A circuit for detecting potential defects in aluminum electrolytic capacitors

Abstract

This invention discloses a detection circuit for hidden defects in aluminum electrolytic capacitors, comprising an AC-AC high-power power frequency converter, a triangular wave signal generation module, an output module, a time detection and judgment system, and an LCD display system. The AC-AC high-power power frequency converter provides a stable and compatible DC power supply, ensuring the stability of subsequent modules. The triangular wave signal generation module can generate triangular waves with adjustable amplitude and frequency to meet the detection requirements of aluminum electrolytic capacitors of different specifications. The output module can accurately capture the charging and discharging characteristics of the capacitor and output a reliable detection signal through voltage division, filtering, and comparison circuits. By combining the time detection and judgment system with the LCD display system, the signal can be quickly analyzed, the results displayed, and automatically classified, improving detection efficiency and accuracy and solving the problem that traditional methods are difficult to identify internal hidden defects.

Description

Technical Field

[0001] This utility model relates to the field of aluminum electrolytic capacitor application technology, and specifically to a circuit for detecting potential defects in aluminum electrolytic capacitors. Background Technology

[0002] Aluminum electrolytic capacitors suffer some damage during the production process. For example, cutting and winding processes can damage the oxide film on the surface of the aluminum foil. Although the aging process can repair the damaged oxide film, aluminum foil dust particles, cutting burrs, and electrolytic paper impurities generated during the process cannot be completely repaired. Most of these defects are eliminated during the aging and testing processes. However, a very small number of capacitors have internal damage but their electrical performance parameters are still qualified. These defects cannot be completely eliminated during the aging, testing, and appearance processes. If these defective products reach the customer, they will pose a great safety hazard, causing the capacitor to explode during testing, or the entire unit to fail prematurely. This leads to customer complaints and quality problems. Summary of the Invention

[0003] The purpose of this invention is to address the potential problems of existing aluminum electrolytic capacitors. This application uses a triangular wave signal generation module to generate triangular waves with adjustable amplitude and frequency, adapting to the testing needs of aluminum electrolytic capacitors of different specifications.

[0004] The technical solution of this invention: A circuit for detecting potential defects in aluminum electrolytic capacitors, characterized in that it includes an AC-AC high-power power frequency converter, a triangular wave signal generation module, an output module, a time detection and judgment system, and an LCD display system; The output terminal of the AC-AC high-power power frequency converter is connected to the power supply terminal of the triangular wave signal generation module and the output module. The output terminal of the triangular wave signal generation module is connected to the control terminal of the output module; The signal output terminal of the output module is connected to the signal input terminal of the time detection and judgment system. The display control terminal of the time detection and judgment system is connected to the LCD display system, and the time detection and judgment system also has output terminals for outputting good product signals and defective product signals respectively.

[0005] The AC-AC high-power power frequency converter includes a fuse FUSE, a transformer T1, and a full-bridge rectifier bridge BRIDGE connected in sequence. The input terminal of the fuse (FUSE) serves as the AC input terminal of the AC-AC high-power power frequency converter, and the output terminal of the full-bridge rectifier (BRIDGE) serves as the DC output terminal of the AC-AC high-power power frequency converter.

[0006] The triangular wave signal generation module includes operational amplifier IC1A, operational amplifier IC1B, potentiometer VR1, potentiometer VR2, potentiometer VR3, resistor R1, resistor R2, and capacitor C1. The first terminal of potentiometer VR1 is connected to DC power supply VCC through resistor R7, the second terminal of potentiometer VR1 is grounded, and the first terminal of potentiometer VR1 is also connected to the non-inverting input terminal of operational amplifier IC1A. The inverting input terminal of the operational amplifier IC1A is grounded, and the non-inverting input terminal is connected to the second terminal of potentiometer VR2 and the second terminal of potentiometer VR3 respectively. The output terminal of the operational amplifier IC1A is connected to the first terminal of resistor R2 and the first terminal of potentiometer VR2. The second end of the resistor R2 is connected to the inverting input of the operational amplifier IC1B, the non-inverting input of the operational amplifier IC1B is connected to the first end of the potentiometer VR1, and the output end of the operational amplifier IC1B is connected in parallel with the first end of the potentiometer VR3 as the output end of the triangular wave signal generation module. The two ends of the capacitor C1 are connected to the inverting input and output terminals of the operational amplifier IC1B, respectively.

[0007] The output module includes a switch Q1, resistor R3, resistor R4, capacitor C3, and operational amplifier IC1C; The control terminal of the switching transistor Q1 is connected to the output terminal of the triangular wave signal generation module. The first terminal of the switching transistor Q1 is connected to the DC output terminal of the AC-AC high-power power frequency converter. The second terminal of the switching transistor Q1 is connected to the anode of the diode D3 and one end of the aluminum electrolytic capacitor under test. The other end of the aluminum electrolytic capacitor under test outputs a feedback voltage V-Fb signal and is grounded through a fuse. The cathode of the diode D3 is connected to resistors R3 and R5 respectively. The other end of resistor R3 outputs a comparison signal V-Rd and is grounded through resistor R4. The other end of resistor R5 is connected to capacitor C3 and resistor R6 in sequence, and resistor R6 is grounded. The non-inverting input of the operational amplifier IC1C is connected to the junction of the resistor R6 and the capacitor C3. The inverting input of the operational amplifier IC1C is connected to the reference voltage V-Ref. The output of the operational amplifier IC1C outputs the judgment signal V-Cd.

[0008] The time detection and determination system includes an MCU. The signal input pins of the MCU are respectively connected to a feedback voltage V-Fb, a comparison signal V-Rd, and a determination signal V-Cd. The output pins output a reference voltage V-Ref. The display control pins of the MCU are connected to the LCD display system.

[0009] The beneficial effects of this invention are as follows: The AC-AC high-power power frequency converter provides a stable and compatible DC power supply, ensuring the stability of subsequent modules; the triangular wave signal generation module can generate triangular waves with adjustable amplitude and frequency to meet the detection requirements of aluminum electrolytic capacitors of different specifications; the output module can accurately capture the charging and discharging characteristics of the capacitor and output reliable detection signals through voltage divider, filter and comparison circuits; through the time detection and judgment system combined with the LCD display system, signals can be quickly analyzed, results displayed and automatically classified, improving detection efficiency and accuracy, and solving the problem that traditional methods are difficult to identify internal hidden defects. Attached Figure Description

[0010] Figure 1 This is a block diagram of the aluminum electrolytic capacitor hidden danger detection system of this utility model; Figure 2 This is a schematic diagram of the circuit for detecting potential defects in aluminum electrolytic capacitors according to this utility model. Figure 3 Waveform diagram of a good quality aluminum electrolytic capacitor; Figure 4 This is a waveform diagram of a potentially hazardous aluminum electrolytic capacitor. Detailed Implementation

[0011] like Figure 1 , Figure 2 As shown, the functions of each main module circuit are as follows: The AC-AC high-power power frequency converter transforms the 220V 50Hz AC power frequency into an adjustable 10V-450V AC power frequency. It can provide all the electrical energy required by the capacitor and, together with the triangular wave signal generation module, generate a signal source and apply it to the test capacitor.

[0012] AC-AC high-power industrial frequency converter: The output terminal is connected to the power supply terminal of the triangular wave signal generation module and the output module, used to convert the input industrial frequency AC power into DC power to power the latter two. This power supply includes a fuse (FUSE), a transformer (T1), and a full-bridge rectifier (BRIDGE) connected in sequence; the input terminal of the fuse (FUSE) is the AC input terminal, providing overcurrent protection; the transformer (T1) adjusts the AC voltage amplitude; the full-bridge rectifier (BRIDGE) rectifies the AC voltage into DC voltage, and its output terminal provides a stable DC power supply to subsequent modules.

[0013] Triangular wave signal generation module: The output terminal is connected to the control terminal of the output module and is used to generate a triangular wave signal to provide excitation control signal for the output module. This module includes a first operational amplifier IC1A, a second operational amplifier IC1B, a first potentiometer VR1, a second potentiometer VR2, a third potentiometer VR3, a first resistor R1, a second resistor R2, and a first capacitor C1; the first potentiometer VR1 provides an adjustable reference voltage to the non-inverting input of the first operational amplifier IC1A; the first operational amplifier IC1A acts as a comparator and outputs a square wave signal; the second operational amplifier IC1B, the second resistor R2, and the first capacitor C1 form an integrating circuit to convert the square wave into a triangular wave; the second potentiometer VR2 adjusts the frequency of the triangular wave, and the third potentiometer VR3 adjusts the amplitude of the triangular wave.

[0014] Output Module: The signal output terminal is connected to the signal input terminal of the time detection and judgment system. It is used to charge and discharge the aluminum electrolytic capacitor under test under the control of a triangular wave signal, and output a detection signal reflecting the charging and discharging characteristics. This module includes a switch Q1, a third resistor R3, a fourth resistor R4, a second capacitor C3, and a third operational amplifier IC1C. The switch Q1 receives the triangular wave signal to control the switching on and off to charge and discharge the capacitor under test. The third resistor R3 and the fourth resistor R4 form a voltage divider to sample the capacitor voltage. The second capacitor C3 filters out high-frequency interference from the sampled voltage. The third operational amplifier IC1C outputs the compared detection signal.

[0015] Time detection and judgment system and LCD display system: The display control terminal of the time detection and judgment system is connected to the LCD display system, and it also has output terminals for outputting good product signals and defective product signals respectively. The system includes an MCU, which collects the detection signals from the output module, drives the LCD to display the results, and outputs classification signals to classify good products and defective products.

[0016] The good / potentially defective product collection module classifies and collects capacitors based on the judgment system signal, distinguishing between good and potential defective products.

[0017] After the test capacitor enters the fixture station, a triangular wave signal is applied to both ends of the test capacitor and held for 0.5 seconds. When the time detection module detects a complete and short triangular wave signal, it is judged as a good product; when the time detection module detects an incomplete and long triangular wave signal, it is judged as a product with potential defects.

[0018] Figure 3 It is a high-quality aluminum electrolytic capacitor with a complete triangular wave signal and a short duration.

[0019] Figure 4 This is a potential problem with aluminum electrolytic capacitors; the triangular wave signal is incomplete and lasts for a long time.

[0020] Comparative analysis can accurately confirm whether the test capacitor is normal, effectively eliminate potential problems, and improve product quality.

[0021] The specific workflow for each module is as follows: Power supply circuit: AC input to DC conversion: Mains frequency AC power → FUSE (overcurrent protection) → T1 primary winding (voltage adjustable, 10V-450V) → T1 secondary winding → BRIDGE full-bridge rectification (AC to DC) → filter capacitor (not specified, filters ripple) → output VCC DC power supply. T1 adjusts the output voltage through the turns ratio to adapt to capacitors under test with different rated voltages (e.g., 16V, 400V), avoiding overvoltage damage or undervoltage detection failure. Power supply distribution for each module: VCC → triangular wave module (IC1A / IC1B power pins) → provides op-amp operating voltage; VCC → output module (Q1 source + IC1C power pins) → ensures switching transistor drive and signal amplification; VCC → MCU power pins → provides power for the judgment system.

[0022] Triangular wave generation process Comparator IC1A current path: VCC → VR1 (voltage divider) → IC1A non-inverting input → IC1A internal amplifier circuit → IC1A output (square wave signal) → R2 / VR2 (parallel) → IC1B inverting input. VR1 changes the reference voltage of the non-inverting input, controlling the square wave flip threshold; VR2 adjusts the parallel resistor value, changing the current magnitude to adjust the subsequent integration rate. Integrator IC1B current path: IC1A output square wave → R2 / VR2 → IC1B inverting input → IC1B internal amplifier circuit → IC1B output (triangular wave) → C1 (feedback to IC1B inverting input, forming an integration loop) + Q1 control electrode.

[0023] When the square wave is high, the current charges C1, and the output of IC1B increases linearly; when the square wave is low, C1 discharges, and the output decreases linearly, forming a triangular wave.

[0024] Capacitance testing process: Charging process (when Q1 is on): VCC → Q1 drain (D) → Q1 source (S, driven to conduct by a high-level triangular wave) → positive terminal of the capacitor under test → negative terminal of the capacitor under test → ground. Good product characteristics: intact oxide film, stable charging current, and capacitor voltage rises linearly and synchronously with the triangular wave. Problematic product characteristics: aluminum foil burrs cause micro-short circuits, resulting in a sudden increase in charging current and a slow voltage rise (slope <2V / ms).

[0025] Voltage sampling and signal output: Voltage of capacitor under test → R3 → R4 (voltage divider) → C3 (filter high-frequency interference) → IC1C non-inverting input → IC1C internal comparator circuit (compared with the reference voltage of the inverting input) → IC1C output detection signal VC1 → MCU signal input pin.

[0026] Decision and output loop (result processing stage) MCU receives VC1 signal → internal AD conversion (analog signal to digital) → logic operation (comparing charge / discharge time and slope threshold) → Good product: MCU outputs high level → IC1C outputs good product → sorting execution unit (connected to good product hopper); Potentially hazardous items: MCU output low level → IC1C no output → sorting execution unit (connected to defective product hopper); Simultaneously, the MCU → LCD driver circuit → displays the detection parameters (charge / discharge time, voltage amplitude).

Claims

1. A circuit for detecting potential defects in aluminum electrolytic capacitors, characterized in that, It includes an AC-AC high-power power frequency converter, a triangular wave signal generation module, an output module, a time detection and judgment system, and an LCD display system; The output terminal of the AC-AC high-power power frequency converter is connected to the power supply terminal of the triangular wave signal generation module and the output module. The output terminal of the triangular wave signal generation module is connected to the control terminal of the output module; The signal output terminal of the output module is connected to the signal input terminal of the time detection and judgment system. The display control terminal of the time detection and judgment system is connected to the LCD display system, and the time detection and judgment system also has output terminals for outputting good product signals and defective product signals respectively.

2. The aluminum electrolytic capacitor hazard detection circuit according to claim 1, characterized in that: The AC-AC high-power power frequency converter includes a fuse FUSE, a transformer T1, and a full-bridge rectifier bridge BRIDGE connected in sequence. The input terminal of the fuse (FUSE) serves as the AC input terminal of the AC-AC high-power power frequency converter, and the output terminal of the full-bridge rectifier (BRIDGE) serves as the DC output terminal of the AC-AC high-power power frequency converter.

3. The aluminum electrolytic capacitor hazard detection circuit according to claim 1, characterized in that: The triangular wave signal generation module includes operational amplifier IC1A, operational amplifier IC1B, potentiometer VR1, potentiometer VR2, potentiometer VR3, resistor R1, resistor R2, and capacitor C1. The first terminal of potentiometer VR1 is connected to DC power supply VCC through resistor R7, the second terminal of potentiometer VR1 is grounded, and the first terminal of potentiometer VR1 is also connected to the non-inverting input terminal of operational amplifier IC1A. The inverting input terminal of the operational amplifier IC1A is grounded, and the non-inverting input terminal is connected to the second terminal of potentiometer VR2 and the second terminal of potentiometer VR3 respectively. The output terminal of the operational amplifier IC1A is connected to the first terminal of resistor R2 and the first terminal of potentiometer VR2. The second end of the resistor R2 is connected to the inverting input of the operational amplifier IC1B, the non-inverting input of the operational amplifier IC1B is connected to the first end of the potentiometer VR1, and the output end of the operational amplifier IC1B is connected in parallel with the first end of the potentiometer VR3 as the output end of the triangular wave signal generation module. The two ends of the capacitor C1 are connected to the inverting input and output terminals of the operational amplifier IC1B, respectively.

4. The aluminum electrolytic capacitor hazard detection circuit according to claim 1, characterized in that: The output module includes a switch Q1, resistor R3, resistor R4, capacitor C3, and operational amplifier IC1C; The control terminal of the switching transistor Q1 is connected to the output terminal of the triangular wave signal generation module. The first terminal of the switching transistor Q1 is connected to the DC output terminal of the AC-AC high-power power frequency converter. The second terminal of the switching transistor Q1 is connected to the anode of the diode D3 and one end of the aluminum electrolytic capacitor under test. The other end of the aluminum electrolytic capacitor under test outputs a feedback voltage V-Fb signal and is grounded through a fuse. The cathode of the diode D3 is connected to resistors R3 and R5 respectively. The other end of resistor R3 outputs a model comparison signal V-Rd and is grounded through resistor R4. The other end of resistor R5 is connected to capacitor C3 and resistor R6 in sequence, and resistor R6 is grounded. The non-inverting input of the operational amplifier IC1C is connected to the junction of the resistor R6 and the capacitor C3. The inverting input of the operational amplifier IC1C is connected to the reference voltage V-Ref. The output of the operational amplifier IC1C outputs the judgment signal V-Cd.

5. The aluminum electrolytic capacitor hazard detection circuit according to claim 1, characterized in that: The time detection and determination system includes an MCU. The signal input pins of the MCU are respectively connected to a feedback voltage V-Fb, a comparison signal V-Rd, and a determination signal V-Cd. The output pins output a reference voltage V-Ref. The display control pins of the MCU are connected to the LCD display system.

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