CN118174242A

CN118174242A - Over-temperature protection circuit and over-temperature protection structure

Info

Publication number: CN118174242A
Application number: CN202410591715.2A
Authority: CN
Inventors: 王加东; 吴忠洁
Original assignee: Shanghai Mindmotion Microelectronics Co ltd
Current assignee: Shanghai Mindmotion Microelectronics Co ltd
Priority date: 2024-05-14
Filing date: 2024-05-14
Publication date: 2024-06-11

Abstract

The application provides an over-temperature protection circuit and an over-temperature protection structure, which relate to the field of over-temperature protection, wherein the over-temperature protection circuit comprises: the current source is used for outputting a first current signal according to the temperature of the object to be detected, and the first current signal is in direct proportion to the temperature; the signal generating circuit is used for receiving the first current signal, outputting a first voltage signal, receiving a shunt signal of the first current signal and outputting a second voltage signal; the signal amplifying circuit is used for receiving the first voltage signal and the second voltage signal, amplifying the difference value between the first voltage signal and the second voltage signal and outputting a third voltage signal; the signal processing circuit is used for receiving the third voltage signal and the zero-degree reference signal and outputting a hysteresis signal according to the third voltage signal and the zero-degree reference signal; and the controller receives the hysteresis signal and determines the triggering time of the over-temperature protection measures according to the hysteresis signal. The application realizes high-precision temperature detection and avoids frequent triggering of over-temperature protection through a hysteresis signal.

Description

Over-temperature protection circuit and over-temperature protection structure

Technical Field

The application relates to the technical field of over-temperature protection, in particular to an over-temperature protection circuit and an over-temperature protection structure.

Background

Because the shell of the whole machine driven by part of the motor is smaller, the temperature in the cavity is higher when the whole machine works, early products do not have any over-temperature protection measures, and after a part of the products are used for a period of time, the critical devices on the circuit board can be abnormal (for example, the temperature resistant point of the electrolytic capacitor is 125 ℃, and the conditions of serious capacitance value reduction and even damage can occur beyond the temperature point of the electrolytic capacitor). In the later stage, although some companies upgrade the products and part of over-temperature protection circuits are added, due to low accuracy of over-temperature protection points (most of the over-temperature protection points are +/-10 degrees due to the process), the consistency of the products is poor, and the critical device damage on the circuit board can occur as well, so that the service life of the whole product is influenced.

Disclosure of Invention

In view of the above, an over-temperature protection circuit and an over-temperature protection structure are provided to detect temperature with high accuracy, and eliminate jitter by hysteresis signals to realize over-temperature protection.

In a first aspect, an over-temperature protection circuit is provided, comprising: the current source is used for outputting a first current signal according to the temperature of the object to be detected, and the first current signal is in direct proportion to the temperature; the signal generating circuit is used for receiving the first current signal, outputting a first voltage signal, receiving a shunt signal of the first current signal and outputting a second voltage signal; the signal amplifying circuit is used for receiving the first voltage signal and the second voltage signal, amplifying the difference value between the first voltage signal and the second voltage signal and outputting a third voltage signal; the signal processing circuit is used for receiving the third voltage signal and the zero-degree reference signal, outputting a hysteresis signal according to the third voltage signal and the zero-degree reference signal, and enabling the zero-degree reference signal to represent the voltage of the object to be detected when the absolute temperature is zero; and the controller receives the hysteresis signal and determines the triggering time of the over-temperature protection measures according to the hysteresis signal.

In one implementation, a signal generation circuit includes a first semiconductor switching element and a plurality of second semiconductor switching elements; the first poles and the second poles of the first semiconductor switching elements are grounded, the first poles and the second poles of the second semiconductor switching elements are grounded, the second poles of the first semiconductor switching elements are also connected with the second poles of any one of the second semiconductor switching elements, the third poles of the second semiconductor switching elements are connected with each other, the third poles of the first semiconductor switching elements receive first current signals, and the third poles of the second semiconductor switching elements respectively receive shunt signals of the first current signals.

In one implementation, the first semiconductor switching element and the plurality of second semiconductor switching elements are PNP transistors; the first semiconductor switching element and the first pole of each second semiconductor switching element are collectors, the second pole is a base, and the third pole is an emitter.

In one implementation, the signal amplifying circuit includes a first operational amplifier, a non-inverting input terminal of the first operational amplifier receives a first voltage signal, an inverting input terminal of the first operational amplifier receives a second voltage signal, and an output terminal of the first operational amplifier outputs a third voltage signal.

In one implementation, the signal amplification circuit further includes a first resistor, a second resistor, a third resistor, and a fourth resistor; the first resistor is connected between the third pole of the first semiconductor switching element and the non-inverting input end of the first operational amplifier; one end of the second resistor is connected with the non-inverting input end of the first operational amplifier, and the other end of the second resistor is connected with the output end of the first operational amplifier; the third resistor is connected between the third pole of any second semiconductor switching element and the inverting input end of the first operational amplifier; one end of the fourth resistor is connected with the inverting input end of the first operational amplifier, and the other end of the fourth resistor is connected with the output end of the first operational amplifier; the resistance of the first resistor is the same as that of the third resistor, the resistance of the second resistor is the same as that of the fourth resistor, and the resistance of the second resistor is a positive integer multiple of that of the first resistor.

In one implementation, a signal generation circuit includes: a third semiconductor switching element and an adjustable resistor; the first pole and the second pole of the third semiconductor switching element are grounded, the third pole of the third semiconductor switching element is connected with one end of the adjustable resistor, and the other end of the adjustable resistor outputs a conversion signal of the zero-degree reference signal.

In one implementation, the third semiconductor switching element is a PNP transistor, the first pole of the third semiconductor switching element is a collector, the second pole is a base, and the third pole is an emitter; the signal processing circuit comprises a buffer circuit, a first switching circuit and a second switching circuit, wherein the buffer circuit is used for receiving a conversion signal of a zero-degree reference signal and outputting the zero-degree reference signal; the buffer circuit comprises a second operational amplifier and a field effect transistor, wherein the non-inverting input end of the second operational amplifier receives a conversion signal of a zero-degree reference signal, the inverting input end of the second operational amplifier is connected with the first pole of the field effect transistor and outputs the zero-degree reference signal, the output end of the second operational amplifier is connected with the second pole of the field effect transistor, and the third pole of the field effect transistor receives a power supply voltage.

In one implementation, a signal processing circuit includes: a first voltage comparator and a second voltage comparator; the non-inverting input ends of the first voltage comparator and the second voltage comparator receive a third voltage signal, the inverting input end of the first voltage comparator receives a first comparison voltage, and the inverting input end of the second voltage comparator receives a second comparison voltage; the first comparison voltage is determined based on the zero-degree reference signal and a first preset temperature, and the second comparison voltage is determined based on the zero-degree reference signal and a second preset temperature, wherein the first preset temperature is smaller than the second preset temperature, so that the first comparison voltage is smaller than the second comparison voltage.

In one implementation, the signal processing circuit further includes a decoding circuit, a first input terminal of the decoding circuit is connected to an output terminal of the first voltage comparator, a second input terminal of the decoding circuit is connected to an output terminal of the second voltage comparator, and an output terminal of the decoding circuit outputs a hysteresis signal; when the level of the first input end of the hysteresis signal jumps from low level to high level and the level of the second input end jumps from low level to high level, the hysteresis signal jumps from low level to high level; the hysteresis signal keeps a high-level state when the level of the first input end is kept in a high-level state and the level of the second input end is jumped from a high level to a low level; the hysteresis signal transitions from a high level to a low level when the level of the first input terminal transitions from a high level to a low level and the level of the second input terminal remains in a low level state.

In a second aspect, an over-temperature protection structure is provided, including any one of the over-temperature protection circuits in the first aspect, where the over-temperature protection circuit is configured to determine a trigger timing of an over-temperature protection measure according to an internal temperature of the over-temperature protection structure.

In summary, the over-temperature protection circuit and the over-temperature protection structure provided by the application have at least the following beneficial effects:

(1) The difference between the two voltages is amplified by the signal generating circuit and the signal amplifying circuit, so that the difference is in direct proportion to the absolute temperature, the current absolute temperature can be represented by the difference, and meanwhile, the temperature is irrelevant to other factors such as a process and the like.

(2) Because the two voltage values output by the signal generating circuit are too small and are not easy to be received by other electronic elements, the amplified voltage difference value can be more easily received by other electronic elements, and further high-precision temperature detection is realized, namely, the difference value of the two voltage values can more accurately represent the current absolute temperature.

(3) The hysteresis signal output by the signal processing circuit can eliminate the influence of jitter on the over-temperature protection circuit, namely, a temperature interval is set so that the working state of the over-temperature protection circuit cannot be changed by the jitter.

Drawings

The drawings that follow are briefly described as applied to the description of embodiments of the present application:

Fig. 1 is a schematic structural diagram of an over-temperature protection circuit according to an embodiment of the present application;

fig. 2 is a schematic diagram of a part of a structure of an over-temperature protection circuit according to an embodiment of the present application;

fig. 3 is a schematic diagram of a part of a structure of an over-temperature protection circuit according to an embodiment of the present application;

Fig. 4 is a schematic diagram of a part of a structure of an over-temperature protection circuit according to an embodiment of the present application;

fig. 5 is a schematic diagram of a part of a structure of an over-temperature protection circuit according to an embodiment of the present application;

FIG. 6 is a schematic diagram of a decoding circuit according to an embodiment of the present application;

FIG. 7 is a schematic diagram showing a part of signals in the over-temperature protection circuit according to the embodiment of the application;

fig. 8 is a schematic diagram of a part of a structure of an over-temperature protection circuit according to an embodiment of the application.

In the figure: 10-over-temperature protection circuit, 100-current source, 200-signal generation circuit, 300-signal amplification circuit, 400-signal processing circuit, 500-controller.

Detailed Description

In order to more clearly describe the technical solution of the embodiment of the present application, a specific embodiment of the present application will be described below with reference to the accompanying drawings. The drawings described below are only examples of the present application, and it is apparent to those skilled in the art that other drawings and other embodiments can be made from these drawings without departing from the spirit of the present application.

For the sake of simplicity of the drawing, only the parts relevant to the corresponding embodiments are schematically represented in the figures, which do not represent their actual structure as a product. In addition, in order to simplify the drawing for understanding, components having the same structure or function are shown only in part schematically in some drawings, and more or fewer components having the same structure or function may actually be present.

In the present application, ordinal terms such as "first," "second," and the like, are used solely to distinguish between the associated objects and are not to be construed as indicating or implying a relative importance or order between such associated objects unless otherwise expressly specified and defined; in addition, the number of associated objects is not represented. "plurality" includes two or more, and the like. "/" is used to describe a relationship between associated objects, which represents an or relationship between associated objects. "and/or" is used to describe a relationship between associated objects that includes any combination of relationships between associated objects, e.g., "a and/or b" includes: "a alone", "b alone", or "a and b". "one or more" or "at least one" of the plurality of objects refers to any object or any combination of the plurality of objects, such as "one or more of a1, a2, a3" or "at least one of a1, a2, a3" includes: "individual a1", "individual a2", "individual a3", "a1 and a2", "a1 and a3", "a2 and a3", or "a1, a2 and a3".

Over-temperature protection refers to a protection mechanism applied in a device or system that is intended to prevent damage to the device or other adverse consequences caused by overheating. Over-temperature protection is typically achieved by monitoring the device temperature and taking action when the temperature exceeds a set threshold. Over-temperature protection is a critical function in many electronic devices and electrical systems. It can be applied to various devices including computers, cell phones, home appliances, car engines, intelligent lighting and motor driven products, etc. Overheating may occur when the device is operating due to ambient temperature, workload, or other factors. If no timely action is taken to reduce the temperature or stop the operation of the device, overheating may lead to circuit damage, battery explosion, melting of electronic components, or other serious consequences. The over-temperature protection is generally implemented by detecting the current temperature of the current circuit board, comparing the current temperature with a preset value according to the current temperature, and if the current temperature exceeds the preset value, turning on the over-temperature protection (e.g. turning on a fan, reducing frequency, and protecting from power failure). However, the above implementation of over-temperature protection has a common problem: frequent activation of over-temperature protection. Illustrating: assuming that the preset temperature protection point is 90 degrees, when the current temperature reaches 91 degrees, for example, the fan is started, the current temperature is reduced to 89 degrees under the action of the fan, and because the current temperature is lower than the preset temperature protection point, the fan is closed, the temperature of the circuit quickly exceeds 90 degrees, when the current temperature is detected to exceed 90 degrees, the fan is restarted, and thus the over-temperature protection measures are repeatedly started, so that the service life of the circuit can be reduced. In addition, the accuracy of the existing temperature detection technology is not very high, the equivalent of the temperature is easily affected by the manufacturing process of the electronic component itself, the equivalent value is inaccurate, and the current temperature cannot be accurately represented, so that the accuracy of temperature detection is also required to be improved. Based on the above discussion, the concept of the application is that an over-temperature protection circuit needs to be designed, so that the over-temperature protection circuit not only can detect the temperature with high precision, but also can eliminate jitter by generating a hysteresis signal, thereby avoiding frequent starting of over-temperature protection measures and prolonging the service life of the circuit. For specific circuit composition, please refer to the following examples.

In one embodiment, as shown in FIG. 1, an over-temperature protection circuit 10 includes: the current source 100 is configured to output a first current signal I0 according to a temperature of an object to be measured, where the first current signal I0 is proportional to the temperature; a signal generating circuit 200 for receiving the first current signal I0, outputting a first voltage signal Vbe1, and for receiving a shunt signal of the first current signal I0, outputting a second voltage signal Vbe2; the signal amplifying circuit 300 is configured to receive the first voltage signal Vbe1 and the second voltage signal Vbe2, amplify a difference between the first voltage signal Vbe1 and the second voltage signal Vbe2, and output a third voltage signal Vo2; the signal processing circuit 400 is configured to receive the third voltage signal Vo2 and a zero degree reference signal, and output a hysteresis signal Vo according to the third voltage signal Vo2 and the zero degree reference signal, where the zero degree reference signal represents a voltage of the object to be measured when the absolute temperature is zero; the controller 500 receives the hysteresis signal Vo and determines a trigger timing of the over-temperature protection measure according to the hysteresis signal Vo.

Specifically, the temperature of the object to be measured refers to the internal temperature of the device in which the over-temperature protection circuit of the present application is installed, and the current source 100 may be a PTAT (proportional to absolute temperature ) current source, and the first current signal I0, that is, the PTAT current, has a magnitude proportional to absolute temperature, and when the temperature increases, the PTAT current increases accordingly. The signal generating circuit 200 receives the first current signal I0 and generates a first voltage signal Vbe1 according to the first current signal I0; and meanwhile, the first current signal I0 is split into a plurality of current component signals, the magnitude of each current component signal is equal, and the second voltage signal Vbe2 is generated according to the plurality of current component signals. The signal amplifying circuit 300 receives the first voltage signal Vbe1 and the second voltage signal Vbe2 from the signal generating circuit 200, performs a difference operation on the first voltage signal Vbe1 and the second voltage signal Vbe2, and then amplifies the obtained difference by a positive integer multiple and outputs the amplified difference as the third voltage signal Vo 2. Since the difference between the first voltage signal Vbe1 and the second voltage signal Vbe2 has a small value, the existing electronic component is not easy to operate, and thus the signal amplifying circuit 300 amplifies the difference by N times and outputs the amplified difference as the third voltage signal Vo2, so that the subsequent electronic component can operate the signal. The other beneficial effect of amplifying the difference between the two signals is that the difference between the two signals is only related to the temperature, and the influence of other factors (such as manufacturing process) on the numerical value can be eliminated after the difference is made, so that the accuracy of temperature detection is improved. The signal processing circuit 400 receives a zero degree reference signal, which characterizes the voltage of the object to be measured at zero absolute temperature, and a third voltage signal Vo 2. The signal processing circuit 400 can generate a comparison voltage corresponding to a preset temperature based on the zero-degree reference signal and the preset temperature to be set, the signal processing circuit 400 processes the third voltage signal Vo2 and the comparison voltage and then outputs a hysteresis signal Vo, and the hysteresis signal Vo can avoid frequent use of over-temperature protection measures caused by temperature jitter, so that the service life of the circuit is prolonged. The controller 500 receives the hysteresis signal Vo output from the signal processing circuit 400, determines whether to perform an over-temperature protection operation (e.g., turning on a fan, down-converting, power-off protection) according to the level state of the hysteresis signal Vo, and implements over-temperature protection of the circuit.

In one embodiment, the signal generating circuit 200 includes a first semiconductor switching element Q1 and a plurality of second semiconductor switching elements Q2; the first pole and the second pole of the first semiconductor switching element Q1 are grounded, the first pole and the second pole of each second semiconductor switching element Q2 are grounded, the second pole of the first semiconductor switching element Q1 is also connected with the second pole of any second semiconductor switching element Q2, the third poles of each second semiconductor switching element Q2 are connected with each other, the third pole of the first semiconductor switching element Q1 receives the first current signal I0, and the third poles of each second semiconductor switching element Q2 receive the shunt signal of the first current signal I0.

Preferably, the first semiconductor switching element Q1 and the plurality of second semiconductor switching elements Q2 are PNP transistors; the first electrode of the first semiconductor switching element Q1 and the respective second semiconductor switching elements Q2 is a collector, the second electrode is a base, and the third electrode is an emitter.

Specifically, taking the number of the second semiconductor switching elements Q2 as an example, please refer to fig. 2, which illustrates a schematic diagram of a part of the structure of an over-temperature protection circuit according to an embodiment of the present application. M in fig. 2 represents the number of second semiconductor switching elements Q2, m=2 in this example. The first semiconductor switching element Q1 and the plurality of second semiconductor switching elements Q2 are PNP transistors, a third electrode (emitter) of the first semiconductor switching element Q1 receives the first current signal I0, outputs the first voltage signal Vbe1, and a first electrode (collector) and a second electrode (base) of the first semiconductor switching element Q1 are grounded; the first current signal I0 is split at the third pole (emitter) of the plurality of second semiconductor switching elements Q2 to form a plurality of equal split signals, each of which flows through each of the second semiconductor switching elements Q2, the plurality of second semiconductor switching elements Q2 commonly output the second voltage signal Vbe2, and the first pole (collector) and the second pole (base) of each of the second semiconductor switching elements Q2 are grounded; and the second pole of the first semiconductor switching element Q1 is also connected to the second pole of any one of the second semiconductor switching elements Q2. The bias current (i.e., the first current signal I0) generated by the current source 100 provides the collector current to the first semiconductor switching element Q1 and the plurality of second semiconductor switching elements Q2. For the sake of simplifying wiring, the second pole of the first semiconductor switching element Q1 may be connected to the second pole of the nearest neighboring second semiconductor switching element Q2. When the number of Q2 is other integers greater than 1, the specific circuit structure can be adaptively adjusted with reference to fig. 2, which is not listed here.

It should be noted that, after the other kinds of semiconductor switching elements are adaptively adjusted, the implementation effect of the PNP transistor can be basically satisfied.

In the present embodiment, when the first semiconductor switching element Q1 and the plurality of second semiconductor switching elements Q2 are PNP transistors, there is a correspondence relationship as follows: vbe1=vt×in (I0/Is 1), vbe2=vt×in (I0/Is 2), vt= (k/Q) ×t, is2=mis 1, vt represents a thermal voltage (a potential difference occurring due to a temperature difference between two points In a closed circuit Is called thermal voltage), k Is boltzmann constant, Q Is a unit charge amount, T Is absolute temperature, is1 and Is2 represent saturated currents of the first semiconductor switching element Q1 and the plurality of second semiconductor switching elements Q2, respectively, m represents a ratio of the number of the second semiconductor switching elements Q2 to the number of the first semiconductor switching elements Q1 (since the number of the first semiconductor switching elements Q1 Is1, m may also represent the number of the second semiconductor switching elements Q2), and m Is an integer greater than 1. Preferred values of m are the integer squares minus 1, e.g. 8, 15, 24, 35.

In one embodiment, the signal amplifying circuit 300 includes a first operational amplifier, a non-inverting input terminal of the first operational amplifier receives the first voltage signal Vbe1, an inverting input terminal of the first operational amplifier receives the second voltage signal Vbe2, and an output terminal of the first operational amplifier outputs the third voltage signal Vo2.

Preferably, the signal amplifying circuit 300 further includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4; the first resistor R1 is connected between the third pole of the first semiconductor switching element Q1 and the non-inverting input end of the first operational amplifier; one end of the second resistor R2 is connected with the non-inverting input end of the first operational amplifier, and the other end of the second resistor is connected with the output end of the first operational amplifier; the third resistor R3 is connected between the third pole of any second semiconductor switching element Q2 and the inverting input end of the first operational amplifier; one end of the fourth resistor R4 is connected with the inverting input end of the first operational amplifier, and the other end of the fourth resistor R4 is connected with the output end of the first operational amplifier; the resistance of the first resistor R1 is the same as that of the third resistor R3, the resistance of the second resistor R2 is the same as that of the fourth resistor R4, and the resistance of the second resistor R2 is a positive integer multiple of that of the first resistor R1.

Specifically, please refer to fig. 3, which illustrates a schematic diagram of a part of an over-temperature protection circuit according to an embodiment of the present application. The first operational amplifier is preferably a low offset operational amplifier (low-offset amp) for accurately amplifying a minute signal (i.e., the difference between the first voltage signal Vbe1 and the second voltage signal Vbe 2). The present embodiment is only one possible implementation manner of the signal amplifying circuit 300, and is configured to receive the first voltage signal Vbe1 and the second voltage signal Vbe2, amplify a difference value between the first voltage signal Vbe1 and the second voltage signal Vbe2, and output an amplified result as the third voltage signal Vo 2. As described above, the function of the signal amplification circuit 300 is to facilitate the operation of the signal by subsequent electronic components. The resistance of the second resistor R2 is a positive integer multiple of the resistance of the first resistor R1, here, N times is taken as an example, i.e. r2=n×r1. The meaning of each parameter in the equation .△Vbe= Vbe1- Vbe2,△Vbe= Vt*In(I0/Is1)- Vt*In(I0/Is2),△Vbe= Vt*In(I0/Is1)- Vt*In(I0/m*Is1),△Vbe= Vt*In(m),△Vbe= (k/q)*T*In(m), for the difference between the first voltage signal Vbe1 and the second voltage signal Vbe2 is described above, and will not be described here. According to the last formula, Δvbe is only related to k, q, T, m parameters, where k and q are constants, m is a set ratio, the same over-temperature protection circuit is not changed after m is set, and can be regarded as a constant value, so that Δvbe is only related to T and is irrelevant to other factors such as a process. The original first voltage signal Vbe1 and the second voltage signal Vbe2 are related to the saturation current Is1 or Is2, that Is, related to the process of the semiconductor switching element. Because ΔVbe is related only to T and is independent of other factors such as process, the circuit arrangement of the present application can achieve high accuracy temperature detection. That is, the signal amplifying circuit 300 is configured such that the difference between the two signals is related to the temperature, and the difference is removed to eliminate the influence of other factors (such as manufacturing process) on the value, thereby improving the accuracy of temperature detection. The signal amplifying circuit 300 outputs the third voltage signal vo2=n×Δvbe. Since the value of Vo2 is amplified based on ΔVbe, vo2 is also correlated only with T and is independent of other factors such as process. Preferably, the value of N is in the range of 2-20. Since the value of m In the above embodiment cannot be set large, while the value of In (m) becomes further smaller due to the logarithmic function; the signal amplifying circuit 300 is an indispensable part since a large signal is required for subsequent signal processing. In a specific implementation, the specific values of the resistors in the signal amplifying circuit 300 may be set according to actual requirements.

In one embodiment, the signal generation circuit 200 includes: a third semiconductor switching element Q3 and an adjustable resistor Rtrim; the first pole and the second pole of the third semiconductor switching element Q3 are grounded, the third pole of the third semiconductor switching element Q3 is connected to one end of the adjustable resistor Rtrim, and the other end of the adjustable resistor Rtrim outputs a switching signal of the zero-degree reference signal.

Preferably, the third semiconductor switching element Q3 is a PNP transistor, the first electrode of the third semiconductor switching element Q3 is a collector, the second electrode is a base, and the third electrode is an emitter; the signal processing circuit 400 includes a buffer circuit for receiving the converted signal of the zero degree reference signal and outputting the zero degree reference signal; the buffer circuit comprises a second operational amplifier and a field effect transistor, wherein the non-inverting input end of the second operational amplifier receives a conversion signal of a zero-degree reference signal, the inverting input end of the second operational amplifier is connected with the first pole of the field effect transistor and outputs the zero-degree reference signal, the output end of the second operational amplifier is connected with the second pole of the field effect transistor, and the third pole of the field effect transistor receives a power supply voltage. The field effect transistor may be a p-type field effect transistor (pmos transistor), a first electrode of the field effect transistor being a drain electrode, a second electrode of the field effect transistor being a gate electrode, and a third electrode of the field effect transistor being a source electrode. In addition, a resistor and a grounding wire can be arranged between the inverting input end of the second operational amplifier and the drain electrode of the field effect transistor for optimizing the buffer circuit.

Specifically, please refer to fig. 4, which illustrates a schematic diagram of a part of an over-temperature protection circuit according to an embodiment of the present application. The zero-degree reference signal is named VREFP, the conversion signal of the zero-degree reference signal is named VREF, the emitter of the third semiconductor switching element Q3 outputs the voltage Vbe3, and the first current signal I0 flows through the adjustable resistor Rtrim and the third semiconductor switching element Q3; according to the connection mode shown in fig. 4, the following correspondence relationship can be obtained by combining the principle of the operational amplifier of short-circuit and short-circuit: vref=i0×rtrim+vbe3, vrefp=vref× (r6/r7+1).

The beneficial effects of this embodiment lie in: by integrating a series of electronic elements in the signal generating circuit and the signal processing circuit, the zero-degree reference signal can be generated inside the over-temperature protection circuit without being acquired from outside through a wire; in addition, the buffer circuit is arranged so that the zero-degree reference signal is not limited by factors such as voltage division and the like, and the zero-degree reference signal can be supplied to other external circuits besides the over-temperature protection circuit.

In one embodiment, a signal processing circuit includes: a first voltage comparator and a second voltage comparator; the non-inverting input ends of the first voltage comparator and the second voltage comparator receive a third voltage signal Vo2, the inverting input end of the first voltage comparator receives a first comparison voltage, and the inverting input end of the second voltage comparator receives a second comparison voltage; the first comparison voltage is determined based on the zero-degree reference signal and a first preset temperature, and the second comparison voltage is determined based on the zero-degree reference signal and a second preset temperature, wherein the first preset temperature is smaller than the second preset temperature, so that the first comparison voltage is smaller than the second comparison voltage.

Preferably, the signal processing circuit further comprises a decoding circuit, a first input end of the decoding circuit is connected with an output end of the first voltage comparator, a second input end of the decoding circuit is connected with an output end of the second voltage comparator, and an output end of the decoding circuit outputs the hysteresis signal Vo; when the level of the first input end of the hysteresis signal Vo jumps from low level to high level and the level of the second input end of the hysteresis signal Vo jumps from low level to high level, the hysteresis signal Vo jumps from low level to high level; the hysteresis signal Vo keeps a high-level state when the level of the first input end is kept in a high-level state and the level of the second input end is jumped from a high level to a low level; the hysteresis signal Vo transitions from a high level to a low level when the level of the first input terminal transitions from a high level to a low level and the level of the second input terminal remains in a low level state.

Specifically, please refer to fig. 5, which illustrates a schematic diagram of a part of an over-temperature protection circuit according to an embodiment of the present application. As shown in fig. 5, the first voltage comparator is comp1, the second voltage comparator is comp2, the Logic is a decoding circuit, the first preset temperature is t_l, and the first comparison voltage is generated according to the zero degree reference signal and the first preset temperature, i.e. the magnitude of the first comparison voltage vo_l can be determined numerically: vo_l= (k/q) In (m) N t_l; similarly, the second preset temperature is t_h, and the second comparison voltage vo_h is: vo_h= (k/q) ×in (m) ×n×t_h. As can be seen from the above formula, the first comparison voltage is smaller than the second comparison voltage because the first preset temperature is smaller than the second preset temperature. The signal processing circuit 400 outputs a hysteresis signal Vo for eliminating jitter according to the magnitude relation between the received third voltage signal Vo2 and the first and second comparison voltages vo_l and vo_h. The generation relationship of the hysteresis signal Vo is as follows: when the temperature T rises to reach the point T_h, namely, vo2 is greater than vo_h, vo jumps from low level to high level, and then when the temperature T falls to the point T_l, namely, vo2 is less than vo_l, vo jumps from high level to low level, thereby generating a hysteresis signal, avoiding frequent use of over-temperature protection measures caused by temperature jitter, and prolonging the service life of the circuit.

As shown in fig. 5, the signal processing circuit 400 includes an eighth resistor R8, a ninth resistor R9, and a tenth resistor R10. The non-inverting input terminals of the first voltage comparator comp1 and the second voltage comparator comp2 receive the third voltage signal Vo2, one end of the R8 receives the zero-degree reference signal VREFP, the other end of the R8 is connected to the inverting input terminal of the second voltage comparator comp2, the other end of the R8 is also connected to the inverting input terminal of the first voltage comparator comp1 through the R9, one end of the R10 is grounded, and the other end is connected to the inverting input terminals of the R9 and the first voltage comparator comp 1. According to the above connection structure, the following correspondence relationship can be obtained: vo_l=vrefp (((r8+r9)/r10) +1), vo_h=vrefp ((r8/(r9+r10)) +1). The values of the first comparison voltage and the second comparison voltage may be determined by controlling the resistance values of R8, R9, and R10, where the formula is identical to the above formula. The magnitude relations between Vo2 and vo_l and between Vo2 and vo_h are compared respectively, and then the output level states of the first voltage comparator comp1 and the second voltage comparator comp2, namely the level states of the first comparison result Vol and the second comparison result Voh, can be obtained respectively according to the properties of the voltage comparators.

In one embodiment, as shown in fig. 1 and 2, the signal processing circuit 400 further includes a decoding circuit, a first input terminal of the decoding circuit is connected to an output terminal of the first voltage comparator comp1, a second input terminal of the decoding circuit is connected to an output terminal of the second voltage comparator comp2, and an output terminal of the decoding circuit outputs the hysteresis signal Vo; when the level of the first input end is changed from low level to high level and the level of the second input end is changed from low level to high level, the hysteresis signal Vo is changed from low level to high level; when the level of the first input end keeps a high level state and the level of the second input end jumps from a high level to a low level, the hysteresis signal Vo keeps a high level state; when the level of the first input terminal transitions from a high level to a low level and the level of the second input terminal remains in a low level state, the hysteresis signal Vo transitions from a high level to a low level.

Specifically, as shown in fig. 6, a first input end of the decoding circuit receives a first comparison result output by an output end of the first voltage comparator comp1, a second input end of the decoding circuit receives a second comparison result output by an output end of the second voltage comparator comp2, two NORs 2 in the figure represent two-input NOR gates, INV represents an inverter, an input end of the inverter is connected with an output end of the two-input NOR gate corresponding to the second comparison result, and an output end of the inverter outputs a hysteresis signal Vo. It should be noted that fig. 6 is only one implementation of the decoding circuit, and any decoding circuit arrangement satisfying the above input-output relationship in a specific implementation is within the scope of the present application.

Referring to fig. 7, a relationship between a part of signals and absolute temperature in the over-temperature protection circuit according to an embodiment of the application is shown. Wherein: since the PN junction is generally a negative temperature characteristic according to the characteristics of the bipolar transistor circuit, vbe1 and Vbe2 decrease as T increases, and the difference Δvbe between them increases as the temperature increases. The slope of the third voltage signal vo2=n×Δvbe is greater than Δvbe. Vol transitions from a low level to a high level when T is greater than T_l, and Voh transitions from a low level to a high level when T is greater than T_h. For the image at the lowest position of fig. 7, the situation of the hysteresis signal Vo with temperature is characterized: when T is raised to be greater than T_h, vo jumps from low level to high level, and when T is lowered to be less than T_l, vo jumps from high level to low level. Between T_l and T_h, vo is in an unstable state, i.e. the characteristic of a hysteresis signal is reflected. It should be noted that, in this embodiment, specific values of t_l and t_h may be set according to actual requirements.

Fig. 8 is a schematic diagram illustrating a part of an over-temperature protection circuit according to an embodiment of the application. As shown in fig. 8, the current source 100 includes: the first PMOS tube MP1, the second PMOS tube MP2, the third PMOS tube MP3, the fourth PMOS tube MP4, the fifth PMOS tube MP5, the sixth PMOS tube MP6, the first NMOS tube MN1, the second NMOS tube MN2, the third NMOS tube MN3, the fourth NMOS tube MN4, the eleventh resistor R11, the twelfth resistor R12 and the thirteenth resistor R13; the source electrodes of the first PMOS tube MP1, the second PMOS tube MP2 and the fifth PMOS tube MP5 are connected with a power supply, the grid electrodes of the first PMOS tube MP1, the second PMOS tube MP2 and the fifth PMOS tube MP5 are connected with each other, the drain electrodes of the first PMOS tube MP1, the second PMOS tube MP2 and the fifth PMOS tube MP5 are respectively connected with the source electrodes of the third PMOS tube MP3, the fourth PMOS tube MP4 and the sixth PMOS tube MP6, the grid electrodes of the third PMOS tube MP3, the fourth PMOS tube MP4 and the sixth PMOS tube MP6 are connected with each other, the drain electrode of the third PMOS tube MP3 is connected with the grid electrode of the first NMOS tube MN1 and one end of an eleventh resistor R11, the other end of the eleventh resistor R11 is connected with the drain electrode of the first NMOS tube MN1, the grid electrode of the first NMOS tube MN1 is connected with the grid electrode of the second NMOS tube MN2, the source electrode of the first NMOS tube MN1 is connected with the drain electrode of the third NMOS tube MN3, the drain electrode of the first NMOS tube MN1 is connected with the grid electrode of the third NMOS tube MN3, the grid electrode of the third NMOS tube MN3 is connected with the grid electrode of the fourth NMOS tube MN4, the drain electrode of the fourth PMOS tube MP4 is connected with one end of a twelfth resistor R12, the other end of the twelfth resistor R12 is connected with the drain electrode of the second NMOS tube MN2, the source electrode of the second NMOS tube MN2 is connected with the drain electrode of the fourth NMOS tube MN4, the source electrode of the fourth NMOS tube MN4 is connected with one end of a thirteenth resistor R13, and the other end of the thirteenth resistor R13, the source electrode of the third NMOS tube MN3 and the drain electrode of the sixth PMOS tube MP6 output a first current signal I0.

The present embodiment is only one possible implementation manner of the current source 100, and is used for outputting a current proportional to the temperature of the object to be measured, and in a specific implementation manner, the connection relationship of the circuit can be changed according to actual requirements.

Further, according to fig. 8, since the gates of MN3 and MN4 are connected to each other, the first current signal I0 flowing therethrough is also uniform, so are the source voltages thereof; the first current signal I0 flowing through the third resistor R3 is the voltage difference between Vbe1 and Vbe2 divided by R3, i.e., i0= Δvbe/R3, and the value of the first current signal I0 is obtained by this equation.

Based on the same technical conception, the application also discloses an over-temperature protection structure, which comprises the over-temperature protection circuit disclosed in the embodiment, wherein the over-temperature protection circuit is used for determining the triggering time of over-temperature protection measures according to the internal temperature of the over-temperature protection structure.

Specifically, the over-temperature protection structure comprises products such as a computer, a mobile phone, a household appliance, an automobile engine, a motor driving product, an intelligent lighting lamp and the like, and the products have the common characteristics that the internal space is relatively airtight and the condition of over-temperature easily occurs, so that an over-temperature protection circuit is required to be configured to monitor the internal temperature in real time, and the triggering time of over-temperature protection measures is determined according to the condition of temperature change, namely, a temperature interval is set so that the working state of the over-temperature protection circuit cannot be changed due to the occurrence of shaking.

In the foregoing embodiments, the descriptions of the embodiments are focused on, and the parts of one embodiment that are not described or depicted in detail in the other embodiment may be referred to as related descriptions of the other embodiment. Furthermore, the above embodiments can be freely combined as needed.

Claims

1. An over-temperature protection circuit, comprising:

the current source is used for outputting a first current signal according to the temperature of an object to be detected, and the first current signal is in direct proportion to the temperature;

a signal generating circuit for receiving the first current signal, outputting a first voltage signal, and receiving a shunt signal of the first current signal, outputting a second voltage signal;

the signal amplifying circuit is used for receiving the first voltage signal and the second voltage signal, amplifying the difference value between the first voltage signal and the second voltage signal and outputting a third voltage signal;

The signal processing circuit is used for receiving the third voltage signal and a zero-degree reference signal and outputting a hysteresis signal according to the third voltage signal and the zero-degree reference signal, and the zero-degree reference signal represents the voltage of the object to be detected when the absolute temperature is zero;

and the controller receives the hysteresis signal and determines the triggering time of the over-temperature protection measures according to the hysteresis signal.

2. The over-temperature protection circuit according to claim 1, wherein the signal generation circuit includes a first semiconductor switching element and a plurality of second semiconductor switching elements;

The first poles and the second poles of the first semiconductor switching elements are grounded, the first poles and the second poles of the second semiconductor switching elements are grounded, the second poles of the first semiconductor switching elements are also connected with the second poles of any one of the second semiconductor switching elements, the third poles of the second semiconductor switching elements are mutually connected, the third poles of the first semiconductor switching elements receive the first current signals, and the third poles of the second semiconductor switching elements receive the shunt signals of the first current signals.

3. The over-temperature protection circuit according to claim 2, wherein the first semiconductor switching element and the plurality of second semiconductor switching elements are PNP transistors; the first semiconductor switching element and each of the second semiconductor switching elements have a first electrode collector, a second electrode base, and a third electrode emitter.

4. The over-temperature protection circuit of claim 2, wherein the signal amplification circuit comprises a first operational amplifier having a non-inverting input receiving the first voltage signal, an inverting input receiving the second voltage signal, and an output outputting the third voltage signal.

5. The over-temperature protection circuit of claim 4, wherein the signal amplification circuit further comprises a first resistor, a second resistor, a third resistor, and a fourth resistor;

the first resistor is connected between a third pole of the first semiconductor switching element and a non-inverting input end of the first operational amplifier;

one end of the second resistor is connected with the non-inverting input end of the first operational amplifier, and the other end of the second resistor is connected with the output end of the first operational amplifier;

The third resistor is connected between the third pole of any one of the second semiconductor switching elements and the inverting input end of the first operational amplifier;

one end of the fourth resistor is connected with the inverting input end of the first operational amplifier, and the other end of the fourth resistor is connected with the output end of the first operational amplifier;

The resistance of the first resistor is the same as that of the third resistor, the resistance of the second resistor is the same as that of the fourth resistor, and the resistance of the second resistor is a positive integer multiple of that of the first resistor.

6. The over-temperature protection circuit according to claim 1, wherein the signal generation circuit includes: a third semiconductor switching element and an adjustable resistor;

The first pole and the second pole of the third semiconductor switching element are grounded, the third pole of the third semiconductor switching element is connected with one end of the adjustable resistor, and the other end of the adjustable resistor outputs the conversion signal of the zero-degree reference signal.

7. The over-temperature protection circuit of claim 6, wherein the third semiconductor switching element is a PNP transistor, a first pole of the third semiconductor switching element is a collector, a second pole is a base, and a third pole is an emitter; and, in addition, the method comprises the steps of,

The signal processing circuit comprises a buffer circuit, a first switching circuit and a second switching circuit, wherein the buffer circuit is used for receiving a conversion signal of the zero-degree reference signal and outputting the zero-degree reference signal;

The buffer circuit comprises a second operational amplifier and a field effect transistor, wherein the non-inverting input end of the second operational amplifier receives the conversion signal of the zero-degree reference signal, the inverting input end of the second operational amplifier is connected with the first pole of the field effect transistor and outputs the zero-degree reference signal, the output end of the second operational amplifier is connected with the second pole of the field effect transistor, and the third pole of the field effect transistor receives the power supply voltage.

8. The over-temperature protection circuit of claim 1, wherein the signal processing circuit comprises: a first voltage comparator and a second voltage comparator;

the non-inverting input ends of the first voltage comparator and the second voltage comparator receive the third voltage signal, the inverting input end of the first voltage comparator receives a first comparison voltage, and the inverting input end of the second voltage comparator receives a second comparison voltage;

The first comparison voltage is determined based on the zero degree reference signal and a first preset temperature, the second comparison voltage is determined based on the zero degree reference signal and a second preset temperature, and the first preset temperature is smaller than the second preset temperature so that the first comparison voltage is smaller than the second comparison voltage.

9. The over-temperature protection circuit according to claim 8, wherein the signal processing circuit further comprises a decoding circuit, a first input terminal of the decoding circuit is connected to an output terminal of the first voltage comparator, a second input terminal of the decoding circuit is connected to an output terminal of the second voltage comparator, and an output terminal of the decoding circuit outputs the hysteresis signal;

the hysteresis signal jumps from low level to high level when the level of the first input end jumps from low level to high level and the level of the second input end jumps from low level to high level;

The hysteresis signal is kept in a high-level state when the level of the first input end is kept in a high-level state and the level of the second input end is jumped from a high level to a low level;

the hysteresis signal jumps from a high level to a low level when the level of the first input terminal jumps from a high level to a low level and the level of the second input terminal remains in a low level state.

10. An overtemperature protection structure, characterized by comprising an overtemperature protection circuit as claimed in any one of claims 1-9, said overtemperature protection circuit being configured to determine a trigger timing of an overtemperature protection measure based on an internal temperature of said overtemperature protection structure.