A switching power supply and power supply system
By using thermistor modules, especially negative temperature coefficient thermistors, inrush current during initial startup is solved, achieving safe startup, cost reduction, and improved power supply stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- EMERSON NETWORK POWER CO LTD
- Filing Date
- 2025-06-30
- Publication Date
- 2026-07-21
AI Technical Summary
When a current switching power supply is first installed and started or is powered on again, the bus capacitor may be de-energized or have insufficient power, resulting in a large voltage difference between the bus capacitor and the external power supply of the switching power supply. This can generate inrush current, which may damage internal components. In addition, the soft-start circuit uses high-cost relays and control devices, which increases costs.
Using thermistor modules, especially negative temperature coefficient thermistors, limits the inrush current during initial startup. As the bus capacitor charges, the thermistor resistance decreases, reducing losses and lowering costs.
It enables safe startup of the switching power supply, reduces the risk of device damage, reduces costs, eliminates the need for additional control devices, and improves power supply stability.
Smart Images
Figure CN224538049U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of power supply technology, and in particular to a switching power supply and power supply system. Background Technology
[0002] Switching power supplies typically incorporate an internal bus capacitor for DC support. This bus capacitor temporarily supplies power to the connected load in the event of an external power supply failure, ensuring power supply stability. Because the bus capacitor's voltage cannot change abruptly, when the switching power supply is initially installed and started up or restarted, the bus capacitor may have little or no stored energy. This can lead to a large voltage difference between the bus capacitor and the external power supply, generating an inrush current in the circuit. This inrush current may damage multiple components within the switching power supply.
[0003] Currently, soft-start circuits are commonly used to reduce the impact of inrush current and ensure the safe startup of switching power supplies. However, the switching devices inside soft-start circuits often use expensive relays, and additional control devices are required to control the switching on and off of these devices. Utility Model Content
[0004] This application provides a switching power supply and power supply system that can ensure the safe startup of the switching power supply and reduce the component cost of the switching power supply.
[0005] In a first aspect, embodiments of this application provide a switching power supply that can be connected to an AC power source and a load, providing a stable power supply voltage to the load. The switching power supply includes at least: a first rectifier circuit, a thermistor module, and a bus capacitor; the input terminal of the first rectifier circuit is connected to the AC power source, and the output terminal of the first rectifier circuit is connected to the bus capacitor through the thermistor module; the output terminal of the first rectifier circuit is also used to connect to the load.
[0006] Using the above-described switching power supply structure, the DC power output from the first rectifier circuit is transmitted to the bus capacitor via the thermistor module. When the switching power supply is initially installed and started or restarted, the thermistor in the thermistor module is in a high-resistance state, thereby reducing the amplitude of the inrush current on the line. The reduced inrush current is then used to charge the bus capacitor. As the charging time increases, the resistance of the thermistor in the thermistor module gradually decreases. Ideally, when the bus capacitor is fully charged and the switching power supply is officially powered, the resistance of the thermistor is at its lowest value, thus reducing the losses generated by the thermistor during normal operation of the switching power supply. In addition, since only a low-cost thermistor module is added to achieve safe startup of the switching power supply, and no additional control devices are required, it helps to reduce the cost of the switching power supply.
[0007] In one possible design, the thermistor module includes a negative temperature coefficient (NTC) thermistor. With this design, since the resistance of the NTC thermistor decreases as temperature rises, it operates at high resistance during initial power-on or power-off of the switching power supply. This effectively suppresses the inrush current amplitude on the line, ensuring safe charging of the bus capacitor. As the charging time of the bus capacitor increases, the voltage difference between the bus capacitor and the AC power supply gradually decreases, and the resistance of the NTC thermistor also decreases with rising temperature. Therefore, the current amplitude on the line decreases until the bus capacitor is fully charged, at which point the switching power supply enters normal power supply mode.
[0008] In one possible design, the first rectifier circuit can be an uncontrolled rectifier circuit.
[0009] In one possible design, to ensure safe power supply, the switching power supply may be equipped with internal electrical isolation devices. Specifically, the switching power supply also includes an inverter circuit and a transformer connected between the first rectifier circuit and the load.
[0010] The input terminal of the inverter circuit is connected to the output terminal of the first rectifier circuit, and the output terminal of the inverter circuit is connected to the first primary winding of the transformer; the secondary winding of the transformer is used to connect to the load.
[0011] In one possible design, the transformer includes multiple secondary windings, each connected to a different load. With this design, if multiple loads connected to the switching power supply have different supply voltage requirements, to meet the power supply needs of these different loads, different numbers of coils are configured for the multiple secondary windings according to the amplitude requirements of the supply voltage. Therefore, the multiple secondary windings can output different voltage amplitudes, thereby meeting the power supply requirements of different loads.
[0012] In one possible design, the electrical energy output from the secondary winding of the transformer is alternating current (AC), while the load connected to the switching power supply is powered by direct current (DC). The switching power supply then includes a second rectifier circuit connected between the load and each secondary winding of the transformer. This second rectifier circuit converts the AC output from the secondary winding of the transformer into DC power, thereby supplying power to the load.
[0013] In one possible design, since the inverter circuit contains multiple switching devices, controlling the on and off states of these devices allows the inverter circuit to convert DC energy from the bus capacitor into AC energy. This AC energy is then transmitted to the secondary winding connected to the load via a transformer. These multiple switching devices can be controlled by an external controller of the switching power supply, or the switching power supply can have an internal controller for controlling these switching devices. Specifically, the switching power supply also includes a controller connected to the second primary winding of the transformer. This controller controls the inverter circuit to convert the received DC energy into AC energy and output it.
[0014] In one possible design, the thermistor module is composed of multiple thermistors connected in series.
[0015] In one possible design, each second rectifier circuit is a half-bridge rectifier circuit.
[0016] Secondly, embodiments of this application provide a power supply system that may include multiple loads and a switching power supply provided in the first aspect of the embodiments of this application and any possible design thereof. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 A schematic diagram of a switching power supply provided in this application embodiment. Figure 1 ;
[0019] Figure 2 This is a schematic diagram of the structure of a three-phase uncontrolled rectifier circuit provided in an embodiment of this application;
[0020] Figure 3 A schematic diagram of a single-phase uncontrolled rectifier circuit provided in an embodiment of this application;
[0021] Figure 4 A schematic diagram illustrating the relationship between the resistance value and temperature of an NTC thermistor, provided for an embodiment of this application;
[0022] Figure 5 A schematic diagram of the current waveform of a switching power supply provided in an embodiment of this application;
[0023] Figure 6 A waveform diagram illustrating the power consumption during the charging process of a bus capacitor, provided in an embodiment of this application. Figure 1 ;
[0024] Figure 7 A waveform diagram illustrating the power consumption during the charging process of a bus capacitor, provided in an embodiment of this application. Figure 2 ;
[0025] Figure 8 A schematic diagram of a switching power supply provided in this application embodiment. Figure 2 ;
[0026] Figure 9 This is a schematic diagram of an inverter circuit provided in an embodiment of this application;
[0027] Figure 10 A schematic diagram of a switching power supply provided in this application embodiment. Figure 3 ;
[0028] Figure 11 This is a schematic diagram of a half-bridge rectifier circuit provided in an embodiment of this application. Detailed Implementation
[0029] The embodiments of this application will now be described in detail with reference to the accompanying drawings.
[0030] The terminology used in the implementation section of this application is only for explaining specific embodiments of this application and is not intended to limit this application. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.
[0031] The following explanations of some terms used in the embodiments of this application are provided to facilitate understanding by those skilled in the art.
[0032] The terms "first," "second," etc., used in the embodiments of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein.
[0033] In this application's embodiments, "multiple" refers to two or more, and other quantifiers are similar. In this application's embodiments, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural.
[0034] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. The switching power supply provided in the embodiments of this application can be applied in multiple power supply scenarios. The switching power supply can be connected between an AC power source and a load. The switching power supply can convert the AC voltage output by the AC power source into the supply voltage for the load and provide a stable supply voltage for the connected load. The switching power supply can output voltages of different power types and different voltage amplitudes; that is, it can be connected to loads powered by DC or AC. Depending on the connected load, the switching power supply can have different circuit topologies.
[0035] When a switching power supply is initially installed and started up, or when it is powered on again, the internal bus capacitor has little or no stored energy. As a result, the voltage difference between the bus capacitor and the AC power supply voltage is too large, which in turn generates an inrush current in the line. The amplitude of this inrush current is much greater than the current amplitude when the switching power supply is operating normally, which affects the service life of the internal components of the switching power supply and, in severe cases, can damage multiple internal components.
[0036] Currently, switching power supplies typically employ soft-start circuits to ensure safe startup. These circuits primarily consist of a current-limiting resistor and a switching device. The current-limiting resistor is connected in parallel with the AC power supply line between the AC power source and the switching power supply. During initial installation and startup, or when the power supply is re-energized, the current-limiting resistor in the main circuit limits the inrush current, ensuring safe charging of the bus capacitor. Once the bus capacitor is fully charged, the power supply enters normal operation. At this point, the switching device connected in parallel with the current-limiting resistor can be closed, bypassing the current-limiting resistor and preventing losses during normal power supply.
[0037] In practical applications, since the switching devices in the soft-start circuit are connected on the line between the switching power supply and the AC power supply, in order to ensure the safe operation of the switching devices, the switching devices often use relays or contactors, which are more expensive and larger in size. In addition, additional control devices are required to control the conduction and cutoff of the switching devices, which increases the cost of the switching power supply and is not conducive to the miniaturization design of the switching power supply.
[0038] Based on this, embodiments of this application provide a switching power supply and power supply system for reducing the cost of the switching power supply while achieving safe startup.
[0039] See Figure 1 The diagram shown is a structural schematic of a switching power supply provided in an embodiment of this application. Figure 1As shown, the switching power supply may include: a first rectifier circuit, a thermistor module, and a bus capacitor C1.
[0040] The input terminal of the first rectifier circuit is used to connect to the AC power supply, and the output terminal of the first rectifier circuit is connected to the bus capacitor C1 through the thermistor module; the output terminal of the first rectifier circuit is also used to connect to the load.
[0041] It should be understood that, Figure 1 The structure of the switching power supply shown is for illustrative purposes only. In practical applications, the switching power supply can have more advanced features than... Figure 1 The components shown may include, for example, overload protection devices and short-circuit protection devices. When the power rating of the switching power supply is high, a surge protection device may also be configured in the switching power supply. Of course, the switching power supply may also include other functional devices, which are not limited in this application.
[0042] See Figure 1 As shown, the switching power supply is connected to an external AC power source and has an internal bus capacitor C1. The first rectifier circuit inside the switching power supply converts the AC voltage output from the AC power source into a DC voltage, which is then output to the bus capacitor C1 through a thermistor module. Because the bus capacitor C1 has the characteristic that its voltage cannot change abruptly, the switching power supply can provide a stable supply voltage to the downstream load, ensuring the safe operation of the load. Furthermore, since the bus capacitor C1 is an energy storage device, it can store electrical energy. When the switching power supply is operating normally, the bus capacitor C1 stores sufficient electrical energy. Therefore, when the AC power source connected to the switching power supply fails, the bus capacitor C1 can use the stored electrical energy to temporarily supply power to the downstream load until the AC power source returns to normal, thereby improving the power supply stability of the switching power supply.
[0043] The first rectifier circuit can be either an uncontrolled rectifier circuit or a controlled rectifier circuit. Since a controlled rectifier circuit requires an additional control device, the switching power supply provided in this embodiment preferably uses an uncontrolled rectifier circuit. Specifically, the uncontrolled rectifier circuit can be composed of multiple diodes with unidirectional conductivity, or it can be composed of other devices with the aforementioned functions. The switching power supply can be connected to a three-phase AC power supply or a single-phase AC power supply. The structure of the uncontrolled rectifier circuit can be configured according to the type of AC power supply connected to the switching power supply. When the switching power supply is connected to a three-phase AC power supply, the first rectifier circuit inside the switching power supply can be a three-phase uncontrolled rectifier circuit; when the switching power supply is connected to a single-phase AC power supply, the first rectifier circuit inside the switching power supply can be a single-phase uncontrolled rectifier circuit.
[0044] Specifically, see Figure 2As shown, a three-phase uncontrolled rectifier circuit can be composed of three bridge arms, each consisting of two diodes connected in series. The middle node of each bridge arm constitutes the input terminal of the three-phase uncontrolled rectifier circuit, and the middle node of each bridge arm is connected to one phase line in the three-phase AC power supply, wherein the phase line connected to the middle node of each bridge arm is different. The two ends of the above three bridge arms constitute the output terminal of the three-phase uncontrolled rectifier circuit. The first ends of the three bridge arms are connected together and connected to the first end of the bus capacitor C1 through a thermistor module, and the second ends of the three bridge arms are connected together and connected to the second end of the bus capacitor C1. Similarly, see Figure 3 As shown, a single-phase uncontrolled rectifier circuit can consist of two bridge arms, each composed of two diodes connected in series. The middle node of each bridge arm forms the input terminal of the single-phase uncontrolled rectifier circuit. The middle nodes of the two bridge arms are connected to the live wire and neutral wire of the single-phase AC power supply, respectively. The two ends of the two bridge arms form the output terminal of the single-phase uncontrolled rectifier circuit. The first ends of the two bridge arms are connected together and then connected to the first end of the bus capacitor C1 through a thermistor module. The second ends of the two bridge arms are connected together and then connected to the second end of the bus capacitor C1. To facilitate understanding of the technical solution claimed in this application, the following explanation uses a switching power supply connected to an external single-phase AC power source as an example.
[0045] It should be noted that, Figure 2 and Figure 3 The first rectifier circuit structure shown is illustrated using a thermistor module that includes a negative temperature coefficient (NTC) thermistor as an example. In practical applications, the thermistor module can also be composed of multiple NTC thermistors connected in series. Of course, the thermistor module can also have other topologies, which are not limited in this application.
[0046] See also Figure 1 As shown, the first rectifier circuit is connected to the bus capacitor C1 through a thermistor module. Since the thermistor in the thermistor module is an NTC thermistor, the relationship between the temperature and resistance of the NTC thermistor is shown in the figure below. Figure 4 As shown, see Figure 4As shown, the resistance of the NTC thermistor decreases as the temperature rises. Therefore, when the switching power supply is initially installed and started up, or when it is powered on again, the NTC thermistor is in a high-resistance state due to the low temperature, which can effectively limit the amplitude of the inrush current on the line, thus safely charging the bus capacitor C1. As the charging time increases, the temperature of the NTC thermistor gradually rises, and the resistance of the NTC thermistor gradually decreases. Although the ability of the NTC thermistor to suppress current decreases due to the decrease in the resistance of the NTC thermistor, the voltage of the bus capacitor C1 gradually increases, and the voltage difference between the bus capacitor C1 and the AC power supply gradually decreases. Therefore, the current amplitude on the line also gradually decreases, and it is still possible to safely charge the bus capacitor C1. The current on the line where the bus capacitor C1 is located can be found in [reference needed]. Figure 5 As shown, see Figure 5 As shown, as the charging time of bus capacitor C1 increases, the current amplitude on the line gradually decreases until bus capacitor C1 is fully charged and the switching power supply enters normal power supply mode. During this period, the current amplitude on the line remains almost constant, only experiencing minor fluctuations due to AC power fluctuations. The type of NTC thermistor in the thermistor module can be set according to the operating parameters of the switching power supply and the rated voltage amplitude when the bus capacitor is fully charged; this will not be discussed in detail here.
[0047] Based on the above description, it can be seen that by charging the bus capacitor C1 to reduce the voltage difference between the bus capacitor C1 and the AC power supply, the normal startup of the switching power supply can be guaranteed. The losses during the charging process of the bus capacitor C1 are mainly determined by the resistance value of the resistors in the charging circuit and the amplitude of the current flowing through the resistors. See [link to relevant documentation]. Figure 6 The diagram shows the power consumption waveform when a fixed current-limiting resistor is connected in series in the charging path of bus capacitor C1, a common practice in the industry. During each cycle of AC power output from the AC power source, the power loss of the current-limiting resistor is significant because its resistance remains constant and the inrush current amplitude is high. (See also...) Figure 7 The diagram shows the power consumption waveform when a thermistor module is connected in series in the charging path of the bus capacitor C1 in this application. Since the thermistor module uses an NTC thermistor, and the resistance of the NTC thermistor decreases as the charging time of the bus capacitor C1 increases, the power consumed by the NTC thermistor also gradually decreases. Therefore, compared to the solution of connecting a current-limiting resistor with a fixed resistance value in series with the bus capacitor, the switching power supply provided in this embodiment can further reduce the losses during the charging process of the bus capacitor C1 by connecting a thermistor module in series with the bus capacitor.
[0048] In practical applications, to ensure the normal operation of the switching power supply, it can also be configured with devices to achieve electrical isolation between the AC power supply and the load. For example, see [link to relevant documentation]. Figure 8As shown, the switching power supply may further include an inverter circuit connected between the first rectifier circuit and the load, and a transformer T with electrical isolation function. See [reference needed] Figure 8 As shown, the input terminal of the inverter circuit is connected to the output terminal of the first rectifier circuit, and the output terminal of the inverter circuit is connected to the first primary winding of the transformer T; the secondary winding of the transformer T is used to connect to the load.
[0049] See also Figure 8 As shown, the inverter circuit is connected to the bus capacitor C1 via a thermistor module. The inverter circuit can obtain DC power from the bus capacitor C1, convert the obtained DC power into AC power, and transmit it through the first primary winding of transformer T to the secondary winding of transformer T, thereby supplying power to the load connected to the secondary winding of transformer T. The inverter circuit can adopt a commonly used circuit topology with single-phase inverter function, for example, see [reference needed]. Figure 9 The diagram shown is a schematic diagram of one type of inverter circuit. Of course, other circuits or chips with the above functions can also be used for the inverter circuit, and this application does not make any specific limitations on this.
[0050] See also Figure 9 As shown, the inverter circuit is equipped with switching devices. The DC power on the bus capacitor C1 is converted into AC power by the on and off states of these switching devices. The on and off states of these switching devices can be controlled by an external controller. Alternatively, a dedicated controller can be configured inside the switching power supply to control the operating state of the inverter circuit. For example, see [reference needed]. Figure 10 As shown, the switching power supply also includes a controller, which is connected to the second primary winding of the transformer T. The controller can control the switching devices in the inverter circuit to convert the received DC power into AC power and output it.
[0051] In practical applications, if the loads connected to the switching power supply have the same supply voltage, transformer T can be configured with a single secondary winding, and all loads can be connected to the secondary winding of transformer T to meet the power supply requirements of all loads. If the multiple loads connected to the switching power supply have different supply voltages, multiple secondary windings can be configured for transformer T to meet the power supply requirements of different loads. Specifically, if the multiple loads connected to the switching power supply have different supply voltages, each secondary winding of transformer T can be configured with a different number of turns. Therefore, each secondary winding of transformer T can output a supply voltage of different amplitudes, thereby meeting the power supply requirements of different loads. The number of secondary windings of transformer T can be configured according to the type of load connected to the switching power supply, and this application does not impose any further limitations on this.
[0052] Specifically, if the switching power supply connects to multiple loads powered by DC, the switching power supply may further include a second rectifier circuit connected between the loads and each secondary winding of the transformer. See also Figure 11 As shown, the second rectifier circuit can adopt a half-bridge rectifier circuit structure. Of course, the second rectifier circuit can also adopt other circuit topologies with the above functions in the industry. This application does not impose any restrictions here.
[0053] It should be noted that, Figure 11 Taking transformer T with two secondary windings as an example, in practical applications, the number of secondary windings of transformer T can be determined according to the type of load connected to the switching module. For example, if the switching power supply is connected to multiple loads powered by DC, and the rated voltages of these multiple loads are 5V, 12V and 24V respectively, then transformer T can be configured with three secondary windings, which output 5V, 12V and 24V respectively, thereby meeting the power demand of multiple loads.
[0054] In practical applications, all components of the switching power supply can be fixed in a single rack. The rack is equipped with multiple mounting interfaces, through which loads and AC power supplies can be connected to the switching power supply. Alternatively, the components within the switching power supply can be flexibly and removably configured, meaning they can be integrated into multiple racks, with connections between internal components and external devices achieved through the rack interfaces. For example, the power supply transformer can be housed in a separate rack, while other components are mounted in another rack, all equipped with mounting interfaces for external connection. Of course, other installation methods can also be used for the switching power supply, which are not limited here.
[0055] Based on the above description, this application also provides a power supply system, which can be located inside a high-power device. The power supply system may include multiple loads to be powered and the aforementioned switching power supply.
[0056] The structure of the switching power supply can be found in the aforementioned description, and will not be repeated here.
[0057] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.
Claims
1. A switching power supply, characterized in that, include: The first rectifier circuit, thermistor module, and bus capacitor; The input terminal of the first rectifier circuit is used to connect to the AC power supply, and the output terminal of the first rectifier circuit is connected to the bus capacitor through the thermistor module. The output terminal of the first rectifier circuit is also used to connect to the load.
2. The switching power supply according to claim 1, characterized in that, The thermistor module includes negative temperature coefficient thermistors.
3. The switching power supply according to claim 1, characterized in that, The first rectifier circuit is an uncontrolled rectifier circuit.
4. The switching power supply according to claim 1, characterized in that, The switching power supply also includes an inverter circuit and a transformer connected between the first rectifier circuit and the load; The input terminal of the inverter circuit is connected to the output terminal of the first rectifier circuit, and the output terminal of the inverter circuit is connected to the first primary winding of the transformer. The secondary winding of the transformer is used to connect to the load.
5. The switching power supply according to claim 4, characterized in that, The transformer includes multiple secondary windings, and each secondary winding of the transformer is connected to a different load.
6. The switching power supply according to claim 5, characterized in that, The switching power supply also includes a second rectifier circuit connected between the load and each secondary winding of the transformer.
7. The switching power supply according to claim 4 or 5, characterized in that, The switching power supply also includes a controller, which is connected to the second primary winding of the transformer. The controller is used to control the inverter circuit to convert the received DC power into AC power and output it.
8. The switching power supply according to claim 1 or 2, characterized in that, The thermistor module is composed of multiple thermistors connected in series.
9. The switching power supply according to claim 6, characterized in that, Each second rectifier circuit is a half-bridge rectifier circuit.
10. A power supply system, characterized in that, It includes the switching power supply and multiple loads as described in any one of claims 1 to 9.