CN116231580B - Self-adaptive temperature difference short-circuit protection circuit and driving device - Google Patents
Self-adaptive temperature difference short-circuit protection circuit and driving device Download PDFInfo
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- CN116231580B CN116231580B CN202310405568.0A CN202310405568A CN116231580B CN 116231580 B CN116231580 B CN 116231580B CN 202310405568 A CN202310405568 A CN 202310405568A CN 116231580 B CN116231580 B CN 116231580B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H1/00—Details of emergency protective circuit arrangements
- H02H1/0007—Details of emergency protective circuit arrangements concerning the detecting means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H5/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection
- H02H5/04—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature
- H02H5/041—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal non-electric working conditions with or without subsequent reconnection responsive to abnormal temperature additionally responsive to excess current
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Abstract
The application discloses a self-adaptive temperature difference short-circuit protection circuit and a driving device, wherein the self-adaptive temperature difference short-circuit protection circuit comprises a current induction circuit and is used for receiving short-circuit current; the drive control circuit is connected with the current induction circuit and used for controlling the current induction circuit to cut off the short-circuit current when the difference value between the induction temperature corresponding to the short-circuit current and the relative temperature is larger than the dynamic temperature difference; wherein the dynamic temperature difference is inversely related to the short circuit current; the application can combine the characteristic of temperature difference between circuit components, and can be applied to short-circuit protection to realize the effect of self-adaptive adjustment, and can simultaneously avoid the problems of too early and too late short-circuit current cutoff.
Description
Technical Field
The application relates to the technical field of protection circuits, in particular to a self-adaptive temperature difference short-circuit protection circuit and a driving device.
Background
Low side switch (IGBT) drive, motor drive, etc., have relatively strict requirements for temperature control, and generally the portion near the load will be higher than the portion near the control circuit, especially in the case of over-current or short-circuit, the temperature near the load may be sixty degrees higher than the control circuit.
In some existing schemes of low-side switches or driving products, a current for driving a load is directly sensed through a resistor, and in particular, when an overcurrent protection or short-circuit protection condition is triggered, the overcurrent protection circuit or the short-circuit protection circuit cuts off the short-circuit current to play a role of short-circuit or overcurrent protection. However, in this technical solution, the short-circuit current cutting operation is usually started after the resistor detects the overcurrent or short-circuit condition, and in this process, the problems of too late closing time and untimely response are easily caused by the internal loop bandwidth and delay.
Disclosure of Invention
One of the purposes of the present application is to provide a self-adaptive temperature difference short-circuit protection circuit, so as to solve the problem that in the prior art, the short-circuit current is detected and then cut off, and the closing time is too late due to the bandwidth and delay of an inner loop.
One of the objects of the present application is to provide a driving device.
In order to achieve one of the above objects, an embodiment of the present application provides an adaptive temperature difference short-circuit protection circuit, including: a current sensing circuit for receiving a short circuit current; the drive control circuit is connected with the current induction circuit and used for controlling the current induction circuit to cut off the short-circuit current when the difference value between the induction temperature corresponding to the short-circuit current and the relative temperature is larger than the dynamic temperature difference; wherein the dynamic temperature difference is inversely related to the short circuit current.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the current sensing circuit is further configured to form a sensing current corresponding to the short-circuit current according to a proportion, and output the sensing current to the driving control circuit; the drive control circuit is also used for forming a first voltage representing the induction temperature according to the induction current, and controlling the current induction circuit to cut off the short-circuit current when a second voltage representing the relative temperature is larger than the first voltage.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the current sensing circuit further comprises an operational amplifier and a third field effect transistor; the non-inverting input end of the operational amplifier is used for receiving the short-circuit current; the output of the operational amplifier is connected with the grid electrode of the third field effect transistor, and the source electrode of the third field effect transistor and the inverting input end of the operational amplifier are grounded; and the drain electrode of the third field effect transistor is connected with the drive control circuit to form and output an induced current corresponding to the induced voltage.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the non-inverting input end of the operational amplifier is grounded through a first resistor, and the inverting input end of the operational amplifier and the source electrode of the third field effect transistor are grounded through a second resistor.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the current induction circuit comprises a first field effect tube and a second field effect tube which are connected in parallel, wherein the grid electrode of the first field effect tube is connected with the grid electrode of the second field effect tube, and the drain electrode of the first field effect tube is connected with the drain electrode of the second field effect tube and is connected with the voltage input end; and the source electrode of the first field effect transistor is connected with the non-inverting input end of the operational amplifier.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the drive control circuit comprises a comparator, a first triode and a second triode; the first triode is connected with a current induction circuit and forms a first voltage representing the induction temperature according to the induction current corresponding to the short-circuit current and the current first temperature; the second triode forms a second voltage representing the relative temperature according to the current second temperature; the current second temperature is lower than or equal to the current first temperature; two input ends of the comparator are respectively connected with the first triode and the second triode, and the output end of the comparator is connected to the current sensing circuit; the comparator is configured to control the current sensing circuit to cut off the short-circuit current when the second voltage is greater than the first voltage; wherein the difference between the first voltage and the second voltage is inversely related to the short-circuit current.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the base electrode of the first triode is connected with the collector electrode of the first triode and the inverting input end of the comparator, and the emitter electrode of the first triode is grounded; the collector of the second triode is connected with the base of the first triode and the non-inverting input end of the comparator, and the emitter of the second triode is grounded.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the drive control circuit comprises a first bias current source and a second bias current source; the first bias current source is connected with the collector electrode of the first triode and outputs a first bias current; and the second bias current source is connected with the collector electrode of the second triode and outputs a second bias current.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the first bias current value is greater than the second bias current value and/or the second transistor has a size greater than the first transistor size.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the current sensing circuit comprises a second field effect transistor, and the short-circuit current flows through the second field effect transistor; the output end of the comparator is connected to the grid electrode of the second field effect transistor and is configured to: when the second voltage is larger than the first voltage, the second field effect transistor is controlled to be turned off so as to cut off the short circuit current; the first voltage is the voltage between the base electrode and the emitter electrode of the first triode, and the second voltage is the voltage between the base electrode and the emitter electrode of the second triode.
As a further improvement of the present application, the adaptive temperature difference short-circuit protection circuit further includes: the drive control circuit also comprises an inverter, an AND gate and a buffer; the output end of the comparator is connected with the input end of the inverter, and the output end of the inverter is connected with the first input end of the AND gate; the second input end of the AND gate is connected with the first signal input end, and the output end of the AND gate is connected with the buffer; and the output end of the buffer is connected with the grid electrode of the second field effect transistor.
The application also provides a driving device, which comprises the self-adaptive temperature difference short-circuit protection circuit.
Compared with the prior art, the technical scheme provided by the application can be applied to short-circuit protection by combining the characteristic that the temperature difference exists between the circuit components so as to realize the effect of self-adaptive adjustment and simultaneously avoid the problems of too early and too late short-circuit current cutoff. Specifically, when the short-circuit protection circuit provided by the application senses that the short-circuit current is large, the dynamic temperature difference used for triggering the short-circuit protection and used as a temperature difference protection point is lower, so that the effect of triggering the large short-circuit current in time is realized; when the short-circuit current is sensed to be small, the dynamic temperature difference is adjusted to be higher, so that the effect of avoiding false triggering of short-circuit protection when the small short-circuit current which does not influence the work exists.
Drawings
Fig. 1 is a schematic diagram of a self-adaptive temperature difference protection circuit according to an embodiment of the application.
Fig. 2 is a circuit configuration diagram of an adaptive temperature difference short-circuit protection circuit according to an embodiment of the present application.
Fig. 3 is a waveform diagram of relevant parameters for implementing an adaptive temperature difference short-circuit protection circuit in accordance with an embodiment of the present application.
Detailed Description
The present application will be described in detail below with reference to specific embodiments shown in the drawings. These embodiments are not intended to limit the application and structural, methodological, or functional modifications of these embodiments that may be made by one of ordinary skill in the art are included within the scope of the application.
It should be noted that the term "comprises," "comprising," or any other variation thereof is intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Furthermore, the terms "first," "second," "third," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the working process of electric equipment, the output current is possibly too large rapidly due to the conditions of suddenly reduced downstream equivalent impedance or sudden short-circuit fault and the like, and the damage of an upstream power supply or a downstream load is further influenced, so that the current is limited in a reasonable range, particularly, a current limiting circuit or an overcurrent circuit is configured, so that the current limiting circuit or the overcurrent circuit is suitable for the working condition with higher precision requirement, and meanwhile, the cost, the circuit complexity and the compensation error or compensation effect are balanced, so that the current limiting circuit is also one of the technical problems to be solved in the technical field.
In a first embodiment of the present application, a self-adaptive temperature difference short-circuit protection circuit is provided, which can induce a short-circuit current. Based on the relative temperature at the protection circuit and the induction temperature formed by the short-circuit current at one side of the protection circuit, and cutting off the short-circuit current when the temperature difference between the induction temperature and the relative temperature is larger than the dynamic temperature difference.
Preferably, in one embodiment of the present application, the two transistors may be configured to have different sizes, or when different bias currents are applied to them, the temperature difference between the induced temperature and the relative temperature is reflected according to the temperature characteristics of the two transistors, so that the short-circuit current in the circuit is selectively turned off according to the relationship between the temperature difference of the two transistors and the dynamic temperature difference. Wherein, because the dynamic temperature difference can be adaptively changed according to the magnitude of the short-circuit current, the effect that the protection circuit adaptively cuts off the short-circuit current according to the internal temperature difference is realized.
In a first embodiment of the present application, as shown in fig. 1, the protection circuit includes:
the current sensing circuit 1 is used for receiving short-circuit current. The short-circuit current may be generated in an external circuit and flow through the current sensing circuit 1; the short-circuit current may be generated inside the current sensing circuit 1 and flow through the current sensing circuit 1.
A drive control circuit 2 connected to the current sensing circuit 1 for controlling the current sensing circuit 1 to cut off the short-circuit current when a difference between the sensed temperature corresponding to the short-circuit current and the relative temperature is greater than a dynamic temperature difference; wherein the dynamic temperature difference is inversely related to the short circuit current.
The short-circuit current flows through the current sensing circuit 1, and the drive control circuit 2 is connected to the current sensing circuit 1. At least a part of the area of the drive control circuit 2 is heated up by the short-circuit current, at least the induced temperature is raised to generate a temperature difference with respect to the relative temperature, so that the relation between the temperature difference and the dynamic temperature difference can be compared to determine whether to control the short-circuit current to be cut off.
Preferably, when a component whose temperature is related to the short-circuit current is disposed in the drive control circuit 2, the component may be specifically a portion of the component that is relatively close to the current sensing circuit 1, and the component is more distant from the current sensing circuit 1, and the component is slower or does not heat; in other words, even if the relative temperature and the sensed temperature rise simultaneously, the temperature difference can be formed based on the speed of the temperature rise thereof.
In a preferred implementation manner of the first embodiment of the present application, a portion of the driving control circuit 2 close to the current sensing circuit 1 may be configured to form the sensing temperature, and a portion of the driving control circuit 2 far from the current sensing circuit 1 may be configured to form the relative temperature, so that the current sensing circuit 1 is controlled to cut off the short-circuit current based on a comparison result between a temperature difference between the two and the dynamic temperature difference.
Therefore, the application uses the temperature and current characteristics of the components and adopts temperature difference control to cut off the short-circuit current, thereby effectively avoiding the time delay problem; the dynamic temperature difference changes along with the change of the short-circuit current, is in negative correlation with the short-circuit current, can adaptively adjust the trigger value for cutting off the short-circuit current, improves the general applicability of the scheme and expands the application scene.
In the first embodiment of the present application, the dynamic temperature difference is inversely related to the short-circuit current, which is characterized by that the larger the short-circuit current is, the smaller the value of the dynamic temperature difference is, and the easier the temperature difference between the sensing temperature and the relative temperature is to approach the dynamic temperature difference, so that the easier the driving control circuit 2 is triggered to control the current sensing circuit 1 to cut off the short-circuit current.
For example: when the short-circuit current is Im, the dynamic temperature difference is set to 40 ℃, and the induction temperature and the relative temperature are respectively raised in response to the short-circuit current Im (the induction temperature is raised faster than the relative temperature), or the induction temperature is raised but the relative temperature is not raised; until the difference between the sensed temperature and the relative temperature is 40 ℃, the trigger drive control circuit 2 controls the current sensing circuit 1 to cut off the short-circuit current.
Also for example: when the induced current is 2Im, the dynamic temperature difference is set to 25 ℃, and the induced temperature and the relative temperature are respectively raised in response to the short-circuit current 2Im (the induced temperature is raised faster than the relative temperature), or the induced temperature is raised but the relative temperature is not raised; until the difference between the sensed temperature and the relative temperature is 25 ℃, the trigger drive control circuit 2 controls the current sensing circuit 1 to cut off the short-circuit current.
The separation looks like the two examples above, and as the sensed temperature increases, the difference between the sensed temperature and the relative temperature gradually increases to more easily approach the corresponding dynamic temperature difference. As can be seen from the above two examples, the smaller the dynamic temperature difference is, the easier the drive control circuit 2 is triggered to control the current sensing circuit 1 to cut off the short-circuit current. In summary, the threshold condition for triggering and cutting off the short-circuit current changes along with the change of the short-circuit current, so that the short-circuit current can be rapidly triggered and cut off when the short-circuit current is overlarge, and the short-circuit current is prevented from affecting the whole short-circuit or burning out components; in contrast, when the short circuit current is too small and the operation is not influenced, the self-adaptive increase of the threshold value is triggered, and the influence on the normal operation of the short circuit caused by the false turn-off is avoided.
In the first embodiment of the present application, the current sensing circuit 1 is further configured to form a sensing current corresponding to the short-circuit current in proportion and output the sensing current to the drive control circuit 2. Preferably, the induced current is smaller than the short-circuit current.
The short-circuit current may be related to the induced temperature by the induced current, for example, the induced current is generated from the current sensing circuit 1 and flows to the connection terminal side of the driving control circuit 2 to form the induced temperature at the corresponding component. The short-circuit current may be related to the relative temperature by the induced current, for example, the induced current flows to a side of the drive control circuit 2 away from the connection terminal, so as to form the relative temperature at the corresponding component. Wherein the connection end represents an end part of the drive control circuit 2 for connection with the current sensing circuit or an end part of the drive control circuit 2 close to a short-circuit current generating source.
The drive control circuit 2 is further configured to form a first voltage representing the induced temperature according to the induced current, and control the current sensing circuit 1 to cut off the short-circuit current when a second voltage representing the relative temperature is greater than the first voltage. Therefore, abstract induction temperature and relative temperature can be converted into first voltage and second voltage with the characteristics, and the realization of a short-circuit protection function is facilitated.
Preferably, the first voltage and the second voltage may also be used as driving sources for controlling the current sensing circuit 1 to cut off the short-circuit current. The first voltage is: a voltage value inversely related to the sensed temperature, the second voltage being: a voltage value inversely related to the relative temperature. Specifically, the sensed temperature increases and the first voltage decreases; the relative temperature increases and the second voltage decreases.
In the first embodiment of the present application, the current sensing circuit 1 includes an operational amplifier 11 and a third fet 12, as shown in fig. 2; the non-inverting input of the operational amplifier 11 is arranged to receive the short-circuit current. In one embodiment, the non-inverting input of the operational amplifier 11 may be used to receive an induced voltage corresponding to the short-circuit current.
The output of the operational amplifier 11 is connected to the gate of the third field effect transistor 12, the source of the third field effect transistor 12 is grounded, and the inverting input of the operational amplifier 11 is grounded. The drain electrode of the third fet 12 is connected to the drive control circuit 2, and the induced current corresponding to the induced voltage is formed and outputted. In this embodiment, the operational amplifier 11 and the third fet 12 may reduce the short-circuit current to a level that the drive control circuit 2 can accept and perform feedback control, so as to avoid that the excessive short-circuit current affects the operation of the drive control circuit 2, and also avoid that the excessive short-circuit current burns out components in the drive control circuit 2.
In the first embodiment of the present application, as shown in fig. 2, the non-inverting input terminal of the operational amplifier 11 is grounded through the first resistor R1; thus, the induced voltage is received through the first resistor R1. The inverting input end of the operational amplifier 11 and the source electrode of the third field effect transistor 12 are grounded through a second resistor R2; in this way, the induced voltage is converted into an induced current through the second resistor R2.
In the first embodiment of the present application, the first fet 13 and the second fet 14 are further included in parallel, as shown in fig. 2, where the gate of the first fet 13 is connected to the gate of the second fet 14. The parallel connection may specifically be that the drain electrode of the first field effect transistor 13 and the drain electrode of the second field effect transistor 14 are connected to the voltage input terminal VIN, the source electrode of the first field effect transistor 13 is directly or indirectly connected to the low level (preferably, grounded through the first resistor R1), and the source electrode of the second field effect transistor 14 is directly or indirectly connected to the low level. In this way, the first field effect tube 13 and the second field effect tube 14 are connected to form a mirror circuit, and the current input to one side of the operational amplifier 11 can be adjusted by adjusting the mirror proportion between the two field effect tubes. Preferably, the mirror circuit may be configured to reduce the magnitude of the short-circuit current and output the short-circuit current to the operational amplifier 11, so that the short-circuit current may be utilized by the operational amplifier 11; it is also possible to avoid the induced voltage level formed by the short-circuit current conversion from being too large to be suitable for the operational amplifier 11.
In one embodiment of the first embodiment of the present application, the second fet 14 may be used as a main power tube, and the first fet 13 may be used as a mirror power tube. The size of the main power tube is n times of that of the mirror power tube (or called the mirror proportion is n). Preferably, n is 100 to 1000.
In this way, the mirror circuit formed by the first field effect transistor 13 and the second field effect transistor 14 serves as a first-order current reduction of the short-circuit current, and the magnitude of the short-circuit current is reduced. The short-circuit current flows through a branch circuit where the main power tube is located, and forms an image current in the branch circuit where the image power tube is located, wherein the short-circuit current is n times of the image current;
then, the mirror current flows into the operational amplifier 11, and the operational amplifier 11 and the third field effect transistor 12 act as a second order down-flow, further reducing the magnitude of the short-circuit current. Specifically, the non-inverting input terminal of the operational amplifier 11 receives the mirror current, and specifically receives the mirror current in a manner of receiving the induced voltage formed on the first resistor R1, so as to achieve the effect of receiving the short-circuit current, the operational amplifier 11 and the third field effect transistor 12 are combined to form a constant current source, and the induced current is formed and outputted to the driving control circuit 2 with the aid of the second resistor R2.
The source of the first field effect transistor 13 is connected to the non-inverting input terminal of the operational amplifier 11, and is used for outputting an induced voltage corresponding to the short-circuit current.
Preferably, the non-inverting input terminal of the operational amplifier 11 is grounded through the first resistor R1, and the induced voltage can be received through the first resistor R1. Wherein, between short-circuit current Im, induced voltage Vsense, first resistance R1 and mirror proportion n, can satisfy at least:
Vsense＝Im*R1/n。
the inverting input terminal of the operational amplifier 11 and the source of the third fet 12 are grounded through the second resistor R2. Specifically, the induced voltage is converted into the induced current Ioc through the series connection of the second resistor R2 and the third fet 12. Wherein, between induced voltage Vsense, second resistance R2 and induced current Ioc, at least can satisfy:
Ioc＝Vsense/R2。
in one embodiment of the present application, the driving control circuit 2 receives the induced current, and a voltage difference may be generated in the driving control circuit 2. The voltage difference is a difference between the first voltage and the second voltage, the first voltage is indicative of the sensed temperature, and the second voltage is indicative of the relative temperature. With the temperature rising, when the second voltage is greater than the first voltage, the current induction circuit 1 is triggered and controlled to cut off the short-circuit current.
In the second embodiment of the present application, the driving control circuit 2 includes a comparator 21, a first transistor 22 and a second transistor 23. As shown in fig. 2, it is preferable that the first transistor 22 is close to the current sensing circuit 1, is more affected by the sensing current, the mirror current or the short-circuit current, and the first transistor 22 is heated up faster and at a higher temperature. Preferably, the second transistor 23 is far from the current sensing circuit 1, is less affected by said sensing current, mirror current or short-circuit current, and the second transistor 23 heats up slowly or not, but at a lower temperature. In this way, by using the relation between the voltage and the temperature characteristics of the first triode 22 and the second triode 23 and combining the comparator 21, the temperature difference between the sensing temperature and the relative temperature can be reflected as the voltage difference between the two input voltages of the comparator 21, and the cut-off control of the short-circuit current is realized through the comparator 21; that is, when the temperature difference reaches a threshold value set by the dynamic temperature difference, the short-circuit current is cut off rapidly, so that the problem of untimely turn-off due to time delay is avoided.
In the second embodiment of the present application, the first voltage may be formed at the first triode 22, and the second voltage may be formed at the second triode 23; the first voltage and the second voltage are affected by the temperature at the first transistor 22 and the second transistor 23, respectively. Further, the comparison and control output between the sensed temperature and the relative temperature can be realized by the first voltage and the second voltage input to the comparator 21. Specific:
the first triode 22 is connected with the current sensing circuit 1 and forms the first voltage representing the sensing temperature according to the sensing current corresponding to the short-circuit current and the current first temperature; the first voltage is affected by the sensed temperature, the sensed temperature increases, and the first voltage decreases. Wherein, between the first voltage temp_vsense and the current first temperature T0 at the first transistor 22, at least:
Temp_Vsense＝VBE0-K0*T0。
wherein VBE0 is the voltage between the base and the emitter of the first triode 22 at normal temperature; k0 is the temperature coefficient of the first transistor 22. Wherein the first temperature T0 may be the sensed temperature.
The second transistor 23 forms said second voltage indicative of said relative temperature in dependence of the current second temperature.
In one embodiment of the application, the current second temperature is less than or equal to the current first temperature; the second voltage is affected by the relative temperature, the relative temperature increases, and the second voltage decreases. Wherein, between the second voltage temp_vref and the current second temperature T1 at the second triode 23, at least:
Temp_Vref＝VBE1-K1*T1。
wherein VBE1 is the voltage between the base and the emitter of the second triode 23 at normal temperature; k1 is the temperature coefficient of the second transistor 23. Wherein the second temperature T1 may be the relative temperature.
The two input terminals of the comparator 21 are respectively connected to the first triode 22 and the second triode 23, and the output terminal of the comparator 21 is connected to the current sensing circuit 1. The comparator 21 is configured to: when the second voltage is greater than the first voltage, the current sensing circuit 1 is controlled to cut off the short-circuit current. In this way, the comparator 21 outputs a high-low level by comparing the input first voltage and the second voltage, and cuts off the short-circuit current rapidly, thereby avoiding the untimely influence of the turn-off on the operation of the circuit.
During the gradual change of the short-circuit current, the temperature difference trigger value of the first triode 22 and the second triode 23, that is, the value of the dynamic temperature difference, also gradually changes. In other words, the difference between the first voltage and the second voltage also gradually changes. It can be understood that: the short-circuit current increases, the dynamic temperature difference decreases, and at least the first transistor 22 heats up; the first transistor 22 warms up such that the first voltage drops and approaches the second voltage such that the difference between the first voltage and the second voltage, which characterizes the dynamic temperature difference, also decreases; when the second voltage drops beyond the critical point "the first voltage and the second voltage are equal", the sensed temperature is characterized as having risen to such an extent that the difference between the sensed temperature and the relative temperature is greater than the dynamic temperature difference ", so that the comparator 21 turns over and intercepts the short-circuit current to protect the circuit.
Wherein, when K' =k0=k1, at least the difference avbe between the first voltage and the second voltage and the difference Dt between the sensed temperature and the relative temperature satisfies:
ΔVBE＝Dt*K’。
wherein K '=k0=k1 characterizes that the temperature coefficient of the first transistor 22 is equal to the temperature coefficient of the second transistor 23 and equal to the temperature coefficient K'.
Thus, the abstract criterion of 'the difference between the sensed temperature and the relative temperature is larger than the dynamic temperature difference' is converted into the explicit criterion of 'the second voltage is larger than the first voltage'. And the abstract relation between the temperature threshold value of the dynamic voltage difference and the short-circuit current is expressed as the relation between the difference value of the first voltage and the second voltage and the short-circuit current.
In the second embodiment of the present application, the first triode 22 is connected to the sensing circuit through its collector, the base of the first triode 22 is connected to the collector of the first triode 22, the base of the first triode 22 is connected to the inverting input terminal of the comparator 21, and the emitter of the first triode 22 is grounded. The collector of the second triode 23 is connected with the base of the first triode 22, the collector of the second triode 23 is connected with the non-inverting input end of the comparator 21, and the emitter of the second triode 23 is grounded.
Thus, the first transistor 22 and the second transistor 23 can output the voltages between the base and the emitter to the comparator 21 according to their own temperature-voltage relationship characteristics. Since the voltage between the base and the emitter changes with the change of the temperature, when the temperature reaches a specific value, that is, when the temperature difference between the first triode 22 and the second triode 23 is greater than the dynamic temperature difference, the trigger comparator 21 turns over the level to cut off the short-circuit current, so that the damage of the short-circuit current is reduced more rapidly. When the short-circuit current is small or harmless, the dynamic temperature difference threshold between the first triode 22 and the second triode 23 is increased accordingly, the level condition triggering the comparator 21 to flip is raised accordingly, and the small short-circuit current is not cut off, so that the circuit is prevented from being turned off by mistake.
In the second embodiment of the present application, the driving control circuit 2 further includes a first bias current source and a second bias current source. The first bias current source is connected with the collector electrode of the first triode 22 and outputs a first bias current; the second bias current source is connected to the collector of the second triode 23 and outputs the second bias current. As such, the first and second bias current sources power the first and second transistors 22 and 23, respectively.
In a preferred implementation of the embodiment of the present application, the value of the first bias current is greater than the value of the second bias current, and/or the size of the second transistor 23 is greater than the size of the first transistor 22. Thus, the first voltage is made larger than the second voltage at normal temperature.
In a preferred implementation of the embodiment of the present application, the size of the second transistor 23 may be 4 times that of the first transistor 22; the first bias current value is 8 times the second bias current value.
When the relation of 4 times is satisfied between the sizes of the two triodes and the relation of 8 times is satisfied between the sizes of the two bias current values, the difference value delta VBE between the first voltage and the second voltage at least satisfies the following conditions:
ΔVBE＝VT*ln4*8＝VT*ln32。
where ln32 represents 32 times the current density of the first transistor 22 than the second transistor 23; vt=kt/Q is the einstein relationship of microscopic currents, and at normal temperature, i.e., t=300K, vt=kt/q=26 mV.
Further, the derivative of ΔVBE on temperature may be obtained:
ΔVBE'/ΔT＝K/Q*ln32。
the method can be obtained by the formula: avbe' exhibits a positive temperature coefficient. That is, the difference avbe between the first voltage and the second voltage increases with an increase in temperature.
Further, in the second embodiment of the present application, when the first voltage or the second voltage characterizes the inter-base and inter-emitter voltages VBE of the corresponding transistor, at least the following is satisfied between the base and inter-emitter voltages VBE and VT:
VBE＝VT*ln(Ic/Is)。
wherein Is the saturated current of the triode; ic is the collector current of the transistor.
Further, the saturation current Is of the triode may at least satisfy:
Is＝bT^(4+m)*exp(-Eg/KT)。
wherein m= -3/2; b is a proportionality coefficient; eg is the forbidden bandwidth of the semiconductor; k is the Boltzmann constant.
The VBE can obtain the negative temperature coefficient voltage K≡after deriving the temperature:
K^＝ΔVBE/ΔT＝(VBE1-(4+m)VT-Eg/q)/T。
the VBE1 is a triode voltage at normal temperature, and it can be seen that the negative temperature coefficient voltage K is related to the inter-base and inter-emitter voltage VBE of the triode and the temperature T, and the inter-base and inter-emitter voltage VBE of the triode is related to the collector current Ic of the triode or the size of the triode.
From the above, it can be seen that the voltage VBE between the base and the emitter of the transistor decreases with the increase of the current temperature (the first temperature, the sensing temperature, or the second temperature, the relative temperature).
According to the formula: dt=avbe/K. The following steps are obtained: as the first transistor 22 and the second transistor 23 are heated differently, the difference between the first voltage and the second voltage increases as the dynamic temperature difference between the first transistor 22 and the second transistor 23 increases, based on the difference in size or the difference in bias current provided.
In the second embodiment of the present application, the voltage difference between the bases and the emitters of the first transistor 22 and the second transistor 23 (i.e., the difference avbe between the first voltage and the second voltage) is:
ΔVBE＝KT/Q*ln(4*(Ibias1-Ioc)/Ibias0)。
wherein Ibias1 is the first bias current value; ibias0 is the second bias current value; ioc is the induced current; 4 characterizes the second transistor 23 as having a size 4 times that of the first transistor 22.
For example, if KT/q=26 mV, and Ibias 1=8×ibias0, avbe=90 mV at ioc=0; when ioc=3 Ibias0, avbe=54 mV; when ioc=7ibias 0, avbe=37 mV.
Heretofore, the temperature coefficients of the first transistor 22 and the second transistor 23 may be adjusted by sizing the first transistor 22 and the second transistor 23. In the scenario described above in this embodiment, the temperature coefficient of the first transistor 22 may be adjusted to 1.8mV/C; the temperature coefficient of the second transistor 23 can be adjusted to 1.5mV/C according to the density relationship of the first transistor 22 and the second transistor 23.
Further, assuming that the temperature of the second transistor 23 is kept constant or changed little when the temperature of the first transistor 22 is changed, the driving control circuit 2 cuts off the short-circuit current when ioc=0, if the temperature of the first transistor 22 is higher by dt=90/1.8=50 ℃ than the temperature of the second transistor 23.
In other words, when ioc=0, only when the difference between the sensed temperature and the relative temperature exceeds 50 ℃ (the current dynamic temperature difference), the first voltage temp_vsense is reduced to a critical point exceeding "temp_vref=temp_vsense", so that the comparator 21 is inverted, thereby controlling the current sensing circuit 1 to cut off the short-circuit current.
Assuming an increase in Ioc, ioc=7ibias 0, dt=37/1.8≡20 ℃. At this time, only when the difference between the sensed temperature and the relative temperature exceeds 20 ℃ (the current dynamic temperature difference), the first voltage temp_vsense is reduced to a critical point exceeding "temp_vref=temp_vsense", so that the comparator 21 is turned over, thereby controlling the current sensing circuit 1 to cut off the short-circuit current.
The beneficial effects of the application are further explained with reference to fig. 3:
when the short-circuit current rises to ioc1=7ibias 0, the value of ioc1 is larger, the change slope is larger, the dynamic temperature difference is set to be 20 ℃, and the short-circuit protection can be triggered before ioc=10a < ioc1. The short-circuit current is cut off in advance before the Ioc rises to the Ioc1, so that the short-circuit protection response time is shortened, and the short-circuit protection efficiency is improved. Continuing, both Ioc2 and Ioc3 are smaller than Ioc1, for example, setting the dynamic temperature difference to 40 ℃ for Ioc2 and 60 ℃ for Ioc3, so that the short-circuit current can be prevented from being cut off too early or too late.
In summary, the dynamic temperature difference (or the critical point of achievement temp_vref=temp_vsense) is dynamically adjusted according to the short-circuit current (or the induced current), so that the correlation between the temperature difference control and the power tube current can be established, that is, the larger the power tube current is, the lower the temperature difference required to trigger the short-circuit protection is, the self-adaptive short-circuit protection is realized, and the premature or too late triggering is avoided.
In the third embodiment of the present application, the current sensing circuit 1 includes the second field effect transistor 14, and the short-circuit current flows through the second field effect transistor 14.
The output of the comparator 21 is connected to the gate of the second fet 14 and is configured to: when the second voltage is greater than the first voltage, the second fet 14 is controlled to turn off to cut off the short-circuit current. Therefore, the cutting-off effect of the short-circuit current can be realized by directly turning off the switch on the branch where the short-circuit current is located.
In one embodiment, the second voltage is coupled to the non-inverting input of the comparator 21 and the first voltage is coupled to the inverting input of the comparator 21. The first voltage may be a voltage between the base and the emitter of the first triode 22, and the second voltage may be a voltage between the base and the emitter of the second triode 23.
In other words, the first transistor 22 is connected to the current sensing circuit 1, and forms a first voltage indicative of the sensed temperature according to the sensed current corresponding to the short-circuit current and the present first temperature; the second transistor 23 forms a second voltage representative of the relative temperature in dependence on the current second temperature; wherein the current second temperature is less than or equal to the current first temperature. The two input ends of the comparator 21 are respectively connected with the first triode 22 and the second triode 23, and the output end of the comparator 21 is connected to the current sensing circuit. The comparator 21 is configured to control the current sensing circuit to cut off the short-circuit current when the second voltage is greater than the first voltage; wherein the difference between the first voltage and the second voltage is positively correlated with the short circuit current.
Of course, in the embodiment where the first fet 13 and the second fet 14 form a mirror circuit, the output end of the comparator 21 may also be connected to the gate of the first fet 13, so as to intercept the short-circuit current by intercepting the mirror current on the branch where the first fet 13 is located.
In the present embodiment, the drive control circuit 2 further includes an inverter 24, an and gate 25, and a buffer 26; the output end of the comparator 21 is connected with the input end of the inverter 24, and the output end of the inverter 24 is connected with the first input end of the AND gate 25; a second input end of the AND gate 25 is connected with a first signal input end 251, and an output end of the AND gate 25 is connected with a buffer 26; the output of buffer 26 is connected to the gate of second fet 14.
In this way, when the output of the comparator 21 is high, the output is turned to low via the inverter 24, the low is output to low via the and gate 25, and the second fet 14 is turned off via the buffer 26. Buffer 26 here serves to connect the output of and gate 25 to the gate of second fet 14, so that the output of and gate 25 can turn off second fet 14.
Of course, between the above three embodiments provided by the present application, features in the above three embodiments do not necessarily exist independently of each other. The above embodiments may be combined with each other to form a preferred embodiment, and the above features may also be combined with each other to form a more detailed connection relationship.
In a fourth embodiment of the present application, a driving device is provided, where the driving device includes the adaptive temperature difference short-circuit protection circuit in the above embodiment.
In summary, the technical scheme provided by the application can be applied to short-circuit protection by combining the characteristics of temperature difference among circuit components so as to realize the effect of self-adaptive adjustment and simultaneously avoid the problems of too early and too late short-circuit current interruption. Specifically, when the short-circuit protection circuit provided by the application senses that the short-circuit current is large, the dynamic temperature difference used for triggering the short-circuit protection and used as a temperature difference protection point is lower, so that the effect of triggering the large short-circuit current in time is realized; when the short-circuit current is sensed to be small, the dynamic temperature difference is adjusted to be higher, so that the effect of avoiding false triggering of short-circuit protection when the small short-circuit current which does not influence the work exists.
Furthermore, the application mainly adopts the temperature difference triggering of two triodes, and adopts a digital circuit to turn on or off the short-circuit current. The self-adaptive temperature difference protection is realized by using two triodes, the triodes with different sizes are set based on the attribute of the voltage value and the temperature change of the triodes, the different temperature properties generated by different distances between the triodes and the heating source are utilized, the voltage relation between the temperature and the triodes is combined, the high-low level is output through the comparator, the comparator is triggered to output the high level when the voltage of the two triodes is overturned, namely, the comparator overturning signal is triggered at the moment of voltage size replacement of the two triodes, and the comparison of the voltage value is output as a digital signal by the digital circuit so as to turn off the circuit.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting thereof; although the application has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application.
Claims (8)
1. An adaptive temperature difference short-circuit protection circuit, comprising:
a current sensing circuit for receiving a short circuit current;
the drive control circuit is connected with the current induction circuit and used for controlling the current induction circuit to cut off the short-circuit current when the difference value between the induction temperature corresponding to the short-circuit current and the relative temperature is larger than the dynamic temperature difference; wherein the dynamic temperature difference is inversely related to the short circuit current;
the current sensing circuit further comprises an operational amplifier and a third field effect transistor; the non-inverting input end of the operational amplifier is used for receiving the short-circuit current;
the output of the operational amplifier is connected with the grid electrode of the third field effect transistor, and the source electrode of the third field effect transistor and the inverting input end of the operational amplifier are grounded; the drain electrode of the third field effect transistor is connected with the drive control circuit to form and output an induced current corresponding to the induced voltage;
the non-inverting input end of the operational amplifier is grounded through a first resistor, and the inverting input end of the operational amplifier and the source electrode of the third field effect transistor are grounded through a second resistor;
the drive control circuit comprises a comparator, a first triode and a second triode;
the first triode is connected with a current induction circuit and forms a first voltage representing the induction temperature according to the induction current corresponding to the short-circuit current and the current first temperature;
the second triode forms a second voltage representing the relative temperature according to the current second temperature; the current second temperature is lower than or equal to the current first temperature;
two input ends of the comparator are respectively connected with the first triode and the second triode, and the output end of the comparator is connected to the current sensing circuit; the comparator is configured to control the current sensing circuit to cut off the short-circuit current when the second voltage is greater than the first voltage; wherein the difference between the first voltage and the second voltage is inversely related to the short-circuit current;
the base electrode of the first triode is connected with the collector electrode of the first triode and the inverting input end of the comparator, and the emitter electrode of the first triode is grounded;
the collector of the second triode is connected with the base of the second triode and the non-inverting input end of the comparator, and the emitter of the second triode is grounded.
2. The adaptive temperature difference short circuit protection circuit according to claim 1, wherein the current sensing circuit is further configured to proportionally form a sensing current corresponding to the short circuit current and output the sensing current to the drive control circuit;
the drive control circuit is also used for forming a first voltage representing the induction temperature according to the induction current, and controlling the current induction circuit to cut off the short-circuit current when a second voltage representing the relative temperature is larger than the first voltage.
3. The adaptive temperature difference short circuit protection circuit according to claim 1, wherein the current sensing circuit comprises a first field effect transistor and a second field effect transistor which are connected in parallel, the gate of the first field effect transistor is connected with the gate of the second field effect transistor, and the drain of the first field effect transistor is connected with the drain of the second field effect transistor at a voltage input end;
and the source electrode of the first field effect transistor is connected with the non-inverting input end of the operational amplifier.
4. The adaptive temperature differential short circuit protection circuit of claim 1, wherein the drive control circuit comprises a first bias current source and a second bias current source;
the first bias current source is connected with the collector electrode of the first triode and outputs a first bias current; and the second bias current source is connected with the collector electrode of the second triode and outputs a second bias current.
5. The adaptive temperature differential short-circuit protection circuit of claim 4, wherein a first bias current value is greater than a second bias current value and/or a size of the second transistor is greater than the first transistor size.
6. The adaptive temperature differential short circuit protection circuit of claim 1, wherein the current sensing circuit comprises a second field effect transistor through which the short circuit current flows;
the output end of the comparator is connected to the grid electrode of the second field effect transistor and is configured to: when the second voltage is larger than the first voltage, the second field effect transistor is controlled to be turned off so as to cut off the short circuit current; the first voltage is the voltage between the base electrode and the emitter electrode of the first triode, and the second voltage is the voltage between the base electrode and the emitter electrode of the second triode.
7. The adaptive temperature differential short-circuit protection circuit according to claim 6, wherein the drive control circuit further comprises an inverter, an and gate, and a buffer; the output end of the comparator is connected with the input end of the inverter, and the output end of the inverter is connected with the first input end of the AND gate; the second input end of the AND gate is connected with the first signal input end, and the output end of the AND gate is connected with the buffer; and the output end of the buffer is connected with the grid electrode of the second field effect transistor.
8. A drive device comprising the adaptive temperature differential short-circuit protection circuit of any one of claims 1-7.
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| CN115085704A (en) * | 2022-07-06 | 2022-09-20 | 电子科技大学 | Protection circuit applied to intelligent power switch |
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| CN105491753A (en) * | 2014-10-02 | 2016-04-13 | 瑞萨电子株式会社 | Semiconductor device, and on-vehicle electronic device and automobile each including semiconductor device |
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