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, a first secondary side coil 22-1, and a second secondary side coil 22-2; a primary side main switch part 10 connected with the primary side coil 21; a first secondary side rectification part 30 connected with the first secondary side coil 22-1; and an OR connection switch 40 in which a body diode is arranged in such a direction that a backflow of current from an output terminal Te3 is prevented. The second secondary side coil 22-2 has one end connected with a gate electrode of the OR connection switch 40 via a diode D5 of a second secondary side rectification part 50, and the other end connected with the first secondary side rectification part 30 and a source electrode of the OR connection switch 40 (an anode of the body diode).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] Figure 5 is a circuit diagram showing a conventional power supply unit 9 and power supply circuit 900. As shown in Figure 5, the conventional power supply unit 9 has multiple power supply circuits 900 connected in parallel, each of which is provided on the output side of the converter unit CONV and is positioned to prevent current from flowing from the output terminal toward the converter unit CONV. Each OR diode 940 in each power supply circuit 900 forms a selective interruption circuit SCC where the cathodes are connected to each other, creating 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 backward from other power supply circuits toward the failed power supply circuit. [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 comprises a transformer having a primary coil, a first secondary coil, and a second secondary coil; a primary main switch section connected to the primary coil and composed of a switching element; a first secondary rectifier section connected to the first secondary coil; and an OR connection switch having a body diode oriented so as to prevent current from flowing backward from the output terminal, wherein one end of the second secondary coil is connected to a gate electrode of the OR connection switch and the other end is connected to the first secondary rectifier section and the body diode of the OR connection switch.

[0008] In addition, when a transformer has three or more terminals, such as when the transformer has a center tap, "one end" of the transformer refers to at least one of the three or more terminals, and "the other end" refers to at least one of the three or more terminals other than the "one end."

[0009] 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]

[0010] According to the power supply circuit and power supply device of the present invention, since an OR connection switch is provided in which a body diode is positioned to prevent current from flowing backward from the output terminal, conduction losses due to forward voltage drop can be reduced compared to the case in which a diode is used.

[0011] Furthermore, according to the power supply circuit and power supply device of the present invention, one end of the second secondary coil is connected to the gate electrode of the OR connection switch, and the other end is connected to the first secondary rectifier and the body diode of the OR connection switch, so that the OR connection switch can be turned on by the induced electromotive force generated in the second secondary coil when current flows through the primary coil of the transformer. Therefore, even when the output voltage is large, there is no need to use an auxiliary power supply to supply a voltage that exceeds the output voltage, and it is possible to control the OR connection switch by the simple method of forming a second secondary coil in the transformer. [Brief explanation of the drawings]

[0012] [Figure 1] This is a circuit diagram showing the power supply device 1 and power supply circuit 100 according to Embodiment 1. The symbol RL indicates a load. The diode indicated by the OR connection switch (symbol 40) is a body diode. [Figure 2] 2 is a circuit diagram illustrating the operation of the power supply circuit 100 when switching elements Q1 and Q4 are turned on. FIG. [Figure 3] 2 is a circuit diagram illustrating the operation of the power supply circuit 100 when switching elements Q2 and Q3 are turned on. FIG. [Figure 4] FIG. 10 is a circuit diagram showing a power supply device 2 and a power supply circuit 102 according to a second embodiment. [Figure 5]This is a circuit diagram showing a conventional power supply unit 9 and power supply circuit 900. Reference numeral 910 denotes the primary side main switch section, reference numeral 920 denotes the transformer, reference numeral 921 denotes the primary side coil, reference numeral 922 denotes the secondary side coil, and reference numeral 930 denotes the secondary side rectifier section. 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 figures. Note that the embodiments described below do not limit the invention as defined in 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 according to Embodiment 1 Figure 1 is a circuit diagram showing a power supply device 1 and power supply circuit 100 according to Embodiment 1. As shown in Figure 1, the power supply device 1 according to Embodiment 1 comprises a plurality (two in Embodiment 1) of power supply circuits 100 connected in parallel. Each power supply circuit 100 is provided with a pair of output terminals Te3 and Te4, and an OR connection switch 40 in which the cathode of a body diode is connected to the output terminal Te3. Each output terminal Te3 is connected to each other, and each output terminal Te4 is connected to each other. As a result, the cathodes of the body diodes of each OR connection switch 40 are connected to each other, forming an OR circuit and constituting a selective cutoff circuit SCC.

[0015] The power supply circuit 100 according to Embodiment 1 includes a primary side main switch unit 10, a transformer 20, a first secondary side rectifier unit 30, an OR connection switch 40, a second secondary side rectifier unit 50, an input capacitor C1, an output capacitor C2, a pair of input terminals Te1, Te2, and a pair of output terminals Te3, Te4. The primary side main switch unit 10, the transformer 20, and the first secondary side rectifier unit 30 constitute a converter unit CONV. The power supply circuit 100 according to Embodiment 1 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 the high-side output terminal and the output terminal Te4 is the 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 Te4 is connected to the power supply line L3.

[0018] The primary side main switch section 10 is a full-bridge type drive circuit in which switching elements Q1 and Q2 connected in series, and switching elements Q3 and Q4 connected in series, are connected in parallel. The midpoint (connection point) of switching elements Q1 and Q2 is connected to one end of the primary side coil 21, and the midpoint of the series-connected switching elements Q3 and Q4 is connected to the other end of the primary side coil 21. The drain electrode of switching element Q1 (Q3) is connected to the high-side input terminal Te1, and the source electrode is connected to the drain electrode of switching element Q2 (Q4). The drain electrode of switching element Q2 (Q4) is connected to the source electrode of switching element Q1 (Q3), and the source electrode is connected to a reference potential. Switching elements Q1, Q2, Q3, and Q4 can be, for example, n-type MOSFETs (n-type field-effect transistors), but other appropriate switching elements such as IGBTs can 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, a first secondary coil 22-1, and a second secondary coil 22-2. In the transformer 20, when a voltage supplied from the primary main switch section 10 is applied to the primary coil 21, an electromotive force is generated according to the winding ratio of the secondary coils 22-1 and 22-2. The first secondary coil 22-1 is connected to the first secondary rectifier section 30. One end of the second secondary coil 22-2 is connected to the gate electrode of the OR switch 40 via diode D5 of the second secondary rectifier section 50, and the other end is connected to the source electrode (anode of the body diode) of the OR switch 40, the rectifier diodes D1 and D3 of the first secondary rectifier section 30, and the output capacitor C2. The electromotive force generated in the second secondary coil 22-2 may be large enough to turn on the OR connection switch 40 described later, and the number of windings in the second secondary coil 22-2 may be smaller than the number of windings in the first secondary coil 22-1.

[0021] The first secondary rectifier section 30 has rectifier diodes D1, D2, D3, and D4, and is a full-bridge type rectifier circuit in which rectifier diodes D1 and D2 connected in series, and rectifier diodes D3 and D4 connected in series, are connected in parallel. The midpoints of rectifier diodes D1 and D2 (the wiring between rectifier diodes D1 and D2) are connected to one end of the first secondary coil 22-1, and the midpoints of rectifier diodes D3 and D4 are connected to the other end of the first secondary coil 22-1. The cathodes of rectifier diodes D1 and D3 are connected to the power supply line L2. The anode of rectifier diode D1 is connected to the cathode of rectifier diode D2 and one end of the first secondary coil 22-1. The anode of rectifier diode D2 is connected to the power supply line L3. The cathode of rectifier diode D3 is also connected to the power supply line L2. The anode of rectifier diode D3 is connected to the cathode of rectifier diode D4 and the other end of the first secondary coil 22-1. The anode of rectifier diode D4 is connected to the power supply line L3. In the first embodiment, a full-bridge rectifier circuit is used as the first secondary-side rectifier unit 30, but a half-bridge rectifier circuit or any other appropriate rectifier circuit may be used.

[0022] The output capacitor C2 is placed between the high-side power supply line L2 and the low-side power supply line L3 to smooth the output voltage.

[0023] The ORing switch 40 (switch Q6) is an n-type MOSFET 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 first secondary-side rectification unit 30. The cathode of the body diode (the drain electrode of the MOSFET) is connected to the output terminal Te3; in other words, the body diode is oriented so as to prevent reverse current flow from the high-side output terminal Te3 toward the first secondary-side rectification unit 30. The gate electrode of the ORing switch 40 is connected to the second secondary-side coil 22-2 via the second secondary-side rectification unit 50, and is configured to turn on when an electromotive force is generated in the second secondary-side coil 22-2.

[0024] The second secondary rectifier 50 is a half-wave rectifier circuit having a diode D5 and a capacitor C3. The second secondary rectifier 50 is connected between the second secondary coil 22-2 and the gate electrode of the OR connection switch 40. The anode of the diode D5 is connected to one end of the second secondary coil 22-2, and the cathode is connected to the gate electrode of the OR connection switch 40 and the capacitor C3. The capacitor C3 has one end connected to the cathode of the diode D5 and the gate electrode of the OR connection switch 40, and the other end connected to the other end of the second secondary coil 22-2 and the power supply line L2.

[0025] Next, the operation of the power supply circuit according to Embodiment 1 will be described. Figure 2 is a circuit diagram illustrating the operation of the power supply circuit 100 when switching elements Q1 and Q4 are turned on. Figure 3 is a circuit diagram illustrating the operation of the power supply circuit 100 when switching elements Q2 and Q3 are turned on.

[0026] When switching elements Q1 and Q4 are turned on, a voltage as shown by the solid line in Figure 2 is applied to the primary coil 21 of the transformer 20. At this time, the transformer 20 generates an electromotive force (see dashed line in Figure 2) in the first secondary coil 22-1 and the second secondary coil 22-2, corresponding to the winding ratio. The electromotive force generated in the first secondary coil 22-1 is rectified by the first secondary rectifier 30, converted to a DC voltage by the output capacitor C2, and applied toward the source electrode of the OR switch 40. The electromotive force generated in the second secondary coil 22-2 is rectified by the second secondary rectifier 50, converted to a DC voltage, and applied toward the gate electrode of the OR switch 40. At this time, the capacitor C3 of the second secondary rectifier 50 is charged. As a result, the OR switch 40 is turned on, and the voltage stored in the output capacitor C2 is applied to the output terminal Te3 through the OR switch 40.

[0027] When the switching elements Q2 and Q3 are turned on, a voltage as shown by the solid line in FIG. 3 is applied to the primary coil 21 of the transformer 20. At this time, the transformer 20 generates electromotive forces in the first secondary coil 22-1 and the second secondary coil 22-2 according to the winding ratio, in the directions shown by the dashed lines in FIG. 3. The electromotive force generated in the first secondary coil 22-1 is rectified by the first secondary rectifier 30, converted into a DC voltage by the output capacitor C2, and applied to the OR connection switch 40. On the other hand, the electromotive force generated in the second secondary coil 22-2 is the reverse voltage of the diode D5 of the second secondary rectifier 50, and is not applied to the gate electrode of the OR connection switch 40. However, a voltage is applied from the capacitor C3, which is charged when the switching elements Q1 and Q4 are turned on, and the gate electrode of the OR connection switch 40 remains on.

[0028] 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 first secondary coil 22-1, and no voltage is applied to the output terminal Te3. Furthermore, since no electromotive force is generated in the second secondary coil 22-2, the gate electrode of the OR connection switch 40 is not turned on (when the switching elements Q1, Q2, Q3, and Q4 are turned off, no voltage is applied after the capacitor C3 is discharged). Therefore, the OR connection switch 40 acts as a diode, preventing a current from flowing back from another power supply circuit to the converter unit CONV.

[0029] 2. Effects of the power supply device 1 and power supply circuit 100 according to Embodiment 1 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 first secondary side rectification unit 30, thereby reducing conduction loss due to forward voltage drop compared to when a diode is used.

[0030] Furthermore, according to the power supply device 1 and power supply circuit 100 of Embodiment 1, one end of the second secondary coil 22-2 is connected to the gate electrode of the OR connection switch 40, and the other end is connected to the first secondary rectifier and the body diode (anode) of the OR connection switch 40. Therefore, when a voltage is applied to the primary coil 21 of the transformer 20, the electromotive force generated in the second secondary coil 22-2 can turn on the OR connection switch. Consequently, even when the output voltage is large, there is no need to use an auxiliary power supply to supply a voltage exceeding the output voltage, and the OR connection switch can be controlled by the simple method of forming the second secondary coil 22-2 in the transformer 20.

[0031] Furthermore, according to the power supply device 1 and power supply circuit 100 of Embodiment 1, a second secondary rectifier 50 is provided connected between the second secondary coil 22-2 and the gate electrode of the OR connection switch 40. Therefore, the electromotive force generated in the second secondary coil 22-2 can be rectified and converted into a DC voltage, which can then be used as the voltage applied to the gate electrode of the OR connection switch 40. Consequently, the on / off state of the OR connection switch 40 can be controlled in accordance with the voltage applied to the primary coil 21.

[0032] Furthermore, according to the power supply device 1 and power supply circuit 100 of Embodiment 1, the second secondary rectifier 50 has a diode D5 (rectifier element) whose anode is connected to one end of the second secondary coil 22-2 and whose cathode is connected to the gate electrode of the OR connection switch 40, and a capacitor C3 connected between the cathode of diode D5 and the other end of the second secondary coil 22-2. Therefore, with a small number of components, the electromotive force generated in the second secondary coil 22-2 can be used as the voltage for turning the OR connection switch 40 on and off. In addition, because of the presence of capacitor C3, the voltage can be maintained when switching elements Q2 and Q3 are turned on using the power charged when switching elements Q1 and Q4 are turned on, and the OR connection switch 40 can be kept on.

[0033] Furthermore, according to the power supply device 1 and power supply circuit 100 of embodiment 1, 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 side, which is likely to be significantly affected when current flows back from another power supply circuit.

[0034] Furthermore, according to the power supply device 1 and power supply circuit 100 of Embodiment 1, since the OR connection switch 40 is a field-effect transistor, the voltage drop is lower and conduction losses can be reduced compared to the case of a diode. In addition, less driving power is required to turn on the gate.

[0035] Furthermore, according to the power supply device 1 of the first embodiment, since the output terminals of the multiple power supply circuits 100 are connected to each other, it is possible to configure a selective cutoff circuit for preventing a drop in output voltage when one of the multiple power supply circuits fails, and it is also possible to prevent current from flowing back from other power supply circuits toward the failed power supply circuit.

[0036] [Embodiment 2] 4 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 the configuration of the second secondary side rectification unit is different from that of the power supply device 1 and the power supply circuit 100 according to embodiment 1. In the power supply device 2 and the power supply circuit 102 according to embodiment 2, the second secondary side rectification unit 52 is a center-tap type full-wave rectification type rectification circuit (see FIG. 4).

[0037] The second secondary rectifier section 52 includes diodes D5 and D6 and a capacitor C3. The anode of diode D5 is connected to one end of the second secondary coil 22-2, and the cathode of diode D5 is connected to capacitor C3, the gate electrode of OR switch 40, and the cathode of diode D6. The anode of the diode D6 is connected to the other end of the second secondary coil 22-2, and the cathode of the diode D6 is connected to the capacitor C3, the gate electrode of the OR connection switch 40, and the cathode of the diode D5. One end of the capacitor C3 is connected to the cathodes of the diodes D5 and D6 and the gate electrode of the OR connection switch 40, and the other end of the capacitor C3 is connected to the center tap of the second secondary coil 22-2 and the power supply line L2.

[0038] In the second secondary side rectifier 52, even when the switching elements Q2 and Q3 are turned on, the electromotive force generated in the second secondary side coil 22-2 passes through the diode D6 of the second secondary side rectifier 50, is converted to DC by the capacitor C3, and is applied to the gate electrode of the OR connection switch 40. Therefore, when an electromotive force is generated in the second secondary side coil 22-2, the OR connection switch 40 can be kept on. Since the OR connection switch 40 can be kept on without relying on the charging of the capacitor C3, this is suitable when the interval between on / off switching of the primary side main switch unit 10 is relatively long.

[0039] In the second embodiment, a center-tap rectifier circuit is used as the second secondary side rectifier section 52, but it may also be a bridge rectifier circuit using four diodes, or a rectifier circuit consisting of two sets of half-wave rectifier circuits connected in series, or any other suitable full-wave rectifier circuit.

[0040] As described above, the power supply device 2 and power supply circuit 102 of the second embodiment differ in the configuration of the second secondary side rectification unit from the power supply device 1 and power supply circuit 100 of the first embodiment, but like the power supply device 1 and power supply circuit 100 of the first embodiment, they are provided with an OR connection switch 40 whose body diode is oriented to prevent current from flowing from the output terminal Te3 toward the first secondary side rectification unit 30, thereby reducing conduction loss due to forward voltage drop compared to when a diode is used.

[0041] Furthermore, according to the power supply device 2 and power supply circuit 102 of Embodiment 2, one end of the second secondary coil 22-2 is connected to the gate electrode of the OR connection switch 40, and the other end is connected to the first secondary rectifier and the body diode (anode) of the OR connection switch. Therefore, when a voltage is applied to the primary coil 21 of the transformer 20, the induced voltage generated in the second secondary coil 22-2 can turn on the OR connection switch. Consequently, even when the output voltage is large, there is no need to use an auxiliary power supply to supply a voltage exceeding the output voltage, and the OR connection switch can be controlled by the simple method of forming the second secondary coil 22-2 in the transformer 20.

[0042] Furthermore, according to the power supply device 2 and power supply circuit 102 of Embodiment 2, since the second secondary rectifier unit 52 is a full-wave rectifier circuit, the on / off switching of the OR connection switch 40 can be controlled even when the on / off switching interval of the primary main switch unit 10 is relatively long.

[0043] Furthermore, since the power supply device 2 and power supply circuit 102 according to Embodiment 2 have the same configuration as the power supply device 1 and power supply circuit 100 according to Embodiment 1 in respect to the configuration of the second secondary rectifier section, they have the same effects as the power supply device 1 and power supply circuit 100 according to Embodiment 1.

[0044] Although the present invention has been described above 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.

[0045] (1) The positions, sizes, numbers, etc. described in each of the above embodiments (including each modified example; the same applies hereinafter) are illustrative examples and can be changed within the scope that does not impair the effects of the present invention.

[0046] (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.

[0047] (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.

[0048] (4) In the above embodiments, the ORing switch is disposed on the high side, but the present invention is not limited to this. The ORing switch may be disposed on the low side. In this case, the anode of the body diode is on the output terminal side, and the cathode is on the first secondary-side rectifier side.

[0049] (5) In each of the above embodiments, an LLC resonant converter was used as the converter unit (DC-DC converter), but the present invention is not limited thereto. A forward converter unit, a flyback converter unit, or any other appropriate converter unit may be used as the converter unit (DC-DC converter). [Explanation of symbols]

[0050] 1,2,9…Power supply unit, 10,910…Primary side main switch section, 20,920…Transformer, 21,921…Primary side coil, 22-1…First secondary side coil, 22-2…Second secondary side coil, 30,930…First secondary side rectifier section, 40…OR connection switch, 50,52…Second secondary side rectifier section, 100,102,900…Power supply circuit, C3…Capacitor, D5,D6…Diode, Q1,Q2,Q3,Q4…Switching element, Te1,Te2…Input terminals, Te3,Te4…Output terminals

Claims

1. a transformer having a primary coil, a first secondary coil, and a second secondary coil; a primary side main switch unit connected to the primary side coil and configured with a switching element; a first secondary-side rectifier connected to the first secondary-side coil; an OR connection switch having a body diode oriented in such a direction as to prevent a current from flowing backward from the output terminal; a second secondary rectifier connected between the second secondary coil and a gate electrode of the OR connection switch, one end of the second secondary coil is connected to the gate electrode of the OR connection switch, and the other end is connected to the first secondary rectifier unit and the body diode of the OR connection switch; the second secondary-side rectifier is a full-wave rectifier circuit, the second secondary coil is a center-tapped coil, The output terminal is a pair of output terminals. a cathode of the body diode of the OR connection switch connected to a high-side output terminal of the pair of output terminals;

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

3. a power supply circuit according to claim 1 or 2; 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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