Over-temperature protection circuit

Abstract

The invention relates to the field of over-temperature protection circuits, in particular to an over-temperature protection circuit which comprises a starting module, a PTAT current source module, a CTAT temperature sensing module and an output module. The first output end of the PTAT current source module is electrically connected with the first voltage input end of the CTAT temperature sensing module and the first voltage input end of the output module; the second output end of the PTAT current source module is electrically connected with the second voltage input end of the CTAT temperature sensing module; the third output end of the PTAT current source module is electrically connected with the current input end of the CTAT temperature sensing module, the output end of the CTAT temperature sensing module is electrically connected with the input end of the output module, the PTAT current source module provides bias voltage and bias current with zero temperature coefficients for the CTAT temperature sensing module, and the protection precision is improved; and the trend that the transconductance of the triode decreases along with the temperature rise is compensated, so that the overall performance stability is improved.

Description

Technical Field

[0001] This invention relates to the field of over-temperature protection circuits, and specifically to an over-temperature protection circuit. Background Technology

[0002] Over-temperature protection circuits are crucial functional modules in electronic devices used to prevent damage to core components or critical areas due to excessively high temperatures. Their core principle is to monitor temperature signals in real time, automatically triggering a protection mechanism when the temperature exceeds a preset threshold, and restoring normal equipment operation once the temperature returns to a safe range. These circuits typically consist of a temperature sensor, signal processing unit, comparator, control logic, and actuators. They collect temperature data using thermistors, thermocouples, or integrated temperature sensors, amplify and filter the data, and compare it with a reference voltage. If the temperature exceeds the limit, a control signal is output to cut off power, reduce power consumption, or activate cooling devices.

[0003] For the temperature sensing section, traditional over-temperature protection circuits typically use a simple, fixed current obtained by resistor voltage division to bias the temperature-sensing transistor (BJT) and measure its V. BE This fixed current itself varies with temperature and power supply voltage. This variation is uncontrolled and constitutes harmful drift, introducing errors into the circuit. This results in poor accuracy of the over-temperature protection circuit and a decrease in the transconductance of the transistor as temperature rises. Consequently, the circuit as a whole is quite sensitive to temperature changes near the critical value, posing a risk of oscillation. Summary of the Invention

[0004] The purpose of this invention is to provide an over-temperature protection circuit, which aims to improve upon the traditional over-temperature protection circuit that uses a simple fixed current obtained by resistor voltage division to bias the temperature-sensing transistor BJT. However, the fixed current itself changes with temperature and power supply voltage, introducing errors into the circuit and resulting in poor accuracy of the over-temperature protection circuit. In addition, the transconductance of the transistor decreases with increasing temperature, making the circuit more sensitive to temperature changes near the critical value and posing a risk of oscillation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: An over-temperature protection circuit includes a startup module, a PTAT current source module, a CTAT temperature sensing module, and an output module; The output terminal of the start-up module is electrically connected to the input terminal of the PTAT current source module to provide a reference voltage for the PTAT current source module. The first output terminal of the PTAT current source module is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module; the second output terminal of the PTAT current source module is electrically connected to the second voltage input terminal of the CTAT temperature sensing module; the third output terminal of the PTAT current source module is electrically connected to the current input terminal of the CTAT temperature sensing module. The first and second output terminals of the PTAT current source module output a zero temperature coefficient bias voltage to the CTAT temperature sensing module and the output module, and the third output terminal of the PTAT current source module outputs a PTAT current to the CTAT temperature sensing module. The PTAT current source module compensates for the decreasing transconductance of the built-in transistor as temperature increases. The output terminal of the CTAT temperature sensing module is electrically connected to the input terminal of the output module, and the output module outputs a voltage V. OTP The CTAT temperature sensing module senses the voltage V. Z The temperature coefficient slope is amplified and the sensing voltage V is output. Z The bias voltage is applied to the input terminal and the second voltage input terminal of the output module to control the output voltage V. OTP Output a high or low level.

[0006] Furthermore, the PTAT current source module includes transistors Q0, Q1, P5, P6, P7, P8, and N5, and resistors R5, R6, R7, R8, R9, R10, R11, and R12. The external power supply VCC is electrically connected to the source of MOSFET P5; the startup module outputs a reference voltage to the gate of MOSFET P5; The drain of the MOSFET P5 is electrically connected to one end of resistor R5, one end of resistor R7, one end of resistor R8, one end of resistor R11, and one end of resistor R12. The other end of resistor R12 serves as the first output terminal and is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module. The other end of resistor R5 is electrically connected to one end of resistor R6, the base of transistor Q0, and the base of transistor Q1, and serves as the second output terminal and is electrically connected to the second voltage input terminal of the CTAT temperature sensing module. The other end of resistor R7 is electrically connected to the source of MOSFET P6. The gate and drain of MOSFET P6 are electrically connected to the gate of MOSFET P7, the gate of MOSFET P8, and the collector of transistor Q0. The other end of resistor R8 is electrically connected to the source of MOSFET P7. The drain of MOSFET P7 is electrically connected to the collector of transistor Q1. The emitter of transistor Q0 is electrically connected to one end of resistor R9. The other end of resistor R9 and the emitter of transistor Q1 are both electrically connected to one end of resistor R10. The other end of the resistor R11 is electrically connected to the source of the MOSFET P8. The drain of the MOSFET P8 is electrically connected to the drain and source of the MOSFET N5, and is electrically connected to the current input terminal of the CTAT temperature sensing module as the third output terminal. The source of the MOS transistor N5, the other end of resistor R6, and the other end of resistor R10 are all grounded.

[0007] Furthermore, the PTAT current source module also includes a MOSFET N3, a resistor R3, a resistor R4, and a capacitor C0; The external power supply VCC is electrically connected to one end of capacitor C0 and one end of resistor R4. The other end of capacitor C0 is electrically connected to one end of resistor R3 and the gate of MOSFET N3. The other end of resistor R4 is electrically connected to the drain of MOSFET N3. The other end of resistor R3 is electrically connected to the source of MOSFET N3 and the gate of MOSFET P5.

[0008] Furthermore, the following condition is satisfied: (W / L) P6 (W / L) P7 (W / L) P8 =5:5:1; Among them, (W / L) P6 The width-to-length ratio (W / L) of MOSFET P6 P7 The width-to-length ratio (W / L) of MOSFET P7. P8 This represents the width-to-length ratio of MOSFET P8.

[0009] Furthermore, the CTAT temperature sensing module includes a bias branch, a CTAT voltage sensing branch, and a hysteresis adjustment branch. The first, second, and third output terminals of the PTAT current source module are electrically connected to the input terminal of the bias branch, outputting the bias voltage and PTAT current to the bias branch; the output terminal of the bias branch is electrically connected to the CTAT voltage sensing branch and the hysteresis adjustment branch, and outputs the sensed voltage V as the output terminal. Z The output terminal of the hysteresis adjustment branch is electrically connected to the CTAT voltage sensing branch.

[0010] Furthermore, the bias branch includes MOSFETs P9, P10, P11, P12, P13, P14, N6, N7, N8, N9, N10, N13 and transistor Q2; The external power supply VCC is electrically connected to the sources of MOSFETs P9, P11, P12, and P14; the first output terminal of the PTAT current source module outputs a bias voltage V. X The bias voltage V is output to the gates of MOSFET N8, MOSFET N9, and MOSFET N10; the second output terminal of the PTAT current source module outputs the bias voltage V. Y The PTAT current is output to the base of transistor Q2; the third output terminal of the PTAT current source module outputs PTAT current to the gate of MOSFET N6 and the gate of MOSFET N7. The gate and drain of MOS transistor P9 are electrically connected to the drain of MOS transistor N8, the gate of MOS transistor P10, the gate of MOS transistor P13, and the hysteresis adjustment branch; the source of MOS transistor N8 is electrically connected to the drain of MOS transistor N6. The gate of MOS transistor P11 is electrically connected to the drain of MOS transistor P10, the drain of MOS transistor N9, the gate of MOS transistor P12, and the gate of MOS transistor P14. The drain of MOS transistor P11 is electrically connected to the source of MOS transistor P10, and the source of MOS transistor N9 is electrically connected to the drain of MOS transistor N7. The drain of MOS transistor P12 is electrically connected to the source of MOS transistor P13, and the drain of MOS transistor P13 is electrically connected to the gate, drain, hysteresis adjustment branch, and output module of MOS transistor N13. The drain of MOSFET P14 is electrically connected to the drain of MOSFET N10, and serves as the output terminal to output the sensing voltage V. Z The hysteresis adjustment branch and output module; the source of the MOS transistor N10 is electrically connected to the collector of the transistor Q2, and the emitter of the transistor Q2 is electrically connected to the CTAT voltage sensing branch; The sources of MOSFETs N5, N6, N7, and N13 are all grounded.

[0011] Furthermore, the CTAT voltage sensing branch includes transistors Q3, Q4, Q5, and Q6, and resistor R13; The output terminal of the bias branch is electrically connected to the base and collector of transistor Q3, the emitter of transistor Q3 is electrically connected to the base and collector of transistor Q4, the emitter of transistor Q4 is electrically connected to the base and collector of transistor Q5, the emitter of transistor Q5 is electrically connected to one end of resistor R13, and the other end of resistor R13 and the output terminal of the hysteresis adjustment branch are electrically connected to the base and collector of transistor Q6. The emitter of the transistor Q6 is grounded.

[0012] Furthermore, the hysteresis adjustment branch includes MOSFET P15, MOSFET P16, MOSFET N14 and MOSFET N15; The external power supply VCC is electrically connected to the source of MOSFET P15, and the output sensing voltage V of the bias branch is... Z The bias branch provides bias voltage to the gate of MOSFET P15 and outputs bias voltage to the gate of MOSFET N15 and the gate of MOSFET P16. The drain of MOS transistor P15 is electrically connected to the source of MOS transistor P16, the drain of MOS transistor P16 is electrically connected to the drain of MOS transistor N15 and the gate of MOS transistor N14, and the drain of MOS transistor N14 is electrically connected to the CTAT voltage sensing branch as an output terminal. The sources of both MOS transistor N14 and MOS transistor N15 are grounded.

[0013] Furthermore, the startup module includes MOSFETs P0, P1, P2, P3, N0, N1, N2, and N4, and resistors R0, R1, and R2. The external power supply VCC is electrically connected to the source of MOSFET P0, the source of MOSFET P1, the source of MOSFET P3, and one end of resistor R0. The other end of resistor R0 is electrically connected to the gate and drain of MOSFET N1 and MOSFET N0, respectively. The gate of MOSFET N0 is electrically connected to the source of MOSFET N1 and one end of resistor R1. The gate and drain of MOSFET P0 are electrically connected to the gates of MOSFET P1 and MOSFET P3 and one end of resistor R2, respectively. The other end of resistor R2 is electrically connected to the gate of MOSFET P2 and the drain of MOSFET N1. The drain of MOSFET P1 is electrically connected to the source of MOSFET P2. The drain of MOSFET P2 is electrically connected to the drain and gate of MOSFET N2 and the gate of MOSFET N4. The drain of MOSFET P3 is electrically connected to the drain of MOSFET N4 and serves as the output terminal to output a reference voltage to the PTAT current source module. The source of MOS transistor N0, the source of MOS transistor N2, the source of MOS transistor N4, and the other end of resistor R1 are all grounded.

[0014] Furthermore, the output module includes MOSFETs P17, P18, N11, N12, N16, and N17. The external power supply VCC is electrically connected to the source of MOSFET P17 and the source of MOSFET P18; the output terminal of the CTAT temperature sensing module outputs the sensing voltage V. Z The bias voltage is output to the gate of MOSFET P17; the bias voltage is output to the gate of MOSFET N11 and the gate of MOSFET N12 by the PTAT current source module; the bias voltage is output to the gate of MOSFET N16 and the gate of MOSFET N17 by the CTAT temperature sensing module. The drain of MOSFET P17 is electrically connected to the drain of MOSFET N11 and the gate of MOSFET P18; the source of MOSFET N11 is electrically connected to the drain of MOSFET N16; the drain of MOSFET P18 is electrically connected to the drain of MOSFET N12, and serves as the output voltage V. OTP The source of the MOS transistor N12 is electrically connected to the drain of the MOS transistor N17. The sources of both MOS transistor N16 and MOS transistor N17 are grounded.

[0015] By adopting the above technical solution, the present invention has the following advantages compared with the prior art: 1. The startup module drives the PTAT current source module to operate, providing the CTAT temperature sensing module with a zero-temperature coefficient bias voltage and bias current, avoiding temperature drift that introduces errors into the circuit and improving protection accuracy. Furthermore, the PTAT current source module compensates for the decreasing transconductance of the transistor with increasing temperature, thus increasing the sensing voltage V of the CTAT temperature sensing module. Z The hysteresis range is reduced, the sensitivity of the circuit at the critical point is decreased, and the output module only changes the output level after the circuit has been completely cooled to the preset safe temperature. This avoids the output module repeatedly switching levels near the critical point due to insufficient circuit cooling, and improves the overall performance stability.

[0016] 2. The CTAT temperature sensing module outputs an enhanced CTAT voltage as the sensing voltage V. Z This amplifies the slope of the temperature coefficient of the sensed voltage, preventing large voltage changes caused by temperature and current variations near the critical point, and reducing the risk of oscillations near the critical point. Attached Figure Description

[0017] Figure 1 This is a circuit diagram of the over-temperature protection circuit described in this invention; Figure 2 This is a simulation diagram of the hysteresis characteristics of the over-temperature protection circuit described in this invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Additionally, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are all based on the orientation or positional relationship shown in the accompanying drawings. They are merely for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element of the present invention must have a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0020] When an element is referred to as being "fixed to," "set on," or "contained on" another element, it can be directly on or indirectly on that other element. When an element is referred to as being "connected to," it can be directly connected to or indirectly connected to that other element.

[0021] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances. Example

[0022] Please refer to Figure 1 As shown, this embodiment provides an over-temperature protection circuit, including a startup module, a PTAT current source module, a CTAT temperature sensing module, and an output module. The output terminal of the startup module is electrically connected to the input terminal of the PTAT current source module, providing a reference voltage for the PTAT current source module.

[0023] The first output terminal of the PTAT current source module is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module; the second output terminal of the PTAT current source module is electrically connected to the second voltage input terminal of the CTAT temperature sensing module; the third output terminal of the PTAT current source module is electrically connected to the current input terminal of the CTAT temperature sensing module. The first and second output terminals of the PTAT current source module output a zero-temperature coefficient bias voltage to the CTAT temperature sensing module and the output module; the third output terminal of the PTAT current source module outputs PTAT current to the CTAT temperature sensing module; the PTAT current source module compensates for the decreasing transconductance of the built-in transistor as temperature increases.

[0024] The output terminal of the CTAT temperature sensing module is electrically connected to the input terminal of the output module, and the output voltage of the output module is V. OTP The CTAT temperature sensing module senses the voltage V. Z The temperature coefficient slope is amplified and the sensing voltage V is output. Z The bias voltage is applied to the input terminal and the second voltage input terminal of the output module to control the output voltage V. OTP Output a high or low level.

[0025] The startup module drives the PTAT current source module to operate, providing the CTAT temperature sensing module with a zero-temperature coefficient bias voltage and bias current, avoiding temperature drift that introduces errors into the circuit and improving protection accuracy. Furthermore, the PTAT current source module compensates for the decreasing transconductance of the transistor with increasing temperature, thus increasing the sensing voltage V of the CTAT temperature sensing module. Z The hysteresis range is reduced, decreasing the circuit's sensitivity at critical points. This ensures the output module only changes its output level after the circuit has fully cooled to the preset safe temperature, preventing insufficient cooling from causing repeated level switching near the critical point and improving overall performance stability. Simultaneously, the CTAT temperature sensing module outputs an enhanced CTAT voltage as the sensing voltage V. Z This amplifies the slope of the temperature coefficient of the sensed voltage, preventing large voltage changes caused by temperature and current variations near the critical point, and reducing the risk of oscillations near the critical point.

[0026] Specifically, the startup module includes MOSFETs P0, P1, P2, P3, N0, N1, N2, and N4, and resistors R0, R1, and R2.

[0027] The external power supply VCC is electrically connected to the source of MOSFET P0, the source of MOSFET P1, the source of MOSFET P3, and one end of resistor R0.

[0028] The other end of resistor R0 is electrically connected to the gate and drain of MOSFET N1. The gate of MOSFET N0 is electrically connected to the source of MOSFET N1 and one end of resistor R1. The gate and drain of MOSFET P0 are both electrically connected to the gates of MOSFET P1 and P3 and one end of resistor R2. The other end of resistor R2 is electrically connected to the gate of MOSFET P2 and the drain of MOSFET N1.

[0029] The drain of MOSFET P1 is electrically connected to the source of MOSFET P2. The drain of MOSFET P2 is electrically connected to the drain and gate of MOSFET N2 and the gate of MOSFET N4. The drain of MOSFET P3 is electrically connected to the drain of MOSFET N4 and serves as the output terminal to output a reference voltage to the PTAT current source module.

[0030] The source of MOSFET N0, the source of MOSFET N2, the source of MOSFET N4, and the other end of resistor R1 are all grounded.

[0031] When the external power supply VCC is powered on, MOSFETs N0 and N1 conduct, and the startup module begins to operate. Resistor R2, MOSFETs P0, P1, P2, P3, N2, and N4 form a current mirror, using the drain voltage of MOSFET P3 as the output voltage, providing a reference voltage to the PTAT current source module. MOSFET P0's gate and drain are shorted to provide the reference current. MOSFETs P1 and N2 replicate this reference current, with MOSFET P2 stabilizing its internal operating point. Resistor R2 raises the drain voltage of MOSFET P0 to prevent it from breaking down. MOSFET P3 acts as a pull-up PMOS for the output reference voltage, and MOSFET N4 acts as a pull-down NMOS for the output reference voltage.

[0032] Specifically, the PTAT current source module includes transistors Q0, Q1, P5, P6, P7, P8, and N5, and resistors R5, R6, R7, R8, R9, R10, R11, and R12.

[0033] The external power supply VCC is electrically connected to the source of MOSFET P5; the startup module outputs a reference voltage to the gate of MOSFET P5, that is, the drain of MOSFET P3 is electrically connected to the gate of MOSFET P5.

[0034] The drain of MOSFET P5 is electrically connected to one end of resistors R5, R7, R8, R11, and R12. The other end of resistor R12 serves as the first output terminal and is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module. The other end of resistor R5 is electrically connected to one end of resistor R6, the base of transistor Q0, and the base of transistor Q1, and serves as the second output terminal and is electrically connected to the second voltage input terminal of the CTAT temperature sensing module.

[0035] The other end of resistor R7 is electrically connected to the source of MOSFET P6. The gate and drain of MOSFET P6 are both electrically connected to the gates of MOSFET P7 and P8, and the collector of transistor Q0. The other end of resistor R8 is electrically connected to the source of MOSFET P7. The drain of MOSFET P7 is electrically connected to the collector of transistor Q1. The emitter of transistor Q0 is electrically connected to one end of resistor R9. The other end of resistor R9 and the emitter of transistor Q1 are both electrically connected to one end of resistor R10.

[0036] The other end of resistor R11 is electrically connected to the source of MOSFET P8. The drain of MOSFET P8 is electrically connected to the drain and source of MOSFET N5, and serves as the third output terminal, which is electrically connected to the current input terminal of the CTAT temperature sensing module, outputting PTAT current to the CTAT temperature sensing module.

[0037] The source of MOSFET N5, the other end of resistor R6, and the other end of resistor R10 are all grounded.

[0038] Furthermore, the PTAT current source module also includes MOSFET N3, resistor R3, resistor R4, and capacitor C0.

[0039] The external power supply VCC is electrically connected to one end of capacitor C0 and one end of resistor R4. The other end of capacitor C0 is electrically connected to one end of resistor R3 and the gate of MOSFET N3. The other end of resistor R4 is electrically connected to the drain of MOSFET N3. The other end of resistor R3 is electrically connected to the source of MOSFET N3 and the gate of MOSFET P5.

[0040] And it satisfies the following condition: (W / L) P6 (W / L) P7 (W / L) P8 =5:5:1; Among them, (W / L) P6 The width-to-length ratio (W / L) of MOSFET P6 P7 The width-to-length ratio (W / L) of MOSFET P7. P8 This represents the width-to-length ratio of MOSFET P8.

[0041] The PTAT current is directly proportional to the absolute temperature. Specifically, the drain voltage of MOSFET P3 is used as the output voltage to supply the gate of MOSFET P5. Resistors R3 and R4, capacitor C0, and MOSFET N3 form a surge suppression branch. When the output voltage changes abruptly, since the voltage across capacitor C0 cannot change abruptly, the gate-source voltage of MOSFET N3 follows suit, and MOSFET N3 enters the saturation region. The current flowing through MOSFET N3 is automatically limited to its maximum current due to the square law characteristic of NMOS transistors, thus suppressing the surge.

[0042] After MOSFET P5 is turned on, it pulls up VCC to power the PTAT current source module; resistors R7, R8, and R11 are passive loads. MOSFETs P6, P7, and P8 form a current mirror branch. Based on their width-to-length ratio and the circuit structure of the PTAT current source module, the current I flowing through resistor R9 is... R9 for, ; Among them, V BE0 and V BE1 V represents the base-emitter voltages of transistors Q0 and Q1, respectively, and ln is the logarithm to the base n, where n is the ratio of the number of transistors Q0 and Q1 connected in parallel; T It is the thermal voltage, and R9 is the resistance value of resistor R9.

[0043] Because, V T =kT / q, where q is the charge of the electron, k is the Boltzmann constant, and T is the temperature, i.e., V. T It is directly proportional to the absolute temperature. Therefore, the current I flowing through resistor R9 is... R9 It is also directly proportional to the absolute temperature, which is the PTAT current. Since MOSFETs P6, P7, and P8 form a current mirror structure, the current flowing through MOSFET P8 is also the PTAT current, which is directly proportional to the absolute temperature.

[0044] Therefore, .

[0045] Combined with appendix Figure 1 The bias voltage V X and bias voltage V Y These are the voltages at node X and node Y, respectively, i.e., V. Y Let be the base voltage of transistors Q0 and Q1, that is, ; Due to V Y For V X The voltage divider due to the resistors can be used to obtain... .

[0046] Due to the process parameters V BE It is a negative temperature coefficient voltage, V T It is a positive temperature coefficient voltage, meaning the magnitude of the positive temperature coefficient can be adjusted by changing the resistance ratio of resistors R10 and R9, thus canceling out the negative temperature coefficient; making V... X and V Y The voltage has a zero temperature coefficient.

[0047] Furthermore, the CTAT temperature sensing module includes a bias branch, a CTAT voltage sensing branch, and a hysteresis adjustment branch. The first, second, and third output terminals of the PTAT current source module are electrically connected to the input terminal of the bias branch, outputting a bias voltage and PTAT current to the bias branch. The output terminal of the bias branch is electrically connected to the CTAT voltage sensing branch and the hysteresis adjustment branch, and outputs the sensed voltage V as its output terminal. Z To the output module. The output terminal of the hysteresis adjustment branch is electrically connected to the CTAT voltage sensing branch.

[0048] Specifically, the bias branch includes MOSFETs P9, P10, P11, P12, P13, P14, N6, N7, N8, N9, N10, N13 and transistor Q2.

[0049] The external power supply VCC is electrically connected to the sources of MOSFETs P9, P11, P12, and P14. The first output terminal of the PTAT current source module outputs a bias voltage V. X The other end of resistor R12 is electrically connected to the gates of MOSFETs N8, N9, and N10. The second output terminal of the PTAT current source module outputs a bias voltage V. Y The other end of resistor R5 is electrically connected to the base of transistor Q2. The third output terminal of the PTAT current source module outputs PTAT current to the gates of MOSFET N6 and MOSFET N7, that is, the drain of MOSFET P8 is electrically connected to the gates of MOSFET N6 and MOSFET N7.

[0050] The gate and drain of MOSFET P9 are electrically connected to the drain of MOSFET N8, the gate of MOSFET P10, the gate of MOSFET P13, and the hysteresis adjustment branch. The source of MOSFET N8 is electrically connected to the drain of MOSFET N6. The gate of MOSFET P11 is electrically connected to the drain of MOSFET P10, the drain of MOSFET N9, the gate of MOSFET P12, and the gate of MOSFET P14. The drain of MOSFET P11 is electrically connected to the source of MOSFET P10. The source of MOSFET N9 is electrically connected to the drain of MOSFET N7. The drain of MOSFET P12 is electrically connected to the source of MOSFET P13. The drain of MOSFET P13 is electrically connected to the gate and drain of MOSFET N13, as well as the hysteresis adjustment branch and the output module.

[0051] The drain of MOSFET P14 is electrically connected to the drain of MOSFET N10, and serves as the output terminal to output the sensed voltage V. Z To hysteresis adjustment branch and output module; refer to appendix Figure 1 It can be seen that the sensed voltage V Z This is the voltage at node Z. The source of MOSFET N10 is electrically connected to the collector of transistor Q2, and the emitter of transistor Q2 is electrically connected to the CTAT voltage sensing branch.

[0052] The sources of MOSFETs N5, N6, N7, and N13 are all grounded.

[0053] Specifically, the CTAT voltage sensing branch includes transistors Q3, Q4, Q5, and Q6, and resistor R13.

[0054] The output of the bias branch is electrically connected to the base and collector of transistor Q3, meaning the emitter of transistor Q2 is electrically connected to the base and collector of transistor Q3. The emitter of transistor Q3 is electrically connected to the base and collector of transistor Q4, and the emitter of transistor Q4 is electrically connected to the base and collector of transistor Q5. The emitter of transistor Q5 is electrically connected to one end of resistor R13, and the other end of resistor R13, along with the output of the hysteresis adjustment branch, is electrically connected to the base and collector of transistor Q6. The emitter of transistor Q6 is grounded.

[0055] Specifically, the hysteresis adjustment branch includes MOSFETs P15, P16, N14, and N15.

[0056] The external power supply VCC is electrically connected to the source of MOSFET P15; the output sensing voltage V of the bias branch is... ZThe gate of MOSFET P15 is connected to the drain of MOSFET P14, which is electrically connected to the gate of MOSFET P15. The bias branch outputs a bias voltage to the gate of MOSFET N15 and the gate of MOSFET P16. That is, the gate and drain of MOSFET P9 are electrically connected to the gate of MOSFET P16, and the drain of MOSFET P13 is electrically connected to the gate of MOSFET N5.

[0057] The drain of MOSFET P15 is electrically connected to the source of MOSFET P16. The drain of MOSFET P16 is electrically connected to the drain of MOSFET N15 and the gate of MOSFET N14. The drain of MOSFET N14 serves as the output terminal and is electrically connected to the CTAT voltage sensing branch; that is, the drain of MOSFET N14 is electrically connected to the base and collector of transistor Q6. The sources of MOSFET N14 and MOSFET N15 are both grounded.

[0058] Transistors Q2, N8, N9, and N10 are bias transistors, using a bias voltage V with a zero temperature coefficient. X and bias voltage V Y As a bias input, it avoids introducing errors. MOSFET N13 is a self-biased transistor, providing bias voltage to the hysteresis adjustment branch and the output branch. MOSFETs N5, N6, and N7 form a current mirror structure, replicating the PTAT current and introducing it into the CTAT temperature sensing module. MOSFETs P9, P10, P11, P12, P13, and P14 also form a current mirror structure, replicating the PTAT current to the CTAT voltage sensing branch. Resistor R13 raises the Z-node potential. The voltage drop generated by shorting and connecting the base-collector of transistors Q3, Q4, Q5, and Q6 in the CTAT voltage sensing branch is used as the sensing voltage. Since when T=300K, a single V BE The temperature coefficient is, ; The four transistors connected in series amplify the slope to approximately -6mV / K. This larger slope allows the circuit to generate a sufficiently large voltage change from a small temperature variation near the critical temperature point, thus maximizing the sensing voltage V. Z It has strong CTAT characteristics.

[0059] Transconductance gm is, ; Among them, I C It is the collector current, V T It is thermal voltage. When I C When it is a constant, the transconductance gm decreases with increasing temperature. In this embodiment, I CThis is the PTAT current. Since the PTAT current is directly proportional to absolute temperature, it increases with increasing temperature. ; In this case, ∝ is a mathematical symbol representing a direct proportional relationship between two quantities. The transconductance gm is a constant, meaning it remains constant regardless of temperature changes. This constant transconductance gm stabilizes the transistor's gain and sensitivity, reducing the impact of temperature fluctuations on circuit performance. In other words, the PTAT current can compensate for the decreasing trend of the transistor's transconductance gm with increasing temperature.

[0060] When I C When V is constant, the transistor's V BE The first and second derivatives with respect to temperature T can be expressed as follows: ; ; When I C When it is the PTAT current, i.e., I C When =NT, where N is a constant and V BE The first and second derivatives with respect to temperature T can be expressed as follows: ; ; Where m≈-3 / 2, V T It is thermal voltage, E g V is the band gap energy of silicon, k is the Boltzmann constant, and q is the charge of an electron. That is, under the influence of a PTAT current, V BE The first-order temperature coefficient of V changes with temperature at a smaller rate. That is, V BE The curvature of the first-order temperature coefficient curve decreases. V... BE The change is closer to linear, reducing the drift of the trigger point and improving the accuracy and consistency of temperature detection.

[0061] As the circuit's operating temperature rises, the PTAT current increases with temperature, consequently increasing the current flowing through MOSFETs N6 and N7. This raises the gate potentials of MOSFETs P9, P11, and P14 through the current mirror structure. Ignoring the slight voltage drop generated when transistors Q2 and N10 are turned on, the Z-node voltage is approximately equal to the sensed voltage, i.e., V. Z For sensing voltage.

[0062] Before the temperature rises to the critical point, V Z It can be represented as, ; Among them, I ZThis is the PTAT current replicated by the current mirror from MOSFET P14, and R13 is the resistance value of resistor R13. Because V BE Its negative temperature characteristic, V when heated Z The temperature will decrease slowly. When it reaches the critical point, MOSFET P15 will turn on instantaneously. The drain potential of MOSFET N15 will change from low to high, turning on MOSFET N14. Transistor Q6 will be short-circuited. Z It is pulled down to a lower potential, at which point, .

[0063] To restore V during cooling Z Potential, the circuit can only be raised by lowering the temperature to a lower level. BE Only then can V Z The original level is restored, that is, a wider hysteresis range is generated.

[0064] Please refer to Figure 2 As shown, attached Figure 2 This is a simulation diagram of the hysteresis characteristics of the over-temperature protection circuit disclosed in this embodiment. Figure 2 It can be seen that the hysteresis range of the over-temperature protection circuit disclosed in this embodiment can reach 30°C, which has a wide hysteresis range and effectively avoids the phenomenon of repeated opening and closing near the critical point due to insufficient circuit cooling.

[0065] Specifically, the output module includes MOSFETs P17, P18, N11, N12, N16, and N17.

[0066] The external power supply VCC is electrically connected to the source of MOSFET P17 and the source of MOSFET P18. The output terminal of the CTAT temperature sensing module outputs the sensing voltage V. Z The drain of MOSFET P14 is electrically connected to the gate of MOSFET P17. The PTAT current source module outputs a bias voltage to the gates of MOSFETs N11 and N12, meaning the other end of resistor R12 is electrically connected to the gates of MOSFETs N11 and N12. The CTAT temperature sensing module outputs a bias voltage to the gates of MOSFETs N16 and N17, meaning the drain of MOSFET P13 is electrically connected to the gates of MOSFETs N16 and N17.

[0067] The drain of MOSFET P17 is electrically connected to the drain of MOSFET N11 and the gate of MOSFET P18. The source of MOSFET N11 is electrically connected to the drain of MOSFET N16. The drain of MOSFET P18 is electrically connected to the drain of MOSFET N12, and serves as the output terminal for the output voltage V. OTPThe source of MOSFET N12 is electrically connected to the drain of MOSFET N17. The sources of MOSFET N16 and MOSFET N17 are both grounded.

[0068] MOSFETs N11, N12, N16, and N17 are all bias transistors used to set the operating point; voltage V OTP This is the output voltage for over-temperature protection. When the sensed voltage V... Z When the voltage rises to the critical point potential, MOSFET P17 turns on and pulls up VCC, turning off MOSFET P18. The voltage V... OTP The voltage flips to output a low-level over-temperature signal. Once the circuit temperature drops to the safe point, MOSFET P17 turns off again, and MOSFET P18 turns on to pull up VCC, resulting in a voltage V... OTP The potential returns to a high level.

[0069] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An over-temperature protection circuit, characterized in that, It includes a startup module, a PTAT current source module, a CTAT temperature sensing module, and an output module; The output terminal of the start-up module is electrically connected to the input terminal of the PTAT current source module to provide a reference voltage for the PTAT current source module. The first output terminal of the PTAT current source module is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module; the second output terminal of the PTAT current source module is electrically connected to the second voltage input terminal of the CTAT temperature sensing module; the third output terminal of the PTAT current source module is electrically connected to the current input terminal of the CTAT temperature sensing module; the first and second output terminals of the PTAT current source module output a zero temperature coefficient bias voltage to the CTAT temperature sensing module and the output module; and the third output terminal of the PTAT current source module outputs a PTAT current to the CTAT temperature sensing module. The PTAT current source module compensates for the decreasing transconductance of the built-in transistor as temperature increases. The output terminal of the CTAT temperature sensing module is electrically connected to the input terminal of the output module, and the output module outputs a voltage V. OTP The CTAT temperature sensing module senses the voltage V. Z The temperature coefficient slope is amplified and the sensing voltage V is output. Z The bias voltage is applied to the input terminal and the second voltage input terminal of the output module to control the output voltage V. OTP Output a high or low level.

2. The over-temperature protection circuit according to claim 1, characterized in that: The PTAT current source module includes transistors Q0, Q1, P5, P6, P7, P8, and N5, and resistors R5, R6, R7, R8, R9, R10, R11, and R12. The external power supply VCC is electrically connected to the source of MOSFET P5; the startup module outputs a reference voltage to the gate of MOSFET P5; The drain of the MOSFET P5 is electrically connected to one end of resistor R5, one end of resistor R7, one end of resistor R8, one end of resistor R11, and one end of resistor R12. The other end of resistor R12 serves as the first output terminal and is electrically connected to the first voltage input terminal of the CTAT temperature sensing module and the first voltage input terminal of the output module. The other end of resistor R5 is electrically connected to one end of resistor R6, the base of transistor Q0, and the base of transistor Q1, and serves as the second output terminal and is electrically connected to the second voltage input terminal of the CTAT temperature sensing module. The other end of resistor R7 is electrically connected to the source of MOSFET P6. The gate and drain of MOSFET P6 are electrically connected to the gate of MOSFET P7, the gate of MOSFET P8, and the collector of transistor Q0. The other end of resistor R8 is electrically connected to the source of MOSFET P7. The drain of MOSFET P7 is electrically connected to the collector of transistor Q1. The emitter of transistor Q0 is electrically connected to one end of resistor R9. The other end of resistor R9 and the emitter of transistor Q1 are both electrically connected to one end of resistor R10. The other end of the resistor R11 is electrically connected to the source of the MOSFET P8. The drain of the MOSFET P8 is electrically connected to the drain and source of the MOSFET N5, and is electrically connected to the current input terminal of the CTAT temperature sensing module as the third output terminal. The source of the MOS transistor N5, the other end of resistor R6, and the other end of resistor R10 are all grounded.

3. The over-temperature protection circuit according to claim 2, characterized in that: The PTAT current source module also includes MOSFET N3, resistor R3, resistor R4, and capacitor C0; The external power supply VCC is electrically connected to one end of capacitor C0 and one end of resistor R4. The other end of capacitor C0 is electrically connected to one end of resistor R3 and the gate of MOSFET N3. The other end of resistor R4 is electrically connected to the drain of MOSFET N3. The other end of resistor R3 is electrically connected to the source of MOSFET N3 and the gate of MOSFET P5.

4. The over-temperature protection circuit according to claim 2, characterized in that: The following conditions must be met. (W / L) P6 :(W / L) P7 :(W / L) P8 =5:5:1; Among them, (W / L) P6 The width-to-length ratio (W / L) of MOSFET P6 P7 The width-to-length ratio (W / L) of MOSFET P7. P8 This represents the width-to-length ratio of MOSFET P8.

5. The over-temperature protection circuit according to claim 1, characterized in that: The CTAT temperature sensing module includes a bias branch, a CTAT voltage sensing branch, and a hysteresis adjustment branch. The first, second, and third output terminals of the PTAT current source module are electrically connected to the input terminal of the bias branch, and output bias voltage and PTAT current to the bias branch. The output terminal of the bias branch is electrically connected to the CTAT voltage sensing branch and the hysteresis adjustment branch, and outputs the sensed voltage V as the output terminal. Z The output terminal of the hysteresis adjustment branch is electrically connected to the CTAT voltage sensing branch.

6. The over-temperature protection circuit according to claim 5, characterized in that: The bias branch includes MOSFETs P9, P10, P11, P12, P13, P14, N6, N7, N8, N9, N10, N13 and transistor Q2; The external power supply VCC is electrically connected to the sources of MOSFETs P9, P11, P12, and P14; the first output terminal of the PTAT current source module outputs a bias voltage V. X The bias voltage V is output to the gates of MOSFET N8, MOSFET N9, and MOSFET N10; the second output terminal of the PTAT current source module outputs the bias voltage V. Y The PTAT current is output to the base of transistor Q2; the third output terminal of the PTAT current source module outputs PTAT current to the gate of MOSFET N6 and the gate of MOSFET N7. The gate and drain of MOS transistor P9 are electrically connected to the drain of MOS transistor N8, the gate of MOS transistor P10, the gate of MOS transistor P13, and the hysteresis adjustment branch; the source of MOS transistor N8 is electrically connected to the drain of MOS transistor N6. The gate of MOS transistor P11 is electrically connected to the drain of MOS transistor P10, the drain of MOS transistor N9, the gate of MOS transistor P12, and the gate of MOS transistor P14. The drain of MOS transistor P11 is electrically connected to the source of MOS transistor P10, and the source of MOS transistor N9 is electrically connected to the drain of MOS transistor N7. The drain of MOS transistor P12 is electrically connected to the source of MOS transistor P13, and the drain of MOS transistor P13 is electrically connected to the gate, drain, hysteresis adjustment branch, and output module of MOS transistor N13. The drain of MOSFET P14 is electrically connected to the drain of MOSFET N10, and serves as the output terminal to output the sensing voltage V. Z The hysteresis adjustment branch and output module; the source of the MOS transistor N10 is electrically connected to the collector of the transistor Q2, and the emitter of the transistor Q2 is electrically connected to the CTAT voltage sensing branch; The sources of MOSFETs N5, N6, N7, and N13 are all grounded.

7. The over-temperature protection circuit according to claim 5, characterized in that: The CTAT voltage sensing branch includes transistors Q3, Q4, Q5, and Q6, and resistor R13. The output terminal of the bias branch is electrically connected to the base and collector of transistor Q3, the emitter of transistor Q3 is electrically connected to the base and collector of transistor Q4, the emitter of transistor Q4 is electrically connected to the base and collector of transistor Q5, the emitter of transistor Q5 is electrically connected to one end of resistor R13, and the other end of resistor R13 and the output terminal of the hysteresis adjustment branch are electrically connected to the base and collector of transistor Q6. The emitter of the transistor Q6 is grounded.

8. The over-temperature protection circuit according to claim 5, characterized in that: The hysteresis adjustment branch includes MOSFET P15, MOSFET P16, MOSFET N14 and MOSFET N15; The external power supply VCC is electrically connected to the source of MOSFET P15, and the output sensing voltage V of the bias branch is... Z The bias branch provides bias voltage to the gate of MOSFET P15 and outputs bias voltage to the gate of MOSFET N15 and the gate of MOSFET P16. The drain of MOS transistor P15 is electrically connected to the source of MOS transistor P16, the drain of MOS transistor P16 is electrically connected to the drain of MOS transistor N15 and the gate of MOS transistor N14, and the drain of MOS transistor N14 is electrically connected to the CTAT voltage sensing branch as an output terminal. The sources of both MOS transistor N14 and MOS transistor N15 are grounded.

9. The over-temperature protection circuit according to claim 1, characterized in that: The startup module includes MOSFETs P0, P1, P2, P3, N0, N1, N2, and N4, and resistors R0, R1, and R2. The external power supply VCC is electrically connected to the source of MOSFET P0, the source of MOSFET P1, the source of MOSFET P3, and one end of resistor R0. The other end of resistor R0 is electrically connected to the gate and drain of MOSFET N1 and MOSFET N0, respectively. The gate of MOSFET N0 is electrically connected to the source of MOSFET N1 and one end of resistor R1. The gate and drain of MOSFET P0 are electrically connected to the gates of MOSFET P1 and MOSFET P3 and one end of resistor R2, respectively. The other end of resistor R2 is electrically connected to the gate of MOSFET P2 and the drain of MOSFET N1. The drain of MOSFET P1 is electrically connected to the source of MOSFET P2. The drain of MOSFET P2 is electrically connected to the drain and gate of MOSFET N2 and the gate of MOSFET N4. The drain of MOSFET P3 is electrically connected to the drain of MOSFET N4 and serves as the output terminal to output a reference voltage to the PTAT current source module. The source of MOS transistor N0, the source of MOS transistor N2, the source of MOS transistor N4, and the other end of resistor R1 are all grounded.

10. The over-temperature protection circuit according to claim 1, characterized in that: The output module includes MOSFETs P17, P18, N11, N12, N16, and N17. The external power supply VCC is electrically connected to the source of MOSFET P17 and the source of MOSFET P18; the output terminal of the CTAT temperature sensing module outputs the sensing voltage V. Z The bias voltage is output to the gate of MOSFET P17; the bias voltage is output to the gate of MOSFET N11 and the gate of MOSFET N12 by the PTAT current source module; the bias voltage is output to the gate of MOSFET N16 and the gate of MOSFET N17 by the CTAT temperature sensing module. The drain of MOSFET P17 is electrically connected to the drain of MOSFET N11 and the gate of MOSFET P18; the source of MOSFET N11 is electrically connected to the drain of MOSFET N16; the drain of MOSFET P18 is electrically connected to the drain of MOSFET N12, and serves as the output voltage V. OTP The source of the MOS transistor N12 is electrically connected to the drain of the MOS transistor N17. The sources of both MOS transistor N16 and MOS transistor N17 are grounded.

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