Capacitor degradation detection device, power supply device, and capacitor degradation detection method

Abstract

This invention provides a capacitor degradation detection device, a power supply device, and a capacitor degradation detection method that can accurately determine the degradation of a capacitor. [Solution] The capacitor degradation determination device comprises a power conversion circuit that converts an input voltage to a DC voltage based on predetermined control parameters, a capacitor connected to the output side of the power conversion circuit, a ripple voltage calculation unit that calculates the ripple voltage of the capacitor, and a determination unit that determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters.

Description

Technical Field

[0001] The present invention relates to a capacitor deterioration determination device, a power supply device, and a capacitor deterioration determination method.

Background Art

[0002] Some power supply devices such as a stabilized power supply device include an electrolytic capacitor on the output side of the power supply device or the like in order to suppress the ripple voltage of the output voltage. When the electrolytic capacitor of such a power supply device deteriorates, it becomes impossible to output a required voltage. Therefore, a technique for detecting the ripple voltage and determining the deterioration of the electrolytic capacitor has been developed.

[0003] Patent Document 1 discloses a method of extracting a ripple waveform of a capacitor, converting the extracted ripple waveform into a DC waveform, and comparing the converted DC waveform with a predetermined reference voltage to determine the presence or absence of deterioration of the capacitor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In order to stabilize the output voltage, such a power supply device has a configuration for controlling the on / off of a switching element inside the power supply device. In order to control the on / off of the switching element, control parameters such as a switching period and a duty value are adjusted. However, when these control parameters fluctuate, the ripple voltage also fluctuates, and there is a possibility that the deterioration of the capacitor cannot be determined.

[0006] This invention has been made in view of the above circumstances, and aims to provide a capacitor degradation detection device, a power supply device, and a capacitor degradation detection method that can accurately determine the degradation of a capacitor. [Means for solving the problem]

[0007] The present invention includes several means for solving the above problems, but to give one example, the capacitor degradation determination device comprises a power conversion circuit that converts an input voltage into a DC voltage based on predetermined control parameters, a capacitor connected to the output side of the power conversion circuit, a ripple voltage calculation unit that calculates the ripple voltage of the capacitor, and a determination unit that determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters. [Effects of the Invention]

[0008] According to the present invention, the degradation of a capacitor can be determined with high accuracy. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows a first example of the configuration of a power supply unit equipped with the capacitor degradation detection device of this embodiment. [Figure 2] This figure shows an example of the configuration of the ripple voltage calculation unit. [Figure 3] This diagram schematically shows an example of a capacitor voltage waveform. [Figure 4] This figure shows an example of a histogram. [Figure 5] This figure shows an example of the frequency difference between frequencies in a histogram. [Figure 6] This figure shows an example of a moving average of frequency differences. [Figure 7] This figure shows an example of a method for calculating ripple voltage. [Figure 8] This diagram schematically shows the relationship between the ripple voltage of a capacitor and its degree of degradation. [Figure 9] This is a diagram showing an example of the configuration of a power conversion circuit. [Figure 10] This is a diagram showing an example of control parameters. [Figure 11] This is a diagram showing an example of an equivalent circuit on the output side of the power conversion circuit. [Figure 12] This is a diagram showing an example of a method for correcting the ripple voltage when considering the duty value. [Figure 13] This is a diagram showing an example of a method for correcting the ripple voltage when considering the switching period. [Figure 14] This is a diagram showing an example of a method for calculating the ripple voltage when the power conversion circuit includes a PFC circuit. [Figure 15] This is a diagram showing a second example of the configuration of a power supply device including a capacitor deterioration determination device. [Figure 16] This is a diagram showing a third example of the configuration of a power supply device including a capacitor deterioration determination device. [Figure 17] This is a diagram showing a fourth example of the configuration of a power supply device including a capacitor deterioration determination device.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described based on the drawings showing embodiments. FIG. 1 is a diagram showing a first example of the configuration of a power supply device 150 including a capacitor deterioration determination device 100 according to the present embodiment. The capacitor deterioration determination device 100 includes a power conversion circuit 10, a capacitor 40 connected to the output side of the power conversion circuit 10, a microcomputer 30, and the like. An AC power supply is connected to the input side terminals P1 and P2 of the capacitor deterioration determination device 100. A load is connected to the output side terminals P3 and P4 of the capacitor deterioration determination device 100. The power supply device 150 includes the capacitor deterioration determination device 100. Specifically, the power supply device 150 may be configured to incorporate the capacitor deterioration determination device 100, or may be configured to externally attach the capacitor deterioration determination device 100 as an optional function.

[0011] The power conversion circuit 10 may be, for example, an AC / DC circuit or a DC / DC circuit. Hereinafter, in this specification, the power conversion circuit 10 will be described as an AC / DC circuit. The power conversion circuit (AC / DC circuit) 10 converts the input AC voltage into a DC voltage and supplies the converted DC voltage to a load.

[0012] The capacitor 40 is an electrolytic capacitor that removes noise from the DC voltage converted by the power conversion circuit 10 and smoothes the DC voltage.

[0013] The microcomputer 30 has functions as a processor and includes, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), an external interface (all not shown), etc., and can implement the functions of the power conversion circuit control unit 70, the ripple voltage calculation unit 50, and the degradation determination unit 60.

[0014] The power conversion circuit control unit 70 controls the operation of the power conversion circuit 10 based on predetermined control parameters. The power conversion circuit control unit 70 designates predetermined control parameters.

[0015] The ripple voltage calculation unit 50 calculates the ripple voltage of the capacitor 40.

[0016] The degradation determination unit 60 has functions as a determination unit and determines the degradation of the capacitor 40 based on the ripple voltage calculated by the ripple voltage calculation unit 50. The determination of degradation may be the presence or absence of degradation, or the degree of degradation may be represented by a numerical value or the like.

[0017] Next, a method for calculating the ripple voltage by the ripple voltage calculation unit 50 will be described.

[0018] FIG. 2 is a diagram showing an example of the configuration of the ripple voltage calculation unit 50. The ripple voltage calculation unit 50 includes an AD conversion unit 51, a histogram generation unit 52, and a statistical quantity calculation unit 53.

[0019] The AD conversion unit 51 samples the voltage waveform of the capacitor 40 at a predetermined sampling period and converts it into a digital value.

[0020] The histogram generation unit 52 generates a histogram showing the frequency of the digital values ​​converted by the AD conversion unit 51 at multiple time points.

[0021] The statistical calculation unit 53 calculates the statistical value of the frequency variation of the histogram generated by the histogram generation unit 52.

[0022] The ripple voltage calculation unit 50 calculates the ripple voltage based on the statistical quantities calculated by the statistical quantity calculation unit 53. This will be explained in detail below.

[0023] Figure 3 schematically shows an example of the voltage waveform of capacitor 40. As shown in Figure 3, the voltage waveform input to the microcontroller 30 (ripple voltage calculation unit 50) has the AC component voltage superimposed with the offset voltage and the ripple voltage (including the ripple noise component). Alternatively, an AC coupling circuit may be provided on the input side of the microcontroller 30 to remove the DC component from the voltage waveform of capacitor 40.

[0024] The AD conversion unit 51 samples the input voltage waveform (analog value) at a predetermined sampling period and converts it into a digital value. The AD conversion unit 51 has, for example, a resolution of 12 bits or less and a sampling rate of 1 Msps or less, but is not limited to these.

[0025] The voltage waveform input to the AD conversion unit 51 includes the AC component with the DC component removed and a ripple voltage. Therefore, the resolution can be effectively reduced by the absence of the DC component, making it possible to convert the voltage waveform (analog value) to a digital value even if the resolution of the AD conversion unit 51 is low.

[0026] The histogram generation unit 52 generates a histogram showing the frequency of the digital values ​​converted by the AD conversion unit 51 over a required period. The required period can be a period during which the number of samples of converted digital values ​​is equal to or greater than a predetermined value. The predetermined value can be, for example, 3000, 4000, or 5000, but is not limited to these. The predetermined value can be determined according to the sampling rate of the AD conversion unit 51, and it is sufficient to obtain a number of digital values ​​that enable statistical calculations. In other words, the AD conversion unit 51 coarsely samples the ripple waveform of the input voltage waveform, but by collecting digital values ​​at multiple points in time over the predetermined period, it is possible to obtain a number of samples equivalent to high-speed sampling within a short period using a high-performance, high-resolution AD converter.

[0027] Figure 4 shows an example of a histogram. The horizontal axis shows the range of digital values ​​converted by the AD conversion unit 51, divided into required sections, and the vertical axis shows the frequency (number) of digital values ​​belonging to each section. Note that the horizontal axis may use a different index instead of digital values. The histogram shown in Figure 4 shows the distribution of digital values ​​sampled at multiple time points.

[0028] The statistical calculation unit 53 calculates the frequency difference between adjacent digital values ​​in the histogram as the fluctuation, and calculates the moving average of the calculated frequency differences as the statistical quantity.

[0029] Figure 5 shows an example of the frequency difference in a histogram. The frequency difference can be calculated as the difference between the frequency of the digital value in a given category and the frequency of the digital value in the category to the right of that category. Figure 5 shows the frequency differences calculated and plotted for all categories in the histogram.

[0030] Figure 6 shows an example of a moving average of frequency differences. The moving average (statistic) of the frequency differences of each digital value is the average value of the frequency differences of the categories within a certain interval that includes that category. The moving average can be a central moving average, which uses the average value of the frequency differences of each category and the categories immediately before and after it; a backward moving average, which uses the average value of each category and the categories before it; or a forward moving average, which uses the average value of each category and the categories after it. By using a moving average, the values ​​of the frequency differences can be smoothed.

[0031] The ripple voltage calculation unit 50 identifies the minimum and maximum digital values ​​from the digital values ​​of the histogram in which the moving average (statistic) of the frequency difference exceeds a predetermined threshold, and calculates the difference between the identified maximum and minimum digital values ​​as the ripple voltage for the required period.

[0032] Figure 7 shows an example of a method for calculating ripple voltage. The horizontal axis shows the digital value (digital value for each section), and the vertical axis shows the moving average of the frequency difference. As shown in Figure 7, thresholds (+ threshold and - threshold) for the moving average are set, and the digital value at which the moving average of the frequency difference first exceeds the threshold (range of + threshold and - threshold) is identified as the minimum digital value. The moving average is then searched for towards the larger digital value, and the digital value at which the threshold (range of + threshold and - threshold) is finally exceeded is identified as the maximum digital value. The ripple voltage can be obtained by subtracting the minimum digital value from the maximum digital value.

[0033] Note that the method for calculating the ripple voltage is not limited to the method described in Figures 2-7, and other known methods may also be used.

[0034] Next, we will explain how to determine the degradation of a capacitor.

[0035] Figure 8 schematically shows the relationship between the ripple voltage and the degree of degradation of capacitor 40. In Figure 8, the horizontal axis represents the ripple voltage, and the vertical axis represents the degree of degradation. The degradation of capacitor 40 can be determined by whether or not it is degraded, or by a numerical value indicating the degree of degradation. As shown in Figure 8, the relationship between ripple voltage and the degree of degradation can be schematically represented by a straight line, for example. In practice, the relationship between ripple voltage and the degree of degradation can also be represented by a curve, but for convenience, it is represented by a straight line in this specification. As can be seen from Figure 8, as the ripple voltage increases, the degree of degradation of capacitor 40 also increases, and degradation progresses. A threshold Vth for the ripple voltage can be set, and if the ripple voltage is less than or equal to Vth, it can be determined that there is no degradation, and if the ripple voltage exceeds Vth, it can be determined that there is degradation. Alternatively, the degree of degradation can be expressed numerically according to the value of the ripple voltage, and the magnitude of the degradation can be determined according to the magnitude of the numerical value.

[0036] Next, the control parameters of the power conversion circuit 10 that affect the fluctuation of the ripple voltage of capacitor 40 will be described. The control parameters are parameters that determine the operation of the power conversion circuit 10, and the power conversion circuit 10 operates by converting AC voltage to DC voltage based on the control parameters.

[0037] Figure 9 shows an example of the configuration of the power conversion circuit 10. Figures 9A to 9C show the main examples of circuits that make up the power conversion circuit 10. Figure 9A is a circuit composed of a combination of a diode bridge and a DC / DC circuit, and includes a full-wave rectifier circuit 11 and a DC / DC circuit 12.

[0038] Figure 9B shows a circuit composed of a diode bridge and a PFC (Power Factor Correction) circuit, comprising a full-wave rectifier circuit 11 and a PFC circuit. The PFC circuit includes a coil (inductor) 13 and a switching element 14. By controlling the on / off state of the switching element 14, the energy stored in the coil 13 can be supplied to the load. In this case, by adjusting the switching frequency, or the on or off time (duty cycle) during switching, the output voltage can be controlled to a required voltage value, and the power factor can be improved by bringing the input current closer to a sine wave.

[0039] Figure 9C shows a bridgeless PFC circuit, which comprises two input coils (inductors) 15 and 16, and switching elements 21, 22, 23, and 24. By controlling the on / off state of the switching elements 21 to 24, the energy stored in coils 15 and 16 can be supplied to the load. In this case, by adjusting the switching frequency, or the on or off time (duty cycle) during switching, the output voltage can be controlled to a required voltage value, and the input current can be made closer to a sine wave to improve the power factor.

[0040] Figure 10 shows an example of control parameters. The control parameters include the switching period (which may also be the switching frequency) and the duty cycle (which may also be the duty cycle ratio). Figure 10 illustrates a rectangular switching waveform. The switching period T1 is the period during which the switching elements in the power conversion circuit 10 are turned on and off.

[0041] Furthermore, the duty cycle value that determines the on-time (or off-time) of a switching element can be set to a smaller value D1 to shorten the on-time, and a larger value D2 to lengthen the on-time. The same applies to the off-time of the switching element.

[0042] Alternatively, the switching period of the switching element may be changed. In this case, the duty cycle may be fixed, and the switching period may be changed between T1 and T2.

[0043] Next, we will explain how the ripple voltage varies depending on the control parameters.

[0044] Figure 11 shows an example of the equivalent circuit on the output side of the power conversion circuit 10. The equivalent circuit on the output side of the power conversion circuit 10 can be represented as shown in Figure 11, where L is the inductance, Zc is the impedance of capacitor 40, and Z is the impedance of the load, as viewed from the output side of the power conversion circuit 10. The current flowing through the inductance L is ΔI. L Let ΔIc be the current flowing through capacitor 40, and ΔIz be the current flowing through the load. Also, let Vr be the ripple voltage of capacitor 40.

[0045] ΔI L is ΔI L =V L It can be expressed as D·T / L. Here, V L ΔI is the voltage across inductance L, D is the duty cycle, T is the switching period, and L is the inductance. L =ΔIc+ΔIz, and since Vr=ΔIc·Zc=ΔIz·Z, Vr=ΔI L The formula becomes {Zc·Z} / [Zc+Z]. In other words, when the duty cycle D and the switching period T change, the ripple voltage Vr also changes.

[0046] In environments where the control parameters of the power conversion circuit 10, such as the duty cycle and switching period, fluctuate (for example, fluctuations in input voltage or load), the ripple voltage of the capacitor 40 also changes, making it difficult to accurately determine the degradation of the capacitor 40. In this embodiment, the degradation of the capacitor 40 can be accurately determined. This point will be explained below.

[0047] As described above, the capacitor degradation determination device 100 includes a power conversion circuit 10 that converts the input voltage to a DC voltage based on predetermined control parameters, a capacitor 40 connected to the output side of the power conversion circuit 10, and a ripple voltage calculation unit 50 that calculates the ripple voltage of the capacitor 40. The degradation determination unit 60 can determine the degradation of the capacitor 40 based on the ripple voltage calculated by the ripple voltage calculation unit 50 and the control parameters. Specifically, the degradation of the capacitor 40 can be determined with high accuracy by correcting the ripple voltage based on the control parameters. The predetermined control parameters are specified by the power conversion circuit control unit 70 in the microcontroller 30.

[0048] By considering the control parameters, the degradation of capacitor 40 can be determined with greater accuracy compared to when the control parameters are not considered.

[0049] The following describes a method for correcting ripple voltage while considering control parameters.

[0050] Figure 12 shows an example of a method for correcting ripple voltage when considering the duty cycle. In Figure 12, the horizontal axis represents time, and the vertical axis represents the ripple voltage of capacitor 40. As shown in Figure 12, the duty cycle at a predetermined reference time is set to D0. The predetermined reference time can be, for example, the time when capacitor 40 is in its initial state, or the time during the operating period when capacitor 40 has been in the same state for a relatively long period of time. After time has passed, the duty cycle at the time of calculating the ripple voltage to determine the degradation of capacitor 40 is set to Dt. If the pre-correction ripple voltage without considering control parameters is Vr, the corrected ripple voltage Vr' can be calculated using the formula Vr' = Vr × Dt / D0.

[0051] As described above, the predetermined control parameters include a duty cycle, and the power conversion circuit 10 includes a switching circuit driven by a switching period, which adjusts the duty cycle of the switching waveform in response to fluctuations in the AC voltage to keep the DC voltage constant. The capacitor 40 divides the output current corresponding to the duty cycle of the power conversion circuit 10. The ripple voltage calculation unit 50 can calculate (correct) the ripple voltage based on the ratio of the duty cycle D0 at a predetermined reference time and the duty cycle Dt at the time of calculation.

[0052] By multiplying the calculation of the ripple voltage by a correction value corresponding to the duty cycle Dt, fluctuations in the ripple voltage caused by the control state of the power conversion circuit 10 can be canceled out, and the ripple voltage caused by the degradation of the capacitor 40 can be calculated, thus enabling accurate determination of the degradation of the capacitor 40.

[0053] Figure 13 shows an example of a method for correcting ripple voltage when considering the switching period. In Figure 13, the horizontal axis represents time, and the vertical axis represents the ripple voltage of capacitor 40. As shown in Figure 13, the switching period at a predetermined reference time is set to T0. After time has elapsed, the switching period at the time of calculating the ripple voltage to determine the degradation of capacitor 40 is set to Tt. If the pre-correction ripple voltage without considering control parameters is Vr, the corrected ripple voltage Vr' can be calculated using the formula Vr' = Vr × Tt / T0.

[0054] As described above, the predetermined control parameters include the switching period, and the capacitor 40 divides the output current corresponding to the switching period of the power conversion circuit 10. The ripple voltage calculation unit 50 can calculate (correct) the ripple voltage based on the ratio of the switching period T0 at a predetermined reference time and the switching period Tt at the time of calculation.

[0055] By multiplying the ripple voltage by a correction value corresponding to the switching period Tt during ripple voltage calculation, fluctuations in ripple voltage caused by the control state of the power conversion circuit 10 can be canceled out, and the ripple voltage caused by the degradation of capacitor 40 can be calculated, thus enabling accurate determination of the degradation of capacitor 40.

[0056] When correcting the ripple voltage by considering both the duty cycle and the switching period, the corrected ripple voltage Vr' can be calculated using the formula Vr' = Vr × {Dt / D0} × {Tt / T0}.

[0057] Next, we will explain how to calculate the ripple voltage when the power conversion circuit 10 includes a PFC circuit.

[0058] Figure 14 shows an example of a method for calculating ripple voltage when a PFC circuit is included in the power conversion circuit 10. As explained in Figures 3 to 7, the ripple voltage calculation unit 50 samples the voltage waveform of the capacitor 40 at multiple time points, generates a histogram, and calculates the ripple voltage.

[0059] On the other hand, the PFC circuit changes the duty cycle during switching according to the phase of the input voltage (AC voltage) in order to improve the power factor. For example, as shown in Figure 14, the duty cycle is changed according to the phase for a sinusoidal input voltage. For example, the duty cycle is minimum at phases of 0°, 180°, and 360°, and maximum at phases of 90° and 270°.

[0060] If the ripple voltage calculation unit 50 randomly samples without considering the phase of the input voltage, as shown in the lower part of Figure 14, the duty cycle will vary with each sample, causing the ripple voltage to fluctuate due to the control state of the power conversion circuit 10, making it impossible to calculate the ripple voltage accurately.

[0061] Therefore, in this embodiment, as shown in the middle diagram of Figure 14, the phase range is determined so that the duty cycle falls within a predetermined range Dw, taking into account the phase of the input voltage, so that the duty cycle does not fluctuate, and the voltage waveform of the capacitor 40 is sampled within the determined phase range.

[0062] As described above, the power conversion circuit 10 includes a PFC circuit and improves the power factor by adjusting the duty cycle of the switching waveform that switches the AC voltage according to the phase of the AC voltage. The ripple voltage calculation unit 50 can calculate the ripple voltage by sampling the voltage waveform of the capacitor 40 within a phase range of the AC voltage (for example, 40° to 50°) in which the duty cycle is within a predetermined range.

[0063] Since the voltage waveform of capacitor 40 is sampled only within the set phase range, variations in the duty cycle can be suppressed, fluctuations in ripple voltage caused by the control state of the power conversion circuit 10 can be canceled out, and the ripple voltage caused by the degradation of capacitor 40 can be calculated, thus enabling accurate determination of the degradation of capacitor 40.

[0064] The microcontroller 30, acting as a processor, includes a ripple voltage calculation unit 50 and a degradation determination unit 60, along with a power conversion circuit control unit 70. Specifically, the degradation determination unit 60 is composed of one microcontroller 30, and this one microcontroller 30 includes a circuit control unit 70 that controls the operation of the power conversion circuit 10.

[0065] As described above, a single microcontroller 30 implements both the degradation detection function and the operation control function of the power conversion circuit 10. By implementing both functions with a single microcontroller 30, it is possible to detect the control state (i.e., control parameters) of the power conversion circuit 10 and correct the ripple voltage based on the detected control state to determine the degradation of the capacitor 40. This allows the control state of the power conversion circuit 10 to be used to improve the robustness of the capacitor 40 degradation detection.

[0066] It should be noted that the above example is not the only possible solution; the microcontroller (processor) that implements the degradation detection function and the microcontroller (processor) that implements the operation control of the power conversion circuit 10 may be separated and configured using individual microcontrollers.

[0067] Figure 15 shows a second example of the configuration of a power supply unit 200 equipped with a capacitor degradation detection device 100. The power supply unit 200 includes a power conversion circuit 10 and a capacitor 40. Multiple DC / DC circuits 80 are connected to the output terminal of the power conversion circuit 10. Capacitors are connected to the output side of the DC / DC circuits 80.

[0068] Each DC / DC circuit 80 operates at a predetermined operating rate according to the load operating rate. On the other hand, the operating rate of the power conversion circuit 10 is assumed to be 100%. In such a power supply unit 200, the power conversion circuit 10 and the capacitor 40 are constantly operating, so the degradation of the capacitor 40 progresses relatively quickly, and the degradation detection by the capacitor degradation detection device of this embodiment is effective. Therefore, as shown in Figure 15, the microcontroller 30 equipped with a degradation detection function can be connected to the power conversion circuit 10 with the highest operating rate.

[0069] Figure 16 shows a third example of the configuration of a power supply unit 200 equipped with a capacitor degradation detection device 100. In the example shown in Figure 16, a microcontroller 30 equipped with a degradation detection function determines the degradation of capacitors in all power conversion circuits (power conversion circuit 10 and DC / DC circuit 80).

[0070] Figure 17 shows a fourth example of the configuration of a power supply unit 200 equipped with a capacitor degradation detection device 100. In the example shown in Figure 17, a microcontroller 30 equipped with a degradation detection function is connected to each of the power conversion circuits (power conversion circuit 10 and DC / DC circuit 80) to determine the degradation of the capacitors.

[0071] (Note 1) The capacitor degradation determination device comprises a power conversion circuit that converts an input voltage into a DC voltage based on predetermined control parameters, a capacitor connected to the output side of the power conversion circuit, a ripple voltage calculation unit that calculates the ripple voltage of the capacitor, and a determination unit that determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters.

[0072] (Note 2) In the capacitor degradation determination device, as described in Note 1, the predetermined control parameter includes a duty cycle, the power conversion circuit includes a switching circuit driven by a switching period, and adjusts the duty cycle of the switching waveform in response to fluctuations in the AC voltage to keep the DC voltage constant, the capacitor divides the output current corresponding to the duty cycle of the power conversion circuit, and the ripple voltage calculation unit calculates the ripple voltage based on the ratio of the duty cycle at a predetermined reference time and the duty cycle at the time of calculation.

[0073] (Note 3) In the capacitor degradation determination device, as described in Note 2, the predetermined control parameters include the switching period, the capacitor receives a divided output current corresponding to the switching period of the power conversion circuit, and the ripple voltage calculation unit calculates the ripple voltage based on the ratio of the switching period at a predetermined reference time and the switching period at the time of calculation.

[0074] (Note 4) In any one of Notes 1 to 3, the capacitor degradation determination device includes a power conversion circuit which includes a PFC circuit and adjusts the duty cycle of the switching waveform which switches the AC voltage according to the phase of the AC voltage to improve the power factor, and the ripple voltage calculation unit calculates the ripple voltage within the phase range of the AC voltage such that the duty cycle is within a predetermined range.

[0075] (Note 5) In the capacitor degradation determination device, according to any one of Notes 1 to 4, the determination unit is composed of a processor, and the processor controls the operation of the power conversion circuit.

[0076] (Note 6) The capacitor degradation determination device, in any one of Notes 1 to 5, includes an AD conversion unit that samples the voltage waveform of the capacitor at a predetermined sampling period and converts it into a digital value, a generation unit that generates a histogram showing the frequency of the digital value converted by the AD conversion unit at multiple time points, and a statistics calculation unit that calculates a statistical quantity of the fluctuation in the frequency of the generated histogram, and the ripple voltage calculation unit calculates the ripple voltage based on the calculated statistics.

[0077] (Note 7) The power supply unit is equipped with the capacitor degradation detection device described above.

[0078] (Note 8) The capacitor degradation determination method involves calculating the ripple voltage of a capacitor connected to the output side of a power conversion circuit that converts an input voltage to a DC voltage, based on predetermined control parameters, and determining the degradation of the capacitor based on the calculated ripple voltage and the control parameters.

[0079] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used. [Explanation of Symbols]

[0080] 10 Power Conversion Circuit 11 Full wave rectifier circuit 12 DC / DC circuit 13, 15, 16 coils 14, 21, 22, 23, 24 Switching elements 30 Microcontrollers 40 Capacitors 50 Ripple Voltage Calculation Unit 51 AD Conversion Unit 52 Histogram generation section 53 Statistics calculation section 60 Deterioration judgment section 70 Power Conversion Circuit Control Unit 80 DC / DC circuit 100 Capacitor Degradation Detection Device 150, 200 power supplies

Claims

1. A power conversion circuit provided in a power supply device that converts an input voltage into a DC voltage based on predetermined control parameters, A capacitor connected to the output side of the power conversion circuit, A ripple voltage calculation unit for calculating the ripple voltage of the capacitor, A determination unit determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters. Equipped with, The predetermined control parameter includes a duty cycle value, The aforementioned power conversion circuit is It includes a switching circuit driven by a switching period, and adjusts the duty cycle of the switching waveform in response to fluctuations in the AC voltage to keep the DC voltage constant. The aforementioned capacitor is The output current corresponding to the duty cycle of the power conversion circuit is divided, The ripple voltage calculation unit is, The ripple voltage is calculated based on the ratio of the duty cycle value at a predetermined reference time and the duty cycle value at the time of calculation. Capacitor degradation detection device.

2. A power conversion circuit provided in a power supply device that converts an input voltage into a DC voltage based on predetermined control parameters, A capacitor connected to the output side of the power conversion circuit, A ripple voltage calculation unit for calculating the ripple voltage of the capacitor, A determination unit determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters. Equipped with, The predetermined control parameters include the switching period, The aforementioned capacitor is The output current corresponding to the switching period of the power conversion circuit is divided, The ripple voltage calculation unit is, The ripple voltage is calculated based on the ratio of the switching period at a predetermined reference time to the switching period at the time of calculation. Capacitor degradation detection device.

3. A power conversion circuit provided in a power supply device that converts an input voltage into a DC voltage based on predetermined control parameters, A capacitor connected to the output side of the power conversion circuit, A ripple voltage calculation unit for calculating the ripple voltage of the capacitor, A determination unit determines the degradation of the capacitor based on the ripple voltage calculated by the ripple voltage calculation unit and the control parameters. Equipped with, The power conversion circuit includes a PFC circuit and is configured to improve the power factor by adjusting the duty cycle of the switching waveform that switches the AC voltage according to the phase of the AC voltage. The ripple voltage calculation unit is, The ripple voltage is calculated within the phase range of the AC voltage, such that the duty cycle is within a predetermined range. Capacitor degradation detection device.

4. The determination unit is composed of a processor. The aforementioned processor, Controlling the operation of the power conversion circuit, A capacitor degradation determination device according to any one of claims 1 to 3.

5. The AD conversion unit samples the voltage waveform of the capacitor at a predetermined sampling period and converts it into a digital value. A generation unit that generates a histogram showing the frequency of digital values ​​converted by the AD conversion unit at multiple points in time, A statistical calculation unit that calculates the statistical value of the frequency variation in the generated histogram. Equipped with, The ripple voltage calculation unit is, The ripple voltage is calculated based on the calculated statistics. A capacitor degradation determination device according to any one of claims 1 to 3.

6. A power supply device comprising a capacitor degradation determination device according to any one of claims 1 to 3.

7. Based on predetermined control parameters, the ripple voltage of the capacitor connected to the output side of a power conversion circuit that converts the input voltage to a DC voltage is calculated. Based on the calculated ripple voltage and the control parameters, the degradation of the capacitor is determined. The predetermined control parameter includes a duty cycle value, The aforementioned power conversion circuit is It includes a switching circuit driven by a switching period, and adjusts the duty cycle of the switching waveform in response to fluctuations in the AC voltage to keep the DC voltage constant. The aforementioned capacitor is The output current corresponding to the duty cycle of the power conversion circuit is divided, The ripple voltage of the capacitor is calculated based on the ratio of the duty cycle value at a predetermined reference time and the duty cycle value at the time of calculation. Method for determining capacitor degradation.

8. Based on predetermined control parameters, the ripple voltage of a capacitor connected to the output side of a power conversion circuit that converts an input voltage to a DC voltage is calculated, Based on the calculated ripple voltage and the control parameters, the degradation of the capacitor is determined. The predetermined control parameters include the switching period, The aforementioned capacitor is The output current corresponding to the switching period of the power conversion circuit is divided, The ripple voltage of the capacitor is calculated based on the ratio of the switching period at a predetermined reference time and the switching period at the time of calculation. Method for determining capacitor degradation.

9. Based on predetermined control parameters, the ripple voltage of a capacitor connected to the output side of a power conversion circuit that converts an input voltage to a DC voltage is calculated, Based on the calculated ripple voltage and the control parameters, the degradation of the capacitor is determined. The power conversion circuit includes a PFC circuit, which improves the power factor by adjusting the duty cycle of the switching waveform that switches the AC voltage according to the phase of the AC voltage. The ripple voltage of the capacitor is calculated within the phase range of the AC voltage such that the duty cycle is within a predetermined range. Method for determining capacitor degradation.

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