DC power supply system

Abstract

Output sides of a plurality of DC power supply devices (10A-10E), which are CVCC power supplies, are connected in parallel to a load (120). In each of the plurality of DC power supply devices (10A-10E), an upper limit current (Icc), which is maintained in a CC mode, is designed to be equal to or smaller than a rated current. The output voltages of the plurality of DC power supply devices (10A-10E) are actually different due to unevenness within an allowable voltage range of the load 120 with respect to an equally set reference voltage Vr. The plurality of DC power supply devices (10A-10E) operates, in response to an increase in an output current (Iout) to the load (120), so as to supply a current accompanied by a transition from a CV mode to the CC mode in an order from a DC power supply device of which an actual output voltage is high.

Description

DC Power System

[0001] The present disclosure relates to a DC power supply system.

[0002] In recent years, DC electrical equipment has been attracting attention for applications such as DC power supply in ZEBs (zero-emission buildings), power supplies for data centers, and electrification of mobility, and demand for such equipment is increasing. Therefore, there is a growing demand for DC power supply systems that supply power to DC electrical equipment, with higher capacity, higher reliability, and smaller size. In particular, in order to meet the demand for higher capacity, in addition to using a single high-capacity DC power supply, configurations in which multiple small-capacity DC power supplies are operated in parallel are being adopted.

[0003] For example, Japanese Patent Laid-Open Publication No. 2006-34047 (Patent Document 1) describes a configuration in which multiple power supply units (DC power supplies) whose drooping characteristic portions operate at constant current are connected in parallel to an external load, in which only the first power supply unit is started up, and when the output current reaches a constant current (maximum current), a start-up signal is sent to the next power supply unit, and the subsequent power supply units are started up in succession. Also, in Patent Document 1, a reference voltage indicating the constant current value due to the drooping characteristic is sent along with the start-up signal, thereby balancing the load between the power supply units when the power supply units are started up sequentially.

[0004] Japanese Patent Application Laid-Open No. 2006-34047

[0005] The configuration of Patent Document 1 makes it possible to supply current to a large-capacity load without using a large-capacity power supply, which tends to be difficult to miniaturize and improve efficiency. However, because coordinated operation is performed between multiple power supply modules, involving the transmission and reception of the above-mentioned start-up signal and reference voltage signal, there are concerns that the control may become more complicated, including an increase in control lines.

[0006] The present disclosure has been made to solve such problems, and an object of the present disclosure is to provide a DC power supply system that realizes power supply corresponding to changes in output current to a load without performing coordinated control through the transmission and reception of signals or information between multiple DC power supplies connected in parallel.

[0007] In one aspect of the present disclosure, a DC power supply system is provided. The DC power supply system supplies a DC voltage and a DC current to a DC load and includes a plurality of DC power supply devices connected in parallel with their outputs electrically connected to the DC load. Each of the DC power supply devices is configured to enter a non-operating state in which it does not output current when the DC voltage supplied to the DC load is higher than the actual output voltage of the DC power supply device, and to enter an operating state according to predetermined output characteristics when the DC voltage is equal to or lower than the output voltage. The output characteristics are configured such that, in each DC power supply device, when the output current is lower than an upper limit current set for each of the DC power supply devices, it operates in a constant voltage mode in which feedback control of the output voltage is performed to maintain the output voltage at a predetermined reference voltage, and when the output current reaches the upper limit current, it operates in a constant current mode in which feedback control of the output current is performed to maintain the output current at the upper limit current. In each DC power supply device, the upper limit current is set to be equal to or lower than the rated current of the DC power supply device. At least some of the DC power supply devices have output voltages in a constant voltage mode with respect to an equally set reference voltage that are different from one another within the voltage tolerance range of the DC load.

[0008] According to the present disclosure, in a DC power supply system that supplies power to a load using a plurality of DC power supply devices connected in parallel, current is output according to the output characteristics of the DC power supply devices, which have different output voltages due to manufacturing variations, in order from the DC power supply device with the highest actual output voltage, thereby making it possible to supply power to the load in response to changes in output current without performing coordinated control between the DC power supply devices.

[0009] 10 is a block diagram illustrating the configuration of a DC power supply system according to the present embodiment. FIG. 11 is a graph illustrating an example of a current distribution profile expected for the load shown in FIG. 1. FIG. 12 is a conceptual diagram illustrating the output characteristics of each DC power supply device shown in FIG. 1. FIG. 13 is a block diagram illustrating the configuration of a DC power supply system according to Embodiment 1. FIG. 14 is a conceptual diagram and a table illustrating the operation of each DC power supply device in the DC power supply system according to Embodiment 1. FIG. 15 is a table illustrating a list of planned operating time values ​​when each DC power supply device operates according to FIG. 5 in the DC power supply system according to Embodiment 1. FIG. 16 is a circuit diagram illustrating a first configuration example and an operation example of a plurality of DC power supply devices shown in FIG. 4. FIG. 17 is a circuit diagram illustrating a second configuration example and an operation example of a plurality of DC power supply devices shown in FIG. 4. FIG. 18 is a conceptual diagram illustrating the output characteristics of each DC power supply device in a DC power supply system according to Embodiment 2. FIG. 19 is a block diagram illustrating the configuration of a DC power supply system according to Embodiment 2. FIG. 19 is a conceptual diagram illustrating the output characteristics of each DC power supply device in FIG. 10. FIG. 19 is a conceptual diagram and a table illustrating the operation of the DC power supply system according to Embodiment 2. FIG. 20 is a conceptual diagram illustrating the output characteristics of each DC power supply device in the DC power supply system according to Embodiment 2. 19 is a conceptual diagram illustrating a specific example of the output characteristics of each DC power supply device to which FIG. 13(b) is applied. FIG. 19 is a conceptual diagram illustrating the operation of a DC power supply system according to embodiment 3. FIG. 20 is a conceptual diagram illustrating the output characteristics of each DC power supply device in a DC power supply system according to a modification of embodiment 3. FIG. 21 is a conceptual diagram illustrating a specific example of the output characteristics of each DC power supply device to which FIG. 16 is applied. FIG. 22 is a conceptual diagram illustrating the operation of a DC power supply system according to a modification of embodiment 3. FIG. 23 is an external view of a DC power supply device constituting a DC power supply system according to embodiment 4. FIG. 24 is an external view of a power supply slot that houses the DC power supply device shown in FIG. 23. FIG. 25 is a conceptual diagram illustrating an example of a state before maintenance of a DC power supply system according to embodiment 4. FIG. 26 is a conceptual diagram illustrating an example of maintenance work for a DC power supply system according to embodiment 4. FIG. 27 is a conceptual diagram illustrating the configuration of a DC power supply system according to embodiment 5 and an example of maintenance work. FIG. 28 is a block diagram illustrating the configuration of a DC power supply system according to embodiment 6. FIG. 29 is a diagram illustrating the operation of each DC power supply device in a DC power supply system according to embodiment 6.Fig. 10 is a block diagram illustrating a configuration of a DC power supply system according to a seventh embodiment. Fig. 11 is a conceptual diagram illustrating an operation of the DC power supply system according to the seventh embodiment. Fig. 12 is a conceptual diagram illustrating a first example of a cooling structure for a DC power supply device in the DC power supply system according to the present embodiment. Fig. 13 is a conceptual diagram illustrating a second example of a cooling structure for a DC power supply device in the DC power supply system according to the present embodiment.

[0010] First Embodiment Fig. 1 shows a block diagram illustrating the configuration of a DC power supply system according to this embodiment.

[0011] Referring to Fig. 1, a DC power supply system 100 according to this embodiment includes N (N: an integer of 2 or greater) DC power supply devices 10(1) to 10(N). Each of the DC power supply devices 10(1) to 10(N) can be configured using power supply modules with the same specifications, and it is assumed that the circuit configuration, capacity (current capacity), and life design of each device are equivalent, but the specifications do not necessarily have to be the same. For example, the capacity (current capacity) may differ between the DC power supply devices 10(1) to 10(N).

[0012] The input side of each of the DC power supply devices 10(1) to 10(N) is connected to a power source 101. As will be described later, in this embodiment, it is assumed that each of the DC power supply devices 10(1) to 10(N) performs DC / DC conversion by turning on and off at least one semiconductor switching element (not shown). Therefore, the power source 101 can be a power converter that converts AC voltage from an AC power source into DC voltage, or a DC power source using a storage element such as a battery.

[0013] Alternatively, by arranging a rectifier circuit in the input stage of the DC power supply devices 10(1) to 10(N), the power source 101 can be configured as an AC power source. Note that, although Fig. 1 shows an example of a configuration in which the input sides of the DC power supply devices 10(1) to 10(N) are connected to a common power source 101, it is also possible to configure a configuration in which a plurality of power sources 101 are connected to the input sides of each of the DC power supply devices 10(1) to 10(N).

[0014] Each of the DC power supply devices 10(1) to 10(N) outputs DC power between DC output terminals P(+) and N(-) with feedback (FB) control of either the output voltage or the output current. The DC output terminals P(+), N(-) of the DC power supply devices 10(1) to 10(N) are connected in parallel to power lines PL, NL for supplying power to a load 120.

[0015] The load 120 is a DC electrical device that requires a load current that exceeds the supply current of one of the DC power supply devices 10(1) to 10(N). The load 120 has a margin (±X%) that allows it to tolerate voltage fluctuations within a predetermined range relative to the standard voltage Vrt. In other words, the output voltage Vout from the DC power supply system 100 to the load 120 must be within the voltage tolerance range of Vo=Vrt±X% in accordance with the margin. The maximum load current Imax for the load 120 is also determined in advance.

[0016] The load 120 is configured by a resistive load, an inductive load, a capacitive load, or a combination of a power converter for DC / AC conversion and an AC electrical device (such as a motor), and is configured by, for example, a load of a DC power distribution facility, an air conditioner, an interior light, an elevator, home appliances, or other device that requires a DC power supply. For example, the load 120 is configured with two or more DC electrical devices, and the output current (load current) from the DC power supply system 100 to the load 120 changes depending on the number of operating devices.

[0017] FIG. 2 shows an example of a current profile assumed in the load 120.

[0018] The horizontal axis of FIG. 2 represents the load current supplied from the DC power supply system 100 to the load 120, and the vertical axis represents the integrated value of the operation time of the load 120.

[0019] Based on the assumed operation frequencies of the two or more DC electrical devices described above, an assumed value of the occurrence frequency (distribution) of each load current value while the load current varies between 0 (A) and Imax (A) is determined in advance. Then, the operation time (Tlim × occurrence frequency) at each load current value is calculated relative to the limit operation time Tlim (e.g., 131,520 (h) corresponding to a planned operation time of 15 years) corresponding to the integrated operation time, which is the design life, and the calculated operation time is integrated from 0 (A), thereby obtaining the current conduction profile shown in FIG. 3 .

[0020] FIG. 3 shows a conceptual diagram illustrating the output characteristics of each of the DC power supply devices 10(1) to 10(N) shown in FIG.

[0021] Referring to FIG. 3 , when the output current is lower than the upper limit current Icc, each of the DC power supply devices 10(1) to 10(N) operates in a constant voltage (CV) mode using voltage feedback control to maintain the output voltage at a predetermined reference voltage Vr. On the other hand, when the output current exceeds the upper limit current Icc, the DC power supply devices 10(1) to 10(N) operate in a constant current (CC) mode to limit the output of the DC power supply devices 10(1) to 10(N) so that the output current does not increase any further. That is, in the CC mode, current feedback control is performed in which the current target value is set to the upper limit current Icc, and the output voltage is no longer directly controlled. Therefore, the output voltage of the DC power supply device decreases depending on the power supplied to the load 120.

[0022] The output voltage-output current control characteristic shown in Figure 3 is called a drooping characteristic, and a DC power supply having such a control characteristic is called a CVCC (Constant Voltage Constant Current) power supply. In this embodiment, in DC power supply devices 10(1) to 10(N), the reference voltage Vr under CVCC control is set equal to the standard voltage Vrt of load 120 and is the same among DC power supply devices 10(1) to 10(N). In contrast, in each DC power supply device 10(1) to 10(N), the output voltage Vo in CV mode relative to the reference voltage Vr actually varies within the voltage tolerance range (±X%) of load 120 described above due to the occurrence of an offset caused by manufacturing variations and the like.

[0023] For example, each DC power supply device 10(1) to 10(N) generates an analog constant voltage (bias voltage) corresponding to a reference voltage Vr and uses it for feedback control in CV mode, but there is variation in the setting of this bias voltage. Furthermore, a voltage divider circuit is typically used for feedback control, but variations also occur in the voltage division ratio. These factors result in variations in the output voltage Vo of each DC power supply device 10(1) to 10(N) relative to the equally set reference voltage Vr.

[0024] If the output voltage Vo falls outside the voltage tolerance range (±X%), the DC power supply device is removed through product testing. As a result, in the DC power supply system 100 according to this embodiment, the output voltage Vo differs between at least some of the parallel-connected DC power supply devices 10(1) to 10(N). As a result, the actual output characteristics of each DC power supply device 10 are shifted upward or downward from the characteristic line shown in FIG. 3 in accordance with the difference (offset) between the actual output voltage Vo and the reference voltage Vr.

[0025] Furthermore, in a typical CVCC power supply, the upper limit current Icc at which the power supply switches from CV mode to CC mode is set to approximately 120% to 140% of the rated current, and each component of the power supply is designed so that operation at the rated current will satisfy the design life (for example, Tlim in FIG. 3). In other words, in a typical CVCC power supply, the design life for operation at the current value (upper limit current Icc) at which constant current control is performed using drooping characteristics is not guaranteed. This is because operation at this current value is in a range exceeding the rated current.

[0026] In contrast, in each of the DC power supply devices 10(1) to 10(N) according to this embodiment, the upper limit current Icc at which constant current control is performed is set to be equal to or lower than the rated current value. That is, in the DC power supply devices 10(1) to 10(N), each component is designed so that the designed life is satisfied even when the device is operated at a current value at which constant current control based on drooping characteristics is performed. In this way, in this embodiment, the relationship between the rated current value and the drooping characteristics (upper limit current Icc) of the parallel-connected DC power supply devices (CVCC power supplies) is uniquely defined, unlike that of conventional CVCC power supplies.

[0027] Next, an embodiment will be described with specific numerical examples of the output voltage and output current of the DC power supply, mainly focusing on an example where N=5.

[0028] FIG. 4 is a block diagram illustrating the configuration of the DC power supply system according to the first embodiment.

[0029] 4, a DC power supply system 100a according to this embodiment includes five (N=5) DC power supply devices 10A-10E, at least the outputs of which are connected in parallel. The rated value (rated voltage) of the output voltage of each of the DC power supply devices 10A-10D and the rated value of the voltage supplied to the load 120 (i.e., standard voltage Vrt) are 15 V. The load 120 corresponds to a "DC load," and the output voltage Vout and output current Iout from the DC power supply system 100a to the load 120 correspond to the "DC voltage" and "DC current," respectively, supplied to the "DC load."

[0030] Each of the DC power supply units 10A to 10E is controlled to have an upper limit current Icc of 100 A in Fig. 3, and outputs a constant current with a drooping characteristic (CC mode) when the output current is 100 A. As described above, the upper limit current Icc is equal to or less than the rated current of the DC power supply units 10A to 10E, and each of the DC power supply units 10A to 10E is designed to be capable of operation for the limit operating time Tlim (e.g., 131,520 h) in Fig. 2 when the output current is 100 A.

[0031] The load 120 can tolerate a power supply voltage fluctuation of ±5% relative to the standard voltage Vrt of 15 V. That is, the voltage tolerance range of the output voltage Vout from the DC power supply system 100a to the load 120 is 15 V ±5% (14.25 to 15.75 V). The maximum load current Imax is 480 A, and the output current Iout from the DC power supply system 100a to the load 120 varies from 20 A to 480 A. The current profile shown in FIG. 2 is predetermined based on the expected operating time at each expected current value within the range of 0 A to 480 A on the horizontal axis of FIG. 2.

[0032] Since the load 120 has an Imax of 480 A, five DC power supply units 10A to 10E, each with an Icc of 100 A, are connected in parallel. That is, because the sum of the upper limit currents Icc of the DC power supply units 10A to 10E is greater than the maximum load current Imax, the parallel operation of the DC power supply units 10A to 10E can supply the load 120 with a maximum current of 480 A.

[0033] The reference voltage Vr of the DC power supply units 10A to 10E is set to the same value as the standard voltage Vrt of the load 120, that is, 15 (V). In contrast, the actual output voltage Vo from the DC power supply units 10A to 10E varies within the voltage tolerance range of 15 (V) ±5% due to offsets caused by the above-mentioned manufacturing variations and the like.

[0034] 4, for example, for DC power supply 10A, Vo = 15 + 0.17 = 15.17 (V), and for DC power supply 10B, Vo = 15 + 0.08 = 15.08 (V). Furthermore, for DC power supply 10C, Vo = 15 + 0.05 = 15.05 (V). Furthermore, for DC power supply 10D, Vo = 15 - 0.03 = 14.97 (V), and for DC power supply 10E, Vo = 15 - 0.18 = 14.82 (V). In other words, FIG. 4 illustrates a case in which the output voltages Vo of DC power supply units 10A to 10E are all different relative to the same set reference voltage Vr.

[0035] FIG. 5 shows a conceptual diagram and a table for explaining the operation of the DC power supply system 100a.

[0036] 5A, the horizontal axis represents the output current Iout (i.e., load current) from the DC power supply system 100a to the load 120, and the vertical axis represents the output voltage Vout from the DC power supply system 100a to the load 120. Due to the drooping characteristics of the DC power supply devices 10A to 10E, which are CVCC power supplies, the output voltage Vout changes as the operating state of the DC power supply devices 10A to 10E changes within the current range IRa to IRe of the output current Iout.

[0037] FIG. 5B shows a diagram illustrating the operating states of the DC power supply devices 10A to 10E in each range of the output current Iout.

[0038] 5(a) and 5(b), in the current region IRa where the output current Iout is 0 to 100 (A), only the DC power supply 10A (Vo = 15.17 (V)), which has the highest output voltage Vo, outputs current, while the remaining DC power supply units 10B to 10E, which have output voltages Vo lower than 15.17 (V), do not supply current. Therefore, the output voltage Vout of the DC power supply system 100a is 15.17 (V), and the output of the DC power supply unit 10A is within the range of 0% to 100% (output current = Icc = 100 (A)). Meanwhile, the DC power supply units 10B to 10E are operating, but their output is 0% (output current = 0 (A)). Hereinafter, for each of DC power supply devices 10A to 10E, the operating state in which current is being supplied will be referred to as the "operating state," and the operating state in which no current is being supplied (output is 0(%)) will be referred to as the "non-operating state." In current region IRa, DC power supply device 10A is in the operating state, while DC power supply devices 10B to 10E are in the non-operating state.

[0039] Next, when the output current Iout reaches 100 A, the output voltage of the DC power supply 10A drops according to the drooping characteristic (Icc = 100 A) shown in FIG. 3 . When the output voltage drops to 15.08 V, the DC power supply 10B, whose output voltage Vo is 15.08 V, also starts supplying current. As a result, the DC power supply 10A operates at 15.08 V x 100 A, while the DC power supply 10B operates at Vo = 15.08 V, supplying the deficiency current within the output range from 0% to 100% (100 A). This operating state continues until the output voltage Vo of the DC power supply 10B drops according to the drooping characteristic, i.e., until Iout = 100 x 2 = 200 A.

[0040] Therefore, in the current region IRb where Iout = 100 to 200 (A), the output voltage Vout of the DC power supply system 100a is 15.08 (V). The output of the DC power supply device 10A (Vo = 15.17 (V)) becomes 100% (100 (A)), and the output of the DC power supply device 10B (Vo = 15.08 (V)) falls within the range of 0% to 100% (100 (A)). On the other hand, the DC power supply devices 10C to 10E, which have output voltages Vo lower than 15.08 (V), do not supply current and remain in a non-operating state, so their output is 0 (%).

[0041] Similarly, when the output current Iout reaches 200 A, the output voltage of DC power supply 10B drops according to the drooping characteristic, and current supply from DC power supply 10C with Vo = 15.05 V begins. Until the output voltage of DC power supply 10C drops according to the drooping characteristic, the output voltage Vout of DC power supply systems 100a and 100b remains at 15.05 V in the current region IRc of Iout = 200 to 300 A. Furthermore, the outputs of DC power supply 10A (Vo = 15.17 V) and DC power supply 10B (Vo = 15.08 V) reach 100% (100 A), while the output of DC power supply 10C (Vo = 15.05 V) falls within the range of 0% to 100% (100 A). On the other hand, the DC power supply units 10D to 10E whose output voltage Vo is lower than 15.05 (V) do not supply current and remain in an inactive state.

[0042] Similarly, in the current region IRd (Iout = 300 to 400 A) as the output current Iout increases, the DC power supply device 10D, with Vo = 14.97 V, also begins to supply current. Therefore, the output voltage Vout of the DC power supply systems 100a to 100c becomes 14.97 V. Furthermore, the output of the DC power supply devices 10A to 10C becomes 100% (100 A), and the output of the DC power supply device 10D (Vo = 14.97 V) becomes within the range from 0% to 100% (100 A). On the other hand, the DC power supply device 10E, whose output voltage Vo is lower than 14.97 V, does not supply current and remains in a non-operating state, so its output is 0%.

[0043] In the current region IRe (Iout = 400 to 500 (A)) where the output current Iout has further increased, the DC power supply device 10E with Vo = 14.82 (V) also begins to supply current. Therefore, the output voltage Vout of the DC power supply systems 100a to 100d becomes 14.82 (V). Furthermore, the output of the DC power supply devices 10A to 10D becomes 100% (100 (A)), and the output of the DC power supply device 10E (Vo = 14.82 (V)) becomes within the range from 0% to 100% (100 (A)). In other words, all of the DC power supply devices 10A to 10E are in an operating state.

[0044] By controlling the operating state in this manner, the parallel operation of DC power supply units 10A to 10E can supply a maximum load current Imax of 480 (A) to load 120, while keeping the drop in output voltage Vout within 5% of the standard value of 15 (V).

[0045] In the drooping characteristic of a CVCC power supply (FIG. 3), it is common for the current under CC control to actually increase slightly above the upper limit current Icc. For example, in this example, the characteristic line for CC control in FIG. 3 may be a diagonal line connecting 100(A)×Vr and 105(A)×0(V) rather than a vertical line connecting 100(A)×Vr and 105(A)×0(V). However, even with such a drooping characteristic line, it is understood that the operating states of DC power supply units 10A-10E with different output voltages Vo can be controlled in the same manner as in FIG. 5(b), even though the boundary values ​​between current regions IRa-IRe are slightly different from those in FIG. 5(b).

[0046] Fig. 6 shows a list of planned operating time values ​​when DC power supply units 10A to 10C in the DC power supply system according to embodiment 1 are operated according to Figs. 5(a) and 5(b). Fig. 6 shows planned operating time values ​​when DC power supply units 10A to 10E are operated according to the characteristics of Figs. 5(a) and 5(b) under the assumed current profile (Fig. 2). In Fig. 6, Tlim is set to 131,520 (h) (approximately 15 years) in Fig. 2.

[0047] Referring to FIG. 6, in accordance with the assumed current profile (FIG. 2), Tlim=131520 (h) is allocated to the cumulative operating time in each current range of the output current Iout (0 to 100 (A), 100 to 200 (A), 200 to 300 (A), 300 to 400 (A), 400 (A) to 500 (A)).

[0048] Then, for each current region, a planned operating time value for each of DC power supply units 10A to 10E is calculated relative to the cumulative operating time for that current region under the output voltage Vo of DC power supply units 10A to 10E in the example of Fig. 4. In each current region, the planned operating time value for a DC power supply unit with an output of 0% (non-operating state) is 0 (h), and for a DC power supply unit in an operating state with an output of 100% or 0 to 100%, the planned operating time value is calculated to be equal to the cumulative operating time for that current region.

[0049] As a result, the planned operation time value for each of the DC power supply units 10A to 10E for Tlim = 131,520 (h) is calculated as the total value in the bottom row of Fig. 6. In the DC power supply system 100a according to the first embodiment, the planned operation time value of the DC power supply unit 10A having the highest output voltage Vo is equal to Tlim, and the DC power supply unit 10A is in a constantly operating state. On the other hand, the lower the output voltage Vo of the DC power supply unit, the lower the planned operation time value is kept.

[0050] If we assume that DC power supply units 10A to 10E are operated for equal periods of time, the average planned operating time of each of DC power supply units 10A to 10E in the bottom row is (131,520 + 116,520 + 110,520 + 58,520 + 2,520) / 5 = 84,120 (h), which is the average operating time. In this case, the operating rate of each of DC power supply units 10A to 10E is 84,120 / 131,520 = 64%.

[0051] In contrast, in the first embodiment, the operating rate of the DC power supply 10A, which is constantly in operation, is 100%. However, when DC power supply units are connected in parallel, the operating rate of the DC power supply unit with a relatively high output voltage increases due to the influence of an output voltage offset caused by manufacturing variations and the like. For this reason, it is difficult to design a lifespan that reflects the above-mentioned average operating rate for each DC power supply unit, and each component is usually designed to ensure a lifespan at a 100% operating rate. Therefore, it is understood that the lifespan of the DC power supply 10A, which has a 100% operating rate in the first embodiment, will not be shorter than that of a conventional DC power supply unit.

[0052] As described above, in the DC power supply system according to the first embodiment, multiple parallel operation that follows the change in the output current Iout to the load 120 is possible simply by connecting the output sides in parallel, without the need for mutual exchange of control signals or information between the plurality of DC power supply devices 10A to 10E that are connected in parallel.

[0053] As will be described later, the smoothing capacitors connected to the output terminals of each of the DC power supply devices 10A to 10E are connected in parallel in the same number as the number of DC power supply devices, so it is easy to ensure a capacitance value for smoothing the output voltage Vout of the DC power supply system 100a. This allows the DC power supply system 100a to have sufficient tolerance to sudden power changes caused by the load 120.

[0054] Generally, when a large-capacity electrolytic capacitor is used as a smoothing capacitor, there is a concern that the ripple voltage and spike voltage of the output voltage Vout will increase due to an increase in ESR (Equivalent Series Resistance) over its lifespan. However, in the DC power supply system according to the first embodiment, as shown in FIG. 6, there are differences in the operating times of the DC power supply devices 10A to 10E, so the ESR increases only in some of the multiple smoothing capacitors connected in parallel. Therefore, it is expected that the DC power supply system 100a as a whole will be able to suppress increases in the ripple voltage and spike voltage of the output voltage Vout.

[0055] Furthermore, since each of the DC power supply units 10A to 10E is constantly operating even when it is not outputting current depending on the voltage level, it can quickly respond to an increase in load current. This makes it possible to configure a DC power supply system that has sufficient instantaneous current supply capacity in response to fluctuations in voltage or current at the load 120.

[0056] Furthermore, because the operating time of DC power supply devices with a relatively high output voltage Vo is concentratedly long, even when a DC power supply device with a relatively long operating time reaches the end of its life, the DC power supply system 100a can resume normal operation by simply replacing only some of the multiple DC power supply devices 10A to 10E. This makes it possible to improve the efficiency of on-site maintenance work and reduce maintenance costs (equipment costs).

[0057] Furthermore, in a configuration in which multiple DC power supply devices are connected in parallel, as in this embodiment, the capacity of each DC power supply device can be reduced. Generally, the size of magnetic components increases in proportion to the volume relative to the current, so the parallel connection configuration of this embodiment makes it possible to reduce the total size, enabling the design of compact equipment with good space efficiency.

[0058] Miniaturization allows components to operate at higher frequencies due to the skin effect and proximity effect, and higher frequencies allow components to be made even smaller. Smaller components, in particular, tend to have more stable quality and be easier to obtain than larger components due to mass production. Furthermore, magnetic components, especially ferrite, tend to have better properties. Thus, reducing the capacity of each DC power supply device can have significant manufacturing benefits.

[0059] Furthermore, if DC power supply units with the same specifications are connected in parallel, the design of the DC power supply units can be standardized, which improves design efficiency and provides cost benefits through increased production volume due to standardization.In addition, if you want to increase the power supply to the load 120, you can do so simply by connecting additional DC power supply units with the same specifications in parallel, which makes it easier to handle larger capacities.

[0060] Next, an example of the configuration and operation of the DC power supply devices 10A to 10E will be described.

[0061] FIG. 7 shows, as a first configuration example, an example in which each of the DC power supply devices 10A to 10E is configured as a flyback type.

[0062] 7, each of DC power supply devices 10A to 10E includes a transformer 110, a semiconductor switching element 112, a diode 113, a capacitor 114, a feedback (FB) circuit 115, a current detection resistor 116, and a control IC (Integrated Circuit) 117.

[0063] The primary winding of the transformer 110, the semiconductor switching element 112, and the current detection resistor 116 are connected in series between input nodes Nip and Nin to which the input voltage Vin from the power source 101 is applied. One end of the secondary winding of the transformer 110 is connected to the positive output terminal (OUT+) via a diode 113. The other end of the secondary winding of the transformer 110 is connected to the negative output terminal (OUT-). A capacitor 114 is connected between the positive output terminal (OUT+) and the negative output terminal (OUT-).

[0064] A pulsed voltage (AC voltage) generated in the primary winding of the transformer 110 by turning on and off the semiconductor switching element 112 is transmitted with reverse polarity to the secondary winding of the transformer 110. The pulsed voltage (AC voltage) transmitted to the secondary winding is rectified by the diode 113 and smoothed by the capacitor 114, thereby generating an output voltage (DC) between the positive output terminal (OUT+) and the negative output terminal (OUT-).

[0065] The voltage across the capacitor 114, i.e., the output voltage of each of the DC power supply devices 10A to 10E, is divided by the FB circuit 115 and input to the control IC 117. Furthermore, the voltage across the terminals of the current detection resistor 116 is input to the control IC 117. This allows the control IC 117 to obtain the detected values ​​of the output voltage and output current of the DC power supply device. The FB circuit 115 and the current detection resistor 116 can be configured using variable resistance elements.

[0066] The control IC 117 outputs a gate signal that is an on / off control signal for the semiconductor switching element 112. The output of each of the DC power supply devices 10A to 10E is controlled by the on-duty ratio of the semiconductor switching element 112 that is on / off controlled.

[0067] A reference voltage Vr and an upper limit current Icc are programmed in the control IC 117. For example, the reference voltage Vr and the upper limit current Icc are set in the control IC 117 using a constant voltage generated in a bias circuit (not shown) provided on the circuit board of each of the DC power supply devices 10A to 10E. Note that it is also possible to realize a configuration in which the reference voltage Vr and the upper limit current Icc can be variably set by changing the voltage division ratio in the FB circuit 115 and the resistance value of the current detection resistor 116.

[0068] In the constant voltage (CV) mode, the control IC 117 generates a gate signal for the semiconductor switching element 112 according to an on-duty ratio set so as to bring the output voltage detected by the FB circuit 115 closer to the reference voltage Vr.

[0069] On the other hand, in the constant current (CC) mode, the control IC 117 generates a gate signal for the semiconductor switching element 112 in accordance with an on-duty ratio controlled so as to maintain the output current detected by the current detection resistor 116 at the upper limit current Icc. Any known method can be applied to the on / off control of the semiconductor switching element in the CV mode and CC mode.

[0070] The DC power supply devices 10A to 10E are connected in parallel to the load 120 by interconnecting the positive output terminal (OUT+) and the negative output terminal (OUT-) of each device. Fig. 7 further shows an example of operation of the DC power supply devices 10A to 10E when Vout = 15.08 (V), i.e., in the current region IRb (100 to 200 (A)) in Fig. 5(b).

[0071] The DC power supply device 10A with Vo=15.17 (V) operates in CC mode, and the on-duty ratio of the semiconductor switching element 112 is controlled so that the output current is equivalent to the upper limit current Icc (100 (A)).

[0072] The DC power supply device 10B, with Vo=15.08 (V), operates in CV mode, and the on-duty ratio of the semiconductor switching element 112 is controlled to maintain the DC voltage detected by the FB circuit 115 at the reference voltage Vr (15.00 (V)). However, due to the influence of an offset caused by manufacturing variations, the actual output voltage Vo is 15.08 (V).

[0073] In the DC power supply 10C with Vo = 15.05 (V), the FB circuit 115 feeds back a DC voltage higher than the actual output voltage Vo, so the on-duty ratio of the semiconductor switching element 112 is 0 or minimal. For example, even if switching occurs due to flyback operation, the semiconductor switching element 112 is immediately turned off. As a result, almost no current is supplied from the DC power supply 10C, and the DC power supply 10C enters an inactive state with an output of 0 (%). Furthermore, the diode 113 is reverse-biased, preventing backflow of current from the load 120.

[0074] DC power supply device 10D with Vo=14.97 (V) and DC power supply device 10E with Vo=14.82 (V) are also placed in a non-operating state, similar to DC power supply device 10C. This allows operation of DC power supply devices 10A to 10E in current region IRb (100 to 200 (A)) in FIG. 5(b).

[0075] 7 , when the output current Iout to the load 120 exceeds 200 A, the detected value of the output current in the DC power supply 10B exceeds the upper limit current Icc, causing a transition from CV mode to CC mode. At this time, the on-duty ratio of the semiconductor switching element 112 reaches its maximum value in CV mode and is then limited in CC mode. As a result, the output power of the DC power supply 10B becomes insufficient, causing the output voltage Vo to fall below 15.08 V.

[0076] As a result, in the DC power supply device 10C, as the output voltage Vout drops below 15.08 (V), the FB circuit 115 detects a voltage close to the actual output voltage Vo (15.05 (V)). As a result, in the DC power supply device 10C, in CV mode, the on-duty ratio of the semiconductor switching element 112 is controlled to maintain the DC voltage detected by the FB circuit 115 at the reference voltage Vr (15.00 (V)). However, due to the influence of an offset caused by manufacturing variations, the actual output voltage Vo is 15.05 (V).

[0077] In contrast, when Vout = 15.05 (V), DC power supply device 10D with Vo = 14.97 (V) and DC power supply device 10E with Vo = 14.82 (V) are in a state where they supply almost no current (non-operating state). As a result, it can be seen that the operating state of DC power supply devices 10A to 10E in the current region IRc (200 to 300 (A)) in Figure 5(b) is realized.

[0078] FIG. 8 shows a second configuration example in which each of the DC power supply devices 10A to 10E is configured in a forward manner.

[0079] 8, each of DC power supply devices 10A to 10E further includes a flywheel diode 118 and a reactor 119 in addition to the flyback configuration in FIG. 7. Reactor 119 is connected between the cathode of diode 113 and the positive output terminal (OUT+). Furthermore, the primary winding and secondary winding of transformer 110 are wound with the same polarity, unlike the flyback system (FIG. 7).

[0080] The flywheel diode 118 is connected so as to continuously form a current loop including the reactor 119 and the capacitor 114 even during the non-conducting period of the diode 113. The forward type is more suitable for large current applications than the flyback type due to the arrangement of the reactor 119. On the other hand, the flyback type has a simpler configuration than the forward type.

[0081] 8, the output of each of the DC power supply devices 10A to 10E is also controlled by the on-duty ratio of the semiconductor switching element 112. That is, the control operations in the CV mode and CC mode are the same as those described in FIG.

[0082] FIG. 8 also shows an example of operation of DC power supplies 10A to 10E when Vout = 15.08 V, i.e., in the current region IRb (100 to 200 A) in FIG. 5B. When Vout = 15.08 V, similar to FIG. 7, DC power supplies 10A and 10B are in an operating state. DC power supply 10A (Vo = 15.17 V) operates in CC mode, while DC power supply 10B (Vo = 15.08 V) operates in CV mode. DC power supplies 10C to 10D are in an inactive state, and diode 113 and flywheel diode 118 are reverse-biased, thereby preventing reverse current from flowing from load 120.

[0083] In this way, it is possible to realize the control of the operating states of DC power supply devices 10A to 10E (FIGS. 5(a) and 5(b)) in the DC power supply system according to embodiment 1 without being limited to the configurations of DC power supply devices 10A to 10E. Furthermore, the configurations of DC power supply devices 10A to 10E are not limited to the examples shown in FIGS. 7 and 8, and any configuration can be used as long as CVCC control (FIG. 3) in accordance with reference voltage Vr and upper limit current Icc is possible.

[0084] 7 and 8, by using an isolated power supply in which the primary side (power source 101 side) and the secondary side (load 120 side) are isolated by a transformer, it becomes easier to prevent reverse current from flowing back from an operating DC power supply in a DC power supply that is outputting almost no current, thereby enabling more stable operation. If the reference potential (ground) is the same between the power source 101 and the load 120, each DC power supply 10 can be configured as a non-insulated type. In other words, in this embodiment, each DC power supply can be either an isolated type or a non-insulated type as long as it is a CVCC power supply to which the above-mentioned life design is applied, and any circuit configuration can be applied.

[0085] It should also be noted that when the power source 101 is an AC power supply, by arranging a rectifier circuit in the input stage, the AC / DC converter can also be applied to the DC power supply devices 10A to 10E.

[0086] Second Embodiment In a second embodiment, a modified example of the output characteristics (CVCC control) of each DC power supply device operating in parallel will be described.

[0087] FIG. 9 is a conceptual diagram illustrating the output characteristics of each DC power supply device in the DC power supply system according to the second embodiment.

[0088] 9, in the second embodiment, the drooping characteristic of each DC power supply includes a region of the derating characteristic (hereinafter referred to as the derating region) in which the output voltage is reduced in response to an increase in output current when the mode is switched from CV mode to CC mode. Specifically, when the output current increases above a determination current I1 that is smaller than the upper limit current Icc by ΔI, the target voltage value of the voltage feedback control is reduced from the reference voltage Vr at a constant rate. The rate of voltage reduction in response to an increase in current in the derating characteristic is expressed as −(ΔV / ΔI).

[0089] For example, by configuring the control IC 117 in Figures 7 and 8 with a programmable digital IC such as a DSP (Digital Signal Processor), it is possible to realize the drooping characteristic with the derating characteristic shown in Figure 9 by programming. Alternatively, it is also possible to realize a similar function by using an analog circuit such as an operational amplifier.

[0090] FIG. 10 is a block diagram illustrating the configuration of a DC power supply system according to the second embodiment.

[0091] As shown in Fig. 10, the DC power supply system 100b according to the second embodiment includes five DC power supply devices 11A-11E (N=5) with at least their outputs connected in parallel, similar to the DC power supply system 100a according to the first embodiment (Fig. 4). The DC power supply devices 11A-11E according to the second embodiment differ from the DC power supply devices 10A-10E according to the first embodiment in that the output characteristics (CVCC control) include the derating characteristic region described in Fig. 9. The DC power supply devices 11A-11E are otherwise similar to the DC power supply devices 10A-10E according to the first embodiment. Furthermore, the remaining components of Fig. 10, including the power source 101 and the load 120, are similar to those of the first embodiment (Fig. 4), and therefore detailed description thereof will not be repeated.

[0092] FIG. 11 is a conceptual diagram illustrating the output characteristics of each of the DC power supply devices 11A to 11E in FIG.

[0093] As shown in FIG. 11, the output characteristics of DC power supply units 11A to 11E correspond to those in FIG. 9 where derating characteristics are set with ΔI=20 (A) and ΔV=0.2 (V) under Icc=100 (A).

[0094] Therefore, when the output current exceeds I1=80 (A), the target voltage of the voltage feedback control decreases from the reference voltage Vr at a constant rate of -0.01 (V / A). Therefore, the CV mode operation of each of the power supply units 11A to 11E is controlled so that when the output current is 90 (A), the output voltage decreases by 0.1 (V) below the reference voltage Vr, and when the output current is 100 (A), the output voltage decreases by 0.2 (V) below the reference voltage Vr. Specifically, the voltage target value of the voltage feedback control in the CV mode is gradually decreased from the reference voltage Vr in accordance with the derating characteristics.

[0095] Referring again to FIG. 10 , the reference voltage Vr of each of the DC power supply units 11A to 11E is set to the same value, 15 V, as that of the DC power supply units 10A to 10E in the first embodiment ( FIG. 4 ). However, the actual output voltage Vo of each of the DC power supply units 11A to 11E has the same manufacturing variation (offset) as that of the DC power supply units 10A to 10E. Specifically, under voltage feedback control with the reference voltage Vr set to 15 V, the output voltage Vo of the DC power supply unit 11A is 15 + 0.17 = 15.17 V, while the output voltage Vo of the DC power supply unit 11B is 15 + 0.08 = 15.08 V. The output voltage Vo of the DC power supply unit 11C is 15 + 0.05 = 15.05 V. Furthermore, in the DC power supply device 11D, Vo=15-0.03=14.97 (V), and in the DC power supply device 11E, Vo=15-0.18=14.82 (V).

[0096] FIG. 12 shows a conceptual diagram and a table for explaining the operation of the DC power supply system according to the second embodiment.

[0097] 12(a), similar to FIG. 5(a), the horizontal and vertical axes represent the output current Iout (i.e., load current) and output voltage Vout from the DC power supply system 100a to the load 120. In the second embodiment, a derating characteristic is provided for the drooping characteristic, so that the current range of the output current Iout is more subdivided than in the first embodiment (FIG. 5(a)).

[0098] Referring to FIG. 12(a), in a current region IR1 where the output current Iout is 0 to 80 (A), only the DC power supply 11A (Vo = 15.17 (V)) with the highest output voltage Vo outputs current, while the remaining DC power supply units 10B to 10E with output voltages Vo lower than 15.17 (V) are in an inoperative state and do not supply current.

[0099] 12(b), in current region IR1, the output of DC power supply 11A is within the range of 0% to 80% (output current of 80 A). On the other hand, DC power supply units 11B to 11E are in an inactive state, with an output of 0% (output current = 0 A), although they are operating.

[0100] 12(a), when output current Iout increases above 80 A, output voltage Vo of DC power supply device 11A decreases at a rate of 0.1 V per current increase of 10 A. As a result, in current region IR2 where output current Iout is 80 to 89 A, the output voltage of DC power supply device 11A decreases at this rate to 15.17 - 0.1 = 15.07 V.

[0101] 12(b), in current region IR2, the output of DC power supply 11A is within the range of 80 to 89% (output current of 80 to 89 A). DC power supply units 11B to 11E are in a non-operating state with an output of 0% (output current = 0 A), similar to current region IR1.

[0102] Referring again to Figure 12(a), when the output voltage Vout drops to 15.08 (V), current supply from DC power supply 11B (Vo = 15.08 (V)) begins while the output current of DC power supply 10A is limited to 89 (A). As a result, DC power supplies 11A and 11B enter an operating state at Vout = 15.08 (V). This operating state continues until the output current of DC power supply 11B reaches 80 (A) in accordance with the output characteristics of Figure 11.

[0103] 12(b), in the current region IR3 of output current 89 to 169 (A), the output of DC power supply 11A is fixed at 89% (output current = 89 (A)), and the output of DC power supply 11B is in the range of 0 to 80% (output current = 0 to 80 (A)). DC power supplies 11C to 11E, which have output voltage Vo lower than 15.08 (V), are in a non-operating state with an output of 0% (output current = 0 (A)), similar to current region IR1.

[0104] 12(a) and 12(b), when the output current Iout rises above 169 A, the output current of the DC power supply 11A operating with the derating characteristics of FIG. 11 increases above 89%. When the output voltage Vo drops to 14.97 V, the output current of the DC power supply 11A reaches an upper limit current Icc of 100 A. The DC power supply 11B also begins to operate with the derating characteristics, and its output current also rises from 80%.

[0105] Therefore, in the current region IR4 where the output current Iout is 169 to 175 (A), the output of DC power supply device 11A is 89 to 92% and the output of DC power supply device 11B is 80 to 83%, so that the load current is secured and the output voltage Vout drops from 15.08 (V) to 15.05 (V).

[0106] Similarly, when the output current of a DC power supply operating in CV mode reaches 80 A, the output voltage Vo drops due to the derating characteristic. Furthermore, when the output current of the DC power supply reaches 100 A, the output voltage Vo drops even further due to operation in CC mode. As the output voltage of the DC power supply drops in this way, the DC power supply with the next highest output voltage Vo operates in CV mode and enters an operating state where it supplies current.

[0107] As a result, in response to an increase in the current demand of the load 120, current regions IR5 to IR11, in which the operating states (operating state / non-operating state) of the DC power supply units 10A to 10E are different, exist on the higher current side than the current region IR4 (169 to 175 (A)).

[0108] Specifically, in current region IR5 (Iout = 175 to 255 (A)), when the output voltage Vout is below 15.05 (V), the outputs of DC power supplies 11A and 11B are fixed at 92% (output current = 92 (A)) and 83% (output current = 83 (A)), respectively. Furthermore, the output of DC power supply 11C is within the range of 0 to 80% (output current 0 to 80 (A)). In DC power supplies 11D and 11E, whose output voltage Vo is lower than 15.05 (V), the output is 0% (output current = 0 (A)).

[0109] In current region IR6 (Iout = 255 to 279 (A)), the outputs of DC power supplies 11A and 11B are fixed at 100% (output current = 100 (A)) and 91% (output current = 91 (A)), respectively, and the output of DC power supply 11C is set to 80 to 91%, thereby ensuring the load current. Meanwhile, due to the derating characteristics, output voltage Vout drops from 15.05 (V) to 14.97 (V).

[0110] Furthermore, in current region IR7 (Iout = 279 to 359 (A)), when the output voltage Vout is below 14.97 (V), the outputs of DC power supplies 11A and 11B are fixed at 100% (output current = 100 (A)) and 91% (output current = 91 (A)), respectively, and the output of DC power supply 11C is fixed at 88% (output current = 88 (A)). Furthermore, the output of DC power supply 11D is within the range of 0 to 80% (output current is 0 to 80 (A)). In DC power supply 11E, where the output voltage Vo is lower than 14.97 (V), the output is 0% (output current = 0 (A)).

[0111] In the current region IR8 (Iout = 359 to 395 (A)), the outputs of DC power supplies 11A to 11C are fixed at 100%, and the output of DC power supply 11D is 80 to 95%, thereby ensuring the load current and reducing the output voltage Vout from 14.97 (V) to 14.82 (V).

[0112] In current region IR9 (Iout = 395 to 475 (A)), when output voltage Vout is below 14.82 (V), the outputs of DC power supply devices 11A to 11C are fixed at 100% (output current = 100 (A)), and the output of DC power supply device 11D is fixed at 95% (output current = 95 (A)). Furthermore, the output of DC power supply device 11E is within the range of 0 to 80% (output current 0 to 80 (A)). In other words, all of DC power supply devices 11A to 11E are in an operating state.

[0113] In the current region IR10 (Iout = 475 to 485 (A)), the outputs of DC power supplies 11A to 11C are fixed at 100%, the output of DC power supply 11D is 95 to 100%, and the output of DC power supply 11E is 80 to 85%, thereby ensuring the load current and reducing the output voltage Vout from 14.82 (V) by 0.05 (V).

[0114] In the current region IR11 (Iout = 485 to 500 (A)), the outputs of DC power supplies 11A to 11D are fixed at 100%, and the output of DC power supply 11E is 85 to 100%, thereby ensuring the load current and reducing the output voltage Vout from 14.77 (V) to 0.15 (V).

[0115] In this way, even by parallel operation of DC power supply units 11A to 11E having drooping characteristics with derating characteristics, it is possible to supply a maximum load current Imax of 480 (A) to load 120 while keeping the drop in output voltage Vout within a range of 5% from the standard value of 15 (V).

[0116] According to the DC power supply system of the second embodiment, a derating characteristic is provided for the drooping characteristic of each of the DC power supply devices 11A to 11E, and therefore, in addition to the effect of the first embodiment, the DC power supply devices 11A to 11C operate in a sequential overlapping manner under the condition that the output voltage Vout changes smoothly in response to an increase in the output current Iout. This suppresses sudden fluctuations in the output voltage Vout supplied to the load 120, improving the operational stability of the load.

[0117] Furthermore, in each of the DC power supply units 11A to 11E, the next-stage DC power supply unit operates and starts supplying current before the output current increases to the upper limit current Icc. This suppresses the output current of the DC power supply unit with the higher actual output voltage Vo compared to the first embodiment. As a result, each of the DC power supply units 11A to 11E is expected to have a longer life than the design life assuming continuous operation at the upper limit current Icc. This makes it possible to extend the life of the DC power supply unit 11A, in particular, which has the highest reference voltage Vr, compared to the first embodiment.

[0118] In the second embodiment, the current-voltage characteristic of the derating characteristic of the drooping characteristic is illustrated as a linear characteristic, i.e., a characteristic in which the output voltage decreases at a constant rate with respect to an increase in current, but the current-voltage characteristic is not limited to this example. That is, the current-voltage characteristic in the derating characteristic for the transition from CV mode to CC mode may be set to a curved shape as long as the output current gradually decreases with an increase in output current.

[0119] Third Embodiment In a third embodiment, a further modification of the output characteristics (CVCC control) of each of the DC power supply devices operating in parallel will be described. That is, the third embodiment shows a variation of the DC power supply device 10 according to the first embodiment.

[0120] FIG. 13 is a conceptual diagram illustrating a first example and a second example of the output characteristics of each DC power supply device in the DC power supply system according to the third embodiment.

[0121] Comparing Figure 13(a) with Figure 3, in the third embodiment, the drooping characteristic of each DC power supply device includes an overcurrent protection function that further limits current when the output voltage drops from the reference voltage Vr to a predetermined drooping voltage Vcc in CC mode, where the upper limit current Icc is maintained. The output characteristic (drooping characteristic) in Figure 13(a) is also referred to as a "foldback characteristic." In the overcurrent protection region, the current reference for the current feedback is reduced from Icc to Is (starting current) in proportion to the reduction in output voltage.

[0122] Fig. 13(b) shows a modification of the foldback characteristic of Fig. 13(a). In the output characteristic of Fig. 13(b), in addition to the overcurrent protection similar to that of Fig. 13(a), load short-circuit protection is added to further limit the output current when the output voltage drops further.

[0123] 13(b), as in FIG. 13(a), when the output voltage drops from the reference voltage Vr to the drooping voltage Vcc in CC mode, overcurrent protection is initiated. In the overcurrent protection region, the current target value of the current feedback is reduced from Icc to the protection current Ip in proportion to the drop in the output voltage.

[0124] If the output voltage further drops to a predetermined protection voltage Vp under overcurrent protection, load short circuit protection is initiated. In the load short circuit protection region, the current target value of the current feedback is reduced from the protection current Ip to the starting current Is in proportion to the drop in the output voltage.

[0125] 13(a) and 13(b), it is possible to limit the output current and protect the DC power supply device when the current flowing to the load 120 increases abnormally due to a load short circuit or the like. The starting current Is can be determined so as to ensure the current required for no-load operation or startup of the load 120, or the current required for control or standby of the load (DC electrical device) 120.

[0126] FIG. 14 is a conceptual diagram illustrating a specific example of the output characteristics of the DC power supply device 10 to which the foldback characteristic of FIG. 13(b) is applied.

[0127] 14, in DC power supply device 10, reference voltage Vr in CV mode can be set to 15 V, and upper limit current Icc in CC mode can be set to 100 A, as in embodiment 1. Furthermore, the values ​​can be set to Vcc = 10 V, Vp = 5 V, Ip = 84 A, and Is = 33 A, as shown in FIG.

[0128] As a result, when Vcc=10(V) in CC mode and the output voltage drops below 10(V), the current target value of the current feedback control is reduced from 100(A) to 84(A) for overcurrent protection.

[0129] When the output voltage drops to 5 V under overcurrent protection, load short circuit protection is initiated, and the current target value of the current feedback control is reduced from 84 A to 33 A in proportion to the drop in output voltage.

[0130] In each actual DC power supply device 10, the characteristic line shown in FIG. 14 becomes an output characteristic that is shifted upward or downward according to the difference (offset) between the actual output voltage Vo and the reference voltage Vr.

[0131] FIG. 15 is a conceptual diagram illustrating the operation of the DC power supply system according to the third embodiment.

[0132] FIG. 15 shows the operation of the DC power supply system shown in FIG. 4 when the output characteristics of the DC power supply devices 10A to 10E are changed from those shown in FIG. 3 to those shown in FIG.

[0133] When the output current Iout from the DC power supply system is 0 to 500 (A) in response to a current request from the load 120, the DC power supply devices 10A to 10E operate in the same manner as in FIG. 5 in the first embodiment, thereby ensuring the output current Iout.

[0134] That is, in the current range where Iout=0 to 100 (A), the output current Iout is supplied only by the DC power supply 10A (Vo=15.17 (V)) that is set to have the highest actual output voltage Vo, and therefore the output voltage Vout is 15.17 (V). In contrast, as the output current Iout increases, the DC power supply units 10B to 10E are operated sequentially starting from the one with the highest actual output voltage Vo, thereby gradually reducing the output voltage Vout and ensuring the output current Iout.

[0135] Above the maximum current of 480 (A) of the load 120, up to Iout=500 (A), DC power supply devices 10A to 10E can all operate in CC mode and supply current to the load 120. If the current demand from the load 120 increases beyond this, the drooping characteristics (CC mode) of DC power supply devices 10A to 10E cause the output voltage Vout to decrease below Iout=500 (A).

[0136] DC power supply units 10A to 10E continue to operate at an output voltage that is reduced in accordance with the drooping characteristic when the current requested by load 120 is within a range of 500 (A), which corresponds to the sum of the upper limit currents Icc of each of DC power supply units 10A to 10E. On the other hand, when the output voltage that is reduced in accordance with the drooping characteristic drops below a value near drooping voltage Vcc (=10 V), the output current of each DC power supply unit 10A to 10E is throttled down in accordance with the drop in output voltage in order to deal with overcurrent due to overload (overcurrent protection region in FIG. 14).

[0137] When the output voltage Vout further decreases in response to a current request from the load 120 and falls below the vicinity of the protection voltage Vp (=5 V), the output current of each of the DC power supply devices 10A to 10E is further reduced in accordance with the load short circuit protection of FIG. 14 in response to the decrease in output voltage. Ultimately, the output current Iout is reduced to the sum of the starting currents Is of each of the DC power supply devices 10A to 10E (33×5=165 A in the example of FIG. 14). In this way, when an abnormal current such as a load short circuit occurs, current limitation can be achieved after the output current Iout reaches 500 A.

[0138] In addition to the effects described in the first embodiment, the DC power supply system according to the third embodiment makes it possible to throttle the output current Iout when an abnormality such as a load short circuit occurs, in accordance with the drooping characteristics (foldback characteristics) of each DC power supply device. As a result, secondary breakdown can be suppressed by suppressing the current that continues to flow through the load 120. Furthermore, when protective control is performed by operating a DC current interrupter (not shown) or the like, arc discharge that occurs in the device can be suppressed.

[0139] Modification of Embodiment 3 The foldback characteristic described in Embodiment 3 can also be combined with Embodiment 2. That is, the modification of Embodiment 3 shows a variation of the DC power supply device 11 according to Embodiment 2.

[0140] FIG. 16 is a conceptual diagram illustrating the output characteristics of each DC power supply device in a DC power supply system according to a modification of the third embodiment.

[0141] Comparing FIG. 16 with FIG. 9, in the modified example of the third embodiment, overcurrent protection and load short-circuit protection are combined with the output characteristics of the DC power supply device 11 according to the second embodiment, similar to those in FIG. 13(b).

[0142] Therefore, in the modification of the third embodiment, similarly to FIG. 9 , the drooping characteristic of each DC power supply device 11 has a region of derating characteristics in which the output voltage is reduced in response to an increase in output current when transitioning from the CV mode to the CC mode.

[0143] Furthermore, the output characteristics are designed so that when the output voltage drops from the reference voltage Vr to a predetermined drooping voltage Vcc in the CC mode in which the upper limit current Icc is maintained, overcurrent protection and load short-circuit protection are performed, similar to those in FIG. 13(b).

[0144] That is, the output characteristic (drooping characteristic) of each DC power supply device in the DC power supply system according to the modified example of the third embodiment is a modified "foldback characteristic" obtained by combining the derating characteristic of FIG. 9 and the foldback characteristic of FIG. 13(b) with respect to the drooping characteristic of FIG. 3.

[0145] As a result, when transitioning from CV mode to CC mode, voltage feedback control is performed so that the output voltage drops below the reference voltage Vr at a constant rate -(ΔV / ΔI) in a region where the output current is greater than the determination current I1 (I1=Icc-ΔI). Furthermore, after transitioning to CC mode, if the output voltage drops below the drooping voltage Vcc while the output current is maintained at the upper limit current Icc, overcurrent protection is performed, in which the output current is reduced from the upper limit current Icc to the protection current Ip in proportion to the drop in output voltage. Furthermore, if the output voltage drops below the protection voltage Vp under overcurrent protection, load short-circuit protection is performed, in which the output current is reduced from the protection current Ip to the starting current Is in proportion to the drop in output voltage.

[0146] In FIG. 16, it is also possible to apply the foldback characteristic of FIG. 13(a) to obtain a drooping characteristic that does not implement load short-circuit protection.

[0147] FIG. 17 is a conceptual diagram illustrating a specific example of the output characteristics of the DC power supply device 11 to which the modified "fold-back characteristics" of FIG. 16 is applied.

[0148] 17, in DC power supply device 10, the reference voltage Vr in CV mode is set to 15 (V), and the upper limit current Icc in CC mode is set to 100 (A), as in embodiment 2. As in Fig. 9, the derating characteristics are set to ΔV = 0.2 (V) and ΔI = 20 (A).

[0149] 14, the voltages that define overcurrent protection and load short-circuit protection can be set to droop voltage Vcc=10 (V), protection voltage Vp=5 (V), Ip=84 (A), and Is=33 (A). That is, in the modification of the third embodiment, the operation of each DC power supply device in overcurrent protection and load short-circuit protection is the same as in the third embodiment.

[0150] 17, as in FIG. 14, in each actual DC power supply device 10, the characteristic line shown in FIG. 14 becomes an output characteristic that is shifted upward or downward according to the difference (offset) between the actual output voltage Vo and the reference voltage Vr.

[0151] FIG. 18 is a conceptual diagram illustrating the operation of the DC power supply system according to a modification of the third embodiment.

[0152] FIG. 18 shows the operation of the DC power supply system shown in FIG. 10 when the output characteristics of the DC power supply devices 11A to 11E are changed from those shown in FIG. 9 to those shown in FIG.

[0153] When the output current Iout from the DC power supply system is 0 to 500 (A) in response to a current request from the load 120, the DC power supply devices 10A to 10E operate in the same manner as in FIG. 12 in the second embodiment, thereby ensuring the output current Iout.

[0154] That is, starting from the current region (Iout = 0 to 80 (A)) in which the output current Iout is supplied only by the DC power supply unit 10A (Vo = 15.17 (V)) with the highest output voltage Vo, when the DC power supply units 10B to 10E are operated sequentially starting from the one with the highest output voltage Vo as the output current Iout increases, the changes in the output voltage Vout and the output current Iout are controlled gradually in accordance with the derating characteristics.

[0155] Up to Iout=500 (A), DC power supply units 10A to 10E can all operate in CC mode and supply current to load 120. Even in this case, if the current demand from load 120 increases, the drooping characteristics (CC mode) of DC power supply units 10A to 10E cause output voltage Vout to decrease below Iout=500 (A).

[0156] DC power supply units 10A to 10E continue to operate at a drooped output voltage when the current requested by load 120 is within a range of 500 (A), which corresponds to the sum of the upper limit currents Icc of each of DC power supply units 10A to 10E. On the other hand, when the output voltage, which decreases due to the drooping characteristic, falls below the vicinity of drooping voltage Vcc (=10 V), overcurrent protection similar to that shown in Fig. 17 is activated, and in response to the drop in output voltage, output current Iout is reduced to 420 (A), which corresponds to Ip x 5.

[0157] Furthermore, if, during overcurrent protection operation, the output voltage Vout drops in response to a current request from the load 120 and falls below the vicinity of the protection voltage Vp (=5 V), load short-circuit protection similar to that shown in FIG. 17 is executed, and the output current Iout is reduced to 165 A, which corresponds to Is×5, in response to the drop in output voltage. In this way, even in the modification of the third embodiment, current limitation can be achieved after the output current Iout reaches 500 A when an abnormal current such as a load short circuit occurs.

[0158] Thus, according to the DC power supply system of the modified example of the third embodiment, in addition to the effects described in the second embodiment, it is possible to throttle the output current Iout when an abnormality such as a load short circuit occurs, in accordance with the drooping characteristic (modified "foldback characteristic") of each DC power supply device. As a result, similar to the third embodiment, by suppressing the current that continues to flow to the load 120, it is possible to suppress secondary breakdown and arc discharge when the DC current interrupter operates.

[0159] Fourth Embodiment In a fourth embodiment, an example of a storage configuration for a plurality of DC power supply devices and an example of maintenance (replacement) work will be described.

[0160] FIG. 19 is an external view of a DC power supply device constituting a DC power supply system according to the fourth embodiment.

[0161] As shown in FIG. 19 , in the DC power supply system according to the fourth embodiment, DC power supply device 10 (collectively referring to devices 10A to 10E) or DC power supply device 11 (collectively referring to devices 11A to 11E) has a shape in which output connection terminals 15P, 15N and input connection terminals 16P, 16N for external connection protrude from module part 14.

[0162] 7 and 8, but as described above, the module unit 14 may store components of a converter with any circuit configuration, including a non-isolated configuration such as a chopper type. A handle 14x is provided on the back surface of the module unit 14, i.e., on the side opposite to the surface on which the output connection terminals 15P, 15N and the input connection terminals 16P, 16N are provided.

[0163] The input connection terminal 16P is electrically connected to the input node Nip in FIGS. 7 and 8, and the input connection terminal 16N is electrically connected to the input node Nin in FIGS.

[0164] Similarly, the output connection terminal 15P is electrically connected to the positive output terminal (OUT+) in Figures 7 and 8, and the output connection terminal 15N is electrically connected to the negative output terminal (OUT-) in Figures 7 and 8. Furthermore, the input connection terminals 16P and 16N are configured so that their protrusion lengths from the module surface are greater than those of the output connection terminals 15P and 15N.

[0165] FIG. 20 is an external view of the power supply slot that accommodates the DC power supply unit shown in FIG.

[0166] 20, a DC power supply system 100c according to the fourth embodiment is configured with a power supply slot 105 and N power supply devices 10 (11) installed in the power supply slot 105. In the fifth embodiment, as in the first embodiment, etc., an example will be described in which N=5, i.e., DC power supply devices 10A to 10E are installed in the power supply slot 105.

[0167] 20, the power supply slot 105 is provided with slots 106A to 106E, the number of which corresponds to N=5. Each of the slots 106A to 106E is provided with a guide rail 107, connectors 108P and 108N for inserting and mounting the output connection terminals 15P and 15N, and connectors 109P and 109N for inserting and mounting the input connection terminals 16P and 16N. Although not shown, the power supply slot 105 is electrically connected to the power source 101 and the load 120 by wiring or the like.

[0168] The connectors 108P, 108N are recessed to fit over the protruding portions of the output connection terminals 15P, 15N, ensuring electrical connection between the connectors 108P, 108N and the output connection terminals 15P, 15N when mated. Similarly, the connectors 109P, 109N are recessed to fit over the protruding portions of the input connection terminals 16P, 16N, ensuring electrical connection between the connectors 109P, 109N and the input connection terminals 16P, 16N when mated.

[0169] Within the power supply slot 105, the connectors 109P are electrically connected to each other and the connectors 109N are electrically connected to each other between the slots 106A to 106E. This allows the outputs of the DC power supplies 10A to 10E installed in the slots 106A to 106E to be connected in parallel. The connectors 109P and 109N in the slots 106A to 106E are also electrically connected to the power source 101 via wiring within the power supply slot 105.

[0170] DC power supply units 10A to 10E are attached to slots 106A to 106E by using handles 14x to push module unit 14 along guide rails 107. DC power supply units 10A to 10E are mounted in power supply slots 105 by ensuring electrical connections between output connection terminals 15P, 15N and input connection terminals 16P, 16N and connectors 108P, 108N and 109P, 109N.

[0171] At this time, due to the difference in shape (specifically, protrusion length) of the output connection terminals 15P, 15N and the input connection terminals 16P, 16N, the input connection terminals 16P, 16N are attached first, and the output connection terminals 15P, 15N are attached after the input connection terminals 16P, 16N.

[0172] Each of the DC power supply devices 10A to 10E automatically starts operation when the input connection terminals 16P, 16N are attached and electrically connected to the power source 101, and is ready to output DC power (output voltage x output current) from the output terminals, i.e., the output connection terminals 15P, 15N. In practice, each of the DC power supply devices 10A to 10E that has started operation will be in either an operating state or a non-operating state depending on the level of the voltage on the output side.

[0173] Furthermore, each of the DC power supply devices 10A to 10E is configured to be removable from the slots 106A to 106E while the output voltage Vout and the output current Iout are being output to the load 120, i.e., even while the DC power supply system 100c is operating. For example, by pulling the handle 14x, the engagement between the output connection terminals 15P, 15N and the input connection terminals 16P, 16N and the connectors 108P, 108N and 109P, 109N is released, and each of the DC power supply devices 10A to 10E is removed from the slots 106A to 106E and electrically disconnected from the power supply slot 105.

[0174] In this way, one embodiment of the "fitting structure" is formed by combining the convex output connection terminals 15P, 15N and input connection terminals 16P, 16N with the concave connectors 108P, 108N and 109P, 109N. The fitting structure is not limited to the examples shown in Figures 19 and 20. For example, it is also possible to provide unevenness on the contact surfaces of the module unit 14 and the slots 106A-106E, thereby enabling the input connection terminals 16P, 16N to be fitted before the output connection terminals 15P, 15N. Alternatively, it is also possible to provide convex portions on the slots 106A-106E side and concave portions on the module unit 14 side of the DC power supply devices 10A-10E.

[0175] FIG. 21 shows a conceptual diagram illustrating an example of a state before maintenance of the DC power supply system 100c according to the fourth embodiment.

[0176] As shown in FIG. 21(a), when the DC power supply devices 10A to 10E are installed in the slots 106A to 106E of the power supply slot 105, the DC power supply system 100c starts operation.

[0177] Figure 21(b) shows the state after 130,000 (h) has passed since the start of operation in Figure 21(a), near Tlim (131,520 (h)), according to the same current profile as in Embodiment 1. As described in Figure 6, the operating time of the DC power supply unit 10A with the highest output voltage Vo is equivalent to the operating time of the DC power supply system 100c.

[0178] 21(b), the accumulated operating time of the DC power supply unit 10A is also 130,000 (h), indicating that the DC power supply unit 10A is nearing the end of its design life. This allows the DC power supply unit 10A to be determined as a replacement target. The DC power supply unit with the highest output voltage Vo (here, DC power supply unit 10A) can be identified in advance when constructing the DC power supply system 100c based on the results of prior manufacturing tests of the DC power supplies 10A-10E (for example, a test to verify that the output voltage Vo is within 15 (V) ±5%).

[0179] FIG. 22 shows a conceptual diagram illustrating the configuration and maintenance work of a DC power supply system according to the fourth embodiment.

[0180] Figure 22(a) shows the state before maintenance work, and it is possible to remove DC power supply units 10A to 10E using handle 14x from any of slots 106A to 106E. In Figure 22(a), as explained in Figure 21(b), the operating time of DC power supply unit 10A has reached 130,000 (h), so maintenance work is planned to replace DC power supply unit 10A.

[0181] Figure 22(b) shows the state in which the DC power supply 10A is removed. In this state, the output current from the DC power supply 10A becomes zero, while the outputs of the DC power supplies 10B to 10E in each current range become equivalent to the outputs of the DC power supplies 10A to 10D in the state shown in Figure 22(a). Therefore, in the state shown in Figure 22(b), the DC power supplies 10B to 10E can supply a maximum current of 400 A.

[0182] 22(b) needs to be performed when the output current Iout to the load 120 is less than 400 (A). For example, taking into consideration the past operating conditions of the load 120, the maintenance work can be performed at a time when the load current is decreasing.

[0183] Figure 22(c) shows a state in which a new DC power supply unit 10F has been installed in the slot 106A from which the DC power supply unit 10A was removed. In the state shown in Figure 22(c), the DC power supply system 100e can supply an output current Iout of up to 500 (A) to the load 120 by parallel operation of the five DC power supply units 10B to 10F, just like in Figure 22(a). In this way, the DC power supply system 100e can replace a DC power supply unit that is nearing the end of its life without stopping operation, using a timing when the output current Iout is relatively small.

[0184] As described above, in embodiment 4, the multiple DC power supply units installed in power supply slot 105 can be any of embodiments 1 to 3 and their modifications. Also, although an example in which some DC power supply units are identified as replacement targets is shown in Figures 22(a) to 22(c), it is also possible to determine at this stage that all DC power supply units 10A to 10E are replacement targets.

[0185] As described above, according to the DC power supply system of the fourth embodiment, in addition to the effects described in the first to third embodiments, some DC power supply devices that are nearing the end of their life can be replaced by hot swapping, without stopping the power supply to the load 120. Therefore, maintenance can be performed without causing inconvenience to the user, such as stopping the power supply to the load 120.

[0186] As a result, the DC power supply system according to the fourth embodiment is suitable for important facilities that are sensitive to power outages, such as data centers, communication infrastructure facilities, production facilities, etc. Furthermore, even if a failure occurs in a DC power supply unit before the end of its life, it is expected that maintenance can be completed in a short time by removing the DC power supply unit from the power supply slot 105 and installing a new DC power supply unit.

[0187] As shown in FIG. 19, each of the DC power supply units 10A to 10E is configured so that it can start up normally when the input connection terminals 16P, 16N are attached before the output connection terminals 15P, 15N.

[0188] On the other hand, even after starting up DC power supply units 10A to 10E, if output connection terminals 15P, 15N are attached when the output voltage is too low, there is a concern that a large abnormal current may momentarily occur that charges capacitor 114 in Figures 7 and 8 due to the difference in output voltage of other DC power supply units. This abnormal current may cause a shortage of electrical contact area on the output side, which may cause deterioration of the terminals, etc.

[0189] For this reason, it is preferable to further provide the output connection terminals 15P, 15N with a structure for avoiding the above-mentioned abnormal current. For example, an anti-intrusion pin (not shown) can be attached to the tip of the output connection terminals 15P, 15N to prevent insertion into the connectors 109P, 109N when the voltage is low. The anti-intrusion pin can be configured to retract when the voltage at the positive output end (OUT+), which is the contact point, reaches a predetermined voltage or higher, thereby allowing the output connection terminals 15P, 15N to be inserted into the connectors 109P, 109N.

[0190] On the other hand, when the voltage at the positive output terminal (OUT+) is lower than the predetermined voltage, the intrusion prevention pin is not retracted, preventing the output connection terminals 15P, 15N from being inserted into the connectors 109P, 109N. For example, the intrusion prevention pin can be realized by a solenoid lock mechanism. By providing such an intrusion prevention pin, it is possible to prevent the generation of abnormal current when installing the DC power supply device during maintenance (replacement) work.

[0191] Fifth Embodiment In a fifth embodiment, a configuration will be described in which the number of slots for maintenance work is increased compared to the fourth embodiment.

[0192] 23A and 23B are conceptual diagrams illustrating the configuration and maintenance work of a DC power supply system according to embodiment 5. Fig. 23A shows the configuration of a DC power supply system 100d according to embodiment 5 in comparison with Fig. 22A.

[0193] As shown in Fig. 23(a), the DC power supply system 100d according to the fifth embodiment differs from the DC power supply system 100c according to the fourth embodiment shown in Fig. 21(a) in that the power supply slot 105 further includes a slot 106X in which no DC power supply unit is installed, in addition to slots 106A to 106E in which DC power supply units 10A to 10E are installed during operation. Slot 106X corresponds to a "spare slot."

[0194] The configuration of slot 106X is the same as that of slots 106A to 106E, and can accommodate DC power supply device 10 (11) according to the present embodiment. The other configurations of DC power supply system 100d according to embodiment 5 are the same as those of DC power supply system 100c according to embodiment 4, and therefore detailed description thereof will not be repeated.

[0195] 23(a), no DC power supply unit is installed in slot 106X, and the DC power supply system 100f starts operation by parallel operation of DC power supply units 10A to 10E installed in slots 106A to 106E. The operating states of DC power supply units 10A to 10E in each current range of output current Iout and the output voltage Vout to load 120 are the same as those described in the first embodiment.

[0196] In FIG. 23(b), as in FIG. 22(a), the operating time of the DC power supply unit 10A with the highest output voltage Vo has reached 130,000 (h), which is close to Tlim (131,520 (h)), which corresponds to the design life, and therefore maintenance work to replace the DC power supply unit 10A is planned.

[0197] As shown in Figure 23(c), during maintenance work on the DC power supply system 100d, a new DC power supply 10F is installed in the empty slot 106X before the DC power supply 10A to be replaced is removed from the slot 106A. For example, assuming a case in which the output voltage Vo of the DC power supply 10F is equivalent to that of the DC power supply 10A and higher than that of the DC power supplies 10B to 10E, as shown in the chart of Figure 23(c), the DC power supply 10F in each current range will be equivalent to that of the DC power supply 10A to be replaced. In this state, the five DC power supplies 10A to 10D and 10F, excluding the DC power supply 10E with the lowest output voltage Vo, can supply an output current Iout of up to 500 A to the load 120.

[0198] Thereafter, as shown in Fig. 23(d), DC power supply unit 10A is removed from slot 106A in the same manner as in Fig. 22(c). In the state after replacement shown in Fig. 23(d), five DC power supply units 10B to 10F can supply an output current Iout of up to 500 (A) to load 120.

[0199] As described above, in the DC power supply system according to the fifth embodiment, in the state shown in FIG. 23(c), unlike in FIG. 22(b), it is possible to supply an output current Iout greater than 400 (A). As a result, even when the load 120 is operating at the maximum current, it is possible to perform the maintenance work shown in FIGS. 23(c) and 23(d). In other words, it is possible to perform maintenance work by replacing the DC power supply device at any time, regardless of the operating state of the load 120.

[0200] Sixth Embodiment In a sixth embodiment, a redundant design in which an excess number of DC power supply devices are connected in parallel relative to the maximum current of the load 120 will be described.

[0201] FIG. 24 is a block diagram illustrating the configuration of a DC power supply system 100e according to the sixth embodiment.

[0202] 24, the DC power supply system 100e according to the sixth embodiment differs from the DC power supply system 100a (FIG. 4) according to the first embodiment in that it further includes a DC power supply unit 10F. The output side of the DC power supply unit 10F is connected in parallel with the output sides of the DC power supply units 10A to 10E.

[0203] In the DC power supply system 100e, the upper limit current Icc of each of the DC power supply devices 10A to 10F is set to 100 (A). Therefore, in the DC power supply system 100e, one more DC power supply device than the number (N=5) required to ensure Imax=480 (A), a total of six DC power supply devices 10A to 10F, are connected in parallel to supply power to the load 120.

[0204] That is, in the DC power supply system 100e, the number of DC power supply devices connected in parallel is determined so that the sum of the upper limit currents Icc of only some of the DC power supply devices is greater than the maximum load current Imax of the load 120. In Fig. 24, a configuration in which there is one extra device is shown as a preferred example.

[0205] The actual output voltage Vo of DC power supply units 10A to 10E is assumed to be the same as in the first embodiment. The reference voltage Vr of DC power supply unit 10F, which is provided as an extra unit for redundancy, is set to be equal to the reference voltage Vr of DC power supply units 10A to 10E (Vr = 15 (V)). The output voltage Vo of DC power supply unit 10F does not necessarily match the reference voltage Vr (15 (V)), but is within the range of 15 (V) ±5%. The configuration of the other parts of DC power supply system 100d, including power source 101 and load 120, is the same as in the first embodiment ( FIG. 4 ), and therefore detailed description will not be repeated.

[0206] Fig. 25 is a diagram for explaining the operation of each DC power supply device in the DC power supply system according to embodiment 6. Fig. 25 shows an example of operation when the output voltage Vo of DC power supply device 10F is lower than that of any of DC power supply devices 10A to 10E (i.e., Vo<14, 82 (V)).

[0207] 25(a) shows the operation of each DC power supply when none of the DC power supply units 10A to 10F has a failure. In this case, the output current Iout is supplied by the five DC power supply units (here, DC power supply units 10A to 10E) with the highest output voltage Vo. As a result, the operating state of each DC power supply unit 10A to 10E in each current range of the output current Iout and the output voltage Vout to the load 120 are determined, as in FIG. 5(b).

[0208] 25(a), the redundant DC power supply 10F is in an inactive state with 0% output even when the output current Iout is in the range of 400 to 500 (A). Even when the maximum current of 480 (A) is supplied to the load 120, the DC power supply 10A to 10E can ensure the output current Iout. Therefore, the output voltage Vout is 14.82 (V), the lowest of the output voltages Vo of the DC power supply 10A to 10E, while the output voltage Vo of the DC power supply 10F is lower. In other words, of the multiple DC power supply 10A to 10F connected in parallel, the one with the lowest actual output voltage Vo is automatically placed in a permanently inactive state as a redundant power supply.

[0209] FIG. 25(b) shows the operation when a failure occurs in one of the DC power supply devices 10A to 10E, in this case, the DC power supply device 10C.

[0210] As shown in Fig. 25(b), the output of the DC power supply 10C (Vr = 15.00 (V)) where a fault has occurred is 0% over the entire current range. Furthermore, the operation of DC power supplies 10A and 10B, which have a higher output voltage Vo than DC power supply 10C, remains unchanged from Fig. 25(a).

[0211] In contrast, DC power supply 10D (Vo = 14.97 (V)), which has the next highest output voltage Vo after DC power supply 10C, operates in the same manner as DC power supply 10C. That is, the output of DC power supply 10D in each current region in FIG. 25(b) is equivalent to the output of DC power supply 10C in FIG. 25(a). Similarly, the output of DC power supply 10E (Vo = 14.82 (V)) in FIG. 25(b) is equivalent to the output of DC power supply 10D in FIG. 25(a). That is, DC power supply 10E operates in the same manner as DC power supply 10D.

[0212] Furthermore, the DC power supply unit 10F, which was in a non-operating state (output 0% in Figure 25(a)), will now operate in the same manner as the DC power supply unit 10E in Figure 25(a) in the current range (400 to 500 (A)) in which the DC power supply unit 10E in Figure 25(a) outputs current in the range of 0 to 100%.

[0213] As a result, the output current Iout can be ensured by the five DC power supply units 10A, 10B, and 10D-10F for each current range similar to that shown in Figure 25(a). In Figure 25(b), the output voltage Vout is lower than that shown in Figure 25(a) in the current range where DC power supply unit 10C outputs current, i.e., in each current range where Iout≧200 (A). However, as mentioned above, even DC power supply unit 10F, which has the lowest output voltage Vo, has an output voltage Vo that is within the voltage tolerance range (±5%) of load 120 as a result of product testing.

[0214] 25(b) in which the DC power supply device 10C has failed, it is possible to supply an output current Iout up to Imax=480 (A) to the load 120 with an output voltage Vout within the voltage tolerance range of the load 120. In other words, it can be seen that a redundant design has been realized to deal with failures in any DC power supply device.

[0215] In this way, in the DC power supply system according to the sixth embodiment, a redundant design can be realized by simply increasing the number of DC power supply devices connected in parallel by one relative to the number required to supply the maximum load current Imax to the load 120. A redundant design in a typical power supply system is realized by arranging two power supply devices in parallel, each with a rated current capable of handling the maximum current of the load. In contrast, according to the present embodiment, a redundant design can be realized by simply connecting one extra (M+1) DC power supply device to the M DC power supply devices that are used to share and supply the maximum current.

[0216] As a result, compared to the general power supply system described above, the cost for the redundant configuration can be reduced. For example, while a general redundant design requires twice the number of power supply devices, this embodiment requires only (M+1) / M times the number of devices, thereby enabling cost reduction. This also makes it possible to reduce the size of the device (system).

[0217] Also in the sixth embodiment, the DC power supply devices 10 and 11 described in the first to third embodiments and their modifications can be used as desired as the respective DC power supply devices.

[0218] Furthermore, it is also possible to mount the DC power supply units 10A to 10F constituting the DC power supply system 100e according to the sixth embodiment in the power supply slot 105 of the fourth or fifth embodiment. In this case, it is possible to remove the DC power supply unit 10C in which a failure has occurred from the state shown in Fig. 25(b) from the power supply slot 105 by hot swapping at any timing without stopping the current supply to the load 120.

[0219] Seventh Embodiment In a seventh embodiment, a configuration example of a DC power supply system using a DC power supply device to which a wide band gap semiconductor such as GaN (gallium nitride) or SiC (silicon carbide) is applied will be described.

[0220] Wide bandgap semiconductor elements using wide bandgap semiconductors such as GaN are capable of high-frequency switching, and DC power supplies that include such wide bandgap semiconductor elements as switching elements have the effects of suppressing output ripple voltage, miniaturizing magnetic components through high-frequency driving, suppressing power loss in the magnetic components due to miniaturization, and suppressing power loss due to low on-resistance of the semiconductor switching elements, and therefore offer significant advantages in terms of miniaturization and high efficiency.On the other hand, the current capacity of wide bandgap semiconductor elements is generally smaller than that of semiconductor elements made from ordinary semiconductor materials.

[0221] For this reason, in the seventh embodiment, a DC power supply system is configured by connecting in parallel a large number of relatively small capacity DC power supply devices configured to include wide band gap semiconductor elements such as GaN.

[0222] FIG. 26 is a block diagram illustrating the configuration of a DC power supply system according to the seventh embodiment.

[0223] 26, a DC power supply system 100f according to the seventh embodiment has a larger number (N) of DC power supply devices connected in parallel than the DC power supply system 100a according to the first embodiment, and the output current from one power supply device is smaller than that of the first embodiment. In Fig. 26, the characteristics of the load 120 are the same as those of the first embodiment, with Imax = 480 (A) and the allowable voltage range being 15 (V) ± 5% (i.e., 14.24 to 15.75 (V)).

[0224] In the configuration example of Fig. 26, 25 DC power supply units 10A to 10Y are arranged for Imax = 480 (A) (N = 25). DC power supply units 10A to 10Y are CVCC power supplies with the same drooping characteristics (Fig. 3) as power supply units 10A to 10E of the first embodiment, and are set to Icc = 20 (A). In other words, DC power supply units 10A to 10Y operate as CVCC power supplies with Vr x 20 (A).

[0225] Each of the DC power supply devices 10A to 10Y is realized, for example, by applying a wide bandgap semiconductor element to the semiconductor switching element 112 in the configuration of a flyback or forward converter shown in FIG. 7 or FIG. 8, but as described above, it can also be realized by configuring the semiconductor switching element that is on / off controlled using a wide bandgap semiconductor element in any insulated or non-insulated circuit configuration.

[0226] The reference voltage is set to the same value (15 V in this example) for the 25 DC power supply devices 10A to 10Y. However, the actual output voltage Vo of the DC power supply devices 10A to 10Y will vary within the voltage tolerance range of the load 120 (15 V ±5%). In other words, they will be set to different values. In the example of FIG. 26, the output voltages Vo of the 25 DC power supply devices 10A to 10Y will differ among at least some of the DC power supply devices within the range of 14.76 to 15.24 V. Here, it is assumed that the power supply devices 10A to 10Y are numbered in order from highest to lowest actual output voltage Vo.

[0227] Therefore, the output voltage Vo of the first power supply unit 10A is lower than +5% of the reference voltage Vr. Similarly, the output voltage Vo of the 25th power supply unit 10Y is higher than -5% of the reference voltage Vr. The output voltages Vo of the other power supply units 10B to 10X are each within a voltage range that is higher than the output voltage Vo of power supply unit 10Y and lower than the output voltage Vo of power supply unit 10A.

[0228] FIG. 27 shows a conceptual diagram illustrating the operation of the DC power supply system according to the seventh embodiment.

[0229] 27, in the current region where output current Iout=0 to 20 (A) in which one DC power supply can ensure output current Iout, current is supplied to load 120 by the output current from only DC power supply 10A, which has the highest output voltage Vo. Therefore, output voltage Vout becomes VoA (V), which is the output voltage Vo of DC power supply 10A, and DC power supply units 10B to 10Y, which have output voltage Vo lower than that of DC power supply 10A, are inactive and do not output current.

[0230] When the output current Iout exceeds 20 A, DC power supply 10A outputs 20 A in CC mode, causing the output voltage Vout to fall below VoA (V). In response, DC power supply 10B and subsequent DC power supplies, starting with DC power supply 10B with the highest output voltage Vo, enter an operating state and begin to output current.

[0231] For example, in the current range of Iout=20 to 40 (A), DC power supply unit 10A operates in CC mode and outputs 20 (A), while DC power supply unit 10B operates in CV mode and supplies a current of 0 to 20 (A) (0 to 100%). As a result, output voltage Vo drops from VoA.

[0232] In the current region where Iout is 40 to 60 A, DC power supplies 10A and 10B operate in CC mode and output 20 A each, while DC power supply 10C operates in CV mode and supplies a current of 0 to 20 A (0 to 100%). As a result, output voltage Vout is lower than in the current region where Iout is 20 to 40 A.

[0233] Furthermore, in the current range of Iout=460 to 480 (A), 23 DC power supply units 10A to 10W operate in CC mode and output 20 (A) each, and the 24th DC power supply unit 10X operates in CV mode and supplies a current of 0 to 20 (A) (0 to 100%).

[0234] Furthermore, in the current range Iout=480 to 500 (A), which is larger than the maximum load current Imax, 24 DC power supply units 10A to 10X operate in CC mode and output 20 (A) each, and the 25th DC power supply unit 10Y operates in CV mode and supplies a current of 0 to 20 (A) (0 to 100%). As a result, the output voltage Vout drops to VoY (V), which is the output voltage Vo of the 25th DC power supply unit 10Y.

[0235] Thus, in addition to the effects described in the first embodiment, the DC power supply system according to the seventh embodiment has an effect unique to this embodiment, in which each DC power supply device using a wide bandgap semiconductor element such as GaN or SiC can be operated at a high frequency. As a result, the ripple in the output voltage of each DC power supply device can be reduced, and a configuration in which a large number of small-capacity DC power supply devices are connected in parallel can be easily realized.

[0236] Furthermore, in conventional high-current DC power supplies, it has been difficult to avoid designs using wiring that is prone to losses due to the skin effect and proximity effect, or large-current magnetic paths that increase iron loss. In contrast, in the DC power supply system according to the seventh embodiment, a large number of small-capacity, high-frequency DC power supplies are connected in parallel, making it possible to reduce the size of the magnetic components in each DC power supply, and to reduce the circuit size by thinning the wiring due to the skin effect and proximity effect. Furthermore, the miniaturization of the circuit enables even higher frequencies, and the even higher frequencies allow for even smaller magnetic components, resulting in a synergistic effect in circuit design.

[0237] Furthermore, each DC power supply uses a wide bandgap semiconductor element such as GaN or SiC, which increases the turn-on and turn-off speeds during switching and reduces the on-resistance, thereby reducing power losses (switching losses and conduction losses). As a result, the power supply can be made more efficient and the associated radiation noise can be suppressed.

[0238] Furthermore, by operating multiple DC power supply devices in parallel, the drive frequencies of the semiconductor switching elements in each DC power supply device will be slightly different and the switching timing will not be simultaneous, which is expected to suppress the superposition of noise that occurs when multiple DC power supply devices are operated synchronously in parallel.

[0239] It should be noted that the configuration of FIG. 26 allows 24 DC power supply units 10A-10X to ensure the output current Iout for a maximum load current Imax of 480 A. By providing a 25th DC power supply unit 10A-10Y, a redundant design similar to that of the sixth embodiment (FIG. 24) in which an extra DC power supply unit 10F is provided can be realized using the DC power supply unit 10Y with the lowest reference voltage Vr. In other words, the sixth embodiment can be combined with the DC power supply system 100f of the seventh embodiment. In particular, in the seventh embodiment, since a large number of DC power supply units are connected in parallel, the cost increase due to the redundant configuration is significantly suppressed. This allows a redundant configuration for improving reliability to be efficiently realized while suppressing cost increases.

[0240] Also in embodiment 7, the DC power supply devices 10 and 11 described in embodiments 1 to 3 and their modifications can be used as desired as each DC power supply device. Also, by installing multiple DC power supply devices in the power supply slot 105 described in embodiments 5 and 6, it is possible to configure a DC power supply system 100h.

[0241] As explained above, in the DC power supply system 100 (100a to 100f) according to this embodiment, differences in operating time occur among the multiple DC power supply devices 10, 11 depending on the level of the actual output voltage Vo. Generally, the DC power supply device 10 (or 11) with a longer operating time tends to have a higher temperature due to a larger increase in the temperature of its components. As a result, there is a concern that the increase in temperature of a particular DC power supply device may hasten the timing of failure of that DC power supply device.

[0242] Generally, the lifespan of the electrolyte and enamel coatings that make up electrolytic capacitors, transformers, inductors, and other components that are considered to have a limited lifespan in many power supply devices can be estimated to double if the temperature drops by 10°C. Therefore, by suppressing the temperature rise of specific DC power supply devices that operate for long periods of time and equalizing the temperature rise of each DC power supply device 10, 11, it is expected that the product lifespan of the DC power supply system can be extended.

[0243] 28 and 29 further show examples of cooling structures for equalizing the temperatures of the DC power supply devices.

[0244] In the first example shown in Fig. 28, a heat sink 200 having heat dissipation fins and a thermal connection member such as a TIM (thermal interface material) 210 are disposed for each of the DC power supply devices 10A to 10E. In the example of Fig. 28, the housings of the DC power supply devices 10A to 10E are in thermal contact with the common heat sink 200 via the TIM 210, which not only dissipates heat from the heat sink 200 but also helps to equalize the temperature between the DC power supply devices via the heat sink 200.

[0245] In a product to which a housing cooling structure such as that shown in Figure 28 is applied, by bringing the housings of adjacent DC power supply units into contact with each other, it is possible to dissipate heat from a DC power supply unit with a long operating time through the housing of a DC power supply unit with a short operating time, thereby making it possible to extend the life of the DC power supply system by equalizing the temperature rise of each DC power supply unit.

[0246] In the second example shown in Fig. 29, in addition to the cooling structure in Fig. 28, a cooling member 220 is further arranged between the housings of adjacent DC power supply units. The cooling member 220 can be configured as a highly thermally conductive partition plate or a heat pipe that is provided in a manner extending from the heat sink 200. This makes it possible to improve the heat dissipation effect from the side surface of each DC power supply unit (the surface facing the other DC power supply unit) compared to the example in Fig. 28.

[0247] 28 and 29, the effect of the cooling structure increases as the number of DC power supply devices connected in parallel increases. Therefore, for example, when combined with the seventh embodiment, it is possible to prevent temperature rises in specific DC power supply devices and enhance the effect of extending the life of the DC power supply system.

[0248] In addition, in the fourth embodiment, by configuring the power supply slot 105 with a metal housing and providing the heat sink 200 shown in FIGS. 28 and 29, an efficient cooling structure can be realized.

[0249] Regarding the multiple embodiments described above, we would like to confirm that it was intended from the beginning of the application to appropriately combine the configurations described in each embodiment, including combinations not mentioned in the specification, within the scope that does not result in inconsistencies or contradictions.

[0250] In addition, in the present embodiment, an example has been described in which the upper limit current Icc in CC mode is the same among the multiple DC power supply devices 10, 11 connected in parallel, but the upper limit current Icc may be set to a different value among at least some of the DC power supply devices as long as it is equal to or less than the rated current. Even in this case, a similar operating mode is realized in which the DC power supply devices are operated in sequence starting from the DC power supply device with the highest reference voltage Vr, and therefore the same effects can be achieved.

[0251] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0252] 10, 10A to 10Y, 11, 11A to 11E power supply device, 14 module part, 14x handle part, 15 standard value, 15N, 15P output connection terminal, 16N, 16P input connection terminal, 100, 100a to 100f DC power supply system, 101 power source, 105 power supply slot, 106A to 106E, 106X slot, 107 guide rail, 108N, 108P, 109N, 109P connector, 110 transformer, 112 semiconductor switching element, 113 diode, 114 capacitor, 115 feedback (FB) circuit, 116 current detection resistor, 117 control IC, 118 flywheel diode, 119 reactor, 120 load, 200 heat sink, 210 thermal interface material (TIM), 220 Cooling element, I1: judgment current, IR1 to IR11, IRa to IRe: current range, Icc: upper limit current, Imax: maximum load current, Iout: output current (DC power supply system), Ip: protection current, Is: starting current, NL, PL: power line, Nip: input node, Tlim: limit operating time, Vcc: droop voltage, Vo: output voltage (DC power supply device), Vout: output voltage (DC power supply system), Vp: protection voltage, Vr: reference voltage, Vrt: standard voltage.

Claims

1. A DC power supply system for supplying a DC voltage and a DC current to a DC load, comprising: a plurality of DC power supply devices, the output sides of which are electrically connected to the DC loads, connected in parallel; each of the plurality of DC power supply devices is configured to be in a non-operating state in which it does not output a current when the DC voltage supplied to the DC load is higher than an actual output voltage of the DC power supply device, and to be in an operating state according to a predetermined output characteristic when the DC voltage is equal to or lower than the output voltage; the output characteristics are set so that, in each of the DC power supply devices, when an output current is smaller than an upper limit current set for each of the plurality of DC power supply devices, the device operates in a constant voltage mode in which feedback control of the output voltage is performed to maintain the output voltage at a predetermined reference voltage, and, when the output current reaches the upper limit current, the device operates in a constant current mode in which feedback control of the output current is performed to maintain the output current at the upper limit current; In each of the DC power supply devices, the upper limit current is set to be equal to or lower than a rated current of the DC power supply device, the output voltages in the constant voltage mode with respect to the reference voltage, which is set equally among at least some of the plurality of DC power supply devices, are different from one another within a voltage tolerance range of the DC load; A DC power supply system, wherein each of the DC power supply devices is designed to ensure a predetermined design life when operated in the assumed continuous operating state at a current value equal to or less than the rated current.

2. A DC power supply system as described in claim 1, wherein a voltage target value of the feedback control of the output voltage is set to the reference voltage when the output current is smaller than a judgment current which is set lower than the upper limit current, and wherein feedback control of the output voltage is performed such that the voltage target value is lowered from the reference voltage as the output current increases when the output current is between the judgment current and the upper limit current.

3. a voltage target value of the feedback control of the output voltage is set to the reference voltage when the output current is smaller than a determination current that is set lower than the upper limit current; the output characteristic is further set so as to provide a derating characteristic region in the middle of the transition of the DC power supply from the constant voltage mode to the constant current mode, 2. The DC power supply system according to claim 1, wherein the derating characteristic is set such that, when the output current is between the determination current and the upper limit current, the voltage target value is gradually lowered from the reference voltage as the output current increases, thereby performing feedback control of the output voltage.

4. a current target value of the feedback control of the output current is set to the upper limit current when the output voltage is higher than a predetermined voltage in the constant current mode; 2. The DC power supply system according to claim 1, wherein the output characteristic is further set such that, in the constant current mode, when the output voltage falls below the predetermined voltage, the current target value falls below the upper limit current.

5. Each of the plurality of DC power supply devices has the same specifications, 5. The DC power supply system according to claim 1, wherein the upper limit current is set equally among the plurality of DC power supply devices.

6. 5. The DC power supply system according to claim 1, wherein the upper limit current is set to a different value among at least some of the plurality of DC power supply devices.

7. a power supply slot electrically connected to a power source and the DC load, the power supply slot including a plurality of slots having a fitting structure for mounting each of the plurality of DC power supply devices; the plurality of DC power supply devices start operating in either the operating state or the non-operating state when attached to the slots, and are capable of being removed from the power supply slots by releasing the engagement by the engagement structure during operation of the DC power supply system, 5. The DC power supply system according to claim 1, wherein output sides of two or more of said DC power supply devices attached to said power supply slots are connected in parallel in said power supply slots.

8. the fitting structure is provided corresponding to each of the output side of each of the DC power supply devices and the input side electrically connected to the power source, 8. The DC power supply system according to claim 7, wherein the fitting structure has a shape such that, when each of the DC power supply devices is attached to the slot, the input side is fitted before the output side.

9. The fitting structure has a first connection terminal on the input side and a second connection terminal on the output side for insertion into a connector of the slot, 9. The DC power supply system according to claim 8, wherein a protruding length of said first connection terminal is greater than a protruding length of said second connection terminal.

10. 8. The DC power supply system according to claim 7, wherein some of said plurality of power supply slots are reserved slots in which no DC power supply device is installed.

11. 5. The DC power supply system according to claim 1, wherein the number of the plurality of DC power supply devices is determined so that the sum of the upper limit currents of some of the plurality of DC power supply devices is greater than the maximum load current of the DC load.

12. 5. The DC power supply system according to claim 1, wherein the plurality of DC power supply devices are configured to control the output voltage or the output current by switching a wide band gap semiconductor element.

13. Each of the plurality of DC power supply devices has the same specifications, 5. The DC power supply system according to claim 1, wherein the number of the plurality of DC power supply devices is determined so that the sum of the upper limit currents of the DC power supply devices excluding one of the plurality of DC power supply devices is greater than the maximum load current of the DC load.

14. The DC power supply system according to any one of claims 1 to 4, wherein the plurality of DC power supply devices are arranged such that the housings of the DC power supply devices are thermally connected to a common heat sink via a thermal interface material.

15. A DC power supply system for supplying a DC voltage and a DC current to a DC load, comprising: A plurality of DC power supply devices, the output sides of which are electrically connected to the DC loads, are connected in parallel; a power supply slot electrically connected to a power source and the DC load, the power supply slot including a plurality of slots each having a fitting structure for mounting each of the plurality of DC power supply devices; the output sides of the two or more DC power supplies attached to the power supply slots are connected in parallel in the power supply slots; the fitting structure is provided corresponding to each of the output side of each of the DC power supply devices and the input side electrically connected to the power source, The fitting structure has a shape such that, when each of the DC power supply devices is attached to the slot, the input side is fitted before the output side.

16. The fitting structure has a first connection terminal on the input side and a second connection terminal on the output side for insertion into a connector of the slot, 16. The DC power supply system according to claim 15, wherein a protruding length of the first connection terminal is greater than a protruding length of the second connection terminal.