Power supply circuit and power supply device

Abstract

To provide a power supply circuit and a power supply device capable of reducing a conduction loss and controlling an OR connection switch by a simple method.SOLUTION: In a power supply device 1, a power supply circuit 100 comprises: a transformer 20 that has a primary side coil 21 and a secondary side coil 22; a primary side main switch part 10; a secondary side rectification part 30; a pair of output terminals Te3 and Te4; an OR connection switch 40 connected with one of the pair of output terminals and in which a body diode is arranged in such a direction that a backflow of current from the output terminal is prevented; an output capacitor C2; a current detector 50 arranged between the secondary side rectification part 30 and the output capacitor C2 to detect a charging current of the output capacitor C2; and an OR connection switch control part 60 that turns on the OR connection switch 40 when the current detector 50 detects the charging current of the output capacitor C2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a power supply circuit and a power supply device. [Background technology]

[0002] Conventionally, power supply devices have been known that have a redundant configuration in which multiple power supply circuits (converters) are connected in parallel. Such power supply devices are provided with a selective shutdown circuit to prevent a drop in output voltage when one of the multiple power supply circuits fails.

[0003] FIG. 3 is a circuit diagram showing a conventional power supply device 9 and a power supply circuit 900. The conventional power supply device 9 has multiple power supply circuits 900 connected in parallel, each including a converter unit CONV and an OR diode 940 provided on the output side of the converter unit CONV and oriented to block current from flowing from the output terminal toward the converter unit CONV. The OR diodes 940 in each power supply circuit 900 form a selective cutoff circuit SCC, with their cathodes connected to each other to form an OR circuit. This prevents a drop in output voltage even if one of the multiple power supply circuits fails. It also prevents current from flowing back toward the failed power supply circuit from other power supply circuits, etc. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 209238 Summary of the Invention [Problem to be solved by the invention]

[0005] Recently, there has been a demand for power supply devices that can reduce conduction loss. To address this issue, it has been considered to use switching elements, which have lower conduction loss than diodes, instead of OR diodes, which have relatively large conduction losses due to voltage drop (see, for example, Patent Document 1). However, to turn on the switching element, a voltage exceeding the output voltage must be applied to the gate electrode, and the gate voltage must be increased using, for example, a floating auxiliary power supply. Therefore, when the output voltage is large (for example, several hundred volts), it is not easy to supply a voltage exceeding the output voltage to control the OR connection switch.

[0006] Therefore, the present invention has been made to solve such problems, and aims to provide a power supply circuit that is capable of reducing conduction loss and capable of controlling an OR connection switch in a simple manner, and to provide a power supply device that includes such a power supply circuit. [Means for solving the problem]

[0007] The power supply circuit of the present invention is characterized by comprising: a transformer having a primary coil and a secondary coil; a primary main switch unit connected to the primary coil and composed of a switching element; a secondary rectifier unit connected to the secondary coil; a pair of output terminals connected to the secondary rectifier unit; an OR connection switch connected to one of the pair of output terminals and having a body diode oriented so as to prevent current from flowing back from the output terminal; an output capacitor having one end connected to one of the pair of output terminals via the OR connection switch and the other end connected to the other of the pair of output terminals; a current detector connected in series between the secondary rectifier unit and the output capacitor and detecting a charging current of the output capacitor; and an OR connection switch control unit that turns on the OR connection switch when the current detector detects a charging current of the output capacitor.

[0008] A power supply device according to the present invention includes a plurality of power supply circuits according to the present invention, and the output terminals of the plurality of power supply circuits are connected to each other. [Effects of the Invention]

[0009] The power supply circuit and power supply device of the present invention are provided with an OR connection switch whose body diode is oriented so as to prevent current from flowing back from the output terminal, and therefore can reduce conduction loss due to forward voltage drop compared to when a diode is used to prevent current from flowing back from the output terminal.

[0010] Furthermore, the power supply circuit and power supply device of the present invention include an output capacitor having one end connected to one of a pair of output terminals via an OR connection switch and the other end connected to the other of the pair of output terminals, a current detector connected in series between the secondary side rectification unit and the output capacitor and detecting a charging current of the output capacitor, and an OR connection switch control unit that turns on the OR connection switch when the current detector detects a charging current of the capacitor, so that the OR connection switch can be turned on when a charging current of the output capacitor is detected. Therefore, even when the output voltage is large, there is no need to use an auxiliary power supply or other configuration to supply a voltage exceeding the output voltage, and it is possible to control the OR connection switch by the relatively simple method of detecting the charging current of the output capacitor.

[0011] Furthermore, the power supply circuit and power supply device of the present invention include an output capacitor having one end connected to one of a pair of output terminals via an OR connection switch and the other end connected to the other of the pair of output terminals, a current detector connected in series between the secondary side rectifier and the output capacitor and detecting a charging current of the output capacitor, and an OR connection switch control unit that turns on the OR connection switch when the current detector detects a charging current of the capacitor, so that when the OR connection switch is operated as a diode (when the OR connection switch is turned off), information other than the charging current of the output capacitor can be input to the OR connection switch control unit for control. In other words, the on / off conditions of the OR connection switch can be set in detail. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a circuit diagram showing a power supply device 1 and a power supply circuit 100 according to Embodiment 1. Note that the reference character RL indicates a load, and the diode shown in the OR connection switch reference character 40 indicates a body diode. [Figure 2] FIG. 10 is a circuit diagram showing a power supply device 2 and a power supply circuit 102 according to a second embodiment. [Figure 3] 1 is a circuit diagram showing a conventional power supply device 9 and a power supply circuit 900. Note that reference numeral 910 denotes a primary side main switch unit, reference numeral 920 denotes a transformer, reference numeral 921 denotes a primary side coil, reference numeral 922 denotes a secondary side coil, and reference numeral 930 denotes a secondary side rectifier unit. DETAILED DESCRIPTION OF THE INVENTION

[0013] The power supply circuit and power supply device of the present invention will be described below based on the embodiments shown in the drawings. Note that the embodiments described below do not limit the invention according to the claims. Furthermore, not all of the elements and combinations thereof described in the embodiments are necessarily essential to the solution of the present invention.

[0014] [Embodiment 1] 1. Configuration of the power supply device 1 and power supply circuit 100 according to the first embodiment Fig. 1 is a circuit diagram showing a power supply device 1 and a power supply circuit 100 according to the first embodiment. As shown in Fig. 1, the power supply device 1 according to the first embodiment includes a plurality of power supply circuits 100 (two in the first embodiment) connected in parallel. Each power supply circuit 100 is provided with a pair of output terminals Te3, Te4 and an OR connection switch 40 having an anode of a body diode connected to the output terminal Te4, and the output terminals Te3 are connected to each other and the output terminals Te4 are connected to each other. As a result, the anodes of the body diodes of the OR connection switches 40 are connected to each other to form an OR circuit, which constitutes a selective shutoff circuit SCC.

[0015] The power supply circuit 100 according to the first embodiment includes a primary-side main switch unit 10, a transformer 20, a secondary-side rectifier unit 30, an ORing switch 40, a current detector 50, an ORing switch control unit 60, an input capacitor C1, an output capacitor C2, a pair of input terminals Te1 and Te2, and a pair of output terminals Te3 and Te4. The primary-side main switch unit 10, the transformer 20, and the secondary-side rectifier unit 30 form a converter unit CONV. The power supply circuit 100 according to the first embodiment is, for example, a DC-DC converter.

[0016] Of the pair of input terminals Te1 and Te2, the input terminal Te1 is connected to a DC power supply (not shown), and the input terminal Te2 is connected to a reference potential, and receives an input voltage (DC voltage) Vin. The input terminal Te1 is also connected to a power supply line L1.

[0017] Of the pair of output terminals Te3 and Te4, the output terminal Te3 is a high-side output terminal and the output terminal Te4 is a low-side output terminal, and they output an output voltage Vout. The output terminal Te3 is connected to the power supply line L2, and the output terminal Te3 is connected to the power supply line L3.

[0018] The primary-side main switch unit 10 is a full-bridge drive circuit in which serially connected switching elements Q1 and Q2 and serially connected switching elements Q3 and Q4 are connected in parallel. The midpoint (connection point) of the switching elements Q1 and Q2 is connected to one end of the primary-side coil 21, and the midpoint of the serially connected switching elements Q3 and Q4 is connected to the other end of the primary-side coil 21. The drain electrode of the switching element Q1 (Q3) is connected to the high-side input terminal Te1, and the source electrode is connected to the drain electrode of the switching element Q2 (Q4). The drain electrode of the switching element Q2 (Q4) is connected to the source electrode of the switching element Q1 (Q3), and the source electrode is connected to a reference potential. The switching elements Q1, Q2, Q3, and Q4 may be, for example, n-type MOSFETs (n-type field-effect transistors), but other suitable switching elements such as IGBTs may also be used. In the first embodiment, a full-bridge type drive circuit is used as the primary side main switch section 10, but a half-bridge type or other appropriate drive circuit can also be used.

[0019] The input capacitor C1 has one end connected to the power supply line L1 and the other end connected to the low-side input terminal Te2 and the reference potential, and smoothes the DC voltage.

[0020] The transformer 20 has a primary coil 21 and a secondary coil 22. In the transformer 20, when a voltage supplied from the primary main switch unit 10 is applied to the primary coil 21, an electromotive force converted in accordance with a winding ratio is generated in the secondary coil 22. The secondary coil 22 is connected to a secondary rectifier unit 30.

[0021] The secondary-side rectifier 30 has rectifier diodes D1, D2, D3, and D4, and is a full-bridge rectifier circuit in which the rectifier diodes D1 and D2 connected in series and the rectifier diodes D3 and D4 connected in series are connected in parallel. The midpoint of the rectifier diodes D1 and D2 (the wiring between the rectifier diodes D1 and D2) is connected to one end of the secondary-side coil 22, and the midpoint of the rectifier diodes D3 and D4 is connected to the other end of the secondary-side coil 22. The cathodes of the rectifier diodes D1 and D3 are connected to the power supply line L2. The anode of the rectifier diode D1 is connected to the cathode of the rectifier diode D2 and one end of the secondary coil 22. The anode of the rectifier diode D2 is connected to the power supply line L3. The cathode of the rectifier diode D3 is connected to the power supply line L2. The anode of the rectifier diode D3 is connected to the cathode of the rectifier diode D4 and the other end of the secondary coil 22. The anode of the rectifier diode D4 is connected to the power supply line L3. In the first embodiment, a full-bridge rectifier circuit is used as the secondary-side rectifier 30, but a half-bridge rectifier circuit or any other appropriate rectifier circuit may be used.

[0022] One end of the output capacitor C2 is connected to the low-side power supply line L3 and to the output terminal Te4 via the OR switch 40, and the other end is connected to the output terminal Te3 via the high-side power supply line L2. The output capacitor C2 smoothes the output voltage.

[0023] The ORing switch 40 (switch Q5) is an n-type MOSFET connected to the low-side output terminal Te4 via the power supply line L3. The ORing switch 40 has an anode (source electrode of the MOSFET) of its body diode connected to the output terminal Te3 and a cathode (drain electrode of the MOSFET) connected to the secondary-side rectifier 30. In other words, the body diode is oriented so as to prevent reverse current flow from the high-side output terminal Te3 toward the secondary-side rectifier 30. The gate electrode of the ORing switch 40 is connected to the ORing switch control unit 60. When a charging current flows through the output capacitor C2, an electromotive force is generated in the Rogowski coil, which is a current detector 50. The electromotive force is amplified and applied to the gate electrode, turning on the ORing switch 40.

[0024] The current detector 50 is a Rogowski coil wound around the power supply line L3 between the secondary-side rectifier 30 and the output capacitor C2. The current detector 50 detects the charging current of the output capacitor C2 when an electromotive force is induced in the Rogowski coil of the current detector 50 due to an electromotive force induced in the secondary coil 22 of the transformer 20, an AC voltage is applied to the secondary-side rectifier 30, and a charging current flows through the output capacitor C2. The electromotive force induced in the Rogowski coil of the current detector 50 applies a voltage to the OR-connection switch control unit 60.

[0025] The ORing switch control unit 60 turns on the ORing switch 40 when the current detector 50 detects a charging current for the output capacitor C2. In the ORing switch control unit 60, the electromotive force generated in the current detector 50 is input to the non-inverting input terminal (V+) of the comparator U1, and is compared with a predetermined value input from the inverting input terminal (V-) of the comparator U1. For example, if the electromotive force generated in the current detector 50 is equal to or greater than a predetermined value, a voltage amplified by a supply voltage (not shown) is applied to the gate electrode of the ORing switch 40. If the electromotive force generated in the current detector 50 is equal to or less than the predetermined value, the ORing switch 40 is turned off, causing the ORing switch 40 to operate as a diode.

[0026] Next, the operation of the power supply circuit 100 according to the first embodiment will be described. When switching elements Q1 and Q4 are turned on, a voltage is applied to primary coil 21 of transformer 20. Transformer 20 generates an electromotive force in secondary coil 22 according to the winding ratio. The electromotive force generated in secondary coil 22 is rectified by secondary rectifier 30, and a voltage is applied to output capacitor C2. At this time, output capacitor C2 converts AC voltage to DC voltage, applies the voltage to output terminal Te3, and charges output capacitor C2. That is, the charging current that charges output capacitor C2 circulates from output capacitor C2 to output capacitor C2 via power supply line L3, secondary rectifier 30, and power supply line L2. When a charging current flows through the output capacitor C2, an electromotive force is generated in the Rogowski coil, which serves as the current detector 50, and therefore the charging current can be detected. The electromotive force induced in the Rogowski coil is applied to the ORing switch control unit 60, and when it reaches a predetermined value or greater, it is amplified and applied to the gate electrode of the ORing switch 40. This turns on the ORing switch 40, and the electromotive force generated in the secondary coil 22 is converted to a DC voltage by the output capacitor C2 and applied to the output terminal Te3.

[0027] If a malfunction occurs on the primary side and no voltage is applied to the primary coil 21, no electromotive force is generated in the secondary coil 22, and no voltage is applied to the output terminal Te3. At this time, the output capacitor C2 is not charged, and no charging current is generated. Therefore, the current detector 50 does not detect a charging current, and the ORing switch 40 is not turned on. Therefore, the ORing switch 40 acts as a diode, preventing current from flowing back from another power supply circuit to the converter unit CONV via the output terminal Te3.

[0028] 2. Effects of the power supply device 1 and the power supply circuit 100 according to the first embodiment The power supply device 1 and power supply circuit 100 according to the first embodiment are provided with an OR connection switch 40 having a body diode oriented to prevent current from flowing from the output terminal Te3 toward the secondary side rectification unit 30, thereby reducing conduction loss due to forward voltage drop compared to when a diode is used.

[0029] Furthermore, the power supply device 1 and power supply circuit 100 according to the first embodiment include an output capacitor C2 having one end connected to the output terminal Te4 via the ORing switch 40 and the other end connected to the output terminal Te3, a current detector 50 disposed between the secondary-side rectification unit 30 and the output capacitor C2 and detecting a charging current of the output capacitor C2, and an ORing switch control unit 60 that turns on the ORing switch 40 when the current detector 50 detects a charging current of the output capacitor C2. Therefore, the ORing switch 40 can be turned on when a charging current of the output capacitor C2 is detected. Therefore, even when the output voltage is large, there is no need to use an auxiliary power supply or other configuration to supply a voltage exceeding the output voltage, and it is possible to control the ORing switch 40 by the relatively simple method of detecting the charging current of the output capacitor C2.

[0030] Furthermore, the power supply device 1 and power supply circuit 100 according to the first embodiment include an output capacitor C2, one end of which is connected to the output terminal Te4 via the OR connection switch 40 and the other end of which is connected to the output terminal Te3, a current detector 50 disposed between the secondary-side rectifier 30 and the output capacitor C2 and which detects the charging current of the output capacitor C2, and an OR connection switch control unit 60 which turns on the OR connection switch 40 when the current detector 50 detects the charging current of the output capacitor C2. Therefore, when the OR connection switch 40 is made to operate as a diode (when the OR connection switch 40 is turned off), information other than information relating to the charging current of the output capacitor C2 (for example, information such as the voltage due to the electromotive force generated in the Rogowski coil) can be input to the OR connection switch control unit 60 for control. In other words, the on / off conditions of the OR connection switch 40 can be set in detail.

[0031] Furthermore, in the power supply device 1 and power supply circuit 100 according to the first embodiment, the current detector 50 is a Rogowski coil, so magnetic saturation due to the presence of a magnetic core and heat generation due to magnetic loss do not occur, and the charging current of the output capacitor C2 can be measured with low loss. Furthermore, because an AC voltage is generated on the secondary side of the transformer 20, a Rogowski coil capable of detecting AC can be suitably used.

[0032] Furthermore, according to the power supply device 1 and power supply circuit 100 of the first embodiment, the anode of the body diode in the OR connection switch 40 is connected to the low-side output terminal Te4 of the pair of output terminals, so that only a small power supply is required to be supplied to the comparator, etc. of the OR connection switch control unit 60 that amplifies the electromotive force generated in the current detector 50.

[0033] Furthermore, in the power supply device 1 and power supply circuit 100 according to the first embodiment, the OR connection switch 40 is a field effect transistor, which results in a lower voltage drop and reduced conduction loss than in the case of a diode. Also, less drive power is required to turn on the gate.

[0034] Furthermore, according to the power supply device 1 of the first embodiment, the output terminals of the multiple power supply circuits 100 are connected to each other, so it is possible to configure a selective shutoff circuit for preventing a drop in output voltage when a failure occurs in one of the multiple power supply circuits 100. It is also possible to prevent current from flowing back from other power supply circuits, etc., toward the failed power supply circuit.

[0035] [Embodiment 2] 2 is a circuit diagram showing a power supply device 2 and a power supply circuit 102 according to embodiment 2. The power supply device 2 and the power supply circuit 102 according to embodiment 2 basically have the same configuration as the power supply device 1 and the power supply circuit 100 according to embodiment 1, but differ from the power supply device 1 and the power supply circuit 100 according to embodiment 1 in that the OR connection switch 40 and the current detector 50 are arranged on the high side.

[0036] In the second embodiment, the ORing switch 40 is connected to the high-side output terminal Te3 via the power supply line L2. In the ORing switch 40, the anode of the body diode (the source electrode of the MOSFET) is connected to the secondary-side rectification unit 30, and the cathode of the body diode (the drain electrode of the MOSFET) is connected to the output terminal Te3 via the power supply line L2. In other words, the body diode is oriented so as to prevent a current from flowing backward from the high-side output terminal Te3 toward the secondary-side rectification unit 30.

[0037] The current detector 50 is a Rogowski coil wound around the power supply line L2 between the secondary side rectifier 30 and the output capacitor C2.

[0038] As described above, the power supply device 2 and power supply circuit 102 according to the second embodiment differ from the power supply device 1 and power supply circuit 100 according to the first embodiment in that the OR connection switch 40 and the current detector 50 are arranged on the high side. However, like the power supply device 1 and power supply circuit 100 according to the first embodiment, the power supply device 2 and power supply circuit 102 are provided with an OR connection switch 40 whose body diode is oriented so as to prevent current from flowing from the output terminal Te3 toward the secondary side rectification unit 30, and therefore, the conduction loss due to forward voltage drop can be reduced compared to when a diode is used.

[0039] Furthermore, according to the power supply device 2 and power supply circuit 102 of the second embodiment, the cathode of the body diode in the OR connection switch 40 is connected to the high-side output terminal Te3 of the pair of output terminals, so that it is possible to reliably protect the high-side, which is likely to be significantly affected when current flows back from another power supply circuit.

[0040] The power supply device 2 and power supply circuit 102 of the second embodiment have the same configuration as the power supply device 1 and power supply circuit 100 of the first embodiment except that the OR connection switch 40 and the current detector 50 are arranged on the high side, and therefore have the corresponding effects of the power supply device 1 and power supply circuit 100 of the first embodiment.

[0041] Although the present invention has been described based on the above embodiment, the present invention is not limited to the above embodiment and can be embodied in various forms without departing from the spirit of the present invention, and for example, the following modifications are also possible.

[0042] (1) The positions, sizes, etc. described in the above embodiments (including the modified examples; the same applies below) are examples and can be changed within the scope that does not impair the effects of the present invention.

[0043] (2) In each of the above embodiments, the power supply device includes two power supply circuits, but the present invention is not limited to this. Three or more power supply circuits may be included.

[0044] (3) In the above embodiments, field-effect transistors (MOSFTs) are used as switching elements, but the present invention is not limited to this. IGBTs, thyristors, triacs, and other suitable switching elements can be used as switching elements.

[0045] (4) In the above embodiments, a Rogowski coil is used as the current detector, but the present invention is not limited to this. A current transformer, a resistor, or any other suitable current detector may also be used as the current detector.

[0046] (5) In the above embodiments, an LLC resonant converter is used as the converter (DC-DC converter), but the present invention is not limited to this. A forward converter, a flyback converter, or any other suitable converter may be used as the converter. [Explanation of symbols]

[0047] 1,2,9...Power supply device, 10,910...Primary side main switch section, 20,920...Transformer, 21,921...Primary side coil, 22,922...Secondary side coil, 30,930...Secondary side rectifier section, 40,940...OR connection switch, 50...Current detector, 60...OR connection switch control section, 100,102,900...Power supply circuit, C3...Capacitor, Q1,Q2,Q3,Q4...Switching elements, Te1,Te2...Input terminal, Te3,Te4...Output terminal

Claims

1. a transformer having a primary coil and a secondary coil; a primary side main switch unit connected to the primary side coil and configured with a switching element; a secondary-side rectifier connected to the secondary-side coil; a pair of output terminals connected to the secondary side rectifier; an OR connection switch connected to one of the pair of output terminals, the body diode of which is oriented in such a direction as to prevent a current from flowing backward from the output terminal; an output capacitor having one end connected to one of the pair of output terminals via the OR connection switch and the other end connected to the other of the pair of output terminals; a current detector disposed between the secondary side rectifier unit and the output capacitor, for detecting a charging current of the output capacitor; an OR connection switch control unit that turns on the OR connection switch when the current detector detects a charging current of the output capacitor, the OR connection switch and the current detector are connected to the same terminal of the pair of output terminals, the current detector detects the charging current of the output capacitor by detecting an electromotive force induced by the charging current of the output capacitor; the OR connection switch control section is composed of a comparator, an output terminal of the comparator is connected to the OR connection switch, and when an electromotive force generated in the current detector is equal to or greater than a predetermined value, the OR connection switch is turned on by applying an output voltage of the comparator to the OR connection switch; A power supply circuit characterized in that, when the electromotive force generated in the current detector is equal to or less than a predetermined value, the OR connection switch is turned off to cause diode operation.

2. 2. The power supply circuit according to claim 1, wherein the current detector is a Rogowski coil.

3. 3. The power supply circuit according to claim 1, wherein the anode of the body diode in the OR connection switch is connected to the low-side output terminal of the pair of output terminals.

4. 4. The power supply circuit according to claim 1, wherein the OR connection switch is a field effect transistor.

5. A power supply circuit according to any one of claims 1 to 4, A power supply device characterized in that output terminals of a plurality of said power supply circuits are connected to each other.

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