A novel MOS tube current detection protection circuit with self-locking function

Abstract

The application discloses a novel MOS tube current detection protection circuit with a self-locking function, which is completely constructed by electronic devices and does not need a single-chip microcomputer and program control. The circuit is characterized in that the current sampling voltage of the MOS tube is continuously compared in multiple stages in a comparison circuit, the instantaneous overcurrent or continuous overcurrent during overcurrent is judged, and the switching of the MOS tube is controlled according to the comparison result by using a subsequent self-locking circuit and a MOS tube driving circuit, so that the repeated turn-on and turn-off of the MOS tube is avoided, and the safety of the device is ensured.

Description

Technical Field

[0001] This invention relates to the field of bus technology, and in particular to a novel MOS transistor current detection and protection circuit with self-locking function. Background Technology

[0002] The use of MOSFETs instead of relays is gradually becoming a trend in the current bus industry. Currently, current detection and protection circuits in buses mostly use resettable fuses or microcontroller sampling. Resettable fuses have relatively large errors and significant time delays; while microcontroller sampling is costly and has sampling intervals, making real-time protection impossible. Summary of the Invention

[0003] In view of this, the present invention provides a novel MOS transistor current detection and protection circuit with self-locking function to solve the problems existing in the background art.

[0004] A novel MOSFET current detection and protection circuit with self-locking function includes a high-side drive circuit, a comparator circuit, a self-locking circuit, and a MOSFET drive circuit.

[0005] The sampling resistor The signal output terminal is connected to the signal input terminal of the comparator circuit, and is used to output the current sampling voltage flowing through the MOSFET;

[0006] The signal output terminal of the comparison circuit is connected to the signal input terminal of the self-locking circuit, and is used to compare the current sampling voltage with its multi-stage overcurrent reference voltage step by step, and output the first control signal according to the comparison result.

[0007] The signal output terminal of the self-locking circuit is connected to the signal input terminal of the MOS transistor drive circuit, and is used to control the self-locking voltage output by the circuit according to the first control signal, so as to lock the self-locking voltage output by the circuit to a low level when a momentary overcurrent or a continuous overcurrent occurs.

[0008] The MOSFET driving circuit is used to control the switching of the MOSFET according to the received second control signal and the self-locking voltage, so that the MOSFET remains closed when a momentary overcurrent or a continuous overcurrent occurs.

[0009] Preferably, the high-side driving circuit includes a MOSFET, a load, and a current sampling resistor. The load is connected to the drain of the MOSFET and the first terminal of the current sampling resistor, respectively. The second terminal of the current sampling resistor is grounded, and the current sampling voltage is the voltage of the current sampling resistor.

[0010] Preferably, the comparison circuit includes a primary comparison module and a secondary comparison module connected in series with the primary comparison module.

[0011] The first-level comparison module is used to compare the current sampling voltage with its first overcurrent reference voltage once, and output a primary comparison signal based on the comparison result;

[0012] The secondary comparison module is used to determine the magnitude of its second overcurrent reference voltage based on the primary comparison signal, and to perform a secondary comparison between the current sampling voltage and the second overcurrent reference voltage, and output a first control signal based on the comparison result.

[0013] Preferably, the first-level comparison module includes a comparator U1A, a first voltage divider unit connected to the negative terminal of the comparator U1A, and the current sampling voltage input to the positive terminal of the comparator U1A.

[0014] Preferably, the first voltage divider unit includes resistors R1 and R2. The first ends of resistors R1 and R2 are both connected to the negative terminal of comparator U1A, the second end of resistor R1 is connected to the power supply, and the second end of resistor R2 is grounded.

[0015] Preferably, the secondary comparison module includes a comparator U1B, a transistor Q1, and a second voltage divider unit connected to the negative terminal of the comparator U1B and the collector of the transistor Q1, respectively. The base of the transistor Q1 is connected to the first terminal of the resistor R6 and the capacitor C1, respectively. The second terminal of the resistor R6 is connected to the output terminal of the comparator U1A. The emitter of the transistor Q1 and the second terminal of the capacitor C1 are both grounded.

[0016] Preferably, the second voltage divider unit includes resistors R3 and R4. The first ends of resistors R3 and R4 are both connected to the negative terminal of comparator U1B, the second end of resistor R3 is connected to the power supply, and the second end of resistor R4 is connected to the collector of transistor Q1.

[0017] Preferably, the self-locking circuit includes a diode D1, resistors R9, R10, R11, and a capacitor C2, all connected to the negative terminal of the diode D1.

[0018] The positive terminal of diode D1 is connected to the signal output terminal of the comparator circuit.

[0019] The second terminal of resistor R9 is connected to resistor R12 and the collector of transistor Q2. The emitter of transistor Q2 is connected to the power supply, and the base is connected to the first terminal of resistor R8. The second terminal of resistor R8 is connected to resistor R7 and the collector of transistor Q3. The second terminal of resistor R7 is connected to the power supply.

[0020] The second terminal of resistor R10 is connected to the base of transistor Q3, and the emitter of transistor Q3 is grounded.

[0021] The second terminals of resistors R11 and R12 and capacitor C2 are all grounded.

[0022] Preferably, the MOS transistor driving circuit includes an AND gate, a resistor R13 connected to the output of the AND gate, a transistor Q4 connected to the resistor R13, and a resistor R16. The collector of the transistor Q4 is connected to the resistor R14, the resistor R14 is connected to the resistor R15 and the gate of the MOS transistor, and the second terminal of the resistor R15 is connected to the source of the MOS transistor.

[0023] The second terminal of resistor R16 and the emitter terminal of transistor Q4 are both grounded.

[0024] The beneficial effects of this invention are:

[0025] 1. The circuit of this invention is entirely constructed from electronic components, requiring no microcontroller or program control. The circuit is simple and has high safety and stability.

[0026] 2. This invention performs multi-level continuous comparisons of the current sampling voltage flowing through the MOSFET in its comparison circuit to determine whether the overcurrent is instantaneous or continuous. Based on the comparison results, the subsequent self-locking circuit and MOSFET driving circuit are used to control the switching of the MOSFET, thereby avoiding the repeated on-off state of the MOSFET.

[0027] 3: The circuit of this invention can adjust the value of the overcurrent threshold and the response speed of the circuit. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a circuit block diagram of a new type of MOSFET current detection and protection circuit.

[0030] Figure 2 This is the circuit diagram of the high-side drive circuit.

[0031] Figure 3 This is the circuit diagram of a comparator circuit.

[0032] Figure 4 This is the circuit diagram of a self-locking circuit.

[0033] Figure 5 This is a circuit diagram of a MOSFET driver circuit. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0036] It should be understood that although the terms first, second, third, etc., may be used in this disclosure to describe various information, such information should not be limited to these terms and should not be construed as indicating or implying relative importance. These terms are used only to distinguish information of the same type from one another. For example, without departing from the scope of this disclosure, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0037] In the description of this invention, unless otherwise specified and limited, it should be noted that the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to electrical connection or internal connection between two components. They can be directly connected or indirectly connected through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms according to the specific circumstances.

[0038] In the following description, suffixes such as “module” or “unit” used to denote elements are used only for the purpose of illustrative purposes and have no specific meaning in themselves.

[0039] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0040] This invention provides a novel MOS transistor current detection and protection circuit with self-locking function. This circuit is constructed entirely of electronic components, without the need for a microcontroller or program control. The circuit is simple and has high safety and stability.

[0041] The novel MOSFET current detection and protection circuit with self-locking function of the present invention includes a high-side drive circuit, a comparator circuit, a self-locking circuit, and a MOSFET drive circuit. For example... Figure 1 As shown, Figure 1This is a circuit block diagram of the present invention. Figure 1 In the circuit MAIN, the high-side drive circuit is used; circuit A is a comparator circuit; circuit B is a self-locking circuit; and circuit C is an AND gate + MOSFET drive circuit. Under normal operating conditions, the MOSFET is on, supplying power to the load LOAD. The voltage across the current sampling resistor Sample R is the current sampling voltage V - SampleR, which is proportional to the current and conforms to the law V = I*R. In this embodiment, a small-value, high-power resistor is selected for Sample R. When a momentary or continuous overcurrent occurs in the circuit, the AND gate + MOSFET drive circuit C outputs a control signal to turn off the MOSFET, stopping power supply to the load.

[0042] The signal output terminal of the high-side drive circuit is connected to the signal input terminal of the comparator circuit, and is used to output the current sampling voltage flowing through the MOS transistor.

[0043] The signal output terminal of the comparison circuit is connected to the signal input terminal of the self-locking circuit, and is used to compare the current sampling voltage with its multi-stage overcurrent reference voltage step by step, and output the first control signal according to the comparison result.

[0044] The signal output terminal of the self-locking circuit is connected to the signal input terminal of the MOS transistor drive circuit, and is used to control its output self-locking voltage according to the first control signal, so as to lock its output self-locking voltage at a low level when instantaneous overcurrent or continuous overcurrent occurs.

[0045] The MOSFET driving circuit is used to control the switching of the MOSFET according to the received second control signal and the self-locking voltage, so that the MOSFET remains closed when a momentary overcurrent or a continuous overcurrent occurs.

[0046] The novel MOSFET current detection and protection circuit with self-locking function of the present invention performs multi-level continuous comparison of the current sampling voltage flowing through the MOSFET in its comparison circuit to determine whether the overcurrent is instantaneous or continuous. Based on the comparison result, the subsequent self-locking circuit and MOSFET driving circuit are used to control the switching of the MOSFET, thereby avoiding the repeated on-off situation of the MOSFET.

[0047] Specifically, such as Figure 2 As shown, Figure 2 This is a circuit diagram of the high-side drive circuit. The high-side drive circuit includes a MOSFET, a load, and a current sampling resistor. The load is connected to the drain of the MOSFET and the first terminal of the current sampling resistor, respectively, while the second terminal of the current sampling resistor is grounded. The high-side drive circuit outputs the current sampling voltage V—SampleR to the comparator circuit.

[0048] The comparison circuit includes a primary comparison module and a secondary comparison module connected in series with the primary comparison module. The primary comparison module compares the current sampling voltage with its first overcurrent reference voltage once, and outputs a primary comparison signal based on the comparison result. The secondary comparison module determines the magnitude of its second overcurrent reference voltage based on the primary comparison signal, compares the current sampling voltage with the second overcurrent reference voltage a second time, and outputs a first control signal based on the comparison result.

[0049] like Figure 3 As shown, Figure 3 This is the circuit diagram for the comparison circuit.

[0050] The first-stage comparison module in the comparison circuit includes a comparator U1A and a first voltage divider unit connected to the negative terminal of the comparator U1A. The first voltage divider unit includes resistors R1 and R2. The first terminals of both resistors R1 and R2 are connected to the negative terminal of the comparator U1A, the second terminal of resistor R1 is connected to the power supply, and the second terminal of resistor R2 is grounded.

[0051] The secondary comparator module in the comparator circuit includes a comparator U1B, a transistor Q1, and a second voltage divider unit connected to the negative terminal of comparator U1B and the collector of transistor Q1, respectively. The second voltage divider unit includes resistors R3 and R4. The first terminals of resistors R3 and R4 are both connected to the negative terminal of comparator U1B, the second terminal of resistor R3 is connected to the power supply, and the second terminal of resistor R4 is connected to the collector of transistor Q1.

[0052] The base of transistor Q1 is connected to the first terminal of resistor R6 and capacitor C1 respectively. The second terminal of resistor R6 is connected to the output terminal of comparator U1A. The emitter of transistor Q1 and the second terminal of capacitor C1 are both grounded.

[0053] When the current sampling voltage V-SampleR is input to the positive terminal of comparator U1A, resistors R1 and R2 generate a first overcurrent reference voltage V1 through voltage division. The current sampling voltage V-SampleR and the first overcurrent reference voltage V1 are compared in comparator U1A.

[0054] When the current sampling voltage V-SampleR is greater than the first overcurrent reference voltage V1, the comparator U1A outputs a high level (primary comparison signal), thus turning on transistor Q1. When transistor Q1 is on, resistors R3 and R4 generate a second overcurrent reference voltage V2 through voltage division. The current sampling voltage V-SampleR and the second overcurrent reference voltage V2 are compared in comparator U1B. When the current sampling voltage V-SampleR is greater than the second overcurrent reference voltage V2, comparator U1B outputs a high level (i.e., ...). Figure 3The first control signal A-OUT); when the current sampling voltage V-SampleR is less than the second overcurrent reference voltage V2, the comparator U1B outputs a low level (i.e., Figure 3 The first control signal A-OUT in the middle),

[0055] When the current sampling voltage V-SampleR is less than the first overcurrent reference voltage V1, comparator U1A outputs a low level (primary comparison signal), and transistor Q1 is turned off. When transistor Q1 is off, the voltage at the negative terminal of comparator U1B is VCC, meaning the second overcurrent reference voltage V2 is VCC. Since the current sampling voltage V-SampleR is necessarily less than VCC, comparator U1B outputs a low level (i.e.,...). Figure 3 The first control signal A-OUT in the process.

[0056] In this embodiment, VCC can be 5V or other voltages, but it must be consistent with the operating voltages of comparators U1A and U1B.

[0057] The first overcurrent reference voltage V1 and the second overcurrent reference voltage V2 are overcurrent threshold values. The comparator circuit outputs a high level only when both of the current sampling voltage V-SampleR comparisons are greater than the overcurrent threshold value; otherwise, it outputs a low level.

[0058] In the comparison circuit, resistor R6 and capacitor C1 form an RC filter delay circuit to control the interval between two comparisons. The length of the interval indicates the length of the overcurrent time, which can avoid interference caused by glitches or instantaneous changes.

[0059] The self-locking circuit is used to control the output of a self-locking voltage B-OUT according to the first control signal A-OUT output by the comparator circuit, so as to lock the output self-locking voltage B-OUT at a low level when a momentary overcurrent or a continuous overcurrent occurs.

[0060] Without a latching circuit, directly using the first control signal A-OUT from the comparator circuit to control the MOSFET will cause repeated switching on and off of the MOSFET, which is very damaging. For example, during normal operation, if the load suddenly short-circuits, the comparator circuit will turn off the MOSFET; however, after turning it off, the current is 0, and the voltage V-Sample R is also 0, so the comparator circuit will turn the MOSFET back on; again, because the load is short-circuited, turning on the MOSFET causes a short circuit in the power supply, resulting in a large current in the circuit, and the comparator circuit will turn the MOSFET off again. This cycle repeats continuously, causing significant damage to both the MOSFET and the load.

[0061] like Figure 4 As shown, Figure 4This is a circuit diagram of a self-locking circuit. The self-locking circuit includes a diode D1, resistors R9, R10, and R11, and a capacitor C2, all connected to the cathode of diode D1.

[0062] The positive terminal of diode D1 is connected to the signal output terminal of the comparator circuit.

[0063] The second terminal of resistor R9 is connected to resistor R12 and the collector of transistor Q2. The emitter of transistor Q2 is connected to the power supply, and the base is connected to the first terminal of resistor R8. The second terminal of resistor R8 is connected to resistor R7 and the collector of transistor Q3. The second terminal of resistor R7 is connected to the power supply.

[0064] The second terminal of resistor R10 is connected to the base of transistor Q3, and the emitter of transistor Q3 is grounded.

[0065] The second terminals of resistors R11 and R12 and capacitor C2 are all grounded.

[0066] When the first control signal A-OUT output by the comparator circuit is low, transistor Q3 is turned off due to the presence of pull-down resistor R11, which causes transistor Q2 to also be turned off. Therefore, its output latching voltage B-OUT is high.

[0067] When the first control signal A-OUT output by the comparator circuit goes high, transistor Q3 turns on, causing transistor Q2 to also turn on. Therefore, its output latching voltage B-OUT is low.

[0068] When the first control signal A-OUT output by the comparator circuit goes low again, due to the unidirectional conduction characteristic of diode D1, the change of the first control signal A-OUT from high to low has no effect on the conduction and turn-off of transistors Q2 and Q3 in the subsequent circuit, so its output latching voltage B-OUT is low.

[0069] Therefore, once an overcurrent occurs in the circuit, the self-locking circuit can lock its output self-locking voltage B-OUT at a low level, and then control the MOSFET to turn off through the self-locking voltage B-OUT and the second control signal MOS-G.

[0070] like Figure 5 As shown, Figure 5 This is a circuit diagram of a MOSFET driver circuit, which is an AND gate + MOSFET driver circuit.

[0071] The MOSFET driver circuit includes an AND gate U201A, a resistor R13 connected to the output of the AND gate U201A, a transistor Q4 connected to the resistor R13, and a resistor R16. The collector of the transistor Q4 is connected to the resistor R14. The resistor R14 is connected to the resistor R15 and the gate of the MOSFET. The second terminal of the resistor R15 is connected to the source of the MOSFET.

[0072] The second terminal of resistor R16 and the emitter terminal of transistor Q4 are both grounded.

[0073] The self-locking voltage B-OUT output by the self-locking circuit and the second control signal MOS-G are the two inputs of the AND gate. The second control signal MOS-G comes from the input of the switch quantity or the MCU. The truth table of the AND gate is as follows:

[0074] 0 0 0 0 1 0 1 0 0 1 1 1

[0075] When the latching voltage B-OUT is low, the AND gate outputs a low level, which in turn controls the MOS to turn off through the transistor Q4.

[0076] When the latching voltage B-OUT is high, the AND gate outputs a high level, which in turn controls the MOS to turn on via transistor Q4.

[0077] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A novel MOSFET current detection and protection circuit with self-locking function, characterized in that, It includes a high-side drive circuit, a comparator circuit, a latching circuit, and a MOSFET drive circuit. The sampling signal output terminal of the high-side drive circuit is connected to the signal input terminal of the comparator circuit, and is used to output the current sampling voltage flowing through the MOS transistor. The signal output terminal of the comparison circuit is connected to the signal input terminal of the self-locking circuit, and is used to compare the current sampling voltage with its multi-stage overcurrent reference voltage step by step, and output the first control signal according to the comparison result. The signal output terminal of the self-locking circuit is connected to the signal input terminal of the MOS transistor drive circuit, and is used to control the self-locking voltage output by the circuit according to the first control signal, so as to lock the self-locking voltage output by the circuit to a low level when a momentary overcurrent or a continuous overcurrent occurs. The MOSFET driving circuit is used to control the switching of the MOSFET according to the received second control signal and the self-locking voltage, so that the MOSFET always remains closed when a momentary overcurrent or a continuous overcurrent occurs. The high-side driving circuit includes a MOSFET, a load, and a current sampling resistor. The load is connected to the drain of the MOSFET and the first terminal of the current sampling resistor, respectively. The second terminal of the current sampling resistor is grounded, and the current sampling voltage is the voltage of the current sampling resistor. The MOS transistor driving circuit includes an AND gate, a resistor R13 connected to the output of the AND gate, a transistor Q4 connected to resistor R13, and a resistor R16. The collector of transistor Q4 is connected to resistor R14. Resistor R14 is connected to resistor R15 and the gate of the MOS transistor. The second terminal of resistor R15 is connected to the source of the MOS transistor. The second terminal of resistor R16 and the emitter terminal of transistor Q4 are both grounded.

2. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 1, characterized in that, The comparison circuit includes a primary comparison module and a secondary comparison module connected in series with the primary comparison module. The first-level comparison module is used to compare the current sampling voltage with its first overcurrent reference voltage once, and output a primary comparison signal based on the comparison result; The secondary comparison module is used to determine the magnitude of its second overcurrent reference voltage based on the primary comparison signal, and to perform a secondary comparison between the current sampling voltage and the second overcurrent reference voltage, and output a first control signal based on the comparison result.

3. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 2, characterized in that, The first-level comparison module includes a comparator U1A, a first voltage divider unit connected to the negative terminal of the comparator U1A, and the current sampling voltage input to the positive terminal of the comparator U1A.

4. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 3, characterized in that, The first voltage divider unit includes resistors R1 and R2. The first ends of resistors R1 and R2 are both connected to the negative terminal of comparator U1A. The second end of resistor R1 is connected to the power supply, and the second end of resistor R2 is grounded.

5. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 3, characterized in that, The secondary comparison module includes a comparator U1B, a transistor Q1, and a second voltage divider unit connected to the negative terminal of the comparator U1B and the collector of the transistor Q1, respectively. The base of the transistor Q1 is connected to the first terminal of the resistor R6 and the capacitor C1, respectively. The second terminal of the resistor R6 is connected to the output terminal of the comparator U1A. The emitter of the transistor Q1 and the second terminal of the capacitor C1 are both grounded.

6. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 5, characterized in that, The second voltage divider unit includes resistors R3 and R4. The first ends of resistors R3 and R4 are both connected to the negative terminal of comparator U1B. The second end of resistor R3 is connected to the power supply, and the second end of resistor R4 is connected to the collector of transistor Q1.

7. The novel MOS transistor current detection and protection circuit with self-locking function according to claim 1, characterized in that, The self-locking circuit includes a diode D1, resistors R9, R10, R11, and a capacitor C2, all connected to the negative terminal of the diode D1. The positive terminal of diode D1 is connected to the signal output terminal of the comparator circuit. The second terminal of resistor R9 is connected to resistor R12 and the collector of transistor Q2. The emitter of transistor Q2 is connected to the power supply, and the base is connected to the first terminal of resistor R8. The second terminal of resistor R8 is connected to resistor R7 and the collector of transistor Q3. The second terminal of resistor R7 is connected to the power supply. The second terminal of resistor R10 is connected to the base of transistor Q3, and the emitter of transistor Q3 is grounded. The second terminals of resistors R11 and R12 and capacitor C2 are all grounded.

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