Fault diagnosis device for LED on printed circuit board
By setting up voltage divider circuits and sampling circuits on printed circuit boards and using detection chips to determine the fault status of LEDs, the problems of high testing difficulty and high cost in existing technologies are solved, and low-cost and rapid fault diagnosis is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-03
- Publication Date
- 2026-03-20
AI Technical Summary
Existing LED fault diagnosis methods are difficult and costly to test on PCBs, especially for small PCBs and surface mount components, requiring specialized skills and expensive testing equipment.
Design a fault diagnosis device for LEDs on a printed circuit board. By setting a voltage divider circuit and a sampling circuit on the LED, the device uses a detection chip to collect voltage changes to determine the fault status, avoiding the use of traditional measuring instruments and simplifying the operation process.
It enables rapid identification of LED short-circuit or open-circuit conditions at low cost and without the need for professional personnel, reducing testing difficulty and labor costs.
Smart Images
Figure CN224019957U_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The utility model relates to electronic information technical field, concretely relates to a short circuit, open circuit's fault diagnosis device of LED on printed circuit board. BACKGROUND
[0002] LED as a kind of photoelectric device widely used in lighting, display, indication and other fields, its application on PCB is also more and more widely.For the short circuit or open circuit etc.that LED can appear on PCB, diagnosis needs to master PCB design and electronic system diagnosis technology, also needs to be familiar with the characteristics and use method of electronic components.
[0003] LED diagnosis can test end or use terminal and feedback in time, the running condition of product, whether component and device work normally etc.Important information, to tester, or terminal customer has indicating effect, prevents fault from further deterioration and expansion, and the endorsement support of result accuracy.
[0004] At present, in the LED diagnosis scheme on PCB, commonly used technology includes using multimeter or oscilloscope etc.Electronic test instrument to measure, and using infrared thermal imaging or optical microscope etc.Equipment to check.These technologies can realize the diagnosis of short circuit and open circuit problem of LED on PCB to some extent, but also have some shortcomings.
[0005] (1) using electronic test instrument to measure, or infrared thermal imaging or optical microscope etc.Equipment to check:
[0006] (2) testing difficulty is greater: especially for some small PCB board and patch type component and device, testing difficulty will be greater.
[0007] (3) need professional skill: the operation of test instrument and the interpretation of result need certain professional skill.
[0008] (4) testing cost is higher: test instrument, for example, multimeter, oscilloscope, infrared thermal imaging detection equipment price is high, and need professional personnel to operate and maintain.
[0009] Summarizing, although the existing LED fault diagnosis technical scheme can complete the diagnosis of short circuit and open circuit problem of LED on PCB, testing difficulty is greater and cost is higher, therefore, how to solve the technical problem existing in the prior art LED fault detection method is the problem to be solved in the field. UTILITY MODEL CONTENT
[0010] In view of the technical problems of the prior art LED fault diagnosis method that testing difficulty is greater and cost is higher, the utility model aims at providing a LED fault diagnosis device on printed circuit board, which can solve the technical problems existing in the prior art LED fault detection method.
[0011] In order to achieve the above object, the utility model provides a kind of LED's fault diagnosis device on printed circuit board, including power supply circuit, voltage division circuit, sampling circuit and the LED circuit to be measured, the power supply circuit is output to voltage division circuit and the LED circuit to be measured respectively, the sampling circuit is connected with the output end of voltage division circuit, the sampling circuit is collected the voltage output by voltage division circuit, and the working condition of the LED circuit to be measured is judged according to the change condition of the voltage collected.
[0012] Further, the power supply circuit includes controllable current source and diode, the diode is connected in series at the output end of controllable current source, and the voltage of controllable current source output is stabilized.
[0013] Further, the voltage division circuit includes first resistance, second resistance and third resistance, the first resistance, second resistance and third resistance are connected in series, and the second resistance and third resistance form monitoring point between them and are connected with sampling circuit.
[0014] Further, the sampling circuit includes detection chip, and the voltage of monitoring point is sampled by the ADC sampling resistance of detection chip.
[0015] Further, the third capacitor is arranged at the ADC sampling resistance of detection chip.
[0016] Further, the LED circuit to be measured is light emitting diode, and the first capacitor is arranged at the light emitting diode.
[0017] Further, the LED circuit to be measured is equipped with brightness adjusting circuit, and the brightness of light emitting diode is adjusted by the brightness adjusting circuit after the LED circuit to be measured is turned on.
[0018] Further, the brightness adjusting circuit includes control chip and conducting triode, the control chip is connected with conducting triode, the conducting triode is connected with light emitting diode, the PWM pulse width modulation signal of control chip is output and is conducted to light emitting diode by conducting triode, and the brightness of light emitting diode is adjusted by the pulse width modulation signal of different waveforms output by control chip.
[0019] Further, the fourth resistance and fifth resistance are arranged at the input end of conducting triode, and the protection circuit of triode is formed by the fourth resistance and fifth resistance.
[0020] Further, the second capacitor is arranged at the output end of control chip.
[0021] The fault diagnosis device for LEDs on printed circuit boards provided by this utility model uses a voltage divider circuit and a sampling circuit to be set on the LED under test. The sampling circuit collects the voltage output by the voltage divider circuit, and the fault condition of the LED is determined based on the voltage drop of the collected voltage. This method does not require the use of traditional additional instruments for measurement, only requires modification of the circuit, and its cost is low. At the same time, it does not require professional personnel to perform disassembly, visual inspection, measurement and other work, saving manpower and eliminating measurement difficulties. Attached Figure Description
[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.
[0023] Figure 1 This is a circuit diagram showing the LED on this printed circuit board when it is in a short-circuit state.
[0024] Figure 2 This is a circuit diagram showing the LEDs on this printed circuit board in an open-circuit state.
[0025] Figure 3 This is a circuit diagram showing the LEDs on a printed circuit board in normal operation. Detailed Implementation
[0026] To make the technical means, creative features, objectives and effects of this utility model easier to understand, the present utility model will be further described below with reference to specific illustrations.
[0027] Existing methods for diagnosing LED faults involve measuring with electronic testing instruments or equipment, which suffers from inconvenient operation. To address these issues, this invention provides a fault diagnosis device for LEDs on a printed circuit board. This device utilizes a voltage divider circuit and a sampling circuit on the LED under test. The sampling circuit collects the voltage output from the voltage divider circuit, and the fault condition of the LED is determined based on the voltage drop. This method eliminates the need for traditional additional instruments; only circuit modifications are required, resulting in low cost. Furthermore, it eliminates the need for professional personnel to perform disassembly, visual inspection, and measurement, saving manpower and reducing measurement difficulty.
[0028] See Figures 1-3 The present invention provides a fault diagnosis device for LEDs on printed circuit boards, which includes a power supply circuit, a voltage divider circuit, a sampling circuit, and the LED circuit under test.
[0029] The power supply circuit is connected to the voltage divider circuit and the LED circuit under test. The power supply circuit includes a controllable current source KL30 and a diode D1. The controllable current source KL30 is used to output voltage, and the diode D1 is connected in series at the output terminal of the controllable current source KL30 to regulate the output voltage of the controllable current source KL30.
[0030] The first capacitor C1 is arranged at the light emitting diode D2 in the LED circuit to be tested, and is used to filter noise at both ends of the light emitting diode D2.
[0031] The voltage output by the power supply circuit is transmitted to the voltage dividing circuit and the circuit in which the LED to be tested is located through two branches, and the voltage output by the voltage dividing circuit is sampled by the sampling circuit, and the running state of the LED is judged according to the change of the sampled voltage value.
[0032] The voltage dividing circuit comprises a first resistor R1, a second resistor R2 and a third resistor R3, the first resistor R1, the second resistor R2 and the third resistor R3 are connected in series, and a monitoring point A is formed between the second resistor R1 and the third resistor R1 and is connected with the sampling circuit.
[0033] The size of the first resistor R1 should be calculated reversely according to the LED brightness-current relationship, for example, if the working current of the LED is 30 mA and the on voltage is 3 V, the first resistor R1 is calculated reversely to divide 9 V, that is, the resistance of the first resistor R1 should be about 300 Ω.
[0034] The second resistor R2 is usually set to 20K-100K to protect the MCU pin, and the third resistor R3 is preferably of the same order of magnitude as the second resistor and can be set to 10K-100K to facilitate voltage division.
[0035] The sampling circuit is a detection chip MCU, and the voltage at the monitoring point A between the second resistor R2 and the third resistor R3 is sampled by the ADC sampling resistor of the MCU, and then the change of the voltage at the point A is transmitted to the detection chip MCU for comparison, so that the fault of the light emitting diode D2 can be judged.
[0036] The third capacitor C3 is arranged at the ADC sampling resistor of the detection chip MCU to filter sampling noise and ensure the accuracy of sampling.
[0037] When the LED is short-circuited, the power supply circuit, the first resistor R1 and the GND form a loop, and the power supply does not pass through the voltage dividing circuit and the circuit in which the LED to be tested is located, at this time, no voltage passes through the monitoring point A, so that the MCU sampling voltage at the point A is 0, and it is judged that the LED is short-circuited.
[0038] When the LED is open-circuited, the power supply circuit forms a loop with the first resistor R1, the second resistor R2, the third resistor R3 and the GND, and the current does not pass through the circuit in which the LED to be tested is located, so that the MCU sampling voltage at the point A is the voltage drop of the driving voltage of the light emitting diode D2 between the second resistor R2 and the third resistor R3, at this time, the voltage at the monitoring point A is abnormally large, so that it can be judged that the LED is open-circuited.
[0039] Secondly, when the light emitting diode D2 is turned on, a brightness adjusting circuit is matched at the measured LED circuit, which is used to control the brightness of the LED lamp.
[0040] The brightness adjusting circuit comprises a control chip MCU and a conducting transistor Q1. The control chip MCU is connected with the base of the conducting transistor Q1. The collector of the conducting transistor Q1 is connected with the light emitting diode D2. The emitter of the conducting transistor Q1 is grounded. The control chip MCU outputs a PWM pulse width modulation signal to the light emitting diode D2 through the conducting transistor Q1. The brightness of the light emitting diode D2 is adjusted by outputting different waveforms of the pulse width modulation signal by the control chip MCU.
[0041] Further, the input end of the conducting transistor Q1 is matched with a fourth resistor R4 and a fifth resistor R5. The fourth resistor R4 is used as a current limiting resistor. The fifth resistor R5 constitutes a base bias resistor. The fourth resistor R4 and the fifth resistor R5 are matched to limit the base current and voltage of the conducting transistor Q1, prevent over-saturation conduction, and improve the reliability of the circuit.
[0042] Secondly, the output end of the control chip MCU is matched with a second capacitor C2, which is used to improve the anti-interference ability of the circuit.
[0043] The following illustrates the detection step of the LED fault diagnosis device on the printed circuit board based on the above-mentioned scheme. The detection step is as follows:
[0044] Firstly, the controllable current source and the LED are connected, and the output current size and direction of the current source are set.
[0045] Referring to Figure 1 , if the LED is short-circuited: the power supply circuit, the first resistor R1, and the GND form a loop. The MCU sampling voltage at point A is 0. It is judged that the LED is short-circuited, and the user or the debugging personnel is informed of the working state of the LED.
[0046] Referring to Figure 2 , if the LED is open-circuited: the power supply circuit, the first resistor R1, the second resistor R2, the third resistor R3, and the GND form a loop. The MCU sampling voltage at point A is the result of the voltage drop between the second resistor R2 and the third resistor R3 of the D2 LED driving voltage. Assuming that KL30=12V, R2=R3=R1=10Ω, the voltage output by the voltage dividing circuit is 10÷30×12=4V.
[0047] That is, the sampling voltage at point A is 4V. Therefore, according to the voltage at point A, it is judged that the LED is short-circuited, and the user or the debugging personnel is informed of the working state of the LED.
[0048] Referring to Figure 3If the LED works normally, the driving voltage of the LED is assumed to be 3V, R2=R3=10Ω, then the voltage outputted by the voltage dividing circuit is 10÷20×3=1.5V.
[0049] That is, the sampling voltage of the point A is 1.5V, at this time, the LED works normally, and the user or the debugging personnel is informed of the working state of the LED.
[0050] Then, the brightness of the LED is adjusted by adjusting the waveform of the PWM outputted by the control chip MCU.
[0051] The LED fault diagnosis device provided by the scheme detects the voltage value between the two ends of the specific resistor, if a certain lamp bead is short-circuited or a lamp string is disconnected, the current cannot pass through the place, the voltage between the two ends of the target resistor is input to the MCU pin through sampling, is converted into an analog quantity, and is output to the end user or the debugging personnel. Compared with the method of directly using a universal meter and the like to measure, the method does not need additional measuring instruments, only needs to modify the circuit, and has low cost. Without the need of matching professional personnel to disassemble, visually measure and the like, manpower is saved, and measurement difficulty is also saved.
[0052] The above shows and describes the basic principle, main features and advantages of the LED fault diagnosis device. It should be understood by the person skilled in the art that the LED fault diagnosis device is not limited to the above-mentioned embodiments, the above-mentioned embodiments and the description in the specification only illustrate the principle of the LED fault diagnosis device, various changes and improvements of the LED fault diagnosis device can be made without departing from the spirit and range of the LED fault diagnosis device, and the changes and improvements all fall within the scope of the LED fault diagnosis device. The protection scope of the LED fault diagnosis device is defined by the appended claims and equivalents thereof.
Claims
1. A fault diagnosis device for LEDs on a printed circuit board, characterized in that, It includes a power supply circuit, a voltage divider circuit, a sampling circuit, and an LED circuit under test. The power supply circuit outputs to both the voltage divider circuit and the LED circuit under test. The sampling circuit is connected to the output terminal of the voltage divider circuit. The sampling circuit collects the voltage output by the voltage divider circuit and determines the working status of the LED circuit under test based on the changes in the collected voltage.
2. The fault diagnosis device for LEDs on a printed circuit board according to claim 1, characterized in that, The power supply circuit includes a controllable current source and a diode. The diode is connected in series with the output terminal of the controllable current source to regulate the output voltage of the controllable current source.
3. The fault diagnosis device for LEDs on a printed circuit board according to claim 1, characterized in that, The voltage divider circuit includes a first resistor, a second resistor, and a third resistor, which are connected in series. A monitoring point is formed between the second and third resistors and connected to the sampling circuit.
4. The fault diagnosis device for LEDs on a printed circuit board according to claim 3, characterized in that, The sampling circuit includes a detection chip, and the ADC sampling resistor of the detection chip samples the voltage at the monitoring point.
5. The fault diagnosis device for LEDs on a printed circuit board according to claim 4, characterized in that, A third capacitor is provided at the ADC sampling resistor of the detection chip.
6. The fault diagnosis device for LEDs on a printed circuit board according to claim 1, characterized in that, The LED circuit under test is a light-emitting diode, and a first capacitor is provided at the light-emitting diode.
7. A fault diagnosis device for LEDs on a printed circuit board according to claim 6, characterized in that, The LED circuit under test is equipped with a brightness adjustment circuit. After the LED circuit under test is turned on, the brightness of the light-emitting diode is adjusted by the brightness adjustment circuit.
8. The fault diagnosis device for LEDs on a printed circuit board according to claim 7, characterized in that, The brightness adjustment circuit includes a control chip and a transistor. The control chip is connected to the transistor, and the transistor is connected to a light-emitting diode (LED). The control chip outputs a PWM (Pulse Width Modulation) signal, which is conducted to the LED through the transistor. The brightness of the LED is adjusted by the control chip outputting PWM signals of different waveforms.
9. A fault diagnosis device for LEDs on a printed circuit board according to claim 8, characterized in that, The input terminal of the conducting transistor is equipped with a fourth resistor and a fifth resistor, which together form a protection circuit for the transistor.
10. A fault diagnosis device for LEDs on a printed circuit board according to claim 8, characterized in that, The output terminal of the control chip is equipped with a second capacitor.