VRD circuit with low cost and improved detection sensitivity

Abstract

The utility model discloses a VRD circuit with low cost and improved detection sensitivity. The VRD circuit comprises a single-chip microcomputer, a first resistor, an optocoupler, a first diode, a second resistor, a common mode inductor and a sampling input circuit. A pin 1 of the optocoupler is connected with 3.3 V voltage through the first resistor, a pin 2 of the optocoupler is connected with a pin 27 of the single chip microcomputer, and a pin 4 of the optocoupler is connected with VCC voltage; the positive electrode of the first diode is connected with the pin 3 of the optocoupler; one end of the second resistor is connected with the negative electrode of the first diode, and the other end of the second resistor is connected with the sampling input circuit and a pin 4 of the common mode inductor; pins 1 and 3 of the common mode inductor are connected with an external output voltage interface; the sampling input circuit is connected with a pin 19 of the single-chip microcomputer. According to the utility model, the power and resistance of the pull-up resistor are reduced, the sampling precision is improved, and the problem of poor batch consistency can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of electric welding machines, in particular to a VRD circuit with low cost and improved detection sensitivity. Background Art

[0002] At present, in the welding machine industry, due to different application fields, the output voltage of various welding machines is generally greater than the national safety voltage, which is dangerous to operators, and the anti-electric shock function is particularly necessary. The general VRD function has poor consistency in low-precision detection results due to the cost and error of the pull-up resistor, while high-precision requires higher pull-up resistor power and resistance value. The higher the power and the smaller the resistance value, the higher the sampling accuracy. Summary of the invention

[0003] According to an embodiment of the utility model, a VRD circuit with low cost and improved detection sensitivity is provided, comprising: a single chip microcomputer, a first resistor, an optical coupler, a first diode, a second resistor, a common mode inductor and a sampling input circuit;

[0004] Pin 1 of the optocoupler is connected to the 3.3V voltage through the first resistor, pin 2 of the optocoupler is connected to pin 27 of the microcontroller, and pin 4 of the optocoupler is connected to the VCC voltage;

[0005] The anode of the first diode is connected to pin 3 of the optocoupler;

[0006] One end of the second resistor is connected to the cathode of the first diode, and the other end of the second resistor is connected to the sampling input circuit and the pin 4 of the common mode inductor;

[0007] Pins 1 and 3 of the common mode inductor are connected to the external output voltage interface;

[0008] The sampling input circuit is connected to pin 19 of the microcontroller.

[0009] Further, the sampling input circuit includes: a third resistor, a first follower, a filter circuit, a second follower, a fourth resistor, a fifth resistor, a sixth resistor and a first capacitor;

[0010] One end of the third resistor is connected to one end of the second resistor and pin 4 of the common mode inductor;

[0011] An input terminal of the first follower is connected to the other terminal of the third resistor;

[0012] The filter circuit is connected to the output end of the first follower;

[0013] The input end of the second follower is connected to the filter circuit;

[0014] One end of the fourth resistor is connected to the output end of the second follower;

[0015] One end of the fifth resistor is connected to the other end of the fourth resistor, and the other end of the fifth resistor is connected to the pin 19 of the single chip computer;

[0016] The sixth resistor is connected to one end of the first capacitor and then to the other end of the fifth resistor. The sixth resistor is connected to the other end of the first capacitor and then to ground.

[0017] Furthermore, the sampling input circuit further includes: a bidirectional diode, one end of the bidirectional diode is connected to the other end of the third resistor, and the other end of the bidirectional diode is grounded.

[0018] Furthermore, the sampling input circuit further comprises: a second capacitor and a seventh resistor;

[0019] One end of the second capacitor is connected between the bidirectional diode and the input end of the first follower;

[0020] One end of the seventh resistor is connected between the second capacitor and the input end of the first follower, and the other end of the seventh resistor is connected to the other end of the second capacitor and then grounded.

[0021] Furthermore, the sampling input circuit further includes: a double diode connected between one end of the bidirectional diode and one end of the second capacitor.

[0022] Further, the filter circuit comprises: an eighth resistor, a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor;

[0023] An eighth resistor, a ninth resistor, and a tenth resistor are connected in series in sequence, one end of the eighth resistor is connected to the output end of the first follower, and one end of the tenth resistor is connected to the input end of the second follower;

[0024] One end of the third capacitor and the fourth capacitor are both connected between the eighth resistor and the ninth resistor, and the other ends of the third capacitor and the fourth capacitor are connected and then grounded;

[0025] One end of the fifth capacitor is connected between one end of the tenth resistor and the input end of the second follower;

[0026] One end of the sixth capacitor is connected between the ninth resistor and the tenth resistor, and the other end of the sixth capacitor is connected to the second follower.

[0027] According to the low-cost VRD circuit with improved detection sensitivity of the embodiment of the utility model, the power and resistance of the pull-up resistor are reduced, the sampling accuracy is improved, and the problem of poor batch consistency can be solved.

[0028] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the technology as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The figure is a circuit diagram of a VRD circuit with low cost and improved detection sensitivity according to an embodiment of the utility model.

[0030] Figure 2 The present invention is a circuit diagram of a single chip microcomputer of a VRD circuit with low cost and improved detection sensitivity according to an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings to further illustrate the present invention.

[0032] First, combine Figure 1~2 A low-cost VRD circuit with improved detection sensitivity according to an embodiment of the utility model is described, which is used in the welding machine industry and has a wide range of application scenarios.

[0033] like Figure 1~2 As shown, a low-cost VRD circuit for improving detection sensitivity according to an embodiment of the utility model comprises a single-chip microcomputer U13, a first resistor R1, an optical coupler U1, a first diode D1, a second resistor R2, a common-mode inductor TR1 and a sampling input circuit;

[0034] Specifically, Figure 1~2 As shown, the model of the single-chip computer U13 may be STM32F103C8T6; Pin 1 of the optocoupler U1 is connected to the 3.3V voltage through the first resistor R1, Pin 2 of the optocoupler U1 is connected to Pin 27 of the single-chip computer U13, Pin 4 of the optocoupler U1 is connected to the VCC voltage, and the model of the optocoupler U1 is EL3H7(C); the anode of the first diode D1 is connected to Pin 3 of the optocoupler U1; one end of the second resistor R2 is connected to the cathode of the first diode D1, and the other end of the second resistor R2 is connected to the sampling input circuit and to Pin 4 of the common-mode inductor TR1; Pins 1 and 3 of the common-mode inductor TR1 are connected to the external output voltage interface; the sampling input circuit is connected to Pin 19 of the single-chip computer U13.

[0035] Further, if Figure 1As shown, the sampling input circuit includes: a third resistor R3, a first follower U2B, a filtering circuit, a second follower U2C, a fourth resistor R7, a fifth resistor R8, a sixth resistor R9 and a first capacitor C6; one end of the third resistor R3 is connected to one end of the second resistor R2 and pin 4 of the common mode inductor TR1; the input end of the first follower U2B is connected to the other end of the third resistor R3, and the model of the first follower U2B is TL074C; the filtering circuit is connected to the output end of the first follower U2B; the input end of the second follower U2C is connected to the filtering circuit, and the model of the second follower U2C is TL074C; one end of the fourth resistor R7 is connected to the output end of the second follower U2C; one end of the fifth resistor R8 is connected to the other end of the fourth resistor R7, and the other end of the fifth resistor R8 is connected to pin 19 of the single-chip computer U13; the sixth resistor R9 is connected to one end of the first capacitor C6, and is connected to the other end of the fifth resistor R8, and the sixth resistor R9 is connected to the other end of the first capacitor C6 and then grounded.

[0036] Further, if Figure 1 As shown, the sampling input circuit further includes: a bidirectional diode Z9, one end of the bidirectional diode Z9 is connected to the other end of the third resistor R3, and the other end of the bidirectional diode Z9 is grounded.

[0037] Further, if Figure 1 As shown, the sampling input circuit also includes: a second capacitor C1 and a seventh resistor R4; one end of the second capacitor C1 is connected between the bidirectional diode Z9 and the input end of the first follower U2B; one end of the seventh resistor R4 is connected between the second capacitor C1 and the input end of the first follower U2B, and the other end of the seventh resistor R4 is connected to the other end of the second capacitor C1 and then grounded.

[0038] Further, if Figure 1 As shown, the sampling input circuit further includes: a double diode D24, and the double diode D24 is connected between one end of the bidirectional diode Z9 and one end of the second capacitor C1.

[0039] Further, if Figure 1As shown, the filtering circuit includes: an eighth resistor R5, a ninth resistor R6, a tenth resistor R10, a third capacitor C2, a fourth capacitor C3, a fifth capacitor C5 and a sixth capacitor C4; the eighth resistor R5, the ninth resistor R6 and the tenth resistor R10 are connected in series in sequence, one end of the eighth resistor R5 is connected to the output end of the first follower U2B, and one end of the tenth resistor R10 is connected to the input end of the second follower U2C; one end of the third capacitor C2 and the fourth capacitor C3 are both connected between the eighth resistor R5 and the ninth resistor R6, and the other ends of the third capacitor C2 and the fourth capacitor C3 are connected and then grounded; one end of the fifth capacitor C5 is connected between one end of the tenth resistor R10 and the input end of the second follower U2C; one end of the sixth capacitor C4 is connected between the ninth resistor R6 and the tenth resistor R10, and the other end of the sixth capacitor C4 is connected to the second follower U2C.

[0040] like Figure 1 As shown, in the VRD state, the output is turned off, the VRD_Control signal outputs a low level through the microcontroller U13, the optocoupler U1 is turned on, and a 15V voltage is added between the positive and negative electrodes of the welding machine. When a 200 ohm load is added between the positive and negative electrodes, the voltage at pin 12 of the first follower U2B decreases and is input into the microcontroller U13 for sampling after filtering.

[0041] When the single chip microcomputer U13 obtains the sampled value, the VRD_Control signal outputs a high level, and the optocoupler U1 is turned off, thereby reducing the loss of the second resistor R2.

[0042] like Figure 2 As shown, for the inconsistency problem of sampling values ​​caused by hardware errors, all machines are debugged with a 200-ohm load, and the arc starting threshold is adjusted using the microcontroller U13 to maintain the 200-ohm arc starting consistency.

[0043] Above, refer to Figure 1~2 A low-cost VRD circuit with improved detection sensitivity according to an embodiment of the utility model is described, which reduces the power and resistance of the pull-up resistor, improves the sampling accuracy, and can solve the problem of poor batch consistency.

[0044] It should be noted that, in this specification, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0045] Although the content of the utility model has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the utility model. After reading the above content, various modifications and substitutions of the utility model will be obvious to those skilled in the art. Therefore, the protection scope of the utility model should be limited by the attached claims.

Claims

1. A low-cost VRD circuit for improving detection sensitivity, characterized in that: It includes: a single chip microcomputer, a first resistor, an optocoupler, a first diode, a second resistor, a common mode inductor and a sampling input circuit; The pin 1 of the optical coupler is connected to the 3.3V voltage through the first resistor, the pin 2 of the optical coupler is connected to the pin 27 of the single-chip computer, and the pin 4 of the optical coupler is connected to the VCC voltage; The anode of the first diode is connected to the pin 3 of the optical coupler; One end of the second resistor is connected to the cathode of the first diode, and the other end of the second resistor is connected to the sampling input circuit and connected to the pin 4 of the common mode inductor; Pins 1 and 3 of the common mode inductor are connected to an external output voltage interface; The sampling input circuit is connected to the pin 19 of the single chip computer.

2. The VRD circuit with low cost and improved detection sensitivity as claimed in claim 1, characterized in that: The sampling input circuit comprises: a third resistor, a first follower, a filter circuit, a second follower, a fourth resistor, a fifth resistor, a sixth resistor and a first capacitor; One end of the third resistor is connected to one end of the second resistor and pin 4 of the common mode inductor; The input end of the first follower is connected to the other end of the third resistor; The filter circuit is connected to the output end of the first follower; The input end of the second follower is connected to the filter circuit; One end of the fourth resistor is connected to the output end of the second follower; One end of the fifth resistor is connected to the other end of the fourth resistor, and the other end of the fifth resistor is connected to the pin 19 of the single chip microcomputer; The sixth resistor is connected to one end of the first capacitor and then to the other end of the fifth resistor. The sixth resistor is connected to the other end of the first capacitor and then to ground.

3. The VRD circuit with low cost and improved detection sensitivity as claimed in claim 2, characterized in that: The sampling input circuit further comprises: a bidirectional diode, one end of which is connected to the other end of the third resistor, and the other end of which is grounded.

4. The VRD circuit with low cost and improved detection sensitivity as claimed in claim 3, characterized in that: The sampling input circuit further comprises: a second capacitor and a seventh resistor; One end of the second capacitor is connected between the bidirectional diode and the input end of the first follower; One end of the seventh resistor is connected between the second capacitor and the input end of the first follower, and the other end of the seventh resistor is connected to the other end of the second capacitor and then grounded.

5. The VRD circuit with low cost and improved detection sensitivity as claimed in claim 4, characterized in that: The sampling input circuit further includes: a double diode connected between one end of the bidirectional diode and one end of the second capacitor.

6. The VRD circuit with low cost and improved detection sensitivity as claimed in claim 2, characterized in that: The filter circuit comprises: an eighth resistor, a ninth resistor, a tenth resistor, a third capacitor, a fourth capacitor, a fifth capacitor and a sixth capacitor; The eighth resistor, the ninth resistor, and the tenth resistor are connected in series in sequence, one end of the eighth resistor is connected to the output end of the first follower, and one end of the tenth resistor is connected to the input end of the second follower; One end of the third capacitor and the fourth capacitor are both connected between the eighth resistor and the ninth resistor, and the other ends of the third capacitor and the fourth capacitor are connected and then grounded; One end of the fifth capacitor is connected between one end of the tenth resistor and the input end of the second follower; One end of the sixth capacitor is connected between the ninth resistor and the tenth resistor, and the other end of the sixth capacitor is connected to the second follower.

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