Power source system

Abstract

To provide a power source system in which outputs of multiple DC power source devices are connected in parallel such that current supply between the DC power source devices is leveled by simple control.SOLUTION: A power source system 100 includes multiple DC power source devices CNV1, CNV2 connected in parallel on a load 20 side. The output of each of the DC power source devices CNV1, CNV2 is controlled by on / off control of a switching element. In each of the DC power source devices CNV1, CNV2, on / off control is performed on the switching element so as to compensate control deviations including an output voltage control deviation which is calculated to bring the output voltage Vo1, Vo2 close to a reference voltage and an input current control deviation which is calculated to bring the input current Io1, Io2 close to a current target value. The current target value of each of the DC power source devices is determined in accordance with an input current in another DC power source device obtained as a result of transmission / reception between the DC power source devices.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to power supply systems. [Background technology]

[0002] One way to increase the capacity of a power supply system is to operate multiple DC power supply devices in parallel. While this configuration eliminates the need for a large-capacity power supply, which tends to be difficult to miniaturize and improve efficiency, there is a concern that the current supply may be uneven due to variations (individual differences) in components, etc., among the multiple DC power supply devices connected in parallel.

[0003] For example, Japanese Patent Application Laid-Open No. 2022-127734 (Patent Document 1) describes a control that equalizes the current supply between isolated switching power supply devices (DC power supply devices) in a circuit configuration in which the outputs of the devices are connected in parallel, using a current balancing circuit placed in each switching power supply device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-127734 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, in each isolated switching power supply, a first output current detection value detected corresponding to the switch current flowing on the primary side is converted by a current detection value converter to a second output current detection value and input to a current balancing circuit. Furthermore, on the secondary sides of the multiple switching power supplies, a current corresponding to the difference between the second output current detection values ​​of the switching power supplies is generated between the current balancing circuits connected via current balancing terminals, thereby balancing the input currents between the multiple switching power supplies. This results in a leveling of the current supply between the multiple switching power supplies.

[0006] However, in the configuration of Patent Document 1, in order to balance the input currents, in addition to the configuration for controlling the on / off of switching elements to maintain a constant output voltage, a current balancing circuit and a current detection value conversion unit must be added to each switching power supply unit as dedicated circuits for leveling the current supply between the switching power supply units, which raises concerns about the increase in the number of parts, resulting in an increase in the size and cost of the device.

[0007] The present disclosure has been made to solve such problems, and an object of the present disclosure is to level the current supply between DC power supply devices through simple control in a power supply system in which the outputs of multiple DC power supply devices are connected in parallel. [Means for solving the problem]

[0008] According to one aspect of the present disclosure, there is provided a power supply system for supplying a DC voltage and a DC current to a load. The power supply system includes a plurality of DC power supply devices connected in parallel with their outputs electrically connected to the load. Each of the plurality of DC power supply devices is configured to control its output by on / off control of a switching element. Each of the plurality of DC power supply devices includes an input current detector that detects an input current to the DC power supply device, and a control circuit that generates an on / off control signal for the switching element. The control circuit has a transceiver unit and a control calculation unit. The transceiver unit is configured to transmit and receive the input current detected by the input current detector to one of the plurality of DC power supply devices other than the DC power supply device. The control calculation unit generates an on / off control signal to compensate for control deviations including an output voltage control deviation calculated to bring the output voltage of the DC power supply device closer to a predetermined reference voltage and an input current control deviation calculated to bring the input current of the DC power supply device closer to a current target value. The current target value is set according to the input current of the other DC power supply device acquired by the transceiver unit. [Effects of the Invention]

[0009] According to the present disclosure, in a power supply system in which the outputs of multiple DC power supply devices are connected in parallel, the current supply between the DC power supply devices can be leveled through simple control by controlling the on / off of semiconductor switching elements in accordance with control calculations for balancing the input current of each DC power supply device. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a block diagram illustrating an example of the configuration of a power supply system according to a first embodiment. [Figure 2] 2 is a circuit diagram illustrating an example of the configuration of each DC power supply device shown in FIG. 1. FIG. [Figure 3] 3 is a schematic waveform diagram of an input current in the DC power supply device shown in FIG. 2. [Figure 4] 3 is a block diagram illustrating a control operation by the control circuit shown in FIG. 2. FIG. [Figure 5] 5 is a flowchart illustrating a calculation process performed by a duty ratio calculation unit shown in FIG. 4. [Figure 6] 5A and 5B are conceptual waveform diagrams illustrating output voltage control by a duty ratio calculation unit. [Figure 7] FIG. 10 is a block diagram illustrating an example of the operation of the power supply system according to the second embodiment. [Figure 8] 10 is a flowchart illustrating a control process in each DC power supply device in the power supply system according to the second embodiment. [Figure 9] FIG. 10 is a conceptual waveform diagram illustrating an example of operation of the power supply system according to the second embodiment. [Figure 10] FIG. 10 is a block diagram illustrating an example of the configuration of a power supply system according to a modification of the second embodiment. [Figure 11] 10 is a flowchart illustrating a control process added to each DC power supply device in a power supply system according to a modification of the second embodiment. [Figure 12] 10 is a flowchart illustrating a control process in each DC power supply device of the power supply system according to the third embodiment. [Figure 13]FIG. 11 is a block diagram illustrating an example of the configuration of a power supply system according to a modification of the third embodiment. [Figure 14] FIG. 11 is a conceptual waveform diagram illustrating an example of operation of a power supply system according to a modification of the third embodiment. [Figure 15] FIG. 4 is a conceptual waveform diagram showing an example of a control operation in each DC power supply device in the current balancing mode described in the first embodiment. [Figure 16] 10 is a flowchart illustrating a control process added to each DC power supply device in the power supply system according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the drawings will be denoted by the same reference numerals, and their description will not be repeated in principle.

[0012] Embodiment 1 FIG. 1 is a block diagram illustrating an example of the configuration of a power supply system according to the first embodiment.

[0013] 1, a power supply system 100 according to the first embodiment includes a plurality of DC power supply devices whose load-side outputs are connected in parallel. For example, the outputs of two DC power supply devices CNV1 and CNV2 are connected in parallel to supply DC power to a load 20.

[0014] The DC power supply CNV1 includes a step-down chopper circuit CHP1, a full-bridge circuit FBC1, an isolation transformer TRF1, a rectifier circuit RCT1, and a control circuit CNT1. The DC power supply CNV2 includes a step-down chopper circuit CHP2, a full-bridge circuit FBC2, an isolation transformer TRF2, a rectifier circuit RCT2, and a control circuit CNT2.

[0015] Because DC power supply devices CNV1 and CNV2 have a common configuration, hereinafter, when DC power supply devices CNV1 and CNV2 are to be collectively referred to as DC power supply device CNV. Similarly, when describing the contents common to DC power supply devices CNV1 and CNV2, the step-down chopper circuits CHP1, CHP2, full-bridge circuits FBC1, FBC2, isolation transformers TRF1, TRF2, and rectifier circuits RCT1, RCT2 will also be collectively referred to as the step-down chopper circuit CHP, full-bridge circuit FBC, isolation transformer TRF, and rectifier circuit RCT, respectively.

[0016] DC power supplies CNV1 and CNV2 convert power supplied from a power supply 10 connected via power lines PL0 and NL0 into power to be supplied to a load 20. As will be described later, the output (output voltage Vo1 and output current Io1) of DC power supply CNV1 is controlled by a control circuit CNT1, and the output (output voltage Vo2 and output current Io2) of DC power supply CNV1 is controlled by a control circuit CNT2.

[0017] The control circuits CNT1 and CNT2 can be configured, for example, by electronic control circuits such as microcomputers, etc. Furthermore, the control circuits CNT1 and CNT2 are connected by a signal line 105 so as to be able to send and receive data to and from each other.

[0018] When the output voltages Vo1 and Vo2 are equal, the output current Io1 from DC power supply CNV1 to load 20 and the output current Io2 from DC power supply CNV2 to load 20 are balanced. In each of DC power supply devices CNV1 and CNV2, the input current Iin1 from power supply 10 and the output current Io1 are equal, and the input current Iin2 from power supply 10 and the output current Io2 are equal, so when the input currents Iin1 and Iin2 are balanced, the output currents Io1 and Io2 are also balanced, and the current supply between DC power supply devices CNV1 and CNV2 is leveled.

[0019] In the following, when referring to symbols indicating voltages and currents such as output voltages Vo1 and Vo2, input currents Iin1 and Iin2, and output currents Io1 and Io2 of each DC power supply CNV in a comprehensive manner, the numerical subscripts will be omitted and they will be referred to as output voltage Vo, input current Iin, output current Io, etc., as appropriate.

[0020] Even if DC power supplies CNV1 and CNV2 each attempt to control their output voltages Vo1 and Vo2 to a common reference voltage Vo*, differences between the output voltages Vo1 and Vo2 may occur due to individual differences in the DC power supplies CNV caused by component variations, etc. In this case, an imbalance in the output current Io occurs, and the DC power supply CNV with the higher output voltage Vo becomes larger. As a result, degradation progresses unevenly, potentially affecting the lifespan of the power supply system. Such an imbalance in current supply results in a difference between the input currents Iin1 and Iin2 of the DC power supplies CNV1 and CNV2.

[0021] In the example of FIG. 1, the DC power supply devices CNV1 and CNV2 are connected to a common power supply 10. However, even if the DC power supply devices CNV1 and CNV2 receive power from separate power supplies, the problem of imbalance in current supply described above occurs in the same way.

[0022] FIG. 2 is a circuit diagram illustrating an example of the configuration of each DC power supply CNV shown in FIG. As shown in FIG. 2, the DC power supply CNV includes a step-down chopper circuit CHP, a full-bridge circuit FBC, an isolation transformer TRF, a rectifier circuit RCT, an output voltage detection circuit 60, and an input current detector .

[0023] The step-down chopper circuit CHP has a semiconductor switching element (hereinafter simply referred to as "switching element") 31, a diode 32, a capacitor 33, and a reactor 34. The switching element 31 is configured, for example, as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), and is controlled to be turned on and off in response to a gate signal Sgt from a control circuit CNT. Note that the switching element 31 is not limited to a MOSFET, and can be configured as any semiconductor element that can be controlled to be turned on and off by a control signal.

[0024] During the on period of the switching element 31, a current path is formed via the input terminal 110 from the power line PL0 to the switching element 31 (on) to the node N1 to the reactor 34 to the power line PL1 to the capacitor 33 to the power line NL1 to the input current detector 70 to the power line NL0, and the input current Iin from the power supply 10 is introduced.

[0025] In contrast, during the off period of switching element 31, the power line PL0 (power supply 10) is disconnected from node N1, and a current path (freewheeling path) is formed via reactor 34, power line PL1, capacitor 33, power line NL1, diode 32 (on), and node N1.

[0026] FIG. 3 shows a schematic waveform diagram of the input current Iin. 3, during the off-period of switching element 31, the current path from power supply 10 is interrupted, so that input current Iin = 0. On the other hand, during the on-period of switching element 31, the input current Iin from power supply 10 forms a charging path for capacitor 33, including reactor 34, so that input current Iin increases at a constant rate. This rate of increase is calculated by dividing the voltage difference between the output voltage of power supply 10 and the DC voltage Vdc between power lines PL1 and NL0, which is maintained by capacitor 33, by the inductance value of reactor 34. When switching element 31 is turned off, input current Iin drops to 0.

[0027] Referring again to FIG. 2, the input current detector 70 can be configured, for example, with a shunt resistor, but a current sensor such as a Hall element can also be used. Because the input current Iin shown in FIG. 3 flows through the input current detector 70, a voltage Vsht proportional to the input current Iin is generated across the shunt resistor. For example, the control circuit CNT can acquire an input current detection signal Iindet indicating the detected value of the input current Iin based on the voltage Vsht immediately before the switching element 31 is turned off. Hereinafter, the current value of the input current detection signal Iindet, i.e., the detected value of the input current Iin acquired by the input current detection signal Iindet, will be denoted using the same symbol as shown in FIG. 3.

[0028] The control circuit CNT generates the gate signal Sgt so as to control the duty ratio, which is the ratio of the on-period in a switching cycle during which the switching element 31 is turned on and off. Due to known characteristics, the DC voltage Vdc, which corresponds to the output voltage of the step-down chopper circuit CHP, can be controlled by the duty ratio of the switching element 31. Specifically, when the duty ratio is increased, the DC voltage Vdc also increases, and when the duty ratio is decreased, the DC voltage Vdc also decreases.

[0029] Full-bridge circuit FBC includes switching elements 41 to 44. Switching element 41 is connected between power line PL1 and node N2, and switching element 42 is connected between node N2 and power line NL1. Switching element 43 is connected between power line PL1 and node N3, and switching element 44 is connected between node N3 and power line NL1.

[0030] The switching elements 41 to 44 are on / off controlled in accordance with gate signals S1 to S4 from the control circuit CNT so as to generate an AC voltage Vac having an amplitude equal to the DC voltage Vdc from the step-down chopper circuit CHP between the nodes N2 and N3.

[0031] The isolation transformer TRF has a primary winding 51, secondary windings 52 and 53, and a core 55. The rectifier circuit RCT has diodes 45 and 46.

[0032] Primary winding 51 is connected between nodes N2 and N3. Secondary windings 52 and 53 are magnetically coupled to primary winding 51 via core 55. One end of secondary winding 52 is connected to power line NL2, and the other end of secondary winding 52 is connected to power line PL2 via diode 45. Similarly, one end of secondary winding 53 is connected to power line NL2, and the other end of secondary winding 53 is connected to power line PL2 via diode 46.

[0033] As a result, the AC voltage Vac input to the primary winding 51 from the full bridge circuit FBC is transmitted to each of the secondary windings 52 and 53 and rectified by the diodes 45 and 46. As a result, an output voltage Vo according to the DC voltage Vdc output from the step-down chopper circuit CHP is generated between the primary-side power lines PL1 and NL1 and the electrically insulated power lines PL2 and NL2 (secondary side).

[0034] Therefore, in each DC power supply CNV, DC power controlled by the step-down chopper circuit CHP can be supplied to the load 20 while being insulated from the power supply 10 side by the insulating transformer TRF.

[0035] Specifically, output voltage control that increases or decreases the output voltage Vo can be achieved by adjusting the DC voltage Vdc through duty ratio control of the switching element 31. Furthermore, as described in Fig. 1, the input currents Iin1 and Iin2 also change depending on the level of the output voltages Vo1 and Vo2 of the DC power supply devices CNV1 and CNV2, so it is possible to control the input current Iin through adjustment of the output voltage Vo using the duty ratio of the step-down chopper circuit CHP (switching element 31). In this embodiment, input current control is performed using the duty ratio, using a control calculation described later, while achieving both output voltage control.

[0036] The output voltage detection circuit 60 used for output voltage control has a reference voltage element 62 for detecting a drop in the output voltage Vo, a photocoupler 65, and resistance elements R1 to R6, and generates an output voltage detection signal Vodet according to the output voltage Vo.

[0037] The reference voltage element 62 is arranged to detect when the output voltage Vo rises above a predetermined reference voltage Vo*. For example, the reference voltage element 62 can be configured as a shunt regulator that divides the output voltage Vo by resistors R1 and R2 to obtain an input voltage Vodv. The shunt regulator is connected between the power line NL2 and a node N4.

[0038] When the input voltage Vodv exceeds the reference voltage Vref, which is a standard value, the shunt regulator (reference voltage element 62) conducts so as to generate a current from node N4 to power line NL2. On the other hand, when the input voltage Vodv is lower than the reference voltage Vref, the shunt regulator remains non-conductive. The reference voltage Vref of the shunt regulator corresponds to the product of the reference voltage Vo* and the voltage division ratio (Vodv / Vo). Conversely, the voltage division ratio of the resistor elements R1 and R2 is determined in accordance with the ratio of the reference voltage Vo* and Vref.

[0039] Photocoupler 65 includes a photodiode 66 and a phototransistor 68 that is conductive when photodiode 66 emits light. Photodiode 66 has an anode electrically connected to power line PL2 via resistor R3 and a cathode connected to node N4. When phototransistor 68 is conductive, it generates a current that corresponds to the amount of light emitted by photodiode 66.

[0040] Therefore, when the input voltage Vodv is higher than the reference voltage Vref (i.e., when the output voltage Vo is higher than the reference voltage Vo*), the photodiode 66 is energized in response to the conduction of the reference voltage element 62 (shunt regulator) and emits light with an amount of light corresponding to the input voltage Vodv (output voltage Vo). On the other hand, when the input voltage Vodv is lower than the reference voltage Vref (i.e., when the output voltage Vo is lower than the reference voltage Vo*), the photodiode 66 does not emit light.

[0041] The phototransistor 68 is connected in series with the resistance element R4 between the node N5 where the output voltage detection signal Vodet is generated and the ground node. Further, the node N5 is electrically connected to the power supply node (power supply voltage Vc) via the resistance element R5 and is also electrically connected to the ground node via the resistance element R6.

[0042] Therefore, the voltage of the node N5 becomes the initial voltage V0 obtained by dividing the power supply voltage Vc by the resistance elements R5 and R6 during the off period of the phototransistor 68. On the other hand, during the on period of the phototransistor 68, a voltage corresponding to the voltage drop amount in the resistance element R4 due to the current of the phototransistor 68 is generated at the node N5. The resistance element R4 is determined such that the voltage of the node N5 decreases from the initial voltage V0 during the on period of the phototransistor 68.

[0043] As a result, the voltage value of the output voltage detection signal Vodet by the output voltage detection circuit 60 is set to the above initial voltage V0 when Vodv < Vref in the shunt regulator (reference voltage element 62), that is, when the output voltage Vo is lower than the reference voltage Vo*. On the other hand, when the output voltage Vo rises above the reference voltage Vo*, the shunt regulator conducts, and the voltage value of the output voltage detection signal Vodet decreases from the initial voltage V0 in response to the conduction amount (current) that increases non-linearly with respect to the rise amount (Vo - Vo*) of the output voltage Vo with respect to the reference voltage Vo*.

[0044] The output voltage detection signal Vodet is insulated from the secondary side (load 20 side) of the isolation transformer TRF, and can therefore be input to the control circuit CNT that controls the step-down chopper circuit CHP and full-bridge circuit FBC on the primary side of the isolation transformer TRF. In the configuration of the DC power supply CNV shown in Fig. 2, the on / off controlled switching elements 31, 41 to 44 are arranged only on the primary side of the isolation transformer TRF, and therefore the output of the DC power supply CNV can be controlled without providing a control circuit on the secondary side of the isolation transformer TRF, thereby enabling the device to be made more compact.

[0045] Next, the control operation by the control circuit CNT will be described with reference to FIGS. FIG. 4 shows a block diagram for explaining the control operation by the control circuit CNT.

[0046] 4, each of the control circuits CNT1 and CNT2 has a serial transmission unit 71, a serial reception unit 72, a duty ratio calculation unit 80, and a PWM (Pulse Width Modulation) control unit 90. The serial transmission unit 71 and the serial reception unit 72 constitute an embodiment of a "transmission / reception unit," and the duty ratio calculation unit 80 and the PWM control unit 90 constitute an embodiment of a "control calculation unit."

[0047] The control circuit CNT1 acquires an input current detection signal Iindet1 indicating the input current Iin1 of the DC power supply CNV1 based on an input from the input current detector 70 of the DC power supply CNV1 (for example, the voltage Vsht of the shunt resistor).

[0048] In the control circuit CNT1, the input current detection signal Iindet1 is input to a duty ratio calculation unit 80 and also to the serial transmission unit 71. The duty ratio calculation unit 80 also receives an output voltage detection signal Vodet1 from the output voltage detection circuit 60.

[0049] The serial transmission unit 71 converts the input current detection signal Iindet1 into a digital signal and outputs the converted digital signal to a signal line 105. The digital signal transmitted from the serial transmission unit 71 of the control circuit CNT1 is received by the serial reception unit 72 of the control circuit CNT2.

[0050] Similarly, the control circuit CNT2 acquires an input current detection signal Iindet2 indicating the input current Iin2 of the DC power supply CNV2 based on an input from the input current detector 70 of the DC power supply CNV2 (for example, the voltage Vsht of the shunt resistor).

[0051] In the control circuit CNT2, the input current detection signal Iindet2 is input to a duty ratio calculation unit 80 and also to the serial transmission unit 71. The duty ratio calculation unit 80 also receives an output voltage detection signal Vodet2 from the output voltage detection circuit 60.

[0052] The serial transmission unit 71 converts the input current detection signal Iindet2 into a digital signal and outputs the converted digital signal to a signal line 105. The digital signal transmitted from the serial transmission unit 71 of the control circuit CNT2 is received by the serial reception unit 72 of the control circuit CNT1.

[0053] In this way, the control circuit CNT1 can acquire the input current detection signal Iindet2 in the DC power supply CNV2 by receiving the digital signal transmitted from the control circuit CNT2 (serial transmission unit 71). Similarly, the control circuit CNT2 can acquire the input current detection signal Iindet1 in the DC power supply CNV1 by receiving the digital signal transmitted from the control circuit CNT1 (serial transmission unit 71). The serial transmission unit 71 and serial reception unit 72 of each control circuit CNT can be configured to transmit and receive digital signals in accordance with a serial transmission standard such as UART (Universal Asynchronous Receiver Transmitter).

[0054] As a result, the control circuit CNT1 can acquire the detected value of the input current Iin2 of the DC power supply CNV2, whose outputs are connected in parallel, in addition to the detected value of the input current Iin1 of the DC power supply CNV1. Similarly, the control circuit CNT2 can acquire the detected value of the input current Iin1 of the DC power supply CNV1, whose outputs are connected in parallel, in addition to the detected value of the input current Iin2 of the DC power supply CNV2. In this way, in the power supply system according to this embodiment, by sharing the detected value of the input current Iin between the multiple DC power supplies CNV, whose outputs are connected in parallel, it is possible to perform input current control that balances the shared input current Iin.

[0055] In addition, in Figure 4, an example of a configuration has been described in which the input current detection signal Iindet is exchanged between multiple DC power supply devices CNV by serial transmission and reception of digital signals, but it is also possible to configure the input current detection signal Iindet to be exchanged by communication of analog signals.

[0056] However, when communicating using analog signals, in order to suppress the effects of disturbance noise, it may be necessary to configure the wiring that transmits the input current detection signal Iindet in the control circuit CNT as a shielded wire and to configure the signal line 105 as a twisted pair wire.In contrast, communication using digital signals has the advantage of being less susceptible to the effects of noise.

[0057] Note that digital signal communication normally requires the placement of a digital integrated circuit (IC). However, by configuring the control circuit CNT with a microcomputer, as shown in the configuration example of Figure 4, it is possible to send and receive the input current detection signal Iindet between multiple DC power supply devices CNV via digital communication without adding an IC dedicated to communication.

[0058] In each control circuit CNT, the duty ratio calculation unit 80 sets the duty ratio DT (0≦DT≦1.0) by control calculation using the output voltage detection signals Vodet and Iindet of the DC power supply device CNV and the input current detection signal Iindet of the other DC power supply device CNV received.

[0059] The PWM control unit 90 generates a gate signal Sgt for the switching element 31 by pulse width modulation control based on a voltage comparison between a periodic carrier wave, such as a sawtooth wave or a triangular wave, and a duty ratio DT. One cycle of the carrier wave corresponds to the switching cycle of the switching element 31.

[0060] Fig. 5 is a flowchart illustrating the calculation process by the duty ratio calculation unit 80. For example, the control process shown in Fig. 5 is common to the duty ratio calculation unit 80 of each DC power supply CNV (control circuit CNT), and can be executed at each predetermined control period by software processing in which a microcomputer constituting the control circuit CNT executes a pre-stored program. Alternatively, at least a portion of the steps described below can be realized by hardware processing using a dedicated electronic circuit or the like.

[0061] In step S110, the control circuit CNT (duty ratio calculation unit 80) acquires (samples) the output voltage detection signal Vodet of the DC power supply device CNV in which the control circuit CNT is mounted, and then in step S120, calculates the output voltage deviation ΔVo between the output voltage detection signal Vodet and the voltage target value Vr (ΔVo=Vr-Vodet). The voltage target value Vr is a voltage value lower than the voltage value (initial voltage V0) of the output voltage detection signal Vodet when the output voltage Vo is lower than the reference voltage Vo*. Conversely, the voltage division ratio of the resistor elements R5 and R6 is designed so that the initial voltage V0 is a voltage value higher than the voltage target value Vr.

[0062] The target voltage value Vr can be arbitrarily set by software processing inside the control circuit CNT (microcomputer). As will be described in the following embodiment, the target voltage value Vr can also be updated online while the power supply control system is operating.

[0063] In step S130, the control circuit CNT (duty ratio calculation unit 80) acquires an input current detection signal Iindet (FIG. 3) indicating the magnitude of the input current Iin of the DC power supply device CNV, based on the input from the input current detector 70. Furthermore, in step S140, the control circuit CNT sets a current target value Ir in the DC power supply device CNV, using the input current detection signal Iindet from another DC power supply device CNV acquired by communication via the signal line 105.

[0064] In the configuration example of Figure 4, in the control circuit CNT1 (DC power supply CNV1), an input current detection signal Iindet1 indicating the input current Iin1 is acquired in step S130, while in step S140, Ir is set to Iindet2 using the input current detection signal Iindet2 (input current Iin2) of the DC power supply CNV2 acquired through communication.

[0065] Conversely, in the control circuit CNT2 (DC power supply CNV2), an input current detection signal Iindet2 indicating the input current Iin2 is acquired in step S130, while in step S140, Ir is set to Iindet1 using the input current detection signal Iindet1 (input current Iin1) of the DC power supply CNV1 acquired through communication.

[0066] In step S150, the control circuit CNT (duty ratio calculation unit 80) calculates the input current deviation ΔIin between the input current detection signal Iindet (S130) and the current target value Ir (S140) (ΔIin=Ir-Iindet). Note that the processing in steps S110 and S120 and the processing in steps S130 to S150 may be executed in reverse order or may be executed in parallel.

[0067] In step S160, the control circuit CNT (duty ratio calculation unit 80) calculates the control deviation ΔDT using the output current deviation ΔVo (S120) and the input current deviation (S150) according to the following equation (1).

[0068] ΔDT=K1·ΔVo+K2·ΔIin…(1) As shown in equation (1), the control deviation ΔDT is calculated to include the output voltage control deviation ΔDTV (= K1 · ΔVo) used for the calculation of bringing the output voltage Vo closer to the reference voltage Vo*, and the input current control deviation ΔDTI (= K2 · ΔIin) used for the calculation of bringing the input current Iin closer to the current target value Ir. Note that the coefficients K1 and K2 are predetermined real numbers. As shown in equation (1), the control deviation ΔDT can be obtained by adding the output voltage control deviation ΔDTV and the input current control deviation ΔDTI.

[0069] In step S170, the control circuit CNT (duty ratio calculation unit 80) sets the duty ratio DT by control calculation using the control deviation ΔDT (S160) as an input, for example, proportional-plus-integral (PI) control calculation.

[0070] Here, in the control calculation of step S170, the control deviation ΔDT acts to increase the duty ratio if ΔDT > 0, decrease the duty ratio if ΔDT < 0, and maintain the current duty ratio DT when ΔDT = 0. Therefore, the duty ratio DT is feedback controlled so as to bring the control deviation ΔDT closer to zero, that is, to compensate for the control deviation ΔDT. Note that the control calculation for calculating the duty ratio DT from the control deviation ΔDT is not limited to PI control calculation, and any control calculation method can be applied.

[0071] FIG. 6 is a conceptual waveform diagram illustrating output voltage control by the duty ratio calculation unit. FIG. 6 shows an example of a control operation when the output voltage Vo is lower than the reference voltage Vo* before time tx, but becomes higher than the reference voltage Vo* at time tx.

[0072] Before the time tx, in the configuration example of FIG. 2, since the reference voltage element 62 (shunt regulator) is non-conductive, the voltage value of the output voltage detection signal Vodet of the DC power supply device on which the control circuit CNT is mounted is set to the initial voltage V0. As described above, since Vr < V0, the output voltage deviation ΔVo (= Vr - Vodet) < 0.

[0073] However, during the period when the output voltage Vo is lower than a predetermined reference voltage, in order to gradually increase the output voltage Vo, the output voltage control deviation ΔDTV (= K1·ΔVo) is set to be positive. That is, the coefficient K1 is set to a negative constant (K1 < 0). Thus, when the output voltage Vo is lower than a predetermined reference voltage (before the time tx), the output voltage control deviation ΔDTV is set so as to have a polarity that increases the duty ratio DT.

[0074] On the other hand, after the time tx, in the configuration example of FIG. 2, in response to the conduction of the reference voltage element 62 (shunt regulator), the output voltage detection signal Vodet decreases from the initial voltage V0. As a result, since the output voltage detection signal Vodet drops below the voltage target value Vr and the output voltage deviation ΔVo becomes positive, the output voltage control deviation ΔDTV becomes a negative value and has a polarity that decreases the duty ratio DT.

[0075] On the other hand, the input current control deviation ΔDTI (= K2·ΔIin) has a polarity that increases the duty ratio DT when the input current Iin of the DC power supply device CNV is smaller than the input current Iin of another DC power supply device CNV, that is, when ΔIin = Ir - Iindet > 0. Therefore, the coefficient K2 for obtaining the input current control deviation ΔDTI is set to a positive value (K2 > 0). Thus, conversely to the above, when the input current Iin of the DC power supply device CNV is larger than the input current Iin of another DC power supply device CNV (ΔIin < 0), the input current control deviation ΔDTI has a polarity that decreases the duty ratio DT in the DC power supply device CNV.

[0076] For example, assuming that the characteristics of the DC power supplies CNV are uniform, when the input current Iin of the DC power supply CNV approaches the input current Iin of the other DC power supplies CNV and the input current control deviation ΔDTI approaches 0, the duty ratio DT is feedback controlled after time tx so that the control deviation ΔDT including the output voltage control deviation ΔDTV and the input current control deviation ΔDTI approaches zero. As a result, the output voltage detection signal Vodet approaches the voltage target value Vr, the input current control deviation ΔDTI becomes 0, and the output voltage control deviation ΔDTV (= K1 ΔVo) converges to zero.

[0077] As described above, according to the DC power supply system of the first embodiment, in a configuration in which the outputs of a plurality of DC power supply devices CNV, whose outputs can be controlled by the duty ratios of the switching elements, are connected in parallel, the duty ratio DT can be set by reflecting the feedback calculation for balancing the input currents Iin of the DC power supply devices CNV.

[0078] This makes it possible to equalize the current supply of multiple DC power supply devices connected in parallel by controlling the output voltage and reflecting the common duty ratio in the feedback control, without the need for an additional dedicated circuit for balancing the output current as in Patent Document 1. As a result, the simplified control makes it possible to reduce the size and cost of the device.

[0079] In particular, in the power supply system of the first embodiment, in a configuration in which the DC power output from each isolated DC power supply CNV is controlled by a primary circuit (step-down chopper circuit CHP and full-bridge circuit FBC) of an isolation transformer TRF, the current supply between the plurality of DC power supply devices CNV is leveled by controlling the input current Iin detected on the primary side of the isolation transformer TRF. Therefore, the detection value (input current Iin) for control for this output leveling can be input to each control circuit CNT without isolation, which is also advantageous for miniaturization and cost reduction of the device.

[0080] Furthermore, according to the above-described configuration example, by configuring the control circuit CNT using a digital IC (microcomputer) that operates on the primary power supply of the isolation transformer TRF, the serial communication function of the digital IC can be used to easily realize digital communication of the input current Iin (input current detection signal Iindet) between multiple DC power supply devices CNV, which is advantageous in terms of noise resistance. Furthermore, by applying a digital filter inside the digital IC (microcomputer), it is possible to further enhance the noise removal effect.

[0081] Embodiment 2 In the second embodiment, an explanation will be given of input current control when an abnormality occurs in the communication of the input current Iin (input current detection signal Iindet) between the plurality of DC power supply devices CNV explained in the first embodiment.

[0082] FIG. 7 is a block diagram illustrating an example of the operation of power supply system 101 according to the second embodiment.

[0083] 7, the configuration of power supply system 101 is similar to that of power supply system 100 according to the first embodiment, and the configuration of each of DC power supply devices CNV1 and CNV2, the outputs of which are connected in parallel, is also similar to that of the first embodiment (FIG. 2).

[0084] In the power supply system 101, input current control will be described in the case where the control circuit CNT of each DC power supply CNV cannot acquire the input current Iin (input current detection signal Iindet) of the other DC power supply CNV.

[0085] Specifically, as shown in Figure 7, when an abnormality occurs in the transmission and reception of input current detection signals Iindet1 and Iindet2 between DC power supply device CNV1 and DC power supply device CNV2, each control circuit CNT controls the duty ratio using a current limit value mode described below, which is different from embodiments 1 and 2.

[0086] FIG. 8 is a flowchart illustrating the control process in each DC power supply CNV in the power supply system according to the second embodiment.

[0087] As shown in FIG. 8, the control circuit CNT determines in step S210 whether the input current detection signal Iindet has been received via the signal line 105, and if it has not been received (NO in S210), it performs a timeout determination in step S220 to determine whether the non-reception state continues for a predetermined period of time.

[0088] If the control circuit CNT receives the input current detection signal Iindet normally before the timeout, it determines that the communication state is normal (YES in S210), and in step S230, executes the on / off control of the switching element 31 that calculates the duty ratio DT according to steps S110 to S170 in FIG. 5, as described in the first embodiment. Hereinafter, the on / off control of the switching element 31 according to the first embodiment will also be referred to as control applying the "current balance mode." The current balance mode corresponds to an example of the "first control mode."

[0089] On the other hand, if a timeout occurs without receiving the input current detection signal Iindet (YES in S220), the control circuit CNT detects an input current communication abnormality in step S240, and then calculates the duty ratio DT of the switching element 31 in step S250 so as to control the input current by applying the "current limit value mode." The current limit value mode corresponds to an example of the "second control mode."

[0090] In the current limit value mode in which a communication abnormality is detected, the control circuit CNT can detect the input current Iin of the other DC power supply CNV, and therefore fixes the input current control deviation DTI to 0. Even in this case, the control circuit CNT can acquire the input current detection signal Iindet indicating the input current Iin of the DC power supply CNV.

[0091] Therefore, in the current limit value mode, the control circuit CNT calculates the output voltage deviation ΔVo according to steps S110 and S120 in FIG. 5, and calculates the basic duty ratio through a control operation that takes the output voltage control deviation ΔDTV in Equation (1) as an input. Further, the preset limit current Ilmt in each DC power supply device CNV is compared with the input current detection signal Iindet. When Iindet < Ilmt, the duty ratio DT is set using the basic duty ratio DT for compensating the output voltage control deviation ΔDTV as it is.

[0092] On the contrary, when Iindet > Ilmt, in order to reduce the output of the DC power supply device CNV from the current value, the duty ratio DT is set through a correction operation process that decreases the duty ratio DT from the current value by an amount corresponding to the magnitude of (Iindet - Ilmt). Thereby, in the current limit value mode, output voltage control for making the output voltage Vo approach the reference voltage Vo* is executed while restricting the input current Iin so that it does not continuously exceed the limit current Ilmt.

[0093] Thus, in the power supply system 101 according to Embodiment 2, each DC power supply device CNV can select the same current balancing mode as in Embodiment 1 or the above current limit value mode to set the duty ratio DT.

[0094] FIG. 9 is a conceptual waveform diagram for explaining an operation example of the power supply system according to Embodiment 2. That is, FIG. 9 shows waveform diagrams when each of the DC power supply devices CNV1 and CNV2 operates in the current limit value mode.

[0095] 9 shows an example of operation in which a difference of Vo1>Vo2 occurs as a result of feedback control (output voltage control based on duty ratio) of output voltages Vo1 and Vo2 due to individual differences between DC power supplies CNV1 and CNV2. The vertical axis of Fig. 9 represents the output current Io (equivalent to the input current Iin) of each of DC power supplies CNV1 and CNV2, and the horizontal axis represents the load current Iout supplied from power supply system 101 to load 20 by DC power supplies CNV1 and CNV2 as a whole. The load current Iout corresponds to the current consumed by load 20.

[0096] As shown in FIG. 9, in a region where the load current Iout is smaller than the limit current Ilmt, the output voltage Vo1>Vo2, so that the load current Iout is supplied intensively from the DC power supply CNV1.

[0097] In the region where the load current Iout is higher than the limit current Ilmt, the duty ratio DT is controlled while limiting the output current Io1 of the DC power supply CNV1 so that it does not exceed the limit current Ilmt. As a result, roughly speaking, the load current Iout is secured by increasing the output current Io2 from the DC power supply CNV2 while maintaining Io1=Ilmt.

[0098] When the load current Iout reaches Ix, the output currents Io1 and Io2 of both DC power supplies CNV1 and CNV2 reach the limit current Ilmt (i.e., Ix ≈ 2 · Ilmt). When the load current Iout increases above Ix, the output voltages Vo1 and Vo2 decrease, and the duty ratio DT increases in each of the DC power supplies CNV1 and CNV2. As a result, the DC power supplies CNV1 and CNV2 operate so that both output currents Io1 and Io2 are increased equally to ensure the load current Iout.

[0099] As described above, according to the power supply system of the second embodiment, when the input current Iin (input current detection signal Iindet) cannot be transmitted or received between the plurality of DC power supply devices CNV connected in parallel, the current limit value mode is applied to control the output current of each DC power supply device CNV so that it does not exceed the limited current, and then current can be supplied from the plurality of DC power supply devices CNV to the load 20. This makes it possible to suppress concentration of current supply to a specific DC power supply device CNV, thereby leveling the current supply among the plurality of DC power supply devices CNV connected in parallel.

[0100] A variation of the second embodiment. In the modification of the second embodiment, a parallel operation will be described in which the current limit value mode described above is applied when a failure occurs in one of three or more DC power supply devices connected in parallel.

[0101] FIG. 10 is a block diagram illustrating an example of the configuration of a power supply system 102 according to a modification of the second embodiment.

[0102] As shown in Fig. 10, a power supply system 102 includes three DC power supply devices CNV1 to CNV3 whose outputs are connected in parallel. In the configuration example of Fig. 10, as in Fig. 1 and Fig. 7, the input sides of DC power supply devices CNV1 to CNV3 are connected to a common power supply 10 via power lines PL0 and NL0, but the power supply of DC power supply devices CNV1 to CNV3 does not necessarily have to be common.

[0103] Each of the DC power supplies CNV1 to CNV3 is configured similarly to each of the DC power supplies CNV1 and CNV2 in embodiment 2. Therefore, in the modified example of embodiment 2 as well, each DC power supply CNV can automatically select the current balance mode (embodiment 1) or the current limit value mode (embodiment 2) in accordance with the control process of Fig. 9 and perform output control based on the duty ratio.

[0104] The input currents Iin1 to Iin3 of the DC power supply devices CNV1 to CNV3 are detected in each DC power supply device CNV using an input current detector 70 (FIG. 2). This allows each DC power supply device CNV to generate an input current detection signal Iindet that indicates the input current Iin of that DC power supply device CNV.

[0105] The input current detection signal Iindet generated in each DC power supply CNV can be transmitted and received in the same manner as in the example of Fig. 4 by connecting the two DC power supplies CNV with a signal line 105. For example, in the example of Fig. 10, serial transmission and reception can be performed such that an input current detection signal (Iindet1) of the input current Iin1 is transmitted from DC power supply CNV1 to DC power supply CNV2, an input current detection signal (Iindet2) of the input current Iin2 is transmitted from DC power supply CNV2 to DC power supply CNV3, and further an input current detection signal (Iindet3) of the input current Iin3 is transmitted from DC power supply CNV3 to DC power supply CNV1.

[0106] Fig. 11 is a flowchart illustrating control processing added in each DC power supply CNV of the power supply system 102. The control circuit CNT of each DC power supply CNV can further execute the control processing shown in Fig. 11 in addition to the control processing (Fig. 9) for selecting the current balance mode (embodiment 1) and the current limit value mode, which has been described in embodiment 2.

[0107] As shown in FIG. 11, when the control circuit CNT detects an abnormality in step S310 (YES determination), the process proceeds to step S330, where the control circuit CNT stops the transmission of the input current detection signal Iindet by the serial transmission unit 71 (FIG. 4).

[0108] In step S310, a YES determination is made when an abnormality is detected in the DC power supply CNV in which the control circuit CNT is mounted. Furthermore, in step S310, a YES determination is made when the control circuit CNT (DC power supply CNV) does not normally receive the input current detection signal Iindet.

[0109] When no abnormality is detected in step S310 (determined as NO), the control circuit CNT advances the process to step S320, where it transmits the input current detection signal Iindet via the serial transmission unit 71 (FIG. 4).

[0110] Referring again to FIG. 10, an operation example of the power supply system 102 will be described in which a failure occurs in the DC power supply CNV2.

[0111] In the DC power supply CNV2, the control circuit CNT2 detects a fault, resulting in a YES judgment in step S310, and therefore the transmission of the input current detection signal (Iindet2) from the DC power supply CNV2 (control circuit CNT2) to the DC power supply CNV3 (control circuit CNT3) is stopped.

[0112] In response to this, the control circuit CNT3 is no longer able to receive the input current detection signal from the control circuit CNT2, and therefore a YES judgment is made in step S220 (FIG. 9), and output control based on the duty ratio in the DC power supply CNV3 is switched from the current balance mode (S230) to the current limit value mode (S250).

[0113] Furthermore, in the control circuit CNT3, for example, in conjunction with the processing of step S240 (FIG. 9), a YES determination is made in step Iin, thereby stopping the transmission of the input current detection signal (Iindet1) from the DC power supply CNV3 (control circuit CNT3) to the DC power supply CNV1 (control circuit CNT1).

[0114] In response to this, the control circuit CNT1 is also unable to receive the input current detection signal from the control circuit CNT3, and a YES judgment is made in step S220 (FIG. 9), so that the output control based on the duty ratio in the DC power supply CNV1 is switched from the current balance mode (S230) to the current limit value mode (S250).

[0115] As a result, in the power supply system 102, the current output from the failed DC power supply CNV2 is stopped, while the remaining DC power supplies CNV1 and CNV3 operate in the current limit value mode to supply current to the load 20. That is, the outputs of the DC power supplies CNV1 and CNV3 are controlled with a corrective calculation process of the duty ratio for input current control in the current limit value mode.

[0116] As a result, by the same operation as in the operation example of FIG. 9, it is possible to supply the current consumed by the load 20 after controlling the output current of each of the DC power supply devices CNV1 and CNV3 to be equal to or less than the limit current Ilmt.

[0117] As described above, according to the power supply system of the modified example of the second embodiment, even if a failure occurs in one of the multiple (three or more) DC power supply devices CNV whose outputs are connected in parallel, the control mode of the input current of each of the remaining DC power supply devices CNV is automatically switched, thereby controlling the output current Io of each DC power supply device CNV so that it does not exceed the limit current Ilmt, and making it possible to continue supplying current to the load 20.

[0118] Embodiment 3 In the third embodiment, a control in which the current balance mode (first embodiment) and the current limit value mode (second embodiment) are combined in each DC power supply CNV will be described.

[0119] In the power supply system according to the third embodiment, the control processing in each DC power supply device CNV differs from that in the first embodiment in the same circuit configuration as in FIG.

[0120] Fig. 12 is a flowchart illustrating control processing in each DC power supply CNV of the power supply system according to embodiment 3. The control processing in Fig. 12 is executed in each DC power supply CNV during normal operation when no abnormality occurs.

[0121] As shown in FIG. 12, when the control circuit CNT obtains an input current detection signal Iindet from the output of the input current detector 70 of the DC power supply device CNV on which the control circuit CNT is mounted in step S410, in step S420, the control circuit CNT compares the input current detection signal Iindet with the limit current Ilmt.

[0122] When the input current detection signal Iindet is smaller than the limit current Ilmt (Indet < Ilmt), step S420 is determined as YES, and the process proceeds to step S430. In step S430, the control circuit CNT applies the current balancing mode of Embodiment 1 to control the duty ratio DT. That is, the duty ratio DT is calculated according to the processing of steps S110 to S170 in FIG. 5.

[0123] On the other hand, when the input current detection signal Iindet becomes greater than or equal to the limit current Ilmt (Indet ≧ Ilmt), step S420 is determined as NO, and the process proceeds to step S440. In step S440, the control circuit CNT sets the duty ratio DT so as to decrease the current duty ratio by a predetermined amount. That is, similar to the current limit value mode of Embodiment 2, a process for decreasing the input current Iin that is greater than or equal to the limit current Ilmt from the current value by an amount corresponding to the magnitude of (Iindet - Ilmt) is executed.

[0124] Thereby, in each DC power supply device CNV, the duty ratio DT is set in a manner that the control mode of the input current (current balancing mode / current limit value mode) is automatically switched based on the comparison between the input current detection signal Iindet and the limit current Ilmt.

[0125] Therefore, in the power supply system according to Embodiment 3, in the region where the load current Iout described in FIG. 9 is smaller than Ix (Ix ≒ 2·Ilmt), each of the DC power supply devices CNV1 and CNV2 operates by applying the current balancing mode (S430) because step S420 is determined as YES.

[0126] As a result, the duty ratio DT in the DC power supplies CNV1 and CNV2 is controlled so that the input currents Iin1 and Iin2 are balanced, and therefore the load current Iout can be supplied equally (Io1≈Io2) from the DC power supplies CNV1 and CNV2.

[0127] On the other hand, in the region where the load current Iout is equal to or greater than Ix, the determination in step S420 is NO in each of the DC power supplies CNV1 and CNV2, and the duty ratio DT is controlled in the current limit value mode (S440). Therefore, similar to the region where Iout≧Ix in FIG. 9, the DC power supplies CNV1 and CNV2 operate so that both the output currents Io1 and Io2 are increased equally with a decrease in the output voltage Vout, thereby ensuring the load current Iout.

[0128] Therefore, according to the power supply system of the third embodiment, it is possible to limit the output current of each DC power supply device CNV so that it does not exceed the limited current, and to level the current supply between the DC power supply devices CNV connected in parallel.

[0129] A variation of the third embodiment. In a variation of the third embodiment, a configuration will be described in which a DC power supply device that operates independently in a current limit value mode is added as a backup to the configuration of the third embodiment, to accommodate applications in which the load current Iout varies over a relatively wide range.

[0130] FIG. 13 is a block diagram illustrating an example of the configuration of a power supply system according to a modification of the third embodiment.

[0131] As shown in Fig. 13, a power supply system 103 according to the third embodiment includes three DC power supply devices CNV1 to CNV3 whose outputs are connected in parallel. Input currents Iin1 and Iin2 are transmitted and received between DC power supply devices CNV1 and CNV2 using a signal line 105. DC power supply devices CNV1 and CNV2 execute the control process shown in Fig. 12 and operate in a current balance mode or a current limit value mode. That is, it can be understood that the power supply system according to the third embodiment described above is configured by DC power supply devices CNV1 and CNV2 of the power supply system 103.

[0132] The power supply system 103 further includes a DC power supply CNV3 that operates in a fixed current limit value mode, in addition to the DC power supplies CNV1 and CNV2 that constitute the power supply system according to embodiment 3. In the power supply system 103, the outputs of the DC power supplies CNV1 to CNV3 are connected in parallel.

[0133] For example, by not connecting the DC power supply CNV3 to the DC power supply CNV1 and CNV2 via the signal line 105, the DC power supply CNV3 can operate independently in the fixed current limit value mode in accordance with the control process of FIG.

[0134] Furthermore, the DC power supply CNV3 is determined so that Vo1>Vo3 and Vo2>Vo3 are satisfied as a result of feedback control (duty ratio control) of the output voltages Vo1-Vo3 of the DC power supply devices CNV1-CNV3. For example, the relationships Vo1>Vo3 and Vo2>Vo3 can be achieved by setting the target voltage value Vr of the DC power supply CNV3 lower than the target voltage values ​​Vr of the DC power supply devices CNV1 and CNV2. Alternatively, the DC power supply with the lowest output voltage Vo can be determined as the DC power supply that operates independently in the current limit value mode (CNV3 in FIG. 13) based on actual measurements of the output voltages Vo of the multiple DC power supply devices CNV1-CNV3 when they are actually operated.

[0135] Fig. 14 is a conceptual waveform diagram illustrating an example of operation of the power supply system 103 according to the modification of the third embodiment. The horizontal axis of Fig. 14, similar to Fig. 9, represents the load current Iout supplied from the power supply system 103 to the load 20. The vertical axis of Fig. 14 represents the output current Io (equivalent to the input current Iin) of each DC power supply device CNV, similar to Fig. 9, and the output voltage Vout supplied from the power supply system 103 to the load 20.

[0136] In FIG. 14, as described above, as a result of the feedback control (duty ratio control) of the output voltages Vo1 to Vo3 in the DC power supply devices CNV1 to CNV3, Vo1>Vo3 and Vo2>Vo3.

[0137] As shown in Fig. 14, in the region where the load current Iout is smaller than Ix (Ix ≈ 2 · Ilmt) as in Fig. 9, the load current Iout can be supplied by the outputs of the two DC power supplies CNV. For this reason, the DC power supply CNV3, which is provided as a backup, outputs almost no current because its output voltage Vo is the lowest, so the load current Iout is supplied by the DC power supplies CNV1 and CNV2.

[0138] At this time, since the determination in step S420 is YES, each of the DC power supplies CNV1 and CNV2 operates in the current balance mode (S430). Therefore, the duty ratio DT of the DC power supplies CNV1 and CNV2 is controlled so that the input currents Iin1 and Iin2 are balanced, and the DC power supplies CNV1 and CNV2 supply the load current Iout with their shares maintained such that Io1=Io2.

[0139] When the load current Iout reaches Ix, in each of the DC power supply devices CNV1 and CNV2, step S420 is determined as NO, and the duty ratio DT is controlled in the current limit value mode (S440). Therefore, in order to increase the load current Iout beyond Ix, the output current Io3 of the DC power supply device CNV3 increases while the output currents Io1 and Io2 of the DC power supply devices CNV1 and CNV2 are maintained at approximately the limit current Ilmt. Accordingly, the output voltage Vo to the load 20 decreases from the voltage level when Iout < Ix.

[0140] Furthermore, when the load current Iout increases to Iy, for the DC power supply device CNV3 as well, the input current Ii3 reaches the limit current Ilmt, and step S420 is determined as NO (i.e., Iy ≈ 3·Ilmt).

[0141] Therefore, when the load current Iout increases beyond Iy, as the output voltages Vo1 to Vo3 further decrease, the duty ratio DT is increased in each of the DC power supply devices CNV1 to CNV3. As a result, the DC power supply devices CNV1 to CNV3 operate such that the output currents Io1 to Io3 increase evenly to ensure the load current Iout. Note that the output voltage Vout to the load 20 decreases as the load current Iout increases.

[0142] Thus, according to the power supply system according to the modification of Embodiment 3, in addition to the effects of Embodiment 3, the number of DC power supply devices CNV that supply current can be flexibly changed according to the change in the load current Iout, and the current supply among the DC power supply devices CNV of that number can be equalized. As a result, for example, in response to an application where the load current Iout changes over a relatively wide range, it is possible to equalize the current supply among a plurality of parallel-connected DC power supply devices with the arrangement of standby DC power supply devices CNV.

[0143] In the modification of the third embodiment (FIG. 13), DC power supplies CNV1 and CNV2 correspond to an example of two or more "first DC power supplies," and DC power supply CNV3 corresponds to an example of one or more "second DC power supplies." That is, a plurality (two or more) of spare DC power supplies (DC power supply CNV3 in FIG. 13) that operate fixedly in the current value limiting mode may be arranged in parallel.

[0144] The control process in Fig. 13 may be executed when step S210 is determined to be YES (normal operation) in the control process in Fig. 8 described in embodiment 2. In this way, it is possible to realize control that combines embodiment 2 with embodiment 3 and its modified examples. Specifically, when an abnormality occurs, the abnormality response in embodiment 2 or its modified examples is applied, and then during normal operation, the control described in embodiment 3 and its modified examples can be executed.

[0145] Embodiment 4 In the fourth embodiment, a control process for further balancing the input currents in the current balancing mode described in the first embodiment will be described.

[0146] 15 is a conceptual waveform diagram showing an example of control operation in each DC power supply CNV in current balancing mode. The horizontal axis of Fig. 15 is the time axis, and the vertical axis represents the output voltage control deviation ΔDTV and the input current control deviation ΔDTI described in the first embodiment.

[0147] As explained in equation (1), the input current control deviation ΔDTI (= K2 · ΔIin) is proportional to the difference between the input currents Iin1 and Iin2 of the DC power supply devices CNV1 and CNV2. Therefore, by setting ΔDTI = 0, Iin1 = Iin2, that is, the current supply of the DC power supply devices CNV1 and CNV2 can be brought into perfect balance.

[0148] As described in Embodiment 1, the voltage target value Vr for obtaining the output voltage control deviation ΔDTV is set lower than the voltage value (initial voltage V0) of the output voltage detection signal Vodet when the output voltage Vo is lower than the reference voltage Vo*. Therefore, the output voltage control deviation ΔDTV is set to a positive value for increasing the duty ratio DT when Vo < Vo*, while it rapidly decreases when Vo ≥ Vo* due to the decrease in the voltage of the output voltage detection signal Vodet.

[0149] In the example of FIG. 15, before time t1, the duty ratio DT is set by a control operation that takes as an input the control deviation ΔDT (Equation (1)) represented by the sum of the output voltage control deviation ΔDTV and the input current control deviation ΔDTI, thereby realizing control in which the absolute values of both the output voltage control deviation ΔDTV and the input current control deviation ΔDTI decrease.

[0150] However, as described above, since this control operation is a feedback control that brings the control deviation ΔDT closer to zero, at time t1, when the equilibrium state of ΔDTV + ΔDTI = ΔDT = 0 is reached, even if the input current control deviation ΔDTI remains (|ΔDTI| > 0), it is understood that the duty ratio cannot be further changed to decrease the input current control deviation ΔDTI.

[0151] In Embodiment 4, in response to the above-described stuck state, a control process for automatically updating the voltage target value Vr is further executed to further reduce the difference between the input currents. However, as will be described below, the automatic update of the voltage target value Vr is not executed in all DC power supply devices CNV. For example, it can be defined in advance such that one of the plurality of DC power supply devices CNV connected in parallel is in charge of the master for which the voltage target value Vr is not updated, and the other DC power supply devices CNV are in charge of the slaves for which the voltage target value Vr can be updated. Data indicating whether it is the master or the slave can be stored in advance in each control circuit CNT before the operation start of the power supply system according to Embodiment 4.

[0152] Fig. 16 is a flowchart illustrating control processing added to each DC power supply in the power supply system according to embodiment 4. In embodiment 4, the control circuit CNT of each DC power supply CNV can further execute the control processing shown in Fig. 16 in addition to the control processing of the current balance mode (Fig. 5) described in embodiment 1.

[0153] As shown in FIG. 16, in step S510, the control circuit CNT determines whether the DC power supply CNV is in charge of the master or the slave, based on the above-mentioned pre-stored data.

[0154] In the DC power supply CNV acting as the master, a NO determination is made in step S510, and the process proceeds to step S520, whereby the voltage target value Vr is fixed to the default value.

[0155] In the DC power supply CNV in the slave configuration that can update the voltage target value Vr, a YES determination is made in step S510, and the process proceeds to step S530. In step S530, the control circuit CNT determines whether a state in which the absolute value of the control deviation ΔDT is smaller than a predetermined determination value ε (|ΔDT|<ε) has continued for a predetermined time period ΔTj. The determination value ε is a constant for detecting the above-mentioned balanced state (ΔDT=0). For example, in the example of FIG. 15, a YES determination is made in step S530 at time t2, which is when ΔTj has elapsed since time t1.

[0156] On the other hand, if |ΔDT|<ε is no longer satisfied before ΔTj continues in the determination of step S530, a NO determination is made in step S530, and the equilibrium state is not detected. In this case, the control circuit CNT maintains the voltage target value Vr at its current value in step S550.

[0157] If the state of |ΔDT|<ε continues for ΔTj (YES in S530), the control circuit CNT detects the balanced state and proceeds to step S540. In step S540, the control circuit CNT executes an update process to change the voltage target value Vr from the current value by ΔVr in a direction to bring the current output voltage control deviation ΔDTV closer to zero (Vr → Vr + ΔVr). For example, the change amount ΔVr in the update process can be calculated as ΔDTV / K1 (ΔV1 / K1 in the example of FIG. 15) in accordance with the output voltage control deviation ΔDTV when the balanced state is detected.

[0158] In response to the update process for the target voltage value Vr, a change in the voltage deviation ΔVo occurs to generate a control deviation ΔDT in a direction that reduces the absolute value of the input current deviation ΔDTI. As a result, as shown in Fig. 15, the output voltage control deviation ΔDTV becomes zero at time t2, and from time t2 onwards, it becomes possible to change the duty ratio DT so that the input current control deviation ΔDTI approaches zero. As a result, it becomes possible to break out of the stalemate between times t1 and t2 and achieve a state in which the input current control deviation ΔDTI = 0, i.e., Iin1 = Iin2.

[0159] As described above, in the power supply system according to the fourth embodiment, when the DC power supply CNV controls the duty ratio in the current balance mode described in the first embodiment, even if a balanced state of control deviation ΔDT=0 is reached, the absolute value of the input current control deviation ΔDTI can be further reduced. This makes it possible to further enhance the effect of balancing the input currents in the current balance mode.

[0160] It should be noted that, with regard to the multiple embodiments described above, it has been planned from the beginning of the application that the configurations described in each embodiment may be appropriately combined, including combinations not mentioned in the specification, within the scope that does not result in inconsistencies or contradictions.

[0161] As can be understood from the description of this embodiment, in the first to fourth embodiments and their modifications, the number of multiple DC power supply devices whose outputs are connected in parallel can be any number equal to or greater than three in the modification of the second embodiment, and any number equal to or greater than two in the other embodiments. Furthermore, transmission and reception of input current detection signals between multiple DC power supply devices is not limited to the above example, and can be performed in any manner. That is, the current target value Ir (S140: FIG. 5) in the current balance mode described in the first embodiment can be set in any manner using the input current detection signals Iindet of the other DC power supply devices CNV. For example, when one DC power supply device CNV receives input current detection signals Iindet from multiple other DC power supply devices CNV, the current target value Ir may be set using the multiple input current detection signals Iindet (for example, using the average value of these signals).

[0162] The configuration example of each DC power supply CNV (Fig. 2) is also just an example, and any switching power supply circuit configuration can be applied as long as the DC output can be controlled by controlling the on / off ratio of the switching element.

[0163] In particular, in this embodiment, an isolated switching power supply in which an input side (power supply 10) and an output side (load 20) are electrically insulated by providing an isolation transformer is exemplified as each DC power supply device CNV, but it will be noted that the output control accompanied by leveling of current supply explained in this embodiment can also be applied to a power supply system in which non-isolated switching power supplies, whose input side and output side are electrically connected, are connected in parallel.

[0164] However, in a configuration using an insulated DC power supply CNV, the input current Iin on the primary side of the insulating transformer TRF according to this embodiment is balanced with transmission and reception between the control circuits CNT, thereby eliminating the need for insulation processing when inputting to the control circuits CNT. This can enhance the effects of miniaturizing and reducing the cost of the device.

[0165] <Additional Notes> The above-described embodiment and modified examples include the following technical ideas. [Configuration 1] A power supply system (100-103) for supplying a DC voltage and a DC current to a load (20), a plurality of DC power supply devices (CNVs) whose output sides are connected in parallel and electrically connected to the load; each of the plurality of DC power supply devices is configured such that an output thereof is controlled by on / off control of a switching element (31); Each of the plurality of DC power supply devices an input current detector (70) that detects an input current (Iin) to the DC power supply; a control circuit (CNT) that generates an on / off control signal (Sgt) for the switching element; The control circuit a transmitting / receiving unit (71, 72) for transmitting and receiving the input current detected by the input current detector to and from any one of the plurality of DC power supply devices other than the DC power supply device in question; a control calculation unit (80, 90) that generates the on / off control signal so as to compensate for a control deviation (ΔT) including an output voltage control deviation (ΔDTV) calculated to bring the output voltage (Vo) of the DC power supply device closer to a predetermined reference voltage (Vo*) and an input current control deviation (ΔDTI) calculated to bring the input current of the DC power supply device closer to a current target value (Ir); A power supply system, wherein the current target value (Ir) is set in accordance with the input current (Iin) of the other DC power supply device acquired by the transmitting / receiving unit. [Configuration 2] Each of the plurality of DC power supply devices (CNV) The DC power supply further includes an output voltage detection circuit (60) configured to generate an output voltage signal (Vodet) based on the output voltage (Vo) of the DC power supply device and input the signal to the control circuit (CNT); the control calculation unit (80) calculates the output voltage control deviation (ΔDTV) according to the deviation between the voltage value of the output voltage signal and a voltage target value (Vr); 2. The power supply system of claim 1, wherein the output voltage detection circuit is configured to set a voltage value of the output voltage signal to a first voltage (V0) higher than the voltage target value when the output voltage (Vo) is lower than the reference voltage (Vo*), and to reduce a voltage value of the output voltage signal to a voltage lower than the voltage target value when the output voltage (Vo) is higher than the reference voltage. [Configuration 3] the control deviation (ΔDT) is calculated by adding the output voltage control deviation (ΔDTV) and the input current control deviation (ΔDTI); The power supply system of configuration 2, wherein, when a state in which the absolute value of the control deviation remains within a certain range continues for a certain time, the control calculation unit (80) updates the voltage target value (Vr) by reflecting the output voltage control deviation at that time in a direction in which the output voltage control deviation approaches zero. [Configuration 4] The control calculation unit (80, 90) When the input current (Iin) of the other DC power supply (CNV) can be received by the transceiver (71, 72), a first control mode is applied to compensate for the control deviation (ΔDT) including the output voltage control deviation (ΔDTV) and the input current control deviation (ΔDTI) to generate the on / off control signal (Sgt); The power supply system according to any one of configurations 1 to 3, wherein when the transceiver cannot receive the input current of the other DC power supply device, a second control mode is applied, and when the input current (Iin) of the DC power supply device is smaller than a predetermined limit current (Ilim), the on / off control signal is generated so as to compensate for the output voltage control deviation (ΔDTV), while when the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from the current level. [Configuration 5] The power supply system of configuration 4, wherein when the control circuit (CNT) of each of the plurality of DC power supply devices (CNV1 to CNV3) detects that one of the plurality of DC power supply devices has failed based on the reception status of the transceiver units (71, 72), it applies the second control mode to generate the on / off control signal in that DC power supply device (CNV). [Configuration 6] The control calculation unit (80, 90) When the input current (Iin) of the DC power supply (CNV) is smaller than a predetermined limit current (Ilmt), the on / off control signal (Sgt) is generated so as to compensate for the control deviation (ΔDT) including the output voltage control deviation (ΔDTV) and the input current control deviation (ΔDTI), The power supply system according to any one of configurations 1 to 3, wherein when the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from its current level. [Configuration 7] When the input current (Iin) of the other DC power supply device cannot be received by the transmitting / receiving unit (71, 72), the control calculation unit (80, 90) The power supply system of configuration 6, wherein when the input current (Iin) of the DC power supply device is smaller than a predetermined limit current (Ilmt), the on / off control signal (Sgt) is generated so as to compensate for the output voltage control deviation (ΔDTV), and when the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from its current level. [Configuration 8] the plurality of DC power supply devices (CNV) include two or more first DC power supply devices (CNV1, CNV2) and one or more second DC power supply devices (CNV3), the output sides of which are connected in parallel, the output voltage (Vo3) of each of the second DC power supplies is set lower than the output voltage (Vo1, Vo2) of each of the first DC power supplies, The control and calculation units (80, 90) of the first DC power supply devices (CNV1, CNV2) each include: When the input current (Iin) of the DC power supply (CNV) is smaller than a predetermined limit current (Ilmt), the on / off control signal (Sgt) is generated so as to compensate for the control deviation (ΔDT) including the output voltage control deviation (ΔDTV) and the input current control deviation (ΔDTI), When the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from the current level; The control and calculation unit (80, 90) of each of the second DC power supply devices (CNV3) The power supply system according to any one of configurations 1 to 3, wherein when the input current (Iin) of the DC power supply device is smaller than a predetermined limit current (Ilmt), the on / off control signal (Sgt) is generated so as to compensate for the output voltage control deviation (ΔDTV), and when the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from its current level. [Configuration 9] When the control calculation unit (80, 90) of each of the first DC power supply devices (CNV1, CNV2) cannot receive the input current (Iin) of the other DC power supply device by the transmitting / receiving unit (71, 72), The power supply system of configuration 8, wherein when the input current (Iin) of the DC power supply device is smaller than a predetermined limit current (Ilmt), the on / off control signal (Sgt) is generated so as to compensate for the output voltage control deviation (ΔDTV), and when the input current (Iin) of the DC power supply device is equal to or greater than the limit current (Ilmt), the on / off control signal is generated so as to reduce the output of the DC power supply device from its current level. [Configuration 10] Each of the plurality of DC power supply devices (CNV) is configured to electrically insulate an input side connected to a power supply (10) for supplying the input current (Iin) from the output side, The power supply system according to any one of configurations 1 to 9, wherein the transmitter / receiver units (71, 72) are configured to transmit and receive a digital signal (Iindet) indicating the input current by serial transmission and reception via a signal line (105) connecting two DC power supply devices among the plurality of DC power supply devices.

[0166] 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 by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0167] 10 power supply, 20 load, 31, 41 to 44 switching element, 32, 45, 46 diode, 33 capacitor, 34 reactor, 51 primary winding, 52, 53 secondary winding, 55 core, 60 output voltage detection circuit, 62 reference voltage element, 65 photocoupler, 66 photodiode, 68 phototransistor, 70 input current detector, 71 serial transmission unit, 72 serial reception unit, 80 duty ratio calculation unit, 90 PWM control unit, 100 to 103 power supply system, 105 signal line, 110 input terminal, CHP, CHP1, CHP2 step-down chopper circuit, CNT, CNT1 to CNT3 control circuit, CNV, CNV1, CNV2, CNV3 DC power supply device, DT duty ratio, FBC, FBC1, FBC2 full bridge circuit, IC Digital, Idet, Iindet, Iindet1 to Iindet3 input current detection signal, Iin, Iin1 to Iin3 input current, Ilmt limit current, Io, Io1 to Io3 output current (DC power supply), Iout load current, Ir current target value, N1 to N5 nodes, NL0 to NL2, PL0 to PL2 power lines, R1 to R6 resistor elements, RCT, RCT1, RCT2 rectifier circuit, S1 to S4, Sgt gate signal, TRF, TRF1, TRF2 isolation transformer, Vc power supply voltage, Vac AC voltage, Vdc DC voltage, Vo* reference voltage (output voltage), Vref reference voltage (shunt regulator), Vo, Vo1 to Vo3 output voltage (DC power supply), Vout output voltage (power supply system), Vodet, Vodet1, Vodet2 output voltage detection signal, Vodv Input voltage (shunt regulator), ΔDT control deviation, ΔDTI input current control deviation, ΔDTV output voltage control deviation.

Claims

1. 1. A power supply system for supplying a DC voltage and a DC current to a load, comprising: a plurality of DC power supply devices whose output sides are connected in parallel and electrically connected to the load; each of the plurality of DC power supply devices is configured such that an output thereof is controlled by on / off control of a switching element; Each of the plurality of DC power supply devices an input current detector that detects an input current to the DC power supply; a control circuit that generates an on / off control signal for the switching element, The control circuit a transmitter / receiver for transmitting and receiving the input current detected by the input current detector to and from any one of the plurality of DC power supply devices other than the DC power supply device in question; a control calculation unit that generates the on / off control signal so as to compensate for control deviations including an output voltage control deviation calculated to make the output voltage of the DC power supply device approach a predetermined reference voltage and an input current control deviation calculated to make the input current of the DC power supply device approach a current target value, a power supply system, wherein the current target value is set in accordance with the input current of the other DC power supply device acquired by the transmitting / receiving unit;

2. Each of the plurality of DC power supply devices an output voltage detection circuit configured to generate an output voltage signal based on the output voltage of the DC power supply device and input the output voltage signal to the control circuit; the control calculation unit calculates the output voltage control deviation according to a deviation between a voltage value of the output voltage signal and a voltage target value; 2. The power supply system of claim 1, wherein the output voltage detection circuit is configured to set a voltage value of the output voltage signal to a first voltage higher than the target voltage value when the output voltage is lower than the reference voltage, and to reduce the voltage value of the output voltage signal to a voltage lower than the target voltage value when the output voltage is higher than the reference voltage.

3. the control deviation is calculated by adding the output voltage control deviation and the input current control deviation; 3. The power supply system according to claim 2, wherein, when a state in which the absolute value of the control deviation remains within a certain range for a certain period of time, the control calculation unit updates the target voltage value by reflecting the output voltage control deviation at that time in a direction in which the output voltage control deviation approaches zero.

4. The control calculation unit When the input current of the other DC power supply device can be received by the transceiver unit, a first control mode is applied to generate the on / off control signal so as to compensate for the control deviation including the output voltage control deviation and the input current control deviation, and 4. The power supply system according to claim 1, wherein, when the input current of the other DC power supply device cannot be received by the transceiver unit, a second control mode is applied, and when the input current of the DC power supply device is smaller than a predetermined limit current, the on / off control signal is generated so as to compensate for the output voltage control deviation, and when the input current of the DC power supply device is equal to or greater than the limit current, the on / off control signal is generated so as to reduce the output of the DC power supply device from its current level.

5. 5. The power supply system according to claim 4, wherein when the control circuit of each of the plurality of DC power supply devices detects that one of the plurality of DC power supply devices has failed based on the reception status at the transceiver unit, the control circuit applies the second control mode to generate the on / off control signal for that DC power supply device.

6. The control calculation unit When the input current of the DC power supply device is smaller than a predetermined limit current, the on / off control signal is generated so as to compensate for the control deviation including the output voltage control deviation and the input current control deviation; 4. The power supply system according to claim 1, wherein when the input current of the DC power supply device is equal to or greater than the limit current, the on / off control signal is generated so as to reduce the output of the DC power supply device from a current level.

7. When the input current of the other DC power supply device cannot be received by the transmitting / receiving unit, the control calculation unit:

7. The power supply system according to claim 6, wherein the on / off control signal is generated so as to compensate for the output voltage control deviation when the input current of the DC power supply device is smaller than a predetermined limit current, and the on / off control signal is generated so as to reduce the output of the DC power supply device from a current level when the input current of the DC power supply device is equal to or greater than the limit current.

8. the plurality of DC power supply devices include two or more first DC power supply devices and one or more second DC power supply devices, the output sides of which are connected in parallel, the output voltage of each of the second DC power supplies is set lower than the output voltage of each of the first DC power supplies, The control and calculation unit of each of the first DC power supply devices When the input current of the DC power supply device is smaller than a predetermined limit current, the on / off control signal is generated so as to compensate for the control deviation including the output voltage control deviation and the input current control deviation; When the input current of the DC power supply device is equal to or greater than the limit current, the on / off control signal is generated so as to reduce the output of the DC power supply device from the current level; The control and calculation unit of each of the second DC power supply devices 4. The power supply system according to claim 1, wherein the on / off control signal is generated so as to compensate for the output voltage control deviation when the input current of the DC power supply device is smaller than a predetermined limit current, and the on / off control signal is generated so as to reduce the output of the DC power supply device from a current level when the input current of the DC power supply device is equal to or greater than the limit current.

9. When the control and calculation unit of each of the first DC power supply devices cannot receive the input current of the other DC power supply devices by the transmitting and receiving unit, 9. The power supply system according to claim 8, wherein the on / off control signal is generated so as to compensate for the output voltage control deviation when the input current of the DC power supply device is smaller than a predetermined limit current, and the on / off control signal is generated so as to reduce the output of the DC power supply device from a current level when the input current of the DC power supply device is equal to or greater than the limit current.

10. each of the plurality of DC power supply devices is configured to electrically insulate an input side connected to a power supply for supplying the input current from the output side; The power supply system according to any one of claims 1 to 3, wherein the transmitter / receiver is configured to transmit and receive a digital signal indicating the input current by serial transmission and reception via a signal line connecting two of the plurality of DC power supply devices.

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