CN112736859B - Overcurrent diagnosis processing circuit and low-side driving circuit - Google Patents
Overcurrent diagnosis processing circuit and low-side driving circuit Download PDFInfo
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- CN112736859B CN112736859B CN202011595337.3A CN202011595337A CN112736859B CN 112736859 B CN112736859 B CN 112736859B CN 202011595337 A CN202011595337 A CN 202011595337A CN 112736859 B CN112736859 B CN 112736859B
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- 238000003745 diagnosis Methods 0.000 title claims abstract description 44
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- 239000003990 capacitor Substances 0.000 claims description 40
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
- H02H7/20—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for electronic equipment
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
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Abstract
The invention discloses an overcurrent diagnosis processing circuit and a low-side driving circuit, which are matched with each other by a current limiting transistor and a transistor control circuit to adjust the current flowing through a low-side switch when the low-side driving circuit has an overcurrent fault. Through the cooperation of the current limiting transistor and the transistor control circuit, the current limiting protection of the low-side switch can be realized when the low-side driving circuit has an overcurrent fault. Since the fault diagnosis and processing process does not use MCU, and the switching speed of the current-limiting transistor is nanosecond, when overcurrent fault occurs, the hardware response time of the overcurrent fault diagnosis processing circuit is longest and is only microsecond. No software is needed to do any operation, the response is quick, the power consumption requirement on the circuit is low, and therefore damage to circuit devices is avoided, and the safety is improved.
Description
Technical Field
The invention relates to the field of circuits, in particular to an overcurrent diagnosis processing circuit and a low-side driving circuit.
Background
The low side driving circuit is a circuit design for providing a long high level signal, a long low level signal or PWM (Pulse width modulation) signals to other controllers, and referring to fig. 1, fig. 1 is a typical low side driving circuit. Wherein U1 is a low-side switch; r1 is a pull-down resistor, and is in a default pull-down state before driving; r2 is a current limiting resistor, C1 is an input filter capacitor, and R2 and C1 form a filter circuit; r3 is a current-limiting voltage-dividing resistor, R4 is a pull-down voltage-dividing resistor, and R3 and R4 form a voltage-dividing diagnosis circuit; r5 is a current limiting resistor, C2 is a filter capacitor of the diagnosis circuit, and R5 and C2 form a filter circuit; d1 is a bi-directional ESD (Electro-STATIC DISCHARGE) diode, C3 is an ESD capacitor, and D1 and C3 are used to protect the low-side switch from damage during ESD shock. In is a control input signal of the circuit and is derived from the output of the MCU (Microcontroller Unit, control chip); diagOut is a diagnostic output signal of the circuit, and the MCU judges whether a fault exists by sampling the voltage state of DiagOut; r load is a pull-up resistor at the load end, which is connected with Output of the controller, and Output is an Output signal of the controller, and provides a voltage state for the load end.
Currently, the fault diagnosis of the low-side driving circuit mainly includes SCB (short circuit to power supply), SCG (short circuit to ground) and OL (open circuit), and the diagnosis requirements are different for different application situations. When the low-side driving circuit is applied to Output a long high level signal and a long low level signal, if the low-side switch is turned off (Output is long and high), the MCU diagnoses whether the SCG and OL faults exist in the low-side driving circuit by sampling DiagOut voltage; if the low side switch is on (Output is low), the MCU diagnoses whether the SCB fault exists in the low side drive circuit by sampling DiagOut voltage analog values. When the low-side driving circuit is applied to output the PWM signal, the MCU can diagnose whether SCB, SCG, and OL are present in the low-side driving circuit by sampling the voltage state of Diagout in one sampling period. The MCU diagnoses the corresponding faults through sampling DiagOut the voltage state and makes the corresponding post-processing. The diagnosis strategy of the low-side driving circuit is that the MCU samples DiagOut voltage states through an AD port to determine whether faults exist or not: for a low-side circuit outputting a normally high and normally low level signal, when a low-side switch is turned on, if no fault occurs, the MCU should sample a voltage value lower than a certain threshold, and if the MCU samples DiagOut voltage higher than the threshold, the SCB fault of the low-side driving circuit can be judged; for a low-side driving circuit outputting PWM signals, when the high-low level changes in the sampling period, the low-side driving circuit is judged to be normal, and when the I/O port of the MCU is kept high by DiagOut voltage in the sampling period, the low-side driving circuit is judged to have SCB fault.
Among the three types of faults SCB (short to power), SCG (short to ground) and OL (open), SCB has the greatest damage to the controller when the low-side drive circuit is in the on state. The inventors found that the following problems exist when using the fault diagnosis circuit proposed in the prior art: if an SCB fault occurs, the diagnosis and processing time of the circuit needs several milliseconds or even tens of milliseconds, and the short-circuit current during the fault can reach tens of amperes, and the following risks are caused by the large current impact above the millisecond level: burn out low side switches, burn out PCB traces, and other security risk issues raised by shutdown times exceeding those required for functional security. In summary, the failure diagnosis circuit proposed in the prior art has poor timeliness of failure confirmation and shutdown, and risks damaging circuit devices.
Therefore, a solution that can improve the failure confirmation and the shutdown timeliness needs to be proposed.
It should be noted that the information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.
Disclosure of Invention
The invention aims to provide an overcurrent diagnosis processing circuit and a low-side driving circuit, which are used for solving the problems that in the prior art, the timeliness of fault confirmation and turn-off is poor and the risk of damaging circuit devices exists.
In order to solve the above technical problem, the present invention provides an overcurrent diagnosis processing circuit for an overcurrent diagnosis processing of a low-side driving circuit, the overcurrent diagnosis processing circuit comprising:
a current limiting transistor configured to adjust a magnitude of a current flowing through a low side switch in the low side driving circuit;
A transistor control circuit configured to implement a low-side drive function and adjust an operating state of the current-limiting transistor based on a current flowing through the low-side switch;
The working state of the current limiting transistor comprises an on state and an off state, and the current limiting transistor is matched with the transistor control circuit to adjust the current flowing through the low-side switch when the low-side driving circuit has an overcurrent fault.
Optionally, the current limiting transistor adjusts the magnitude of the current flowing through the low-side switch by turning on or off;
When the current flowing through the low-side switch is smaller than a set value, the current limiting transistor is in an off state, and when the low-side switch has an overcurrent fault, the current limiting transistor is in an on state so as to reduce the current flowing through the low-side switch.
Optionally, when the current flowing through the low-side switch is greater than a first threshold, the transistor control circuit adjusts the current limiting transistor to be in a conductive state;
When the current flowing through the low-side switch is smaller than or equal to the first threshold value, the transistor control circuit adjusts the current limiting transistor to be in an off state;
wherein the first threshold is a maximum current allowed to flow through the low-side switch.
Optionally, the method further comprises:
A first filter circuit configured to filter an output of the transistor control circuit and transmit to the current limiting transistor.
Optionally, the transistor control circuit includes a voltage dividing resistor and a sampling resistor;
one end of the voltage dividing resistor is connected with the low-side switch, the other end of the voltage dividing resistor and one end of the sampling resistor are connected to a first intersection point, and the other end of the sampling resistor is grounded;
The input end of the first filter circuit is connected with the first intersection point, the output end of the first filter circuit is connected with the control end of the current-limiting transistor, the first end of the current-limiting transistor is connected with the control end of the low-side switch, and the second end of the current-limiting transistor is grounded.
Optionally, the resistance value of the sampling resistor is R8, the on threshold voltage of the current limiting transistor is V th, and the first threshold is I th, where I th＝Vth/R8.
Optionally, when the low-side drive fails, the current limiting transistor is configured to cooperate with the transistor control circuit to make the current flowing through the low-side switch I th.
Optionally, the first filter circuit includes a first filter capacitor and a first filter resistor;
One end of the first filter resistor is connected with the first intersection point, the other end of the first filter resistor and one end of the first filter capacitor are connected with the second intersection point, and the other end of the first filter capacitor is grounded;
and the control end of the current limiting transistor is connected with the second intersection point.
Optionally, the current limiting transistor is a bipolar transistor.
Based on the same inventive concept, the invention also provides a low-side driving circuit, which comprises the overcurrent diagnosis processing circuit of any one of the characteristic descriptions.
Compared with the prior art, the invention has the following beneficial effects:
1. The invention provides an overcurrent diagnosis processing circuit, which utilizes a current-limiting transistor and a transistor control circuit to adjust the current flowing through a low-side switch when the low-side driving circuit has an overcurrent fault. The transistor control circuit is used for adjusting the working state of the current-limiting transistor based on the current flowing through the low-side switch, and the current-limiting transistor is used for adjusting the magnitude of the current flowing through the low-side switch. Through the cooperation of the current limiting transistor and the transistor control circuit, the current limiting protection of the low-side switch can be realized when the low-side driving circuit has an overcurrent fault. Since the fault diagnosis and processing process does not use MCU, and the switching speed of the current-limiting transistor is nanosecond, when overcurrent fault occurs, the hardware response time of the overcurrent fault diagnosis processing circuit is longest and is only microsecond. No software is needed to do any operation, the response is quick, the power consumption requirement on the circuit is low, and therefore damage to circuit devices is avoided, and the safety is improved.
2. When the low-side driving circuit has overcurrent faults, the current limiting transistor is matched with the transistor control circuit, so that the current flowing through the low-side switch is ensured to be constant to be the first threshold value, after the overcurrent faults disappear, the whole circuit continues to normally work without any operation of software, the power consumption requirements on the current limiting resistor and the sampling resistor are very low, and the current capability of the current limiting transistor is also reduced by adopting a conventional small-packaged resistor. For the part of the circuit, a double-channel integrated chip can be selected, the circuit area of the whole module can be greatly reduced, and the hardware cost can be reduced.
The low-side driving circuit provided by the invention and the overcurrent diagnosis processing circuit belong to the same invention conception, so that the low-side driving circuit has the same beneficial effects.
Drawings
FIG. 1 is a schematic diagram of a low-side driving circuit according to the prior art;
FIG. 2 is a schematic diagram of a bottom side driving circuit with an over-current diagnosis processing circuit according to an embodiment of the present invention;
Wherein, in fig. 1: u1-low side switch; r1-pull-down resistor, R2 is a current limiting resistor, C1-input filter capacitor, R3-current limiting divider resistor, R4-pull-down divider resistor, R5-current limiting resistor, filter capacitor of C2-diagnostic circuit, D1-bidirectional ESD (Electro-STATIC DISCHARGE) diode, C3-ESD capacitor, in-control input signal, diagOut-diagnostic Output signal, pull-up resistor of R load -load end, output signal of Output-controller;
In fig. 2: r1-first resistor, R2-second resistor, R3-third resistor, R4-fourth resistor, R5-fifth resistor, R6-divider resistor, R7-first filter resistor, C1-first capacitor, C2-second capacitor, C3-third capacitor, C4-first filter capacitor, D1-first diode, Q1-low side switch, Q2-current limiting transistor, R load -pull-up resistor, R8-sampling resistor, in-control input signal, diagOut-diagnostic Output signal, output signal of Output-controller, 10-overcurrent diagnostic processing circuit, 100-transistor control circuit, 101-first filter circuit.
Detailed Description
Specific embodiments of the present invention will be described in more detail below with reference to the drawings. The advantages and features of the present invention will become more apparent from the following description. It should be noted that the drawings are in a very simplified form and are all to a non-precise scale, merely for convenience and clarity in aiding in the description of embodiments of the invention.
In the description of the present invention, it should be understood that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", etc., are based on the directions or positional relationships shown in the drawings, are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
Referring to fig. 2, an embodiment of the present invention proposes an overcurrent diagnosis processing circuit 10 for an overcurrent diagnosis processing of a low-side driving circuit, the overcurrent diagnosis processing circuit 10 includes: a current limiting transistor Q2 and a transistor control circuit 100, wherein the current limiting transistor Q2 is used for adjusting the current flowing through the low-side switch Q1 in the low-side driving circuit. The transistor control circuit 100 is configured to implement a low-side driving function and adjust the operating state of the current limiting transistor Q2 based on the current flowing through the low-side switch Q1. The working states of the current limiting transistor Q2 include an on state and an off state, and the current limiting transistor Q2 cooperates with the transistor control circuit 100 to adjust the current flowing through the low-side switch Q1 when the low-side driving circuit has an overcurrent fault.
Referring to fig. 2, when the low-side driving circuit works normally, the low-side switch Q1 is In a conducting state, and when the low-side switch Q1 is conducting, due to a larger load resistance (generally 2kΩ) on a path, the current flowing through the low-side switch Q1 is smaller, at this time, the voltage on the transistor control circuit 100 is lower than the turn-on voltage of the current-limiting transistor Q2, the current-limiting transistor Q2 keeps In an off state, at this time, the current of the low-side switch Q1 is controlled by the control input signal In, and the low-side driving circuit keeps In a normal working state; when the SCB fault occurs in the low-side driving circuit, the on-current flowing through the low-side switch Q1 is large, and at this time, the voltage on the transistor control circuit 100 is higher than the on-voltage of the current-limiting transistor Q2, and the current-limiting transistor Q2 is turned on. When the current limiting transistor Q2 is turned on, the control terminal of the low-side switch Q1 is pulled down, the low-side switch Q1 is turned off, and at this time, the voltage on the transistor control circuit 100 decreases again, and after the voltage is lower than the turn-on voltage of the current limiting transistor Q2, the current limiting transistor Q2 is turned off, so that the low-side switch Q1 is turned on again. This conditioning process is repeated as long as the SCB failure is still present at this time, and eventually an equilibrium state is reached. When the SCB fault disappears, the voltage on the transistor control circuit 100 returns to be lower than the turn-on voltage of the current limiting transistor Q2, so that the low-side switch Q1 returns to a normal on state, and the low-side driving circuit can continue to work normally. Because the switching speeds of the low-side switch Q1 and the current-limiting transistor Q2 in the circuit are both nanosecond, when the SCB fault occurs, the hardware response time of the overcurrent diagnosis processing circuit 10 is longest and only microsecond, and during the SCB fault, the current flowing through the low-side switch Q1 can be automatically limited, and when the SCB fault disappears, the low-side driving circuit can continue to work normally without any operation of software, so that the power consumption requirement on devices in the circuit is very low, and the type selection requirement on the current capability of the low-side switch Q1 and the current-limiting transistor Q2 is also reduced. The low-side switch Q1 and the current-limiting transistor Q2 can use a dual-channel integrated chip, so that the circuit area of the whole module can be greatly reduced, and the cost can be reduced.
Unlike the prior art, the overcurrent diagnosis processing circuit 10 according to the embodiment of the invention utilizes the current limiting transistor Q2 and the transistor control circuit 100 to adjust the current flowing through the low-side switch Q1 when the low-side driving circuit has an overcurrent fault. The transistor control circuit 100 is configured to adjust an operation state of the current limiting transistor Q2 based on a current flowing through the low-side switch Q1, and the current limiting transistor Q2 is configured to adjust a magnitude of the current flowing through the low-side switch Q1. By matching the current limiting transistor Q2 with the transistor control circuit 100, current limiting protection of the low-side switch Q1 can be achieved when the low-side driving circuit has an overcurrent fault. Since the fault diagnosis and processing process does not use the MCU, and the switching speed of the current limiting transistor Q2 is in nanosecond level, when an overcurrent fault occurs, the hardware response time of the overcurrent fault diagnosis processing circuit is longest and is only in microsecond level. No software is needed to do any operation, the response is quick, the power consumption requirement on the circuit is low, and therefore damage to circuit devices is avoided, and the safety is improved.
In the embodiment of the present invention, the current limiting transistor Q2 is a bipolar transistor, and may be configured as an NPN transistor or a PNP transistor, and it is understood that the current limiting transistor Q2 is a bipolar transistor, which has an on threshold voltage on a base, and when the voltage generated by the current flowing through the low-side switch Q1 on the resistor R8 is higher than the on pre-fabricated voltage of the current limiting transistor Q2, the current limiting transistor Q2 starts to perform the current limiting operation, and in other embodiments, may be implemented by other devices having similar characteristics. For example, a transistor, a MOS transistor, or IGBT (Insulated Gate Bipolar Transistor) may be selected, but not limited to, and other types of transistors may be selected, where the types of the current limiting transistor Q2 are not described in detail, and may be selected according to actual needs in specific applications. For the convenience of explanation of the technical solution of the present invention, in the embodiment of the present invention, the current limiting transistor Q2 is a bipolar transistor, and the implementation manners of other types of transistors are similar to those of the bipolar transistor, and will not be described herein.
Further, the current limiting transistor Q2 adjusts the magnitude of the current flowing through the low-side switch Q1 by being turned on or off. When the current flowing through the low-side switch Q1 is smaller than a set value, the current limiting transistor Q2 is in an off state, and when the low-side switch Q1 has an overcurrent fault, the current limiting transistor Q2 is in an on state to reduce the current flowing through the low-side switch Q1. Referring to fig. 2, since the current limiting transistor Q2 and the low-side switch Q1 can be regarded as a parallel relationship in the circuit, when the current limiting transistor Q2 is in a conducting state, the current limiting transistor Q2 is equivalent to the current limiting circuit of the low-side switch Q1, so that the current flowing through the low-side switch Q1 can be reduced, and when an overcurrent fault occurs, the current flowing through the low-side switch Q1 can be effectively reduced to protect the low-side driving circuit.
Further, when the current flowing through the low-side switch Q1 is greater than the first threshold, the transistor control circuit 100 adjusts the current limiting transistor Q2 to be in a conductive state. When the current flowing through the low-side switch Q1 is less than or equal to the first threshold, the transistor control circuit 100 adjusts the current limiting transistor Q2 to be in an off state. Wherein the first threshold is a maximum current allowed to flow through the low-side switch Q1.
Optionally, referring to fig. 2, the over-current diagnosis processing circuit 10 further includes a first filter circuit 101, where the first filter circuit 101 is configured to filter the output of the transistor control circuit 100 and transmit the filtered output to the current limiting transistor Q2.
Specifically, the transistor control circuit 100 includes a voltage dividing resistor R6 and a sampling resistor R8. One end of the voltage dividing resistor R6 is connected with the low-side switch Q1, the other end of the voltage dividing resistor R6 and one end of the sampling resistor R8 are connected to a first intersection point, and the other end of the sampling resistor R8 is grounded. The input end of the first filter circuit 101 is connected with the first intersection point, the output end of the first filter circuit 101 is connected with the control end of the current-limiting transistor Q2, the first end of the current-limiting transistor Q2 is connected with the control end of the low-side switch Q1, and the second end of the current-limiting transistor Q2 is grounded. It will be appreciated that, when the current limiting transistor Q2 is a bipolar transistor, the control terminal of the current limiting transistor Q2 is a base of the bipolar transistor, and the first terminal and the second terminal of the current limiting transistor Q2 are a collector and an emitter of the bipolar transistor, and the specific connection method may be selected according to the actual type of the current limiting transistor Q2, which is not limited herein.
It should be noted that the type of the first filter circuit 101 includes, but is not limited to, a filter circuit formed by a resistor and a capacitor, and filtering is implemented by only using a capacitor, and the specific type of the first filter circuit 101 is not limited and may be specifically selected according to actual needs. For convenience in explaining the technical solution of the present invention, in the embodiment of the present invention, the first filter circuit 101 is a filter circuit formed by using resistors and capacitors, please continue to refer to fig. 2. Specifically, the first filter circuit 101 includes a first filter capacitor C4 and a first filter resistor R7. One end of the first filter resistor R7 is connected with the first intersection point, the other end of the first filter resistor R7 and one end of the first filter capacitor C4 are connected with the second intersection point, and the other end of the first filter capacitor C4 is grounded. The control end of the current limiting transistor Q2 is connected with the second intersection point.
Further, the resistance value of the sampling resistor is R8, the turn-on threshold voltage of the current limiting transistor Q2 is V th, and the first threshold value is I th, where I th＝Vth/R8.
Preferably, when the low-side driving fails, the current limiting transistor Q2 cooperates with the transistor control circuit 100 to make the current flowing through the low-side switch Q1I th. When the low-side driving circuit has an overcurrent fault, the current limiting transistor Q2 is matched with the transistor control circuit 100, so that the current flowing through the low-side switch Q1 is ensured to be constant to be the first threshold value, after the overcurrent fault disappears, the whole circuit continues to normally work without any operation of software, so that the power consumption requirements on the current limiting resistor and the sampling resistor R8 are very low, and the current capability selection requirement on the current limiting transistor Q2 is also reduced by adopting a conventional small-package resistor. For the part of the circuit, a double-channel integrated chip can be selected, the circuit area of the whole module can be greatly reduced, and the hardware cost can be reduced.
When the low-side driving circuit works normally, the low-side switch Q1 is In an on or off state, and when the low-side switch Q1 is In an on state, as the load resistance on the path is larger (generally 2 k), the on current of the low-side switch Q1 is smaller, then the voltage on the sampling resistor R8 is lower than the on voltage of the current-limiting transistor Q2, the current-limiting transistor Q2 is kept In an off state, and at this time, the low-side switch Q1 is controlled by the control input signal In, and the low-side driving circuit keeps In a normal working state. When the SCB fault occurs in the low-side driving circuit, the on current of the low-side switch Q1 is larger, the voltage formed on the sampling resistor R8 is higher than the on voltage of the current-limiting transistor Q2, the current-limiting transistor Q2 is turned on, and then the control end of the low-side switch Q1 is pulled down, the low-side switch Q1 is turned off, at this time, the voltage of the sampling resistor R8 is reduced, the current-limiting transistor Q2 is turned off after the on voltage of the current-limiting transistor Q2 is lower, the low-side switch Q1 is turned on again, and the regulation process is repeated until the balance state is finally reached, and the current value flowing through the low-side switch Q1 is stabilized as V th/R8. When the SCB fault disappears, the voltage on the sampling resistor R8 returns to be lower than the turn-on voltage of the current limiting transistor Q2, so that the low-side switch Q1 is caused to return to a normal on state, and the low-side driving circuit continues to work normally. The switching speed of the low-side switch Q1 and the current limiting transistor Q2 in the circuit is nanosecond, the hardware response time of the overcurrent diagnosis processing circuit 10 is microsecond when the SCB fault occurs, and the current during the SCB fault is automatically limited to be approximately equal to V th/R8. When the SCB fault of the low-side driving circuit disappears, the low-side driving circuit can continue to work normally without any operation by software, so that the power consumption requirements on the voltage dividing resistor R6 and the sampling resistor R8 are very low, and the selection requirements on the current capability of the low-side switch Q1 and the current limiting transistor Q2 are also reduced by preferably adopting a conventional small-package resistor implementation. For the part of the circuit, a double-channel integrated chip can be selected, the area of the whole module circuit can be greatly reduced, and the cost can be reduced.
Based on the same inventive concept, another embodiment of the present invention also proposes a low-side driving circuit, including the overcurrent diagnosis processing circuit 10 as described in any one of the above features.
In order to facilitate understanding of the technical scheme of the present invention, a more specific low-side driving circuit structure is provided below. The low-side driving circuit includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a first diode D1, a pull-up resistor R load, a low-side switch Q1, and the overcurrent diagnosis processing circuit 10. The diagnosis processing circuit comprises a sampling resistor R8, a voltage dividing resistor R6, a first filter resistor R7, a first filter capacitor C4 and a current limiting transistor Q2.
One end of the first resistor R1 is connected with one end of the second resistor R2 and is connected with a control input signal, and the other end of the first resistor R1 is grounded; the other end of the second resistor R2 is connected with one end of the first capacitor C1 and is connected to the control end of the low-side switch Q1 and the first end of the current-limiting transistor Q2, and the other end of the second capacitor C2 is grounded; the first end of the low-side switch Q1 is connected with one end of the third resistor R3, and the second end of the low-side switch Q1 is connected with one end of the voltage dividing resistor R6; the other end of the third resistor R3 is connected with one end of the fourth resistor R4 and one end of the fifth resistor R5, and the other end of the fourth resistor R4 is grounded; the other end of the fifth resistor R5 is connected with one end of the second capacitor C2 and is used as an output end of a diagnosis output signal of the circuit, and the other end of the second capacitor C2 is grounded; one end of the third resistor R3 is further connected to one end of the third capacitor C3, the other end of the third capacitor C3 is grounded, one end of the third capacitor C3 is further connected to one end of the first diode D1, the other end of the first diode D1 is grounded, and one end of the first diode D1 is further connected to the pull-up resistor R load. The first resistor R1 is a pull-down resistor and is in a default pull-down state before driving; the second resistor R2 and the first capacitor C1 form a filter circuit; the third resistor R3 and the fourth resistor R4 form a voltage division diagnosis circuit; the fifth resistor R5 and the second capacitor C2 form a filter circuit; the first diode D1 and the third capacitor C3 are used to protect the low-side switch Q1 from damage during ESD strike. In is a control input signal of the circuit and can be derived from the output of the MCU; diagOut is a diagnostic output signal of the circuit, and the MCU judges whether a fault exists by sampling the voltage state of DiagOut; r load is a pull-up resistor R load at the load end, which is connected with Output of the controller, and Output is an Output signal of the controller, and provides a voltage state for the load end. One end of the voltage dividing resistor R6 is connected with the second end of the low-side switch Q1, the other end of the voltage dividing resistor R6 and one end of the sampling resistor R8 are connected to a first intersection point, and the other end of the sampling resistor R8 is grounded. One end of the first filter resistor R7 is connected with the first intersection point, the other end of the first filter resistor R7 and one end of the first filter capacitor C4 are connected with the second intersection point, and the other end of the first filter capacitor C4 is grounded. The control end of the current limiting transistor Q2 is connected with the second intersection point. The first end of the current limiting transistor Q2 is connected with the control end of the low-side switch Q1, and the second end of the current limiting transistor Q2 is grounded.
When the low-side driving circuit is In normal operation, the low-side switch Q1 has two states of on-off, and when the low-side switch Q1 is on, as the load resistance on the path is larger (generally 2 k), the on-current of the low-side switch Q1 is smaller, the voltage on the sampling resistor R8 is lower than the on-voltage of the current-limiting transistor Q2, the current-limiting transistor Q2 is kept In an off state, and at this time, the low-side switch Q1 is controlled by the control input signal In, and the low-side driving circuit is kept In a normal operation state; when the output of the low-side driving circuit has SCB fault, the on current of the low-side switch Q1 is larger, the voltage formed on the sampling resistor R8 is higher than the on voltage of the current-limiting transistor Q2, the on of the current-limiting transistor Q2 pulls down the control end of the low-side switch Q1, the low-side switch Q1 is turned off, the voltage of the sampling resistor R8 is reduced, the current-limiting transistor Q2 is turned off after the voltage is lower than the on voltage of the current-limiting transistor Q2, the low-side switch Q1 is turned on again, and the regulation process is repeated as long as the SCB fault of the low-side driving circuit is still, and finally, the balance state is reached, and the current value flowing through the low-side switch Q1 is approximately V th/R8. When the SCB fault of the low-side driving circuit disappears, the voltage on the sampling resistor R8 is restored below the turn-on voltage of the current-limiting transistor Q2, so that the low-side switch Q1 is restored to a normal conduction state, and the low-side driving circuit continues to work normally.
The low-side switch Q1 and the current limiting transistor Q2 in the low-side driving circuit are bipolar transistors, the switching speed is nanosecond, when SCB faults occur, the hardware response time of the low-side driving circuit is as long as microsecond, the current can be automatically limited to be approximately equal to V th/R8 during the SCB faults, after the SCB faults disappear, the low-side driving circuit can continue to normally work without software to do any operation, so that the power consumption requirements of the voltage dividing resistor R6 and the sampling resistor R8 are very low, and the current capability selection requirements of the low-side switch Q1 and the current limiting transistor Q2 can be reduced by adopting a conventional small-package resistor. For the part of the circuit, the integrated chip with double channels can be utilized, the area of the whole module circuit can be greatly reduced, and the cost can be reduced. Through increasing the low side drive circuit that has diagnosis processing circuit, low side drive circuit is in ON or PWM state and after the circuit takes place SCB trouble, originally is the millisecond and carries out the shutoff processing, and turn-off time is long, has the risk of damaging the controller, and the circuit after the improvement is automatic to carry out the current-limiting protection to the fault state, and current-limiting state consumption is less can not damage TCU (Transmission Control Unit, automatic gearbox control unit), need not the software and does any operation, and the response is fast, and is low to the circuit consumption requirement to avoid the damage to the controller, improved the security.
In the embodiment of the invention, the low-side switch Q1 is configured as a bipolar transistor, the control of the low-side switch Q1 is a base electrode of the bipolar transistor, and the first end and the second end of the low-side switch Q1 are a collector electrode and an emitter electrode of the bipolar transistor. It should be understood that in other embodiments, the low-side switch Q1 may be of other types, and the connection manner of the low-side switch Q1 of other types is similar, which is not described herein, and may be specifically selected according to actual needs. It should be noted that, as is apparent from the above description, the low-side driving circuit includes a plurality of filter circuits, and the types of the filter circuits include, but are not limited to, filter circuits formed by resistors and capacitors, filter circuits formed by resistors and inductors, and filtering implemented by capacitors alone, and the specific types of the filter circuits are not limited and may be specifically selected according to practical needs.
In summary, the invention has the following beneficial effects:
1. The invention provides an overcurrent diagnosis processing circuit, which utilizes a current-limiting transistor and a transistor control circuit to adjust the current flowing through a low-side switch when the low-side driving circuit has an overcurrent fault. The transistor control circuit is used for adjusting the working state of the current-limiting transistor based on the current flowing through the low-side switch, and the current-limiting transistor is used for adjusting the magnitude of the current flowing through the low-side switch. Through the cooperation of the current limiting transistor and the transistor control circuit, the current limiting protection of the low-side switch can be realized when the low-side driving circuit has an overcurrent fault. Since the fault diagnosis and processing process does not use MCU, and the switching speed of the current-limiting transistor is nanosecond, when overcurrent fault occurs, the hardware response time of the overcurrent fault diagnosis processing circuit is longest and is only microsecond. No software is needed to do any operation, the response is quick, the power consumption requirement on the circuit is low, and therefore damage to circuit devices is avoided, and the safety is improved.
2. When the low-side driving circuit has overcurrent faults, the current limiting transistor is matched with the transistor control circuit, so that the current flowing through the low-side switch is ensured to be constant to be the first threshold value, after the overcurrent faults disappear, the whole circuit continues to normally work without any operation of software, the power consumption requirements on the current limiting resistor and the sampling resistor are very low, and the current capability of the current limiting transistor is also reduced by adopting a conventional small-packaged resistor. For the part of the circuit, a double-channel integrated chip can be selected, the circuit area of the whole module can be greatly reduced, and the hardware cost can be reduced.
The low-side driving circuit provided by the invention and the overcurrent diagnosis processing circuit belong to the same invention conception, so that the low-side driving circuit has the same beneficial effects.
In the description of the present specification, a description of the terms "one embodiment," "some embodiments," "examples," or "particular examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments. Further, one skilled in the art can engage and combine the different embodiments or examples described in this specification.
The foregoing is merely a preferred embodiment of the present invention and is not intended to limit the scope of the present invention, which includes but is not limited to the configurations set forth in the foregoing description. Various modifications and variations of the embodiments of the invention will be apparent to those skilled in the art in light of the foregoing description. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. An overcurrent diagnostic processing circuit for an overcurrent diagnostic processing of a low-side drive circuit, the overcurrent diagnostic processing circuit comprising:
a current limiting transistor configured to adjust a magnitude of a current flowing through a low side switch in the low side driving circuit;
A transistor control circuit configured to implement a low-side drive function and adjust an operating state of the current-limiting transistor based on a current flowing through the low-side switch;
the working state of the current limiting transistor comprises an on state and an off state, and the current limiting transistor is matched with the transistor control circuit to adjust the current flowing through the low-side switch when the low-side driving circuit has an overcurrent fault;
the fault diagnosis and processing process of the transistor control circuit does not use an MCU;
the transistor control circuit comprises a voltage dividing resistor and a sampling resistor;
one end of the voltage dividing resistor is connected with the low-side switch, the other end of the voltage dividing resistor and one end of the sampling resistor are connected to a first intersection point, and the other end of the sampling resistor is grounded;
the first intersection point is indirectly connected with the control end of the current-limiting transistor, the first end of the current-limiting transistor is connected with the control end of the low-side switch, and the second end of the current-limiting transistor is grounded.
2. The overcurrent diagnostic processing circuit of claim 1, wherein the current limiting transistor adjusts the magnitude of the current flowing through the low-side switch by turning on or off;
When the current flowing through the low-side switch is smaller than a set value, the current limiting transistor is in an off state; when the low-side switch has an overcurrent fault, the current limiting transistor is in a conducting state to reduce the current flowing through the low-side switch.
3. The overcurrent diagnostic processing circuit of claim 1, wherein the transistor control circuit adjusts the current limiting transistor to be in an on state when the current flowing through the low-side switch is greater than a first threshold;
When the current flowing through the low-side switch is smaller than or equal to the first threshold value, the transistor control circuit adjusts the current limiting transistor to be in an off state;
wherein the first threshold is a maximum current allowed to flow through the low-side switch.
4. The overcurrent diagnostic processing circuit of claim 3, further comprising:
A first filter circuit configured to filter an output of the transistor control circuit and transmit to the current limiting transistor.
5. The overcurrent diagnostic processing circuit of claim 4, wherein an input of the first filter circuit is connected to the first junction, and an output of the first filter circuit is connected to the control terminal of the current limiting transistor.
6. The overcurrent diagnostic processing circuit of claim 5, wherein the sampling resistor has a resistance of R8, the current limiting transistor has a turn-on threshold voltage of V th, and the first threshold is I th, wherein I th=Vth/R8.
7. The overcurrent diagnostic processing circuit of claim 6 wherein the current limiting transistor is configured to cooperate with the transistor control circuit to provide a current I th through the low-side switch when an overcurrent fault occurs in the low-side drive.
8. The overcurrent diagnostic processing circuit of claim 5, wherein the first filter circuit comprises a first filter capacitor and a first filter resistor;
One end of the first filter resistor is connected with the first intersection point, the other end of the first filter resistor and one end of the first filter capacitor are connected with the second intersection point, and the other end of the first filter capacitor is grounded;
and the control end of the current limiting transistor is connected with the second intersection point.
9. The overcurrent diagnostic processing circuit of any one of claims 1-8, wherein the current limiting transistor is a bipolar transistor.
10. A low-side drive circuit comprising the overcurrent diagnostic processing circuit of any one of claims 1-8.
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