Short-circuit protection circuit for high-side drive relay coil

Abstract

The present invention relates to a short-circuit protection circuit for a high-side drive relay coil, wherein the protection circuit comprises: an internal high-side voltage drive module and an external relay coil processing module, wherein the internal high-side voltage drive module is connected to the external relay coil processing module via an external pin, and the external relay coil processing module monitors the state of the relay coil of the external relay coil processing module according to the voltage-dividing resistor of the internal high-side voltage drive module, and controls the conduction state of the transistor in the internal high-side voltage drive module to achieve rapid protection processing of the short-circuit protection circuit. The short-circuit protection circuit for the high-side drive relay coil of the present invention has obvious cost advantages compared to the intelligent power chip driving relay, and the cost of two transistors, a diode and a plurality of resistors and capacitors is significantly lower than the price of the mainstream intelligent power chip on the market.

Description

Technical Field

[0001] The invention relates to the technical field of automobile electronic control, in particular to the technical field of short-circuit protection of vehicle-mounted relay output drive, and specifically refers to a short-circuit protection circuit of a high-side drive relay coil. Background Art

[0002] Many loads in a car are controlled by relays. There are usually 30 to 50 relays in the central power distribution box of a car. These relays are controlled by different automotive electronic controllers. By outputting high level (high-side drive) or low level (low-side drive), the relay coil is energized, the normally open contacts of the relay are closed, and the load can work normally.

[0003] When designing the hardware circuit of the automotive electronic controller to control the relay, it is necessary to consider the short circuit and open circuit of the external relay, as well as the fault of the controller output port short-circuiting to the power supply or ground. When the above fault conditions occur, it is necessary to stop the output of the corresponding port of the automotive electronic controller in time to avoid external short circuit faults from damaging the automotive electronic controller.

[0004] Therefore, a relay drive circuit with fast short-circuit protection is required in the relay drive circuit of the automotive electronic controller. This circuit is mainly used for high-side drive relay control, and can promptly shut down the corresponding output of the automotive electronic controller when the external relay is short-circuited. At the same time, this hardware circuit can also measure the output port status (output port: open circuit, short circuit, normal connection) through its diagnostic circuit when the output is not turned on, and feed back the measured results to the automotive electronic controller MCU. If the output port status is abnormal when the output is not turned on, the output will no longer be turned on. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned shortcomings of the prior art and provide a short-circuit protection circuit for a high-side drive relay coil which has a simple structure and low application cost.

[0006] In order to achieve the above object, the short-circuit protection circuit of the high-side drive relay coil of the present invention is as follows:

[0007] The short-circuit protection circuit of the high-side drive relay coil has the following main features: the protection circuit includes: an internal high-side voltage drive module and an external relay coil processing module, the internal high-side voltage drive module is connected to the external relay coil processing module through an external pin, and the external relay coil processing module will monitor the state of the relay coil of the external relay coil processing module according to the voltage-dividing resistor of the internal high-side voltage drive module, and based on controlling the conduction state of the transistor in the internal high-side voltage drive module, to achieve rapid protection processing of the short-circuit protection circuit.

[0008] Preferably, the internal high-side voltage driving module comprises:

[0009] A PNP transistor, an NPN transistor and a second diode, wherein the base of the NPN transistor is connected to the MCU control port through a third resistor and a fourth resistor, the collector of the NPN transistor is connected to the base of the PNP transistor through a second resistor, and the emitter of the NPN transistor is grounded; when the MCU control port outputs a high level of 5V, the base of the NPN transistor is in a conducting state after obtaining a forward voltage, and the base of the PNP transistor is also in a conducting state after obtaining a reverse voltage.

[0010] Preferably, the emitter of the PNP transistor is connected to the power supply, and the collector of the PNP transistor is connected to the external port. When the PNP transistor is turned on, the controller power supply is connected to the external port, so that the relay coil of the external relay coil processing module is energized, and the relay coil is attracted.

[0011] Preferably, the PNP transistor is also provided with a set of voltage-dividing resistors, and the voltage-dividing resistors specifically include a seventh resistor, an eighth resistor and a ninth resistor connected in series with each other, wherein the first end of the seventh resistor is connected to the controller power supply, and the second end of the ninth resistor is grounded.

[0012] Preferably, the protection circuit transmits the voltage-dividing resistance between the eighth resistor and the ninth resistor to the AD sampling port of the MCU through the sixth resistor, and determines the state of the relay coil by the voltage value collected by the AD sampling port.

[0013] Preferably, the collector of the PNP transistor is connected to the cathode of the second diode, the base of the NPN transistor is connected to the anode of the second diode via the fourth resistor, and the second diode is used for short-circuit protection.

[0014] Preferably, a first sampling point is provided between the collector of the PNP transistor and the external port, and a second sampling point is provided between the third resistor and the fourth resistor. When the collector of the PNP transistor is short-circuited, the voltage at the first sampling point becomes 0V, at which time the second diode is turned on so that the voltage at the second sampling point is pulled down, and the MCU control port is forcibly turned off to control the second sampling point.

[0015] Preferably, when the second diode is turned on, the base of the NPN transistor becomes a low level and enters a cut-off state, and at the same time, the base of the PNP transistor becomes a high level and also enters a cut-off state.

[0016] Preferably, when the protection circuit is in a normal working state, the voltage collected by the AD sampling port through AD diagnosis is the 5V voltage output by the MCU control port;

[0017] When the protection circuit is in a short-circuit grounding state, the voltage collected by the AD sampling port through AD diagnosis is 0V;

[0018] When the protection circuit is in a short circuit and the power supply and normal drive cannot be distinguished, it is necessary to shut down the circuit output for judgment.

[0019] Preferably, the external relay coil processing module specifically includes: a relay and a first diode, wherein the first diode is respectively connected to the ninth pin of the relay and the external port, the tenth pin of the relay is grounded, one end of the sixth contact of the relay is grounded through a load resistor, and the other end of the sixth contact is attracted by the seventh contact or the eighth contact to achieve the attraction or disconnection processing of the relay coil, and the seventh contact or the eighth contact is connected to an external power supply.

[0020] The short-circuit protection circuit of the high-side drive relay coil of the present invention has obvious cost advantages compared to the intelligent power chip driving relay. The cost of two transistors, a diode and a number of resistors and capacitors is significantly lower than the price of mainstream intelligent power chips on the market. In this circuit, a group of voltage-dividing resistors connected to the collector of the PNP transistor can monitor the state of the external port. When the external port is already in a short-circuit or open-circuit state, the output is no longer turned on. The diode between the base of the NPN transistor and the collector of the PNP transistor can quickly lower the base voltage of the NPN transistor when a short circuit occurs in the external port (relay coil), so that the base of the NPN transistor is in a low voltage state, the NPN transistor is cut off, and the PNP transistor is turned off at the same time, so that the controller power supply stops outputting. This circuit is simple and easy to operate, and the maximum current conducted by the PNP transistor used for output can meet the driving requirements of most vehicle-mounted relay coils. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The diagram is a structural diagram of a short-circuit protection circuit for a high-side drive relay coil of the present invention. DETAILED DESCRIPTION

[0022] In order to more clearly describe the technical content of the present invention, further description is given below in conjunction with specific embodiments.

[0023] Before describing in detail embodiments according to the present invention, it should be noted that, hereinafter, the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, whereby a process, method, article or apparatus comprising a series of elements includes not only these elements, but also other elements not explicitly listed or inherent to such process, method, article or apparatus.

[0024] See also Figure 1 As shown, the short-circuit protection circuit of the high-side drive relay coil, wherein the protection circuit includes: an internal high-side voltage drive module and an external relay coil processing module, the internal high-side voltage drive module is connected to the external relay coil processing module through an external pin, and the external relay coil processing module will monitor the state of the relay coil of the external relay coil processing module according to the voltage-dividing resistor of the internal high-side voltage drive module, and based on controlling the conduction state of the transistor in the internal high-side voltage drive module, to achieve rapid protection processing of the short-circuit protection circuit.

[0025] As a preferred embodiment of the present invention, the internal high-side voltage driving module comprises:

[0026] A PNP transistor Q1, an NPN transistor Q2 and a second diode D2, wherein the base of the NPN transistor Q2 is connected to the MCU control port through a third resistor R3 and a fourth resistor R4, the collector of the NPN transistor Q2 is connected to the base of the PNP transistor Q1 through a second resistor R2, and the emitter of the NPN transistor Q2 is grounded; when the MCU control port outputs a high level of 5V, the base of the NPN transistor Q2 is in a conducting state after obtaining a forward voltage, and the base of the PNP transistor Q1 is also in a conducting state after obtaining a reverse voltage.

[0027] As a preferred embodiment of the present invention, the emitter of the PNP transistor Q1 is connected to the power supply, and the collector of the PNP transistor Q1 is connected to the external port. When the PNP transistor Q1 is turned on, the controller power supply is connected to the external port, so that the relay coil of the external relay coil processing module is energized, and the relay coil is attracted.

[0028] As a preferred embodiment of the present invention, the PNP transistor Q1 is also provided with a group of voltage-dividing resistors, and the voltage-dividing resistors specifically include a seventh resistor R7, an eighth resistor R8 and a ninth resistor R9 connected in series with each other, wherein the first end of the seventh resistor R7 is connected to the controller power supply VBB, and the second end of the ninth resistor R9 is grounded.

[0029] As a preferred embodiment of the present invention, the protection circuit transmits the voltage divider resistance between the eighth resistor R8 and the ninth resistor R9 to the AD sampling port of the MCU through the sixth resistor R6, and determines the state of the relay coil through the voltage value collected by the AD sampling port.

[0030] As a preferred embodiment of the present invention, the collector of the PNP transistor Q1 is connected to the cathode of the second diode D2, the base of the NPN transistor Q2 is connected to the anode of the second diode D2 through the fourth resistor R4, and the second diode D2 is used for short-circuit protection.

[0031] As a preferred embodiment of the present invention, a first sampling point A is provided between the collector of the PNP transistor Q1 and the external port, and a second sampling point B is provided between the third resistor R3 and the fourth resistor R4. When the collector of the PNP transistor Q1 is short-circuited, the voltage at the first sampling point A becomes 0V. At this time, the second diode D2 is turned on so that the voltage at the second sampling point B is pulled down, and the MCU control port is forcibly turned off to control the second sampling point B.

[0032] As a preferred embodiment of the present invention, when the second diode D2 is turned on, the base of the NPN transistor Q2 becomes a low level and enters a cut-off state, and at the same time, the base of the PNP transistor Q1 becomes a high level and also enters a cut-off state.

[0033] As a preferred embodiment of the present invention, when the protection circuit is in a normal working state, the voltage collected by the AD sampling port through AD diagnosis is the 5V voltage output by the MCU control port;

[0034] When the protection circuit is in a short-circuit grounding state, the voltage collected by the AD sampling port through AD diagnosis is 0V;

[0035] When the protection circuit is in a short circuit and the power supply and normal drive cannot be distinguished, it is necessary to shut down the circuit output for judgment.

[0036] As a preferred embodiment of the present invention, the external relay coil processing module specifically includes: a relay and a first diode D1, wherein the first diode D1 is respectively connected to the ninth pin of the relay and the external port, the tenth pin of the relay is grounded, one end of the sixth contact of the relay is grounded through a load resistor (R), and the other end of the sixth contact is attracted by the seventh contact or the eighth contact to realize the attraction or disconnection processing of the relay coil, and the seventh contact or the eighth contact is connected to an external power supply.

[0037] In practical application, the short-circuit protection circuit of the present invention is: an NPN transistor is used to control the conduction and cutoff of another PNP transistor, and the base of the NPN transistor is connected to the MCU control port. When the MCU control port outputs a 5V high level, the NPN transistor base obtains a forward voltage, and the NPN transistor is in a conducting state (operating in a saturation region). At this time, the base of the PNP transistor obtains a reverse voltage, and the PNP transistor is in a conducting state (operating in a saturation region). After the PNP transistor is turned on, the controller power supply is connected to the controller external port, the external relay coil is energized, and the relay is closed. There is a group of voltage dividers at the collector of the PNP transistor, which is used to monitor the state of the external port (relay coil). This group of voltage dividers is composed of three resistors in series, one end is connected to the controller power supply, and the other end is connected to GND. Through resistor voltage division, the resistor voltage close to GND in the voltage divider resistor is transmitted to the AD sampling port of the MCU, and the voltage value sampled by the AD is used to judge the state of the external port (relay coil). The base of the NPN transistor is connected to the collector of the PNP transistor through a diode, and the function of this diode is to provide fast short-circuit protection. When the external port of the controller (collector of the PNP transistor) is short-circuited to the ground, the voltage at point A is pulled down to 0V. At this time, the D2 diode is turned on, which pulls down the voltage at point B, so that the base of the NPN transistor is at a low level, and the NPN transistor enters the cut-off state. Since the NPN transistor is cut off, the base of the PNP transistor becomes high level, and the PNP transistor is also cut off. Through the above process, the output port is quickly closed, achieving the purpose of fast short-circuit protection.

[0038] In a specific embodiment of the present invention, when the relay is driven normally, the MCU control port outputs a 5V high level to the base of the NPN transistor, and the NPN transistor is turned on. At this time, the base of the PNP transistor obtains a reverse voltage, and the PNP transistor is turned on. After the PNP transistor is turned on, the controller power supply is turned on with the external port of the controller, the external relay coil is powered, and the relay is closed. When the external port (relay coil) is short-circuited to the ground, the diode connected between the base of the NPN transistor and the collector of the PNP transistor is turned on, so that the base of the NPN transistor is in a low voltage state, the NPN transistor is cut off, and the PNP transistor is turned off at the same time, so that the controller power supply stops outputting, which plays a role in fast short circuit protection. The voltage divider resistor of the collector of the PNP transistor is used to monitor the state of the external port (relay coil). The voltage value of the voltage divider resistor R9 is used as the AD diagnostic voltage value. When this voltage value is between 1.68V and 2.7V, it indicates that the external port is open. When this voltage value is 0V, it indicates that the external port is short-circuited to the ground. When the external port detects a fault, the control circuit does not turn on the output.

[0039] It should be understood that each part of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution device.

[0040] A person of ordinary skill in the art may understand that all or part of the steps of the method for implementing the above-mentioned embodiment may be completed by instructing the relevant hardware through a program, and the program may be stored in a computer-readable storage medium, which, when executed, includes one of the steps of the method embodiment or a combination thereof.

[0041] The storage medium mentioned above can be a read-only memory, a magnetic disk or an optical disk, etc.

[0042] In the description of this specification, the description with reference to the terms "an embodiment", "some embodiments", "example", "specific example", or "embodiment" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0043] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0044] The short-circuit protection circuit of the high-side drive relay coil of the present invention has obvious cost advantages compared to the intelligent power chip driving relay. The cost of two transistors, a diode and a number of resistors and capacitors is significantly lower than the price of mainstream intelligent power chips on the market. In this circuit, a group of voltage-dividing resistors connected to the collector of the PNP transistor can monitor the state of the external port. When the external port is already in a short-circuit or open-circuit state, the output is no longer turned on. The diode between the base of the NPN transistor and the collector of the PNP transistor can quickly lower the base voltage of the NPN transistor when a short circuit occurs in the external port (relay coil), so that the base of the NPN transistor is in a low voltage state, the NPN transistor is cut off, and the PNP transistor is turned off at the same time, so that the controller power supply stops outputting. This circuit is simple and easy to operate, and the maximum current conducted by the PNP transistor used for output can meet the driving requirements of most vehicle-mounted relay coils.

[0045] In this specification, the present invention has been described with reference to specific embodiments thereof. However, it is apparent that various modifications and variations may be made without departing from the spirit and scope of the present invention. Therefore, the specification and drawings should be regarded as illustrative rather than restrictive.

Claims

1. A short-circuit protection circuit for a high-side drive relay coil, characterized in that: The protection circuit includes: an internal high-side voltage driving module and an external relay coil processing module, wherein the internal high-side voltage driving module is connected to the external relay coil processing module through an external pin, and the external relay coil processing module monitors the state of the relay coil of the external relay coil processing module according to the voltage-dividing resistor of the internal high-side voltage driving module, and controls the conduction state of the transistor in the internal high-side voltage driving module to realize rapid protection processing of the short-circuit protection circuit; The internal high-side voltage driver module comprises: A PNP transistor (Q1), an NPN transistor (Q2) and a second diode (D2), wherein the base of the NPN transistor (Q2) is connected to the MCU control port via a third resistor (R3) and a fourth resistor (R4), the collector of the NPN transistor (Q2) is connected to the base of the PNP transistor (Q1) via a second resistor (R2), and the emitter of the NPN transistor (Q2) is grounded; when the MCU control port outputs a high level of 5V, the base of the NPN transistor (Q2) is in a conducting state after obtaining a forward voltage, and the base of the PNP transistor (Q1) is also in a conducting state after obtaining a reverse voltage; A first capacitor (C1) is provided between the base and the emitter of the NPN transistor (Q2), and a second capacitor (C2) is provided at the AD sampling detection port of the protection circuit; The collector of the PNP transistor (Q1) is also provided with a group of voltage-dividing resistors, the voltage-dividing resistors specifically comprising a seventh resistor (R7), an eighth resistor (R8) and a ninth resistor (R9) connected in series with each other, wherein a first end of the seventh resistor (R7) is connected to a controller power supply (VBB), and a second end of the ninth resistor (R9) is grounded; The emitter of the PNP transistor (Q1) is connected to a power source, and the collector of the PNP transistor (Q1) is connected to an external port. When the PNP transistor (Q1) is turned on, the controller power source is turned on to the external port, so that the relay coil of the external relay coil processing module is energized, and the relay coil is attracted. The protection circuit transmits the divided voltage between the eighth resistor (R8) and the ninth resistor (R9) to the AD sampling port of the MCU through the sixth resistor (R6), and determines the state of the relay coil through the voltage value collected by the AD sampling port.

2. The short-circuit protection circuit of the high-side drive relay coil according to claim 1, characterized in that: The collector of the PNP transistor (Q1) is connected to the cathode of the second diode (D2), the base of the NPN transistor (Q2) is connected to the anode of the second diode (D2) via the fourth resistor (R4), and the second diode (D2) is used for short-circuit protection.

3. The short-circuit protection circuit of the high-side drive relay coil according to claim 2, characterized in that: A first sampling point (A) is provided between the collector of the PNP transistor (Q1) and the external port, and a second sampling point (B) is provided between the third resistor (R3) and the fourth resistor (R4). When the collector of the PNP transistor (Q1) is short-circuited, the voltage at the first sampling point (A) becomes 0V, and at this time, the second diode (D2) is turned on so that the voltage at the second sampling point (B) is pulled down, and the MCU control port is forcibly turned off to control the second sampling point (B).

4. The short-circuit protection circuit of the high-side drive relay coil according to claim 3, characterized in that: When the second diode (D2) is turned on, the base of the NPN transistor (Q2) becomes a low level and enters a cut-off state, and at the same time, the base of the PNP transistor (Q1) becomes a high level and also enters a cut-off state.

5. The short-circuit protection circuit of the high-side drive relay coil according to claim 1, characterized in that: When the protection circuit is in normal working state, the voltage collected by the AD sampling port through AD diagnosis is the 5V voltage output by the MCU control port; When the protection circuit is in a short-circuit grounding state, the voltage collected by the AD sampling port through AD diagnosis is 0V; When the protection circuit is in a short circuit and the power supply and normal drive cannot be distinguished, it is necessary to shut down the circuit output for judgment.

6. The short-circuit protection circuit of the high-side drive relay coil according to any one of claims 1 to 5, characterized in that: The external relay coil processing module specifically includes: a relay and a first diode (D1), wherein the first diode (D1) is respectively connected to the ninth pin of the relay and the external port, the tenth pin of the relay is grounded, one end of the sixth contact of the relay is grounded through a load resistor (R), and the other end of the sixth contact is attracted by the seventh contact or the eighth contact to realize the attraction or disconnection processing of the relay coil, and the seventh contact or the eighth contact is connected to an external power supply.

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