Wide voltage input isolation switching value input detection circuit with protection function

Abstract

The invention discloses a wide voltage input isolation switching value input detection circuit with a protection function, which comprises a self-fusing fuse, a first diode, a TVS (Transient Voltage Suppressor) tube, a second diode, a first resistor, a second resistor, a first capacitor and a photoelectric coupler. It is ensured that the optocoupler is not conducted beyond a set voltage range value, false triggering caused by cable interference voltage is prevented, the interface protection function is achieved, interface burning caused by misconnection of external cables is prevented, surge voltage suppression is achieved, the safety of the circuit is improved, meanwhile, a resettable fuse is connected in series, and the service life of the circuit is prolonged. Isolation between an input signal and a system is realized through a photoelectric coupler, and universality and safety of an acquisition interface are improved.

Description

Technical Field

[0001] The invention belongs to the field of switch quantity acquisition, and in particular relates to a wide voltage input isolation switch quantity input detection circuit with a protection function. Background Art

[0002] In the fields of mechanical control, equipment operation, and signal detection, it is often necessary to collect external energized switch quantities. The processor determines the switch status of the external device through the collected switch quantities and takes corresponding processing measures.

[0003] The external environment faced by switch quantity acquisition cables is full of uncertainties. In order to protect the acquisition and processor systems, isolated optocouplers are often used for switch quantity acquisition. However, due to factors such as the uncertainty of the external voltage and large external interference, the switch quantity acquisition interface often has misjudgments and the acquisition circuit is overvoltage or overcurrent and burns out. Summary of the invention

[0004] In view of the above problems, the object of the present invention is to provide a wide voltage input isolation switch input detection circuit with protection function.

[0005] The specific technical solution for achieving the purpose of the present invention is:

[0006] A wide voltage input isolation switch quantity input detection circuit with protection function, comprising a self-fuse fuse, a first diode, a TVS tube, a second diode, a first resistor, a second resistor, a first capacitor and a photoelectric coupler;

[0007] One end of the self-fuse fuse is connected to the positive electrode of the input voltage, and the other end is respectively connected to the negative electrode of the first diode and the positive electrode of the TVS tube, the positive electrode of the first diode is connected to one end of the first resistor, and the negative electrode of the TVS tube is connected to the negative electrode of the input voltage;

[0008] The other end of the first resistor is simultaneously connected to the cathode of the second diode and one end of the second resistor, the anode of the cathode of the second diode is connected to the negative electrode of the input voltage, the other end of the second resistor is respectively connected to one end of the first capacitor and the positive input electrode of the photocoupler, and the other end of the first capacitor and the negative input electrode of the photocoupler are connected to the negative electrode of the input voltage.

[0009] Furthermore, the circuit sets the maximum input voltage V according to the requirements. max and minimum input voltage V min , that is, when the input voltage is at the maximum input voltage V max and minimum input voltage V min When the photocoupler is turned on, it prevents false triggering.

[0010] Furthermore, the maximum input voltage Vmax for:

[0011] V max =I max R1+V1+V2

[0012]

[0013] Wherein, V1 is the breakdown voltage of the first diode, V2 is the breakdown voltage of the second diode, R1 is the resistance value of the first resistor, and P represents the maximum dissipated power of the first resistor.

[0014] Furthermore, the minimum input voltage V min for:

[0015] V min =V1+V F +I min (R1+R2)

[0016] Where V1 is the breakdown voltage of the first diode, V F is the forward conduction voltage of the optocoupler, I min is the minimum on-state current of the photocoupler, R1 and R2 are the resistance values ​​of the first resistor and the second resistor respectively;

[0017] The minimum input voltage V min It is used to ensure that the interference signal of this value cannot enter the optocoupler circuit to prevent false triggering.

[0018] Furthermore, the circuit sets a conventional input voltage V according to requirements. nomal By adjusting the parameters of the first resistor, the second resistor, and the second diode, the current of the input photocoupler meets its conduction condition, thereby realizing adaptive wide voltage input acquisition.

[0019] Furthermore, when the input voltage is V nomal When the input current of the optocoupler is:

[0020]

[0021] Wherein, V1 is the breakdown voltage of the first diode, R1 and R2 are the resistance values ​​of the first resistor and the second resistor respectively;

[0022] By selecting appropriate parameters of the first diode, the first resistor, and the second resistor, the input current I of the photocoupler is ensured to be F Greater than the minimum on-state current of the optocoupler;

[0023] As the input voltage continues to increase, I F Increase until the voltage value of the second resistor is greater than the breakdown voltage V2 of the second diode, and the input current of the optocoupler remains By selecting the appropriate parameters of the second resistor, the input current I of the optocoupler is guaranteed to be F Not greater than the maximum input current of the optocoupler;

[0024] When the input voltage increases to the maximum input voltage V max When , the current flowing through the first resistor is:

[0025]

[0026] By selecting appropriate parameters of the first resistor, it is ensured that the power of the first resistor is not greater than its dissipated power.

[0027] Furthermore, the self-fusing fuse is a self-recovering fuse, which is used to ensure that the circuit is not burned by excessive current when abnormal input occurs.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The scheme of the present invention connects a resettable fuse in series in the circuit to realize the overcurrent protection function. At the same time, by setting the first diode, the TVS tube, and the second diode, devices with appropriate parameters are selected to ensure that the optocoupler is not turned on outside the set voltage range value, thereby preventing false triggering caused by cable interference voltage and interface protection functions, preventing the interface from being burned due to misconnection of external cables and realizing surge voltage suppression, thereby improving the safety of the circuit;

[0030] The solution of the present invention realizes the isolation of input signals from the system through a photoelectric coupler, thereby increasing the versatility and safety of the acquisition interface.

[0031] The present invention is further described below in conjunction with specific implementation modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a topological diagram of a wide voltage input isolation switch quantity input detection circuit with a protection function of the present invention.

[0033] Figure 2 This is a topological diagram of a wide voltage input isolation switch quantity input detection circuit with protection function in an embodiment of the present invention. DETAILED DESCRIPTION

[0034] Example

[0035] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings in the embodiments of the present invention. The described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an kind" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0037] Unless otherwise specifically stated, the relative arrangement, numerical expressions and numerical values ​​of the parts and steps set forth in these embodiments do not limit the scope of the present application. At the same time, it should be understood that, for ease of description, the sizes of the various parts shown in the accompanying drawings are not drawn according to the actual proportional relationship. The technology, method and equipment known to those of ordinary skill in the relevant field may not be discussed in detail, but in appropriate cases, the technology, method and equipment should be considered as a part of the authorization specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters represent similar items in the following drawings, so that once a certain item is defined in an accompanying drawing, it does not need to be further discussed in subsequent drawings.

[0038] Combination Figure 1 , a wide voltage input isolation switch input detection circuit with protection function, including a self-fuse fuse F1, a first diode D1, a TVS tube D2, a second diode D3, a first resistor R1, a second resistor R2, a first capacitor C1 and a photocoupler U1;

[0039] One end of the self-fusing fuse F1 is connected to the positive electrode of the input voltage, and the other end is respectively connected to the negative electrode of the first diode D1 and the positive electrode of the TVS tube D2. The positive electrode of the first diode D1 is connected to one end of the first resistor R1, and the negative electrode of the TVS tube D2 is connected to the negative electrode of the input voltage.

[0040] The other end of the first resistor R1 is simultaneously connected to the cathode of the second diode D3 and one end of the second resistor R2, the anode of the cathode of the second diode D3 is connected to the negative electrode of the input voltage, the other end of the second resistor R2 is respectively connected to one end of the first capacitor C1 and the input positive electrode of the photocoupler U1, and the other end of the first capacitor C1 and the input negative electrode of the photocoupler U1 are connected to the negative electrode of the input voltage.

[0041] The circuit sets the maximum input voltage V according to the requirements max and minimum input voltage V min , that is, when the input voltage is at the maximum input voltage V maxand minimum input voltage V min When the photocoupler U1 is turned on, it can prevent false triggering.

[0042] Among them, the maximum input voltage V max for:

[0043] V max =I max R1+V1+V2

[0044]

[0045] Wherein, V1 is the breakdown voltage of the first diode D1, V2 is the breakdown voltage of the second diode D3, R1 is the resistance value of the first resistor R1, and P represents the maximum dissipated power of the first resistor R1;

[0046] When the abnormal input voltage is greater than the designed maximum input voltage Vmax, the detection circuit is protected by the fuse and TVS tube D2. At this time, the breakdown voltage of TVS tube D2 needs to be greater than the maximum input voltage Vmax to absorb the surge voltage greater than Vmax at the input interface.

[0047] The minimum input voltage V min for:

[0048] V min =V1+V F +I min (R1+R2)

[0049] Wherein, V1 is the breakdown voltage of the first diode D1, V F is the forward conduction voltage of the optocoupler U1, I min is the minimum on-state current of the photocoupler U1, R1 and R2 are the resistance values ​​of the first resistor R1 and the second resistor R2 respectively;

[0050] The minimum input voltage V min It is used to ensure that the interference signal of this value cannot enter the optocoupler circuit to prevent false triggering.

[0051] In addition, the circuit sets the normal input voltage V according to the requirements. normal By adjusting the parameters of the first resistor R1, the second resistor R2, and the second diode D3, the current input to the photoelectric coupler U1 meets its conduction condition, thereby realizing adaptive wide voltage input acquisition.

[0052] When the input voltage is V normal When , the input current of the optocoupler U1 is:

[0053]

[0054] Wherein, V1 is the breakdown voltage of the first diode D1, R1 and R2 are the resistance values ​​of the first resistor R1 and the second resistor R2 respectively;

[0055] By selecting appropriate parameters of the first diode D1, the first resistor R1, and the second resistor R2, the input current I of the photocoupler U1 is ensured. F Greater than the minimum on-state current of the optocoupler;

[0056] As the input voltage continues to increase, I F Increases until the voltage value of the second resistor R2 is greater than the breakdown voltage V2 of the second diode D3, and the input current of the optocoupler U1 remains By selecting the appropriate parameters of the second resistor R2, the input current I of the optocoupler U1 is ensured. F Not greater than the maximum input current of the optocoupler;

[0057] When the input voltage increases to the maximum input voltage V max When , the current flowing through the first resistor R1 is:

[0058]

[0059] By selecting appropriate parameters of the first resistor R1 , it is ensured that the power of the first resistor R1 is not greater than its dissipated power.

[0060] Maximum input voltage V max , minimum input voltage V min 、Normal input voltage V normal The normal input voltage V normal is the actual design application value, the maximum input voltage V max and the maximum input voltage V max The value between is the design margin, the minimum input voltage V min The setting can ensure that the optocoupler is not conducting when it is less than this value;

[0061] Minimum input voltage V min and the normal input voltage V normal When between, the conduction state of the optocoupler is uncertain;

[0062] Normal input voltage V normal and the maximum input voltage V max When the optocoupler is connected, it is guaranteed to be conductive.

[0063] In addition, the self-fusing fuse F1 is a self-resetting fuse, which is used to ensure that the circuit is not burned by excessive current when abnormal input occurs. That is, when there is a large abnormal voltage input that exceeds the dissipated power of R1, in order to ensure that R1 does not continue to heat up and burn, the self-fusing fuse F1 will automatically melt and disconnect the input.

[0064] The topology diagram of the wide voltage input isolation switch input detection circuit with protection function in this embodiment is as follows: Figure 2 As shown;

[0065] First, the input interface is connected in series with an F1 self-recovery fuse with a fusing current of 100mA to prevent the input interface from being accidentally connected to a voltage far exceeding 48V and burning the interface circuit. The voltage of 48V is set here to ensure that it is less than 50V and retain a design margin;

[0066] The breakdown voltage of TVS tube D2 is selected to be 50V, which is used to absorb the surge voltage greater than 50V of the input interface. Zener diode D1 is connected in series at the input end, with a breakdown voltage of 5V, to ensure that interference signals with a voltage lower than 5V cannot enter the optocoupler circuit to prevent false triggering; the circuit composed of R1, D3, and R2 is used to achieve 12-48V wide voltage adaptive acquisition. When the input voltage is 12V, the voltage added to point 1 on the left end of the first resistor R1 through Zener diode D1 is 12V-5V=7V. At this time, the current of the optocoupler input is about I F =(7V-1.5V) / (R1+R2)=5mA, which is greater than the minimum on-current of the optocoupler. At this time, the output end can normally collect the switching signal.

[0067] When the input voltage continues to increase, IF increases until the voltage at point 2 on the left end of the second resistor R2 is greater than 7V. At this time, the Zener diode D1 clamps the voltage at point 2 at 7V, and the input current I F =(7V-1.5V) / R2=10mA, to ensure that the optocoupler will not be burned by overcurrent;

[0068] When the input voltage is 48V, the current flowing through R1 is I1=(48V-5V-7V) / R1=65.5mA, the power of resistor R1 is 65.5mA*65.5mA*550=2.3W, and 1.5V is the on-state voltage drop of the optocoupler, which can ensure the normal operation of the circuit under the voltage state of 48V.

[0069] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A wide voltage input isolation switch input detection circuit with protection function, characterized in that: It includes a self-fusing fuse (F1), a first diode (D1), a TVS tube (D2), a second diode (D3), a first resistor (R1), a second resistor (R2), a first capacitor (C1) and a photocoupler (U1); One end of the self-fusing fuse (F1) is connected to the positive electrode of the input voltage, and the other end is respectively connected to the negative electrode of the first diode (D1) and the positive electrode of the TVS tube (D2); the positive electrode of the first diode (D1) is connected to one end of the first resistor (R1), and the negative electrode of the TVS tube (D2) is connected to the negative electrode of the input voltage; The other end of the first resistor (R1) is simultaneously connected to the cathode of the second diode (D3) and one end of the second resistor (R2); the anode of the cathode of the second diode (D3) is connected to the negative electrode of the input voltage; the other end of the second resistor (R2) is respectively connected to one end of the first capacitor (C1) and the input anode of the photoelectric coupler (U1); the other end of the first capacitor (C1) and the input cathode of the photoelectric coupler (U1) are connected to the negative electrode of the input voltage.

2. The wide voltage input isolation switch input detection circuit with protection function according to claim 1 is characterized in that: The circuit sets the maximum input voltage V according to the requirements max and minimum input voltage V min , that is, when the input voltage is at the maximum input voltage V max and minimum input voltage V min When the photocoupler (U1) is turned on, it prevents false triggering.

3. The wide voltage input isolation switch input detection circuit with protection function according to claim 2 is characterized in that: The maximum input voltage V max for: V max =I max ·R1+V1+V2 Wherein, V1 is the breakdown voltage of the first diode (D1), V2 is the breakdown voltage of the second diode (D3), R1 is the resistance value of the first resistor (R1), and P represents the maximum dissipated power of the first resistor (R1).

4. The wide voltage input isolation switch input detection circuit with protection function according to claim 2, characterized in that: The minimum input voltage V min for: IN min =V1+V F +I min ·(R1+R2) Where V1 is the breakdown voltage of the first diode (D1), V F is the forward voltage of the optocoupler (U1), I min is the minimum on-state current of the photocoupler (U1), R1 and R2 are the resistance values ​​of the first resistor (R1) and the second resistor (R2), respectively; The minimum input voltage V min It is used to ensure that the interference signal of this value cannot enter the optocoupler circuit to prevent false triggering.

5. The wide voltage input isolation switch input detection circuit with protection function according to claim 3, characterized in that: The circuit sets the normal input voltage V according to the requirements normal By adjusting the parameters of the first resistor (R1), the second resistor (R2), and the second diode (D3), the current of the input photocoupler (U1) meets its conduction condition, thereby realizing adaptive wide voltage input acquisition.

6. The wide voltage input isolation switch input detection circuit with protection function according to claim 5, characterized in that: When the input voltage is V normal When , the input current of the optocoupler (U1) is: Wherein, V1 is the breakdown voltage of the first diode (D1), R1 and R2 are the resistance values ​​of the first resistor (R1) and the second resistor (R2), respectively; By selecting appropriate parameters of the first diode (D1), the first resistor (R1), and the second resistor (R2), the input current I of the photocoupler (U1) is ensured. F Greater than the minimum on-state current of the optocoupler; As the input voltage continues to increase, I F Increases until the voltage value of the second resistor (R2) is greater than the breakdown voltage V2 of the second diode (D3), and the input current of the optocoupler (U1) remains By selecting the appropriate parameters of the second resistor (R2), the input current I of the optocoupler (U1) is guaranteed. F Not greater than the maximum input current of the optocoupler; When the input voltage increases to the maximum input voltage V max When , the current flowing through the first resistor (R1) is: By selecting appropriate parameters of the first resistor (R1), it is ensured that the power of the first resistor (R1) is not greater than its dissipated power.

7. The wide voltage input isolation switch input detection circuit with protection function according to claim 1, characterized in that: The self-fusing fuse (F1) is a self-recovering fuse used to ensure that the circuit is not burned by excessive current when abnormal input occurs.

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