Low-power-consumption over-temperature protection circuit

Abstract

The invention discloses a low-power-consumption over-temperature protection circuit which comprises a positive temperature coefficient voltage generation circuit and a comparator circuit. The positive temperature coefficient voltage generation circuit part is used for generating voltage in direct proportion to the working environment temperature, the comparator circuit part is used for detecting voltage generated by a pre-stage circuit, when the circuit temperature rises and the voltage exceeds a set value, the comparator circuit outputs low level, the post-stage circuit is turned off, and the over-temperature protection function is achieved, and when the circuit temperature is reduced again, the comparator circuit part outputs low level. And the output of the comparator circuit returns to normal, and the post-stage circuit works normally. The circuit is simple in structure and low in cost, and can be widely applied to analog integrated circuits such as bus transceivers, drivers, controllers and protection ICs.

Description

Technical Field

[0001] The invention relates to an over-temperature protection circuit, and in particular to a low-power over-temperature protection circuit applicable to analog integrated circuits. Background Art

[0002] When many analog integrated circuits such as bus transceivers, drivers, controllers, and protection ICs are working normally, excessively high working environment temperature will cause circuit performance to degrade or even fail to work properly. If no protective measures are taken for a long time, some components in the circuit will be damaged, posing a potential risk of accidents. Therefore, when the circuit temperature rises to a certain level, the power supply needs to be cut off to prevent electronic equipment from being damaged due to abnormal voltage or sudden current changes when the operating temperature is too high.

[0003] With the rapid development of electronic science and technology in recent years, the demand for over-temperature protection technology of circuits in various industries has become more urgent. Over-temperature protection circuits are widely used in various fields, such as consumer electronics, communication equipment, industrial control, automotive electronics, aerospace and military equipment, etc. When the working environment temperature of the circuit rises significantly, if there is no over-temperature protection circuit, the circuit will malfunction or even be damaged. Therefore, it is necessary to add a reliable over-temperature protection structure unit in the analog integrated circuit.

[0004] In recent years, with the trend of localized production of semiconductor devices, domestic enterprises have begun to independently design and manufacture over-temperature protection circuits, reducing dependence on external supply chains and enhancing the security and controllability of the supply chain. At present, the mainstream over-temperature protection circuits in China mainly adopt the traditional structure of bandgap reference plus comparator. This structure has problems such as high circuit power consumption, more components, and complicated circuit structure. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, propose a low-power over-temperature protection circuit, adopt a new structure of a positive temperature coefficient voltage generating circuit plus a comparison circuit, realize over-temperature protection for analog integrated circuits, significantly simplify the circuit structure, and reduce the working power consumption of the circuit.

[0006] The technical solution of the present invention is:

[0007] A low power consumption over-temperature protection circuit comprises a positive temperature coefficient voltage generating circuit and a comparator circuit;

[0008] Positive temperature coefficient voltage generating circuit, used to generate an output voltage proportional to temperature;

[0009] The comparator circuit has an input of the output voltage generated by the positive temperature coefficient voltage generating circuit. The comparator circuit is used to detect whether the output voltage exceeds the set value. When the set value is exceeded, the output drops to 0, shutting down the analog circuit connected downstream, and providing over-temperature protection for the analog circuit; when the set value is not exceeded, the comparator output end provides normal power supply for the analog circuit.

[0010] Furthermore, the positive temperature coefficient voltage generating circuit includes a resistor R 1 , R 2 , R 3 , R 4 , transistor Q 1 , Q 2 , Q 3 , Q 4 , Q 5 ;

[0011] Resistor R 1 One end is connected to the power supply VCC, and the other end is connected to the transistor Q 1 The collector of the resistor R 2 One end is connected to VCC, and the other end is connected to the transistor Q 1 The base and transistor Q 2 The collector of transistor Q 1 The emitter and transistor Q 2 and Q 3 The base of transistor Q 2 The emitter of transistor Q 4 The collector and transistor Q 5 The base of transistor Q 3 The emitter of transistor Q 4 The base and transistor Q 5 The collector of transistor Q 4 The emitter of transistor Q is connected to GND. 5 The emitter and resistor R 4 One end of the resistor R 4 The other end is connected to GND, and the resistor R 3 One end is connected to VCC, R 3 The other end of the transistor Q 3 The collector of is connected, the potential at the connection is a, which serves as the output.

[0012] Furthermore, the value of the current flowing through point a is determined by adjusting the resistance value of resistor R4, so that an output voltage proportional to the temperature is generated at point a.

[0013] Furthermore, the comparator circuit includes a resistor R 5 , R 6 , transistor Q 6 , Q 7and NNOS tube N 1 ;

[0014] Transistor Q 6 The base of NMOS tube N 1 The drain and gate of transistor Q are connected to point a. 6 The emitter of transistor Q is connected to VCC. 6 The collector and resistor R 5 One end and transistor Q 7 The base of the resistor R 5 The other end is connected to GND, and the resistor R 6 One end is connected to VCC, and the resistor R 6 The other end is connected to the NMOS tube N 1 The source and transistor Q 7 The collector of transistor Q is connected to the output terminal VO. 7 The emitter is connected to GND.

[0015] Furthermore, through NNOS 1 The size design controls the NMOS tube N 1 Saturation leakage current to achieve temperature hysteresis.

[0016] Furthermore, when the circuit is working normally, the transistor Q 6 In the cut-off state, as the circuit temperature rises, the potential at point a decreases, that is, the voltage V between the emitter and the base be6 Increase, that is, the current I between the emitter and the base be6 Increase, so the current I between the collector and the base ce6 Increase, transistor Q 7 The base potential increases.

[0017] Furthermore, adjusting the resistor R 4 The resistance value makes the transistor Q6 in the cut-off state when the circuit is working normally; where:

[0018] Setting transistor Q 2 and Q 4 The area ratio is 2:1, and the transistor Q 3 and Q 5 The area ratio is 1:3, so:

[0019] V be2 +V be5 +V R4 =V be3 +V be4

[0020] Where V be2 Q is the transistor 2 The voltage between emitter and base, Vbe5 Q is the transistor 5 The voltage between emitter and base, V be3 Q is the transistor 3 The voltage between emitter and base, V be4 Q is the transistor 4 The voltage between emitter and base, V R4 is the resistance R 4 Voltage across both ends;

[0021] Adjustment resistor R 4 When the circuit is working normally, the potential at point a is high enough to make Q 6 The be junction of the tube is in the cut-off state.

[0022] Furthermore, as the circuit temperature continues to rise, when the potential at point a reaches a critical value, the over-temperature protection is activated: transistor Q 7 The emitter junction is forward biased, and the transistor Q 7 Tube open, NNOS tube N 1 In the on state, the output terminal VO potential drops to 0.

[0023] Furthermore, when the circuit is in over-temperature protection, when the temperature drops, the transistor Q 6 The base potential of the NNOS tube N increases; after the circuit temperature is lower than the temperature of the over-temperature protection state, 1 Re-closed.

[0024] The advantages of the present invention compared with the prior art are:

[0025] The present invention controls the on and off of the over-temperature protection circuit by the power supply voltage of the analog integrated circuit to achieve under-over-temperature protection of the analog circuit. It not only has a simple structure and low cost, but also can extend the service life of the analog circuit and prevent accidents. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0027] Figure 1 A circuit diagram of a low power consumption over-temperature protection circuit according to an embodiment of the present invention;

[0028] Figure 2 The present invention is a schematic diagram of a positive temperature coefficient voltage generating circuit and a comparator circuit.

[0029] Figure 3A circuit diagram of a positive temperature coefficient voltage generating circuit according to an embodiment of the present invention;

[0030] Figure 4 is a circuit diagram of a comparator circuit according to an embodiment of the present invention;

[0031] Figure 5 This is a simulation curve showing that the output voltage varies with the operating temperature according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0033] The present invention proposes a low power consumption over-temperature protection circuit, such as Figure 1 As shown in the figure, when the working environment temperature of the circuit is normal, the over-temperature protection circuit can supply power to the subsequent analog circuit normally. When the working environment temperature of the circuit rises to a certain level and reaches the over-temperature value, the output voltage is 0 after passing through the over-temperature protection circuit, and the entire analog integrated circuit stops working, effectively achieving the over-temperature protection effect on the circuit.

[0034] The circuit can be divided into two parts, such as Figure 2 As shown, one part is a positive temperature coefficient voltage generating circuit, which is used to generate an output voltage proportional to the temperature, and the other part is a comparator circuit, whose input is the output voltage generated by the positive temperature coefficient voltage generating circuit. The comparator circuit is used to detect whether the output voltage is too high. When the output voltage is too high, the output of the circuit drops to 0.

[0035] The positive temperature coefficient voltage generating circuit includes a resistor R 1 , R 2 , R 3 , R 4 , transistor Q 1 , Q 2 , Q 3 , Q 4 , Q 5 , with R 3 and Q 3 The potential between the collectors is the output. Figure 3 As shown, the resistor R 1 One end is connected to the power supply VCC, and the other end is connected to the transistor Q 1 The collector of the resistor R 2 One end is connected to VCC, and the other end is connected to the transistor Q 1 The base and transistor Q 2The collector of transistor Q 1 The emitter and transistor Q 2 and Q 3 The base of transistor Q 2 The emitter of transistor Q 4 The collector and transistor Q 5 The base of transistor Q 3 The emitter of transistor Q 4 The base and transistor Q 5 The collector of transistor Q 4 The emitter of transistor Q is connected to GND. 5 The emitter and resistor R 4 One end of the resistor R 4 The other end is connected to GND, and the resistor R 3 One end is connected to VCC, R 3 The other end of the transistor Q 3 The collector of is connected, and the connection point is a, which serves as the output.

[0036] The comparator circuit includes a resistor R 5 , R 6 , transistor Q 6 , Q 7 and NNOS tube N 1 .like Figure 4 As shown, transistor Q 6 The base of NMOS tube N 1 The drain and gate of transistor Q are connected to point a. 6 The emitter of transistor Q is connected to VCC. 6 The collector and resistor R 5 One end and transistor Q 7 The base of the resistor R 5 The other end is connected to GND, and the resistor R 6 One end is connected to VCC, and the resistor R 6 The other end is connected to the NMOS tube N 1 The source and transistor Q 7 The collector of transistor Q is connected to the output terminal VO. 7 The emitter is connected to GND.

[0037] Setting transistor Q 2 and Q 4 The area ratio is 2:1, and the transistor Q 3 and Q 5 The area ratio is 1:3, Figure 3 It can be seen that:

[0038] V be2 +V be5+V R4 =V be3 +V be4

[0039] Where V be2 Q is the transistor 2 The voltage between emitter and base, V be5 Q is the transistor 5 The voltage between emitter and base, V be3 Q is the transistor 3 The voltage between emitter and base, V be4 Q is the transistor 4 The voltage between emitter and base, V R4 is the resistance R 4 Voltage across both ends.

[0040] Since the transistor I c / V be Characteristic formula:

[0041] I c =J 0 Aexp(V be / V T )

[0042] Where A is the area of ​​the transistor, V T is the voltage equivalent, I PTAT is the current value flowing through point a, it can be deduced that:

[0043] I PTAT =V T ×In6 / R 4

[0044] It can be seen that when the power supply voltage is normal, by adjusting the resistor R 4 resistance, set the appropriate I PTAT , that is, when the circuit operates within the normal temperature range, the potential at point a is high enough to make Q 6 The be junction of the tube is in the cut-off state. As the circuit temperature rises, the potential at point a decreases, that is, Q 6 The voltage between the emitter and the base of the tube is V be6 Increase, that is, the current I between the emitter and the base be6 Increase, so the current I between the collector and the base ce6 Increase, Q 7 The base potential increases, when Q 7 The base potential gradually increases until the emitter junction is forward biased and turned on, Q 7 The tube is turned on, the output terminal VO potential drops to 0, and the circuit achieves over-temperature protection. When in the over-temperature protection state, N 1 When the tube is in the on state, the current at point a increases and the potential decreases. When the temperature drops, Q6 The base potential of N 1 The tube is in the closed state again, so the temperature for the circuit to work again is lower than the temperature at which the circuit is in the over-temperature protection state when the temperature rises, that is, the principle of temperature hysteresis. The present invention has a simple structure, a small number of overall circuit components, and realizes the over-temperature protection function of the analog integrated circuit under low power consumption conditions.

[0045] like Figure 5 As shown in the figure, when the circuit temperature rises to about 170℃, after the temperature protection circuit, the output voltage is 0, and the subsequent circuit is in the off state, thereby achieving the protection of the entire circuit. When the circuit temperature drops back to about 155℃, the output voltage returns to normal, and the subsequent circuit works normally.

[0046] The above-described embodiments are only preferred specific implementations of the present invention. Common changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A low power consumption over-temperature protection circuit, characterized in that: It includes a positive temperature coefficient voltage generating circuit and a comparator circuit; Positive temperature coefficient voltage generating circuit, used to generate an output voltage proportional to temperature; The comparator circuit has an input of the output voltage generated by the positive temperature coefficient voltage generating circuit. The comparator circuit is used to detect whether the output voltage exceeds the set value. When the set value is exceeded, the output drops to 0, shutting down the analog circuit connected downstream, and providing over-temperature protection for the analog circuit; when the set value is not exceeded, the comparator output end provides normal power supply for the analog circuit.

2. A low power consumption over-temperature protection circuit according to claim 1, characterized in that: The positive temperature coefficient voltage generating circuit includes resistors R1, R2, R3, R4, transistors Q1, Q2, Q3, Q4, Q5; One end of resistor R1 is connected to the power supply VCC, and the other end is connected to the collector of transistor Q1. One end of resistor R2 is connected to VCC, and the other end is connected to the base of transistor Q1 and the collector of transistor Q2. The emitter of transistor Q1 is connected to the bases of transistors Q2 and Q3. The emitter of transistor Q2 is connected to the collector of transistor Q4 and the base of transistor Q5. The emitter of transistor Q3 is connected to the base of transistor Q4 and the collector of transistor Q5. The emitter of transistor Q4 is connected to GND. The emitter of transistor Q5 is connected to one end of resistor R4, and the other end of resistor R4 is connected to GND. One end of resistor R3 is connected to VCC, and the other end of R3 is connected to the collector of transistor Q3. The potential at the connection is a, which serves as output.

3. A low power consumption over-temperature protection circuit according to claim 2, characterized in that: The value of the current flowing through point a is determined by adjusting the resistance value of resistor R4, thereby generating an output voltage proportional to the temperature at point a.

4. A low power consumption over-temperature protection circuit according to claim 2, characterized in that: The comparator circuit includes resistors R5, R6, transistors Q6, Q7 and NNOS tube N1; The base of transistor Q6, the drain and the gate of NMOS tube N1 are all connected to point a, the emitter of transistor Q6 is connected to VCC, the collector of transistor Q6 is connected to one end of resistor R5 and the base of transistor Q7, the other end of resistor R5 is connected to GND, one end of resistor R6 is connected to VCC, the other end of resistor R6 is connected to the source of NMOS tube N1, the collector of transistor Q7 and the output terminal VO, and the emitter of transistor Q7 is connected to GND.

5. A low power consumption over-temperature protection circuit according to claim 4, characterized in that: By designing the size of the NMOS tube N1, the saturation leakage current of the NMOS tube N1 is controlled to achieve temperature hysteresis.

6. A low power consumption over-temperature protection circuit according to claim 4, characterized in that: When the circuit is working normally, transistor Q6 is in the cut-off state. As the circuit temperature rises, the potential at point a decreases, that is, the voltage V between the emitter and the base decreases. be6 Increase, that is, the current I between the emitter and the base be6 Increase, so the current I between the collector and the base ce6 Increases, and the base potential of transistor Q7 rises.

7. A low power consumption over-temperature protection circuit according to claim 6, characterized in that: Adjust the resistance value of resistor R4 so that transistor Q6 is in the cut-off state when the circuit works normally; where: Assuming the area ratio of transistors Q2 and Q4 is 2:1, and the area ratio of transistors Q3 and Q5 is 1:3, we have: V be2 +V be5 +V R4 =V be3 +V be4 Where V be2 is the voltage between the emitter and base of transistor Q2, V be5 is the voltage between the emitter and base of transistor Q5, V be3 is the voltage between the emitter and base of transistor Q3, V be4 is the voltage between the emitter and base of transistor Q4, V R4 is the voltage across resistor R4; Adjust the resistance value of resistor R4. When the circuit works normally, the potential at point a is high enough to make the be junction of Q6 tube in the cut-off state.

8. A low power consumption over-temperature protection circuit according to claim 4, characterized in that: As the circuit temperature continues to rise, when the potential at point a reaches the critical value, the over-temperature protection is activated: the emitter junction of transistor Q7 is forward-biased, transistor Q7 is turned on, NNOS tube N1 is in the on state, and the potential of the output terminal VO drops to 0.

9. A low power consumption over-temperature protection circuit according to claim 8, characterized in that: When the circuit is in over-temperature protection, when the temperature drops, the base potential of transistor Q6 increases; after the circuit temperature is lower than the temperature of the over-temperature protection state, NNOS tube N1 is closed again.

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