Surge current prevention circuit of switching power supply

Abstract

The utility model discloses an anti-surge current circuit of a switching power supply. The anti-surge current circuit comprises a first current limiting unit, a relay module, a time delay module, an energy storage unit and a voltage division module, the first current-limiting unit is connected in series with a live wire L. The relay module is connected in parallel with two ends of the first current-limiting unit. The input end of the time delay module is connected with the output end of the first current limiting unit, and the output end of the time delay module is connected with the input end of the relay module, the input end of the energy storage unit and the input end of the voltage division module; the output end of the energy storage unit is respectively connected with the output end of the voltage division module and a zero line N; the voltage dividing module is connected in parallel with the relay module, and the voltage dividing module is respectively connected with the time delay module and the energy storage unit.

Description

Technical Field

[0001] The utility model relates to the technical field of surge current protection of switching power supplies, and specifically, to a surge current prevention circuit for a switching power supply. Background Art

[0002] When a medium or high power charger switching power supply is powered on and turned on, due to the existence of a large electrolytic capacitor at the input backend (approximately short-circuited at the moment of power-on), a large surge current (above 150A, with a duration of 10ms) will be generated, and this current can damage power devices.

[0003] To prevent the surge current from damaging the circuit, a surge current prevention circuit is usually set up. Currently, the input current overshoot limiting circuit is integrated in the switching power supply and implemented by using a relay in parallel with a thermistor or a cement resistor.

[0004] Please refer to Figure 1 , Figure 1 for the prior art surge current prevention circuit. Figure 1 The resistor R1 in is used to limit the surge current generated at the moment of power-on. After the resistor R1 suppresses the surge current, the relay JD1 is controlled by the Relay control signal. Under the action of the DC power supply provided by Vcc, the contact is closed to short-circuit the resistor R1, thereby improving the power supply efficiency. However, generally, the relay JD1 requires a control signal and a power supply. The relay JD1 needs to be directly or indirectly controlled by the Relay signal (indirect control: the control signal controls the DC power supply of the relay JD1). Therefore, the complete relay control circuit also includes a rectifier bridge BD1, a conversion power supply, and the corresponding control signal part, and the circuit is complex and the cost is high. Summary of the Utility Model

[0005] In view of the deficiencies of the prior art, a surge current prevention circuit for a switching power supply is provided.

[0006] To achieve the above object, the utility model provides a surge current prevention circuit for a switching power supply, including a first current limiting unit, a relay module, a delay module, an energy storage unit, and a voltage dividing module; the first current limiting unit is connected in series to the live wire L, and the relay module is connected in parallel to both ends of the first current limiting unit; the input end of the delay module is connected to the output end of the first current limiting unit, and the output end of the delay module is respectively connected to the input end of the relay module, the input end of the energy storage unit, and the input end of the voltage dividing module; the output end of the energy storage unit is respectively connected to the output end of the voltage dividing module and the neutral wire N; the voltage dividing module is connected in parallel to the relay module, and the voltage dividing module is respectively connected to the delay module and the energy storage unit.

[0007] According to an embodiment of the utility model, a linear voltage stabilizing module is further included, and the linear voltage stabilizing module is respectively connected to the relay module, the delay module, the energy storage unit, and the voltage dividing module.

[0008] According to an embodiment of the present utility model, the relay module includes a relay, which has a switch terminal and a winding terminal. The switch terminal is connected in parallel to both ends of the first current limiting unit. The positive pole of the winding terminal is connected to the output terminal of the delay module, and the negative pole of the winding terminal is connected to the voltage dividing module.

[0009] According to an embodiment of the present utility model, the delay module includes a rectifying unit and a second current limiting unit. One end of the rectifying unit is connected to the output terminal of the first current limiting unit, and the other end is connected to the second current limiting unit. The other end of the second current limiting unit is respectively connected to the input terminal of the relay module, the input terminal of the energy storage unit, and the input terminal of the voltage dividing module.

[0010] According to an embodiment of the present utility model, the voltage dividing module includes a first voltage dividing unit and a second voltage dividing unit. One end of the first voltage dividing unit is respectively connected to the input terminal of the relay module and the input terminal of the energy storage unit, and the other end is respectively connected to the output terminal of the relay module and the second voltage dividing unit. One end of the second voltage dividing unit is respectively connected to the first voltage dividing unit and the output terminal of the relay module, and the other end is connected to the output terminal of the energy storage unit and the neutral line N.

[0011] According to an embodiment of the present utility model, the linear voltage stabilizing module includes a triode Q1, a voltage stabilizing unit, and a third current limiting unit. The emitter E of the triode Q1 is connected to the relay module. The collector C of the triode Q1 is connected to the output terminal of the delay module. The base B of the triode Q1 is respectively connected to one end of the voltage stabilizing unit and the third current limiting unit. The other end of the voltage stabilizing unit is respectively connected to the output terminal of the relay module and the output terminal of the voltage dividing module. The other end of the third current limiting unit is respectively connected to the collector C of the triode Q1 and the output terminal of the delay module.

[0012] According to an embodiment of the present utility model, the relay module further includes a freewheeling unit, which is connected in parallel to the winding terminal of the relay.

[0013] According to an embodiment of the present utility model, the first current limiting unit is a thermistor or a cement resistor.

[0014] According to an embodiment of the present utility model, the freewheeling unit is an ultra-fast recovery diode.

[0015] The beneficial effect of the present utility model is that, compared with the existing surge current protection circuit of the switching power supply, the power supply to the relay module is delayed by the delay module, the energy storage unit, and the voltage dividing module, thereby controlling the on-off state of the relay module, avoiding using a rectifier bridge, a switching power supply, and a control signal generation circuit to generate an external control signal to control the on-off state of the relay module, thus simplifying the circuit structure and effectively saving costs. Description of the Drawings

[0016] The accompanying drawings described herein are used to provide a further understanding of the present application and form a part of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation of the present application. In the drawings:

[0017] Figure 1 is a circuit diagram for preventing inrush current in the prior art;

[0018] Figure 2 is a block diagram of a surge current protection circuit for a switching power supply in an embodiment;

[0019] Figure 3 is a circuit diagram of a surge current protection circuit for a switching power supply in an embodiment.

[0020] Explanation of Reference Numerals

[0021] 1 - First current limiting unit; 2 - Relay module; 21 - Relay; 22 - Freewheeling unit; 211 - Switch terminal; 212 - Winding terminal; 3 - Delay module; 31 - Rectifying unit; 32 - Second current limiting unit; 4 - Energy storage unit; 5 - Voltage dividing module; 51 - First voltage dividing unit; 52 - Second voltage dividing unit; 6 - Linear voltage regulation module; 61 - Voltage regulation unit; 62 - Third current limiting unit. Detailed implementation manners

[0022] The following will disclose multiple embodiments of the present invention with reference to the drawings. For the sake of clarity, many practical details will be described together in the following description. However, it should be understood that these practical details are not used to limit the present invention. That is to say, in some embodiments of the present invention, these practical details are not necessary. In addition, for the purpose of simplifying the drawings, some conventional structures and components will be shown in a simple schematic manner in the drawings.

[0023] In addition, in the present invention, descriptions such as "first" and "second" are only for descriptive purposes and do not specifically refer to the order or sequence. Nor are they used to limit the present invention. They are merely used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the fact that those skilled in the art can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0024] Please refer to Figure 2 , Figure 2It is a circuit block diagram of a surge current protection circuit for a switching power supply. The surge current protection circuit of the switching power supply in this embodiment includes a first current limiting unit 1, a relay module 2, a delay module 3, an energy storage unit 4, and a voltage dividing module 5. Among them, the first current limiting unit 1 is connected in series to the live wire L, and is used to limit the surge current generated at the moment of power-on. The relay module 2 is connected in parallel to both ends of the first current limiting unit 1. By controlling the switching state of the relay module 2, the first current limiting unit 1 can work normally or be short-circuited. The input end of the delay module 3 is connected to the output end of the first current limiting unit 1, and the output end of the delay module 3 is respectively connected to the input end of the relay module 2, the input end of the energy storage unit 4, and the input end of the voltage dividing module 5. The output end of the energy storage unit 4 is respectively connected to the output end of the voltage dividing module 5 and the neutral wire N.

[0025] The delay module 3 is used to limit the charging current of the energy storage unit 4 to delay the charging time of the energy storage unit 4; and the energy storage unit 4 is used to delay the power supply to the relay module 2 by using the charging and energy storage time.

[0026] The voltage dividing module 5 is connected in parallel to the relay module 2, and the voltage dividing module 5 is respectively connected to the delay module 3 and the energy storage unit 4. The voltage dividing module 5 is used for voltage division.

[0027] In this embodiment, the first current limiting unit 1 can be selected as a thermistor or a cement resistor. Preferably, the first current limiting unit 1 is a cement resistor, and the cement resistor has good heat resistance and heat dissipation. The energy storage unit 4 includes a capacitor C1.

[0028] In an actual application scenario, at the moment of circuit power-on, the voltage of the live wire L is higher than the voltage of the neutral wire L. The surge current is limited by the first current limiting unit 1, thereby reducing the impact of the surge current on the circuit. At the same time, the current output by the first current limiting unit 1 charges the capacitor C1. As the charging time becomes longer, the voltage of the capacitor C1 continuously rises. At the same time, the current passes through the voltage dividing module 5 to supply power to the relay module 2, so that the voltage across the relay module 2 gradually rises during the duration of the surge current. When the voltage across the relay module 2 reaches the working voltage, the surge current disappears, and the relay module 2 short-circuits the first current limiting unit 1. Thus, at the initial stage of power-on when a surge current is generated, the relay module 2 remains closed, and the first current limiting unit 1 limits the surge current to keep the circuit stable. After the surge current disappears, the relay module 2 is controlled to work and the first current limiting unit 1 is short-circuited to reduce the circuit loss, so that the mains current normally supplies power to the circuit and improves the working efficiency.

[0029] Compared with the existing inrush current prevention circuit of the switching power supply, this solution delays the power supply to the relay module 2 through the delay module 3, the energy storage unit 4 and the voltage dividing module 5, thereby controlling the switching state of the relay module 2, avoiding the use of a rectifier bridge, a switching power supply and a control signal generation circuit to generate an external control signal to control the switching state of the relay module 2, thus simplifying the circuit structure and effectively saving costs.

[0030] Please refer to Figure 3 , Figure 3 which is the inrush current prevention circuit diagram of the switching power supply. Specifically, the relay module 2 includes a relay 21, and the relay 21 has a switch terminal 211 and a winding terminal 212. The switch terminal 211 of the relay 21 is connected in parallel across both ends of the first current limiting unit 1, the positive pole of its winding terminal 212 is connected to the output terminal of the delay module 3, and the negative pole of the winding terminal 212 is connected to the voltage dividing module 5.

[0031] In this example, the relay module 2 further includes a freewheeling unit 22, and the freewheeling unit 22 is connected in parallel across the winding terminal 212 of the relay 21. The freewheeling unit 22 is used for freewheeling when the switch terminal 211 of the relay 21 is disconnected, so as to eliminate the voltage spike at the winding terminal 212 of the relay 21 and maintain the circuit stability. Preferably, the freewheeling unit 22 is selected as an ultra-fast recovery diode.

[0032] The delay module 3 includes a rectifying unit 31 and a second current limiting unit 32. One end of the rectifying unit 31 is connected to the output terminal of the first current limiting unit 1, and the other end is connected to one end of the second current limiting unit 32. The rectifying unit 31 is used for rectification. The other end of the second current limiting unit 32 is respectively connected to the input terminal of the relay module 2, the input terminal of the energy storage unit 4 and the input terminal of the voltage dividing module 5. The second current limiting unit 32 is used for voltage division and current limiting of the energy storage unit 4 to achieve delay during the charging of the energy storage unit 4.

[0033] In this embodiment, the rectifying unit 31 includes a diode D1, and the second current limiting unit includes a resistor R3. The positive pole of the diode D1 is connected to the output terminal of the first current limiting unit 1, and its negative pole is connected to one end of the resistor R3. The other end of the resistor R3 is respectively connected to the positive pole of the winding terminal 212 of the relay 21, the input terminal of the energy storage unit 4 and the input terminal of the voltage dividing module 5.

[0034] In the actual application scenario, the current of the live wire L flows through the first current limiting unit 1 for current limiting and then flows to the diode D1. The diode D1 rectifies the current, and then the current passes through the resistor R3 for current limiting and charges the energy storage unit 4, so that on the basis of not significantly increasing the charging time of the capacitor C1, the charging energy on the capacitor C1 is reduced, and the voltage stress of the capacitor C1 is reduced.

[0035] Further, the voltage dividing module 5 includes a first voltage dividing unit 51 and a second voltage dividing unit 52. One end of the first voltage dividing unit 51 is respectively connected to the input end of the relay module 2 and the input end of the energy storage unit 4, and the other end thereof is respectively connected to the output end of the relay module 2 and the second voltage dividing unit 52. One end of the second voltage dividing unit 52 is respectively connected to the first voltage dividing unit 51 and the output end of the relay module 2, and the other end thereof is connected to the output end of the energy storage unit 4 and the neutral line N. The first voltage dividing unit 51 and the second voltage dividing unit 52 are used for voltage division during the charging of the energy storage unit 4, and at the same time, during the discharging of the energy storage unit 4, they are used for the rapid discharging of the energy storage unit 4.

[0036] In this embodiment, the first voltage dividing unit 51 includes a resistor R4, and the second voltage dividing unit 52 includes a resistor R2. One end of the resistor R4 is respectively connected to the positive pole of the relay winding end 212, the resistor R3, and the positive pole of the capacitor C1, and the other end thereof is respectively connected to the negative pole of the relay winding end 212 of the relay 21 and the resistor R2. One end of the resistor R2 is respectively connected to the negative pole of the relay 21 winding end 212 and the resistor R4, and the other end thereof is respectively connected to the negative pole of the capacitor C1 and the neutral line L.

[0037] Further, the switch power supply surge protection circuit further includes a linear voltage stabilization module 6. The linear voltage stabilization module 6 is respectively connected to the relay module 2, the energy storage unit 4, and the voltage dividing module 5. The linear voltage stabilization module 6 is used for stabilizing the current generated during the discharging of the energy storage unit 4, so that the voltage across the relay module 2 is maintained at a stable value.

[0038] Specifically, the linear voltage stabilization module 6 includes a triode Q1, a voltage stabilization unit 61, and a third current limiting unit 62. The emitter E of the triode Q1 is connected to the relay module 2, the collector B of the triode Q1 is connected to the energy storage unit 4, the base B of the triode Q1 is respectively connected to the voltage stabilization unit 61 and the third current limiting unit 62, and the other end of the voltage stabilization unit 61 is respectively connected to the output end of the relay module 2 and the output end of the voltage dividing module 5. The other end of the third current limiting unit 62 is respectively connected to the collector C of the triode Q1 and the output end of the delay module 3.

[0039] In this embodiment, the voltage stabilization unit 61 includes a voltage stabilizing diode D2, and the third current limiting module includes a resistor R5. The emitter E of the triode Q1 is respectively connected to the positive pole of the relay winding end 212 of the relay 21 and the triode D3; the collector C of the triode Q1 is respectively connected to the resistor R3, the resistor R5, and the positive pole of the capacitor C1; the base B of the triode Q1 is respectively connected to the voltage stabilizing diode D2 and the resistor R5. The other end of the voltage stabilizing diode D2 is respectively connected to the diode D2 and the resistor R4. The other end of the resistor R5 is respectively connected to the collector C of the triode Q1, the resistor R3, the negative pole of the capacitor C1, and the resistor R4. It should be noted that the voltage stabilizing diode D2 can be selected according to the closing threshold of the relay 21. In this example, the closing threshold of the relay 21 is 8V, and the voltage stabilizing diode is selected as 10V.

[0040] In an actual usage scenario, the current of the live wire L is limited by the first current limiting unit 1 to limit the inrush current generated in the initial stage of power-on. After passing through the first current limiting unit 1, the current of the live wire L sequentially passes through the diode D1 and the resistor R3 and then charges the capacitor C1. The resistor R3 limits the charging current to achieve the purpose of time delay. The resistor R4 divides the voltage of the capacitor C1, and the voltage of the capacitor C1 gradually rises, and the voltage across the resistor R4 also gradually rises. Since the voltage across the resistor R4 is equal to the voltage at the relay winding terminal, when the voltage across the resistor R4 reaches the closing voltage value of the relay winding terminal, the relay switch terminal 211 closes. At this time, the relay switch terminal 211 closes and shorts the first current limiting unit 1. At this time, the current is not limited by the first current limiting unit 1, and the circuit is normally powered to improve the power supply efficiency. The current of the live wire L continues to charge the capacitor C1, the voltage across the capacitor C1 rises, the voltage across the resistor R4 increases, the current is limited by the resistor R5, and then flows to the zener diode D2 and the resistor R2. The zener diode D2 stabilizes the voltage. At the same time, the emitter E of the triode Q1 is stepped down by 0.6V by Vbe and the voltage is limited by the zener diode D2, so that the emitter of the triode Q1 stably outputs. When the voltages of the live wire L and the neutral wire N are reversed, that is, the voltage of the neutral wire N is higher than that of the live wire L, the diode D1 is cut off and the capacitor C1 stops charging. The capacitor C1 discharges, and its discharge current is divided by the resistor R4 and the resistor R2. At this time, the voltage across the resistor R4 is higher than 10V. The zener diode D2 stabilizes the voltage to 10V, and then uses the triode Q1 to generate a voltage drop to stabilize the voltage at the relay winding terminal 212 at 9.4V, thereby enabling the relay to work stably.

[0041] The above description is only for the embodiments of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A surge current protection circuit for a switching power supply, characterized in that: include: A first current limiting unit (1), a relay module (2), a delay module (3), an energy storage unit (4) and a voltage dividing module (5); the first current limiting unit (1) is connected in series to a live wire L, and the relay module (2) is connected in parallel to both ends of the first current limiting unit (1); the input end of the delay module (3) is connected to the output end of the first current limiting unit (1), and the output end of the delay module (3) is respectively connected to the input end of the relay module (2), the input end of the energy storage unit (4) and the input end of the voltage dividing module (5); the output end of the energy storage unit (4) is respectively connected to the output end of the voltage dividing module (5) and a neutral wire N; the voltage dividing module (5) is connected in parallel to the relay module (2), and the voltage dividing module (5) is respectively connected to the delay module (3) and the energy storage unit (4).

2. The surge current protection circuit of the switching power supply according to claim 1, characterized in that: It also comprises a linear voltage stabilizing module (6), wherein the linear voltage stabilizing module (6) is respectively connected to the relay module (2), the delay module (3), the energy storage unit (4) and the voltage dividing module (5).

3. The surge current protection circuit of the switching power supply according to claim 1, characterized in that: The relay module (2) comprises a relay (21), wherein the relay (21) has a switch end (211) and a winding end (212), wherein the switch end (211) is connected in parallel to two ends of the first current limiting unit (1), the positive electrode of the winding end (212) is connected to the output end of the delay module (3), and the negative electrode of the winding end (212) is connected to the voltage dividing module (5).

4. The surge current protection circuit of the switching power supply according to claim 1, characterized in that: The delay module (3) comprises a rectifier unit (31) and a second current limiting unit (32); one end of the rectifier unit (31) is connected to the output end of the first current limiting unit (1), and the other end is connected to the second current limiting unit (32); the other end of the second current limiting unit (32) is respectively connected to the input end of the relay module (2), the input end of the energy storage unit (4), and the input end of the voltage divider module (5).

5. The surge current protection circuit of the switching power supply according to claim 1, characterized in that: The voltage dividing module (5) comprises a first voltage dividing unit (51) and a second voltage dividing unit (52); one end of the first voltage dividing unit (51) is respectively connected to the input end of the relay module (2) and the input end of the energy storage unit (4), and the other end thereof is respectively connected to the output end of the relay module (2) and the second voltage dividing unit (52); one end of the second voltage dividing unit (52) is respectively connected to the first voltage dividing unit (51) and the output end of the relay module (2), and the other end thereof is connected to the output end of the energy storage unit (4) and a neutral line N.

6. The surge current protection circuit of the switching power supply according to claim 2, characterized in that: The linear voltage stabilizing module (6) comprises a transistor Q1, a voltage stabilizing unit (61) and a third current limiting unit (62); the emitter E of the transistor Q1 is connected to the relay module (2); the collector C of the transistor Q1 is connected to the output end of the delay module (3); the base B of the transistor Q1 is respectively connected to one end of the voltage stabilizing unit (61) and the third current limiting unit (62); the other end of the voltage stabilizing unit (61) is respectively connected to the output end of the relay module (2) and the output end of the voltage dividing module (5); and the other end of the third current limiting unit (62) is respectively connected to the collector C of the transistor Q1 and the output end of the delay module (3).

7. The surge current protection circuit of the switching power supply according to claim 3, characterized in that: The relay module (2) further comprises a freewheeling unit (22), wherein the freewheeling unit (22) is connected in parallel to the winding end (212) of the relay (21).

8. The surge current protection circuit of the switching power supply according to claim 1, characterized in that: The first current limiting unit (1) is a thermistor or a cement resistor.

9. The surge current protection circuit of the switching power supply according to claim 7, characterized in that: The freewheeling unit (22) is an ultrafast recovery diode.

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