CN210326997U - Overload and short-circuit protection circuit - Google Patents
Overload and short-circuit protection circuit Download PDFInfo
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- CN210326997U CN210326997U CN201921105352.8U CN201921105352U CN210326997U CN 210326997 U CN210326997 U CN 210326997U CN 201921105352 U CN201921105352 U CN 201921105352U CN 210326997 U CN210326997 U CN 210326997U
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Abstract
The utility model discloses an overload and short-circuit protection circuit, the current detection circuit is used for detecting the load current flowing through the load, the protection response circuit comprises a first charge-discharge circuit connected with the current detection circuit and a first comparison circuit connected with the first charge-discharge circuit, the output control circuit comprises a second comparison circuit and a switch circuit connected with the first comparison circuit, when the circuit of the load is overloaded or short-circuited, the load current is larger than the protection starting current, the first charge-discharge circuit is charged until the first comparison circuit outputs a first control signal, so that the second comparison circuit controls the switch circuit to be disconnected to cut off the circuit of the load to enter the protection mode, after the switch circuit is disconnected, the first charge-discharge circuit discharges until the first comparison circuit outputs a second control signal, so that the second comparison circuit controls the switch circuit to be switched on to connect the load circuit again to enter the working mode, therefore, the automatic starting protection mechanism and the self-recovery when the circuit where the load is located is overloaded or short-circuited can be realized without software.
Description
Technical Field
The utility model relates to a circuit protection technical field, in particular to overload and short-circuit protection circuit.
Background
When the circuit is overloaded, the current exceeds the current carrying capacity of the electric wire, the electric wire is heated, when the circuit is short-circuited, electric sparks are generated between two electrodes of the circuit, and if the electric wire is heated or the electric sparks cannot be processed in time, accidents can be caused.
At present, in order to avoid an electrical accident, a circuit protection device is usually equipped in an alternating current circuit, but most of the existing technologies are passive protection schemes, such as fuses, circuit breakers and the like, however, the fuses and the circuit breakers in the passive protection schemes belong to consumables, have no self-recovery function, and are not suitable for electrified products which need small-volume large-current and have recoverable alternating current short-circuit protection. Therefore, the design of a proper overload and short-circuit protection circuit to realize the overload short-circuit protection of the circuit has great practical significance in a protection scheme which has a self-recovery function and does not consume materials.
SUMMERY OF THE UTILITY MODEL
In order to solve the technical problem that exists now, the embodiment of the utility model provides an overload and short-circuit protection circuit with self-resuming function is provided.
The embodiment of the utility model provides a technical scheme is so realized:
an overload and short-circuit protection circuit comprises a current detection circuit, a protection response circuit and an output control circuit, wherein the current detection circuit is used for detecting load current flowing through a load, the protection response circuit comprises a first charge-discharge circuit connected with the current detection circuit and a first comparison circuit connected with the first charge-discharge circuit, the output control circuit comprises a second comparison circuit and a switch circuit connected with the first comparison circuit, when the circuit where the load is located is overloaded or short-circuited, the load current is larger than protection starting current, the first charge-discharge circuit is charged until voltages of a positive phase input end and a negative phase input end of the first comparison circuit meet a first condition, the first comparison circuit outputs a first control signal, and the second comparison circuit controls the switch circuit to be disconnected so as to cut off the circuit where the load is located to enter a protection mode, after the switching circuit is switched off, the first charge-discharge circuit discharges until the voltages of the positive phase input end and the negative phase input end of the first comparison circuit meet a second condition, and the first comparison circuit outputs a second control signal, so that the second comparison circuit controls the switching circuit to be switched on to connect the circuit where the load is located again to enter a working mode.
Wherein the current detection circuit includes a detection resistor connected between one end of the load and ground.
The first charging and discharging circuit comprises a first resistor and a first charging capacitor, one end of the first resistor is connected with a node between the first detection resistor and the load, the other end of the first resistor is connected with a positive phase input end of the first comparison circuit, and the first charging capacitor is connected between the node between the first resistor and the positive phase input end and the ground.
The first comparison circuit comprises a first comparator, the positive phase input end is connected with the first charge-discharge circuit, the negative phase input end is connected with the power supply, and the output end of the first comparator is connected with the output control circuit.
The second comparison circuit comprises a second comparator, the positive phase input end of the second comparator is connected with the output end of the first comparator, the negative phase input end of the second comparator is connected with the IO end of the microcontroller, and the output end of the second comparator is connected with the switch circuit.
The output control circuit further comprises a first switching element connected between the output end of the first comparator and the positive phase input end of the second comparator and a second charging and discharging circuit connected with the positive phase input end of the second comparator, and when the first switching element is closed, the second charging and discharging circuit is charged to enable the voltages of the positive phase input end and the negative phase input end of the second comparator to meet a first condition, so that the second comparator outputs a first control signal to enable the switching circuit to be disconnected; when the first switch element is switched off, the second charge-discharge circuit discharges until the voltages of the positive input end and the negative input end of the second comparator meet a second condition, so that the second comparator outputs the second control signal to enable the switch circuit to be switched on.
The first switch element is a triode, a base of the triode is connected with an output end of the first comparator, an emitter is connected with a positive phase input end of the second comparator, a collector is connected with a power supply, and a junction point of the positive phase input end and the emitter is connected with the second charge-discharge circuit.
And the node of the positive phase input end and the emitter is connected with a power supply through a divider resistor.
The second charging and discharging circuit comprises a second charging capacitor and a second resistor which are connected in parallel, one end of the second charging capacitor and one end of the second resistor are connected with the first switch element, and the other end of the second charging capacitor and the other end of the second resistor are connected with the ground.
The switch circuit comprises a PMOS field effect transistor connected between the load and the second comparison circuit, the grid electrode of the PMOS field effect transistor is connected with the output end of the second comparison circuit, the source electrode of the PMOS field effect transistor is connected with the load, and the drain electrode of the PMOS field effect transistor is connected with a load power supply.
In the overload and short-circuit protection circuit provided by the embodiment, the current detection circuit detects the load current flowing through the load, when the overload or short-circuit of the circuit where the load is located is determined according to the load current, the protection response circuit responds, the response time of the protection response circuit charges the first charge-discharge circuit until the voltages of the positive phase input end and the negative phase input end of the first comparison circuit meet the time of a first condition, and the first comparison circuit outputs a first control signal after the response time is reached, so that the second comparison circuit controls the switch circuit to be switched off to cut off the circuit where the load is located to enter a protection mode, and thus, the automatic protection of the circuit where the load is located when the overload or short-circuit occurs is realized; after the switching circuit is disconnected, the first charge-discharge circuit discharges until the voltages of the positive phase input end and the negative phase input end of the first comparison circuit meet a second condition, the first comparison circuit outputs a second control signal, and the second comparison circuit controls the switching circuit to be switched on to be communicated with the circuit where the load is located again to enter a working mode.
Drawings
FIG. 1 is a schematic diagram of an exemplary application environment of an overload and short-circuit protection circuit according to an embodiment of the present disclosure;
FIG. 2 is a schematic diagram of an overload and short-circuit protection circuit according to an embodiment of the present application;
fig. 3 is a schematic circuit diagram of an overload and short-circuit protection circuit according to an embodiment of the present application.
Detailed Description
The technical solution of the present invention will be further described in detail with reference to the drawings and specific embodiments.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items.
In the following description, reference is made to the expression "some embodiments" which describes a subset of all possible embodiments, but it is understood that "some embodiments" may be the same subset or different subsets of all possible embodiments, and may be combined with each other without conflict.
Referring to fig. 1, an optional application scenario diagram of an overload and short-circuit protection circuit provided in this embodiment of the present application is that the overload and short-circuit protection circuit is configured to protect a circuit where an electrical device is located, and includes a current detection circuit 10, a protection response circuit 20, and an output control circuit 30, where the current detection circuit 10 is configured to detect a magnitude of a real-time current flowing through the circuit where the electrical device is located, and when the circuit where the electrical device is located is determined to be in an overload or short-circuit state according to the magnitude of the real-time current, after the protection response circuit 20 delays for a set time, output of the output control circuit 30 is turned off by outputting a corresponding control signal, so that after the circuit where the electrical device is located is cut off and enters a protection mode for the electrical device, and after the protection response circuit 20 delays for a preset time, output of the corresponding control signal is turned on by outputting the control circuit 30, and then the circuit where the electric equipment is located is communicated again, so that the electric equipment enters a working mode. Therefore, the overload and short-circuit protection circuit realizes overload and short-circuit protection on the circuit of the electric equipment without consuming materials such as fuses, circuit breakers and the like, and has a self-recovery function; secondly, the overload and short-circuit protection circuit can realize overload and short-circuit protection of the circuit where the load is located in a pure hardware mode without software, and is simple in structure and stable in function. The electric equipment can comprise household appliances, such as air conditioners, humidifiers, washing machines, electric cookers, air purifiers and other equipment which need to consume electric energy in any work.
The electric device may also be another load 40 that converts electric energy into another form of energy, please refer to fig. 2 and fig. 3, in the overload and short-circuit protection circuit, the current detection circuit 10 is configured to detect a load current flowing through the load 40, the protection response circuit 20 includes a first charge-discharge circuit 22 connected to the current detection circuit 10 and a first comparison circuit 21 connected to the first charge-discharge circuit 22, the output control circuit 30 includes a second comparison circuit 31 and a switch circuit 33 connected to the first comparison circuit 21, when the circuit of the load is in an overload or short-circuit state, the load current is greater than a protection starting current, the first charge-discharge circuit 22 charges until voltages at a positive phase input end and a negative phase input end of the first comparison circuit 21 satisfy a first condition, the first comparison circuit 21 outputs a first control signal, the second comparison circuit 31 controls the switch circuit 33 to be switched off to cut off the circuit where the load is located to enter a protection mode, after the switch circuit 33 is switched off, the first charge-discharge circuit 22 discharges until the voltages of the positive phase input end and the negative phase input end of the first comparison circuit 21 meet a second condition, the first comparison circuit 21 outputs a second control signal, and the second comparison circuit 31 controls the switch circuit 33 to be switched on to be connected with the circuit where the load is located again to enter a working mode.
In the above embodiment, the current detection circuit 10 detects the load current flowing through the load 40, when it is determined that the circuit where the load is located is overloaded or short-circuited according to the load current, the protection response circuit 20 responds, the response time of the protection response circuit 20 charges the first charge-discharge circuit 22 until the voltages of the positive phase input terminal U5 and the negative phase input terminal U4 of the first comparison circuit 21 meet the time of the first condition, and after the response time is reached, the first comparison circuit 21 outputs the first control signal, so that the second comparison circuit 31 controls the switch circuit 33 to be switched off to cut off the circuit where the load is located to enter the protection mode, and thus, automatic protection when the circuit where the load is located is overloaded or short-circuited is realized; after the switch circuit 33 is switched off, the first charge-discharge circuit 22 discharges until the voltages U5 at the positive phase input end and the negative phase input end of the first comparison circuit 21 and the voltage U4 at the negative phase input end meet a second condition, the first comparison circuit 21 outputs a second control signal, so that the second comparison circuit 31 controls the switch circuit 33 to be switched on to connect the circuit where the load is located again, and then the circuit enters a working mode.
Wherein, the time period from the overload or short circuit of the load to the time period that the overload protection circuit opens the circuit of the load and enters the protection mode is the response time of the overload protection circuit for starting protection. The overload protection circuit can adjust the response time of the start protection by protecting the charging time T2 of the first charge-discharge circuit 22 in the response circuit 20, the charging time T2 of the first charge-discharge circuit 22 can be determined according to the magnitudes of the first charging capacitor C1C1 and the first resistor R3R3 in the first charge-discharge circuit 22, and the voltage U3 at the positive phase input end and the voltage U4 at the negative phase input end of the first comparison circuit 21, and specifically can be represented by the following formula one:
t2 ═ R3 ═ C1 ═ Ln [ U3/(U3-U4) ] (formula one)
In an alternative embodiment, when the circuit in which the load is located is in the normal operation mode, the voltage of the positive phase input terminal U5 of the first comparing circuit 21 is less than the voltage of the negative phase input terminal U4, the first comparing circuit 21 outputs the second control signal, and the circuit in which the load is located maintains the normal operation mode; when the circuit of the load is in an overload circuit state, the first charging circuit is charged to enable the voltage U5 of the positive phase input end of the first comparing circuit 21 to be larger than the voltage U4 of the negative phase input end, the first comparing circuit 21 outputs a first control signal, and the circuit of the load enters a protection mode; after the circuit where the load is located is in the protection mode, the first charge-discharge circuit 22 discharges and makes the voltage of the positive phase input end of the first comparison circuit 21 smaller than the voltage of the negative phase input end, and the first comparison circuit 21 outputs the second control signal, so that self-recovery after protection starting is realized.
The current detection circuit 10 includes a detection resistor R1 connected between one end of the load 40 and ground. The detection resistor R1 is a resistor of a material having high accuracy and high temperature characteristics, and may be a high copper resistance, for example. The sensing resistor R1 is connected in series with the load 40 between the load supply and ground, and the first protection response circuit 20 is connected to the junction between the sensing resistor R1 and the load 40. The current detection circuit 10 can determine the actual current flowing through the load 40, i.e. the load current, according to the voltage across the detection resistor R1 and the resistance of the detection resistor R1. In this embodiment, the load power source is a 12V dc power source. Optionally, the load power supply may also be a battery or other ac to dc power supply device.
In some embodiments, the first charge-discharge circuit 22 includes a first resistor R3 and a first charge capacitor C1, and specifically, one end of the first resistor R3 is connected to a node between the first detection resistor R1 and the load 40, the other end of the first resistor R3 is connected to the positive-phase input terminal of the first comparison circuit 21, and the first charge capacitor C1 is connected between a node between the first resistor R3 and the positive-phase input terminal and ground. The negative phase input terminal of the first comparison circuit 21 is connected to a power supply through another resistor R4, and a resistor R5 and a second capacitor C2 connected in parallel are provided between the node of the negative phase input terminal and the resistor R4 and the ground. Therefore, the voltage U5 at the non-inverting input terminal of the first comparison circuit 21 is equal to the voltage U3 measured at the detection resistor R1; the voltage U4 at the negative phase input of the first comparison circuit 21 is determined by the power supply and the size of the resistor R4. In this embodiment, the power supply refers to an operating power supply of the overload and short-circuit protection circuit, and may be a 3.3V dc power supply.
The first comparison circuit 21 includes a first comparator 211, the positive phase input end is connected to the first charge-discharge circuit 22, the negative phase input end is connected to the power supply, and the output end of the first comparator 211 is connected to the output control circuit 30. Here, the first comparator circuit 21 includes the first comparator 211, the positive phase input terminal of the first comparator 211 is the positive phase input terminal of the first comparator circuit 21, the negative phase input terminal of the first comparator 211 is the negative phase input terminal of the first comparator circuit 21, and the output terminal of the first comparator 211 is connected to the power supply through a resistor R2. When the voltage of the positive phase input terminal U5 of the first comparator 211 is greater than the voltage of the negative phase input terminal U4, the first comparator 211 outputs a high level as a first control signal; when the voltage of the negative phase input terminal U4 of the first comparator 211 is greater than the voltage of the positive phase input terminal U5, the first comparator 211 outputs a low level as the second control signal.
In some embodiments, the second comparator circuit 31 includes a second comparator 311, a positive phase input terminal of the second comparator 311 is connected to the output terminal of the first comparator 211, a negative phase input terminal of the second comparator 311 is connected to an IO terminal of a Microcontroller (MCU), and an output terminal of the second comparator 311 is connected to the switch circuit 33. Here, the second comparator 31 includes a second comparator 311, a positive phase input terminal of the second comparator 311 is a positive phase input terminal of the second comparator 31, a negative phase input terminal of the second comparator 311 is a negative phase input terminal of the second comparator 31, and when a voltage U2 at the positive phase input terminal of the second comparator 311 is greater than a voltage U1 at the negative phase input terminal, the second comparator 311 outputs a high level to control the switch circuit 33 to open to cut off the circuit where the load is located, so as to enter a protection mode, thereby implementing overload or short-circuit protection on the circuit where the load is located; when the voltage U1 at the negative phase input terminal of the second comparator 311 is greater than the voltage U2 at the positive phase input terminal, the second comparator 311 outputs a low level to control the switch circuit 33 to be closed to connect the circuit where the load is located again to enter a working mode, so that self-recovery after protection is started is realized. The negative phase input end of the second comparator 311 is connected to the IO end of the microcontroller through a resistor R9, the resistor R11 is connected between the node of the negative phase input end and the resistor R9 and the ground, the positive phase input end of the second comparator 311 is connected to the output end of the first comparator 211, when the IO port of the microcontroller is in an inoperative or initial state, the voltage U1 at the negative phase input end of the second comparator 311 is less than the voltage U2 at the positive phase input end, and when the IO port of the microcontroller outputs a high level, the voltage U1 at the negative phase input end of the second comparator 311 is greater than the voltage U2 at the positive phase input end.
In some embodiments, the output control circuit 30 further includes a first switching element Q1 connected between the output terminal of the first comparator 211 and the positive phase input terminal of the second comparator 311, and a second charging and discharging circuit 312 connected to the positive phase input terminal of the second comparator 311, wherein when the first switching element Q1 is closed, the second charging and discharging circuit 312 is charged such that the voltages at the positive phase input terminal and the negative phase input terminal of the second comparator 311 satisfy a first condition, such that the second comparator 311 outputs a first control signal such that the switching circuit 33 is turned off; when the first switching element Q1 is turned off, the second charge and discharge circuit 312 discharges until the voltages of the positive phase input terminal and the negative phase input terminal of the second comparator 311 satisfy the second condition, so that the second comparator 311 outputs the second control signal to turn on the switching circuit 33. Here, the second charge/discharge circuit 312 is connected to the positive phase input terminal of the second comparator 311, and the node between the positive phase input terminal of the second comparator 311 and the second charge/discharge circuit 312 is connected to the power supply through the resistor R7, when the first switching element Q1 is closed, the second charge/discharge circuit 312 is in a charged state, the positive phase input terminal voltage U2 of the second comparator 311 is greater than the negative phase input terminal voltage U1, and the output terminal of the second comparator 311 outputs a high level to control the switching circuit 33 to be turned off; when the first switching element Q1 is turned off, the second charge-discharge circuit 312 is switched from the charge state to the discharge state, and during a time period T1 when the second charge-discharge circuit 312 is discharging, thermal energy caused by overload or short circuit is released from the circuit where the load is located in the protection mode until the voltage U2 at the positive phase input end of the second comparator 311 is smaller than the voltage U1 at the negative phase input end, the output end of the second comparator 311 is changed from the high level to the low level to control the switching circuit 33 to be turned on again, and the circuit where the load is located automatically returns to the working mode.
The first switching element Q1 is a triode, a base of the triode is connected to an output terminal of the first comparator 211, an emitter is connected to a positive input terminal of the second comparator 311, a collector is connected to a power supply, and a junction of the positive input terminal and the emitter is connected to the second charge/discharge circuit 312. Here, the positive phase input terminal of the second comparator 311 is connected to the output terminal of the first comparator 211 through a first switching element Q1, and the first switching element Q1 is switched between off and on according to a corresponding control signal output from the output terminal of the first comparator 211, thereby changing the magnitude of the voltage of the positive phase input terminal of the second comparator 311 and changing the conditions that the voltages of the positive phase input terminal and the negative phase input terminal of the second comparator 311 satisfy. The junction between the non-inverting input terminal and the emitter of the second comparator 311 is connected to a power supply through a voltage dividing resistor R7.
In an optional embodiment, the second charge-discharge circuit 312 includes a second charge capacitor C3 and a second resistor R6 connected in parallel, one end of the second charge capacitor C3 and one end of the second resistor R6 are connected to the first switch element Q1, and the other end of the second charge capacitor C3 and the other end of the second resistor R6 are connected to ground. Specifically, one end of the second charge/discharge circuit 312 is connected to the emitter of the first switching element Q1, and the other end is connected to ground. The time period T1 for the second charge/discharge circuit 312 to discharge can be adjusted by the second charging capacitor C3C3, the second resistor R6R6, and the voltage U1 at the positive phase input terminal and the voltage U2 at the negative phase input terminal of the second comparator 311, which can be specifically expressed by the following formula two:
t1 ═ R6 ═ C3 ═ Ln [ U2/(U2-U1) ] (formula two)
When the first switching element Q1 is turned off, the second charge-discharge circuit 312 is switched into a discharge state, during the time period T1 when the second charge/discharge circuit 312 discharges, the thermal energy of the circuit where the load is under the protection mode due to overload or short circuit is released until the voltage U2 of the positive phase input terminal of the second comparator 311 is less than the voltage U1 of the negative phase input terminal, at this time, the output terminal of the second comparator 311 changes from high level to low level to control the switch circuit 33 to conduct again, and the circuit where the load is located automatically returns to the working mode from the protection mode, the time period T1 for the second charge/discharge circuit 312 to discharge can be adjusted according to the formula, thereby controlling the time required for the circuit in which the load is located to switch from the protection mode to the working mode, so that the heat energy caused by overload or short circuit in the protection mode of the circuit with the load can be released in enough time.
The switch circuit 33 includes a PMOS fet connected between the load 40 and the second comparator circuit 31, a gate of the PMOS fet is connected to an output terminal of the second comparator circuit 31, a source of the PMOS fet is connected to the load 40, and a drain of the PMOS fet is connected to a load power supply. Alternatively, the load power supply may be a 12V dc power supply. It should be noted that the switch circuit 33 may not be limited to a PMOS fet, as long as it can realize a switch electronic component or a combination of switch electronic components, such as a relay, a breaker, etc., for turning off or on the circuit in which the load is located according to the output control signal of the second comparator circuit 31.
In order to better understand the working principle of the overload and short-circuit protection circuit provided by the embodiment of the present invention, an alternative embodiment is taken as an example to illustrate the working mode of the overload and short-circuit protection circuit.
When the circuit where the load is located is in an operating state, the IO port of the microcontroller outputs a high level, and at this time, the voltage U4 at the negative phase input end of the first comparator 211 is the divided voltage of the power supply VCC across the resistor R5, and the calculation formula is U4 ═ VCC R5/(R4+ R5); the voltage U2 at the non-inverting input terminal of the second comparator 311 is the divided voltage of the power VCC across the second resistor R6, and the calculation formula is U2 ═ VCC R6/(R6+ R7); the voltage U1 at the negative input terminal of the second comparator 311 is the divided voltage of the power VCC across the resistor R11, and the calculation formula is U1 ═ VCC R11/(R11+ R10); the resistors R6 and R7 and the resistors R11 and R10 can be selected, so that U1 is greater than U2.
The detected voltage U3 at the detection resistor R1 is equal to the voltage U5 at the positive phase input end of the first comparator 211, when the voltage U5 at the positive phase input end of the first comparator 211 is greater than the voltage U4 at the negative phase input end thereof, the overload protection circuit starts the protection mechanism, so that the critical point of the overload and short-circuit protection circuit start protection mechanism is that the voltage U5 at the positive phase input end of the first comparator 211 is equal to the voltage U4 at the negative phase input end, and the overload current I of the circuit design is the ratio of the voltage at the critical point to the resistance value of the detection resistor R1, that is, I is U3/R1-U4/R1. The overload current I is also the protection starting current of the overload and protection starting circuit triggering the starting protection mechanism.
When U1> U2, the output terminal of the second comparator 311 outputs a low level, the PMOS fet in the switch circuit 33 is turned on, and the circuit in which the load is located maintains a normal operating state.
When the current detection circuit 10 detects that the current flowing through the load 40 is larger than the overload current I, the voltage U5 at the positive input terminal of the first comparator 211 charges the first charging capacitor C1 through the first resistor R3, and the response time T2 that the voltage U5 at the positive input terminal of the first comparator 211 rises to be equal to the voltage U4 at the negative input terminal can be determined according to the aforementioned formula one. When the time T2 is reached, U5> U4, the output terminal of the first comparator 211 changes from output low level to output high level, the first switch element Q1 is turned on, the power supply charges the second charging capacitor C3 in the second charging and discharging circuit 312 through the first switch element Q1, when the voltage on the second charging capacitor C3 is charged to be greater than the voltage U1 at the negative input terminal of the second comparator 311, the output terminal of the second comparator 311 changes from output low level to output high level, and the PMOS fet is turned off to cut off the circuit where the load is located, so as to enter the protection mode. In addition, since the first switching element Q1 is turned on and then is directly charged by the power supply, the charging time of the second charging capacitor C3 can be very short.
During the protection mode, after the PMOS fet is turned off, the voltage U3 detected at the detection resistor R1 is 0, the first charging capacitor C1 in the first charging/discharging circuit 22 is discharged, the output of the first comparator 211 becomes low, and the first switching element Q1 is turned off. At this time, the voltage U2 at the non-inverting input terminal of the second comparator 311 is still greater than the voltage U1 at the inverting input terminal, and after the voltage U2 at the non-inverting input terminal of the second comparator 311 is discharged to a voltage value less than the voltage U1 at the inverting input terminal through the second resistor R6R6, the output terminal of the second comparator 311 becomes low, and the PMOS fet is turned on again to connect the circuit where the load is located to recover to the operating mode. The discharge time T1 of the second charging capacitor C3 can be determined according to the second formula. And when the PMOS field effect transistor is conducted again and the circuit is recovered to work normally, if overload current exists, the overload protection circuit is switched between the working mode and the protection mode in a circulating mode according to the steps, and if the overload current disappears after self recovery, the circuit where the load is located is maintained in a normal working state.
When the short-circuit current flowing through the load is larger than the overload current I of the circuit design when the circuit of the load is in the short-circuit state, the voltage U3 detected at the detection resistor R1 is the product of the short-circuit current and the detection resistor R1, and the response time T2 when the voltage U5 at the positive phase input end of the first comparator 211 rises to be equal to the voltage U4 at the negative phase input end can still be determined according to the above formula one. When the time T2 is reached, U5> U4, the output terminal of the first comparator 211 changes from output low level to output high level, the first switch element Q1 is turned on, the power supply charges the second charging capacitor C3 in the second charging and discharging circuit 312 through the first switch element Q1, when the voltage on the second charging capacitor C3 is charged to be greater than the voltage U1 at the negative input terminal of the second comparator 311, the output terminal of the second comparator 311 changes from output low level to output high level, and the PMOS fet is turned off to cut off the circuit where the load is located, so as to enter the protection mode. In addition, since the first switching element Q1 is turned on and then is directly charged by the power supply, the charging time of the second charging capacitor C3 can be very short.
During the protection mode, after the PMOS fet is turned off, the voltage U3 detected at the detection resistor R1 is 0, the first charging capacitor C1 in the first charging/discharging circuit 22 is discharged, the output of the first comparator 211 becomes low, and the first switching element Q1 is turned off. At this time, the voltage U2 at the non-inverting input terminal of the second comparator 311 is still greater than the voltage U1 at the inverting input terminal, and after the voltage U2 at the non-inverting input terminal of the second comparator 311 is discharged to a voltage value less than the voltage U1 at the inverting input terminal through the second resistor R6R6, the output terminal of the second comparator 311 becomes low, and the PMOS fet is turned on again to connect the circuit where the load is located to recover to the operating mode. The discharge time T1 of the second charging capacitor C3 can be determined according to the second formula. And after the PMOS field effect transistor is conducted again and the circuit is recovered to work normally, if a short circuit phenomenon exists, the overload protection circuit is switched between the working mode and the protection mode in a circulating mode according to the steps, and if the short circuit phenomenon disappears after self recovery, the circuit where the load is located is maintained in a normal working state.
As described above, the embodiment of the utility model provides an overload and short-circuit protection circuit need not the consumptive material and realizes overload and short-circuit protection to load circuit, need not with the help of software, only can be according to overload or short circuit phenomenon to overload and short circuit automatic start protection mechanism to the circuit at load place through the form of pure hardware, and can self-resuming after the start protection, simple structure and stable in function.
The above description is only for the specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present invention, and all should be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. An overload and short-circuit protection circuit is characterized by comprising a current detection circuit, a protection response circuit and an output control circuit, wherein the current detection circuit is used for detecting load current flowing through a load, the protection response circuit comprises a first charge-discharge circuit connected with the current detection circuit and a first comparison circuit connected with the first charge-discharge circuit, the output control circuit comprises a second comparison circuit and a switch circuit connected with the first comparison circuit, when the circuit where the load is located is overloaded or short-circuited, the load current is larger than protection starting current, the first charge-discharge circuit is charged until voltages of a positive phase input end and a negative phase input end of the first comparison circuit meet a first condition, the first comparison circuit outputs a first control signal, so that the second comparison circuit controls the switch circuit to be disconnected to cut off the circuit where the load is located to enter a protection mode, after the switching circuit is switched off, the first charge-discharge circuit discharges until the voltages of the positive phase input end and the negative phase input end of the first comparison circuit meet a second condition, and the first comparison circuit outputs a second control signal, so that the second comparison circuit controls the switching circuit to be switched on to connect the circuit where the load is located again to enter a working mode.
2. The protection circuit of claim 1, wherein the current sensing circuit comprises a sense resistor connected between one end of the load and ground.
3. The protection circuit according to claim 2, wherein the first charge-discharge circuit includes a first resistor and a first charge capacitor, one end of the first resistor is connected to a node between the detection resistor and the load, the other end of the first resistor is connected to a positive input terminal of the first comparison circuit, and the first charge capacitor is connected between a node between the first resistor and the positive input terminal and ground.
4. The protection circuit of claim 1, wherein the first comparator circuit comprises a first comparator, the positive phase input terminal is connected to the first charge-discharge circuit, the negative phase input terminal is connected to a power supply, and the output terminal of the first comparator is connected to the output control circuit.
5. The protection circuit of claim 4, wherein the second comparator circuit comprises a second comparator having a positive phase input connected to the output of the first comparator, a negative phase input connected to the IO terminal of the microcontroller, and an output connected to the switching circuit.
6. The protection circuit according to claim 5, wherein the output control circuit further includes a first switching element connected between an output terminal of the first comparator and the positive phase input terminal of the second comparator, and a second charge and discharge circuit connected to a positive phase input terminal of the second comparator, and when the first switching element is closed, the second charge and discharge circuit is charged so that voltages at the positive phase input terminal and the negative phase input terminal of the second comparator satisfy a first condition, so that the second comparator outputs a first control signal so that the switching circuit is turned off;
when the first switch element is switched off, the second charge-discharge circuit discharges until the voltages of the positive input end and the negative input end of the second comparator meet a second condition, so that the second comparator outputs the second control signal to enable the switch circuit to be switched on.
7. The protection circuit of claim 6, wherein the first switching element is a triode, a base of the triode is connected with an output end of the first comparator, an emitter of the triode is connected with a positive input end of the second comparator, a collector of the triode is connected with a power supply, and a junction of the positive input end and the emitter of the triode is connected with the second charge and discharge circuit.
8. The protection circuit of claim 7, wherein a junction of the non-inverting input terminal and the emitter is connected to a power supply through a voltage dividing resistor.
9. The protection circuit according to claim 6, wherein the second charge-discharge circuit includes a second charge capacitor and a second resistor connected in parallel, one end of the second charge capacitor and one end of the second resistor are connected to the first switching element, and the other end of the second charge capacitor and the other end of the second resistor are connected to ground.
10. The protection circuit according to any one of claims 1 to 9, wherein the switching circuit comprises a PMOS fet connected between the load and the second comparator circuit, a gate of the PMOS fet being connected to an output of the second comparator circuit, a source of the PMOS fet being connected to the load, and a drain of the PMOS fet being connected to a load power supply.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201921105352.8U CN210326997U (en) | 2019-07-15 | 2019-07-15 | Overload and short-circuit protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921105352.8U CN210326997U (en) | 2019-07-15 | 2019-07-15 | Overload and short-circuit protection circuit |
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| CN210326997U true CN210326997U (en) | 2020-04-14 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110265966A (en) * | 2019-07-15 | 2019-09-20 | 深圳市图灵科创产业发展有限公司 | Overload and short-circuit protection circuit |
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2019
- 2019-07-15 CN CN201921105352.8U patent/CN210326997U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110265966A (en) * | 2019-07-15 | 2019-09-20 | 深圳市图灵科创产业发展有限公司 | Overload and short-circuit protection circuit |
| CN110265966B (en) * | 2019-07-15 | 2024-03-12 | 深圳市图灵科创产业发展有限公司 | Overload and short-circuit protection circuit |
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Inventor after: Xiang Hua Inventor after: Wang Hongyuan Inventor after: Li Yong Inventor after: Liu Jiajin Inventor after: Zhang Baocang Inventor after: Zheng Yu Inventor before: Xiang Hua Inventor before: Dong Chaoyang Inventor before: Wang Hongyuan Inventor before: Li Yong Inventor before: Liu Jiajin Inventor before: Zhang Baocang Inventor before: Zheng Yu |
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