A device and method for improving the efficiency of current surge testing of capacitors

Abstract

The application provides a device and method for improving the efficiency of current surge test of capacitors, and the circuit comprises a direct current power supply, a surge power supply and a plurality of parallel capacitors; each capacitor is connected with the surge power supply and provided with a first switch on a first circuit and a second switch on a second circuit; the first switch of one capacitor is closed for a first time length and then opened; at the moment of opening, the second switch of the capacitor is closed for a second time length and then opened; at the moment of opening, the first switch of the next capacitor is closed for a first time length and then opened; each capacitor in the current surge test circuit experiences the process of closing and opening of the first switch and the second switch, so that the surge power supply and the direct current power supply charge each capacitor. The application satisfies the high-quality current surge test at low cost and greatly reduces the production cost of capacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of current detection, and in particular to a device and method for improving the efficiency of a current surge test of a capacitor. Background Art

[0002] Current surge devices are commonly used for surge testing of capacitor products. They typically require a low discharge loop internal resistance (less than 1Ω, for example, 0.4Ω), a short current rise time (less than 10µS, for example, 4-5µS), and the ability to measure peak current (ranging from 10A to 200A) and current drop curves. A surge power supply typically involves a power supply charging a set of high-capacity energy storage capacitors. These capacitors are connected to a capacitor under test via a discharge switch, forming a surge discharge circuit with the capacitor under test.

[0003] When the discharge switch is turned on, the energy storage capacitor quickly discharges the capacitor to be tested, forming a current surge peak (usually from a few amperes to more than 100 amperes). The current then drops rapidly, usually to a few mA after 10mS, until the capacitor to be tested is fully charged. At this point, the current will drop to the order of 1mA or even lower. However, surge current devices are now required to not only measure the peak surge current (10A to 200A), but also be able to test currents below mA after the capacitor is almost fully charged. This means that the current measurement range is very large, with a current dynamic range that varies by more than tens of thousands of times. Currently, current surge technologies and devices that can achieve the above measurement requirements during current surges exist, but the cost of such fully functional devices is extremely high.

[0004] In the existing technology, the specifications for current surge tests generally require that the charging time required for the current surge test be at least 1 second and the discharging time be at least 1 second, that is, each current surge test cycle requires at least 2 seconds. If 10 surge cycle tests are required, it will take 20 seconds. In mass production, each capacitor requires 20 seconds to perform such a current surge test, which is extremely inefficient. If multiple current surge devices are used to perform parallel current surge tests on multiple capacitors at the same time, the efficiency can be doubled, but the overall production cost will also increase exponentially.

[0005] Existing technologies, whether conducting production tests at room temperature or in high or low temperature environments, typically use multiple current surge devices to improve efficiency. Each current surge device tests only one capacitor. By testing multiple capacitors simultaneously, efficiency can be multiplied. However, this method is expensive and falls short of low-cost requirements. To reduce costs, some existing technologies employ simplified devices that compromise surge current measurement performance. This sacrifices key performance for cost control and fails to meet the demand for high performance. Summary of the Invention

[0006] An object of the present invention is to provide a device and method for improving the efficiency of a current surge test of a capacitor, thereby meeting high-quality current surge testing at a low cost and greatly reducing the production cost of the capacitor.

[0007] In particular, the present invention provides a device for improving the efficiency of a current surge test of a capacitor. A current surge test circuit includes: a DC power supply, a surge power supply, and a plurality of capacitors connected in parallel; each capacitor is connected to the surge power supply and the DC power supply through two independent circuits, wherein a first switch is provided on the first circuit connected to the surge power supply, and a second switch is provided on the second circuit connected to the DC power supply.

[0008] The first switch of a capacitor is opened after being closed for a first time period. At the same time as the first switch is opened, the second switch of the capacitor is closed and opened after a second time period. After the first switch is closed for an interval of time, the first switch of the next capacitor is closed and opened after a first time period.

[0009] Each capacitor in the current surge test circuit undergoes a process of closing and opening the first switch and the second switch thereof, so that the surge power supply and the DC power supply charge each capacitor.

[0010] Preferably, a set of current surge test circuits also includes: multiple resistors; each capacitor is connected to a resistor through an independent third circuit, and the third circuit is provided with a third switch; the second switch of a capacitor is disconnected after being closed for a second time period, and at the same time as being disconnected, the third switch of the capacitor is closed and disconnected after a third time period, so that the capacitor is discharged.

[0011] Preferably, the first duration ranges from 10ms to 100ms, the second duration ranges from 990ms to 900ms, the third duration is the sum of the first duration and the second duration, and the interval duration is greater than or equal to 20ms.

[0012] Preferably, in the current surge test circuit, the third switch of the first capacitor is closed for a third period of time and then disconnected, completing a complete charge and discharge cycle; at the same time, the first switch of the first capacitor is closed again to start the next charge and discharge cycle.

[0013] Preferably, the number of charge and discharge cycles of each capacitor is at least 10 times.

[0014] According to another aspect of the present invention, the present invention also discloses a method for improving the efficiency of a current surge test of a capacitor, using the above-mentioned current surge test circuit, wherein a plurality of capacitors connected in parallel in the circuit are arranged in sequence, and the method for improving the test efficiency comprises the following steps:

[0015] S1: Close the first switch of a capacitor to allow the surge power to charge the capacitor;

[0016] S2: Determine whether the closing time of the first switch of the capacitor reaches the first time length. If so, proceed to S3. If not, the surge power supply continues to charge the capacitor.

[0017] S3: Disconnect the first switch of this capacitor and perform S4a and S4b respectively;

[0018] S4a: while the capacitor is disconnected, the second switch of the capacitor is closed, so that the DC power supply charges the capacitor, and the second switch of the capacitor is disconnected after the second time period;

[0019] S4b: Determine whether this capacitor is the last capacitor in the sequence. If so, end the loop. If not, proceed to S5b.

[0020] S5b: After the disconnection interval, the next capacitor of this capacitor is charged and the process returns to S1 until each capacitor in the circuit has experienced the process of its first switch closing and opening.

[0021] Preferably, the current surge test circuit further includes: a plurality of resistors, each capacitor is connected to a resistor via an independent third circuit, and the third circuit is provided with a third switch; after S4a, the method for improving the test efficiency further includes the following steps:

[0022] S5a: After the second switch of the capacitor is turned off, the third switch of the capacitor is closed and turned off after a third time period, so that the capacitor is discharged.

[0023] The present invention improves the efficiency of capacitor current surge testing. Using a single surge power supply and a single DC power supply, the surge power supply provides current surges for multiple capacitors using a time-sharing switching method. This means that a single, fully functional current surge source is shared by multiple capacitors within a group. Furthermore, a single DC power supply can also be used for multiple groups of multiple capacitors, providing DC power to a greater number of capacitors simultaneously. Therefore, the present invention can significantly improve the efficiency of capacitor current surge testing at a limited cost.

[0024] Furthermore, the DC power supply has an output current limiting function. The current limit value can be set closely according to the actual charging current (usually in the range of 1mA to 50mA, determined by the remaining charge capacity of the capacitor under test after charging with the surge power supply), but must be higher than the actual charging current value. The current limiting function not only protects the power supply in the event of a capacitor failure and short circuit, but also has a suppressive effect on capacitor explosion in the event of a short circuit, thus reducing the chance of defective capacitors exploding during current surge testing. It also effectively protects the capacitor fixture used for current surge testing from damage caused by capacitor explosion.

[0025] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Hereinafter, some specific embodiments of the present invention will be described in detail in an illustrative and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0027] Figure 1 is a partial flow chart of a method for current surge testing efficiency of high capacitance of the present invention;

[0028] Figure 2 4 is a schematic diagram of a circuit for improving the efficiency of a capacitor current surge test according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] The present invention adopts a mode of conducting current surge tests on multiple capacitors. The characteristic is that the current surge test time of each capacitor is divided into two stages, and two power sources with current limits are provided to the capacitors in the two stages, one is a full-function current surge source, and the other is a conventional DC power supply. Among them, only one current surge source is used to test a group of multiple capacitors, and a time-sharing switching method is used to provide current surge impacts for multiple capacitors, that is, a full-function current surge source is shared by multiple capacitors in a group in a time-sharing manner. Only one DC power supply is also used, which can correspond to multiple groups of multiple capacitors and can provide DC power to more capacitors at the same time, because each capacitor only needs a smaller current in the later stage of charging. After each capacitor has completed the surge test, a discharge resistor can be connected to discharge it.

[0030] Therefore, the current surge test circuit of the device of the present invention includes: a DC power supply, a surge power supply, multiple resistors, and multiple capacitors connected in parallel. Each resistor corresponds to a capacitor. Each capacitor has three independent circuits. The first circuit of a capacitor is connected to the surge power supply, and a first switch is provided on the first circuit; the second circuit is connected to the DC power supply, and a second switch is provided on the second circuit; the third circuit is connected to the resistor, and a third switch is provided on the third circuit. In other words, each capacitor is connected to three selection switches, which can respectively select to connect to the surge power supply, the DC power supply, or the discharge resistor. The selection switch used is a power MOS switching device, and its switching speed is much faster than that of the IGBT.

[0031] The following describes three time periods of the same capacitor.

[0032] The first time period is the stage of applying a current surge to the capacitor, which includes a large current surge impact process in the range of 10A to 200A on the capacitor. The main impact process is mainly concentrated in the first 100us. The time length of the first stage arranged by the present invention, that is, the first duration is 10ms to 100ms. The range selection of the first duration not only includes the main current impact part, but also includes the buffer part of waiting for the current to drop to a sufficiently low stage before the surge power supply is withdrawn. In the first time period, the first switch of the capacitor is closed, the surge power supply charges the capacitor for the first duration, and then the first switch is disconnected.

[0033] The principle of selecting the duration of the surge power supply is: after the capacitor is connected to the surge source, the current surge will quickly reach its peak value in only about 10us. The peak current is the voltage of the surge discharge source divided by the internal resistance of the discharge circuit (usually around 1Ω). The current peak is usually around 10A to 200A; then the current decreases rapidly. For a normal capacitor, the current drops to less than 95% of the peak value in about 100us, and to less than 99% in 10ms. It then slowly approaches the leakage current value of the capacitor, and reaches less than 99.9% in about 100ms.

[0034] The second time period applies a DC voltage to the capacitor after the current surge to continue charging. The DC power supply charging starts at the end of the first time period. That is, when the first switch is opened, the DC power supply continues to charge the capacitor for the second time period until the required current surge charging time (typically 1000mS) is complete, at which point the second switch is opened.

[0035] The principle for selecting the duration of a DC power supply is as follows: In the second stage, a conventional DC power supply is used, with a voltage that is fixed throughout the entire current surge. At this point, the capacitor is over 99% charged, and the charging current has dropped to tens to a few mA. The DC power supply has an output current limiting function. The current limit value can be set closely based on the actual charging current (usually in the range of 1mA to 50mA, determined by the remaining charge capacity of the capacitor under test after the surge power supply), but must be higher than the actual charging current value. The current limiting function not only protects the power supply in the event of a capacitor failure and short circuit, but also suppresses the capacitor from exploding in the event of a short circuit. This effectively protects the capacitor fixture during the current surge from damage caused by the capacitor exploding.

[0036] The third time period is the discharge phase of the capacitor. At this time, the second switch is opened and the third switch of the capacitor is closed, so that the capacitor discharges to the resistor in the third circuit and lasts for a third time period. Typically, the third time period is selected as the sum of the first time period and the second time period. The first time period ranges from 10ms to 100ms, and the second time period ranges from 990ms to 900ms. If the first time period is selected as 10ms and the second time period is selected as 990ms, the third time period is 1000ms to ensure sufficient consumption of the capacitor.

[0037] The following describes the charging and discharging of multiple capacitors connected in parallel in detail. Since the charging time of each capacitor by the surge power supply is very short, the present invention adopts a time-sharing switching method to fully utilize the surge power supply.

[0038] Multiple capacitors are arranged in sequence. After the first switch of the first capacitor is closed, the surge power supply charges the first capacitor for a first period of time, and then disconnects. After the interval of the first switch of the first capacitor being disconnected, the first switch of the second capacitor is closed, the surge power supply charges the second capacitor for a first period of time, and then disconnects. ... After the interval of the first switch of the nth capacitor being disconnected, the first switch of the n+1th capacitor is closed, the surge power supply charges the n+1th capacitor for a first period of time, and then disconnects. In this process, while the first switch of each capacitor is disconnected, its corresponding second switch is closed, and the DC power supply provides power to this capacitor. Therefore, at the same time, the surge power supply only serves one capacitor, while the DC power supply needs to serve multiple or even all capacitors connected in parallel in the circuit.

[0039] The interval duration must be greater than the first duration. During the interval, the surge power supply does not discharge externally, and the large-capacity energy storage capacitor in the surge power supply is fully recharged internally. If the first duration is 10ms, the interval duration can be set to be greater than or equal to 20ms.

[0040] Each capacitor in the current surge test circuit undergoes a process of closing and opening its first and second switches to allow the surge power supply and DC power supply to charge each capacitor. Each capacitor also undergoes a process of closing and opening its third switch to fully discharge each capacitor.

[0041] The three time periods of the same capacitor and the charging and discharging of multiple parallel capacitors described above all belong to one charge and discharge cycle of the current surge test circuit of the present invention. A capacitor may require at least 10 charge and discharge cycles. After the third switch of the first capacitor is disconnected, that is, after the charge and discharge cycle of the first capacitor is completed, the first switch of the first capacitor is closed again, and the first capacitor starts the next charge and discharge cycle... until all capacitors meet the number of charge and discharge cycles, the current surge test of the present device ends.

[0042] In summary, if Figure 1 As shown, a flow chart of a method for improving the efficiency of a capacitor current surge test is provided, taking a charging cycle of the current surge test circuit of the present invention as an example. Initially, the first capacitor is charged with n=1.

[0043] S1: Close the first switch of capacitor n to allow the surge power to charge capacitor n;

[0044] S2: Determine whether the closing time of the first switch of capacitor n reaches the first time length. If so, proceed to S3; if not, the surge power supply continues to charge capacitor n.

[0045] S3: Disconnect the first switch of capacitor n and perform S4a and S4b respectively;

[0046] S4a: while the capacitor n is disconnected, the second switch of the capacitor n is closed, so that the DC power supply charges the capacitor n, and the second switch of the capacitor n is disconnected after the second time period;

[0047] S4b: Determine whether capacitor n is the last capacitor in the sequence. If so, end the loop. If not, proceed to S5b.

[0048] S5b: After the disconnection interval, charge the capacitor n=n+1 and return to S1 until each capacitor in the circuit has experienced the process of its first switch closing and opening.

[0049] S1 to S4a are the charging process of capacitor n. After S4a, capacitor n also has a discharging process. S5a: After the second switch of capacitor n is opened, the third switch of capacitor n is closed and opened after a third time period, thereby discharging capacitor n.

[0050] like Figure 1 The figure shows an embodiment. Four capacitors are grouped together, sharing a surge power supply and a DC power supply. Each capacitor is connected to the surge power supply and the DC power supply via switches K1 and K2, forming a current surge charging circuit and a DC steady-state charging circuit, respectively. Another switch, K3, connects to a discharge resistor, forming a discharge circuit.

[0051] When the surge begins, the current surge switch K1-1 of capacitor C1 is connected to the surge power supply for 10mS or extended to 100mS. Then K1-1 is disconnected and K1-2 is immediately connected. The capacitor is connected to the DC power supply to continue charging capacitor C1.

[0052] At least 20mS after C1's power supply switches, K2-1 of capacitor C2 connects to the surge power supply for the same duration as C1's connection. K2-1 then disconnects, and K2-2 immediately connects, connecting C2 to the DC power supply and continuing to charge C2. At this point, C1's DC charging time has not yet concluded, having only lasted approximately 100mS (or less, depending on the specific duration of a surge period), and further charging is required (the surge period plus the DC charging period equals at least 1000mS).

[0053] By the time C3's inrush period ends and begins DC charging, C1 has already been charged with DC power for two surge periods, C2 has only been charged with DC power for one surge period, C3 has just begun DC charging, and then C4 begins its inrush period. By the time C4 begins DC charging, C1's total charging time has not yet reached 1000ms. The DC power supply then simultaneously charges all four capacitors until C1's DC charging time expires first.

[0054] At this point, K1-2 of C1 is disconnected, K1-3 is connected, and C1 begins discharging, which lasts for 1000mS. Shortly after C1's time is up, C2's time is up, and K-3 also begins the discharge phase, which lasts for 1000mS, until C3 and C4 successively begin the discharge phase. At this point, all four capacitors are in the discharge phase. Until C1 takes the lead in completing the first charge and discharge cycle of the entire surge test and then begins the charge and discharge cycle of the second surge test, the other capacitors also successively begin their own second test cycles. This process is repeated 10 times, and each capacitor has completed 10 current surge tests. The total time to complete the test process of the four capacitors is about 20 seconds, which is comparable to the total time of using four surge sources to perform surge tests on four capacitors simultaneously in the prior art, but the surge power supply of the present invention only uses one.

[0055] In summary, the present invention's device for improving the efficiency of capacitor current surge testing requires only one surge power supply and one DC power supply. Using a time-sharing switching method, one surge power supply provides current surges for multiple capacitors. This means that a single, fully functional current surge source is shared by multiple capacitors within a group. Furthermore, one DC power supply can also serve multiple groups of multiple capacitors, providing DC power to a greater number of capacitors simultaneously. Therefore, the present invention can significantly improve the efficiency of capacitor current surge testing at a limited cost.

[0056] At this point, those skilled in the art will recognize that, although a number of exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications consistent with the principles of the present invention may be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the present invention. Therefore, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.

Claims

1. A device for improving the efficiency of a capacitor current surge test, characterized in that: A current surge test circuit includes: a DC power supply, a surge power supply, and multiple capacitors connected in parallel; each capacitor is connected to the surge power supply and the DC power supply through two independent circuits, the first circuit connected to the surge power supply is provided with a first switch, and the second circuit connected to the DC power supply is provided with a second switch; The first switch of a capacitor is opened after being closed for a first time period. At the same time as the first switch is opened, the second switch of the capacitor is closed and opened after a second time period. After the first switch is closed for an interval of time, the first switch of the next capacitor is closed and opened after a first time period. Each capacitor in the current surge test circuit undergoes a process of closing and opening the first switch and the second switch thereof, so that the surge power supply and the DC power supply charge each capacitor.

2. The device for improving the efficiency of a capacitor current surge test according to claim 1, characterized in that: A set of current surge test circuits also includes: multiple resistors; each capacitor is connected to a resistor through an independent third circuit, and the third circuit is provided with a third switch; the second switch of a capacitor is opened after being closed for a second time period, and at the same time as being opened, the third switch of the capacitor is closed and opened after a third time period, so that the capacitor is discharged.

3. The device for improving the efficiency of a capacitor current surge test according to claim 2, characterized in that: The first duration ranges from 10ms to 100ms, the second duration ranges from 990ms to 900ms, the third duration is the sum of the first duration and the second duration, and the interval duration is greater than or equal to 20ms.

4. The device for improving the efficiency of a capacitor current surge test according to claim 2 or 3, characterized in that: In the current surge test circuit, the third switch of the first capacitor is closed for a third time and then disconnected to complete a complete charge and discharge cycle; at the same time, the first switch of the first capacitor is closed again to start the next charge and discharge cycle.

5. The device for improving the efficiency of a capacitor current surge test according to claim 4, characterized in that: The number of charge and discharge cycles for each capacitor is at least 10 times.

6. A method for improving the efficiency of a capacitor current surge test, comprising: using the current surge test circuit of claim 1; wherein a plurality of capacitors connected in parallel are arranged in sequence; and wherein the method for improving the test efficiency comprises the following steps: S1: Close the first switch of a capacitor to allow the surge power to charge the capacitor; S2: Determine whether the closing time of the first switch of the capacitor reaches the first time length. If so, proceed to S3. If not, the surge power supply continues to charge the capacitor. S3: Disconnect the first switch of the capacitor and proceed to S4a and S4b respectively; S4a: while the capacitor is disconnected, the second switch of the capacitor is closed, so that the DC power supply charges the capacitor, and the second switch of the capacitor is disconnected after the second time period; S4b: Determine whether this capacitor is the last capacitor in the sequence. If so, end the loop. If not, proceed to S5b. S5b: After the disconnection interval, the next capacitor is charged and the process returns to S1 until each capacitor in the circuit has experienced the process of its first switch closing and opening. The current surge test circuit further includes: a plurality of resistors, each capacitor is connected to a resistor via an independent third circuit, and the third circuit is provided with a third switch; after S4a, the method for improving test efficiency further includes the following steps: S5a: After the second switch of the capacitor is turned off, the third switch of the capacitor is closed and turned off after a third time period, so that the capacitor is discharged.

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