Power supply system and control method thereof

Abstract

A power supply system for converting three-phase AC voltage to DC output voltage includes a first capacitor and a second capacitor electrically connected in series between a first output terminal and a second output terminal, three bridge arm circuits, a protection circuit, a voltage detection circuit, and a control circuit. The protection circuit includes a current-limiting element electrically connected in series with the first and second capacitors and a bypass circuit connected in parallel with the current-limiting element. The voltage detection circuit detects the voltage across the current-limiting element. When the voltage across the current-limiting element is higher than a predetermined value, the control circuit disables the bypass circuit and activates the protection circuit via the current-limiting element. When the voltage across the current-limiting element is lower than the predetermined value, the control circuit activates the bypass circuit and activates the protection circuit via the bypass circuit.

Description

[Technical Field]

[0001] This case relates to a power supply system, and more particularly to a power supply system with surge current protection. [Previous Technology]

[0002] In modern power supply systems, surge protection circuits are typically placed between the AC input and the boost inductor to suppress inrush current. As the required input and output power increases, the input current also increases significantly, requiring larger or more surge protection circuits to suppress the larger inrush current on the AC side. This results in a larger space occupied by the power supply system and a decrease in power density, making it difficult for the power supply system to provide the required power output within a limited space.

[0003] Therefore, how to provide a power supply system to solve the above problems is an important issue in this field. [Summary of the Invention]

[0004] This disclosure provides a power supply system for converting three-phase AC voltage to DC output voltage. The power supply system includes a first output terminal, a second output terminal, a first capacitor, a second capacitor, three bridge arm circuits, a protection circuit, a voltage detection circuit, and a control circuit. The first capacitor and a second capacitor are electrically connected in series between the first output terminal and the second output terminal. The three bridge arm circuits are connected in parallel between the first DC terminal and the second DC terminal, each bridge arm circuit having an input point for receiving one of the three-phase AC voltages and electrically connected to the neutral point between the first capacitor and the second capacitor. The protection circuit is electrically connected in series with the first capacitor and the second capacitor between the first DC terminal and the second DC terminal, wherein the protection circuit includes a current limiting element and a bypass circuit. The current limiting element is electrically connected in series with the first capacitor and the second capacitor. The bypass circuit is connected in parallel with the current limiting element. The voltage detection circuit is used to detect the voltage across the current limiting element. The control circuit is electrically connected to the voltage detection circuit and the protection circuit. The control circuit is used to perform the following steps. When the voltage across the circuit exceeds a predetermined value, the control circuit disables the bypass circuit and instead uses a current-limiting element to conduct across the protection circuit. When the voltage across the circuit falls below a predetermined value, the control circuit enables the bypass circuit, which in turn conducts across the protection circuit.

[0005] This disclosure provides a control method for a power supply system. The power supply system includes a first output terminal, a second output terminal, a first capacitor and a second capacitor electrically connected in series between the first and second output terminals, three bridge arm circuits connected in parallel between a first DC terminal and a second DC terminal, a protection circuit electrically connected in series with the first and second capacitors between the first and second DC terminals, a voltage detection circuit, and a control circuit electrically connected to the voltage detection circuit and the protection circuit. Each bridge arm circuit has an input point for electrically connecting to one of the three-phase AC voltages. Each bridge arm circuit is electrically connected to a neutral point between the first and second capacitors. The protection circuit includes a current limiting element electrically connected in series with the first and second capacitors and a bypass circuit connected in parallel with the current limiting element. The control method includes the following steps: When the voltage across the circuit is higher than a predetermined value, the control circuit disables the bypass circuit and connects the two ends of the protection circuit using the current limiting element. When the voltage across the circuit is lower than a predetermined value, the control circuit enables the bypass circuit to conduct and connects the two ends of the protection circuit using the bypass circuit.

[0006] This disclosure provides a power supply system. The power supply system is used to convert three-phase alternating current (AC) to DC output voltage. The power supply system includes a first output terminal, a second output terminal, a first capacitor, a second capacitor, three bridge arm circuits, a protection circuit, a control circuit, and an auxiliary power converter. The first and second capacitors are electrically connected in series between the first and second output terminals. The three bridge arm circuits are connected in parallel between the first and second DC terminals, each bridge arm circuit having an input point for electrically connecting to one of the three phases and electrically connected to a neutral point between the first and second capacitors. The protection circuit is electrically connected in series with the first and second capacitors between the first and second DC terminals. The protection circuit includes a current limiting element and a bypass circuit. The current limiting element is electrically connected in series with the first and second capacitors. The bypass circuit is connected in parallel with the current limiting element. The control circuit is electrically connected to the protection circuit. The auxiliary power converter is electrically connected to the control circuit for converting the three-phase AC voltage to power the control circuit. The control circuit performs the following steps: timing the duration of the three-phase AC voltage applied from the start. If the duration is less than the preset duration, the control circuit disables the bypass circuit and instead uses a current-limiting element to connect both ends of the protection circuit. If the duration is greater than the preset duration, the control circuit enables the bypass circuit and connects both ends of the protection circuit via the bypass circuit.

[0007] In summary, the power supply system disclosed herein can suppress surge current and, due to the higher voltage on the DC side, the current flowing through it is smaller, which can reduce the selection specifications and number of devices in the protection circuit, thereby reducing the system size, increasing power density and reducing cost.

Implementation Method

[0009] The following embodiments are described in detail with reference to the accompanying drawings. However, the provided embodiments are not intended to limit the scope of this disclosure, and the description of the structural operation is not intended to limit the order of execution. Any structure resulting from the recombination of elements and producing a device with equivalent functionality is within the scope of this disclosure. Furthermore, the illustrations are for illustrative purposes only and are not drawn to their original dimensions. For ease of understanding, the same or similar elements will be labeled with the same symbols in the following description.

[0010] Unless otherwise specified, the terms used throughout this specification and the claims generally have their ordinary meaning in the context of the art, the content disclosed herein, and the specific content. Furthermore, the terms "comprising," "including," "having," "containing," etc., used herein are open-ended terms, meaning "including but not limited to." Additionally, the term "and / or" as used herein includes any one or more of the related listed items and all combinations thereof.

[0011] Please refer to Figure 1A, which is a schematic diagram of a power supply system 100 according to some embodiments of the present disclosure. As shown in Figure 1A, the power supply system 100 includes inductors La~Lc, a three-phase AC-to-DC converter 110, main capacitors BC1 and BC2, and one or more protection circuits 120. The input terminals of the three-phase AC-to-DC converter 110 are electrically connected to the three phases of a three-phase power supply via inductors La~Lc to convert the three-phase AC voltage Va~Vc into DC voltage, and provide DC voltage through DC terminals (e.g., DC terminals p and n). In some embodiments, the three-phase AC-to-DC converter 110 may be implemented using a neutral point clamped (NPC) circuit, an active neutral point clamped (NPC) circuit, a Vienna power factor correction circuit, or other suitable power conversion circuits.

[0012] In some embodiments, the main capacitors BC1 and BC2 form a DC-link circuit, which is electrically connected between the three-phase AC to DC converter 110 and the load or the next stage circuit, so as to provide a stable DC output voltage Vo to the next stage converter through the output terminal.

[0013] The protection circuit 120 is electrically connected in series with the main capacitors BC1 and BC2 between the DC terminals p and n, and the protection circuit 120 is used to limit the surge current that may be generated when the three-phase AC voltage Va~Vc is initially applied to charge the main capacitors BC1 and BC2. In some embodiments, the main capacitors BC1 and BC2 have high capacitance values, so that the output current of the power supply system 100 is much smaller than the input current on the AC side. This can reduce the specifications and number of components selected in the protection circuit 120, thereby reducing the system size and cost.

[0014] In some embodiments, the protection circuit 120 may be disposed in at least one of the following four locations: between the DC terminal p and the first terminal of the main capacitor BC1, between the second terminal of the main capacitor BC1 and the neutral point G of the DC link circuit, between the neutral point G of the DC link circuit and the first terminal of the main capacitor BC2, and between the second terminal of the main capacitor BC2 and the DC terminal n. An appropriate number of protection circuits 120 may be disposed in each of the above four locations. In some embodiments, if the power supply system 100 includes N protection circuits 120 connected in series with the DC link circuit, the starting current when the three-phase AC to DC converter 110 is started can be expressed by the following formula.

[0015] In the above formula, represents the starting current. represents the voltage across the main capacitors BC1 and BC2 respectively. represents the resistance value of the current limiting element in the protection circuit 120. N represents the number of protection circuits 120. It should be noted that in the following embodiments, for simplicity, only one protection circuit 120 will be described, but when the power supply system 100 includes multiple protection circuits, they can still operate in the same or similar manner.

[0016] Please refer to Figure 1B, which is a schematic diagram of a power supply system 100B according to some embodiments of the present disclosure. As shown in Figure 1B, the power supply system 100B includes inductors La~Lc, a three-phase AC-to-DC converter 110, main capacitors BC1 and BC2, a protection circuit 120, a voltage detection circuit 130, and a control circuit 140. As shown in Figure 1B, the protection circuit 120 includes a current limiting element 121 and a bypass circuit 122.

[0017] The current limiting element 121 is electrically connected to the main capacitors BC1 and BC2 between the DC terminals p and n to suppress potential surge currents during startup, thereby preventing damage to components in the three-phase AC-to-DC converter 110 due to excessive current. In some embodiments, the current limiting element 121 is a current limiting resistor, and the current limiting resistor may be one or more suitable circuit elements such as a positive temperature coefficient thermistor, a negative temperature coefficient thermistor, and a cement resistor. In the embodiment of Figure 1B, the protection circuit 120 is electrically connected between the DC terminal p and the first terminal of the main capacitor BC1 to suppress the startup current flowing through the output terminal.

[0018] The bypass circuit 122 is connected in parallel with the current limiting element 121. The resistance value of the bypass circuit 122 when it is turned on is much smaller than the resistance value of the current limiting element 121. When the start-up operation is completed, the control circuit 140 sets the bypass circuit 122 to be turned on to bypass the current limiting element 121, so that the DC terminal p and the first terminal of the main capacitor BC1 are mainly connected by the bypass circuit 122. In some embodiments, the bypass circuit 122 can be implemented by a suitable circuit element such as a relay or switch.

[0019] Voltage detection circuit 130 is electrically connected to current limiting element 121 to detect the voltage across current limiting element 121. In some embodiments, voltage detection circuit 130 may be implemented by comparator circuit, and voltage detection circuit 130 compares whether the voltage across current limiting element 121 exceeds a predetermined value to generate a corresponding detection signal to control circuit 140. In some embodiments, during startup, the voltage across current limiting element 121 exceeds the predetermined value, causing the startup current to rise (i.e., inrush current occurs). On the other hand, after startup operation is completed, the voltage across current limiting element 121 will be lower than the predetermined value.

[0020] The control circuit 140 is electrically connected to the voltage detection circuit 130, and generates a control signal CS based on the detection signal from the voltage detection circuit 130 to control the bypass circuit 122 to be turned on or off. When the bypass circuit 122 is not turned on, the protection circuit 120 conducts current through the current limiting element 121. When the bypass circuit 122 is turned on, since the resistance of the bypass circuit 122 is much smaller than that of the current limiting element 121, the protection circuit 120 conducts current through the bypass circuit 122.

[0021] In some embodiments, the three-phase AC-to-DC converter 110 includes three bridge arm circuits 111-113. The input terminals of the three bridge arm circuits 111-113 are used to receive the three input terminals A-C of the three-phase AC power, respectively, and the midpoint of the bridge arm circuits 111-113 is connected to the neutral point G of the DC link circuit. In some embodiments, the neutral point G of the DC link circuit is connected to the junction of the second terminal of the main capacitor BC1 and the first terminal of the main capacitor BC2.

[0022] Please refer to Figure 1C, which is a schematic diagram of a power supply system 100C according to some embodiments of the present disclosure. As shown in Figure 1C, the power supply system 100C includes inductors La~Lc, a three-phase AC-to-DC converter 110, main capacitors BC1 and BC2, a protection circuit 120, a control circuit 140, and an auxiliary power converter 150. As shown in Figure 1C, the auxiliary power converter 150 is used to convert three-phase AC voltages Va~Vc into DC voltages to power the control circuit 140. In some embodiments, when the power supply system 100C is powered on, three-phase AC power is applied to the auxiliary power converter 150, causing the auxiliary power converter 150 to power the control circuit 140. The control circuit 140 times the duration of the three-phase AC voltage application to generate a control signal CS based on the duration. In some embodiments, the duration can be set according to the startup period, so that the bypass circuit 122 is not turned on during startup and is turned on after startup is completed. In Figure 1C, the operation of other components is similar to that of the corresponding components in Figure 1B.

[0023] Please refer to Figure 2. Figure 2 is a schematic diagram of the bridge arm circuit 200 of a three-phase AC-to-DC converter according to some embodiments of the present disclosure. In some embodiments, any one of the bridge arm circuits 111-113 of the three-phase AC-to-DC converter 110 of the power supply system 100B in Figure 1B and the power supply system 100C in Figure 1C can be implemented by the bridge arm circuit 200 of Figure 2, and the input terminal X in Figure 2 corresponds to one of the AC power input terminals A-C in Figure 1B. As shown in Figure 2, the bridge arm circuit 200 includes switches SP, SN, QP and QN and diodes D1 and D2. Architecturally, diode D1, switches SP and SN and diode D4 are electrically connected in series at the two DC terminals of the three-phase AC-to-DC converter, and the connection point of switches SP and SN is electrically connected to the input terminal X. Diode D1 and switch QP are electrically connected in series between the DC terminal of the three-phase AC-to-DC converter and the neutral point G of the DC link circuit, and diode D4 and switch QN are electrically connected in series between the other DC terminal of the three-phase AC-to-DC converter and the neutral point G of the DC link circuit.

[0024] Please refer to Figure 3. Figure 3 is a schematic diagram of the bridge arm circuit 300 of a three-phase AC-to-DC converter according to some embodiments of the present disclosure. In some embodiments, any one of the bridge arm circuits 111-113 of the three-phase AC-to-DC converter 110 of the power supply system 100B in Figure 1B and the power supply system 100C in Figure 1C can be implemented by the bridge arm circuit 300 in Figure 3, and the input terminal X in Figure 3 corresponds to one of the three input terminals A-C of the AC power supply in Figure 1B. As shown in Figure 3, the bridge arm circuit 300 includes switches QP and QN and diodes D1-D4. Architecturally, diodes D1-D4 are electrically connected in series at the two DC terminals of the three-phase AC-to-DC converter, and the connection point of diodes D2-D3 is electrically connected to the input terminal X. Diode D1 and switch QP are electrically connected in series between the DC terminal of the three-phase AC-to-DC converter and the neutral point G of the DC link circuit, and diode D4 and switch QN are electrically connected in series between the other DC terminal of the three-phase AC-to-DC converter and the neutral point G of the DC link circuit.

[0025] Please refer to Figure 4, which is a schematic diagram of a power supply system 400 according to some embodiments of the present disclosure. As shown in Figure 4, the power supply system 400 includes inductors La~Lc, bridge arm circuits 411~413, protection circuit 420, and main capacitors BC1 and BC2.

[0026] Bridge arm circuit 411 includes diodes D11-D14 and switches QAP and QAN. Bridge arm circuit 412 includes diodes D21-D24 and switches QBP and QBN. Bridge arm circuit 413 includes diodes D31-D34 and switches QCP and QCN. In this embodiment, the topology of each of bridge arm circuits 411-413 corresponds to the topology of bridge arm circuit 300 in Figure 3. In the embodiment of Figure 4, protection circuit 420 includes current limiting resistor R1 and relay 421.

[0027] The current limiting resistor R1 is electrically connected between the DC terminal p and the main capacitor BC1.

[0028] Relay 421 is connected in parallel with current-limiting resistor R1. In this embodiment, relay 421 can be implemented by a magnetically excited relay. In this case, the control signal CS can be a suitable signal format such as a pulse signal to turn relay 421 on or off. When relay 421 is not conducting, protection circuit 420 conducts current through current-limiting resistor R1. When relay 421 is conducting, protection circuit 420 conducts current primarily through relay 421.

[0029] Please refer to Figure 5, which is a schematic diagram of a power supply system 500 according to some embodiments of the present disclosure. As shown in Figure 5, the power supply system 500 includes inductors La~Lc, bridge arm circuits 511~313, protection circuit 520, and main capacitors BC1 and BC2. In some embodiments, the topology of each of the bridge arm circuits 511~513 corresponds to the topology of the bridge arm circuit 300 in Figure 3. In the embodiment of Figure 5, the protection circuit 520 includes a current limiting resistor R1 and a switch S1.

[0030] The current limiting resistor R1 is electrically connected between the DC terminal p and the main capacitor BC1.

[0031] Switch S1 is connected in parallel with current limiting resistor R1. Switch S1 is turned on or off according to control signal CS. When switch S1 is not turned on, protection circuit 520 conducts current through current limiting resistor R1. When switch S1 is turned on, protection circuit 520 conducts current mainly through switch S1.

[0032] In summary, the power supply system disclosed herein can suppress surge current, and by setting up the DC side, the specifications and number of devices selected in the protection circuit can be reduced, thereby reducing system size, increasing power density and reducing cost.

[0033] Although the present disclosure has been disclosed above with reference to embodiments, it is not intended to limit the present disclosure. Any person with ordinary knowledge in the art may make various modifications and alterations without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the appended claims. [Simplified Explanation of the Diagram]

[0008] To make the above and other objects, features, advantages and embodiments of this disclosure more apparent and understandable, the accompanying drawings are described below: Figure 1A is a schematic diagram of a power supply system according to some embodiments of this disclosure. Figure 1B is a schematic diagram of a power supply system according to some embodiments of this disclosure. Figure 1C is a schematic diagram of a power supply system according to some embodiments of this disclosure. Figure 2 is a schematic diagram of the bridge arm circuit of a power supply system according to some embodiments of this disclosure. Figure 3 is a schematic diagram of the bridge arm circuit of a power supply system according to some embodiments of this disclosure. Figure 4 is a schematic diagram of a power supply system according to some embodiments of this disclosure. Figure 5 is a schematic diagram of a power supply system according to some embodiments of this disclosure. [Biomaterial Storage]

[0035] Domestic storage information (please note in order of storage institution, date, and number): None. International storage information (please note in order of storage country, institution, date, and number): None.

Claims

1. A power supply system for converting three-phase AC voltage to DC output voltage, comprising: a first output terminal and a second output terminal; a first capacitor and a second capacitor electrically connected in series between the first output terminal and the second output terminal; three bridge arm circuits connected in parallel between a first DC terminal and a second DC terminal, each bridge arm circuit having an input point for receiving one of the three-phase AC voltages and electrically connected to a neutral point between the first capacitor and the second capacitor; and a protection circuit electrically connected in series with the first capacitor and the second capacitor between the first DC terminal and the second DC terminal, wherein the protection circuit comprises: a current limiting element electrically connected in series with the first capacitor and the second capacitor; and a bypass circuit connected in parallel with the current limiting element; a voltage detection circuit for detecting a voltage across the current limiting element; and a control circuit electrically connected to the voltage detection circuit and the protection circuit, wherein the control circuit is used to: When the voltage across the circuit is higher than a predetermined value, the control circuit disables the bypass circuit and connects the two ends of the protection circuit using the current limiting element; and when the voltage across the circuit is lower than the predetermined value, the control circuit enables the bypass circuit to connect and connects the two ends of the protection circuit using the bypass circuit.

2. The power supply system as claimed in claim 1, wherein the protection circuit is located in one of the following four positions: between the first DC terminal and the first terminal of the first capacitor; between the second terminal of the first capacitor and the neutral point; between the neutral point and the first terminal of the second capacitor; and between the second terminal of the second capacitor and the second DC terminal.

3. The power supply system as claimed in claim 1, wherein each of the three bridge arm circuits comprises: a first diode, a first switch, a second switch and a second diode, electrically connected in series between the first DC terminal and the second DC terminal; a third switch electrically connected in series with the first diode between the first DC terminal and the neutral point; and a fourth switch electrically connected in series with the second diode between the neutral point and the second DC terminal.

4. The power supply system as claimed in claim 1, wherein each of the three bridge arm circuits comprises: four diodes electrically connected in series between the first DC terminal and the second DC terminal; a first switch electrically connected in series with one of the four diodes between the first DC terminal and the neutral point; and a second switch electrically connected in series with the other of the four diodes between the neutral point and the second DC terminal.

5. The power supply system as claimed in claim 1, wherein the bypass circuit includes a relay, and wherein when the voltage across the current limiting element is higher than the predetermined value, the control circuit controls the relay to turn on to bypass the current limiting element.

6. The power supply system as claimed in claim 1, wherein the bypass circuit includes a switch, and wherein if the voltage across the current limiting element is higher than the predetermined value, the control circuit controls the switch to turn on to bypass the current limiting element.

7. The power supply system as claimed in claim 2 further includes one or more first protection circuits disposed in at least one of the following four locations: between the first DC terminal and the first terminal of the first capacitor; between the second terminal of the first capacitor and the neutral point; between the neutral point and the first terminal of the second capacitor; and between the second terminal of the second capacitor and the second DC terminal.

8. A control method for a power supply system, wherein the power supply system includes a first output terminal, a second output terminal, a first capacitor and a second capacitor electrically connected in series between the first output terminal and the second output terminal, three bridge arm circuits connected in parallel between a first DC terminal and a second DC terminal, a protection circuit electrically connected in series with the first capacitor and the second capacitor between the first DC terminal and the second DC terminal, a voltage detection circuit, and a control circuit electrically connected to the voltage detection circuit and the protection circuit, wherein each bridge arm circuit has an input point for electrically connecting to one of the three-phase AC voltages, wherein each bridge arm circuit is electrically connected to a neutral point between the first capacitor and the second capacitor, wherein the protection circuit includes a current limiting element electrically connected in series with the first capacitor and the second capacitor and a bypass circuit connected in parallel with the current limiting element, wherein the control method includes: detecting a voltage across the current limiting element by the voltage detection circuit; When the voltage across the circuit is higher than a predetermined value, the control circuit sets the bypass circuit to be closed, and the current limiting element connects the two ends of the protection circuit; and when the voltage across the circuit is lower than the predetermined value, the control circuit sets the bypass circuit to be open, and the bypass circuit connects the two ends of the protection circuit.

9. A power supply system for converting three-phase AC voltage to DC output voltage, comprising: a first output terminal and a second output terminal; a first capacitor and a second capacitor electrically connected in series between the first output terminal and the second output terminal; three bridge arm circuits connected in parallel between a first DC terminal and a second DC terminal, each bridge arm circuit having an input point for electrically connecting one of the three-phase AC voltages and electrically connected to a neutral point between the first capacitor and the second capacitor; and a protection circuit electrically connected in series with the first capacitor and the second capacitor between the first DC terminal and the second DC terminal, wherein the protection circuit comprises: a current limiting element electrically connected in series with the first capacitor and the second capacitor; and a bypass circuit connected in parallel with the current limiting element; a control circuit electrically connected to the protection circuit; and an auxiliary power converter electrically connected to the control circuit for converting the three-phase AC voltage to power the control circuit, wherein the control circuit is used to: The timing starts from a duration during which the three-phase AC voltage is applied; and if the duration is less than a preset duration, the control circuit disables the bypass circuit and connects the two ends of the protection circuit with the current limiting element; and if the duration is greater than the preset duration, the control circuit enables the bypass circuit to connect and connects the two ends of the protection circuit with the bypass circuit.

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