A circuit for suppressing inrush current of a switch

Abstract

The utility model relates to a switch's impulse current suppression circuit relates to electronic circuit technical field. Switch's impulse current suppression circuit includes switching power supply, current -limiting module and short -circuit module. Switching power supply includes power module and transformer T1, power module's input end connects switching power supply's input end, and power module's output end connects switching power supply's output end, transformer T1's first input end connects power module's input end, and transformer T1's second input end connects power module's output end, transformer T1's first output end connects switching power supply's voltage output end, current -limiting module is used for when switching power supply starts, and impulse current is suppressed, when switching power supply works, and short -circuit module's first control end receives the voltage output of switching power supply's voltage output end, and second control end receives the voltage output of transformer T1's second output end, to maintain impulse current suppression circuit normal work.

Description

Technical Field

[0001] This invention relates to the field of electronic circuit technology, and more specifically to a circuit for suppressing inrush current in a switch. Background Technology

[0002] Inrush current refers to the peak current flowing into a switching power supply at the instant it is switched on. During startup, the charging of large-capacity capacitors generates a large current, which is several times or even tens of times larger than the normal system current (i.e., surge current). This can cause a voltage drop on the AC power supply line, affecting the operation of all equipment connected to the same AC power supply line, and sometimes even blowing fuses and rectifier diodes. Therefore, it must be limited.

[0003] In the design of switching power supplies, inrush current is a crucial factor that must be considered. The maximum inrush current needs to be limited to prevent circuit damage or disruption to the normal operation of other electrical equipment. Currently, the following methods are commonly used to suppress inrush current:

[0004] 1. A thermistor is used in series with the input circuit. At room temperature (25℃), the thermistor maintains a certain resistance value, suppressing inrush current during power-on. Once the power supply is operating normally, the temperature rises, causing the thermistor's resistance to decrease, maintaining the current required for normal operation and reducing line losses. However, when the power supply is in a warm-up state, the thermistor is approximately in a short-circuit state. In this condition, the thermistor loses its ability to suppress inrush current during power-on.

[0005] 2. Using a power resistor in parallel with a thyristor or MOSFET reduces the inrush current when the switching power supply is turned on, before the thyristor or MOSFET conducts. Once the thyristor or MOSFET is operating normally, the power resistor is short-circuited. However, when using a thyristor, the minimum current required for conduction increases power consumption and reduces efficiency. When using a MOSFET, the presence of a body diode means it cannot completely disconnect the circuit in AC circuits, limiting its use to DC circuits.

[0006] 3. Using a relay connected in parallel with a power resistor reduces the inrush current when the switching power supply is turned on; when the relay is working normally, the power resistor is short-circuited. However, because the electromagnetic winding of the relay consumes a certain amount of power when it is working, the standby power consumption is relatively large. In addition, when the switching power supply is switched on and off quickly, the output voltage of the switching power supply cannot drop quickly with the AC power being turned off, and the relay cannot be reset at any time and thus loses its function. Summary of the Invention

[0007] The main technical problem solved by this invention is that the presence of inrush current during startup of a switching power supply can easily lead to circuit damage.

[0008] According to a first aspect, one embodiment provides an inrush current suppression circuit for a switch, comprising: a switching power supply, the switching power supply including an input terminal, an output terminal, and a voltage output terminal; the input terminal being connected to a live wire, and the output terminal being connected to a neutral wire; when the switching power supply is started, the input terminal is connected to the output terminal; when the switching power supply is operating, the input terminal is connected to the voltage output terminal; the switching power supply includes a power module and a transformer T1, the input terminal of the power module being connected to the input terminal of the switching power supply, and the output terminal of the power module being connected to the output terminal of the switching power supply; the input terminal of the transformer T1 including a first input terminal and a second input terminal, the first input terminal of the transformer T1 being connected to the input terminal of the power module, and the second input terminal of the transformer T1 being connected to the output terminal of the power module; the output terminal of the transformer T1 including a first output terminal and a second output terminal, the first output terminal of the transformer T1 being connected to the voltage output terminal of the switching power supply;

[0009] A current limiting module is used to suppress inrush current when the switching power supply starts up; the first end of the current limiting module is used to connect to the neutral wire, and the second end of the current limiting module is used to connect to the load of the inrush current suppression circuit.

[0010] A short-circuit module is provided, wherein the first terminal of the short-circuit module is connected to the first terminal of the current limiting module, the second terminal of the short-circuit module is connected to the second terminal of the current limiting module, the first control terminal of the short-circuit module is connected to the voltage output terminal of the switching power supply, and the second control terminal of the short-circuit module is connected to the second output terminal of the transformer T1. When the switching power supply is working, the first control terminal of the short-circuit module receives the voltage output from the voltage output terminal of the switching power supply, and the second control terminal receives the voltage output from the second output terminal of the transformer T1 to maintain the normal operation of the inrush current suppression circuit.

[0011] In one embodiment, the short-circuit module includes transistor Q1 and transistor Q2. The first terminal of transistor Q1 serves as the first terminal of the short-circuit module. The second terminal of transistor Q1 is connected to the first terminal of transistor Q2 and serves as the second control terminal of the short-circuit module. The second terminal of transistor Q2 serves as the second terminal of the short-circuit module. The control terminals of transistor Q1 and transistor Q2 are connected to serve as the first control terminal of the short-circuit module.

[0012] In one embodiment, the current limiting module includes a current limiting resistor R1, with a first end of the current limiting resistor R1 serving as a first end of the current limiting module and a second end of the current limiting resistor R1 serving as a second end of the current limiting module.

[0013] In one embodiment, the switching power supply further includes a rectifier module; a first end of the rectifier module is connected to a first output end of the transformer T1, and a second end of the rectifier module is connected to the voltage output end of the switching power supply; the rectifier module is used to rectify the voltage output from the output end of the transformer T1.

[0014] In one embodiment, the rectifier module includes a rectifier diode D1, the input terminal of the rectifier diode D1 serving as the first terminal of the rectifier module, and the output terminal of the rectifier diode D1 serving as the second terminal of the rectifier module.

[0015] In one embodiment, the switching power supply further includes a filtering module, which is used to filter the voltage output from the first output terminal and the second output terminal of the rectified transformer T1; the first terminal of the filtering module is connected to the first output terminal of the transformer T1, and the second terminal of the filtering module is connected to the second output terminal of the transformer T1.

[0016] In one embodiment, the filtering module includes a filtering capacitor C1, wherein the first end of the filtering capacitor C1 serves as the first end of the filtering module, and the second end of the filtering capacitor C1 serves as the second end of the filtering module.

[0017] In one embodiment, the inrush current suppression circuit further includes a step-down module, which is used to reduce the voltage input from the voltage output terminal of the switching power supply to the first control terminal of the short-circuit module; the first terminal of the step-down module is connected to the voltage output terminal of the switching power supply, and the second terminal of the step-down module is connected to the second control terminal of the short-circuit module.

[0018] In one embodiment, the step-down module includes a step-down resistor R2, with a first end of the step-down resistor R2 serving as a first end of the step-down module and a second end of the step-down resistor R2 serving as a second end of the step-down module.

[0019] In one embodiment, both transistor Q1 and transistor Q2 are bipolar transistors or field-effect transistors.

[0020] According to the above embodiment, a surge current suppression circuit for a switch includes a switching power supply, a current limiting module, and a short-circuit module. When the switching power supply starts up, the current limiting module suppresses the surge current; when the switching power supply is operating, the short-circuit module short-circuits the current limiting module to maintain the normal operation of the surge current suppression circuit. The switching power supply includes a power module and a transformer T1. While the transformer T1 transforms the voltage, it also isolates the voltage connected to the switching power supply from the voltage connected to the short-circuit module, thereby ensuring the safe operation of the entire surge current suppression circuit. Simultaneously, the short-circuit module is connected to the voltage output terminal of the switching power supply. When the switching power supply is operating, it can output voltage normally. Therefore, the short-circuit module can conduct when the switching power supply can output voltage normally, thereby reducing the power consumption of the current limiting module in the surge current suppression circuit. Attached Figure Description

[0021] Figure 1 A schematic diagram of the inrush current suppression circuit of a switch according to one embodiment. Figure 1 ;

[0022] Figure 2 A schematic diagram of the structure of a switching power supply according to one embodiment. Figure 1 ;

[0023] Figure 3 This is a circuit connection diagram of an inrush current suppression circuit for a switch according to one embodiment.

[0024] Figure 4 A schematic diagram of the structure of a switching power supply according to one embodiment. Figure 2 ;

[0025] Figure 5 A schematic diagram of the inrush current suppression circuit of a switch according to one embodiment. Figure 2 ;

[0026] Figure 6 This is a circuit connection diagram of an inrush current suppression circuit for a switch with a load, according to one embodiment. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. Similar elements in different embodiments are referred to by associated similar element reference numerals. In the following embodiments, many details are described to facilitate a better understanding of this application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other elements, materials, or methods. In some cases, certain operations related to this application are not shown or described in the specification. This is to avoid obscuring the core parts of this application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0028] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the order of the steps or actions in the method description can be changed or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0029] The serial numbers assigned to components in this document, such as "first" and "second," are used only to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages).

[0030] Please refer to Figure 1 This application provides a circuit for suppressing inrush current of a switch, including a switching power supply 100, a current limiting module 200, and a short-circuit module 300.

[0031] In some embodiments, the switching power supply 100 includes an input terminal, an output terminal, and a voltage output terminal. The input terminal of the switching power supply 100 is connected to the live wire, and the output terminal is connected to the neutral wire. When the switching power supply 100 starts up, the voltage output from the live and neutral wires first charges the internal filter and energy storage capacitor. The charging current of the filter and energy storage capacitor is very large, resulting in a heavy load on the switching power supply 100. Therefore, the voltage output from the voltage output terminal of the switching power supply 100 is very small at this time, almost negligible. Thus, the input and output terminals of the switching power supply are connected at this time. After tens of milliseconds, the voltage output terminal of the switching power supply 100 can output voltage normally. At this time, the switching power supply 100 is operating normally, and the input and output terminals are connected.

[0032] Please refer to Figure 2In some embodiments, the switching power supply 100 includes a power module 110 and a transformer T1120. Please refer to... Figure 3 The input terminal of power module 110 is connected to the input terminal of switching power supply 100, and the output terminal of power module 110 is connected to the output terminal of switching power supply 100. The input terminal of transformer T1120 includes a first input terminal (i.e....) Figure 3 The terminal marked as 1) and the second input terminal (i.e. Figure 3 (Connection port number 2), the first input terminal of transformer T1120 is connected to the input terminal of power module 110, and the second input terminal of transformer T1120 is connected to the output terminal of power module 110. The output terminal of transformer T1120 includes the first output terminal (i.e., Figure 3 The terminal marked 3) and the second output terminal (i.e. Figure 3 (The terminal marked 4) connects the first output terminal of transformer T1120 to the voltage output terminal of switching power supply 100.

[0033] When the switching power supply 100 starts up, current flows through the live wire into the input terminal of the switching power supply 100, then through the output terminal into the neutral wire. Since the inrush current suppression circuit of the switch uses alternating current, the current can also flow through the neutral wire into the output terminal of the switching power supply 100, then through the input terminal into the live wire. When the switching power supply 100 is working, the power module 110 can discharge normally, thus allowing the transformer T1120 to operate normally. At this time, the voltage output terminal of the switching power supply 100 can output voltage normally.

[0034] In some embodiments, the current limiting module 200 is used to suppress the inrush current of the switching power supply 100 when the switching power supply 100 is started. The first terminal of the current limiting module 200 is connected to the neutral wire, and the second terminal of the current limiting module is used to connect to the load of the inrush current suppression circuit.

[0035] In some embodiments, please refer to Figure 3 The current limiting module 200 includes a current limiting resistor R1. The first terminal of the current limiting resistor R1 serves as the first terminal of the current limiting module 200, and the second terminal of the current limiting resistor R1 serves as the second terminal of the current limiting module 200. When the switching power supply 100 starts up, since the initial voltage of the filter energy storage capacitor is zero, a large surge current (i.e., inrush current) will be generated at the instant the filter energy storage capacitor charges. Therefore, to prevent the inrush current from affecting the inrush current suppression circuit when the switching power supply 100 starts up, the inrush current is suppressed by the current limiting resistor R1.

[0036] In some embodiments, the first terminal of the short-circuit module 300 is connected to the first terminal of the current-limiting module 200, the second terminal of the short-circuit module 300 is connected to the second terminal of the current-limiting module 200, the first control terminal of the short-circuit module 300 is connected to the voltage output terminal of the switching power supply 100, and the second control terminal of the short-circuit module 300 is connected to the second output terminal of the transformer T1120. When the switching power supply 100 is working, the first and second output terminals of the transformer T1120 can output voltage normally. Therefore, the first control terminal of the short-circuit module 300 receives the voltage output from the voltage output terminal of the switching power supply 100, and the second control terminal of the short-circuit module 300 receives the voltage output from the second output terminal of the transformer T1120, thereby enabling the short-circuit module 300 to operate, short-circuiting the current-limiting resistor R1 to maintain the normal operation of the inrush current suppression circuit.

[0037] In some embodiments, please refer to Figure 3 The short-circuit module 300 includes transistor Q1 and transistor Q2. The first terminal of transistor Q1 serves as the first terminal of the short-circuit module 300. The second terminal of transistor Q1 is connected to the first terminal of transistor Q2 and serves as the second control terminal of the short-circuit module 300. The second terminal of transistor Q2 serves as the second terminal of the short-circuit module 300. The control terminals of transistor Q1 and transistor Q2 are connected and serve as the first control terminal of the short-circuit module 300.

[0038] It should be noted that the transistor in this application can be a transistor of any structure, such as a bipolar junction transistor (BJT) or a field-effect transistor (FET). When the transistor is a bipolar junction transistor, its control terminal refers to the gate of the bipolar junction transistor. The first terminal can be the collector or emitter of the bipolar junction transistor, and the corresponding second terminal can be the emitter or collector of the bipolar junction transistor. In practical applications, the "emitter" and "collector" can be interchanged according to the signal flow direction. When the transistor is a field-effect transistor, its control terminal refers to the gate of the field-effect transistor. The first terminal can be the drain or source of the field-effect transistor, and the corresponding second terminal can be the source or drain of the field-effect transistor. In practical applications, the "source" and "drain" can be interchanged according to the signal flow direction.

[0039] Taking transistors Q1 and Q2 as two field-effect transistors with their sources connected together as an example, when the switching power supply 100 is working, the output terminal of transformer T1120 outputs a normal voltage, and the voltage output terminal of the switching power supply 100 also outputs a normal voltage. When the voltage output by transformer T1120 is applied to the sources of transistors Q1 and Q2 through the second control terminal of short-circuit module 300, and when the voltage output terminal of switching power supply 100 is applied to the drains of transistors Q1 and Q2 through the first control terminal of short-circuit module 300, transistors Q1 and Q2 will conduct, thus short-circuiting the current-limiting resistor R1. At this time, the load of the inrush current suppression circuit will return to the original load of the circuit, and the current flowing through the inrush current suppression circuit will also be of normal magnitude, thus maintaining the normal operation of the inrush current suppression circuit.

[0040] Please refer to Figure 4 In some embodiments, the switching power supply 100 further includes a rectifier module 130 and a filter module 140.

[0041] In some embodiments, the rectifier module 130 is used to rectify the voltage output from the output terminal of the transformer T1120. The first terminal of the rectifier module 130 is connected to the first output terminal of the transformer T1, and the second terminal of the rectifier module 130 is connected to the voltage output terminal of the switching power supply.

[0042] In some embodiments, please refer to Figure 3 The rectifier module 130 includes a rectifier diode D1. The input terminal of the rectifier diode D1 serves as the first terminal of the rectifier module 130, and the output terminal of the rectifier diode D1 serves as the second terminal of the rectifier module 130. When the first output terminal of the transformer T1120 outputs a voltage, it is rectified by the rectifier diode D1.

[0043] In some embodiments, the filter module 140 is used to filter the voltage output from the rectified transformer T1120. The first end of the filter module 140 is connected to the first output terminal of the transformer T1120, and the second end of the filter module 140 is connected to the second output terminal of the transformer T1120.

[0044] In some embodiments, please refer to Figure 3 The filter module 140 includes a filter capacitor C1, with the first end of the filter capacitor C1 serving as the first end of the filter module 140 and the second end of the filter capacitor C1 serving as the second end of the filter module 140.

[0045] Please refer to Figure 5 In some embodiments, the inrush current suppression circuit of the switch also includes a step-down module 400.

[0046] In some embodiments, the step-down module 400 is used to reduce the voltage input from the voltage output terminal of the switching power supply 100 to the first control terminal of the short-circuit module 300. The first terminal of the step-down module 400 is connected to the voltage output terminal of the switching power supply 100, and the second terminal of the step-down module 400 is connected to the second control terminal of the short-circuit module 300.

[0047] In some embodiments, please refer to Figure 3 The step-down module 400 includes a step-down resistor R2, with the first end of the step-down resistor R2 serving as the first end of the step-down module 400 and the second end of the step-down resistor R2 serving as the second end of the step-down module 400.

[0048] Please refer to Figure 6 When the inrush current suppression circuit of the switch is connected to the load corresponding to the switching power supply 100, the positive terminal of the load is connected to the live wire, and the negative terminal of the load is connected to the second terminal of the current-limiting resistor R1, which is also the second terminal of transistor Q2. When the switching power supply 100 starts up, the current flow path at the switching power supply 100 is as follows: the current flows through the live wire into the input terminal of the power module 110 inside the switching power supply 100, and then flows through the output terminal of the power module 110 into the neutral wire. At this time, the switching power supply 100 will generate an inrush current. Therefore, the current flow path at the load is as follows: the current flows through the live wire into the positive terminal of the load, then through the negative terminal of the load into the current-limiting resistor R1. After the current-limiting resistor R1 cancels out the inrush current, it flows into the neutral wire. Since the current connected to the inrush current suppression circuit is alternating current, the current flow direction for the other half of the alternating current cycle is the same as the above-described flow path, but in the opposite direction.

[0049] When the switching power supply 100 is operating, there is no inrush current, and the current flow path at the switching power supply 100 is the same as the current flow path when the switching power supply 100 is started. The current flow path at the load is as follows: the current enters the positive terminal of the load through the live wire, then flows through the negative terminal of the load into the short-circuit module 300. Transistors Q1 and Q2 in the short-circuit module 300 are turned on, and the current flows into the neutral wire through transistors Q1 and Q2. Since the current connected to the inrush current suppression circuit is alternating current, the current flow direction in the other half-cycle of the alternating current is the same as the above-mentioned flow path, but in the opposite direction. In this application, two transistors are connected in series, with the positive terminals of their body diodes connected in series. This ensures that transistors Q1 and Q2 will not conduct when the alternating current flows through the short-circuit module 300 during the positive half-cycle; similarly, transistors Q1 and Q2 will not conduct when the alternating current flows through the short-circuit module 300 during the negative half-cycle. This allows the inrush current suppression circuit of this application to be safely used in AC circuits. Furthermore, devices using transistors are less expensive than relays.

[0050] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A circuit for suppressing inrush current in a switch, characterized in that, include: A switching power supply, comprising an input terminal, an output terminal, and a voltage output terminal; The input terminal is connected to the live wire, and the output terminal is connected to the neutral wire. When the switching power supply is started, the input terminal is connected to the output terminal; when the switching power supply is working, the input terminal is connected to the voltage output terminal. The switching power supply includes a power module and a transformer T1. The input terminal of the power module is connected to the input terminal of the switching power supply. The input terminal of the transformer T1 includes a first input terminal and a second input terminal. The first input terminal of the transformer T1 is connected to the output terminal of the power module, and the second input terminal of the transformer T1 is connected to the output terminal of the power module. The output terminal of the transformer T1 includes a first output terminal and a second output terminal. The first output terminal of the transformer T1 is connected to the voltage output terminal of the switching power supply. A current limiting module is used to suppress inrush current when the switching power supply starts up; the first end of the current limiting module is connected to the neutral wire, and the second end of the current limiting module is used to connect to the load of the inrush current suppression circuit. A short-circuit module is provided, wherein the first terminal of the short-circuit module is connected to the first terminal of the current limiting module, the second terminal of the short-circuit module is connected to the second terminal of the current limiting module, the first control terminal of the short-circuit module is connected to the voltage output terminal of the switching power supply, and the second control terminal of the short-circuit module is connected to the second output terminal of the transformer T1. When the switching power supply is working, the first control terminal of the short-circuit module receives the voltage output from the voltage output terminal of the switching power supply, and the second control terminal receives the voltage output from the second output terminal of the transformer T1 to maintain the normal operation of the inrush current suppression circuit.

2. The inrush current suppression circuit for the switch as described in claim 1, characterized in that, The short-circuit module includes transistor Q1 and transistor Q2. The first terminal of transistor Q1 serves as the first terminal of the short-circuit module. The second terminal of transistor Q1 is connected to the first terminal of transistor Q2 and serves as the second control terminal of the short-circuit module. The second terminal of transistor Q2 serves as the second terminal of the short-circuit module. The control terminals of transistor Q1 and transistor Q2 are connected to serve as the first control terminal of the short-circuit module.

3. The inrush current suppression circuit for the switch as described in claim 1, characterized in that, The current limiting module includes a current limiting resistor R1, with the first end of the current limiting resistor R1 serving as the first end of the current limiting module and the second end of the current limiting resistor R1 serving as the second end of the current limiting module.

4. The inrush current suppression circuit for the switch as described in claim 1, characterized in that, The switching power supply also includes a rectifier module; the first end of the rectifier module is connected to the first output end of the transformer T1, and the second end of the rectifier module is connected to the voltage output end of the switching power supply; the rectifier module is used to rectify the voltage output from the output end of the transformer T1.

5. The inrush current suppression circuit for the switch as described in claim 4, characterized in that, The rectifier module includes a rectifier diode D1, the input terminal of which serves as the first terminal of the rectifier module, and the output terminal of which serves as the second terminal of the rectifier module.

6. The inrush current suppression circuit for the switch as described in claim 4, characterized in that, The switching power supply also includes a filtering module, which is used to filter the voltage output from the first and second output terminals of the rectified transformer T1; the first end of the filtering module is connected to the first output terminal of the transformer T1, and the second end of the filtering module is connected to the second output terminal of the transformer T1.

7. The inrush current suppression circuit for the switch as described in claim 6, characterized in that, The filtering module includes a filtering capacitor C1, with the first end of the filtering capacitor C1 serving as the first end of the filtering module and the second end of the filtering capacitor C1 serving as the second end of the filtering module.

8. The inrush current suppression circuit for the switch as described in claim 1, characterized in that, The inrush current suppression circuit further includes a step-down module, which is used to reduce the voltage input from the voltage output terminal of the switching power supply to the first control terminal of the short-circuit module; the first terminal of the step-down module is connected to the voltage output terminal of the switching power supply, and the second terminal of the step-down module is connected to the second control terminal of the short-circuit module.

9. The inrush current suppression circuit for the switch as described in claim 8, characterized in that, The step-down module includes a step-down resistor R2, with the first end of the step-down resistor R2 serving as the first end of the step-down module and the second end of the step-down resistor R2 serving as the second end of the step-down module.

10. The inrush current suppression circuit for the switch as described in claim 2, characterized in that, Both transistors Q1 and Q2 are bipolar transistors or field-effect transistors.

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