CN113014236B - Hysteresis over-temperature protection circuit without comparator - Google Patents

Abstract

A hysteresis over-temperature protection circuit without a comparator utilizes a positive temperature coefficient voltage generation module to generate a first control voltage which is in direct proportion to absolute temperature; the over-temperature protection core module controls the base voltage of the second PNP type triode according to the first control voltage, and further controls the collector current of the second PNP type triode to rise along with the rise of the temperature, so that the collector potential of the first NPN type triode is controlled, and the collector potential of the first NPN type triode is driven and enhanced to obtain an output signal of the hysteresis over-temperature protection circuit; in addition, the hysteresis module is arranged to enable all collector currents of the first PNP type triode to flow out through the first NMOS tube when the chip works normally, and enable all collector currents of the first PNP type triode to flow out through the fourth resistor, the fourth PNP type triode and the sixth resistor when the chip is in an over-temperature state, so that the hysteresis window is introduced. The invention saves the area of the chip, reduces the time delay of signal transmission and can prevent the service life of the device from being influenced by overhigh temperature of the chip.

Description

A Hysteresis Over-temperature Protection Circuit Without Comparator

technical field

The invention belongs to the technical field of basic electronic circuits, and relates to a hysteresis over-temperature protection circuit without a comparator.

Background technique

With the development of integrated circuit technology, the integration of chips is getting higher and higher, and the density of devices and energy consumption is also increasing. The power consumption will cause the temperature of the chip to rise, and it is easy to cause the thermal breakdown of the PN junction and the overcurrent will cause the chip to not work properly. Therefore, in an integrated circuit system, in order to avoid permanent damage to the chip due to high operating temperature, and to ensure the reliability and stability of the chip's operation, an over-temperature protection circuit is very necessary.

The traditional over-temperature protection circuit is shown in Figure 1. The transistor Q1 with a negative temperature coefficient threshold is used to achieve over-temperature comparison. Its working principle is: the voltage of the positive input terminal of the comparator depends on the threshold voltage of the transistor Q1, and its negative input terminal The voltage is a fixed value; as the temperature increases, the voltage at the positive input terminal of the comparator decreases. When the temperature continues to rise, so that the voltage at the positive input terminal of the comparator is lower than the voltage at the negative input terminal, the output of the comparator is reversed, and the generated output signal jumps. It can be used as an over-temperature flag signal to control other modules in the chip.

However, the traditional over-temperature protection circuit has a comparator, which will make the chip area too large, and the signal transmission delay will increase. In addition, the traditional over-temperature protection circuit only sets one temperature detection value. When the temperature exceeds a certain threshold, the chip will only output the shutdown signal, which has a certain hysteresis. Obviously, such a hysteresis will cause some temperatures to be higher. The semiconductor components are overheated and burned out, which seriously affects the life of the device.

SUMMARY OF THE INVENTION

Aiming at the problems of the above-mentioned traditional over-temperature protection circuit having a large chip area, increased transmission delay due to having a comparator, and easy burnout of the device due to only one temperature detection value, the present invention proposes a non-comparator with hysteresis The functional over-temperature protection circuit can trigger the over-temperature signal when the chip temperature is too high, turn off the internal modules of the chip, and turn on the protection; and when the temperature drops to a normal allowable range, the chip is enabled and starts to work again.

The technical scheme of the present invention is:

A hysteresis over-temperature protection circuit without comparator, comprising a positive temperature coefficient voltage generating module, an over-temperature protection core module and a hysteresis module;

The positive temperature coefficient voltage generating module is used for generating the first control voltage proportional to the absolute temperature;

The over-temperature protection core module includes a fifth resistor, a sixth resistor, a seventh resistor, a first NPN transistor, a second PNP transistor and an output drive unit;

The base of the second PNP transistor is connected to the first control voltage, the emitter is connected to the reference voltage, and the collector is connected to the base of the first NPN transistor and grounded through the series structure of the fifth resistor and the sixth resistor;

The collector of the first NPN transistor is connected to the input end of the output driving unit and connected to the power supply voltage after passing through the seventh resistor, and its emitter is grounded;

The output end of the output driving unit is used as the output end of the hysteresis over-temperature protection circuit;

The hysteresis module includes a first PNP-type transistor, a fourth PNP-type transistor, a fourth resistor and a first NMOS transistor, and the hysteresis module and the over-temperature protection core module share a sixth resistor;

The base of the first PNP transistor is connected to the first control voltage, its emitter is connected to the reference voltage, and its collector is connected to the drain of the first NMOS transistor and is connected to the emitter of the fourth PNP transistor after passing through a fourth resistor pole;

The gate of the first NMOS transistor is connected to the collector of the first NPN transistor, and the source thereof is grounded;

The base electrode of the fourth PNP type triode is connected to the base electrode of the first NPN type triode, and the collector electrode is connected to the series point of the fifth resistor and the sixth resistor.

Specifically, the positive temperature coefficient voltage generating module includes a first resistor, a second resistor, a third resistor and a third PNP transistor, wherein the first resistor is used as a trim resistor, and its resistance value is adjustable;

The first resistor and the second resistor are connected in series to form a series structure, one end of the series structure is connected to the reference voltage, and the other end is connected to the base of the first PNP type triode and the base of the second PNP type triode and passes through the third resistor. The emitter of the third PNP triode is connected; the base and the collector of the third PNP triode are grounded; the voltage across the series structure is the first control voltage proportional to the absolute temperature.

Specifically, the output drive unit includes a first inverter and a second inverter, the input end of the first inverter is used as the input end of the output drive unit, and the output end of the first inverter is connected to the input of the second inverter terminal; the output terminal of the second inverter is used as the output terminal of the output driving unit.

The working principle of the present invention is:

The present invention uses the positive temperature coefficient voltage generating module to generate a voltage proportional to the absolute temperature, which is called the first control voltage. The first control voltage proportional to the temperature can control the second PNP transistor to generate a current that increases with temperature (ie, the collector current I1 of the second PNP transistor), and I1 flows through the fifth resistor and the sixth resistor to generate a current. The voltage that increases with the increase of temperature is connected to the base of the first NPN transistor, and is used to control the opening and closing of the first NPN transistor, thereby controlling the potential of the collector of the first NPN transistor, the first NPN transistor The collector signal of the triode can be used as a criterion for judging over temperature. After passing the collector signal of the first NPN triode through the output driving unit, the output signal OUT of the hysteresis over temperature protection circuit is obtained. In addition, the hysteresis module introduced in the present invention uses the collector signal of the first NPN transistor to connect the gate of the first NMOS transistor to control the opening and closing of the first NMOS transistor, and then controls the collector of the first PNP transistor. Whether the current I2 flows out through the first NMOS transistor, or flows out through the path of the fourth resistor, the fourth PNP transistor and the sixth resistor, realizes the temperature comparison in the hysteresis interval.

The beneficial effects of the present invention are:

The present invention uses the positive temperature coefficient voltage generating module to generate a PTAT voltage proportional to the absolute temperature, that is, the first control voltage, and can read the temperature change according to the change of the first control voltage, and then firstly the first control voltage The voltage signal is converted into a current signal (ie, I1), and then into a voltage signal (ie, V _A ), and finally the voltage signal (ie, V _A ) that changes with temperature is used to control the opening and closing of the first NPN transistor NPN1 to ensure the stability of the circuit.

The invention can be used in various integrated circuit chips, switching power supplies and other products, so as to output an effective over-temperature protection signal when the product temperature is too high, and control the product to enter the temperature protection state; and when the temperature drops to a normal allowable range, the output The over-temperature unlock signal controls the product to enter the normal working state.

Compared with the traditional structure, the present invention does not use a comparator, which greatly saves the area of the chip and reduces the delay of signal transmission; in addition, the hysteresis module is introduced to solve the hysteresis caused by only setting one temperature detection value in the traditional over-temperature protection circuit. To avoid the problem that the device is easy to burn out due to the hysteresis, the reliability of the circuit is improved by setting the hysteresis comparison interval to prevent the chip temperature from being too high and affecting the life of the device.

Description of drawings

A better understanding of the following description of various embodiments of the present invention is facilitated by the following drawings, which schematically illustrate the main features of some embodiments of the present invention. These figures and examples provide some embodiments of the invention in a non-limiting, non-exhaustive manner. For the sake of brevity, the same or similar components or structures that have the same function in different figures are provided with the same reference numerals.

FIG. 1 is a schematic diagram of the principle of a conventional over-temperature protection circuit.

FIG. 2 is a specific structural diagram of a comparator-free hysteresis over-temperature protection circuit in an embodiment of the present invention.

FIG. 3 is a working state diagram of the over-temperature protection circuit of the embodiment structure when the chip is in normal operation.

FIG. 4 is a working state diagram of the over-temperature protection circuit of the embodiment structure when the chip is over-temperature.

FIG. 5 is a schematic diagram of the inversion point of a hysteresis over-temperature protection circuit without a comparator proposed by the present invention.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only some, but not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

A hysteresis over-temperature protection circuit without a comparator proposed by the present invention includes a positive temperature coefficient voltage generating module, an over-temperature protection core module and a hysteresis module; wherein the positive temperature coefficient voltage generating module is used to generate a first voltage proportional to the absolute temperature. Control voltage; as shown in FIG. 2, a realization structure of the positive temperature coefficient voltage generation module is given, but the structure of the positive temperature coefficient voltage generation module in this embodiment is not used to limit the present invention, other can generate proportional to the absolute temperature The structure of the first control voltage can also be used in the present invention. As shown in FIG. 2, the positive temperature coefficient voltage generating module in this embodiment includes a first resistor R1, a second resistor R2, a third resistor R3 and a third PNP transistor PNP3, wherein the first resistor R1 is used as a trimming resistor, and its resistance The value is adjustable; the first resistor R1 and the second resistor R2 are connected in series to form a series structure, one end of the series structure is connected to the reference voltage VREF, and the other end is connected to the base of the first PNP transistor PNP1 and the base of the second PNP transistor PNP2. The emitter of the third PNP transistor PNP3 is connected through the third resistor R3; the base and collector of the third PNP transistor PNP3 are grounded; the voltage across the series structure is the first control voltage V1 proportional to the absolute temperature.

V_{BE_PNP3}第三PNP型三极管PNP3的基极-发射极电压，具有CTAT(与绝对温度呈反比)特性，通过设置第一电阻R1、第二电阻R2和第三电阻R3的阻值比可以调节PTAT电压(即第一控制电压V1)的温度系数。In this embodiment, the voltage obtained by subtracting the voltage from the emitter of the third PNP transistor PNP3 to the ground from the reference voltage VREF and dividing it with the third resistor R3 is the trimming resistor, that is, the first resistor R1 and the resistor R2 are connected in series. The magnitude of the voltage V1 across the series structure, namely

V _{BE_PNP3} The base-emitter voltage of the third PNP transistor PNP3 has the characteristic of CTAT (inversely proportional to absolute temperature), and PTAT can be adjusted by setting the resistance ratio of the first resistor R1, the second resistor R2 and the third resistor R3 The temperature coefficient of the voltage (ie the first control voltage V1).

As shown in Figure 2, the core module of over-temperature protection includes a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, a first NPN transistor NPN1, a second PNP transistor PNP2 and an output drive unit; the second PNP transistor The base of PNP2 is connected to the first control voltage, that is, one end of the series structure is connected to the reference voltage VREF, and the other end is connected to the base of the second PNP transistor PNP2; the emitter of the second PNP transistor PNP2 is connected to the reference voltage VREF, and its collector is connected to The base of the first NPN transistor NPN1 is grounded through the series structure of the fifth resistor R5 and the sixth resistor R6; the collector of the first NPN transistor NPN1 is connected to the input end of the output drive unit and connected through the seventh resistor R7 The power supply voltage INTVCC, its emitter is grounded; the output end of the output drive unit is used as the output end of the hysteresis over-temperature protection circuit.

The PTAT voltage (ie the first control voltage V1) generated by the positive temperature coefficient voltage generation module controls the base voltage of the second PNP transistor PNP2, that is, the potential at point D, and can control the collector current I1 of the second PNP transistor PNP2 to follow. The temperature rises and rises, so that the potential of the collector of the first NPN transistor NPN1 can be controlled, and the output driving unit is used to drive the collector signal of the first NPN transistor to obtain the output of the hysteresis over-temperature protection circuit. signal OUT. As shown in FIG. 2, an implementation structure of the output driving unit is given, including a first inverter INV1 and a second inverter INV2. The input end of the first inverter INV1 is used as the input end of the output driving unit, and its The output terminal is connected to the input terminal of the second inverter INV2; the output terminal of the second inverter INV2 is used as the output terminal of the output driving unit.

The present invention introduces a hysteresis module, so that the over-temperature protection circuit not only has a temperature detection value, as shown in FIG. 2, the hysteresis module includes a first PNP type triode PNP1, a fourth PNP type triode PNP4, a fourth resistor R4 and a first NMOS transistor NMOS1, and the hysteresis module and the over-temperature protection core module share the sixth resistor R6; the base of the first PNP transistor PNP1 is connected to the first control voltage, its emitter is connected to the reference voltage VREF, and its collector is connected to the first NMOS transistor NMOS1 The drain is connected to the emitter of the fourth PNP transistor PNP4 after passing through the fourth resistor R4; the gate of the first NMOS transistor NMOS1 is connected to the collector of the first NPN transistor NPN1, and its source is grounded; the fourth PNP transistor PNP4 The base of the first NPN transistor NPN1 is connected to the base, and its collector is connected to the series point of the fifth resistor R5 and the sixth resistor R6.

The working process of the present invention will be described in detail below with reference to the accompanying drawings.

The present invention utilizes the voltage VA with PTAT (proportional to absolute temperature) characteristic (ie the base voltage of the first NPN transistor _NPN1 ) and the turn-on of the first NPN transistor NPN1 with CTAT (inversely proportional to absolute temperature) characteristic The voltage V _BE is compared, so as to control the turn-on and turn-off of the first NPN transistor NPN1 to obtain the over-temperature flag signal OUT. _The principle of the PTAT voltage VA generated in this embodiment can be obtained from FIG. 2 .

First of all, according to the above analysis, it can be known that the first control voltage V1 has PTAT characteristics, and its expression is:

Among them, V _REF is the voltage value of the externally provided reference voltage VREF, which has zero temperature characteristics, V _{BE_PNP3} is the base-emitter voltage of the third PNP transistor PNP3, and has CTAT characteristics, set the first resistor R1, the second resistor The resistance ratio of R2 and the third resistor R3 adjusts the temperature coefficient of the first control voltage V1.

Therefore, the current I1 flowing through the second PNP transistor PNP2 also has the characteristic of increasing with the increase of temperature, and the expression of its magnitude changing with the change of V1 is as follows:

where _IS is the reverse saturation current and _VT is the thermal voltage.

When the chip is working normally, the potential of point B (ie, the first NPN transistor NPN1 ) and the over-temperature flag signal OUT generated at the output end of the over-temperature protection circuit are high, as shown in FIG. 3 . At this time, the first NMOS transistor NMOS1 is turned on, and the collector current I2 of the first PNP transistor PNP1 all flows out through the first NMOS transistor NMOS1. Therefore, the expression of the voltage V _A at point A can be obtained as:

V _A- =I1·(R5+R6)

In the over-temperature state of the chip, the potential at point B and the over-temperature flag signal OUT generated at the output of the over-temperature protection circuit are low, as shown in Figure 4. At this time, the first NMOS transistor NMOS1 is turned off, and the collector current I2 of the first PNP-type transistor PNP1 all flows out through the path of the fourth resistor R4-fourth PNP-type transistor PNP4-sixth resistor R6, which introduces a hysteresis window for the circuit. Therefore, the expression of the voltage V _A at point A can be obtained as:

V _A+ =I1·(R5+R6)+I2·R6

In addition, the relationship between the turn-on voltage of the transistor NPN1 and the temperature T can be approximated as:

V _BE3 =Y ₀ -k ₀ T

Among them, Y ₀ and k ₀ represent constants. By combining the above expressions, the upper and lower limit temperature values T ₊ and T _- of the hysteresis window of temperature detection can be obtained:

The sizes of T ₊ and T ₋ can be set by adjusting the sizes of the fifth resistor R5 and the sixth resistor R6 to determine the hysteresis amount of the hysteresis window. Specifically, the specific working principle of the over-temperature protection circuit to achieve hysteresis is as follows:

When the temperature gradually changes from low to high, the first control voltage V1 increases, the current I1 flowing through the second PNP transistor PNP2 also increases, and the potential of point A increases gradually, as shown in Figure 5, when the temperature When it rises to the set overtemperature point T ₊ , the first NPN transistor NPN1 is turned on, pulling down the potential of point B, and the overtemperature flag signal OUT generated at the output end of the overtemperature protection circuit also turns down. During this process, the first NMOS transistor NMOS1 is turned on, and the collector current I2 of the first PNP transistor PNP1 all flows out through the first NMOS transistor NMOS1.

When the temperature gradually changes from high to low, the first control voltage V1 decreases, the current I1 flowing through the second PNP transistor PNP2 also decreases, and the potential at point A decreases gradually, as shown in Figure 5, when the temperature decreases When the set over-temperature point T _- is reached, the first NPN transistor NPN1 is turned off, the potential at point B is raised, and the over-temperature flag signal OUT generated at the output end of the over-temperature protection circuit also turns high. During this process, the first NMOS transistor NMOS1 is turned off, and the collector current I2 of the first PNP transistor PNP1 all flows out through the R4-PNP4-R6 path.

To sum up, the present invention proposes a hysteresis over-temperature protection circuit without a comparator, which controls the opening and closing of the first NPN transistor _NPN1 through the PTAT voltage VA proportional to the temperature, thereby obtaining the over-temperature flag. Signal OUT, and by introducing a hysteresis module, it solves the problem that the device is easily burned out due to the hysteresis caused by only setting a temperature detection value in the traditional over-temperature protection circuit, and prevents the device from being affected by excessively high chip temperature; It can be used for various integrated circuit chips , switching power supply and other products, in order to achieve when the product temperature is too high, output over-temperature protection signal, control the product to enter the temperature protection state, when the product temperature drops back to normal, output the over-temperature unlock signal, control the product to enter the normal working state.

Those skilled in the art can make various other specific modifications and combinations without departing from the essence of the present invention according to the technical teaching disclosed in the present invention, and these modifications and combinations still fall within the protection scope of the present invention.

Claims (3)

1. A hysteresis over-temperature protection circuit without a comparator is characterized by comprising a positive temperature coefficient voltage generation module, an over-temperature protection core module and a hysteresis module;

the positive temperature coefficient voltage generating module is used for generating a first control voltage in direct proportion to absolute temperature;

the over-temperature protection core module comprises a fifth resistor, a sixth resistor, a seventh resistor, a first NPN type triode, a second PNP type triode and an output driving unit;

the base electrode of the second PNP type triode is connected with the first control voltage, the emitting electrode of the second PNP type triode is connected with the reference voltage, and the collector electrode of the second PNP type triode is connected with the base electrode of the first NPN type triode and is grounded after passing through the series connection structure of the fifth resistor and the sixth resistor;

the collector of the first NPN type triode is connected with the input end of the output driving unit and is connected with power voltage after passing through the seventh resistor, and the emitter of the first NPN type triode is grounded;

the output end of the output driving unit is used as the output end of the hysteresis over-temperature protection circuit;

the hysteresis module comprises a first PNP type triode, a fourth resistor and a first NMOS (N-channel metal oxide semiconductor) tube, and the hysteresis module and the over-temperature protection core module share a sixth resistor;

the base electrode of the first PNP type triode is connected with the first control voltage, the emitting electrode of the first PNP type triode is connected with the reference voltage, and the collector electrode of the first PNP type triode is connected with the drain electrode of the first NMOS tube and is connected with the emitting electrode of the fourth PNP type triode after passing through the fourth resistor;

the grid electrode of the first NMOS tube is connected with the collector electrode of the first NPN type triode, and the source electrode of the first NMOS tube is grounded;

and the base electrode of the fourth PNP type triode is connected with the base electrode of the first NPN type triode, and the collector electrode of the fourth PNP type triode is connected with the series point of the fifth resistor and the sixth resistor.

2. The comparator-less hysteresis overheat protection circuit of claim 1, wherein the ptc voltage generating module comprises a first resistor, a second resistor, a third resistor and a third PNP transistor, wherein the first resistor is used as a trimming resistor and has an adjustable resistance;

the first resistor and the second resistor are connected in series to form a series structure, one end of the series structure is connected with the reference voltage, and the other end of the series structure is connected with a base electrode of the first PNP type triode and a base electrode of the second PNP type triode and is connected with an emitting electrode of the third PNP type triode through a third resistor; the base electrode and the collector electrode of the third PNP type triode are grounded; the voltage at the two ends of the series structure is the first control voltage which is in direct proportion to the absolute temperature.

3. The comparator-less hysteresis overheat protection circuit according to claim 1 or 2, wherein the output driving unit comprises a first inverter and a second inverter, an input terminal of the first inverter is used as an input terminal of the output driving unit, and an output terminal of the first inverter is connected to an input terminal of the second inverter; the output end of the second inverter is used as the output end of the output driving unit.

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