A low-side control circuit for reverse connection protection

Abstract

This invention discloses a reverse-connection-protected low-side control circuit, comprising a main switch module, a control module, and a load R_Load. The main switch module receives signals from the control module and generates corresponding switching actions, and also has a reverse-connection protection function. The control module includes start and stop buttons for transmitting, driving, or indicating signals to the next-level circuit. This reverse-connection-protected low-side control circuit overcomes the shortcomings of existing technologies, has a wide voltage adaptability range, and does not require extensive consideration of level conversion circuits when applied to control circuits with different voltage ranges. It also prevents DC power supply reverse connection and adds a new option to the electrical control field that can achieve start, hold (self-locking), and stop functions while simultaneously meeting the requirements of simple structure, low cost, small size, low power consumption, and high versatility.

Description

Technical Field

[0001] This invention relates to the field of DC electrical control, and in particular to a low-side control circuit that prevents reverse connection. Background Technology

[0002] Control circuits employing start, hold (self-locking), and stop functions are widely used in the field of electrical control. They feature clearly marked and easy-to-operate start and stop buttons to connect and disconnect the controlled circuit. Similar to RAM in a computer, they possess a "memory retention" function: they are easily lost when power is off, but not easily lost when power is restored. That is, when the control circuit loses power, it automatically disconnects the controlled circuit, requiring manual intervention upon power restoration. Pressing the start button at this point will "memorize" and retain the powered-on start state; similarly, pressing the stop button will "memorize" and retain the power-off stop state. Because of this reliable safety advantage, they have been widely used by industry professionals since their inception.

[0003] Currently, the control circuits that use DC control circuits to achieve start, hold (self-locking) and stop functions are different from AC control circuits. They have positive and negative polarities and cannot be reversed. In addition, DC control circuits are divided into high-side control mode and low-side control mode. The so-called high-side control mode means that the DC control circuit is connected between the power supply and the load, while the low-side control mode means that the DC control circuit is connected between the load and the power supply ground.

[0004] The inventors discovered during the implementation of the embodiments of the present invention that: 1) At present, circuits using low-side control have a narrow voltage range adaptability. When used in control circuits with different voltage ranges, level conversion circuits need to be added, and the versatility is poor. If pure electromagnetic relay control is used, although it is simple and reliable, it is large in size, consumes a lot of power and has a relatively high cost. 2) At present, the circuits using the low-side control method are powered by DC power supply. The DC power supply has positive and negative polarity requirements, and even the DC load has positive and negative polarity restrictions. Therefore, the problem of reverse connection protection must be considered, otherwise the power supply or components with polarity requirements in the circuit may be burned out. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a low-side control circuit for preventing reverse connection, the specific technical solution of which is as follows: A low-side control circuit for reverse connection protection includes a main switch module, a control module, and a load R_Load; The main switch module includes a bias resistor R3, a bias resistor R4, a MOSFET Q2, and a MOSFET Q3; both MOSFET Q2 and MOSFET Q3 are N-channel MOSFETs. The control module includes a start button S1, a stop button S2, bias resistors R1, R2, and R5, capacitors C1 and C2, and a transistor Q1; the transistor Q1 is an NPN type BJT transistor; wherein the start button S1 is a normally closed button, and the stop button S2 is a normally open button. In the main switch module, MOSFETs Q2 and Q3 are connected in reverse series to prevent reverse connection of the DC power supply. That is, the source of MOSFET Q2 is connected to the source of MOSFET Q3, while the gate of MOSFET Q2 is connected to the gate of MOSFET Q3. The drain of MOSFET Q2 is connected to the power supply ground, and the drain of MOSFET Q3 is connected to one end of the load R_Load. One end of the bias resistor R3 is connected to the power supply ground, and the other end is connected to one end of the bias resistor R4. The connection point of R4 is connected to the gate of MOSFET Q2 or the gate of MOSFET Q3. In the control module, one end of the bias resistor R1 is connected to the power supply VCC, and the other end of the bias resistor R1 is connected to the collector of transistor Q1, one end of capacitor C2, the other end of bias resistor R4, and one end of stop button S2. The other end of capacitor C2 is connected to the power supply ground. The emitter of transistor Q1 is connected to the power supply ground. The base of transistor Q1 is connected to one end of bias resistor R2 and one end of capacitor C1. The other end of capacitor C1 is connected to the power supply ground. The other end of bias resistor R2 is connected not only to the other end of stop button S2 but also to one end of start button S1. The other end of start button S1 is connected to one end of bias resistor R5. The other end of bias resistor R5 is connected to the drain of MOSFET Q3. The other end of the load R_Load is connected to the power supply VCC.

[0006] The beneficial effects of this invention are that the reverse connection-protected low-side position control circuit provided by this invention overcomes the defects of the prior art, has a wide voltage adaptation range, does not require much consideration of level conversion circuit when applied to control circuits in different voltage ranges, can also prevent DC power supply reverse connection, and adds a technical application option to the field of electrical control that can realize start, hold (self-locking) and stop functions, while also meeting the requirements of simple structure, low cost, small size, low power consumption and strong versatility. Attached Figure Description

[0007] Figure 1 This is a typical schematic diagram of a low-side position control circuit for preventing reverse connection according to the present invention.

[0008] Figure 2 This is a specific example of a low-side position control circuit for preventing reverse connection according to the present invention.

[0009] Figure 3This is a specific example of a reverse connection prevention low-side position control circuit according to the present invention. Detailed Implementation

[0010] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0011] Appendix Figure 1 The diagram shown is a typical schematic of a low-side control circuit for reverse connection protection according to the present invention, including a main switch module, a control module and a load R_Load; The main switch module includes a bias resistor R3, a bias resistor R4, a MOSFET Q2, and a MOSFET Q3; both MOSFET Q2 and MOSFET Q3 are N-channel MOSFETs. The control module includes a start button S1, a stop button S2, bias resistors R1, R2, and R5, capacitors C1 and C2, and a transistor Q1; the transistor Q1 is an NPN type BJT transistor; wherein the start button S1 is a normally closed button, and the stop button S2 is a normally open button. In the main switch module, MOSFETs Q2 and Q3 are connected in reverse series to prevent reverse connection of the DC power supply. That is, the source of MOSFET Q2 is connected to the source of MOSFET Q3, while the gate of MOSFET Q2 is connected to the gate of MOSFET Q3. The drain of MOSFET Q2 is connected to the power supply ground, and the drain of MOSFET Q3 is connected to one end of the load R_Load. One end of the bias resistor R3 is connected to the power supply ground, and the other end is connected to one end of the bias resistor R4. The connection point of R4 is connected to the gate of MOSFET Q2 or the gate of MOSFET Q3. In the control module, one end of the bias resistor R1 is connected to the power supply VCC, and the other end of the bias resistor R1 is connected to the collector of transistor Q1, one end of capacitor C2, the other end of bias resistor R4, and one end of stop button S2. The other end of capacitor C2 is connected to the power supply ground. The emitter of transistor Q1 is connected to the power supply ground. The base of transistor Q1 is connected to one end of bias resistor R2 and one end of capacitor C1. The other end of capacitor C1 is connected to the power supply ground. The other end of bias resistor R2 is connected not only to the other end of stop button S2 but also to one end of start button S1. The other end of start button S1 is connected to one end of bias resistor R5. The other end of bias resistor R5 is connected to the drain of MOSFET Q3. The other end of the load R_Load is connected to the power supply VCC.

[0012] The entire work process can be divided into four states: (1) In the initial state, when the power is first turned on, neither the start button S1 nor the stop button S2 is pressed. Although there will be a brief surge of voltage, the bias resistor R1 and the capacitor C2 form an RC buffer circuit. The R_Load load, the bias resistor R5, the start button S1, the bias resistor R2 and the capacitor C1 form another RC buffer circuit. Both of these RC buffer circuits can prevent the MOSFETs Q2 and Q3 in the main switch module from being falsely triggered by the bias resistors R3 and R4 when the power is first turned on. After a short time, the voltage on the capacitor C1 rises rapidly, causing the bias voltage between the base and emitter of the transistor Q1 to be formed. When this bias voltage is greater than the turn-on voltage of the transistor Q1, the transistor Q1 will be turned on, causing its collector to be at a low potential. Therefore, there will be no voltage difference greater than the turn-on voltage between the gate and source of the MOSFETs Q2 and Q3. That is, the MOSFETs Q2 and Q3 have not met the turn-on conditions and are in the off state. (2) Start-up state: After power-on, when the start button S1 is pressed, the start button S1 disconnects the branch consisting of power supply VCC, load R_Load, bias resistor R5 and bias resistor R2. Then, capacitor C1 and the base and emitter of transistor Q1 form a discharge circuit, which causes the voltage drop between the base and emitter of transistor Q1 to decrease rapidly, so that transistor Q1 is in the cut-off state and turned off. Its collector is at a high potential. At this time, this high potential is applied to the branch consisting of bias resistor R3 and bias resistor R4, so that a voltage difference greater than the turn-on voltage of MOSFET Q2 and MOSFET Q3 will be formed between the gate and source of MOSFET Q2 and MOSFET Q3. When this voltage difference is greater than the turn-on voltage of MOSFET Q2 and MOSFET Q3, MOSFET Q2 and MOSFET Q3 will quickly turn on, realizing the start-up control function. (3) Maintaining state: After the above start-up process is completed, when the start button S1 is released, since the drain of MOSFET Q3 is at a low potential, the bias resistor R5, start button S1, bias resistor R2 and capacitor C1 will also maintain a low potential. Therefore, transistor Q1 will remain off and remain turned off, and its collector will remain at a high potential, causing MOSFET Q2 and MOSFET Q3 to remain on, thus realizing the "memory" holding control function. (4) In the stopped state, after the above start-up and holding process is completed, since the collector of transistor Q1 was previously at a high potential, and the capacitor C2 connected to the bias resistor R1 was also at a high potential, when the stop button S2 is pressed, the capacitor C2, the stop button S2, the bias resistor R2, and the emitter and base of transistor Q1 form a discharge circuit, and transistor Q1 will immediately turn on, making the collector of transistor Q1 become low potential. At this time, this low potential is applied to the branch composed of bias resistor R3 and bias resistor R4, so that the gate and source of MOSFET Q2 and MOSFET Q3 are connected to a high potential. The voltage difference between them decreases rapidly, causing MOSFETs Q2 and Q3 to turn off. As a result, the drain of MOSFET Q3 becomes high. Even if the stop button S2 is reset and disconnected, the high potential on the drain of MOSFET Q3 is applied to the bias resistor R5, the start button S1, the bias resistor R2, and the base and emitter of transistor Q1 to form a circuit, causing transistor Q1 to conduct. Its collector remains at a low potential, so MOSFETs Q2 and Q3 in the main switch module remain in the off state, realizing the "memory" stop control function.

[0013] Appendix Figure 2 The diagram shows a specific example of a low-side bit control circuit for reverse polarity protection according to the present invention. (See attached diagram.) Figure 1 As shown, the load R_Load is replaced with a series branch consisting of a current-limiting resistor R6 and an LED; the LED is used to indicate the operation of the main switch module; after testing, the device parameters provided in this example can ensure reliable operation within the voltage range of 8V to 32V of the power supply VCC, which is relatively wider than the operating voltage range of using a pure relay control method; the working process of this example is analyzed in detail below: (1) In the initial state, when the power is first turned on, neither the start button S1 nor the stop button S2 is pressed, and the light-emitting diode LED will not be lit. (2) Start-up state: After power-on, when the start button S1 is pressed, the light-emitting diode (LED) lights up. (3) Maintain the state, release the start button S1, and the light-emitting diode LED will continue to light up; (4) In the stop state, press the stop button S2 and the light-emitting diode LED will turn off.

[0014] Appendix Figure 3 The image shows a specific example of a reverse connection prevention low-side position control circuit according to the present invention; in the appendix... Figure 2Based on this, if the power supply VCC and power supply ground are reversed, a voltage difference greater than the turn-on voltage of the MOSFETs Q2 and Q3 cannot be formed between their gates and sources. Therefore, the MOSFETs Q2 and Q3 will not meet the turn-on condition and will be in the off state. As a result, the LED will not be lit, thus achieving the reverse connection protection function.

Claims

1. A low-side position control circuit for reverse connection protection, characterized in that, Includes the main switch module, control module, and load R_Load; The main switch module includes a bias resistor R3, a bias resistor R4, a MOSFET Q2, and a MOSFET Q3; both MOSFET Q2 and MOSFET Q3 are N-channel MOSFETs. The control module includes a start button S1, a stop button S2, bias resistors R1, R2, and R5, capacitors C1 and C2, and a transistor Q1; the transistor Q1 is an NPN type BJT transistor; wherein the start button S1 is a normally closed button, and the stop button S2 is a normally open button. In the main switch module, MOSFETs Q2 and Q3 are connected in reverse series to prevent reverse connection of the DC power supply. That is, the source of MOSFET Q2 is connected to the source of MOSFET Q3, while the gate of MOSFET Q2 is connected to the gate of MOSFET Q3. The drain of MOSFET Q2 is connected to the power supply ground, and the drain of MOSFET Q3 is connected to one end of the load R_Load. One end of the bias resistor R3 is connected to the power supply ground, and the other end is connected to one end of the bias resistor R4. The connection point of R4 is connected to the gate of MOSFET Q2 or the gate of MOSFET Q3. In the control module, one end of the bias resistor R1 is connected to the power supply VCC. The other end of the bias resistor R1 is connected to the collector of transistor Q1, one end of capacitor C2, the other end of bias resistor R4, and one end of stop button S2. The other end of capacitor C2 is connected to power ground. The emitter of transistor Q1 is connected to power ground. The base of transistor Q1 is connected to one end of bias resistor R2 and one end of capacitor C1. The other end of capacitor C1 is connected to power ground. The other end of bias resistor R2 is connected not only to the other end of stop button S2 but also to one end of start button S1. The other end of start button S1 is connected to one end of bias resistor R5. The other end of bias resistor R5 is connected to the drain of MOSFET Q3. The other end of the load R_Load is connected to the power supply VCC.

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