A short circuit protection circuit structure

Abstract

The present application discloses a short-circuit protection circuit structure, including an input module; a fourth resistor and a fifth resistor; a second capacitor; a first diode and a third diode; an operational amplifier; wherein: the anode of the first diode is connected to the COMP pin of the LM5020 control chip, the cathode of the first diode is connected to one end of the fourth resistor, the other end of the fourth resistor is respectively connected to one end of the fifth resistor, one end of the second capacitor and the negative input terminal of the operational amplifier; the other end of the fifth resistor is connected to the other end of the second capacitor and is grounded; the input module is connected to the positive input terminal of the operational amplifier; the output end of the operational amplifier is connected to the cathode of the third diode, and the anode of the third diode is connected to the SS pin of the LM5020 control chip.

Description

Technical Field

[0001] The present application relates to the technical field of electronic devices, and in particular to a short-circuit protection circuit structure. Background Art

[0002] LM5020, the most commonly used control chip for flyback switching power supplies, has been copied by many domestic manufacturers in recent years.

[0003] At present, most short-circuit protection for LM5020 control chips is of the current-cutoff type, which has the following problems: when the load is overcurrent or short-circuited, the voltage of the current-cutoff circuit protection will drop, but the power consumption will increase, and the risk of circuit damage is very high. Utility Model Content

[0004] The embodiment of the present application solves the problem of high risk of overload damage of the LM5020 control chip in the prior art by providing a short-circuit protection circuit structure, thereby achieving the beneficial effect of reducing power consumption while performing short-circuit protection on the chip and ensuring normal use of the chip.

[0005] The present invention provides a short circuit protection circuit structure, which includes:

[0006] input module; a fourth resistor and a fifth resistor; a second capacitor; a first diode and a third diode; an operational amplifier; wherein:

[0007] The anode of the first diode is connected to the COMP pin of the LM5020 control chip, the cathode of the first diode is connected to one end of the fourth resistor, the other end of the fourth resistor is respectively connected to one end of the fifth resistor, one end of the second capacitor and the negative input terminal of the operational amplifier; the other end of the fifth resistor is connected to the other end of the second capacitor and is grounded;

[0008] The input module is connected to the positive input terminal of the operational amplifier;

[0009] The output end of the operational amplifier is connected to the cathode of the third diode, and the anode of the third diode is connected to the SS pin of the LM5020 control chip.

[0010] In a possible implementation, the input module includes a first resistor, a third resistor and a three-terminal reference source; wherein:

[0011] One end of the first resistor is connected to the power supply; the other end of the first resistor is connected to the first end of the reference source, and the first end of the first resistor and the second end of the reference source are also connected to one end of the third resistor; the other end of the third resistor is connected to the positive input terminal of the operational amplifier;

[0012] The third terminal of the reference source is grounded.

[0013] In a possible implementation, a hysteresis module is further included, and the hysteresis module includes a second resistor and a second diode; wherein:

[0014] The anode of the second diode is connected in series with the second resistor and connected to the positive input terminal of the operational amplifier;

[0015] The cathode of the second diode is connected to the cathode of the third diode.

[0016] In one possible implementation,

[0017] The negative power supply electrode of the operational amplifier is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the power supply; the negative power supply electrode of the operational amplifier is also grounded.

[0018] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0019] The short-circuit protection circuit structure provided by the embodiment of the present application, wherein the COMP pin voltage of the LM5020 control chip is charged to the second capacitor through the first diode through the fourth resistor and the fifth resistor voltage division, and enters the negative input terminal of the operational amplifier; when the LM5020 is working normally, the negative terminal voltage entering the operational amplifier is lower than the positive terminal voltage of the operational amplifier, the output of the operational amplifier is high level, the output voltage is supported by the third diode, and this protection circuit structure does not work; when there is an overcurrent, the voltage of the COMP pin increases, and the input negative terminal voltage of the operational amplifier is increased at the same time. At this time, the input negative terminal voltage of the operational amplifier is higher than the input positive terminal voltage of the operational amplifier, and the output of the operational amplifier is low level. The SS pin of the chip LM5020 is pulled down through the third diode, and the chip enters a restart state. Due to the presence of the second capacitor, the input negative terminal voltage of the operational amplifier drops very slowly. When the input negative terminal voltage of the operational amplifier is lower than the input positive terminal voltage of the operational amplifier again, the main power circuit resumes normal operation and detects whether there is an overcurrent. If there is an overcurrent, this process is repeated to achieve the short-circuit protection function. Through the above technical scheme, the embodiment of the present application solves the problem in the prior art that short-circuit protection is performed on the LM5020 control chip while the power consumption increases sharply, causing the chip to be overloaded and damaged, and achieves the technical effect of being able to cut off the chip COMP pin voltage multiple times during short-circuit protection and gradually start slowly to reduce power consumption and avoid overload. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 A schematic diagram of the short-circuit protection circuit structure provided in an embodiment of the present application.

[0022] Figure symbols: D1-first diode; D2-second diode; D3-third diode; R1-first resistor; R2-second resistor; R3-third resistor; R4-fourth resistor; R5-fifth resistor; C1-first capacitor; C2-second capacitor; IC1-operational amplifier; IC2-three-terminal reference source; VCC-power supply. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present utility model, not all of the embodiments. Based on the embodiments in the present utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present utility model.

[0024] In the description of the embodiments of the present application, it should be noted that the orientation or positional relationship indicated by the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present utility model. The terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0025] The present application embodiment provides a short circuit protection circuit structure, such as Figure 1 As shown, it includes

[0026] Input module; fourth resistor R4 and fifth resistor R5; second capacitor C2; first diode D1 and third diode D3; operational amplifier IC1; wherein:

[0027] The anode of the first diode D1 is connected to the COMP pin of the LM5020 control chip, the cathode of the first diode D1 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is respectively connected to one end of the fifth resistor R5, one end of the second capacitor C2 and the negative input terminal of the operational amplifier IC1; the other end of the fifth resistor R5 is connected to the other end of the second capacitor C2 and is grounded;

[0028] The input module is connected to the positive input terminal of the operational amplifier IC1;

[0029] The output end of the operational amplifier IC1 is connected to the cathode of the third diode D3 , and the anode of the third diode D3 is connected to the SS pin of the LM5020 control chip.

[0030] The short-circuit protection circuit structure provided in this embodiment, wherein the voltage of the COMP pin of the LM5020 control chip is divided by the first diode D1 through the fourth resistor R4 and the fifth resistor R5 to charge the second capacitor C2, and enters the negative input terminal of the operational amplifier IC1; when the LM5020 works normally, the voltage entering the negative terminal of the operational amplifier IC1 is lower than the positive terminal voltage of the operational amplifier IC1, the output of the operational amplifier IC1 is high level, the output voltage is supported by the third diode D3, and this protection circuit structure does not work; when overcurrent occurs, the voltage of the COMP pin increases, and at the same time, the input negative terminal of the operational amplifier IC1 is The terminal voltage rises. At this time, the input negative terminal voltage of the operational amplifier IC1 is higher than the input positive terminal voltage of the operational amplifier IC1. The output of the operational amplifier IC1 is low level. The SS pin of the chip LM5020 is pulled down through the third diode D3, and the chip enters the restart state. Due to the existence of the second capacitor C2, the input negative terminal voltage of the operational amplifier IC1 drops very slowly. When the input negative terminal voltage of the operational amplifier IC1 is lower than the input positive terminal voltage of the operational amplifier IC1 again, the main power circuit resumes normal operation and detects whether it is overcurrent. If it is overcurrent, this process is repeated to achieve the short-circuit protection function.

[0031] In a preferred implementation of this embodiment, the input module includes a first resistor R1, a third resistor R3 and a three-terminal reference source IC2; wherein:

[0032] One end of the first resistor R1 is connected to the power supply VCC; the other end of the first resistor R1 is connected to the first end of the reference source, and the end of the first resistor R1 is also connected to the second end of the three-terminal reference source IC2 and one end of the third resistor R3; the other end of the third resistor R3 is connected to the positive input end of the operational amplifier IC1;

[0033] The third terminal of the reference source is grounded.

[0034] In a preferred implementation of this embodiment, a hysteresis module is further included, and the hysteresis module includes a second resistor R2 and a second diode D2; wherein:

[0035] The anode of the second diode D2 is connected in series with the second resistor R2 and connected to the positive input terminal of the operational amplifier IC1;

[0036] The cathode of the second diode D2 is connected to the cathode of the third diode D3.

[0037] Specifically, the hysteresis module can further increase the pull-down time of the SS pin of the LM5020 control chip and delay the voltage drop time of the negative terminal of the operational amplifier IC1, thereby further avoiding increased power consumption and improving protection performance.

[0038] In a preferred embodiment of this embodiment,

[0039] The negative power supply electrode of the operational amplifier IC1 is connected to one end of the first capacitor C1, and the other end of the first capacitor C1 is connected to the power supply VCC; the negative power supply electrode of the operational amplifier IC1 is also grounded.

[0040] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other. Each embodiment focuses on the differences from other embodiments.

[0041] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit the present application. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some or all of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the present application.

Claims

1. A short circuit protection circuit structure, used for LM5020 control chip, characterized in that: include input module; a fourth resistor and a fifth resistor; a second capacitor; a first diode and a third diode; an operational amplifier; The input module includes a first resistor, a third resistor and a three-terminal reference source; One end of the first resistor is connected to the power supply; the other end of the first resistor is connected to the first end of the reference source, and the first end of the first resistor and the second end of the reference source are also connected to one end of the third resistor; the other end of the third resistor is connected to the positive input end of the operational amplifier; the third end of the reference source is grounded; in: The anode of the first diode is connected to the COMP pin of the LM5020 control chip, the cathode of the first diode is connected to one end of the fourth resistor, the other end of the fourth resistor is respectively connected to one end of the fifth resistor, one end of the second capacitor and the negative input terminal of the operational amplifier; the other end of the fifth resistor is connected to the other end of the second capacitor and is grounded; The input module is connected to the positive input terminal of the operational amplifier; The output end of the operational amplifier is connected to the cathode of the third diode, and the anode of the third diode is connected to the SS pin of the LM5020 control chip.

2. A short circuit protection circuit structure according to claim 1, characterized in that: It also includes a hysteresis module, which includes a second resistor and a second diode; wherein: The anode of the second diode is connected in series with the second resistor and connected to the positive input terminal of the operational amplifier; The cathode of the second diode is connected to the cathode of the third diode.

3. A short circuit protection circuit structure according to claim 1, characterized in that: The negative power supply electrode of the operational amplifier is connected to one end of the first capacitor, and the other end of the first capacitor is connected to the power supply; the negative power supply electrode of the operational amplifier is also grounded.

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