Power supply device

Abstract

In this power supply device (1) comprising a plurality of converters (CNV) connected in parallel, a lifetime determining unit (3), in a determination mode, stops the operation of a target converter to be subjected to lifetime determination while causing the other converters to operate and determines whether the target converter will last its lifetime on the basis of the level of voltage reduction due to the discharge of a smoothing capacitor (C4) of the target converter. When it is determined that none of the converters have lasted their lifetimes in the determination mode, the lifetime determining unit (3) switches the operation mode to a normal mode for causing the converters to operate without limiting the outputs of the plurality of converters. When there is a deteriorated converter that has lasted its lifetime in the determination mode, the lifetime determining unit (3) switches the operation mode to a limited mode in which the output of the deteriorated converter is limited.

Description

power equipment

[0001] The present disclosure relates to power supply equipment.

[0002] In recent years, there has been a growing demand for higher power, higher reliability, and smaller size of power supply devices that supply DC to loads. In particular, there has been an increasing demand for higher power DC power supply devices used for DC power supply in ZEBs (zero emission buildings), data centers, and the like.

[0003] A method of connecting a plurality of converters in parallel is known as a method for realizing a larger current and a larger capacity of a power supply device (see, for example, Japanese Patent Laid-Open Publication No. 2006-034047 (Patent Document 1)).

[0004] Japanese Patent Application Laid-Open No. 2006-034047

[0005] In power supply equipment with converters connected in parallel, if one of the converters fails, the entire power supply will stop working. Therefore, when converters are connected in parallel, it is necessary to replace a deteriorated converter before it fails, in order to prevent a power supply outage.

[0006] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide a method for checking the deterioration status of each converter in a power supply device having converters connected in parallel before each converter fails.

[0007] In one embodiment, a power supply device includes a plurality of converters connected in parallel between an input node and an output node, and a lifespan determination unit. The power supply device has operating modes including a normal mode, a determination mode, and a limit mode. In the determination mode, the lifespan determination unit stops operation of a target converter whose lifespan is being determined while leaving the other converters operating, and determines whether the target converter has reached the end of its life based on the degree of voltage drop due to discharge of the smoothing capacitor of the target converter. If the lifespan determination unit determines in the determination mode that none of the converters has reached the end of its life, it transitions the operating mode to a normal mode in which the multiple converters operate without output limiting. If, in the determination mode, there is a degraded converter that has reached the end of its life, the lifespan determination unit transitions the operating mode to a limit mode in which the output of the degraded converter is limited.

[0008] According to the above embodiment, in the determination mode, the life determination unit stops the operation of the target converter whose life is to be determined while leaving the other converters operating, and determines whether the target converter has reached the end of its life based on the degree of voltage drop due to discharge of the smoothing capacitor of the target converter. Therefore, in a power supply device having converters connected in parallel, it is possible to check the deterioration status of each converter before it fails.

[0009] 13 is a block diagram showing the overall configuration of a power supply device of a first embodiment. FIG. 14 is a circuit diagram showing an example of the internal configuration of the converter of FIG. 1. FIG. 15 is a block diagram showing an example configuration of the shunt regulator of FIG. 2. FIG. 16 is a block diagram showing an example configuration of the current control unit of FIG. 2. FIG. 17 is a state transition diagram showing transitions between operation modes of the power supply device. FIG. 18 is a flowchart showing a lifespan determination procedure by a lifespan determination unit. FIG. 19 is a timing diagram showing the time change in output current of each converter in a determination mode. FIG. 19 is a diagram showing a discharge path of a smoothing capacitor on the secondary side of a transformer. FIG. 19 is a diagram for explaining the principle of converter lifespan determination. FIG. 20 is a flowchart showing the operation of the lifespan determination unit in a limit mode. FIG. 21 is a timing diagram showing the time change in output current of each converter in a limit mode. FIG. 22 is a circuit diagram showing an example configuration of a flyback DC / DC converter with a negative voltage output. FIG. 23 is a circuit diagram showing an example configuration of a converter in a power supply device of a second embodiment. FIG. 24 is a diagram for explaining the effect of the discharge circuit of FIG. 23. FIG. 25 is a circuit diagram showing an example configuration of a converter in a power supply device of a third embodiment. FIG. 26 is a flowchart showing a lifespan determination procedure by a lifespan determination unit in a power supply device of a fourth embodiment. FIG. 27 is a diagram for explaining the principle of converter lifespan determination in a power supply device of the fourth embodiment. FIG. 28 is a flowchart showing a lifespan determination procedure by a lifespan determination unit in a power supply device of a fifth embodiment. FIG. 29 is a timing diagram showing the operation of each converter constituting the power supply device of the fifth embodiment. 13 is a flowchart showing the operation of a lifespan determination unit in limit mode in the power supply device of embodiment 6. FIG. 14 is a timing diagram showing changes in the target value of the output voltage of each converter in limit mode in the power supply device of embodiment 6. FIG. 15 is a flowchart showing the operation of a lifespan determination unit in limit mode in the power supply device of embodiment 7. FIG. 16 is a timing diagram showing changes in the target value of the output voltage of each converter in limit mode in the power supply device of embodiment 7. FIG. 17 is a diagram for explaining a two-stage method of lifespan determination. FIG. 18 is a flowchart showing a lifespan determination procedure when thresholds are set in two stages. FIG. 19 is a flowchart showing an operating procedure in maintenance mode. FIG. 19 is a diagram for explaining a lifespan determination threshold in maintenance mode. FIG. 19 is a circuit diagram showing an example configuration of a converter in the power supply device of embodiment 11.1 is a diagram showing the relationship between the ambient temperature of a smoothing electrolytic capacitor and the frequency of lifespan determination, and a flowchart showing a procedure for changing the frequency of lifespan determination according to the ambient temperature of the smoothing electrolytic capacitor.

[0010] Each embodiment will be described in detail below with reference to the drawings. The same or corresponding parts will be denoted by the same reference characters and description thereof will not be repeated.

[0011] Embodiment 1 [Overall Configuration of Power Supply Device 1] Fig. 1 is a block diagram showing the overall configuration of a power supply device 1 according to embodiment 1. Fig. 1(A) shows a block diagram of the power supply device 1 for DC (direct current) input, and Fig. 1(B) shows a block diagram of the power supply device 1 for AC (alternating current) input.

[0012] The power supply device 1 includes a plurality of converters CNV1 to CNV3 (hereinafter referred to as converter CNV when referring to them collectively or when referring to any one of them) and a life determination unit 3. Although three converters CNV are shown in Fig. 1 as an example, any number of converters CNV may be connected in parallel depending on the required output voltage, as long as they are two or more, and there is no particular limitation.

[0013] Converters CNV1 to CNV3 are connected in parallel between an input node N1 and an output node N2. In the case of FIG. 1A, an external DC power supply V1 is connected between the input node N1 and an input-side ground node N3. In the case of FIG. 1B, an external AC power supply V2 is connected between the input node N1 and the input-side ground node N3. Meanwhile, in both FIGS. 1A and 1B, a load 2 is connected between the output node N2 and an output-side ground node N4.

[0014] Each converter CNV converts DC power or AC power into DC power. A more detailed configuration example of the converter CNV will be described later with reference to FIG.

[0015] The load 2 is a medium- or large-capacity DC electrical device, such as a lighting device or an inverter device for driving an AC motor.

[0016] The life determination unit 3 is connected to each converter CNV by signal wiring, and controls the operation of each converter CNV via a control signal (S1 in FIG. 2), and determines the life of each converter CNV. Hereinafter, a converter CNV that is the subject of life determination will be referred to as a "target converter," and a converter CNV that is not the subject of life determination will be referred to as a "non-target converter."

[0017] A detailed method for determining the lifespan will be described later with reference to Figures 5 to 12. In this disclosure, the state in which the "lifespan" has been reached does not refer to the state immediately before a failure causes a shutdown, but rather to the state in which the initial failure period and random failure period have passed and the wear-out failure period has begun. Therefore, a converter CNV that has reached the end of its lifespan can continue to operate for several hundred hours before actually failing and shutting down.

[0018] The lifespan determination unit 3 is configured based on a computer including a CPU (Central Processing Unit) and a memory, or at least a part of the lifespan determination unit 3 may be configured with a dedicated circuit such as a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array) and / or an ASIC (Application Specific Integrated Circuit).

[0019] [Example of Internal Configuration of Converter CNV] Fig. 2 is a circuit diagram showing an example of the internal configuration of the converter CNV of Fig. 1. Fig. 2 shows a flyback DC / DC converter as an example of the converter CNV. Instead of the flyback type, a forward type or other type may be used. Furthermore, the converter CNV is not limited to an isolated DC / DC converter (or switching power supply), and may be a non-isolated DC / DC converter (or switching power supply).

[0020] 2, the converter CNV includes a transformer TF and, as components on the primary side of the transformer TF, a power supply smoothing capacitor C1, a main circuit capacitor C2, a semiconductor switching element Q1 (also referred to as a first switching element), a power supply control circuit 4, and a snubber circuit 7. As components on the secondary side of the transformer TF, the converter CNV also includes diodes D2 and D3, resistors R2, R3, and R4, a shunt regulator SR1, a smoothing capacitor C4, a voltage detection unit 5, and a current control unit 6. The converter CNV also includes a photocoupler PC for feeding back output voltage information from the secondary side to the primary side of the transformer TF. In FIG. 2, the LED (Light Emitting Diode) and phototransistor TR that constitute the photocoupler are shown separately.

[0021] The connections and functions of the components of the converter CNV shown in Fig. 2 will be described below. First, the primary side of the transformer TF will be described.

[0022] The power supply smoothing capacitor C1 and the main circuit capacitor C2 are connected in parallel between the input node N1 and the input-side ground node N3. The power supply smoothing capacitor C1 is provided to absorb noise and ensure stable operation of the converter CNV. The main circuit capacitor C2 is provided to absorb ripples and noise generated during switching of the semiconductor switching element Q1.

[0023] The primary winding W1 of the transformer TF and the semiconductor switching element Q1 are connected in series with each other and in parallel with the power supply smoothing capacitor C1 and the main circuit capacitor C2 between the input node N1 and the ground node N3. As will be described later, the switching of the semiconductor switching element Q1 is controlled by a gate signal supplied from the power supply control circuit 4. The switching of the semiconductor switching element Q1 stores energy in the transformer TF (or reactor) and transmits power from the primary side to the secondary side of the transformer TF.

[0024] The snubber circuit 7 is connected in parallel with the primary winding W1 of the transformer TF. The snubber circuit 7 suppresses surge voltages generated by switching of the semiconductor switching element Q1, thereby reducing switching noise when the semiconductor switching element Q1 is turned off. More specifically, the snubber circuit 7 includes a capacitor C3, a resistor R1, and a diode D1. The capacitor C3 and the resistor R1 are connected in parallel with each other between a first end of the primary winding W1 of the transformer TF and the cathode of the diode D1. The anode of the diode D1 is connected to a second end of the primary winding W1 of the transformer TF.

[0025] The power supply control circuit 4 monitors and controls the overall operation of the converter CNV. Specifically, the power supply control circuit 4 controls the output voltage Vo and the output current Io by adjusting the duty ratio of a PWM (Pulse Width Modulation) signal supplied to the gate of the semiconductor switching element Q1. Furthermore, the power supply control circuit 4 has an overvoltage protection function and an overcurrent protection function.

[0026] Next, the secondary side of the transformer TF will be described. As shown in Fig. 2, an intermediate node N5 is provided between a first end (high potential side) of a secondary winding W2 of the transformer TF and an output node N2, and an intermediate node N6 is provided between a second end (low potential side) of the secondary winding W2 of the transformer TF and a ground node N4. In the case of Fig. 2, the low potential side intermediate node N6 is directly connected to the second end of the secondary winding W2 of the transformer TF.

[0027] The anode of the diode D2 is connected to the first end (high potential side) of the secondary winding W2 of the transformer TF, and the cathode of the diode D2 is connected to the intermediate node N5. The diode D2 is provided to rectify the AC power transmitted to the secondary side of the transformer TF.

[0028] Smoothing capacitor C4 is connected between intermediate node N5 on the high potential side and intermediate node N6 on the low potential side. Smoothing capacitor C4 smoothes the voltage rectified by diode D2. As a result, a DC output voltage Vo is generated across smoothing capacitor C4.

[0029] The resistor element R2, the LED of the photocoupler PC, and the shunt regulator SR1 are connected in series with each other and in parallel with the smoothing capacitor C4, in this order, between the intermediate nodes N5 and N6. The resistor elements R3 and R4 are connected in series with each other and in parallel with the smoothing capacitor C4, in this order, between the intermediate nodes N5 and N6. The voltage at the connection node between the resistor elements R3 and R4 is taken into the shunt regulator SR1 as a monitor voltage Vmon for monitoring the output voltage Vo.

[0030] The shunt regulator SR1 keeps the output voltage Vo constant by increasing the cathode current flowing through the shunt regulator SR1 when the output voltage Vo rises and by reducing the cathode current flowing through the shunt regulator SR1 when the output voltage Vo falls.

[0031] Fig. 3 is a block diagram showing an example of the configuration of the shunt regulator shown in Fig. 2. The shunt regulator SR1 shown in Fig. 3 includes an error amplifier EA, a voltage source that generates a reference voltage Vref, and an NPN transistor TR1. Fig. 3 also shows other components on the secondary side of the transformer TF of the converter CNV.

[0032] 3, resistor R2, the LED of photocoupler PC, and NPN transistor TR1 are connected in series with each other and in parallel with smoothing capacitor C4, in that order, between intermediate nodes N5 and N6. A monitor voltage Vmon is input to the non-inverting input node of error amplifier EA, and a reference voltage Vref is input to the inverting input node of error amplifier EA. The output node of error amplifier EA is connected to the base of NPN transistor TR1.

[0033] According to the above-described configuration of the shunt regulator SR1, a current corresponding to the difference between the monitor voltage Vmon and the reference voltage Vref flows between the collector and emitter of the NPN transistor TR1 (i.e., between the cathode and anode of the shunt regulator SR1). The LED of the photocoupler PC emits light in response to this current, and the phototransistor TR of the photocoupler PC receives the light emitted by the LED. As a result, a current corresponding to the amount of received light flows between the collector and emitter of the phototransistor TR. As a result, information on the value of the output voltage Vo can be transmitted to the power supply control circuit 4.

[0034] 2 , diode D3 is provided to prevent current from flowing in from other non-target converters during lifespan determination of the target converter. Specifically, the anode of diode D3 is connected to intermediate node N5, and the cathode of diode D3 is connected to output node N2. Therefore, the cathode of diode D3 is also connected to the cathode of diode D3 of other converters CNV connected to output node N2. Diode D3 is provided to prevent current from flowing into the target converter CNV for which lifespan determination is being performed from non-target converters CNV for which lifespan determination is not being performed (i.e., to prevent backflow).

[0035] The voltage detection unit 5 is connected to both ends of the smoothing capacitor C4 to detect the voltage Vc (also referred to as the capacitor voltage Vc) stored in the smoothing capacitor C4. The voltage detection unit 5 transmits the detected capacitor voltage Vc to the life determination unit 3.

[0036] The current control unit 6 is connected between the intermediate node N6 on the low potential side and the ground node N4 on the secondary side. The current control unit 6 detects the output current Io of the converter CNV, and when the output current Io exceeds a current limit value IL, outputs a control signal S3 to the power supply control circuit 4 to reduce the output current Io.

[0037] Fig. 4 is a block diagram showing an example of the configuration of current control unit 6 of Fig. 2. Referring to Fig. 4, current control unit 6 includes a current sensor IS, a current detection unit 6A, a storage unit 6B, and a comparator 6C. Current control unit 6 is formed of a dedicated circuit such as a PLD such as an FPGA and / or an ASIC.

[0038] The current detection unit 6A detects the output current Io of the converter CNV via the current sensor IS. The memory unit 6B stores a current limit value IL set in accordance with a setting signal S2 from the life determination unit 3. The comparator 6C compares the detected output current Io with the set current limit value IL, and activates a control signal S3 if the output current Io exceeds the current limit value IL. When the control signal S3 is activated, the power supply control circuit 4 reduces the output current Io by adjusting the conduction rate of the semiconductor switching element Q1.

[0039] 5 is a state transition diagram showing transitions between operation modes of the power supply device 1. The operation modes of the power supply device 1 include three modes: a normal mode 20, a determination mode 21, and a limit mode 22.

[0040] The normal mode 20 refers to an operating mode in which each converter CNV supplies power to the load 2 within a preset current range for normal operation. When a lifespan determination of each converter CNV is not being executed, the power supply device 1 operates in the normal mode 20. The lifespan determination unit 3 shifts the operating mode from the normal mode 20 to the determination mode 21 at predetermined determination cycles (i.e., when the determination cycle has elapsed) or based on an instruction from a user or a service technician, etc. The shift from the normal mode 20 to the determination mode 21 may occur not only when the determination cycle has elapsed, but also, for example, when a user or a service technician presses a manual switch provided on the power supply device 1.

[0041] The judgment mode 21 is an operating mode in which the life judgment unit 3 is conducting a life judgment for each converter CNV. In the judgment mode 21, the life judgment unit 3 sequentially executes the life judgment for each converter CNV. When the life judgment for all converters is completed, the operating mode returns to the normal mode 20 or transitions to the restriction mode 22. Specifically, if there is no converter judged to have reached the end of its life (hereinafter referred to as a "deteriorated converter"), the life judgment unit 3 returns the operating mode to the normal mode 20. On the other hand, if there is one or more deteriorated converters, the life judgment unit 3 transitions the operating mode from the judgment mode 21 to the restriction mode 22.

[0042] The limit mode 22 is an operating mode in which, when one or more converters CNV have reached the end of their lifespan as a result of the lifespan assessment, the output current Io of the deteriorated converters is limited. The lifespan assessment unit 3 keeps the current limit value of the deteriorated converters low and raises the current limit value of the converters CNV that have been determined not to have reached the end of their lifespan (hereinafter referred to as "normal converters").

[0043] [Operation in Determination Mode] Next, the operation of the life determination section 3 of the power device 1 in the determination mode will be described with reference to Fig. 6 to Fig. 9. Fig. 6 is a flowchart showing the life determination procedure performed by the life determination section.

[0044] 6, the life determination unit 3 determines a target converter for life determination from among the converters CNV included in the power supply device 1. The life determination is performed sequentially for all converters CNV, and this order is not particularly limited. In the example of FIG. 1, the life determination is performed in the order of converter CNV3, converter CNV2, and converter CNV1.

[0045] In the next step S20, the life determination unit 3 sends a setting signal S2 to the current control unit 6 of the non-target converter so as to raise the current limit value of the non-target converter other than the target converter above the setting value in normal mode. Note that the current limit value of the non-target converter is raised only during the determination mode, so there is no risk of degrading the non-target converter. Furthermore, when the load current during normal operation is small and light, there is no particular need to raise the current limit value.

[0046] In the next step S30, the life determination unit 3 sends a control signal S1 to the power supply control circuit 4 to stop the switching of the semiconductor switching element Q1 of the target converter. This stops the transmission of power from the primary side to the secondary side of the transformer TF, and the output current Io of the target converter CNV becomes zero. Furthermore, when the transmission of power from the primary side to the secondary side by the transformer TF stops, the discharge of the smoothing capacitor C4 on the secondary side of the transformer TF begins.

[0047] 7 is a timing diagram showing the time change of the output current of each converter in the evaluation mode. In FIG. 7, the period before time t10 corresponds to the normal mode, and the period from time t10 to time t11 corresponds to the period during which the life evaluation of the target converter CNV3 is being performed in the evaluation mode.

[0048] In the normal mode before time t10, each of the converters CNV1 to CNV3 outputs a current of 100 A to the load 2. Therefore, the power device 1 as a whole supplies an output current Io of 300 A to the load 2.

[0049] After time t10, when the lifespan determination of converter CNV3 begins, the operation of target converter CNV3 is stopped. As a result, the output current Io of converter CNV3 becomes zero. Meanwhile, the output current Io of each of non-target converters CNV1 and CNV2 is increased to 150 A. As a result, the output current Io supplied from the entire power supply device 1 to the load 2 in the determination mode becomes 300 A, which is equal to the output current Io in the normal mode.

[0050] If the current limit value of the asymmetric converter in the normal mode is less than 150 A, it is necessary to increase the current limit value of the asymmetric converter in the determination mode to 150 A or more. Also, although the above description has been given of the case where the output current Io of each converter in the normal mode is shared equally, it may also be shared unevenly.

[0051] 8 is a diagram showing the discharge path of smoothing capacitor C4 on the secondary side of transformer TF. When switching of semiconductor switching element Q1 is stopped in FIG. 8, discharge of smoothing capacitor C4 on the secondary side of transformer TF begins. The discharge path Idc from smoothing capacitor C4 runs from the positive electrode of smoothing capacitor C4 through resistor elements R3 and R4 and back to the negative electrode of smoothing capacitor C4. The voltage between both electrodes of smoothing capacitor C4 is monitored by voltage detection unit 5.

[0052] 6 , in the next step S40, the life determination unit 3 measures the discharge time from when the switching of the semiconductor switching element Q1 is stopped to start discharging the smoothing capacitor C4 until the voltage of the smoothing capacitor C4 reaches a determination value. For example, a counter built into the life determination unit 3 is used to measure the time. If the discharge time is shorter than a threshold time (YES in step S50), the life determination unit 3 determines that the target converter has reached the end of its life and sets a life flag for the target converter (step S60). On the other hand, if the discharge time is equal to or longer than the threshold time (NO in step S50), the life determination unit 3 determines that the target converter has not yet reached the end of its life and does not set a life flag.

[0053] The threshold time is calculated in advance based on the characteristics of the smoothing capacitor C4. As an example, an upper limit of the voltage ripple amount allowed by the system is set, and the lower limit of the required capacitance is calculated from that upper limit of the voltage ripple amount. Then, a lower limit of the discharge time is derived from the lower limit of the capacitance, and the threshold of the discharge time is determined taking into account the time until an actual failure occurs.

[0054] Fig. 9 is a diagram for explaining the principle of determining the lifespan of a converter. Fig. 9 shows an example of a discharge curve (dashed line) in the initial state of a converter product and an example of a discharge curve (solid line) after long-term use. The rated value of the voltage Vc of the smoothing capacitor C4 in normal mode is 12.0 V.

[0055] At time t0 in FIG. 9, the life determination unit 3 switches the control signal S1 sent to the power supply control circuit 4 to stop the switching of the semiconductor switching element Q1.

[0056] The life determination unit 3 measures the time until the voltage Vc of the smoothing capacitor C4 reaches the determination value Vd. When the converter product is in its initial state, the voltage Vc reaches the determination value Vd at time t2, so the discharge time is T2. On the other hand, after a long period of use, the voltage Vc reaches the determination value Vd at time t1, so the discharge time is T1, which is shorter than the discharge time T2 in the initial state. The life determination unit 3 determines that the target converter has reached the end of its life if the discharge time is shorter than the threshold time.

[0057] 6, after the life determination unit 3 has determined whether the target converter has reached the end of its life (steps S50 and S60), it sends a control signal S1 to the power supply control circuit 4 in order to start switching of the semiconductor switching element Q1 in the next step S70. This causes the target converter to start power conversion operation. As shown after time t11 in FIG. 7, the target converter starts outputting current, and the output current Io of the non-target converter returns to its original state.

[0058] In the next step S80, the life determination unit 3 returns the current limit value IL stored in the current control unit 6 of the non-target converter to the original value.

[0059] This completes the lifespan determination for the currently set target converter. If the lifespan determination for all converters CNV has not been completed (NO in step S90), the lifespan determination unit 3 returns the process to step S10, sets a converter CNV for which lifespan determination has not yet been performed as the target converter, and performs lifespan determination for that converter (steps S20 to S80).

[0060] If the lifespan determination for all converters CNV has been completed (YES in step S90), the lifespan determination unit 3 checks in the next step S100 whether the number of set lifespan flags is 1 or more. If no lifespan flag has been set (NO in step S100), the lifespan determination unit 3 returns the operation mode to the normal mode (step S110). If one or more lifespan flags have been set (YES in step S100), the lifespan determination unit 3 transitions the operation mode to the limited mode (step S120).

[0061] [Operation in Restricted Mode] Next, the operation of the life determination unit 3 of the power device 1 in the restricted mode will be described with reference to FIGS. 10 and 11. FIG.

[0062] 10 is a flowchart showing the operation of the lifespan determination unit in the limit mode. Referring to FIG. 10, in step S200, lifespan determination unit 3 notifies the user of a deteriorated converter determined to have reached the end of its life in the determination mode. For example, lifespan determination unit 3 may sound an alarm for the deteriorated converter or turn on an abnormality lamp for the deteriorated converter.

[0063] In the next step S210, the life determination unit 3 sends a setting signal S2 to the current control unit 6 of the normal converter to change the current limit value IL of the normal converter to a larger current value.

[0064] In the next step S220, life determination unit 3 sends setting signal S2 to current control unit 6 of the deteriorated converter to change current limit value IL of the deteriorated converter to a smaller current value. The limit mode continues until the deteriorated converter is replaced.

[0065] 11 is a timing chart showing the time change of the output current of each converter in the limit mode. In the configuration of the power supply device 1 in FIG. 1, as a result of the lifespan determination in the determination mode, it is assumed that the converters CNV1 and CNV2 are normal converters and the converter CNV3 is a deteriorated converter.

[0066] The limit mode is started at time t20. Before time t20, when any of the converters CNV is not undergoing lifespan determination, a current of 100 A is output from each of the converters CNV1 to CNV3 to the load 2, and an output current Io of 300 A is supplied to the load 2 by the power supply device 1 as a whole.

[0067] When the limit mode is initiated, the current limit value IL of the normal converters CNV1 and CNV2 is increased from 100 A to 125 A, and the current limit value IL of the degraded converter CNV3 is reduced from 100 A to 50 A. As a result, the output current Io of each of the normal converters CNV1 and CNV2 increases from 100 A to 125 A, and the output current Io of the degraded converter CNV3 decreases from 100 A to 50 A. The total output current Io supplied to the load 2 becomes 300 A, which is unchanged from before the limit mode was initiated.

[0068] In addition, the current limit value IL of the normal converters CNV1 and CNV2 is increased only when the load is high and the total current supplied to the load 2 is large, and there is no need to increase the current limit value IL of the normal converters CNV1 and CNV2 when the load is low and the total current supplied to the load 2 is small.

[0069] The limit mode continues until the degraded converter CNV3 is replaced. As described above, by limiting the output current Io of the degraded converter CNV3, the life of the degraded converter CNV3 can be extended until it is replaced.

[0070] Effects of the First Embodiment The power supply device 1 of the first embodiment has the following effects. First, the device periodically switches to a determination mode, and in the determination mode, the degradation state of the capacitor built into the converter CNV is determined based on the capacitor's discharge time. This makes it possible to urge the user to replace the degraded converter by issuing an alarm or the like before the degraded converter completely fails and the power supply device stops.

[0071] If a deteriorated converter is found, the system switches to a limiting mode, in which the output current Io of the deteriorated converter is limited, thereby extending the life of the deteriorated converter until it can be replaced.

[0072] In the determination mode, the operation of the target converter, whose lifespan is to be determined, is stopped. The current output of the target converter is borne by the non-target converter, whose lifespan is not to be determined, so the output current Io of the power supply device 1 as a whole does not change. Therefore, the lifespan of the target converter can be determined without stopping the operation of the power supply device 1 and without affecting the load 2.

[0073] Furthermore, when the lifespan of a target converter is assessed in assessment mode, the operation of the target converter is stopped, eliminating the influence of switching noise and other factors from the target converter itself. This allows for stable and highly accurate lifespan assessment.

[0074] [Modification 1] The lifespan determination method of the first embodiment can be applied not only to cases where the output of the power supply device is a positive voltage, but also to cases where the output is a negative voltage.

[0075] Fig. 12 is a circuit diagram showing an example of the configuration of a negative voltage output flyback DC / DC converter. Fig. 12 shows the configuration of the secondary side of a transformer TF. In Fig. 12, parts corresponding to those in the positive voltage output flyback DC / DC converter of Fig. 2 are given the same reference numerals. In Fig. 12, a rectifying diode D2 and a reverse current prevention diode D3 are arranged on the negative voltage side. Other points in Fig. 12 are the same as those in Fig. 2, and therefore description thereof will not be repeated.

[0076] [Modification 2] The lifespan determination method of the first embodiment can be applied not only to an isolated DC / DC converter such as that shown in FIG. 2 but also to a non-isolated DC / DC converter. In the case of a non-isolated DC / DC converter, when the switching of the semiconductor switching element is stopped for lifespan determination, it is necessary to separate the smoothing capacitor used to measure the discharge time from the DC power supply on the input side. For example, in the case of a step-down chopper or a step-up / step-down chopper, the semiconductor switching element can be opened when lifespan determination is performed. In the case of a step-up chopper, a synchronous rectification switching element can be provided instead of a rectification diode, and this synchronous rectification switching element can be opened when lifespan determination is performed.

[0077] Second Embodiment [Features of the Second Embodiment] As described with reference to Fig. 8, in the converter CNV of the first embodiment, the smoothing capacitor C4 is discharged using the resistance elements R3 and R4 for monitoring the output voltage Vo. In the converter CNV of the second embodiment, a dedicated circuit for discharging is provided. This makes it possible to shorten the discharge time. This will be described in detail below with reference to the drawings.

[0078] [Example of Internal Configuration of Converter] FIG. 13 is a circuit diagram showing an example of the configuration of a converter in the power supply device according to the second embodiment.

[0079] 2 in that the converter CNV in Fig. 13 further includes a discharge circuit 8 that is provided in parallel with the smoothing capacitor C4 between the high-potential side intermediate node N5 and the low-potential side intermediate node N6. The discharge circuit 8 includes a resistance element R5 and a semiconductor switching element SW2 that are connected in series between the intermediate nodes N5 and N6.

[0080] The life determination unit 3 outputs a control signal S4 that controls the opening and closing of the semiconductor switching element SW2. When the life determination of the converter CNV is not being performed, the semiconductor switching element SW2 is controlled to the open state. When the life determination unit 3 stops the switching of the semiconductor switching element Q1 and starts the life determination of the converter CNV (step S30 in FIG. 6), it switches the semiconductor switching element SW2 from the open state to the closed state. When the life determination unit 3 starts the switching of the semiconductor switching element Q1 to end the life determination of the converter CNV (step S70 in FIG. 6), it switches the semiconductor switching element SW2 from the closed state to the open state.

[0081] Other points in FIG. 13 are similar to those in FIG. 2, so the same or corresponding parts are given the same reference numerals and description thereof will not be repeated.

[0082] Fig. 14 is a diagram for explaining the effect of the discharge circuit of Fig. 13. Fig. 13 shows the change over time in voltage Vc of smoothing capacitor C4 when determining the life of converter CNV.

[0083] 14, at time t30, the switching of semiconductor switching element Q1 is stopped in order to determine the life span of converter CNV, thereby starting the discharge of smoothing capacitor C4.

[0084] The dashed curve in Fig. 14 shows the discharge curve of smoothing capacitor C4 when semiconductor switching element SW2 is maintained in the OFF state. Discharge time T12 is measured from time t30 to time t32 when the voltage value Vc of smoothing capacitor C4 drops to the determination value Vd. As described with reference to Fig. 8, the resistance value of the discharge path in this case is the combined series resistance of resistor elements R3 and R4.

[0085] 14 shows the discharge curve of smoothing capacitor C4 when semiconductor switching element SW2 is switched from the OFF state to the ON state at time t30. In this case, the discharge path includes a path via resistor element R5 in parallel with the path via resistor elements R3 and R4, so the combined resistance is smaller than when only resistor elements R3 and R4 are used. Therefore, the discharge time T11 from time t30 to time t31, when the voltage value Vc of smoothing capacitor C4 decreases to the determination value Vd, is shorter than the discharge time T12.

[0086] [Effects of Embodiment 2] As described above, according to the power supply device of Embodiment 2, when the operation of the target converter is stopped for lifespan assessment, the discharge of smoothing capacitor C4 can be accelerated. Therefore, the lifespan assessment can be performed in a shorter time than in Embodiment 1. In the normal mode and the limited mode, the semiconductor switching element SW2 of the discharge circuit 8 is maintained in the open state, so there is no effect on the operation of converter CNV in these operating modes.

[0087] Third Embodiment [Features of Third Embodiment] In the converter CNV shown in Fig. 2, a diode D3 for preventing backflow was provided between the intermediate node N5 on the high potential side and the output node N2. In the converter CNV provided in the power supply device of the third embodiment, a semiconductor switching element is provided in place of the diode D3. Note that the third embodiment can be combined with the second embodiment.

[0088] [Example of Internal Configuration of Converter] FIG. 15 is a circuit diagram showing an example of the configuration of a converter in the power supply device according to the third embodiment.

[0089] The converter CNV in Fig. 15 includes a semiconductor switching element 9 (also referred to as a second switching element) instead of the backflow prevention diode D3 in Fig. 2. Opening and closing of the semiconductor switching element 9 is controlled by a control signal S5 output from the life determination unit 3.

[0090] 15, an N-channel MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) Q2 is provided as the semiconductor switching element 9. The source of the N-channel MOSFET Q2 is connected to an intermediate node N5 on the high potential side, and the drain of the N-channel MOSFET Q2 is connected to an output node N2. That is, the N-channel MOSFET Q2 is connected so that the direction from the intermediate node N5 to the output node N2 is the forward direction of the parasitic diode of the N-channel MOSFET Q2.

[0091] A P-channel MOSFET may be used in place of the N-channel MOSFET Q2. In this case, the drain of the P-channel MOSFET is connected to the intermediate node N5 on the high potential side, and the source of the P-channel MOSFET is connected to the output node N2. That is, the P-channel MOSFET is connected so that the direction from the intermediate node N5 to the output node N2 is the forward direction of the parasitic diode of the P-channel MOSFET.

[0092] To ensure a larger conduction current, a plurality of MOSFETs may be connected in parallel, and to ensure a larger reverse voltage resistance, a plurality of MOSFETs may be connected in series.

[0093] The life determination unit 3 outputs a control signal S5 that controls the opening and closing of the semiconductor switching element 9. When the life determination of the converter CNV is not being performed, the semiconductor switching element 9 is controlled to a closed state. When the life determination unit 3 stops the switching of the semiconductor switching element Q1 and starts the life determination of the converter CNV (step S30 in FIG. 6), it switches the semiconductor switching element 9 from a closed state to an open state. When the life determination unit 3 starts the switching of the semiconductor switching element Q1 to end the life determination of the converter CNV (step S70 in FIG. 6), it switches the semiconductor switching element 9 from an open state to a closed state.

[0094] Other points in FIG. 15 are similar to those in FIG. 2, so the same or corresponding parts are given the same reference numerals and description thereof will not be repeated.

[0095] [Effects of the Third Embodiment] In the first embodiment, the diode D3 is used for preventing backflow, and the forward voltage of the diode D3 is large, about 1 V, and the product of the current flowing through the diode D3 and the forward voltage is the diode loss. Therefore, the loss of the diode D3 cannot be ignored. In the third embodiment, the semiconductor switching element 9 is used to prevent backflow during the lifespan determination, thereby reducing the loss more than in the first embodiment.

[0096] Embodiment 4. [Features of Embodiment 4] In the lifespan determination in the case of Embodiment 1, the discharge time from when the discharge of smoothing capacitor C4 started until the voltage value Vc of smoothing capacitor C4 reached the determination value Vd was measured. In the case of Embodiment 4, the residual voltage of smoothing capacitor C4 when a specified time Ts has elapsed since the discharge of smoothing capacitor C4 started is measured. Then, it is determined whether the residual voltage is lower than a threshold voltage. This will be described in detail below with reference to the drawings.

[0097] An example of the hardware configuration of the power supply device according to the fourth embodiment is similar to that described with reference to Figures 1 to 4 in the first embodiment, and therefore the description will not be repeated. Furthermore, the fourth embodiment can be combined with either the second or third embodiment.

[0098] [Operation in Determination Mode] Figure 16 is a flowchart showing the lifespan determination procedure performed by the lifespan determination unit in the power supply device of embodiment 4. The flowchart in Figure 16 differs from the flowchart in Figure 6 in that steps S40A and S50A are executed instead of steps S40 and S50. The other steps in Figure 16 are the same as those in Figure 6, so the same or corresponding steps are given the same reference numerals and description thereof will not be repeated.

[0099] Specifically, in step S30, the life determination unit 3 outputs a control signal S1 to the power supply control circuit 4 to stop switching of the semiconductor switching element Q1 of the target converter, and the smoothing capacitor C4 starts discharging.

[0100] In the next step S40A, the life determination unit 3 measures the elapsed time from when the switching of the semiconductor switching element Q1 is stopped to start discharging the smoothing capacitor C4. For example, a counter built in the life determination unit 3 is used to measure the time. Then, the life determination unit 3 measures, via the voltage detection unit 5, the residual voltage of the smoothing capacitor C4 when a predetermined specified time Ts has elapsed since the discharge of the smoothing capacitor C4 started.

[0101] If the residual voltage of smoothing capacitor C4 is lower than the threshold voltage (YES in step S50A), life determination unit 3 determines that the target converter has reached the end of its life and sets a life flag for the target converter (step S60).On the other hand, if the residual voltage of smoothing capacitor C4 is equal to or higher than the threshold voltage (NO in step S50A), life determination unit 3 determines that the target converter has not yet reached the end of its life and does not set a life flag.

[0102] When the life determination unit 3 has completed the determination of whether the target converter has reached the end of its life (steps S50A and S60), in the next step S70, it sends a control signal S1 to the power supply control circuit 4 to start switching of the semiconductor switching element Q1. The subsequent procedure is the same as that described with reference to FIG. 6, and therefore description will not be repeated.

[0103] 17 is a diagram illustrating the principle of determining the lifespan of a converter in a power supply device according to embodiment 4. Fig. 17 shows an example of a discharge curve (dashed line) in the initial state of a converter product, and an example of a discharge curve (solid line) after long-term use. The rated value of the voltage Vc of smoothing capacitor C4 in normal mode is 12.0 V.

[0104] 17, the life determination unit 3 stops the switching of the semiconductor switching element Q1 by switching the control signal S1 sent to the power supply control circuit 4. This causes the smoothing capacitor C4 to start discharging.

[0105] The life determination unit 3 measures the voltage Vc of the smoothing capacitor C4 via the voltage detection unit 5 at time t41, when a specified time Ts has elapsed since the smoothing capacitor C4 started to discharge. When the converter product is in its initial state, the measured voltage of the smoothing capacitor C4 at time t41 is Vm1. On the other hand, after a long period of use, the measured voltage of the smoothing capacitor C4 at time t41 is Vm2, which is lower than the measured voltage Vm1 in the initial state. When the measured voltage of the smoothing capacitor C4 at time t41 is lower than the threshold voltage, the life determination unit 3 determines that the target converter has reached the end of its life.

[0106] [Effects of Embodiment 4] The power supply device of Embodiment 4 basically achieves the same effects as the power supply device of Embodiment 1. In particular, in the case of Embodiment 4, the residual voltage of smoothing capacitor C4 is measured when a specified time Ts has elapsed since the start of discharge of smoothing capacitor C4, which has the advantage that the time required to determine the life of the target converter does not change depending on the degree of deterioration of the converter. On the other hand, in the case of Embodiment 1, the discharge time until the voltage Vc of smoothing capacitor C4 reaches the determination value is measured, so the time required to determine the life of the target converter changes depending on the degree of deterioration of the converter. In this respect, the two devices differ.

[0107] 6 and 16 of the first and fourth embodiments, the target value of the output voltage Vo suddenly becomes zero by stopping the switching of the semiconductor switching element Q1 when the lifespan of the target converter is determined. The power supply device of the fifth embodiment is characterized in that when the lifespan of the target converter is determined, the output voltage Vo is once reduced to a voltage lower than the value in normal mode, and then reduced to zero. This will be described in detail below with reference to the drawings. The above features of the fifth embodiment can be combined with any of the first to fourth embodiments.

[0108] [Operation in Determination Mode] FIG. 18 is a flowchart showing the procedure for determining a life span by the life span determination unit in the power supply device according to the fifth embodiment.

[0109] The flowchart in Fig. 18 differs from the flowchart in Fig. 16 in that step S25 is provided between step S20 and step S30. That is, before stopping the switching of the semiconductor switching element Q1 of the target converter in step S30, the life determination unit 3 reduces the target value of the output voltage Vo of the target converter to a constant voltage lower than the value in the normal mode in step S25.

[0110] 18 is otherwise similar to that of FIG. 16, the same or corresponding steps are designated by the same reference numerals and description thereof will not be repeated. Note that life determination unit 3 may execute steps S40 and S50 in FIG. 6 instead of steps S40A and S50A in FIG. 18, respectively.

[0111] Fig. 19 is a timing diagram showing the operation of each converter CNV constituting the power supply device of embodiment 5. Fig. 19 shows the target values ​​of the output voltage Vo and the values ​​of the output current Io of the converters CNV1 to CNV3 constituting the power supply device 1 of Fig. 1.

[0112] 19 , in the normal mode before the lifespan of converter CNV3 is determined, the target values ​​of the output voltage Vo of converters CNV1 to CNV3 are 12.0 V, 12.1 V, and 12.2 V, respectively. In addition, the output current Io of each of converters CNV1 to CNV3 is 100 A.

[0113] At time t50, the life determination unit 3 changes the control signal S1 sent to the power supply control circuit 4 of the target converter CNV3, thereby lowering the target value of the output voltage Vo of the converter CNV3 from 12.2 V to 11.9 V. The power supply control circuit 4 performs CVCC control, that is, performs constant voltage operation (constant voltage) and constant current operation (constant current) so as to achieve the set target voltage value and target current value, and therefore, by reducing the target value of the output voltage Vo as described above, the output current Io of the converter CNV3 becomes zero.

[0114] At the next time t50, the life determination unit 3 outputs a control signal S1 to the power supply control circuit 4 of the converter CNV3 to stop switching of the semiconductor switching element Q1 of the converter CNV3, thereby setting the target value of the output voltage Vo of the converter CNV3 to zero, and the life determination (i.e., discharging of the smoothing capacitor C4) is started.

[0115] Effect of Embodiment 5 As described above, according to the power supply device of Embodiment 5, before starting a lifespan assessment of the target converter, the target value of the output voltage of the target converter is reduced to a low voltage, thereby setting the output current of the target converter to zero. Thereafter, switching of the semiconductor switching element Q1 is stopped to assess the lifespan of the target converter. Therefore, when the lifespan assessment of the target converter starts, no abrupt change occurs in the output current Io, eliminating the generation of noise due to such a change, and improving the accuracy of the lifespan assessment.

[0116] Sixth Embodiment. [Features of Sixth Embodiment] In the limit mode of the power supply device of the first embodiment, the current limit value IL of the degraded converter is lowered and the current limit value IL of the normal converter is raised, thereby extending the life of the degraded converter. In the limit mode of the power supply device of the sixth embodiment, the target value of the output voltage Vo of the degraded converter is lowered below the target value of the output voltage Vo of the normal converter. This reduces the availability of the degraded converter. This will be described in detail below with reference to Figures 20 and 21. Note that the operation of the limit mode of the sixth embodiment can be combined with any of the features of the second to fifth embodiments.

[0117] [Operation in Restricted Mode] FIG. 20 is a flowchart showing the operation of the life determination unit in the restricted mode in the power supply device according to the sixth embodiment.

[0118] In step S300 of FIG. 20, life determination unit 3 notifies the user of a deteriorated converter that has been determined to have reached the end of its life in the determination mode, for example by causing the deteriorated converter to issue an alarm.

[0119] In the next step S310, the life judgment unit 3 changes the control signal S1 sent to the power supply control circuit 4 of the degraded converter, thereby lowering the target value of the output voltage Vo of the degraded converter to the lowest value among the converters CNV that make up the power supply equipment.

[0120] In the next step S320, lifespan determination unit 3 transmits setting signal S2 to current control unit 6 of the deteriorated converter to change current limit value IL of the deteriorated converter to a smaller current value. The limit mode continues until the deteriorated converter is replaced.

[0121] Fig. 21 is a timing diagram showing changes in the target value of the output voltage of each converter in the limit mode in the power supply device of embodiment 6. In Fig. 21, it is assumed that, of the converters CNV1 to CNV3 constituting the power supply device 1 of Fig. 1, converter CNV3 is determined to have reached the end of its life in the determination mode.

[0122] When the limit mode is started at time t60, the life determination unit 3 changes the control signal S1 sent to the power supply control circuit 4 of the degraded converter CNV3, thereby lowering the target value of the output voltage Vo of the degraded converter CNV3 from 12.2 V to 11.9 V. 11.9 V is the lowest value among the target values ​​of the output voltage Vo of the converters CNV1 to CNV3. The effect of this setting change will be described below.

[0123] Assume that the rated output current of converters CNV1 to CNV3 is 100 A. When the load current is 300 A, each of converters CNV1 to CNV3 outputs a current of 100 A. When the load current is 200 A, due to the CVCC control of each power supply control circuit 4, converters CNV1 and CNV2 each pass an output current Io of 100 A, and converter CNV3 does not pass an output current Io because its target value for output voltage Vo is the lowest among converters CNV1 to CNV3. As the load current increases from 200 A, converter CNV3 begins to output the increased load current.

[0124] In this way, assuming CVCC operation of the power supply control circuit 4 that constitutes each converter CNV, the operating rate of the degraded converter can be reduced by setting the target value of the output voltage Vo of the degraded converter lower than the target value of the output voltage Vo of other normal converters.

[0125] [Effects of the Sixth Embodiment] As described above, according to the power supply device of the sixth embodiment, in the limited mode, the target value of the output voltage Vo of a degraded converter is set lower than the target value of the output voltage Vo of the other normal converters. As a result, while the load current is low, the load current is borne only by the normal converter, so that the operating rate of the degraded converter can be reduced. As a result, the degraded converter can be effectively used as an auxiliary power source until it is replaced, thereby extending the life of the degraded converter.

[0126] Seventh Embodiment [Features of Seventh Embodiment] In the seventh embodiment, an operation different from the operation in the limit mode described in the first and sixth embodiments will be described. Specifically, in the power supply device of the seventh embodiment, for a deteriorated converter determined in the determination mode to have reached the end of its life, the power supply control circuit 4 is powered off in the limit mode. This will be specifically described below with reference to FIGS. 22 and 23. Note that the operation in the limit mode of the seventh embodiment can be combined with any of the features of the second to fifth embodiments.

[0127] [Operation in Restricted Mode] FIG. 22 is a flowchart showing the operation of the life determination unit in the restricted mode in the power supply device according to the seventh embodiment.

[0128] In step S400 of FIG. 22, life determination unit 3 notifies the user of a deteriorated converter that has been determined to have reached the end of its life in the determination mode, for example by causing the deteriorated converter to issue an alarm.

[0129] In the next step S410, life determination unit 3 changes control signal S1 sent to power supply control circuit 4 of the degraded converter to turn off the power supply to power supply control circuit 4 of the degraded converter. This stops the operation of the degraded converter, and both the target value of its output voltage Vo and output current Io become zero. Therefore, the load current supplied to load 2 is supplied from converters CNV1 and CNV2, and is no longer supplied from converter CNV3, so it is reduced compared to the normal mode.

[0130] Fig. 23 is a timing diagram showing changes in the target value of the output voltage of each converter in the limit mode in the power supply device of embodiment 7. In Fig. 23, it is assumed that, of converters CNV1 to CNV3 constituting power supply device 1 in Fig. 1, converter CNV3 is determined to have reached the end of its life in the determination mode.

[0131] When starting the restriction mode at time t70, the life determination unit 3 changes the control signal S1 sent to the power supply control circuit 4 of the degraded converter CNV3 to turn off the power supply to the power supply control circuit 4 of the degraded converter CNV3.

[0132] [Effects of embodiment 7] According to the power supply device of the embodiment, by turning off the power supply control circuit 4 of the degraded converter, current is no longer output from the degraded converter, thereby preventing the degraded converter from breaking down.

[0133] 10, 20, and 22, in the limit mode, the life determination unit 3 notifies the user or maintenance personnel of a deteriorated converter that has been determined to have reached the end of its life in the determination mode, for example by causing the deteriorated converter to issue an alarm. In the eighth embodiment, the means for notifying the user or maintenance personnel will be described in more detail.

[0134] [Configuration and Operation of Notification Device] Each converter CNV constituting the power supply equipment is provided with a notification device for notifying a user or maintenance personnel that the converter has reached the end of its life. The user or maintenance personnel who is notified by the notification device that the converter has reached the end of its life can replace the deteriorated converter.

[0135] The alarm device may include a light-emitting component such as an LED (Light Emitting Diode) and / or an acoustic component such as a speaker to notify a user or the like. These components are provided to enable a user or maintenance personnel to identify a deteriorated converter. For example, a deteriorated converter may flash an error lamp such as an LED or sound a speaker.

[0136] Furthermore, the alarm device may be equipped with a wireless communication device. For example, the deteriorated converter may notify its own identification number via the wireless communication device to a mobile information terminal of a maintenance person or to a terminal device such as a management computer. Another example is a method using IoT technology in which the lifespan determination unit 3 detects the end of its lifespan and sends an alarm signal to a data server, causing an error dialog box to be displayed on the management computer.

[0137] The alarm device is connected to the lifespan determination unit 3 via wired or wireless communication. When the lifespan determination unit 3 detects that a converter CNV has reached the end of its lifespan, it sends an alarm signal (included in the control signal S1 in FIG. 2 ) to the alarm device provided in that deteriorated converter to issue an alarm. Upon receiving the alarm signal, the alarm device notifies the user of the alarm by light, sound, or the like. An example of the operating procedure of the lifespan determination unit 3 and the alarm device is shown below.

[0138] (1) When the lifespan determination unit 3 detects that a certain converter CNV has reached the end of its lifespan, it transmits an alarm signal (included in the control signal S1 in FIG. 2) to the alarm device provided in the deteriorated converter CNV that has reached the end of its lifespan. Furthermore, the lifespan determination unit 3 may transmit the alarm signal to a data server. The alarm signal may be transmitted multiple times.

[0139] (2) Upon receiving the alarm signal, the alarm device issues an alarm. For example, the alarm device may blink an LED or output a warning sound from a speaker. The user can cancel the alarm. The alarm may be issued periodically, and the interval can be set by the user. When the data server receives an alarm signal from the lifespan determination unit 3, the data server stores the reception history in a log file and notifies the administrator.

[0140] (3) When the life determination unit 3 detects the removal of a deteriorated converter, it stops transmitting the alarm signal. The life determination unit 3 can detect the removal of a deteriorated converter by, for example, a disconnection of communication with the converter CNV.

[0141] Effect of the Eighth Embodiment The deteriorated converter issues an alarm, allowing the user to easily identify a deteriorated converter that has reached the end of its life. Furthermore, by proactively issuing an alarm when the end of its life is detected, it is possible to avoid a situation in which the converter CNV suddenly fails and the power supply device becomes inoperable.

[0142] Ninth Embodiment [Features of Ninth Embodiment] In the ninth embodiment, a case where the threshold value for determining the life span is divided into multiple stages will be described.

[0143] [Principle of Multi-Stage Lifespan Judgment] Fig. 24 is a diagram for explaining a two-stage method of lifespan judgment. In Fig. 24, the discharge curve of smoothing capacitor C4 of converter CNV that has reached the first stage of its lifespan is shown by a dashed line, and the discharge curve of smoothing capacitor C4 of converter CNV that has reached the second stage of its lifespan is shown by a solid line.

[0144] 24 , discharge of smoothing capacitor C4 begins at time t80, and the discharge time until the voltage Vc of smoothing capacitor C4 reaches the determination value Vd is measured. For converter CNV that has reached the end of its life in the first stage, discharge time T21 until the voltage Vc of smoothing capacitor C4 reaches the determination value Vd (until time t82) is shorter than the first-stage threshold time. For converter CNV that has reached the end of its life in the second stage, discharge time T20 until the voltage Vc of smoothing capacitor C4 reaches the determination value Vd (until time t81) is shorter than the second-stage threshold time. The second-stage threshold time is shorter than the first-stage threshold time.

[0145] 24 , when the voltage value of the smoothing capacitor C4 when the specified time Ts has elapsed since the start of discharge of the smoothing capacitor C4 is compared with the threshold voltage as described in the fourth embodiment, the threshold voltage may be set in multiple stages, in which case the second-stage threshold voltage is lower than the first-stage threshold voltage.

[0146] The thresholds (threshold time, threshold voltage) may be set at the time of manufacturing the power supply device 1, or may be set arbitrarily by the user. A first-stage alarm is issued when the first-stage threshold is reached, and a second-stage alarm is issued when the second-stage threshold is reached.

[0147] 25 is a flowchart showing a lifespan determination procedure when thresholds are set in two stages. In the first step S500, the lifespan determination unit 3 sets the thresholds (threshold time, threshold voltage) for lifespan determination to a first threshold.

[0148] When the operating mode transitions from the normal mode to the determination mode (YES in step S505), in the next step S510, the life determination unit 3 determines the life of each converter CNV constituting the power supply device 1. The procedure in step S510 is the same as steps S10 to S100 in the flowchart of Fig. 6 or 18. Specifically, the life determination unit 3 determines for each converter CNV whether the measured discharge time of the smoothing capacitor C4 or the voltage Vc of the smoothing capacitor C4 has reached a first threshold value (threshold time or threshold voltage).

[0149] If the result of the above determination is that the measured value for none of the converter CNVs has reached the first threshold (NO in step S515), the life determination unit 3 returns to step S505. On the other hand, if the measured value for any of the converter CNVs has reached the first threshold (YES in step S515), the life determination unit 3 determines that the converter has reached the end of its life and notifies the user or maintenance personnel that the converter has reached the first threshold (step S520). The user or maintenance personnel may replace the deteriorated converter at this stage. Then, in the next step S525, the life determination unit 3 sets the thresholds for life determination (threshold time, threshold voltage) to the second thresholds.

[0150] When the operating mode transitions from the normal mode to the determination mode (YES in step S530), in the next step S535, the life determination unit 3 determines the life of each converter CNV constituting the power supply device 1. The procedure in step S535 is the same as steps S10 to S100 in the flowchart of Fig. 6 or 18. Specifically, the life determination unit 3 determines for each converter CNV whether the measured discharge time of the smoothing capacitor C4 or the voltage Vc of the smoothing capacitor C4 has reached a second threshold value (threshold time or threshold voltage).

[0151] If the measured value of any converter CNV has not reached the second threshold (NO in step S540), the lifespan determination unit 3 returns to step S530. On the other hand, if the measured value of any converter CNV has reached the second threshold (YES in step S540), the lifespan determination unit 3 determines that the converter has reached the end of its life and notifies the user or maintenance personnel that the converter has reached the second threshold (step S545). Then, at the end of the determination mode, the lifespan determination unit 3 transitions the operating mode to the restricted mode (step S550).

[0152] [Effects of the Ninth Embodiment] As described above, according to the power supply device of the ninth embodiment, the lifespan determination unit 3 sets a threshold for determining the lifespan in multiple stages, and when the result of the lifespan determination reaches the threshold for each stage, an alarm is issued to the deteriorated converter. This allows a replacement converter CNV to be prepared in advance, preventing a situation in which a replacement converter CNV is not available when the target converter CNV reaches the end of its lifespan. Furthermore, by setting the threshold in multiple stages, the remaining time until the end of the lifespan of the target converter CNV can be estimated.

[0153] Tenth Embodiment. [Features of Tenth Embodiment] In the power supply device of the tenth embodiment, a maintenance mode is provided as an operating mode in addition to a determination mode. In the maintenance mode, the threshold value for determining the lifespan is changed to a value that makes it easier for the lifespan to be reached than in the determination mode. The purpose of providing the maintenance mode is to allow maintenance personnel to replace normal converter CNVs that are nearing the end of their lifespan when replacing deteriorated converter CNVs. This will be described in detail below with reference to FIGS. 26 and 27.

[0154] [Maintenance Mode Operation] Figure 26 is a flowchart showing the operation procedure of the maintenance mode. In the first step S600, the lifespan determination unit 3 determines whether or not an instruction to transition to the maintenance mode has been issued. The means for transitioning to the maintenance mode should preferably be operable only by maintenance personnel and not by general users. One example is to repeatedly press a manual switch provided on the power supply device to transition to the determination mode, or to hold the switch down for a long time.

[0155] If an instruction to transition to the maintenance mode has been issued (YES in step S600), the life determination unit 3 changes the threshold value for determining the life to a value that makes it easier for the smoothing capacitor C4 to reach its end of life (S610). For example, as described in the first embodiment, when measuring the discharge time from when the smoothing capacitor C4 starts discharging until the voltage Vc of the smoothing capacitor C4 reaches the determination value Vd, the threshold time is changed to a longer value. Also, as described in the fourth embodiment, when measuring the voltage value Vc of the smoothing capacitor C4 when a specified time Ts has elapsed since the smoothing capacitor C4 started discharging, the threshold voltage is changed to a higher value.

[0156] In the next step S620, the life determination unit 3 performs a life determination for all normal converters CNV. If the result of the life determination is that any converter has reached the end of its life (YES in step S630), the life determination unit 3 notifies maintenance personnel of the converter that has reached the end of its life (step S640).

[0157] [Regarding Life Determination Threshold in Maintenance Mode] FIG. 27 is a diagram for explaining the life determination threshold in the maintenance mode.

[0158] 27, the value of 100% indicates the measured value in the lifespan determination for the initial state immediately after the manufacture of converter CNV. For example, as described in the first embodiment, when measuring the discharge time from when smoothing capacitor C4 starts discharging until the voltage Vc of smoothing capacitor C4 reaches the determination value Vd, the value of 100% indicates the measured value of the discharge time immediately after the manufacture of converter CNV. Also, as described in the fourth embodiment, when measuring the voltage value Vc of smoothing capacitor C4 when a specified time Ts has elapsed since the start of discharge of smoothing capacitor C4, the value of 100% indicates the measured value of the voltage immediately after the manufacture of converter CNV.

[0159] 27, for example, the judgment threshold in the judgment mode is set to 50% of the measurement value in the initial state, and the judgment threshold in the maintenance mode is set to 65% of the measurement value in the initial state. Therefore, in the judgment mode, the target converter is determined to have reached the end of its life if the measurement value is less than 50%, and in the maintenance mode, the target converter is determined to have reached the end of its life if the measurement value is less than 65%.

[0160] If the measured value in the lifespan determination of the target converter is between 50% and 65% of the measured value in the initial state, the target converter will not be determined to have reached the end of its life in the determination mode, but will be determined to have reached the end of its life in the maintenance mode.

[0161] By providing the maintenance mode as described above, it is possible to identify in advance converters that are close to the judgment threshold (50%) of the judgment mode, i.e., converters CNV that will soon reach the end of their lifespan. This has the advantage that, in addition to degraded converters that have already been judged to have reached the end of their lifespan in the judgment mode, converters that are nearing the end of their lifespan can also be replaced together during maintenance.

[0162] As described above, according to the power supply device of the tenth embodiment, by providing a maintenance mode, it is possible to identify normal converters CNV that are nearing the end of their life and are predicted to reach the end of their life in a short period of time. Therefore, by replacing normal converters that are nearing the end of their life during maintenance, it is possible to avoid repeatedly replacing converters in a short period of time, which leads to cost reduction.

[0163] Embodiment 11. [Features of Embodiment 11] In the power supply device of Embodiment 11, the life determination unit 3 periodically shifts the operating mode from the normal mode to the determination mode, and periodically performs life determination on each converter CNV. When the ambient temperature of the electrolytic capacitor inside each converter CNV becomes high, the life determination unit 3 automatically increases the frequency of life determination. Hereinafter, a state in which life determination is performed more frequently than normal will be referred to as the high-temperature mode, and a state in which life determination is performed at a normal frequency will be referred to as the normal temperature mode.

[0164] [Converter Configuration] Figure 28 is a circuit diagram showing an example configuration of converter CNV in the power supply device of embodiment 11. Converter CNV in Figure 28 differs from converter CNV in Figure 2 of embodiment 1 in that it further includes a temperature sensor 25 for detecting the ambient temperature of smoothing capacitor C4. Smoothing capacitor C4 is formed by an electrolytic capacitor. Hereinafter, smoothing capacitor C4 will also be referred to as smoothing electrolytic capacitor C4.

[0165] For example, a thermocouple or a thermistor can be used as the temperature sensor 25. The temperature sensor 25 may be attached directly to the smoothing capacitor C4 or may be installed in close proximity to the smoothing capacitor C4 in order to detect the ambient temperature of the smoothing capacitor C4.

[0166] The detection signal S6 from the temperature sensor 25 is input to the life determination unit 3. The life determination unit 3 determines whether the ambient temperature of the smoothing electrolytic capacitor C4 detected by the temperature sensor 25 exceeds a threshold temperature set by the user. If the ambient temperature exceeds the threshold temperature, the life determination unit 3 switches the operation mode from the normal temperature mode to the high temperature mode.

[0167] 2 , the same or corresponding parts are denoted by the same reference numerals, and description thereof will not be repeated. Note that, although Fig. 28 shows an example in which temperature sensor 25 and the high temperature mode are combined with converter CNV of Fig. 2 according to the first embodiment, it is also possible to combine converter CNV of another embodiment with temperature sensor 25 and the high temperature mode of this embodiment, instead of converter CNV of Fig. 2 .

[0168] [Relationship between Ambient Temperature and Lifespan of Electrolytic Capacitors] The higher the ambient temperature, the shorter the lifespan of an electrolytic capacitor tends to be. This phenomenon is related to the evaporation of the electrolyte inside the electrolytic capacitor. When the electrolyte decreases, the capacitance decreases, which increases the ESR (Equivalent Series Resistance), resulting in increased self-heating. As a result, the lifespan of the capacitor is shortened, and so is the lifespan of the converter.

[0169] The life of an electrolytic capacitor due to ambient temperature is approximated by the Arrhenius law, i.e., L = L ０ ×2 （Ｔ－Ｔｏ）／10 ...(1) In the above formula (1), L: estimated life [hours], L ０ : Life [hours] at rated temperature, T: rated temperature, To: ambient temperature.

[0170] [Relationship Between Ambient Temperature and Lifespan Determination Frequency] Figure 29 is a diagram showing the relationship between the ambient temperature of the smoothing electrolytic capacitor and the lifespan determination frequency. Figure 29(A) shows an example in which the lifespan determination frequency is changed in two stages, and Figure 29(B) shows an example in which the lifespan determination frequency is changed in five stages. In Figures 29(A) and 29(B), the vertical axis represents the ambient temperature of the smoothing capacitor C4, and the horizontal axis represents the time interval for performing lifespan determination. The time interval for performing lifespan determination in normal temperature mode is t, and the reference value of the ambient temperature is To [°C]. The time interval t is set by the user.

[0171] Referring to FIG. 29A, when the ambient temperature of smoothing electrolytic capacitor C4 exceeds the temperature threshold (i.e., To+10°C), the lifespan determination unit 3 changes the time interval for performing lifespan determination to t / 2 (i.e., the determination frequency is doubled). Furthermore, when the ambient temperature of smoothing capacitor C4 exceeds To+40°C, the lifespan determination unit 3 sets the time interval for performing lifespan determination to t / 16 (i.e., the determination frequency is 16 times that of the normal temperature mode). In this way, it is desirable to set the time interval t in accordance with the 10°C doubling rule, which is the Arrhenius law. The 10°C doubling rule is an empirical rule that states that a 10°C increase in temperature doubles the rate of material degradation, thereby halving the lifespan.

[0172] 29(B) is a diagram showing a case where the frequency of lifespan determination is changed in five stages. As shown in FIG. 29(B), the time interval for performing lifespan determination in normal temperature mode is t, and the reference value of the ambient temperature is To [°C]. When the ambient temperature reaches or exceeds To+10, To+20, To+30, To+40, or To+50, the lifespan determination unit 3 sets the time interval for performing lifespan determination to t / 2, t / 4, t / 8, t / 16, or t / 32, respectively.

[0173] The above examples of changing the lifespan determination frequency in two and five stages are merely examples. Various other examples of changing the lifespan determination frequency, such as three stages or six stages, are conceivable.

[0174] In the case of power supply equipment such as AC / DC converters, the ambient temperature of an electrolytic capacitor is generally considered to be high when it is 70 to 100°C or higher. The standard operating temperature range for equipment varies depending on the product, but one example is -10°C to 65°C.

[0175] [Operation of Lifetime Determination Unit Based on Ambient Temperature] In the normal temperature mode, the lifetime determination unit 3 transitions to the determination mode at every time interval t set by the user to determine the lifetime of the smoothing electrolytic capacitor C4. The lifetime determination unit 3 transitions to the high-temperature mode when the ambient temperature of the smoothing electrolytic capacitor C4 reaches or exceeds the temperature threshold. The lifetime determination unit 3 performs the lifetime determination of the smoothing electrolytic capacitor C4 when the mode is transitioned to the high-temperature mode, when a predetermined time has elapsed since the mode is transitioned to the high-temperature mode, or when a changed time interval (e.g., t / 2) has elapsed since the previous lifetime determination. Thereafter, the lifetime determination unit 3 performs the lifetime determination of the smoothing electrolytic capacitor C4 at every changed time interval (e.g., t / 2, t / 4, ...) depending on the ambient temperature of the smoothing electrolytic capacitor C4.

[0176] When the ambient temperature of smoothing electrolytic capacitor C4 falls below the temperature threshold, life determination unit 3 returns the operating mode from high temperature mode to normal temperature mode. In this case, if the normal temperature mode is returned to before the first life determination is performed after switching to high temperature mode (i.e., if no life determination is performed during high temperature mode), life determination unit 3 switches to normal temperature mode and simultaneously performs a life determination of smoothing electrolytic capacitor C4 in order to determine the degree of deterioration of smoothing electrolytic capacitor C4. The operation of life determination unit 3 in embodiment 11 will be described in more detail below with reference to FIG. 30 .

[0177] FIG. 30 is a flowchart showing a procedure for changing the frequency of performing lifespan determination in accordance with the ambient temperature of the smoothing electrolytic capacitor.

[0178] 30, in step S700 in the normal temperature mode, life determination unit 3 accepts a temperature threshold setting from the user.

[0179] In the next step S710, the life determination unit 3 monitors the ambient temperature of the smoothing electrolytic capacitor C4 using the temperature sensor 25. In the next step S720, the life determination unit 3 determines whether the ambient temperature detected by the temperature sensor 25 is equal to or higher than the temperature threshold value set by the user. If the ambient temperature is lower than the temperature threshold value (NO in step S720), the life determination unit 3 returns the process to step S710 and continues monitoring the ambient temperature of the smoothing electrolytic capacitor C4.

[0180] On the other hand, if the ambient temperature is equal to or higher than the temperature threshold (YES in step S720), the lifespan determination unit 3 proceeds to step S730. In step S730, the lifespan determination unit 3 shifts the operating mode from the normal temperature mode to the high temperature mode. In the high temperature mode, the frequency of lifespan determination is increased.

[0181] In the next step S740, the life determination unit 3 monitors the ambient temperature of the smoothing electrolytic capacitor C4 using the temperature sensor 25. In the next step S750, the life determination unit 3 determines whether the ambient temperature detected by the temperature sensor 25 is equal to or higher than the temperature threshold. If the ambient temperature is equal to or higher than the temperature threshold, the high-temperature mode continues. In this case, the life determination unit 3 may further increase the frequency of the life determination in accordance with the ambient temperature (step S760). Thereafter, the life determination unit 3 returns to step S740 and continues monitoring the ambient temperature of the smoothing electrolytic capacitor C4.

[0182] On the other hand, if the ambient temperature is below the temperature threshold (NO in step S750), the lifespan determination unit 3 proceeds to step S770. In step S770, the lifespan determination unit 3 changes the operating mode from the high temperature mode to the normal temperature mode. In the normal temperature mode, the frequency of lifespan determination is reduced to the original frequency.

[0183] At the time of transition to the normal temperature mode, the life determination unit 3 determines whether a life determination has been performed at least once during the high temperature mode period from the transition to the high temperature mode until the return to the normal temperature mode (step S780). If a life determination has not been performed at least once during the high temperature mode period (NO in step S780), the life determination unit 3 transitions to the normal temperature mode and simultaneously performs a life determination to determine the degree of deterioration of the smoothing electrolytic capacitor C4 due to the temporary high temperature environment (step S790). Then, the process returns to the initial step S710.

[0184] [Effects of Eleventh Embodiment] As described above, according to the eleventh embodiment, even if the product life of the converter is shortened due to high ambient temperatures around the converter and electrolytic capacitor, early detection of the end of the product life can be achieved by increasing the frequency of life assessment. This allows maintenance work such as converter replacement to be performed early before a serious failure occurs, thereby preventing end-of-life failures during continuous operation in a high-temperature environment. Note that the technology of this embodiment can be applied to any product to which the Arrhenius law can be applied.

[0185] The various aspects of the present disclosure are summarized below as appendices. (Appendix 1) A power supply device comprising: a plurality of converters connected in parallel to each other between an input node and an output node; and a lifespan determination unit, the power supply device having operating modes including a normal mode, a determination mode, and a limit mode, wherein in the determination mode, the lifespan determination unit stops operation of a target converter whose lifespan is to be determined while leaving the other converters operating, and determines whether the target converter has reached the end of its life based on the degree of voltage drop due to discharge of a smoothing capacitor of the target converter, and when it is determined in the determination mode that none of the converters has reached the end of its life, the lifespan determination unit transitions the operating mode to the normal mode in which the plurality of converters operate without limiting their output, and when, in the determination mode, there is a degraded converter that has reached the end of its life, the lifespan determination unit transitions the operating mode to the limit mode in which the output of the degraded converter is limited. (Supplementary Note 2) The power supply device according to Supplementary Note 1, wherein each of the plurality of converters includes: a first semiconductor switching element, a power supply control circuit that controls switching of the first semiconductor switching element, a reactor or a transformer that stores energy in accordance with the switching operation of the first semiconductor switching element, the smoothing capacitor connected between the output node and the reactor or the transformer, and a backflow prevention element that is connected between the smoothing capacitor and the output node and that prevents current from flowing from an operating converter to the smoothing capacitor of the target converter in the determination mode, and the power supply control circuit stops the switching operation of the first semiconductor switching element in the determination mode in accordance with a command from the life determination unit. (Supplementary Note 3) The power supply device according to Supplementary Note 2, wherein the life determination unit measures a discharge time from when discharging of the smoothing capacitor is started by stopping the switching operation of the first semiconductor switching element of the target converter to when the voltage of the smoothing capacitor reaches a determination value, and determines that the target converter has reached the end of its life if the discharge time is shorter than a threshold time.(Supplementary Note 4) The power supply device according to Supplementary Note 3, wherein the threshold time is set in a plurality of stages. (Supplementary Note 5) The power supply device according to Supplementary Note 2, wherein the life determination unit, in the determination mode, measures a residual voltage of the smoothing capacitor when a specified time has elapsed since discharging of the smoothing capacitor was started by stopping the switching operation of the first semiconductor switching element of the target converter, and determines that the target converter has reached the end of its life if the residual voltage is smaller than a threshold voltage. (Supplementary Note 6) The power supply device according to Supplementary Note 5, wherein the threshold voltage is set in a plurality of stages. (Supplementary Note 7) The power supply device according to any one of Supplementary Notes 2 to 6, wherein each of the plurality of converters further includes a discharge circuit connected in parallel with the smoothing capacitor, the discharge circuit including a resistor element and a switch connected in series with each other, and the life determination unit, in the determination mode, stops the switching operation of the first semiconductor switching element of the target converter and switches the switch of the discharge circuit from off to on. (Supplementary Note 8) The power supply device according to any one of Supplementary Notes 2 to 7, wherein the backflow prevention element includes a second semiconductor switching element, and wherein the life determination unit stops the switching operation of the first semiconductor switching element of the target converter and switches the second semiconductor switching element from on to off in the determination mode. (Supplementary Note 9) The power supply device according to any one of Supplementary Notes 2 to 7, wherein the backflow prevention element includes a diode. (Supplementary Note 10) The power supply device according to any one of Supplementary Notes 2 to 9, wherein the life determination unit reduces the target value of the output voltage of the target converter to a value lower than that in the normal mode before stopping the switching operation of the first semiconductor switching element of the target converter in the determination mode. (Supplementary Note 11) The power supply device according to any one of Supplementary Notes 2 to 10, wherein limiting the output of the degraded converter in the limit mode includes setting the target value of the output voltage of the degraded converter to a voltage lower than the target values ​​of the output voltages of the other converters.(Supplementary Note 12) The power supply device according to any one of Supplementary Notes 2 to 10, wherein limiting the output of the degraded converter in the limit mode includes turning off the operating power supply of the power supply control circuit of the degraded converter. (Supplementary Note 13) The power supply device according to any one of Supplementary Notes 2 to 10, wherein, in each of the plurality of converters, the power supply control circuit controls switching of the first semiconductor switching element so that the output current of the converter does not exceed a current limit value, and the life determination unit, in the limit mode, lowers the current limit value of the degraded converter and raises the current limit values ​​of the other converters. (Supplementary Note 14) The power supply device according to any one of Supplementary Notes 1 to 13, wherein the life determination unit notifies a user of the degraded converter in the limit mode. (Supplementary Note 15) The power supply device according to any one of Supplementary Notes 1 to 14, wherein the power supply device further has a maintenance mode as one of the operation modes, and the life determination unit, in the maintenance mode, stops operation of a target converter that is a life determination target while leaving other converters operating, and determines whether the target converter has reached the end of its life based on the degree of voltage drop due to discharge of a smoothing capacitor of the target converter, and the life determination unit determines the degree of voltage drop of the smoothing capacitor in the maintenance mode so that the target converter may be determined to have reached its life even if it was not determined to have reached its life in the determination mode. (Supplementary Note 16) The power supply device according to any one of Supplementary Notes 1 to 15, wherein the life determination unit periodically transitions the operation mode from the normal mode to the determination mode, thereby periodically determining the life of the multiple converters, and each of the multiple converters includes a temperature sensor for measuring an ambient temperature of the smoothing capacitor, and the life determination unit increases the frequency of performing the life determination when the ambient temperature of the smoothing capacitor becomes equal to or higher than a temperature threshold.

[0186] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0187] 1 power supply equipment, 2 load, 3 life determination unit, 4 power supply control circuit, 5 voltage detection unit, 6 current control unit, 6A current detection unit, 6B memory unit, 6C comparator, 7 snubber circuit, 8 discharge circuit, 9 second semiconductor switching element, 20 normal mode, 21 determination mode, 22 limit mode, 25 temperature sensor, C1 power supply smoothing capacitor, C2 main circuit capacitor, C3 capacitor, C4 smoothing capacitor, CNV, CNV1 to CNV3 converter, D1 to D3 diode, EA error amplifier, IL current limit value, IS current sensor, Idc discharge path, Io output current, N1 input node, N2 output node, N3, N4 ground node, N5, N6 intermediate node, PC photocoupler, Q1 first semiconductor switching element, Q2 MOSFET, R1 to R5 resistance elements, S1, S3, S4, S5 control signal, S2 Setting signal, SR1 shunt regulator, TF transformer, TR phototransistor, TR1 transistor, Ts specified time, V1 external DC power supply, V2 external AC power supply, Vc capacitor voltage, Vd judgment value, Vo output voltage, Vref reference voltage, W1 primary winding, W2 secondary winding.

Claims

1. A power supply device, a plurality of converters connected in parallel with each other between an input node and an output node; a lifespan determination unit, The power supply device, wherein the life determination unit determines whether a target converter that is a target of life determination among the plurality of converters has reached the end of its life based on the degree of voltage drop due to discharge of a smoothing capacitor in the target converter.

2. The power supply equipment described in claim 1, wherein the life determination unit stops the operation of the target converter while leaving other converters in the plurality of converters operating, and determines whether the target converter has reached its lifespan.

3. The power supply device has a determination mode and a restriction mode as operation modes, 3. The power supply device according to claim 2, wherein the life determination unit determines in the determination mode whether the target converter has reached the end of its life, and if the target converter is a degraded converter that has reached the end of its life, transitions the operating mode to the limit mode in which the output of the degraded converter is limited.

4. The power supply device further has a normal mode as an operating mode, 4. The power supply device according to claim 3, wherein when the life determination unit determines in the determination mode that none of the plurality of converters has reached the end of its life, the operation mode is transitioned to the normal mode in which the plurality of converters are operated without output restriction.

5. Each of the plurality of converters a first semiconductor switching element; a power supply control circuit that controls switching of the first semiconductor switching element; a reactor or a transformer that stores energy in response to a switching operation of the first semiconductor switching element; the smoothing capacitor connected between the output node and the reactor or the transformer; a backflow prevention element connected between the smoothing capacitor and the output node, for preventing current from flowing from an operating converter into the smoothing capacitor of the target converter during the determination mode; 5. The power supply device according to claim 4, wherein the power supply control circuit stops the switching operation of the first semiconductor switching element in accordance with a command from the life determination unit in the determination mode.

6. 6. The power supply device according to claim 5, wherein in the determination mode, the life determination unit measures a discharge time from when discharging of the smoothing capacitor is started by stopping the switching operation of the first semiconductor switching element of the target converter until the voltage of the smoothing capacitor reaches a determination value, and determines that the target converter has reached the end of its life if the discharge time is shorter than a threshold time.

7. The power supply device according to claim 6 , wherein the threshold time is set in a plurality of stages.

8. 6. The power supply device according to claim 5, wherein in the determination mode, the life determination unit measures a residual voltage of the smoothing capacitor when a specified time has elapsed since discharging of the smoothing capacitor was started by stopping the switching operation of the first semiconductor switching element of the target converter, and determines that the target converter has reached the end of its life if the residual voltage is smaller than a threshold voltage.

9. The power supply device according to claim 8 , wherein the threshold voltage is set in a plurality of stages.

10. Each of the plurality of converters further comprising a discharge circuit connected in parallel with the smoothing capacitor; the discharge circuit includes a resistor element and a switch connected in series with each other; The power supply device according to any one of claims 5 to 9, wherein in the determination mode, the life determination unit stops the switching operation of the first semiconductor switching element of the target converter and switches the switch of the discharge circuit from off to on.

11. the backflow prevention element includes a second semiconductor switching element; The power supply device according to any one of claims 5 to 9, wherein, in the determination mode, the life determination unit stops the switching operation of the first semiconductor switching element of the target converter and switches the second semiconductor switching element from on to off.

12. 10. The power supply device according to claim 5, wherein the backflow prevention element includes a diode.

13. The power supply device according to any one of claims 5 to 9, wherein in the determination mode, the life determination unit lowers the target value of the output voltage of the target converter below that in the normal mode before stopping the switching operation of the first semiconductor switching element of the target converter.

14. The power supply device according to any one of claims 5 to 9, wherein limiting the output of the degraded converter in the limit mode includes setting a target value of the output voltage of the degraded converter to a voltage lower than the target values ​​of the output voltages of other converters.

15. 10. The power supply device according to claim 5, wherein limiting the output of the degraded converter in the limit mode includes turning off the operating power of the power supply control circuit of the degraded converter.

16. In each of the plurality of converters, the power supply control circuit controls switching of the first semiconductor switching element so that the output current of the converter does not exceed a current limit value; 10. The power supply device according to claim 5, wherein, in the limit mode, the life determination unit lowers the current limit value of the deteriorated converter and raises the current limit values ​​of the other converters.

17. 10. The power supply device according to claim 5, wherein the life determination unit notifies a user of the deteriorated converter in the restricted mode.

18. the power supply device further has a maintenance mode as one of the operation modes, the life determination unit, in the maintenance mode, stops operation of a target converter that is a life determination target while keeping other converters in operation, and determines whether or not the target converter has reached the end of its life based on the degree of voltage drop caused by discharge of a smoothing capacitor of the target converter; The power supply device according to any one of claims 5 to 9, wherein the life determination unit determines the degree of voltage drop of the smoothing capacitor in the maintenance mode so that the smoothing capacitor may be determined to have reached its life even if it is not determined to have reached its life in the determination mode.

19. the life determination unit periodically transitions an operation mode from the normal mode to the determination mode, thereby periodically determining the lifespan of the plurality of converters; each of the plurality of converters includes a temperature sensor for measuring an ambient temperature of the smoothing capacitor; 10. The power supply device according to claim 5, wherein the life determination unit increases the frequency of performing the life determination when the ambient temperature of the smoothing capacitor becomes equal to or higher than a temperature threshold value.