A load short circuit protection circuit

Abstract

The embodiment of the present invention provides a load short-circuit protection circuit, comprising: a sampling resistor and a load tube unit connected in sequence, a load short-circuit protection trigger unit and a control unit; the sampling resistor and the load tube unit include a sampling resistor and a load tube connected to each other, which are used to connect the load, supply power to the load, and collect load current information; the load short-circuit protection trigger unit outputs a short-circuit protection trigger signal to the control unit when a load short circuit occurs; after receiving the short-circuit protection trigger signal, the control unit outputs a load tube drive control signal to turn off the drive signal of the load tube, thereby turning off the load tube. The load short-circuit protection circuit provided by the embodiment of the present invention realizes the collection of load current information, outputs a short-circuit protection trigger signal after judging that a fault occurs, and controls the closing of the load tube through a hardware circuit, thereby improving the rapidity and reliability of the load short-circuit protection, and improving the load carrying capacity of the capacitive load.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and in particular to a load short-circuit protection circuit. Background Art

[0002] In existing electronic circuits, batteries or other power sources are generally used to power the load. During the operation of the circuit, a short circuit may occur. A sampling resistor is usually set in the circuit because once a short circuit occurs, the current will increase rapidly, and the voltage across the sampling resistor will also increase rapidly, thereby capturing the short circuit signal. By setting the software logic of a controller such as a single-chip microcomputer, short circuit information can be obtained when a short circuit occurs, and corresponding measures can be taken.

[0003] Taking the photovoltaic power generation field as an example, the photovoltaic charge and discharge controller is a device that controls the charge and discharge of batteries in photovoltaic power generation systems. The photovoltaic charge and discharge controller includes controllers such as single-chip microcomputers, which control the on and off of the battery to the load device through the load tube. Usually, a sampling resistor is connected in series between the battery and the load, and the device collects discharge information such as the load current through the sampling resistor. In actual applications, when the external load device at the load end of the controller fails or short-circuits, the load current will rise sharply and burn out devices such as the load tube. In general, when the load short-circuit protection circuit detects that the load current is too large through the sampling resistor, a trigger signal is generated. After the software detects the load short-circuit trigger signal, it turns off the load to play a role in short-circuit protection.

[0004] However, there is a risk of protection failure due to weaknesses such as software failure and slow response speed when detecting load short circuits through software, and reliable protection cannot be achieved. Summary of the invention

[0005] To solve the problems in the prior art, an embodiment of the present invention provides a load short-circuit protection circuit, comprising: a sampling resistor and a load tube unit, a load short-circuit protection trigger unit and a control unit; the sampling resistor and the load tube unit are connected to the load short-circuit protection trigger unit, and the load short-circuit protection trigger unit is connected to the control unit; the sampling resistor and the load tube unit include a sampling resistor and a load tube connected to each other, and the sampling resistor and the load tube unit are used to connect a load and power the load, collect load current information and feed it back to the load short-circuit protection trigger unit; the load short-circuit protection trigger unit is used to output a short-circuit protection trigger signal to the control unit when a load short circuit occurs; the control unit includes a control circuit, and the control circuit is used to output a load tube drive control signal to turn off the drive signal of the load tube after receiving the short-circuit protection trigger signal, thereby turning off the load tube and disconnecting the sampling resistor and the load tube unit from the load.

[0006] Further, the load short-circuit protection trigger unit includes a first load short-circuit protection trigger subunit and / or a second load short-circuit protection trigger subunit; the first load short-circuit protection trigger subunit outputs a first short-circuit protection trigger signal when the short-circuit current is greater than a first preset threshold; the second load short-circuit protection trigger subunit outputs a second short-circuit protection trigger signal when the short-circuit current is greater than a second preset threshold; the first preset threshold is greater than the second preset threshold; the first short-circuit protection trigger signal and the second short-circuit protection trigger signal are combined into one to form the short-circuit protection trigger signal to the control unit.

[0007] Furthermore, the control unit also includes a self-locking circuit, and the self-locking circuit is used to lock the load tube drive control signal.

[0008] Furthermore, the control unit also includes an unlocking circuit, and the unlocking circuit is used to unlock the load tube driving control signal after the load tube is turned off.

[0009] Further, the first end of the sampling resistor is connected to the load power supply, and the second end of the sampling resistor is connected to the load tube; the first load short-circuit protection trigger subunit includes a first comparator, a second resistor, a fifth resistor, a sixth resistor, a fourth resistor and a second capacitor; wherein the second end of the second resistor is connected to the first end of the fifth resistor and the positive input end of the first comparator, the second end of the fifth resistor is connected to the first end of the sixth resistor, the first end of the second resistor is connected to the first power supply, and the second end of the sixth resistor is connected to the common end of the sampling resistor and the load tube; the second end of the fourth resistor is connected to the first end of the second capacitor and the negative input end of the first comparator, the first end of the fourth resistor is connected to the load power supply, and the second end of the second capacitor is connected to the common end of the sampling resistor and the load tube; the first power pin of the first comparator is connected to the first power supply, the second power pin of the first comparator is connected to the common end of the sampling resistor and the load tube, and the first output end of the first comparator is connected to the control unit.

[0010] Furthermore, the second load short-circuit protection trigger subunit includes a second comparator, a third resistor, a third capacitor, the second resistor, the fifth resistor and the sixth resistor; wherein the first end of the third resistor is connected to the load power supply, the second end of the third resistor is connected to the first end of the third capacitor and the negative input end of the second comparator, the second end of the third capacitor is connected to the common end of the sampling resistor and the load tube, the positive input end of the second comparator is connected to the second end of the fifth resistor, the first power pin of the second comparator is connected to the first power supply, the second power pin of the second comparator is connected to the common end of the sampling resistor and the load tube, and the second output end of the second comparator and the first output end of the first comparator are combined into one path connected to the control unit.

[0011] Further, the resistance value of the fourth resistor is smaller than the resistance value of the third resistor.

[0012] Further, the control circuit includes a first NAND gate, a second NAND gate, a third NAND gate, an optocoupler, a seventh resistor, an eighth resistor and a ninth resistor; the optocoupler includes a light emitting diode and a phototransistor; wherein: the first end of the seventh resistor is connected to the first power supply, the second end of the seventh resistor is connected to the positive electrode of the light emitting diode, the negative electrode of the light emitting diode is connected to the first output end and / or the second output end, the first end of the eighth resistor is connected to the second power supply, the second end of the eighth resistor is connected to the first end of the ninth resistor and the collector of the phototransistor, the emitter of the phototransistor is grounded, the second end of the ninth resistor is connected to the two input ends of the first NAND gate, the output end of the first NAND gate is connected to the two input ends of the second NAND gate, the output end of the second NAND gate is connected to the first input end of the third NAND gate, the second input end of the third NAND gate is connected to the load tube control signal of the central processing unit, and the output end of the third NAND gate is connected to the control end of the load tube through the load driver.

[0013] Furthermore, the self-locking circuit includes an eleventh resistor and a transistor, the first end of the eleventh resistor is connected to the two input ends of the second NAND gate, the second end of the eleventh resistor is connected to the base of the transistor, the collector of the transistor is connected to the second end of the eighth resistor, and the emitter of the transistor is grounded.

[0014] Furthermore, the unlocking circuit includes a fourth NAND gate and a diode, the two input ends of the fourth NAND gate are connected to the second input end of the third NAND gate, the output end of the fourth NAND gate is connected to the anode of the diode, and the cathode of the diode is connected to the second end of the ninth resistor; the output end of the second NAND gate is connected to the central processing unit so that the central processing unit changes the load tube control signal according to the received signal.

[0015] The load short-circuit protection circuit provided in the embodiment of the present invention realizes the collection of load current information through a hardware circuit, outputs a short-circuit protection trigger signal after determining that a fault has occurred, and a control unit controls the shutdown of the load tube according to the short-circuit protection trigger signal. The load short-circuit protection is realized by using a hardware circuit, thereby improving the rapidity and reliability of the load short-circuit protection and improving the load-carrying capacity of the capacitive load. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention 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 some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 is a structural schematic diagram of a load short-circuit protection circuit provided by an embodiment of the present invention;

[0018] Figure 2 is a schematic structural diagram of a sampling resistor and a load tube unit in a load short-circuit protection circuit provided by another embodiment of the present invention;

[0019] Figure 3 is a structural schematic diagram of a load short-circuit protection trigger unit in a load short-circuit protection circuit provided by another embodiment of the present invention;

[0020] Figure 4 is a schematic structural diagram of a control unit provided by another embodiment of the present invention;

[0021] Figure 5 is a structural schematic diagram of a load short-circuit protection trigger unit in a load short-circuit protection circuit provided by another embodiment of the present invention;

[0022] Figure 6 It is a structural schematic diagram of a control unit in a load short-circuit protection circuit provided by another embodiment of the present invention. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0025] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] Figure 1 Schematic diagram of the structure of the load short-circuit protection circuit provided by the embodiment of the present invention. Figure 1 As shown, the load short-circuit protection circuit includes a sampling resistor and a load tube unit 10, a load short-circuit protection trigger unit 20 and a control unit 30; the sampling resistor and the load tube unit 10 are connected to the load short-circuit protection trigger unit 20, and the load short-circuit protection trigger unit 20 is connected to the control unit 30; the sampling resistor and the load tube unit 10 include a sampling resistor and a load tube connected to each other, and the sampling resistor and the load tube unit 10 are used to connect the load and power the load, collect load current information and feed it back to the load short-circuit protection trigger unit 20; the load short-circuit protection trigger unit 20 is used to output a short-circuit protection trigger signal to the control unit 30 when a load short circuit occurs; the control unit 30 includes a control circuit, and the control circuit is used to output a load tube drive control signal to turn off the drive signal of the load tube after receiving the short-circuit protection trigger signal, thereby turning off the load tube and disconnecting the sampling resistor and the load tube unit 10 from the load.

[0027] The load short-circuit protection circuit includes a sampling resistor and a load tube unit 10, a load short-circuit protection trigger unit 20 and a control unit 30; the sampling resistor and the load tube unit 10 are connected to the load short-circuit protection trigger unit 20, and the load short-circuit protection trigger unit 20 is connected to the control unit 30.

[0028] The sampling resistor and load tube unit 10 includes a sampling resistor and a load tube connected to each other. The sampling resistor and load tube unit 10 is used to connect a load and supply power to the load, collect load current information and feed it back to the load short circuit protection trigger unit 20.

[0029] The load short circuit protection trigger unit 20 is used to output a short circuit protection trigger signal to the control unit 30 when a load short circuit occurs; the control unit 30 includes a control circuit, which is used to output a load tube drive control signal after receiving the short circuit protection trigger signal and can turn off the drive signal of the load tube through the load driver to turn off the load tube, thereby disconnecting the sampling resistor and the load tube unit 10 from the load. When the load is working normally, that is, when there is no short circuit, the load tube drive control signal controls the drive signal of the load tube through the load driver, and the circuit operates normally.

[0030] Because when a surge current or other conditions occur in a capacitive load, it is equivalent to a circuit short circuit. Therefore, improving the reliability of short-circuit protection can improve the load capacity of the capacitive load and improve the redundancy of the capacitive load.

[0031] The load tube is an electronic switch and can be implemented by a MOS tube, a relay, an IGBT (insulated gate bipolar transistor), etc.

[0032] The embodiment of the present invention realizes the collection of load current information through a hardware circuit, outputs a short-circuit protection trigger signal after determining that a fault has occurred, and the control unit controls the shutdown of the load tube according to the short-circuit protection trigger signal. The hardware circuit is used to realize load short-circuit protection, thereby improving the rapidity and reliability of the load short-circuit protection and improving the load-carrying capacity of the capacitive load.

[0033] Further, based on the above embodiment, the load short-circuit protection trigger unit 20 includes a first load short-circuit protection trigger subunit and / or a second load short-circuit protection trigger subunit; the first load short-circuit protection trigger subunit outputs a first short-circuit protection trigger signal when the short-circuit current is greater than a first preset threshold; the second load short-circuit protection trigger subunit outputs a second short-circuit protection trigger signal when the short-circuit current is greater than a second preset threshold; the first preset threshold is greater than the second preset threshold; the first short-circuit protection trigger signal and the second short-circuit protection trigger signal are combined into one to form the short-circuit protection trigger signal to the control unit.

[0034] The load short-circuit protection trigger unit 20 includes a first load short-circuit protection trigger subunit and / or a second load short-circuit protection trigger subunit, that is, the load short-circuit protection trigger unit 20 can include only the first load short-circuit protection trigger subunit, or only the second load short-circuit protection trigger subunit, or both the first load short-circuit protection trigger subunit and the second load short-circuit protection trigger subunit.

[0035] When only the first load short circuit protection trigger subunit or only the second load short circuit protection trigger subunit is included, it means there is only one level of load short circuit protection trigger subunit. When both the first load short circuit protection trigger subunit and the second load short circuit protection trigger subunit are included, two levels of load short circuit protection trigger subunit are formed.

[0036] The advantage of having two-stage load short-circuit protection trigger subunits is that it can realize protection of different short-circuit current thresholds, thereby realizing multi-level reliable protection. By setting different action conditions, the first load short-circuit protection trigger subunit outputs a first short-circuit protection trigger signal when the short-circuit current is greater than a first preset threshold; the second load short-circuit protection trigger subunit outputs a second short-circuit protection trigger signal when the short-circuit current is greater than a second preset threshold; the first preset threshold is greater than the second preset threshold.

[0037] In addition, the reaction speeds of the first load short-circuit protection trigger subunit and the second load short-circuit protection trigger subunit may also be set, thereby achieving fast protection for large currents and slow protection for small currents.

[0038] The first short circuit protection trigger signal and the second short circuit protection trigger signal are combined into one to form the short circuit protection trigger signal to the control unit. When there is only the first load short circuit protection trigger subunit or only the second load short circuit protection trigger subunit, the short circuit protection trigger signal is the first short circuit protection trigger signal or the second short circuit protection trigger signal.

[0039] Based on the above embodiments, the embodiments of the present invention can achieve fast protection for large currents and slow protection for small currents by setting a load short-circuit protection trigger unit including a first load short-circuit protection trigger subunit and / or a second load short-circuit protection trigger subunit, thereby improving flexibility and reliability.

[0040] Further, based on the above embodiment, the control unit also includes a self-locking circuit, and the self-locking circuit is used to lock the load tube drive control signal.

[0041] If a circuit short circuit occurs, the load tube drive control signal output by the control circuit will turn off the drive signal of the load tube through the load driver to turn off the load tube, thereby disconnecting the sampling resistor and the load tube unit from the load. Since the current may be an unstable current, a large current may form a short circuit at a certain moment, and it may return to normal at the next moment. It takes a certain amount of time for the load tube drive control signal to drive the load tube to turn off. In order to achieve reliable closure of the load tube when a load short circuit occurs, a self-locking circuit is set. The self-locking circuit is used to lock the load tube drive control signal after the load short circuit occurs and before the load tube is turned off, even if the current returns to normal, that is, the load tube drive control signal can realize the closure of the load tube through the load driver.

[0042] In the prior art, the current is detected by software to control the on and off of the load tube, which will cause the load tube to be frequently on and off when the current changes, which may easily cause damage to the load tube. However, the embodiment of the present invention can not only realize the reliable shutdown of the load tube when the load is short-circuited, but also avoid the frequent opening and closing of the load tube, effectively protect the load tube, and extend the service life.

[0043] On the basis of the above-mentioned embodiment, the embodiment of the present invention realizes reliable shutdown of the load tube when a load short circuit occurs by setting a self-locking circuit, and avoids frequent switching on and off of the load tube.

[0044] Further, based on the above embodiment, the control unit further includes an unlocking circuit, and the unlocking circuit is used to unlock the load tube driving control signal after the load tube is turned off.

[0045] After the circuit returns to normal, it needs to return to the normal working state. If the load tube drive control signal is locked, after the load tube is turned on, it will continue to drive the load tube to be turned off, and the normal operation of the circuit cannot be achieved. Therefore, the control unit also includes an unlocking circuit, which is used to unlock the load tube drive control signal after the load tube is turned off.

[0046] On the basis of the above-mentioned embodiment, the embodiment of the present invention realizes unlocking of the load tube driving control signal after the load tube is turned off by setting an unlocking circuit, thereby ensuring the normal operation of the circuit.

[0047] Further, based on the above embodiment, the first end of the sampling resistor is connected to the load power supply, and the second end of the sampling resistor is connected to the load tube; the first load short-circuit protection trigger subunit includes a first comparator, a second resistor, a fifth resistor, a sixth resistor, a fourth resistor and a second capacitor; wherein the second end of the second resistor is connected to the first end of the fifth resistor and the positive input end of the first comparator, the second end of the fifth resistor is connected to the first end of the sixth resistor, the first end of the second resistor is connected to the first power supply, and the second end of the sixth resistor is connected to the common end of the sampling resistor and the load tube; the second end of the fourth resistor is connected to the first end of the second capacitor and the negative input end of the first comparator, the first end of the fourth resistor is connected to the load power supply, and the second end of the second capacitor is connected to the common end of the sampling resistor and the load tube; the first power pin of the first comparator is connected to the first power supply, the second power pin of the first comparator is connected to the common end of the sampling resistor and the load tube, and the first output end of the first comparator is connected to the control unit.

[0048] On the basis of the above-mentioned embodiments, the embodiments of the present invention provide a specific implementation of the first load short-circuit protection triggering subunit, thereby improving the practicality.

[0049] Further, based on the above embodiment, the second load short-circuit protection trigger subunit includes a second comparator, a third resistor, a third capacitor, the second resistor, the fifth resistor and the sixth resistor; wherein, the first end of the third resistor is connected to the load power supply, the second end of the third resistor is connected to the first end of the third capacitor and the negative input end of the second comparator, the second end of the third capacitor is connected to the common end of the sampling resistor and the load tube, the positive input end of the second comparator is connected to the second end of the fifth resistor, the first power pin of the second comparator is connected to the first power supply, the second power pin of the second comparator is connected to the common end of the sampling resistor and the load tube, and the second output end of the second comparator and the first output end of the first comparator are combined into one path connected to the control unit.

[0050] On the basis of the above-mentioned embodiments, the embodiments of the present invention provide a specific implementation of the second load short-circuit protection triggering subunit, thereby improving the practicality.

[0051] Further, based on the above embodiment, the resistance value of the fourth resistor is smaller than the resistance value of the third resistor.

[0052] If the resistance value of the fourth resistor is smaller than the resistance value of the third resistor, the charging speed of the second capacitor will be greater than the charging speed of the third capacitor. By reasonably setting the resistance values ​​of the second resistor, the third resistor and the sixth resistor, the action time of the first load short-circuit protection trigger subunit can be smaller than that of the second load short-circuit protection trigger subunit, thereby achieving fast protection for large currents and slow protection for small currents.

[0053] Further, based on the above embodiment, the control circuit includes a first NAND gate, a second NAND gate, a third NAND gate, an optocoupler, a seventh resistor, an eighth resistor and a ninth resistor; the optocoupler includes a light emitting diode and a phototransistor; wherein: the first end of the seventh resistor is connected to the first power supply, the second end of the seventh resistor is connected to the positive electrode of the light emitting diode, the negative electrode of the light emitting diode is connected to the first output end and / or the second output end, the first end of the eighth resistor is connected to the second power supply, the second end of the eighth resistor is connected to the first end of the ninth resistor and the collector of the phototransistor, the emitter of the phototransistor is grounded, the second end of the ninth resistor is connected to the two input ends of the first NAND gate, the output end of the first NAND gate is connected to the two input ends of the second NAND gate, the output end of the second NAND gate is connected to the first input end of the third NAND gate, the second input end of the third NAND gate is connected to the load tube control signal of the central processing unit, and the output end of the third NAND gate is connected to the control end of the load tube through the load driver.

[0054] On the basis of the above embodiments, the embodiments of the present invention provide a specific implementation of the control circuit, thereby improving practicality.

[0055] Further, based on the above embodiment, the self-locking circuit includes an eleventh resistor and a transistor, the first end of the eleventh resistor is connected to the two input ends of the second NAND gate, the second end of the eleventh resistor is connected to the base of the transistor, the collector of the transistor is connected to the second end of the eighth resistor, and the emitter of the transistor is grounded.

[0056] The transistor is a switch device and can be replaced by a MOS tube, an optical coupler, etc., as long as the corresponding function can be achieved.

[0057] On the basis of the above embodiments, the embodiments of the present invention provide a specific implementation of a self-locking circuit, thereby improving practicality.

[0058] Further, based on the above embodiment, the unlocking circuit includes a fourth NAND gate and a diode, the two input ends of the fourth NAND gate are connected to the second input end of the third NAND gate, the output end of the fourth NAND gate is connected to the anode of the diode, and the cathode of the diode is connected to the second end of the ninth resistor; the output end of the second NAND gate is connected to the central processing unit so that the central processing unit changes the load tube control signal according to the received signal.

[0059] On the basis of the above embodiments, the embodiments of the present invention provide a specific implementation of the unlocking circuit, thereby improving the practicality.

[0060] Figure 2 is a schematic structural diagram of a sampling resistor and a load tube unit in a load short-circuit protection circuit provided by another embodiment of the present invention; Figure 3 is a structural schematic diagram of a load short-circuit protection trigger unit in a load short-circuit protection circuit provided by another embodiment of the present invention; Figure 4 This is a schematic diagram of the structure of a control unit provided by another embodiment of the present invention. Figure 2 , Figure 3 and Figure 4 , further illustrating the working principle of the load short-circuit protection circuit provided in an embodiment of the present invention.

[0061] like Figure 2 As shown, the first end of the sampling resistor RS1 is connected to the load power supply (BAT+), and the second end of the sampling resistor RS1 is connected to the load tube Q2. LOAD+ is the common end of the sampling resistor RS1 and the load tube Q2. The LOAD-OUT+ terminal of the load tube Q2 is used to connect the load device. When the circuit is working normally, the central processing unit (such as a single-chip microcomputer, ARM, etc., not shown in the figure) controls the on and off of the load device by controlling the on and off of the load tube Q2. The sampling resistor RS1 collects the load current information and feeds it back to the load short-circuit protection trigger unit. When the load tube Q2 is turned on and the load is short-circuited, the current flowing through the sampling resistor RS1 and the load tube Q2 will rise sharply, generating a rising voltage signal at both ends of RS1.

[0062] like Figure 3As shown, the negative input terminal of the first comparator U1A is connected to BAT+ through R4 (fourth resistor), and the capacitor C2 (second capacitor) is connected between the negative input terminal and LOAD+. The negative input terminal of the second comparator U1B is connected to BAT+ through R3 (third resistor), and the capacitor C3 (third capacitor) is connected between the negative input terminal and LOAD+. Resistors R2 (second resistor), R5 (fifth resistor) and R6 (sixth resistor) are connected in series, and the first end of R2 is connected to the first power supply (which can be +12V-LOAD+, indicating that the voltage between and LOAD+ is 12V); the positive input terminal of U1A is connected to the common end of R2 and R5 after the resistors R2, R5, and R6 are connected in series and divided, and the input voltage is the voltage at both ends of R5 and R6 after the resistors R2, R5, and R6 are connected in series and divided, and the positive input terminal of U1B is connected to the common end of R5 and R6 after the resistors R2, R5, and R6 are connected in series and divided, and the input voltage is the voltage at both ends of resistor R6. The positive input voltage of U1A must be higher than the positive input voltage of U1B. Different protection threshold voltages of U1A and U1B are set by adjusting the voltage divider value of resistors R2, R5, and R6 connected in series.

[0063] like Figure 4 As shown, the output terminal SD-OCER signals of U1A and U1B are both connected to the cathode of the light emitting diode of the optocoupler U3. When the output terminal SD-OCER signals of U1A and U1B are both high level, the output terminals SD-OCER of U1A and U1B are in a floating state, and the signal at the cathode of the light emitting diode of the optocoupler U3 is high level; conversely, as long as one of the output terminals SD-OCER signals of U1A and U1B is low level, the signal at the cathode of the light emitting diode of the optocoupler U3 is low level.

[0064] When the load current is normal, by reasonably setting the values ​​of R2, R5 and R6 according to the value of the first power supply and the value of BAT+, the negative input voltage of U1A and U1B is less than the positive input voltage of U1A and U1B, and the output terminal SD-OCER signal of U1A and U1B is high level, that is, +12V-LOAD+ pulls up the input terminal of the optocoupler U3 through the resistor R7, and the signal at the cathode of the light-emitting diode of the optocoupler U3 is high level. At this time, the output terminal of the optocoupler U3 is not conducting. VCC (second power supply) is connected to the input of U4C (first NAND gate) through resistors R8 (eighth resistor) and R9 (ninth resistor) in series. U4C outputs a low level. The output of U4C is connected to the input of U4D (second NAND gate) and resistor R11 (eleventh resistor). The other end of resistor R11 is connected to the base of transistor Q1. The emitter of transistor Q1 is grounded. The collector of transistor Q1 is connected to the common end of R8 and R9 and the collector of optocoupler U3. Transistor Q1 is not conducting. The input of U4D is low level, and the output DLBH signal is high level. The DLBH signal is connected to the central processing unit. When the DLBH signal is high level, it means that the load state is normal. The LOAD-ONOFF signal is the load tube control signal output by the central processing unit. It is high level when the load is turned on and low level when the load is turned off. When the load is turned on and the load state is normal, the input pins 4 and 5 of U4B (the third NAND gate) are both high level, and the output DRV-ONOFF signal is low level. At this time, the load is turned on normally.

[0065] The output of U4A (the fourth NAND gate) is also low, the diode D1 is not conducting, and the input of U4C remains high. The DRV-ONOFF signal controls the drive signal LOAD-DRV of the load tube Q2 by controlling the load driver. The driver is not marked in the figure. At this time, the circuit works normally.

[0066] When the load is short-circuited, if the load short-circuit current rises rapidly and the current is large, the voltage generated across the sampling resistor RS1 charges the capacitor C2 through the resistor R4. When the voltage of the capacitor C2 is higher than the threshold voltage of the positive input terminal of the first comparator U1A, the output signal SD-OCER of U1A is low. If the load short-circuit current rises slowly and (the voltage between BAT+ and LOAD+) is lower than the threshold voltage of the positive input terminal of U1A and higher than the threshold voltage of the positive input terminal of U1B, BAT+ charges the capacitor C3 through the resistor R3. When the voltage of the capacitor C3 is higher than the threshold voltage of the positive input terminal of the second comparator U1B, the output signal SD-OCER of U1B is low. When the signal SD-OCER is at a low level, the optocoupler U3 is turned on, the common end of the resistors R8 and R9 is pulled low, the input end of U4C is at a low level, and the output end is at a high level. At this time, the transistor Q1 is turned on, and the common end of the resistors R8 and R9 is pulled low again by the transistor Q1. Even if the short-circuit current disappears, SD-OCER becomes a high level, and the common end of the resistors R8 and R9 is also pulled low, thereby achieving the locking of the load tube drive control signal DRV-ONOFF. The input end of U4D is at a high level, and the output end DLBH signal is at a low level, indicating that the load is short-circuited. At this time, the 5-pin input of U4B is at a low level, the 4-pin input of U4B is at a high level, and the output signal DRV-ONOFF is at a high level. The DRV-ONOFF signal controls the load driver to turn off the drive signal LOAD-DRV of the load tube Q2, and the load is turned off, which plays a role in load short-circuit protection.

[0067] When the central processing unit detects that the DLBH signal is at a low level, the LOAD-ONOFF signal outputs a low level, the output end of U4A is at a high level, and is connected to the input end of U4C through diode D1. U4C outputs a low level, and transistor Q1 is in the cut-off state. The common terminal voltage of resistors R8 and R9 is VCC, and the short-circuit self-locking state is released. After the short-circuit fault disappears, the load is turned on again.

[0068] The load short-circuit protection circuit provided by the embodiment of the present invention overcomes the risk of unreliable protection when the software detects a load short circuit, and the risk of the load burning due to slow software response or failure. By adopting a two-stage short-circuit trigger protection circuit, it has two different short-circuit current trigger conditions. By setting different protection thresholds, it meets the characteristics of fast protection for large currents and slow protection for small currents, thereby maximizing the reliability of short-circuit protection and the load-carrying capacity of capacitive loads. In addition, when the load short-circuit protection occurs, the fault trigger signal is locked by the self-locking circuit, and at the same time, a fault signal is sent to feedback to the central processing unit, and the control drive signal turns off the load tube, thereby avoiding damage caused by frequent switching of the load tube when the short-circuit current decreases.

[0069] Figure 5FIG. 1 is a schematic diagram of the structure of a load short circuit protection trigger unit in a load short circuit protection circuit provided by another embodiment of the present invention. Figure 5 As shown, the load short circuit protection trigger unit also includes a filter circuit, which includes a resistor R1, a voltage regulator U1 and a capacitor C1. The first end of the resistor R1 is connected to the first power supply, the second end of the resistor R1 is connected to the first end of the resistor R2, and the voltage regulator U1 and the capacitor C1 are connected in parallel at both ends of the resistor R2 and the resistor R6. A stable voltage is generated by the resistor R1 (first resistor) and the voltage regulator U2. R2, R5 and R6 are connected in series and then connected in parallel at both ends of the voltage regulator U2 to ensure the stability of the voltage. C1 is connected in parallel at both ends of the voltage regulator U2 to play a filtering and voltage stabilization role.

[0070] Figure 6 FIG. 1 is a schematic diagram of the structure of a control unit in a load short-circuit protection circuit provided by another embodiment of the present invention. Figure 6 As shown, the control unit further includes a resistor R10, a first end of the resistor R10 is connected to the two input ends of the fourth NAND gate U4A and the second input end of the third NAND gate U4B, and a second end of the resistor R10 is grounded. The resistor R10 plays a pull-down role, and is used to protect the circuit during initial power-on.

[0071] The embodiments of the present invention can be applied to the application of photovoltaic charge and discharge controller, and can also be applied to other application occasions.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A load short-circuit protection circuit, characterized in that: include: Sampling resistor and load tube unit, load short circuit protection trigger unit and control unit; The sampling resistor and the load tube unit are connected to the load short-circuit protection trigger unit, and the load short-circuit protection trigger unit is connected to the control unit; The sampling resistor and load tube unit comprises a sampling resistor and a load tube connected to each other, and the sampling resistor and load tube unit is used to connect a load and supply power to the load, collect load current information and feed it back to the load short circuit protection trigger unit; The load short-circuit protection trigger unit is used to output a short-circuit protection trigger signal to the control unit when a load short-circuit occurs; The control unit includes a control circuit, and the control circuit is used to output a load tube drive control signal to turn off the drive signal of the load tube after receiving the short-circuit protection trigger signal, thereby turning off the load tube and disconnecting the sampling resistor and the load tube unit from the load; The load short circuit protection trigger unit includes a first load short circuit protection trigger sub-unit and a second load short circuit protection trigger sub-unit; The first load short-circuit protection trigger subunit outputs a first short-circuit protection trigger signal when the short-circuit current is greater than a first preset threshold; the second load short-circuit protection trigger subunit outputs a second short-circuit protection trigger signal when the short-circuit current is greater than a second preset threshold; The first preset threshold is greater than the second preset threshold; The first short-circuit protection trigger signal and the second short-circuit protection trigger signal are combined into one short-circuit protection trigger signal to be sent to the control unit; The first end of the sampling resistor is connected to the load power supply, and the second end of the sampling resistor is connected to the load tube; The first load short circuit protection trigger subunit includes a first comparator, a second resistor, a fifth resistor, a sixth resistor, a fourth resistor and a second capacitor; wherein the second end of the second resistor is connected to the first end of the fifth resistor and the positive input end of the first comparator, the second end of the fifth resistor is connected to the first end of the sixth resistor, the first end of the second resistor is connected to the first power supply, and the second end of the sixth resistor is connected to the common end of the sampling resistor and the load tube; The second end of the fourth resistor is connected to the first end of the second capacitor and the negative input end of the first comparator, the first end of the fourth resistor is connected to the load power supply, and the second end of the second capacitor is connected to the common end of the sampling resistor and the load tube; The first power pin of the first comparator is connected to the first power supply, the second power pin of the first comparator is connected to the common end of the sampling resistor and the load tube, and the first output end of the first comparator is connected to the control unit; The second load short-circuit protection trigger subunit includes a second comparator, a third resistor, a third capacitor, the second resistor, the fifth resistor and the sixth resistor; wherein the first end of the third resistor is connected to the load power supply, the second end of the third resistor is connected to the first end of the third capacitor and the negative input end of the second comparator, the second end of the third capacitor is connected to the common end of the sampling resistor and the load tube, the positive input end of the second comparator is connected to the second end of the fifth resistor, the first power pin of the second comparator is connected to the first power supply, the second power pin of the second comparator is connected to the common end of the sampling resistor and the load tube, and the second output end of the second comparator and the first output end of the first comparator are combined into one path connected to the control unit; wherein the resistance value of the fourth resistor is less than the resistance value of the third resistor; The control circuit includes a first NAND gate, a second NAND gate, a third NAND gate, an optical coupler, a seventh resistor, an eighth resistor and a ninth resistor; the optical coupler includes a light emitting diode and a phototransistor; wherein: The first end of the seventh resistor is connected to the first power supply, the second end of the seventh resistor is connected to the positive electrode of the light-emitting diode, the negative electrode of the light-emitting diode is connected to the first output end and / or the second output end, the first end of the eighth resistor is connected to the second power supply, the second end of the eighth resistor is connected to the first end of the ninth resistor and the collector of the phototransistor, the emitter of the phototransistor is grounded, the second end of the ninth resistor is connected to the two input ends of the first NAND gate, the output end of the first NAND gate is connected to the two input ends of the second NAND gate, the output end of the second NAND gate is connected to the first input end of the third NAND gate, the second input end of the third NAND gate is connected to the load tube control signal of the central processing unit, and the output end of the third NAND gate is connected to the control end of the load tube through the load driver.

2. The load short-circuit protection circuit according to claim 1, characterized in that: The control unit also includes a self-locking circuit, and the self-locking circuit is used to lock the load tube drive control signal.

3. The load short-circuit protection circuit according to claim 2, characterized in that: The control unit further includes an unlocking circuit, and the unlocking circuit is used to unlock the load tube driving control signal after the load tube is turned off.

4. The load short-circuit protection circuit according to claim 2, characterized in that: The self-locking circuit includes an eleventh resistor and a transistor, the first end of the eleventh resistor is connected to the two input ends of the second NAND gate, the second end of the eleventh resistor is connected to the base of the transistor, the collector of the transistor is connected to the second end of the eighth resistor, and the emitter of the transistor is grounded.

5. The load short-circuit protection circuit according to claim 3, characterized in that: The unlocking circuit includes a fourth NAND gate and a diode, two input ends of the fourth NAND gate are connected to the second input end of the third NAND gate, the output end of the fourth NAND gate is connected to the anode of the diode, and the cathode of the diode is connected to the second end of the ninth resistor; The output end of the second NAND gate is connected to the central processing unit so that the central processing unit can change the load tube control signal according to the received signal.

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