CN113253151B - Short circuit detection circuit, short circuit protection circuit and chip - Google Patents
Short circuit detection circuit, short circuit protection circuit and chip Download PDFInfo
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- CN113253151B CN113253151B CN202110663764.9A CN202110663764A CN113253151B CN 113253151 B CN113253151 B CN 113253151B CN 202110663764 A CN202110663764 A CN 202110663764A CN 113253151 B CN113253151 B CN 113253151B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/50—Testing of electric apparatus, lines, cables or components for short-circuits, continuity, leakage current or incorrect line connections
- G01R31/52—Testing for short-circuits, leakage current or ground faults
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
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- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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Abstract
The invention provides a short circuit detection circuit, a short circuit protection circuit and a chip. Wherein the short detection circuit comprises a signal processing unit. When the input end signal of the short-circuit detection circuit accords with a first preset condition, the signal processing unit delays the signal, so that the short-circuit detection circuit does not directly output a short-circuit alarm signal until the time length which accords with the first preset condition exceeds the preset time length, and the short-circuit detection circuit outputs the short-circuit alarm signal. Meanwhile, the temperature compensation element is used for correcting the signal processing unit, so that the signal processing unit has higher precision under different temperature environments. The configuration solves the problem that the short circuit detection circuit in the prior art is easy to misjudge whether the system has a short circuit or not, and has the advantages of accurate timing and easy chip formation.
Description
Technical Field
The invention relates to the technical field of power supply chips, in particular to a short-circuit detection circuit, a short-circuit protection circuit and a chip.
Background
When the power supply system is in output short circuit, if the protection is improper, the chip is easy to lose efficacy or the energy loss is large, the heating is large, and therefore various short circuit protection circuits are arranged on the power supply. The common short circuit judgment is to detect the voltage of a feedback pin of a chip, if the voltage of the feedback pin is obviously lower than the voltage during normal work, the system is considered to be short-circuited, but when the system is started or the load suddenly changes, the method possibly has the phenomenon of misjudgment to interfere with the normal work.
This method has the following problems:
1) when the system is just powered on and the output voltage is not established, the voltage of a feedback pin of the chip is also obviously lower than the voltage during normal work, and at the moment, the chip considers that the output is in a short-circuit state, so that the starting time is overlong or the normal starting cannot be performed;
2) when the load suddenly changes, for example, the load suddenly changes from light load to heavy load, the output voltage may be pulled relatively low, so that the system misjudges, and the output voltage cannot be reconstructed, or the speed of reconstructing the output voltage is too low;
3) when the temperature changes, part of key current in the circuit changes, so that the judgment is inaccurate.
In short, in the prior art, the short circuit detection circuit is prone to misjudge whether the system is short-circuited or not.
Disclosure of Invention
The invention aims to provide a short circuit detection circuit, a short circuit protection circuit and a chip, and aims to solve the problem that whether a short circuit occurs in a system or not is easily judged by mistake by the short circuit detection circuit in the prior art.
In order to solve the above technical problem, according to a first aspect of the present invention, a short circuit detection circuit is provided, which includes a signal processing unit, wherein the signal processing unit receives a first level when a signal at an input terminal of the short circuit detection circuit meets a first preset condition.
The signal processing unit comprises a first triode and a first capacitor, base current of the first triode is used for charging the first capacitor when the signal processing unit receives the first level, and when voltage of the first capacitor meets a second preset condition, the short circuit detection circuit outputs a short circuit alarm signal.
The signal processing unit comprises a temperature compensation element; the magnitude of the base current of the first triode is influenced by the magnitude of the reference current flowing through the temperature compensation element; when the environment temperature changes, the temperature compensation element changes the circuit parameters of the temperature compensation element, so that the reference current changes towards the trend of offsetting the influence of the temperature change on the base current of the first triode.
And when the signal processing unit receives the first level with the duration exceeding the preset duration, the short circuit detection circuit outputs the short circuit alarm signal.
Optionally, the signal processing unit further includes a second triode, a third triode, a first resistor, a second resistor, a first switching element, and a second switching element, the second triode is a PNP-type triode, an emitter of the second triode is connected to the power supply, a collector of the second triode is connected to the first connection terminal of the first switching element, and a base of the second triode is connected to the collector of the second triode.
The second connection terminal of the first switch element is connected to the first terminal of the temperature compensation element, the control terminal of the first switch element is configured as the input terminal of the signal processing unit, and the first switch element is configured to turn on the first connection terminal and the second connection terminal of the first switch element when the control terminal of the first switch element receives the first level.
The second end of the temperature compensation element is grounded through the first resistor.
The third triode is a PNP type triode, an emitting electrode of the third triode is connected with the power supply through the second resistor, a base electrode of the third triode is connected with a base electrode of the second triode, and a collecting electrode of the third triode is connected with an emitting electrode of the first triode.
The first triode is a PNP type triode, the base of the first triode is connected with one end of the first capacitor, the other end of the first capacitor is grounded, and the collector of the first triode is grounded.
The control end of the second switch element is connected with the control end of the first switch element, the first connection end of the second switch element is connected with the base electrode of the first triode, the second connection end of the second switch element is grounded, and the second switch element is configured to conduct the first connection end and the second connection end of the second switch element when the control end of the second switch element does not receive the first level.
Optionally, the short circuit detection circuit further includes a signal measurement unit and a signal stabilization unit.
The input end of the signal measuring unit is configured as the input end of the short circuit detection circuit, the input end of the signal measuring unit is used for obtaining a characteristic value of the output voltage of a power supply system to be protected, the output end of the signal measuring unit is connected with the input end of the signal processing unit, and when the input end of the signal measuring unit meets a first preset condition, the signal measuring unit outputs a first level.
The output end of the signal stabilizing unit is configured as the output end of the short circuit detection circuit, the input end of the signal stabilizing unit is used for obtaining the voltage of the first capacitor, and when the voltage of the first capacitor meets a second preset condition, the signal stabilizing unit outputs a short circuit alarm signal.
Optionally, the temperature compensation element includes a diode or includes at least two diodes connected in series in the same direction, one end of the temperature compensation element in the same direction as the anode of the diode is configured as a first end of the temperature compensation element, and one end of the temperature compensation element in the same direction as the cathode of the diode is configured as a second end of the temperature compensation element.
Optionally, the first preset condition includes: when the signal measuring unit does not output the first level, the voltage of the input end of the signal measuring unit is lower than a first preset voltage; and when the signal measuring unit outputs the first level, the voltage of the input end of the signal measuring unit is lower than a second preset voltage.
The signal measuring unit comprises a first comparator, a third resistor, a fourth resistor and a fifth resistor, wherein the first end of the third resistor is used for obtaining a reference voltage, and the first preset voltage and the second preset voltage are obtained based on the reference voltage.
The signal negative input end of the first comparator is set as the input end of the signal measurement unit, the signal positive input end of the first comparator is connected with the second end of the third resistor, the positive power supply input end of the first comparator is connected with a power supply, the negative power supply input end of the first comparator is grounded, and the output end of the first comparator is configured as the output end of the signal measurement unit.
One end of the fourth resistor is connected with the second end of the third resistor, and the other end of the fourth resistor is grounded.
One end of the fifth resistor is connected with the signal positive input end of the first comparator, and the other end of the fifth resistor is connected with the output end of the first comparator.
Optionally, the second preset condition includes: when the signal stabilizing unit does not output the short-circuit alarm signal, the voltage of the first capacitor is higher than a third preset voltage; and when the signal stabilizing unit outputs the short-circuit alarm signal, the voltage of the first capacitor is higher than a fourth preset voltage.
The signal stabilizing unit comprises a second comparator, a sixth resistor, a seventh resistor and an eighth resistor, wherein a first end of the sixth resistor is used for obtaining the reference voltage, and the third preset voltage and the fourth preset voltage are obtained based on the reference voltage.
The signal negative input end of the second comparator is set as the input end of the signal stabilizing unit, the signal positive input end of the second comparator is connected with the second end of the sixth resistor, the positive power supply input end of the second comparator is connected with a power supply, the negative power supply input end of the second comparator is grounded, and the output end of the second comparator is configured as the output end of the signal stabilizing unit.
One end of the seventh resistor is connected with the second end of the sixth resistor, and the other end of the seventh resistor is grounded.
One end of the eighth resistor is connected to the signal positive input end of the second comparator, and the other end of the eighth resistor is connected to the output end of the second comparator.
In order to solve the above technical problem, according to a second aspect of the present invention, a short-circuit protection circuit is provided, where the short-circuit protection circuit includes the above short-circuit detection circuit and a protection signal generation unit, a first input end of the protection signal generation unit is configured to receive a characteristic value of an output current of a power supply system to be protected, and a second input end of the protection signal generation unit is connected to an output end of the short-circuit detection circuit.
When the protection signal generating unit does not receive the short-circuit alarm signal and the output current of the power supply system to be protected is larger than a first threshold value, the protection signal generating unit outputs a current-limiting signal; when the protection signal generating unit receives the short-circuit alarm signal and the output current of the power supply system to be protected is larger than a second threshold value, the protection signal generating unit outputs a current-limiting signal; the first threshold is greater than the second threshold.
Optionally, the protection signal generating unit includes a third switching element, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a third comparator, and a second capacitor.
The control end of the third switching element is configured as the second input end of the protection signal generation unit, and the third switching element is configured to conduct the first connection end and the second connection end of the third switching element when the control end of the third switching element receives the short-circuit alarm signal.
The first end of the ninth resistor is used for obtaining the reference voltage, the second end of the ninth resistor is connected with one end of the eleventh resistor, the other end of the eleventh resistor is connected with the first connection end of the third switching element, and the second connection end of the third switching element is grounded.
One end of the tenth resistor is connected with the second end of the ninth resistor, and the other end of the tenth resistor is grounded.
A first end of the twelfth resistor is configured as a first input end of the protection signal generation unit, a second end of the twelfth resistor is connected with one end of the second capacitor, and the other end of the second capacitor is grounded.
A positive signal input end of the third comparator is connected to the second end of the twelfth resistor, a negative signal input end of the third comparator is connected to the second end of the ninth resistor, a positive power input end of the third comparator is connected to a power supply, a negative power input end of the third comparator is grounded, and an output end of the third comparator is configured as an output end of the protection signal generating unit.
The first input end of the protection signal generating unit is used for receiving a voltage signal converted from the output current of the power supply system to be protected.
In order to solve the above technical problem, according to a third aspect of the present invention, there is provided a chip including the above short circuit detection circuit, or the chip including the above short circuit protection circuit.
In order to solve the technical problem, according to a fourth aspect of the present invention, a chip is provided, where the chip includes the short-circuit protection circuit, the voltage stabilization module, the power tube, and the control module.
The chip is used for obtaining electric energy from the outside and supplying power to a load; the voltage stabilizing module is used for providing a power supply and the reference voltage for the short-circuit protection circuit and providing a power supply for the control module.
The power tube is used for being coupled in an output loop of the chip and is used for connecting or disconnecting the output loop of the chip in response to a control signal so as to control the output characteristic of the chip.
The control module is used for driving the power tube to disconnect the circuit when receiving the current limiting signal, and is used for generating a signal received by the first input end of the protection signal generating unit according to the current flowing through the power tube.
The chip further comprises an error amplifier; or the chip further comprises an error amplifier and a frequency compensation module.
The error amplifier is used for amplifying the difference between the characteristic value of the output voltage of the chip and the reference voltage and sending the difference to the control module.
The control module is also used for turning on or turning off the power tube according to a signal sent by the error amplifier so that the output voltage of the chip meets the control expectation.
The frequency compensation module is used for correcting the signal sent by the error amplifier.
Compared with the prior art, the short circuit detection circuit, the short circuit protection circuit and the chip provided by the invention comprise the signal processing unit. When the input end signal of the short-circuit detection circuit accords with a first preset condition, the signal processing unit delays the signal, so that the short-circuit detection circuit does not directly output a short-circuit alarm signal until the time length which accords with the first preset condition exceeds the preset time length, and the short-circuit detection circuit outputs the short-circuit alarm signal. Meanwhile, the temperature compensation element is used for correcting the signal processing unit, so that the signal processing unit has higher precision under different temperature environments. The configuration solves the problem that the short circuit detection circuit in the prior art is easy to misjudge whether the system has a short circuit or not, and has the advantages of accurate timing and easy chip formation.
Drawings
It will be appreciated by those skilled in the art that the drawings are provided for a better understanding of the invention and do not constitute any limitation to the scope of the invention. Wherein:
FIG. 1 is a schematic circuit diagram of a short-circuit protection circuit according to an embodiment of the invention;
FIG. 2 is a waveform diagram of a first comparator under an operating condition according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of a chip according to an embodiment of the invention;
FIG. 4 is a waveform diagram of a chip under an operating condition according to an embodiment of the invention.
In the drawings:
1-a signal measurement unit; 2-a signal processing unit; 3-a signal stabilization unit; 4-a protection signal generating unit; 21-a temperature compensation element; 22-a second switching element; 41-a third switching element; 5-a voltage stabilizing module; 6-power tube; 7-a control module; 8-frequency compensation module.
Detailed Description
To further clarify the objects, advantages and features of the present invention, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. It is to be noted that the drawings are in greatly simplified form and are not to scale, but are merely intended to facilitate and clarify the explanation of the embodiments of the present invention. Further, the structures illustrated in the drawings are often part of actual structures. In particular, the drawings may have different emphasis points and may sometimes be scaled differently.
As used in this application, the singular forms "a", "an" and "the" include plural referents, the term "or" is generally employed in a sense including "and/or," the terms "a" and "an" are generally employed in a sense including "at least one," the terms "at least two" are generally employed in a sense including "two or more," and the terms "first", "second" and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicit to the number of technical features indicated. Thus, features defined as "first", "second" and "third" may explicitly or implicitly include one or at least two of the features, "one end" and "the other end" and "proximal end" and "distal end" generally refer to the corresponding two parts, which include not only the end points, but also the terms "mounted", "connected" and "connected" should be understood broadly, e.g., as a fixed connection, as a detachable connection, or as an integral part; can be mechanically or electrically connected; either directly or indirectly through intervening media, either internally or in any other relationship. Furthermore, as used in the present invention, the disposition of an element with another element generally only means that there is a connection, coupling, fit or driving relationship between the two elements, and the connection, coupling, fit or driving relationship between the two elements may be direct or indirect through intermediate elements, and cannot be understood as indicating or implying any spatial positional relationship between the two elements, i.e., an element may be in any orientation inside, outside, above, below or to one side of another element, unless the content clearly indicates otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
The core idea of the invention is to provide a short circuit detection circuit, a short circuit protection circuit and a chip, so as to solve the problem that the short circuit detection circuit in the prior art is easy to make a misjudgment on whether a system is short-circuited.
The following description refers to the accompanying drawings.
Referring to fig. 1 to 4, in which fig. 1 is a circuit schematic diagram of a short-circuit protection circuit according to an embodiment of the invention; FIG. 2 is a waveform diagram of a first comparator under an operating condition according to an embodiment of the present invention; FIG. 3 is a circuit diagram of a chip according to an embodiment of the invention; FIG. 4 is a waveform diagram of a chip under an operating condition according to an embodiment of the invention.
As shown in fig. 1, the present embodiment provides a short-circuit protection circuit, which includes a short-circuit detection circuit and a protection signal generation unit 4, and the short-circuit detection circuit is mainly designed to determine whether a short circuit occurs in a power supply system to be protected by checking whether an output voltage of the power supply system to be protected is lower than a fixed value. Meanwhile, the capacitor is charged for timing, and the short-circuit signal is output only after the capacitor is charged to reach a certain voltage (which is equivalent to timing for a certain time). In the subsequent part of the description, a chip for supplying power is described, which chip itself is the power supply system to be protected. In other embodiments, the power supply system to be protected may be other forms of power supply circuits or chips.
The short circuit detection circuit includes a signal measurement unit 1, a signal processing unit 2, and a signal stabilization unit 3.
The input end of the signal measuring unit 1 is configured as the input end of the short-circuit detection circuit, the input end of the signal measuring unit is used for obtaining the characteristic value VFB of the output voltage of the power supply system to be protected, the output end of the signal measuring unit is connected with the input end of the signal processing unit, and when the input end of the signal measuring unit meets a first preset condition, the signal measuring unit outputs a first level.
The characteristic value of the output voltage of the power supply system to be protected should be understood according to the following concept, where the characteristic value may be the output voltage of the power supply system to be protected, a voltage value obtained after the output voltage of the power supply system to be protected is subjected to voltage division or voltage boost, a current value obtained after the output voltage of the power supply system to be protected is converted by another element, or another signal. In summary, if a signal value is generated based on the output voltage of the power supply system to be protected, and the output voltage of the power supply system to be protected can be obtained by the back-stepping of the signal, the signal value can be regarded as the characteristic value of the output voltage of the power supply system to be protected. The subsequent characteristic value of the output current of the power supply system to be protected is also to be understood in accordance with this concept. In this embodiment, the characteristic value VFB of the output voltage of the power supply system to be protected is obtained by dividing the output voltage of the power supply system to be protected by resistors.
The first level may be set to a low level or a high level as required, and in this embodiment, the first level is a high level.
The first preset condition includes: when the signal measuring unit 1 does not output the first level, the voltage of the input end of the signal measuring unit 1 is lower than a first preset voltage; and when the signal measuring unit 1 outputs the first level, the voltage of the input terminal of the signal measuring unit is lower than a second preset voltage. In order to ensure the stability of the signal, the first preset voltage is smaller than the second preset voltage.
Referring to fig. 1, the signal measuring unit 1 includes a first comparator OP1, a third resistor R3, a fourth resistor R4, and a fifth resistor R5, wherein a first end of the third resistor R3 is used for obtaining a reference voltage VREF, and the first preset voltage and the second preset voltage are obtained based on the reference voltage VREF. It is to be understood that "… … is derived based on the reference voltage VREF", it is to be understood that the object to be described is physically derived by dividing, adding, superimposing, transforming, etc. based on the reference voltage VREF; will vary in value with the variation in the reference voltage VREF. The same descriptions in the following can also be understood in light of the above-described ideas.
It is to be understood that the reference voltage VREF is provided by external circuitry for the short protection circuit and the short detection circuit. In the short circuit detection circuit, only the short circuit detection circuit is used as a basis for logic judgment. The specific value of the reference voltage VREF can be set according to actual needs.
A signal negative input terminal of the first comparator OP1 is set as an input terminal of the signal measuring unit 1, a signal positive input terminal of the first comparator OP1 is connected with a second terminal of the third resistor R3, a positive power input terminal of the first comparator OP1 is connected with a power supply VCC, a negative power input terminal of the first comparator OP1 is grounded, and an output terminal of the first comparator OP1 is configured as an output terminal of the signal measuring unit 1.
One end of the fourth resistor R4 is connected to the second end of the third resistor R3, and the other end of the fourth resistor R4 is grounded.
One end of the fifth resistor R5 is connected to the positive signal input end of the first comparator OP1, and the other end of the fifth resistor R5 is connected to the output end of the first comparator OP 1.
The first preset voltage and the second preset voltage may be calculated according to the connection relationship, and specifically, the first preset voltage may be calculated according to the following formula:
wherein VL1 represents the first predetermined voltage, and R3, R4 and R5 all represent the resistance of the same-sign element.
The second preset voltage may be calculated by the following equation:
wherein VH1 represents the second predetermined voltage.
Based on the above calculation, a waveform diagram of the first comparator OP1 under a working condition, that is, fig. 2, can be obtained. In fig. 2, VA is a voltage at the output terminal of the first comparator OP 1. As can be seen from fig. 2, when the input signal rises and falls, the switching point of the output level of the first comparator OP1 is different. With the adoption of the configuration, when the characteristic value VFB voltage of the output voltage of the power supply system to be protected is at a critical point, the VA voltage is prevented from fluctuating, so that the system misjudgment is avoided. Furthermore, the voltages of the first preset voltage and the second preset voltage are set to be closer, so that the accuracy of the FB voltage determination value is improved. The setting method can be that the resistance value settings of the third resistor R3, the fourth resistor R4 and the fifth resistor R5 are adjusted by combining the calculation formulas of VL1 and VH 1.
In this embodiment, the first comparator OP1 is a rail-to-rail output comparator, thereby increasing circuit accuracy.
The signal processing unit 2 includes a first transistor Q1, a second transistor Q2, a third transistor Q3, a first resistor R1, a second resistor R2, a first switching element, a second switching element 22, a first capacitor C1, and a temperature compensation element 21.
The second triode Q2 is a PNP triode, an emitter of the second triode Q2 is connected to a power VCC, a collector of the second triode Q2 is connected to the first connection terminal of the first switching element, and a base of the second triode Q2 is connected to a collector of the second triode Q2.
The second connection terminal of the first switch element is connected to the first terminal of the temperature compensation element 21, the control terminal of the first switch element is configured as the input terminal of the signal processing unit 2, and the first switch element is configured to turn on the first connection terminal and the second connection terminal of the first switch element when the control terminal of the first switch element receives the first level.
The second terminal of the temperature compensation element 21 is connected to ground through the first resistor R1.
The third triode Q3 is PNP type triode, the projecting pole of third triode Q3 passes through the power VCC is connected to second resistance R2, the base of third triode Q3 with the base of second triode Q2 is connected, the collecting electrode of third triode Q3 with the projecting pole of first triode Q1 is connected.
The first triode Q1 is a PNP type triode, the base of the first triode Q1 is connected with one end of the first capacitor C1, the other end of the first capacitor C1 is grounded, and the collector of the first triode Q1 is grounded.
The control terminal of the second switch element 22 is connected to the control terminal of the first switch element, the first connection terminal of the second switch element 22 is connected to the base of the first transistor Q1, the second connection terminal of the second switch element is grounded, and the second switch element is configured to turn on the first connection terminal and the second connection terminal of the second switch element when the control terminal of the second switch element does not receive the first level.
The magnitude of the base current of the first transistor Q1 is influenced by the magnitude of the reference current flowing through the temperature compensation element 21; when the ambient temperature changes, the temperature compensation element 21 changes its circuit parameters, so that the reference current changes along a trend of offsetting the influence of the ambient temperature change on the base current of the first triode. In an exemplary embodiment, at the ambient temperature T1, the reference current is 10uA, and the base current of the first transistor Q1 is K × 10uA, where K is the base current of Q1 and the reference current is 0.04 based on a proportionality coefficient obtained by a circuit structure, and at this time, the base current of Q1 is 0.4 uA. At the ambient temperature T2, the coefficient K is affected by temperature and becomes 0.05, at which time the base current of Q1 is 0.5uA if the temperature compensation element 21 is not present, the reference current is adjusted to 8uA due to the presence of the temperature compensation element 21, and finally the base current of Q1 is still 0.4 uA. It should be understood that the compensation result of the temperature compensation element 21 does not need to completely cancel the influence of the change of the ambient temperature, and the change of the base current of the final Q1 can be made smaller than the change in the case where the temperature compensation element 21 is not provided, so that the description of the temperature compensation element 21 can be considered to be satisfied. The specific working principle of the temperature compensation element 21 may be that the temperature change directly brings the circuit parameter change of the element itself, or the effect is achieved by measuring the temperature change and then actively changing the circuit result inside the temperature compensation element 21. The temperature compensation element 21 may be a circuit element, a circuit composed of a plurality of circuit elements, an integrated circuit or a chip, or the like. For example, the temperature compensation element 21 may include one diode or at least two diodes connected in series in the same direction (in this embodiment, the number is 3, and D1, D2 and D3 are respectively, the end of the temperature compensation element in the same direction as the anode of the diode is configured as the first end of the temperature compensation element, and the end of the temperature compensation element in the same direction as the cathode of the diode is configured as the second end of the temperature compensation element.
In this embodiment, the signal processing unit 2 further includes a first mos transistor M1, a first inverter N1, and a second mos transistor M2, the first mos transistor M1 is configured as the first switching element, an output terminal of the first inverter N1 is connected to a gate of the second mos transistor, and the first inverter N1 and the second mos transistor constitute the second switching element 22. The first mos tube is an N-channel enhanced mos tube, and the second mos tube is an N-channel enhanced mos tube. In other embodiments, the first switch element and the second switch element 22 may be implemented by selecting other elements according to the relevant description in the specification.
According to the above circuit configuration, it is understood that the signal processing unit 2 realizes the charging of the first capacitor C1 by forming a micro current source. The short circuit detection circuit can be applied to a capacitor with a small capacitance value, so that the short circuit detection circuit has the advantage of being easy to chip. Specifically, the analysis is as follows:
when the first mos transistor M1 is turned on, the base current of the first transistor Q1 charges the first capacitor C1, and the base currents of the second transistor Q2 and the third transistor Q3 and the turn-on voltage drop of the first mos transistor M1 are ignored, and the following formula is given:
where I1 is Q2 collector current, I2 is Q3 collector current, UTIs thermal voltage, about 26mV, V at room temperatureEB2The voltage difference between the emitter and the base is about 0.7V, V of Q2DThe voltage drop of the single-tube diodes D1, D2, and D3 is N, where N is the number of diodes, and in this embodiment, N = 3. R1 and R2 represent the resistance values of the same-sign elements.
The charging current I3 and the C1 voltage VB of the first capacitor C1 can be calculated by the following formula:
where β is the dc amplification of Q1, C1 represents the capacitance of the first capacitor C1, and t is the charging duration.
The operating logic of the signal processing unit 2 is as follows: when VA is high (i.e. the VFB voltage is too low and may be short circuited), M1 turns on, M2 turns off, the trickle current source starts operating, C1 is charged through Q1, and the C1 voltage gradually rises. When VA is low level (namely VFB voltage is high and non-short circuit state), M1 is turned off, M2 is turned on, the micro-current source stops working, M2 discharges C1, and M2 can rapidly release charges of the capacitor because the capacitor of C1 is usually in pF level, so that normal timing can be guaranteed when short circuit occurs next time. Preferably, the capacitance value of the first capacitor C1 is less than or equal to 20 pF.
To solve the problem that the beta value of the first triode Q1 is positively correlated with the temperature, which leads to the reduction of the C1 charging current I3 when the temperature is high, diodes D1, D2 and D3 are added, and when the temperature is increased, the V of the diodes is increasedDWhen the value is decreased, the value of I1 is increased, and the current value of I2 is increased to compensate the influence of the I3 current caused by the increase of beta, and the reduction of the I3 current caused by the change of the beta value can be compensated by properly selecting the number of the diodes connected in series. The number of diodes can be selected by theoretical solution or by experimental determination. And will not be described in detail in this specification.
In this embodiment, the second comparator OP2 is also a rail-to-rail output comparator, thereby increasing circuit accuracy.
The output end of the signal stabilizing unit 3 is configured as the output end of the short circuit detection circuit, the input end of the signal stabilizing unit 3 is used for obtaining the voltage of the first capacitor C1, and when the voltage of the first capacitor C1 meets a second preset condition, the signal stabilizing unit 3 outputs a short circuit alarm signal. The short circuit alarm signal may be set according to actual needs and development costs of subsequent circuits, in this embodiment, the short circuit alarm signal is at a low level, and in other embodiments, the short circuit alarm signal may be at a high level or a signal with a special waveform.
The second preset condition includes: when the signal stabilizing unit 3 does not output the short-circuit alarm signal, the voltage of the first capacitor C1 is higher than a third preset voltage; and when the signal stabilizing unit 3 outputs the short-circuit alarm signal, the voltage of the first capacitor C1 is higher than a fourth preset voltage. In order to ensure the stability of the signal, the third preset voltage is greater than the fourth preset voltage.
The signal stabilizing unit 3 includes a second comparator OP2, a sixth resistor R6, a seventh resistor R7, and an eighth resistor R8, wherein a first end of the sixth resistor R6 is used for obtaining the reference voltage VREF, and the third preset voltage and the fourth preset voltage are obtained based on the reference voltage VREF.
A signal negative input terminal of the second comparator OP2 is set as the input terminal of the signal stabilization unit 3, a signal positive input terminal of the second comparator OP2 is connected with the second terminal of the sixth resistor R6, a positive power input terminal of the second comparator OP2 is connected with a power supply, a negative power input terminal of the second comparator OP2 is grounded, and an output terminal of the second comparator OP2 is configured as the output terminal of the signal stabilization unit 3. Preferably, the negative signal input terminal of the second comparator OP2 is a high impedance input terminal, and the second comparator OP2 does not affect the charge of the first capacitor C1 when obtaining the voltage signal of the first capacitor C1.
One end of the seventh resistor R7 is connected to the second end of the sixth resistor R6, and the other end of the seventh resistor R7 is grounded.
One end of the eighth resistor R8 is connected to the positive signal input end of the second comparator OP2, and the other end of the eighth resistor R8 is connected to the output end of the second comparator OP 2.
Based on the above circuit connection relationship, the third preset voltage may be calculated by the following formula:
in the formula, VH2 represents the third predetermined voltage, and R6, R7, and R8 all represent resistances of elements of the same sign.
The fourth preset voltage may be calculated by:
finally, the time t from when the FB voltage goes low to when the system outputs the short-circuit warning signal can be calculated by the following formula.
A first input end of the protection signal generating unit 4 is configured to receive a characteristic value CS of an output current of a power supply system to be protected, and a second input end of the protection signal generating unit 4 is connected to an output end of the short circuit detection circuit 3.
When the protection signal generating unit 4 does not receive the short-circuit alarm signal, and the output current of the power supply system to be protected is greater than a first threshold value, the protection signal generating unit 4 outputs a current-limiting signal; when the protection signal generating unit 4 receives the short-circuit alarm signal and the output current of the power supply system to be protected is greater than a second threshold value, the protection signal generating unit 4 outputs a current-limiting signal; the first threshold is greater than the second threshold. It should be understood that there is a mapping relationship between the output current of the power supply system to be protected and the characteristic value CS of the output current of the power supply system to be protected, in this embodiment, there is a direct proportional relationship between the output current of the power supply system to be protected and the characteristic value CS of the output current of the power supply system to be protected is a voltage signal.
Referring to fig. 1, the protection signal generating unit 4 includes a third switching element 41, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a third comparator COMP1 and a second capacitor C2.
Wherein a control terminal of the third switching element 41 is configured as a second input terminal of the protection signal generating unit 4, and the third switching element 41 is configured to turn on a first connection terminal and a second connection terminal of the third switching element when the control terminal of the third switching element 41 receives the short-circuit alarm signal.
In this embodiment, the protection signal generating unit 4 further includes a second inverter N2 and a third mos transistor M3, an output terminal of the second inverter N2 is connected to a gate of the third mos transistor, and the second inverter N2 and the third mos transistor constitute the third switching element 41. The third mos tube is an N-channel enhanced mos tube. In other embodiments, the third switching element 41 may be implemented by selecting other elements according to the relevant description in the specification.
A first end of the ninth resistor R9 is configured to obtain the reference voltage VREF, a second end of the ninth resistor R9 is connected to one end of the eleventh resistor R11, another end of the eleventh resistor R11 is connected to the first connection end of the third switching element 41, and a second connection end of the third switching element 41 is grounded. It should be understood that the purpose of the protection signal generating unit 4 obtaining the reference voltage VREF is to obtain a fifth preset voltage and a sixth preset voltage based on the reference voltage VREF, determine whether the output current of the power supply system to be protected is greater than the first threshold according to a magnitude relationship between a signal of the first input end of the protection signal generating unit 4 and the fifth preset voltage, and determine whether the output current of the power supply system to be protected is greater than the second threshold according to a magnitude relationship between a signal of the first input end of the protection signal generating unit 4 and the sixth preset voltage.
One end of the tenth resistor R10 is connected to the second end of the ninth resistor R9, and the other end of the tenth resistor R10 is grounded.
A first terminal of the twelfth resistor R12 is configured as a first input terminal of the protection signal generating unit 4, a second terminal of the twelfth resistor R12 is connected to one terminal of the second capacitor C2, and the other terminal of the second capacitor C2 is grounded. In order to prevent the output current of the power supply system to be protected from generating a large instantaneous current, after the first end of the protection signal generating unit 4 receives a signal, the signal is filtered through R12 and C2, so as to achieve the purpose of leading edge blanking. R12 and C2 need to pay attention to the selection of the time constant, and an excessively small time constant may result in failure to achieve the purpose of leading edge blanking, resulting in erroneous determination of the protection signal generation unit 4, and an excessively large time constant may result in excessively slow OCP response speed, which affects system stability. The specific selection results can be obtained by calculation or experiment according to actual needs by those skilled in the art, and are not described in detail in the specification.
A signal positive input end of the third comparator COMP1 is connected to the second end of the twelfth resistor R12, a signal negative input end of the third comparator COMP1 is connected to the second end of the ninth resistor R9, a positive power input end of the third comparator COMP1 is connected to a power supply, a negative power input end of the third comparator COMP1 is grounded, and an output end of the third comparator COMP1 is configured as an output end of the protection signal generating unit 4.
As mentioned above, the first input terminal of the protection signal generating unit 4 is configured to receive a voltage signal converted from the output current of the power supply system to be protected.
R9, R10, R11, and M3 are configured to set a threshold voltage of the third comparator COMP1, and when M3 is turned off, the threshold voltage of the third comparator COMP1 is the fifth preset voltage, specifically:
in the formula, VTH1 represents the fifth predetermined voltage, and R9 and R10 represent the resistances of the same-sign elements.
When M3 is turned on, the threshold voltage of the third comparator COMP1 is the sixth preset voltage, specifically:
in the formula, the "|" symbol represents the resistance value of the two parallel elements, VTH2 represents the sixth preset voltage, R11 represents the resistance value of the eleventh resistor, and Rdson represents the on-resistance of the third mos tube.
It should be understood that a mapping relationship exists between the fifth preset voltage and the first threshold, and a mapping relationship exists between the sixth preset voltage and the second threshold. The mapping relationship can be obtained according to a specific obtaining manner of the characteristic value CS of the output current of the power supply system to be protected and the element parameter of the protection signal generating unit 4, and will not be described in detail in this specification.
When the CS signal is greater than the threshold voltage of the third comparator COMP1, the signal at the output terminal of the third comparator COMP1, i.e. the OCP signal in fig. 1, is at a high level, and the subsequent circuits may accordingly turn off the output of the power supply system in one clock cycle; when the CS signal is less than the threshold voltage of the third comparator COMP1, the OCP signal is low, and the subsequent circuits may not be operated.
The threshold voltage of the third comparator COMP1 is controlled by the signal of the short-circuit detection circuit, when the signal output by the short-circuit detection circuit is low, M3 is turned on, and the threshold voltage of the third comparator COMP1 is the sixth preset voltage VTH2 and is smaller than the fifth preset voltage VTH1 during normal operation, so that the output current is small, the short-circuit loss is reduced, and the operation safety of the system is ensured. When the short-circuit state is removed, M3 is turned off, the threshold voltage value of the third comparator COMP1 is increased to VTH1, the output current is increased, and the current limiting point in the normal state can ensure that the system starts to work normally when the system is loaded.
The embodiment also provides a chip, wherein the chip comprises the short circuit detection circuit, or the chip comprises the short circuit protection circuit. The chip can also solve the problem that the short circuit detection circuit in the prior art is easy to misjudge whether the system is short-circuited or not.
Referring to fig. 3, the present embodiment further provides another chip, where the chip includes the short-circuit protection circuit, the voltage stabilizing module 5, the power tube 6, and the control module 7.
Wherein the chip is used for obtaining electric energy from the outside and supplying power to a load (not shown); the voltage stabilizing module 5 is used for providing a power source VCC for the short-circuit protection circuit and the reference voltage VREF, and providing the power source VCC for the control module 7.
The power tube 6 is used for being coupled in an output loop of the chip and is used for connecting or disconnecting the output loop of the chip in response to a control signal so as to control the output characteristic of the chip. Specifically, the power tube 6 is connected between VIN and SW pins of the chip, and can be switched on and off between VIN and SW. The output characteristic comprises an output voltage and/or an output current. In a preferred embodiment, the control signal of the power transistor 6 is a pwm signal, and the control module 7 controls the output characteristic of the chip by adjusting the duty ratio of the pwm signal. The specific logic of the control module 7 for generating the pwm signal may be set according to the common knowledge in the art, for example, the duty ratio of the pwm signal is obtained by scaling according to a control command sent by a controller (not shown).
The control module 7 is configured to drive the power tube 6 to open the circuit when receiving the current limiting signal, and is configured to generate a signal received by the first input terminal of the protection signal generating unit 4 according to the current flowing through the power tube 6. It is to be understood that the specific logic of the control module 7 may vary in different embodiments. For example, in one embodiment, the control module 7 may only respond mechanically to the current limit signal, and immediately drive the power tube 6 into circuit if the current limit signal disappears. In this embodiment, the control module 7 drives the power tube 6 to open the circuit when receiving the current limiting signal, then maintains the off state of the power tube 6 until the current period of the pwm signal is over, and drives the power tube 6 to open the circuit when the next period starts. The implementation manner of the control module 7 generating the signal according to the current flowing through the power tube 6 may be set by those skilled in the art according to actual needs, and the relationship between the generated signal and the current flowing through the power tube 6 may be estimated according to the actual implementation manner, which is not described in detail in this specification.
The connection pattern between the control module 7 and the power tube 6 is not specified in fig. 3, and it cannot be understood that there is only one line connection between the control module 7 and the power tube 6. The connection between the two may be through one or more wires and/or through one or more circuit elements.
In this embodiment, the chip further includes an error amplifier OTA1 and a frequency compensation module 8.
The error amplifier OTA1 is configured to compare and amplify a difference between the characteristic VFB of the output voltage of the chip and the reference voltage VREF, and send the difference to the control module 7.
The control module 7 is also used to turn on or off the power transistor 6 according to the signal sent by the error amplifier OTA1 so that the output voltage of the chip meets the control expectations. Satisfying control expectations it can be understood that the control module 7 controls the output voltage of the chip to be within a desired range by turning the power transistor 6 on or off so that VFB is equal to VREF. In the actual design process, an expected value of the output voltage of the chip and VREF are determined, then an expected VFB (VFB = VREF) is obtained, and finally a voltage division circuit is set according to the expected value of the output voltage of the chip and the expected VFB.
The frequency compensation module 8 is configured to modify the signal sent by the second comparator OTA 1.
The operation details of the modules in the chip, which are not mentioned, and the connection manner between the modules may be set by those skilled in the art according to the prior art and fig. 3, and are not described in detail in this specification.
The chip can prevent the problem of difficulty in starting with a load when a system is powered on while normally outputting a short-circuit signal, and can also prevent the load from instantly drawing a large current to be misjudged as a short circuit. When the system is in short circuit, the threshold voltage determined by OCP is reduced, the output current is reduced, and the system is more stable in a short circuit state. The problem that the short circuit detection circuit easily makes misjudgment on whether the system is short-circuited in the prior art can be solved.
Referring to fig. 4, fig. 4 is a waveform diagram of a critical voltage signal in the chip. The measurement points of the waveform diagrams are understood with reference to fig. 3. In the embodiment shown in fig. 4: VH1 (i.e., the second preset voltage) is set to 0.7V, VL1 (i.e., the first preset voltage) is set to 0.5V, VH2 (i.e., the third preset voltage) is set to 1.1V, VL2 (i.e., the fourth preset voltage) is set to 0.9V, the threshold voltage high value (i.e., the fifth preset voltage) VTH1 of the third comparator COMP1 is 0.35V, and the low value VTH2 (i.e., the sixth preset voltage) is 0.15V.
As can be seen from fig. 4, when the VFB voltage drops to about 0.5V, the output voltage VA of the first comparator OP1 is high, and at the same time the first capacitor C1 starts to charge, the voltage VB of the first capacitor C1 starts to rise with a fixed slope, when the voltage VB rises to about 1.1V, vshirt starts to be high, indicating a system short circuit, and the threshold voltage VTH of the third comparator COMP1 drops from 0.35V to 0.15V, ensuring stable system operation; when VFB rises to 0.7V, VA is at a low level, M2 discharges the capacitor, the discharge is almost instantly completed due to the fact that the first capacitor C1 is small, VB drops to 0V from 5V, VSHORT is at a low level when the capacitor is also turned on, the short-circuit state is relieved, and the threshold voltage VTH of the third comparator COMP1 rises to 0.35V from 0.15V, so that the system can be guaranteed to output a large current. When the output end is short-circuited, the output voltage ratio is low, the VFB voltage is certainly less than 0.5V, after a period of time t (the delay time can avoid the phenomenon that the load is suddenly increased, the output voltage drops in a short time and the short-circuit protection function is triggered by mistake), VSHORT outputs high level, reduces the current-limiting point in the chip, realizes that the system short-circuit output current is in a small value, and improves the short-circuit protection stability; when the short circuit state is removed, the output voltage can be slowly increased, the corresponding VFB voltage can also be increased, when the VFB voltage is greater than 1.1V, the VSHORT signal becomes low level, the current-limiting point in the chip is recovered to a normal value, and the chip can output large current to supply power to a load.
In summary, the short circuit detection circuit, the short circuit protection circuit and the short circuit detection circuit in the chip provided by the embodiment include the signal processing unit 2. When the input end signal of the short circuit detection circuit accords with a first preset condition, the signal processing unit 2 delays the signal, so that the short circuit detection circuit does not directly output a short circuit alarm signal until the time length which accords with the first preset condition exceeds a preset time length, and the short circuit detection circuit outputs the short circuit alarm signal. Meanwhile, the signal processing unit 2 is also corrected by the temperature compensation element 21, so that the signal processing unit has higher precision under different temperature environments. The configuration solves the problem that the short circuit detection circuit in the prior art is easy to misjudge whether the system has a short circuit or not, and has the advantages of accurate timing and easy chip formation.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art according to the above disclosure are within the scope of the present invention.
Claims (6)
1. A short circuit detection circuit, characterized in that the short circuit detection circuit comprises a signal processing unit,
when the input end signal of the short circuit detection circuit meets a first preset condition, the signal processing unit receives a first level;
the signal processing unit comprises a first triode and a first capacitor, the base current of the first triode is used for charging the first capacitor when the signal processing unit receives the first level, and the short circuit detection circuit outputs a short circuit alarm signal when the voltage of the first capacitor meets a second preset condition;
the signal processing unit comprises a temperature compensation element; the magnitude of the base current of the first triode is influenced by the magnitude of the reference current flowing through the temperature compensation element; when the environment temperature changes, the temperature compensation element changes the circuit parameters of the temperature compensation element, so that the reference current changes towards the trend of offsetting the influence of the temperature change on the base current of the first triode;
when the signal processing unit receives the first level with the duration exceeding the preset duration, the short circuit detection circuit outputs the short circuit alarm signal;
the signal processing unit further comprises a second triode, a third triode, a first resistor, a second resistor, a first switching element and a second switching element,
the second triode is a PNP triode, an emitting electrode of the second triode is connected with a power supply, a collector electrode of the second triode is connected with the first connecting end of the first switching element, and a base electrode of the second triode is connected with the collector electrode of the second triode;
the second connection end of the first switch element is connected with the first end of the temperature compensation element, the control end of the first switch element is configured as the input end of the signal processing unit, and the first switch element is configured to turn on the first connection end and the second connection end of the first switch element when the control end of the first switch element receives the first level;
the second end of the temperature compensation element is grounded through the first resistor;
the third triode is a PNP triode, an emitting electrode of the third triode is connected with a power supply through the second resistor, a base electrode of the third triode is connected with a base electrode of the second triode, and a collector electrode of the third triode is connected with an emitting electrode of the first triode;
the first triode is a PNP triode, the base of the first triode is connected with one end of the first capacitor, the other end of the first capacitor is grounded, and the collector of the first triode is grounded;
the control end of the second switch element is connected with the control end of the first switch element, the first connection end of the second switch element is connected with the base electrode of the first triode, the second connection end of the second switch element is grounded, and the second switch element is configured to conduct the first connection end and the second connection end of the second switch element when the control end of the second switch element does not receive the first level;
the short circuit detection circuit further comprises a signal measurement unit and a signal stabilization unit, wherein,
the input end of the signal measuring unit is configured as the input end of the short circuit detection circuit, the input end of the signal measuring unit is used for obtaining the characteristic value of the output voltage of the power supply system to be protected, the output end of the signal measuring unit is connected with the input end of the signal processing unit, and when the input end of the signal measuring unit meets a first preset condition, the signal measuring unit outputs a first level;
the output end of the signal stabilizing unit is configured as the output end of the short circuit detection circuit, the input end of the signal stabilizing unit is used for obtaining the voltage of the first capacitor, and when the voltage of the first capacitor meets a second preset condition, the signal stabilizing unit outputs the short circuit alarm signal;
the first preset condition includes:
when the signal measuring unit does not output the first level, the voltage of the input end of the signal measuring unit is lower than a first preset voltage; when the signal measuring unit outputs the first level, the voltage of the input end of the signal measuring unit is lower than a second preset voltage;
the signal measuring unit includes a first comparator, a third resistor, a fourth resistor, and a fifth resistor, wherein,
the first end of the third resistor is used for acquiring a reference voltage, and the first preset voltage and the second preset voltage are obtained based on the reference voltage;
the signal negative input end of the first comparator is set as the input end of the signal measurement unit, the signal positive input end of the first comparator is connected with the second end of the third resistor, the positive power supply input end of the first comparator is connected with a power supply, the negative power supply input end of the first comparator is grounded, and the output end of the first comparator is configured as the output end of the signal measurement unit;
one end of the fourth resistor is connected with the second end of the third resistor, and the other end of the fourth resistor is grounded;
one end of the fifth resistor is connected with the signal positive input end of the first comparator, and the other end of the fifth resistor is connected with the output end of the first comparator;
the second preset condition includes:
when the signal stabilizing unit does not output the short-circuit alarm signal, the voltage of the first capacitor is higher than a third preset voltage; when the signal stabilizing unit outputs the short-circuit alarm signal, the voltage of the first capacitor is higher than a fourth preset voltage;
the signal stabilizing unit includes a second comparator, a sixth resistor, a seventh resistor, and an eighth resistor, wherein,
the first end of the sixth resistor is used for acquiring the reference voltage, and the third preset voltage and the fourth preset voltage are obtained based on the reference voltage;
a signal negative input end of the second comparator is set as an input end of the signal stabilizing unit, a signal positive input end of the second comparator is connected with a second end of the sixth resistor, a positive power supply input end of the second comparator is connected with a power supply, a negative power supply input end of the second comparator is grounded, and an output end of the second comparator is configured as an output end of the signal stabilizing unit;
one end of the seventh resistor is connected with the second end of the sixth resistor, and the other end of the seventh resistor is grounded;
one end of the eighth resistor is connected to the signal positive input end of the second comparator, and the other end of the eighth resistor is connected to the output end of the second comparator.
2. The short-circuit detection circuit according to claim 1, wherein the temperature compensation element comprises a diode or at least two diodes connected in series in the same direction, one end of the temperature compensation element in the same direction as the anode of the diode is configured as a first end of the temperature compensation element, and one end of the temperature compensation element in the same direction as the cathode of the diode is configured as a second end of the temperature compensation element.
3. A short-circuit protection circuit, characterized in that it comprises a short-circuit detection circuit according to claim 1 or 2 and a protection signal generation unit, a first input of which is configured to receive a characteristic value of an output current of a power supply system to be protected, and a second input of which is connected to an output of the short-circuit detection circuit;
when the protection signal generating unit does not receive the short-circuit alarm signal and the output current of the power supply system to be protected is larger than a first threshold value, the protection signal generating unit outputs a current-limiting signal; when the protection signal generating unit receives the short-circuit alarm signal and the output current of the power supply system to be protected is larger than a second threshold value, the protection signal generating unit outputs a current-limiting signal; the first threshold is greater than the second threshold.
4. The short-circuit protection circuit according to claim 3, wherein the protection signal generation unit includes a third switching element, a ninth resistor, a tenth resistor, an eleventh resistor, a twelfth resistor, a third comparator, and a second capacitor, wherein,
the control end of the third switching element is configured as the second input end of the protection signal generation unit, and the third switching element is configured to conduct the first connection end and the second connection end of the third switching element when the control end of the third switching element receives the short-circuit alarm signal;
a first end of the ninth resistor is used for obtaining the reference voltage, a second end of the ninth resistor is connected with one end of the eleventh resistor, the other end of the eleventh resistor is connected with a first connection end of the third switching element, and a second connection end of the third switching element is grounded;
one end of the tenth resistor is connected with the second end of the ninth resistor, and the other end of the tenth resistor is grounded;
a first end of the twelfth resistor is configured as a first input end of the protection signal generation unit, a second end of the twelfth resistor is connected with one end of the second capacitor, and the other end of the second capacitor is grounded;
a positive signal input end of the third comparator is connected to the second end of the twelfth resistor, a negative signal input end of the third comparator is connected to the second end of the ninth resistor, a positive power input end of the third comparator is connected to a power supply, a negative power input end of the third comparator is grounded, and an output end of the third comparator is configured as an output end of the protection signal generating unit;
the first input end of the protection signal generating unit is used for receiving a voltage signal converted from the output current of the power supply system to be protected.
5. A chip comprising a short detection circuit as claimed in any one of claims 1 to 2, or a short protection circuit as claimed in any one of claims 3 to 4.
6. A chip, characterized in that the chip comprises the short-circuit protection circuit, the voltage stabilization module, the power tube and the control module according to any one of claims 3 to 4,
the chip is used for obtaining electric energy from the outside and supplying power to a load;
the voltage stabilizing module is used for providing a power supply and the reference voltage for the short-circuit protection circuit and providing a power supply for the control module;
the power tube is used for being coupled in an output loop of the chip and is used for connecting or disconnecting the output loop of the chip in response to a control signal so as to control the output characteristic of the chip;
the control module is used for driving the power tube to disconnect the circuit when receiving the current limiting signal, and is used for generating a signal received by a first input end of the protection signal generating unit according to the current flowing through the power tube;
the chip further comprises an error amplifier; or the chip further comprises an error amplifier and a frequency compensation module, wherein,
the error amplifier is used for amplifying the difference between the characteristic value of the output voltage of the chip and the reference voltage and sending the difference to the control module;
the control module is also used for turning on or turning off the power tube according to a signal sent by the error amplifier so that the output voltage of the chip meets the control expectation;
the frequency compensation module is used for correcting the signal sent by the error amplifier.
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