Protection circuit and fault detection circuit

Abstract

The utility model discloses a protection circuit and a fault detection circuit. The protection circuit comprises a Schottky diode, an R6, an R7, a standard hysteresis comparator and an I / O port of a control chip. The VCC is connected in series with the R6 and the R7 and then is grounded, an anode of the Schottky diode is connected in parallel at a point A between the R6 and the R7, and a cathode of the Schottky diode is respectively connected to an output end of the standard hysteresis comparator and an IO port of the control chip. Various protections can be realized by constructing a modularized hardware protection circuit and matching the modularized hardware protection circuit with a simple program, so that the system design is more simplified and convenient on the premise that the reliability of a product is not sacrificed.

Description

Technical Field

[0001] The utility model relates to a power supply protection and fault detection technology, in particular to a protection circuit and a fault detection circuit. Background Art

[0002] Power supplies have many applications in test systems, electronic product development, and industrial fields. As a qualified power supply, it must not only ensure stability and reliability under normal working conditions, but also ensure fault detection, protection, alarm and other functions under abnormal conditions. In this way, during the application process, it can not only ensure the safety of the experimenters, but also protect the power supply side and the load side from damage. Therefore, protection and fault detection circuits are very important parts in power supply products. The protection of traditional analog power supplies is generally integrated inside the IC, and only needs to be designed according to the chip manual. But sometimes a separate design is also required, which can reduce costs, and building a separate protection circuit is more flexible and targeted, which can better meet your design goals.

[0003] In the prior art, there are several ways to start the ACDC switching power supply:

[0004] Method 1: Traditional analog power supplies use fixed IC pin functions to implement overvoltage, overcurrent, and overtemperature protection. Overvoltage protection is generally implemented through TL431 and type 2 or type 3 compensation networks, and then fed back to the chip through optocouplers. Overcurrent protection is fed back to the chip through sampling resistors and LEBs. Overtemperature protection can be implemented by connecting NTC resistors.

[0005] Method 2: Implemented by building a separate protection circuit. This method is generally implemented in a variety of ways. Based on different usage scenarios and cost considerations, a suitable circuit can be built to achieve the corresponding protection function.

[0006] Disadvantages of prior art 1:

[0007] Regarding method 1: The circuit is relatively simple and debugging is simple, but the cost is relatively high and lacks flexibility. When multiple protections are involved, more peripheral circuits are required, making it complicated. Sometimes it is even necessary to build a separate protection circuit (some ICs may lack some protection functions), and some protection functions may not be used, resulting in a waste of resources.

[0008] Regarding method 2: This method has great advantages when designing a small number of protection circuits, but when multiple protection circuits need to be designed, the design complexity is relatively large. Since the structure is not unified enough, relatively more components are required, which increases the design complexity. During the debugging process, it may not be known which protection circuit is working, and it is necessary to search one by one, resulting in low work efficiency.

[0009] In view of this, the present utility model is proposed. Utility Model Content

[0010] The purpose of the utility model is to provide a protection circuit and a fault detection circuit to solve the above technical problems existing in the prior art.

[0011] The purpose of this utility model is achieved through the following technical solutions:

[0012] The protection circuit and fault detection circuit of the utility model include a Schottky diode, R6, R7, a standard hysteresis comparator and an I / O port of a control chip;

[0013] VCC is connected in series with R6 and R7 and then grounded. The anode of the Schottky diode is connected in parallel at point A between R6 and R7. The cathode of the Schottky diode is connected to the output end of the standard hysteresis comparator and the I\O port of the control chip respectively.

[0014] Compared with the prior art, the protection circuit and fault detection circuit provided by the utility model are applicable to the modular design of various protections, making the system design simpler and more flexible. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 A schematic diagram of the protection circuit and fault detection circuit structure provided by the embodiment of the utility model;

[0016] Figure 2 This is a schematic diagram of a standard hysteresis comparator circuit in an embodiment of the utility model;

[0017] Figure 2a , Figure 2b They are Figure 2 Schematic diagram of the local equivalent circuit of the two states. DETAILED DESCRIPTION

[0018] The following is a clear and complete description of the technical solutions in the embodiments of the utility model in conjunction with the drawings in the embodiments of the utility model; it is obvious that the described embodiments are only part of the embodiments of the utility model, not all of the embodiments, which does not constitute a limitation of the utility model. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of the utility model.

[0019] First, the terms that may be used in this article are explained as follows:

[0020] The term “and / or” means that either or both of them can be realized at the same time. For example, X and / or Y means both “X” or “Y” and “X and Y”.

[0021] The terms "include", "comprises", "contains", "has" or other descriptions with similar semantics should be interpreted as non-exclusive inclusion. For example, including certain technical feature elements (such as raw materials, components, ingredients, carriers, dosage forms, materials, dimensions, parts, components, mechanisms, devices, steps, procedures, methods, reaction conditions, processing conditions, parameters, algorithms, signals, data, products or products, etc.) should be interpreted as including not only certain technical feature elements explicitly listed, but also other technical feature elements known in the art that are not explicitly listed.

[0022] The term "consisting of..." means excluding any technical feature elements not explicitly listed. If this term is used in a claim, it will make the claim closed, so that it does not contain technical feature elements other than the technical feature elements explicitly listed, except for the conventional impurities related to them. If this term only appears in a clause of a claim, it only limits the elements explicitly listed in the clause, and the elements recorded in other clauses are not excluded from the overall claim.

[0023] Unless otherwise specified or limited, the terms "installed", "connected", "connected", "fixed" and the like 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 a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this article can be understood according to specific circumstances.

[0024] The contents not described in detail in the examples of the present utility model belong to the prior art known to professionals in the field. If no specific conditions are specified in the examples of the present utility model, the conditions are carried out according to the conventional conditions in the field or the conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments used in the examples of the present utility model are not specified, they are all conventional products that can be purchased commercially.

[0025] The protection circuit and fault detection circuit of the utility model include a Schottky diode, R6, R7, a standard hysteresis comparator and an I / O port of a control chip;

[0026] VCC is connected in series with R6 and R7 and then grounded. The anode of the Schottky diode is connected in parallel at point A between R6 and R7. The cathode of the Schottky diode is connected to the output end of the standard hysteresis comparator and the I\O port of the control chip respectively.

[0027] The standard hysteresis comparator comprises:

[0028] Vi is the voltage to be protected, which is connected in series with R4 to the negative input of the comparator LM393, and connected in parallel with R5 and C2 to SAGND;

[0029] Vo is the output voltage of the comparator LM393, which is connected to the cathode of the Schottky diode;

[0030] VCC is connected to the positive input terminal of the comparator LM393 after being in series with R1, and is connected to SAGND after being in parallel with R2 and C3;

[0031] The positive input terminal of the comparator LM393 is connected to the output terminal of the comparator LM393 after being in series with R3;

[0032] VCC is connected to the output terminal of the comparator LM393 after being in series with Rpu.

[0033] VH is the threshold voltage when Vo is at a high level, and VL is the threshold voltage when Vo is at a low level;

[0034] When Vi < VL, Vo switches to Vcc, and Vcc is grounded after being in parallel with R1 and R3 and then in series with R2.

[0035] When Vi > VH, Vo switches to Vee, and after VCC is in series with R1, it is then grounded through the parallel connection of R2 and R3.

[0036] The Schottky diode includes multiple pairs of parallel-connected diodes.

[0037] In summary, the protection circuit and the fault detection circuit of the embodiment of the present invention can achieve multiple protections by constructing a modular hardware protection circuit and matching it with a simple program. Without sacrificing the reliability of the product, the system design has the characteristics of being more simplified and convenient.

[0038] In order to more clearly show the technical solutions provided by the present invention and the technical effects generated, the following will describe in detail the embodiments provided by the present invention with specific examples.

[0039] Embodiment 1

[0040] As Figure 1 shown:

[0041] This circuit mainly consists of a Schottky diode, R6, R7, a standard hysteresis comparator, and the I / O port of a control chip (MCU).

[0042] VCC is grounded after being in series with R6 and R7. At point A between R6 and R7, the anodes of Schottky diodes (such as D1, D2, D3, D4, D5, D6, D7, D8, D9, D10, etc.) are connected in parallel, and the cathodes of the diodes are respectively connected to the Vo shown in the standard hysteresis comparator Figure 2 and the I / O port of the control chip.

[0043] This circuit is mainly used when the circuit generates overvoltage or overcurrent protection. The standard hysteresis comparator pulls down the cathode level of the Schottky diode by comparing with the reference voltage, and then pulls down the anode level. The inverse logic is realized by the MOS tube, and the control of the enable end of the driver chip can be realized. Since the circuit is relatively simple, its response speed can reach the microsecond level, which can realize the protection of most systems. Moreover, since it belongs to hardware protection, as long as there are no problems with materials, welding and other links, its reliability and stability are also guaranteed. In addition, since the output of the hysteresis comparator has the characteristic of recovery, it is necessary to achieve locking through simple software.

[0044] The cathode of the Schottky diode is connected to the I / O port of the MCU. The MCU can determine which circuit is protected by polling. In addition, it can also shut down the MCU driver by entering an interrupt (just add two more diodes, connect the anode and cathode of the diode to the I / O port. When the software is protected, the MCU driver is turned off and the driver chip can also be disabled). In addition, in the face of some environments with complex electromagnetic interference, we need to add some capacitors to the output of the hysteresis comparator or the cathode and anode of the Schottky diode to filter out some high-frequency electromagnetic interference and further improve the stability of the circuit. When there is a high voltage that needs to be protected, the protection circuit can be protected by optical coupling isolation to make it more reliable.

[0045] When the system is powered on, the voltage at point A is high, and the circuit is in normal working condition. When there are abnormal conditions such as overvoltage or overcurrent, the voltage at point A is pulled down to achieve protection function.

[0046] Figure 1 The parameter design steps are as follows:

[0047] Step 1: Create Figure 1 In the circuit shown, connect the positive and negative poles of the diode to the relevant positions of the circuit.

[0048] Step 2: Set the overvoltage and overcurrent protection points and the corresponding hysteresis. Here you can set the hysteresis comparator resistance and reference voltage as needed. For specific steps, see Figure 2 design steps.

[0049] Step 3: Set the voltage value at point A (according to your own needs), and there is a relationship: VA = VCC * R7 / R6 + R7. When there are multiple Schottky diodes, using a multimeter to directly measure the impedance value can debug the circuit parameters more quickly.

[0050] Step 4: Write interrupt program and polling program, etc.

[0051] Step 5: Perform comprehensive debugging of the circuit to achieve dual protection of software and hardware. This will prevent the circuit from being easily damaged and make subsequent debugging and testing more convenient.

[0052] As Figure 2 and its equivalent circuit Figure 2a , Figure 2b shown below:

[0053] Vi is the voltage quantity to be protected, and Vo is connected to Figure 1 the cathode of the diode. The two equivalent circuits Figure 2a , 2b are for facilitating the calculation of Figure 2 parameters.

[0054] VCC is connected in series with R1 to the 5th pin of the comparator LM393, and then the parallel connection of R2 and C3 is connected to SAGND. The 5th pin of the comparator LM393 is connected in series with R3 to the 7th pin of the comparator LM393. VCC is connected in series with Rpu to the 7th pin of the comparator LM393. Vi is connected in series with R4 to the 6th pin of the comparator LM393, and then the parallel connection of R5 and C2 is connected to SAGND.

[0055] Figure 2 The parameter design steps are as follows:

[0056] Step 1: Select R1.

[0057] Step 2: Solve for R2 according to the required threshold voltage.

[0058]

[0059] Step 3: Derive the calculation formula for VH (this is the threshold voltage when Vo is at a high level). For simplicity, assume that when Vi < VL, Vo switches to Vcc. When this occurs, R1 and R3 are in parallel. As Figure 2a shown below, Vcc is in parallel with R1, R3 and then in series with R2 to ground.

[0060]

[0061] Step 5: Derive the calculation formula for VL (this is the threshold voltage when Vo is at a low level). For simplicity, assume that when Vi > VH, Vo switches to Vee. When this occurs, R2 and R3 are in parallel. As Figure 2b shown below, Vcc is in series with R1, and then in series with the parallel connection of R2 and R3 to ground.

[0062]

[0063] Step 6: Derive the calculation formula for VHYS .

[0064]

[0065] Step 7: Solve for R3.

[0066]

[0067] Step 8: Verify the calculated value.

[0068]

[0069]

[0070] V HYS =V H -V L

[0071] Beneficial effects brought by the technical solution of the present invention:

[0072] 1. Simple circuit, low cost and space saving;

[0073] 2. No need for complicated programming, improving development efficiency;

[0074] 3. Compared with traditional solutions, it is easier to achieve modularity and can be used on different platforms.

[0075] The above is only a preferred specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed in the utility model should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims. The information disclosed in the background technology section of this article is only intended to deepen the understanding of the overall background technology of the utility model, and should not be regarded as an admission or in any form that the information constitutes prior art known to those skilled in the art.

Claims

1. A protection circuit and a fault detection circuit, characterized in that: It includes a Schottky diode, resistor six (R6), resistor seven (R7), a standard hysteresis comparator, and the I / O port of a control chip; VCC is connected to ground in series with resistor six (R6) and resistor seven (R7). The anode of the Schottky diode is connected in parallel at point A between resistor six (R6) and resistor seven (R7). The cathode of the Schottky diode is respectively connected to the output terminal of the standard hysteresis comparator and the I / O port of the control chip.

2. The protection circuit and fault detection circuit according to claim 1, characterized in that: The standard hysteresis comparator includes: Vi is the voltage to be protected. It is connected to the negative input terminal of the comparator (LM393) in series with resistor four (R4), and is connected to SAGND in parallel with resistor five (R5) and (C2); Vo is the output terminal voltage of the comparator (LM393), and is connected to the cathode of the Schottky diode; VCC is connected to the positive input terminal of the comparator (LM393) in series with resistor one (R1), and is connected to SAGND in parallel with resistor two (R2) and (C3); The positive input terminal of the comparator (LM393) is connected to the output terminal of the comparator (LM393) in series with resistor three (R3); VCC is connected to the output terminal of the comparator (LM393) in series with Rpu; 3. The protection circuit and fault detection circuit according to claim 2, characterized in that: VH is the threshold voltage when Vo is at a high level, and VL is the threshold voltage when Vo is at a low level; When Vi < VL, Vo switches to Vcc. Vcc is connected to ground in parallel with resistor one (R1) and resistor three (R3), and then in series with resistor two (R2); When Vi > VH, Vo switches to Vee. Vcc is connected in series with resistor one (R1), and then the parallel combination of resistor two (R2) and resistor three (R3) is connected to ground; 4. The protection circuit and fault detection circuit according to claim 1, 2 or 3, characterized in that: The Schottky diode includes multiple pairs of parallel diodes.

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