A method for on-line detection of operating state of buck converter in CCM mode

Abstract

The application discloses a kind of Buck converter operating state online detection methods under CCM mode, parallel a known capacity capacitor at the output of Buck converter, collect the output voltage ripple before parallel capacitor and the output voltage ripple after parallel capacitor, then combine the average value of output voltage, the parameter of output filter capacitor can be calculated, and the performance of switching power supply will not be affected by parallel capacitor;Without additional excitation auxiliary measurement, without disassembling power supply, the operating state of Buck converter can be detected online, and Buck converter is not impacted in any way;In the long-term operation process of Buck converter, the working state and aging condition of Buck converter can be judged according to the parameter of capacitor, to achieve the purpose of Buck converter fault detection.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply fault detection technology, specifically relating to an online detection method for the operating status of a Buck converter in CCM mode. Background Technology

[0002] Switching power supplies are widely used in electronic products due to their advantages, and their proper functioning directly affects the safety of power electronic equipment. Buck converters are a commonly used main topology for switching power supplies. Buck converters generally operate in two modes: CCM (Continuous Computational Management) and DCM (Distributed Computational Management). The output filter capacitor has a significant impact on the overall performance of the converter, and during use, the capacitance value is prone to decrease, while the equivalent series resistance (ESR) increases. Degradation of capacitor parameters leads to a decrease in the performance of the Buck converter; when the capacitor parameters degrade to the point where they can no longer maintain normal operation, the Buck converter fails. The output capacitor is the weakest link and core component of the Buck converter. Detecting the capacitance value (C) and the equivalent series resistance (ESR) of the output capacitor in the Buck converter topology directly relates to the lifespan and failure characteristics of the Buck converter. Currently, there is a lack of methods for detecting the operating status of Buck converters; therefore, existing technologies need improvement. Summary of the Invention

[0003] In view of this, the present invention provides an online detection method for the operating status of a Buck converter in CCM mode, which is applicable to AC-DC and DC-DC Buck converters in various CCM modes.

[0004] This invention is achieved through the following technical solution:

[0005] An online detection method for the operating status of a Buck converter in CCM mode, the specific steps of which are as follows:

[0006] Step 1: During normal operation of the Buck converter, acquire the output voltage ripple signal v of the Buck converter. o (t) and average output voltage V o And calculate any one or more switching periods T s The output voltage difference Δv at times t1 and t3 oc3 and output voltage ripple Δv o ;

[0007] Step 2: Connect a capacitor with a known capacitance value C in parallel to the output of the Buck converter. m After the capacitor is removed, the output voltage ripple signal v of the Buck converter is then acquired. om (t) and average output voltage V o And calculate any one or more switching periods T sThe output voltage difference Δv at times t1 and t3 ocm3 ;

[0008] Step 3: Based on the capacitance value C of the parallel capacitor m The output voltage ripple signal v of the Buck converter before the capacitor o (t), find the duty cycle D and switching frequency f of the Buck converter. s reuse Calculate the size of const1;

[0009] Step 4: Based on the capacitance value C of the parallel capacitor m The output voltage ripple signal v of the Buck converter after the capacitor om (t), find the new duty cycle D of the Buck converter. m reuse Calculate the size of const2;

[0010] Step 5: Utilize Calculate the capacitance C of the output filter capacitor of the Buck converter;

[0011] Step 6: Utilize Calculate the equivalent series resistance (ESR) of the output filter capacitor of the Buck converter;

[0012] Step 7: Detect the operating status of the Buck converter based on the capacitance value C of the output filter capacitor, the standard capacitance value of the capacitor, the resistance value ESR of the equivalent series resistance, and the standard resistance value of the equivalent series resistance.

[0013] Furthermore, in step 5, The calculation process is as follows:

[0014] From v o (t1) to v o (t3), there is a relationship between the output voltage and the capacitor current, as shown in equation (2).

[0015]

[0016] In the formula, v o (t3) represents the output voltage at time t3, v o (t1) represents the output voltage at time t1, i c (t1) represents the capacitor current at time t1, i c (t3) is the capacitor current at time t3, ESR is the resistance of the equivalent series resistance, and C is the capacitance of the filter capacitor C.

[0017] In equation (2), due to the choice of i c (t1)=i c(t3)=0, which can eliminate the effect of ESR, and Equation (2) becomes Equation (3); at this time, the capacitance value of the filter capacitor C of the Buck converter can be derived as shown in Equation (4), and the capacitor current ripple is shown in Equation (5).

[0018]

[0019]

[0020] Δi C =8f s Δv oC3 C (5)

[0021] In the formula, ΔQ represents the change in charge of the output filter capacitor from time t1 to time t3. Δv oC3 Let Δv be the output voltage difference between time t1 and time t3. oC3 =v o (t3)-v o (t1), Δi C This refers to capacitor current ripple.

[0022] The ripple of the inductor current is known to be expressed as Equation (6). Since the ripple change of the load current is ignored, the ripple of the inductor current is equal to the ripple of the capacitor current. Then, the product of the filter inductor and filter capacitor of the Buck converter can be derived from Equations (5) and (6), as shown in Equation (7).

[0023]

[0024]

[0025] In the formula, Δi L The current ripple is the inductor current, and L is the inductance value of the filter inductor L.

[0026] A capacitor with a known capacitance value C is connected in parallel at the output of the Buck converter. m The expression for the product of the filter inductance and the filter capacitor is derived from equation (8). Since the inductance value of the filter inductance is fixed, the capacitance value of the filter capacitor of the Buck converter can be derived from equations (7) and (8) as shown in equation (9).

[0027]

[0028]

[0029] In the formula, D m To connect a known capacitance C in parallel at the output of the Buck converter mAfter the capacitor is removed, the duty cycle of the Buck converter in CCM mode; Δv oc3m To connect a known capacitance C in parallel at the output of the Buck converter m After the capacitor is installed, the output voltage difference between time t1 and time t3 is calculated.

[0030] Furthermore, in step 6, The calculation process is as follows:

[0031] From v o (t0) to v o (t2), the output voltage ripple Δv of the Buck converter o and capacitor current ripple Δi C The relationship between them is shown in Equation (10), and the ESR calculation can then be derived as shown in Equation (11).

[0032] v o (t2)-v o (t0)=v ESR (t2)-v ESR (t0)=Δv o =ESRΔi C (10)

[0033]

[0034] v o (t2) represents the output voltage at time t2, v o (t0) is the output voltage at time t0, v ESR (t2) is the equivalent series resistance voltage at time t2, v ESR (t0) is the equivalent series resistance voltage at time t0, Δvo is the output voltage ripple, and Δi C This refers to capacitor current ripple.

[0035] Furthermore, in step 7, the detection process for the operating state of the Buck converter is as follows:

[0036] Determine whether the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or determine whether the capacitance of the output filter capacitor is lower than the standard capacitance.

[0037] If the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or the capacitance of the output filter capacitor is lower than the standard capacitance, the Buck converter is malfunctioning; otherwise, the Buck converter is operating normally.

[0038] Furthermore, a switching cycle T s It includes the turn-on stage and the turn-off stage of the switching transistor.

[0039] Beneficial effects:

[0040] (1) The present invention proposes an online detection method for the operating status of a Buck converter in CCM mode. It only requires connecting a capacitor of known capacitance in parallel at the output terminal of the Buck converter, collecting the output voltage ripple before and after connecting the capacitor, and combining it with the average output voltage to calculate the parameters of the output filter capacitor. The parallel capacitor will not affect the performance of the switching power supply. The online detection of the operating status of the Buck converter can be performed without external excitation or power supply disassembly, without any impact on the Buck converter. During the long-term operation of the Buck converter, the working status and aging of the Buck converter can be judged based on the capacitor parameters, thus achieving the purpose of Buck converter fault detection.

[0041] (2) The method proposed in this invention is The calculation process is independent of the input signal at the front end of the Buck converter, and is only related to the voltage signal at the output end of the Buck converter and the parameters of the parallel capacitor. Therefore, this method is applicable to both AC-DC and DC-DC Buck converters with the main topology of the DC-DC converter module being CCM mode.

[0042] (3) The method proposed in this invention can detect the working status of the Buck converter and determine its fault status by measuring the capacitance value of the filter capacitor and the resistance value of the equivalent series resistance. By conducting long-term testing during the use of the power supply, the parameters of the capacitor at different usage times can be obtained. Based on the changes in the capacitor parameters, the aging status and lifespan of the power supply can be determined. Attached Figure Description

[0043] Figure 1 This is a basic structural diagram of a Buck converter;

[0044] Figure 2 The topology diagram of the switching transistors of the Buck converter is shown below.

[0045] Figure 3 This is the topology diagram of the Buck converter in the off-state of the switching transistors;

[0046] Figure 4 This is a schematic diagram of the electrical waveforms of the Buck circuit. Detailed Implementation

[0047] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0048] This embodiment provides an online detection method for the operating status of a Buck converter in CCM mode;

[0049] The basic structural diagram of the Buck converter is as follows: Figure 1 As shown, the input current of the Buck converter is i s The current through the filter inductor L is i L (Hereinafter referred to as inductor current), the current through the filter capacitor C is i C (Hereinafter referred to as capacitive current), through the load R L The current is i o (Hereinafter referred to as load current); the input voltage of the Buck converter is V. in The average output voltage of the Buck converter is V. o The average voltage across the filter capacitor C is the average output voltage V of the Buck converter. o .

[0050] When the MOSFET of the Buck converter is turned on, the topology of the Buck converter is as follows: Figure 2 As shown (dashed lines in the figure indicate disconnection), the topology of the Buck converter when the MOSFET is off is as follows. Figure 3 As shown in the figure (the dashed line indicates that the circuit is off), regardless of whether the MOSFET is on or off, the relationship between the various currents is as shown in equation (1):

[0051] i L =i C +i o (1)

[0052] The calculation process for the capacitance value of the filter capacitor C in the Buck converter is as follows:

[0053] When the Buck converter operates in CCM mode, the filter inductor and current have two operating modes (i.e., the MOSFET is on or off). The waveform diagrams of the electrical parameters of each component are shown below. Figure 4 As shown;

[0054] Buck converters always have ripple. When the switch is on, the output voltage rises and when the switch is off, the output voltage falls. Ignoring the ripple changes of the load current, the ripple of the capacitor current and the ripple of the inductor current are the same. For a Buck converter in CCM mode, the duty cycle is D.

[0055] At t0 = 0, the capacitor current reaches its trough; At t2 = DT, the capacitor current is 0; s At that time, the capacitor current reached its peak; When T is zero, the capacitor current is zero; where T s For switching cycles;

[0056] exist Figure 4 In the middle, from v o (t1) to v o (t3), there is a relationship between the output voltage and the capacitor current, as shown in equation (2).

[0057]

[0058] In the formula, v o (t3) represents the output voltage at time t3, v o (t1) represents the output voltage at time t1, i c (t1) represents the capacitor current at time t1, i c (t3) is the capacitor current at time t3, ESR is the resistance of the equivalent series resistance, and C is the capacitance of the filter capacitor.

[0059] In equation (2), due to the choice of i c (t1)=i c (t3)=0, which can eliminate the effect of ESR, and Equation (2) becomes Equation (3); at this time, the capacitance value of the filter capacitor C of the Buck converter can be derived as shown in Equation (4), and the capacitor current ripple is shown in Equation (5).

[0060]

[0061]

[0062] Δi C =8f s Δv oC3 C (5)

[0063] In the formula, ΔQ represents the change in charge of the output filter capacitor from time t1 to time t3. Δv oC3 Let Δv be the output voltage difference between time t1 and time t3. oC3 =v o (t3)-v o (t1), Δi C For capacitor current ripple, f s The switching frequency;

[0064] The ripple of the inductor current is known to be expressed as Equation (6). Since the ripple change of the load current is ignored, the ripple of the inductor current is equal to the ripple of the capacitor current. Then, the product of the filter inductor and filter capacitor of the Buck converter can be derived from Equations (5) and (6), as shown in Equation (7).

[0065]

[0066]

[0067] In the formula, Δi L This represents the inductor current ripple, where L is the inductance value of the filter inductor L; const1 has no specific meaning.

[0068] A capacitor with a known capacitance value C is connected in parallel at the output of the Buck converter. m The expression for the product of the filter inductance and the filter capacitor is derived from equation (8). Since the inductance value of the filter inductance is fixed, the capacitance value of the filter capacitor of the Buck converter can be derived from equations (7) and (8) as shown in equation (9).

[0069]

[0070]

[0071] In the formula, D m To connect a known capacitance C in parallel at the output of the Buck converter m After the capacitor is removed, the duty cycle of the Buck converter in CCM mode; Δv oc3m To connect a known capacitance C in parallel at the output of the Buck converter m After the capacitor is applied, the output voltage difference between time t1 and time t3; const2 has no specific meaning;

[0072] The calculation process for the ESR (equivalent series resistance) of the filter capacitor C of the Buck converter is as follows:

[0073] For a Buck converter, the equivalent model of the output filter capacitor is a pure capacitor C and an equivalent series resistance ESR connected in series. Therefore, the output voltage consists of two parts: the pure capacitor voltage and the equivalent series resistance voltage.

[0074] like Figure 4 As shown, at t0 = 0, the voltage v across the equivalent series resistance is... ESR It reached its lowest value, while the voltage v of the pure capacitor... C The average value of the output voltage V o ;exist When, the voltage v of the equivalent series resistance ESR The voltage v of a pure capacitor is 0. C The trough was reached; at t2 = DT s When, the voltage v of the equivalent series resistance ESR It reached its peak value, while the voltage v of the pure capacitor... C The average value of the output voltage V o ;

[0075] From the above relationships, we can deduce that from v o (t0) to v o(t2), the output voltage ripple Δv of the Buck converter o and capacitor current ripple Δi C The relationship between them is shown in Equation (10), and the ESR calculation can then be derived as shown in Equation (11).

[0076] v o (t2)-v o (t0)=v ESR (t2)-v ESR (t0)=Δv o =ESRΔi C (10)

[0077]

[0078] v o (t2) represents the output voltage at time t2, v o (t0) is the output voltage at time t0, v ESR (t2) is the equivalent series resistance voltage at time t2, v ESR (t0) is the equivalent series resistance voltage at time t0, Δvo is the output voltage ripple, and Δi C This refers to capacitor current ripple.

[0079] The specific steps of the operating status detection method for the Buck converter in CCM mode are as follows:

[0080] Step 1: During normal operation of the Buck converter, acquire the output voltage ripple signal v of the Buck converter. o (t) and average output voltage V o And calculate any one or more switching periods T s The output voltage difference Δv at times t1 and t3 oc3 and output voltage ripple Δv o ; where one switching cycle T s This includes the turn-on phase and the turn-off phase of the switching transistor;

[0081] Step 2: Connect a capacitor of known capacitance C in parallel to the output of the Buck converter. m After the capacitor is removed, the output voltage ripple signal vo of the Buck converter is then acquired. m (t) and average output voltage V o And calculate any one or more switching periods T s The output voltage difference Δv at times t1 and t3 ocm3 ;

[0082] Step 3: Based on the capacitance value C of the parallel capacitor mThe output voltage ripple signal v of the Buck converter before the capacitor o (t), find the duty cycle D and switching frequency f of the Buck converter. s reuse Calculate the size of const1;

[0083] Step 4: Based on the capacitance value C of the parallel capacitor m The output voltage ripple signal v of the Buck converter after the capacitor om (t), find the new duty cycle D of the Buck converter. m reuse Calculate the size of const2;

[0084] Step5: Utilize Calculate the capacitance C of the output filter capacitor of the Buck converter;

[0085] Step 6: Utilize Calculate the equivalent series resistance (ESR) of the output filter capacitor of the Buck converter;

[0086] Step 7: Based on the capacitance value of the output filter capacitor, the standard capacitance value of the capacitor, the equivalent series resistance value, and the standard resistance value of the equivalent series resistance, check the operating status of the Buck converter (i.e., whether a fault has occurred). The detection process is as follows:

[0087] Determine whether the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or determine whether the capacitance of the output filter capacitor is lower than the standard capacitance.

[0088] If the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or the capacitance of the output filter capacitor is lower than the standard capacitance, the Buck converter is malfunctioning; otherwise, the Buck converter is operating normally.

[0089] In summary, the above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for online detection of the operating status of a Buck converter in CCM mode, characterized in that, The specific steps are as follows: Step 1: Acquire the output voltage ripple signal of the Buck converter during normal operation. and average output voltage And calculate any one or more switching cycles. Output voltage difference at times t1 and t3 and output voltage ripple ; Step 2: Connect a capacitor of known capacitance value in parallel with the output of the Buck converter. After the capacitor is removed, the output voltage ripple signal of the Buck converter is then collected. and average output voltage And calculate any one or more switching cycles. Output voltage difference at times t1 and t3 ; Step 3: Based on the capacitance value of the parallel capacitor Output voltage ripple signal of the Buck converter before the capacitor Find the duty cycle of the Buck converter. and switching frequency reuse Calculate Size; Step 4: Based on the capacitance value of the parallel capacitor Output voltage ripple signal of the Buck converter after capacitor Find the new duty cycle of the Buck converter. reuse Calculate Size; Step 5: Utilize Calculate the capacitance value of the output filter capacitor of the Buck converter. ; Step 6: Utilize Calculate the equivalent series resistance (ESR) of the output filter capacitor of the Buck converter; Step 7: Based on the capacitance value of the output filter capacitor The standard capacitance value, the equivalent series resistance (ESR), and the standard resistance value of the equivalent series resistance are used to detect the operating status of the Buck converter.

2. The online detection method for the operating status of a Buck converter in CCM mode as described in claim 1, characterized in that, In step 5, The calculation process is as follows: from to There is a relationship between the output voltage and the capacitor current, as shown in equation (2). （2） In the formula, for Output voltage at any given time for Output voltage at any given time for The capacitor current at time t, for The capacitor current at time t, C is the resistance value of the equivalent series resistance, and C is the capacitance value of the filter capacitor C. In equation (2), due to the choice The effect of ESR can be eliminated, and equation (2) becomes equation (3). At this time, the capacitance value of the filter capacitor C of the Buck converter can be derived as shown in equation (4), and the capacitor current ripple is shown in equation (5). （3） （4） （5） In the formula, for Time's up The change in charge of the output filter capacitor at any given time. = , for Time's up The output voltage difference at any given time. , This refers to capacitor current ripple. The ripple of the inductor current is known to be expressed as Equation (6). Since the ripple change of the load current is ignored, the ripple of the inductor current is equal to the ripple of the capacitor current. Then, the product of the filter inductor and filter capacitor of the Buck converter can be derived from Equations (5) and (6), as shown in Equation (7). （6） （7） In the formula, For inductor current ripple, For filter inductors L Sensitivity value; A capacitor of known capacitance is connected in parallel at the output of the Buck converter. The expression for the product of the filter inductance and the filter capacitor is derived from equation (8). Since the inductance value of the filter inductance is fixed, the capacitance value of the filter capacitor of the Buck converter can be derived from equations (7) and (8) as shown in equation (9). （8） （9） In the formula, To connect a capacitor of known capacitance value in parallel at the output of the Buck converter After the capacitor is removed, the duty cycle of the Buck converter in CCM mode is determined. To connect a capacitor of known capacitance value in parallel at the output of the Buck converter After the capacitor, Time's up The difference in output voltage at any given moment.

3. The online detection method for the operating status of a Buck converter in CCM mode as described in claim 2, characterized in that, In step 6, The calculation process is as follows: from to Output voltage ripple of the Buck converter and capacitor current ripple The relationship between them is shown in Equation (10), and the ESR calculation can then be derived as shown in Equation (11). （10） （11） for Output voltage at any given time for Output voltage at any given time for The equivalent series resistance voltage at time t. for The equivalent series resistance voltage at time t. For output voltage ripple, This refers to capacitor current ripple.

4. The online detection method for the operating status of a Buck converter in CCM mode as described in any one of claims 1-3, characterized in that, In step 7, the detection process for the operating status of the Buck converter is as follows: Determine whether the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or determine whether the capacitance of the output filter capacitor is lower than the standard capacitance. If the equivalent series resistance of the output filter capacitor is higher than the standard equivalent series resistance, or the capacitance of the output filter capacitor is lower than the standard capacitance, the Buck converter is malfunctioning; otherwise, the Buck converter is operating normally.

5. The online detection method for the operating status of a Buck converter in CCM mode as described in any one of claims 1-3, characterized in that, One switching cycle It includes the turn-on stage and the turn-off stage of the switching transistor.

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