photoelectric performance degradation during long-term operation. Current technologies for testing LED flicker frequency and lifetime typically rely on simulating operation with the entire device under full load. This type of test solution has significant technical bottlenecks: due to the lack of independent frequency adjustment and current control mechanisms, the test system can only load the LED under fixed conditions. It cannot flexibly set the flicker frequency according to the actual operating parameters of different LED specifications (such as high-frequency or low-frequency PWM dimming scenarios), nor can it accurately adjust the test current to adapt to diverse devices under test. This "extensive" whole-device testing mode, limited by complex environmental interference, cannot accurately isolate the LED's performance changes under specific frequency and current conditions during testing. This not only causes deviations and insufficient reliability in test results but also significantly reduces test efficiency due to the inability to reuse the circuit, failing to meet the current LED industry's demand for refined and professional testing. Therefore, how to design a test circuit that can independently adjust the flicker frequency and test current, adapt to different LED specifications, and eliminate environmental interference has become an urgent technical problem to be solved in this field. Utility Model Content

[0003] This disclosure presents an LED lighting frequency life test circuit, which aims to overcome at least one of the defects existing in the prior art.

[0004] To achieve the above objectives, the technical solution disclosed in this utility model is as follows:

[0005] According to one aspect of this disclosure, an LED lighting frequency life test circuit is provided, including a 555 timer, whose power supply terminal is connected to an external DC power supply for receiving the operating voltage; its reset terminal is connected to the power supply terminal through a first adjustable resistor; its output terminal is connected in series with the anode of the LED under test through a second adjustable resistor, the cathode of the LED under test is grounded, and the second adjustable resistor is used to adjust the test current flowing through the LED under test to adapt to LEDs of different specifications; its discharge terminal is connected to the power supply terminal through a third adjustable resistor and connected to one end of a first discharge capacitor through a fourth adjustable resistor, the other end of the first discharge capacitor is grounded, and the third adjustable resistor, the fourth adjustable resistor, and the first discharge capacitor together constitute an oscillation circuit; its low trigger terminal and high trigger terminal are connected together at the node between the fourth adjustable resistor and the first discharge capacitor for acquiring the voltage signal of the oscillation circuit; its control voltage terminal is grounded through the second discharge capacitor, and the second discharge capacitor is used to stabilize the potential of the control voltage terminal;

[0006] The oscillation circuit sets the frequency and duty cycle of the 555 timer output pulse by adjusting the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor, so that the output terminal outputs a rectangular pulse signal of the corresponding frequency to drive the LED under test to blink.

[0007] Furthermore, the first adjustable resistor is a fixed resistor used to set the reference voltage of the reset terminal; the second, third, and fourth adjustable resistors are all sliding rheostats or potentiometers, the adjustment range of the second adjustable resistor covers from 0Ω to the current limiting resistor value corresponding to the rated operating current of the LED under test, and the third and fourth adjustable resistors are used to adjust the charging resistance value and the discharging resistance value of the oscillation circuit, respectively.

[0008] Furthermore, the first discharge capacitor is an electrolytic capacitor or a ceramic capacitor, and its capacitance value, together with the resistance values ​​of the third and fourth adjustable resistors, determines the oscillation frequency of the oscillation circuit; the second discharge capacitor is a ceramic capacitor, one end of which is directly connected to the control voltage terminal, and the other end is directly grounded, used to filter out high-frequency interference to stabilize the potential of the control voltage terminal.

[0009] Furthermore, the cathode of the LED under test is directly connected to the ground terminal of the 555 timer via a wire. The ground terminal shares a common ground with the negative terminal of the external DC power supply, forming a complete current loop to ensure the normal operation of the LED under test.

[0010] Furthermore, the pulse oscillation period of the oscillation circuit is jointly determined by the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor. The 555 timer outputs a rectangular pulse signal corresponding to the oscillation period through the output terminal to adjust the flashing frequency of the LED under test.

[0011] Furthermore, the discharge terminal is connected to the power supply terminal through the third adjustable resistor, which is used to provide a discharge circuit for the first discharge capacitor when the 555 timer outputs a low level, and the duty cycle of the oscillation circuit is adjusted by the resistance difference between the fourth adjustable resistor and the third adjustable resistor.

[0012] Furthermore, the test circuit also includes a circuit board, on which the 555 timer, the first adjustable resistor, the second adjustable resistor, the third adjustable resistor, the fourth adjustable resistor, the first discharge capacitor, and the second discharge capacitor are all soldered. The LED under test is detachably connected to the output terminal and the ground terminal via a connector or wire to allow for the replacement of LEDs of different specifications.

[0013] Furthermore, the second adjustable resistor is connected in series between the output terminal and the anode of the LED under test. By changing its own resistance value, the operating current of the LED under test is adjusted, so that the test circuit can adapt to the LED testing requirements of different rated currents.

[0014] Furthermore, the high trigger terminal and the low trigger terminal are connected together to the node between the fourth adjustable resistor and the first discharge capacitor, so that the 555 timer switches the output state according to the voltage signal of the node to maintain the continuous oscillation of the oscillation circuit.

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

[0016] This invention systematically solves the problems of non-adjustable test parameters and poor adaptability in existing technologies by constructing a dedicated test circuit with a 555 timer as its core. Specifically, the 555 timer, together with the oscillation circuit composed of a third adjustable resistor, a fourth adjustable resistor, and a first discharge capacitor, allows for precise setting of the frequency and duty cycle of the output pulse by adjusting the resistance and capacitance values. This enables the test circuit to output rectangular pulse signals covering a wide frequency range, thereby achieving precise control of the LED flicker frequency and meeting the testing needs of different dimming scenarios such as high frequency and low frequency.

[0017] Furthermore, a second adjustable resistor is connected in series between the output of the 555 timer and the LED under test. The test current flowing through the LED can be directly controlled by adjusting the resistance value, forming a current regulation mechanism independent of the overall machine environment, which can effectively adapt to LED devices with different rated current specifications. The control voltage terminal is grounded through the design of the second discharge capacitor, which stabilizes the internal reference potential of the timer and improves the stability of the pulse signal.

[0018] Furthermore, the detachable connection structure between the LED under test and the output and ground terminals, combined with the integrated layout of the circuit board, not only facilitates quick replacement of the test object, but also eliminates interference from the complex environment of the whole machine by simplifying the circuit connection.

[0019] The technical solutions of this utility model work together to form a professional test circuit that integrates adjustable frequency, controllable current, and strong device adaptability. This not only improves the accuracy of LED lighting frequency life test, but also greatly improves test efficiency through flexible parameter configuration and structural optimization design.

[0020] The above description is only an overview of the technical solution of this utility model. In order to better understand the technical means of this utility model and to implement it in accordance with the contents of the specification, the preferred embodiments of this utility model are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0021] Figure 1 This is a circuit diagram of the present invention;

[0022] Figure 2 This is a pin diagram of the 555 timer in one embodiment of the present invention;

[0023] Figure 3 This is a diagram showing the internal structure of the 555 timer in one embodiment of the present invention;

[0024] Figure 4 This is a schematic diagram of the operation process of the LED lighting frequency life test circuit in one embodiment of the present invention. Detailed Implementation

[0025] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are some embodiments of the present utility model, but not all embodiments.

[0026] Please refer to Figures 1 to 4 As shown, the present invention provides the following preferred embodiments:

[0027] Example 1

[0028] To address the limitations of insufficient parameter adjustment and adaptability in existing LED lighting frequency lifespan testing methods, this embodiment further refines the test circuit architecture centered on a 555 timer. The power supply terminal of the 555 timer is directly connected to an external DC power supply, providing a stable operating voltage for the entire circuit. Its reset terminal is connected to the power supply terminal via a first adjustable resistor. The resistance value of this resistor sets the reference potential of the reset terminal, ensuring the stability of the timer's initial state. A second adjustable resistor is connected in series between the output terminal and the anode of the LED under test. This resistor forms an adjustable current-limiting mechanism. By changing the resistance value, the test current flowing through the LED under test can be precisely controlled to match the rated operating current requirements of LEDs of different specifications.

[0029] The discharge terminal is connected to the power supply terminal via a third adjustable resistor, and simultaneously connected to one end of the first discharge capacitor via a fourth adjustable resistor. The other end of the capacitor is grounded, and the three together form an RC oscillation circuit. Both the low-trigger and high-trigger terminals are connected to the node between the fourth adjustable resistor and the first discharge capacitor, used to acquire the voltage signal of the oscillation circuit in real time, which serves as the trigger condition for the timer output state switching. The control voltage terminal is grounded through the second discharge capacitor, utilizing the capacitor's filtering characteristics to stabilize the potential at this port and reduce high-frequency noise interference to the timer's internal reference voltage.

[0030] During operation, the oscillation circuit adjusts the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor to change the RC charging and discharging time constant. This, in turn, sets the frequency and duty cycle of the 555 timer output pulse, generating a rectangular pulse signal at a specific frequency at the output terminal, driving the LED under test to blink at the preset frequency. It is important to understand that the adjustment range of the second adjustable resistor covers the current-limiting resistor value corresponding to the rated current of the LED under test, ensuring that devices of different specifications can be tested within their safe operating range.

[0031] The advantage of this embodiment is that by clarifying the electrical connection and parameter adjustment mechanism of each functional module, a dedicated test circuit with controllable frequency and adjustable current is constructed, which effectively solves the problems of single test conditions and insufficient adaptability in the prior art, and provides a reliable hardware foundation for the life evaluation of LED devices under different operating parameters.

[0032] Example 2

[0033] To address the issue of unclear resistor adjustment mechanisms in test circuits, this embodiment further refines the selection and functional division of resistor components. The first adjustable resistor is a fixed resistor, with one end connected to the reset terminal of a 555 timer and the other end connected to the power supply. A fixed resistance value sets the reference voltage at the reset terminal, ensuring the timer maintains a stable operating threshold in its initial state. The second, third, and fourth adjustable resistors are all sliding rheostats or potentiometers. The second adjustable resistor is connected in series between the output terminal and the anode of the LED under test. Its adjustment range covers from 0Ω to the current-limiting resistance value corresponding to the rated operating current of the LED under test. By changing the position of the sliding contact, the test current flowing through the LED can be linearly adjusted to meet the current adaptation requirements of devices with different specifications.

[0034] The third and fourth adjustable resistors are connected to the discharge terminal and the oscillation circuit, respectively. The third adjustable resistor is used to adjust the equivalent resistance value of the oscillation circuit during the charging process, while the fourth adjustable resistor corresponds to the resistance adjustment during the discharge process. Together with the first discharge capacitor, they form an RC charging and discharging circuit. It is important to understand that the continuous adjustment characteristic of the sliding rheostat allows the tester to precisely set the resistance values ​​of the charging and discharging resistors according to actual test requirements, thereby flexibly controlling the charging and discharging time constant of the oscillation circuit.

[0035] The advantage of this embodiment is that by clearly defining the type and functional partition of the resistive devices, a hardware architecture with finely adjustable parameters is constructed, which makes the adjustment of the test current and oscillation resistance continuous and controllable, and provides a standardized adjustment method for achieving parameter matching under different test conditions, effectively improving the applicability and adjustment accuracy of the test circuit.

[0036] Example 3

[0037] To optimize the frequency stability of the oscillation circuit and the anti-interference capability of the control voltage terminal, this embodiment further defines the selection and function of the discharge capacitor. The first discharge capacitor can be an electrolytic capacitor or a ceramic capacitor. Its capacitance value, together with the resistance values ​​of the third and fourth adjustable resistors, forms an RC parameter match, jointly determining the oscillation frequency of the oscillation circuit. Electrolytic capacitors are suitable for low-frequency oscillation scenarios requiring larger capacitance values, while ceramic capacitors are more suitable for high-frequency oscillation requirements. By combining the selection of capacitor type with resistance adjustment, a wide range of frequency testing intervals can be covered.

[0038] The second discharge capacitor is a ceramic capacitor, with one end directly connected to the control voltage terminal of the 555 timer and the other end grounded. Utilizing the high-frequency filtering characteristics of the ceramic capacitor, it filters out high-frequency interference signals introduced from the power supply or external sources, stabilizing the reference potential of the control voltage terminal. It is understandable that the potential stability of the control voltage terminal directly affects the threshold accuracy of the comparator inside the timer, and consequently, the frequency stability of the pulse signal. The grounding design of the ceramic capacitor effectively suppresses voltage fluctuations, ensuring the stability of the oscillation process.

[0039] The advantage of this embodiment is that by clarifying the selection criteria and connection method of capacitor components, a hardware foundation for oscillation frequency adjustment and potential stabilization is established, enabling the test circuit to maintain signal output stability under different frequency conditions. At the same time, it enhances the anti-interference capability of the control voltage terminal, providing a reliable circuit guarantee for accurately testing the performance changes of LEDs at specific frequencies.

[0040] Example 4

[0041] To ensure the integrity of the current loop and the consistency of the signal reference for the LED under test, this embodiment further clarifies the electrical connection method of the grounding structure. The cathode of the LED under test is directly connected to the ground terminal of the 555 timer via a wire. This ground terminal also shares a common ground with the negative terminal of the external DC power supply, forming a closed current loop. It is important to understand that this common ground design ensures that the potential reference between the power supply voltage, the timer output signal, and the LED operating circuit is unified, avoiding current abnormalities or signal distortion caused by potential differences, thereby ensuring that the LED can blink normally according to the preset pulse signal during the test.

[0042] In terms of circuit layout, single-point grounding or star grounding is used at the grounding terminal to reduce stray inductance and resistance in the grounding loop and reduce ground loop interference between different modules. The wire connection between the cathode of the LED under test and the grounding terminal uses a low-impedance wire to ensure the continuity of the current loop and avoid the influence of contact resistance on the test current. It is understandable that a complete current loop is a necessary condition for the normal operation of an LED. By clearly defining the direct connection between the cathode and the grounding terminal and using a common ground design, test failures caused by loop breaks or potential drift can be effectively avoided, improving the reliability of the testing process.

[0043] The advantage of this embodiment is that by standardizing the grounding structure and connection method, the integrity of the current loop and the consistency of the potential reference in the test circuit are ensured, providing a stable working environment for the LED under test, avoiding test errors caused by improper grounding, and ensuring the accuracy and validity of the test data.

[0044] Example 5

[0045] To achieve precise adjustment of the LED blinking frequency, this embodiment further clarifies the frequency determination mechanism and signal output principle of the oscillation circuit. The pulse oscillation period of the oscillation circuit is jointly determined by the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor, specifically following the RC charging and discharging formula:

[0046] T = 0.7(RP4 + 2RP5)C1, where PR4 is the resistance of the third adjustable resistor, PR5 is the resistance of the fourth adjustable resistor, and C1 is the capacitance of the first discharge capacitor. By adjusting the parameters of PR4, PR5, and C1, the oscillation period can be changed, thereby adjusting the oscillation frequency of the rectangular pulse signal output by the 555 timer. Specifically, the expression for calculating the oscillation frequency is:

[0047] The expression for calculating the duty cycle D is:

[0048] The test frequency and pulse duty cycle are adjusted by changing the resistance values ​​of RP4 and RP5 and the capacitance value of C1 to meet the testing requirements of different LED specifications.

[0049] Understandably, the 555 timer's output alternates between high and low levels during oscillation, forming periodic rectangular pulses that drive the LED under test to blink at the corresponding frequency. It's important to understand that frequency adjustment essentially changes the charging and discharging time constant of the RC circuit, altering the trigger state switching frequency of the comparator inside the timer, thereby achieving continuous adjustment of the output signal frequency. This frequency adjustment mechanism based on the RC oscillation principle is characterized by its simple structure and wide adjustment range, meeting the needs of various testing scenarios such as high-frequency PWM dimming and low-frequency blinking.

[0050] The benefit of this embodiment is that by revealing the mathematical principle of the oscillation period and the frequency adjustment mechanism, it clarifies the core technical path for the test circuit to achieve frequency controllability, enabling testers to accurately set the flashing frequency of the LED by configuring the resistor and capacitor parameters according to specific test requirements, and providing a theoretically traceable adjustment method for the life assessment of LEDs under different frequency conditions.

[0051] Example 6

[0052] To address the unclear duty cycle adjustment mechanism of the oscillation circuit, this embodiment further refines the connection structure of the discharge terminal and the duty cycle adjustment principle. The discharge terminal is connected to the positive terminal of an external DC power supply via a third adjustable resistor. When the 555 timer outputs a low level, this resistor, along with the fourth adjustable resistor and the first discharge capacitor, forms a discharge circuit, allowing the charge stored in the capacitor to be released through the fourth adjustable resistor. It is important to understand that the duty cycle of the oscillation circuit is defined as the ratio of the high-level output signal time to the period, and its magnitude is determined by the time constants of both the charging and discharging processes.

[0053] When the timer outputs a high level, the power supply charges the first discharge capacitor through the third and fourth adjustable resistors. The charging time constant is determined by the sum of the resistance values ​​of the two resistors and the capacitance value. When the output is low, the capacitor discharges through the fourth adjustable resistor. The discharge time constant is determined solely by the resistance value of the fourth adjustable resistor and the capacitance value. By adjusting the resistance difference between the third and fourth adjustable resistors, the ratio of charging to discharging time can be changed, thereby achieving dynamic adjustment of the duty cycle. This design, which uses two resistors to independently adjust the charging and discharging circuit, provides greater flexibility in duty cycle adjustment, meeting the specific requirements of different test scenarios for the pulse signal duty cycle.

[0054] The advantage of this embodiment is that by clarifying the structure of the discharge circuit and the resistance adjustment mechanism, a duty cycle adjustment method based on resistance difference is established, enabling the test circuit to output rectangular pulses with different duty cycles. This provides diverse test conditions for studying the life cycle characteristics of LEDs under different operating cycles and enhances the functional adaptability of the circuit.

[0055] Example 7

[0056] To improve the structural integration and ease of use of the test circuit, this embodiment further defines the physical implementation of the circuit. The test circuit is configured with a circuit board. The 555 timer, first adjustable resistor, second adjustable resistor, third adjustable resistor, fourth adjustable resistor, first discharge capacitor, and second discharge capacitor are all fixed to the circuit board using surface mount or through-hole soldering processes, forming a standardized hardware integrated unit. The LED under test is connected to the output terminal and ground terminal on the circuit board via a connector or wire. The connector can use a detachable connection structure such as a pin header or terminal block, and the wire connection is achieved through soldering or terminal crimping to achieve electrical connection.

[0057] It's important to understand that the detachable connection method allows testers to quickly replace components with different package types based on the specifications of the LED under test, avoiding damage to the circuit board caused by repeated soldering. The circuit board layout follows electromagnetic compatibility principles, separating the high-frequency oscillation module and power supply module to reduce mutual interference; the mounting positions of adjustable resistors and capacitors are designed with adjustment space in mind, facilitating real-time parameter adjustments during testing. This structured design ensures both the stability of the circuit connections and ease of component replacement and parameter adjustment, enhancing the engineering practicality of the test system.

[0058] The advantage of this embodiment is that by constructing an integrated circuit board structure and a detachable connection method, the modular design of the test circuit is realized, which not only meets the requirements of circuit stability, but also improves the compatibility efficiency of LEDs of different specifications, and provides hardware support for the standardization and convenience of testing work.

[0059] Example 8

[0060] To address the compatibility issue of LEDs with different rated currents, this embodiment further clarifies the functional positioning and connection method of the second adjustable resistor. The second adjustable resistor is connected in series between the output of the 555 timer and the anode of the LED under test, and its resistance value can be continuously adjusted via a sliding contact or knob. According to Ohm's law, the loop current is determined by the power supply voltage, the LED forward voltage drop, and the resistance value of the second adjustable resistor. By changing this resistor value, the operating current flowing through the LED can be linearly adjusted to match the rated current parameters of the LED under test.

[0061] It's important to understand that the adjustment range of the second adjustable resistor covers from 0Ω to the current-limiting resistor value corresponding to the rated operating current of the LED under test. This range ensures that the test current can be gradually adjusted from zero while reaching the device's rated operating point within a safe threshold. For example, when the rated current of the LED under test is 20mA and the forward voltage drop is 3V, if the external power supply voltage is 5V, adjusting the second adjustable resistor to 100Ω will allow the LED to operate at its rated current. For LEDs with lower rated currents, reducing the resistance value can lower the loop current and prevent overcurrent damage to the device.

[0062] The advantage of this embodiment is that by placing the second adjustable resistor between the output terminal and the LED anode, a continuously adjustable current limiting mechanism is constructed, enabling the test circuit to accurately match the operating parameters according to the rated current requirements of different LEDs. This effectively avoids the problem of insufficient adaptability caused by fixed resistor current limiting, and provides a safe and reliable current control method for life testing of diverse LED devices.

[0063] Example 9

[0064] To ensure the continuous and stable operation of the oscillation circuit, this embodiment further clarifies the connection node and state switching mechanism of the trigger terminal. The high trigger terminal (threshold terminal) and low trigger terminal (trigger terminal) of the 555 timer are connected to the node between the fourth adjustable resistor and the first discharge capacitor. The voltage of this node changes periodically with the charging and discharging process of the capacitor, serving as the input signal for the comparator inside the timer and driving the output state switching. When the capacitor charges to the point where the node voltage reaches the high trigger threshold (approximately 2 / 3 of the power supply voltage), the timer output flips to a low level, initiating the discharge process; when the capacitor discharges to the point where the node voltage drops to the low trigger threshold (approximately 1 / 3 of the power supply voltage), the output flips to a high level, restarting the charging process.

[0065] It's important to understand that this design, with dual trigger terminals connected to the same node, allows the timer to automatically switch between charging and discharging states based on a single voltage signal, forming a continuous RC oscillation process. The rate of change of the node voltage is determined by the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor. By adjusting the resistor or capacitor parameters, the threshold arrival time of the trigger signal can be changed, thereby adjusting the frequency and duty cycle of the output pulse. The direct connection between the trigger terminal and the node ensures real-time acquisition of the voltage signal and timely state switching, avoiding the impact of signal transmission delay on oscillation stability.

[0066] The advantage of this embodiment is that by clarifying the connection nodes of the high and low trigger terminals and the threshold switching principle, an oscillation maintenance mechanism based on single voltage feedback is constructed, enabling the 555 timer to automatically switch the output state according to the dynamic changes of the node voltage, ensuring the continuous and stable operation of the oscillation circuit, and providing a reliable signal triggering basis for the precise control of the LED blinking frequency.

[0067] Although the present invention has been specifically described above with reference to preferred embodiments, it should be understood that the present invention is not limited to the embodiments described above. Rather, various modifications and variations can be made by those skilled in the art without departing from the essence of the present invention, and such modifications and variations should fall within the scope defined by the appended claims and their equivalents.

Claims

1. An LED lighting frequency lifespan testing circuit, characterized in that, It includes a 555 timer, whose power supply terminal is connected to an external DC power supply for input of working voltage; its reset terminal is connected to the power supply terminal through a first adjustable resistor; its output terminal is connected in series with the anode of the LED under test and a second adjustable resistor is connected in series. The cathode of the LED under test is grounded. The second adjustable resistor is used to adjust the test current flowing through the LED under test to adapt to LEDs of different specifications. Its discharge terminal is connected to the power supply terminal through a third adjustable resistor, and is connected to one end of the first discharge capacitor through a fourth adjustable resistor. The other end of the first discharge capacitor is grounded. The third adjustable resistor, the fourth adjustable resistor, and the first discharge capacitor together constitute an oscillation circuit. Its low trigger terminal and high trigger terminal are connected together at the node between the fourth adjustable resistor and the first discharge capacitor to obtain the voltage signal of the oscillation circuit; its control voltage terminal is grounded through the second discharge capacitor, which is used to stabilize the potential of the control voltage terminal. The oscillation circuit sets the frequency and duty cycle of the 555 timer output pulse by adjusting the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor, so that the output terminal outputs a rectangular pulse signal of the corresponding frequency to drive the LED under test to blink.

2. The LED lighting frequency lifespan test circuit as described in claim 1, characterized in that, The first adjustable resistor is a fixed resistor used to set the reference voltage of the reset terminal; the second, third, and fourth adjustable resistors are all sliding rheostats or potentiometers. The adjustment range of the second adjustable resistor covers from 0Ω to the current limiting resistor value corresponding to the rated operating current of the LED under test. The third and fourth adjustable resistors are used to adjust the charging resistance value and the discharging resistance value of the oscillation circuit, respectively.

3. The LED lighting frequency lifespan test circuit as described in claim 1, characterized in that, The first discharge capacitor is an electrolytic capacitor or a ceramic capacitor, and its capacitance value, together with the resistance values ​​of the third and fourth adjustable resistors, determines the oscillation frequency of the oscillation circuit. The second discharge capacitor is a ceramic capacitor, one end of which is directly connected to the control voltage terminal, and the other end is directly grounded, used to filter out high-frequency interference to stabilize the potential of the control voltage terminal.

4. The LED lighting frequency lifespan test circuit as described in claim 1, characterized in that, The cathode of the LED under test is directly connected to the ground terminal of the 555 timer via a wire. The ground terminal shares a common ground with the negative terminal of the external DC power supply, forming a complete current loop to ensure that the LED under test operates normally.

5. The LED lighting frequency lifespan test circuit as described in claim 1, characterized in that, The pulse oscillation period of the oscillation circuit is determined by the resistance values ​​of the third and fourth adjustable resistors and the capacitance value of the first discharge capacitor. The 555 timer outputs a rectangular pulse signal corresponding to the oscillation period through the output terminal to adjust the flashing frequency of the LED under test.

6. The LED lighting frequency life test circuit as described in claim 1, characterized in that, The discharge terminal is connected to the power supply terminal through the third adjustable resistor, which is used to provide a discharge circuit for the first discharge capacitor when the 555 timer outputs a low level. The duty cycle of the oscillation circuit is adjusted by the resistance difference between the fourth adjustable resistor and the third adjustable resistor.

7. The LED lighting frequency life test circuit as described in claim 1, characterized in that, The test circuit also includes a circuit board, on which the 555 timer, the first adjustable resistor, the second adjustable resistor, the third adjustable resistor, the fourth adjustable resistor, the first discharge capacitor, and the second discharge capacitor are all soldered. The LED under test is detachably connected to the output terminal and the ground terminal via a connector or wire to allow for the replacement of LEDs of different specifications.

8. The LED lighting frequency life test circuit as described in claim 1, characterized in that, The second adjustable resistor is connected in series between the output terminal and the anode of the LED under test. By changing its own resistance value, the operating current of the LED under test is adjusted, so that the test circuit can adapt to the LED testing requirements of different rated currents.

9. The LED lighting frequency life test circuit as described in claim 1, characterized in that, The high trigger terminal and the low trigger terminal are connected together to the node between the fourth adjustable resistor and the first discharge capacitor, so that the 555 timer switches the output state according to the voltage signal of the node to maintain the continuous oscillation of the oscillation circuit.

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