Automatic packaging detection circuit for tantalum capacitor

Abstract

The utility model discloses an automatic packaging detection circuit for a tantalum capacitor, which comprises a square-wave generator, a current reversing switch, a first detection branch and a second detection branch, and is characterized in that the square-wave generator and the current reversing switch are connected in series and then are sequentially connected with a resistor Rcs and a detected capacitor CDUT; the first detection branch and the second detection branch are connected in parallel; the square wave generator is used for charging the tested capacitor CDUT; the current reversing switch is used for controlling the charging and discharging current of the capacitor CDUT; the first detection branch is used for carrying out open circuit detection on the capacitor CDUT; and the second detection branch is used for carrying out short circuit detection on the detected capacitor CDUT. According to the utility model, the tantalum capacitor packaging is detected by adopting the circuit, the detection circuit is simple in structure, low in cost, high in detection speed and very suitable for automatic detection equipment, multiple groups of circuits can be tested at the same time, multiple devices can be tested at a time, and the test efficiency is greatly improved.

Description

Technical Field

[0001] The utility model relates to the field of electronic circuits, in particular to an automatic packaging detection circuit for tantalum capacitors. Background Art

[0002] Tantalum capacitors are small in size but have a large capacitance. They were first developed by Bell Laboratories in the United States in 1956 and have excellent performance. Tantalum capacitors have a variety of shapes and are made into small and chip components suitable for surface mounting. Tantalum capacitors are not only used in military communications, aerospace and other fields, but also in industrial control, film and television equipment, communication instruments and other products.

[0003] The preparation principle of tantalum capacitors mainly includes four steps: raw material preparation, electrode preparation, dielectric preparation and assembly packaging. In the fourth step of the assembly packaging process, the prepared electrodes and dielectrics are assembled and packaged into capacitors, and then filled with electrolyte or solid-state packaging is performed in a sealed environment to ensure the stability and long life of the capacitor.

[0004] Tantalum capacitors need to be tested for electrical properties after packaging. During the test, it is necessary to first determine whether the anode and cathode of the tantalum capacitor are properly packaged in the shell. If not packaged normally, an empty shell will be produced. However, since the shell of the tantalum capacitor has electrodes, the empty shell will have a smaller capacitance value due to the presence of the electrodes. If a short circuit occurs when the anode and cathode of the tantalum capacitor are packaged, a large current will be generated during the withstand voltage test, which may affect the test equipment.

[0005] The existing tantalum capacitor packaging test technology mainly relies on existing instruments, which have a small detection range, are inconvenient to change, have slow test speeds, and are expensive.

[0006] Therefore, it is necessary to further improve the existing detection technology to reduce the cost of testing and improve the convenience and efficiency of testing. Utility Model Content

[0007] In order to solve the above technical problems, an automatic packaging detection circuit for tantalum capacitors is proposed.

[0008] To achieve the above purpose, the technical solution adopted by the utility model is as follows: a tantalum capacitor automatic packaging detection circuit, including a square wave generator, a current reversing switch, a first detection branch and a second detection branch, wherein:

[0009] The square wave generator is connected in series with the current reversing switch and then connected to the resistor Rcs and the capacitor to be measured CDUT in sequence; the first detection branch and the second detection branch are connected in parallel;

[0010] The first detection branch includes a resistor Rcs, a first differential amplifier circuit, a peak sampling circuit and an open circuit comparator connected in sequence;

[0011] The second detection branch includes a capacitor to be tested CDUT, a second differential amplifier circuit, a low-pass filter circuit and a short-circuit comparator connected in sequence;

[0012] The square wave generator is used to charge the capacitor CDUT under test; the current switching switch is used to control the direction of the charging and discharging current of the capacitor CDUT under test;

[0013] The first detection branch is used to make the voltage across the capacitor CDUT to be zero and perform open circuit detection on the capacitor CDUT;

[0014] The second detection branch is used to perform short circuit detection on the capacitor CDUT when the capacitor CDUT is charged.

[0015] Preferably, the output end of the open circuit comparator is connected to the IO circuit indication circuit.

[0016] Preferably, the output end of the short-circuit comparator is connected to the IO circuit indication circuit.

[0017] Preferably, the square wave generator adopts a pulse width modulation circuit to generate square wave pulses.

[0018] Preferably, the frequency of the square wave pulse is 1 kHz.

[0019] Preferably, the duty cycle of the square wave pulse is greater than 50%.

[0020] Preferably, the source current Isource of the current switching switch is 3 mA, and the sink current Isink is 3 mA. The source current and the sink current are equal, and different current values ​​can be selected according to the actual range of the capacitor to be tested CDUT.

[0021] Preferably, the open-circuit comparator includes a comparator U2, resistors R1, R2 and R3, one end of the resistor R1 is connected to the output end of the comparator U2, and one end is connected to the power supply VCC; one end of the resistor R2 is connected to the positive input end of the comparator U2, and one end is connected to the power supply VCC; one end of the resistor R3 is connected to the negative input end of the comparator U2, and one end is grounded.

[0022] Preferably, the short-circuit comparator includes a comparator U5, resistors R5, R6 and R7, one end of the resistor R5 is connected to the output end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R6 is connected to the positive input end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R7 is connected to the negative input end of the comparator U5, and the other end is grounded.

[0023] The utility model has the following beneficial technical effects: the utility model uses a circuit to detect the tantalum capacitor package, the detection circuit structure is simple, the cost is low, the detection speed is fast, and it is very suitable for use in automated detection equipment. At the same time, the utility model can also test multiple groups of circuits at the same time, and test multiple devices at a time, which greatly improves the test efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The utility model is a circuit schematic diagram of a tantalum capacitor automatic packaging detection circuit. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is further described in detail below in conjunction with embodiments, but the scope of protection claimed in the utility model is not limited to the following specific embodiments.

[0026] like Figure 1 As shown, a tantalum capacitor automatic packaging detection circuit includes a square wave generator, a current reversing switch, a first detection branch and a second detection branch, wherein:

[0027] The square wave generator is connected in series with the current switching switch and then connected to the resistor Rcs and the capacitor CDUT in sequence;

[0028] Specifically, the square wave generator uses a pulse width modulation circuit to generate square wave pulses for charging the capacitor CDUT under test. The current switching switch is used to control the direction of the charging and discharging current of the capacitor CDUT under test.

[0029] The current reversing switch is composed of four diode bridge circuits D1, D2, D3 and D4.

[0030] If the square wave generator directly charges the capacitor CDUT, the charging and discharging currents cannot be limited. Therefore, this solution adds a current reversing switch to control the size of the charging and discharging currents.

[0031] During the actual test, the square wave generator generates a 1kHz square wave pulse, and the generated duty cycle is greater than 50%, and 75% is used in this embodiment. The source current Isource controlled by the current switching switch is 3mA, and the sink current Isink is 3mA. The source current and the sink current are equal. Different current values ​​can be selected according to the actual range of the capacitor to be tested CDUT. In actual applications, the detection range of tantalum capacitors is set to 0.1uF~330uF, and the detection can be completed within 50ms.

[0032] The first detection branch and the second detection branch are connected in parallel; the first detection branch includes a resistor Rcs, a first differential amplifier circuit, a peak sampling circuit and an open-circuit comparator connected in sequence; the second detection branch includes a measured capacitor CDUT, a second differential amplifier circuit, a low-pass filter circuit and a short-circuit comparator connected in sequence.

[0033] The first detection branch is used to perform an open circuit detection on the measured capacitor CDUT when the voltage across the measured capacitor CDUT is zero; the second detection branch is used to perform a short circuit detection on the measured capacitor CDUT when the measured capacitor CDUT is charged.

[0034] Specifically, the output end of the open circuit comparator is connected to the IO circuit indication circuit. The output end of the short circuit comparator is connected to the IO circuit indication circuit.

[0035] The specific circuit structure of the open circuit comparator and the short circuit comparator is as follows:

[0036] The open circuit comparator includes a comparator U2, resistors R1, R2 and R3, one end of the resistor R1 is connected to the output end of the comparator U2, and the other end is connected to the power supply VCC; one end of the resistor R2 is connected to the positive input end of the comparator U2, and the other end is connected to the power supply VCC; one end of the resistor R3 is connected to the negative input end of the comparator U2, and the other end is grounded.

[0037] Preferably, the short-circuit comparator includes a comparator U5, resistors R5, R6 and R7, one end of the resistor R5 is connected to the output end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R6 is connected to the positive input end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R7 is connected to the negative input end of the comparator U5, and the other end is grounded.

[0038] The working process of the utility model when it actually works is as follows:

[0039] When the test starts, the voltage across the capacitor CDUT under test is zero, and the charging current is the largest, so the current flowing through the resistor Rcs is the largest. The voltage across the resistor Rcs is detected using the first differential amplifier circuit, and connected to the peak sampling circuit, so that the peak current of the capacitor CDUT under test can be obtained. The smaller the capacitance of the capacitor CDUT under test, the smaller the peak current of charging. In this way, by setting the reference comparison voltage of the open-circuit comparator U2, the lower limit of the capacitor CDUT under test can be controlled. When it is lower than the lower limit of the capacitor CDUT under test, the open-circuit comparator outputs a low-level signal to the IO level indication circuit, indicating that the anode and cathode of the tantalum capacitor are in an open-circuit state, and it is determined that the tantalum capacitor may be an empty shell, and the tantalum capacitor is not packaged normally.

[0040] When the capacitor CDUT is charged, the voltage on both sides of the capacitor CDUT gradually increases. The larger the capacitor CDUT is, the slower the charging is. Within the specified time range, if the voltage across the capacitor CDUT does not rise to the reference comparison voltage of the short-circuit comparator U5, the short-circuit comparator U5 generates a low-level short-circuit indication signal and outputs it to the IO level indication circuit, indicating that the tantalum capacitor is short-circuited internally and the tantalum capacitor is not packaged normally.

[0041] If the anode and cathode of the tantalum capacitor are short-circuited, it will not charge during the test and the voltage across the tantalum capacitor will not rise. If the anode and cathode are short-circuited during packaging, it also means that the tantalum capacitor is not packaged properly. If the anode and cathode are short-circuited during packaging, the tantalum capacitor will generate a large current during the withstand voltage test, which will affect the test equipment.

[0042] Only when the test results show that the anode and cathode of the tantalum capacitor are neither open circuit nor short circuit, can it be said that the tantalum capacitor is correctly packaged.

[0043] The comparison reference voltage for the tantalum capacitor open circuit detection is determined by the voltage divider of R2 and R3, and uses an adjustable resistor, which can be set according to the capacitance range of the product.

[0044] The comparison reference circuit for tantalum capacitor short circuit detection is determined by the voltage divider of R6 and R7, and uses adjustable resistors, which can also be set according to the capacitance range of the product.

[0045] The square wave generator is designed with a pulse width modulation circuit, which can control the charging speed of the tantalum capacitor and control the test time. If the duty cycle of the pulse is not adjusted, the constant current source circuit controlled by the current commutation switch can also be adjusted to control the charging speed of the tantalum capacitor.

[0046] According to the disclosure and teaching of the above description, those skilled in the art to which the utility model belongs can also change and modify the above implementation. Therefore, the utility model is not limited to the specific implementation methods disclosed and described above, and some modifications and changes to the utility model should also fall within the scope of protection of the claims of the utility model. In addition, although some specific terms are used in this specification, these terms are only for convenience and do not constitute any limitation to the utility model.

Claims

1. A tantalum capacitor automatic packaging detection circuit, characterized in that: The invention comprises a square wave generator, a current switching switch, a first detection branch and a second detection branch, wherein: The square wave generator is connected in series with the current reversing switch and then connected to the resistor Rcs and the capacitor to be measured CDUT in sequence; the first detection branch and the second detection branch are connected in parallel; The first detection branch includes a resistor Rcs, a first differential amplifier circuit, a peak sampling circuit and an open circuit comparator connected in sequence; The second detection branch includes a capacitor to be tested CDUT, a second differential amplifier circuit, a low-pass filter circuit and a short-circuit comparator connected in sequence; The square wave generator is used to charge the capacitor CDUT under test; the current switching switch is used to control the direction of the charging and discharging current of the capacitor CDUT under test; The first detection branch is used to make the voltage across the capacitor CDUT to be zero and perform open circuit detection on the capacitor CDUT; The second detection branch is used to perform short circuit detection on the capacitor CDUT when the capacitor CDUT is charged.

2. The tantalum capacitor automatic packaging detection circuit according to claim 1, characterized in that: The output end of the open circuit comparator is connected to the IO circuit indication circuit.

3. The tantalum capacitor automatic packaging detection circuit according to claim 2, characterized in that: The output end of the short-circuit comparator is connected to the IO circuit indication circuit.

4. The tantalum capacitor automatic packaging detection circuit according to claim 1, characterized in that: The square wave generator adopts a pulse width modulation circuit to generate square wave pulses.

5. The tantalum capacitor automatic packaging detection circuit as claimed in claim 4, characterized in that: The frequency of the square wave pulse is 1 kHz.

6. The tantalum capacitor automatic packaging detection circuit as claimed in claim 5, characterized in that: The duty cycle of the square wave pulse is greater than 50%.

7. The tantalum capacitor automatic packaging detection circuit according to claim 1, characterized in that: The source current Isource of the current switching switch is 3 mA, and the sink current Isink is 3 mA.

8. The tantalum capacitor automatic packaging detection circuit according to claim 1, characterized in that: The open circuit comparator includes a comparator U2, resistors R1, R2 and R3, one end of the resistor R1 is connected to the output end of the comparator U2, and the other end is connected to the power supply VCC; one end of the resistor R2 is connected to the positive input end of the comparator U2, and the other end is connected to the power supply VCC; one end of the resistor R3 is connected to the negative input end of the comparator U2, and the other end is grounded.

9. The tantalum capacitor automatic packaging detection circuit according to claim 1, characterized in that: The short-circuit comparator includes a comparator U5, resistors R5, R6 and R7, one end of the resistor R5 is connected to the output end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R6 is connected to the positive input end of the comparator U5, and the other end is connected to the power supply VCC; one end of the resistor R7 is connected to the negative input end of the comparator U5, and the other end is grounded.

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