A black box off-line switching power supply output capacitance detection method and medium

Abstract

The present invention provides a black box off-line switching power supply output capacitance detection method, comprising the following steps: S1, adding a detection current to the output end of the switching power supply; S2, synchronously collecting the output voltage signal and the detection current signal of the switching power supply; S3, judging the situation of the output end of the switching power supply, if there is a dummy load branch, then entering step S4, if there is a leakage current branch, then entering step S5, if there is neither a dummy load branch nor a leakage current branch, then entering step S6; S4, calculating the instantaneous current of the dummy load and the dummy load branch; S5, calculating the leakage current; S6, calculating the current of the output capacitor; S7, calculating the capacitance of the output capacitor; S8, calculating the ESR value of the output capacitor. The beneficial effects of the present invention are: considering the situation that the output end of the switching power supply may have a dummy load and a leakage current, the accuracy of the output capacitance detection is improved.

Description

Technical Field

[0001] The invention relates to a switching power supply, and in particular to a black box off-line switching power supply output capacitance detection method and medium. Background Art

[0002] The structure of the switching power supply is complex. When the AC-DC switching power supply converts AC power into constant DC power, it often contains multiple modules, and each module has a different topology. The DC-DC switching power supply is equivalent to a part of the AC-DC switching power supply. There are many types of DC-DC converters in the switching power supply, and there are inevitably various forms of filtering circuits at the output end. Some switching power supply topologies even have dummy loads. The existence of dummy loads increases the difficulty of black box detection of the output capacitor parameters of the switching power supply. The output end of the switching power supply often uses a large-capacitance electrolytic capacitor as the output capacitor. During the use of the capacitor, it is very easy for the capacitance to decrease and the equivalent series resistance to increase. The output capacitor is the weak link of the switching power supply and has a great impact on the performance of the entire switching power supply. Detecting the parameters of the output capacitor in the switching power supply is directly related to the failure of the power supply and its service life. Disassembling the switching power supply or removing the capacitor for detection may cause damage to the power supply.

[0003] In order to detect the parameters of the output capacitor in the switching power supply without disassembling the switching power supply or removing the capacitor, the inventor proposed CN114460488A, a non-intrusive black box offline switching power supply fault detection method, at an earlier stage. However, the method does not consider the possibility of false load and leakage current at the output end of the switching power supply, resulting in low accuracy of output capacitor detection.

[0004] Therefore, how to improve the accuracy of output capacitance detection is a technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0005] In order to solve the problems in the prior art, the present invention provides a black box offline switching power supply output capacitance detection method and medium.

[0006] The present invention provides a black box off-line switching power supply output capacitance detection method, comprising the following steps:

[0007] S1, add detection current to the output end of the switching power supply;

[0008] S2, synchronously collecting the output voltage signal and detection current signal of the switching power supply;

[0009] S3, judging the situation of the output end of the switching power supply, if there is a dummy load branch, proceeding to step S4, if there is a leakage current branch, proceeding to step S5, if there is neither a dummy load branch nor a leakage current branch, proceeding to step S6;

[0010] S4, calculating the instantaneous current of the dummy load and the dummy load branch, and then proceeding to step S6;

[0011] S5, calculate the leakage current, and then go to step S6;

[0012] S6. Calculate the current of the output capacitor;

[0013] S7. Calculate the capacitance of the output capacitor;

[0014] S8. Calculate the ESR value of the output capacitor, where ESR is the equivalent series resistance of the output capacitor.

[0015] S9. End.

[0016] As a further improvement of the present invention, in step S1, when the switching power supply is shut down, the voltage applied to the output terminal of the switching power supply is limited to a safe voltage range, and a detection current i is added to the output terminal of the switching power supply. s (t), until the output voltage remains constant, where the safety voltage limit value applied by the switching power supply is V c The output voltage is expressed as V L express;

[0017] In step S2, the output voltage u(t) signal and the detection current i of the switching power supply are synchronously collected. s (t)Signal.

[0018] As a further improvement of the present invention, in step S3, according to the output terminal voltage u(t) signal and the detection current i s The (t) signal classifies the output end of the switching power supply into the following three situations:

[0019] 1) There is a false load branch;

[0020] 2) There is a leakage current branch;

[0021] 3) There is neither a false load branch nor a leakage current branch.

[0022] As a further improvement of the present invention, in step S4, using Calculate the dummy load size and then use Calculate the instantaneous current of the dummy load, where R is the dummy load resistance, V L is the voltage stability value at the output end, I L is the current stable value, u(t) is the output voltage, i R (t) is the instantaneous current of the resistive dummy load.

[0023] As a further improvement of the present invention, in step S5, i leak (t) = I L Find the leakage current, where I L is the current stable value, i leak (t) is the leakage current.

[0024] As a further improvement of the present invention, in step S6, according to the classification of the output terminal of the switching power supply, the current i actually flowing through the output capacitor is calculated. c (t) size, where

[0025] As a further improvement of the present invention, when there is a false load branch, i c (t) = i s (t)-i R (t) Calculate, i s (t) is the detection current at the output end, i R (t) is the instantaneous current of the resistive dummy load; when there is a leakage current branch, i c (t) = i s (t)-i leak (t) Calculate, i s (t) is the detection current at the output end, i leak (t) is the leakage current;

[0026] When there is neither a false load branch nor a leakage current branch, use i c (t) = i s (t) Calculate, i s (t) is the detection current at the output end.

[0027] As a further improvement of the present invention, in step S7, during the charging phase of the output capacitor, any two time points at which the capacitor currents are equal are selected, and the output capacitor currents are charged. Find the output capacitor value,

[0028] Where C is the capacitance of the output capacitor, i c (t) is the actual current flowing through the output capacitor, t1 and t3 are the time points when the two capacitor currents are equal, and u(t1) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply corresponding to t1 and t3.

[0029] As a further improvement of the present invention, in step S8, during the charging phase of the output capacitor, any two time points at which the capacitor currents are not equal are selected, and the capacitance of the output capacitor is combined to use Find the ESR value of the capacitor,

[0030] Where ESR is the equivalent series resistance of the output capacitor, t2 and t3 are the time points when the two capacitor currents are not equal, u(t2) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply at t2 and t3, C is the capacitance of the output capacitor, i c (t) is the actual current flowing through the output capacitor, i c (t2) and i c (t3) is the instantaneous value of the current actually flowing through the output capacitor corresponding to the times t2 and t3.

[0031] The present invention also provides a medium, including a readable storage medium, wherein the readable storage medium stores execution instructions, and the execution instructions are used to implement the method when executed by a processor.

[0032] The beneficial effect of the present invention is that: through the above scheme, the possibility of false load and leakage current at the output end of the switching power supply is taken into consideration, and the accuracy of output capacitance detection is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other solutions can be obtained based on these drawings without paying creative work.

[0034] Figure 1 This is a schematic diagram of possible situations at the output end of a switching power supply.

[0035] Figure 2 This is a schematic diagram for detecting the capacitance and equivalent series resistance value of the output capacitor of the switching power supply.

[0036] Figure 3 This is a schematic diagram of the switching power supply output voltage and external detection current.

[0037] Figure 4 This is the current detection circuit diagram.

[0038] Figure 5 The present invention is a flow chart of a method for detecting output capacitance of a black box offline switching power supply. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0040] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the scope of protection of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0041] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0042] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation methods.

[0043] There are many types of switching power supplies with complex structures. Their output filters may be included in the DC-DC converter module, or they may use LC filters, or they may be a combination of multiple filter forms. Switching power supplies often use large-capacitance electrolytic capacitors for filtering. During the use of capacitors, parameter degradation is very likely to occur. At the same time, there may be a false load at the output end of the switching power supply. The presence of false loads increases the difficulty of output capacitor parameter detection.

[0044] The possible situations at the output of the switching power supply are as follows: Figure 1 As shown, it can be roughly divided into three types, namely, the situation where there is a dummy load branch, the situation where there is a leakage current branch, and the situation where there is no other current branch (that is, there is no dummy load and no leakage current branch). Figure 1 (a) in the figure indicates the presence of a false load branch. Figure 1 (b) in the figure indicates the presence of a leakage current branch. Figure 1 (c) in the figure indicates the case where there is no other current branch (i.e., there is no dummy load and no leakage current branch), where i s (t) is the set detection current, i R(t) is the current of the resistive dummy load, i c (t) is the actual current flowing through the output capacitor, i leak (t) is the leakage current, C is the capacitance of the output capacitor, ESR is the equivalent series resistance of the output capacitor, and R represents the dummy load.

[0045] Limit the voltage applied by the switching power supply to a safe voltage range, with V C It means that when a detection current is added to the output end of the switching power supply, when the output voltage no longer increases, the external detection current drops to 0, indicating that there are no other current branches at the output end of the switching power supply. When a detection current is added to the output end of the switching power supply, when the output voltage no longer increases, there is still a constant current at the output end, indicating that there is a dummy load branch or a leakage current branch at the output end of the switching power supply. When there are no other current branches at the output end of the switching power supply, under the condition that the capacitor current is constant, the output voltage increases linearly; when the capacitor current slowly drops to 0, the output voltage increases slowly. When there is a dummy load branch at the output end of the switching power supply, after adding a detection current to the output end of the switching power supply, the capacitor current will change with the change of the output voltage, and the output voltage does not increase linearly at this time. When there is a leakage current branch at the output end of the switching power supply, the output voltage phenomenon is similar to the situation without other current branches, except that the actual current passing through the capacitor will be lower than the set detection current.

[0046] Taking the case of a false load branch as an example, the output capacitor equivalent model of the switching power supply is composed of a capacitance C and an equivalent series resistance ESR in series. The output capacitor parameter detection schematic diagram is shown in the figure. Figure 2 As shown, where V L is the voltage regulation value at the output of the switching power supply, I L is the stable current value, u(t) is the voltage at the output of the switching power supply.

[0047] The schematic diagram of the switching power supply output voltage and external detection current is as follows Figure 3 As shown, when the switching power supply is shut down, a detection current i is added to the power output terminal. s (t), measure the output voltage u(t) of the switching power supply, and then the C and ESR of the output capacitor can be calculated. u(t) is the output voltage of the switching power supply, V L is the regulated voltage value of the switching power supply output voltage, I L is the current stable value, V ref is the reference voltage for detecting current, R s is the detection resistor for detecting current, V s (t) is the reference voltage of the actual detection current added to the output end of the switching power supply, and Q is the linear module.

[0048] The schematic diagram of the external detection current circuit is as follows Figure 4As shown, where V c Indicates the voltage limit value of the output terminal of the switching power supply, Q is the linear module, V ref is the reference voltage for detecting current, V s (t) represents the reference voltage of the actual detection current applied to the output of the switching power supply, R s is the detection resistor for detecting current. By controlling the reference voltage V ref The size of the actual detection current is measured at the same time. s (t), the actual applied detection current i s (t) is shown in formula (1). The detection current circuit mainly includes a current source module built using an operational amplifier, a linear module that uses a switch tube to adjust the voltage, and a switch power supply to be tested. The switch power supply to be tested can be connected to the high side position of the detection current circuit or to the low side position of the detection current circuit.

[0049]

[0050] Output capacitor value detection principle:

[0051] Limit the voltage applied to the output terminal of the switching power supply to within the safe voltage range, and add a detection current i to the output terminal of the switching power supply. s (t), the output voltage u(t) and the detection current i of the switching power supply are obtained by sampling with the sensor. s (t) signal. The switching power supply output voltage u(t) and the detection current i s (t) Waveform diagram Figure 3 As shown in the figure, when the detection current is added to the output end of the switching power supply, if the output voltage does not increase any more, there is still a stable current I at the output end. L , the output voltage shows a nonlinear increase, indicating that there is a false load branch at the output end of the switching power supply. L And the output voltage stability value V L The size of the dummy load resistor R at the output end of the switching power supply can be obtained, and the calculation of the dummy load resistor is shown in formula (2). During the charging process of the output capacitor, after the size of the dummy load resistor is calculated, the instantaneous current of the dummy load branch can be calculated as shown in formula (3), and the actual current flowing through the output capacitor is derived as shown in formula (4-1). If there is a leakage current branch at the output end of the switching power supply, the actual current flowing through the output capacitor is shown in formula (4-2). If there is no other current branch at the output end of the switching power supply, the actual current flowing through the output capacitor is shown in formula (4-3).

[0052]

[0053]

[0054] i c (t) = i s (t)-i R (t) (4-1)

[0055] i c (t) = i s (t)-i leak (t) (4-2)

[0056] i c (t) = i s (t) (4-3)

[0057] The relationship between the output voltage and the actual current flowing through the capacitor is shown in equation (5). During the output capacitor charging phase, any two points in time when the capacitor currents are equal are selected, as Figure 3 t1 and t3 in the above example, at this time i c (t1) = i c (t3), since the capacitor currents at these two moments are equal, the capacitance value can be directly calculated as shown in formula (6). c (t1) and i c (t3) is the instantaneous value of the current actually flowing through the output capacitor at the time t1 and t3, and u(t1) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply at the time t1 and t3. In practical applications, multiple groups of time points with equal current can be selected to calculate the capacitance of the capacitor, and then the average value can be calculated to reduce the error.

[0058]

[0059]

[0060] Output capacitor ESR detection principle:

[0061] In the capacitor charging stage, select any two time points where the capacitor currents are not equal, such as Figure 3 The ESR value of the capacitor is calculated using t2 and t3 in the figure. During the time period from t2 to t3, the relationship between the output voltage of the switching power supply and the actual current flowing through the capacitor is shown in equation (7). The integral value of the capacitor current during the time period from t2 to t3 is calculated, and the instantaneous currents at these two time points are substituted into equation (7). The ESR value can be deduced as shown in equation (8). c (t2) and i c(t3) is the instantaneous value of the current actually flowing through the output capacitor at t2 and t3, and u(t2) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply at t2 and t3. In practical applications, multiple groups of unequal current points can be selected to calculate the ESR value of the output capacitor, and the average value can be calculated to reduce the error. Therefore, according to the output voltage u(t) of the switching power supply and the external detection current i s (t), combined with the calculated output capacitor value, the ESR value of the output capacitor can be calculated.

[0062]

[0063]

[0064] like Figure 5 As shown, a black box offline switching power supply output capacitance detection method, the specific process is as follows:

[0065] Step 1: When the switching power supply is shut down, limit the voltage applied to the output terminal of the switching power supply to within the safe voltage range of the switching power supply to be tested, and add a detection current i to the output terminal of the switching power supply. s (t), until the output voltage remains constant. The safety voltage limit value applied by the switching power supply is V c The output voltage stability value is expressed as V L express.

[0066] Step 2: Synchronously collect the voltage u(t) signal and detection current i at the output of the switching power supply s (t)Signal.

[0067] Step 3: According to the output voltage signal u(t) and the detection current signal i s (t) The output end of the switching power supply is classified into the case where there is a false load branch, the case where there is a leakage current branch, and the case where there is no other current branch.

[0068] Step 4: If there is a false load branch, use Calculate the dummy load size and then use Calculate the instantaneous current of the dummy load; if there is a leakage current branch, use i leak (t) = I L Find the magnitude of the leakage current.

[0069] Step 5: According to the classification of the output end of the switching power supply, calculate the actual current i flowing through the output capacitor c (t) size, where i is used when there is a false load branch c (t) = i s (t)-iR (t) calculation, when there is a leakage current branch, use i c (t) = i s (t)-i leak (t) calculation, when there is no other current branch, use i c (t) = i s (t) Calculation.

[0070] Step 6: During the output capacitor charging phase, select any two points in time when the capacitor currents are equal, such as Figure 3 In t1 and t3, use Find the output capacitor value;

[0071] Step7: During the output capacitor charging phase, select any two points in time when the capacitor currents are not equal, such as Figure 3 In the example, t2 and t3 are combined with the output capacitor value to make use of Find the ESR value of the capacitor.

[0072] The present invention provides a black box off-line switching power supply output capacitance detection method, which has the following advantages:

[0073] (1) The black box offline switching power supply output capacitance parameter detection method proposed in the present invention is a non-invasive detection method, which does not require disassembly of the power supply, will not damage the structure of the switching power supply, and has no impact on the switching power supply;

[0074] (2) The detection method proposed by the present invention takes into account the possible existence of false load branches, leakage current branches and other current branches at the output end of the switching power supply DC-DC converter, and classifies and calculates the parameters of the output capacitor to make the measurement result more accurate;

[0075] (3) The detection method proposed by the present invention only needs to limit the voltage applied to the output end of the switching power supply to within the safe voltage range of the power supply to be tested, add a detection current to the output end of the switching power supply, and use the linear module of the detection current circuit to adjust the voltage without additionally controlling the magnitude of the detection current;

[0076] (4) The detection method proposed by the present invention is applicable to the capacitance and equivalent series resistance detection of almost all switching power supply output capacitors, is not affected by the topology changes in the DC-DC converter, and has a wide range of applications;

[0077] (5) The detection method proposed by this invention is based on the voltage u(t) at the output end of the switching power supply and the external detection current i s (t), the capacitance of the output capacitor and the equivalent series resistance can be calculated. The operation is convenient and the measurement accuracy is high.

[0078] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A black box offline switching power supply output capacitance detection method, characterized in that: The following steps are involved: S1, add detection current to the output end of the switching power supply; S2, synchronously collecting the output voltage signal and detection current signal of the switching power supply; S3, judging the situation of the output end of the switching power supply, if there is a dummy load branch, proceeding to step S4, if there is a leakage current branch, proceeding to step S5, if there is neither a dummy load branch nor a leakage current branch, proceeding to step S6; S4, calculating the instantaneous current of the dummy load and the dummy load branch, and then proceeding to step S6; S5, calculate the leakage current, and then go to step S6; S6. Calculate the current of the output capacitor; S7. Calculate the capacitance of the output capacitor; S8. Calculate the ESR value of the output capacitor, where ESR is the equivalent series resistance of the output capacitor. S9, end; In step S1, when the switching power supply is shut down, the voltage applied to the output terminal of the switching power supply is limited to a safe voltage range, and a detection current i is added to the output terminal of the switching power supply. s (t), until the output voltage remains constant, where the safety voltage limit value applied by the switching power supply is V c The output voltage is expressed as V L express; In step S2, the output voltage u(t) signal and the detection current i of the switching power supply are synchronously collected. s (t) signal; In step S3, according to the output terminal voltage u(t) signal and the detection current i s The (t) signal classifies the output end of the switching power supply into the following three situations: 1) There is a false load branch; 2) There is a leakage current branch; 3) There is neither a false load branch nor a leakage current branch; In step S4, using Calculate the dummy load size and then use Calculate the instantaneous current of the dummy load, where R is the dummy load resistance, V L is the voltage stability value at the output end, I L is the current stable value, u(t) is the output voltage, i R (t) is the instantaneous current of the resistive dummy load; in step S5, ileak(t)=I L Find the leakage current, where I L is the current stable value, i leak (t) is the leakage current; In step S6, according to the classification of the output terminal of the switching power supply, the current i actually flowing through the output capacitor is calculated. c (t) size, where When there is a false load branch, use i c (t) = i s (t)-i R (t) Calculate, i s (t) is the detection current at the output end, i R (t) is the instantaneous current of the resistive dummy load; When there is a leakage current branch, use i c (t) = i s (t)-i leak (t) Calculate, i s (t) is the detection current at the output end, i leak (t) is the leakage current; When there is neither a false load branch nor a leakage current branch, use i c (t) = i s (t) Calculate, i s (t) is the detection current at the output end.

2. The black box offline switching power supply output capacitance detection method according to claim 1, characterized in that: In step S7, during the charging phase of the output capacitor, any two points in time when the capacitor currents are equal are selected, and the output capacitor currents are charged. Find the output capacitor value, Where C is the capacitance of the output capacitor, i c (t) is the actual current flowing through the output capacitor, t1 and t3 are the time points when the two capacitor currents are equal, and u(t1) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply corresponding to t1 and t3.

3. The black box off-line switching power supply output capacitance detection method according to claim 2, characterized in that: In step S8, during the charging phase of the output capacitor, any two time points at which the capacitor currents are not equal are selected, and the output capacitor capacitance is combined to obtain the output capacitor current. Find the ESR value of the capacitor, Where ESR is the equivalent series resistance of the output capacitor, t2 and t3 are the time points when the two capacitor currents are not equal, u(t2) and u(t3) are the instantaneous values ​​of the output voltage of the switching power supply at t2 and t3, C is the capacitance of the output capacitor, i c (t) is the actual current flowing through the output capacitor, i c (t2) and i c (t3) is the instantaneous value of the current actually flowing through the output capacitor corresponding to the times t2 and t3.

4. A readable storage medium, characterized in that: The readable storage medium stores execution instructions, which are used to implement the method according to any one of claims 1 to 3 when executed by a processor.

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