Multi-output power supply device

Abstract

To provide a multi-output power supply that prevents current imbalance in the line filter circuits contained in each of the multiple power supply units. [Solution] The multi-output power supply unit 10A comprises a first power supply unit 20 that outputs a first DC voltage, a second power supply unit 30A that outputs a second DC voltage, and a first switch 11, and can operate in a first mode that outputs both the first and second DC voltages and a second mode that outputs only the second DC voltage. The second power supply unit 30A includes a second switch 38 provided on the current path (second low-potential DC line 36) from the second voltage conversion circuit 34 to the second line filter circuit 31. The first switch 11 is configured to be closed in the first mode and open in the second mode. The second switch 38 is configured to be open in the first mode and closed in the second mode.

Description

Technical Field

[0001] The present invention relates to a multi-output power supply device capable of outputting a plurality of different DC voltages.

Background Art

[0002] Conventionally, in various electronic devices, a multi-output power supply device that outputs a plurality of different DC voltages has been used. For example, in an image forming apparatus (copier), a first DC voltage (e.g., 24 [V]) for driving a paper feeding mechanism or the like and a second DC voltage (e.g., 5 [V]) for driving a control circuit having lower power consumption than the paper feeding mechanism or the like are output, and a multi-output power supply device is used.

[0003] FIG. 5 shows a conventional multi-output power supply device 100. The multi-output power supply device 100 includes a line filter circuit 101 having one end connected to an AC power supply G such as a commercial AC power supply, a first power supply unit 110 connected to the other end of the line filter circuit 101 via a switch 102 that takes an open state or a closed state according to an external signal S1, and a second power supply unit 120 directly connected to the other end of the line filter circuit 101.

[0004] The first power supply unit 110 includes a first diode bridge circuit 111, a power factor correction circuit 112, a first voltage conversion circuit 113, a first smoothing capacitor 116, a first high-potential-side DC line 114 and a first low-potential-side DC line 115 that connect the power factor correction circuit 112 and the first voltage conversion circuit 113. The first power supply unit 110 outputs 24 [V] when the switch 102 is in the closed state.

[0005] The second power supply unit 120 includes a second diode bridge circuit 121, a second voltage conversion circuit 123, a second smoothing capacitor 126, a second high-potential-side DC line 124 and a second low-potential-side DC line 125 that connect the second diode bridge circuit 121 and the second voltage conversion circuit 123. The second power supply unit 120 always outputs 5 [V] regardless of the state of the switch 102.

[0006] The multi-output power supply unit 100 further includes a high-potential interconnection line 103 connecting high-potential DC lines 114 and 124, a low-potential interconnection line 104 connecting low-potential DC lines 115 and 125, and a diode 105 provided on the high-potential interconnection line 103. The high-potential interconnection line 103 and the diode 105 supply current to the second voltage conversion circuit 123 in place of the second diode bridge circuit 121 when the first power supply unit 110 is outputting 24[V].

[0007] In this multi-output power supply unit 100, when the switch 102 is closed, the sum of the circuit current of the first power supply unit 110 and the circuit current of the second power supply unit 120 flows through the line filter circuit 101. Therefore, in this multi-output power supply unit 100, if the power consumption of an unillustrated load circuit that receives a 24[V] or 5[V] supply increases, it becomes necessary to increase the thickness of the windings or the core size of the line filter circuit 101 in order to reduce the resistance of the line filter circuit 101. However, increasing the thickness of the windings or the core size increases the size and cost of the line filter circuit 101.

[0008] This problem can be resolved by adopting a configuration like the multi-output power supply device 100' shown in Figure 6, referencing the configuration in Patent Document 1 in which filters are provided in each power supply unit, that is, a configuration in which the line filter circuit 101 is omitted, a first power supply unit 110' including a first line filter circuit 117 is adopted instead of the first power supply unit 110, and a second power supply unit 120' including a second line filter circuit 127 is adopted instead of the second power supply unit 120.

[0009] However, with this configuration, when switch 102 is in the closed position, the balance between the current flowing through the first line filter circuit 117 and the current flowing through the second line filter circuit 127 may be disrupted.

[0010] For example, assuming that the current flowing from the first power supply unit 110' towards a load circuit (not shown) is Ia and the current flowing from the second power supply unit 120' towards the load circuit (not shown) is Ib, the current flowing through the first line filter circuit 117 from left to right in the figure is Ia + Ib. This is because the voltage output by the power factor improvement circuit 112 of the first power supply unit 110' is higher than the voltage output by the second diode bridge circuit 121 of the second power supply unit 120'. Therefore, no current flows from the AC power supply G into the second power supply unit 120', and current flows from the first power supply unit 110' into the second power supply unit 120'. On the other hand, the low-potential side DC lines 115 and 125 have low impedance and are at almost the same potential. Thus, the current flowing from the load circuit (not shown) towards the second power supply circuit 120' is divided into the current flowing through the first line filter circuit 117 and the current flowing through the second line filter circuit 127. Therefore, the current flowing through the first line filter circuit 117 from right to left becomes Ia + Ib1 (Ib1 < Ib), and a difference of Ib - Ib1 occurs in the current flowing through the same circuit 117. At the same time, the current flowing through the second line filter circuit 127 from right to left becomes Ib2 (where Ib2 = Ib - Ib1), and a difference of Ib2 occurs in the current flowing through the same circuit 127. At this time, a forward current Ib flows through the diode 105. If the balance of the current flowing through the first line filter circuit 117 and the current flowing through the second line filter circuit 127 is disrupted, another problem occurs, that is, the first line filter circuit 117 and the second line filter circuit 127 cannot fully perform their functions as filters.

[0011] Figure 7 shows the conducted noise characteristics of the multi-output power supply unit 100' when switch 102 is in the closed state. Waveform W1 is the quasi-peak value (QP value) obtained by measurement, and waveform W2 is the average value (AV value) obtained by measurement. Line L1 is the limit value for the QP value as defined by the standard (e.g., VCCI Class B), and line L2 is the limit value for the AV value as defined by the standard (e.g., VCCI Class B). This figure shows that the QP value and AV value exceeded the limit values ​​as a result of the first line filter circuit 117 and the second line filter circuit 127 no longer being able to fully perform their filtering functions.

[0012] Please note that the multi-output power supply device 100' shown in Figure 6 was conceived by the inventor during the process of completing the present invention and is not prior art. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Patent No. 3822779 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] The present invention has been made in view of the above circumstances, and aims to provide a multi-output power supply device in which the current balance is not disrupted in the line filter circuits included in each of the multiple power supply units. [Means for solving the problem]

[0015] To solve the above problems, the multi-output power supply device according to the present invention comprises a first power supply unit that outputs a first DC voltage and a second power supply unit that outputs a second DC voltage, and is capable of operating in a first mode that outputs both the first DC voltage and the second DC voltage and a second mode that outputs only the second DC voltage, wherein the first power supply unit includes a first line filter circuit connected to an AC power supply via a first switch, a first DC conversion circuit including a diode bridge circuit that converts the AC voltage output by the first line filter circuit to DC, and a first voltage conversion circuit that converts the DC voltage output by the first DC conversion circuit to a first DC voltage, and the second power supply unit includes a second line filter circuit connected to an AC power supply and a diode bridge circuit that converts the AC voltage output by the second line filter circuit to DC The DC conversion circuit includes a second DC conversion circuit including a bridge circuit, a second voltage conversion circuit that converts the DC voltage output by the second DC conversion circuit into a second DC voltage, and a current control means for a second power supply unit provided on the current path from the second voltage conversion circuit to the second line filter circuit. The DC conversion circuit further includes an interconnection line for a second power supply unit that connects the outputs of the first DC conversion circuit and the second DC conversion circuit to each other. The DC voltage output by the first DC conversion circuit in the first mode is higher than the DC voltage output by the second DC conversion circuit. The first switch is configured to be closed in the first mode and open in the second mode. The current control means for the second power supply unit is configured not to conduct in the first mode and to conduct in the second mode.

[0016] In this configuration, when the multi-output power supply is operating in the first mode, the first DC conversion circuit outputs a DC voltage higher than the DC voltage output by the second DC conversion circuit, and the current path from the second voltage conversion circuit to the second line filter circuit is blocked by the current control means for the second power supply unit. In other words, in this configuration, all the current flowing from the AC power supply to the first and second voltage conversion circuits, and all the current flowing from the first and second voltage conversion circuits to the AC power supply, passes through the first line filter circuit but not through the second line filter circuit. Therefore, with this configuration, the current in the first and second line filter circuits can be balanced.

[0017] The current control means for the second power supply unit of the above-mentioned multi-output power supply device may be, for example, a second switch configured to be open in the first mode and closed in the second mode.

[0018] With this configuration, when the multi-output power supply is operating in the first mode, the current path from the second voltage conversion circuit to the second line filter circuit can be interrupted by the second switch.

[0019] The first and second switches of the above-mentioned multi-output power supply unit take an open or closed state, for example, according to the same or different external signals.

[0020] The current control means for the second power supply section of the above-mentioned multi-output power supply device may be, for example, a diode provided on the current path from the second voltage conversion circuit to the second line filter circuit so as to be in the forward direction of the current.

[0021] In this configuration, when the multi-output power supply is operating in the first mode, the voltage required to pass current through the path from the second voltage converter to the second line filter circuit is higher than the voltage required to pass current through the path from the second voltage converter to the first line filter circuit by the forward voltage of the diode. Therefore, with this configuration, the former path can be effectively blocked by the diode only when the multi-output power supply is operating in the first mode.

[0022] The first DC conversion circuit of the above-mentioned multi-output power supply device preferably further includes a power factor correction circuit.

[0023] This configuration allows for more effective use of AC power supplied from an AC power source in the first DC conversion circuit.

[0024] Further, the multi-output power supply device further includes a third power supply unit that outputs a third DC voltage in both the first mode and the second mode. The third power supply unit includes a third line filter circuit connected to an AC power supply, a third rectification circuit including a diode bridge circuit that rectifies the AC voltage output from the third line filter circuit, a third voltage conversion circuit that converts the DC voltage output from the third rectification circuit into the third DC voltage, and third power supply unit current control means provided on the path of the current from the third voltage conversion circuit toward the third line filter circuit. The multi-output power supply device further includes a third power supply unit interconnection line that interconnects the outputs of the first rectification circuit and the third rectification circuit. The DC voltage output by the first rectification circuit in the first mode is higher than the DC voltage output by the third rectification circuit. The third power supply unit current control means is configured not to conduct in the first mode and to conduct in the second mode. It may have the above-described configuration.

[0025] According to this configuration, it is possible to output the first DC voltage, the second DC voltage, and the third DC voltage while balancing the currents in the first line filter circuit, the second line filter circuit, and the third line filter circuit.

Advantages of the Invention

[0026] According to the present invention, it is possible to provide a multi-output power supply device in which the current balance in the line filter circuits included in each of the plurality of power supply units does not collapse.

Brief Description of the Drawings

[0027] [Figure 1] It is a circuit diagram of a multi-output power supply device according to a first embodiment of the present invention. [Figure 2] It is a waveform diagram showing the conducted noise characteristics of the multi-output power supply device shown in FIG. 1. [Figure 3] It is a circuit diagram of a multi-output power supply device according to a second embodiment of the present invention. [Figure 4] It is a circuit diagram of a multi-output power supply device according to a third embodiment of the present invention. [Figure 5] It is a circuit diagram of a conventional multi-output power supply device. [Figure 6] This is a circuit diagram of a multi-output power supply device conceived by the inventor during the process of completing the present invention. [Figure 7] Figure 6 shows a waveform diagram illustrating the conducted noise characteristics of a multi-output power supply. [Modes for carrying out the invention]

[0028] Hereinafter, an embodiment of the multi-output power supply device according to the present invention will be described with reference to the attached drawings.

[0029] [First Embodiment] Figure 1 shows a multi-output power supply device 10A according to a first embodiment of the present invention. As shown in the figure, the multi-output power supply device 10A includes a first switch 11, a first power supply unit 20 connected to an AC power source G, such as a commercial AC power source, via the first switch 11, and a second power supply unit 30A directly connected to the AC power source G without going through the first switch 11.

[0030] The first switch 11 is configured to be open or closed according to an external signal S1. In this embodiment, the external signal S1 is a signal output by a higher-level control circuit. When the multi-output power supply 10A is operated in the first mode, the higher-level control circuit outputs an external signal S1 that causes the first switch 11 to be closed. As a result, the first power supply unit 20 is connected to the AC power supply G. On the other hand, when the multi-output power supply 10A is operated in the second mode, the higher-level control circuit outputs an external signal S1 that causes the first switch 11 to be open. As a result, the first power supply unit 20 is disconnected from the AC power supply G.

[0031] The first power supply unit 20 outputs 24[V], which corresponds to the "first DC voltage" of the present invention, to a load circuit (not shown) when the first switch 11 is in the closed state. As shown in Figure 1, the first power supply unit 20 includes a first line filter circuit 21, one end of which is connected to an AC power supply G via the first switch 11; a first diode bridge circuit 22, the AC end of which is connected to the other end of the first line filter circuit 21; a power factor correction circuit 23, the input end of which is connected to the DC end of the first diode bridge circuit 22; a first voltage conversion circuit 24, connected to the output end of the power factor correction circuit 23 via a first high-potential DC line 25 and a first low-potential DC line 26; and a first smoothing capacitor 27 connected between the first high-potential DC line 25 and the first low-potential DC line 26.

[0032] The first diode bridge circuit 22, the power factor correction circuit 23, and the first smoothing capacitor 27 constitute the "first DC conversion circuit" of the present invention. The first DC conversion circuits 22, 23, and 27 convert the AC voltage output by the first line filter circuit 21 to DC and supply it to the first voltage conversion circuit 24. In this embodiment, the voltage after DC conversion (i.e., the potential of the first high-potential DC line 25 with respect to the potential of the first low-potential DC line 26) is set to 400[V].

[0033] The first voltage conversion circuit 24 is a chopper circuit that steps down the aforementioned 400[V] to 24[V]. The first voltage conversion circuit 24 outputs the 24[V] obtained by stepping down the voltage to a load circuit (not shown).

[0034] The second power supply unit 30A outputs 5[V], which corresponds to the "second DC voltage" of the present invention, to a load circuit (not shown), regardless of the state of the first switch 11. As shown in Figure 1, the second power supply unit 30A includes a second line filter circuit 31 with one end connected to an AC power supply G, a second diode bridge circuit 32 with its AC end connected to the other end of the second line filter circuit 31, a second voltage conversion circuit 34 connected to the DC end of the second diode bridge circuit 32 via a second high-potential DC line 35 and a second low-potential DC line 36, a second smoothing capacitor 37 connected between the second high-potential DC line 35 and the second low-potential DC line 36, and a second switch 38 provided on the second low-potential DC line 36.

[0035] The second diode bridge circuit 32 and the second smoothing capacitor 37 constitute the "second DC conversion circuit" of the present invention. The second DC conversion circuits 32 and 37 convert the AC voltage output by the second line filter circuit 31 to DC and supply it to the second voltage conversion circuit 34. In this embodiment, the voltage after DC conversion (i.e., the potential of the second high-potential DC line 35 with respect to the potential of the second low-potential DC line 36) is set to a voltage sufficiently lower than 400[V].

[0036] The second voltage conversion circuit 34 is a chopper circuit that steps down or steps up the DC voltage supplied by the second DC conversion circuits 32 and 37 to 5[V]. The second voltage conversion circuit 34 outputs the 5[V] obtained by stepping down or stepping up to a load circuit (not shown).

[0037] The second switch 38 corresponds to the "current control means for the second power supply unit" of the present invention and is configured to be open or closed according to an external signal S2. In this embodiment, the external signal S2 is a signal output by a higher-level control circuit. When the multi-output power supply unit 10A is operated in the first mode, the higher-level control circuit outputs an external signal S2 such that the second switch 38 is in the open state. This interrupts the current path (second low-potential DC line 36) from the second voltage conversion circuit 34 to the second line filter circuit 31. On the other hand, when the multi-output power supply unit 10A is operated in the second mode, the higher-level control circuit outputs an external signal S2 such that the second switch 38 is in the closed state. This establishes the current path (second low-potential DC line 36) from the second voltage conversion circuit 34 to the second line filter circuit 31.

[0038] Thus, in the first mode, the multi-output power supply 10A has the first switch 11 closed and the second switch 38 open, outputting both 24[V] and 5[V]. In the second mode, the first switch 11 is open and the second switch 38 is closed, outputting only 5[V]. It can also be said that the multi-output power supply 10A is in operation when operating in the first mode and in standby mode when operating in the second mode.

[0039] The multi-output power supply unit 10A further comprises a high-potential interconnection line 12 for the second power supply unit connecting the first high-potential DC line 25 and the second high-potential DC line 35, a low-potential interconnection line 13 for the second power supply unit connecting the first low-potential DC line 26 and the second low-potential DC line 36, and a first diode 14 provided on the high-potential interconnection line 12 for the second power supply unit. The first diode 14 has an anode directed toward the first power supply unit 20 (first high-potential DC line 25) and a cathode directed toward the second power supply unit 30A (second high-potential DC line 35). The high-potential interconnection line 12 for the second power supply unit, the low-potential interconnection line 13 for the second power supply unit, and the first diode 14 correspond to the "interconnection line for the second power supply unit" of the present invention.

[0040] As mentioned above, when the multi-output power supply unit 10A is in operation (first switch 11: closed, second switch 38: open), the voltage supplied by the second DC conversion circuits 32 and 37 of the second power supply unit 30A is sufficiently lower than the voltage supplied by the first DC conversion circuits 22, 23, and 27 of the first power supply unit 20 (400[V]). Therefore, the voltage appearing between the second high-potential DC line 35 and the second low-potential DC line 36 is 400[V] minus the forward voltage of the first diode 14 (approximately 0.7[V]). At this time, the first diode 14 supplies current to the second voltage conversion circuit 34 in place of the second diode bridge circuit 32. In this case, the second voltage conversion circuit 34 steps down the DC voltage supplied by the first diode 14, which is 400[V] - approximately 0.7[V], to 5[V], rather than the DC voltage supplied by the second DC conversion circuits 32 and 37.

[0041] On the other hand, when the multi-output power supply unit 10A is in standby mode (first switch 11: open, second switch 38: closed), the voltage supplied by the second DC conversion circuits 32 and 37 of the second power supply unit 30A is higher than the voltage (0[V]) provided by the first DC conversion circuits 22, 23, and 27 of the first power supply unit 20. Therefore, the voltage appearing between the second high-potential DC line 35 and the second low-potential DC line 36 is equal to the voltage supplied by the second DC conversion circuits 32 and 37 to the second voltage conversion circuit 34. At this time, the first diode 14 does not supply current to the second voltage conversion circuit 34.

[0042] When the multi-output power supply unit 10A is in operation, let Ia be the current flowing from the first power supply unit 20 toward the unshown load circuit, and let Ib be the current flowing from the second power supply unit 30A toward the unshown load circuit. Then the currents flowing through each part are as follows. • Current flowing from left to right in the first line filter circuit 21: Ia + Ib • Current flowing from right to left in the first line filter circuit 21: Ia + Ib • Current flowing from left to right in the second line filter circuit 31: 0 • Current flowing from right to left in the second line filter circuit 31: 0 • Current flowing from top to bottom in the high-potential interconnection line 12 for the second power supply unit: Ib • Current flowing from bottom to top in the low-potential interconnection line 13 for the second power supply unit: Ib

[0043] The current flowing through the first line filter circuit 21 from left to right in the diagram, and the current flowing through the same circuit 21 from right to left, are both Ia + Ib, indicating a balance. Similarly, the current flowing through the second line filter circuit 31 from left to right in the diagram, and the current flowing through the same circuit 31 from right to left, are both 0, indicating a balance here as well. This is because the second switch 38, which is open in the operating state, blocks the current path from the second voltage conversion circuit 34 to the second line filter circuit 31.

[0044] Figure 2 shows the conducted noise characteristics of the multi-output power supply unit 10A in operation. Waveform W1 is the quasi-peak value (QP value) obtained by measurement, and waveform W2 is the average value (AV value) obtained by measurement. Line L1 is the limit value for the QP value as defined by the standard (e.g., VCCI Class B), and line L2 is the limit value for the AV value as defined by the standard (e.g., VCCI Class B). This figure shows that the first line filter circuit 21 and the second line filter circuit 31 fully perform their filtering functions, resulting in the QP value and AV value remaining below the limit values.

[0045] [Second Example] Figure 3 shows a multi-output power supply device 10B according to a second embodiment of the present invention. As shown in the figure, the multi-output power supply device 10B differs from the multi-output power supply device 10A in that it has a second power supply unit 30B instead of the second power supply unit 30A, but it is common with the multi-output power supply device 10A in other respects, for example, that it outputs both 24[V] and 5[V] in the first mode and outputs only 5[V] in the second mode.

[0046] The second power supply unit 30B includes a second line filter circuit 31 with one end connected to an AC power supply G, a second diode bridge circuit 32 with its AC end connected to the other end of the second line filter circuit 31, a second voltage conversion circuit 34 connected to the DC end of the second diode bridge circuit 32 via a second high-potential DC line 35 and a second low-potential DC line 36, a second smoothing capacitor 37 connected between the second high-potential DC line 35 and the second low-potential DC line 36, and a second diode 39 provided on the second low-potential DC line 36.

[0047] The second diode 39 corresponds to the "current control means for the second power supply unit" of the present invention and has an anode connected to the second voltage conversion circuit 34 and a cathode connected to the second diode bridge circuit 32.

[0048] The current path from the second voltage conversion circuit 34 to the AC power supply G includes the path from the second low-potential DC line 36 → second low-potential interconnection line 13 for the power supply unit → first low-potential DC line 26 → power factor correction circuit 23 → first diode bridge circuit 22 → first line filter circuit 21 → first switch 11 (hereinafter referred to as the "first path") and the path from the second low-potential DC line 36 (second diode 39) → second diode bridge circuit 32 → second line filter circuit 31 (hereinafter referred to as the "second path").

[0049] The first path is only valid when the first switch 11 is closed, that is, when the multi-output power supply 10B is in operation. In other words, the current from the second voltage conversion circuit 34 to the AC power supply G cannot pass through the first path when the multi-output power supply 10B is in standby mode. Therefore, the current from the second voltage conversion circuit 34 to the AC power supply G passes through the second path when the multi-output power supply 10B is in standby mode.

[0050] On the other hand, when the multi-output power supply 10B is in operation, the current from the second voltage conversion circuit 34 to the AC power supply G passes through the first path. This is because the first path has only one forward diode, diode 22a, which constitutes the first diode bridge circuit 22, while the second path has two forward diodes (the second diode 39 and diode 32a, which constitutes the second diode bridge circuit 32), and the sum of the forward voltages in the first path (approximately 0.7[V]) is smaller than the sum of the forward voltages in the second path (approximately 1.4[V]).

[0051] When the multi-output power supply unit 10B is in operation, let Ia be the current flowing from the first power supply unit 20 toward the unshown load circuit, and let Ib be the current flowing from the second power supply unit 30B toward the unshown load circuit. Then the currents flowing through each part are as follows. • Current flowing from left to right in the first line filter circuit 21: Ia + Ib • Current flowing from right to left in the first line filter circuit 21: Ia + Ib • Current flowing from left to right in the second line filter circuit 31: 0 • Current flowing from right to left in the second line filter circuit 31: 0 • Current flowing from top to bottom in the high-potential interconnection line 12 for the second power supply unit: Ib • Current flowing from bottom to top in the low-potential interconnection line 13 for the second power supply unit: Ib

[0052] The current flowing through the first line filter circuit 21 from left to right in the diagram, and the current flowing through the same circuit 21 from right to left, are both Ia + Ib, indicating a balance. Similarly, the current flowing through the second line filter circuit 31 from left to right in the diagram, and the current flowing through the same circuit 31 from right to left, are both 0, indicating a balance here as well. This is because the second diode 39, which generates a forward voltage, has blocked the current path from the second voltage conversion circuit 34 to the second line filter circuit 31, i.e., the second path.

[0053] The conducted noise characteristics of the multi-output power supply unit 10B in operation were similar to those of the multi-output power supply unit 10A shown in Figure 2.

[0054] [Third Embodiment] Figure 4 shows a multi-output power supply device 10C according to a third embodiment of the present invention. As shown in the figure, the multi-output power supply device 10C differs from the multi-output power supply device 10A in that it further includes a third power supply unit 40 that outputs 12[V] corresponding to the "third DC voltage" of the present invention in both the first and second modes, and further includes a high-potential side interconnection line 15 for the third power supply unit, a low-potential side interconnection line 16 for the third power supply unit, and a third diode 17 which constitute the "interconnection line for the third power supply unit" of the present invention. However, it is common with the multi-output power supply device 10A in other respects, for example, that the first power supply unit 20 outputs 24[V] only in the first mode, and the second power supply unit 30A outputs 5[V] in both the first and second modes.

[0055] The third power supply unit 40 includes a third line filter circuit 41 with one end connected to an AC power supply G, a third diode bridge circuit 42 with its AC end connected to the other end of the third line filter circuit 41, a third voltage conversion circuit 44 connected to the DC end of the third diode bridge circuit 42 via a third high-potential DC line 45 and a third low-potential DC line 46, a third smoothing capacitor 47 connected between the third high-potential DC line 45 and the third low-potential DC line 46, and a third switch 48 provided on the third low-potential DC line 46.

[0056] The third diode bridge circuit 42 and the third smoothing capacitor 47 constitute the "third DC conversion circuit" of the present invention. The third DC conversion circuits 42 and 47 convert the AC voltage output by the third line filter circuit 41 to DC and supply it to the third voltage conversion circuit 44. In this embodiment, the voltage after DC conversion (i.e., the potential of the third high-potential DC line 45 with respect to the potential of the third low-potential DC line 46) is set to a voltage sufficiently lower than 400[V].

[0057] The third voltage conversion circuit 44 is a chopper circuit that steps down or steps up the DC voltage supplied by the third DC conversion circuits 42 and 47 to 12[V]. The third voltage conversion circuit 44 outputs the 12[V] obtained by stepping down or stepping up to a load circuit (not shown).

[0058] The third switch 48 corresponds to the "current control means for the third power supply unit" of the present invention and is configured to be open or closed according to an external signal S3. In this embodiment, the external signal S3 is a signal output by a higher-level control circuit. When the multi-output power supply unit 10C is operated in the first mode, the higher-level control circuit outputs an external signal S3 such that the third switch 48 is in the open state. This interrupts the current path (third low-potential DC line 46) from the third voltage conversion circuit 44 to the third line filter circuit 41. On the other hand, when the multi-output power supply unit 10C is operated in the second mode, the higher-level control circuit outputs an external signal S3 such that the third switch 48 is in the closed state. This establishes a current path (second low-potential DC line 36) from the third voltage conversion circuit 44 to the third line filter circuit 41.

[0059] The high-potential interconnection line 15 for the third power supply unit connects the first high-potential DC line 25 and the third high-potential DC line 45. The low-potential interconnection line 16 for the third power supply unit connects the first low-potential DC line 26 and the third low-potential DC line 46. The third diode 17 is provided on the high-potential interconnection line 15 for the third power supply unit and has an anode directed toward the first power supply unit 20 (first high-potential DC line 25) and a cathode directed toward the third power supply unit 40 (third high-potential DC line 45).

[0060] When the multi-output power supply unit 10C operates in the first mode (first switch 11: closed, second switch 38: open, third switch 48: open), the voltage supplied by the third DC conversion circuits 42 and 47 of the third power supply unit 40 is sufficiently lower than the voltage supplied by the first DC conversion circuits 22, 23, and 27 of the first power supply unit 20 (400[V]). Therefore, the voltage appearing between the third high-potential DC line 45 and the third low-potential DC line 46 is 400[V] minus the forward voltage of the third diode 17 (approximately 0.7[V]). At this time, the third diode 17 supplies current to the third voltage conversion circuit 44 instead of the third diode bridge circuit 42. In this case, the third voltage conversion circuit 44 steps down the DC voltage supplied by the third diode 17, which is 400[V] - approximately 0.7[V], to 12[V], rather than the DC voltage supplied by the third DC conversion circuits 42 and 47.

[0061] On the other hand, when the multi-output power supply unit 10C operates in the second mode (first switch 11: open, second switch 38: closed, third switch 48: closed), the voltage supplied by the third DC conversion circuits 42 and 47 of the third power supply unit 40 is higher than the voltage (0[V]) provided by the first DC conversion circuits 22, 23, and 27 of the first power supply unit 20. Therefore, the voltage appearing between the third high-potential DC line 45 and the third low-potential DC line 46 is equal to the voltage supplied by the third DC conversion circuits 42 and 47 to the third voltage conversion circuit 44. At this time, the third diode 17 does not supply current to the third voltage conversion circuit 44.

[0062] The multi-output power supply 10C according to this embodiment can output three different voltages (24[V], 12[V], 5[V]) while balancing the currents in the first line filter circuit 21, the second line filter circuit 31, and the third line filter circuit 41. If an imbalance occurs in the currents of the second line filter circuit 31 and the third line filter circuit 41 during operation in the second mode, either the second switch 38 or the third switch 48 can be opened.

[0063] Although the first, second, and third embodiments of the multi-output power supply device according to the present invention have been described above, the configuration of the present invention is not limited to these embodiments.

[0064] For example, the first DC voltage output by the first power supply unit 20 may be a DC voltage other than 24[V]. Similarly, the second DC voltage output by the second power supply units 30A and 30B may be a DC voltage other than 5[V], and the third DC voltage output by the third power supply unit 40 may be a DC voltage other than 12[V] (for example, a voltage equal to the second DC voltage).

[0065] Furthermore, the external signal S1 that controls the first switch 11, the external signal S2 that controls the second switch 38, and the external signal S3 that controls the third switch 48 may be the same signal.

[0066] Furthermore, in the third embodiment, a power supply unit similar to the second power supply unit 30A was used as the third power supply unit 40, but the third power supply unit 40 may be a power supply unit similar to the second power supply unit 30B.

[0067] Furthermore, the multi-output power supply device according to the present invention may include four or more power supply units. In this case, the additional power supply unit may be similar to the second power supply unit 30A, or similar to the second power supply unit 30B. [Explanation of Symbols]

[0068] 10A,10B,10C multi-output power supply 11. Switch 1 12. High-potential side interconnection line for the second power supply unit 13. Low-potential interconnection line for the second power supply unit 14. First Diode 15. High-potential side interconnection line for the third power supply unit 16. Low-potential interconnection line for the third power supply unit 17 Third Diode 20 1st power supply section 21. First line filter circuit 22. First Diode Bridge Circuit 23 Power Factor Correction Circuit 24. First Voltage Conversion Circuit 25. First high-potential DC line 26. First low-voltage DC line 27. First smoothing capacitor 30A,30B 2nd power supply section 31. Second line filter circuit 32. Second Diode Bridge Circuit 34. Second Voltage Conversion Circuit 35. Second high-potential DC line 36. Second Low-Voltage DC Line 37. Second smoothing capacitor 38. Second switch 39. Second Diode 40 Third power supply section 41 Third line filter circuit 42 Third Diode Bridge Circuit 44 Third Voltage Conversion Circuit 45. Third high-potential DC line 46. ​​Third Low-Voltage DC Line 47. Third smoothing capacitor 48. Third switch

Claims

1. A multi-output power supply device comprising a first power supply unit that outputs a first DC voltage and a second power supply unit that outputs a second DC voltage, and capable of operating in a first mode that outputs both the first DC voltage and the second DC voltage and a second mode that outputs only the second DC voltage, The first power supply unit includes a first line filter circuit connected to an AC power supply via a first switch, a first DC conversion circuit including a diode bridge circuit that converts the AC voltage output by the first line filter circuit into DC, and a first voltage conversion circuit that converts the DC voltage output by the first DC conversion circuit into a first DC voltage. The second power supply unit includes a second line filter circuit connected to the AC power supply, a second DC conversion circuit including a diode bridge circuit that converts the AC voltage output by the second line filter circuit into DC, a second voltage conversion circuit that converts the DC voltage output by the second DC conversion circuit into the second DC voltage, and a current control means for the second power supply unit provided on the current path from the second voltage conversion circuit to the second line filter circuit. The system further includes a second power supply interconnection line that connects the outputs of the first DC conversion circuit and the second DC conversion circuit to each other, The DC voltage output by the first DC conversion circuit in the first mode is higher than the DC voltage output by the second DC conversion circuit. The first switch is configured to be in a closed state in the first mode and in an open state in the second mode. The current control means for the second power supply unit is configured to not conduct in the first mode and to conduct in the second mode. A multi-output power supply device characterized by the following features.

2. The current control means for the second power supply unit is a second switch, which is configured to be open in the first mode and closed in the second mode. The multi-output power supply device according to claim 1.

3. The first switch and the second switch take an open or closed state according to the same or different external signals. The multi-output power supply device according to feature 2.

4. The current control means for the second power supply unit is a diode provided on the current path from the second voltage conversion circuit to the second line filter circuit so as to be in the forward direction of the current. The multi-output power supply device according to claim 1.

5. The first DC conversion circuit further includes a power factor correction circuit. A multi-output power supply device according to any one of claims 1 to 4, characterized by the above.

6. The system further includes a third power supply unit that outputs a third DC voltage in both the first and second modes, The third power supply unit includes a third line filter circuit connected to the AC power supply, a third DC conversion circuit including a diode bridge circuit that converts the AC voltage output by the third line filter circuit into DC, a third voltage conversion circuit that converts the DC voltage output by the third DC conversion circuit into the third DC voltage, and a current control means for the third power supply unit provided on the current path from the third voltage conversion circuit to the third line filter circuit. The system further includes a third power supply interconnection line that interconnects the outputs of the first DC conversion circuit and the third DC conversion circuit, The DC voltage output by the first DC conversion circuit in the first mode is higher than the DC voltage output by the third DC conversion circuit. The current control means for the third power supply unit is configured to not conduct in the first mode and to conduct in the second mode. A multi-output power supply device according to any one of claims 1 to 4, characterized by the above.

Images