Power supply protection circuit and weighing instrument

Abstract

The utility model discloses a power supply protection circuit and a weighing instrument. The power supply protection circuit comprises a rectification circuit, a filtering voltage stabilizing circuit, a divider resistance circuit, a first MOS tube and a second MOS tube. An external power supply input end is connected with a first input end of the rectifying circuit, the divider resistance circuit is connected between the rectifying circuit and the first MOS tube, and a first output end of the rectifying circuit is connected with a grid electrode of the first MOS tube through the divider resistance circuit; the first end and the second end of the filtering voltage stabilizing circuit are respectively connected with the first output end and the second output end of the rectifying circuit; the drain electrode of the first MOS tube is connected with the grid electrode of the second MOS tube, and the source electrode of the first MOS tube and the source electrode of the second MOS tube are connected with the second output end of the rectifying circuit; the drain electrode of the second MOS tube is used for being connected with the input end of an internal working power supply; through the rectification circuit, the filtering voltage stabilizing circuit, the first MOS tube and the second MOS tube, rapid overvoltage protection is provided, and the problem of instrument damage caused by misconnection of high voltage is solved.

Description

Technical Field

[0001] This utility model belongs to the field of power protection technology, and relates to a power protection circuit and a weighing instrument. Background Technology

[0002] In weighing instrument applications, control equipment with different power supply types often exists, resulting in control boxes containing both AC 220V and DC 24V power supplies. When the instrument uses a lower voltage power supply (e.g., DC 24V), there is often a lack of effective protection against 220V high-voltage input or abnormally high DC power surges. Incorrect wiring or contact issues at the instrument's power input can lead to high voltage input or transient voltage spikes, potentially damaging the instrument circuitry and causing inaccurate measurements or equipment malfunction. Utility Model Content

[0003] This utility model provides a power supply protection circuit and a weighing instrument. Through a rectifier circuit, a filter and voltage regulator circuit, a voltage divider resistor circuit, a first MOSFET and a second MOSFET, it provides fast overvoltage protection and solves the problem of instrument damage caused by accidental connection to high voltage.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A power protection circuit is used between the external power input terminal and the internal working power input terminal of a weighing instrument, including a rectifier circuit, a filter and voltage regulator circuit, a voltage divider resistor circuit, a first MOSFET and a second MOSFET.

[0006] The external power input terminal is connected to the first input terminal of the rectifier circuit, the voltage divider resistor circuit is connected between the rectifier circuit and the first MOS transistor, and the first output terminal of the rectifier circuit is connected to the gate of the first MOS transistor through the voltage divider resistor circuit.

[0007] The first and second terminals of the filter and voltage regulator circuit are respectively connected to the first and second output terminals of the rectifier circuit.

[0008] The drain of the first MOSFET and the gate of the second MOSFET are connected, and the source of the first MOSFET and the source of the second MOSFET are connected to the second output terminal of the rectifier circuit.

[0009] The drain of the second MOSFET is used to connect to the internal operating power input terminal;

[0010] The second input terminal of the rectifier circuit is grounded.

[0011] Furthermore, the filtering and voltage regulation circuit includes a first electrolytic capacitor, the anode of the first electrolytic capacitor is connected to the first output terminal of the rectifier circuit, and the cathode of the first electrolytic capacitor is connected to the source of the first MOSFET.

[0012] Furthermore, the voltage divider resistor circuit includes a first resistor and a third resistor;

[0013] The first resistor is connected in series between the rectifier circuit and the first MOSFET;

[0014] The two ends of the first resistor are respectively connected to the first output terminal of the rectifier circuit and the gate of the first MOS transistor.

[0015] The third resistor is connected in parallel with the first MOS transistor, and the two ends of the third resistor are respectively connected to the gate of the first MOS transistor and the second output terminal of the rectifier circuit.

[0016] Furthermore, the filtering and voltage regulation circuit also includes a second Zener diode;

[0017] The positive terminal of the second Zener diode is connected between the first resistor and the gate of the first MOSFET;

[0018] The negative terminal of the second Zener diode is connected to the source terminal of the first MOSFET.

[0019] Furthermore, a second resistor is connected in series between the first output terminal of the rectifier circuit and the gate of the second MOS transistor;

[0020] The drain of the first MOSFET is connected between the second resistor and the gate of the second MOSFET.

[0021] Furthermore, a third Zener diode is connected in parallel with the second MOS transistor, and the positive and negative terminals of the third Zener diode are connected to the gate and source of the second MOS transistor, respectively.

[0022] Furthermore, a fuse is connected between the external power input terminal and the rectifier circuit.

[0023] Furthermore, the power protection circuit also includes an interface terminal, which is connected in parallel with the rectifier circuit. The first end and the second end of the interface terminal are respectively connected to the first input end and the second output end of the rectifier circuit.

[0024] A weighing instrument, wherein the weighing instrument applies the aforementioned power protection circuit.

[0025] The beneficial effects of this utility model are as follows: When a high voltage or transient voltage spike is applied due to incorrect wiring or line contact problems at the instrument's power input terminal, a rectifier circuit converts the accidentally applied high-voltage AC voltage into DC voltage. Through a filter and voltage regulator circuit, a voltage divider resistor circuit, a first MOSFET, and a second MOSFET, abnormal voltages can be quickly detected. If there are significant power changes or a high voltage is mistakenly applied, the power supply is quickly cut off to prevent damage to the instrument circuit and significantly reduce the equipment failure rate. When a high voltage is applied to the power supply circuit, the power input circuit is quickly shut off. Even if a high voltage is applied for a long time, it effectively prevents the downstream instrument circuit from being burned out. When the required voltage is applied again, the instrument resumes normal operation. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall circuit of this utility model.

[0027] Figure 2 This is a schematic diagram of the instrument power supply protection circuit of this utility model. Detailed Implementation

[0028] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. It should be understood that this application is not limited to the exemplary embodiments disclosed herein. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0029] In the description of this utility model, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0030] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0031] In the embodiments of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in this utility model can be understood according to the specific circumstances.

[0032] This utility model provides an appendix. Figures 1-2 In this embodiment of the utility model, a power protection circuit is applied to the external power input terminal and the internal working power input terminal of the weighing instrument, including a rectifier circuit D1, a filter voltage regulator circuit, a voltage divider resistor circuit, a first MOSFET Q1 and a second MOSFET Q2.

[0033] The external power input terminal is connected to the first input terminal of the rectifier circuit D1, the voltage divider resistor circuit is connected between the rectifier circuit D1 and the first MOS transistor Q1, and the first output terminal of the rectifier circuit D1 is connected to the gate of the first MOS transistor Q1 through the voltage divider resistor circuit.

[0034] The first and second terminals of the filter voltage regulator circuit are respectively connected to the first and second output terminals of the rectifier circuit D1.

[0035] The drain of the first MOSFET Q1 and the gate of the second MOSFET Q2 are connected, and the source of the first MOSFET Q1 and the source of the second MOSFET Q2 are connected to the second output terminal of the rectifier circuit D1.

[0036] The drain of the second MOSFET Q2 is used to connect to the internal operating power input terminal;

[0037] The second input terminal of the rectifier circuit D1 is grounded.

[0038] Specifically, when the input voltage is 24VDC, the gate voltage of the first MOSFET Q1 is below the threshold voltage and is in the off state. At this time, the gate voltage of the second MOSFET Q2 is above the threshold voltage, so the second MOSFET Q2 is turned on, and current flows from the source to the drain of the second MOSFET Q2, allowing the weighing instrument to work normally. The filter and voltage regulator circuit performs voltage regulation and filtering on the output voltage of the rectifier circuit, and its output DC voltage is approximately 1.414 times the input AC voltage of the rectifier circuit. When the input AC voltage of the rectifier circuit is 220VAC, the output DC voltage of the filter and voltage regulator circuit is approximately 311VDC (220V*1.414≈311V). At this time, the gate voltage of the first MOSFET Q1 is higher than the threshold voltage, so the first MOSFET Q1 is turned on. The drain of the first MOSFET Q1 is connected to the gate of the second MOSFET Q2. Therefore, the drain voltage of the first MOSFET Q1 affects the gate voltage of the second MOSFET Q2. When the first MOSFET Q1 is turned on, its drain voltage usually decreases, approaching the source voltage, which is usually zero. When the gate voltage of the second MOSFET Q2 decreases below the threshold voltage of the second MOSFET Q2, the second MOSFET Q2 is turned off. The channel between the source and drain of the second MOSFET Q2 is closed, the current stops flowing, and the loop to the internal working power supply is cut off.

[0039] The output terminal of the MOS shutdown protection circuit is connected to the second input terminal of the rectifier circuit D1 and the internal working power supply, respectively. The second output terminal of the rectifier circuit D1 is used to connect with the terminal interface to form a loop. The terminal interface can be connected to a real-time monitoring system to monitor the power supply status and the health status of the circuit.

[0040] The filtering and voltage regulation circuit includes a first electrolytic capacitor C1. The anode of the first electrolytic capacitor C1 is connected to the first output terminal of the rectifier circuit D1, and the cathode of the first electrolytic capacitor C1 is connected to the source of the first MOSFET Q1. The filtering and voltage regulation circuit performs voltage regulation and filtering on the output voltage of the rectifier circuit, and its output DC voltage is approximately 1.414 times the input AC voltage of the rectifier circuit. When the input AC voltage of the rectifier circuit is 220VAC, the output DC voltage of the filtering and voltage regulation circuit is approximately 311VDC (220V × 1.414 ≈ 311V). At this time, the gate voltage of the first MOSFET Q1 is higher than the threshold, and the first MOSFET Q1 is turned on.

[0041] The voltage divider resistor circuit includes a first resistor R1 and a third resistor R3. The first resistor R1 is connected in series between the rectifier circuit D1 and the first MOSFET Q1. The two ends of the first resistor R1 are connected to the first output terminal of the rectifier circuit D1 and the gate of the first MOSFET Q1, respectively. The third resistor R3 is connected in parallel with the first MOSFET Q1, and the two ends of the third resistor R3 are connected to the gate of the first MOSFET Q1 and the second output terminal of the rectifier circuit D1, respectively. The first MOSFET Q1 requires a certain gate voltage to conduct. The first resistor R1 and the third resistor R3 form a voltage divider to provide a suitable gate drive voltage. By selecting appropriate resistor values, the voltage on the MOSFET gate can be controlled, thereby finely controlling the conduction level of the MOSFET.

[0042] The filtering and voltage regulation circuit also includes a second Zener diode D2; the positive terminal of the second Zener diode D2 is connected between the first resistor R1 and the gate of the first MOSFET Q1;

[0043] The positive terminal of the second Zener diode D2 is connected to the source terminal of the first MOSFET Q1. The second Zener diode D2 is a 12V Zener diode, and its main function is to maintain a stable voltage between the gate and source of the first MOSFET Q1. When the input voltage or load changes, the Zener diode can absorb excess voltage, ensuring that the gate voltage of the first MOSFET Q1 does not exceed its rated value, thereby preventing damage to the MOSFET due to overvoltage.

[0044] A second resistor R2 is connected in series between the first output terminal of the rectifier circuit D1 and the gate of the second MOS transistor Q2.

[0045] The drain of the first MOSFET Q1 is connected between the second resistor R2 and the gate of the second MOSFET Q2.

[0046] The second resistor R2 is connected in series between the output of rectifier circuit D1 and the gate of the second MOSFET Q2. Its main functions are to pull up the gate voltage of the second MOSFET Q2 and limit current. When 24VDC is input, the output voltage of rectifier circuit D1 is low (approximately 23VDC). The second resistor R2 pulls up the gate voltage of the second MOSFET Q2 (equal to the Zener diode D3's voltage regulation value), while limiting the current flowing through Zener diode D3, thus protecting it. Simultaneously, the source and gate of the second MOSFET Q2 are turned on, allowing the 23VDC power supply to be transmitted to the instrument's internal operating power input. When 220VAC is input, the source and drain of the first MOSFET Q1 are turned on. The end of the second resistor R2 connected to the first MOSFET Q1 is pulled down to a low voltage, turning off the second MOSFET Q2. This cuts off the high voltage (approximately 311VDC) flow into the instrument's internal operating power input, thus protecting the instrument circuit.

[0047] The second MOSFET Q2 is connected in parallel with a third Zener diode D3. The positive and negative terminals of the third Zener diode D3 are connected to the gate and source of the second MOSFET Q2, respectively. The third Zener diode D3 is used to stabilize the gate voltage of the second MOSFET Q2, preventing voltage fluctuations or excessively high voltages from damaging the MOSFET. When the gate voltage exceeds the rated voltage of the Zener diode, the Zener diode conducts, limiting the gate voltage and thus protecting the MOSFET from high voltage surges. Specifically, when the forward conduction voltage of the third Zener diode D3 is lower than the gate voltage of the second MOSFET Q2, the Zener diode conducts, clamping the gate voltage at the Zener diode's stable voltage level. When the gate voltage is lower than the forward conduction voltage of the Zener diode, the Zener diode is cut off, not affecting the normal operation of the MOSFET.

[0048] A fuse F1 is connected between the external power input terminal and the rectifier circuit D1. Fuse F1 prevents excessive current caused by short circuits or overloads, which could damage the rectifier circuit D1 or subsequent electronic components. When the current exceeds the rated value of fuse F1, it will melt, cutting off the current and protecting the circuit.

[0049] The weighing instrument protection circuit also includes an interface terminal J1, which is connected in parallel with the rectifier circuit D1. The first and second ends of the interface terminal are connected to the first input and second output ends of the rectifier circuit, respectively. The interface terminal is used to connect to an external power input (e.g., DC 24V) to provide power to the instrument. The first end of the interface terminal J1 is connected to the positive terminal of the external power input and, through a fuse, to the first input end of the rectifier circuit. The other end of the interface terminal is connected to the negative terminal of the external power input, corresponding to the ground signal of the instrument circuit, and is connected to the second input end of the rectifier circuit.

[0050] A weighing instrument employs the aforementioned instrument power protection circuit. This weighing instrument power protection circuit is particularly suitable for protecting the instrument from damage caused by operator errors in wiring or power line faults (short circuits, damaged external power modules, etc.) resulting from multiple power supply systems (including 220VAC and 24VDC) within a control box in industrial environments. The circuit enables the instrument to respond quickly to high voltage or transient voltage spikes at the power input port to protect the equipment. Specifically, fuse F1 provides overcurrent protection in the circuit. Once the current exceeds the rated value, fuse F1 will blow, cutting off the power supply and controlling the output voltage. Specifically, when the input voltage is 24VDC, the gate voltage of the first MOSFET Q1 is below the threshold voltage and is in the off state. At this time, the gate voltage of the second MOSFET Q2 is above the threshold voltage, and the second MOSFET Q2 is turned on. Current flows from the source to the drain of the second MOSFET Q2, allowing the weighing instrument to operate normally. When the input voltage is 220VAC, the filter and voltage regulator circuit stabilizes the voltage at approximately 311VDC. At this time, the gate voltage of the first MOSFET Q1 is higher than the threshold voltage, so Q1 is turned on. The drain of Q1 is connected to the gate of the second MOSFET Q2. Therefore, the drain voltage of Q1 affects the gate voltage of Q2. When Q1 is turned on, its drain voltage typically decreases, approaching its source voltage, usually reaching zero. When the gate voltage of Q2 drops below its threshold voltage, Q2 is turned off. The channel between the source and drain of Q2 is closed, current flow stops, and the circuit to the internal power supply of the weighing instrument is cut off. In practical applications, this power protection circuit ensures the stable operation of the weighing instrument under various power conditions, significantly improving the reliability and safety of the equipment.

[0051] It should also be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0052] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A power supply protection circuit, applied between the external power input terminal and the internal working power input terminal of a weighing instrument, characterized in that, Includes a rectifier circuit, a filter and voltage regulator circuit, a voltage divider resistor circuit, a first MOSFET, and a second MOSFET; The external power input terminal is connected to the first input terminal of the rectifier circuit, the voltage divider resistor circuit is connected between the rectifier circuit and the first MOS transistor, and the first output terminal of the rectifier circuit is connected to the gate of the first MOS transistor through the voltage divider resistor circuit. The first and second terminals of the filter and voltage regulator circuit are respectively connected to the first and second output terminals of the rectifier circuit. The drain of the first MOSFET and the gate of the second MOSFET are connected, and the source of the first MOSFET and the source of the second MOSFET are connected to the second output terminal of the rectifier circuit. The drain of the second MOSFET is used to connect to the internal operating power input terminal; The second input terminal of the rectifier circuit is grounded.

2. The power supply protection circuit according to claim 1, characterized in that, The filtering and voltage regulation circuit includes a first electrolytic capacitor, the anode of the first electrolytic capacitor is connected to the first output terminal of the rectifier circuit, and the cathode of the first electrolytic capacitor is connected to the source of the first MOSFET.

3. The power supply protection circuit according to claim 2, characterized in that, The voltage divider resistor circuit includes a first resistor and a third resistor; The first resistor is connected in series between the rectifier circuit and the first MOSFET; The two ends of the first resistor are respectively connected to the first output terminal of the rectifier circuit and the gate of the first MOS transistor. The third resistor is connected in parallel with the first MOS transistor, and the two ends of the third resistor are respectively connected to the gate of the first MOS transistor and the second output terminal of the rectifier circuit.

4. A power supply protection circuit according to claim 3, characterized in that, The filtering and voltage regulation circuit also includes a second Zener diode; The positive terminal of the second Zener diode is connected between the first resistor and the gate of the first MOSFET; The negative terminal of the second Zener diode is connected to the source terminal of the first MOSFET.

5. A power supply protection circuit according to claim 1, characterized in that, A second resistor is connected in series between the first output terminal of the rectifier circuit and the gate of the second MOS transistor; The drain of the first MOSFET is connected between the second resistor and the gate of the second MOSFET.

6. A power supply protection circuit according to claim 5, characterized in that, The second MOS transistor is connected in parallel with a third Zener diode, the positive and negative terminals of which are connected to the gate and source of the second MOS transistor, respectively.

7. A power supply protection circuit according to claim 1, characterized in that, A fuse is connected between the external power input terminal and the rectifier circuit.

8. A power supply protection circuit according to claim 1, characterized in that, The power protection circuit also includes an interface terminal, which is connected in parallel with the rectifier circuit. The first end and the second end of the interface terminal are respectively connected to the first input end and the second output end of the rectifier circuit.

9. A weighing instrument, characterized in that, The weighing instrument uses the power protection circuit described in any one of claims 1 to 8.

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