A low-side load driving circuit with an open-circuit diagnosis function

Abstract

The present invention relates to a low-side load driving circuit with an open-circuit diagnosis function, which includes a low-side driving chip, a freewheeling module, and an internal power supply. The low-side load driving circuit further includes a field-effect transistor, a current-sensing resistor, an inductive load, a feedback resistor, a pull-up resistor, and a current detection module. The low-side driving chip is sequentially connected to the field-effect transistor, the current-sensing resistor, and one end of the inductive load. The other end of the inductive load is used to connect to the battery power supply. The low-side driving chip is also sequentially connected to the feedback resistor and the output end of the field-effect transistor. The connection line between the field-effect transistor and the current-sensing resistor is also connected to the freewheeling module and the internal power supply in sequence through a branch. The pull-up resistor is connected in parallel across the two ends of the freewheeling module. The current-sensing resistor is also connected to the current detection module through a branch. Compared with the prior art, the present invention has the advantages of greatly improving the accuracy of load open-circuit diagnosis, facilitating the troubleshooting of on-vehicle field faults, having simple wiring, and being easy to implement, etc.

Description

Technical Field

[0001] The present invention relates to the field of low-side load driving circuits, and particularly to a low-side load driving circuit with an open-circuit diagnosis function. Background Art

[0002] At present, inductive loads such as fuel inlet metering valves and HC nozzle metering valves in automobiles mostly adopt low-side driving, and it is necessary to monitor the current passing through the load in real time. Special low-side driving chips can not only realize the driving of multiple low-sides, but also have built-in electrical fault diagnosis. At the same time, due to the high integration of the chips, the layout space of the PCB is greatly saved, so they are widely used in automotive electronics. To protect the load and the driving circuit, a freewheeling diode with its anode connected to the low side and its cathode connected to the internal power supply of the ECU is usually used to realize the return of the low-side driving inductive load.

[0003] When the load is normally connected and there is no driving, the output voltage of the low-side driving will be pulled up to the battery voltage. When an open-circuit fault occurs, the driving chip will modulate the low-side output voltage to a certain diagnostic threshold voltage (3V) through the output terminal feedback loop.

[0004] For example, the utility model with the publication number CN205244354U discloses a low-side driving circuit for a reverse solenoid valve on an AMT shifter gear. The low-side driving module is composed of an integrated low-drive chip. The load diagnosis module includes a load positive signal diagnosis branch and a load negative signal diagnosis branch. The MCU electronic control module is connected to the filtering module, the filtering module is connected to the enable terminal of the low-side driving module, the driving terminal of the low-side driving module is connected to the negative terminal of the reverse solenoid valve, the positive terminal of the reverse solenoid valve is connected to the power supply module, the driving terminal of the low-side driving module is connected to one end of the freewheeling module, one end of the load positive signal diagnosis branch and the load negative signal diagnosis branch are respectively connected to the positive and negative terminals of the reverse solenoid valve, and the other end is connected to the MCU electronic control module. The freewheeling module includes a freewheeling diode D1 and an electrolytic capacitor E1. The positive terminal of the diode D1 is connected to the negative terminal of the reverse solenoid valve, the negative terminal of the diode D1 is connected to one end of the electrolytic capacitor E1, and the other end of the electrolytic capacitor E1 is grounded.

[0005] There are the following two problems when using the internal diagnosis logic of the driving chip: 1) At high temperatures, when the load is truly open-circuited, due to the large leakage current of the freewheeling diode, the voltage value of the low-side output is pulled up to be close to the cathode voltage of the freewheeling diode, and this voltage is much greater than the open-circuit diagnosis threshold voltage, resulting in the driving chip being unable to accurately report the open-circuit fault; 2) When the external load is not connected, the driving circuit cannot output the correct PWM waveform, and thus it is impossible to initially judge the integrity of the components of the driving circuit. Summary of the Invention

[0006] The object of the present invention is to overcome the defect that the driving chip cannot accurately report an open - circuit fault at high temperature in the above - mentioned existing technology, and to provide a low - side load driving circuit with an open - circuit diagnosis function.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A low - side load driving circuit with an open - circuit diagnosis function, including a low - side driving chip, a free - wheeling module and an internal power supply. The low - side load driving circuit further includes a field - effect transistor, a current - sensing resistor, an inductive load, a feedback resistor, a pull - up resistor and a current - detection module;

[0009] The low - side driving chip is sequentially connected to the field - effect transistor, the current - sensing resistor and one end of the inductive load. The other end of the inductive load is used to connect to a battery power supply. The low - side driving chip is also sequentially connected to the feedback resistor and the output end of the field - effect transistor. The connection line between the field - effect transistor and the current - sensing resistor is also connected to the free - wheeling module and the internal power supply through a branch. The pull - up resistor is connected in parallel across the two ends of the free - wheeling module. The current - sensing resistor is also connected to the current - detection module through a branch;

[0010] The low - side driving chip is used to provide a driving voltage for the field - effect transistor and perform fault diagnosis on the current flowing through the feedback resistor;

[0011] The current - detection module is used to perform fault diagnosis on the current flowing through the current - sensing resistor.

[0012] Further, the current - detection module includes a main control chip, a filtering module and a current - detection amplification module connected in sequence. The current - detection amplification module is connected to the current - sensing resistor.

[0013] Further, the filtering module includes a filtering capacitor and a filtering resistor. The two ends of the filtering resistor are respectively connected to the main control chip and the current - detection amplification module. A branch in the connection line between the filtering resistor and the main control chip is also connected to the filtering capacitor and then grounded.

[0014] Further, the current - detection amplification module is a current - detection amplification chip.

[0015] Further, the main control chip is a chip with 12 - bit AD sampling accuracy.

[0016] Further, the model of the low - side driving chip is C3MIO.

[0017] Further, the free - wheeling module is a free - wheeling diode.

[0018] Further, the cathode of the freewheeling diode is connected to the internal power supply, and the anode is connected to the connection line between the field effect transistor and the current detection resistor.

[0019] Further, the internal power supply is the internal power supply of the ECU.

[0020] Further, the low-side load driving circuit is encapsulated in the ECU.

[0021] Further, the resistance value of the pull-up resistor satisfies the following conditions:

[0022]

[0023] In the formula, R 2 is the resistance value of the pull-up resistor; U 1 is the threshold value of the short circuit fault of the load terminal to the power supply when the field effect transistor is turned on as set by the driving chip; R 1 is the resistance value when the field effect transistor is turned on; U ECU is the internal power supply voltage.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] By cooperating the pull-up resistor pulled up to the internal power supply of the ECU and the current detection resistor, the present invention avoids the occurrence that the driving chip cannot correctly diagnose the load open circuit situation due to the leakage current of the freewheeling diode at high temperature, greatly improves the accuracy of load open circuit diagnosis, and can also simulate and output a PWM waveform without connecting a load to preliminarily diagnose the integrity of the driving circuit, greatly facilitating the troubleshooting of on-vehicle field faults. At the same time, the scheme has simple wiring, no special components, and is easy to implement. Description of the Drawings

[0026] Figure 1 is a schematic diagram of the installation state of the low-side load driving circuit of the present invention;

[0027] Figure 2 is a schematic diagram of the circuit structure of the low-side load driving circuit of the present invention;

[0028] In the figure, 1. low-side driving chip, 2. field effect transistor, 3. current detection resistor, 4. inductive load, 5. feedback resistor, 6. freewheeling diode, 7. pull-up resistor, 8. main control chip, 9. filter capacitor, 10. filter resistor, 11. current detection and amplification chip. Detailed Embodiment

[0029] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and gives detailed implementation manners and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.

[0030] Embodiment 1

[0031] This embodiment provides a low-side load driving circuit with an open-circuit diagnosis function, including a low-side driving chip 1, a freewheeling module, and an internal power supply. It is characterized in that the low-side load driving circuit further includes a field-effect transistor 2, a current-sensing resistor 3, an inductive load 4, a feedback resistor 5, a pull-up resistor 7, and a current detection module;

[0032] The low-side driving chip 1 is sequentially connected to the field-effect transistor 2, the current-sensing resistor 3, and one end of the inductive load 4. The other end of the inductive load 4 is used to connect to the battery power supply. The low-side driving chip 1 is also sequentially connected to the feedback resistor 5 and the output end of the field-effect transistor 2. The connection line between the field-effect transistor 2 and the current-sensing resistor 3 is also connected to the freewheeling module and the internal power supply through a branch. The pull-up resistor 7 is connected in parallel across the two ends of the freewheeling module. The current-sensing resistor 3 is also connected to the current detection module through a branch;

[0033] The low-side driving chip 1 is used to provide a driving voltage for the field-effect transistor 2 and perform fault diagnosis on the current flowing through the feedback resistor 5;

[0034] The current detection module is used to perform fault diagnosis on the current flowing through the current-sensing resistor 3.

[0035] As a preferred implementation manner, the current detection module includes a main control chip 8, a filtering module, and a current detection and amplification module connected in sequence. The current detection and amplification module is connected to the current-sensing resistor 3.

[0036] As a preferred implementation manner, the filtering module includes a filtering capacitor 9 and a filtering resistor 10. The two ends of the filtering resistor 10 are respectively connected to the main control chip 8 and the current detection and amplification module. A branch in the connection line between the filtering resistor 10 and the main control chip 8 is also connected to the filtering capacitor 9 and then grounded.

[0037] As a preferred implementation manner, the current detection and amplification module is a current detection and amplification chip 11.

[0038] As a preferred implementation manner, the main control chip 8 is a chip with a 12-bit AD sampling accuracy.

[0039] As a preferred implementation manner, the model of the low-side driving chip 1 is C3MIO.

[0040] As a preferred implementation manner, the freewheeling module is a freewheeling diode 6.

[0041] As a preferred implementation manner, the cathode of the freewheeling diode 6 is connected to the internal power supply, and the anode is connected to the connection line between the field-effect transistor 2 and the current-sensing resistor 3.

[0042] As a preferred implementation manner, the internal power supply is the internal power supply of the ECU.

[0043] As a preferred embodiment, the low-side load driving circuit is encapsulated in the ECU.

[0044] As a preferred embodiment, the resistance value of the pull-up resistor satisfies the following conditions:

[0045]

[0046] In the formula, R 2 is the resistance value of the pull-up resistor; U 1 is the threshold value of the short-circuit fault of the load terminal to the power supply when the field effect transistor is turned on as set by the driving chip; R 1 is the resistance value when the field effect transistor is turned on; U ECU is the internal power supply voltage.

[0047] This embodiment also provides an optimal implementation manner, which is specifically described as follows:

[0048] Aiming at the disadvantages that the prior art cannot accurately diagnose open-circuit faults and cannot judge the integrity of the components of the driving circuit when no load is connected, this embodiment provides a low-side load driving circuit with circuit integrity detection and open-circuit diagnosis, which mainly adopts a current detection resistor and a method of pulling up the low-side drive output to the internal power supply of the ECU to achieve accurate open-circuit diagnosis and driving circuit integrity detection. The technical solution is as follows:

[0049] As Figure 1 and Figure 2 shown, a low-side load driving circuit with circuit integrity detection and open-circuit diagnosis functions includes an inductive load 4, a current detection resistor 3, a current detection and amplification chip 11, a filtering resistor 10, a filtering capacitor 9, a main control chip 8, a freewheeling diode 6, a pull-up resistor 7, a feedback resistor 5, and a low-side drive chip 1 and a field effect transistor 2. Among them, the low-side drive chip 1 is the Delphi special low-side drive chip C3MIO, and the main control chip 8 has a 12-bit AD sampling accuracy.

[0050] One end of the inductive load 4 is connected to the battery power supply, and the other end is subjected to current sampling through a current detection resistor 3. After the voltage across the sampled current detection is processed by the current detection and amplification chip 11, it is filtered by the filtering circuit composed of resistors 10 and 9 and then sent to the main control chip 8, and the main control chip monitors the current passing through the load 4 in real time.

[0051] One end of the current detection resistor 3 is connected to the inductive load, and the other end is connected to the output end of the field effect transistor 2. The low-side drive chip 1 provides the drive voltage for the gate of the field effect transistor 2 to realize the output of the PWM wave of the field effect transistor 2. At the same time, the output end of the field effect transistor 2 is sent to the low-side drive chip 1 through the feedback resistor 5 to realize the real-time monitoring of the output end and the diagnosis of the load electrical fault.

[0052] The cathode of the freewheeling diode 6 is connected to the internal power supply of the ECU, and the anode is connected between the output terminal of the field effect transistor 2 and the current detection resistor 3, realizing the freewheeling of the inductive load 4 when the field effect transistor 2 conducts and turns off, providing circuit protection and load protection.

[0053] One end of the pull-up resistor 7 is connected to the internal power supply of the ECU, and the other end is connected between the output terminal of the field effect transistor 2 and the current detection resistor 3.

[0054] The low-side drive chip 1 enables the gate of the field effect transistor 2 and outputs a PWM wave. When the inductive load is working normally, the current Current_Feedback passing through the inductive load 4 can be monitored by the main control chip 8. Considering the influence of factors such as interference, when the feedback current value is less than 60 pulses, that is, when the feedback current is infinitely close to 0A, it is determined that the load is open. Since when the load is open, the drive chip will modulate the voltage at the output terminal of the field effect transistor 2 to a certain fixed threshold (usually 3V), and the large leakage current of the freewheeling diode at high temperature will make the voltage at the output terminal of the field effect transistor 2 close to the internal power supply voltage of the ECU at the cathode of the diode (usually equal to the battery voltage), resulting in the drive chip being unable to make a correct diagnosis of the load open circuit fault at high temperature. For this characteristic of the drive chip, the open circuit diagnosis function of the drive chip is shielded by the pull-up resistor 7 pulled up to the internal power supply of the ECU, and the accurate diagnosis of the load open circuit fault is realized based on the current feedback value detected by the main control chip 8.

[0055] As Figure 2 shown, when there is no load connected, driving Gate_Drive (gate drive) makes the field effect transistor 2 output a PWM wave. Normally, the same PWM waveform as when the actual load is connected cannot be measured at the Low_Side_Drive_Output (low-side drive output) terminal, so the state of the components in the drive circuit cannot be accurately judged. A loop is formed by the pull-up resistor 7 pulled up to the internal power supply of the ECU and the field effect transistor 2. Even when the load is open, a PWM wave similar to that when the load is connected can be output at the Low_Side_Drive_Output terminal, so that the integrity of the components in the drive circuit can be conveniently diagnosed preliminarily. The resistance value of the pull-up resistor 7 cannot be too small, otherwise when the field effect transistor 2 conducts, the current value flowing through the field effect transistor 2 will be too large, which will not only cause circuit damage but also make the drive chip misreport a short circuit fault of the load to the power supply.

[0056] The selection of the resistance value of the pull-up resistor 7 depends on the threshold of the short circuit fault of this channel to the power supply.

[0057]

[0058] That is,

[0059]

[0060] R 2 is the resistance value of the pull-up resistor; U 1 is the threshold value of the short-circuit fault of the load terminal to the power supply when the field-effect transistor set by the driving chip is turned on; R 1 is the resistance value when the field-effect transistor is turned on; U ECU is the internal power supply voltage of the ECU.

[0061] Assume that the threshold value of the short-circuit fault of the load terminal to the power supply is set to 0.5V, and the resistance value when the field-effect transistor Q1 is turned on is 50mΩ. Then the resistance value satisfies: R2 ≧ 100 times the internal power supply voltage of the ECU - 50, and the unit of R2 is mΩ.

[0062] Figure 2 In it, Current_Feedback is current feedback, and Drian_Feedback is drain feedback.

[0063] The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations according to the concept of the present invention without creative labor. Therefore, all technical solutions that can be obtained by those skilled in the art in the technical field of the present invention based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art should be within the protection scope determined by the claims.

Claims

1. A low-side load driving circuit with open-circuit diagnosis function, comprising a low-side driving chip (1), a freewheeling module and an internal power supply, Characterized in that, The low-side load driving circuit further includes a field effect transistor (2), a current sensing resistor (3), an inductive load (4), a feedback resistor (5), a pull-up resistor (7) and a current detection module; The low-side driving chip (1) is sequentially connected to the output end of the feedback resistor (5) and the field effect transistor (2), the current sensing resistor (3) and one end of the inductive load (4), and the other end of the inductive load (4) is used to connect to the battery power supply. The connection line between the output end of the field effect transistor (2) and the current sensing resistor (3) is also connected to the freewheeling module and the internal power supply through a branch. The pull-up resistor (7) is connected in parallel across the freewheeling module, and the current sensing resistor (3) is also connected to the current detection module through a branch; The low-side driving chip (1) is used to provide a driving voltage for the gate of the field effect transistor (2) and perform fault diagnosis on the current flowing through the feedback resistor (5); The current detection module is used to perform fault diagnosis on the current flowing through the current sensing resistor (3); The current detection module includes a main control chip (8), a filtering module and a current detection and amplification module connected in sequence. The current detection and amplification module is connected to the current sensing resistor (3); The freewheeling module is a freewheeling diode (6).

2. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The filtering module includes a filtering capacitor (9) and a filtering resistor (10). The two ends of the filtering resistor (10) are respectively connected to the main control chip (8) and the current detection and amplification module. A branch in the connection line between the filtering resistor (10) and the main control chip (8) is also connected to the filtering capacitor (9) and then grounded.

3. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The current detection and amplification module includes a current detection and amplification chip (11).

4. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The main control chip (8) is a chip with 12-bit AD sampling accuracy.

5. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The model of the low-side driving chip (1) is C3MIO.

6. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The cathode of the freewheeling diode (6) is connected to the internal power supply, and the anode is connected to the connection line between the output end of the field effect transistor (2) and the current sensing resistor (3).

7. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The resistance value of the pull-up resistor satisfies the following conditions: Wherein, R 2 is the resistance value of the pull-up resistor; U 1 is the threshold value of the short-circuit fault of the load terminal to the power supply when the field-effect transistor is turned on as set by the driving chip; R 1 is the resistance value when the field-effect transistor is turned on; U ECU is the internal power supply voltage.

8. A low-side load driving circuit with open-circuit diagnosis function according to claim 1, Characterized in that, The low-side load driving circuit is encapsulated in an ECU.

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