Protection circuit and switching power supply

Abstract

The utility model discloses a protection circuit and a switching power supply. The protection circuit is applied to the switching power supply, the switching power supply comprises a main loop relay, and the main loop relay comprises a voltage reduction module of which the input end is connected with a direct-current bus of the switching power supply and which is used for reducing the voltage of the direct-current bus and outputting the voltage to a variable resistance module; the input end of the variable resistance module is respectively connected with the voltage reduction module and the direct current bus, the output end of the variable resistance module is connected with the input end of a coil of the main loop relay, and the control end of the variable resistance module is connected with a control chip; the variable resistance module is used for reducing the voltage of the input end of the coil of the main loop relay by changing the resistance value of the variable resistance module; and the control chip is used for outputting a control signal so as to change the resistance value of the variable resistance module. According to the utility model, the heating of the main loop relay can be reduced, the service life of the main loop relay is prolonged, and the reliability of the switching power supply is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic circuits, and more specifically, to a protection circuit and a switching power supply. Background Art

[0002] Currently, for the inrush current of a switching power supply, a bypass circuit is generally used in parallel with the main circuit relay to suppress it. And the output voltage of the switching power supply is used to supply power to the main circuit relay. If the main circuit relay is in a high pull-in voltage for a long time, it will cause the main circuit relay to heat up, which will have an adverse effect on the service life of the main circuit relay and affect the reliability of the entire switching power supply.

[0003] Regarding the problem that the main circuit relay of the switching power supply in the prior art is in a high pull-in voltage for a long time, which will cause the main circuit relay to heat up, have an adverse effect on the service life of the main circuit relay, and affect the reliability of the entire switching power supply, no effective solution has been proposed yet. Summary of the Utility Model

[0004] An embodiment of the utility model provides a protection circuit and a switching power supply to solve the problem that the main circuit relay of the switching power supply in the prior art is in a high pull-in voltage for a long time, which will cause the main circuit relay to heat up, have an adverse effect on the service life of the main circuit relay, and affect the reliability of the entire switching power supply.

[0005] To solve the above technical problems, the utility model provides a protection circuit applied to a switching power supply. The switching power supply includes a main circuit relay. The protection circuit includes:

[0006] A buck module, whose input terminal is connected to the DC bus of the switching power supply, is used to reduce the DC bus voltage and then output it to the variable resistor module;

[0007] The variable resistor module, whose input terminals are respectively connected to the buck module and the DC bus, whose output terminal is connected to the input terminal of the coil of the main circuit relay, and whose control terminal is connected to a control chip; the variable resistor module is used to reduce the voltage at the input terminal of the coil of the main circuit relay by changing its own resistance value;

[0008] The control chip is used to output a control signal to change the resistance value of the variable resistor module.

[0009] Further, the first terminal of the input terminal of the buck module is connected to the positive connection terminal of the DC bus of the switching power supply, and the second terminal of the input terminal of the buck module is connected to the negative connection terminal of the DC bus;

[0010] The first terminal of the input end of the variable resistor module is connected to the first terminal of the output end of the buck module, the second terminal of the input end of the variable resistor module is connected to the second terminal of the output end of the buck module, and the third terminal of the input end of the variable resistor module is connected to the negative connection terminal of the DC bus through a fixed-value resistor.

[0011] Further, the variable resistor module includes:

[0012] A first resistor, whose first end is connected to the first terminal of the output end of the buck module, and whose second end is connected to the second terminal of the output end of the buck module;

[0013] An optocoupler, whose first terminal on the input side is connected to the control chip, whose second terminal on the input side is grounded, and whose first terminal on the output side is connected to the first end of the first resistor;

[0014] A second resistor, whose first end is connected to the second terminal of the output side of the optocoupler, and whose second end is connected to the second end of the first resistor.

[0015] Further, the variable resistor module includes:

[0016] A photoresistor, whose first end is connected to the first terminal of the output end of the buck module, and whose second end is connected to the second terminal of the output end of the buck module;

[0017] A light-emitting diode, arranged within a preset distance around the photoresistor, the anode of the light-emitting diode is connected to the control chip, and the cathode is grounded.

[0018] The present utility model also provides a switching power supply, including the above protection circuit.

[0019] Applying the technical solution of the present utility model, after the main circuit relay is reliably energized, by outputting a control signal through the control chip to change the resistance value of the variable resistor module, and then reducing the input voltage of the coil of the main circuit relay, it can be realized that under the state of ensuring the energization of the main circuit relay, the input voltage of the coil of the main circuit relay is minimized, effectively reducing the loss of the main circuit relay, reducing the heat generation of the main circuit relay, prolonging the service life of the main circuit relay, and improving the reliability of the switching power supply. Description of the Drawings

[0020] Figure 1 is the circuit structure diagram of the existing switching power supply;

[0021] Figure 2 is the structural block diagram of the protection circuit according to the embodiment of the present utility model;

[0022] Figure 3 is the structure diagram of the protection circuit according to another embodiment of the present utility model;

[0023] Figure 4 Structural diagram of a protection circuit according to another embodiment of the present utility model;

[0024] Figure 5 Circuit structural diagram of a switching power supply according to an embodiment of the present utility model; Detailed implementation manners

[0025] In order to make the objectives, technical solutions and advantages of the present utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings. Apparently, the described embodiments are only a part rather than all of the embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0026] The terms used in the embodiments of the present utility model are only for the purpose of describing specific embodiments and are not intended to limit the present utility model. The singular forms "a", "the" and "said" used in the embodiments of the present utility model and the appended claims are also intended to include the plural forms unless the context clearly dictates otherwise. "Plural" generally includes at least two.

[0027] It should be understood that the term "and / or" used herein is only a kind of association relationship describing associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " herein generally represents an "or" relationship between the associated objects before and after.

[0028] It should be understood that although the terms first, second, etc. may be used to describe resistors in the embodiments of the present utility model, these resistors should not be limited to these terms. These terms are only used to distinguish different resistors. For example, without departing from the scope of the embodiments of the present utility model, the first resistor can also be called the second resistor, and similarly, the second resistor can also be called the first resistor.

[0029] Depending on the context, the words "if", "when" as used herein can be interpreted as "when...", "when...", "in response to determining" or "in response to detecting". Similarly, depending on the context, the phrase "if determined" or "if detecting (stated condition or event)" can be interpreted as "when determined", "in response to determining", "when detecting (stated condition or event)", or "in response to detecting (stated condition or event)".

[0030] It should also be noted that the term "including", "comprising" or any other variant thereof is intended to cover non-exclusive inclusion, such that a commodity or device including a series of elements not only includes those elements but also includes other elements not explicitly listed, or elements inherent to such commodity or device. Without further limitation, an element defined by the statement "including one..." does not exclude the presence of additional identical elements in the commodity or device including said element.

[0031] The optional embodiments of the present utility model will be described in detail below with reference to the accompanying drawings.

[0032] Embodiment 1

[0033] Figure 1 is a circuit structure diagram of an existing switching power supply. When the input side of the switching power supply takes power from a single-phase 220V, the voltage after the rectifier bridge will pass through an electrolytic capacitor, and at this time, there will be a relatively large inrush current. This current being too large may damage the switching power supply or even cause harmonic interference to the power grid, as Figure 1 shown. For the inrush current of the switching power supply, generally, a bypass circuit is used in parallel with the main circuit relay K1 to suppress the inrush current. Specifically, resistors R02, R03, and R04 are added after the rectifier bridge. The above three bypass resistors can effectively suppress the relatively large inrush current generated when charging the electrolytic capacitor during startup. Since the above bypass resistors consume power, after the main circuit relay coil is energized, the above three resistors will be short-circuited, successfully solving the problem of the reduction in the efficiency of the switching power supply caused by the resistors. However, at the same time, using the output-side voltage of the switching power supply to supply power to the main circuit relay will also cause the main circuit relay to have an excessively high temperature and reduce its lifespan, and affect the reliability of the entire switching power supply.

[0034] Regarding the problem in the prior art that the main circuit relay of the switching power supply is in a relatively high pulling-in voltage for a long time, which will cause the main circuit relay to heat up, have an adverse effect on the service life of the main circuit relay, and affect the reliability of the entire switching power supply, this embodiment provides a protection circuit applied to the switching power supply. The switching power supply includes a main circuit relay. Figure 2 is a structural block diagram of the protection circuit according to the embodiment of the present utility model. As Figure 2 shown, this protection circuit includes:

[0035] Step-down module 1, whose input terminal is connected to the DC bus of the switching power supply, is used to reduce the DC bus voltage and then output it to variable resistor module 2.

[0036] Variable resistor module 2, whose input terminals are respectively connected to step-down module 1 and the DC bus of the switching power supply. The output terminal RLY_Voltage of variable resistor module 2 is connected to the Figure 1The input terminal RLY_P of the coil of the main circuit relay K1 in it is used to achieve the input voltage to the coil of the main circuit relay, and then control the main circuit relay to close. The control terminal of the variable resistance module 2 is connected to the control chip; the variable resistance module 2 is used to reduce the voltage at the input terminal of the coil of the main circuit relay K1 by changing its own resistance value. When the main circuit relay switches from the off state to the on state, a relatively large voltage is output to the coil of the main circuit relay to control the main circuit relay K1 to successfully complete the state switch; after the main circuit relay is reliably closed, by changing the resistance value of the variable resistance module 2, the input voltage of the coil of the main circuit relay is reduced.

[0037] The control chip 3 is used to output a control signal to change the resistance value of the variable resistance module. Specifically, in implementation, by changing the circuit connection relationship of the variable resistance module or the environment where the variable resistor in the variable resistance module is located, the resistance value of the variable resistance module is changed, and then the input voltage of the coil of the main circuit relay is reduced. When the main circuit relay switches from the off state to the on state, a relatively large voltage is output to the coil of the main circuit relay to control the main circuit relay K1 to successfully complete the state switch; after the main circuit relay is reliably closed, by changing the resistance value of the variable resistance module 2, the input voltage of the coil of the main circuit relay is reduced.

[0038] For the protection circuit of this embodiment, after the main circuit relay K1 is reliably closed, the control chip 3 outputs a control signal to change the resistance value of the variable resistance module 2, and then reduces the input voltage of the coil of the main circuit relay K1, which can achieve controlling the lowest input voltage of the coil of the main circuit relay K1 while ensuring the closed state of the main circuit relay K1, effectively reducing the loss of the main circuit relay K1, reducing the heat generation of the main circuit relay K1, prolonging the service life of the main circuit relay K1, and improving the reliability of the switching power supply.

[0039] Figure 3 As shown in the structural diagram of the protection circuit according to another embodiment of the present invention, Figure 3 As shown, the first terminal of the input end of the buck module 1 is connected to the positive connection terminal DC+ of the DC bus of the switching power supply, and the second terminal of the input end of the buck module is connected to the negative connection terminal DC- of the DC bus; the first terminal of the input end of the variable resistance module 2 is connected to the first terminal of the output end of the buck module, the second terminal of the input end of the variable resistance module 2 is connected to the second terminal of the output end of the buck module, and the third terminal of the input end of the variable resistance module 2 is connected to the negative connection terminal DC- of the DC bus through a fixed value resistor R0.

[0040] As described above, the resistance value of the variable resistor module can be adjusted by changing the circuit connection relationship of the variable resistor module. To achieve this purpose, the above-mentioned variable resistor module 2 includes: a first resistor R1, whose first end is connected to the first terminal of the output end of the buck module 1, and whose second end is connected to the second terminal of the output end of the buck module 1; an optocoupler OC, whose first terminal on the input side is connected to the control chip 3, whose second terminal on the input side is grounded, and whose first terminal on the output side is connected to the first end of the first resistor R1. A second resistor R2, whose first end is connected to the second terminal of the output side of the optocoupler OC, and whose second end is connected to the second end of the first resistor R1.

[0041] In the protection circuit of this embodiment, the core protected device is the main circuit relay. When single-phase 220V AC power is connected to the input side of the switching power supply and there is an output, the switching power supply outputs a pull-in voltage RLY_Voltage through the buck module 1. At this time, the main circuit relay is energized, and the control chip does not output a control signal at this time. After a time t1, the control chip outputs a control signal (such as a high level). At this time, the light-emitting diode on the input side of the optocoupler OC conducts, and then the triode on the output side of the optocoupler OC conducts, and the branch where the second resistor R2 is located conducts. The second resistor R2 is in parallel with the first resistor R1, and the circuit mode changes, thereby changing the output voltage of RLY_Voltage to keep it at the holding voltage value of the main circuit relay. Specifically, before the triode on the output side of the optocoupler OC conducts: After the triode on the output side of the optocoupler OC conducts: Where U' is the voltage at the point between the first resistor R1 and the second terminal of the output end of the buck module. Because the total resistance decreases after paralleling R2, that is, R1 > R1 / / R2, So RLY_Voltage decreases after the triode on the output side of the optocoupler OC conducts.

[0042] In summary, when the light-emitting diode on the input side of the optocoupler OC is not conducting, the variable resistor module 2 outputs a pull-in voltage at the output terminal RLY_Voltage. At this time, the pull-in voltage is smaller than the power supply on the output side of the switching power supply because the voltage on the output side of the switching power supply passes through the buck module 1, ensuring that the pull-in voltage does not exceed the voltage on the output side of the switching power supply. After the main circuit relay K1 has been pulled in for a duration t1, the control chip 3 outputs a control signal to enable the light-emitting diode on the input side of the optocoupler OC to conduct, and then the triode on the output side of the optocoupler OC conducts, causing the output of RLY_Voltage to maintain a voltage, that is, the preset minimum voltage to maintain the pull-in of the main circuit relay K1. At this time, the holding voltage is much smaller than the pull-in voltage, but it can still ensure that the main circuit relay remains pulled in. This achieves an extension of the service life of the main circuit relay after voltage reduction and also ensures the safety of the switching power supply.

[0043] The protection circuit principle of this embodiment is simple and the cost is low, which plays a positive role in extending the life of the main circuit relay. Utilizing the characteristics of the pull-in voltage and holding voltage of the main circuit relay can ensure the long-term continuous use of the main circuit relay, and at the same time improve the overall reliability and safety of the switching power supply.

[0044] Embodiment 2

[0045] According to the above description, it is also possible to change the resistance value of the variable resistor module by changing the environment in which the variable resistor in the variable resistor module is located, thereby changing the voltage input to the coil of the main circuit relay. And according to the analysis of the above embodiment, the smaller the resistance value of the variable resistor module, the smaller the voltage input to the coil of the main circuit relay. Therefore, in order to achieve changing the resistance value of the variable resistor module by changing the environment in which the variable resistor in the variable resistor module is located, this embodiment provides another protection circuit. Figure 4 For the structural diagram of the protection circuit according to another embodiment of the present invention, as Figure 4 shown, the variable resistor module 20 of this protection circuit includes: a photoresistor RL, whose first end is connected to the first terminal of the output terminal of the buck module, and whose second end is connected to the second terminal of the output terminal of the buck module; a light-emitting diode D, arranged within a preset distance around the photoresistor RL, with the anode of the light-emitting diode D connected to the control chip and the cathode grounded.

[0046] When the single-phase 220V AC power is connected to the input side of the switching power supply and there is an output, the switching power supply outputs the pull-in voltage RLY_Voltage through the buck module 1. At this time, the main circuit relay is energized, and the control chip does not output a control signal at this time. After a duration of t1, the control chip outputs a control signal (such as a high level), controlling the light-emitting diode D to conduct. According to the characteristics of the photoresistor, the resistance value decreases as the received light intensity becomes stronger. After the light-emitting diode D conducts, the resistance value of the photoresistor RL becomes smaller, thereby making the output voltage of RLY_Voltage smaller, and finally maintaining at the holding voltage value of the main circuit relay.

[0047] Embodiment 3

[0048] This embodiment provides a switching power supply. Figure 5 For the circuit structure diagram of the switching power supply according to the embodiment of the present invention, as Figure 5 shown, the switching power supply includes the protection circuit of the above embodiment, which is used to achieve the lowest voltage input to the coil of the main circuit relay K1 while ensuring the pulling-in state of the main circuit relay K1, effectively reducing the loss of the main circuit relay K1, reducing the heat generation of the main circuit relay K1, extending the service life of the main circuit relay K1, and improving the reliability of the switching power supply.

[0049] The circuit embodiments described above are merely illustrative. The modules described as separate components may or may not be physically separated, and the components shown as modules may or may not be physical modules, that is, they may be located in one place or distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. However, such modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A protection circuit, applied to a switching power supply, the switching power supply comprising a main circuit relay, characterized in that: The protection circuit comprises: A step-down module, whose input end is connected to the DC bus of the switching power supply, is used to reduce the DC bus voltage and then output it to the variable resistance module; The variable resistor module has an input end connected to the step-down module and the DC bus, an output end connected to the input end of the coil of the main circuit relay, and a control end connected to the control chip; the variable resistor module is used to reduce the voltage at the input end of the coil of the main circuit relay by changing its own resistance value; The control chip is used to output a control signal to change the resistance value of the variable resistance module.

2. The protection circuit according to claim 1, characterized in that: A first terminal of the input end of the step-down module is connected to a positive terminal of a DC bus of the switching power supply, and a second terminal of the input end of the step-down module is connected to a negative terminal of the DC bus; The first terminal of the input end of the variable resistor module is connected to the first terminal of the output end of the buck module, the second terminal of the input end of the variable resistor module is connected to the second terminal of the output end of the buck module, and the third terminal of the input end of the variable resistor module is connected to the negative terminal of the DC bus through a fixed resistor.

3. The protection circuit according to claim 2, characterized in that: The variable resistance module comprises: A first resistor, a first end of which is connected to a first terminal of the output end of the step-down module, and a second end of which is connected to a second terminal of the output end of the step-down module; a photoelectric coupler, wherein a first terminal on an input side is connected to the control chip, a second terminal on an input side is grounded, and a first terminal on an output side is connected to a first end of the first resistor; A second resistor has a first end connected to a second terminal at the output side of the photocoupler, and a second end connected to the second end of the first resistor.

4. The protection circuit according to claim 2, characterized in that: The variable resistance module comprises: A photoresistor, a first end of which is connected to a first terminal of the output end of the step-down module, and a second end of which is connected to a second terminal of the output end of the step-down module; A light emitting diode is arranged within a preset distance around the photoresistor, wherein an anode of the light emitting diode is connected to the control chip and a cathode is grounded.

5. A switching power supply, characterized in that: A protection circuit comprising the protection circuit described in any one of claims 1 to 4.

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