Power supply system

Abstract

The utility model provides a power supply system. The power supply system comprises a DC-DC circuit, a first input end, a second input end, an input switching unit, a relay, a step-down circuit and a controller, the input switching unit switches the first power supply or the second power supply as an input source received by the DC-DC circuit. The relay is electrically connected between the input switching unit and the first input end of the DC-DC circuit. The first input end and the first output end of the step-down circuit are connected to the two ends of the relay respectively, and the second input end and the second output end of the step-down circuit are connected to the second input end of the DC-DC circuit. When the difference value between the output voltage of the input switching unit and the input voltage of the DC-DC circuit is larger than a threshold value, the controller controls the relay to be turned off and controls the switch of the step-down circuit to work in a chopping state. The controller is configured to control the relay to be switched on when the difference value is smaller than or equal to the threshold value.

Description

Technical Field

[0001] This case relates to a power supply system, and more particularly to a power supply system capable of soft start and current limiting. Background Technology

[0002] In centralized power supply architectures, compared to single-input power supplies or redundant structures, power supplies with automatic ATS (autotransfer switch) functionality can significantly reduce power supply cost and size while simultaneously improving power supply reliability. High-power power supply products such as switching power supplies typically contain large electrolytic capacitors. During power-on startup or when the input power is interrupted and then restored (i.e., during ride-through), the charging current for these downstream electrolytic capacitors is substantial, resulting in large peak currents.

[0003] Considering the inrush current that charges the downstream electrolytic capacitors during startup or switching between multiple input power sources, a traditional inrush current suppression method involves connecting a thermistor (i.e., a current-limiting resistor) in series in the circuit to limit the inrush current generated during startup or switching. However, because the transient power of the current-limiting resistor is relatively large (depending on the capacitance of the electrolytic capacitor and the output power of the power supply system), it requires a sufficiently large volume for heat dissipation, thus occupying a significant amount of space within the power supply system. Furthermore, the current-limiting resistor is highly susceptible to temperature variations.

[0004] Therefore, there is an urgent need to provide a power supply system that can improve upon the aforementioned existing technology. Utility Model Content

[0005] The purpose of this invention is to provide a power supply system that can limit the inrush current generated during startup to achieve soft starting. Furthermore, the power supply system of this invention can also limit the inrush current generated when the received power supply changes.

[0006] To achieve the above objectives, this application provides a power supply system comprising a DC-DC circuit, a first input terminal, a second input terminal, an input switching unit, a relay, a buck circuit, and a controller. The DC-DC circuit is configured to receive an input source and provide energy to a load. The first input terminal is electrically connected to a first power source. The second input terminal is electrically connected to a second power source. The input switching unit is configured to switch between connecting to the first input terminal and connecting to the second input terminal, such that one of the first power source and the second power source serves as the input source received by the DC-DC circuit. The first and second terminals of the relay are respectively electrically connected to the first output terminal of the input switching unit and the first input terminal of the DC-DC circuit, wherein the second output terminal of the input switching unit is connected to the second input terminal of the DC-DC circuit. The buck circuit includes a switch, wherein the first input terminal and the first output terminal of the buck circuit are respectively connected to the first and second terminals of the relay, and the second input terminal and the second output terminal of the buck circuit are connected to the second input terminal of the DC-DC circuit. The controller is electrically connected to the input switching unit, the relay, and the buck circuit, and is configured to control the input switching unit, the relay, and the buck circuit. When the difference between the first voltage between the first and second output terminals of the input switching unit and the second voltage between the first and second input terminals of the DC-DC circuit is greater than a threshold, the controller architecture is configured to control the relay to turn off and control the switch of the buck circuit to operate in chopping mode; when the difference is less than or equal to the threshold, the controller architecture is configured to control the relay to turn on.

[0007] In some embodiments, the DC-DC circuit and the buck circuit are started synchronously.

[0008] In some embodiments, the controller architecture is configured to control the switch of the buck circuit to be in the on state when the relay switches.

[0009] In some embodiments, when the switch of the buck circuit is operating in a chopping state, the controller architecture is configured to control the rise rate of the second voltage by controlling the duty cycle of the switch of the buck circuit in the chopping state.

[0010] In some embodiments, the controller is configured to control the duty cycle of the buck circuit in the chopping state based on the second voltage and / or the current flowing through the inductor of the buck circuit.

[0011] In some embodiments, the power supply system further includes a bus capacitor, wherein the bus capacitor is electrically connected between a first input terminal and a second input terminal of the DC-DC circuit, and the controller is configured to obtain a second voltage by sampling the voltage on the bus capacitor.

[0012] In some embodiments, the power supply system further includes a sampling resistor, wherein the sampling resistor is electrically connected between the second output terminal of the input switching unit and the second input terminal of the DC-DC circuit, and the controller is configured to obtain the current flowing through the inductor of the buck circuit by sampling the current flowing through the sampling resistor.

[0013] In some embodiments, the buck circuit further includes an inductor and a freewheeling diode. The first terminal of the switch of the buck circuit is electrically connected to the first output terminal of the input switching unit, and the second terminal of the switch of the buck circuit is electrically connected to the first terminal of the inductor and the first terminal of the freewheeling diode. The second terminal of the inductor is electrically connected to the first input terminal of the DC-DC circuit, and the second terminal of the freewheeling diode is electrically connected to the second input terminal of the DC-DC circuit.

[0014] In some embodiments, the freewheeling diode is a freewheeling diode or a power transistor.

[0015] In some embodiments, the power supply system further includes a reverse protection circuit, wherein the reverse protection circuit includes a first diode and a second diode, the anode and cathode of the first diode being electrically connected to the first output terminal of the input switching unit and the first terminal of the relay, respectively, and the anode and cathode of the second diode being electrically connected to the second output terminal of the input switching unit and the first terminal of the relay, respectively.

[0016] In some embodiments, at least one of the first diode and the second diode is replaced by a power transistor.

[0017] In some embodiments, the power supply system further includes a reverse protection circuit, wherein the reverse protection circuit includes a first bridge arm and a second bridge arm, the first bridge arm includes a first diode and a second diode connected in series between a first terminal of the relay and a second input terminal of the DC-DC circuit, and the connection point between the first diode and the second diode is coupled to a first output terminal of the input switching unit; the second bridge arm includes a third diode and a fourth diode connected in series between a first terminal of the relay and a second input terminal of the DC-DC circuit, and the connection point between the third diode and the fourth diode is coupled to a second output terminal of the input switching unit.

[0018] In some embodiments, at least one of the first diode, the second diode, the third diode, and the fourth diode is replaced by a power transistor.

[0019] In some embodiments, the power supply system further includes a startup current limiting circuit connected in parallel to the relay, wherein the startup current limiting circuit includes a current limiting switch and a current limiting resistor connected in series between a first terminal and a second terminal of the relay; the current limiting switch is configured to be turned on when the power supply system is started, so that the current limiting resistor limits the current flowing through the DC-DC circuit.

[0020] In some embodiments, the current-limiting switch is configured to be turned on by the difference between a first voltage and a second voltage.

[0021] In some embodiments, the current limiting circuit further includes a first voltage divider resistor and a second voltage divider resistor. The two ends of the first voltage divider resistor are electrically connected to the first terminal of the relay and the control terminal of the current limiting switch, respectively. The two ends of the second voltage divider resistor are electrically connected to the control terminal of the current limiting switch and the second terminal of the relay, respectively. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the power supply system architecture according to one embodiment of this case.

[0023] Figure 2 This is a schematic diagram of the circuit structure of the power supply system in the first embodiment of this case.

[0024] Figure 3 for Figure 2 The waveform diagram of the power supply system when starting with the first power source as the input source.

[0025] Figure 4 In order to be in Figure 2 The waveform diagram of the first power source, which serves as the input source, recovering to normal after a brief failure during the operation of the power supply system.

[0026] Figure 5 for Figure 2 A waveform diagram showing the power supply system switching to a second power source when the first power source fails during operation.

[0027] Figure 6 This is a schematic diagram of the circuit structure of the power supply system in the second embodiment of this case.

[0028] Figure 7 This is a schematic diagram of the circuit structure of the power supply system in the third embodiment of this case.

[0029] Figure 8 This is a schematic diagram of the circuit structure of the power supply system in the fourth embodiment of this case.

[0030] Figure 9 This is a schematic diagram of the circuit structure of the power supply system in the fifth embodiment of this case.

[0031] The reference numerals in the attached figures are explained as follows:

[0032] 1: Power supply system

[0033] 11: First input terminal

[0034] 12: Second input terminal

[0035] 13: Input switching unit

[0036] RL: Relay

[0037] 14: Step-down circuit

[0038] 15: DC-DC circuit

[0039] 16: Controller

[0040] 21: First Power Supply

[0041] 22: Second power supply

[0042] V1: First voltage

[0043] V2: Second voltage

[0044] Vo: Output voltage

[0045] 11a: First positive input terminal

[0046] 11b: First input negative terminal

[0047] 12a: Positive second input terminal

[0048] 12b: Negative terminal of the second input

[0049] 1a: Power supply system

[0050] Q1: Switch

[0051] L1: Inductor

[0052] D1: Freewheeling tube

[0053] C1: Bus capacitor

[0054] TR: Transformer

[0055] S1, S2, S3, S4: Switches

[0056] C2: Capacitor

[0057] L2: Inductor

[0058] S5, S6, S7, S8: Switches

[0059] C3: Capacitor

[0060] V21: The power supply voltage provided by the first power source

[0061] V22: Power supply voltage provided by the second power source

[0062] DR: Control Signal

[0063] SW21, SW22: Switching status of input switching unit

[0064] T1, T2, T3, T4, T5, T6: Time points

[0065] Vset: Preset voltage

[0066] T8, T9, T10, T11, T12, T13, T14, T15, T16, T17: Time

[0067] T19, T20, T21, T22, T23, T24, T25, T26, T27, T28: Time

[0068] 1b: Power supply system

[0069] Rs: Sampling resistor

[0070] 1c: Power supply system

[0071] 17: Anti-reverse circuit

[0072] D2, D3: Diodes

[0073] 1d: Power supply system

[0074] 18: Anti-reverse circuit

[0075] D4, D5, D6, D7: Diodes

[0076] 1e: Power supply system

[0077] 19: Start the current limiting circuit

[0078] Q2: Current limiting switch

[0079] R1: Current-limiting resistor

[0080] R2, R3: Voltage dividing resistors Detailed Implementation

[0081] Some typical embodiments embodying the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations under different implementation methods, all of which do not depart from the scope of this invention, and the descriptions and illustrations therein are for illustrative purposes only and are not intended to limit this invention.

[0082] Please see Figure 1 , Figure 1 This is a schematic diagram of the power supply system architecture according to one embodiment of this case. Figure 1As shown, the power supply system 1 includes a first input terminal 11, a second input terminal 12, an input switching unit 13, a relay RL, a step-down circuit 14, a DC-DC circuit 15, and a controller 16. The first input terminal 11 is electrically connected to a first power supply 21, and the second input terminal 12 is electrically connected to a second power supply 22. In some embodiments, the first power supply 21 and the second power supply 22 are DC power supplies. The input switching unit 13 is used to switch between connecting to the first input terminal 11 and connecting to the second input terminal 12, so that one of the first power supply 21 and the second power supply 22 serves as an input source to power the DC-DC circuit 15, wherein the DC-DC circuit 15 receives the input source and provides energy to the load. The first terminal of the relay RL is electrically connected to the first output terminal of the input switching unit 13, and the second terminal of the relay RL is electrically connected to the first input terminal of the DC-DC circuit 15. In addition, the second output terminal of the input switching unit 13 is connected to the second input terminal of the DC-DC circuit 15. The first input and first output terminals of the step-down circuit 14 are connected to the first and second terminals of the relay RL, respectively. The second input and second output terminals of the step-down circuit 14 are both connected to the second output terminal of the input switching unit 13 and the second input terminal of the DC-DC circuit 15. The step-down circuit 14 is designed to limit the inrush current generated when the power supply system 1 starts up and the inrush current generated during power supply anomalies (e.g., when power is restored after a brief input source failure, or when switching the power source used as the input source). The controller 16 is electrically connected to the input switching unit 13, the relay RL, and the step-down circuit 14, and is designed to control the input switching unit 13, the relay RL, and the step-down circuit 14.

[0083] When the difference between the first voltage V1 between the first and second output terminals of the input switching unit 13 and the second voltage V2 between the first and second input terminals of the DC-DC circuit 15 is greater than a first threshold, the controller 16 controls the relay RL to turn off and controls the switch of the step-down circuit 14 to operate in a chopping state, where the chopping state means that the switch operates in a high-frequency switching mode. When the difference between the first voltage V1 and the second voltage V2 is less than or equal to the first threshold, the controller 16 controls the relay RL to turn on. The control method of the controller 16 for the power supply system 1 is described in detail below.

[0084] Before power supply system 1 starts, relay RL and buck circuit 14 are disconnected. When power supply system 1 starts, buck circuit 14 is turned on under control. At this time, the difference between the first voltage V1 and the second voltage V2 is greater than the first threshold, so controller 16 controls the switch of buck circuit 14 to operate in chopping mode to limit the current flowing through buck circuit 14 and gradually increase the second voltage V2 between the first and second input terminals of DC-DC circuit 15. When the difference between the first voltage V1 and the second voltage V2 is less than or equal to the first threshold (e.g., but not limited to 20V), controller 16 controls the switch of buck circuit 14 to operate in fully conducting mode and controls relay RL to turn on. The first threshold is set to ensure that the voltage difference across relay RL is not too large when it is closed. This enables soft-start functionality. Furthermore, after relay RL is fully turned on, controller 16 can control the switch of buck circuit 14 to turn off.

[0085] Since the current flowing through the buck circuit 14 can be limited when the switch of the buck circuit 14 is in chopping mode, in some embodiments, the DC-DC circuit 15 can also be started simultaneously when the power supply system 1 is started. The current limiting effect of the buck circuit 14 can reduce the current surge experienced by the DC-DC circuit 15 during startup. Therefore, the DC-DC circuit 15 does not need to wait for the second voltage V2 to increase to a certain value before starting, thus shortening the startup time. Furthermore, during the startup process of the DC-DC circuit 15, the controller 16 can control the output voltage Vo of the DC-DC circuit 15 to gradually increase to achieve a soft start.

[0086] When the relay RL is conducting and supplying power to the DC-DC circuit 15 normally, the controller 16 is configured to disconnect the relay RL in the event of an input source failure originating from the first power supply 21 or the second power supply 22. After the relay RL is disconnected, the input switching unit 13 can switch. When switching to another power supply, i.e., when the input switching unit 13 switches from one of the first input terminals 11 and the second input terminal 12 to the other, the controller 16 controls the switch of the buck circuit 14 to operate in a chopping state or a fully conducting state based on a comparison of the magnitudes of the first voltage V1 and the second voltage V2. Specifically, when the difference between the first voltage V1 and the second voltage V2 is greater than a second threshold, in order to avoid inrush current, the controller 16 controls the switch of the buck circuit 14 to operate in a chopping state to limit the current flowing through the buck circuit 14. When the difference between the first voltage V1 and the second voltage V2 is less than or equal to the second threshold, it indicates that the first voltage V1 and the second voltage V2 are relatively close. Therefore, the controller 16 controls the switch of the step-down circuit 14 to operate in a fully conducting state, so as not to generate a large current due to the large voltage difference, and controls the relay RL to conduct. It should be understood that the second threshold may be equal to or different from the first threshold.

[0087] In some embodiments, the controller 16 is configured to control the switch of the buck circuit 14 to be in an on state when the relay RL switches, thereby reducing the voltage or current during relay RL switching. Furthermore, in some embodiments, when the switch of the buck circuit 14 operates in a chopping state, the controller 16 is configured to control the rise rate of the second voltage V2 by controlling the duty cycle of the switch of the buck circuit 14 in the chopping state, wherein the magnitude of the duty cycle of the switch of the buck circuit 14 is positively correlated with the rise rate of the second voltage V2. For example, the controller 16 may control the duty cycle of the switch in the chopping state based on the error value between the second voltage V2 and a reference voltage, wherein the reference voltage gradually increases over time.

[0088] In some embodiments, the input switching unit 13 is connected by default to one of the first input terminal 11 and the second input terminal 12. For example, the input switching unit 13 may be connected by default to the first input terminal 11, with the first power supply 21 as the default input source. Specifically, the input switching unit 13 includes an input relay. When the first power supply 21 is normal, the input relay is connected to the first input terminal 11 without additional control; when the first power supply 21 fails, the input relay switches to be connected to the second input terminal 12, and once the first power supply 21 returns to normal, the input relay switches back to be connected to the first input terminal 11. In other embodiments, the input switching unit 13 is equivalent to both the first power supply 21 and the second power supply 22.

[0089] Please see Figure 2 , Figure 2 This is a schematic diagram of the circuit structure of the power supply system 1a according to the first embodiment of this case. Figure 2 In, with Figure 1 Components with similar functions are represented by the same reference numerals, and will not be described again here. In this embodiment, such as Figure 2 As shown, the first input terminal 11 includes a first positive input terminal 11a and a first negative input terminal 11b, wherein the first positive input terminal 11a and the first negative input terminal 11b are electrically connected to the positive and negative terminals of the first power supply 21, respectively. The second input terminal 12 includes a second positive input terminal 12a and a second negative input terminal 12b, wherein the second positive input terminal 12a and the second negative input terminal 12b are electrically connected to the positive and negative terminals of the second power supply 22, respectively. The input relay of the input switching unit 13 may, for example, but not limited to, be a double-pole double-throw switch illustrated in the figure. The step-down circuit 14 includes a switch Q1, an inductor L1, and a freewheeling diode D1. It should be understood that the freewheeling diode D1 may be a freewheeling diode or a power transistor (e.g., but not limited to a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor). In this case, the freewheeling diode D1 is used as an example for illustration. In this circuit, the first terminal of switch Q1 is electrically connected to the first output terminal of input switching unit 13 and the first terminal of relay RL. The second terminal of switch Q1 is electrically connected to the first terminal of inductor L1 and the cathode (i.e., the first terminal) of freewheeling diode D1. The second terminal of inductor L1 is electrically connected to the second terminal of relay RL and the first input terminal of DC-DC circuit 15. The anode (i.e., the second terminal) of freewheeling diode D1 is electrically connected to the second output terminal of input switching unit 13 and the second input terminal of DC-DC circuit 15. Furthermore, switch Q1 is not limited to the configuration shown in the figure and can be, for example, but not limited to, a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor. In some embodiments, the power supply system 1a further includes a bus capacitor C1, which is electrically connected between the first and second input terminals of DC-DC circuit 15.

[0090] In this embodiment, the DC-DC circuit 15 includes a full-bridge LLC circuit. Specifically, the DC-DC circuit 15 includes a primary circuit, a transformer TR, and a secondary circuit. The primary circuit includes switches S1, S2, S3, and S4, a capacitor C2, and an inductor L2. The first switch bridge arm formed by the series-connected switches S1 and S2 is connected in parallel to the second switch bridge arm formed by the series-connected switches S3 and S4. The capacitor C2 and the inductor L2 are connected in series between the connection point between switches S1 and S2 and the first end of the primary winding of the transformer TR. The second end of the primary winding of the transformer TR is electrically connected to the connection point between switches S3 and S4. The secondary circuit includes switches S5, S6, S7, and S8, and capacitor C3. Switches S5 and S6, connected in series, form the third switch arm, and switches S7 and S8, also connected in series, form the fourth switch arm. The third and fourth switch arms and capacitor C3 are connected in parallel. The secondary winding of transformer TR is electrically connected to the connection point between switches S5 and S6, and the second terminal of the secondary winding of transformer TR is electrically connected to the connection point between switches S7 and S8. It should be noted that the circuit topology of the DC-DC circuit 15 shown in the figure is merely an example, and possible implementations of the DC-DC circuit 15 in this case are not limited to this.

[0091] The following is Figure 2 Using the circuit topology shown as an example, the operation of the power supply system will be explained in detail.

[0092] Figure 3 This is a waveform diagram of the power supply system 1a when it starts up with the first power supply 21 as the input source. Figure 3 In the diagram, the horizontal axis represents time t, V21 represents the power supply voltage provided by the first power supply 21, V22 represents the power supply voltage provided by the second power supply 22, Q1 represents the switching state of switch Q1, DR represents the control signal of relay RL, and RL represents the switching state of relay RL. SW21 reflects the switching state of input switching unit 13; SW21 at a high level indicates that input switching unit 13 is connected to the first input terminal 11, and SW21 at a low level indicates that input switching unit 13 is not connected to the first input terminal 11. Please refer to [link / reference]. Figure 3 and paired Figure 2Since the first power supply 21 is supplying power normally while the second power supply 22 is not, at time T1, the input switching unit 13 switches to the connection to the first input terminal 11 to receive the power supply voltage provided by the first power supply 21 as the input source. At this time, both the relay RL and the switch Q1 are in the off state. Then, after confirming that the first voltage V1 is normal, at time T2, the controller 16 controls the switch Q1 to operate in the chopping state. During the period from time T2 to T3, the current received by the power supply system 1a flows to the DC-DC circuit 15 through the step-down circuit 14. Since the switch Q1 is operating in the chopping state, the current flowing through the step-down circuit 14 can be limited, causing the second voltage V2 to gradually rise. At time T3, the second voltage V2 rises to the preset voltage Vset. At this time, the difference between the first voltage V1 and the second voltage V2 is less than the first threshold, and the controller 16 controls the switch Q1 to operate in the fully conducting state and sends a control signal DR to control the relay RL to conduct. At time T4, relay RL turns on. It should be understood that a certain time (i.e., relay closing time) is required between the issuance of the control signal DR to relay RL and its full conduction. The specific duration is determined by the characteristics of relay RL. After relay RL turns on, at time T5, controller 16 controls switch Q1 to turn off. Theoretically, time T5 can coincide with time T4, meaning switch Q1 can turn off when relay RL is fully on. However, time T5 can also be later than time T4 to ensure that relay RL is fully on when switch Q1 turns off. Furthermore, when power supply system 1a starts, DC-DC circuit 15 also starts synchronously, and the output voltage Vo of DC-DC circuit 15 gradually increases during startup. At time T6, DC-DC circuit 15 ends its soft start and begins normal operation.

[0093] Figure 4 This is a waveform diagram illustrating the recovery of the first power supply 21, which serves as the input source, after a brief fault during the operation of power supply system 1a. Figure 4 In the diagram, SW22 reflects the switching state of input switching unit 13. A high level SW22 indicates that input switching unit 13 is connected to the second input terminal 12, while a low level SW22 indicates that input switching unit 13 is not connected to the second input terminal 12. Please refer to [link / reference]. Figure 4 and paired Figure 2Before time T8, input switching unit 13 is connected to the first input terminal 11, and the first power supply 21 serves as the input source, enabling the DC-DC circuit 15 to operate normally. At this time, relay RL is in the on state, and switch Q1 is in the off state. At time T8, the first power supply 21 fails and loses power. After a certain delay (to avoid misoperation), at time T9, controller 16 controls switch Q1 to turn on, preparing for the switching of relay RL. It should be understood that the on state of switch Q1 at this time is only an example; switch Q1 only needs to be turned on before time T10 (i.e., before controller 16 controls relay RL to turn off), so that current can flow through switch Q1 when relay RL turns off, achieving soft turn-off of relay RL. At time T10, controller 16 sends a control signal DR to control relay RL to turn off. It should be understood that a certain time is required between the issuance of control signal DR and the complete turn-off of relay RL (i.e., relay turn-off time), the specific length of which is determined by the characteristics of relay RL. After the relay turn-off time, at time T11, relay RL turns off. Then, at time T12, controller 16 controls switch Q1 to turn off. It should be understood that, theoretically, time T12 can coincide with time T11, meaning switch Q1 can turn off when relay RL is completely off. However, time T12 can also be later than time T11 to ensure that relay RL is completely off when switch Q1 turns off. It should be understood that, according to regulations, input switching unit 13 only needs to be controlled to switch to another input source if the input source power failure time exceeds a predetermined time. At this time, because the power failure time of the first power supply 21 is still short, controller 16 does not control input switching unit 13 to switch. Until time T13, the first power supply 21 resumes normal power supply. Since the predetermined time has not yet exceeded, input switching unit 13 does not need to operate. SW21 remains at a high level. After confirming that the first voltage V1 is normal, at time T14, controller 16 controls switch Q1 to operate in chopping mode to limit inrush current and allow the second voltage V2 to gradually rise. At time T15, the difference between the first voltage V1 and the second voltage V2 is less than the second threshold, and the controller 16 controls switch Q1 to operate in a fully conducting state, and sends a control signal DR to control relay RL to conduct. During the relay closing time, at time T16, relay RL conducts. After relay RL conducts, at time T17, the controller 16 controls switch Q1 to turn off.

[0094] Figure 5 This is a waveform diagram illustrating the switching of power supply system 1a to the second power supply 22 as the input source due to a failure of the first power supply 21 during operation. Please refer to [link / reference]. Figure 5 and paired Figure 2Before time T19, input switching unit 13 is connected to the first input terminal 11, and the first power supply 21 serves as the input source, enabling the DC-DC circuit 15 to operate normally. At this time, relay RL is in the on state, and switch Q1 is in the off state. At time T19, the first power supply 21 fails and loses power. During the period from time T19 to T23, the controller 16 controls switch Q1 and relay RL... Figure 4 The time intervals from T8 to T12 are the same, so they will not be described again here. At time T23, both switch Q1 and relay RL are in the off state. After a delay (greater than the preset time for waiting for power to be restored), since the second power supply 22 is supplying power normally, at time T24, controller 16 controls input switching unit 13 to switch to the connection to the second input terminal 12, thereby using the second power supply 22 as the input source. This case uses a double-pole double-throw integrated relay as an example for the input switching unit 13. It should be understood that the input switching unit 13 can also use two separate relays. If two separate relays are used, the first relay is connected to the first power supply 21 and the second relay is connected to the second power supply 22. Then, the second relay can be turned on at the same time as the first relay is turned off, or the second relay can be turned on after the first relay is turned off. After confirming that the first voltage V1 is normal, at time T25, controller 16 controls switch Q1 to work in chopping mode to limit the surge current and make the second voltage V2 gradually rise. At time T26, the difference between the first voltage V1 and the second voltage V2 is less than the second threshold, and the controller 16 controls switch Q1 to operate in the fully on state, and sends a control signal DR to control relay RL to conduct. After the relay RL has been closed for its designated time, at time T27, relay RL conducts. After relay RL conducts, at time T28, the controller 16 controls switch Q1 to turn off.

[0095] Figure 6 This is a schematic diagram of the circuit structure of the power supply system 1b according to the second embodiment of this case. Figure 6 In, with Figure 2 Components with similar functions and structures are represented by the same reference numerals, and will not be described again here. In this embodiment, such as Figure 6 As shown, the power supply system 1b also includes a sampling resistor Rs, which is electrically connected between the second output terminal of the input switching unit 13 and the second input terminal of the DC-DC circuit 15. The controller 16 is configured to obtain the current flowing through the inductor L1 of the buck circuit 14 by sampling the current flowing through the sampling resistor Rs. In some embodiments, a current sampling signal is obtained by sampling the current flowing through the sampling resistor Rs. When the current sampling signal is greater than a current threshold, the switch Q1 is turned off, and when the current sampling signal is less than the current threshold, the switch Q1 is turned on, thereby avoiding inrush current; or the current sampling signal is maintained at a small value by controlling the duty cycle of the switch Q1 in the chopping state, thereby avoiding inrush current.

[0096] Furthermore, in some embodiments, the controller 16 is configured to obtain the second voltage V2 by sampling the voltage on the bus capacitor C1, and control the duty cycle of the switch Q1 in the chopping state based on the second voltage V2 and the current flowing through the inductor L1 of the step-down circuit 14. Specifically, based on the second voltage V2 and the current flowing through the inductor L1 of the step-down circuit 14, the controller 16 can adjust the duty cycle of the switch Q1 in the chopping state through dual-loop control (voltage outer loop and current inner loop), thereby controlling the input current and output voltage Vo of the DC-DC circuit 15. This avoids large inrush currents caused by excessively large differences between the first voltage V1 and the second voltage V2, while allowing flexible control of the rise rate of the second voltage V2, which is beneficial for stabilizing the output voltage Vo of the power supply system 1a. In other embodiments, it may be possible to control the inductor L1 of the step-down circuit 14 without sampling the current, using only a single voltage loop. The control voltage reference signal gradually increases from the real-time value of the second voltage V2 to the desired value, thereby gradually increasing the duty cycle of the switch Q1 and limiting the current flowing through the inductor L1. It should be understood that the control methods for limiting inrush current are not limited to the above-mentioned methods, and all existing control methods that can achieve the above functions are within the protection scope of this invention.

[0097] Figure 7 This is a schematic diagram of the circuit structure of the power supply system 1c according to the third embodiment of this case. Figure 7 In, with Figure 2 Components with similar functions and structures are represented by the same reference numerals, and will not be described again here. In this embodiment, such as Figure 7 As shown, the power supply system 1c also includes a reverse polarity protection circuit 17, which includes diodes D2 and D3. The anode and cathode of diode D2 are electrically connected to the first output terminal of input switching unit 13 and the first terminal of relay RL, respectively. The anode and cathode of diode D3 are electrically connected to the second output terminal of input switching unit 13 and the first terminal of relay RL, respectively. Therefore, when the input source fails and power is lost, the reverse polarity protection circuit 17 prevents energy from flowing back onto the input side from the bus capacitor C1. Furthermore, when the power supply system 1c is connected to a power source, if there is no reverse polarity protection circuit 17 and the positive and negative terminals of the power source are reversed, it will cause damage to the devices. Therefore, the addition of the reverse polarity protection circuit 17 can avoid the above situation.

[0098] Figure 8 This is a schematic diagram of the circuit structure of the power supply system 1d according to the fourth embodiment of this case. Figure 8 In, with Figure 2 Components with similar functions and structures are represented by the same reference numerals, and will not be described again here. In this embodiment, such as Figure 8As shown, the power supply system 1d also includes an anti-reverse circuit 18, which includes a first bridge arm and a second bridge arm. The first bridge arm includes diodes D4 and D5 connected in series between the first terminal of the relay RL and the second input terminal of the DC-DC circuit 15. The cathode and anode of diode D4 are electrically connected to the first terminal of the relay RL and the cathode of diode D5, respectively. The anode of diode D5 is electrically connected to the second input terminal of the DC-DC circuit 15, and the connection point between diodes D4 and D5 is coupled to the first output terminal of the input switching unit 13. The second bridge arm includes diodes D6 and D7 connected in series between the first terminal of the relay RL and the second input terminal of the DC-DC circuit 15. The cathode and anode of diode D6 are electrically connected to the first terminal of the relay RL and the cathode of diode D7, respectively. The anode of diode D7 is electrically connected to the second input terminal of the DC-DC circuit 15, and the connection point between diodes D6 and D7 is coupled to the second output terminal of the input switching unit 13. Therefore, when the input source fails and loses power, the reverse protection circuit 18 can also prevent energy backflow onto the bus capacitor C1. It can also provide a path even when the positive and negative terminals of the power supply are reversed, preventing damage to the components. Furthermore, when a negative surge suddenly occurs during the operation of the power supply system 1d, diode D6, relay RL, bus capacitor C1, and diode D5 can work together to form a corresponding path for the negative surge (as shown by the arrows in the figure), preventing damage to the components of the power supply system 1d.

[0099] It should be understood that Figure 7 and Figure 8 The diode in the design can also be a power transistor (e.g., but not limited to, a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor), and this invention does not limit this to the latter.

[0100] Figure 9 This is a schematic diagram of the circuit structure of the power supply system 1e according to the fifth embodiment of this case. Figure 9 In, with Figure 2 Components with similar functions and structures are represented by the same reference numerals, and will not be described again here. In this embodiment, such as Figure 9As shown, the power supply system 1e also includes a startup current limiting circuit 19 connected in parallel to the relay RL. The startup current limiting circuit 19 includes a current limiting switch Q2 and a current limiting resistor R1 connected in series between a first terminal and a second terminal of the relay RL. The current limiting switch Q2 is configured to conduct when the power supply system 1e starts, so that the current limiting resistor R1 limits the current flowing through the bus capacitor C1. In some embodiments, the current limiting switch Q2 is configured to conduct under the control of the difference between a first voltage V1 and a second voltage V2. Furthermore, the startup current limiting circuit 19 also includes a voltage dividing resistor R2 and a voltage dividing resistor R3, wherein the two ends of the voltage dividing resistor R2 are electrically connected to the first terminal of the relay RL and the control terminal of the current limiting switch Q2, respectively, and the two ends of the voltage dividing resistor R3 are electrically connected to the control terminal of the current limiting switch Q2 and the second terminal of the relay RL, respectively. When the power supply system 1e starts, since the second voltage V2 is zero, the difference between the first voltage V1 and the second voltage V2 is large. Therefore, the voltage drop across the voltage divider resistor R3 can turn on the current limiting switch Q2. Thus, when using voltage divider resistors R2 and R3, it is not necessary to use a separate power supply to drive the current limiting switch Q2. Of course, in some embodiments, voltage divider resistors R2 and R3 may not be provided.

[0101] In some embodiments, the start-up current limiting circuit 19 is used to limit the inrush current generated when the power supply system 1e starts up, and the step-down circuit 14 is used to limit the inrush current generated when the power supply changes.

[0102] In detail, when the power supply system 1e starts, the current limiting switch Q2 is turned on by the difference between the first voltage V1 and the second voltage V2. At this time, the first voltage V1 charges the bus capacitor C1 through the current limiting switch Q2 and the current limiting resistor R1, causing the second voltage V2 to gradually rise. As the second voltage V2 rises, when the difference between the first voltage V1 and the second voltage V2 is less than or equal to the first threshold, the controller 16 controls the relay RL to turn on. At this time, because the impedance of the relay RL is small, the current will automatically switch and flow to the DC-DC circuit 15 through the relay RL, regardless of whether the current limiting switch Q2 is turned on or not.

[0103] It should be noted that the above are merely preferred embodiments for illustrating this case, and this case is not limited to the described embodiments. The scope of this case is determined by the appended claims. Furthermore, this case can be modified in various ways by those skilled in the art, but all modifications shall not depart from the protection sought by the appended claims.

Claims

1. A power supply system characterized by comprising: Include: A DC-DC circuit is designed to receive an input source and provide power to a load; A first input terminal is electrically connected to a first power source; A second input terminal is electrically connected to a second power supply; An input switching unit is configured to switch between a connection to a first input terminal and a connection to a second input terminal, so that one of the first power supply and the second power supply is used as the input source received by the DC-DC circuit; A relay, the first terminal of which is electrically connected to the first output terminal of the input switching unit and the first input terminal of the DC-DC circuit, respectively, wherein the second output terminal of the input switching unit is connected to the second input terminal of the DC-DC circuit; A step-down circuit includes a switch, wherein a first input terminal and a first output terminal of the step-down circuit are respectively connected to a first terminal and a second terminal of a relay, and a second input terminal and a second output terminal of the step-down circuit are connected to a second input terminal of a DC-DC circuit; and A controller is electrically connected to the input switching unit, the relay, and the step-down circuit, and is configured to control the input switching unit, the relay, and the step-down circuit. Wherein, when the difference between a first voltage between the first output terminal and the second output terminal of the input switching unit and a second voltage between the first input terminal and the second input terminal of the DC-DC circuit is greater than a threshold, the controller is configured to control the relay to turn off and control the switch of the buck circuit to operate in chopping state; the controller is configured to control the relay to turn on when the difference is less than or equal to the threshold.

2. The power supply system of claim 1, wherein, The DC-DC circuit starts up synchronously with the buck circuit.

3. The power supply system of claim 1, wherein, The controller architecture is based on the switch of the buck circuit being in the on state when the relay switches.

4. The power supply system of claim 1, wherein, When the switch of the step-down circuit is operating in the chopping state, the controller is configured to control the rise rate of the second voltage by controlling the duty cycle of the switch of the step-down circuit in the chopping state.

5. The power supply system of claim 4, wherein, The controller is designed to control the duty cycle of the switch of the buck circuit in the chopping state based on the second voltage and / or the current flowing through the inductor of the buck circuit.

6. The power supply system of claim 5, wherein, It also includes a bus capacitor, wherein the bus capacitor is electrically connected between the first input terminal and the second input terminal of the DC-DC circuit, and the controller is configured to obtain the second voltage by sampling the voltage on the bus capacitor.

7. The power supply system of claim 5, wherein, It also includes a sampling resistor, wherein the sampling resistor is electrically connected between the second output terminal of the input switching unit and the second input terminal of the DC-DC circuit, and the controller is configured to obtain the current flowing through the inductor of the buck circuit by sampling the current flowing through the sampling resistor.

8. The power supply system of claim 1, wherein, The buck circuit also includes an inductor and a freewheeling diode. The first terminal of the switch of the buck circuit is electrically connected to the first output terminal of the input switching unit. The second terminal of the switch of the buck circuit is electrically connected to the first terminal of the inductor and the first terminal of the freewheeling diode. The second terminal of the inductor is electrically connected to the first input terminal of the DC-DC circuit, and the second terminal of the freewheeling diode is electrically connected to the second input terminal of the DC-DC circuit.

9. The power supply system of claim 8, wherein, The freewheeling diode is either a freewheeling diode or a power transistor.

10. The power supply system of claim 1, wherein, It also includes an anti-reverse circuit, wherein the anti-reverse circuit includes a first diode and a second diode, the anode and cathode of the first diode being electrically connected to the first output terminal of the input switching unit and the first terminal of the relay, respectively, and the anode and cathode of the second diode being electrically connected to the second output terminal of the input switching unit and the first terminal of the relay, respectively.

11. The power supply system of claim 10, wherein, At least one of the first diode and the second diode is replaced with a power transistor.

12. The power supply system of claim 1, wherein, It also includes an anti-reverse circuit, wherein the anti-reverse circuit includes a first bridge arm and a second bridge arm. The first bridge arm includes a first diode and a second diode connected in series between the first terminal of the relay and the second input terminal of the DC-DC circuit, and the connection point between the first diode and the second diode is coupled to the first output terminal of the input switching unit. The second bridge arm includes a third diode and a fourth diode connected in series between the first terminal of the relay and the second input terminal of the DC-DC circuit, and the connection point between the third diode and the fourth diode is coupled to the second output terminal of the input switching unit.

13. The power supply system of claim 12, wherein, At least one of the first diode, the second diode, the third diode, and the fourth diode is replaced by a power transistor.

14. The power supply system of claim 1, wherein, It also includes a startup current limiting circuit connected in parallel to the relay, wherein the startup current limiting circuit includes a current limiting switch and a current limiting resistor connected in series between the first terminal and the second terminal of the relay; the current limiting switch is configured to be turned on when the power supply system is started, so that the current limiting resistor limits the current flowing through the DC-DC circuit.

15. The power supply system of claim 14, wherein, The current limiting switch is designed to be turned on by the difference between the first voltage and the second voltage.

16. The power supply system of claim 14, wherein, The starting current limiting circuit also includes a first voltage dividing resistor and a second voltage dividing resistor. The two ends of the first voltage dividing resistor are respectively electrically connected to the first terminal of the relay and the control terminal of the current limiting switch. The two ends of the second voltage dividing resistor are respectively electrically connected to the control terminal of the current limiting switch and the second terminal of the relay.

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