CN118920399A - Protection method for preventing reverse connection and overcurrent and overvoltage of DC power input - Google Patents

Abstract

The invention provides a protection method for preventing reverse connection and overcurrent and overvoltage of DC power input, which comprises the following steps: step one: reverse connection prevention protection of MOS tube: the switching characteristic design circuit of the MOS tube is utilized, the MOS tube is conducted when the power supply is normally connected, and the MOS tube is cut off when the power supply is reversely connected. According to the invention, the MOS tube is used in series at the input end, the unidirectional conductivity or the switching characteristic of the MOS tube element is utilized to prevent the reverse current from flowing, so that the reverse connection prevention protection function is realized, the fuse is added in the input end or the circuit, so that the over-current prevention protection function is realized, the overvoltage protection circuit is added at the input end, for example, a voltage stabilizing diode is used, when the input voltage exceeds a set threshold value, the elements can limit the voltage or cut off the power supply, so that the over-voltage prevention protection function is realized, the circuit and equipment damage risk caused by the abnormal input of the power supply can be remarkably reduced through the reverse connection prevention, over-current prevention and over-voltage prevention protection measures, and the reliability and stability of the equipment are improved.

Description

A DC power supply input protection method for preventing reverse connection and overcurrent and overvoltage

Technical Field

The present invention relates to a protection method, in particular to a protection method for preventing reverse connection and overcurrent and overvoltage of a DC power supply input, belonging to the technical field of DC power supply input protection.

Background Art

DC power input protection refers to a series of measures taken to protect electronic equipment from abnormalities and faults at the power input. These measures are designed to ensure the stability and safety of the power input, thereby extending the service life of the equipment and improving its reliability and stability.

Specifically, DC power input protection mainly includes the following aspects:

(1) Overvoltage protection: When the input voltage exceeds the maximum value that the device or power module can withstand, the overvoltage protection circuit will quickly cut off the power input to prevent the high voltage from damaging the device. This is achieved by monitoring the input voltage and triggering the protection mechanism when the voltage exceeds the set threshold.

(2) Overcurrent protection: An overcurrent protection circuit is added to the power input end. When the input current exceeds the rated value, the overcurrent protection circuit will immediately cut off the power input to prevent excessive current from damaging the device or power module. This helps prevent current abnormalities caused by short circuits, overloads, etc.

(3) Input reverse polarity protection: To prevent users from mistakenly connecting the positive and negative poles of the power supply in reverse, which could cause equipment damage or safety accidents, a reverse polarity protection circuit is usually designed at the DC power supply input. When it is detected that the positive and negative poles of the power supply are connected in reverse, the protection circuit will immediately cut off the power input to protect the equipment from damage.

In the prior art, a diode is often connected in series at the input end of a DC power supply to achieve the purpose of reverse connection protection. Although this solution can achieve reverse connection protection, there is a problem that the voltage drop affects the efficiency of the entire machine, and in the case of overcurrent or overvoltage, the protection capability of the input end of the device is limited. Therefore, a protection method for preventing reverse connection and overcurrent and overvoltage of a DC power supply input is proposed.

Summary of the invention

In view of this, the present invention provides a protection method for preventing reverse connection of a DC power input and preventing overcurrent and overvoltage, so as to solve or alleviate the technical problems existing in the prior art and at least provide a beneficial option.

The technical solution of the embodiment of the present invention is implemented as follows: a DC power supply input protection method for preventing reverse connection and overcurrent and overvoltage, comprising the following steps:

Step 1: MOS tube reverse connection protection: Design the circuit using the switching characteristics of the MOS tube. The MOS tube is turned on when the power is normally connected, and the MOS tube is turned off when the power is reversely connected.

Step 2: Overcurrent protection: Connect a fuse in series in the circuit. When the current is too large, the fuse will blow and cut off the circuit.

Step 3: Overvoltage protection: Connect to the linear voltage regulator circuit. When the input voltage is less than the reference voltage, the device works normally. When the input voltage is greater than the reference voltage, the voltage is clamped to the reference voltage.

Further preferably, in step 1, the MOS tube reverse connection protection method comprises the following steps:

S1: Select a MOS tube according to the circuit requirements. The drain of the MOS tube is connected to the negative pole of the power supply, and the gate is turned on at a high level.

S2: Connect the S and D poles of the MOS tube in series in the negative circuit of the power supply. When the power supply is connected normally, the MOS tube is turned on. When the power supply is reversed, the MOS tube is not turned on.

S3: Provides a bias resistor for the MOS tube, and provides a gate-source voltage to make the MOS tube saturated and turned on when the power supply is normally connected;

S4: Use circuit simulation software to simulate the designed anti-reverse connection circuit to verify whether its behavior is as expected when the power supply is connected forward and reverse.

Further preferably, in S1, the on-resistance of the MOS tube and the withstand voltage value of the MOS tube are determined according to circuit requirements, and a MOS tube of mΩ level is selected.

Further preferably, in S3, the resistance of the bias resistor is selected according to the characteristics of the MOS tube and circuit requirements;

A voltage regulator is connected across the gate-source voltage of the MOS tube, and the voltage regulation value of the voltage regulator is selected according to the maximum withstand voltage value of the gate-source voltage of the MOS tube.

Further preferably, in step 2, the overcurrent protection method comprises the following steps:

A1: Select the rated current of the fuse according to the operating current range of the circuit, and select the fuse according to the rated voltage, breaking capacity and appearance parameters of the fuse;

A2: Install the fuse at the input end or key branch path of the circuit, and connect the fuse pins to the pads or terminals on the circuit board;

A3: Before the circuit is powered on, use a test instrument to perform a functional test on the fuse to verify that it will not blow under normal current and will blow in time when overcurrent occurs.

Further preferably, in A1, the rated current of the fuse is greater than the maximum normal operating current of the circuit.

Further preferably, in A3, an overcurrent is simulated to observe the blowing condition of the fuse, and the fuse can be reliably blown within a set overcurrent threshold.

Further preferably, in step three, the overvoltage protection method comprises the following steps:

D1: Select a linear regulator based on circuit requirements. Factors to consider include input voltage range, output voltage range, output current capability, efficiency, and packaging.

D2: Connect the linear regulator to the circuit, connect the input end to the power input end that needs to be protected, and connect the output end to the subsequent circuit;

D3: According to the circuit requirements, the reference voltage is set through external resistor voltage division or internal reference voltage source. The reference voltage is the reference value of the linear regulator output voltage. When the input voltage exceeds the reference voltage, the output voltage will be clamped to the reference voltage.

D4: After the circuit is built, use a test instrument to test the circuit to verify whether its output voltage meets the requirements under normal input voltage.

Further preferably, in D2, suitable input and output filter capacitors and resistor elements are designed according to the data sheet of the linear regulator.

Further preferably, in D4, after the circuit is built, the circuit overvoltage is simulated, the input voltage is gradually increased, and it is observed whether the output voltage can be clamped and remain stable when the reference voltage is reached.

Since the embodiment of the present invention adopts the above technical solution, it has the following advantages: the present invention uses MOS tubes in series at the input end, utilizes the unidirectional conductivity or switching characteristics of the MOS tube elements to prevent the flow of reverse current, thereby playing a protective role against reverse connection; a fuse is added to the input end or the circuit, when the current exceeds the set threshold, these elements will quickly cut off the power supply or limit the current, thereby playing a protective role against overcurrent; by adding an overvoltage protection circuit at the input end, such as using a voltage regulator diode, when the input voltage exceeds the set threshold, these elements will limit the voltage or cut off the power supply, thereby playing a protective role against overvoltage; through the protective measures against reverse connection, overcurrent, and overvoltage, the risk of circuit and equipment damage caused by abnormal power input can be significantly reduced, and the reliability and stability of the equipment can be improved.

The above summary is for illustrative purposes only and is not intended to be limiting in any way. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features of the present invention will be readily apparent by reference to the accompanying drawings and the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

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 or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a flow chart of the steps of a protection method for preventing reverse connection and overcurrent and overvoltage of a DC power input according to the present invention;

FIG2 is a flowchart of the steps of the MOS tube reverse connection protection method of the present invention;

FIG3 is a flow chart of the steps of the overcurrent protection method of the present invention;

FIG4 is a flow chart of the steps of the overvoltage protection method of the present invention;

FIG5 is a circuit diagram of an anti-reverse connection circuit according to the present invention;

FIG6 is a circuit diagram of an input voltage regulator according to the present invention.

DETAILED DESCRIPTION

In the following, only some exemplary embodiments are briefly described. As those skilled in the art will appreciate, the described embodiments may be modified in various ways without departing from the spirit or scope of the present invention. Therefore, the drawings and descriptions are considered to be exemplary and non-restrictive in nature.

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

As shown in FIG. 1-6 , an embodiment of the present invention provides a DC power supply input protection method for preventing reverse connection and overcurrent and overvoltage, comprising the following steps:

Step 1: MOS tube reverse connection protection: Design the circuit using the switching characteristics of the MOS tube. The MOS tube is turned on when the power is normally connected, and the MOS tube is turned off when the power is reversely connected.

Step 2: Overcurrent protection: Connect a fuse in series in the circuit. When the current is too large, the fuse will blow and cut off the circuit.

Step 3: Overvoltage protection: Connect to the linear voltage regulator circuit. When the input voltage is less than the reference voltage, the device works normally. When the input voltage is greater than the reference voltage, the voltage is clamped to the reference voltage.

MOS tube, or metal oxide semiconductor field effect transistor, is a semiconductor device that works based on the field effect principle.

In one embodiment, in step 1, the MOS tube reverse connection protection method includes the following steps:

S1: Select a MOS tube according to the circuit requirements. The drain of the MOS tube is connected to the negative pole of the power supply, and the gate is turned on at a high level.

S2: Connect the S and D poles of the MOS tube in series in the negative circuit of the power supply. When the power supply is connected normally, the MOS tube is turned on. When the power supply is reversed, the MOS tube is not turned on.

S3: Provides a bias resistor for the MOS tube, and provides a gate-source voltage to make the MOS tube saturated and turned on when the power supply is normally connected;

S4: Use circuit simulation software to simulate the designed anti-reverse connection circuit to verify whether its behavior is as expected when the power supply is connected forward and reverse.

In one embodiment, in S1, the on-resistance and withstand voltage of the MOS tube are determined according to circuit requirements, and a MOS tube of mΩ level is selected. NMOS or PMOS is selected according to requirements. The on-resistance of NMOS is usually smaller than that of PMOS, and it is cost-effective, so it is often used as a switch element in an anti-reverse connection circuit.

There is a body diode (also called a parasitic diode) inside the NMOS tube, with its anode connected to the D pole and its cathode connected to the S pole. When the power is just turned on, due to the existence of the body diode, the ground loop may be connected through the body diode, but as the gate-source voltage gradually increases and exceeds the threshold voltage, the MOS tube will be officially turned on and the effect of the body diode will weaken.

In one embodiment, in S3, the resistance of the bias resistor is selected according to the characteristics of the MOS tube and circuit requirements;

A voltage regulator is connected across the gate-source voltage of the MOS tube. The voltage regulator value is selected according to the maximum withstand voltage of the gate-source voltage of the MOS tube. The voltage regulator can prevent the gate-source voltage from being too high and breaking down the MOS tube.

Build an anti-reverse connection circuit in the actual circuit, and use a power supply tester and other equipment to perform actual tests to check whether the circuit works normally when the power supply is connected in the forward direction, and whether it can effectively protect the load from damage when the power supply is connected in the reverse direction;

By connecting a diode in series at the input end, using a MOS tube or other anti-reverse connection circuit, and utilizing the unidirectional conductivity or switching characteristics of these components, the flow of reverse current is prevented, thereby protecting the circuit and equipment.

In one embodiment, in step 2, the overcurrent protection method includes the following steps:

A1: Select the rated current of the fuse according to the operating current range of the circuit, and select the fuse according to the rated voltage, breaking capacity and appearance parameters of the fuse;

A2: Install the fuse at the input end or key branch path of the circuit, and connect the fuse pins to the pads or terminals on the circuit board;

A3: Before the circuit is powered on, use a test instrument to perform a functional test on the fuse to verify that it will not blow under normal current and will blow in time when overcurrent occurs.

In one embodiment, in A1, the rated current of the fuse is greater than the maximum normal operating current of the circuit to ensure that it will not blow accidentally under normal operating conditions. A suitable fuse type is selected according to application requirements, such as a fast fuse, a slow fuse, a polysilicon fuse, a smart fuse, etc.

In one embodiment, in A3, an overcurrent is simulated to observe the fusing condition of the fuse, and the fuse can be reliably blown within the set overcurrent threshold;

After the circuit or equipment has been operating normally for a period of time, check the status of the fuse regularly to ensure that it has good long-term stability and does not cause false fusing or failure.

By adding fuses at the input or in the circuit, these components quickly cut off the power supply or limit the current when the current exceeds the set threshold, thus protecting the circuit and equipment.

In one embodiment, in step three, the overvoltage protection method includes the following steps:

D1: Select a linear regulator based on circuit requirements. Factors to consider include input voltage range, output voltage range, output current capability, efficiency, and packaging.

D2: Connect the linear regulator to the circuit, connect the input end to the power input end that needs to be protected, and connect the output end to the subsequent circuit;

D3: According to the circuit requirements, the reference voltage is set through external resistor voltage division or internal reference voltage source. The reference voltage is the reference value of the linear regulator output voltage. When the input voltage exceeds the reference voltage, the output voltage will be clamped to the reference voltage.

D4: After the circuit is built, use a test instrument to test the circuit to verify whether its output voltage meets the requirements under normal input voltage;

In power supply systems or electronic devices, the input voltage may suddenly increase due to various reasons (such as power failure, load mutation, etc.). If there is no protection measure for the subsequent circuit, the excessively high voltage may damage the components in the circuit or even cause the entire system to fail. By connecting a linear voltage regulator circuit, the input voltage can be clamped to the reference voltage when it exceeds the reference voltage, thereby protecting the subsequent circuit from damage.

In one embodiment, in D2, appropriate input and output filter capacitors and resistor elements are designed according to the data sheet of the linear regulator. In the design of the linear regulator, it is crucial to select appropriate input and output filter capacitors and resistor elements, which can jointly ensure that the regulator can work stably and reliably.

In one embodiment, in D4, after the circuit is built, the circuit overvoltage is simulated, the input voltage is gradually increased, and it is observed whether the output voltage can be clamped and remain stable when the reference voltage is reached. According to the test results, the circuit is adjusted and optimized, and the parameters of components such as resistors and capacitors may need to be adjusted to improve the performance and stability of the circuit;

Add overvoltage protection circuits at the input end, such as using Zener diodes. When the input voltage exceeds the set threshold, these components will limit the voltage or cut off the power supply to protect circuits and equipment.

As shown in Figure 6, the input voltage stabilization circuit diagram,

Here’s how it works:

1. The voltage regulator Dz is connected in series with the current limiting resistor R to obtain the reference voltage V _REF ;

2. R ¹ , R ^P and R ² form a feedback network to obtain a feedback voltage V _F ＝/fracR' ₂ R' ₁ +R' ₂ V _O ;

3. The change of net input V _REF -V _F causes the change of _VB ;

4.The change of VB changes the voltage drop V _CE between the ce electrodes of the adjustment tube T, thereby stabilizing the output of V _O.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of various changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims (10)

1. The protection method for preventing reverse connection and overcurrent and overvoltage of the DC power input is characterized by comprising the following steps of:

step one: reverse connection prevention protection of MOS tube: designing a circuit by utilizing the switching characteristics of the MOS tube, switching on the MOS tube when the power supply is normally connected, and switching off the MOS tube when the power supply is reversely connected;

Step two: overcurrent protection: the fuse is connected in series in the circuit, and when the current is overlarge, the fuse is fused to cut off the circuit;

step three: overvoltage protection: and the linear voltage stabilizing circuit is connected, when the input voltage is smaller than the reference voltage, the device works normally, and when the input voltage is larger than the reference voltage, the voltage is embedded into the reference voltage.

2. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 1, wherein the method comprises the following steps: in the first step, the reverse connection prevention protection method for the MOS tube comprises the following steps:

s1: selecting an MOS tube according to the circuit requirement, wherein the drain electrode of the MOS tube is connected with the negative electrode of the power supply, and the grid electrode is conducted at a high level;

S2: the S pole and the D pole of the MOS tube are connected in series in a negative circuit of the power supply, when the power supply is normally connected, the MOS tube is conducted, and when the power supply is reversely connected, the MOS tube is not conducted;

S3: providing a bias resistor for the MOS tube, and providing a gate-source voltage to enable the MOS tube to be saturated and conducted when a power supply is normally connected;

S4: and using circuit simulation software to perform simulation test on the designed reverse connection prevention circuit to verify whether the behavior of the reverse connection prevention circuit accords with the expectations when the power supply is connected in the forward and reverse directions.

3. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 2, wherein the method comprises the following steps: in S1, the on-resistance of the MOS tube and the withstand voltage value of the MOS tube are confirmed according to the circuit requirement, and the mΩ -level MOS tube is selected.

4. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 2, wherein the method comprises the following steps: in S3, the resistance value of the bias resistor is selected according to the characteristics of the MOS tube and the circuit requirement;

and a voltage stabilizing tube is connected across the gate-source voltage of the MOS tube, and the voltage stabilizing value of the voltage stabilizing tube is selected according to the maximum withstand voltage value of the gate-source voltage of the MOS tube.

5. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 1, wherein the method comprises the following steps: in the second step, the overcurrent protection method includes the following steps:

A1: selecting a rated current of the fuse according to the working current range of the circuit, and selecting the fuse according to rated voltage, breaking capacity and appearance shape parameters of the fuse;

A2: mounting a fuse on an input end or a key branch path of a circuit, and connecting pins of the fuse with bonding pads or wiring terminals on a circuit board;

a3: before the circuit is electrified, a testing instrument is used for carrying out functional test on the fuse, so that the fuse is verified to be not fused under normal current, and is fused in time when overcurrent occurs.

6. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 5, wherein the method comprises the following steps: in A1, the rated current of the fuse is greater than the maximum normal operating current of the circuit.

7. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 5, wherein the method comprises the following steps: in A3, the fusing condition of the fuse is simulated and observed, and the fuse can be reliably fused in a set overcurrent threshold.

8. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 1, wherein the method comprises the following steps: in the third step, the overvoltage protection method includes the following steps:

D1: selecting a linear voltage stabilizer according to circuit requirements, wherein factors to be considered include an input voltage range, an output voltage range, output current capability, efficiency and packaging form;

D2: the linear voltage stabilizer is connected into a circuit, the input end of the linear voltage stabilizer is connected to the power input end to be protected, and the output end of the linear voltage stabilizer is connected to a subsequent circuit;

D3: setting a reference voltage, which is a reference value of an output voltage of the linear voltage regulator, through external resistor voltage division or an internal reference voltage source according to circuit requirements, wherein the output voltage is embedded into the reference voltage when the input voltage exceeds the reference voltage;

D4: after the circuit is built, a testing instrument is used for testing the circuit, and whether the output voltage of the circuit under the normal input voltage meets the requirement is verified.

9. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 8, wherein the method comprises the following steps: in D2, appropriate input and output filter capacitors and resistor elements are designed according to the data manual of the linear voltage regulator.

10. The method for protecting the DC power input from reverse connection and over-current and over-voltage according to claim 8, wherein the method comprises the following steps: in D4, after the circuit is built up, the analog circuit is over-voltage, the input voltage is gradually increased, and it is observed whether the output voltage can be clamped and kept stable when reaching the reference voltage.