Capacitance value monitoring method, system and switching power supply device

Abstract

Embodiments of the present application provide a capacitor capacity monitoring method, system and switching power supply device. The capacitor capacity monitoring system comprises a PFC main circuit, which comprises a rectifying unit, a boosting unit, a to-be-monitored capacitor and a load. The to-be-monitored capacitor and the load are connected in parallel on both sides of the output end of the boosting unit. The capacitor capacity monitoring method comprises: determining an input voltage peak value, an input current peak value and an input frequency value corresponding to a first signal of the input end of the rectifying unit; and determining an output voltage parameter corresponding to a second signal of the output end of the boosting unit; and determining the capacity of the to-be-monitored capacitor according to the input voltage peak value, the input current peak value, the input frequency value and the output voltage parameter. In this way, the capacity of the output capacitor of the PFC circuit can be monitored at a lower cost, and the situation that the switching power supply cannot operate normally due to the failure to discover the failure of the output capacitor in time is avoided.

Description

Technical Field

[0001] This application relates to the field of circuit technology, and in particular to a method, system, and switching power supply device for monitoring capacitance value. Background Technology

[0002] A switching power supply is a capacitor-input type circuit. The phase difference between its current and voltage causes power loss during switching, which necessitates a power factor correction (PFC) circuit to improve the power factor. However, as the operating time of a switching power supply increases, its reliability and lifespan also decrease. As a crucial component of the switching circuit, the output capacitor of the PFC circuit is highly susceptible to failure because it frequently operates at high voltage. Once it fails, the switching power supply will malfunction.

[0003] Therefore, to ensure the normal operation of switching power supplies, it is often necessary to monitor the capacitance value of the output capacitor of the PFC circuit in actual production practice to determine whether it has failed. However, existing methods for monitoring the capacitance value of the output capacitor of PFC circuits require the addition of complex circuits or sensors, resulting in excessively high monitoring costs. Therefore, how to monitor the capacitance value of the output capacitor of PFC circuits at a low cost has become an urgent problem to be solved. Summary of the Invention

[0004] This application provides a capacitance value monitoring method, system, and switching power supply device to solve the problem of high cost in monitoring the output capacitance value of the PFC circuit in a switching power supply in the prior art.

[0005] To address the aforementioned problems, this application provides a capacitance value monitoring method applied to a capacitance value monitoring system. The system includes a PFC main circuit, comprising a rectifier unit, a boost unit, a capacitor to be monitored, and a load. The capacitor to be monitored and the load are connected in parallel across the output terminals of the boost unit. The capacitance value monitoring method includes: determining the peak value of the input voltage, the peak value of the input current, and the input frequency value corresponding to a first signal at the input terminal of the rectifier unit; determining the output voltage parameters corresponding to a second signal at the output terminal of the boost unit; and determining the capacitance value of the capacitor to be monitored based on the peak value of the input voltage, the peak value of the input current, the input frequency value, and the output voltage parameters.

[0006] In one embodiment, determining the output voltage parameter corresponding to the second signal at the output terminal of the boost unit includes: determining the voltage fluctuation difference and the real-time output voltage value corresponding to the second signal at the output terminal of the boost unit; determining the capacitance value of the capacitor to be monitored based on the input voltage peak value, input current peak value, input frequency value, and output voltage parameter includes: determining the capacitance value of the capacitor to be monitored based on the input voltage peak value, input current peak value, input frequency value, voltage fluctuation difference, and real-time output voltage value.

[0007] In one embodiment, determining the voltage fluctuation difference corresponding to the second signal at the output terminal of the boost unit includes: determining the maximum and minimum output voltage values ​​corresponding to the second signal at the output terminal of the boost unit; and determining the voltage fluctuation difference corresponding to the second signal at the output terminal of the boost unit based on the difference between the maximum and minimum output voltage values.

[0008] In one embodiment, determining the capacitance value of the capacitor to be monitored based on the peak input voltage, peak input current, input frequency, voltage fluctuation difference, and real-time output voltage includes: determining the capacitance value of the capacitor to be monitored using a preset calculation formula, wherein the preset calculation formula is:

[0009]

[0010] Among them, V P For the peak input voltage, I p ΔU is the peak value of the input current, f is the input frequency value, ΔU is the voltage fluctuation difference, and V0 is the real-time output voltage value.

[0011] In one embodiment, the method further includes: issuing an early warning in response to the capacitance value of the capacitor to be monitored meeting a set capacitance value condition; wherein the set capacitance value condition is determined by the initial capacitance value of the capacitor to be monitored.

[0012] To address the aforementioned problems, this application provides a capacitance value monitoring system, comprising: a PFC main circuit, which includes a rectifier unit, a boost unit, a capacitor to be monitored, and a load, wherein the capacitor to be monitored and the load are connected in parallel across the output terminals of the boost unit; and a monitoring circuit connected to the input terminal of the rectifier unit and the output terminal of the boost unit; wherein the monitoring circuit is configured to: sample a first signal at the input terminal of the rectifier unit, sample a third signal at the output terminal of the rectifier unit, and sample a second signal at the output terminal of the boost unit, and determine the capacitance value of the capacitor to be monitored according to the method described above.

[0013] In one embodiment, the monitoring circuit includes: a first sampling unit connected to the input terminal of a rectifier unit, used to sample the voltage of a first signal at the input terminal of the rectifier unit to obtain an input voltage value; a second sampling unit connected to the output terminal of the rectifier unit, used to sample the current of a third signal at the output terminal of the rectifier unit to obtain an input current value; a third sampling unit connected to the output terminal of a boost unit, used to sample the voltage of a second signal at the output terminal of the boost unit to obtain an output voltage parameter; and a processing unit connected to the first sampling unit, the second sampling unit, and the third sampling unit, configured to determine the capacitance value of the capacitor to be monitored according to the method described above.

[0014] In one embodiment, the first sampling unit includes: a first resistor, the first end of which is connected to the first input terminal of the rectifier unit, and the second end of which is connected to the processing unit; a second resistor, the first end of which is connected to the second input terminal of the rectifier unit, and the second end of which is connected to the processing unit; the second sampling unit includes: a first capacitor, the first end of which is connected to the second output terminal of the rectifier unit, and the second end of which is grounded; a third resistor, the first end of which is connected to the first end of the first capacitor, and the second end of which is grounded, and the first and second ends of which are connected to the processing unit; the third sampling unit includes: a fourth resistor, the first end of which is connected to the first output terminal of the boost unit, and the second end of which is connected to the processing unit; and a fifth resistor, the first end of which is connected to the first output terminal of the boost unit, and the second end of which is connected to the processing unit.

[0015] In one embodiment, the capacitance value monitoring system further includes: an early warning unit connected to the monitoring circuit, and the monitoring circuit is also used to control the early warning unit to issue an early warning when the capacitance value of the capacitor to be monitored meets the set capacitance value condition; wherein, the set capacitance value condition is determined by the initial capacitance value of the capacitor to be monitored.

[0016] To address the aforementioned issues, this application provides a switching power supply device, which includes the capacitor value monitoring system described above.

[0017] This application provides a capacitance value monitoring method applied to a capacitance value monitoring system. The system includes a PFC main circuit, comprising a rectifier unit, a boost unit, a capacitor to be monitored, and a load. The capacitor to be monitored and the load are connected in parallel across the output terminals of the boost unit. The capacitance value monitoring method includes: determining the peak input voltage, peak input current, and input frequency corresponding to a first signal at the input terminal of the rectifier unit; determining the output voltage parameters corresponding to a second signal at the output terminal of the boost unit; and determining the capacitance value of the capacitor to be monitored based on the peak input voltage, peak input current, input frequency, and output voltage parameters. Therefore, this application only needs to collect relevant parameters from the PFC main circuit to monitor the capacitance value of the output capacitor (i.e., the capacitor to be monitored) in the switching power supply in real time, without requiring additional complex circuits or sensors. This achieves low-cost monitoring of the output capacitor's capacitance value, avoiding situations where the switching power supply malfunctions due to the failure to detect output capacitor failure in a timely manner. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a flowchart illustrating a capacitance value monitoring method provided in this application;

[0020] Figure 2 This is a schematic diagram of the topology of an embodiment of the PFC main circuit provided in this application;

[0021] Figure 3 This is a comparative schematic diagram of the AC waveform after rectification unit 10 in one embodiment of this application;

[0022] Figure 4 This is a flowchart illustrating another capacitance value monitoring method provided in this application;

[0023] Figure 5 This is a schematic diagram of the capacitance value monitoring system provided in this application;

[0024] Figure 6 This is a schematic diagram of another capacitance value monitoring system provided in this application;

[0025] Figure 7 yes Figure 6 A circuit diagram of one embodiment of the first sampling unit;

[0026] Figure 8 yes Figure 6 A circuit diagram of one embodiment of the second sampling unit;

[0027] Figure 9 yes Figure 6 A circuit diagram of one embodiment of the third sampling unit;

[0028] Figure 10 This is a schematic diagram of the switching power supply device provided in this application. Detailed Implementation

[0029] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] "A and / or B" includes the following three combinations: A only, B only, and a combination of A and B.

[0032] The use of "applies to" or "configured to" in this application implies open and inclusive language, which does not exclude the applicability to or configuration to devices performing additional tasks or steps. Additionally, the use of "based on" implies openness and inclusivity, because processes, steps, calculations, or other actions "based on" one or more of the stated conditions or values ​​may in practice be based on additional conditions or values ​​beyond those stated.

[0033] In this application, the term "exemplary" is used to mean "used as an example, illustration, or description." Any embodiment described as "exemplary" in this application is not necessarily to be construed as being more preferred or advantageous than other embodiments. The following description is provided to enable any person skilled in the art to make and use this application. Details are set forth in the following description for purposes of explanation. It should be understood that those skilled in the art will recognize that this application can be made without using these specific details. In other instances, well-known structures and processes are not described in detail to avoid obscuring the description of this application with unnecessary detail. Therefore, this application is not intended to be limited to the embodiments shown, but is consistent with the broadest scope of the principles and features disclosed in this application.

[0034] Please see Figure 1 , Figure 1 This paper illustrates a flowchart of a capacitance value monitoring method provided in this application, applied to a capacitance value monitoring system. The capacitance value monitoring system includes a PFC main circuit 100, which comprises a rectifier unit 10, a boost unit 20, and a capacitor C to be monitored. out and load R LPlease refer to the topology of the PFC main circuit 100. Figure 2 .

[0035] Specifically, the rectifier unit 10 includes a rectifier bridge formed by a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The output terminal of the first diode D1 is connected to the output terminal of the third diode D3 and serves as the first output terminal of the rectifier unit 10. The output terminal of the second diode D2 is connected to the input terminal of the first diode D1 and serves as the first input terminal of the rectifier unit 10. The output terminal of the fourth diode D4 is connected to the input terminal of the third diode D3 and serves as the second input terminal of the rectifier unit 10. The input terminals of the second diode D2 and the fourth diode D4 are grounded (GND).

[0036] Specifically, the boost unit 20 includes an inductor L, a fifth diode D5, and a switch Q. The first terminal of the inductor L is connected to the first output terminal of the rectifier unit 10; the input terminal of the fifth diode D5 is connected to the second terminal of the inductor L, and the output terminal of the fifth diode D5 is connected to the load R. L The capacitor to be monitored, C out The first terminal is connected to the output terminal of the fifth diode D5, and the capacitor to be monitored is C. out The second terminal of the switch is grounded; the first terminal of the switch Q is connected to the second terminal of the inductor L, the second terminal of the switch Q is grounded, and the control terminal of the switch Q is used to receive control signals to achieve conduction or cutoff. It can be understood that in the embodiments of this application, the rectifier unit 10 and the boost unit 20 are components of the PFC circuit, and the PFC circuit is a component of the PFC main circuit 100.

[0037] In some implementations, the switch Q can be an NMOS transistor, whose control terminal is connected to a processing unit (such as an MCU, microcontroller) to receive control signals sent by the processing unit. If the control signal is a high-level signal "1", the switch Q is turned on; if the control signal is a low-level signal "0", the switch Q is turned off.

[0038] It should be noted that, Figure 2 The topology shown is merely an example; the rectifier unit 10 and boost unit 20 can have any topology, therefore other topologies of the rectifier unit 10 and boost unit 20 are also applicable to this application. Meanwhile, the load R... L It can be the load resistance equivalent to any topology.

[0039] The capacitance value monitoring method includes at least steps S110 to S130, as detailed below:

[0040] Step S110: Determine the peak value of the input voltage, the peak value of the input current, and the input frequency value corresponding to the first signal at the input terminal of the rectifier unit.

[0041] Among them, such as Figure 2 As shown, the first signal is the signal input to the rectifier unit 10 in the PFC main circuit 100, specifically the signal input between the input of the first diode D1 (output of the second diode D2) and the input of the third diode D3 (output of the fourth diode D4). Understandably, the input of the rectifier unit 10 is generally connected to AC mains power. Therefore, the first signal is AC. The input of the rectifier unit 10 can also incorporate circuit structures such as a common-mode inductor to filter common-mode electromagnetic interference signals, which will not be elaborated here.

[0042] Alternating current (AC) refers to electric current whose direction changes periodically with time. The average current within one cycle is zero, and the waveform of AC is typically a sine curve. The characteristic parameters of AC generally include voltage, current, and frequency. The frequency of AC refers to the number of periodic changes it undergoes per unit time, measured in Hertz (Hz), and is inversely related to the period.

[0043] Wherein, the peak input voltage is the maximum voltage value determined after multiple voltage samplings within one voltage ripple cycle of the first signal; the peak input current is the maximum current value determined after multiple current samplings within one current ripple cycle of the first signal; and the input frequency value is the input AC voltage V. in Or alternating current I in The number of times a periodic change is completed per unit of time.

[0044] Step S120: Determine the output voltage parameters corresponding to the second signal at the output terminal of the boost unit.

[0045] Among them, such as Figure 2 As shown, the second signal is the signal output from the boost unit 20 in the PFC main circuit 100, specifically the signal from the output of the fifth diode D5. In other words, it is the signal from the capacitor C to be monitored. out The signal or load R at the first end L The signal at the first terminal. Understandably, the direction of the second signal output by the boost unit 20 remains unchanged, but its amplitude still changes continuously based on the period of the alternating current. Therefore, the output voltage corresponding to the second signal is constantly changing.

[0046] Furthermore, due to the control of switch Q, when switch Q is turned off, the output terminal of boost circuit 20 normally outputs voltage to the load R. L And the capacitor C to be monitored out When charging, when switch Q is turned on, the voltage between inductor L and fifth diode D5 is pulled low, and the capacitor C under monitoring is no longer monitored. out Charging is initiated, but due to the unidirectional conductivity of the fifth diode D5, the capacitor C to be monitored... outThe voltage at the first terminal remains unchanged for the time being, controlled by the capacitor C to be monitored. out For load R L Provide voltage.

[0047] The output voltage parameter is a parameter obtained by sampling the voltage of the second signal, including the voltage fluctuation difference and the real-time output voltage value. Therefore, the step of determining the voltage fluctuation difference corresponding to the second signal at the output of the boost unit includes: determining the maximum and minimum output voltage values ​​corresponding to the second signal at the output of the boost unit; and determining the voltage fluctuation difference corresponding to the second signal output from the output of the boost unit based on the difference between the maximum and minimum output voltage values.

[0048] The real-time output voltage value is the voltage value obtained by real-time voltage sampling of the second signal, and this real-time output voltage is continuously updated with the sampling frequency (sampling time); the voltage fluctuation difference is the difference between the maximum and minimum voltage values ​​within one voltage ripple cycle when the second signal is sampled.

[0049] In this embodiment, the order of steps S110 and S120 is not limited. Steps S110 and S120 can be executed sequentially according to a preset order, or they can be executed simultaneously.

[0050] Step S130: Determine the capacitance value of the capacitor to be monitored based on the peak input voltage, peak input current, input frequency, and output voltage parameters.

[0051] Specifically, in this embodiment, after determining the peak input voltage, peak input current, input frequency, and output voltage parameters in real time, the capacitance monitoring system can determine the capacitance C to be monitored by performing relevant calculations on these parameters. out Real-time capacitance value.

[0052] Furthermore, since the output voltage parameters include the voltage fluctuation difference and the real-time output voltage value, the capacitance value of the capacitor to be monitored can be determined based on the peak input voltage, peak input current, input frequency, voltage fluctuation difference, and real-time output voltage value. Specifically, after determining the peak input voltage, peak input current, input frequency, voltage fluctuation difference, and real-time output voltage value, the capacitance value monitoring system calculates the capacitance C to be monitored using a preset calculation formula. out Real-time capacitance value C.

[0053] The preset calculation formula is as follows:

[0054]

[0055] Among them, V P For the peak input voltage, Ip ΔU is the peak value of the input current, f is the input frequency value, ΔU is the voltage fluctuation difference, and V0 is the real-time output voltage value.

[0056] The principle behind the above formula is explained below:

[0057] like Figure 2 As shown, when switch Q in the PFC main circuit 100 is turned on, the voltage at the input terminal of the fifth diode D5 is directly pulled down to "0". Only when switch Q is turned off does current flow through the fifth diode D5 and into the capacitor C to be monitored. out Let T be the on / off period of switch Q. off Given the time when switch Q is open, the time during which current flows through the fifth diode D5 is T. off / T.

[0058] like Figure 3 As shown, Figure 3 This is a comparative schematic diagram of the AC waveform after rectification unit 10 in one embodiment of this application. In this embodiment, the waveform of the first signal (AC) is a sine wave, i.e., the input voltage is V. in =V P *sin(ωt), input current is I in =I P *sin(ωt), where V P For the peak input voltage, I P Let ω be the peak value of the input current and ω be the angular frequency of the first signal. After rectification by the rectifier unit, the waveform of the first signal becomes an "m"-shaped wave, thus the waveform of the current output to the inductor L also becomes an "m"-shaped wave. Therefore:

[0059] The voltage of the intermediate signal (the signal at the output of the rectifier unit 10, or the signal at the input of the boost unit 20) after the first signal is rectified by the rectifier unit 10 is:

[0060] V out =V P *|sin(ωt)| (1)

[0061] The current of the intermediate signal after the first signal is rectified by rectifier unit 10 is:

[0062] I out =I P *|sin(ωt)| (2)

[0063] Furthermore, current only flows through the monitored capacitor C when switch Q is open, because the fifth diode D5 will only have current flowing through it. out Therefore, the final current flowing through the fifth diode D5 is:

[0064]

[0065] Among them, according to the boost formula Formula (3) can be rearranged as follows:

[0066]

[0067] Among them, V o The real-time output voltage value is the load R. L The voltage at both ends.

[0068] According to formula (1), V out =V P Therefore, formula (4) can be converted to: |sin(ωt)|.

[0069]

[0070] Simplifying formula (5), we get:

[0071]

[0072] Among them, according to the trigonometric function product-to-sum conversion formula Formula (6) can be rearranged as follows:

[0073]

[0074] Furthermore, by rearranging formula (7), we can obtain:

[0075]

[0076] It can be known that the current flowing through the fifth diode D5 is divided into an AC part and a DC part. Combining this with formula (8), we know that the AC part of the current flowing through the fifth diode D5 is... DC section is And based on the capacitor C to be monitored out Due to its characteristic of allowing alternating current and blocking direct current, the alternating current portion of the current flowing through the fifth diode D5 flows to the capacitor C to be monitored. out The DC portion of the current flowing through the fifth diode D5 flows to the load R. L Therefore, the flow is directed to the capacitor C to be monitored. out The current is:

[0077]

[0078] Furthermore, based on the capacitor C to be monitored out The ripple voltage and the capacitor C to be monitored out Current conversion formula It can be seen that the flow is directed to the capacitor C to be monitored. out Voltage U across the terminals Xfor:

[0079]

[0080] Where C is the capacitance to be monitored. out The capacitance value can be obtained by further integrating formula (10);

[0081]

[0082] According to formula (11), when sin 2ωt is equal to 1 and -1 respectively, the voltage U across capacitor C is... X The maximum and minimum values ​​were obtained respectively, therefore, the capacitor C to be monitored is... out Voltage U across the terminals X The maximum value of the fluctuation is:

[0083]

[0084] Simplifying formula (12) yields:

[0085]

[0086] For ΔU in formula (13) M Taking the absolute value and simplifying, we get:

[0087]

[0088] According to the conversion formula between angular frequency and frequency, ω=2πf, we know that:

[0089]

[0090] Among them, V P For the peak input voltage, I p ΔU is the peak value of the input current, f is the input frequency value, ΔU is the maximum value of the voltage fluctuation difference, and V0 is the real-time output voltage value.

[0091] Due to the capacitor C to be monitored out and load R L The capacitor C to be monitored is connected in parallel. out Voltage at both ends and load R L The voltage across is the same, and the capacitor C to be monitored is... out The voltage across the terminals is equal to the DC output voltage; therefore, the capacitor C to be monitored... out The maximum value of the voltage fluctuation across the two ends, ΔU M for:

[0092] ΔU M =V o_max -V o_min (16)

[0093] Among them, V o_max V represents the maximum value of the output voltage parameter. o_min This represents the minimum value of the output voltage parameter.

[0094] According to formula (16):

[0095]

[0096] It should be noted that the output voltage parameter V in formula (17) o The value should be the actual (real-time) value of the DC output voltage. When sampling error is not considered, the output voltage value V... o This can be a real-time sampled value, that is, the value of the capacitor C to be monitored is collected in real time. out The DC output voltage value is obtained by measuring the voltage at both ends. However, due to sampling errors, in some embodiments, the output voltage value V... o It can also be the average value of the DC output voltage obtained from multiple samplings.

[0097] In some embodiments, due to the calculation of the output voltage value V o The maximum value of the fluctuation needs to be obtained using the output voltage value V. o The maximum value and output voltage value V o The minimum value, while the acquired output voltage value V o When the peak value (maximum value) is reached, direct sampling results in a large error. Therefore, multiple points are sampled first to obtain multiple output voltage values ​​V. o The value is based on the multiple output voltage values ​​V collected. o Calculate the output voltage value V o The effective value (RMS value), and then based on the output voltage value V o Calculation of the effective value of DC output voltage V o The maximum value of the fluctuation.

[0098] In some embodiments, the DC output voltage V can be calculated according to the formula for calculating the peak / valley and RMS values ​​in sinusoidal alternating current. o Peak value (maximum value) and output voltage value V o The valley value (minimum value), the formula for calculating the peak / valley and RMS value in sinusoidal alternating current is:

[0099]

[0100] Where PEAK is the output voltage value V o Peak value and output voltage V o The absolute value of the valley, therefore:

[0101] Output voltage value V o The maximum value is:

[0102]

[0103] Output voltage value V o The minimum value is;

[0104]

[0105] The maximum value of the DC output voltage fluctuation is calculated using the formula for calculating the maximum voltage fluctuation value. The formula for calculating the maximum voltage fluctuation value is as follows:

[0106] ΔU M =V O_max -V O_min (twenty one)

[0107] Wherein, ΔU M The output voltage value V o The maximum value of the fluctuation, V O_Max The capacitor to be monitored, C out The peak value of the voltage across the terminals, V O_Min The capacitor to be monitored, C out The valley value of the voltage across the two ends.

[0108] According to formulas (19), (20), and (21):

[0109]

[0110] This embodiment provides a capacitance value monitoring method applied to a capacitance value monitoring system. The system includes a PFC main circuit, comprising a rectifier unit, a boost unit, a capacitor to be monitored, and a load. The capacitor to be monitored and the load are connected in parallel across the output terminals of the boost unit. The capacitance value monitoring method includes: determining the peak input voltage, peak input current, and input frequency corresponding to a first signal at the input terminal of the rectifier unit; determining the output voltage parameters corresponding to a second signal at the output terminal of the boost unit; and determining the capacitance value of the capacitor to be monitored based on the peak input voltage, peak input current, input frequency, and output voltage parameters. Therefore, this application only needs to collect relevant parameters from the PFC main circuit to monitor the capacitance value of the output capacitor (i.e., the capacitor to be monitored) in the switching power supply in real time, without requiring additional complex circuits or sensors. This achieves low-cost monitoring of the output capacitor's capacitance value, avoiding situations where the switching power supply cannot operate normally due to the failure to detect output capacitor failure in a timely manner.

[0111] Please see Figure 4 , Figure 4A flowchart illustrating another capacitance value monitoring method provided in this application is shown, applied to a capacitance value monitoring system. The method includes steps S210 to S240:

[0112] Step S210: Determine the peak value of the input voltage, the peak value of the input current, and the input frequency value corresponding to the first signal at the input terminal of the rectifier unit.

[0113] Step S220: Determine the output voltage parameters corresponding to the second signal at the output terminal of the boost unit.

[0114] Step S230: Determine the capacitance value of the capacitor to be monitored based on the peak input voltage, peak input current, input frequency, and output voltage parameters.

[0115] For a detailed description of steps S210 to S230, please refer to the description in the foregoing embodiments, which will not be repeated here.

[0116] Step S240: In response to the capacitance value of the capacitor to be monitored meeting the set capacitance value condition, an early warning reminder is issued.

[0117] The capacitance value setting is determined by the initial capacitance value of the capacitor to be monitored, which is the capacitance of the capacitor under normal operating conditions.

[0118] Specifically, the capacitance value of the capacitor under test meeting the set capacitance value condition can be: the capacitance value of the capacitor under test exceeding the set capacitance value range. The set capacitance value range has a first capacitance value as the upper limit and a second capacitance value as the lower limit. The first capacitance value = (initial capacitance value + 20% × initial capacitance value), and the second capacitance value = (initial capacitance value - 20% × initial capacitance value). In other words, when the capacitance value of the capacitor under test is detected to be greater than the first capacitance value or less than the second capacitance value, the capacitor under test in the PFC main circuit of the switching power supply is considered to have failed. An early warning should be issued to inform the user that the switching power supply is at risk of failure and should be replaced in a timely manner.

[0119] Furthermore, since the obtained parameters may contain errors, the range of capacitance values ​​can be increased to avoid generating false warnings. Specifically, the first capacitance value = (initial capacitance value + 25% × initial capacitance value), and the second capacitance value = (initial capacitance value - 25% × initial capacitance value).

[0120] This implementation not only achieves low-cost monitoring of the capacitance value of the output capacitor, but also provides early warning when the capacitance value of the monitored capacitor exceeds the set capacitance value range. This allows the user to be promptly reminded to replace the switching power supply when the capacitance value of the monitored capacitor is abnormal, effectively avoiding the situation where the switching power supply cannot operate normally due to the failure of the output capacitor to be detected in time.

[0121] Please see Figure 5 , Figure 5 This application provides a schematic diagram of the capacitance value monitoring system 600, which includes a PFC main circuit 100 and a monitoring circuit 200. Figure 2 The PFC main circuit 100 includes a rectifier unit 10, a boost unit 20, and a capacitor C to be monitored. out and load R L The capacitor to be monitored, C out and load R L Connected in parallel to both sides of the output terminal of the boost unit, its specific connection method and working principle can be found in [reference needed]. Figure 2 The specific implementation examples are not described here.

[0122] The monitoring circuit 200 is configured to: sample the first signal input to the input terminal of the rectifier unit 10 in the PFC main circuit 100, sample the third signal output to the rectifier unit 10, and sample the second signal output to the output terminal of the boost unit 20, and calculate the capacitor C to be monitored in the PFC circuit according to the method in the above embodiment. out The capacitance value.

[0123] Further as Figure 6 As shown, Figure 6 This is a schematic diagram of another capacitance value monitoring system provided in this application. The capacitance value monitoring system 600 includes a PFC main circuit 100 and a monitoring circuit 200. The monitoring circuit 200 includes a first sampling unit 211, a second sampling unit 212, a third sampling unit 213, and a processing unit 220.

[0124] The first sampling unit 211 is connected to the input terminal of the rectifier unit 10 in the PFC main circuit 100, and is used to sample the voltage of the first signal (AC signal) at the input terminal of the rectifier unit 10 to obtain the input voltage value. The second sampling unit 212 is connected to the output terminal of the rectifier unit 10 in the PFC main circuit 100, and is used to sample the current of the third signal at the output terminal of the rectifier unit 10 to obtain the input current value. The third sampling unit 213 is connected to the output terminal of the boost unit 20 in the PFC main circuit 100, and is used to sample the voltage of the second signal at the output terminal of the boost unit 20 to obtain the output voltage parameter. The processing unit 220 is connected to the first sampling unit 211, the second sampling unit 212, and the third sampling unit 213, and is configured to calculate the capacitance C to be monitored in the PFC main circuit 100 according to the method of the above embodiment. ou The capacitance value.

[0125] Optionally, the processing unit 220 mentioned above can be a chip with processing functions such as MCU (Microcontroller Unit), DSP (Digital Signal Processing), or single-chip microcomputer.

[0126] The first sampling unit 211, the second sampling unit 212, and the third sampling unit 213 are described below:

[0127] like Figure 7 As shown, Figure 7 yes Figure 6 A circuit diagram of an embodiment of the first sampling unit is shown. The first sampling unit 211 includes a first resistor R1 and a second resistor R2. The first end of the first resistor R1 is connected to the first input terminal (+ input terminal) of the rectifier unit 10, and the second end of the first resistor R1 is connected to the processing unit 220. The first end of the second resistor R2 is connected to the second input terminal (- input terminal) of the rectifier unit 10, and the second end of the second resistor R2 is connected to the processing unit 220.

[0128] Specifically, the processing unit 220 samples the first voltage on the live wire (i.e., the output terminal of the first diode D1) through the first resistor R1, and then samples the second voltage on the neutral wire (i.e., the input terminal of the second diode D2) through the second resistor R2. Then, it uses a comparator to determine the difference between the first and second voltages to determine the voltage value of the first signal at the input terminal of the rectifier unit 10. Finally, it uses multiple sets of voltage values ​​V obtained from historical sampling... in Then, based on multiple sets of voltage values ​​V in The maximum value in determines its peak value V. P .

[0129] like Figure 8 As shown, Figure 8 yes Figure 6 A circuit diagram of an embodiment of the second sampling unit is shown. The second sampling unit 212 includes a first capacitor C1 and a third resistor R3. The first end of the first capacitor C1 is connected to the second output terminal of the rectifier unit 10, and the second end of the first capacitor C1 is grounded. The first end of the third resistor R3 is connected to the first end of the first capacitor C1, and the second end of the third resistor R3 is grounded. The first end and the second end of the third resistor R3 are connected to the processing unit 220.

[0130] Specifically, the processing unit 220 samples the voltage across the third resistor R3, and then calculates the current flowing through the third resistor R3 using the formula I = U / R. Understandably, since the input current and output current of the rectifier unit 10 can be considered equal in this embodiment, the current flowing through the third resistor R3 can be taken as the input current value I of the rectifier unit 10.in Furthermore, multiple sets of input current values ​​I obtained through historical sampling... in The peak value I is determined based on the maximum value among them. P .

[0131] like Figure 9 As shown, Figure 9 yes Figure 6 A circuit diagram of an embodiment of the third sampling unit is shown. The third sampling unit 213 includes a fourth resistor R4 and a fifth resistor R5. The first end of the fourth resistor R4 is connected to the first output terminal of the boost unit 20, and the second end of the fourth resistor R4 is connected to the processing unit. The first end of the fifth resistor R5 is connected to the first output terminal of the boost unit 20, and the second end of the fifth resistor R5 is connected to the processing unit.

[0132] Specifically, the processing unit 220 samples the voltage at the first terminal of the load RL through the fourth resistor R4, or samples the voltage at the first terminal of the load RL through the fifth resistor R5, as the output voltage parameter. Understandably, the output voltage parameter includes the voltage fluctuation difference and the real-time output voltage value. The voltage fluctuation difference is obtained by the difference between the historically sampled maximum and minimum output voltages, and the real-time output voltage value is the latest sampled output voltage value.

[0133] Understandably, in this embodiment, setting a fourth resistor R4 and a fifth resistor R5 (two resistors) can sample two voltage values ​​for calculating the average value. In other embodiments, a single resistor can also be used for sampling.

[0134] In an optional embodiment, the capacitance value monitoring system 600 further includes an early warning unit connected to the monitoring circuit 200, specifically connected to the processing unit 220. The processing unit 220 is further configured to control the early warning unit to issue an early warning when the capacitance value of the capacitor under monitoring meets a set capacitance value condition. The method used to determine whether the capacitance value of the capacitor under monitoring meets the set capacitance value condition is similar to that described in the above embodiment, and will not be repeated here. The warning unit can use sound, light, or vibration to issue a warning.

[0135] Understandably, using a notification method makes it easier for users to know if the capacitance value of the capacitor under monitoring is abnormal, so that the switching power supply can be replaced in time, effectively avoiding the situation where the switching power supply cannot operate normally because the failure of the output capacitor is not detected in time.

[0136] See Figure 10 , Figure 10This is a schematic diagram of the structure of the switching power supply device provided in this application. The switching power supply device 800 includes a capacitor value monitoring system 600, which is the capacitor value monitoring system described in the above embodiments, and will not be repeated here.

[0137] The capacitance value monitoring method, system, and switching power supply device provided in the embodiments of this application have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method of monitoring a capacitance value, characterized by, The application is applied to a capacitor capacity monitoring system, the capacitor capacity monitoring system comprises a PFC main circuit, the PFC main circuit comprises a rectifier unit, a boost unit, a to-be-monitored capacitor and a load, the to-be-monitored capacitor and the load are connected in parallel on both sides of the output end of the boost unit, and the capacitor capacity monitoring method comprises: determining an input voltage peak value, an input current peak value and an input frequency value corresponding to a first signal of the input end of the rectifier unit; determining an output voltage parameter corresponding to a second signal of the output end of the boost unit; wherein the output voltage parameter comprises a voltage fluctuation difference value and a real-time output voltage value, and the voltage fluctuation difference value is determined according to a difference between the maximum output voltage value and the minimum output voltage value of the second signal in a voltage ripple cycle; according to the input voltage peak value, the input current peak value, the input frequency value, the voltage fluctuation difference value and the real-time output voltage value, a capacity of the to-be-monitored capacitor is calculated by using a pre-designed calculation formula, and the pre-designed calculation formula is: wherein, is the input voltage peak value, is the input current peak value, is the input frequency value, is the voltage fluctuation difference value, is the real-time output voltage value.

2. The capacitance value monitoring method according to claim 1, wherein the method further comprises: in response to the capacity of the to-be-monitored capacitor meeting a set capacity condition, a pre-warning is given; wherein the set capacity condition is determined by an initial capacity of the to-be-monitored capacitor.

3. A system for monitoring the capacitance of a capacitor, comprising: the capacitor capacity monitoring system comprises: a PFC main circuit, the PFC main circuit comprises a rectifier unit, a boost unit, a to-be-monitored capacitor and a load, the to-be-monitored capacitor and the load are connected in parallel on both sides of the output end of the boost unit; a monitoring circuit, the monitoring circuit is connected to the input end of the rectifier unit and the output end of the boost unit; wherein the monitoring circuit is configured to sample a first signal of the input end of the rectifier unit, sample a third signal of the output end of the rectifier unit and sample a second signal of the output end of the boost unit, and determine the capacity of the to-be-monitored capacitor according to the method in any one of claims 1-2.

4. The capacitance value monitoring system according to claim 3, characterized by the monitoring circuit comprises: a first sampling unit, the first sampling unit is connected to the input end of the rectifier unit, and is used for voltage sampling of the first signal of the input end of the rectifier unit to obtain an input voltage value; a second sampling unit, the second sampling unit is connected to the output end of the rectifier unit, and is used for current sampling of the third signal of the output end of the rectifier unit to obtain an input current value; a third sampling unit, the third sampling unit is connected to the output end of the boost unit, and is used for voltage sampling of the second signal of the output end of the boost unit to obtain an output voltage parameter; a processing unit, the processing unit is connected to the first sampling unit, the second sampling unit and the third sampling unit, and the processing unit is configured to determine the capacity of the to-be-monitored capacitor according to the method in any one of claims 1-2.

5. The capacitance value monitoring system according to claim 4, wherein the first sampling unit comprises: a first resistor, a first end of the first resistor is connected to a first input end of the rectifier unit, and a second end of the first resistor is connected to the processing unit; a second resistor, a first end of the second resistor is connected to a second input end of the rectifier unit, and a second end of the second resistor is connected to the processing unit; The second sampling unit comprises: a first capacitor, a first end of the first capacitor being connected to a second output end of the rectifying unit, and a second end of the first capacitor being grounded; a third resistor, a first end of the third resistor being connected to the first end of the first capacitor, a second end of the third resistor being grounded, and the first end and the second end of the third resistor being connected to the processing unit; The third sampling unit comprises: a fourth resistor, a first end of the fourth resistor being connected to a first output end of the boosting unit, and a second end of the fourth resistor being connected to the processing unit; a fifth resistor, a first end of the fifth resistor being connected to the first output end of the boosting unit, and a second end of the fifth resistor being connected to the processing unit.

6. The capacitance value monitoring system according to claim 3, wherein The capacitor capacity monitoring system further comprises: a pre-warning reminding unit, the pre-warning reminding unit being connected to the monitoring circuit, and the monitoring circuit being further configured to control the pre-warning reminding unit to perform pre-warning reminding when the capacity of the to-be-monitored capacitor meets a set capacity condition, wherein the set capacity condition is determined by an initial capacity of the to-be-monitored capacitor.

7. A switching power supply apparatus characterized by comprising: The switching power supply device comprises the capacitor capacity monitoring system according to any one of claims 3-6.

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